Exacerbation of diabetes-induced testicular apoptosis by zinc deficiency is most likely associated with oxidative stress, p38 MAPK activation, and p53 activation in mice

Use of medicinal doses of zinc as a safe and efficient coadjutant in the treatment of male hypogonadism

Hypogonadism affects an extensive part of the male population, especially among the elderly. The quest for treatment regarding low levels of serum testosterone and male infertility has, therefore, worldwide relevance. Zinc has important biological actions insofar as the male reproductive physiology and endocrine system. In general, a common and safe recommendation for zinc in the treatment of male hypogonadism is 220 mg of zinc sulfate (equivalent to 50 mg of elemental zinc) twice a day, over one to four months. Additionally, it may be further required to extend, both the treatment, dose and daily fractionation of this mineral. Albeit medicinal doses of zinc may increase total testosterone and improve sperm count, the current body of evidence does not suggest broad recommendations regarding the use of zinc for all types of hypogonadism. In many cases, the use of zinc supplements is insufficient, with the use of surgery and drugs being required for an effective treatment.

Zinc L-Carnosine Protects CCD-18co Cells from L-Buthionine Sulfoximine-Induced Oxidative Stress via the Induction of Metallothionein and Superoxide Dismutase 1 Expression

Zinc L-carnosine (ZnC) is the chelate form of zinc and L-carnosine and is one of the zinc supplements available in the market. This study aims to determine the protective effects of ZnC against L-buthionine sulfoximine (BSO)-induced oxidative stress in CCD-18co human normal colon fibroblast cell line. CCD-18co cells were pretreated with ZnC (0-100 μM) for 24 h before the induction of oxidative stress by BSO (1 mM) for another 24 h. Results from this present study demonstrated that ZnC up to the concentration of 100 μM was not cytotoxic to CCD-18co cells. Induction with BSO significantly increased the intracellular reactive oxygen species (ROS) levels and reduced the intracellular glutathione (GSH) levels in CCD-18co cells. Pretreatment with ZnC was able to attenuate the increment in intracellular ROS level in CCD-18co cells significantly in a concentration-dependent manner. However, ZnC did not have any effects on intracellular GSH levels and Nrf2 activation. Mechanistically, pretreatment with ZnC was able to upregulate the expression of metallothionein (MT) and superoxide dismutase 1 (SOD1) in CCD-18co cells. Results from dual-luciferase reporter gene assay reported that ZnC was able to increase the MRE-mediated relative luciferase activities in a concentration-dependent manner, suggesting that the induction of MT expression by ZnC was due to the activation of MTF-1 signaling pathway. Taken together, our current findings suggest that ZnC can protect CCD-18co cells from BSO-induced oxidative stress via the induction of MT and SOD1 expression.

Diabetes-induced testicular oxidative stress, inflammation, and caspase-dependent apoptosis: the protective role of metformin

Context: Metformin's effect on glycaemic control is well documented, but its effect on diabetes-induced testicular impairment has been scarcely reported.Objective: To investigate the effects of metformin on testicular oxidative stress, inflammation, and apoptosis, which largely contribute to fertility decline in diabetic state.Methods: Male Sprague-Dawley rats were divided into 3 groups (n = 6/group) namely: normal control (NC), diabetic control (DC), and metformin (300 mg/kg b.w./d)-treated diabetic groups. Metformin was administrated for 4 weeks.Results: Decreased mRNA expressions and activities of antioxidant enzymes were seen in the testes of DC group. mRNA and protein expressions of pro-inflammatory and pro-apoptotic markers increased, while interleukin-10 and proliferating cell nuclear antigen (PCNA) decreased in the testes of DC group. Treatment with metformin up-regulated antioxidant enzymes, down-regulated inflammation, and apoptosis and increased PCNA immunoexpression in the testes.Conclusions: Metformin protects the testes from diabetes-induced impairment and may improve male reproductive health in diabetic state.

Modulation of reproductive dysfunctions associated with streptozocin-induced diabetes by Artemisia judaica extract in rats fed a high-fat diet

We investigated the palliative effect of Artemisia judaica extract (AjE) on testicular deterioration induced by DM in high-fat diet/streptozocin (HFD/STZ)-injected rats. Forty rats were allocated to the following five groups: control, AjE, HFD/STZ, HFD/STZ-AjE, and HFD/STZ-metformin. HFD/STZ-diabetic rats showed a marked decrease in testicular weight and male sex hormones. There was significant suppression of testicular antioxidant enzymes and glutathione content in HFD/STZ-diabetic rats. However, rats that had received the STZ injection and the high-fat diet displayed increased malondialdehyde content and nitric oxide levels as well as tumour necrosis factor-alpha. High levels of Bax and low levels of Bcl-2 were detected after the STZ injection. Obvious pathological alterations were found in the testicular tissue of the HFD/STZ-diabetic rats. Thus, the administration of AjE attenuated the biochemical, molecular, and histopathological changes in the testes of the diabetic rats. The obtained findings showed that AjE treatment attenuated the diabetes-induced reprotoxicity in male rats via its antioxidant, anti-inflammatory, and antiapoptotic properties.

Diabetes mellitus and the impairment of male reproductive function: Possible signaling pathways

BACKGROUND AND AIMS

Today, it has been shown that diabetes mellitus (DM) can affect male fertility. Glucose metabolism is a vital process in spermatogenesis that is impacted by diabetes condition. But the mechanisms by which DM causes male infertility are not wholly clarified. The aim of this review is to provide brief information about the influence of hyperglycemia on male fertility and specific emphasis on the molecular signaling pathway that is involved.

METHODS

Broad literature search in the electronic database "Pubmed", "Google Scholar", the website of "World Health Organization" (WHO) and Control Disease and Prevention (CDC) took place. There was no time restriction. A key criterion for the selection of articles was English and language. Finally, one hundred thirty seven articles were included in the review.

RESULTS

Diabetes mellitus affects many signaling pathways that involved in the spermatogenesis. It seems that increased ROS and oxidative stress in the diabetes is the beginning of all fertility problems and affects all of involved signaling pathways in the spermatogenesis.

CONCLUSIONS

It seems that there was strong interconnected between oxidative stress and all of involved signaling pathways in the reproductive problems in diabetes. So, approaches that diminish oxidative stress in the testis can be effective in improving diabetes related infertility complications.

Effect of moderate-intensity exercise training on GDNF signaling pathway in testicles of rats after experimental diabetes type 1 induction

AIMS

The spermatogenesis failure is reported as the main complication for diabetes and the moderate-intensity exercise (EX) is shown to ameliorate the diabetes-induced impairments both at spermatogenesis and sperm levels. Thus, the current study was done to investigate the possible effect of EX in the sole and simultaneous form with insulin on the network between Sertoli and spermatogonial stem cells (SSCs) by focusing on niche factor Glial cell-derived neurotrophic factor (GDNF).

METHODS

For this purpose, 30 mature male Wistar rats were divided into control and experimental type 1 diabetes (T1D)-induced groups. Then the T1D-induced animals were subdivided to sedentary T1D-induced (ST1D), EX + T1D, insulin (INS) + T1D and EX + INS + T1D groups. The general histological changes of testicles, mRNA and protein contents of GDNF and its special receptors gfrα1 and c-RET were evaluated and compared between groups.

RESULTS

EX in the sole and simultaneous form with INS significantly (p < 0.05) diminished the T1D-induced histological damages, amplified the GDNF expression, and enhanced the gfrα1 and c-RET mRNA and protein contents compared to ST1D group.

CONCLUSION

In conclusion, the EX in the sole form promotes spermatogenesis by up-regulating the GDNF signaling system. Moreover, EX remarkably amplifies the insulin-induced ameliorative effect on spermatogenesis.

Experimental diabetes negatively affects the spermatogonial stem cells' self-renewal by suppressing GDNF network interactions

The present study was done to analyse the time-dependent effects of diabetes on Sertoli cells-spermatogonial stem cells' (SSCs) network interaction by focusing on glial cell line-derived neurotrophic factor (GDNF) and its special receptors, gfrα1 and c-RET as well as the Bcl-6b. In total, 40 Wistar rats were considered in; control, 20, 45 and 60 days diabetes-induced groups. An experimental diabetes was induced by STZ. The GDNF, gfrα1, c-RET and Bcl-6b expressions were evaluated. The serum level of testosterone, tubular repopulation (RI) and spermiogenesis (SPI) indices, general histological alterations, germ cells, mRNA damage, sperm count and viability were assessed. The diabetes, in a time-dependent manner, diminished mRNA and protein levels of GDNF, gfrα1, c-RET and Bcl-6b versus control group (p < .05), enhanced percentage of seminiferous tubules with negative RI, SPI, and diminished Leydig and Sertoli cells distribution, serum levels of testosterone, sperm count and viability. Finally, the number, percentage of cells and seminiferous tubules with normal mRNA content were significantly (p < .05) diminished. In conclusion, as a new data, we showed that the diabetes by inducing severe mRNA damage and suppressing GDNF, gfrα1, c-RET and Bcl-6b expressions, potentially affects the Sertoli-SSCs' network and consequently inhibits the SSCs' self-renewal process.

Nrf2 participates in the anti-apoptotic role of zinc in Type 2 diabetic nephropathy through Wnt/β-catenin signaling pathway

Zinc (Zn), as an essential trace element, has been approved to serve many roles in diabetic studies. Also Zn deficiency will aggravate renal damage in diabetes through suppression of nuclear factor-erythroid 2-related factor 2 (Nrf2) expression and function. The purpose of this study was to illustrate the role of Zn in renal apoptosis in diabetes and whether Nrf2 participated in the process. Type 2 diabetes mice model was induced by a single dose of streptozotocin (STZ) injection after high-fat diet (HFD) feeding for 3 months, then the mice were given diets supplemented with different concentrations of Zn (control, 30 ppm; low-concentration, 0.85 ppm). After 12-week treatment, morphology and associated protein expressions were examined. The results showed that low Zn diet significantly aggravated the level of renal apoptosis during diabetes, performed as the upregulation of caspase-3 expression. In addition, either low Zn diet or diabetes or both dramatically decreased the expression of Nrf2 and P-AKT in kidney. Moreover, the expression of β-catenin in kidney was increased markedly in diabetic groups. Mechanistic study applying human renal tubular epithelial cells (HK11) confirmed the role of Nrf2, as silencing Nrf2 expression abolished Zn supplementation protection against high sugar + high fat + low Zn-induced apoptosis and downregulation of β-catenin expression. All these results suggest that Nrf2 plays a key role in Zn protection against Type 2 diabetes induced renal apoptosis, which might be through Wnt/β-catenin signaling pathway.

Zinc Deficiency Promotes Testicular Cell Apoptosis in Mice

Zinc (Zn) plays an important role in spermatogenesis, and carbon tetrachloride (CCl₄) induces testicular oxidative damage and cell death. The objective of the present study was to define the effects of Zn deficiency in combination with CCl₄ treatment on testicular apoptosis and the associated mechanisms. Mice were fed the following diets with three different Zn levels for 6 weeks: normal zinc (ZN) diet (30 mg Zn/kg), zinc-deficient (ZD) diet (2 mg Zn/kg), and adequate zinc (ZA) diet (100 mg Zn/kg). Beginning in the third week, CCl₄ was intraperitoneally injected into half of the mice in each diet group six times over 3 weeks. We found that Zn was distributed in various tissues and organs in normal mice and that the zinc content in the testis of normal mice was high. The Zn-deficient diet reduced the zinc concentration in the testis tissue, and the testicular/body weight ratio significantly decreased. Moreover, the TUNEL results proved that CCl₄ stimulation of mice fed with a zinc-deficient diet caused marked apoptosis of testicular cells. Furthermore, the ROS levels in the testes obviously increased after Zn-deficient mice were stimulated with CCl₄, whereas reduced glutathione (GSH) and glutathione peroxidase (GSH-Px) showed reduced activities. In addition, proteins associated with the apoptosis signaling pathway were detected with ELISA kits. P-p53, cleaved caspase-3, cleaved PRAP, p-Bad, p-JNK, p-ERK, and p-NF-κB p65 increased by varying degrees under zinc deficiency or CCl₄ stimulation. All the data indicated that Zn deficiency significantly enhanced the harm to the testis induced by oxidative stress and damage, while CCl₄ stimulation exacerbated the oxidative damage in testicular cells, leading to apoptosis through the activation of p53, MAPK, and NF-κB.

The protective effect of recombinant globular adiponectin on testis by modulating autophagy, endoplasmic reticulum stress and oxidative stress in streptozotocin-induced diabetic mice

This study was to investigate whether recombinant globular adiponectin produced its protective effect on the testis of diabetic mice by modulating autophagy, endoplasmic reticulum stress and oxidative stress. Male mice were randomly divided into control, diabetic, diabetic treated with low and high dose of adiponectin. Mice were killed at the termination after 4 weeks and 8 weeks of adiponectin treatment. Serum levels of glucose, lipids, testosterone, insulin, LH and FSH were measured. The protein expression of glucose-regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), Caspase12, Beclin1, microtubule-associated protein light chain 3 (LC3) and p62 was determined by western blotting. The mRNA expression of adiponectin receptor 1 (AdipoR1), p22phox, p47phox, nuclear factor erythroid2-related factor 2 (Nrf2), NAD(P)H-quinone oxidoreductase 1(NQO1), heme oxygenase-1 (HO-1) and superoxide dismutase (SOD) were determined by real-time fluorescence quantitative PCR. The testicular weight, the sperm number and motility, and the serum levels of testosterone and insulin were significantly decreased in diabetic mice (P < 0.05). The expression of Beclin1, LC3, Nrf2, NQO1, HO-1, SOD and AdipoR1 were significantly decreased (P < 0.05), while the expression of GRP78, CHOP, Caspase12, p62, p22phox and p47phox were notably increased in the testes of diabetic mice (P < 0.05). Adiponectin treatment significantly reversed the above-mentioned changes in the testes of diabetic mice, some of which were dose- and time-dependent (P < 0.05). These data suggested that recombinant globular adiponectin may produce the protective effect on the testes of diabetic mice by inducing autophagy and inhibiting ER stress and oxidative stress.

Zingiber officinale preserves testicular structure and the expression of androgen receptors and proliferating cell nuclear antigen in diabetic rats

The aim of this study was to assess the efficacy of Zingiber officinale, commonly referred to as ginger, in preserving the structural integrity of testis in streptozotocin (STZ)-induced diabetic rats compared to the efficacy of metformin, the traditional effective antidiabetic drug. STZ was utilised for the induction of diabetes mellitus in male Sprague Dawley rats. The study included five groups (n = 6 each), namely the normal control, ginger-treated normal, nontreated diabetic, metformin-treated diabetic and ginger-treated diabetic groups. Biochemical assessment of fasting blood glucose level (BGL) and total antioxidant capacity (TAC) was performed. Histopathological assessment of the testes was performed using routine and immunohistochemical techniques. Fasting BGL significantly (p = .01) reduced, whereas TAC significantly increased (p < .001) in metformin- and ginger-treated diabetic rats compared to those in untreated diabetic rats. Metformin and ginger reduced the degenerative changes observed in the testes of diabetic rats, significantly reduced (p < .001) caspase-3 immunoexpression, and significantly increased (p < .001) the immune-expression of androgen receptors and proliferating cell nuclear antigen. Ginger has antidiabetic effects and preserves testicular structural integrity and, thus, is recommended as an adjuvant therapy for male diabetic patients in the reproductive period.

Antioxidant and Anti-Inflammatory Effects of Different Zinc Sources on Diquat-Induced Oxidant Stress in a Piglet Model

Zinc (Zn) plays a crucial role in reducing oxidative stress and diarrhea in postweanling piglets. This study is aimed at comparing the effects of zinc chelate of 2-hydroxy-4 methyl-thio butanoic acid (HMZn) and ZnSO₄ on the oxidative stress in weaned piglets. A total of 32 piglets were randomly divided into 4 treatments: CON: basal diet+80 mg/kg Zn as ZnSO₄; DIQ: basal diet+80 mg/kg Zn as ZnSO₄; HMZn: basal diet+200 mg/kg Zn as HMZn; and ZnSO₄: basal diet+200 mg/kg Zn as ZnSO₄. On day 15, the DIQ, HMZn, and ZnSO₄ groups were injected intraperitoneally with diquat except for the CON group. The trial lasted 21 days. The results showed that zinc sources did not influence the growth performance during the first 14 days. But HMZn increased activities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and total antioxidant capacity (T-AOC) in serum (P < 0.05). After diquat injection, the fecal score was decreased in the HMZn group. Both HMZn and ZnSO₄ increased the activities of GPX and T-AOC in serum and the relative mRNA expressions of hepatic and renal Nrf2, SOD1, and GPX compared with the DIQ group (P < 0.05). Moreover, the relative mRNA expression of inflammatory factors in the small intestine, liver, and kidney was downregulated; the phosphorylation of NF-κB protein was inhibited in the HMZn group compared with the DIQ and ZnSO₄ groups (P < 0.05). In general, HMZn showed notable advantage over ZnSO₄ in reducing diarrhea and improving antioxidant and anti-inflammatory ability in piglets challenged with diquat.

Combination of Broccoli Sprout Extract and Zinc Provides Better Protection against Intermittent Hypoxia-Induced Cardiomyopathy Than Monotherapy in Mice

Nuclear factor-E2-related factor 2 (Nrf2) and metallothionein have each been reported to protect against chronic intermittent hypoxia- (IH-) induced cardiomyopathy. Sulforaphane-rich broccoli sprout extract (BSE) and zinc can effectively induce Nrf2 and metallothionein, respectively, to protect against IH-induced cardiomyopathy via antioxidative stress. However, whether the cardiac protective effects of the combination of BSE and zinc can be synergistic or the same has not been evaluated. In this study, we treated 8-week-old C57BL/6J mice with BSE and/or zinc during exposure to IH for 8 weeks. Cardiac dysfunction, as determined by echocardiography, and pathological remodeling and abnormalities, including cardiac fibrosis, inflammation, and oxidative damage, examined by histopathology and western blotting, were clearly observed in IH mice but were not significant in IH mice treated with either BSE, zinc, or zinc/BSE. Furthermore, the effects of the combined treatment with BSE and zinc were always greater than those of single treatments. Nrf2 function and metallothionein expression in the heart increased to a greater extent using the combination of BSE and zinc than using BSE or zinc alone. These findings for the first time indicate that the dual activation of Nrf2 and metallothionein by combined treatment with BSE and zinc may be more effective than monotherapy at preventing the development of IH-induced cardiomyopathy.

Oxidative Stress, NF-κB-Mediated Inflammation and Apoptosis in the Testes of Streptozotocin-Induced Diabetic Rats: Combined Protective Effects of Malaysian Propolis and Metformin

Oxidative stress, inflammation and apoptosis are major complications that trigger organ failure in diabetes mellitus (DM), and are proven to adversely affect the male reproductive system. Clinical and experimental studies have demonstrated the promising protective effects of propolis in DM and its associated systemic effects. Herein, we investigated the effect of Malaysian propolis (MP) on testicular oxidative stress, inflammation and apoptosis in diabetic rats. Further, the possibility of a complementary effect of MP with the anti-hyperglycaemic agent, metformin (Met), was studied with the idea of recommending its use in the event that Met alone is unable to contain the negative effects of DM on the male reproductive system in mind. Male Sprague-Dawley rats were either gavaged distilled water (normoglycaemic control and diabetic control groups), MP (diabetic rats on MP), Met (diabetic rats on Met) or MP+Met (diabetic rats on MP+Met), for 4 weeks. MP decreased oxidative stress by up-regulating (p < 0.05) testicular mRNA levels of nuclear factor erythroid 2-related factor 2, superoxide dismutase, catalase and glutathione peroxidase; increasing (p < 0.05) the activities of antioxidant enzymes; and decreasing (p < 0.05) lipid peroxidation in the testes and epididymis of diabetic rats. Further, MP down-regulated (p < 0.05) testicular mRNA and protein levels of pro-inflammatory mediators (nuclear factor kappa B, inducible nitric oxide synthase, tumour necrosis factor-α and interleukin (IL)-1β), decreased (p < 0.05) the nitric oxide level, and increased (p < 0.05) IL-10 mRNA and protein levels. MP also down-regulated (p < 0.05) Bax/Bcl-2, p53, casapase-8, caspase-9 and caspase-3 genes, and increased (p < 0.05) testicular germ cell proliferation. MP's effects were comparable to Met. However, the best results were achieved following co-administration of MP and Met. Therefore, we concluded that administration of the MP+Met combination better attenuates testicular oxidative stress, inflammation and apoptosis in DM, relative to MP or Met monotherapy, and may improve the fertility of males with DM.

Chronic exposure to arsenic and high fat diet induces sex-dependent pathogenic effects on the kidney

Both obesity and arsenic exposure are global public health problems that are associated with increased risk of renal disease. The effect of whole-life exposure to environmentally relevant levels of arsenic within dietary high fat diet on renal pathogenesis were examined. In this study, C57BL/6 J mice were parentally exposed to 100 ppb arsenic before conception. After weaning, both male and female offspring were maintained on 100 ppb arsenic and fed either a normal (LFD) or high fat diet (HFD). At 10 and 24 weeks of age, the offspring were sacrificed and kidneys collected. Exposure to arsenic led to an increase body-weight in LFD diet-fed female but not male mice. This response was not observed in HFD-fed female mice; however male mice showed significant increases in body weight in both As- and non-treated animals. Histological analysis shows that arsenic exposure significantly increases HFD-induced glomerular area expansion, mesangial matrix accumulation and fibrosis compared to LFD control animals. HFD alone increases renal inflammation and fibrosis; reflected by increases in IL-1β, ICAM-1 and fibronectin levels. Arsenic exposure significantly increases HFD-induced inflammatory and oxidative stress responses. In general, male mice have more severe responses than female mice to HFD or arsenic treatment. These results demonstrate that arsenic exposure causes sex-dependent alterations in HFD-induced kidney damage.

Protection against diabetic cardiomyopathy is achieved using a combination of sulforaphane and zinc in type 1 diabetic OVE26 mice

Sulforaphane (SFN) can effectively induce nuclear factor E2-related factor 2 (Nrf2), and zinc (Zn) can effectively induce metallothionein (MT), both of which have been shown to protect against diabetic cardiomyopathy (DCM). However, it is unclear whether combined treatment with SFN and Zn offers better cardiac protection than either one alone. Here, we treated 5-week-old OVE mice that spontaneously develop type 1 diabetes with SFN and/or Zn for 18 weeks. Cardiac dysfunction, by echocardiography, and pathological alterations and remodelling, shown by cardiac hypertrophy, fibrosis, inflammation and oxidative damage, examined by histopathology, Western blotting and real-time PCR, were observed in OVE mice. All these dysfunction and pathological abnormalities seen in OVE mice were attenuated in OVE mice with treatment of either SFN, Zn or SFN/Zn, and the combined treatment with SFN/Zn was better than single treatments at ameliorating DCM. In addition, combined SFN and Zn treatment increased Nrf2 function and MT expression in the heart of OVE mice to a greater extent than SFN or Zn alone. This indicates that the dual activation of Nrf2 and MT by combined treatment with SFN and Zn may be more effective than monotherapy at preventing the development of DCM via complementary, additive mechanisms.

The Role of Endoplasmic Reticulum Stress Response in Male Reproductive Physiology and Pathology: A Review

Endoplasmic reticulum (ER) stress, defined as prolonged disturbances in protein folding and accumulation of unfolded proteins in the ER. Perturbation of the ER, such as distribution of oxidative stress, iron imbalance, Ca²⁺ leakage, protein overload, and hypoxia, can cause ER stress. The cell reacts to ER stress by activating protective pathways, called the unfolded protein response (UPR), which is comprised of cellular mechanisms aimed for maintaining cellular homeostasis or, in case of excessively severe stress, at the initiation of cellular apoptosis. The three UPR signaling pathways from the ER stress sensors are initiated by activating transcription factor 6, inositol requiring enzyme 1, and protein kinase RNA-activated-like ER kinase. A number of physiological and pathological conditions, environmental toxicants and variety of pharmacological agents showed disruption of proper ER functions and thereby cause ER stress in male reproductive organ in rat model. The present review summarizes the existing data concerning the molecular and biological mechanism of ER stress in male reproduction and male infertility. ER stress initiated cell death pathway has been related to several diseases, including hypoxia, heath disease, diabetes, and Parkinson's disease. Although there is not enough evidence to prove the relationship between ER stress and male infertility in human, most studies in this review found that ER stress was correlated with male reproduction and infertility in animal models. The ER stress could be novel signaling pathway of regulating male reproductive cellular apoptosis. Infertility might be a result of disturbing the ER stress response during the process of male reproduction.

Molecular Mechanisms of Zinc as a Pro-Antioxidant Mediator: Clinical Therapeutic Implications

The essentiality of zinc as a trace mineral in human health has been recognized for over five decades. Zinc deficiency, caused by diet, genetic defects, or diseases, can cause growth retardation, delayed sexual maturation, depressed immune response, and abnormal cognitive functions in humans. Zinc supplementation in zinc-deficient individuals can overcome or attenuate these abnormalities, suggesting zinc is an essential micro-nutrient in the body. A large number of in vitro and in vivo experimental studies indicate that zinc deficiency also causes apoptosis, cellular dysfunction, deoxyribonucleic acid (DNA) damage, and depressed immune response. Oxidative stress, due to the imbalance of reactive oxygen species (ROS) production and detoxification in the anti-oxidant defense system of the body, along with subsequent chronic inflammation, is believed to be associated with many chronic degenerative diseases such as diabetes, heart diseases, cancers, alcohol-related disease, macular degenerative disease, and neuro-pathogenesis. A large number of experimental studies including cell culture, animal, and human clinical studies have provided supportive evidence showing that zinc acts as an anti-oxidative stress agent by inhibition of oxidation of macro-molecules such as (DNA)/ribonucleic acid (RNA) and proteins as well as inhibition of inflammatory response, eventually resulting in the down-regulation of (ROS) production and the improvement of human health. In this article, we will discuss the molecular mechanisms of zinc as an anti-oxidative stress agent or mediator in the body. We will also discuss the applications of zinc supplementation as an anti-oxidative stress agent or mediator in human health and disease.

PGAM1 knockdown is associated with busulfan‑induced hypospermatogenesis and spermatogenic cell apoptosis

Phosphoglycerate mutase 1 (PGAM1) is reported to be involved in spermatogenic dysfunction. However, the association between PGAM1 and busulfan‑induced hypospermatogenesis and spermatogenic cell apoptosis remains unclear. The aim of the current study was to investigate the association between PGAM1 expression and busulfan‑induced hypospermatogenesis, and the effect of PGAM1 expression on spermatogenic cell apoptosis. PGAM1 expression was detected in mouse models of busulfan‑induced hypospermatogenesis by western blotting, reverse transcription‑quantitative polymerase chain reaction and immunohistochemistry. Then, spermatogenic cell apoptosis in mouse models of busulfan‑induced hypospermatogenesis was assessed by TUNEL assay. The effect and potential mechanism of PGAM1 downregulation on spermatogenic cells were further investigated. The results indicated that PGAM1 expression was significantly downregulated in the mouse models of busulfan‑induced hypospermatogenesis, compared with those with normal spermatogenesis (P<0.05). Furthermore, the TUNEL assay revealed that the apoptosis of spermatogenic cells was accelerated in the mouse model of busulfan‑induced hypospermatogenesis. In addition, PGAM1 knockdown promoted the apoptosis of spermatogenic cells in vitro, which was associated with the P53/Caspase 3/Caspase 6/Caspase 9 signaling pathway. In conclusion, these data indicate that PGAM1 knockdown is associated with busulfan‑induced hypospermatogenesis and contributes to spermatogenic cell apoptosis by regulating the P53/Caspase 3/Caspase 6/Caspase 9 signaling pathway.

Taurine ameliorates oxidative stress induced inflammation and ER stress mediated testicular damage in STZ-induced diabetic Wistar rats

One of the major consequences of diabetes is reproductive dysfunction but the fundamental mechanisms are still poorly known. The objective of the present study was to explore the beneficial role of taurine against streptozotocin induced testicular dysfunctions in diabetic male Wister rats and understanding the underlying intricate molecular mechanisms. Exposure to streptozotocin (50 mg kg-1 body weight, i.p., once) elevated blood glucose level, induced testicular histological alterations and reduced testis-to-body weight ratio, serum testosterone, testicular markers and activity of antioxidant enzymes. Generation of ER stress (increased expression of calpain-1, caspase-12 and upregulation of CHOP, GRP78 via eIF2α signaling), translocation of NF κB in the nucleus (leading to the upregulation in the levels of inflammatory cytokines), activation of mitochondria dependent apoptotic pathway and DNA fragmentation were revealed from this study. However, administration of taurine at a dose of 100 mg kg-1 body weight for 6 weeks post diabetic induction, successfully ameliorated all these adverse effects. Thus, taurine, as a potential therapeutic agent, may hold promise in preventing oxidative and ER stress mediated diabetic testicular complications in rats.

Beneficial treatment effects of dietary nitrate supplementation on testicular injury in streptozotocin-induced diabetic male rats

RESEARCH QUESTION

Do low doses of dietary nitrate help to attenuate the progression of diabetic reproductive disorders in streptozotocin-induced diabetic male rats?

DESIGN

Fifty male Wistar rats were divided into five groups: controls receiving distilled water; controls receiving 100 mg/l nitrate in distilled water; diabetic rats receiving distilled water; diabetic rats receiving insulin 2-4 U/day of neutral protamine hagedorn insulin; and diabetic rats receiving 100 mg/l nitrate in distilled water. Diabetes was induced by 45 mg/kg streptozotocin. Nitrate and insulin treatment were started 4 weeks after diabetes induction for 8 weeks. Serum insulin, nitrogen oxide, stereology of testis, apoptosis, sperm parameters, and mRNA expression of Pdcd4, Pacs2, p53 and miR-449a were assessed at the end of the study.

RESULTS

Blood glucose, apoptotic index of seminiferous tubules and expression of p53, Pdcd4, and Pacs2 mRNA were significantly higher in the diabetic rats (P < 0.001). Decreased body weight, serum insulin and nitrogen oxide level, and miR-449a were observed in the diabetic group (P < 0.01 for insulin; P < 0.001 for others). Most sperm parameters and stereological results differed between diabetic and control rats; nitrate recovered almost all these alterations, including dead spermatozoa, sperm motility grade, sperm deformity index, spermatozoa with damaged DNA, malformations in abnormal spermatozoa, total volume of seminiferous tubule, germinal epithelium, capsule, lumen, interstitial tissue, seminiferous tubule diameter, germinal epithelium height, the number of spermatogenic, Sertoli and Leydig cells.

CONCLUSIONS

Treatment with sodium nitrate could modulate apoptosis, which is a major cause of diabetic testicular disorder. These experiments suggest that nitric oxide plays an important role in the function of the reproductive system.

Beneficial effects of 6-shogaol on hyperglycemia, islet morphology and apoptosis in some tissues of streptozotocin-induced diabetic mice

BACKGROUND

Diabetes is characterized by hyperglycemia due to impaired insulin secretion and aberrant glucagon secretion resulting from changes in pancreatic islet cell function and/or mass. The aim of the present study was to investigate the effects of ginger on various tissues (i.e., pancreas, kidney, and liver) and insulin resistance in streptozotocin-induced diabetic mice. The pleasant aroma of ginger comes from the constituents present in its volatile oil, while its non-volatile pungent phytochemicals consist of gingerols, shogaols, and paradols.

METHODS

This research was conducted to determine the effects of 6-shogaol administration on blood glucose and insulin production in type 1 diabetic mice. Mice were intraperitoneally injected with shogaol at 5 or 10 mg/kg body weight. Untreated mice were injected with an equivalent volume of buffer, three times a week for 2 weeks. The animals were randomly divided into four experimental groups: control group mice (n = 3) were given an intraperitoneal (IP) injection of streptozotocin (STZ) vehicle (1 mL citrate buffer/100 g body weight) at day 1 and received an IP injection of 6-shogaol vehicle [1 mL buffer (0.5% DMSO, 10% Tween 20, and 89.5% PBS)/100 g body weight] every other day for 4 consecutive days.

RESULTS

6-Shogaol exhibited an antidiabetic effect by significantly decreased the level of blood glucose, body weight and attenuated the above pathological changes to the normal levels in the diabetic mice, and has effect against pancreas, kidney, liver damage in the diabetic mice. Since, 6-shogaol prevented the damage for STZ induced stress.

CONCLUSION

6-Shogaol can be used as a therapeutic agent for preventing complications in diabetic patients. Diabetic treatment consider the 6-shogaol as a pharmatheuticals or combination drug with herbal plant or others 6-shogaol may be a good therapeutic drug because it covers not only pancreatic β-cell but also liver and kidney. Ginger may be ideal because they contain a variety of pharmacological compounds with different known pharmacological actions.

Naringin protects against perfluorooctane sulfonate-induced liver injury by modulating NRF2 and NF-κB in mice

Perfluorooctane sulfonate (PFOS), a persistent organic pollutant, has been demonstrated to cause multiple toxicities. In this study, we explored the role of naringin (Nar) in alleviating PFOS-caused mouse liver injury and its potential mechanisms. Male mice were intragastrically administered PFOS (10 mg/kg/day) alone or with Nar (100 mg/kg/day) for 3 weeks. Nar supplementation led to resumption of elevated serum hepatic enzyme activities and increased relative liver weight in PFOS-challenged mice. Moreover, Nar treatment increased hepatic expression of transcription factor NRF2 protein and its regulated antioxidative enzyme genes heme oxygenase‑1, superoxide dismutase and catalase, with an inhibition of malondialdehyde and hydrogen peroxide production. Furthermore, simultaneous administration of Nar suppressed PFOS-induced elevation in NF-κB activity and generation of inflammatory cytokines TNF-α and IL-6 in the liver. In addition, Nar enhanced anti-apoptotic Bcl-2 expression, decreased pro-apoptotic Bax expression and inhibited caspase‑3 activation in liver tissue in mice exposed to PFOS. Our results indicate that Nar protects against PFOS-induced hepatotoxicity in mice via modulating oxidative, inflammatory and apoptotic pathways.

Nrf2 expression and function, but not MT expression, is indispensable for sulforaphane-mediated protection against intermittent hypoxia-induced cardiomyopathy in mice

We reported previously that nuclear factor erythroid 2-related factor 2 (Nrf2) and metallothionein (MT) play critical roles in preventing intermittent hypoxia (IH)-induced cardiomyopathy. In addition, positive feedback regulation between Nrf2 and MT is required for the efficient compensative responses of the heart to IH. As an activator of Nrf2, sulforaphane (SFN) has attracted attention as a potential protective agent against cardiovascular disease. Here, we investigated whether SFN can up-regulate cardiac Nrf2 expression and function, as well as MT expression, to prevent IH-induced cardiomyopathy, and if so, whether Nrf2 and MT are indispensable for this preventive effect. Nrf2-knock-out (Nrf2-KO) or MT-KO mice and their wild-type (WT) equivalents were exposed to IH for 4 weeks with or without SFN treatment. SFN almost completely prevented IH-induced cardiomyopathy in WT mice, and this preventive effect was abolished in Nrf2-KO mice but retained in MT-KO mice. In IH-exposed WT mice, SFN induced significant increases in the expression levels of Nrf2 and its downstream antioxidant target genes, as well as those of MT, but these effects were not seen in IH-exposed Nrf2-KO mice. By contrast, KO of MT did not affect the ability of SFN to up-regulate the expression of Nrf2 and its downstream antioxidant targets. These results suggest that SFN-induced MT expression is Nrf2-dependent, and SFN prevents IH-induced cardiomyopathy in a Nrf2-dependent manner, for which MT is dispensable. This study provides important information that is relevant to the potential use of SFN to prevent IH-induced cardiomyopathy.

Antioxidant, anti-inflammatory, and anti-apoptotic effects of zinc supplementation in testes of rats with experimentally induced diabetes

One of the major obstacles that males with diabetes may confront is subfertility or infertility. Thus, the present study investigated the effect of co-administration of metformin and zinc (Zn) on the testes of streptozotocin-induced diabetic rats. Male albino rats were randomly divided into 4 groups: control group; untreated diabetic group; diabetic + metformin group, in which diabetic rats were treated orally with metformin (250 mg/kg) once daily for 4 weeks; and diabetic + metformin + Zn group, in which diabetic rats were treated orally with metformin in combination with Zn (10 mg/kg) once daily for 4 weeks. Concomitant administration of metformin and Zn produced a significant decrease in serum levels of glucose and insulin and testicular levels of malondialdehyde and tumor necrosis factor α. Additionally, there was a significant increase in serum levels of Zn, testosterone, and follicle-stimulating hormone, as well as testicular total antioxidant capacity and anti-apoptotic protein Bcl-2, when compared with both the diabetic and metformin-treated diabetic groups. Moreover, co-administration of Zn and metformin significantly improved testicular histopathology, with a significant reduction in percent area of collagen fibers and nuclear factor kappa B (p65) immunoreactivity and a significant increase in seminiferous tubule diameter and connexin 43 immunoreactivity as compared with the diabetic and metformin-treated diabetic groups. In conclusion, the combination of Zn and metformin was an efficacious and safe alternative treatment, as it had superior antihyperglycemic efficacy and provided additional benefits over metformin alone in rats with type 2 diabetes.

Melatonin attenuates detrimental effects of diabetes on the niche of mouse spermatogonial stem cells by maintaining Leydig cells

Diabetes mellitus affects a large number of men of reproductive age and it usually leads to serious reproductive disorders. However, the underlying mechanisms and specific therapies still remain largely unknown. We observed Leydig cell loss in the testes of diabetic mice. Continuous high glycemic status of testes stimulated expression of Caspase12, Grp78, and Chop, the three ERS response factors; this might induce cell cycle arrest and apoptosis of Leydig cells in response to ERS. In these diabetic mouse models, melatonin alleviated apoptosis of testicular stromal cell induced by ERS, and promoted SSCs self-renewal by recovering Leydig cells secretion of CSF1 after 8 weeks of treatment. To explore the relationship between CSF-1 and ERS in Leydig cells, we treated Leydig tumor cell line with an activator Tuniamycin and an inhibitor 4-Phenylbutyrate of ERS. Our data showed that the CSF-1 expression in mouse Leydig cell lines decreased six-fold while reversely increasing five-fold in the 4-Phenylbutyrate-treated group. Thus, melatonin likely alleviates the loss of Leydig cells in diabetic testes and provides a healthier niche for SSCs to self-renew and continually provide healthy sperm for male fertility.

Protective effects of sodium nitrate against testicular apoptosis and spermatogenesis impairments in streptozotocin-induced diabetic male rats

AIMS

As nitric oxide (NO) production is essential for insulin signaling, glucose uptake, endothelial function, and regulation of apoptosis, the loss of bioavailable NO may be a mechanism underlying the development of diabetes complication. Dietary nitrate acts as a substrate for NO generation, thus serving as a physiological source of NO. This study evaluated the therapeutic effects of nitrate supplementation on the apoptosis-induced testicular disorders in diabetic rats.

MAIN METHODS

Fifty male Wistar rats were divided into five groups; control, control with 100 mg/L nitrate in distilled drinking water, diabetes, diabetes treated with 2-4 U/day NPH insulin, diabetes treated with 100 mg/L nitrate in distilled drinking water. After 8 weeks, blood samples, testis, and epididymis were collected to assess the apoptosis process and the stereology of testis tissue, sperm motility, morphology and DNA fragmentation, and also mRNA expression of miR-449a, p53, Pdcd4, and Pacs2 mRNA, as well as serum glucose, insulin, and NOx levels were investigated.

KEY FINDINGS

The results of this study indicated that nitrate treatment ameliorated the sperm parameters, testicular morphometrical and stereological alterations, reduced blood glucose, the number of TUNEL positive cells and tubules, and testicular expressions of p53, Pdcd4, and Pacs2 mRNA as well as increased body weight, serum insulin and NOx levels, and testicular expression of miR-449a in streptozotocin-induced diabetic rats.

SIGNIFICANCE

Our in vivo evidence revealed that nitrate treatment may has a favorable effect as an exogenous NO donor on experimental diabetic testicular damages in which NO bioavailability is impaired.

Curcumin Attenuates Testicular Injury in Rats with Streptozotocin-Induced Diabetes

Oxidative damage, inflammation, and apoptosis are the primary features of diabetic testicular damage. Curcumin protects against diabetic testicular injury, but the underlying mechanisms remain obscure. This study examined the effect of curcumin on type 2 diabetes mellitus- (T2DM-) induced testicular injury, oxidative stress, and apoptotic changes. T2DM rats were intraperitoneally injected with 40 mg/kg STZ after being fed a high-fat diet for 8 weeks. One week after STZ injection, 100 or 200 mg/kg curcumin was administered orally to the diabetic rats for 16 weeks. Histological changes in the testes were determined by HE staining. Serum testosterone was measured. Markers of superoxide levels, such as SOD activity and MDA content, and markers of cell death, including the expression of Bax, Bcl-2, and MAPK family members, were measured by molecular biology or immunohistochemical techniques. Degeneration and disruption of seminiferous tubule structure were observed in diabetic rats. Serum testosterone levels were markedly lower in diabetic rats than in control rats. Moreover, testicular apoptosis and Bax expression were much higher in diabetic rats than in control rats. Superoxide generation, the NADP⁺/NADPH ratio, and NADPH oxidase subunit expression, including expression of the gp91^phox, p47^phox, and p67^phox subunits, increased, while antioxidant enzyme levels decreased in diabetic rats. Furthermore, the MAPK signaling pathway was activated in diabetic rats. Curcumin partially prevented diabetes-induced microstructural abnormalities and significantly increased serum testosterone levels compared to untreated T2DM rats. Additionally, curcumin reduced testicular apoptosis by regulating apoptotic proteins and markedly inhibited oxidative stress levels by downregulating MDA expression, decreasing NADPH activity, and restoring antioxidant enzymes. Remarkably, curcumin treatment also suppressed MAPK activation. Thus, curcumin may have therapeutic value in the treatment of diabetes-induced testicular injury due to its prevention of testicular apoptosis and attenuation of oxidative stress.

Resveratrol attenuates testicular apoptosis in type 1 diabetic mice: Role of Akt-mediated Nrf2 activation and p62-dependent Keap1 degradation

Infertility is a common complication in diabetic men, mainly due to the loss of germ cells by apoptotic cell death. However, effective and safe approaches to prevent diabetic induction of testicular apoptosis for diabetic patients have not been available. Resveratrol (RSV), a group of compounds called polyphenols from plants, has been indicated its promising used clinically for cancers and cardiovascular diseases. Therefore, the present study aimed determining whether RSV attenuates type 1 diabetes (T1D)-induced testicular apoptotic cell death in a mouse model. We found that testicular apoptosis and oxidative stress levels were significantly higher in T1D mice than control mice. In addition, the phosphorylation level of metabolism-related Akt and GSK-3β was downregulated and Akt negative regulators PTEN, PTP1B and TRB3 were upregulated in the T1D group. These effects were partially prevented by RSV treatment. Nrf2 and its downstream genes, such as NQO-1, HO-1, SOD, catalase and metallothionein were significantly upregulated by RSV treatment. In addition, RSV-induced Nrf2 activation was found due to Keap1 degradation, mainly reliant on p62 that functions as an adaptor protein during autophagy. These results indicate that the attenuation of T1D-induced testicular oxidative stress and apoptosis by RSV treatment was mainly related to Akt-mediated Nrf2 activation via p62-dependent Keap1 degradation.

The beneficial effects of Zn on Akt-mediated insulin and cell survival signaling pathways in diabetes

Zinc is one of the essential trace elements and participates in numerous physiological processes. Abnormalities in zinc homeostasis often result in the pathogenesis of various chronic metabolic disorders, such as diabetes and its complications. Zinc has insulin-mimetic and anti-diabetic effects and deficiency has been shown to aggravate diabetes-induced oxidative stress and tissue injury in diabetic rodent models and human subjects with diabetes. Akt signaling pathway plays a central role in insulin-stimulated glucose metabolism and cell survival. Anti-diabetic effects of zinc are largely dependent on the activation of Akt signaling. Zn is also an inducer of metallothionein that plays important role in anti-oxidative stress and damage. However, the exact molecular mechanisms underlying zinc-induced activation of Akt signaling pathway remains to be elucidated. This review summarizes the recent advances in deciphering the possible mechanisms of zinc on Akt-mediated insulin and cell survival signaling pathways in diabetes conditions. Insights into the effects of zinc on epigenetic regulation and autophagy in diabetic nephropathy are also discussed in the latter part of this review.

Berberine reinforces Sertoli cells niche and accelerates spermatogonial stem cells renewal in experimentally-induced varicocele condition in rats

BACKGROUND

Varicocele is present in 10-20% of the male infertile population.

PURPOSE

Present study was done to demonstrate the reinforcing effect of berberine (BBR), as an antioxidant and anti-inflammatory agent, on Sertoli cells-related niche and spermatogonial stem cells (SSCs) self-renewal in experimentally-induced VCL condition.

STUDY DESIGN

50 mature male Wistar rats were divided into control, control-sham, non-treated VCL-induced, 50 mg kg^-1 and 100 mg kg^-1 BBR-treated VCL-induced groups.

METHODS

The Leydig and Sertoli cells distribution and Leydig cells steroidogenic activity, expression of glial cell line-derived neurotrophic factor (GDNF), proto-oncogene Rearranged during Transfection (c-RET) receptor, Ets variant gene 5 (Etv5) and B-cell chronic lymphocytic leukemia (CLL)/lymphoma 6, member B (Bcl-6b) at mRNA and protein levels were analyzed. The mRNA integrity and DNA fragmentation were assessed. Finally, the serum levels of testosterone, inhibin B and testicular total antioxidant capacity, total thiol molecules, catalase, and malondialdehyde were evaluated.

RESULTS

Observations revealed that, the BBR significantly enhanced VCL-reduced Leydig and Sertoli cells population, maintained Leydig-Sertoli cells network, enhanced GDNF, c-RET Etv5 and Bcl6b expression, up-regulated testicular antioxidant and endocrine status.

CONCLUSION

The BBR by boosting Leydig-Sertoli cells network up-regulates the GDNF, Etv5 and Bcl-6b expression/synthesis in SSCs, which in turn improves SSCs self-renewal activities. Thus, the BBR could be considered as an appropriate agent for antioxidant therapy of VCLs. However, more studies with bigger sample number and focus on BBR-induced effects on other genes involving in the self-renewal process are needed to have more deterministic results.

Zinc deficiency promotes cystitis-related bladder pain by enhancing function and expression of Cav3.2 in mice

Ca_v3.2 T-type Ca²⁺ channel activity is suppressed by zinc that binds to the extracellular histidine-191 of Ca_v3.2, and enhanced by H₂S that interacts with zinc. Ca_v3.2 in nociceptors is upregulated in an activity-dependent manner. The enhanced Ca_v3.2 activity by H₂S formed by the upregulated cystathionine-γ-lyase (CSE) is involved in the cyclophosphamide (CPA)-induced cystitis-related bladder pain in mice. We thus asked if zinc deficiency affects the cystitis-related bladder pain in mice by altering Ca_v3.2 function and/or expression. Dietary zinc deficiency for 2 weeks greatly decreased zinc concentrations in the plasma but not bladder tissue, and enhanced the bladder pain/referred hyperalgesia (BP/RH) following CPA at 200mg/kg, a subeffective dose, but not 400mg/kg, a maximal dose, an effect abolished by pharmacological blockade or gene silencing of Ca_v3.2. Acute zinc deficiency caused by systemic N,N,N',N'-tetrakis-(2-pyridylmethyl)-ethylendiamine (TPEN), a zinc chelator, mimicked the dietary zinc deficiency-induced Ca_v3.2-dependent promotion of BP/RH following CPA at 200mg/kg. CPA at 400mg/kg alone or TPEN plus CPA at 200mg/kg caused Ca_v3.2 overexpression accompanied by upregulation of Egr-1 and USP5, known to promote transcriptional expression and reduce proteasomal degradation of Ca_v3.2, respectively, in the dorsal root ganglia (DRG). The CSE inhibitor, β-cyano-l-alanine, prevented the BP/RH and upregulation of Ca_v3.2, Egr-1 and USP5 in DRG following TPEN plus CPA at 200mg/kg. Together, zinc deficiency promotes bladder pain accompanying CPA-induced cystitis by enhancing function and expression of Ca_v3.2 in nociceptors, suggesting a novel therapeutic avenue for treatment of bladder pain, such as zinc supplementation.

Intermittent hypoxia-induced cardiomyopathy and its prevention by Nrf2 and metallothionein

The mechanism for intermittent hypoxia (IH)-induced cardiomyopathy remains obscure. We reported the prevention of acute and chronic IH-induced cardiac damage by selective cardiac overexpression of metallothionein (MT). Herein we defined that MT-mediated protection from IH-cardiomyopathy is via activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a critical redox-balance controller in the body. For this, mice were exposed to IH for 3 days (acute) or 4 or 8 weeks (chronic). Cardiac Nrf2 and MT expression in response to IH were significantly increased acutely yet decreased chronically. Interestingly, cardiac overexpression (Nrf2-TG) or global deletion of the Nrf2 gene (Nrf2-KO) made mice highly resistant or highly susceptible, respectively, to IH-induced cardiomyopathy and MT expression. Mechanistically, 4-week IH exposure significantly decreased cardiac Nrf2 binding to the MT gene promoter, and thus, depressed both MT transcription and translation in WT mice but not Nrf2-TG mice. Likewise, cardiac MT overexpression prevented chronic IH-induced cardiomyopathy and down-regulation of Nrf2 likely via activation of a PI3K/Akt/GSK-3β/Fyn-dependent signaling pathway. These results reveal an integrated relationship between cardiac Nrf2 and MT expression in response to IH -- acute compensatory up-regulation followed by chronic down-regulation and cardiomyopathy. Cardiac overexpression of either Nrf2 or MT offered cardioprotection from IH via complicated PI3K/Akt/GSK3B/Fyn signaling. Potential therapeutics may target either Nrf2 or MT to prevent chronic IH-induced cardiomyopathy.

Diabetes Mellitus induces alterations in metallothionein protein expression and metal levels in the testis and liver

Objective

To investigate the effect of diabetes with and without vitamin E treatment on testicular metallothionein (MT) and metal (zinc, copper and iron) changes.

Methods

Diabetes was induced with a single intraperitoneal injection (i.p.) of streptozotocin in rats, and diabetic rats were given Vitamin E by i.p. every other day for 4 weeks. MT protein was measured by the cadmium-haeme assay and metal levels were detected by an atomic absorption spectrophotometer.

Results

Diabetes did not change testicular MT protein, but significantly increased hepatic MT protein. Diabetes significantly decreased testicular copper, but not hepatic copper. Zinc and iron levels were unchanged in both diabetic testis and liver. Vitamin E significantly enhanced both testicular and hepatic MT, and zinc levels in diabetic rats. Vitamin E slightly decreased the copper levels, but did not change the testicular and hepatic iron in diabetic rats.

Conclusions

Testicular MT protein expression was not increased, even though hepatic MT significantly increased independent of metal changes, in diabetic rats. Vitamin E enhanced testicular and hepatic MT, which correlated with increased zinc levels.

NRF2 Plays a Critical Role in Both Self and EGCG Protection against Diabetic Testicular Damage

Activation of nuclear factor erythroid 2-related factor 2 (NRF2) has been found to ameliorate diabetic testicular damage (DTD) in rodents. However, it was unclear whether NRF2 is required for these approaches in DTD. Epigallocatechin gallate (EGCG) is a potent activator of NRF2 and has shown beneficial effects on multiple diabetic complications. However, the effect of EGCG has not been studied in DTD. The present study aims to explore the role of NRF2 in both self and EGCG protection against DTD. Therefore, streptozotocin-induced diabetic C57BL/6 wild type (WT) and Nrf2 knockout (KO) mice were treated in the presence or absence of EGCG, for 24 weeks. The Nrf2 KO mice exhibited more significant diabetes-induced loss in testicular weight and spermatozoa count, and increase in testicular apoptotic cell death, as compared with the WT mice. EGCG activated NRF2 expression and function, preserved testicular weight and spermatozoa count, and attenuated testicular apoptotic cell death, endoplasmic reticulum stress, inflammation, and oxidative damage in the WT diabetic mice, but not the Nrf2 KO diabetic mice. The present study demonstrated for the first time that NRF2 plays a critical role in both self and EGCG protection against DTD.

Zinc rescues obesity-induced cardiac hypertrophy via stimulating metallothionein to suppress oxidative stress-activated BCL10/CARD9/p38 MAPK pathway

Obesity often leads to obesity-related cardiac hypertrophy (ORCH), which is suppressed by zinc-induced inactivation of p38 mitogen-activated protein kinase (p38 MAPK). In this study, we investigated the mechanisms by which zinc inactivates p38 MAPK to prevent ORCH. Mice (4-week old) were fed either high fat diet (HFD, 60% kcal fat) or normal diet (ND, 10% kcal fat) containing variable amounts of zinc (deficiency, normal and supplement) for 3 and 6 months. P38 MAPK siRNA and the p38 MAPK inhibitor SB203580 were used to suppress p38 MAPK activity in vitro and in vivo, respectively. HFD activated p38 MAPK and increased expression of B-cell lymphoma/CLL 10 (BCL10) and caspase recruitment domain family member 9 (CARD9). These responses were enhanced by zinc deficiency and attenuated by zinc supplement. Administration of SB203580 to HFD mice or specific siRNA in palmitate-treated cardiomyocytes eliminated the HFD and zinc deficiency activation of p38 MAPK, but did not significantly impact the expression of BCL10 and CARD9. In cultured cardiomyocytes, inhibition of BCL10 expression by siRNA prevented palmitate-induced increased p38 MAPK activation and atrial natriuretic peptide (ANP) expression. In contrast, inhibition of p38 MAPK prevented ANP expression, but did not affect BCL10 expression. Deletion of metallothionein abolished the protective effect of zinc on palmitate-induced up-regulation of BCL10 and phospho-p38 MAPK. HFD and zinc deficiency synergistically induce ORCH by increasing oxidative stress-mediated activation of BCL10/CARD9/p38 MAPK signalling. Zinc supplement ameliorates ORCH through activation of metallothionein to repress oxidative stress-activated BCL10 expression and p38 MAPK activation.

Evaluation of anti-inflammatory and ulcerogenic potential of zinc-ibuprofen and zinc-naproxen complexes in rats

Because of numerous indications and high availability, non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed and used medicines in the world. However, long-term therapy with and improper use of NSAIDs may lead to gastrointestinal damage. Therefore, improving the therapeutic index of the existing drugs has become a priority over the past decades. Considerable attention in the field has been concentrated on metal complexes of non-steroidal anti-inflammatory drugs. The aim of this study is to evaluate the effect of complexation with zinc on the anti-inflammatory and ulcerogenic effects of ibuprofen and naproxen after single and triple intragastric administration to rats. The anti-inflammatory effect was assessed in carrageenan-induced inflammatory edema in the hind paw of male albino Wistar rats. The mucosal lesions were inspected and evaluated for gross pathology. Single administration of both the investigated complexes, namely zinc-ibuprofen and zinc-naproxen (20 mg/kg equivalent to ibuprofen and naproxen, respectively) and their parent drugs and physical mixtures with zinc hydroaspartate (ZHA doses: 16.05 and 14.37 mg/kg), caused a significant reduction of the edema after the same time from the carrageenan injection in comparison to the control groups. However, no statistically significant differences between the investigated drugs were observed after their single administration. The mean ulceration score for the mixture of ibuprofen and ZHA was statistically lower than the mean score achieved in rats after treatment with ibuprofen alone. On the other hand, triple intragastric administration of the ZHA-ibuprofen and ZHA-naproxen combination showed substantial enhancement of the anti-inflammatory activity against control groups, as well as against the parent NSAIDs. The most potent anti-inflammatory activity was demonstrated after 2 h from the carrageenan injection in animals receiving ZHA together with naproxen. The edema growth was reduced in these animals by 80.9% as compared to the control group. This result was significantly higher than the results achieved in animals receiving zinc-naproxen (50.2%) or naproxen alone (47.9%). Both NSAID complexes with zinc and mixtures with ZHA alleviated ulcerations caused by parent NSAIDs; however, the mixtures of both ibuprofen and naproxen with ZHA after triple administration were the least damaging. In view of the above results, zinc supplementation during NSAID therapy may have a beneficial effect on ulcer prevention and healing by reducing the effective dose of the parent drug and increasing its potency.

Metal ions influx is a double edged sword for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a common form of dementia in aged people, which is defined by two pathological characteristics: β-amyloid protein (Aβ) deposition and tau hyperphosphorylation. Although the mechanisms of AD development are still being debated, a series of evidence supports the idea that metals, such as copper, iron, zinc, magnesium and aluminium, are involved in the pathogenesis of the disease. In particular, the processes of Aβ deposition in senile plaques (SP) and the inclusion of phosphorylated tau in neurofibrillary tangles (NFTs) are markedly influenced by alterations in the homeostasis of the aforementioned metal ions. Moreover, the mechanisms of oxidative stress, synaptic plasticity, neurotoxicity, autophagy and apoptosis mediate the effects of metal ions-induced the aggregation state of Aβ and phosphorylated tau on AD development. More importantly, imbalance of these mechanisms finally caused cognitive decline in different experiment models. Collectively, reconstructing the signaling network that regulates AD progression by metal ions may provide novel insights for developing chelators specific for metal ions to combat AD.

Antioxidant and anti-inflammatory effects of zinc. Zinc-dependent NF-κB signaling

Zinc is a nutritionally fundamental trace element, essential to the structure and function of numerous macromolecules, including enzymes regulating cellular processes and cellular signaling pathways. The mineral modulates immune response and exhibits antioxidant and anti-inflammatory activity. Zinc retards oxidative processes on a long-term basis by inducing the expression of metallothioneins. These metal-binding cysteine-rich proteins are responsible for maintaining zinc-related cell homeostasis and act as potent electrophilic scavengers and cytoprotective agents. Furthermore, zinc increases the activation of antioxidant proteins and enzymes, such as glutathione and catalase. On the other hand, zinc exerts its antioxidant effect via two acute mechanisms, one of which is the stabilization of protein sulfhydryls against oxidation. The second mechanism consists in antagonizing transition metal-catalyzed reactions. Zinc can exchange redox active metals, such as copper and iron, in certain binding sites and attenuate cellular site-specific oxidative injury. Studies have demonstrated that physiological reconstitution of zinc restrains immune activation, whereas zinc deficiency, in the setting of severe infection, provokes a systemic increase in NF-κB activation. In vitro studies have shown that zinc decreases NF-κB activation and its target genes, such as TNF-α and IL-1β, and increases the gene expression of A20 and PPAR-α, the two zinc finger proteins with anti-inflammatory properties. Alternative NF-κB inhibitory mechanism is initiated by the inhibition of cyclic nucleotide phosphodiesterase, whereas another presumed mechanism consists in inhibition of IκB kinase in response to infection by zinc ions that have been imported into cells by ZIP8.

Is p53 Involved in Tissue-Specific Insulin Resistance Formation?

p53 constitutes an extremely versatile molecule, primarily involved in sensing the variety of cellular stresses. Functional p53 utilizes a plethora of mechanisms to protect cell from deleterious repercussions of genotoxic insults, where senescence deserves special attention. While the impressive amount of p53 roles has been perceived solely by the prism of antioncogenic effect, its presence seems to be vastly connected with metabolic abnormalities underlain by cellular aging, obesity, and inflammation. p53 has been found to regulate multiple biochemical processes such as glycolysis, oxidative phosphorylation, lipolysis, lipogenesis, β-oxidation, gluconeogenesis, and glycogen synthesis. Notably, p53-mediated metabolic effects are totally up to results of insulin action. Accumulating amount of data identifies p53 to be a factor activated upon hyperglycemia or excessive calorie intake, thus contributing to low-grade chronic inflammation and systemic insulin resistance. Prominent signs of its actions have been observed in muscles, liver, pancreas, and adipose tissue being associated with attenuation of insulin signalling. p53 is of crucial importance for the regulation of white and brown adipogenesis simultaneously being a repressor for preadipocyte differentiation. This review provides a profound insight into p53-dependent metabolic actions directed towards promotion of insulin resistance as well as presenting experimental data regarding obesity-induced p53-mediated metabolic abnormalities.

Attenuation of perfluorooctanoic acid-induced testicular oxidative stress and apoptosis by quercetin in mice

Quercetin treatment attenuated PFOA-induced oxidative stress and apoptosis in the testes of mice.

Zinc Is Indispensable in Exercise-Induced Cardioprotection against Intermittent Hypoxia-Induced Left Ventricular Function Impairment in Rats

In obstructive sleep apnea (OSA), recurrent obstruction of the upper airway leads to intermittent hypoxia (IH) during sleep, which can result in impairment of cardiac function. Although exercise can have beneficial effects against IH-induced cardiac dysfunction, the mechanism remains unclear. This study aimed to investigate the interactions of zinc and exercise on IH-triggered left ventricular dysfunction in a rat model that mimics IH in OSA patients. Nine-week-old male Sprague-Dawley rats were randomly assigned to either a control group (CON) or to a group receiving 10 weeks of exercise training (EXE). During weeks 9 and 10, half the rats in each group were subjected to IH for 8 h per day for 14 days (IHCON, IHEXE), whereas the remainder continued to breathe room air. Rats within each of the CON, IHCON, EXE, and IHEXE groups were further randomly assigned to receive intraperitoneal injections of either zinc chloride, the zinc chelator N,N,N',N'-tetrakis(2-pyridylmethyl) ethylenediamine (TPEN), or injection vehicle only. IH induced a lower left ventricular fractional shortening, reduced ejection fraction, higher myocardial levels of inflammatory factors, increased levels oxidative stress, and lower levels of antioxidative capacity, all of which were abolished by zinc treatment. IHEXE rats exhibited higher levels of cardiac function and antioxidant capacity and lower levels of inflammatory factors and oxidative stress than IHCON rats; however, IHEXE rats receiving TPEN did not exhibit these better outcomes. In conclusion, zinc is required for protecting against IH-induced LV functional impairment and likely plays a critical role in exercise-induced cardioprotection by exerting a dual antioxidant and anti-inflammatory effect.

Dietary zinc modifies diabetic-induced renal pathology in rats

This study was conducted to investigate how far dietary zinc (Zn) modifies the histomorphological alterations induced by diabetes in rat kidneys. The animals were divided into negative control group (10 rats). Diabetes was induced in thirty animals by streptozotocin. After confirming diabetes, the animals were divided into three groups (n = 10). Group II served as the positive control group (fed on standard diet), group III was fed on Zn deficient diet, and group IV was fed on Zn supplemented diet. Caspase-3 immune staining was used to estimate the caspase activity. Stereological procedures were used to measure the quantity of the immune stain and the surface area of the Bowman’s space. The renal cortices of group II rats revealed apparent widening of Bowman’s spaces with few apoptotic figures. The filtration barrier showed thickening of the basement membrane. The proximal convoluted tubules showed patchy loss of the apical microvilli with swollen mitochondria. The distal convoluted tubules revealed area of irregular basal enfolding. The picture was aggravated by Zn deficiency in group III besides areas of cortical interstitial fibrosis. The histopathological alterations were minimal in the cortices of group IV. A significant increase of the Bowman’s space surface area in group II and IV while decrease in group III compared with group I. The expression of Caspase-3 density was significantly increased in group II and III compared with group I while in group IV was non significant. In conclusion, dietary Zn modulated renal cortical changes caused by diabetes in rats.

The role of the p53 tumor suppressor in metabolism and diabetes

In the context of tumor suppression, p53 is an undisputedly critical protein. Functioning primarily as a transcription factor, p53 helps fend off the initiation and progression of tumors by inducing cell cycle arrest, senescence or programmed cell death (apoptosis) in cells at the earliest stages of precancerous development. Compelling evidence, however, suggests that p53 is involved in other aspects of human physiology, including metabolism. Indeed, recent studies suggest that p53 plays a significant role in the development of metabolic diseases, including diabetes, and further that p53's role in metabolism may also be consequential to tumor suppression. Here, we present a review of the literature on the role of p53 in metabolism, diabetes, pancreatic function, glucose homeostasis and insulin resistance. Additionally, we discuss the emerging role of genetic variation in the p53 pathway (single-nucleotide polymorphisms) on the impact of p53 in metabolic disease and diabetes. A better understanding of the relationship between p53, metabolism and diabetes may one day better inform the existing and prospective therapeutic strategies to combat this rapidly growing epidemic.