Complex Contributions of Methylglyoxal to Pain, Axon Degeneration, and Diabetic Peripheral Neuropathy

ABSTRACT

Methylglyoxal is a highly reactive by‐product of glycolysis that is elevated in diabetes and contributes to the development of diabetic peripheral neuropathy (DPN). DPN is characterized by nerve degeneration, typically manifesting in patients' extremities. This leads to patients experiencing numbness, burning, and pain. It has been established that elevated methylglyoxal levels lead to nociception, but the broader cellular effects of methylglyoxal on neurons in the dorsal root ganglia (DRG) remain poorly understood. This review provides mechanistic insight regarding methylglyoxal's impact on various cell types and disease contexts. Five main mechanisms were identified: protein glycation, proteostasis change, oxidative stress, metabolic changes, and increased inflammation. These mechanisms are thoroughly interconnected, contributing to cellular dysfunction associated with DPN. We propose that methylglyoxal functions as a central mediator in cellular stress, linking hyperglycemia and elevated glycolysis to neuronal dysfunction in DPN. There is extensive evidence that these mechanisms are methylglyoxal‐driven in other cell types and diseases, but a gap in the field remains in determining whether and how they occur in DRG neurons. This is particularly important, as DPN is a frequent comorbidity in diabetes and metabolic diseases and greatly affects patients' quality of life. Understanding the effect of methylglyoxal on DRG in relation to these mechanisms will provide novel insights into the development of DPN and lead to new therapeutic targets.

This work reviews how the metabolic by‐product methylglyoxal may contribute to the development of diabetic peripheral neuropathy (DPN), a common complication of diabetes characterized by nerve damage and chronic pain in the extremities. In diabetes, methylglyoxal levels rise due to increased glucose metabolism and reduced detoxification capacity. While it is already known to trigger pain by increasing neuronal excitability, this review highlights its broader role in damaging peripheral sensory neurons in the dorsal root ganglia (DRG), which are key drivers of pain and sensory signaling in DPN. Across multiple biological systems, there is an observed pattern of methylglyoxal driving five main cellular stress mechanisms. Methylglyoxal increases protein glycation and formation of advanced glycation end products (AGEs), disrupts protein homeostasis (proteostasis), increases oxidative stress, contributes to mitochondrial dysfunction, and promotes inflammatory signaling. These processes reinforce one another, and this review suggests these mechanisms may also occur in DRG leading to neuronal injury, likely contributing to both axon degeneration and persistent neuropathic pain. The central message is that methylglyoxal is not just a pain‐inducing molecule, but a broader metabolic stress mediator that may link diabetes to progressive nerve degeneration. However, its specific effects within DRG neurons remain insufficiently studied, highlighting a key gap in understanding DPN and a potential direction for future therapeutic development.

Abbreviations

AGE

advanced glycation end products

ATP

adenosine triphosphate

DHAP

dihydroxyacetone phosphate

DNA

deoxyribose nucleic acid

DPN

diabetic peripheral neuropathy

DRG

dorsal root ganglion

G3P

glyceraldehyde 3‐phosphate

GAPDH

glyceraldehyde 3‐phosphate dehydrogenase

GLO1

glyoxalase 1

GLO2

glyoxalase 2

GLUT1

glucose transporter 1

GLUT3

glucose transporter 3

IL‐#

interleukin #

LPS

lipopolysaccharide

NAD⁺

nicotinamide adenine dinucleotide

NAV1.8

voltage‐gated sodium channel 1.8

NF‐kB

nuclear factor kappa‐light‐chain‐enhancer of activated B cells

NMN

nicotinamide mononucleotide

RAGE

receptor of advanced glycation end products

ROS

reactive oxygen species

SARM1

sterile alpha and Toll/interleukin‐1 receptor motif‐containing protein 1

TRP

transient receptor potential

TRPA1

transient receptor potential ankyrin 1

TRPV1

transient receptor potential vanilloid 1

1. Background

In 2025, it is reported that 1 in 9 adults is living with diabetes (International Diabetes Federation ²⁰²⁶). Diabetic peripheral neuropathy (DPN) is a comorbidity of diabetes that affects up to half of patients with diabetes and is characterized by degeneration of peripheral nerves, typically manifesting in the extremities (Mauermann and Staff NP ²⁰²⁶; Staehelin Jensen ²⁰²³; Slouma et al. ²⁰²⁴; Dave and Patel ²⁰²⁵). Patients experience numbness, tingling, and pain, which can result in reduced mobility and autonomy.

Despite the high prevalence and clinical burden, there are few effective treatment options, despite many failed attempts to identify new approaches (Table 1). Existing treatments are limited to symptom management, particularly mitigating pain and glycemic control. There have been multiple clinical trials for diabetes, diabetic peripheral neuropathy, and diabetic nephropathy that have failed. These treatments targeted mechanisms such as reducing oxidative stress, AGE cross‐linking, and microvascular complications, and increasing the survival of small nerve fibers (Table 1). However, glucose regulation is often ineffective in preventing neuropathy in type 2 diabetes. This highlights that hyperglycemia is not the sole contributor to DPN progression, underscoring the need to understand other factors that contribute to DPN and its associated pain.

TABLE 1.

Highlight of clinical trials for diabetes therapeutics.

Intervention	Mechanism	Trial design	Main outcomes measured	Main result	Conclusion	Citations
Benfotiamine	Body converts to thiamine or vitamin B1. Seen to decrease glycemia and leptin concentrations.	BOND study: randomized, double‐blind, placebo‐controlled, 12 months; type 2 diabetes with mild‐moderate symptomatic DSPN; n = 57 randomized.	Corneal nerve fiber density, intraepidermal nerve fiber density, SOD2 area, motor nerve conduction velocity, Cold detection threshold, or secondary morphometric, functional, clinical, or QoL endpoints	No significant difference vs. placebo in primary and secondary outcomes.	Benfotiamine didn't improve outputs compared to placebo control.	(Barragan‐Iglesias et al. 2019)
Benfotiamine		24‐month randomized, double‐blind, placebo‐controlled trial in longstanding type 1 diabetes n = 59.	Peripheral nerve function assessed longitudinally.	No significant effect on nerve conduction velocity or inflammatory markers, although there was a significant increase in thiamine levels.	There was no increase in peripheral never function or inflammatory markers in patients from long‐term high‐dose benfotiamine.	(Yousuf et al. 2025)
Pyridoxine (vitamin B6)	Pyridoxine, also known as vitamin B6 functions as an antioxidant that suppresses both reactive oxygen species and advanced glycation end products.	This study was randomized control open label interventional study over 4 weeks, where participants were given either metformin (500 mg/day), Metformin (500 mg/day) with pyridoxine (300 mg/day), or a non‐pharmacological therapy. Participants were 30–65 years old with Type 2 diabetes and HbA1c less than or equal to 7.5%. N = 108.	Primary outcomes of fasting plasma glucose and glycated hemoglobin, and secondary outcomes of fasting plasma insulin, insulin resistance, vitamin B6 and indoleamine 2,3 dioxygenase levels.	All treatment groups saw a significant decrease over 4 weeks in the primary outcomes secondary outcomes of fasting plasma insulin and insulin resistance. Both metformin groups saw significant changes in vitamin B6 and indoleamine 2,3 dioxygenase levels.	Adding B6 to metformin treatment had a positive effect as diabetes contributes to a vitamin B6 deficiency.	(Enders et al. 2022)
Aminoguanidine (pimagedine)	Aminoguanidine prevents AGE facilitated cross‐linking of proteins in tissue.	ACTION II: A double‐blind, randomized, placebo‐controlled trial comparing a placebo to two different dose of aminoguanidine on the progression of nephropathy in type 2 diabetic patients. Participants were between 30 and 70 years of age with a diabetes diagnosis for atleast a year. N = 599.	Progression of diabetic nephropathy.	The trial was ended early due to safety concerns and the benefit of aminoguanidine on nephropathy progression being tenuous.	Important question for the pathway overall, but not a neuropathy‐specific efficacy trial. It likely helps explain why this mechanistically attractive target did not mature into successful DPN therapy.	(Liu et al. 2017; Griggs et al. 2017)
Tolrestat	Is an inhibitor of aldose reductase, which is in the polyol pathway and in hyperglycemic conditions converts glucose to sorbitol leading to oxidative stress.	A double‐blinded, placebo controlled trial for 52 weeks. N = 372.	Motor nerve conduction velocity (MNCV).	Patients in placebo group had significantly reduced MNCV. With‐drawal from long term tolrestat treatment led to a harmful impact on DPN outcomes.	Polyol pathway may be an effective target for DPN treatment. Studies discontinued in 1997 due to severe liver toxicity and death.	(Mian et al. 2025; Sima et al. 1993)
Recombinant human NGF	As a neurotrophic factor, NGF helps the survival of small fiber sensory neurons.	12‐month, Randomized, double‐blind, placebo‐controlled phase 3 trial in males and females from 18 to 74 years old. N = 1019.	Neuropathy Impairment Score at baseline, 12, 24, and 48 weeks.	There was not improvement in the Neuropathy Impairment Score or Quantitative Sensory Testing in the treatment group.	Phase 3 trial failed due to no observed benefit from treatment.	(Tolrestat 2005)
α‐lipoic acid	α‐lipoic acid shows functions as a reducer of oxidative stress.	NATHAN 1 Trial: randomized double‐blind parallel‐group trial in patients with mild to moderate distal symmetric sensorimotor polyneuropathy. Patients were either given 600mg of α‐lipoic acid once daily or a placebo for 4 years. N = 460.	Neuropathy impairment score.	From baseline to end of trial there were not any significant differences between groups.	There was not a significant decline in the end point for the placebo group, indicating that the treatment was not beneficial.	(Bonhof et al. 2022)
Engensis (VM202)	DNA plasmid that encodes for hepatocyte growth factor which has previously been seen in phase II to alleviate pain in DPN.	A two‐part, double‐blind, randomized, parallel design, placebo‐controlled phase III trial. The first part is 9‐montsh (N = 500) and then an extension in a subset of patients (N = 101) to 12 months. Treatment was given to patients in the calf muscles on Days 0, 14, 90, and 104.	Numerical rating scale to record a pain score.	In the first section of the trial, VM202 didn't meet any endpoints. However, in the second section there was pain relief between VM202 and placebo groups.	Due to the differences between the two sections of the studies, there is need for an additional trial.	(Fraser et al. 2012)
C‐Peptide	Decrease of C‐peptide seen in diabetes that may contribute to micorvascular complications.	Phase 2 trial conducted on patients with diabetes and peripheral neuropathy either received a weekly low dose or high dose of C‐peptide or a placebo for 52 weeks. N = 250.	Sural nerve conduction velocity (SNCV) and vibration perception threshold (VPT) at Weeks 0, 26, and 52.	C‐peptide did not improve SNCV but did improve VCT.	Did not have robust efficacy.	(College A‐RU 2023)
Trans‐resveratrol and hesperetin	Induces expression of Glyoxalase‐1	This study was conducted over 8‐weeks and was double‐blinded, randomized, placebo‐controlled crossover study. 29 subjects with 9 participants having pre‐diabetes and all 29 participants with impaired metabolic health. Participants took a oral capsule prior to breakfast daily of either placebo or tRES‐HESP (90 mg tRES, 120 mg HESP).	Insulin sensitivity via oral glucose insulin sensitivity (OGIS) index in oral glucose tolerance tests (GTTs).	Reduced insulin resistance and decreased dysglycemia, blood pressure, vascular inflammation, dyslipidemia, and plasma methylglyoxal.	Modulating glyoxalase 1 and reducing methylglyoxal had a positive impact on metabolic impairment.	(Xue et al. 2025)
Combinations of amitriptyline, pregabalin, and duloxetine	Testing combinations of leading diabetic peripheral neuropathic pain therapies: amitriptyline, pregabalin, and duloxetine, which act by enhancing serotonin/norepinephrine signaling or reducing neurotransmitter release.	Multicenter, double‐blind, randomized, crossover trial in patients with diabetic peripheral neuropathic pain at a daily pain numeral rating scale (NRS) of 4 or higher using 130 participants over the 16 week trial.	Primary outcome was difference in daily NRS averaged over 7‐days.	In every treatment plan, the averaged NRS score decreased from baseline to the 16‐week timepoint.	All treatment pathways and monotherapies had similar analgesic efficacy.	(Tesfaye et al. 2022)
High frequency spinal cord stimulation (HF‐SCS)	Spinal cord stimulation has been used as a nonpharmacological pain relief approach.	Randomized, 6‐month trial with 216 particpants. Conventional medical management (CMM) used as control group.	Primary outcome was percentage of participants with 50% or more pain relief using visual analogue scale (VAS) compared to baseline at 3 months and 6 months.	79% of the HF‐SCS group saw improved VAS scores compared to 5% in the CMM group.	Potential nonpharmacological approach for painful diabetic peripheral neuropathy.	(Petersen et al. 2021)
Capsaicin	Activates and desensitizes TRPV1‐expressing nociceptive nociceptors leading to the pain reduction.	Randomized, double‐blind, placebo‐controlled 12‐week trial of 369 adults with painful diabetic peripheral neuropathy (PDPN). Patients received a single 30‐min application of either capsaicin 8% patch (n = 186) or placebo patch (n = 183) to painful areas of the feet.	Primary outcome: Percent reduction in average daily pain score from baseline to Weeks 2–8. Secondary outcomes included time to treatment response, sleep interference, safety, and sensory function.	Capsaicin 8% patch produced a greater reduction in pain than placebo by week 2 and slight improvements in sleep quality. Adverse events were similar between groups except for application‐site reactions, and no sensory deterioration was observed.	A single 30‐min application of capsaicin 8% patch provided modest but significant pain relief and improved sleep in PDPN patients, with minimal systemic side effects and no evidence of worsening sensory function.	(Simpson et al. 2017)
SGLT2 inhibitor (empagliflozin)	Promotes increased urinary excretion of glucose, improving glucose metabolism and reducing glucotoxicity.	20 week study that included 50 participants with diabetic neuropathy randomly assigned to either control or treatment group. Treatment group given 10 mg of empagliflozin daily.	Outcomes of fasting blood glucose, hemoglobin A1c, serum creatinine levels and nerve conduction velocity measured for baseline and at the 20‐week timepoint.	Significant reduction in fasting blood glucose, hemoglobin A1c, and serum creatinine levels and improved nerve conduction velocity in the treatment group at week 20 compared to baseline.	Had benefits for DPN symptoms and could be a potential therapeutic option.	(Vafaeinasab et al. 2025)

Note: This table highlights prominent clinical trials aimed at mitigating diabetes related complications, including DPN, DPN related pain, and metabolic changes. These trials had mixed results, with many of the trials aimed at alleviating pain and metabolic outcomes having successful findings, while trials geared towards neuropathy and nerve health did not see robust benefit (Sima et al. 1993; Tolrestat ²⁰⁰⁵; Bonhof et al. ²⁰²²; Fraser et al. ²⁰¹²; College A‐RU ²⁰²³; Thornalley ²⁰⁰³; Freedman et al. ¹⁹⁹⁹; Santiago et al. ¹⁹⁹³; Apfel et al. ²⁰⁰⁰; Ziegler et al. ²⁰¹¹; Kessler et al. ²⁰²¹; Wahren et al. ²⁰¹⁶; Tesfaye et al. ²⁰²²; Petersen et al. ²⁰²¹; Xue et al. ²⁰²⁵; Vafaeinasab et al. ²⁰²⁵; Simpson et al. ²⁰¹⁷).

Dorsal root ganglia (DRG) are essential to DPN pathology, as they house the cell bodies of peripheral sensory nerves, which are typically affected by DPN and related neuropathic pain (Bhandari et al. 2021; Doty et al. ²⁰²²). Sensory neurons in the DRG are particularly vulnerable to metabolic stress due to their preference for glucose and their long axonal projections, which require substantial energy for maintenance (Miyashita et al. 2023). Interestingly, DRG neurons express GLUT1 and GLUT3, both insulin‐independent glucose transporters, thereby permitting intracellular glucose accumulation even in insulin‐resistant contexts (Rawat and Morrison 2021). This positions DRG neurons as especially susceptible to hyperglycemia‐related stressors.

Among these stresses, methylglyoxal has been identified as a key candidate to link altered glucose metabolism to neuronal dysfunction (Griggs et al. 2021; Huang et al. ²⁰¹²). Methylglyoxal is a by‐product of glycolysis that is made at physiological levels and elevated in diabetes (Allaman et al. 2015; Beisswenger ²⁰¹⁴; Coccini et al. ²⁰²³; Bierhaus et al. ²⁰¹²). It is a highly reactive glycation agent leading to the formation of advanced glycation end products (AGEs) (Schalkwijk and Stehouwer 2020; Price and Knight ²⁰⁰⁷; Ramasamy et al. ²⁰⁰⁶; Maessen et al. ²⁰¹⁵). Under physiological conditions, methylglyoxal is scavenged by the glyoxalase system (Maessen et al. 2015; Thornalley ²⁰⁰⁸; Stratmann et al. ²⁰¹⁷). However, in hyperglycemic conditions, methylglyoxal levels increase while glyoxalase activity diminishes, leading to methylglyoxal levels exceeding the glyoxalase's capacity (Stratmann et al. 2017; Cianfruglia et al. ²⁰²⁰; Kim et al. ²⁰²⁰; Queisser et al. ²⁰¹⁰). Increased methylglyoxal levels have been strongly associated with diabetic complications, including DPN (Beisswenger 2014; Bierhaus et al. ²⁰¹²; Schalkwijk and Stehouwer ²⁰²⁰; Maessen et al. ²⁰¹⁵; Nigro et al. ²⁰¹⁷) (Figure 1).

FIGURE 1.

Five proposed mechanisms underlying neuronal dysfunction. Schematic illustration of possible mechanisms that contribute to cellular stress and neuronal dysfunction.

The relationship between methylglyoxal and neuropathy has been extensively explored in the context of nociception. Methylglyoxal modifies transient receptor potential ankyrin 1 (TRPA1), leading to TRPA1 activation (Andersson et al. 2013; Eberhardt et al. ²⁰¹²). Through post‐translational modifications, methylglyoxal modifies the voltage‐gated sodium channel NAV1.8, increasing neuronal excitability and leading to nociception (Bierhaus et al. 2012; Andersson et al. ²⁰¹³; Eberhardt et al. ²⁰¹²; Huang et al. ²⁰¹⁶; Ueno et al. ²⁰²⁴). Additionally, work has shown that methylglyoxal leads to Nav1.7‐mediated hyperalgesia through increased expression of the channel (Cheng et al. 2019). Methylglyoxal has also been shown to sensitize sensory neurons in DPN, inducing neuropathic pain by activating the integrated stress response (Mian et al. 2025; Barragan‐Iglesias et al. ²⁰¹⁹; Yousuf et al. ²⁰²⁵). Previous research has utilized various experimental paradigms demonstrating the noxious impact of methylglyoxal in both rats and mice through assessing itch, mechanical threshold, thermal latency, and nociceptive behavior (Huang et al. 2016; Cheng et al. ²⁰¹⁹; Yousuf et al. ²⁰²⁵; Enders et al. ²⁰²²; Liu et al. ²⁰¹⁷; Griggs et al. ²⁰¹⁷). While these results solidify methylglyoxal as a causative agent of pain, they do not fully explain its role in axon degeneration and broader neuronal dysfunction within DRG in DPN. Understanding these mechanisms is crucial to the development of novel therapeutics.

2. Methylglyoxal: Sources, Metabolism, and Detoxification

2.1. Production of Methylglyoxal

Methylglyoxal is a by‐product of glycolysis that is endogenously produced at physiological levels. The rate of methylglyoxal formation varies across tissues and cells and is influenced by cellular metabolism and physiological conditions. Because it is formed by glycolysis, it is produced in almost every cell. Methylglyoxal is formed from the intermediates dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3‐phosphate (G3P), which can spontaneously degrade to methylglyoxal (Allaman et al. 2015; Murata‐Kamiya and Kamiya ²⁰⁰¹). Methylglyoxal can be formed through additional pathways, including lipid peroxidation, DNA degradation, and aminoacetone oxidation.

Exogenous sources can also contribute to methylglyoxal accumulation. In particular, methylglyoxal is abundant in lipid‐rich foods. The most prominent way it is produced in foods is through the Maillard reaction, which causes meats and breads to brown and form a crust. Additionally, animal products high in protein and fat are also methylglyoxal‐rich. Thus, dietary choices can contribute to methylglyoxal accumulation (IARC ¹⁹⁹¹; Li et al. ²⁰²⁴; Uribarri et al. ²⁰¹⁰; Tan et al. ²⁰⁰⁸).

Methylglyoxal is incredibly reactive and has a short half‐life, making it difficult to measure the levels. It is estimated that free methylglyoxal ranges from 1 to 5 μM intracellularly (Jun and Kool 2020). However, due to its short half‐life, the location and time of formation can lead to significantly higher local concentrations. It has been shown that 90%–99% of cellular methylglyoxal is bound. It is predicted that the total cellular amount of methylglyoxal, which includes both free and bound, can be up to 300 μM (Allaman et al. 2015; Rabbani and Thornalley ^2014a). Methylglyoxal is a ubiquitous by‐product of glycolysis whose production varies with tissue type and metabolic state, reflecting cellular metabolism. Its accumulation arises from multiple endogenous pathways and dietary sources, linking it to broader metabolic and oxidative stress. Although free levels are low, its high reactivity, protein binding, and localized spikes suggest that total methylglyoxal burden drives its biological impact.

2.2. Detoxification Pathways

The primary route for methylglyoxal detoxification in the cell is via the glyoxalase pathway. The glyoxalase pathway uses two enzymes, glyoxalase 1 (GLO1) and glyoxalase 2 (GLO2), with GLO1 being the rate‐limiting enzyme. Methylglyoxal combines with glutathione to form hemithioacetal. Then, in the first enzyme‐mediated reaction, GLO1 converts hemithioacetal into S‐lactoylglutathione. GLO2 makes S‐lactoylglutathione into D‐lactate while recycling glutathione.

There are additional ways methylglyoxal is degraded in the cell. Glyoxalase III, which is also known as DJ‐1 or PARK7, is an enzyme that can degrade methylglyoxal into D‐lactate without glutathione (Jun and Kool 2020; Choi et al. ²⁰²³; Yumnam et al. ²⁰²⁰). In instances of reduced GLO1, compensatory mechanisms involving aldose reductase and aldehyde dehydrogenase (ALDH) can help detoxify methylglyoxal. Aldose reductase is more efficient than ALDH at breaking down methylglyoxal due to its higher affinity for methylglyoxal. Aldose reductase is associated with diabetic complications. It can convert methylglyoxal into acetol through a glutathione‐dependent pathway or can form propanediol through a glutathione‐independent pathway. Additionally, ALDH can convert methylglyoxal into pyruvate via an NAD‐dependent mechanism (Lai et al. 2024). Thus, methylglyoxal formation and breakdown are highly regulated and robust processes, underscoring the importance of maintaining low levels.

2.3. Factors Elevating Methylglyoxal in Diabetes

There are multiple factors in diabetes that contribute to the elevated levels of methylglyoxal. First, methylglyoxal is a conventional by‐product of glycolysis, and increasing glycolysis increases methylglyoxal levels, as seen in diabetes. In diabetes, hyperglycemia increases methylglyoxal levels (Silhavy et al. 2020). Second, GLO1 levels are well characterized as decreased in diabetes (Rabbani and Thornalley ^2014b). Because GLO1 is the rate‐limiting enzyme in the glyoxalase system, its downregulation in diabetes reduces glyoxalase pathway activity and limits methylglyoxal detoxification (Silhavy et al. 2020).

Third, cellular levels of reactive oxygen species (ROS) are increased in diabetes. An increase in ROS levels can decrease glutathione levels. It is well documented that glutathione levels decrease during diabetes (Sekhar et al. 2011; Darmaun et al. ²⁰⁰⁵). Glutathione is a vital cofactor for the glyoxalase cycle. Decreases in glutathione can reduce the efficiency of the glyoxalase cycle, thereby contributing to methylglyoxal accumulation (Rabbani et al. 2018; Masterjohn et al. ²⁰¹³). Together, diabetes promotes methylglyoxal accumulation through hyperglycemia‐driven increased production and impaired detoxification due to reduced glyoxalase‐1 activity and glutathione depletion.

3. Key Mechanisms Underlying Methylglyoxal Cellular Impact

3.1. Protein Glycation

Methylglyoxal is a strong glycating agent that modifies lipids and proteins, creating AGEs (Beisswenger 2014). Methylglyoxal is a small, polar molecule. As a dicarbonyl, methylglyoxal is highly reactive (Allaman et al. 2015; Schalkwijk and Stehouwer ²⁰²⁰; Ramasamy et al. ²⁰⁰⁶; Nigro et al. ²⁰¹⁷). Through non‐enzymatic reactions, it binds to amino groups, leading to irreversible modification (Schalkwijk and Stehouwer 2020; Rabbani and Thornalley ^2014b; Lai et al. ²⁰²²). Although methylglyoxal has a short half‐life, AGEs are stable and can remain in the body for months. AGEs can have detrimental impacts through crosslinking to structural and basement membranes (Semba et al. 2010). or even years (Fournet et al. 2018). Consequently, AGEs that disrupt cellular structures affect permeability and cell motility (Allaman et al. 2015).

Methylglyoxal glycates cellular molecules to form AGEs (Allaman et al. 2015; Schalkwijk and Stehouwer ²⁰²⁰; Ramasamy et al. ²⁰⁰⁶; Lai et al. ²⁰²²), and glycation can affect metabolic enzymes, mitochondrial proteins, transcriptional regulators, cytoskeletal components, and extracellular matrix proteins. Glycation impairs protein–protein interactions, modifies catalytic activity, and decreases protein stability. This effect contributes to the mechanistic basis of stress responses in cells observed across various diseases (Rabbani and Thornalley ^2014a; Fournet et al. ²⁰¹⁸; Zgutka et al. ²⁰²³; Ott et al. ²⁰¹⁴).

Additionally, AGEs can activate the receptor for advanced glycation end products (RAGE). RAGE is involved in numerous cell signaling pathways. Through RAGE activation, AGEs can upregulate inflammatory molecules (Ramasamy et al. 2006; Vlassara and Uribarri ²⁰¹⁴). Methylglyoxal can also cause nucleic acid damage and chromosomal instability. By modifying deoxyguanosine residues, methylglyoxal can induce breaks in double‐stranded DNA (Donnellan et al. 2025).

The relationship between methylglyoxal, AGE formation, and RAGE activation is an important mechanism contributing to various diseases. Research has aimed to inhibit RAGE as a potential therapeutic option. Azileragon is a RAGE inhibitor that prevents STZ‐induced DPN and mechanical hypersensitivity in mice. Additionally, Azileragon is expected to reduce cognitive impairment in mild Alzheimer's Disease cases (Reddy et al. 2023). Additional work has demonstrated the role of RAGE in proinflammatory macrophage infiltration in DPN, leading to insulin sensitivity and reduced retrograde axonal transport in the sciatic nerve, both of which were protected against by bone marrow transplants from RAGE‐null mice (Osonoi et al. 2022). This research further supports the clinical application of understanding and targeting methylglyoxal‐mediated AGE formation mechanisms that contribute to DPN.

Methylglyoxal‐induced protein glycation has also been implicated in cancer. Diabetes increases cancer risk because higher fasting glucose levels correlate with increased risk for cancer and cancer mortality (Giovannucci et al. 2010; Chiavarina et al. ²⁰¹⁴). Interestingly, methylglyoxal acts as both a promoter and an inhibitor of tumorigenesis depending on the concentration (Rabbani et al. 2018; Wang et al. ²⁰²⁵; Kim et al. ²⁰²²; Kong et al. ²⁰²⁴).

Shifting focus to specific cancers, diabetes increases breast cancer mortality, while metformin has been shown to lower cancer risk (Chiavarina et al. 2014; Parsons et al. ²⁰²⁶; Saraei et al. ²⁰¹⁹). Interestingly, there is a lower amount of methylglyoxal‐derived AGEs in triple‐negative breast cancers (Chiavarina et al. 2014). In melanoma, AGEs stimulated tumor growth and migration, and RAGE inhibition was protective against tumor growth and metastasis in mice (Nakamura et al. 2017). In pancreatic cancer, RAGE activation promoted autophagy and the development of pancreatic tumors (Kang et al. 2012). In lung cancer, AGEs were identified in tumors, and in some patients, higher AGE fluorescence was associated with better survival (Bartling et al. 2011). Advanced glycation end product generation of AGEs and RAGE activation can activate various transcription factors, resulting in tumor‐promoting inflammation (Azizian‐Farsani et al. ²⁰²⁰). AGEs and RAGE activation are also associated with activation of carbohydrate response element‐binding protein (ChREBP), leading to increased glycolysis and anabolic metabolism that support the proliferation of cancer cells, resulting in a Warburg‐like metabolic shift (Chen et al. 2017).

From the current research, its clear that methylglyoxal plays a complex role in cancer: AGE formation promotes tumorigenesis via RAGE, but methylglyoxal is also toxic to cancer cells, leading to apoptosis (Rabbani et al. 2018; Kim et al. ²⁰²²; Kong et al. ²⁰²⁴). Ultimately, methylglyoxal appears to be a contributing factor in cancer progression through oxidative stress, inflammation, migration, and metastasis, and metabolic reprogramming (Kong et al. 2024; Yamagishi et al. ²⁰¹⁵).

There is already a close relationship between diabetes and cardiovascular disease, with methylglyoxal playing a role in both pathologies. Within cardiovascular disease, AGEs can lead to atherosclerosis and plaque rupture, which is a main contributor to cardiovascular disease‐related death (Hanssen et al. 2014). Additionally, methylglyoxal can lead to endothelial cell damage and vascular dysfunction, both of which are risk factors for cardiovascular disease (Price and Knight 2007; Vulesevic et al. ²⁰¹⁴).

Ultimately, methylglyoxal, which promotes protein glycation and leads to the accumulation of AGEs, forms the foundation on which many of the mechanisms addressed below are built. Methylglyoxal‐induced protein glycation is interconnected with metabolic changes, oxidative stress, inflammation, and proteostasis, as it drives these mechanisms through glycation.

3.2. Proteostasis Disruption

Methylglyoxal's role as a potent glycating agent can lead to protein misfolding, activation of the unfolded protein response signaling pathway, proteasomal overload, apoptosis, cellular senescence, and dysregulation of various cell signaling pathways (Queisser et al. 2010). A subset of studies has identified a pattern of proteostasis stress caused by methylglyoxal‐induced protein damage. In SH‐SY5Y human neuroblastoma cells, methylglyoxal induced significant changes in protein synthesis and cellular structural integrity, leading to endoplasmic reticulum stress (Wang, Boeren, et al. ²⁰²⁴). It is also known that methylglyoxal can cause toxic DNA‐protein crosslinks. Their interactions can prevent DNA replication, transcription, and repair. DNA‐protein crosslinks can also affect protein expression and function. Human embryonic kidney cells (HEK293T) were treated with 50 μM–10 mM methylglyoxal for 2, 4, or 24 h, resulting in 256 proteins identified as occurring in methylglyoxal‐induced DNA‐protein cross‐linking (Hurben et al. 2024). It has also been observed that this cross‐linking results in the accumulation of damaged proteins. Methylglyoxal also impairs the ubiquitin‐proteasome system (Bento et al. 2010), and the accumulation of AGEs can inhibit the function of the ubiquitin‐proteasome system (Queisser et al. 2010; Ott et al. ²⁰¹⁴). These studies highlight the pattern of proteostasis disruption acting as an intermediate connecting carbonyl stress to cellular dysfunction.

3.3. Oxidative Stress

Methylglyoxal also plays a key role in the accumulation of ROS. Methylglyoxal treatment led to oxidative stress, accumulation of ROS, and decreased levels of antioxidants and ROS‐scavenging proteins (Coccini et al. 2023). This has been reported in a variety of tissues and cell types, including human umbilical vein endothelial cells (HUVEC), human endothelial cells, H9c2 cardiomyoblasts, rat INS‐1 pancreatic beta cells, the intestinal cell line CaCo‐2, brain tissue from humans and mice, the kidney epithelial cell line HK‐1, HepG2 cells, and the human endothelial cell line EA.hy926. Although methylglyoxal treatment increased ROS across cell types, the proposed mechanisms varied (Seo et al. 2014; Chen et al. ²⁰²²; Suantawee et al. ²⁰²⁰; Wang et al. ²⁰²²; Wang, Chen, et al. ²⁰²⁴).

Methylglyoxal also contributes to oxidative stress by generating AGEs that activate RAGE (Wautier et al. 2001). Through RAGE signaling, NADPH oxidase is activated, leading to nitric oxide (NOX) production (Seryogina et al. 2024; Chen et al. ²⁰¹⁸). NOX is a type of ROS, and ROS formation can activate the transcription factors NF‐κB and AP‐1, leading to inflammation through the release of chemokines and proinflammatory cytokines (Wang, Chen, et al. ²⁰²⁴; Kim et al. ²⁰²¹).

As discussed above, the glyoxalase system is the primary pathway for methylglyoxal degradation. In the glyoxalase system, glutathione, a prominent antioxidant, is used as a cofactor. Although glutathione isn't consumed, increases in methylglyoxal concentration require more glutathione; this could result in less available glutathione to be used as an antioxidant (de Bari et al. ²⁰²⁰). Additionally, methylglyoxal was found to decrease glutathione levels and activity in both in vitro and in vivo settings. In vitro, methylglyoxal decreases glutathione levels in HUVECs, HepG2 cells, and INS‐1 pancreatic beta cells from rats (Seo et al. 2014; Suantawee et al. ²⁰²⁰; Wang et al. ²⁰²²; Wang, Chen, et al. ²⁰²⁴; Deng et al. ²⁰²⁴). In vivo, glutathione was decreased in male C57BL/6 mice (Wang et al. 2022; Wang, Chen, et al. ²⁰²⁴; Deng et al. ²⁰²⁴).

The methylglyoxal‐induced accumulation of ROS was attenuated by antioxidant treatment (Deng et al. 2024; Jarisarapurin et al. ²⁰²¹). In human brain microvascular endothelial cells, methylglyoxal increased ROS release, which was reversed by aminoguanidine and N‐acetylcysteine (Chen et al. 2022; Deng et al. ²⁰²⁴; Jarisarapurin et al. ²⁰²¹).

Methylglyoxal has been consistently shown to induce oxidative stress and promote ROS accumulation across multiple experimental models. Elevated ROS levels are a hallmark of cellular stress and contribute to the pathogenesis of numerous diseases. Determining whether methylglyoxal drives ROS accumulation in peripheral nerve tissue will provide important insight into the cellular stress mechanisms underlying diabetes and DPN.

3.4. Mitochondrial Impairment

Several recent studies have reported oxidative stress from methylglyoxal exposure, mediated by a variety of pathways. ROS production associated with methylglyoxal glycation disrupts glutathione metabolism and the activity of antioxidants (Wang, Chen, et al. ²⁰²⁴; Deng et al. ²⁰²⁴; Liccardo et al. ²⁰²⁴). Multiple studies have postulated that oxidative stress contributes to mitochondrial dysfunction, as evidenced by reduced ATP production, increased mitochondrial ROS generation, changes in mitochondrial membrane potential, and impaired activity of electron transport complex proteins (Bhatti et al. 2017; Shibanuma et al. ²⁰¹¹). Additionally, methylglyoxal can glycate mitochondrial proteins, leading to mitochondrial impairment, ROS production, and oxidative stress (Stratmann et al. 2017). These changes contributed to metabolic impairment and cellular injury.

A common effect across multiple cell types was disruption of mitochondrial membrane potential (MMP). MMP is a measurement of the electrical gradient derived from the electron transport chain, which pumps electrons across the inner mitochondrial membrane. Measuring changes in MMP indicates mitochondrial disruption. A decrease in MMP after methylglyoxal treatment was seen in HUVEC, human endothelial cells, H9c2 cardiomyoblasts, and rat INS‐1 pancreatic beta cells (Wang, Chen, et al. ²⁰²⁴; Liccardo et al. ²⁰²⁴; Nuamnaichati et al. ²⁰²⁰; Yoo et al. ²⁰²⁰).

In SH‐SY5Y human neuroblastoma cells, a proteomic and metabolomic study revealed that methylglyoxal caused significant alterations in multiple metabolic pathways, including the mitochondria, the tricarboxylic acid cycle, cysteine and methionine metabolism, and arginine biosynthesis (Wang, Boeren, et al. ²⁰²⁴).

In patients with type 2 diabetes and DPN, magnesium levels were decreased and were inversely related to methylglyoxal levels. In DRG, one group observed that diminished mitochondrial activity, together with triosephosphate supplementation, which generates endogenous methylglyoxal, led to neurite degeneration. The authors suggested that magnesium supplementation was protective and concluded that axon degeneration is associated with impaired energy metabolism and magnesium deficiency (Strom et al. 2021).

Treatment with N‐acetyl cysteine, a precursor to glutathione, reversed methylglyoxal‐mediated mitochondrial damage and mitophagy. This study proposed that oxidative stress induced by increased methylglyoxal, as seen in diabetes, contributes to mitochondrial damage and mitophagy (Kim et al. 2020). This points to either the effect of scavenging methylglyoxal alleviating mitochondrial damage, or to ROS accumulation resulting from methylglyoxal accumulation causing mitochondrial damage.

Exercise is often tested as an intervention for disease prevention due to its many positive effects. In preclinical studies, methylglyoxal was administered to mice undergoing endurance training. Methylglyoxal causes exercise resistance, meaning it prevents mitochondrial adaptations, activation of insulin signaling, and upregulation of proteins involved in mitochondrial biogenesis in fast‐twitch muscles, as seen in the exercise group (Egawa et al. 2022). Studies indicate that methylglyoxal causes detrimental metabolic changes, but this study also shows that it can prevent beneficial metabolic changes. Exercise is often used as an intervention for diabetes and DPN due to its positive effects on insulin resistance and blood glucose control. Understanding the role of methylglyoxal in metabolism and its relationship with exercise is important for the development of treatments for diabetes and DPN.

Although methylglyoxal is a by‐product of glycolysis, some studies report that its formation can increase glycolytic activity, thereby contributing to inflammation and metabolic impairment (Yang et al. 2022). One study using in vitro approaches and preclinical mouse models found that hyperglycemia resulted in decreased GLO1 (Rabbani and Thornalley ^2014b). This effect on GLO1 led to increased methylglyoxal, thereby perpetuating a cycle of hyperglycemia, elevated methylglyoxal, and reduced GLO1 (Rabbani and Thornalley ^2014b; Rabbani et al. ²⁰¹⁸; Cortizo et al. ²⁰²²; Rabbani and Thornalley ²⁰¹⁹). The glycolytic enzyme glyceraldehyde‐3‐phosphate dehydrogenase (GAPDH) is inhibited by methylglyoxal in mammalian neural stem cells, indicating another mechanism by which methylglyoxal can alter metabolic pathways (Rodrigues et al. 2020).

As previously discussed, methylglyoxal accumulation is associated with dysregulation of various metabolic pathways. Specically in cancer this includes impaired insulin signaling, altered glucose metabolism, and metabolic reprogramming. Methylglyoxal's glycation results in transcription factors and intermediates in signaling pathways being modified, resulting in metabolic flux. For example, methylglyoxal can impair the tumor suppressor BRCA2, inducing cancer‐associated DNA damage. This metabolic mechanism suggests that elevated methylglyoxal levels may bypass Knudson's two‐hit requirement, linking metabolic stress or increased glycolysis to the accumulation of mutations during cancer development (Kong et al. 2024).

Recent work has shown that elevated methylglyoxal levels can alter axon morphology and structure (Griggs et al. 2021; Coccini et al. ²⁰²³; Yousuf et al. ²⁰²⁵; Griggs et al. ²⁰¹⁸). The mechanisms underlying axon degeneration are still being explored, but it has been suggested that these metabolic changes are key features leading to axon degeneration and loss (Baltan et al. 2010; Beirowski ²⁰²²; Harun‐Or‐Rashid et al. ²⁰¹⁸). Additionally, new research has highlighted the relationship between mitochondria and SARM1 (Murata et al. 2013). SARM1, an enzyme involved in Wallerian degeneration, can be activated by metabolic changes and, once activated, contributes to mitochondrial changes that are likely upstream of, and directly related to, subsequent axon degeneration (Harun‐Or‐Rashid et al. ²⁰¹⁸; Figley et al. ²⁰²¹; Loreto et al. ²⁰²⁵; Sato‐Yamada et al. ²⁰²²). Many other neurodegenerative diseases, including Alzheimer's and Parkinson's, are also tightly coupled to metabolic changes (Griffith et al. 2008; Stinson et al. ²⁰²⁵). This highlights a key need for future research into whether the methylglyoxal‐related changes in axon morphology have underlying metabolic mechanisms. Taken together, this information indicates that methylglyoxal not only acts as a toxic carbonyl species but also powerfully regulates metabolic signaling pathways under both cellular and systemic stress conditions.

3.5. Inflammatory and Immune Signaling Activation

Numerous studies have examined changes in inflammatory signaling pathways following methylglyoxal exposure (Kim et al. 2021; Prantner et al. ²⁰²¹; Prantner and Vogel ²⁰²⁵; Medeiros et al. ²⁰²¹). Oxidative stress led to increased cytokine expression, immune cell activation, and inflammatory transcriptional responses associated with inflammation (Wang, Chen, et al. ²⁰²⁴; Medeiros et al. ²⁰²¹). The immune and inflammatory responses were observed across various disease contexts, including cardiovascular disease, neurodegeneration, cancer, and metabolic disease (Wang et al. 2025; Medeiros et al. ²⁰²¹; Vulesevic et al. ²⁰¹⁶; Berdowska et al. ²⁰²³; Lin et al. ²⁰¹⁸; Willemen et al. ²⁰²³). This highlights immune response as a prominent downstream effect of methylglyoxal‐linked pathology.

A clinical study has reported that methylglyoxal is upregulated in patients with sepsis (Prantner et al. 2021). Similarly, LPS‐treated mice had increased levels of macrophage‐produced methylglyoxal (Prantner et al. 2021; Prantner and Vogel ²⁰²⁵). In a different preclinical LPS model, LPS was used to induce acute lung injury in mice. Mice were then treated with methylglyoxal, which increased neutrophil infiltration in the airways and mRNA expression of IL‐1β and TNF‐α (Medeiros et al. 2021). In a different preclinical LPS model, LPS was used to induce acute lung injury in mice. Mice were then treated with methylglyoxal, which increased neutrophil infiltration in the airways and mRNA expression of IL‐1β and TNF‐α (Medeiros et al. 2021). In a rectal cancer model, methylglyoxal released by gut microbiota facilitated ROS‐induced ER stress, leading to immunogenic cell death and CD8+ T cells in the tumor microenvironment (Zhou et al. 2023). In a cardiovascular disease model, mice given methylglyoxal had significantly higher circulating levels of neutrophils, T‐cells, and CD68+ macrophages, indicating that increased methylglyoxal levels can contribute to inflammation (Hanssen et al. 2023).

In C57/BL6 male mice, methylglyoxal increased the pro‐inflammatory cytokines IL‐6 and IL‐1β and decreased the anti‐inflammatory cytokine IL‐10, providing strong in vivo evidence for a role of methylglyoxal in inflammation (Wang et al. 2022; Wang, Chen, et al. ²⁰²⁴). Collectively, these findings demonstrate that elevated methylglyoxal promotes inflammatory and immune activation across diverse disease models, likely through mechanisms involving ROS generation and cellular stress signaling. These observations, taken together, support a framework in which methylglyoxal functions as a central cellular stress mediator, integrating protein glycation, proteostasis disruption, oxidative stress, metabolic dysfunction, and immune activation into a unified network of cellular damage. This integrated model provides a foundational understanding of how methylglyoxal may drive neuronal dysfunction in diabetes and DPN (Figure 2).

FIGURE 2.

Five central mechanisms of methylglyoxal in cellular stress. Diagram demonstrating the five central mechanisms: Protein glycation, proteostasis changes, oxidative stress, metabolic changes, and immune response, and how they may be interconnected. Methylglyoxal is a potent glycating agent that binds to proteins, forming AGEs (protein glycation). As a glycating molecule, methylglyoxal can also modify mitochondrial proteins (metabolic changes). The formed AGEs bind to RAGE, leading to alterations in cellular pathways (proestasis changes) that contribute to inflammation (immune response) or to NOX activation. NOX activation promotes ROS accumulation (oxidative stress), which can lead to cytokine release (immune response) or mitochondrial impairment (metabolic changes). This diagram illustrates the interconnectedness of these mechanisms, highlighting methylglyoxal as a central mediator of cellular stress. We propose that the convergence of these mechanisms within DRG neurons contributes to axon degeneration and nociceptor sensitization in DPN.

4. Methylglyoxal and the DRG: the Missing Link

Despite extensive research on methylglyoxal across various disease contexts and cell types, little work has examined its impact on DRG beyond nociception and pain. Methylglyoxal is estimated to be at a plasma concentration around 60–250 nM with intracellular levels estimated to be between 1 and 5 μM in healthy patients (Berdowska et al. 2023). However, it is elevated in the plasma of patients with diabetes, exceeding 800 nM (Bierhaus et al. 2012; Eberhardt et al. ²⁰¹²; Huang et al. ²⁰¹⁶). It is also a noxious agent and has become an important molecule in diabetes and DPN research due to its role in nociception. Methylglyoxal‐related nociception occurs through its activation of TRPA1 and modification of NAV1.8 (Eberhardt et al. 2012; Huang et al. ²⁰¹⁶). Methylglyoxal contributes to the development and prolongation of chronic pain in DPN through neuronal sensitization (Andersson et al. 2013; Basu et al. ²⁰²⁵). Methylglyoxal can also induce axon degeneration, making it an effective tool for investigating the relationship between pain and nerve degeneration (Griggs et al. 2021; Yousuf et al. ²⁰²⁵). Additionally, it is an efficient model for investigating the mechanistic changes underlying DPN development.

In peripheral neuropathy, sensory neurons are affecected more than motor neurons, making the DRG a vital tissue to study peripheral neuropathy (Mauermann and Staff NP ²⁰²⁶). Peripheral afferent sensory neurons are highly vulnerable to degeneration in DPN, as DPN degeneration typically starts as small‐fiber neuropathy, in which smaller‐diameter neurons are initially affected. Additionally, DPN tends to be length‐dependent, with the longest axons affected first (Mauermann and Staff NP ²⁰²⁶). As the condition progresses, larger‐diameter neurons and shorter axons can also degenerate. As a result, nociceptors are often the first neuronal subtype affected in neuropathy (Kobayashi and Zochodne 2018).

DRG expresses the glucose transporters GLUT1 and GLUT3, which are not insulin‐mediated and are upregulated during hyperglycemia (Rawat and Morrison 2021; Ebeling et al. ¹⁹⁹⁸). As a result, they are particularly vulnerable to high blood glucose levels in insulin‐resistant conditions, since insulin‐mediated cells are unable to take up glucose. Instead, high glucose levels readily enter peripheral nerves via non‐insulin‐mediated mechanisms. This increases glycolysis and leads to high levels of methylglyoxal accumulating in the DRG during diabetes. Additionally, GLO1 activity is impaired in diabetes (Rabbani and Thornalley ^2014b; Rabbani and Thornalley ²⁰¹⁹; Rasul et al. ²⁰¹⁸; Pacal et al. ²⁰¹⁸) and is reduced in peripheral nerves (Bierhaus et al. 2012), leaving DRG vulnerable to elevated methylglyoxal levels under hyperglycemic conditions.

Given the roles of both DRG and methylglyoxal in diabetes and DPN, determining whether the methylglyoxal effect observed in other cell types is also present in DRG could provide a better understanding of methylglyoxal's contribution to diabetes complications and DPN. Below, we discuss what is known about the five key mechanisms in DRG and whether methylglyoxal affects DRG neurons in similar ways.

4.1. Protein Glycation in DRG

Methylglyoxal is a potent glycating agent that has an affinity for lysine, arginine, and cysteine residues to form AGEs (Maessen et al. 2015; Donnellan et al. ²⁰²⁵; Rosca et al. ²⁰⁰⁵). Formation of AGEs results in altered protein structure, disrupted enzyme activity, impaired protein–protein interactions, and DNA damage (Donnellan et al. 2025; Yamagishi et al. ²⁰¹⁵; Najjar and Calvert ²⁰²⁴). The accumulation of glycated proteins has been implicated in multiple neurodegenerative and metabolic disorders and is increasingly recognized as a contributor to peripheral neuropathy and axonal degeneration (Ott et al. 2014; Najjar and Calvert ²⁰²⁴; Vicente Miranda et al. ²⁰¹⁶; Rabbani and Thornalley ²⁰²¹; Thornalley ²⁰⁰²; Ryle et al. ¹⁹⁹⁷).

There are various avenues through which protein glycation can lead to cellular stress within the DRG. AGEs have been observed in DRG and are attributed to playing a role in nociception (Liu et al. 2017; Bufalo et al. ²⁰¹⁹). Cytoskeletal proteins, including tubulin and neurofilaments, have been observed to have increased protein glycation in diabetic rats within 8 months, which may interfere with axonal transport, neurite stability, and mitochondrial trafficking (Ryle et al. 1997). Glycation of mitochondrial proteins can impair mitochondria by disrupting the electron transport chain and ATP production, resulting in altered bioenergetics (Rosca et al. 2005; Naudi et al. ²⁰¹⁰). Ultimately, this could be detrimental to the energetic demands required to maintain peripheral axons. Additionally, glycation of mitochondrial proteins may lead to increased oxidative stress, creating a positive feedback loop of cellular stress (Rosca et al. 2005). Protein glycation prevents protein degradation, leading to the accumulation of misfolded and aggregated proteins (Ott et al. 2014; Vicente Miranda et al. ²⁰¹⁶). This could lead to disruption of proteostasis pathways, resulting in ER stress and ultimately, axon degeneration. AGEs are also known to drive neuroinflammation through activating RAGE in neurons. RAGE is expressed in both DRG and Schwann cells (Bufalo et al. 2019). RAGE activation leads to NF‐κB signaling, cytokine release, oxidative stress, and neuroinflammation‐associated axonal injury (Piras et al. 2016; Tobon‐Velasco et al. ²⁰¹⁴). Protein glycation connects metabolic changes, oxidative stress, inflammation, and proteostasis disruption and warrants further investigation into methylglyoxal‐driven glycation in DRG as an initiator of the interconnected cellular stress pathways that contribute to neuronal dysfunction.

4.2. Oxidative Stress in DRG

Multiple studies have examined how methylglyoxal generates ROS via AGEs. ROS can induce nociception through TRP receptors (Ueno et al. 2024). Most of our understanding of methylglyoxal‐induced ROS in DRGs is within the context of TRP channel‐mediated nociception, in which TRPV1 activation increases ROS (Ma et al. 2009). Within DPN, research indicates that hyperglycemia increases oxidative stress in the DRG more than in the peripheral axons and Schwann cells (Schmeichel et al. 2003). There is a need to understand the mechanisms underlying methylglyoxal‐induced accumulation of ROS in DRG and its implications.

4.3. Immune Signaling in DRG

It is likely that the methylglyoxal‐induced pro‐inflammatory immune response observed in various cell types also occurs in DRG. DRGs also contain non‐neuronal support cells capable of secreting cytokines, including satellite glial cells, Schwann cells, and immune cells such as macrophages and lymphocytes. It is plausible that methylglyoxal induces a direct immune response within DRG neurons, but it is also very likely that it elicits an immune response in the non‐neuronal cells surrounding DRG that indirectly impact DRG neurons. This key cellular communication within the DRG remains to be explored in response to methylglyoxal. Additionally, many sensory neurons express TRPA1, an ion channel in nociceptors that is directly activated by methylglyoxal, as discussed above. TRPA1 is also a pronociceptive channel that responds to inflammatory mediators (Andersson et al. 2013), providing a clear pathway by which DRGs can respond to immune threats. Additionally, low concentrations of methylglyoxal in DRG activate the integrated stress response, a key mediator of immune cell function and inflammation (Barragan‐Iglesias et al. ²⁰¹⁹). Taken together, the immune‐responsive microenvironment of the DRG, the presence of methylglyoxal‐sensitive pathways such as TRPA1, and evidence that methylglyoxal activates stress‐response signaling in these neurons suggest that methylglyoxal may contribute to inflammatory signaling within the DRG. It will be important to identify the cellular sources and communications underlying these effects to better design pharmacological treatments.

4.4. Proteostasis Changes in DRG

Proteostasis changes are a distinctive feature of neurodegenerative diseases, demyelinating peripheral neuropathy, and spinal cord injury, as they lead to the accumulation of dysfunctional proteins that can become cytotoxic (Libberecht et al. 2023). Interestingly, activation of the unfolded protein response promoted axonal regeneration in peripheral nerves following injury, indicating that proteostasis regulation is already an important factor in DRG in the context of peripheral neuropathy (Onate et al. 2016). Additionally, proteomic analyses in paclitaxel‐induced neuropathy and spinal nerve ligation models both showed significant protein changes in the DRG (Komori et al. 2007). Notably, in the paclitaxel model, 165 proteins were significantly altered following the same paradigm previously used by this research group to induce both thermal and mechanical hypersensitivity, further highlighting the link between proteostasis changes and painful neuropathy (Hanna, Graur, Sinclair, McKiver, et al. ²⁰²⁴). The proteomics analysis of spinal ligation demonstrated protein changes involved in host defense, antioxidant defense, metabolism, and cellular stress responses. Additionally, there was increased expression of proteins involved in actin cytoskeletal organization, suggesting cytoskeletal stabilization as a critical response to peripheral nerve injury. Protein changes in injured DRG were similar to prior ligation nerve injury studies, with the added data on changes in metabolic enzyme regulation. Ultimately, this study suggests the importance of metabolic regulation and proteostasis in the cellular response to peripheral nerve injury (Komori et al. 2007).

This data highlights the prevalence of proteostasis changes occurring in DRG in the context of neuropathy. Future research is needed to investigate whether methylglyoxal, within DPN, triggers a proteostasis stress response that contributes to neuropathy.

4.5. Metabolic Regulation in DRG

Research addressing acute and chronic pain has increasingly focused on the role of metabolism in the development and chronification of pain. Multiple groups have begun to link changes in cellular metabolism to pain (Willemen et al. 2023; Li et al. ²⁰²⁵). Additionally, metabolic changes appear to play a key role in axon degeneration (Sasaki 2019; Griffin and Ackerman ²⁰²⁰; Brull et al. ²⁰²⁵). Sarm1 is an enzyme involved in Wallerian degeneration and appears to act as a metabolic sensor, with its activity regulated by metabolic intermediates, including nicotinamide mononucleotide (NMN) and NAD+ (Figley et al. 2021). Given the growing interest in metabolic reprogramming in pain and axon degeneration, and the established role of methylglyoxal in altering cellular metabolism in other systems, it is critical to determine whether similar effects occur in DRG neurons. Defining methylglyoxal‐induced metabolic changes in DRG may provide novel insight into mechanisms of pain and SARM1‐mediated axon degeneration in diabetic peripheral neuropathy.

5. Therapeutic Strategies Targeting Methylglyoxal

Understanding the role of methylglyoxal in cellular metabolism in DRG creates new opportunities for therapeutic development. If methylglyoxal similarly induces oxidative stress and ROS accumulation in DRG, targeting oxidative stress could be a potential therapeutic approach. Multiple studies in vitro and in vivo have mitigated the effects of methylglyoxal through either reducing methylglyoxal‐induced oxidative stress or using an antioxidant (Wang et al. 2022; Wang, Chen, et al. ²⁰²⁴; Jarisarapurin et al. ²⁰²¹; Nuamnaichati et al. ²⁰²⁰). However, multiple clinical trials targeting diabetic peripheral neuropathy with antioxidant interventions have not been effective (Sima et al. 1993; Tolrestat ²⁰⁰⁵; College A‐RU ²⁰²³; Santiago et al. ¹⁹⁹³; Ziegler et al. ²⁰¹¹) (Table 1). It is logical to hypothesize that an increase in methylglyoxal, which decreases glutathione through the glyoxalase system, would increase ROS. Additionally, increasing glutathione could be a potential therapeutic route to explore. Using improved antioxidants to target the increased ROS induced by methylglyoxal could be a potential therapeutic approach. Previous work has suggested an intervention targeting the glyoxalase system (Kim et al. 2022; Rabbani and Thornalley ²⁰²²). A plausible therapeutic option is targeting AGEs, as they strongly contribute to ROS accumulation (Soulis et al. 1996). Potential interventions include aminoguanidine, which can effectively reduce the accumulation of AGEs but is hampered by toxic side effects (Thornalley 2003; Freedman et al. ¹⁹⁹⁹). Identifying novel drugs with fewer side effects that target key cells will be essential to developing better clinical treatments.

Additionally, it is important to consider the limitations of the studies analyzed in this review. Although immortalized and transformed cell lines have provided important insight into the mechanism of methylglyoxal biology, transformed cell lines often exhibit altered metabolic states, stress responses, and gene expression compared with primary neurons and in vivo systems. As a result, there may be significant different responses to methylglyoxal‐induced glycation and downstream signaling pathways. Consequently, responses observed in such models may not fully reflect those occurring in primary sensory neurons or in vivo. Validation in primary neuronal cultures and animal models is therefore essential to support translational interpretation in the context of diabetic peripheral neuropathy. This further highlights the need to investigate the role of methylglyoxal in DRG and in vivo to understand its biological effects and identify potential mechanisms that could be targeted for novel DPN therapeutics.

6. Conclusion

DPN remains a highly prevalent and debilitating complication of diabetes with limited effective disease‐modifying therapies. While hyperglycemia has long been implicated, growing evidence highlights methylglyoxal as a key metabolic mediator, linking altered glucose metabolism to neuronal dysfunction. As a reactive by‐product of glycolysis, methylglyoxal accumulates in diabetes due to increased production and impaired detoxification, particularly in metabolically vulnerable DRG neurons. Beyond its emerging role in nociception, methylglyoxal exerts widespread effects through interconnected mechanisms: protein glycation, disruption of proteostasis, oxidative stress, mitochondrial and metabolic dysfunction, and activation of inflammatory signaling. These pathways form a self‐reinforcing network of cellular stress that likely contributes to both axonal degeneration and persistent pain in DPN. Despite extensive evidence in other tissues, the impact of these mechanisms in DRG neurons remains underexplored. Given the unique metabolic profile and anatomical vulnerability of DRG neurons, methylglyoxal accumulation may represent a critical and underappreciated cause of neuropathic progression and pain. Integrating these mechanistic insights with new and emerging information about pain‐ and axon‐degeneration‐associated signaling pathways will be critical for understanding how to pharmacologically address methylglyoxal's role in peripheral nerve dysfunction. We believe that targeting methylglyoxal production, detoxification pathways, or its downstream effects remains a promising therapeutic opportunity.

Author Contributions

Douglas E. Wright: funding acquisition, writing – review and editing, resources, supervision. Gentry Totta‐Griese: conceptualization, investigation, writing – original draft, writing – review and editing, visualization.

Funding

This work was supported by National Institutes of Health, R01NS043314, RO1NS144393. Kansas INBRE, P20GM1033418.

Conflicts of Interest

The authors declare no conflicts of interest.

Data Availability Statement

The authors have nothing to report.