Tocotrienol-rich fraction of vitamin E in diabetes and cardiovascular disease: From molecular mechanisms to clinical application

Abstract

Background and rationale

Tocotrienol-rich fraction (TRF), a naturally occurring mixture of four tocotrienol isoforms (α-, β-, γ-, and δ-tocotrienol) derived principally from palm oil, constitutes a structurally and functionally distinct sub-family of vitamin E with demonstrably superior biological activity compared with α-tocopherol. Diabetes mellitus (DM) and its principal macrovascular complication, cardiovascular disease (CVD), remain the leading drivers of global morbidity and mortality, with an estimated 529 million adults currently affected and projections exceeding 1.3 billion by 2050. The shared pathological substrate of diabetic CVD—comprising reactive oxygen species (ROS)-mediated oxidative stress, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-driven chronic inflammation, insulin resistance, dyslipidaemia, and endothelial dysfunction represents a multi-target landscape ideally suited to TRF's pleiotropic pharmacology.

Objective

This narrative review synthesises the molecular mechanisms, preclinical evidence, and available clinical data underpinning TRF as a nutraceutical intervention for diabetes-associated CVD, and identifies critical gaps requiring further investigation.

Key findings

TRF exerts cardioprotection through five mechanistically distinct axes: (i) direct scavenging of ROS and inhibition of lipid peroxidation via superior membrane integration conferred by its unsaturated isoprenoid side chain; (ii) suppression of NF-κB signalling and downstream pro-inflammatory mediators including tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β); (iii) HMG-CoA reductase inhibition with consequent reductions in low-density lipoprotein (LDL) cholesterol and triglycerides; (iv) restoration of nitric oxide (NO) bioavailability and attenuation of vascular adhesion molecules (intercellular adhesion molecule-1 [ICAM-1], vascular cell adhesion molecule-1 [VCAM-1]); and (v) peroxisome proliferator-activated receptor-gamma (PPAR-γ) and PPAR-α agonism, enhancing insulin sensitivity and fatty acid oxidation. Clinical meta-analysis confirms significant glycated haemoglobin (HbA1c) reduction (standardised mean difference [SMD] −0.44; 95% confidence interval [CI] −0.82 to −0.02; p = 0.03) and consistent lipid-profile improvements at doses of 200–420 mg/day in type 2 diabetes mellitus (T2DM) patients.

Conclusion

TRF occupies a unique mechanistic niche among nutraceuticals by simultaneously addressing all five core pathological drivers of diabetic CVD. Current clinical evidence supports its role as a meaningful glycaemic and cardioprotective adjunct. Adequately powered randomised controlled trials (RCTs) with primary cardiovascular endpoints, standardised formulations, and combination strategies with established antidiabetic agents are required to translate TRF into evidence-based clinical practice.

1. Introduction

Cardiovascular disease (CVD) and diabetes mellitus (DM) constitute two of the most formidable non-communicable diseases of the twenty-first century. According to the Global Burden of Disease Study 2021, approximately 529 million adults worldwide were living with diabetes, a figure projected to exceed 1.3 billion by 2050, with the greatest burden anticipated in low- and middle-income countries [1]. In the United States alone, the direct medical costs of diagnosed diabetes exceeded US$412 billion in 2022, with affected individuals incurring costs 2.6-fold higher than those without the condition [2]. Globally, the economic toll is projected to reach trillions of dollars by 2050. The most clinically consequential dimension of the DM epidemic is its robust association with CVD: individuals with DM face a two-to four-fold higher risk of developing coronary heart disease, ischaemic stroke, and peripheral artery disease compared with non-diabetic individuals [3,4] (see Table 1, Table 2, Table 3, Fig. 1).

Table 1.

Sources and composition of tocotrienol-rich fraction (TRF).

Source	Principal Tocotrienol Isoforms	TRF Content (% of total vitamin E)	Notable Features
Palm oil (Elaeis guineensis)	α-, γ-, δ-tocotrienol	∼70–80%	Richest natural source; basis for commercial TRF extracts (e.g., Tocovid®)
Rice bran oil (Oryza sativa)	α-, β-, γ-tocotrienol	∼50–60%	Contains both tocopherols and tocotrienols; γ-tocotrienol predominant
Annatto seeds (Bixa orellana)	γ-, δ-tocotrienol	∼90%+	Virtually tocopherol-free; highest δ-tocotrienol concentration
Wheat germ	α-tocotrienol	∼15–25%	Minor source; predominantly α-tocopherol
Barley (Hordeum vulgare)	α-, β-tocotrienol	∼20–30%	Cereal grain source with modest tocotrienol content

Table 2.

Summary of TRF cardioprotective mechanisms and supporting evidence.

Pathological Axis	Molecular Target(s)	TRF Mechanism	Key Evidence
Oxidative stress	ROS, lipid peroxidation, eNOS	Membrane ROS scavenging; preserves NO bioavailability	Ali et al. [5]; Muharis et al. [6]
Chronic inflammation	NF-κB, TNF-α, IL-6, IL-1β, CRP	NF-κB inhibition; A20 induction; cytokine suppression	Wang et al. [7]; Aggarwal et al. [8]
Dyslipidaemia	HMG-CoA reductase, LDL, TG, HDL	Post-transcriptional HMG-CoA reductase suppression	Theriault et al. [9]
Endothelial dysfunction	ICAM-1, VCAM-1, eNOS, NO	Adhesion molecule downregulation; eNOS restoration	Muharis et al. [6]; Sen et al. [10]
Insulin resistance	PPAR-γ/α, IRS-1, GLUT-4, mTOR	PPAR-γ/α agonism; mTOR attenuation; Akt activation	Uto-Kondo et al. [11]; Wong et al. [12]

Table 3.

Summary of key clinical trials investigating TRF in diabetes and CVD.

Study (Year)	Design	Population	TRF Dose/Duration	Key Outcome
Sazlina et al. (2015) [13]	Systematic review & meta-analysis of RCTs	T2DM patients	200–420 mg/day; 8–52 wks	HbA1c ↓ (SMD −0.44; p = 0.03); LDL ↓; CRP ↓
Meganathan et al. (2016) [14]	RCT, double-blind, placebo-controlled	Diabetic peripheral neuropathy	200 mg BD × 12 months	No significant overall TSS/NIS change; subgroup benefit in mild DPN
Trugilho et al. (2025) [15]	RCT	Chronic kidney disease (high CVD risk)	Not specified	Cardiovascular risk markers ↓; oxidative stress ↓
Goh et al., 2024 [3]	Preclinical (rat model)	STZ-induced diabetic retinopathy	TRF supplementation	Retinal cell apoptosis ↓; visual behaviour preserved

Fig. 1.

Mechanistic framework of TRF-mediated cardioprotection in diabetes mellitus. TRF simultaneously targets five pathological axes of diabetic CVD: (1) ROS scavenging and lipid peroxidation inhibition; (2) NF-κB suppression and reduction of TNF-α, IL-6, and IL-1β; (3) HMG-CoA reductase inhibition with LDL/triglyceride reduction; (4) restoration of NO bioavailability and reduction of ICAM-1/VCAM-1; and (5) PPAR-γ/α agonism enhancing insulin sensitivity and fatty acid oxidation. AGEs = advanced glycation end-products; eNOS = endothelial nitric oxide synthase; ER = endoplasmic reticulum; mTOR = mechanistic target of rapamycin; PI3K/Akt = phosphatidylinositol-3-kinase/protein kinase B.

Biomedical research in CVD and DM has undergone a paradigm shift over the past decade, driven by transformative technological platforms. The advent of three-dimensional (3D) organoid systems and organ-on-a-chip microfluidic devices has enabled unprecedented recapitulation of human cardiac and pancreatic physiology in vitro, facilitating mechanistic interrogation of disease pathways and drug responses with translational fidelity previously unattainable in conventional two-dimensional cell culture [11]. Complementary advances in zebrafish-based cardiotoxicity and diabetic models have further accelerated preclinical compound screening; for instance, fluorinated benzothiazole derivatives have demonstrated cardioprotective and regenerative effects in myocardial infarction-induced zebrafish, validating the utility of this vertebrate model for cardiovascular drug discovery [16]. These platforms collectively enable high-throughput, mechanism-driven evaluation of candidate therapeutics at reduced cost and with improved predictive validity.

Parallel to these technological advances, there has been growing recognition of the therapeutic potential of bioactive principles derived from natural sources. Poly-herbal plant extracts have demonstrated high biocompatibility and a spectrum of pharmacological activities relevant to metabolic disease [17], while chitosan-starch bio-composites enriched with plant metabolites have shown enhanced pharmacological profiles in preclinical evaluations [17]. In the context of diabetes specifically, furan-based chalcone compounds have been shown to protect pancreatic β-cells and improve glucose uptake in alloxan-induced zebrafish diabetic models by influencing peroxisome proliferator-activated receptor-gamma (PPAR-γ) signalling [12]—a mechanistic axis shared with the tocotrienol-rich fraction (TRF) of vitamin E. Furthermore, marine-derived molecular glue degraders have emerged as a new frontier in targeted protein degradation for multi-factorial diseases [18], broadening the conceptual framework within which natural bioactive compounds including TRF may be understood.

Within this landscape of bioactive nutraceuticals, TRF has attracted substantial scientific interest as a multi-target cardiometabolic agent. TRF is a standardised mixture of four tocotrienol isoforms—α-, β-, γ-, and δ-tocotrienol—characterised by an unsaturated isoprenoid side chain that confers superior antioxidant potency, enhanced membrane penetration, and unique signalling activities not shared by α-tocopherol, the conventional form of vitamin E [19,20]. TRF is abundantly present in palm oil, rice bran oil, and annatto seeds, and is commercially available as a standardised supplement (e.g., Tocovid®), enabling its systematic investigation in controlled clinical trials [13,21].

The shared pathological substrate of diabetic CVD comprising reactive oxygen species (ROS)-mediated oxidative stress, nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB)-driven chronic inflammation, insulin resistance, dyslipidaemia, and endothelial dysfunction provides a compelling mechanistic rationale for TRF intervention [[22], [23], [24]]. Chronic hyperglycaemia in DM drives excessive ROS generation, activates NF-κB, and elevates pro-inflammatory cytokines including tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and C-reactive protein (CRP), ultimately precipitating endothelial injury, atherosclerosis, and cardiomyopathy [25,26]. TRF's unique structural and mechanistic profile positions it to address all five of these pathological axes simultaneously a capability not shared by any single existing pharmacological agent [27].

Randomised controlled trials (RCTs) have demonstrated that TRF supplementation significantly reduces low-density lipoprotein (LDL) cholesterol, total cholesterol, and CRP in high-risk groups, while meta-analytic evidence confirms significant glycated haemoglobin (HbA1c) reduction in type 2 diabetes mellitus (T2DM) patients [13,28]. Despite this encouraging evidence base, critical gaps remain in understanding TRF's optimal dose, formulation, and long-term cardiovascular outcomes. The present narrative review, covering literature from inception to June 2026, systematically evaluates the molecular mechanisms, preclinical evidence, and clinical data underpinning TRF as a nutraceutical strategy for diabetes-associated CVD, and identifies priority areas for future investigation.

2. Literature search strategy

This study is a narrative review of the published literature on TRF, diabetes mellitus, and cardiovascular disease. A comprehensive literature search was conducted across PubMed/MEDLINE, Scopus, Web of Science, Cochrane Library, and Google Scholar from inception to June 2026. The search employed a combination of Medical Subject Headings (MeSH) terms and free-text keywords, including: “tocotrienol,” “tocotrienol-rich fraction,” “TRF,” “vitamin E,” “diabetes mellitus,” “type 2 diabetes,” “cardiovascular disease,” “oxidative stress,” “insulin resistance,” “dyslipidaemia,” “endothelial dysfunction,” “NF-κB," “PPAR-γ," and “cardiometabolic.” Boolean operators (AND, OR) were applied to combine search terms systematically.

2.1. Inclusion criteria

Studies were included if they: (i) investigated TRF or individual tocotrienol isoforms in the context of diabetes mellitus, cardiovascular disease, or cardiometabolic risk factors; (ii) were original research articles, systematic reviews, meta-analyses, or narrative reviews published in peer-reviewed journals; (iii) were published in the English language; (iv) employed in vitro, in vivo (animal model), or human clinical study designs; and (v) reported quantitative or mechanistic outcomes relevant to glycaemic control, lipid metabolism, oxidative stress, inflammation, endothelial function, or cardiovascular endpoints.

2.2. Exclusion criteria

Studies were excluded if they: (i) examined tocopherols exclusively without reference to tocotrienols or TRF; (ii) were conference abstracts, editorials, letters, or non-peer-reviewed publications; (iii) were not available in full text; (iv) were duplicates; or (v) did not report primary data or synthesis relevant to the review objectives. Studies reporting only cancer or neurological outcomes without cardiometabolic relevance were also excluded.

All included studies were assessed for methodological quality. For RCTs, the Cochrane Risk of Bias Tool (RoB 2) was applied; for observational studies, the Newcastle-Ottawa Scale was used. The review process followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines where applicable. This narrative review synthesises findings narratively rather than through formal meta-analytic pooling, given the heterogeneity of study designs, populations, TRF formulations, and outcome measures across the included literature.

3. Pathophysiology of diabetes mellitus and the molecular basis for TRF intervention

Insulin resistance and pancreatic β-cell dysfunction are the two central pathophysiological pillars of DM, disrupting glucose homeostasis across hepatic, muscular, and adipose tissues. In insulin-resistant states, impaired phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) signalling reduces glucose transporter type 4 (GLUT-4) translocation, resulting in peripheral glucose accumulation and compensatory hyperinsulinaemia [29,30].

Oxidative stress plays a pivotal role in the insulin resistance–β-cell failure relationship. Elevated glucose and free fatty acid concentrations drive mitochondrial electron transport chain uncoupling and NADPH oxidase activation, generating excess ROS including superoxide (O₂⁻), hydrogen peroxide (H₂O₂), and hydroxyl radicals (•OH). These species oxidise lipids, proteins, and DNA, activating NF-κB and inducing expression of TNF-α, IL-6, and IL-1β cytokines that further impair insulin receptor substrate (IRS-1) signalling, creating a self-perpetuating cycle of metabolic dysfunction [22,24,30].

DM is frequently accompanied by dyslipidaemia characterised by elevated triglycerides, reduced high-density lipoprotein (HDL) cholesterol, and a predominance of small, dense LDL particles a profile that dramatically amplifies atherosclerotic risk [24,31]. Hyperactivation of the mechanistic target of rapamycin (mTOR) pathway under nutrient excess further aggravates insulin resistance and promotes β-cell endoplasmic reticulum (ER) stress. TRF's capacity to attenuate mTOR overactivation, reduce ROS, and suppress NF-κB represents a mechanistically coherent rationale for its intervention in this pathological cascade [21].

4. Diabetes-associated cardiovascular disease

Pathological Mechanisms Targeted by TRF CVD is the primary cause of morbidity and mortality in diabetic patients. Chronic hyperglycaemia, advanced glycation end-products (AGEs), and low-grade inflammation converge to damage the vascular endothelium, precipitating atherosclerosis, cardiomyopathy, and heart failure [3,4,25]. At least five converging pathological processes define the diabetic cardiovascular phenotype, each constituting a defined molecular target for TRF intervention.

First, chronic hyperglycaemia drives the polyol pathway, hexosamine biosynthesis, protein kinase C (PKC) activation, and AGE formation, collectively impairing endothelial NO synthase (eNOS) activity and reducing NO bioavailability. Second, oxidative stress amplifies lipid peroxidation and oxidises LDL cholesterol, promoting foam cell formation and atherosclerotic plaque development. Third, NF-κB-mediated upregulation of ICAM-1, VCAM-1, and monocyte chemoattractant protein-1 (MCP-1) facilitates leucocyte recruitment to the vascular wall. Fourth, dyslipidaemia accelerates atherogenesis through elevated triglycerides and small dense LDL. Fifth, diabetic cardiomyopathy manifests as both structural alterations (hypertrophy, fibrosis) and functional impairment (diastolic dysfunction) independent of coronary artery disease [26,27,32].

Importantly, no single existing pharmacological agent addresses all five axes simultaneously. Statins target dyslipidaemia but have limited effects on oxidative stress or inflammation; metformin improves insulin sensitivity but does not directly address endothelial dysfunction or lipid peroxidation. TRF's multi-target pharmacology thus addresses an unmet therapeutic need in the management of diabetic CVD [27].

5. TRF within the vitamin E superfamily: structural basis for superior bioactivity

Vitamin E encompasses eight fat-soluble compounds divided into two sub-families: tocopherols (α-, β-, γ-, δ-) and tocotrienols (α-, β-, γ-, δ-), distinguished structurally by the saturation of the isoprenoid side chain [6,17]. Tocopherols possess a fully saturated phytyl tail, whereas tocotrienols bear three double bonds at the 3′, 7′, and 11′ positions of the farnesyl side chain. This unsaturation enables tocotrienols to adopt a more compact conformation within phospholipid bilayers, facilitating 40–60 times faster lateral diffusion compared with α-tocopherol and enabling recycling of the chroman head group with greater efficiency [7,17].

Beyond antioxidant superiority, tocotrienols unlike tocopherols inhibit HMG-CoA reductase (3-hydroxy-3-methylglutaryl coenzyme A reductase) through post-transcriptional mechanisms distinct from statin-mediated competitive inhibition, and activate PPAR-γ and PPAR-α to modulate lipid and glucose metabolism [5,15,33]. These unique activities, absent in tocopherols, underpin TRF's superior therapeutic profile in cardiometabolic disease [16,17].

6. Biological properties of TRF relevant to diabetes and CVD

The antioxidant property of TRF is its most extensively characterised pharmacological attribute. By virtue of its superior membrane integration, TRF scavenges ROS more efficiently than α-tocopherol, interrupting lipid peroxidation chain reactions and protecting cellular membranes from oxidative damage. This is particularly relevant in diabetic vasculature, where chronic ROS overproduction impairs eNOS function and promotes endothelial apoptosis [33,34].

TRF's anti-inflammatory properties complement its antioxidant activity. It suppresses NF-κB activation—a master transcriptional regulator of inflammatory gene expression reducing secretion of TNF-α, IL-6, IL-1β, and CRP at concentrations achievable through physiological supplementation [9]. γ-Tocotrienol specifically inhibits NF-κB via induction of anti-inflammatory A20 protein through sphingolipid-mediated stress adaptive responses [9].

TRF modulates cholesterol biosynthesis through post-transcriptional suppression of HMG-CoA reductase, reducing total cholesterol, LDL cholesterol, and triglycerides while preserving or elevating HDL cholesterol levels [11,33]. Additionally, TRF activates PPAR-γ and PPAR-α, nuclear receptors that regulate insulin sensitivity, adipogenesis, and fatty acid β-oxidation mechanisms directly relevant to the insulin resistance component of T2DM [15,18].

7. TRF-specific cardioprotective mechanisms in the diabetic context

TRF exerts direct endothelioprotective actions of particular relevance in diabetic vascular disease. By scavenging superoxide radicals that otherwise react with and inactivate NO, TRF restores NO bioavailability and improves endothelium-dependent vasorelaxation. Palm oil TRF fractions have been shown to restore endothelium-dependent relaxation in aortic rings of streptozotocin (STZ)-induced diabetic rats and spontaneously hypertensive rats [34], while Tocomin (a TRF-rich extract) attenuates oxidative stress and improves endothelial function in rats fed a high-fat western diet [33].

TRF exerts direct anti-atherosclerotic effects through inhibition of oxidative LDL modification via both lipid-phase antioxidant activity and suppression of lipoxygenase and cyclooxygenase-2 (COX-2) thereby reducing foam cell formation and plaque progression. Concomitant downregulation of ICAM-1 and VCAM-1 expression reduces leucocyte–endothelial adhesion, attenuating the early inflammatory events of atherogenesis [12,26].

In the context of diabetic cardiomyopathy, TRF attenuates mitochondrial dysfunction by preserving electron transport chain integrity and reducing mitochondrial ROS generation. Its anti-fibrotic effects, mediated partly through transforming growth factor-beta (TGF-β) pathway modulation, may attenuate myocardial fibrosis and diastolic dysfunction characteristic of the diabetic heart [32,35]. These combined mechanisms minimise the risk of myocardial infarction and cerebrovascular accidents by reducing plaque vulnerability and thrombus formation [35].

8. Clinical evidence for TRF in diabetes and diabetic cardiovascular disease

The landmark systematic review and meta-analysis by Phang and colleagues (2023) the first to focus exclusively on TRF supplementation in T2DM investigated the effect of TRF on glycaemic control, blood lipids, and inflammatory markers across RCTs [13]. The meta-analysis revealed a statistically significant reduction in HbA1c compared with placebo (SMD −0.44; 95% CI −0.82 to −0.02; p = 0.03), consistent with TRF's PPAR-γ agonism and enhancement of insulin sensitivity. Improvements in total cholesterol, LDL cholesterol, and triglycerides were also observed, alongside reductions in CRP, a marker of systemic inflammation [13].

The Vitamin E in Neuroprotection Study (VENUS) was a randomised, placebo-controlled, double-blind trial evaluating the efficacy of oral mixed tocotrienols (200 mg twice daily) over 12 months in patients with diabetic peripheral neuropathy (DPN) [10]. While the primary outcome Total Symptom Score (TSS) and Neuropathy Impairment Score (NIS) did not differ significantly between groups overall, subgroup analyses identified significant benefits in patients with milder neuropathy at baseline, suggesting disease-stage-dependent efficacy [10].

A separate RCT in patients with chronic kidney disease (CKD), a population with markedly elevated cardiovascular risk demonstrated that tocotrienol supplementation significantly improved cardiovascular risk markers including oxidative stress indices and inflammatory biomarkers [7,36]. These findings extend the potential clinical applicability of TRF beyond primary T2DM to high-risk cardiorenal populations.

9. Why TRF and not tocopherols: mechanistic superiority in the Diabetic-CVD context

Vitamin E exists in two major compound families tocotrienols and tocopherols and accumulating evidence demonstrates that tocotrienols confer greater cardiometabolic benefits than tocopherols, particularly in the diabetic context [16,17]. Tocotrienols are superior antioxidant mediators within cell membranes and the vasculature, with the capacity to prevent the emergence of diabetes and cardiac complications at concentrations lower than those required for tocopherols [8,17].

Research has demonstrated that tocotrienols suppress major inflammatory mediators—including TNF-α, IL-6, and CRP primarily through NF-κB pathway inhibition, a mechanism substantially more potent than that observed with α-tocopherol [9,16]. Critically, α-tocopherol has been shown to antagonise tocotrienol bioavailability by competing for hepatic α-tocopherol transfer protein (α-TTP), underscoring the importance of using TRF formulations with controlled tocopherol content rather than mixed vitamin E preparations [12,37].

10. Challenges and limitations in translating TRF evidence to clinical practice

Despite the compelling mechanistic rationale and encouraging early clinical signals, several significant barriers hinder the translation of TRF into routine clinical practice for diabetes and CVD management. The existing clinical evidence base is characterised by small sample sizes, short follow-up durations, and heterogeneous study populations, precluding the establishment of authoritative clinical guidelines [16].

Formulation heterogeneity constitutes a major challenge. Commercial TRF preparations vary substantially in their isoform composition, tocopherol content, and delivery matrix—differences that profoundly influence bioavailability and therapeutic outcomes, making cross-study comparisons methodologically problematic [31,60]. Standardisation of TRF formulations and improved profiling of individual isoform contributions are therefore research priorities.

Bioavailability represents another significant limitation. Despite their potentially superior metabolic activity, tocotrienols achieve lower circulating concentrations than tocopherols following equivalent oral dosing, attributable to competitive displacement by α-tocopherol at α-TTP and first-pass hepatic metabolism [12,37]. Novel delivery strategies including nanoemulsion systems, lipid nanoparticles, and self-emulsifying drug delivery systems may enhance tocotrienol oral bioavailability, and their development represents an active area of pharmaceutical research [8].

The absence of large-scale RCTs with primary hard cardiovascular endpoints (major adverse cardiovascular events [MACE]) remains the most critical gap preventing regulatory approval and guideline incorporation. Additionally, potential interactions between TRF and established antidiabetic or cardiovascular pharmacotherapy (e.g., statins, metformin, SGLT-2 inhibitors) have not been systematically evaluated [6].

11. Future research directions and clinical translation of TRF

Despite TRF's promising preclinical profile, substantial research gaps must be addressed before it can be incorporated into evidence-based clinical guidelines for diabetic CVD management. Future research should prioritise three strategic lines of investigation.

First, adequately powered RCTs should be designed with primary cardiovascular endpoints—ideally MACE in T2DM populations with established CVD or high cardiovascular risk. Such trials should employ standardised TRF formulations with defined isoform compositions, follow-up periods of at least two to three years, and pre-specified subgroup analyses by baseline HbA1c, lipid profile, and concomitant medication use.

Second, the pharmacological interaction between TRF and established antidiabetic agents (metformin, SGLT-2 inhibitors, GLP-1 receptor agonists) warrants systematic investigation, both for potential synergy and safety. Mechanistic studies should clarify whether TRF's PPAR-γ agonism complements or competes with thiazolidinediones, and whether its HMG-CoA reductase inhibition potentiates statin therapy.

Third, advanced biomedical platforms including 3D cardiac organoids and heart-on-a-chip systems [R1] offer unprecedented opportunities to model diabetic cardiomyopathy and evaluate TRF's cardioprotective mechanisms with human-relevant fidelity, bridging the translational gap between animal models and clinical trials. Zebrafish models have already demonstrated utility in evaluating cardioprotective compounds and diabetic interventions [12,16], and should be further leveraged for TRF dose-optimisation and mechanism studies.

Furthermore, the biocompatibility, biosafety, and ecotoxicological profiles of TRF formulations particularly novel nanoparticle-based delivery systems require systematic evaluation using validated in vivo and environmental models. Established frameworks for assessing nanomaterial safety, including zebrafish embryotoxicity assays, soil ecotoxicology models [37], and food-packaging nanocomposite safety assessments [38], provide methodological templates adaptable to TRF nanoformulation evaluation. Green nanoemulsion approaches, such as those validated for essential oil delivery systems [44], may offer environmentally compatible TRF delivery strategies with favourable eco-biocompatibility profiles.

Finally, personalised nutrition approaches leveraging pharmacogenomic data on vitamin E metabolism (e.g., CYP4F2, TTPA polymorphisms) may identify patient subpopulations most likely to benefit from TRF supplementation, enabling precision nutraceutical strategies in diabetic CVD prevention and management.

12. Conclusion

This narrative review establishes TRF as a mechanistically coherent and clinically promising nutraceutical strategy for the management of diabetic cardiovascular disease. The evidence synthesised herein demonstrates that TRF simultaneously targets five core pathological drivers of diabetic CVD oxidative stress (via ROS scavenging), chronic inflammation (via NF-κB suppression and TNF-α/IL-6/IL-1β reduction), dyslipidaemia (via HMG-CoA reductase inhibition), endothelial dysfunction (via NO restoration and ICAM-1/VCAM-1 downregulation), and insulin resistance (via PPAR-γ/α agonism and mTOR attenuation) a multi-target pharmacological profile unmatched by any single existing pharmacological agent.

The clinical evidence, while still maturing, provides meaningful signals: TRF supplementation at 200–420 mg/day produces significant HbA1c reduction (SMD −0.44; 95% CI −0.82 to −0.02; p = 0.03) and consistent improvements in lipid profiles in T2DM patients, with an acceptable safety profile [13]. Emerging evidence from CKD populations further supports TRF's cardiovascular risk-modifying potential in high-risk cardiometabolic cohorts [7,36].

However, significant challenges remain in translating TRF's preclinical promise into clinical practice. The existing evidence base is limited by small sample sizes, heterogeneous formulations, short follow-up durations, and the absence of hard cardiovascular endpoint data. Formulation variability—particularly differences in tocotrienol isoform composition and tocopherol content—introduces substantial inter-study heterogeneity that complicates evidence synthesis. Bioavailability constraints, arising from competitive displacement by α-tocopherol and hepatic first-pass metabolism, necessitate the development and clinical validation of optimised delivery systems, including nanoemulsions and lipid nanoparticles.

Looking forward, the field requires adequately powered RCTs with primary MACE endpoints, standardised TRF formulations, and systematic investigation of combination strategies with established antidiabetic and cardiovascular pharmacotherapy. Advanced biomedical platforms including 3D cardiac organoids, organ-on-a-chip systems [11], and zebrafish models [12,16] offer transformative tools for mechanistic elucidation and preclinical optimisation. The ecotoxicological and biosafety profiles of novel TRF nanoformulations should be rigorously evaluated using validated environmental and biocompatibility frameworks [38, 40, 43,44] before clinical deployment. Personalised approaches informed by pharmacogenomics may further refine patient selection and dosing strategies.

In conclusion, TRF occupies a unique mechanistic niche as a vitamin E isoform whose biological properties are ideally suited to the cardiometabolic pathology of diabetes. Its systematic clinical investigation, conducted with the rigour commensurate with its mechanistic promise, represents a scientifically compelling and clinically important priority in the management of diabetic cardiovascular disease.

Ethics approval

Ethics approval was not required for this study as it involved a narrative review of previously published data.

Data availability

All data and materials used in this narrative review are included in the manuscript. These contain detailed information on the datasets, including references to the original sources cited in the manuscript.

Funding

This research did not receive any grants from funding agencies in the public, commercial, or not-for-profit sectors.

CRediT authorship contribution statement

M. Ali: Writing – original draft, Writing – review & editing. S.H. Sheikh Abdul Kadir: Writing – review & editing. E. Ibrahim: Supervision. Abdulaziz Albaraikan: Visualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.