Influence of vitamin E supplementation on glycaemic control: a meta-analysis of randomised controlled trials

Single and mixed associations of composite antioxidant diet on triglyceride-glucose index

BACKGROUND

Although the relationship between oxidative stress and insulin resistance (IR) has been established, the associations of the composite dietary antioxidant index (CDAI) and its components with the surrogate index of insulin resistance (IR), triglyceride-glucose index (TyG), is still not clear.

METHODS

This study analyzed the cross-sectional data of the National Health and Nutrition Examination Survey (NHANES) from 2003 to 2018. Multivariate linear regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR) were used to analyze the associations of the CDAI and its components with the TyG. In addition, subgroup analysis and several sensitivity analyses were conducted.

RESULTS

A total of 14,673 participants with complete data were included, with a median age of 50 years and 7,257 women (49%). Multivariate linear regression showed that after full adjustment, the CDAI was significantly negatively associated with the TyG [β: -0.005, 95% CI: (-0.008, -0.002), p = 0.002]. The model in which six nutrients were mutually corrected showed that vitamin E (per-SD increase) was most strongly associated with the TyG [β: -0.062, 95% CI: (-0.074, -0.050), p < 0.0001]. In the WQS model, the WQS index of the antioxidant diet was negatively associated with the TyG (β: -0.060; P < 0.0001). Similar effects were observed in the BKMR analysis. Notably, in the WQS and BKMR models, vitamin E became the most influential component. In addition, in the subgroup analysis, the association between the CDAI and the TyG in overweight or obese and diabetic populations was significantly weaker.

CONCLUSION

Antioxidant diets, especially vitamin E, are significantly negatively correlated with TyG. This study emphasizes the important value of supplementing vitamin E to improve IR. However, patients with poor weight management and diabetes seem to benefit less from antioxidant diets.

Metabolic profiling reveals the nutraceutical effect of Gongolaria abies-marina and Rosmarinus officinalis extracts in a type 1 diabetes animal model

Nutraceuticals have gained increasing interest, prompting the need to investigate plant extracts for their beneficial properties and potential side effects. This study aimed to assess the nutraceutical effects of environmentally clean extracts from Rosmarinus officinalis and Gongolaria abies-marina (formerly Cystoseira abies-marina (Phaeophyceae)) on the metabolic profile of streptozotocin-induced diabetic rats. We conducted untargeted LC-QTOF-MS metabolic profiling on six groups of rats: three diabetic groups receiving either a placebo, R. officinalis, or G. abies-marina extracts, and three corresponding control groups. The metabolic analysis revealed significant alterations in the levels of various glycerophospholipids, sterol lipids, and fatty acyls. Both extracts influenced the metabolic profile, partially mitigating diabetes-induced changes. Notably, G. abies-marina extract had a more pronounced impact on the animals' metabolic profiles compared to R. officinalis. In conclusion, our findings suggest that environmentally clean extracts from R. officinalis and G. abies-marina possess nutraceutical potential, as they were able to modulate the metabolic profile in streptozotocin-induced diabetic rats. G. abies-marina extract exhibited a more substantial effect on metabolic alterations induced by diabetes compared to R. officinalis. These results warrant further exploration of these plant extracts for their potential in managing diabetes-related metabolic disturbances.

Correlation Between Serum Vitamin E and HOMA-IR in Patients with T2DM

Background

Peroxidation is one of the important causes of insulin resistance (IR), and vitamin E is a natural antioxidant, and there may be some correlation between serum vitamin E levels and insulin resistance.

Purpose

The correlation between serum vitamin E and insulin resistance in type 2 diabetes mellitus (T2DM) population.

Methods

Two hundred and forty-two people (119 with T2DM) were included. One hundred and nineteen patients with T2DM were selected as the case group, and 123 people with non-T2DM were selected as the control group. People insulin resistance was detected by the homeostasis model assessment method (HOMA-IR) greater than 2.69 were included in the diabetic insulin resistance group, and those with HOMA-IR less than 2.69 were included in the diabetic non-insulin resistance group. Record the general body indicators, biochemical indicators, hepatic function indicators, vitamin E, and other indicators. Correlation analysis, logistic regression, trend analysis, and restricted cubic spline (RCS) were performed using SPSS 25.0 and R 4.1.1 software. Correlation analysis, logistic regression, trend analysis, restricted cubic spline (RCS) analysis were conducted on general body indicators, biochemical indicators, hepatic function indicators, vitamin E, and other indicators.

Results

The logistic regression results showed that after adjusting for confounding factors, vitamin E was an independent influencing factor for insulin resistance in T2DM patients (P < 0.001). The trend analysis results show that with the decrease of serum vitamin E levels, the risk of insulin resistance in T2DM patients gradually increases. The RCS results showed that the risk of insulin resistance was significantly increased when the serum vitamin E level was lower than 10,575.23 ng/mL.

Conclusion

Serum vitamin E levels are lower in T2DM patients than in healthy populations; Vitamin E is an independent influencing factor for HOMA-IR in T2DM patients. The risk of insulin resistance gradually increases in T2DM patients as serum vitamin E levels decrease. Vitamin E is a risk factor for insulin resistance at serum vitamin E levels below 10,575.23 ng/mL. At higher serum vitamin E levels than 10,575.23 ng/mL, vitamin E is a protective factor for insulin resistance.

A Narrative Review on Strategies for the Reversion of Prediabetes to Normoglycemia: Food Pyramid, Physical Activity, and Self-Monitoring Innovative Glucose Devices

In 2019, "Nutrition Therapy for Adults with Diabetes or Prediabetes: A Consensus Report" was published. This consensus report, however, did not provide an easy way to illustrate to subjects with prediabetes (SwPs) how to follow a correct dietary approach. The purpose of this review is to evaluate current evidence on optimum dietary treatment of SwPs and to provide a food pyramid for this population. The pyramid built shows that everyday consumption should consist of: whole-grain bread or potatoes eaten with their skins (for fiber and magnesium) and low glycemic index carbohydrates (GI < 55%) (three portions); fruit and vegetables (5 portions), in particular, green leafy vegetables (for fiber, magnesium, and polyphenols); EVO oil (almost 8 g); nuts (30 g, in particular, pistachios and almonds); three portions of dairy products (milk/yogurt: 300-400 g/day); mineral water (almost 1, 5 L/day for calcium intake); one glass of wine (125 mL); and three cups of coffee. Weekly portions should include fish (four portions), white meat (two portions), protein plant-based food (four portions), eggs (egg portions), and red/processed meats (once/week). At the top of the pyramid, there are two pennants: a green one means that SwPs need some personalized supplementation (if daily requirements cannot be satisfied through diet, vitamin D, omega-3, and vitamin B supplements), and a red one means there are some foods and factors that are banned (simple sugar, refined carbohydrates, and a sedentary lifestyle). Three to four times a week of aerobic and resistance exercises must be performed for 30-40 min. Finally, self-monitoring innovative salivary glucose devices could contribute to the reversion of prediabetes to normoglycemia.

Vitamin E and Multiple Health Outcomes: An Umbrella Review of Meta-Analyses

The relationship between vitamin E intake or circulating α-tocopherol and various health outcomes is still debatable and uncertain. We conducted an umbrella review to identify the relationships between vitamin E intake or circulating tocopherol and health outcomes by merging and recalculating earlier meta-analyses. The connections that were found to be statistically significant were then classified into different evidence levels based on p values, between-study heterogeneity, prediction intervals, and small study effects. We finally included 32 eligible meta-analyses with four vitamin E sources and 64 unique health outcomes. Only the association between circulating α-tocopherol and wheeze or asthma in children was substantiated by consistent evidence. Suggestive evidence was suggested for seven results on endothelial function (supplemental vitamin E): serum C-reactive protein (CRP) concentrations (supplemental vitamin E), cervical cancer (dietary vitamin E), esophageal cancer (dietary vitamin E), cervical intraepithelial neoplasia (CIN, dietary vitamin E), pancreatic cancer (total vitamin E intake), and colorectal cancer (circulating α-tocopherol levels); all of these showed a protective effect consistent with the vitamin E source. In conclusion, our work has indicated that vitamin E is protective for several particular health outcomes. Further prospective studies are required when other factors that may contribute to bias are considered.

Plant bioactive compounds from Mediterranean diet improve risk factors for metabolic syndrome

Mediterranean (Med) dietary pattern consists of moderate or high consumption of foods that are linked to reduced risk factors for metabolic syndrome (MetS). This comprehensive review evaluates studies on Med diet-representative foods and beverages, such as red wine and olive oil, to understand the inverse associations of Med diet and MetS. The intake of dietary fibre, unsaturated fatty acids, vitamins, and polyphenols - including flavonoids and stilbenes - help to explain the benefits of Med diet on abdominal adiposity, glucose intolerance, hyperlipidaemia, and high blood pressure to some extent. Antioxidant and anti-inflammatory properties of polyphenols as well as the effects of unsaturated fatty acids on lipid metabolism are part of the underlying mechanisms. Overall, this review shows that dietary interventions using Med diet components improve MetS health markers in humans and/or rodents.

Redox Balance in Type 2 Diabetes: Therapeutic Potential and the Challenge of Antioxidant-Based Therapy

Oxidative stress is an important factor in the development of type 2 diabetes (T2D) and associated complications. Unfortunately, most clinical studies have failed to provide sufficient evidence regarding the benefits of antioxidants (AOXs) in treating this disease. Based on the known complexity of reactive oxygen species (ROS) functions in both the physiology and pathophysiology of glucose homeostasis, it is suggested that inappropriate dosing leads to the failure of AOXs in T2D treatment. To support this hypothesis, the role of oxidative stress in the pathophysiology of T2D is described, together with a summary of the evidence for the failure of AOXs in the management of diabetes. A comparison of preclinical and clinical studies indicates that suboptimal dosing of AOXs might explain the lack of benefits of AOXs. Conversely, the possibility that glycemic control might be adversely affected by excess AOXs is also considered, based on the role of ROS in insulin signaling. We suggest that AOX therapy should be given in a personalized manner according to the need, which is the presence and severity of oxidative stress. With the development of gold-standard biomarkers for oxidative stress, optimization of AOX therapy may be achieved to maximize the therapeutic potential of these agents.

Effect of vitamin E intake on glycemic control and insulin resistance in diabetic patients: an updated systematic review and meta-analysis of randomized controlled trials

Since a 2014 meta-analysis, several randomized controlled trials (RCTs) evaluating the effect of vitamin E intake on glycemic indices and insulin resistance in adults with diabetes have reached inconsistent conclusions. Therefore, we updated the previous meta-analysis to summarize the current evidence in this regard. Online databases including PubMed, Scopus, ISI Web of Science, and Google Scholar were searched to identify relevant studies published up to September 30, 2021, using relevant keywords. Random-effects models were used to obtain overall mean difference (MD) comparing vitamin E intake with a control group. In total, 38 RCTs with a total sample size of 2171 diabetic patients (1110 in vitamin E groups and 1061 in control groups) were included. Combining the results from 28 RCTs on fasting blood glucose, 32 RCTs on HbA1c, 13 RCTs on fasting insulin, and 9 studies on homeostatic model assessment for insulin resistance (HOMA-IR) showed a summary MD of -3.35 mg/dL (95% CI: -8.10 to 1.40, P = 0.16), -0.21% (95% CI: -0.33 to -0.09, P = 0.001), -1.05 µIU/mL (95% CI: -1.53 to -0.58, P < 0.001), and -0.44 (95% CI: -0.82 to -0.05, P = 0.02), respectively. This indicates a significant lowering effect of vitamin E on HbA1c, fasting insulin and HOMA-IR, while no significant effect on fasting blood glucose in diabetic patients. However, in subgroup analyses, we found that vitamin E intake significantly reduced fasting blood glucose in studies with an intervention duration of < 10 weeks. In conclusion, vitamin E intake has a beneficial role in improving HbA1c and insulin resistance in a population with diabetes. Moreover, short-term interventions with vitamin E have resulted in lower fasting blood glucose in these patients. This meta-analysis was registered in PROSPERO with code CRD42022343118.

A meta-analysis of effects of vitamin E supplementation alone and in combination with omega-3 or magnesium on polycystic ovary syndrome

Vitamin E supplementation might have favorable effects on risk factors of polycystic ovary syndrome (PCOS). This systematic review and meta-analysis aimed to summarize the effects of vitamin E supplementation or vitamin E in combination with omega-3 or magnesium on PCOS. PubMed, Scopus, ISI Web of Science, Cochrane, Embase electronic databases, and Google scholar were searched for all available articles up to September 2022. Randomized controlled trials (RCTs) that examined the effect of vitamin E supplementation or vitamin E in combination with omega-3 or magnesium on lipid and glycemic profiles, anthropometric measurements, biomarkers of inflammation and oxidative stress, hormonal profile, and hirsutism score in patients with PCOS were included. Ten RCTs (with 504 participants) fulfilled the eligible criteria. Vitamin E supplementation or vitamin E in combination with omega-3 or magnesium in comparison to placebo could significantly reduce serum levels of TG (weighted mean difference: - 18.27 mg/dL, 95% CI - 34.68 to - 1.87), VLDL (- 5.88 mg/dL, 95% CI - 8.08 to - 3.68), LDL-c (- 12.84 mg/dL, 95% CI - 22.15 to - 3.52), TC (- 16.30 mg/dL, 95% CI - 29.74 to - 2.86), TC/HDL-c ratio (- 0.52, 95% CI - 0.87 to - 0.18), hs-CRP (- 0.60 ng/mL, 95% CI - 0.77 to - 0.44), hirsutism score (- 0.33, 95% CI - 0.65 to - 0.02) and significantly increase nitric oxide levels (2.79 µmol/L, 95% CI 0.79-4.79). No significant effect was found on HDL-c, glycemic indices, hormonal profile, anthropometric measurements, and other biomarkers of inflammation or oxidative stress. This meta-analysis highlights the potential anti-hyperlipidemic, anti-oxidant, and anti-inflammatory properties of vitamin E supplementation alone or in combination with omega-3 or magnesium on PCOS patients.

Influence of biotin intervention on glycemic control and lipid profile in patients with type 2 diabetes mellitus: A systematic review and meta-analysis

Background

Biotin is a water-soluble vitamin acting as a covalently bound coenzyme in regulating energy production. Previous studies have reported that biotin supplementation may influence blood glucose and lipid level in patients with type 2 diabetes mellitus (T2DM).

Methods

We searched Pubmed, Embase, and Cochrane library databases up to 8th August 2022 for studies examining the effects of biotin supplementation in T2DM patients. Pooled effects were measured by weighted mean differences (WMDs) with 95% confidence intervals (CI) using random effects models. Inter-study heterogeneity was assessed and quantified.

Results

A total of five random controlled trials (RCT), involving 445 participants were included. It was suggested that biotin supplementation for 28 to 90 days significantly decreased the level of fasting blood glucose (FBG) (MD: -1.21 mmol/L, 95% CI: -2.73 to 0.31), total cholesterol (TC) (MD: -0.22 mmol/L, 95% CI: -0.25 to -0.19) and triglycerides (TG) (MD: -0.59 mmol/L, 95% CI: -1.21 to 0.03). No significant beneficial effects were observed on insulin (MD: 1.88 pmol/L 95% CI: -13.44 to 17.21). Evidence for the impact of biotin supplementation on the levels of glycated hemoglobin (HbA1c), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C) and very low-density lipoprotein cholesterol (VLDL-C) was limited to draw conclusion.

Conclusions

Biotin supplementation may decrease FBG, TC and TG levels. However, its influence on insulin is not significant and further studies on the effects of biotin on HbA1c, LDL-C, HDL-C and VLDL-C are expected.

Vitamin E supplementation improves testosterone, glucose- and lipid-related metabolism in women with polycystic ovary syndrome: a meta-analysis of randomized clinical trials

AIM

This systematic review and meta-analysis assessed the effect of vitamin E supplementation on testosterone, glucose, lipid profile, pregnancy rate, hirsutism, and body mass index (BMI) in women with polycystic ovary syndrome (PCOS).

METHODS

A multi-database search was performed from inception to January 2022 for randomized controlled trials (RCTs) reporting the effects of vitamin E supplementation with or without another nutritional supplement on women with PCOS. A random-effects model was used to obtain mean differences (MDs) and its 95% confidence intervals (95%CI). Evidence certainty was assessed with GRADE methodology.

RESULTS

We meta-analyzed eight RCTs reporting vitamin E supplementation alone or combined with other individual substances like omega-3, vitamin D3, or magnesium oxide in adult women ≤40 years old with PCOS. Vitamin E supplementation reduced fasting glucose (MD: -1.92 mg/dL, 95%CI: -3.80 to -0.05), fasting insulin (MD: -2.24 µIU/mL, 95%CI: -3.34 to -1.14), HOMA-IR (MD: -0.42, 95%CI: -0.65 to -0.19), total cholesterol (MD: -18.12 mg/dL, 95%CI: -34.37 to -1.86), LDL-cholesterol (MD: -15.92 mg/dL, 95%CI: -29.93 to -1.90), triglycerides (MD: -20.95 mg/dL, 95%CI: -37.31 to -4.58), total testosterone (MD: -0.42 ng/mL, 95%CI: -0.55 to -0.29), and increased sex hormone-binding globulin (MD: 7.44 nmol/L, 95%CI: 2.68 to 12.20). However, it had no impact on female sex hormones, HDL-cholesterol, BMI, and hirsutism. Two RCTs assessed pregnancy and implantation rates with inconsistent results. The certainty of the evidence was very low to moderate.

CONCLUSION

Vitamin E supplementation improves glucose, lipid, and androgenic-related biomarkers in women with PCOS.

Co-Administration of Vitamin E and Atorvastatin Improves Insulin Sensitivity and Peroxisome Proliferator-Activated Receptor-γ Expression in Type 2 Diabetic Patients: A Randomized Double-Blind Clinical Trial

Background

Negative effects of statins on glucose metabolism have been reported. The present study aimed to investigate the effects of co-administration of vitamin E and atorvastatin on glycemic control in hyperlipidemic patients with type 2 diabetes mellitus (T2DM).

Methods

A randomized double-blind clinical trial was conducted at Vali-e-Asr Teaching Hospital (Zanjan, Iran) from July 2017 to March 2018. A total of 30 T2DM female patients were allocated to two groups, namely atorvastatin with placebo (n=15) and atorvastatin with vitamin E (n=15). The patients received daily 20 mg atorvastatin and 400 IU vitamin E or placebo for 12 weeks. Anthropometric and biochemical measures were recorded pre- and post-intervention. Peroxisome proliferator-activated receptor-γ (PPAR-γ) expression was measured in peripheral blood mononuclear cells (PBMCs). Independent sample t test and paired t test were used to analyze between- and within-group variables, respectively. The analysis of covariance (ANCOVA) was used to adjust the effect of baseline variables on the outcomes. P<0.05 was considered statistically significant.

Results

After baseline adjustment, there was a significant improvement in homeostatic model assessment for insulin resistance (HOMA-IR) (P=0.04) and serum insulin (P<0.001) in the atorvastatin with vitamin E group compared to the atorvastatin with the placebo group. In addition, co-administration of vitamin E with atorvastatin significantly upregulated PPAR-γ expression (OR=5.4, P=0.04) in the PBMCs of T2DM patients.

Conclusion

Co-administration of vitamin E and atorvastatin reduced insulin resistance and improved PPAR-γ mRNA expression. Further studies are required to substantiate our findings.

Trial registration number

IRCT 20170918036256N.

Associations of Dietary Antioxidants with Glycated Hemoglobin and Insulin Sensitivity in Adults with and without Type 1 Diabetes

Type 1 diabetes (T1D) has been associated with increased risks of atherosclerotic cardiovascular disease, and poor glycemic control and oxidative stress play a major role in its pathology. There is a lack of data on the role of dietary antioxidant micronutrients, including vitamins and trace elements, in glycemic control in T1D. The aim of this study is to examine associations of dietary intakes of micronutrients with glycemic status. We report data from a cross-sectional analysis from the coronary artery calcification in type 1 diabetes (CACTI) study (n = 1257; T1D: n = 568; nondiabetic controls: n = 689) collected between the years 2000 and 2002. Participants completed a validated food frequency questionnaire, a physical examination, and biochemical analyses. Linear regression was used to examine the associations of dietary antioxidant micronutrients with HbA1c and estimated insulin sensitivity (eIS) in models adjusted for relevant covariates and stratified by diabetes status. In adults with T1D, we observed higher dietary manganese intake associated with higher eIS in the model adjusted for age, sex, diabetes duration, and total calories. In nondiabetic controls, higher intake of manganese associated with lower HbA1c and higher eIS values that persisted in models adjusted for all relevant covariates. On the other hand, dietary copper revealed a positive association with HbA1c in models adjusted for all covariates, except BMI and plasma lipids. No associations were noted for vitamins C and E and dietary carotenoids in either group. These findings reveal dietary antioxidant micronutrients, especially trace elements such as copper and manganese deserve special attention in glycemic control in adults with T1D as well as in nondiabetic controls.This trial is register with NCT00005754.

Systematic review and meta-analyses of vitamin E (alpha-tocopherol) supplementation and blood lipid parameters in patients with diabetes mellitus

BACKGROUND AND AIMS

The studies have shown that α-tocopherol supplementation could improve lipid profile in diabetes mellitus (DM) patients. Nonetheless, the result remains inconsistent. Therefore, this meta-analysis was performed to evaluate the efficacy of α-tocopherol supplement on lipid parameters in DM patients.

METHODS

We conducted an extensive search via Cochrane Library, PubMed, Scopus, and Web of Science databases to acquire the reported RCTs up to October 2020.

RESULTS

The results showed no effects of α-tocopherol supplementation on lipid profile in DM patients except when used ≥12 weeks.

CONCLUSIONS

α-tocopherol supplementation in DM patients had no significant effect on lipid profiles.

Higher intake of microbiota-accessible carbohydrates and improved cardiometabolic risk factors: a meta-analysis and umbrella review of dietary management in patients with type 2 diabetes

BACKGROUND

Microbiota-accessible carbohydrates (MACs) are critical substrates for intestinal microbes; the subsequent production of SCFAs may have some potential benefits for patients with type 2 diabetes mellitus (T2DM).

OBJECTIVES

We conducted a meta-analysis of randomized controlled trials (RCTs) to assess the effects of higher compared with lower MAC intakes on cardiovascular risk factors in T2DM patients and performed an umbrella review of RCTs to evaluate the evidence quality concerning existing dietary T2DM interventions.

METHODS

Publications were identified by searching MEDLINE, EMBASE, and CINAHL. In the meta-analysis, random-effects models were used to calculate pooled estimates, and sensitivity analyses, meta-regression, subgroup analyses, and Egger's test were performed. For the umbrella review, we summarized pooled estimates, 95% CIs, heterogeneity, and publication bias. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) and modified NutriGrade were used to assess the quality of evidence in the meta-analysis and umbrella review, respectively.

RESULTS

Forty-five RCTs with 1995 participants were included in the meta-analysis. High MAC intake significantly reduced glycated hemoglobin (HbA1c) (weighted mean difference [WMD] -0.436% [-0.556, -0.315]), fasting glucose (WMD -0.835 mmol/L [-1.048, -0.622]), total cholesterol (WMD -0.293 mmol/L [-0.397, -0.190]), triglycerides (WMD -0.118 mmol/L [-0.308, -0.058]), BMI (WMD -0.476 [-0.641, -0.312]), and systolic blood pressure (WMD -3.066 mmHg [-5.653, -0.478]), with a moderate-to-high quality of evidence, compared with low intake. Region, dose, and MAC type were key variables. The umbrella review of all dietary interventions for cardiovascular risk factors in patients with T2DM included 26 meta-analyses with 158 pooled estimates. The evidence quality of MACs, dietary fiber, high-protein diet, ω-3 (n-3), viscous fiber, vitamin D, and vitamin E intake was moderate to high.

CONCLUSIONS

When compared with lower intake, increased MAC intake improved glycemic control, blood lipid, body weight, and inflammatory markers for people with T2DM. This trial was registered at PROSPERO (https://www.crd.york.ac.uk/PROSPERO/#recordDetails) as CRD42019120531.

Independent predictors of insulin resistance in Brazilian adolescents: Results of the study of cardiovascular risk in adolescents-Brazil

Considering the current changes in dietary patterns and the increasing prevalence of excess weight throughout the world, several studies have reported insulin resistance, which is a key driver of many chronic diseases, to be an important public health problem in all age groups. Therefore, the aim of the present study was to identify the prevalence and independent predictors of insulin resistance in Brazilian adolescents. A cross-sectional study was conducted with a probabilistic, representative sample of Brazilian adolescents (n = 37,023) who participated in the Study of Cardiovascular Risk in Adolescents. Data were collected on demographic, socioeconomic, lifestyle, anthropometric, and biochemical characteristics as well as antioxidant micronutrient intake (vitamins A, C, E, zinc, and selenium). Insulin resistance was determined using the Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and classified based on the 75th percentile of the sample distribution. Insulin resistance was detected in 27% of the adolescents and was more prevalent among those aged 12 to 14 years (PR: 1.26 [95%CI: 1.13;1.41]), those residing in the southern and south-eastern regions of the country (PR: 1.47 [95%CI: 1.27;1.70]), those who were physically inactive (PR: 1.12 [95%CI: 1.02;1.23]), and those did not consume alcohol (PR: 1.50 [95%CI: 1.13;1.99]). The prevalence of insulin resistance was 2.5-fold higher among individuals with severe obesity (PR: 2.49 [95%CI: 2.07;3.00]). Waist circumference indicative of cardiovascular risk and high serum triglyceride levels increased the likelihood of insulin resistance (PR: 1.37 [95%CI: 1.19;1.59] and 1.60 [95%CI: 1.45;1.78], respectively). The prevalence of the outcome was higher among adolescents in the lower quartiles of vitamin E intake (p<0.05). In the present study, the prevalence of insulin resistance was high among Brazilian adolescents and we identified sociodemographic, lifestyle, anthropometric, biochemical, and dietary predictors of this outcome.

A Phase IIb Randomized Controlled Trial Investigating the Effects of Tocotrienol-Rich Vitamin E on Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a debilitating complication of diabetes, which develops in 40% of the diabetic population and is responsible for up to 50% of end-stage renal disease (ESRD). Tocotrienols have shown to be a potent antioxidant, anti-inflammatory, and antifibrotic agent in animal and clinical studies. This study evaluated the effects of 400 mg tocotrienol-rich vitamin E supplementation daily on 59 DKD patients over a 12-month period. Patients with stage 3 chronic kidney disease (CKD) or positive urine microalbuminuria (urine to albumin creatinine ratio; UACR > 20–200 mg/mmol) were recruited into a randomized, double-blind, placebo-controlled trial. Patients were randomized into either intervention group (n = 31) which received tocotrienol-rich vitamin E (Tocovid SupraBio^TM; Hovid Berhad, Ipoh, Malaysia) 400 mg daily or a placebo group which received placebo capsules (n = 28) for 12 months. HbA1c, renal parameters (i.e., serum creatinine, eGFR, and UACR), and serum biomarkers were collected at intervals of two months. Tocovid supplementation significantly reduced serum creatinine levels (MD: −4.28 ± 14.92 vs. 9.18 ± 24.96), p = 0.029, and significantly improved eGFR (MD: 1.90 ± 5.76 vs. −3.29 ± 9.24), p = 0.011 after eight months. Subgroup analysis of 37 patients with stage 3 CKD demonstrated persistent renoprotective effects over 12 months; Tocovid improved eGFR (MD: 4.83 ± 6.78 vs. −1.45 ± 9.18), p = 0.022 and serum creatinine (MD: −7.85(20.75) vs. 0.84(26.03), p = 0.042) but not UACR. After six months post washout, there was no improvement in serum creatinine and eGFR. There were no significant changes in the serum biomarkers, TGF-β1 and VEGF-A. Our findings verified the results from the pilot phase study where tocotrienol-rich vitamin E supplementation at two and three months improved kidney function as assessed by serum creatinine and eGFR but not UACR.

The Influence of Gender and Menopausal Status on Hba1c Variation in a Big Data Study of a Saudi Population

BACKGROUND

Glycated haemoglobin (HbA1c) is the gold standard measurement in the screening, diagnosis and monitoring of diabetes mellitus. Saudi Arabia has a high prevalence of diabetes mellitus that is expected to rise, and the HbA1c test is commonly used in the screening, diagnosis and monitoring of diabetes.

OBJECTIVE

This study aims to assess the impact of age and gender on HbA1c levels, and the influence of menopausal status on HbA1c variation in a large group of Saudis.

METHODS

Age, gender, and HbA1c results of 168,614 Saudi adult individuals were obtained from their medical records. Patients' records were extracted irrespective of their status regarding the presence of diabetes and the status of glycaemic control. Linear regression models were used for predicting HbA1c from age and gender, and their interaction term. HbA1c levels were compared between genders in different age groups and different HbA1c categories.

RESULTS

There was a statistically significant positive correlation between age and HbA1c levels, where for each ten years increase in age, HbA1c increased by 0.35%. Although the overall mean HbA1c in women was significantly lower than in men (P < 0.001), women showed a significant increase in HbA1c with older age compared to men (B = 0.014, P < 0.001). Furthermore, the mean HbA1c levels in the age group > 50 years was significantly higher than before that age (P < 0.001). Thus, HbA1c increased by 1.118% in age > 50 years group compared to age ≤ 50 years, and this increase in HbA1c was significantly higher in women compared to men (B = 0.495, P < 0.001).

CONCLUSION

HbA1c levels are lower in women before the estimated menopausal age, which should be taken into consideration when using HbA1c for screening, diagnosis, and monitoring of diabetes in Saudi adult women. The short lifespan of red blood cells, due to loss of blood through menstruation, in women before menopause age, is a possible reason for these variations.

Cardiovascular and Metabolic Protection by Vitamin E: A Matter of Treatment Strategy?

Cardiovascular diseases (CVD) cause about 1/3 of global deaths. Therefore, new strategies for the prevention and treatment of cardiovascular events are highly sought-after. Vitamin E is known for significant antioxidative and anti-inflammatory properties, and has been studied in the prevention of CVD, supported by findings that vitamin E deficiency is associated with increased risk of cardiovascular events. However, randomized controlled trials in humans reveal conflicting and ultimately disappointing results regarding the reduction of cardiovascular events with vitamin E supplementation. As we discuss in detail, this outcome is strongly affected by study design, cohort selection, co-morbidities, genetic variations, age, and gender. For effective chronic primary and secondary prevention by vitamin E, oxidative and inflammatory status might not have been sufficiently antagonized. In contrast, acute administration of vitamin E may be more translatable into positive clinical outcomes. In patients with myocardial infarction (MI), which is associated with severe oxidative and inflammatory reactions, decreased plasma levels of vitamin E have been found. The offsetting of this acute vitamin E deficiency via short-term treatment in MI has shown promising results, and, thus, acute medication, rather than chronic supplementation, with vitamin E might revitalize vitamin E therapy and even provide positive clinical outcomes.

Ascorbic Acid and Alpha-Tocopherol Contribute to the Therapy of Polycystic Ovarian Syndrome in Mouse Models

Polycystic ovary syndrome (PCOS) affects up to 10% of women within reproductive ages and has been a cause of infertility and poor quality of life. Alteration in the oxidant-antioxidant profile occurs in PCOS. This study, therefore, investigates the contribution of ascorbic acid (AA) and alpha-tocopherol(ATE) on different PCOS parameters. The mifepristone and letrozole models were used, and young mature female mice were randomly assigned to groups of six per group. On PCOS induction with either mifepristone or letrozole, mice were administered AA and ATE at doses ranging from 10-1000mg/kg to 0.1-1000 mg/kg in the respective models. Vaginal cytology, body weights, and temperature, as well as blood glucose, testosterone, and insulin levels, were measured. Total antioxidant capacity and malondialdehyde levels were analyzed. Determination of gene expression of some reactive oxygen species and histomorphological analysis on the ovaries and uteri were performed. At the end of the experiments, AA and ATE restored reproductive cycling, with AA being more effective. AA and ATE increased fasting blood glucose but had no significant effect on serum insulin levels. AA decreased testosterone levels, but ATE caused slight increases. AA and ATE both increased total antioxidant capacity and decreased malondialdehyde levels. AA and ATE also slightly upregulated the mRNA expressions of catalase, superoxide dismutase, and heme oxygenase 1 mainly. AA and ATE also decreased ovarian weight and mostly resolved cysts in the ovaries and congestion in the uterus. This study has shown that AA and ATE are beneficial in the therapy of PCOS.

Combined effect of high-dose vitamin A, vitamin E supplementation, and zinc on adult patients with diabetes: A randomized trial

In type 2 diabetes mellitus (T2DM), hyperglycemia leads to oxidative insult. Vitamins A and E have antioxidant potentials and may help in managing diabetes. The combined effect of high-dose vitamin A plus E supplementation with and without zinc on T2DM, has never been examined. Thus, this study aimed to evaluate and compare the effect of high-dose vitamin A plus E supplementation (AE) versus high-dose vitamin A plus E with zinc (AEZ), on different diabetic parameters. Ninety-eight patients with T2DM were randomized to receive either: 50,000 IU vitamin A and 100 mg vitamin E (AE group, N = 36), an equivalent dose of vitamin A and E combined with 25 mg zinc (AEZ group, N = 35), or no supplements (control group, N = 27) for three months. Compared to control, AEZ group showed significant reductions in fasting blood glucose, 2 h postprandial blood glucose, and glycated hemoglobin (HbA1c) with significant increases in homeostasis model assessment of beta-cell function and difference value of fasting insulin. Two hair loss cases were recorded in both treated groups. Although vitamin A needs dose moderation, these results suggest that, high-dose vitamin A plus E supplementation combined with zinc may improve glycemic control, β-cell function, and insulin secretion in adults with T2DM.

Tocotrienol-rich vitamin E improves diabetic nephropathy and persists 6-9 months after washout: a phase IIa randomized controlled trial

Chronic hyperglycemia in type 2 diabetes mellitus increases oxidative stress and inflammation which contributes to long-term diabetic kidney disease. Tocotrienol-rich vitamin E, as Tocovid, has been shown to reduce oxidative stress and inflammation to ameliorate diabetes in rat models and human subjects. In this prospective, multicenter, double-blinded, placebo-controlled clinical trial, 54 patients (duration = 18.4 years, HbA1c = 8.8%) with diabetic nephropathy were randomized to receive Tocovid 200 mg or placebo for 12 weeks. Fasting blood samples were taken to measure HbA1c, serum creatinine, estimate glomerular filtration rate (eGFR), urine albumin:creatinine ratio, malondialdehyde, tumor necrosis factor receptor-1, vascular cell adhesion molecule-1 (VCAM-1), and thromboxane-B2. Patients were reassessed 6-9 months post-washout. After 12 weeks of supplementation, Tocovid significantly decreased serum creatinine levels (mean difference: -3.3 ± 12.6 versus 5.4 ± 14.2, p = 0.027) and significantly increase eGFR (mean difference: 1.5 ± 7.6 versus -2.9 ± 8.0, p = 0.045) compared with placebo. There were no significant changes in HbA1c, blood pressure, and other parameters. Subgroup analysis revealed that in patients with low serum vitamin E concentrations at baseline, Tocovid reduced serum creatinine, eGFR, and VCAM-1 significantly. After 6-9 months of washout, persistent difference in serum creatinine remained between groups (mean difference: 0.82 ± 8.33 versus 11.26 ± 15.47, p = 0.031), but not eGFR. Tocovid at 400 mg/day significantly improved renal function in 12 weeks of supplementation, as assessed by serum creatinine and eGFR, which remained significant 6-9 months post-washout.

Dietary Patterns Emphasizing the Consumption of Plant Foods in the Management of Type 2 Diabetes: A Narrative Review

The prevalence of type 2 diabetes (T2D) is increasing worldwide. This complex and multifactorial metabolic condition affects both the quality and expectancy of life in adults. Therefore, appropriate lifestyle strategies are needed in order to reduce the burden of T2D. Dietary patterns characterized by a high consumption of fruits, vegetables, whole grains, legumes, nuts, and seeds, and a minimal consumption of animal products, have been suggested as a dietary approach to prevent and control T2D and related micro- and macrovascular complications. This narrative review summarizes epidemiologic and clinical trial evidence on the role of the most widely studied dietary patterns that emphasize the consumption of plant foods [vegetarian, vegan, Mediterranean, and DASH (Dietary Approaches to Stop Hypertension) diets] in the management of T2D and its complications. Furthermore, their potential underlying mechanisms are discussed. Dietary patterns emphasizing the consumption of plant foods appear to confer beneficial effects on glycemic control in different diabetic populations. Several components of these dietary patterns might confer benefits on glycemia and counterbalance the detrimental effects of animal-based foods. The limited evidence on T2D-related complications makes it difficult to draw solid conclusions.

Antioxidant, Anti-Inflammatory, and Metabolic Properties of Tocopherols and Tocotrienols: Clinical Implications for Vitamin E Supplementation in Diabetic Kidney Disease

Diabetes mellitus is a metabolic disorder characterized by the development of vascular complications associated with high morbidity and mortality and the consequent relevant costs for the public health systems. Diabetic kidney disease is one of these complications that represent the main cause of end-stage renal disease in Western countries. Hyperglycemia, inflammation, and oxidative stress contribute to its physiopathology, and several investigations have been performed to evaluate the role of antioxidant supplementation as a complementary approach for the prevention and control of diabetes and associated disturbances. Vitamin E compounds, including different types of tocopherols and tocotrienols, have been considered as a treatment to tackle major cardiovascular outcomes in diabetic subjects, but often with conflicting or even negative results. However, their effects on diabetic nephropathy are even less clear, despite several intervention studies that showed the improvement of renal parameters after supplementation in patients with diabetic kidney disease. Then we performed a review of the literature about the role of vitamin E supplementation on diabetic nephropathy, also describing the underlying antioxidant, anti-inflammatory, and metabolic mechanisms to evaluate the possible use of tocopherols and tocotrienols in clinical practice.

Plasma metabolites associated with homeostatic model assessment of insulin resistance: metabolite-model design and external validation

Different plasma metabolites have been related to insulin resistance (IR). However, there is a lack of metabolite models predicting IR with external validation. The aim of this study is to identify a multi-metabolite model associated to the homeostatic model assessment (HOMA)-IR values. We performed a cross-sectional metabolomics analysis of samples collected from overweight and obese subjects from two independent studies. The training step was performed in 236 subjects from the SATIN study and validated in 102 subjects from the GLYNDIET study. Plasma metabolomics profile was analyzed using three different approaches: GC/quadrupole-TOF, LC/quadrupole-TOF, and nuclear magnetic resonance (NMR). Associations between metabolites and HOMA-IR were assessed using elastic net regression analysis with a leave-one-out cross validation (CV) and 100 CV runs. HOMA-IR was analyzed both as linear and categorical (median or lower versus higher than the median). Receiver operating characteristic curves were constructed based on metabolites’ weighted models. A set of 30 metabolites discriminating extremes of HOMA-IR were consistently selected. These metabolites comprised some amino acids, lipid species and different organic acids. The area under the curve (AUC) for the discrimination between HOMA-IR extreme categories was 0.82 (95% CI: 0.74–0.90), based on the multi-metabolite model weighted with the regression coefficients of metabolites in the validation dataset. We identified a set of metabolites discriminating between extremes of HOMA-IR and able to predict HOMA-IR with high accuracy.

Dietary Approaches to Stop Hypertension (DASH): potential mechanisms of action against risk factors of the metabolic syndrome

The metabolic syndrome is a cluster of disorders dominated by abdominal obesity, hypertriacylglycerolaemia, low HDL-cholesterol, high blood pressure and high fasting glucose. Diet modification is a safe and effective way to treat the metabolic syndrome. Dietary Approaches to Stop Hypertension (DASH) is a dietary pattern rich in fruits, vegetables and low-fat dairy products, and low in meats and sweets. DASH provides good amounts of fibre, K, Ca and Mg, and limited quantities of total fat, saturated fat, cholesterol and Na. Although DASH was initially designed for the prevention or control of hypertension, using a DASH diet has other metabolic benefits. In the present review, the effect of each dietary component of DASH on the risk factors of the metabolic syndrome is discussed. Due to limited fat and high fibre and Ca content, individuals on the DASH diet are less prone to overweight and obesity and possess lower concentrations of total and LDL-cholesterol although changes in TAG and HDL-cholesterol have been less significant and available evidence in this regard is still inconclusive. Moreover, high amounts of fruit and vegetables in DASH provide great quantities of K, Mg and fibre, all of which have been shown to reduce blood pressure. K, Mg, fibre and antioxidants have also been effective in correcting glucose and insulin abnormalities. Evidence is provided from cross-sectional investigations, cohort studies and randomised controlled trials, and, where available, from published meta-analyses. Mechanisms are described according to human studies and, in the case of a lack of evidence, from animal and cell culture investigations.

The effects of magnesium and vitamin E co-supplementation on wound healing and metabolic status in patients with diabetic foot ulcer: A randomized, double-blind, placebo-controlled trial

This study was carried out to determine the effects of magnesium and vitamin E co-supplementation on wound healing and metabolic status in patients with diabetic foot ulcer (DFU). The current randomized, double-blind, placebo-controlled trial was conducted among 57 patients with grade 3 DFU. Participants were randomly divided into two groups to take either 250 mg magnesium oxide plus 400 IU vitamin E (n = 29) or placebo per day (n = 28) for 12 weeks. Compared with the placebo, taking magnesium plus vitamin E supplements reduced ulcer length (β [difference in the mean of outcomes measures between treatment groups] -0.56 cm; 95% CI, -0.92, -0.20; p = 0.003), width (β -0.35 cm; 95% CI, -0.64, -0.05; p = 0.02) and depth (β -0.18 cm; 95% CI, -0.33, -0.02; p = 0.02). In addition, co-supplementation led to a significant reduction in fasting plasma glucose (β -13.41 mg/dL; 95% CI, -20.96, -5.86; p = 0.001), insulin (β -1.45 μIU/ml; 95% CI, -2.37, -0.52; p = 0.003), insulin resistance (β -0.60; 95% CI, -0.99, -0.20; p = 0.003) and HbA1c (β -0.32%; 95% CI, -0.48, -0.16; p < 0.003), and a significant elevation in insulin sensitivity (β 0.007; 95% CI, 0.003, 0.01; p < 0.001) compared with the placebo. Additionally, compared with the placebo, taking magnesium plus vitamin E supplements decreased triglycerides (β -10.08 mg/dL; 95% CI, -19.70, -0.46; p = 0.04), LDL-cholesterol (β -5.88 mg/dL; 95% CI, -11.42, -0.34; p = 0.03), high sensitivity C-reactive protein (hs-CRP) (β -3.42 mg/L; 95% CI, -4.44, -2.41; p < 0.001) and malondialdehyde (MDA) (β -0.30 μmol/L; 95% CI, -0.45, -0.15; p < 0.001), and increased HDL-cholesterol (β 2.62 mg/dL; 95% CI, 0.60, 4.63; p = 0.01) and total antioxidant capacity (TAC) levels (β 53.61 mmol/L; 95% CI, 4.65, 102.57; p = 0.03). Overall, magnesium and vitamin E co-supplementation for 12 weeks to patients with DFU had beneficial effects on ulcer size, glycemic control, triglycerides, LDL- and HDL-cholesterol, hs-CRP, TAC, and MDA levels.

HbA1c: a review of non-glycaemic variables

Identification of the correlation between HbA1c and diabetic complications has yielded one of the most clinically useful biomarkers. HbA1c has revolutionised the diagnosis and monitoring of diabetes mellitus. However, with widespread adoption of HbA1c has come increasing recognition that non-glycaemic variables can also affect HbA1c, with varying clinical significance. Furthermore, the identification of a discrepancy between predicted and measured HbA1c in some individuals, the so-called 'glycation gap', may be clinically significant. We aimed to review the current body of evidence relating to non-glycaemic variables to quantify any significance and provide subsequent suggestions. A PubMed-based literature search was performed, using a variety of search terms, to retrieve articles detailing the non-glycaemic variables suggested to affect HbA1c. Articles were reviewed to assess the relevance of any findings in clinical practice and where possible guidance is given. A range of non-glycaemic variables have statistically significant effects on HbA1c. While the clinical implications are generally irrelevant, a small number of non-glycaemic variables do have clinically significant effects and alternative biomarkers should be considered instead of, or in addition to, HbA1c. There are a small number of non-glycaemic variables which have a clinically significant effect on HbA1c, However, the vast majority of non-glycaemic variables have no clinical relevance. While clinicians should have an awareness of those non-glycaemic variables with clinical significance, in the vast majority of clinical scenarios HbA1c should continue to be used with confidence.

The effects of magnesium and vitamin E co-supplementation on parameters of glucose homeostasis and lipid profiles in patients with gestational diabetes

BACKGROUND

Magnesium and vitamin E are known to exert multiple beneficial effects, such as anti-glycemic and anti-lipidemic properties. The aim of this study was to determine the effects of magnesium and vitamin E co-supplementation on metabolic status of women with gestational diabetes (GDM).

METHODS

This randomized, double-blinded, placebo-controlled trial was conducted among 60 subjects diagnosed with GDM, aged 18-40 years. Subjects were randomly allocated into two groups to receive 250 mg/day magnesium oxide plus 400 IU/day vitamin E supplements or placebo (n = 30 each group) for 6 weeks. Participants' blood samples were taken to determine their metabolic profiles.

RESULTS

Subjects who received magnesium plus vitamin E supplements had significantly lower fasting plasma glucose (β - 5.20 mg/dL; 95% CI, - 7.88, - 2.52; P = 0.002), serum insulin levels (β - 2.93 μIU/mL; 95% CI, - 5.68, - 0.18; P = 0.02) and homeostasis model of assessment-insulin resistance (β - 0.78; 95% CI, - 1.42, - 0.14; P = 0.01), and higher quantitative insulin sensitivity check index (β 0.01; 95% CI, 0.005, 0.02; P = 0.002) compared with placebo. In addition, magnesium plus vitamin E supplementation resulted in a significant reduction in serum triglycerides (β - 50.31 mg/dL; 95% CI, - 67.58, - 33.04; P < 0.001), VLDL- (β - 10.06 mg/dL; 95% CI, - 13.51, - 6.60; P < 0.001), total- (β - 26.10 mg/dL; 95% CI, - 41.88, - 10.33; P = 0.004), LDL- (β - 15.20 mg/dL; 95% CI, - 29.50, - 0.91; P = 0.03) and total-/HDL-cholesterol ratio (β - 0.46; 95% CI, - 0.72, - 0.19; P < 0.001) compared with placebo. Magnesium and vitamin E co-supplementation did not affect HDL-cholesterol levels.

CONCLUSIONS

Overall, magnesium and vitamin E co-supplementation for 6 weeks in women with GDM significantly improved glycemic control and lipid profiles, except for HDL-cholesterol levels.

CLINICAL TRIAL REGISTRATION NUMBER

http://www.irct.ir : IRCT20170513033941N24.

α-Tocopherol influences glycaemic control and miR-9-3 DNA methylation in overweight and obese women under an energy-restricted diet: a randomized, double-blind, exploratory, controlled clinical trial

Background

Excess weight is a strong risk factor for the development of dysglycaemia. It has been suggested that changes in the metabolism microRNAs, small non-coding RNAs that regulate gene expression, could precede late glycaemic changes. Vitamin E in turn may exert important functions in methylation and gene expression processes. This study aimed to determine the effect of α-tocopherol on glycaemic variables and miR-9-1 and miR-9-3 promoter DNA methylation in overweight women.

Methods

A randomized, double-blind, exploratory, placebo-controlled study was conducted in overweight and obese adult women (n = 44) who ingested synthetic vitamin E (all-rac-α-tocopherol), natural source vitamin E (RRR-rac-α-tocopherol) or placebo capsules and were followed up for a period of 8 weeks. Supplemented groups also received dietary guidance for an energy-restricted diet. An additional group that received no supplementation and did not follow an energy-restricted diet was also followed up. The intervention effect was evaluated by DNA methylation levels (quantitative real-time PCR assay) and anthropometric and biochemical variables (fasting plasma glucose, haemoglobin A1C, insulin, and vitamin E).

Results

Increased methylation levels of the miR-9-3 promoter region (P < 0.001) and reduced haemoglobin A1C (P < 0.05) were observed in the natural source vitamin E group after intervention. Increased fasting plasma glucose was observed in the synthetic vitamin E group, despite the significant reduction of anthropometric variables compared to the other groups.

Conclusions

α-Tocopherol from natural sources increased methylation levels of the miR-9-3 promoter region and reduced haemoglobin A1C in overweight women following an energy-restricted diet. These results provide novel information about the influence of vitamin E on DNA methylation.

Trial registration

ClinicalTrials.gov, NCT02922491. Registered 4 October, 2016.

Electronic supplementary material

The online version of this article (10.1186/s12986-018-0286-7) contains supplementary material, which is available to authorized users.

Prebiotics, Prosynbiotics and Synbiotics: Can They Reduce Plasma Oxidative Stress Parameters? A Systematic Review

This study assessed the effectiveness of presybiotics, prosybiotics and synbiotics on reducing serum oxidative stress parameters. PubMed/Medline, Ovid, Google Scholar, ISI Web of Science and SCOPUS were searched up to September 2016. English language randomized clinical trials reporting the effect of presybiotics, prosybiotics or synbiotic interventions on serum oxidative stress parameters in human adults were included. Twenty-one randomized clinical trials met the inclusion criteria for systematic review. Two studies investigated prebiotics, four studies synbiotics and fifteen studies probiotics. According to our systematic review, prebiotic could decrease malondialdehyde and increase superoxidative dismutase, but evidence is not enough. In comparison with fructo-oligosaccharide, inulin is much more useful for oxidative stress reduction. Using probiotics with dairy products could reduce oxidative stress significantly, but probiotic in form of supplementation did not have any effect on oxidative stress. There is limited but supportive evidence that presybiotics, prosybiotics and synbiotics are effective for reducing oxidative stress parameters. Further randomized clinical trials with longer duration of intervention especially on population with increased oxidative stress are needed to provide more definitive results before any recommendation for clinical use of these interventions.

Antioxidant effects of vitamins in type 2 diabetes: a meta-analysis of randomized controlled trials

BACKGROUND

Vitamins are essential micronutrients with antioxidant potential that may provide a complementary treatment for patients with chronic diseases. Our aim was to assess the effect of vitamin supplementation on the antioxidant status and glycemic index of type 2 diabetes mellitus patients.

METHODS

We performed a systematic review with meta-analyses. Electronic searches were conducted in PubMed, Scopus, and Web of Science (December 2017). Randomized controlled trials evaluating the effect of any vitamin or vitamin complex supplementation on antioxidant status as primary outcome were included. The outcomes considered were: reduction of malondialdehyde (MDA); augmentation of glutathione peroxidase (GPx); changes in total antioxidant capacity (TAC), enhance in superoxide dismutase enzyme-SOD, and thiobarbituric acid reactive substances (TBARS). Outcomes of glycemic control were also evaluated. Pairwise meta-analyses were performed using software Review Manager 5.3.

RESULTS

Thirty trials fulfilled the inclusion criteria, but only 12 could be included in the meta-analyses of antioxidant outcomes. The most commonly studied vitamins were B, C, D and E. Vitamin E was related to significant reduction of blood glucose as well as glycated hemoglobin compared to placebo, while both vitamins C and E were mainly associated with reducing MDA and TBARS and elevating GPx, SOD and TAC, compared to placebo. However, outcome reports in this field are still inconsistent (e.g. because of a lack of standard measures).

CONCLUSIONS

Supplementation of vitamin E may be a valuable strategy for controlling diabetes complications and enhancing antioxidant capacity. The effects of other micronutrients should be further investigated in larger and well-designed trials to properly place these complementary therapies in clinical practice.

Clinical and Vitamin Response to a Short-Term Multi-Micronutrient Intervention in Brazilian Children and Teens: From Population Data to Interindividual Responses

SCOPE

Micronutrients are in small amounts in foods, act in concert, and require variable amounts of time to see changes in health and risk for disease. These first principles are incorporated into an intervention study designed to develop new experimental strategies for setting target recommendations for food bioactives for populations and individuals.

METHODS AND RESULTS

A 6-week multivitamin/mineral intervention is conducted in 9-13 year olds. Participants (136) are (i) their own control (n-of-1); (ii) monitored for compliance; (iii) measured for 36 circulating vitamin forms, 30 clinical, anthropometric, and food intake parameters at baseline, post intervention, and following a 6-week washout; and (iv) had their ancestry accounted for as modifier of vitamin baseline or response. The same intervention is repeated the following year (135 participants). Most vitamins respond positively and many clinical parameters change in directions consistent with improved metabolic health to the intervention. Baseline levels of any metabolite predict its own response to the intervention. Elastic net penalized regression models are identified, and significantly predict response to intervention on the basis of multiple vitamin/clinical baseline measures.

CONCLUSIONS

The study design, computational methods, and results are a step toward developing recommendations for optimizing vitamin levels and health parameters for individuals.

Effect of Vitamin E and omega 3 fatty acids in type 2 diabetes mellitus patients

Diabetes mellitus (DM) and its complications have been implicated in hyperglycemia-induced oxidative stress. Antioxidants can improve glycemic control, lipid profile, and cognitive functions. We assessed the effect of Vitamin E and omega 3 fatty acids (OFA) on the above parameters. One hundred patients with type 2 DM receiving metformin 500 mg and glimepiride 1 mg were randomized to receive add-on therapy of Vitamin E 400 mg or OFA once daily for 12 weeks and the third group served as control. Fasting blood sugar (FBS), postprandial blood sugar (PPBS), glycated hemoglobin (HbA1c), body mass index (BMI), waist-hip ratio (WHR), lipid profile, and mini-mental state examination were done at baseline and 12 weeks. Eighty-seven patients completed the study. A significant reduction in FBS, PPBS, and HbA1c was observed in all the three groups at 12 weeks. There was significant reduction in total cholesterol and triglycerides (TG) in patients receiving either of the antioxidants and also significant reduction in low-density lipoprotein in patients receiving OFA at 12 weeks compared to baseline. BMI and WHR were significantly increased in control group. Intergroup analysis showed that in patients receiving Vitamin E and OFA, the reduction of FBS, PPBS, and HbA1c were similar. The patients receiving OFA had significant reduction in TG compared to control. There was no significant effect on cognitive function. Vitamin E and OFA had beneficial effects on lipid profile and anthropometric measurements; however, the glycemic control was similar to the patients in control group.

Biomarkers of food intake and nutrient status are associated with glucose tolerance status and development of type 2 diabetes in older Swedish women

Background: Diet is frequently associated with both the development and prevention of type 2 diabetes (T2D), but there is a lack of objective tools for assessing the relation between diet and T2D. Biomarkers of dietary intake are unconfounded by recall and reporting bias, and using multiple dietary biomarkers could help strengthen the link between a healthy diet and the prevention of T2D.Objective: The objective of this study was to explore how diet is related to glucose tolerance status (GTS) and to future development of T2D irrespective of common T2D and cardiovascular disease risk factors by using multiple dietary biomarkers.Design: Dietary biomarkers were measured in plasma from 64-y-old Swedish women with different GTS [normal glucose tolerance (NGT; n = 190), impaired glucose tolerance (IGT; n = 209), and diabetes (n = 230)]. The same subjects were followed up after 5 y to determine changes in glucose tolerance (n = 167 for NGT, n = 174 for IGT, and n = 159 for diabetes). ANCOVA and logistic regression were used to explore baseline data for associations between dietary biomarkers, GTS, and new T2D cases at follow-up (n = 69).Results: Of the 10 dietary biomarkers analyzed, β-alanine (beef) (P-raw < 0.001), alkylresorcinols C17 and C19 (whole-grain wheat and rye) (P-raw = 0.003 and 0.011), eicosapentaenoic acid (fish) (P-raw = 0.041), 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) (fish) (P-raw = 0.002), linoleic acid (P-raw < 0.001), oleic acid (P-raw = 0.003), and α-tocopherol (margarine and vegetable oil) (P-raw < 0.001) were associated with GTS, and CMPF (fish) (OR: 0.72; 95% CI: 0.56, 0.93; P-raw = 0.013) and α-tocopherol (OR: 0.71; 95% CI: 0.51, 0.98; P-raw = 0.041) were inversely associated with future T2D development.Conclusions: Several circulating dietary biomarkers were strongly associated with GTS after correction for known T2D risk factors, underlining the role of diet in the development and prevention of T2D. To our knowledge, this study is the first to use multiple dietary biomarkers to investigate the link between diet and disease risk.

Early metabolic markers identify potential targets for the prevention of type 2 diabetes

AIMS/HYPOTHESIS

The aims of this study were to evaluate systematically the predictive power of comprehensive metabolomics profiles in predicting the future risk of type 2 diabetes, and to identify a panel of the most predictive metabolic markers.

METHODS

We applied an unbiased systems medicine approach to mine metabolite combinations that provide added value in predicting the future incidence of type 2 diabetes beyond known risk factors. We performed mass spectrometry-based targeted, as well as global untargeted, metabolomics, measuring a total of 568 metabolites, in a Finnish cohort of 543 non-diabetic individuals from the Botnia Prospective Study, which included 146 individuals who progressed to type 2 diabetes by the end of a 10 year follow-up period. Multivariate logistic regression was used to assess statistical associations, and regularised least-squares modelling was used to perform machine learning-based risk classification and marker selection. The predictive performance of the machine learning models and marker panels was evaluated using repeated nested cross-validation, and replicated in an independent French cohort of 1044 individuals including 231 participants who progressed to type 2 diabetes during a 9 year follow-up period in the DESIR (Data from an Epidemiological Study on the Insulin Resistance Syndrome) study.

RESULTS

Nine metabolites were negatively associated (potentially protective) and 25 were positively associated with progression to type 2 diabetes. Machine learning models based on the entire metabolome predicted progression to type 2 diabetes (area under the receiver operating characteristic curve, AUC = 0.77) significantly better than the reference model based on clinical risk factors alone (AUC = 0.68; DeLong's p = 0.0009). The panel of metabolic markers selected by the machine learning-based feature selection also significantly improved the predictive performance over the reference model (AUC = 0.78; p = 0.00019; integrated discrimination improvement, IDI = 66.7%). This approach identified novel predictive biomarkers, such as α-tocopherol, bradykinin hydroxyproline, X-12063 and X-13435, which showed added value in predicting progression to type 2 diabetes when combined with known biomarkers such as glucose, mannose and α-hydroxybutyrate and routinely used clinical risk factors.

CONCLUSIONS/INTERPRETATION

This study provides a panel of novel metabolic markers for future efforts aimed at the prevention of type 2 diabetes.

Gene-Diet Interactions in Type 2 Diabetes: The Chicken and Egg Debate

Consistent evidence from both experimental and human studies indicates that Type 2 diabetes mellitus (T2DM) is a complex disease resulting from the interaction of genetic, epigenetic, environmental, and lifestyle factors. Nutrients and dietary patterns are important environmental factors to consider in the prevention, development and treatment of this disease. Nutritional genomics focuses on the interaction between bioactive food components and the genome and includes studies of nutrigenetics, nutrigenomics and epigenetic modifications caused by nutrients. There is evidence supporting the existence of nutrient-gene and T2DM interactions coming from animal studies and family-based intervention studies. Moreover, many case-control, cohort, cross-sectional cohort studies and clinical trials have identified relationships between individual genetic load, diet and T2DM. Some of these studies were on a large scale. In addition, studies with animal models and human observational studies, in different countries over periods of time, support a causative relationship between adverse nutritional conditions during in utero development, persistent epigenetic changes and T2DM. This review provides comprehensive information on the current state of nutrient-gene interactions and their role in T2DM pathogenesis, the relationship between individual genetic load and diet, and the importance of epigenetic factors in influencing gene expression and defining the individual risk of T2DM.

Does bilirubin protect against developing diabetes mellitus?

After 25 years of evaluating bilirubin as a possible protective agent in neonatal and cardiovascular disease, interest has moved on to a exploring a possible protective role in diabetes mellitus (DM). This review finds conflicting prospective data for a protective relationship though there are retrospective, case-controlled data, that can only show association, which is not causality. Only prospective studies can show causality. Also, it would appear that the underlying biochemical assumptions do not readily translate from the animal to the human setting. Given that many factors impact on circulating bilirubin levels, it is not surprising that a clear-cut answer is not available; the jury is still out. Any relationship between DM and bilirubin might relate to intermediates in bilirubin metabolism, including relationships involving the genes for the enzymes participating in those steps. Nevertheless, the pursuit of bilirubin in disease causation is opening new avenues for research and if it is established that serum bilirubin can predict risks, much will have been achieved. The answer may have to come from molecular genetic analyses.

Significance of HbA1c Test in Diagnosis and Prognosis of Diabetic Patients

Diabetes is a global endemic with rapidly increasing prevalence in both developing and developed countries. The American Diabetes Association has recommended glycated hemoglobin (HbA1c) as a possible substitute to fasting blood glucose for diagnosis of diabetes. HbA1c is an important indicator of long-term glycemic control with the ability to reflect the cumulative glycemic history of the preceding two to three months. HbA1c not only provides a reliable measure of chronic hyperglycemia but also correlates well with the risk of long-term diabetes complications. Elevated HbA1c has also been regarded as an independent risk factor for coronary heart disease and stroke in subjects with or without diabetes. The valuable information provided by a single HbA1c test has rendered it as a reliable biomarker for the diagnosis and prognosis of diabetes. This review highlights the role of HbA1c in diagnosis and prognosis of diabetes patients.

Effect of vitamins C and E on insulin resistance in diabetes: a meta-analysis study

BACKGROUND

Data regarding the effect of vitamin C (VC) and vitamin E (VE) supplementation on insulin resistance in type 2 diabetes mellitus (T2DM) are controversial. We aimed to systematically review the current data on this topic.

MATERIALS AND METHODS

All randomized controlled trials (RCTs) conducted to assess the effect of VC and/or VE on insulin resistance in diabetes published in Google Scholar and PubMed web databases until January 2014 were included. Exclusion criteria were studies conducted in animal, type 1 DM, children or pregnant women. Main outcome measure was insulin resistance by homoeostasis model assessment (HOMA) index. According to degree of heterogeneity, fixed- or random-effect model was employed by stata software (11.0).

RESULTS

We selected 14 RCTs involving 735 patients with T2DM. VE or mixture-mode supplementation did not have any significant effect on HOMA with a standardized mean difference (SMD): 0·017, 95% CI: -0·376 to 0·411 (P = 0·932); and SMD: -0·035, 95% CI: -0·634 to 0·025 (P = 0·070), respectively, by random-effect model. VC supplement alone did not improve insulin resistance with a SMD: -0·150, 95% CI: -0·494 to 0·194 (P = 0·391), by fixed-effect model. Meta-regression test demonstrated that HOMA index may have not been influenced by the year of publication, dosage or duration of treatment.

CONCLUSIONS

The sole intake of VC, VE or their combination with other antioxidants could not improve insulin resistance in diabetes.

Intake of Vitamin and Mineral Supplements and Longitudinal Association with HbA1c Levels in the General Non-Diabetic Population--Results from the MONICA/KORA S3/F3 Study

Background

Lower levels of hemoglobin A_1c (HbA_1c) are associated with a decreased risk of cardiovascular complications in diabetic and non-diabetic individuals. The aim of the study was to longitudinally investigate the association between the use of 11 vitamins and minerals (vitamins E, C, D, B₁, folic acid, carotenoids, calcium, magnesium, zinc, iron, and selenium) and change in HbA_1c levels over 10 years in non-diabetic individuals drawn from the general population.

Methods

Baseline data were available from 4447 subjects included in the population-based “Monitoring of Trends and Determinants in Cardiovascular Diseases” (MONICA) Augsburg S3 survey (1994/95). Follow-up data were derived from 2774 participants in the follow-up survey named “Cooperative Health Research in the Region of Augsburg” (KORA) F3 (2004/05). Vitamin/mineral intake from supplements and medications was assessed in a personal interview, where participants were asked to bring product packages of preparations that had been ingested during the last 7 days prior to the examination. Associations between regular vitamin/mineral intake amounts and HbA_1c levels measured at baseline and follow-up were investigated using generalized estimating equation models. For carotenoids, analyses were stratified by smoking status.

Results

None of the investigated nutrients except for carotenoids was significantly associated with changes in HbA_1c levels after 10 years. Regular intake of carotenoids from supplements and medications in amounts > 6.8mg/d (upper tertile) was associated with an absolute –0.26% (95% CI: –0.43 to –0.08) lower increase in HbA_1c levels compared with no intake of carotenoids. An inverse association was observed in those who never smoked but not in (former) smokers.

Conclusion

Larger prospective and intervention studies in non-diabetic/non-smoking individuals are needed to confirm the results and to assess whether the observed associations between carotenoid intake and change in HbA_1c levels are causal. If our results are confirmed, high carotenoid intake could be one strategy for the prevention of cardiovascular complications in non-diabetic people.

Targeting metabolic disorders by natural products

The most prevalent metabolic disorders are diabetes mellitus, obesity, dyslipidemia, osteoporosis and metabolic syndrome, which are developed when normal metabolic processes are disturbed. The most common pathophysiologies of the above disorders are oxidative stress, Nrf2 pathways, epigenetic, and change in miRNA expression. There is a challenge in the prevention and treatment of metabolic disorders due to severe adverse effects of some synthetic drugs, their high cost, lack of safety and poverty in some conditions, and insufficient accessibility for the general population in the world. With increasing interest in shifting from synthetic drugs to phytotherapy as an alternative treatment, there is still a gap in scientific evidences of plant-derived therapeutic benefits. One reason may be slow rate of translation of animal studies' findings into human clinical trials. Since metabolic disorders are multifactorial, it seems that poly-herbal medications, or drug-herbal combination are needed for their treatment. However, further researches to determine the most effective plant-derived metabolites, and their cellular mechanism in order to set priorities for well-designed animal and clinical trials, and also more studies with strong scientific evidences such as systematic review and meta-analysis of controlled studies are needed.