Zinc supplementation improves glycemic control for diabetes prevention and management: a systematic review and meta-analysis of randomized controlled trials

Dietary zinc supplements: beneficial health effects and application in food, medicine and animals

Zinc, a crucial trace element is vital for the growth and development of humans. It is frequently described as 'the flower of life' and 'the source of intelligence'. Zinc supplements play a pivotal role in addressing zinc deficiency by serving as a vital source of this essential micronutrients, effectively replenishing depleted zinc levels in the body. In this paper, we first described the biological behavior of zinc in the human body and briefly described the physiological phenomena associated with zinc levels. The benefits and drawbacks of various zinc supplement forms are then discussed, with emphasis on the most recent zinc supplement formulations. Finally, the application of zinc supplements in food, medicine, and animal husbandry is further summarized. © 2024 Society of Chemical Industry.

Effects of Zinc Supplementation on Inflammatory Status and Nonalcoholic Steatohepatitis in Overweight or Obese Children: a Randomized Clinical Trial

The purpose of the present clinical trial was to determine the impact of zinc supplementation on serum liver enzymes, steatosis severity, lipid profile, and inflammatory status in overweight or obese children with nonalcoholic steatohepatitis (NASH). This randomized controlled trial was conducted by enrolling 60 children with NASH, aged 10-18 years old. The participants were randomly assigned to two groups that received either 30 mg/day of elemental zinc or placebo for 16 weeks. The severity of liver steatosis was evaluated using liver ultrasonography. Fasting blood samples were collected from each patient at the beginning and after 16 weeks of intervention to measure biochemical parameters. Following a 16-week intervention, zinc supplementation compared with placebo significantly decreased serum alanine aminotransferase (ALT) concentrations and high-sensitivity C-reactive protein and considerably enhanced HDL-cholesterol values. However, zinc intake had no considerable impact on aspartate aminotransferase, the severity of liver steatosis, anthropometric parameters, and other lipid indices versus the placebo group. Overall, zinc supplementation showed a promising impact on serum ALT, HDL-cholesterol, and inflammatory status in overweight or obese children suffering from NASH. Zinc supplementation may be a new strategy for the amelioration of NASH in overweight or obese children. This trial has been registered on the Iranian website for registration of clinical trials with the special ID of IRCT20200531047614N1 ( https://www.irct.ir/trial/48543 ).

Association Between Circulating Zinc Levels and Risk Factors of Metabolic Syndrome: Insights from a Bi-directional Mendelian Randomization Analysis and Cross-Sectional Study

Previous studies on the relationship between zinc and metabolic syndrome (MetS) have yielded inconsistent results. This comprehensive study aimed to elaborately explore the impact of zinc on MetS risk factors. The bi-directional Mendelian randomization (MR) analyses were performed to estimate the causal relationship between zinc and MetS risk factors. Additionally, a retrospective cross-sectional study incorporated 4389 subjects to provide a broader perspective in conjunction with the MR analyses. In the MR analyses, genetically instrumented zinc was positively associated with five of the MetS components in Europeans, including BMI, FBG, HbA1c, TC, and LDL-c (β (95%CI) = 0.023 (0.019-0.027), 0.019 (0.013-0.025), 0.041 (0.022-0.060), 0.027 (0.013-0.042), and 0.018 (0.010-0.026), respectively). In the cross-sectional study, higher concentration of zinc was strongly associated with increased BMI, LDL-c, and UA (β (95%CI) = 0.040 (0.010-0.085), 0.026 (0.018-0.035), and 1.529 (0.614-2.445), respectively). Moreover, these unfavorable associations were more obvious in women compared to men, with a borderline significant interaction effect for BMI (P=0.051). Our study showed that higher blood concentration of zinc, an essential trace element, was associated with unfavorable changes of the component metabolic risk factors of MetS, especially with BMI and LDL-c. Notably, these associations seemed to be more pronounced in women rather than in men. Further studies are warranted to elucidate the role of zinc status in the underlying mechanisms of MetS.

Marginal Zinc Deficiency Promotes Pancreatic Islet Enlargement While Zinc Supplementation Improves the Pancreatic Insulin Response in Zucker Diabetic Fatty Rats

Zinc deficiency has been associated with the worsening of diabetes while zinc supplementation has been proposed to ameliorate diabetes. This study examined the effects of marginal zinc deficiency (MZD) and zinc supplementation (ZS) on obesity, glycemic control, pancreatic islets, hepatic steatosis and renal function of Zucker diabetic fatty (ZDF) rats. Male ZDF rats were fed an MZD, zinc control (ZC) or ZS diet (4, 30 and 300 mg Zn/kg diet, respectively), and lean Zucker rats were fed a ZC diet for 8 weeks. MZD and ZS did not alter body weight or whole-body composition in ZDF rats. MZD ZDF rats had reduced zinc concentrations in the femur and pancreas, a greater number of enlarged pancreatic islets and a diminished response to an oral glucose load based on a 1.8-fold greater incremental area-under-the-curve (AUC) for glucose compared to ZC ZDF. ZS ZDF rats had elevated serum, femur and pancreatic zinc concentrations, unchanged pancreatic parameters and a 50% reduction in the AUC for insulin compared to ZC ZDF rats, suggesting greater insulin sensitivity. Dietary zinc intake did not alter hepatic steatosis, creatinine clearance, or levels of proteins that contribute to insulin signaling, inflammation or zinc transport in epididymal fat. Potential adverse effects of ZS were suggested by reduced hepatic copper concentrations and elevated serum urea compared to ZC ZDF rats. In summary, ZS improved the pancreatic insulin response but not the glucose handling. In contrast, reduced zinc status in ZDF rats led to impaired glucose tolerance and a compensatory increase in the number and size of pancreatic islets which could lead to β-cell exhaustion.

Effect of zinc supplementation on glycemic biomarkers: an umbrella of interventional meta-analyses

BACKGROUND

Several studies have evaluated the effects of zinc supplementation on glycemic biomarkers in humans and have demonstrated varying results. We systematically evaluated the literature and performed an umbrella meta-analysis of the effects of zinc supplementation on type 2 diabetes biomarkers.

METHODS

A comprehensive literature search was conducted in the following databases; PubMed, Embase, Embase, Cochrane Library, Scopus, and Web of Science for studies published up to March 10, 2024.

RESULTS

Zinc supplementation was effective in reducing serum FBS (WMD: - 13.58, 95% CI: - 17.38, - 9.77; p < 0.001; SMD: - 0.52, 95% CI - 0.79, - 0.25; p =  < 0.001), insulin (SMD: - 0.67, 95% CI - 0.96, - 0.38; p < 0.001), HOMA-IR levels (WMD - 0.52, 95% CI - 0.66, - 0.38; p < 0.001; SMD: - 0.78, 95% CI - 1.02, - 0.42; p < 0.001), and HbA1c (WMD: - 0.35, 95% CI - 0.43, - 0.27; p < 0.001).

CONCLUSION

Zinc supplementation significantly reduced FBS, HOMA-IR, insulin and HbA1c. These findings suggest that zinc is potentially an effective complementary intervention to improve type 2 diabetes biomarkers.

Zinc utilization by microglia in Alzheimer's disease

Alzheimer's disease (AD) is the most common form of dementia defined by two key pathological characteristics in the brain, amyloid-β (Aβ) plaques and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau. Microglia, the primary innate immune cells of the central nervous system (CNS), provide neuroprotection through Aβ and tau clearance but may also be neurotoxic by promoting neuroinflammation to exacerbate Aβ and tau pathogenesis in AD. Recent studies have demonstrated the importance of microglial utilization of nutrients and trace metals in controlling their activation and effector functions. Trace metals, such as zinc, have essential roles in brain health and immunity, and zinc dyshomeostasis has been implicated in AD pathogenesis. As a result of these advances, the mechanisms by which zinc homeostasis influences microglial-mediated neuroinflammation in AD is a topic of continuing interest since new strategies to treat AD are needed. Here, we review the roles of zinc in AD, including zinc activation of microglia, the associated neuroinflammatory response, and the application of these findings in new therapeutic strategies.

Zinc deficiency affects insulin secretion and alters insulin-regulated metabolic signaling in rats

BACKGROUND

The essential trace element zinc is important in stabilizing pancreatic insulin secretion. Zinc not only influences the synthesis of insulin but also affects its activity. Insulin not only exerts a hypoglycemic effect but also regulates glucose and lipid metabolisms in insulin target organs. In this study, we aimed to determine changes to pancreatic β cells and insulin secretion induced by different zinc concentrations and to evaluate the effect of zinc deficiency on glucose intolerance, insulin resistance, and insulin target organs via changing insulin levels.

METHODS

We set up two experimental trials. In the first trial, male Sprague Dawley (SD) rats were divided into three groups. Group one (ZnC) received a standard diet, group two (ZnF) was given a zinc-free diet, and group three (ZnFC) was initially fed a zinc-free diet followed by a reversion to the standard diet. After sacrifice, we observed changes in blood parameters, including insulin, and examined alterations in pancreatic tissue using immunostaining, with focus on the localization of pancreatic β-cells. In the second trial, male SD rats were split into two groups, with one receiving a standard diet and the other a zinc-free diet. Oral glucose tolerance and insulin tolerance tests were then performed. After sacrifice, we evaluated changes in lipid and glucose metabolism within insulin target organs using quantitative polymerase chain reaction.

RESULTS

In the first trial, blood insulin levels and the area of insulin-positive staining in pancreatic β-cells decreased in the ZnF compared to the ZnC group. The ZnFC group did not show recovery in either blood insulin levels or the area of insulin-positive staining in pancreatic β-cells. In the second trial, no differences were observed in glucose tolerance or insulin resistance between the ZnC and ZnF groups. However, changes in the expression of insulin target genes were noted in the liver and adipose tissue in the ZnF group.

CONCLUSION

We reveal that dietary zinc concentrations not only affect the concentration of insulin in the blood but also impact the localization of pancreatic β-cells involved in insulin production. Furthermore, our results suggest that changes in blood insulin levels, induced by different zinc concentrations, could cause metabolic alterations in insulin target organs such as the liver and adipose tissue. This study sheds more light on the role of zinc in insulin-regulated metabolic diseases.

Co-administration of "L-Lysine, Vitamin C, and Zinc" increased the antioxidant activity, decreased insulin resistance, and improved lipid profile in streptozotocin-induced diabetic rats

PURPOSE

We previously showed the beneficial effect of L-Lysine (Lys), a chemical chaperone, on reducing diabetic complications in diabetic rats and type 2 diabetic patients. Herein, we evaluated the effect of Lys co-administration with Vitamin C and Zinc (Lys+VC+Zn), in diabetic rats.

METHODS

The streptozotocin (50 mg/Kg) was injected into male adult Wistar rats to induce diabetes. Then, different groups of normal and diabetic rats were treated with Lys and Lys+VC+Zn for five months. So, there were 0.1 % Lys in the drinking water of both groups. The control groups received water alone. During the experiment, the body weight, and various parameters were determined in the blood, serum/plasma, and urine of the rats.

RESULTS

The determination of biochemical indexes confirmed diabetes induction and its complications in rats. Treatment with either Lys or Lys+VC+Zn resulted in reduced blood glucose and protein glycation (decreasing AGEs and HbA1c), increased insulin secretion, alleviated insulin resistance and HOMA-IR, improved lipid profile and HDL functionality (LCAT and PON1), enhanced antioxidant status (FRAP and AOPP), improved kidney function (decreased microalbuminuria, serum urea, and creatinine), and increased chaperone capacity (HSP70). Lys+VC+Zn showed better effects on these parameters than Lys alone.

CONCLUSIONS

The results of this study indicated that co-administration of Lys, a chemical chaperone, with two antioxidants (VC and Zn) potentiates its antidiabetic effects and prevent diabetic complications in rat model of diabetes.

Effect of Zinc Supplementation on Lipid Profile and Body Composition in Patients with Type 2 Diabetes Mellitus: A GRADE-Assessed Systematic Review and Dose-Response Meta-analysis

The aim of this systematic review and meta-analysis of randomized controlled trials (RCTs) is to investigate the overall effects of zinc supplementation on lipid profile and body composition such as body weight (BW), body mass index (BMI), triglycerides (TG), total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C) in patients with type 2 diabetes mellitus (T2DM). Scopus, Web of Science, PubMed, and Embase databases were searched from inception through October, 2023. The I2 and Cochran's Q tests were used to assess heterogeneity between studies. Nineteen RCTs (n = 1357 participants) were included in the meta-analysis. Zinc supplementation significantly reduced TG (WMD = - 17.41 mg/dL; 95% CI: - 22.60, - 12.22; P < 0.001), TC (WMD: - 19.60 mg/dL; 95% CI: - 28.46, - 10.73, P < 0.001), LDL-C (WMD = - 8.80 mg/dL; 95% CI: - 14.80, - 2.81; P = 0.004), and BMI (WMD = - 0.53 kg/m2; 95% CI: - 1.05, - 0.01; P = 0.046) but not BW (WMD: - 0.51 kg, 95 % CI: - 1.99, 0.97, P = 0.498). Moreover, zinc supplementation increased HDL-C (WMD = 4.82 mg/dL; 95% CI: 0.88, 8.76; P = 0.016) in patients with T2DM. Our results propose that zinc supplementation may be an effective strategy for improving lipid profile and body composition in patients with T2DM.

Two risk factors for hypozincemia in diabetic β-thalassemia patients: Hepatitis C and deferasirox

BACKGROUND AND AIM

Hypozincemia is a prevalent adverse consequence in diabetes mellitus (DM) and β-Thalassemia patients. We aimed to evaluate the level of serum zinc in β-thalassemia patients with DM and a risk assessment for hypozincemia.

METHODS

The study population included transfusion-dependent thalassemia (TDT) and non-transfusion-dependent thalassemia (NTDT) with overt DM (fasting plasma glucose (FPG) ≥126 mg/dL, and/or 2-h plasma glucose≥200 mg/dL). Serum zinc concentration was measured by the colorimetric method, and the values below 70 μg/dL were defined as hypozincemia. Myocardial and liver T2*-weighted magnetic resonance imaging (MRI T2*, millisecond [ms]) were valued by a free contrast MRI. The demographic, clinical, paraclinical, and laboratory data were also recorded. The data belonged to the period from December 2018 until December 2020.

RESULTS

Of 64 diabetic β-thalassemia patients, 41 cases had zinc data in their medical files (aged 38 ± 9 years, 48.8% female). 78.05% of patients (n = 32) were TDT, and 21.95% were NTDT (n = 9). The mean ± standard deviation of zinc level was 110.2 ± 127.6 μg/dL. The prevalence of hypozincemia was 9.76%, 95% confidence interval [CI] 0.27 to 19.24 (four cases). After controlling age, the odds of hypozincemia for using deferasirox (DFX) was 8.77, 95% CI 0.60 to 127.1. In β-thalassemia patients, the age-adjusted risk of hypozincemia was calculated at 15.85, 95% CI 0.47 to 529.3 for hepatitis C. The adjusted risk of hypozincemia based on age for antacid use was 6.34, 95% CI 0.39 to 102.7.

CONCLUSION

In light of this study, as well as hepatitis C, using DFX and antacids is associated with a high risk of hypozincemia amid diabetic β-thalassemia cases. However, upward bias should be taken into consideration.

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.

The association between plasma zinc concentrations and markers of glucose metabolism in adults in Cameroon

An abnormal Zn status has been suggested to play a role in the pathogenesis of type 2 diabetes. However, epidemiological studies of the relationship between plasma Zn concentrations and diabetes are sparse and inconclusive. We aimed to investigate the association between plasma Zn concentrations and glycaemic markers (fasting glucose, 2-h glucose and homeostatic model assessment of insulin resistance) in rural and urban Cameroon. We studied 596 healthy adults (63·3 % women) aged 25-55 years in a population-based cross-sectional study. The mean plasma Zn concentration was 13·7 ± 2·7 µmol/L overall, with higher levels in men (14·4 ± 2·9 µmol/l) than in women (13·2 ± 2·6 µmol/l), P-value < 0·0001. There was an inverse relationship between tertiles of plasma Zn and 2-h glucose concentrations (P-value for linear trend = 0·002). The difference in 2-h glucose between those in the highest tertile of plasma Zn compared to the lowest was -0·63 (95 % CI - 1·02, -0·23) mmol/l. This remained significant after adjusting for age, sex, smoking status, alcohol intake, education level, area of residence, adiposity and objectively measured physical activity -0·43(-0·82, -0·04). Similar inverse associations were observed between plasma Zn concentrations and fasting glucose and homeostatic model assessment of insulin resistance when adjusted for socio-demographic and health-related behavioural characteristics. The current findings of an inverse association between plasma Zn concentrations and several markers of glucose homeostasis, together with growing evidence from intervention studies, suggest a role for Zn in glucose metabolism. If supported by further evidence, strategies to improve Zn status in populations may provide a cheap public health prevention approach for diabetes.

Urinary essential and toxic metal mixtures, and type 2 diabetes mellitus: Telomere shortening as an intermediary factor?

The joint effect of metal mixtures on telomere function and type 2 diabetes mellitus (T2DM) is unclear. This large-scale cross-sectional study sought to assess the role of telomere length (TL) in the relationship between urinary essential and toxic metal mixtures, and T2DM in 7410 Chinese adults ≥ 60 years of age. Essential (Cr, Cu, Zn, Se) and non-essential metals (V, Al, Sb, Sn, Cd, Pb) in urine samples were quantified, while leukocyte TL was measured from blood samples. Restricted cubic splines regression showed nonlinear relationships between single metal and T2DM, and between TL and T2DM. Bayesian kernel machine regression and quantile-based g-computation showed that the overall status of urinary metals was positively associated with risk of developing T2DM, which was mainly explained by exposure to Pb, Cd, and Sb, excessive Se intake, and high excretion of Zn. Mediation analyses showed that shortened TL mediated 27.9% of the overall positive effect of metal exposure on T2DM, and this mediation was mainly explained by toxic metal exposure and excessive Se intake. Tobacco smoke exposure, extensive cooking at home, and black tea consumption were found to be important contributors of toxic metal exposures. Further studies are needed to explore the recommended Zn dosage for T2DM patients at different stages, which may ameliorate pancreatic senescence and glycemic progression.

The Link between Trace Metal Elements and Glucose Metabolism: Evidence from Zinc, Copper, Iron, and Manganese-Mediated Metabolic Regulation

Trace metal elements are of vital importance for fundamental biological processes. They function in various metabolic pathways after the long evolution of living organisms. Glucose is considered to be one of the main sources of biological energy that supports biological activities, and its metabolism is tightly regulated by trace metal elements such as iron, zinc, copper, and manganese. However, there is still a lack of understanding of the regulation of glucose metabolism by trace metal elements. In particular, the underlying mechanism of action remains to be elucidated. In this review, we summarize the current concepts and progress linking trace metal elements and glucose metabolism, particularly for the trace metal elements zinc, copper, manganese, and iron.

Lower serum zinc level is associated with higher fasting insulin in type 2 diabetes mellitus (T2DM) and relates with disturbed glucagon suppression response in male patients

AIMS

Zinc ion can play critical role in glycemic control in diabetes mellitus (DM), contributing to both insulin synthesis and secretion. In this study, we aimed to investigate the level of zinc in diabetic patients and its association with glycemic parameters, insulin, and glucagon level.

METHODS

112 individuals (59 cases of type 2DM and 53 non-diabetic controls) were included in this study. Biochemical parameters (FBG, 2hpp, HbA1C), and zinc level in the serum were measured using colorimetric assays. Insulin and glucagon were measured by ELISA method. HOMA-IR, HOMA-B, reciprocal HOMA-B, and Quicki indices were calculated using appropriate formula. For further analysis, patients were divided into two groups: high (>135.5 μg/dl) and low (<135.5 μg/dl) zinc. Glucagon suppression was considered yes if 2hpp glucagon < fasting glucagon.

RESULTS

Our results showed that serum Zn level in type 2 DM patients was lower than control (P value=0.02). Patients with lower Zn had higher fasting insulin (P value=0.006) and higher β-cell activity index (HOMA-B, p value=0.02), however fasting glucagon and parameters of hyperglycemia (FBG, 2hpp, Hba1C) were not different. Moreover, insulin sensitivity and resistance indices (Quicki, HOMA-IR,1/HOMA-IR) showed non-significantly improved status in high Zn group. We found non-significant association between glucagon suppression and Zn level in both genders (N = 39, p value = 0.07), however, it was significant in males (N = 14, p value = 0.02).

CONCLUSION

Altogether, our results indicated reduced serum Zn in type 2DM can exacerbate hyperinsulinemia and glucagon suppression (only significant in the male), highlighting its importance in type 2DM control.

Dietary Patterns, Foods, and Nutrients to Ameliorate Non-Alcoholic Fatty Liver Disease: A Scoping Review

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease without pharmacological treatment yet. There is also a lack of specific dietary recommendations and strategies to treat the negative health impacts derived from NAFLD.

OBJECTIVE

This scoping review aimed to compile dietary patterns, foods, and nutrients to ameliorate NAFLD.

METHODS

A literature search was performed through MEDLINE, Scopus, Web of Science, and Google Scholar.

RESULTS

Several guidelines are available through the literature. Hypocaloric Mediterranean diet is the most accepted dietary pattern to tackle NAFLD. Coffee consumption (sugar free) may have a protective effect for NAFLD. Microbiota also plays a role in NAFLD; hence, fibre intake should be guaranteed.

CONCLUSIONS

A high-quality diet could improve liver steatosis. Weight loss through hypocaloric diet together with physical activity and limited sugar intake are good strategies for managing NAFLD. Specific dietary recommendations and a Mediterranean plate have been proposed to ameliorate NAFLD.

Multifunctional role of zinc in human health: an update

Zinc is a multipurpose trace element for the human body, as it plays a crucial part in various physiological processes, such as cell growth and development, metabolism, cognitive, reproductive, and immune system function. Its significance in human health is widely acknowledged, and this has led the scientific community towards more research that aims to uncover all of its beneficial properties, especially when compared to other essential metal ions. One notable area where zinc has shown beneficial effects is in the prevention and treatment of various diseases, including cancer. This review aims to explain the involvement of zinc in specific health conditions such as cancer, coronavirus disease 2019 (COVID-19) and neurological disorders like Alzheimer's disease, as well as its impact on the gut microbiome.

Zinc supplementation ameliorates type 2 diabetes markers through the enhancement of total antioxidant capacity in overweight patients

BACKGROUND

Evidence show that the recommended dose of zinc may not be sufficient for controlling pathological conditions such as type 2 diabetes mellitus (T2DM).

AIM

This study aimed to evaluate the effects of zinc supplementation on the oxidative status in overweight T2DM. In addition, the routine glycaemic parameters were determined and compared in zinc-treated and placebo groups.

METHODS

In this randomised, double-blind, placebo-controlled trial, 70 patients with T2DM were selected. They were divided into two groups for supplementation of 50 mg zinc gluconate or placebo (zinc group, n=35; placebo group, n=35) per day for 8 weeks. Blood samples were collected from all the individuals in the zinc group and controls for analysis.

RESULTS

The results showed that zinc supplementation to patients with T2DM for 8 weeks significantly inhibited serum levels of lipid peroxidation (25%), nitrotyrosine (30%) and total oxidant status levels (25%, p<0.05). Nevertheless, the total antioxidant capacity was significantly elevated (16%) following zinc intake by patients with T2DM.

CONCLUSIONS

These data, together with our previous report, may suggest that the control in the glycaemic condition in overweight patients with T2DM is correlated with the antioxidative/oxidative balance following intake of 50 mg zinc supplementation for 8 weeks. Under these circumstances, the clinical and glycaemic indices, including fasting blood glucose, insulin, haemoglobin A1c and homeostasis model of assessment-insulin resistance, were controlled.

TRIAL REGISTRATION NUMBER

IRCT2015083102.

Effect of zinc supplementation on blood sugar control in the overweight and obese population: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Although overweight and obese people have a higher risk of type 2 diabetes incidence than normal-weight individuals, the efficacy of zinc supplementation in blood sugar control in overweight and obese people remained unknown. This meta-analysis attempted to address this issue.

METHODS

Databases including PubMed, Embase, and the Cochrane Library were searched from inception until May 2022 to identify randomized controlled trials (RCTs) investigating the effects of zinc supplementation among participants who were overweight or obese without language restriction. It is a random-effect meta-analysis that analyzed the impact of zinc supplementation on fasting glucose (FG) (i.e., primary outcome) and other variables including fasting insulin (FI), homeostasis model assessment-insulin resistance index (HOMA-IR), glycated hemoglobin (HbA1c), high-sensitivity C-reactive protein (hs-CRP), and 2-hour postprandial glucose (2 h- PG).

RESULTS

Analysis of 12 eligible RCTs involving 651 overweight/obese participants demonstrated that zinc supplementation significantly improves FG (weighted mean difference [WMD]: -8.57 mg/dL; 95% confidence interval [CI]: -14.04 to -3.09 mg/dL, p = 0.002), HOMA-IR (WMD: -0.54; 95% CI: -0.78 to -0.30, p < 0.001), HbA1c (WMD: -0.25%; 95% CI: -0.43% to -0.07%, p = 0.006), and 2 h-PG (WMD: -18.42 mg/dL; 95% CI: -25.04 to -11.79 mg/dL, p < 0.001) compared to those in the control group. After conducting subgroup analyses, we found that the primary outcome, FG, showed more significant results in the subgroups with Asia, Zinc supplementation alone, higher dose (≥30 mg) and patients with diabetes.

CONCLUSION

Our meta-analysis indicated that zinc supplementation benefits blood sugar control in overweight and obese populations, with an especially significant reduction in FG.

Can Nutrition Contribute to a Reduction in Sarcopenia, Frailty, and Comorbidities in a Super-Aged Society?

Many countries are facing the advent of super-aging societies, where sarcopenia and frailty will become pertinent problems. The prevalence of comorbidities is a major problem in countries with aged populations as elderly people suffer from various diseases, such as diabetes, heart failure, chronic kidney disease and dementia. All of these diseases are associated with sarcopenia and frailty, and they frequently cause falls, fractures, and a decline in activities of daily living. Fractures in the elderly people are associated with bone fragility, which is influenced by diabetes and chronic kidney disease. Nutritional support for chronic disease patients and sarcopenic individuals with adequate energy and protein intake, vitamin D supplementation, blood glucose level management for individuals with diabetes, obesity prevention, nutritional education for healthy individuals, and the enlightenment of society could be crucial to solve the health-related problems in super-aging societies.

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.

Effect of zinc supplementation in the management of type 2 diabetes: A grading of recommendations assessment, development, and evaluation-assessed, dose-response meta-analysis of randomized controlled trials

The question of whether zinc supplementation may improve cardio-metabolic health in patients with type 2 diabetes mellitus (T2DM) remains controversial and require further evaluation. This study aimed to summarize the effectiveness of oral zinc supplementation in improving cardio-metabolic risk markers in people with T2DM. We searched PubMed, Scopus, and Web of Science from inception to April 2023, for randomized controlled trials (RCTs). RCTs of type 2 diabetic adults (aged ≥18 years) comparing zinc supplementation with placebo were included. We excluded studies if not randomized, involved co-supplementation, and were conducted in children or pregnant women. Glycemic indices, lipid profiles, blood pressure, anthropometric measure, c-reactive protein (CRP), creatinine, and serum zinc were extracted. Certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) methods. We used a random-effect model to perform the dose-response analysis. Effect sizes were presented as mean difference (MD) and 95% confidence interval (CI). 22 studies (n = 1442 participants) were included. The certainty of the evidence was rated as moderate to high. Zinc supplementation significantly reduced glycemic indices: including two-hour postprandial glucose (2hpp) (mean difference (MD): -34.34 mg/dl; 95%CI: -51.61∼ -17.07), fast blood sugar (FBS) (MD: -23.32 mg/dl; 95% CI: -33.81∼ -12.83), and hemoglobin A1c (HbA1c) (MD: -0.47; 95% CI: -0.71∼ -0.23). Zinc had a favorable effect on lipid profiles low-density lipoprotein (LDL) (MD: -10.76 mg/dl; CI: -17.79∼-3.73), triglyceride (TG) (MD: -18.23 mg/dl; CI: -32.81∼-3.65), total cholesterol (TC) (MD: -12.74 mg/dl; CI: -21.68∼-3.80), VLDL (MD: -5.39 mg/dl; CI: -7.35∼-3.43) and high-density lipoprotein (HDL) (MD: 4.04 mg/dl; CI: 0.96 ∼ 7.12). Systolic blood pressure (SBP) (MD): -3.64 mmHg; 95% CI: -6.77∼ -0.52), weight (MD: 1.00 kg; 95% CI: 0.34∼1.66), CRP (MD: -3.37 mg/l, 95% CI: -4.05∼ -2.70), and serum zinc (MD: 15.38 µg/dl; 95% CI: 10.74∼ 20.02) changed to a statistically significant extent with zinc supplementation. There was also a linear association between additional 10 mg/d zinc treatment with FBS, HbA1c, HDL, LDL, TG, TC, and serum zinc. A non-linear dose-response gradient was seen for FBS, HDL, and SBP (p < 0.05). Egger's test showed no substantial publication bias. Our findings strongly suggest a potential beneficial effect of zinc supplementation on type 2 diabetic patients. Further high-quality research is needed to determine the optimal form, dosage, and duration of zinc supplementation for this population.

The Sweet Side of HIPK2

HIPK2 is an evolutionary conserved protein kinase which modulates many molecular pathways involved in cellular functions such as apoptosis, DNA damage response, protein stability, and protein transcription. HIPK2 plays a key role in the cancer cell response to cytotoxic drugs as its deregulation impairs drug-induced cancer cell death. HIPK2 has also been involved in regulating fibrosis, angiogenesis, and neurological diseases. Recently, hyperglycemia was found to positively and/or negatively regulate HIPK2 activity, affecting not only cancer cell response to chemotherapy but also the progression of some diabetes complications. The present review will discuss how HIPK2 may be influenced by the high glucose (HG) metabolic condition and the consequences of such regulation in medical conditions.

The Molecular Basis for Zinc Bioavailability

Zinc is an essential micronutrient, and its deficiency is perhaps the most prevalent and least understood worldwide. Recent advances have expanded the understanding of zinc’s unique chemistry and molecular roles in a vast array of critical functions. However, beyond the concept of zinc absorption, few studies have explored the molecular basis of zinc bioavailability that determines the proportion of dietary zinc utilized in zinc-dependent processes in the body. The purpose of this review is to merge the concepts of zinc molecular biology and bioavailability with a focus on the molecular determinants of zinc luminal availability, absorption, transport, and utilization.

Capsaicin and Zinc Signalling Pathways as Promising Targets for Managing Insulin Resistance and Type 2 Diabetes

The global burden of type 2 diabetes (T2DM) has led to significant interest in finding novel and effective therapeutic targets for this chronic disorder. Bioactive food components have effectively improved abnormal glucose metabolism associated with this disease. Capsaicin and zinc are food components that have shown the potential to improve glucose metabolism by activating signalling events in the target cells. Capsaicin and zinc stimulate glucose uptake through the activation of distinct pathways (AMPK and AKT, respectively); however, calcium signal transduction seems to be the common pathway between the two. The investigation of molecular pathways that are activated by capsaicin and zinc has the potential to lead to the discovery of new therapeutic targets for T2DM. Therefore, this literature review aims to provide a summary of the main signalling pathways triggered by capsaicin and zinc in glucose metabolism.

The protective effect of zinc, selenium, and chromium on myocardial fibrosis in the offspring of rats with gestational diabetes mellitus

The offspring of gestational diabetes mellitus (GDM) mothers are considered to be at the risk of cardiovascular diseases due to intrauterine hyperglycemia exposure. Our previous study showed that zinc, selenium, and chromium dramatically alleviated glucose intolerance in GDM rats and their offspring (P < 0.05). However, the effects of these elements on the damage of the cardiac myocytes of GDM offspring and the underlying mechanisms have not been demonstrated. Here, we investigated the beneficial effects of zinc (10 mg per kg bw), selenium (20 μg per kg bw), and chromium (20 μg per kg bw) supplementation on myocardial fibrosis in the offspring of GDM rats induced by a high-fat and sucrose (HFS) diet. The results showed that maternal GDM induced glucose intolerance, oxidative stress, cardiac inflammation and myocardial fibrosis in offspring rats during different ages (3 days, 3 weeks, and adulthood), which were ameliorated by zinc, selenium and chromium supplementation (P < 0.05). The activity of cardiac damage markers such as creatine kinase-myocardial band isoenzyme (CK-MB), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) decreased by 40-60% in element-supplemented offspring compared to that in non-supplemented offspring of GDM dams (P < 0.05). Moreover, maternal GDM-induced expression of fibrosis-related proteins and the transforming growth factor-beta 1 (TGF-β1)/small mothers against decapentaplegic homolog 3 (Smad3) signaling pathway in the heart tissue of offspring was down-regulated by zinc, selenium, and chromium supplementation (P < 0.05). In conclusion, zinc, selenium, and chromium may play a protective role in maternal GDM-induced myocardial fibrosis in offspring from birth to adulthood by inactivating the TGF-β1/Smad3 pathway.

Evaluation among trace elements, clinical parameters and type 1 diabetes according to sex: A new sight of auxiliary prediction in negative insulin auto-antibodies population

BACKGROUND

Type 1 diabetes (T1D) exhibited sex-specific metabolic status including oxidative stress with dynamic change of trace elements, which emphasized the importance of the evaluation of trace elements according to sex. Besides, the most significant characteristic, insulin auto-antibodies, could not be found in all T1D patients, which needed the auxiliary prediction of clinical parameters. And it would benefit the early detection and treatment if some high-risk groups of T1D could predict and prevent the occurrence of disease through common clinical parameters. Hence, there was an urgent need to construct more effective and scientific statistical prediction models to serve clinic better. This study aimed to evaluate the sex-specific levels of trace elements and the relationship between trace elements and clinical parameters in T1D, and construct sex-specific auxiliary prediction model combined with trace elements and clinical parameters.

METHODS

A total of 105 T1D patients with negative insulin auto-antibodies and 105 age/sex-matched healthy individuals were enrolled in First Hospital of Jilin University. Inductively Coupled Plasma Mass Spectrometry was performed for the measurement of calcium (Ca), magnesium (Mg), zinc (Zn), copper (Cu), iron (Fe), selenium (Se) in the serum, and the data of clinical parameters were received from medical record system. The lambda-mu-sigma method was used to evaluate the relationship between abnormal clinical parameters and trace elements. Training set and validation set were divided for the construction of predictable models in males and females: clinical parameters model, trace element model and the combined model (clinical parameters and trace elements). Goodness fit test, decision curve analysis and other related statistical methods were used to perform data analysis.

RESULTS

Lower levels of Mg, Ca, Fe in the serum were found in T1D population in females compared with healthy population, while levels of Fe, Zn and Cu of serum in T1D individuals were higher than those of healthy population in males. Levels of serum Mg, Fe and Cu in T1D group were found with significant sex difference for (P < 0.05), and the levels of Fe and Cu in serum of males were higher than those of females, level of serum Mg in males was lower than those of females. Levels of serum Mg and Zn showed fluctuation trend with increased numbers of abnormal clinical parameters (NACP) in males. Serum Zn in females showed consistent elevated trend with NACP; serum Se increased first and then decreased with NACP in males and females. The auxiliary prediction model (Triglyceride, Total protein, serum Mg) was found with the highest predicted efficiency in males (AUC=0.993), while the model in females (Apolipoprotein A, Creatinine, Fe, Se, Zn/Cu ratio) showed the best predicted efficiency (AUC=0.951). The models had passed the verification in validation set, and Chi-square goodness-of-fit test, DCA results both confirmed their satisfactory clinical applicability.

CONCLUSION

Sex-specific difference were found in serum Mg, Fe and Cu in T1D. The combination of triglyceride, total protein and serum Mg for males, and apolipoprotein A, creatinine, Fe, Se, Zn/Cu ratio for females could effectively predict T1D in patients with negative anti-bodies, which would provide alarm for the population with high-risk of T1D and serve the T1D prediction in patients with negative anti-bodies.

[Nutrition for diabetic patients (Update 2023)]

All patients with diabetes require individual and personalized nutritional consultation with professionals. The patient's needs should be the primary focus of the dietary therapy, taking their lifestyle and the type of diabetes into consideration. With the recommendations to the patient's diet, there need to be specific metabolic goals to reduce the disease's progression and to avoid long term health effects. Therefore, practical guidelines such as portion size and meal planning tips should be the main focus.According to the latest national and international standards, patients suffering from diabetes should have access to nutrition consulting and nutritional training. During consultation they can be supported on- how to manage their health condition and choosing food and beverage to improve their health.These practical recommendations sum up the latest literature on nutritional aspects of diabetes treatment.

Serum Zinc Levels in Chronic Kidney Disease Patients, Hemodialysis Patients, and Healthy Controls: Systematic Review and Meta-Analysis

OBJECTIVES

Patients with chronic kidney disease (CKD) are susceptible to changes in zinc homeostasis through anorexia and dietary restrictions, as well as hemodialysis (HD). Changes in zinc homeostasis might predispose CKD and HD patients to specific adverse effects, including erythropoietin-resistant anemia, oxidative stress, atherosclerosis, and cardiovascular disease. Because serum zinc levels are rarely measured in CKD and HD patients, zinc supplementations do not represent a routine therapy for CKD and dialysis patients. Therefore, in this meta-analysis, we aimed to assess serum zinc levels in CKD and HD patients compared with healthy controls (HC). In addition, we investigated whether HD affects serum zinc levels by comparing serum zinc levels in HD versus CKD patients and comparing serum zinc pre- versus post-HD.

DESIGN AND METHODS

A comprehensive search of databases was conducted to identify either observational studies or randomized trials that assessed serum zinc levels in either CKD and/or HD patients in comparison to HC. We conducted a random-effects meta-analysis.

RESULTS

Our meta-analysis included 42 studies with a total of 4,161 participants, of whom 460 were CKD patients, 2,047 were HD patients, and 1,654 were HCs. Both CKD and HD patients showed lower serum zinc levels compared with HC (mean difference = -22.86 μg/dL, 95% CI -33.25 to -12.46; mean difference = -13.64 μg/dL, 95% CI -21.47 to -53.80, respectively). CKD and HD patients showed no significant difference in serum zinc levels (mean difference = 15.39, 95% CI -8.91 to 39.68). Pre-HD serum zinc levels were significantly lower than those post-HD (mean difference = -7.51 μg/dL, 95% CI -14.24 to -0.78).

CONCLUSION

In the current study, the serum zinc levels were lower in CKD and HD patients compared to HCs and appears to be more common than reported in daily clinical practice. It may be beneficial to assess serum zinc levels in CKD and HD patients. More research on zinc in kidney disease is encouraged.

Transgenerational effects of zinc, selenium and chromium supplementation on glucose homeostasis in female offspring of gestational diabetes rats

Clinical studies have demonstrated that maternal gestational diabetes mellitus (GDM) increases the offspring's risk of developing glucose intolerance. Our previous study reported that co-supplementation with zinc, selenium, and chromium improved insulin resistance in diet-induced GDM rats. Here, Transgenerational effects of supplementation with zinc (10 mg/kg.bw), selenium (20 μg/kg.bw), and chromium (20 μg/kg.bw) in F1 female offspring of both zinc, selenium and chromium (ZnSeCr)-treated, and untreated GDM rats daily by gavage from weaning to the postpartum were investigated in the present study. Glucose homeostasis in the F1 female offspring of GDM at different stages were evaluated. Maternal GDM did increase the birth mass of newborn F1 female offspring, as well as the serum glucose and insulin levels. Zinc, selenium and chromium supplementation attenuated the GDM-induced mass gain, increased serum glucose and insulin levels in the female neonates. The high fat and sucrose (HFS) diet-fed GDM-F1 offspring developed GDM, with glucose intolerance, hyperglycemia and insulin resistance during pregnancy. Moreover, endoplasmic reticulum (ER) stress-related protein levels were increased and the activation of insulin signaling pathways were reduced in the liver of HFS-fed GDM-F1 offspring. Whereas glucose homeostasis in parallel with insulin sensitivity was normalized in the female offspring of GDM by supplementation both F0 dams and F1 offspring with zinc, selenium and chromium, not in those either F0 or F1 elements supplemented offspring. Therefore, we speculate that zinc, selenium and chromium supplementation may have a potential beneficial transgenerational effect on the glucose homeostasis in the female offspring of GDM.

Cross-sectional and longitudinal associations of urinary zinc with glucose-insulin homeostasis traits and type 2 diabetes: Exploring the potential roles of systemic inflammation and oxidative damage in Chinese urban adults

The link between zinc exposure and glucose metabolism or the development of type 2 diabetes (T2D) is controversial, and underlying mechanisms are unclear. This study aimed to explore the associations of zinc exposure with glucose-insulin homeostasis traits and the long-term effects of zinc on the development of T2D, and further to estimate the potential roles of inflammation and oxidative damage in such relationships. We investigated 3890 urban adults from the Wuhan-Zhuhai cohort, and followed up every three years. Mixed linear model was applied to estimate dose-response associations between urinary zinc and glycemia traits [fasting plasma insulin (FPI), fasting plasma glucose (FPG), insulin resistance (homeostasis model assessment of insulin resistance, HOMA-IR), and β-cell dysfunction (homeostasis model assessment of β-cell function, HOMA-B)], as well as zinc and biomarkers for systemic inflammation (C-reactive protein) and oxidative damage (8-isoprostane and 8-hydroxy-2'-deoxyguanosine). Logistic regression model and Cox regression model were conducted to evaluate the relationships between urinary zinc and prevalence and incidence of T2D, respectively. We further performed mediation analysis to assess the roles of inflammation and oxidative damage biomarkers in above associations. At baseline, we observed significant dose-response relationships of elevated urinary zinc with increased FPI, FPG, HOMA-IR, and T2D prevalence and decreased HOMA-B, and such associations could be strengthened by increased C-reactive protein, 8-isoprostane, and 8-hydroxy-2'-deoxyguanosine. Elevated C-reactive protein significantly mediated 9.09% and 17.67% of the zinc-related FPG and HOMA-IR increments, respectively. In longitudinal analysis, a significantly positive association between urinary zinc and T2D incidence was observed among subjects with persistent high urinary zinc levels when compared with those with persistent low zinc levels. Our results suggested that high levels of zinc exposure adversely affected on glucose-insulin homeostasis and further contributed to increased risk of T2D cross-sectionally and longitudinally. Moreover, inflammatory response might play an important role in zinc-related glucose metabolic disorder.

Urinary Zinc and Incident Type 2 Diabetes: Prospective Evidence From the Strong Heart Study

OBJECTIVE

Hyperglycemia can increase urinary zinc excretion. We evaluated the association of higher urinary zinc level with new diagnosis of incident type 2 diabetes mellitus (T2DM) in adult populations with a high burden of T2DM from AZ, OK, and ND and SD. We also assessed the cross-sectional association of urinary zinc levels with prevalent prediabetes.

RESEARCH DESIGN AND METHODS

We included 1,339 adults free of T2DM at baseline (1989-1991) followed through 1998-1999 in the Strong Heart Study (SHS) and 1,905 family members of SHS participants followed as part of the Strong Heart Family Study (SHFS) through 2006-2009.

RESULTS

T2DM incidence was 14.7% (mean follow-up 6.6 years) in the SHS and 13.5% (mean follow-up 5.6 years) in the SHFS. After adjustment for sex, site, education, smoking status, BMI, and estimated glomerular filtration rate, the hazard ratio of T2DM in comparing 75th vs. 25th percentiles of urinary zinc distribution was 1.21 (95% CI 1.08, 1.36) in the SHS and 1.12 (0.96, 1.31) in the SHFS. These associations were attenuated but significant in the SHS after adjustment for HOMA of insulin resistance (HOMA-IR) score. With exclusion of participants with prediabetes at baseline, urinary zinc remained significantly associated with T2DM in the SHS. In cross-sectional analyses, prediabetes was associated with higher urinary zinc levels.

CONCLUSIONS

Urinary zinc levels were associated with T2DM incidence and prediabetes prevalence even after adjustment for HOMA-IR in populations with a high burden of T2DM. These results highlight the importance of zinc metabolism in diabetes development.

Modulation of Zinc Transporter Expressions by Additional Zinc in C2C12 Cells Cultured in a High Glucose Environment and in the Presence of Insulin or Interleukin-6

Zn status has been related to various chronic diseases presenting oxidative stress and inflammation, such as type 2 diabetes. Zn supplementation has been suggested to be a potential coadjuvant in the management of this condition. Zn transporters constitute a key component in the maintenance of Zn homeostasis. Our aim was to evaluate the modulatory effect of additional Zn (10 or 100 µM; as a ZnSO₄*7H₂0) on the mRNA relative expression of selected Zn transporters (ZnT1, ZnT5, ZnT7, ZIP6, ZIP7, ZIP10, ZIP14), in myoblast (C2C12) cells cultured in normal (10 mM) and high glucose (30 mM), and in the absence or presence of insulin (1 nM), and interleukin-6 (IL-6; 5 nM) for 24 h. The main findings of our study were that in high glucose conditions in absence of insulin or IL-6, additional Zn increased ZnT1 and ZIP6, and decreased ZnT5 and ZIP7 expressions. However, this situation is modified by insulin, where incremental Zn induced increased expressions of ZnT1, ZnT5, and all the ZIP transporters studied. In high glucose conditions and in the presence of IL-6, additional Zn caused increased expressions of ZnT7, ZIP7, and ZIP14, compared with results in the absence of IL-6. This study provides preliminary evidence for the differential expression of selected Zn transporters in C2C12 cells subjected to high glucose and incremental Zn, suggesting that important changes in intracellular Zn distribution take place in response to inflammatory and high-insulin environments. Further study is necessary to understand the implications of these findings.

The effects of medicinal herbs on gut microbiota and metabolic factors in obesity models: A systematic review

BACKGROUND AND AIMS

This systematic review of animal studies aimed to identify anti-obesity medicinal herbs with prebiotic properties, and investigate their effects on gut microbiota and metabolic disorders.

METHODS

To obtain the relevant publications, four electronic databases were systematically searched up to June 2019.

RESULTS

Out of 1949 publications, 20 articles met the inclusion criteria in this study. Apart from body weight, some cases (n = 11) had reported the effects of medicinal herbs on metabolic parameters, including lipid profile (n = 7) and glycemic status (n = 4).

CONCLUSION

Although some medicinal herbs could be effective in modulating metabolic status and body weight, through making changes in the gut flora, further studies are needed to confirm the efficacy of such herbs in clinical trials.

Triangulating evidence for the causal impact of single-intervention zinc supplement on glycaemic control for type 2 diabetes: systematic review and meta-analysis of randomised controlled trial and two-sample Mendelian randomisation

Although previous studies suggested the protective effect of Zn for type 2 diabetes (T2D), the unitary causal effect remains inconclusive. We investigated the causal effect of Zn as a single intervention on glycaemic control for T2D, using a systematic review of randomised controlled trials and two-sample Mendelian randomisation (MR). Four primary outcomes were identified: fasting blood glucose/fasting glucose, HbA1c, homeostatic model assessment for insulin resistance (HOMA-IR) and serum insulin/fasting insulin level. In the systematic review, four databases were searched until June 2021. Studies, in which participants had T2D and intervention did not comprise another co-supplement, were included. Results were synthesised through the random-effects meta-analysis. In the two-sample MR, we used single-nucleotide polymorphisms (SNP) from MR-base, strongly related to Zn supplements, to infer the relationship causally, but not specified T2D. In the systematic review and meta-analysis, fourteen trials were included with overall 897 participants initially. The Zn supplement led to a significant reduction in the post-trial mean of fasting blood glucose (mean difference (MD): −26·52 mg/dl, 95 % CI (−35·13, −17·91)), HbA1c (MD: −0·52 %, 95 % CI: (−0·90, −0·13)) and HOMA-IR (MD: −1·65, 95 % CI (−2·62, −0·68)), compared to the control group. In the two-sample MR, Zn supplement with two SNP reduced the fasting glucose (inverse-variance weighted coefficient: −2·04 mmol/l, 95 % CI (−3·26, −0·83)). From the two methods, Zn supplementation alone may causally improve glycaemic control among T2D patients. The findings are limited by power from the small number of studies and SNP included in the systematic review and two-sample MR analysis, respectively.

Neuroinflammatory responses following zinc or branched-chain amino acids supplementation in obese rats

The excessive production of pro-inflammatory mediators, characteristic of obesity, leads to neuroinflammation. Zinc (Zn) and the branched-chain amino acids (BCAA) are supplements known for their immunomodulatory properties. Our goal was to evaluate if Zn or BCAA supplementation can affect long-term recognition memory and neuroinflammatory parameters of obese rats after a high-fat diet (HFD). Three-month-old Wistar rats were divided into six groups: Standard diet (SD) + vehicle; SD + Zn; SD + BCAA; High-fat diet (HFD) + vehicle; HFD + Zn; and HFD + BCAA. Diets were administrated for 19 weeks, Zn (1,2 mg/kg/day) or BCAA (750 mg/kg/day) supplementation was conducted in the last 4 weeks. Long-term recognition memory was evaluated by the novel object recognition test. IL-1β immunoreactivity in the cortex and hippocampus, and IL-6 levels in the cortex tissue were assessed. Astrogliosis were evaluated through GFAP + cell count and morphological analysis (Sholl Method). Zn supplementation improved object recognition memory in HFD-fed rats, which was not observed following BCAA supplementation. The levels of IL-6 in the cerebral cortex were higher after HFD, which was not diminished after neither supplementation. Obesity also led to increased IL-1β immunoreactivity in the cerebral cortex and hippocampus, which was reduced by Zn. BCAA supplementation also diminished IL-1β immunoreactivity, but only in the hippocampus. We also showed that astrocyte reactivity caused by HFD is area-dependent, being the cerebral cortex more susceptible to the diet. Even though BCAA and Zn can affect IL-1β immunoreactivity and astrocyte morphology, only Zn improved memory. Future studies are needed to clarify the pathways by which Zn improves cognition in obesity.

Nonpharmacological Interventions for the Management of Testosterone and Sperm Parameters: A Scoping Review

PURPOSE

Testosterone replacement and associated pharmacologic agents are effective strategies to treat male hypogonadism; however, nutraceutical agents and lifestyle modification approaches have gained medical interest. The purpose of this scoping review is to highlight the evidence (or lack thereof) of nutraceuticals and lifestyle modification approaches in the management of testosterone levels and sperm parameters.

METHODS

A scoping review of nonpharmacologic interventions (supplements, herbal medicines, diets, sleep, and exercise) with the potential to improve male health was undertaken to elucidate changes in testosterone levels and sperm parameters in men with hypogonadism or infertility compared with healthy patients.

FINDINGS

A multitude of nutraceuticals and functional nutrients are purported to stimulate testosterone production; however, only a select few have had promising results, such as zinc, vitamin D (in case of hypovitaminosis D), l-arginine, mucuna, and ashwagandha, based on well-controlled randomized clinical trials of men with low testosterone levels and related problems. Except for l-arginine, these natural agents, as well as tribulus and ω3 fatty acids, can improve some degree of sperm parameters in infertile men. Before implementing these nutraceutical agents, adequate sleep, exercise, and weight loss in patients with obesity are imperative. The effects of nonpharmacologic interventions on testosterone levels are modest and hence do not directly translate into clinical benefits. Correspondingly, androgen receptor content, but not endogenous androgens, has been regarded as the principal factor in muscle hypertrophy.

IMPLICATIONS

A limited number of supplements and herbal medicines can be considered as adjunctive approaches in the management of testosterone levels and sperm parameters, primarily in men with low testosterone levels and infertility, whereas most nonpharmacologic supplements appear to lack evidence. Although proper physical exercise, sleep, and diet are indisputable approaches because of the general benefits to health, the use of nutraceuticals, if considered, must be personalized by physicians and/or registered dietitians.

The effect of zinc supplementation on glucose homeostasis: a randomised double-blind placebo-controlled trial

AIMS

The burden and health costs of Type 2 Diabetes Mellitus continue to increase globally and prevention strategies in at-risk people need to be explored. Previous work, in both animal models and humans, supports the role of zinc in improving glucose homeostasis. We, therefore, aimed to test the effectiveness of zinc supplementation on glycaemic control in pre-diabetic adults.

METHODS

We conducted a randomized, double-blind, placebo-controlled trial across 10 General Practitioner (GP) practices in NSW, Australia. The trial is known as Zinc in Preventing the Progression of pre-Diabetes (ZIPPeD)Study. Pre-diabetic (haemoglobin A1c [HbA1c] 5.7-6.4%, 39-46 mmol/mol) men and women (N = 98) were all assigned to a free state government telephone health coaching service (New South Wales Get Healthy Information and Coaching Service) and then randomised to either daily 30 mg zinc gluconate or placebo. Blood tests were collected at baseline, 1, 6 and 12 months for the primary outcomes (HbA1c, fasting blood glucose (FBG)); secondary outcomes included Homeostasis Model Assessment 2 (HOMA 2) parameters, lipids, body weight, height, waist circumference, blood pressure and pulse.

RESULTS

The baseline-adjusted mean group difference at 6 months, expressed as treatment-placebo, (95% CI) was -0.02 (-0.14, 0.11, p = 0.78) for HbA1c and 0.17 (-0.07, 0.42; p = 0.17) for FBG, neither of which were statistically significant. There were also no significant differences between groups in any of the secondary outcomes. Zinc was well tolerated, and compliance was high (88%).

CONCLUSION

We believe our results are consistent with other Western clinical trial studies and do not support the use of supplemental zinc in populations with a Western diet. There may still be a role for supplemental zinc in the developing world where diets may be zinc deficient.

TRIAL REGISTRATION

Australian and New Zealand Clinical Trials Registry, ACTRN12618001120268. Registered on 6 July 2018.

The impact of zinc supplementation on galectin-3 and metabolic markers in diabetic patients on hemodialysis: A randomized, double-blind, placebo-controlled trial

Purpose

There is little information about the association between zinc sulfate (ZnSO4) supplementation and metabolic profiles in zinc-deficient diabetic patients on hemodialysis (DHPs). Therefore, we aimed to investigate the association between ZnSO4 supplementation and serum levels of galectin-3 (Gal-3) and cardiometabolic parameters in zinc-deficient DHPs.

Methods

In the present randomized double-blind placebo-controlled clinical trial, 46 zinc-deficient DHPs (35-62 years) were included and assigned to receive either 220 mg/d ZnSO4 or placebo for 8 weeks. Serum levels of Gal-3, lipid profile, and blood pressure (BP) were assessed at baseline and the end of trial.

Results

We found a significant effect of ZnSO4 intake on the reduction of serum Gal-3 (P =  < 0.001), triglycerides (P =  < 0.001), total cholesterol (P =  < 0.001), low-density lipoprotein cholesterol (P =  < 0.001) and increased high-density lipoprotein cholesterol (P =  < 0.001) as compared to the control group. Additionally, systolic blood pressure (SBP) (P = 0.006) and diastolic blood pressure (DBP) (P = 0.01) were significantly reduced following 8 weeks of ZnSO4 supplementation.

Conclusion

Taken together, 220 mg ZnSO4 supplementation per day for 8 weeks among zinc-deficient DHPs had beneficial effects on Gal-3 and metabolic profiles.

Iranian Registry of Clinical Trials Identifier

IRCT20191217045765N1, date of registration: 2020-02-09.

Efficacy and Safety of Nutrient Supplements for Glycaemic Control and Insulin Resistance in Type 2 Diabetes: An Umbrella Review and Hierarchical Evidence Synthesis

Background: Nutrient supplements are widely used for type 2 diabetes (T2D), yet evidence-based guidance for clinicians is lacking. Methods: We searched the four electronic databases from November 2015−December 2021. The most recent, most comprehensive, high-ranked systematic reviews, meta-analyses, and/or umbrella reviews of randomised controlled trials in adults with T2D were included. Data were extracted on study characteristics, aggregate outcome measures per group (glycaemic control, measures of insulin sensitivity and secretion), adverse events, and Grading of Recommendations Assessment, Development, and Evaluation (GRADE) assessments. Quality was assessed using A Measurement Tool to Assess Systematic Reviews Version 2.0 (AMSTAR 2). Results: Twelve meta-analyses and one umbrella review were included. There was very low certainty evidence that chromium, Vitamin C, and omega-3 polyunsaturated fatty acids (Ω-3 PUFAs) were superior to placebo for the primary outcome of glycated hemoglobin (HbA1c) (Mean Difference/MD −0.54, −0.54 and ES −0.27, respectively). Probiotics were superior to placebo for HbA1c (Weighted Mean Difference/WMD −0.43%). There was very low certainty evidence that Vitamin D was superior to placebo for lowering HbA1c in trials of <6 months (MD −0.17%). Magnesium, zinc, Vitamin C, probiotics, and polyphenols were superior to placebo for FBG. Vitamin D was superior to placebo for insulin resistance. Data on safety was limited. Conclusions: Future research should identify who may benefit from nutrient supplementation, safety, and optimal regimens and formulations.

Can nutrition interventions tackle the global insulin affordability via improving diabetes management and reducing insulin demand?

Diabetes, a global health concern, requires insulin therapy. As insulin demand and prices rise dramatically, insulin affordability has increasingly become an issue facing patients with diabetes worldwide. To cut insulin costs, many patients ration their supply, which may have dire health consequences. This particularly affects lower-income populations, who are often forced to choose between purchasing their medications or paying for other necessities. Nutrition might be one solution for this. This commentary aims to provide comprehensive insight with historical context into intersectional components of diabetes in the global arena through analyses of insulin affordability, coupled with the critical role of nutrition intervention after searching the PubMed for relevant articles. More studies in personalized nutrition, supplementations, and dietary behaviors may develop evidence-based nutrition interventions to control diabetes. We argue that alongside price regulation, a greater focus to nutrition to address issues of food insecurity and food assistance programs may help to improve insulin affordability.

Randomised controlled trials on prevention, diagnosis and treatment of diabetes in African countries: a systematic review

OBJECTIVES

The epidemiological transition from infectious to chronic diseases leads to novel challenges in African health systems. The prevalence of diabetes mellitus (DM) is increasing dramatically. Undiagnosed and undertreated DM leads to numerous complications including end-organ damage and death. Our objectives were to collect the best locally generated evidence on DM interventions, identify knowledge gaps and determine underexplored research areas.

DESIGN

A systematic review and meta-analysis of randomised controlled trials.

PARTICIPANTS AND SETTING

African patients in primary, secondary and tertiary prevention, diagnosis and treatment DM type 1 (DM1), type 2 (DM2) and gestational DM (GDM).

OUTCOME

All-cause mortality, glycaemic control, complications, quality of life, hospital admission, treatment adherence and costs.

DATA SOURCES

Articles published in MEDLINE Ovid, CENTRAL, CINAHL, African Journals Online and African Index Medicus and the International Clinical Trials Registry Platform in English language without time restrictions. The systematic search was last updated in October 2020.

RESULTS

Out of 3736 identified publications, we included 60 eligible studies conducted in 15 countries, 75% were conducted in urban healthcare settings, including 10 112 participants. We included 8 studies on DM1, 6 on GDM, 2 on pre-DM, 37 on mainly DM2 including 7 on DM-related complications. The design of the studied intervention was heterogeneous with a focus on educational strategies. The other studies investigated the efficacy of nutritional strategies including food supplementations, pharmacological strategies and strategies to enhance physical activity. Seven studies included interventions on DM-related complications.

CONCLUSIONS

Research activities increased in recent years, but available evidence is still not representative for all African countries. There is a big lack of evidence in primary healthcare and rural settings, implementation research, pharmacological interventions, especially in poorer countries. Nevertheless, the identified studies offer a variety of effective interventions that can inform medical care and future research.

PROSPERO REGISTRATION NUMBER

CRD42019122785.

Association of Serum Magnesium with Insulin Resistance and Type 2 Diabetes among Adults in China

Magnesium is an essential mineral for the human body and a cofactor or activator for more than 300 enzymatic reactions, including blood glucose control and insulin release. Diabetes is a well-known global burden of disease with increasing global prevalence. In China, the prevalence of diabetes in adults is higher than the global average. Evidence shows that magnesium is a predictor of insulin resistance and diabetes. However, the majority of studies focus on dietary magnesium instead of serum magnesium concentration. We study the correlation of serum magnesium levels with insulin resistance and Type 2 diabetes. In this prospective cohort study, we included 5044 participants aged 18 years and older without insulin resistance (IR) and diabetes at the baseline from China Health and Nutrition Survey (CHNS). A fasting blood sample was taken for the measurement of both types of magnesium, fasting blood glucose, hemoglobin A1c (HbA1c), and fasting insulin. The homeostatic model (HOMA-IR) was calculated. Demographic characteristics of participants, and risk factors such as intensity of physical activities, smoking status, drinking habit, and anthropometric information were recorded. IR was defined as HOMA-IR ≥ 2.5, and Type 2 diabetes mellitus was defined as fasting plasma glucose ≥ 7.0 mmol/L or HbA1c ≥ 6.5%, or a self-reported diagnosis or treatment of diabetes. A total of 1331 incident insulin resistance events and 429 incident diabetic events were recorded during an average follow-up of 5.8 years. The serum magnesium concentration was categorized into quintiles. After adjusting for relevant covariates, the third quintile of serum magnesium (0.89−0.93 mmol/L) was correlated with 29% lower risk of incident insulin resistance (hazard ratio = 0.71, 95% CI 0.58, 0.86) and with a lower risk of Type 2 diabetes. Multivariable-adjusted hazard ratios (95% confidence intervals) for insulin resistance were compared with the lowest quintile of serum magnesium (<0.85). We found similar results when evaluating serum magnesium as a continuous measure. Restricted cubic spline (RCS) curves showed a nonlinear dose−response correlation in both serum magnesium levels and insulin resistance, and in serum magnesium levels and Type 2 diabetes. Lower serum magnesium concentration was associated with a higher risk of insulin resistance and diabetes.

The effects of dietary supplements and natural products targeting glucose levels: an overview

Identifying effective dietary supplements and medicinal herbs has attracted the attention of clinicians and researchers to complement the standard treatment in controlling diabetes mellitus. In the present overview, we aimed to collect studies with the highest level of evidence to shed light on detecting the most effective dietary supplements and medicinal herbs for controlling glycemic status. For the current overview, four electronic databases, including PubMed, Scopus, Web of Science, and Cochrane Library, were systematically searched from inception to 31 December 2020 and then updated until 1 October 2021 to obtain eligible meta-analyses on either dietary supplements or medicinal herbs and their effects on glycemic status. Fasting blood sugar (FBS) and Hemoglobin A1C (HbA1C) were considered as primary outcomes. Finally, ninety-one meta-analyses on dietary supplements (n = 55) and herbs (n = 36) were included. Evidence showed positive effects of chromium, zinc, propolis, aloe vera, milk thistle, fenugreek, cinnamon, ginger, and nettle on FBS and/or HbA1C. However, mostly the heterogeneity (I2) was high. Other supplements and herbs also showed no reduction in glucose levels or their effects were small. Although some dietary supplements and medicinal herbs showed a significant reduction in FBS and/or HbA1C, mostly their effects from the clinical point of view were not remarkable. In addition, due to high heterogeneity, publication bias, and a limited number of included studies in most cases further clinical trials are needed for making decision on anti-diabetic supplement efficacy.

U-shaped Association Between Dietary Zinc Intake and New-onset Diabetes: A Nationwide Cohort Study in China

AIMS

We aimed to investigate the relationship of dietary zinc intake with new-onset diabetes among Chinese adults.

MATERIALS AND METHODS

A total of 16 257 participants who were free of diabetes at baseline from the China Health and Nutrition Survey were included. Dietary intake was measured by 3 consecutive 24-hour dietary recalls combined with a household food inventory. Participants with self-reported physician-diagnosed diabetes, or fasting glucose ≥ 7.0 mmol/L, or glycated hemoglobin ≥ 6.5% during the follow-up were defined as having new-onset diabetes.

RESULTS

A total of 1097 participants developed new-onset diabetes during a median follow-up duration of 9.0 years. Overall, the association between dietary zinc intake and new-onset diabetes followed a U-shape (P for nonlinearity < 0.001). The risk of new-onset diabetes was significantly lower in participants with zinc intake < 9.1 mg/day (per mg/day: hazard ratio [HR], 0.73; 95% CI, 0.60-0.88), and higher in those with zinc intake ≥ 9.1 mg/day (per mg/day: HR, 1.10; 95% CI, 1.07-1.13). Consistently, when dietary zinc intake was assessed as deciles, compared with those in deciles 2-8 (8.9 -<12.2 mg/day), the risk of new-onset diabetes was higher for decile 1 (<8.9 mg/day: HR, 1.29; 95% CI, 1.04-1.62), and deciles 9 to 10 (≥12.2 mg/day: HR, 1.62; 95% CI, 1.38-1.90). Similar U-shaped relations were found for plant-derived or animal-derived zinc intake with new-onset diabetes (all P for nonlinearity < 0.001).

CONCLUSIONS

There was a U-shaped association between dietary zinc intake and new-onset diabetes in general Chinese adults, with an inflection point at about 9.1 mg/day.