Effect of a fermented dietary supplement containing chromium and zinc on metabolic control in patients with type 2 diabetes: a randomized, placebo-controlled, double-blind cross-over study

Fermented foods and metabolic outcomes in diabetes and prediabetes: A systematic review and meta-analysis of randomized controlled trials

Several randomized controlled trials (RCTs) have investigated the effects of fermented foods on metabolic outcomes in adult patients suffering from diabetes and prediabetes. However, the results of these RCTs are conflicting. This systematic review and meta-analysis was carried out on data from RCTs to evaluate the effects of fermented foods in patients with diabetes and prediabetes. The PubMed, Web of Science, Embase, the Cochrane Library and Scopus databases were searched up to 21 June, 2022. English-language RCTs of fermented foods consumption were included which gave metabolic outcomes on body composition, glucose control, insulin sensitivity, lipid profile, as well as blood pressure. Eighteen RCTs met the inclusion criteria and 843 participants were included in the final analysis. The pooled results showed a significant reduction of fasting blood glucose (FBG), the homeostatic model assessment of insulin resistance (HOMA-IR), total cholesterol (TC), low density lipid cholesterol (LDL-C) and diastolic blood pressure (DBP) in the intervention group versus the control group. The results of this research showed that fermented foods have the potential to improve some metabolic outcomes, including FBG, HOMA-IR, TC, LDL-C, and DBP in patients with diabetes and prediabetes.

Zinc and Diabetes: A Connection between Micronutrient and Metabolism

Diabetes mellitus is a global health problem and a major contributor to mortality and morbidity. The management of this condition typically involves using oral antidiabetic medication, insulin, and appropriate dietary modifications, with a focus on macronutrient intake. However, several human studies have indicated that a deficiency in micronutrients, such as zinc, can be associated with insulin resistance as well as greater glucose intolerance. Zinc serves as a chemical messenger, acts as a cofactor to increase enzyme activity, and is involved in insulin formation, release, and storage. These diverse functions make zinc an important trace element for the regulation of blood glucose levels. Adequate zinc levels have also been shown to reduce the risk of developing diabetic complications. This review article explains the role of zinc in glucose metabolism and the effects of its inadequacy on the development, progression, and complications of diabetes mellitus. Furthermore, it describes the impact of zinc supplementation on preventing diabetes mellitus. The available information suggests that zinc has beneficial effects on the management of diabetic patients. Although additional large-scale randomized clinical trials are needed to establish zinc's clinical utility further, efforts should be made to increase awareness of its potential benefits on human health and disease.

Effects of zinc supplementation on lipid profile in patients with type 2 diabetes mellitus: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND AND AIM

Findings on the effects of zinc supplementation on the lipid profile in patients with type 2 diabetes mellitus (T2DM) are conflicting. The current comprehensive systematic review and meta-analysis aimed to summarize available evidence in this regard.

METHODS AND RESULTS

After a systematic search in the online databases, we included the randomized controlled trials (RCTs) investigating the effect of zinc supplementation on lipid profile [total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG)] in patients with T2DM. Altogether, 9 studies with a total sample size of 424 patients with T2DM were included in the analysis. Combining 9 effect sizes from 9 RCTs, we found a significant lowering effect of zinc supplementation on serum levels of TG (weighted mean difference (WMD): -17.08, 95% CI: -30.59, -3.58 mg/dL, P = 0.01) and TC (WMD: -26.16, 95% CI: -49.69, -2.62 mg/dL, P = 0.02). Although the overall effect of zinc supplementation on LDL-C levels was not significant, a beneficial effect was seen in studies that administered <100 mg/d zinc. Based on the non-linear dose-response analysis, a greater reduction in serum levels of TC and LDL-C following zinc supplementation was seen at <12 weeks' duration of intervention. Unlike the overall effect size, we found a significant increasing effect of zinc supplementation on serum HDL-C concentrations in most subgroups of RCTs according to the subgroup analyses.

CONCLUSION

We found that zinc supplementation may beneficially influence lipid profile in patients with T2DM.

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.

Meta-Analysis: Effects of Zinc Supplementation Alone or with Multi-Nutrients, on Glucose Control and Lipid Levels in Patients with Type 2 Diabetes

The present study aims to assess the effects of zinc supplementation on metabolic parameters in patients with type 2 diabetes. A literature search was conducted in PubMed^TM, Google Scholar^TM, and Scopus^TM up to March 2018. Twenty randomized controlled trials met the predefined inclusion criteria and were included in the meta-analysis. Weighted mean difference (WMD) with 95% confidence intervals (CIs) were calculated for net changes in glycemic indices including fasting blood glucose (FBG) and hemoglobin A1c (HbA1c), and in lipid markers including total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-c), and high density lipoprotein cholesterol (HDL-c). Subgroup analyses were performed based on intervention and study quality. Compared to controls, zinc supplementation significantly reduced the concentrations of both FBG and HbA1c (FBG WMD: −19.66 mg/dL, 95% CI: −33.71, −5.62; HbA1c WMD: −0.43 mg/dL, 95% CI: −0.80, −0.07). The pooled estimate showed a significant decrease in serum TC and LDL-c, and increase in serum HDL-c levels in treatment group compared with the control group (TC WMD: −18.51 mg/dL, 95% CI: −21.36, −15.66; LDL-c WMD: −4.80 mg/dL, 95% CI: −6.07, −3.53; HDL-c WMD: 1.45 mg/dL, 95% CI: 1.40, 1.51). Subgroup analysis of “no co-supplement” intervention demonstrated significant differences for mean changes in HDL-c and FBG levels, whereas subgroup analysis of high quality studies showed significant differences for mean changes of LDL-c, HDL-c, and FBG levels. Results suggested that zinc supplementation reduces FBG, HbA1c and LDL-c levels and increases HDL-C levels; however, these changes were related to intervention and quality of studies.

A Mini Review on Antidiabetic Properties of Fermented Foods

In general, fermented foods (FFs) are considered as functional foods. Since the awareness about the health benefits of FFs has increased, the consumption of FF also improved significantly in recent decades. Diabetes is one of the leading threats of the health span of an individual. The present manuscript details the general methods of the production of FFs, and the results of various studies (in vitro, in vivo, and clinical studies) on the antidiabetic properties of FFs. The fermentation method and the active microbes involved in the process play a crucial role in the functional properties of FFs. Several in vitro and in vivo studies have been reported on the health-promoting properties of FFs, such as anti-inflammation, anticancer, antioxidant properties, improved cognitive function and gastrointestinal health, and the reduced presence of metabolic disorders. The studies on the functional properties of FFs by randomized controlled clinical trials using human volunteers are very limited for several reasons, including ethical reasons, safety concerns, approval from the government, etc. Several scientific teams are working on the development of complementary and alternative medicines to improve the treatment strategies for hyperglycemia.

Impact of Labile Zinc on Heart Function: From Physiology to Pathophysiology

Zinc plays an important role in biological systems as bound and histochemically reactive labile Zn²⁺. Although Zn²⁺ concentration is in the nM range in cardiomyocytes at rest and increases dramatically under stimulation, very little is known about precise mechanisms controlling the intracellular distribution of Zn²⁺ and its variations during cardiac function. Recent studies are focused on molecular and cellular aspects of labile Zn²⁺ and its homeostasis in mammalian cells and growing evidence clarified the molecular mechanisms underlying Zn²⁺-diverse functions in the heart, leading to the discovery of novel physiological functions of labile Zn²⁺ in parallel to the discovery of subcellular localization of Zn²⁺-transporters in cardiomyocytes. Additionally, important experimental data suggest a central role of intracellular labile Zn²⁺ in excitation-contraction coupling in cardiomyocytes by shaping Ca²⁺ dynamics. Cellular labile Zn²⁺ is tightly regulated against its adverse effects through either Zn²⁺-transporters, Zn²⁺-binding molecules or Zn²⁺-sensors, and, therefore plays a critical role in cellular signaling pathways. The present review summarizes the current understanding of the physiological role of cellular labile Zn²⁺ distribution in cardiomyocytes and how a remodeling of cellular Zn²⁺-homeostasis can be important in proper cell function with Zn²⁺-transporters under hyperglycemia. We also emphasize the recent investigations on Zn²⁺-transporter functions from the standpoint of human heart health to diseases together with their clinical interest as target proteins in the heart under pathological condition, such as diabetes.