Zinc transporter gene expression and glycemic control in post-menopausal women with Type 2 diabetes mellitus

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.

Zinc Supplementation in Individuals with Prediabetes and type 2 Diabetes: a GRADE-Assessed Systematic Review and Dose-Response Meta-analysis

Zinc supplementation has therapeutic effects on cardiovascular disease (CVD) risk factors, including dyslipidemia, hyperglycemia, and inflammation as the main contributors to CVD pathogenesis. Since CVD is a major cause of mortality among people with type 2 diabetes mellitus (T2DM), this study aimed to overview the potential effects of zinc supplementation on CVD risk factors in T2DM patients. To determine appropriate randomized clinical trials (RCTs) investigating the effects of zinc supplementation on CVD risk factors, electronic sources including PubMed, Web of Science, and Scopus were systematically searched until January 2023. The heterogeneity of trials was checked using the I2 statistic. According to the heterogeneity tests, random-effects models were estimated, and pooled data were defined as the weighted mean difference (WMD) with a 95% confidence interval (CI). Of the 4004 initial records, 23 studies that met inclusion criteria were analyzed in this meta-analysis. The pooled findings indicated the significant lowering effects of zinc supplementation on triglycerides (TG), total cholesterol (TC), fasting blood glucose (FBG), hemoglobin A1C (HbA1C), and C-reactive protein (CRP), while high-density cholesterol (HDL) concentrations showed an elevation after zinc supplementation. In addition to statistical significance, the effect of zinc supplementation on most of the variables was clinically significant; however, the quality of evidence in the included studies is regarded as low or very low for most variables. Our study demonstrated that zinc supplementation has beneficial effects on glycemic control markers, lipid profile, and CRP levels as a classic marker of inflammation in T2DM. Due to the high degree of heterogeneity between studies and the low rate of quality in them, further well-designed studies are necessitated to strengthen our findings.

Cellular zinc metabolism and zinc signaling: from biological functions to diseases and therapeutic targets

Zinc metabolism at the cellular level is critical for many biological processes in the body. A key observation is the disruption of cellular homeostasis, often coinciding with disease progression. As an essential factor in maintaining cellular equilibrium, cellular zinc has been increasingly spotlighted in the context of disease development. Extensive research suggests zinc's involvement in promoting malignancy and invasion in cancer cells, despite its low tissue concentration. This has led to a growing body of literature investigating zinc's cellular metabolism, particularly the functions of zinc transporters and storage mechanisms during cancer progression. Zinc transportation is under the control of two major transporter families: SLC30 (ZnT) for the excretion of zinc and SLC39 (ZIP) for the zinc intake. Additionally, the storage of this essential element is predominantly mediated by metallothioneins (MTs). This review consolidates knowledge on the critical functions of cellular zinc signaling and underscores potential molecular pathways linking zinc metabolism to disease progression, with a special focus on cancer. We also compile a summary of clinical trials involving zinc ions. Given the main localization of zinc transporters at the cell membrane, the potential for targeted therapies, including small molecules and monoclonal antibodies, offers promising avenues for future exploration.

The Role of Trace Elements and Minerals in Osteoporosis: A Review of Epidemiological and Laboratory Findings

The objective of the present study was to review recent epidemiological and clinical data on the association between selected minerals and trace elements and osteoporosis, as well as to discuss the molecular mechanisms underlying these associations. We have performed a search in the PubMed-Medline and Google Scholar databases using the MeSH terms "osteoporosis", "osteogenesis", "osteoblast", "osteoclast", and "osteocyte" in association with the names of particular trace elements and minerals through 21 March 2023. The data demonstrate that physiological and nutritional levels of trace elements and minerals promote osteogenic differentiation through the up-regulation of BMP-2 and Wnt/β-catenin signaling, as well as other pathways. miRNA and epigenetic effects were also involved in the regulation of the osteogenic effects of trace minerals. The antiresorptive effect of trace elements and minerals was associated with the inhibition of osteoclastogenesis. At the same time, the effect of trace elements and minerals on bone health appeared to be dose-dependent with low doses promoting an osteogenic effect, whereas high doses exerted opposite effects which promoted bone resorption and impaired bone formation. Concomitant with the results of the laboratory studies, several clinical trials and epidemiological studies demonstrated that supplementation with Zn, Mg, F, and Sr may improve bone quality, thus inducing antiosteoporotic effects.

Zinc supplementation and cardiovascular disease risk factors: A GRADE-assessed systematic review and dose-response meta-analysis

BACKGROUND AND OBJECTIVE

A deficit in zinc has been related to a higher probability of developing cardiovascular diseases (CVDs). The anti-inflammatory and anti-oxidative capabilities of zinc may have a wide range of therapeutic impacts on CVDs. We conducted a comprehensive systematic review and meta-analysis of the possible impacts that zinc supplementation may have on the risk factors associated with CVDs.

METHODS

To identify eligible randomized clinical trials (RCTs) evaluating the effects of zinc supplementation on CVDs risk factors, electronic databases including PubMed, Web of Science, and Scopus were systematically searched up to January 2023. The heterogeneity of trials was checked using the I² statistic. According to the heterogeneity tests, random effects models were estimated and pooled data were defined as the weighted mean difference (WMD) with a 95% confidence interval (CI).

RESULTS

Of 23165 initial records, 75 studies that met inclusion criteria were analyzed in this meta-analysis. The pooled findings indicated the significant lowering effects of zinc supplementation on triglycerides (TG), total cholesterol (TC), fasting blood glucose (FBG), Hemoglobin A1C (HbA1C), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), C-reactive protein (CRP), interleukin-6 (IL-6), Tumor necrosis factor-α (TNF-α), nitric oxide (NO), malondialdehyde (MDA), total antioxidant capacity (TAC), and glutathione (GSH), with no noticeable effects on low-density lipoprotein (LDL), high-density lipoprotein (HDL), insulin, systolic blood pressure (SBP), diastolic blood pressure (DBP), aspartate transaminase (AST), and Alanine aminotransferase (ALT).

CONCLUSION

Overall, zinc supplementation may boost recognized coronary risk factors that contribute to the development of CVDs. Future research should be conducted to bolster our results.

ZnT8 autoantibody prevalence is low in youth with type 2 diabetes and associated with higher insulin sensitivity, lower insulin secretion, and lower disposition index

Aim

ZnT8 autoantibody positivity (ZnT8+) is associated with risk for type 1 diabetes and with metabolic complications in adults. Our aim was to assess prevalence of ZnT8 + in the Treatment of T2D in Adolescents and Youth (TODAY) cohort and describe associated phenotypic outcomes.

Methods

TODAY participants were 13.98 ± 2.03 years with a confirmed diagnosis of T2D, BMI percentile of 97.69 ± 3.32 (64% female), and GAD- and IA2- at baseline. ZnT8 autoantibodies were measured at baseline and end of study.

Results

3 of 687 participants (0.29%) were ZnT8 + and there was one conversion (0.15%) from ZnT8- to ZnT8 + during the study. ZnT8A + individuals had higher HbA1c, HDL and LDL cholesterol, and IL-1β concentrations, and lower BMI, IL-6, and triglyceride concentrations compared to the TODAY cohort and ZnT8A- individuals. They also had higher insulin sensitivity with lower insulin secretion and disposition index, metabolically resembling T1D. All ZnT8 + participants experienced loss of glycemic control on randomized treatment, but exhibited lower rates of diabetic complications than other groups.

Conclusion

Given the low rate of complications in ZnT8 + individuals, ZnT8 likely does not impact the clinical course of the disease in this population.

Zinc Modulates the Response to Apoptosis in an In Vitro Model with High Glucose and Inflammatory Stimuli in C2C12 Cells

Apoptosis is programmed cell death and its alteration is related to cancer, neurologic, autoimmune, and chronic diseases. A number of factors can affect this process. The aim of this paper is to study the effect of supplemental zinc on apoptosis-related genes in C2C12 myoblast cells after being challenged with a series of stimuli, such as high glucose, insulin, and an inflammatory agent. C2C12 myoblast cells were cultured for 24 h with zinc (Zn) (ZnSO₄) 10 or 100 μM and/or glucose 10 or 30 mM. In addition to these stimuli, the cells were challenged with insulin 1 nM or interleukin-6 (IL-6) 5 nM. The mRNA expression of proapoptotic genes caspase 3 and Fas, the antiapoptotic genes, Xiap and Bcl-xL and the ratio of pro-/antiapoptotic genes Bax/Bcl-2, were determined by qRT-PCR. The expression of caspase-3 gene was significantly increased in the presence of the combination high Zn/high glucose with and without the presence of insulin and IL6 in the culture medium Fas expression instead, showed uneven responses. The expression of Bcl-xL and Xiap was increased in most conditions by having high Zn in the medium regardless of the presence of insulin or IL6. Bax/Bcl2 ratio was decreased in the presence of high Zn. Zn was able to stimulate the expression of antiapoptotic genes. This effect was specially noted in high-glucose conditions with and without the presence of insulin. This effect is partially overridden by the presence of an inflammatory agent such as IL-6.

Medicinal Plants and Phytochemicals Regulating Insulin Resistance and Glucose Homeostasis in Type 2 Diabetic Patients: A Clinical Review

Diabetes is a major health problem affecting more than four hundred million adults worldwide. The transition from normal glucose tolerance to type 2 diabetes (T2D) is preceded by increased Insulin resistance (IR), an independent predictor of the development of T2D in high risk (e.g. obese populations, pre-diabetes) individuals. Insulin deficiency resulting from increased IR results in progressive glucose homeostasis dysfunction. Data has shown that IR is affected by many different factors such as genetics, age, exercise, dietary nutrients, obesity, and body fat distribution. One of the most important factors is diet, which plays an essential role in addressing T2D and metabolic syndrome. Nutraceuticals and medicinal plants have been shown to have efficacy in preventing chronic diseases like cancer, non-alcoholic fatty liver disease (NAFLD), cardiovascular disease, diabetes mellitus and metabolic syndrome, likely through the anti-inflammatory properties found in nutraceuticals. However, the effect of these compounds, including traditional plant medicines, herbal formulations or their extracts on IR have not been systematically investigated. The objective of this review was to assess the reported effects of medicinal plants and bioactive natural compounds on IR. The findings confirm that most of the herbal bioactive compounds including resveratrol, garlic, curcumin, cinnamon, ginger, nuts, berberine, anthocyanin, soybean, flaxseed, vegetable oils, and soluble fibers have benefit in their efficacy for decreasing IR, fasting blood sugar (FBS), fasting insulin and HbA1c.

Diabetes and zinc dyshomeostasis: Can zinc supplementation mitigate diabetic complications?

Zinc present in the islet cells of the pancreas is crucial for the synthesis, storage, and secretion of insulin. The excretion of large amounts of zinc from the body is reported in diabetic situations. Zinc depletion and increased oxidative stress have a major impact on the pathogenesis of diabetic complications. It would be most relevant to ascertain if intervention with supplemental zinc compensating for its depletion would beneficially mitigate hyperglycemia and the attendant metabolic abnormalities, and secondary complications in diabetes. An exhaustive literature search on this issue indicates: (1) Concurrent hypozincemia and decreased tissue zinc stores in diabetes as a result of its increased urinary excretion and/or decreased intestinal absorption, (2) Several recent experimental studies have documented that supplemental zinc has a potential hypoglycemic effect in the diabetic situation, and also beneficially modulate the attendant metabolic abnormalities and compromised antioxidant status, and (3) Supplemental zinc also alleviates renal lesions, cataract and the risk of cardiovascular disease accompanying diabetes mellitus, and help restore gastrointestinal health in experimental diabetes. These studies have also attempted to identify the precise mechanisms responsible for zinc-mediated beneficial effects in diabetic situation. The evidence discussed in this review highlights that supplemental zinc may significantly contribute to its clinical application in the management of diabetic hyperglycemia and related metabolic abnormalities, and in the alleviation of secondary complications resulting from diabetic oxidative stress.

Clinical effectiveness of zinc supplementation on the biomarkers of oxidative stress: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Oxidative stress plays an important role in the occurrence of chronic diseases. Zinc supplementation is also known to be an antioxidant agent. While, there is no review on the effects of zinc supplementation on oxidative stress, this study aimed to systematically summarize randomized clinical trials (RCTs) which have evaluated the impacts of zinc supplementation on oxidative stress biomarkers.

METHODS

Systematic searches were performed using the PubMed/Medline, Scopus, and Google Scholar databases, up to April 2020. All RCTs assessed the effect of oral zinc supplementation on serum malondialdehyde (MDA), total antioxidant capacity (TAC), glutathione (GSH), and nitric oxide (NO) levels, were included. For each variable, mean differences (MD) and standard deviations (SDs) were combined using the random-effects model, and the fractional polynomial model was used to implement the dose-response analysis.

RESULTS

Ten RCTs were included. The pooled analysis of data showed that zinc supplementation significantly reduced MDA levels (MD: -0.42 μmol/L; 95 % CI: -0.71 to -0.13), increased serum TAC (MD: 225.96 mmol/L; 95 % CI: 68.42-383.5) and GSH levels (MD: 49.99 μmol/L; 95 % CI: 2.25 t 97.73), compared with the placebo group. In contrast, no significant changes were seen in NO levels following zinc supplementation (MD: -1.66 μmol/L; 95 % CI: -5.89 to 2.57). Dose-response analysis showed a significant non-linear relationship between zinc supplementation dosage and serum levels of MDA (p < 0.01), but not other biomarkers.

CONCLUSIONS

The current study showed that zinc supplementation would significantly decrease MDA and increase TAC and GSH, but not NO levels. Thus, it encourages the use of zinc supplementation in oxidative stress-related diseases.

Effects of zinc supplementation on serum adiponectin concentration and glycemic control in patients with type 2 diabetes

BACKGROUND

Previous studies have suggested that zinc is involved in insulin homeostasis. Adiponectin is a well-known adipokine with anti-diabetic, anti-atherogenic, and anti-inflammatory properties. The aim of this study was to investigate the effect of zinc supplementation on glycemic control, and the potential mediating role of adiponectin, in patients with type 2 diabetes.

METHODS

In this randomized double-blind placebo-controlled clinical trial, 60 patients with diabetes, 30-60 years, were randomized to receive either 30 mg/d zinc (as zinc gluconate) or placebo for 12 weeks. Circulating levels of adiponectin, zinc, glucose homeostasis parameters, and lipid profiles, as well as anthropometric parameters and dietary intakes, were assessed.

RESULTS

About 53.3% of the patients had zinc insufficiency at baseline. Serum zinc levels improved significantly in the intervention than control group following 12 weeks supplementation (P < 0.001). Adiponectin (1.23 ± 2.23 μg/ml, P = 0.006) and insulin (3.6 ± 4.66 μIU/ml, P = 0.001) levels increased significantly compared to baseline in the zinc group; but this change was not significant compared with the control group. Following supplementation, there were no significant differences in glycemic control and anthropometric parameters between the two groups. Serum HDL levels increased significantly in the zinc (5.37 ± 14.8 mg/dl) compared to control (-1.53 ± 6.9 mg/dl) group following supplementation (P = 0.039).

CONCLUSION

Despite a significant increase in serum zinc level, no improvement was observed in glycemic control, following 12 weeks supplementation with 30 mg/d zinc (as zinc gluconate). Zinc supplementation restored adiponectin concentrations partly within the intervention group, and increased HDL levels compared to the control group. The current findings did not support improvement in glucose homeostasis following zinc supplementation in patients with type 2 diabetes under the present study design.

Gadolinium Retention and Clearance in the Diabetic Brain after Administrations of Gadodiamide, Gadopentetate Dimeglumine, and Gadoterate Meglumine in a Rat Model

Purpose

To evaluate gadolinium (Gd) retention and clearance in the brain of diabetic rats after administrations of gadodiamide, gadopentetate dimeglumine, and gadoterate meglumine.

Materials and Methods

Both diabetic rats (n = 52) and normal rats (n = 52) intravenously received 20 injections of 0.6 mmol Gd/kg gadodiamide, gadopentetate dimeglumine, gadoterate meglumine, or saline. Both diabetic rats and normal rats were divided into 2 subgroups of 24 and 28 rats for the 7-day and 42-day evaluations (i.e., they were sacrificed at 7 days (n = 6 per group) and 42 days (n = 7 per group)), respectively, after the last injection. For the 7-day subgroup, 6 rats were euthanized for inductively coupled plasma mass spectrometry (ICP-MS) analysis. For the 42-day subgroup, 6 rats underwent T1-weighted magnetic resonance imaging (MRI) and ICP-MS, and 1 rat was analyzed by transmission electron microscopy (TEM).

Results

The T1 enhancements in the deep cerebellar nuclei (DCNs) of diabetic rats were lower than those of normal rats in both linear Gd-based contrast agent (GBCA) groups (p < 0.05). The average Gd concentrations in the brains of diabetic rats were significantly lower than those of healthy rats in both the short-term groups and long-term groups (p < 0.05). The highest Gd retentions were in the olfactory bulb, DCN, and striatum with gadodiamide. Compared with the results obtained 7 days after the last injection, the residual Gd concentrations of the 42-day subgroups in the brains of diabetic rats showed no significant difference in both linear GBCA groups (p>0.05).

Conclusions

Compared with normal rats, the diabetic status decreased the residual Gd concentrations in the brain after multiple administrations of gadodiamide, gadopentetate dimeglumine, and gadoterate meglumine. The clearable fraction of Gd in the brain was eliminated faster in diabetic rats than in normal rats.

Nutritional Effects of Zinc on Metabolic Syndrome and Type 2 Diabetes: Mechanisms and Main Findings in Human Studies

Zinc (Zn) plays crucial roles in mammalian metabolism. There is increasing interest about the potential beneficial effects of Zn on the prevention or treatment of non-communicable diseases. This review critically analyzes the information related to the role of Zn on the metabolic syndrome (MetS) as well as type 2 diabetes (T2D), and summarizes the biological basis of these potential effects of Zn. There are several mechanisms by which Zn may help to prevent the development or progression of MetS and T2D, respectively. Zn is involved in both insulin secretion and action in peripheral tissues. Specifically, Zn has insulin-mimetic properties that increase the activity of the insulin signaling pathway. Zn modulates long-chain polyunsaturated fatty acids levels through its action on the absorption of essential fatty acids in the intestine and its subsequent desaturation. Zn is also involved in both the assembly of chylomicrons and lipoproteins as well as their clearance, and thus, plays a role in lipolysis regulation. Finally, Zn has been found to play a role in redox metabolism, and in turn, on blood pressure. The evidence related to the association between Zn status and occurrence of MetS is inconsistent. Although there are several studies reporting an inverse relationship between Zn status or dietary Zn intake and MetS prevalence, others found a direct relationship between Zn status and MetS prevalence. Intervention studies also provide confusing information about this issue, making it hard to reach firm conclusions. Zn as part of the treatment for patients with T2D has been shown to have positive responses in terms of glucose control outcomes, but only among those with Zn deficiency.

Zinc and Insulin Resistance: Biochemical and Molecular Aspects

Studies have shown the participation of minerals in mechanisms involved in the pathogenesis of insulin resistance. Zinc, in particular, seems to play an important role in the secretion and action of this hormone. Therefore, the aim of this review is to understand the role of zinc in increasing insulin sensitivity. We conducted a search of articles published in the PubMed and ScienceDirect database selected from March 2016 to February 2018, using the keywords "zinc," "insulin," "insulin resistance," "insulin sensitivity," and "supplementation." Following the eligibility criteria were selected 53 articles. The scientific evidences presented in this review show the importance of zinc and their carrier proteins in the synthesis and secretion of insulin, as well as in the signaling pathway of action of this hormone. Zinc deficiency is associated with glucose intolerance and insulin resistance; however, the effectiveness of the intervention with the zinc supplementation is still inconclusive.

Genetic risk score of common genetic variants for impaired fasting glucose and newly diagnosed type 2 diabetes influences oxidative stress

We tested the hypothesis that the cumulative effects of common genetic variants related to elevated fasting glucose are collectively associated with oxidative stress. Using 25 single nucleotide polymorphisms (SNPs), a weighted genetic risk score (wGRS) was constructed by summing nine risk alleles based on nominal significance and a consistent effect direction in 1,395 controls and 718 patients with impaired fasting glucose (IFG) or newly diagnosed type 2 diabetes. All the participants were divided into the following three groups: low-wGRS, middle-wGRS, and high-wGRS groups. Among the nine SNPs, five SNPs were significantly associated with IFG and type 2 diabetes in this Korean population. wGRS was significantly associated with increased IFG and newly diagnosed type 2 diabetes (p = 6.83 × 10⁻¹⁴, odds ratio = 1.839) after adjusting for confounding factors. Among the IFG and type 2 diabetes patients, the fasting serum glucose and HbA_1c levels were significantly higher in the high-wGRS group than in the other groups. The urinary 8-epi-PGF_2α and malondialdehyde concentrations were significantly higher in the high-wGRS group than in the other groups. Moreover, general population-level instrumental variable estimation (using wGRS as an instrument) strengthened the causal effect regarding the largely adverse influence of high levels of fasting serum glucose on markers of oxidative stress in the Korean population. Thus, the combination of common genetic variants with small effects on IFG and newly diagnosed type 2 diabetes are significantly associated with oxidative stress.

Implications of impaired zinc homeostasis in diabetic cardiomyopathy and nephropathy

Impaired zinc homeostasis is observed in diabetes mellitus (DM2) and its complications. Zinc has a specific role in pancreatic β-cells via insulin synthesis, storage, and secretion. Intracellular zinc homeostasis is tightly controlled by zinc transporters (ZnT and Zip families) and metallothioneins (MT) which modulate the uptake, storage, and distribution of zinc. Several investigations in animal models demonstrate the protective role of MT in DM2 and its cardiovascular or renal complications, while a copious literature shows that a common polymorphism (R325W) in ZnT8, which affects the protein's zinc transport activity, is associated with increased DM2 risk. Emerging studies highlight a role of other zinc transporters in β-cell function, suggesting that targeting them could make a possible contribution in managing the hyperglycemia in diabetic patients. This article summarizes the current findings concerning the role of zinc homeostasis in DM2 pathogenesis and development of diabetic cardiomyopathy and nephropathy and suggests novel therapeutic targets. © 2017 BioFactors, 43(6):770-784, 2017.

Association of trace metal elements with lipid profiles in type 2 diabetes mellitus patients: a cross sectional study

BACKGROUND

It is well known that dyslipidemia and chronic hyperglycemia increase the onset of diabetes and diabetic complication. The aim of this study is to see the association of trace metals elements and lipid profile among type 2 diabetes mellitus patients.

METHODS

The study was conducted on 214 type 2 diabetic patients at Jimma University Specialized Hospital, Jimma, Ethiopia. All the eligible study participants responded to the structured interviewer administered questionnaire and fasting venous blood was drawn for biochemical analysis. Trace metal elements (zinc(Zn⁺²), magnesium(Mg⁺²), chromium(Cr⁺³), calcium(Ca⁺²), phosphorus(Po₄^-3), manganese(Mn⁺²), copper(Cu⁺²), and iron(Fe⁺³)) and lipid profiles (total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein (HDL-C), and triglycerides (TG)) were measured by atomic absorption spectrophotometry and enzymatic determination method respectively. Data were analyzed by SPSS version 24 software for windows. Bonferroni correction for multiple statistical comparisons was used and a p-value less than 0.01 were accepted as a level of significance.

RESULT

The mean age of study participants was 42.95(±12.6) with an average of 5.83(±3.1) years being diagnosed with diabetes mellitus. The BMI of female (27.1(±4.9)) was significantly higher than male (25.21(±4.2)). BMI shows positive and significant (p < 0.01) association with lipid profiles (TC, LDL-C, and TG) among type 2 diabetic patients in the liner regression model. In addition, WH-R was positively associated with TG. In Pearson partial correlation adjusted for sex and age, Za⁺² shown to have statistically significant and negative correlations with TC, LDL-C and with TG. Mg⁺² and Cr⁺² negatively and significantly correlated with the lipid profile TC and LDL-C. Ca⁺² negatively correlated with TC and TG. Po^-3₄ positively correlated with HDL-C; iron negatively correlated with TC. However, in the liner regression model, only calcium positively and significantly (Beta = -0.21, p < 0.01) associated with TG.

CONCLUSION

In the current study, a negative correlation was observed between trace metal elements (Zn⁺², Mg⁺², Cr⁺³, Ca⁺² and Fe⁺³) and lipid profile (TC, LDL-C and TG) among type 2 diabetes mellitus patients. In addition, Ca⁺² observed to be associated with TG. Future studies are highly advised to uncover the bidirectional association between trace metal element and dyslipidemia in diabetic patients.

Metabolic relationship between diabetes and Alzheimer's Disease affected by Cyclo(His-Pro) plus zinc treatment

BACKGROUND

Association of Alzheimer's Disease (AD) with Type 2 Diabetes (T2D) has been well established. Cyclo(His-Pro) plus zinc (Cyclo-Z) treatment ameliorated diabetes in rats and similar improvements have been seen in human patients. Treatment of amyloid precursor protein (APP) transgenic mice with Cyclo-Z exhibited memory improvements and significantly reduced Aβ-40 and Aβ-42 protein levels in the brain tissues of the mice.

SCOPE OF REVIEW

Metabolic relationship between AD and T2D will be described with particular attention to insulin sensitivity and Aβ degradation in brain and plasma tissues. Mechanistic effect of insulin degrading enzyme (IDE) in decreasing blood glucose and brain Aβ levels will be elucidated. Cyclo-Z effects on these biochemical parameters will be discussed.

MAJOR CONCLUSION

Stimulation of IDE synthesis is effective for the clinical treatment of metabolic diseases including AD and T2D.

GENERAL SIGNIFICANCE

Cyclo-Z might be the effective treatment of AD and T2D by stimulating IDE synthesis.

The effect of alpha-linolenic acid on glycemic control in individuals with type 2 diabetes: A systematic review and meta-analysis of randomized controlled clinical trials

BACKGROUND

Polyunsaturated fats (PUFAs) have been shown to reduce type 2 diabetes (T2DM) risk and improve insulin responsiveness in T2DM subjects, but whether the plant sources of omega-3 PUFA (alpha-linolenic acid [ALA]) have an effect on glycemic control requires further investigation.

METHODS

The parameters of interest were glycated hemoglobin (HbA1c), fasting blood glucose (FBG), fasting blood insulin (FBI), homeostatic model assessment for insulin resistance (HOMA-IR), fructosamine, and glycated albumin. A comprehensive search was conducted with MEDLINE, Embase, CINAHL, and Cochrane. Eligible studies included randomized controlled trials (RCTs) ≥1 month in duration that compared diets enriched in ALA with usual diets on glycemic parameters. For each study, the risk of bias as well as the study quality was assessed. Using the statistical software RevMan (v5.3), data were pooled using the generic inverse method with random effects model, and final results were expressed as mean differences (MD) with 95% confidence intervals (CI). Heterogeneity was assessed by the Cochran Q statistic and quantified by the I statistic.

RESULTS

A total of 8 trials (N = 212) were included in the meta-analysis. Compared to a control diet, a median dose of 4.4 g/day of ALA intake for a median duration of 3 months did not affect HbA1c (%) (MD = -.01; [95%: -.32, .31], P = .96). A median ALA dose of 5.4 g/day did not lower FBG (MD = .07; [95% CI: -.61, .76], P = .84) or FBI (MD = 7.03, [95% CI: -5.84, 19.89], P = .28). Summary effect estimates were generally compromised by considerable and unexplained heterogeneity (I ≥75%). In the subgroup analysis of continuous predictors, a reduction in HbA1c (%) and FBG (mmol/L) was significantly associated with an increased intake of ALA. Further adjustment for Publication Bias using Duval and Tweedie's trim-and-fill analysis provided an adjusted, significant MD of -.25 (95% CI: -.38, -.12; P <.001) for HbA1c (%).

CONCLUSIONS

ALA-enriched diets did not affect HbA1c, FBG, or FBI. The scarce number of existing RCTs and the presence of heterogeneity in our meta-analysis limit the ability to make firm conclusions about ALA in T2DM management. The potential for ALA to have dose-dependent effects warrants further research in this area.

The Role of Oxidative Stress and Hypoxia in Pancreatic Beta-Cell Dysfunction in Diabetes Mellitus

SIGNIFICANCE

Metabolic syndrome is a frequent precursor of type 2 diabetes mellitus (T2D), a disease that currently affects ∼8% of the adult population worldwide. Pancreatic beta-cell dysfunction and loss are central to the disease process, although understanding of the underlying molecular mechanisms is still fragmentary. Recent Advances: Oversupply of nutrients, including glucose and fatty acids, and the subsequent overstimulation of beta cells, are believed to be an important contributor to insulin secretory failure in T2D. Hypoxia has also recently been implicated in beta-cell damage. Accumulating evidence points to a role for oxidative stress in both processes. Although the production of reactive oxygen species (ROS) results from enhanced mitochondrial respiration during stimulation with glucose and other fuels, the expression of antioxidant defense genes is unusually low (or disallowed) in beta cells.

CRITICAL ISSUES

Not all subjects with metabolic syndrome and hyperglycemia go on to develop full-blown diabetes, implying an important role in disease risk for gene-environment interactions. Possession of common risk alleles at the SLC30A8 locus, encoding the beta-cell granule zinc transporter ZnT8, may affect cytosolic Zn2+ concentrations and thus susceptibility to hypoxia and oxidative stress.

FUTURE DIRECTIONS

Loss of normal beta-cell function, rather than total mass, is increasingly considered to be the major driver for impaired insulin secretion in diabetes. Better understanding of the role of oxidative changes, its modulation by genes involved in disease risk, and effects on beta-cell identity may facilitate the development of new therapeutic strategies to this disease. Antioxid. Redox Signal. 26, 501-518.

Zinc and Oxidative Stress: Current Mechanisms

Oxidative stress is a metabolic dysfunction that favors the oxidation of biomolecules, contributing to the oxidative damage of cells and tissues. This consequently contributes to the development of several chronic diseases. In particular, zinc is one of the most relevant minerals to human health, because of its antioxidant properties. This review aims to provide updated information about the mechanisms involved in the protective role of zinc against oxidative stress. Zinc acts as a co-factor for important enzymes involved in the proper functioning of the antioxidant defense system. In addition, zinc protects cells against oxidative damage, acts in the stabilization of membranes and inhibits the enzyme nicotinamide adenine dinucleotide phosphate oxidase (NADPH-Oxidase). Zinc also induces the synthesis of metallothioneins, which are proteins effective in reducing hydroxyl radicals and sequestering reactive oxygen species (ROS) produced in stressful situations, such as in type 2 diabetes, obesity and cancer. Literature provides strong evidence for the role of zinc in the protection against oxidative stress in several diseases.

Zinc supplementation mitigates its dyshomeostasis in experimental diabetic rats by regulating the expression of zinc transporters and metallothionein

Zinc depletion during diabetes projects a role for zinc nutrition in this condition.

Does Zinc Really "Metal" with Diabetes? The Epidemiologic Evidence

Zinc (Zn) is important in a number of processes related to insulin secretion and insulin activity in peripheral tissues, making this element an interesting potential co-adjuvant in the treatment of patients with type 2 diabetes (T2D). This issue has been matter of interest in recent years. The available evidence is analyzed in this review. Information from epidemiologic studies evaluating the relationship between Zn and T2D is inconsistent. Furthermore, few studies examined the association between Zn status and insulin action and/or glucose homeostasis. In terms of usefulness of Zn as a preventive agent for T2D development, information is insufficient to reach firm conclusions. Results from Zn supplementation trials found some positive effects only in those with initial sub normal Zn status in a significant proportion of individuals. In conclusion, the effect of Zn on patients with type 2 diabetes is still an open question, and better study designs are needed to clarify the real impact and characteristics of the Zn-diabetes interaction.

Antioxidant role of zinc in diabetes mellitus

Chronic hyperglycemia statue noticed in diabetes mellitus favors the manifestation of oxidative stress by increasing the production of reactive oxygen species and/or by reducing the antioxidant defense system activity. Zinc plays an important role in antioxidant defense in type 2 diabetic patients by notably acting as a cofactor of the superoxide dismutase enzyme, by modulating the glutathione metabolism and metallothionein expression, by competing with iron and copper in the cell membrane and by inhibiting nicotinamide adenine dinucleotide phosphate-oxidase enzyme. Zinc also improves the oxidative stress in these patients by reducing chronic hyperglycemia. It indeed promotes phosphorylation of insulin receptors by enhancing transport of glucose into cells. However, several studies reveal changes in zinc metabolism in individuals with type 2 diabetes mellitus and controversies remain regarding the effect of zinc supplementation in the improvement of oxidative stress in these patients. Faced with the serious challenge of the metabolic disorders related to oxidative stress in diabetes along with the importance of antioxidant nutrients in the control of this disease, new studies may contribute to improve our understanding of the role played by zinc against oxidative stress and its connection with type 2 diabetes mellitus prognosis. This could serve as a prelude to the development of prevention strategies and treatment of disorders associated with this chronic disease.

Zinc transporters and zinc signaling: new insights into their role in type 2 diabetes

Zinc is an essential trace element that plays a vital role in many biological processes including growth and development, immunity, and metabolism. Recent studies have highlighted zinc's dynamic role as a "cellular second messenger" in the control of insulin signaling and glucose homeostasis. Accordingly, mechanisms that contribute to dysfunctional zinc signaling are suggested to be associated with metabolic disease states including cancer, cardiovascular disease, Alzheimer's disease, and diabetes. The actions of the proteins that control the uptake, storage, and distribution of zinc, the zinc transporters, are under intense investigation due to their emerging role in type 2 diabetes. The synthesis, secretion, and action of insulin are dependent on zinc and the transporters that make this ion available to cellular processes. This suggests that zinc plays a previously unidentified role where changes in zinc status over time may affect insulin activity. This previously unexplored concept would raise a whole new area of research into the pathophysiology of insulin resistance and introduce a new class of drug target with utility for diabetes pharmacotherapy.

TNF-α gene expression is increased following zinc supplementation in type 2 diabetes mellitus

Chronic low-grade inflammation in type 2 diabetes mellitus (DM) can elicit changes in whole-body zinc metabolism. The interaction among the expression of inflammatory cytokines, zinc transporter and metallothionein (MT) genes in peripheral blood mononuclear cells in type 2 DM remains unclear. In a 12-week randomized controlled trial, the effects of zinc (40 mg/day) supplementation on the gene expression of cytokines, zinc transporters and MT in women with type 2 DM were examined. In the zinc-supplemented group, gene expression of tumour necrosis factor (TNF)-α tended to be upregulated by 27 ± 10 % at week 12 compared to baseline (P = 0.053). TNF-α fold change in the zinc-treated group was higher than in those without zinc supplementation (P < 0.05). No significant changes were observed in the expression or fold change of interleukin (IL)-1β or IL-6. Numerous bivariate relationships were observed between the fold changes of cytokines and zinc transporters, including ZnT7 with IL-1β (P < 0.01), IL-6 (P < 0.01) and TNF-α (P < 0.01). In multiple regression analysis, IL-1β expression was predicted by the expression of all zinc transporters and MT measured at baseline (r (2) = 0.495, P < 0.05) and at week 12 (r (2) = 0.532, P < 0.03). The current study presents preliminary evidence that zinc supplementation increases cytokine gene expression in type 2 DM. The relationships found among zinc transporters, MT and cytokines suggest close  interactions between zinc homeostasis and inflammation.