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. 2025 Jul 9;25:243. doi: 10.1186/s12906-025-04974-z

Probiotic preserving extract supplementation as a novel attitude in managing diabetes mellitus

Afrooz Saadatzadeh 1,2, Seyed Mohammad Kazem Emamifar 2, Seyyed Ali Mard 3, Akram Ahangarpour 1,3, Kambiz Ahmadi Angali 4, Sanaz Mehdialamdarlou 5,6,✉
PMCID: PMC12239367  PMID: 40634920

Abstract

Type 2 diabetes is a metabolic disease characterized by insulin resistance. This study evaluated the effects of oral supplementation with a lyophilized probiotic extract (LPE) of Lactobacillus acidophilus and Lactobacillus plantarum on insulin resistance and inflammation reduction in rats with diabetes induced by streptozocin and nicotinamide. To induce diabetes, a single intraperitoneal injection of streptozocin (90 mg/kg) was administered following a dose of nicotinamide (105 mg/kg). In this experimental study, 36 adult male rats were randomly divided into six groups: a negative control group, a sham group, a positive control group (treated with metformin), and three groups treated with varying doses of LPE (60, 120, and 240 mg/ml). The LPE and metformin supplements were given orally daily for two weeks. Blood samples were collected the day before the treatment began and on the 15th. Results showed that diabetes significantly increased levels of TNF-α (an inflammatory marker), fasting blood sugar (FBS), and insulin levels, and leading to increased insulin resistance across all groups. However, the parameters measured in the LPE-treated groups showed significant differences compared to the other groups (P < 0.05 in all cases). LPE supplementation improved insulin sensitivity in diabetic rats through its hypoglycemic and anti-inflammatory effects.

Clinical trial number Not applicable.

Keywords: Type II diabetes, LPE, Streptozotocin-Nicotinamide, Lactobacillus acidophilus, Lactobacillus plantarum, Probiotic, Rat

Introduction

Diabetes mellitus (DM) is classified into four types, including T2DM, gestational diabetes, and special types. T1DM is caused by pancreatic β-cell damage, resulting in insulin deficiency [1]. T2DM is caused by insulin resistance and damaged pancreatic β-cell implementation. Type 2 diabetes mellitus (T2DM) accounts for approximately 90% of all diabetes cases and consists of two main components: peripheral insulin resistance and a relative deficiency in insulin secretion. Diabetes mellitus (DM) is a chronic and diverse condition with a hereditary predisposition [2]. Behavioral and environmental factors, such as poor dietary habits and an unhealthy lifestyle, influence it. The disease is characterized by chronic hyperglycemia, which results from alterations in the metabolism of carbohydrates, fats, and proteins due to defects in the pancreas’s ability to produce, secrete, and utilize insulin effectively [3].

DM, just after cardiovascular disease and cancer disorder, is a severe chronic disease that causes high mortality and morbidity rates, characterized by hyperglycemia and multiple organ complications [4]. Unfortunately, the prevalence of diabetes is increasing as the population grows. In 2004, around 143 million people with T2DM worldwide are expected to rise to 200 million by 2030. Oxidative stress and factors such as Free Fatty Acids (FFA) and hyperglycemia increase the production of cellular ROSs and RNSs, leading to insulin resistance [5]. Recently indicated that a direct relationship between insulin resistance development and the secretion of inflammatory mediators like TNF-α (tumor necrosis factor-alpha) and IL-6 (interleukine-6) inflammatory cytokines was shown [6]. The pathogenesis and complications of T2DM are closely related to inflammation, oxidative stress, and innate immunity processes [7]. Diabetes mellitus is caused by different factors, including genetic impairment, environmental conditions, microbial infection, immune system dysfunction, insufficient insulin secretion, and resistance.

DM causes different organ impairments that reduce the quality of life, such as diabetic retinopathy, nephropathy, diabetic cardiovascular disease, and hypertension [8, 9]. Diet modification, exercise, glucose monitoring, and medication are recommended in diabetes management protocol [10]. DM is a chronic condition that affects millions of people worldwide, and while there are many antidiabetic drugs available, a complete cure for this disease is still not available [11]. Antidiabetic therapeutic compounds include insulin, analogs, and non-insulin hypoglycemic oral therapeutic compounds. Other compounds like DPP-4 inhibitors and agonists of glucagon-like peptide-1 receptors have been developed recently. These compounds can be grouped into insulin-sensitizing, secreting, and glucose-regulating agents [12]. Numerous therapeutic compounds have been developed to regulate blood glucose levels. These drugs have several intrinsic deficiencies and adverse effects that hinder their effectiveness [13]. Acute severe hypoglycemia caused by sulfonylurea and profound lactic acidosis induced by biguanide, moreover, gastrointestinal and renal adverse effects caused by metformin. Conventional dosage forms cannot adjust intelligently for the wide fluctuation in glucose concentration, which increases the risk of hypoglycemia [14]. These drugs are also unable to accumulate at the desired site, which can lead to severe side effects on other organs. Moreover, drug therapy has different challenges like absorption problems, high drug distribution volume, short plasma distribution half time, small therapeutic window causing higher drug side effects, and poor patient compliance over a long time [15]. Therefore, urgent attempts are required to overcome these challenges and develop more effective treatments to manage diabetes mellitus.

Improving the gut microbiota through probiotics, prebiotics, or fecal microbiota transplantation (FMT) is possible. Probiotics are live microorganisms that can enhance the host’s health by being consumed properly as functional foods or as dietary supplements [16]. Preclinical studies have shown that probiotics benefit glycemia and other metabolic factors associated with T2DM [16]. However, various studies have been performed regarding the efficacy of probiotics in managing T2DM. In these experiments, fasting blood glucose (FBG), glycated hemoglobin (HbA1c), and homeostatic model assessment of insulin resistance (HOMA-IR) are used as parameters for therapeutic effects comparison [17].

Probiotics are live microorganisms (MO) that can provide health benefits when consumed sufficiently. While our body already contains such MOs, we can also obtain them through food supplements [18]. Recent studies have shown that probiotics, particularly the lactobacillus species, can be effective in managing type 2 diabetes. People with T2DM have been found to have a different gut microbiome compared to healthy individuals [19]. Patients with T2DM had lower amounts of Firmicutes bacteria but higher amounts of Bacteroides and Proteobacteria in their gastrointestinal tract. It has been suggested that the ratio of Bacteroides and Firmicutes species positively affects insulin resistance decrease [20]. Adopting innovative dietary strategies may allow for maintaining normal blood sugar levels by normalizing the microbiome and limiting long-term micro- and macrovascular impairment in T2DM. Probiotics, prebiotics, or fecal microbiota transplantation (FMT) can improve the gut microbiota [21]. Although research on the effectiveness of probiotics in managing T2DM is inconclusive, they have been shown to improve blood sugar levels and other metabolic factors in individuals with T2DM [22]. Several studies suggest that individuals with diabetes have lower levels of antioxidants in their plasma. Therefore, it may be beneficial to use antioxidants to prevent and treat diabetic complications. In addition, various in vivo and clinical trial studies have shown that both acute and chronic use of antioxidants can improve the insulin sensitivity of the cells [23].

Research involving human studies and animal models has identified several mechanisms linking changes in the gut microbiota to obesity, insulin resistance, and, eventually, T2DM. These mechanisms include increased energy extraction from food, distorted fatty acid metabolism, particularly of short-chain fatty acids (SCFAs), altered composition of adipose tissue and its insulin sensitivity, metabolic endotoxemia, increased systemic inflammation, enhanced intestinal permeability Together, these factors contribute to the development of metabolic disorders related to obesity and diabetes. Thus, it is hypothesized that the gut microbiota significantly contributes to the onset and progression of T2DM [24]. It is possible to improve gut microbiota by applying probiotics, prebiotics, or fecal microbiota transplantation (FMT). The popularity of probiotics as functional foods and dietary supplements has increased. Probiotics are live microorganisms that enhance the host’s health when consumed in adequate amounts. Preclinical data from animal and human studies have shown the beneficial effects of probiotics in improving glycemia and other related metabolic factors in T2DM [25].

Recent studies have found that certain probiotic species exhibit appropriate antioxidant activity [26]. Probiotics can enhance the normal microflora in the host’s body and benefit their health [27]. These beneficial effects include anti-inflammatory, immunomodulatory, and antioxidant effects [28]. Extensive research has shown that probiotics such as Lactobacillus acidophilus, Lactobacillus casei, and plantarum have significant antidiabetic effects [29].

Various methods are developed, including encapsulation of probiotic bacteria, freeze-drying, and spray-drying methods. Lyophilized cell-free probiotic extract (LPE) is a novel technology that has been found to exhibit practical antioxidant activities without any toxic effects, even in high quantities [30]. An alternative attitude, modifying the gut microbiome has been proposed as a new complementary approach. Studies suggest that the gut microbiota modulation by probiotics and prebiotics has beneficial outcomes in managing and preventing diabetes progression [31].

This study investigates the multiple antidiabetic effects of lyophilized probiotic extract (LPE) obtained from Lactobacillus acidophilus and Lactobacillus plantarum on a murine model with diabetes.

Materials and methods

Microorganisms and culture media

The probiotics strain was Lactobacillus Plantarum (PTCC:1058) and Lactobacillus acidophilus (PTCC:1643), all purchased from the Persian Type culture collection (PTCC). The bacteria were propagated and identified using the following culture media: de Man Rogosa Sharpe (MRS) broth and agar obtained from Merck (Himedia, Germany). Rat-specific tumor necrosis factor-alpha (TNF-a) ELISA kits and Rat-specific Insulin ELISA kits bought from Bioassay Technology (Tecan, Austria), Streptozocin(STZ), Nicotinamide(NA) from Sigma-Aldrich Chemical Co, Apo-Metformin from Apotex (Canada) and D-Mannitol, Citric acid, Sodium citrate, ethylene diamine tetra acetic acid (EDTA), Normal saline 0.9%, Dextrose 5%, Ether, which were all obtained from the stock cultures of the Department of Drug and Food Control, Faculty of Pharmacy, Ahvaz Jundishapur University of Medical Sciences, Iran.

Microbial culture

Pure probiotic bacteria were individually cultured in MRS Broth under anaerobic conditions at 37 °C for 24 h. The anaerobic environment was created using an Anoximat incubator from Germany with 5% CO2.

Growth rate determination of probiotics Bacteria

1 mL (equal to 103 Cfu/ml) of the freshly cultured probiotic bacteria was added to 100 mL of MRS broth to obtain the growth rate of probiotic bacteria. The flask was then shaken and incubated at 37˚C for 36 h, and the growth rate was calculated every three hours using the Optical-Density method [32].

Supernatant Cell-free probiotics bacteria Preparation

After 24 h, the supernatant was obtained by centrifuging the media at 4000 rpm for 15 min at 20˚C. The resulting supernatant was then passed through a sterile filter with a pore size of 0.22 µ to collect the mixture of metabolites from both probiotic bacteria. This mixture was then stored at 4˚C [23, 33].

Stable probiotic powder Preparation

The probiotic supernatant was stabilized using the freeze-drying method. The supernatant was transferred into 300 and 1000 ml flasks, and subsequently freeze-dried at -50 °C. After 48 h, a stable powder was obtained [32].

Animals and experimental design

All procedures in this study complied with the ethical standards of Ahvaz Jundishapur University of Medical Sciences (AJUMS). Male Wistar rats weighing 200–250 g were obtained from the animal house at AJUMS and fed conventional diets with tap water ad libitum. The rats were kept in standard humidity conditions, temperature (maintained at 23 °C), and light-dark cycle (12 h light, 12 h dark). The animal study procedures, protocols, and experiments used in this study were approved by the Ethics Committee of AJUMS (IR.AJUMS.REC.1395.105).

The blood samples were initially collected from the tail of the rat groups. At the end of the treatment, blood samples were drawn from the hearts of the groups under deep anesthesia using intraperitoneal injection of ketamine (70 mg/kg) and xylazine (7 mg/kg), followed by euthanizing the animal. Finally, after sampling time, the rats were decapitated).

Inducing diabetes type II

This experiment used Streptozotocin (STZ) and Nicotinamide (NA) as chemical agents to induce type 2 diabetes in animals. All animal groups, except for the Sham group, were subjected to type 2 diabetes induction. Prior to induction, animals were fasted overnight. NA was dissolved in 0.9% normal saline and injected intraperitoneally at 105 mg/kg-0.2 mL per injection. After 15 min, STZ was injected intraperitoneally at a dose of 90 mg/kg-0.2 mL per injection. The Streptozotocin was dissolved in a citrate buffer with a pH of 4.5. 5% dextrose was administered orally to prevent hypoglycemia. After 72 h, rats were fasted again for 12 h, and their fasting blood glucose (FBS) was measured by withdrawing blood from a tail vein using a glucometer (Bionime SuperSensor, Allmedicus, Korea). Rats with FBS levels greater than 250 mg/dl were considered diabetic [32].

The study involved diabetic rats randomly divided into six groups, each containing six rats. The groups were as follows: a negative control group (Neg), which received no treatment. A positive standard group (Pos) which received metformin (200 mg/kg) orally gavage solution, a low dose LPE-treated group (T-1) which received orally gavage 1 mL of LPE solution once daily at a dose of 60 mg (equal to 273 mg/kg of body weight), a moderate dose LPE-treated group (T-2) which received 120 mg/mL (equal to 540 mg/kg) orally gavage solution and a high dose LPE-treated group (T-3) which received 240 mg/mL (equal to 1080 mg/kg) orally gavage solution. On the same day, the rats were grouped, and they were anesthetized with an intra-peritoneal injection (IP) of a mixture of ketamine and xylazine (70, 7 mg/kg). Blood was then collected via heart puncture with a 19.5-gauge needle into EDTA vacutainer tubes. Then, plasma was separated by centrifugation of blood at (5000 rpm, 10 min, and 4˚C) and samples stored at -20 ° C [34, 35]. The study lasted for two weeks. Each rat in the respective group was given the appropriate doses of LPE or metformin daily for two weeks through oral gavage using 20-gauge feeding needles (Popper and Sons, New Hyde Park, NY). Rats in negative control received supplemented with distilled water.

The rats’ weight was measured regularly during the study period, and the changes were documented for further analysis. At the end of the study, the rats were fasted overnight and anesthetized, and blood samples were collected from the heart.

Fasting blood glucose levels

Fasting Blood Sugar (FBS) is one of the primary indicators used to evaluate Type 2 diabetes. In this study, the FBS levels of rats were compared before and after a two-week treatment. Blood samples were obtained through tail incision and the glucose concentration was measured using a glucometer both before and after the LPE therapy.

Determination of insulin and TNF-α

Blood samples were obtained by performing heart puncture using a 19.5-gauge needle into EDTA vacutainer tubes. The levels of TNF-α were determined using the sandwich ELISA method, by employing a commercially available kit from Fisher Thermo Scientific Co.

Measurement of insulin resistance

Insulin plasma levels were measured in two steps after the induction of diabetes: before and after treatment. The ELISA method with Rat Insulin Enzyme-Linked Immunosorbent Assay (ELISA) was used to evaluate insulin levels in rat plasma samples.

Insulin levels were measured using rat-specific Insulin ELISA kits before and after LPE therapy. The homeostatic model assessment values for insulin resistance were calculated using the below formula [36].

HOMA-IR = [(FBS in mg/dL × 0.05551) × Fasting Insulin in MU/L] / 22.5.

Glucose in the formula is in mmol/L (mg/dL × 0.05551), and insulin is in MU/L.

Statistical analysis

The data were analyzed using one-way analysis of variance (ANOVA) followed by Tukey’s tests. P < 0.05 indicated statistical significance. Results are presented as (Mean ± SEM). Statistical analysis was conducted with SPSS software (SPSS 24, SPSS, Inc).

Weight variation evaluation

The animal’s weight was a critical parameter in evaluating the general health condition of rats. The weight of rats was obtained before and after diabetes induction, on the first day of treatment, during 2 weeks of treatment, and finally evaluated.

Results

Growth kinetic of L. plantarum and L. acidophilus

Bacterial growth curves were determined by measuring Optical Density after 36 h. The figure depicts the bacteria cultivated together, showing the maximum growth rate at around 18 h. In contrast, the growth kinetics for each bacterium alone took approximately 24–26 h to reach the maximum level [33] (Fig. 1).

Fig. 1.

Fig. 1

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The Growth Kinetic of mixed of Lactobacillus plantrum and Lactobacillus acidophilus in MRS Media Incubated at 37˚C for 36 h

The level of FBS

Figure 2 shows that the level of FBS significantly increased after the induction of diabetes, in comparison to the Sham group (P < 0.05 in all groups). However, LPE supplementation at all studied doses and metformin significantly reduced this level (P < 0.05 in all groups). The level of FBS in the negative control group remained unchanged. The results showed no significant difference in the FBS levels among positive control, sham, and LPE-treated groups. Furthermore, the results demonstrated that the highest studied LPE dose (240 mg/ml) had the most potent effect on FBS levels. The FBS level in the T-3 group was significantly lower than that of the other groups (P < 0.05).

Fig. 2.

Fig. 2

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Changes of FBS in diabetic rats. Values are presented Mean ± SEM. Primary and Secondary respectively represented the FBS level just after inducing diabetes type 2, and at the end of study. Neg control: Diabetic rat group did not receive treatment. SHAM: Positive control group. T1: The diabetic rat group was treated with 60 mg/ml LPE. T2: The diabetic rat group was treated with 120 mg/ml LPE. T3: The diabetic rat group was treated with 240 mg/ml LPE. *Significant differences with other groups. ** Significant differences with T1, T2, T3. ***Significant differences with T1, T2

Plasma TNF-α level

The study aimed to evaluate oxidative stress and inflammatory cytokines in T2DM by measuring TNF-α plasma content. The results indicated a significant increase in TNF-α content in the plasma of the Neg. group compared to the Sham group (P < 0.001). This indicated that the induction of diabetes significantly increased TNF-α content. However, administration of LPE at all treated doses significantly reduced TNF-α plasma levels compared to the negative control group (P < 0.001). There was no significant difference in TNF-α plasma level between the LPE-treated and control groups. TNF-α levels in these groups were similar to the levels in the sham group. Despite FBS results, TNF-α level in the treated group at the dose of 240 mg/ml has no significant difference with other treatment doses, and TNF-α levels in the three treated groups are close to one another. Treatment of the rats using Cell-Free LPE at all three treatment doses of 60, 120, and 240 mg/ml decreased the studied cytokine level significantly (Fig. 3).

Fig. 3.

Fig. 3

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Plasma TNF-α level of rats. Values are presented as (Mean ± SEM). *Significant differences with T1, T2, T3. Neg control: Diabetic rat group did not receive treatment. SHAM: Positive control group. T1: The diabetic rat group was treated with 60 mg/ml LPE. T2: The diabetic rat group was treated with 120 mg/ml LPE. T3: The diabetic rat group was treated with 240 mg/ml LPE

Insulin resistance index

After diabetes was induced, the insulin plasma level was measured before and after treatment. Figure 4 shows the results of insulin resistance factors. The results showed that all diabetic groups significantly increased insulin resistance (P < 0.001), meaning that diabetes induction significantly increased cells’ resistance to insulin. However, insulin resistance was significantly reduced in all groups treated with LPE (P < 0.001). The final value of the HOMA-IR index in the negative control group had no significant change. A comparison of the two groups revealed a significant difference between the final value of the HOMA-IR index in the negative control group and the treated groups (P < 0.05). However, there was no significant difference between the treatment groups and the sham control group. HOMA-IR levels in the treated group at the 240 mg/ml dose were similar to the other treated doses. In conclusion, Cell-Free LPE reduces the HOMA-IR index rate at all treatment doses.

Fig. 4.

Fig. 4

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Changes of HOMA-IR in diabetic rats. Values are presented as (Mean ± SEM). *Significant differences with other groups. **Significant differences with T1, T2, T3. Neg control: Diabetic rat group did not receive treatment. SHAM: Positive control group. T1: The diabetic rat group was treated with 60 mg/ml LPE. T2: The diabetic rat group was treated with 120 mg/ml LPE. T3: The diabetic rat group was treated with 240 mg/ml LPE

Weight variation evaluation

The graph of weight variation showed that all treated rats, except those in the Sham group, experienced weight loss over time. This weight loss was significant in the negative control group (P < 0.001). The most significant decline was observed in the negative control group, while the LPE-treated and positive control groups displayed a slower decreasing trend in weight.

Fig. 5.

Fig. 5

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The Mean weight of animals during treatment. Values are presented as (mean ± SEM).*Significant differences with other groups**Significant differences with T1, T2, T3Neg control: Diabetic rat group did not receive treatmentSHAM: Positive control groupT1: The diabetic rat group was treated with 60mg/ml LPET2: The diabetic rat group was treated with 120 mg/ml LPET3: The diabetic rat group was treated with 240 mg/ml LPE

Discussion

T2DM is characterized by hyperglycemia and reduced cellular sensitivity to insulin caused by increasing cellular insulin resistance. This type of diabetes is also an inflammatory disease in which pro-inflammatory cytokines such as TNF-α and IL-6 are increased. Induction of TNF-α can cause insulin resistance, while neutralization of the cytokine can improve cellular sensitivity to insulin [4].

The present study found that inducing type T2D diabetes in rats using the STZ-NA method resulted in hyperglycemia and increased HOMAIR factor (Figs. 2 and 4). However, all doses of cell-free LPEs significantly reduced these levels in diabetic rats. Additionally, the anti-inflammatory effect of the product was evaluated by measuring the TNF-α pro-inflammatory cytokine. The cell-free LPE treatment significantly reduced TNF-α plasma levels in all diabetic groups (Fig. 3).

A study by Matsuzaki et al. has demonstrated that Lactobacillus casei can improve blood glucose levels and modify the immune response in diabetic mice. Additionally, Tabuchi et al. showed that Lactobacillus rhamnose can decrease blood HbA1c (glycated hemoglobin) and suppress oxidative stress in STZ-induced diabetic rats [37]. Lu et al. found that Lactobacillus restart can decrease glycated hemoglobin and blood glucose in STZ-induced diabetic rats [38]. Furthermore, AL Salami et al. indicated that a probiotic mixture containing Lactobacillus acidophilus, Lactobacillus rhamnose, and Bifidobacterium lactis could reduce blood glucose levels by improving gliclazide bioavailability in alloxan-induced diabetic rats [39].

Yadave et al. conducted a study that indicated that Lactobacillus acidophilus and Lactobacillus casei can reduce blood glucose levels and HbA1c in rats with diabetes caused by fructose [40]. Similarly, Andersson et al. discovered that Lactobacillus plantarum could lower plasma glucose levels in mice on a high-fat diet (HFD) [41]. These studies and other findings suggest that probiotics can improve blood glucose levels and HbA1c and reduce oxidative stress in diabetic animals.

According to different studies, insulin resistance is influenced by oxidative stress, which activates signals sensitive to stress. The significant signals, including NF-κB (nuclear factor kappa B), P38MAPK (p 38 mitogen-activated protein kinases), and JNK/SAPK (stress-activated protein kinase/jun N-terminal kinase), are activated by a wide range of stimuli such as hyperglycemia, IL-1β, TNF-α, and other factors. Activating these pathways results in impaired performance of the cellular membrane’s glucose transporters (GLUTs), leading to reduced glucose absorption by the cell under the influence of insulin. This reduction in the sensitivity of the cells to insulin is known as “insulin resistance.” Oxidative stress and inflammatory cytokines play a significant role in insulin resistance development, as scientists highlighted [42].

Saadatzadeh et al. conducted a study to investigate the effectiveness of probiotics in controlling inflammatory cytokines in the treatment of ulcerative colitis (UC). They found that the induction of UC increases proinflammatory cytokines (TNF-α and IL-1β) in mice. The study showed that treatment with LPE at all doses can decrease these factors [32]. Another study by Resta Lenert et al. revealed that both TNF-α and IFN-γ cytokines could reduce trans-epithelial resistance (TER) and increase epithelial permeability. However, probiotics can inhibit these effects. Therefore, treatment using probiotics can reverse the inflammatory cytokines-induced dysfunction in epithelial cells [43].

Egazy et al. performed a study that revealed that patients with UC had increased colonic protein expression of TNF-α and NF-κB P65. However, treatment with probiotics led to a decrease in colonic IL-6 and reduced the expression of TNF-α and NF-κB P65 [44]. Similarly, a recent study showed that probiotics significantly reduced TNF-α in T2DM rats. Other animal and cell line studies have demonstrated that some probiotic species exhibit appropriate antioxidant activity and have the potential to prevent the severity of T2DM [45]. Carotenoid antioxidants have also been found to have beneficial effects on T2DM. However, some antioxidants are more effective than others. Anderson’s study showed that oxidative stress causes insulin resistance through NF-κB, p38 MAPK, and JNK/SAPK pathways [42]. Although probiotics are effective in treating T2DM, they do have some limitations. For example, live cells may cause infections in immunocompromised patients [46]. However, probiotics can still provide their beneficial effects by producing metabolites containing a variety of organic acids, enzymes, and peptide compounds. One study added Lactobacillus plantarum l-U14 probiotic metabolite extract to the drinking water of rats and examined its effect on reducing cholesterol plasma levels [47].

Recent research has offered probiotics as promising complementary candidates for the gut microbiome in managing diabetes. The gut microbiome is a complex microorganism that maintains intestine microenvironment health, playing a vital role in controlling metabolic pathways. T1DM occurs when the immune system damages insulin-producing beta cells, causing insulin deficiency. Studies have shown specific changes in the gut microbiome, indicating a potential link between changes in microbiota and the autoimmune responses that may induce the severity of the disease [48]. T2DM is primarily linked to insulin resistance, which genetic factors and lifestyle choices can influence. This condition is often associated with gut dysbiosis, leading to increased permeability and chronic inflammation, worsening insulin resistance. Probiotics are live microorganisms that offer health benefits to hosts and are developing as a promising therapeutic strategy for Type 1 and Type 2 diabetes. They may help restore the balance of the gut microbiome, enhance gut barrier function, and reduce inflammation, potentially improving the management and prevention of diabetes. Additionally, there is growing interest in applying synbiotics in diabetes management, which combines probiotics and prebiotics to enhance their effectiveness. Given the potential benefits of probiotics in diabetes management, the combined impact of synbiotics could theoretically provide even more significant advantages for conditions that require a comprehensive approach to gut health and metabolic regulation [49]. Considering the dietary challenges faced by patients with diabetes, it is essential for them to have effective self-care behaviors to limit the disease’s progression. Therefore, the potential benefits of probiotics and synbiotics become increasingly relevant [50].

This study has found that cell-free lipopolysaccharide extract (LPE) from certain bacteria can effectively improve Type 2 Diabetes Mellitus (T2DM). Probiotics act as antioxidants that can reduce levels of TNF-α and other diabetic markers. These findings indicate that probiotics can help regulate inflammatory cytokines, such as NF-κB, and initiate oxidative pathways. The project evaluated the effectiveness of probiotic metabolites from Lactobacillus plantarum and Lactobacillus acidophilus on T2DM. The results showed that the metabolites from these probiotic bacteria can reduce hyperglycemia and enhance cellular insulin sensitivity. These effects are achieved alongside the inhibition of the inflammatory cytokine TNF-α.

Additionally, probiotic metabolites play a role in managing oxidative stress and innate inflammation and improving insulin resistance. The current study suggests that probiotics may assist in treating diabetes. However, further research involving animal models and human studies is needed to validate this hypothesis. Long-term studies on the administration of probiotics in humans are also necessary, and it is vital to assess any potential toxicity associated with their extended use.

Acknowledgements

not applicable.

Abbreviations

T2DM

Type 2 Diabetes Mellitus

LPE

Lipopolysaccharide extract

NF-κB

Nuclear factor kappa B

TER

Trans-epithelial resistance

UC

Ulcerative colitis

P38MAPK

p 38 mitogen-activated protein kinases

JNK/SAPK

Stress-activated protein kinase/Jun N-terminal kinase).

GLUTs

Glucose transporters

FBS

Fasting blood glucose

FMT

Fecal microbiota transplantation

TNF-α

Tumor necrosis factor-alpha

IL-6

Interleukine-6

Author contributions

Afrooz Saadatzadeh, Sanaz Mehdialamdarlou, Sayyed Ali Mard designed, directed the project. Seyed Mohammad Kazem Emamifar, Akram Ahangarpour performed the expriments. Sanaz Mehdialamdarlou, Afrooz Saadatzadeh, Sayyed Ali Mard, Sayyed Mohammad Kazem Emamifar, Kambiz Ahmadi Angali and Akram Ahangarpour analyzed data and wrote the manuscript.

Funding

The work was financially supported by AJUMS of research center and technology, Diabetes Research Center of Jundishapur University of Medical Sciences (D-9502), Ahvaz, Iran.

Data availability

All data supporting the findings of this study are available within the paper.

Declarations

Ethics approval

All procedures were conducted by ethical standards of Ahvaz Jundishapur University of Medical Sciences (IR.AJUMS.REC.1395.105).

Consent to participate

Not applicable.

Consent for publication

All authors have declared their agreement to publish this manuscript in this journal.

Financial disclosure

None declared.

Competing interests

The authors declare no competing interests.

Footnotes

The original online version of this article was revised: "Following publication of the original article [1], the authors would like to correct the ethics code in the Ethics approval section.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Change history

10/16/2025

The original online version of this article was revised: Following publication of the original article [1], the authors would like to correct the ethics code in the Ethics approval section.

Change history

10/15/2025

A Correction to this paper has been published: 10.1186/s12906-025-05120-5

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Data Availability Statement

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