Zinc deficient diet exacerbates the testicular and epididymal damage in type 2 diabetic rat: Studies on oxidative stress-related mechanisms

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 Ameliorates Tripterygium Glycosides-Induced Reproductive Impairment in Male Rats by Regulating Zinc Homeostasis and Expression of Oxidative Stress-Related Genes

Tripterygium glycosides (TG) can seriously damage male reproductive function, and the reproductive system is difficult to restore after stopping the administration of TG in male rats. Zinc (Zn) is one of the most important trace elements in the human body and plays an important role in maintaining male fertility. The aim of this study was to investigate whether zinc supplementation could improve the testicular reproductive damage induced by TG toxicity in rats and to investigate its mechanism of action. The results showed that zinc sulfate (ZnSO4) could improve testicular tissue structure and semen parameters, promote testosterone synthesis, increase zinc-containing enzyme activity, increase zinc concentration in serum and testicular tissues, and maintain zinc homeostasis in male rats induced by TG toxicity. Zinc supplementation activated relevant signalling molecules in the KEAP1-NRF2/ARE pathway and alleviated TG-induced oxidative stress. Therefore, this study concluded that zinc supplementation could improve reproductive damage by regulating zinc homeostasis and the expression of genes related to oxidative stress.

Effects of Zinc Combined with Metformin on Zinc Homeostasis, Blood-Epididymal Barrier, and Epididymal Absorption in Male Diabetic Mice

Diabetes increases the likelihood of germ cell damage, hypogonadism, and male infertility. Diabetes leads to lower zinc (Zn) levels, an important micronutrient for maintaining male fertility, and zinc deficiency can lead to decreased male fertility through multiple mechanisms. The aim of this study was to investigate the effect of combined metformin and zinc administration on epididymis in diabetic mice; 10 of 50 male mice were randomly selected as the control group (group C), and the remaining 40 mice were randomly divided into untreated diabetes group (group D), diabetes + zinc group (group Z), diabetes + metformin group (group M), and diabetes + metformin + zinc group (group ZM) with 10 mice each. Diabetic mice in group Z received oral zinc (10 mg/kg) once daily for 4 weeks; diabetic mice in group M received oral metformin (200 mg/kg) once daily for 4 weeks; diabetic mice in group ZM received oral metformin and zinc once daily for 4 weeks; and groups C and D received the same amount of sterile water by gavage. Overnight fasted mice were sacrificed, and blood samples, mouse epididymides, and sperm were collected for further experiments. In group D, fasting blood glucose and insulin resistance index increased significantly, semen quality, serum insulin, and testosterone decreased, and epididymal structure was disordered. In group D, epididymal tissue zinc, free zinc ions in the caput, and cauda of epididymis and zinc transporter (ZnT2) decreased significantly, while ZIP12, metallothionein (MT), and metal transcription factor (MTF1) increased significantly. In addition, the expressions of blood-epididymal barrier (BEB)-related molecules (including ZO-1 β-catenin and N-cadherin) and aquaporins (AQPs, including AQP3, AQP9, and AQP11) in the epididymis of mice in group D were significantly decreased. In addition, compared with groups D, Z, and M, in the ZM group, the expression of BEB-related molecules (including ZO-1, β-catenin, and N-cadherin) and aquaporins (AQP3, AQP9, and AQP11) in epididymis tissue were significantly increased, and sperm motility and serum testosterone were significantly increased. It was concluded that male diabetic mice have a disturbed epididymal structure and decreased semen quality by causing an imbalance in epididymal zinc homeostasis, BEB, and impaired absorptive function. The combination of zinc and metformin is an effective and safe alternative treatment and provides additional benefits over metformin alone.

Mechanisms of damage to sperm structure in mice on the zinc-deficient diet

BACKGROUND

Zinc (Zn)is an essential trace element for spermatogenesis and its deficiency causes abnormal spermatogenesis.

OBJECTIVE

The present study was conducted to examine the mechanisms by which Zn-deficient diet impairs sperm morphology and its reversibility.

METHODS

30 SPF grade male Kunming (KM) mice were randomly divided into three groups, 10 mice per group. Zn-normal diet group (ZN group) was given Zn-normal diet（Zn content= 30 mg/kg）for 8 weeks. Zn-deficienct diet group (ZD group) was given Zn-deficienct diet（Zn content< 1 mg/kg）for 8 weeks. Zn-deficient and Zn-normal diet group（ZDN group）was given 4 weeks Zn-deficienct diet followed by 4 weeks Zn-normal diet. After 8 weeks, the overnight fasted mice were sacrificed, and blood and organs were collected for further analysis.

RESULTS

The experimental results showed that Zn-deficienct diet leads to increased abnormal morphology sperm and testicular oxidative stress.The rate of abnormal morphology sperm, chromomycin A3(CMA3), DNA fragmentation index (DFI), malondialdehyde (MDA) were significantly increased, and a-kinase anchor protein 4(AKAP4), dynein axonemal heavy chain 1(DNAH1), sperm associated antigen 6(SPAG6), cilia and flagella associated protein 44(CFAP44), glutathione peroxidase (GSH-PX), superoxide dismutase (SOD), total antioxidant capacity (T-AOC), nuclear factor erythroid 2-related factor (NRF2), NAD(P)H:quinone oxidoreductase 1(NQO1)and heme oxygenase 1(HO1) were significantly decreased in the ZD group mice. While the changes in above indicators caused by Zn-deficient diet were significantly alleviated in the ZDN group.

CONCLUSION

It was concluded that Zn-deficient diet causes abnormal morphology sperm and testicular oxidative stress in male mice. Abnormal morphology sperm caused by Zn-deficient diet are reversible, and Zn-normal diet can alleviate them.

Correlation between serum zinc and testosterone: A systematic review

Zinc is a vital trace element for normal function of the living system. In male, zinc is involved in various biological processes, an important function of which is as a balancer of hormones such as testosterone. For this purpose, studies related to the influence of zinc on serum testosterone were selected and summarized, including the effect of dietary zinc deficiency and zinc supplementation on testosterone concentrations. After preliminary searching of papers on databases, 38 papers including 8 clinical and 30 animal studies were included in this review. We concluded that zinc deficiency reduces testosterone levels and zinc supplementation improves testosterone levels. Furthermore, the effect degree of zinc on serum testosterone may vary depending on basal zinc and testosterone levels, zinc dosage form, elementary zinc dose, and duration. In conclusion, serum zinc was positively correlated with total testosterone, and moderate supplementation plays an important role in improving androgen.

Association of CYP19A1 Gene, Plasma Zinc, and Urinary Zinc with the Risk of Type 2 Diabetes Mellitus in a Chinese Population

To explore the effects of CYP19A1 gene polymorphisms, plasma zinc, and urinary zinc levels and their interactions on type 2 diabetes mellitus (T2DM) in residents of Gongcheng County, Guangxi, China. The case-control study was used for the investing. The MassARRAY System was applied to genotype the CYP19A1 genes rs752760, rs10046, rs10459592, and rs700518 in 540 study subjects. Plasma and urinary zinc concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS). Conditional logistic regression showed that rs752760 and plasma zinc were associated with T2DM risks with ORs of 0.593 (95% CI: 0.371-0.948) and 0.563 (95% CI: 0.356-0.889), respectively. Unconditional logistic regression analysis showed an association between urinary zinc levels and the risk of T2DM as well, with an OR of 0.352 (95% CI: 0.212-0.585). The results of the multiplicative interaction model showed that the rs752760 T allele was associated with a significantly reduced risk of T2DM with moderate/low plasma zinc levels, with ORs of 0.340 (95% CI: 0.161-0.715) and 0.583 (95% CI: 0.346-0.981), respectively, and the rs752760 T allele was also associated with a significantly decreased risk of T2DM with moderate/low urinary zinc levels, with ORs of 0.358 (95% CI: 0.201-0.635) and 0.321 (95% CI: 0.183-0.562), respectively. CYP19A1 rs752760 T allele and moderate/low plasma/urinary zinc levels reduce the risk of T2DM.

Cordycepin, a major bioactive component of Cordyceps militaris, ameliorates diabetes-induced testicular damage through the Sirt1/Foxo3a pathway

Diabetes-induced male dysfunction is considered as a worldwide challenge, and testicular damage mainly caused by oxidative stress is its most common manifestation. Cordycepin, a natural antioxidant, has been used in the treatment of diabetic complications. However, the protective action and underlying mechanism of cordycepin on hyperglycaemia-induced testicular damage are unclear. This study aimed to investigate the protective effects and molecular mechanisms of cordycepin against diabetes-induced testicular damage. The type 2 diabetes model was established in C57BL/6 male mice via high-fat diet for 4 weeks and injected intraperitoneally with 50 mg/kg/day streptozotocin for five consecutive days. Then mice were treated with cordycepin (10 and 20 mg/kg, respectively) for 8 weeks. At the end of experiment, biochemical indicators, microstructure of testicular tissue, sperm morphology, TUNEL staining and protein expressions were evaluated. In the present study, cordycepin alleviated the testicular damage, restored disruption of the blood-testis barrier, and improved spermatogenic function via the antiapoptotic and antioxidant capacity. Mechanistically, cordycepin significantly enhanced SIRT1 expression and triggered the activity of Foxo3a, further to induce the expression of its downstream antioxidant enzymes, including Mn-SOD and CAT. These findings indicated that cordycepin could improve hyperglycaemia-induced testicular damage by regulating downstream antioxidant enzymes activity through the SIRT1/Foxo3a signalling pathway.

NmFGF1-Regulated Glucolipid Metabolism and Angiogenesis Improves Functional Recovery in a Mouse Model of Diabetic Stroke and Acts via the AMPK Signaling Pathway

Diabetes increases the risk of stroke, exacerbates neurological deficits, and increases mortality. Non-mitogenic fibroblast growth factor 1 (nmFGF1) is a powerful neuroprotective factor that is also regarded as a metabolic regulator. The present study aimed to investigate the effect of nmFGF1 on the improvement of functional recovery in a mouse model of type 2 diabetic (T2D) stroke. We established a mouse model of T2D stroke by photothrombosis in mice that were fed a high-fat diet and injected with streptozotocin (STZ). We found that nmFGF1 reduced the size of the infarct and attenuated neurobehavioral deficits in our mouse model of T2D stroke. Angiogenesis plays an important role in neuronal survival and functional recovery post-stroke. NmFGF1 promoted angiogenesis in the mouse model of T2D stroke. Furthermore, nmFGF1 reversed the reduction of tube formation and migration in human brain microvascular endothelial cells (HBMECs) cultured in high glucose conditions and treated with oxygen glucose deprivation/re-oxygenation (OGD). Amp-activated protein kinase (AMPK) plays a critical role in the regulation of angiogenesis. Interestingly, we found that nmFGF1 increased the protein expression of phosphorylated AMPK (p-AMPK) both in vivo and in vitro. We found that nmFGF1 promoted tube formation and migration and that this effect was further enhanced by an AMPK agonist (A-769662). In contrast, these processes were inhibited by the application of an AMPK inhibitor (compound C) or siRNA targeting AMPK. Furthermore, nmFGF1 ameliorated neuronal loss in diabetic stroke mice via AMPK-mediated angiogenesis. In addition, nmFGF1 ameliorated glucose and lipid metabolic disorders in our mouse model of T2D stroke without causing significant changes in body weight. These results revealed that nmFGF1-regulated glucolipid metabolism and angiogenesis play a key role in the improvement of functional recovery in a mouse model of T2D stroke and that these effects are mediated by the AMPK signaling pathway.

Momordica cymbalaria improves reproductive parameters in alloxan-induced male diabetic rats

Male reproductive dysfunction is one of the common complications of diabetes mellitus that causes infertility. This study was designed to investigate the protective effect of Momordica cymbalaria (M. cymbalaria) extracts on diabetes mediated reproductive toxicity in male Wistar rats. The induction of diabetes was performed using a single intraperitoneal injection of alloxan (120 mg/kg). Skin and seed extracts (250 and 500 mg/kg) of M. cymbalaria were orally administered to alloxan-induced diabetic male rats for 28 days. Postprandial blood glucose (PBG) levels were recorded at 7-day interval for four weeks. The effects of the treatment on blood glucose, weight of reproductive organs, sperm count, testosterone levels, antioxidant capacity, and histomorphology were evaluated. Treatment with the above extracts of M. cymbalaria significantly (p < 0.05) improved the reproductive parameters as well as the antioxidant levels superoxide dismutase (SOD) and glutathione-s-transferase (GST) in the diabetic rats. Also, oral treatment with M. cymbalaria extracts significantly reduced the PBG and malondialdehyde (MDA) levels. Further, it revived the histomorphology of reproductive organs in diabetic rats. Interestingly, skin extract at a dose of 500 mg/kg was found to be more efficient in elevating the level of testosterone and sperm count in the diabetic rats. Based on the results, it is clear that M. cymbalaria not only regulates the postprandial blood glucose levels but also improves the reproductive health in the diabetic state.

Dolichandrone serrulata flower extract ameliorates male reproductive damages in type 2 diabetic rats

Dolichandrone serrulata flower (DSF) has been believed to reduce blood glucose in hyperglycaemic persons with sub-fertility but its effect on improvement of male reproductive impairment has never been elucidated scientifically. This study attempted to investigate the hypoglycaemic effects of DSF on male reproductive damages in type 2 diabetes mellitus (T2DM) rats. Adult Sprague Dawley rats were divided into four groups (control, T2DM, DSF200 + T2DM and DSF600 + T2DM; n = 10/each). Control rats received low-fat diet for 14 days before saline injection while streptozocin (50 mg/kg BW) induced T2DM groups received high-fat diet and were orally administered with DSF (200 and 600 mg/kg BW) for 28 days. At the end, fasted blood glucose (FBG), malondialdehyde (MDA), testosterone, sperm quality, histology and protein expressions were examined. The result showed that DSF decreased high FBG and testicular MDA and increased testosterone levels of T2DM-treated rats. Low-sperm quality and histological malfunction were ameliorated in DSF-treated group. There was significant decrease in the expression of androgen receptor, heat-shock 70 and steroidogenic acute regulatory proteins of T2DM-treated rats. Our study demonstrated changes of six bands (116, 51, 45, 39, 35 and 29 kDas) of tyrosine-phosphorylated proteins. In conclusion, DSF could reduce the FBGand ameliorate the reproductive damages in male T2DM rats.