Selenium acts as an insulin-like molecule for the down-regulation of diabetic symptoms via endoplasmic reticulum stress and insulin signalling proteins in diabetes-induced non-obese diabetic mice

Beta Cell Dysfunction in Youth- and Adult-Onset Type 2 Diabetes: An Extensive Narrative Review with a Special Focus on the Role of Nutrients

Traditionally a disease of adults, type 2 diabetes (T2D) has been increasingly diagnosed in youth, particularly among adolescents and young adults of minority ethnic groups. Especially, during the recent COVID-19 pandemic, obesity and prediabetes have surged not only in minority ethnic groups but also in the general population, further raising T2D risk. Regarding its pathogenesis, a gradually increasing insulin resistance due to central adiposity combined with a progressively defective β-cell function are the main culprits. Especially in youth-onset T2D, a rapid β-cell activity decline has been observed, leading to higher treatment failure rates, and early complications. In addition, it is well established that both the quantity and quality of food ingested by individuals play a key role in T2D pathogenesis. A chronic imbalance between caloric intake and expenditure together with impaired micronutrient intake can lead to obesity and insulin resistance on one hand, and β-cell failure and defective insulin production on the other. This review summarizes our evolving understanding of the pathophysiological mechanisms involved in defective insulin secretion by the pancreatic islets in youth- and adult-onset T2D and, further, of the role various micronutrients play in these pathomechanisms. This knowledge is essential if we are to curtail the serious long-term complications of T2D both in pediatric and adult populations.

Selenium Deficiency Leads to Reduced Skeletal Muscle Cell Differentiation by Oxidative Stress in Mice

Selenium (Se) is one of the essential trace elements in animal organisms with good antioxidant and immune-enhancing abilities. In this study, we investigated the effect and mechanism of Se deficiency on skeletal muscle cell differentiation. A selenium-deficient skeletal muscle model was established. The skeletal muscle tissue and blood Se content were significantly reduced in the Se deficiency group. HE staining showed that the skeletal muscle tissue had a reduced myofiber area and nuclei and an increased myofascicular membrane with Se deficiency. The TUNEL test showed massive apoptosis of skeletal muscle cells in Se deficiency. With Se deficiency, reactive oxygen species (ROS) and malondialdehyde (MDA) increased, and the activities of glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), superoxide dismutase (SOD), and catalase (CAT) were inhibited. In in vitro experiments, microscopic observations showed that the low-Se group had reduced C2C12 cell fusion and a reduced number of differentiated myotubes. In addition, qPCR results showed that differentiation genes (Myog, Myod, Myh2, Myh3, and Myf5) were significantly reduced in the low Se group. Meanwhile, Western blot analysis showed that the levels of differentiation proteins (Myog, Myod, and Myhc) were significantly reduced in the low-Se group. This finding indicates that Se deficiency reduces the expression of skeletal muscle cell differentiation factors. All the above data suggest that Se deficiency can lead to oxidative stress in skeletal muscle, resulting in a reduction in the differentiation capacity of muscle cells.

Effect of Selenium Nanoparticles and/or Bee Venom against STZ-Induced Diabetic Cardiomyopathy and Nephropathy

The main purpose of our study was to examine the role of selenium nanoparticles (SeNPs) and/or bee venom (BV) in ameliorating diabetic cardiomyopathy (DCM) and nephropathy (DN) at the biochemical, histopathological and molecular levels. Fifty male albino rats were used in this experiment, divided into five groups: control, Streptozocin (STZ) diabetic, STZ-diabetic treated with SeNPs, STZ-diabetic treated with BV, and STZ-diabetic treated with SeNPs and BV. Biochemically, STZ injection resulted in a significant increase in serum glucose, BUN, creatinine, CRP, CK-MB, AST, LDH and cardiac troponins with a significant decrease in the serum insulin and albumin concentrations. Histopathologically, STZ injection resulted in diabetes, as revealed by glomerulonephritis, perivascular hemorrhage, inflammatory cell infiltrations and fibrosis, with widening of interstitial spaces of cardiomyocytes, loss of muscle cells continuity and some hyaline degeneration. At the molecular levels, the expression levels of miRNA 328, miRNA-21, TGFβ1, TGFβ1R, JAK1, STST-3, SMAD-1 and NFκβ genes were significantly up-regulated, whereas the expression levels of SMAD-7 were significantly down-regulated. It is concluded that SeNPs and/or BV administration ameliorates the deleterious effects resulting from STZ administration through improving the biochemical, histopathological and molecular effects, suggesting their protective role against the long-term diabetic complications of DCM and DN.

Selenium in Bodily Homeostasis: Hypothalamus, Hormones, and Highways of Communication

The ability of the body to maintain homeostasis requires constant communication between the brain and peripheral tissues. Different organs produce signals, often in the form of hormones, which are detected by the hypothalamus. In response, the hypothalamus alters its regulation of bodily processes, which is achieved through its own pathways of hormonal communication. The generation and transmission of the molecules involved in these bi-directional axes can be affected by redox balance. The essential trace element selenium is known to influence numerous physiological processes, including energy homeostasis, through its various redox functions. Selenium must be obtained through the diet and is used to synthesize selenoproteins, a family of proteins with mainly antioxidant functions. Alterations in selenium status have been correlated with homeostatic disturbances in humans and studies with animal models of selenoprotein dysfunction indicate a strong influence on energy balance. The relationship between selenium and energy metabolism is complicated, however, as selenium has been shown to participate in multiple levels of homeostatic communication. This review discusses the role of selenium in the various pathways of communication between the body and the brain that are essential for maintaining homeostasis.

The Effect and Potential Mechanism of Maternal Micronutrient Intake on Offspring Glucose Metabolism: An Emerging Field

Diabetes has become the most common metabolic disease around the world. In addition to genetic and environmental factors in adulthood, the early life environment is critical to the progression of diabetes in adults, especially the environment during the fetal period; this concept is called “fetal programming.” Substantial evidence has illustrated the key role of early life macronutrient in programming metabolic diseases. Recently, the effect of maternal micronutrient intake on offspring glucose metabolism during later life has become an emerging field. This review focuses on updated human and animal evidence about the effect of maternal micronutrient status on offspring glucose metabolism and the underlying mechanism.

Therapeutic Potential and Main Methods of Obtaining Selenium Nanoparticles

This review presents the latest data on the importance of selenium nanoparticles in human health, their use in medicine, and the main known methods of their production by various methods. In recent years, a multifaceted study of nanoscale complexes in medicine, including selenium nanoparticles, has become very important in view of a number of positive features that make it possible to create new drugs based on them or significantly improve the properties of existing drugs. It is known that selenium is an essential trace element that is part of key antioxidant enzymes. In mammals, there are 25 selenoproteins, in which selenium is a key component of the active site. The important role of selenium in human health has been repeatedly proven by several hundred works in the past few decades; in recent years, the study of selenium nanocomplexes has become the focus of researchers. A large amount of accumulated data requires generalization and systematization in order to improve understanding of the key mechanisms and prospects for the use of selenium nanoparticles in medicine, which is the purpose of this review.

Advances in Research on the Toxicological Effects of Selenium

Selenium is a trace element necessary for the growth of organisms. Moreover, selenium supplementation can improve the immunity and fertility of the body, as well as its ability to resist oxidation, tumors, heavy metals, and pathogenic microorganisms. However, owing to the duality of selenium, excessive selenium supplementation can cause certain toxic effects on the growth and development of the body and may even result in death in severe cases. At present, increasing attention is being paid to the development and utilization of selenium as a micronutrient, but its potential toxicity tends to be neglected. This study systematically reviews recent research on the toxicological effects of selenium, aiming to provide theoretical references for selenium toxicology-related research and theoretical support for the development of selenium-containing drugs, selenium-enriched dietary supplements, and selenium-enriched foods.

Selenium nanoparticles and metformin ameliorate streptozotocin-instigated brain oxidative-inflammatory stress and neurobehavioral alterations in rats

Selenium nanoparticles (SeNPs) are well reported to exhibit pharmacological activities both in vitro and in vivo. However, literature is devoid of studies on the impact of SeNPs and/or metformin (M) against streptozotocin (STZ)-mediated oxidative brain injury and behavioral impairment. Consequently, to fill this gap, diabetes was induced in male Wistar rats by feeding with 10% fructose solution for 2 weeks, followed by a single dose intraperitoneal injection of STZ (40 mg/kg body weight [bwt]). After rats were confirmed diabetic, they were treated orally with 0.1 mg/kg bwt of SeNPs ± M (50 mg/kg bwt), and normal control (NC) received citrate buffer (2 mg/mL) for 5 weeks. In comparison with the diabetic control (DC), SeNPs, and/or M significantly (p < 0.05) lowered blood glucose levels, but increased insulin secretion and pancreatic β-cell function. An increase in locomotor and motor activities evidenced by improved spontaneous alternation, locomotor frequency, hinding, and increased mobility time were observed in treated groups. In addition, there was enhanced brain antioxidant status with a lower acetylcholinesterase (AChE) activity and oxidative-inflammatory stress biomarkers. A significant downregulation of caspase 3 and upregulation of parvalbumin and Nrf2 protein expressions was observed in treated groups. In some of the studied parameters, treated groups were statistically (p < 0.05) insignificant compared with the normal control (NC) group. Overall, co-treatment elicited more efficacy than that of the individual regimen.

Co-administration of Selenium Nanoparticles and Metformin Abrogate Testicular Oxidative Injury by Suppressing Redox Imbalance, Augmenting Sperm Quality and Nrf2 Protein Expression in Streptozotocin-Induced Diabetic Rats

Selenium nanoparticles (SeNPs) and metformin (Met) elicit individually protective effects against testicular oxidative injury in diabetic rats. However, the combined effects of both compounds have not been investigated. We investigated the effects of SeNPs and Met individual/co-treatment on testicular oxidative injury in diabetic rats. Diabetes was induced by a single intraperitoneal administration of streptozotocin (STZ-40 mg/kg bwt). The rats were equally divided into 6 groups: Group one-non-diabetic; group two-diabetic untreated; and group six-non-diabetic received citrate buffer (2 mL/kg bwt), while group three, four, and five received SeNPs (0.1 mg/kg bwt), Met (50 mg/kg bwt), and SeNPs/Met combined respectively, for 42 days. Results revealed that SeNPs, as well as Met treatment significantly (p < 0.001), lowered blood glucose levels and improved relative organ weights in treated rats than those of the untreated group. Moreover, a synergistic effect was observed in the co-administration group. Additionally, combined treatment elicited better effect, in augmenting the pituitary and testicular hormone (LH, FSH, prolactin, and testosterone) levels, marker enzymes/protein associated with steroidogenesis (3-βHSD, 17-βHSD, and StAR protein), and sperm functional parameters than those of individual treatment groups, when compared with control. Furthermore, the combinatorial effects of SeNPs and Met surpassed their influence in attenuating testicular oxidative stress/inflammation and upregulation of Nrf2 protein expression in diabetic rats when compared with control. Overall, normal rats, co-treated with SeNPs and Met, did not reveal any deleterious effect. Therefore, SeNPs and Met combined treatment may better improve testes function in diabetic conditions than an individual regimen.

Role of Minerals and Trace Elements in Diabetes and Insulin Resistance

Minerals and trace elements are micronutrients that are essential to the human body but present only in traceable amounts. Nonetheless, they exhibit well-defined biochemical functions. Deficiencies in these micronutrients are related to widespread human health problems. This review article is focused on some of these minerals and trace element deficiencies and their consequences in diabetes and insulin resistance. The levels of trace elements vary considerably among different populations, contingent on the composition of the diet. In several Asian countries, large proportions of the population are affected by a number of micronutrient deficiencies. Local differences in selenium, zinc, copper, iron, chromium and iodine in the diet occur in both developed and developing countries, largely due to malnutrition and dependence on indigenous nutrition. These overall deficiencies and, in a few cases, excess of essential trace elements may lead to imbalances in glucose homeostasis and insulin resistance. The most extensive problems affecting one billion people or more worldwide are associated with inadequate supply of a number of minerals and trace elements including iodine, selenium, zinc, calcium, chromium, cobalt, iron, boron and magnesium. This review comprises various randomized controlled trials, cohort and case-controlled studies, and observational and laboratory-based studies with substantial outcomes of micronutrient deficiencies on diabetes and insulin resistance in diverse racial inhabitants from parts of Asia, Africa, and North America. Changes in these micronutrient levels in the serum and urine of subjects may indicate the trajectory toward metabolic changes, oxidative stress and provide disease-relevant information.

Hypoglycemic potential of selenium nanoparticles capped with polyvinyl-pyrrolidone in streptozotocin-induced experimental diabetes in rats

This study was aimed to evaluate the efficacy of synthesized selenium nanoparticles (SeNPs) capped with glucose and polyvinyl-pyrrolidone (PVP) on the hyperglycemia and prooxidants/antioxidants imbalance present in model streptozotocin (STZ)-induced diabetic rats. SeNPs were synthesized and characterized. Twenty-four albino male rats were grouped into four different groups. After the rats were induced to have type 2 diabetes by STZ, the SeNPs-treated groups received a dose of 0.5 mg/ml of SeNPs for seven days. Plasma glucose and insulin levels, pancreatic insulin expression, the levels of lipid peroxidation (LPO), nitric oxide (NO), glutathione peroxidase (GPx) and glutathione (GSH) were evaluated. TEM images revealed the formation of semispherical particles with average size between 40 and 50 nm. SeNPs administration successfully reduced the hyperglycemia, raised the levels of insulin in both the pancreas and the plasma and restored the damaged pancreatic tissue. SeNPs also showed enhancement of the elimination of the diabetes-induced oxidative stress injuries by decreasing the pancreatic LPO and NO levels. Furthermore, the activities of the antioxidant enzyme GPx and GSH levels of the diabetic rats were increased. In conclusion, SeNPs capped with PVP could be used in the future as an agent that could manage Diabetes mellitus.

A comparative evaluation of the micronutrient profile in the serum of diabetes mellitus Type II patients and healthy individuals with periodontitis

Background

Micronutrients play an important part in metabolism and maintenance of tissue function the maintenance of the integrity and vitality of the periodontal tissues depends on the availability of adequate nutrients, and it is possible that deficiencies can produce pathological alterations in the periodontal tissues. However, the association between nutritional factors and periodontal health is not fully understood. The essential micronutrients for maintaining health include zinc, copper, selenium, and iron. These micronutrients are required for a variety of biomolecules to maintain the normal structure, function, and proliferation of cells and also immune functions. Periodontal disease and diabetes mellitus (DM) are considered to have a bidirectional relationship, and periodontitis is recognized as the 6^th major complication of DM. The number of studies on the role of micronutrients with regard to periodontal disease is limited.

Aims

This study aims to evaluate the role of micronutrients-zinc, copper, selenium, and iron, in the serum of chronic periodontitis patients and chronic periodontitis with DM Type II patients, to see whether they can serve as potential markers for chronic periodontitis and also to assess whether periodontitis can have systemic effects.

Materials and Methods

A volume of 5 ml of venous blood was collected from each of the study participants, from the antecubital vein. The blood was then centrifuged and stored at -20°C before being analyzed. Zinc, copper, and selenium were estimated by the atomic absorption spectrophotometry, bathophenanthroline method was used to estimate iron.

Statistical Analysis

It was carried out using Student's t-test and analysis of variance. The honestly significant difference Tukey test and Pearson's correlation was also used.

Results

The mean serum zinc levels were significantly higher in healthy controls as compared to Periodontitis and Periodontitis with DM type II. The mean serum copper levels were significantly higher in Periodontitis with diabetes as compared to controls and periodontitis. Serum selenium levels were significantly higher in controls as compared to periodontitis with diabetes. The mean serum iron levels were significantly higher in periodontitis with diabetes. The Zinc: Copper (Zn: Cu) ratio was found to be significant for the periodontitis with diabetes group.

Conclusion

The results obtained from this study suggests that the serum levels of micronutrients Zn and Se were decreased and levels of Cu and Fe are increased in chronic periodontitis as compared to healthy control. There was a potentiated difference in the values in patients with DM Type II. The results show that the levels of these micronutrients can be used as effective biomarkers for chronic periodontitis and that periodontitis has systemic manifestations.

Cadmium-mediated miR-30a-GRP78 leads to JNK-dependent autophagy in chicken kidney

Cadmium-mediated microRNAs have become a heavily researched topic. Few studies mention the regulation of autophagy by cadmium through microRNAs, especially regarding poultry. The kidney is one of the organs most severely affected by cadmium, as it is involved in the accumulation of metal ions; causing such types of damage as apoptosis, necrosis and autophagy to the body. However, the relationship between miR-30a and GRP78 in the chicken kidney during ER stress and autophagy via JNK has not been thoroughly elucidated to date. In our research, we randomly assigned 128 Hy-Line Brown laying chickens to four groups with different diet treatments. The four groups consisted of the control group (0.2 mg Se kg-1), the Se group (2 mg kg-1 of Na₂SeO₃), the Se + Cd group (150 mg kg-1 of CdCl₂ and 2 mg kg-1 of Na₂SeO₃) and the Cd group (150 mg kg-1 of CdCl₂). On the 90th day, we detected the expression of miR-30a, GRP78, ER stress-related genes, IRE-1-JNK and autophagy-related genes. Compared with the control group, the mRNA levels of IRE-1-JNK, ER stress-related genes, autophagy-related genes and GRP78 were significantly increased (P < 0.05), while the expression of miR-30a was significantly decreased (p < 0.05) in the Cd group. However, those changes were clearly alleviated in the Se + Cd group (p < 0.05). In summary, we demonstrated that Cd triggered an miR-30a-GRP78 signaling axis disorder, increasing ER stress and activating the IRE-1-JNK pathway, thereby promoting autophagy in the chicken kidney. Moreover, Se could antagonize the negative impact of Cd.

Effects of Selenium Supplementation on the Diabetic Condition Depend on the Baseline Selenium Status in KKAy Mice

Oxidative stress in obesity leads to insulin resistance in type 2 diabetes. Some selenoproteins possess antioxidant properties, suggesting that selenium (Se) may protect against type 2 diabetes; however, evidence from epidemiological studies is contradictory. We hypothesized that Se status before supplementation (baseline) contributes to the supplementation outcome. This study aimed to clarify the influence of baseline Se status on the effect of Se supplementation on the diabetic condition. Six-week-old KKAy mice were fed a diet without supplemental Se or with 0.1 ppm Se in the form of L-selenomethionine (SeM) for 2 weeks to create low-Se and sufficient-Se baseline statuses, respectively. For the next 4 weeks, low-Se mice were given a SeM (0.5 ppm Se)-supplemented diet, and sufficient-Se mice were given either a SeM (0.5 ppm Se)- or sodium selenite (0.5 ppm Se)-supplemented diet; control groups continued on baseline diets. Serum Se concentrations, glutathione peroxidase (GPx) activities, adiponectin levels, glucose tolerance, and insulin sensitivity were analyzed. All mice became diabetic during the 2-week baseline induction period. At the end of the supplementation period, Se-receiving groups demonstrated significantly higher Se concentrations and GPx activities than their respective controls. Sufficient-Se mice receiving SeM had lower blood glucose levels and better insulin sensitivity than control and sodium selenite-receiving mice, whereas low-Se mice receiving SeM showed no such improvements compared with their controls. Our results suggest that Se supplementation in the form of SeM may help prevent type 2 diabetes aggravation in people taking the 55 μg/day Se recommended dietary allowance.

Effects of exendin-4 and selenium on the expression of GLP-1R, IRS-1, and preproinsulin in the pancreas of diabetic rats

The mechanisms by which exendin-4 and selenium exert their antidiabetic actions are still unclear. Here, we investigated the effects of exendin-4 or selenium administration on the expression of glucagon-like peptide-1 receptor (GLP-1R), insulin receptor substrate-1 (IRS-1), and preproinsulin in the pancreas of diabetic rats. Diabetes was induced by streptozotocin administration. Diabetic rats were injected intraperitoneally with 0.03 μg exendin-4/kg body weight/daily or treated with 5 ppm selenium in drinking water for a period of 4 weeks. GLP-1R and IRS-1 levels were decreased while the level of preproinsulin messenger RNA (mRNA) was increased in the pancreas of diabetic untreated rats, as compared to that in control rats. Treatment of diabetic rats with exendin-4 increased protein and mRNA levels of GLP-1R, and IRS-1, and the mRNA level of preproinsulin in the pancreas, as compared to their levels in diabetic untreated rats. Selenium treatment of diabetic rats increased the pancreatic mRNA levels of GLP-1R, IRS-1, and preproinsulin. Exendin-4 or selenium treatment of diabetic rats also increased the numbers of pancreatic islets and GLP-1R molecules in the pancreas. Therefore, exendin-4 and selenium may exert their antidiabetic effects by increasing GLP-1R, IRS-1, and preproinsulin expression in the pancreas and by increasing the number of pancreatic islets.

A gene-environment interaction analysis of plasma selenium with prevalent and incident diabetes: The Hortega study

Background

Selenium and single-nucleotide-polymorphisms in selenoprotein genes have been associated to diabetes. However, the interaction of selenium with genetic variation in diabetes and oxidative stress-related genes has not been evaluated as a potential determinant of diabetes risk.

Methods

We evaluated the cross-sectional and prospective associations of plasma selenium concentrations with type 2 diabetes, and the interaction of selenium concentrations with genetic variation in candidate polymorphisms, in a representative sample of 1452 men and women aged 18–85 years from Spain.

Results

The geometric mean of plasma selenium levels in the study sample was 84.2 µg/L. 120 participants had diabetes at baseline. Among diabetes-free participants who were not lost during the follow-up (N=1234), 75 developed diabetes over time. The multivariable adjusted odds ratios (95% confidence interval) for diabetes prevalence comparing the second and third to the first tertiles of plasma selenium levels were 1.80 (1.03, 3.14) and 1.97 (1.14, 3.41), respectively. The corresponding hazard ratios (95% CI) for diabetes incidence were 1.76 (0.96, 3.22) and 1.80 (0.98, 3.31), respectively. In addition, we observed significant interactions between selenium and polymorphisms in PPARGC1A, and in genes encoding mitochondrial proteins, such as BCS1L and SDHA, and suggestive interactions of selenium with other genes related to selenoproteins and redox metabolism.

Conclusions

Plasma selenium was positively associated with prevalent and incident diabetes. While the statistical interactions of selenium with polymorphisms involved in regulation of redox and insulin signaling pathways provide biological plausibility to the positive associations of selenium with diabetes, further research is needed to elucidate the causal pathways underlying these associations.

Selenoprotein SelK increases the secretion of insulin from MIN6 β cells

The expression of selenoprotein SelK triggers the secretion of insulin from MIN6 β cells by increasing the cytosolic free Ca²⁺ level, resulting from the up-regulated IP3R3 expression.

Selenium Supplementation Affects Insulin Resistance and Serum hs-CRP in Patients with Type 2 Diabetes and Coronary Heart Disease

To our knowledge, this study is the first indicating the effects of selenium supplementation on metabolic status of patients with type 2 diabetes mellitus (T2DM) and coronary heart disease (CHD). This study was conducted to evaluate the effects of selenium supplementation on metabolic profiles, biomarkers of inflammation, and oxidative stress of patients with T2DM and CHD. This randomized, double-blind, placebo-controlled trial was performed among 60 patients with T2DM and CHD aged 40-85 years. Participants were randomly divided into 2 groups. Group A received 200 μg selenium supplements (n=30) and group B received placebo per day (n=30) for 8 weeks. Fasting blood samples were taken at the beginning of the study and after 8-week intervention to quantify metabolic profiles. After 8 weeks, compared with the placebo, selenium supplementation resulted in a significant decrease in serum insulin levels (- 2.2±4.6 vs. + 3.6±8.4 μIU/ml, p=0.001), homeostasis model of assessment-insulin resistance (HOMA-IR) (- 0.7±1.3 vs. + 0.9±2.4, p=0.004), homeostatic model assessment-beta cell function (HOMA-B) (- 7.5±17.2 vs. + 15.1±34.5, p=0.002) and a significant increase in quantitative insulin sensitivity check index (QUICKI) (+0.01±0.03 vs. - 0.01±0.03, p=0.02). In addition, patients who received selenium supplements had a significant reduction in serum high-sensitivity C-reactive protein (hs-CRP) (- 1 372.3±2 318.8 vs. - 99.8±1 453.6 ng/ml, p=0.01) and a significant rise in plasma total antioxidant capacity (TAC) concentrations (+ 301.3±400.6 vs. - 127.2±428.0 mmol/l, p<0.001) compared with the placebo. A 200 μg/day selenium supplementation among patients with T2DM and CHD resulted in a significant decrease in insulin, HOMA-IR, HOMA-B, serum hs-CRP, and a significant increase in QUICKI score and TAC concentrations.

Selenium downregulates oxidative stress-induced activation of leukotriene pathway in experimental rats with diabetic cardiac hypertrophy

Cardiac hypertrophy has been considered as an important risk factor of morbidity and mortality. It is characterized as thickening of ventricle wall of the heart and consequent reduction in the contracting ability of the heart to pump the blood. Hyperglycemia-induced reactive oxygen species act as major mediators of diabetic complications. Inflammation plays an essential role in the development of diabetic cardiac hypertrophy. Selenium has been shown to induce insulin-like and anti-inflammatory effects in human and experimental animals. But, its mechanism of action has not been elucidated. Hence, in order to probe into its mechanism at molecular level, we designed an experiment to study the effect of selenium as sodium selenite in streptozotocin-induced diabetic rats. The rats were divided into four groups and maintained as follows: (1) controls, (2) sodium selenite-treated controls, (3) diabetic, and (4) sodium selenite-treated diabetic rats. Duration of the experiment was 30 days. Selenium supplementation enhanced the streptozotocin-induced reduction in the activities of antioxidant enzymes, decreased the serum glucose level, glycated hemoglobin content, concentration of high-sensitivity C-reactive protein, levels of lipid peroxidation products, as well as inflammatory parameters. Decrease in the phospholipase activity by selenium supplementation also contributed to the downregulation of leukotriene pathway. It also downregulated the expressions of nuclear transcription factor κB (NFκB), lipoxygenase, cyclooxygenase, 5-lipoxygenase-activating protein, and receptor for leukotriene B4. Hence, selenium decreased the production of reactive oxygen species and inhibited the activation of NFκB-mediated transcription of pro-inflammatory mediators which resulted in the downregulation of leukotriene pathway in diabetic cardiac hypertrophy.

Region-specific vulnerability to endoplasmic reticulum stress-induced neuronal death in rat brain after status epilepticus

We sought to clarify the involvement and the intra-cerebral distribution variability of C/EBP homologous protein (CHOP), a representative molecule related to endoplasmic reticulum (ER) stress-induced cell death signalling pathways, in neuronal death resulting from status epilepticus in rats. The expression patterns of CHOP and glucose-regulated protein (GRP) 78, a good marker of ER stress, were assessed by Western blotting, real-time PCR, Hoechst and immunohistochemistry in the hippocampus, cortex and striatum on a status epilepticus (SE) model. Double-fluorescent staining of CHOP and the terminal deoxynucleotidyl transferase-mediated DNA nick-end labelling (TUNEL) method were performed to clarify the involvement of CHOP in cell death. SE resulted in a timedependent increase in the expression of GRP78 and CHOP. The expression of GRP78 protein was increased at 3, 6 and 12 h after SE and no brain region variability was found. The expression of CHOP protein was also increased, reached its peak at 24 h and remained high at 48 h. CHOP protein expression, however, showed brain region variability with highest expression noted in the hippocampus followed by the striatum, and lowest in the cortex. The up-regulation of CHOP occurring at the transcriptional level was demonstrated by real-time PCR. Double fluorescence showed that CHOP expression strongly correlated with neurons undergoing apoptosis. The results indicated that SE compromises the function of the ER and that the hippocampus is more vulnerable than the cortex and the striatum.

The role of antioxidants and other agents in alleviating hyperglycemia mediated oxidative stress and injury in liver

Several antioxidants and agents having similar antioxidant effects are known to exert beneficial effects in ameliorating the injurious effects of hyperglycemia on liver in different diabetic in vitro and in vivo models. The review deals with some of the agents which have been shown to exert protective effects on liver against hyperglycemic insult and the various mechanisms involved. The different classes of agents which protect the diabetic liver or decrease the severity of hyperglycemia mediated injury include flavonoids, catechins, and other polyphenolic compounds, curcumin and its derivatives, certain vitamins, hormones and drugs, trace elements, prototypical antioxidants and amino acids. Some of the pronounced changes mediated by the antioxidants in liver exposed to hyperglycemia include decreased oxidative stress, and alterations in carbohydrate and lipid metabolism. Other mechanisms through which the agents ameliorate hyperglycemia mediated liver injury include decrease in oxidative DNA and protein damage, restoration of mitochondrial structural and functional integrity, decrease in inflammation and improved insulin signaling. Thus, antioxidants may prove to be an important mode of defense in maintaining normal hepatic functions in diabetes.

Proteomic analysis of kidneys from selenoprotein M transgenic rats in response to increased bioability of selenium

BACKGROUND

To characterize changes in global protein expression in kidneys of transgenic rats overexpressing human selenoprotein M (SelM) in response to increased bioabivility of selenium (Sel), total proteins extracted from kidneys of 10-week-old CMV/hSelM Tg and wild-type rats were separated by 2-dimensional gel electrophoresis and measured for changes in expression.

RESULTS

Ten and three proteins showing high antioxidant enzymatic activity were up- and down-regulated, respectively, in SelM-overexpressing CMV/hSelM Tg rats compared to controls based on an arbitrary 2-fold difference. Up-regulated proteins included LAP3, BAIAP2L1, CRP2, CD73 antigen, PDGF D, KIAA143 homolog, PRPPS-AP2, ZFP313, HSP-60, and N-WASP, whereas down-regulated proteins included ALKDH3, rMCP-3, and STC-1. After Sel treatment, five of the up-regulated proteins were significantly increased in expression in wild-type rats, whereas there were no changes in CMV/hSelM Tg rats. Only two of the down-regulated proteins showed reduced expression in wild-type and Tg rats after Sel treatment.

CONCLUSIONS

These results show the primary novel biological evidences that new functional protein groups and individual proteins in kidneys of Tg rats relate to Sel biology including the response to Sel treatment and SelM expression.

Selenium supranutrition: are the potential benefits of chemoprevention outweighed by the promotion of diabetes and insulin resistance?

Selenium was considered a toxin until 1957, when this mineral was shown to be essential in the prevention of necrotic liver damage in rats. The hypothesis of selenium chemoprevention is principally formulated by the observations that cancer incidence is inversely associated with selenium status. However, recent clinical and epidemiological studies demonstrate a role for some selenoproteins in exacerbating or promoting other disease states, specifically type 2 diabetes, although other data support a role of selenium in stimulating insulin sensitivity. Therefore, it is clear that our understanding in the role of selenium in glucose metabolism and chemoprevention is inadequate and incomplete. Research exploring the role of selenium in individual healthcare is of upmost importance and possibly will help explain how selenium is a double-edged sword in the pathologies of chronic diseases.

Selenium significantly inhibits adipocyte hypertrophy and abdominal fat accumulation in OLETF rats via induction of fatty acid β-oxidation

A combination of selenium (Se) with other trace element is associated with partially modulate fatty acid distribution as well as reduction of the body weight and feed efficiency. To investigate whether or not Se treatment has an impact on lipid metabolism, we examined the levels of lipid metabolism-related factors, including abdominal fat, adiponectin, cholesterol, very long chain dehydrogenase (VLCAD), and medium chain acyl-CoA dehydrogenase (MCAD) in 20-week-old Otsuka Long-Evans Tokushima Fatty (OLETF) rats following sodium selenite treatment for 2 weeks. Herein, we observed that (a) Se treatment induced insulin-like effects by lowering the serum glucose level in rats; (b) Se-treated rats showed significance values decreases in abdominal fat mass, adipocyte size, and adiponectin, which are associated with lipid metabolism; (c) Se treatment led to reduced levels of cholesterol, triglycerides, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol; (d) fat tissue in Se-treated rats displayed significantly lower expression of adipocyte marker genes along with increased expression of VLCAD and MCAD; and (e) fatty liver formation and β-oxidation gene expression were both significantly reduced in liver tissue of Se-treated rats. Therefore, our results suggest that Se may induce inhibition of adipocyte hypertrophy and abdominal fat accumulation along with suppression of fatty liver formation by the differential regulation of the gene expression for fatty acid β-oxidation in the OLETF model.

Selenium downregulates RAGE and NFκB expression in diabetic rats

Diabetes is one of the leading causes of death in developed and developing countries. Oxidative stress has been proposed to play a crucial role in the pathogenesis of diabetic vascular complications. In recent years, selenium has been shown to mediate a number of insulinlike actions in a dose-dependent fashion both in vitro and in vivo. In this study, the effect of selenium as sodium selenite was investigated in streptozotocin-induced diabetic rats at the dose of 1 μg sodium selenite/kg body weight. Selenium supplementation restored the streptozotocin-induced alterations in the activities of antioxidant enzymes, decreased the serum glucose level, glycated hemoglobin content as well as the levels of lipid peroxidation products, and downregulated the expressions of both NFkB and RAGE. The histopathological studies also reinforce our findings. Hence, selenium has a protective role in streptozotocin-induced diabetes mellitus.

Effect of selenium in organic and inorganic form on liver, kidney, brain and muscle of Wistar rats

Selenium is a micronutrient, localized in the active sites of enzymes such as glutathione peroxidase and thioredoxin reductase, and participating together with these enzymes in an antioxidant defence system of organisms against free radicals. Administration of selenium is necessary for maintaining oxidative homeostasis. The present experiment is aimed at investigation of selenium impact on basal metabolic processes and selected antioxidants in a Wistar rat model, fed selenium in organic and inorganic forms. Liver, kidney, brain and muscle were sampled during a month-long feeding with four different doses of selenium (0.075 mg or 1.5 mg of inorganic and/or organic selenium per kg of feed). We found a significant reduction in glutathione level in liver tissue regardless of the form of the administered selenium. On the other hand, selenium caused a decreased glutathione reductase level in the liver and metallothionein level in the liver, kidney and muscle.

Exercise training and selenium or a combined treatment ameliorates aberrant expression of glucose and lactate metabolic proteins in skeletal muscle in a rodent model of diabetes

Exercise training (ET) and selenium (SEL) were evaluated either individually or in combination (COMBI) for their effects on expression of glucose (AMPK, PGC-1α, GLUT-4) and lactate metabolic proteins (LDH, MCT-1, MCT-4, COX-IV) in heart and skeletal muscles in a rodent model (Goto-Kakisaki, GK) of diabetes. Forty GK rats either remained sedentary (SED), performed ET, received SEL, (5 µmol·kg body wt^-1·day^-1) or underwent both ET and SEL treatment for 6 wk. ET alone, SEL alone, or COMBI resulted in a significant lowering of lactate, glucose, and insulin levels as well as a reduction in HOMA-IR and AUC for glucose relative to SED. Additionally, ET alone, SEL alone, or COMBI increased glycogen content and citrate synthase (CS) activities in liver and muscles. However, their effects on glycogen content and CS activity were tissue-specific. In particular, ET alone, SEL alone, or COMBI induced upregulation of glucose (AMPK, PGC-1α, GLUT-4) and lactate (LDH, MCT-1, MCT-4, COX-IV) metabolic proteins relative to SED. However, their effects on glucose and lactate metabolic proteins also appeared to be tissue-specific. It seemed that glucose and lactate metabolic protein expression was not further enhanced with COMBI compared to that of ET alone or SEL alone. These data suggest that ET alone or SEL alone or COMBI represent a practical strategy for ameliorating aberrant expression of glucose and lactate metabolic proteins in diabetic GK rats.

Selenium in human health and disease

This review covers current knowledge of selenium in the environment, dietary intakes, metabolism and status, functions in the body, thyroid hormone metabolism, antioxidant defense systems and oxidative metabolism, and the immune system. Selenium toxicity and links between deficiency and Keshan disease and Kashin-Beck disease are described. The relationships between selenium intake/status and various health outcomes, in particular gastrointestinal and prostate cancer, cardiovascular disease, diabetes, and male fertility, are reviewed, and recent developments in genetics of selenoproteins are outlined. The rationale behind current dietary reference intakes of selenium is explained, and examples of differences between countries and/or expert bodies are given. Throughout the review, gaps in knowledge and research requirements are identified. More research is needed to improve our understanding of selenium metabolism and requirements for optimal health. Functions of the majority of the selenoproteins await characterization, the mechanism of absorption has yet to be identified, measures of status need to be developed, and effects of genotype on metabolism require further investigation. The relationships between selenium intake/status and health, or risk of disease, are complex but require elucidation to inform clinical practice, to refine dietary recommendations, and to develop effective public health policies.