The role of selenium in insulin resistance

Association Between Selenium and Circulating Adipokine Levels in Patients with Polycystic Ovary Syndrome

There is increasing evidence that selenium (Se) and its major transport protein, selenoprotein-P (SePP), may be associated with polycystic ovary syndrome (PCOS). However, the association of serum Se and SePP levels with circulating adipokines in this population has not received sufficient attention. In the present study, we aimed to investigate the associations of serum Se and SePP with circulating adipokine levels in patients with PCOS. In this cross-sectional study, 115 patients aged 18-45 years with PCOS diagnosed according to the Rotterdam Consensus Criteria were recruited. The general characteristics of the participants were collected using a general questionnaire and anthropometric measurements were taken. Blood samples were obtained and serum levels of leptin, adiponectin, visfatin, resistin, and omentin-1, as well as markers of glucose metabolism, were measured. Serum levels of Se and SePP were inversely correlated with fasting blood glucose (FBS), serum insulin, and homeostatic model assessment for insulin resistance (HOMA-IR). In addition, serum levels of Se and SePP were positively correlated with serum levels of adiponectin and visfatin. Although there was no significant correlation between serum Se and serum omentin-1 levels, a significant positive correlation was found between serum SePP levels and this adipokine. The present study found that serum Se and SePP levels were positively correlated with serum adiponectin and visfatin levels. Further studies are needed to confirm these findings.

Selenium Species in Diabetes Mellitus Type 2

Selenium is an important trace element for humans and animals as it plays a key role in several major metabolic pathways. Several studies were conducted to better understand the role of selenium against diabetes mellitus (DM), particularly type 2 (T2DM), but the obtained conclusions are contradictory. A simple linear relationship does not exist between the risk of T2DM and selenium levels but is best represented in a dose-dependent manner, getting often the U-graph. This relation also depends on selenium chemical forms that are present in a diet or supplements. Both too low and too high selenium intakes could increase the risk of diabetes. Moreover, the baseline status of Se should be taken into consideration to avoid over-supplementation. The focus of this brief overview is to report the recent updates concerning selenium participation in diabetes mellitus.

Mesenchymal Stem Cell-Derived Exosomes Loaded with Selenium or Nano Selenium as a Novel Therapeutic Paradigm for Streptozotocin-Induced Type 1 Diabetes in Rats

Type 1 diabetes mellitus (T1DM) is a metabolic disorder characterized by hyperglycemia due to insulin insufficiency as a consequence of the pancreatic β-cells' auto-immune attack. Nowadays, the application of mesenchymal stem cell-derived exosomes (MSCs-Exs) as the main cell-free therapy for diabetes treatment is becoming more and more extensive. In non-autologous therapy, researchers are moving towards a new strategy based on loading MSC-Exs with certain drugs, aimed at maintaining and maximizing the function of exosomes at the function site and enhancing their efficiency and safety. This study aims to explore and compare the therapeutic potentialities of mesenchymal stem cell-derived exosomes (MSCs-Exs) loaded with either selenium (Se) or nano selenium (NSe), a natural antioxidant micronutrient, in the management of T1DM in rats. In our 4-week experiment, six rat groups were included, namely, control, Ex+Se, Ex+NSe, STZ-diabetic (D), D+ Ex+Se, and D+Ex+NSe groups. Both diabetic-treated groups showed marked pancreatic regenerative antioxidant, immunomodulatory, anti-inflammatory, and anti-apoptotic capacities, with the D+Ex+NSe injection showing superiority in managing diabetes hazards, as evidenced by various biochemical and histological assessments.

Selenium supplementation effect on glycemic control: A GRADE-assessed systematic review and dose-response meta-analysis of randomized controlled trials

Results from different studies on the effects of selenium supplementation on glycemic control are still debated. To fill this knowledge gap, we investigated the overall effects of selenium supplementation on some glycemic parameters such as fasting blood sugar (FBS), hemoglobinA1c (HbA1c), fasting insulin, quantitative insulin sensitivity check index (QUICKI), and homeostatic model assessment of insulin resistance (HOMA-IR). A comprehensive literature search was conducted from inception to April 2023 on Scopus, Web of Science, PubMed, Google Scholar, and Cochrane databases. All randomized controlled trials (RCTs) which reported an effect of selenium supplementation on glycemic parameters were included. A random-effects model was used to estimate the weighted mean difference (WMD) and 95% CI for each outcome. Between-studies heterogeneity was assessed by the I2 and Cochran's Q test. 20 trials were included in the meta-analysis. Pooled analysis showed that selenium intake significantly reduced fasting insulin (WMD: -3.02 µIu/mL, 95% CI; -5.13, -0.90, P = 0.005) and increased QUICKI levels (WMD: 0.01, 95% CI: 0.01, 0.02, P = 0.005). However, selenium supplementation did not change FBS (WMD: -1.32 mg/dL, 95% CI; -4.02, 1.37, P = 0.332), HbA1c (WMD = 0.05%, 95% CI: -0.19, 0.28, p = 0.701), and HOMA-IR (WMD: -0.82, 95% CI; -2.14, 0.50, P = 0.223). Moreover, we found that there is a non-linear association between selenium supplementation dosage and FBS (P-nonlinearity = 0.008). In conclusion, our study findings indicate some benefits of selenium on fasting insulin, and QUICKI compared with placebo, but elicits no effect on HbA1c, HOMA-IR, and FBS. Further well-designed RCTs with larger samples are necessary to ascertain the effects of selenium supplementation on glycemic control.

The HbA1c and blood glucose response to selenium-rich polysaccharide from Fomes fomentarius loaded solid lipid nanoparticles as a potential antidiabetic agent in rats

Fomes fomentarius is a medicinal fungus used in traditional Chinese medicine to treat various illnesses. Antidiabetic effects of F. fomentarius extracts have been reported recently. In this study, F. fomentarius extracellular polysaccharide (PS) was prepared, and then to enhance its antidiabetic effects, Na₂SeO₃ was added to the culture medium, and selenium-polysaccharide (PS-Se) was obtained. Also, solid lipid nanoparticles containing PS (SLN-PS) and PS-Se (SLN-PS-Se) were synthesized by the microemulsion method to compare their effects with free polysaccharides in streptozotocin (STZ) diabetic rats. Optimized SLNs had a size of 170.5 nm and drug loading of 9.27 %. EDS analysis confirmed that Se presence in PS-Se. Characterization analyses such as FTIR, DSC, TGA, and XRD suggested that SLNs have good thermal stability and crystalline nature. Release of PS from SLNs demonstrated sustained profile, and MTT assay proved that PSs and SLNs have no cytotoxicity. Furthermore, oral administration of PS, PS-Se, SLN-PS, and SLN-PS-Se for 28 days to diabetic rats significantly declined blood glucose by 48.24 %, 49.96 %, 55.50 %, and 60.47 %, respectively. Also, insulin secretion and body weight improved, and HbA1c levels decreased. Treatment by PS, PS-Se, SLN-PS, and SLN-PS-Se alleviated lipid profiles, liver enzymes, and serum proteins. Liver anti-oxidant parameters and histopathological observation of the liver, pancreas, and kidney confirmed that F. fomentarius PSs and SLNs have antidiabetic impacts. Moreover, supplementation of PS with selenium improves its anti-hyperglycemic effects. Finally, SLN-PS and SLN-PS-Se showed a higher antidiabetic impact than free PS and PS-Se.

Participation of Magnesium in the Secretion and Signaling Pathways of Insulin: an Updated Review

Several studies have demonstrated the participation of various minerals in mechanisms involving insulin. Magnesium, in particular, plays an important role in the secretion and action of this hormone. Therefore, this review aimed to examine the latest insights into the biochemical and molecular aspects of the participation of magnesium in insulin sensitivity. Magnesium plays a vital role in the activity of intracellular proteins involved in insulin secretion in β-pancreatic cells, such as glucokinase, ATPase, and protein kinase C. In addition, evidence suggests that this mineral participates directly in insulin sensitivity and signaling in peripheral tissues, acting in the phosphorylation of the receptor tyrosine kinase and the insulin receptor substrates 1, insulin receptor substrates 2, phosphatidylinositol 3-kinase, and protein kinase B, and indirectly by reducing oxidative stress and chronic low-grade inflammation, which also lead to insulin resistance. Thus, magnesium deficiency is associated with glucose intolerance, while magnesium supplementation stimulates insulin secretion in pancreatic cells and improves insulin sensitivity in peripheral tissues. However, studies must consider assess short- and long-term nutritional status of mineral before performing intervention, the relevance of the balance of other nutrients that influence hormone secretion and sensibility, and health status of the assessed population.

A Comprehensive Review on Selenium and Its Effects on Human Health and Distribution in Middle Eastern Countries

Selenium (Se) is an important microelement with numerous positive effects on human health and diseases. It is important to specify that the status and consumption of Se are for a specific community as the levels of Se are extremely unpredictable between different populations and regions. Our existing paper was based on the impacts of Se on human health and disease along with data on the Se levels in Middle Eastern countries. Overall, the findings of this comprehensive review show that the consumption and levels of Se are inadequate in Middle Eastern nations. Such findings, together with the growing awareness of the importance of Se to general health, require further work primarily on creating an acceptable range of blood Se concentration or other measures to determine optimal Se consumption and, consequently, to guarantee adequate Se supplementation in populations at high risk of low Se intake.

The Symbiotic Effect of a New Nutraceutical with Yeast β-Glucan, Prebiotics, Minerals, and Silybum marianum (Silymarin) for Recovering Metabolic Homeostasis via Pgc-1α, Il-6, and Il-10 Gene Expression in a Type-2 Diabetes Obesity Model

The use of natural products and derivatives for the prevention and control of non-communicable chronic diseases, such as type-2 diabetes (T2D), obesity, and hepatic steatosis is a way to achieve homeostasis through different metabolic pathways. Thus, male C57BL/6 mice were divided into the following groups: high-fat diet (HFD) vehicle, HFD + Supplemented, HFD + Supplemented_S, and isolated compounds. The vehicle and experimental formulations were administered orally by gavage once a day over the four weeks of the diet (28 consecutive days). We evaluated the energy homeostasis, cytokines, and mitochondrial gene expression in these groups of mice. After four weeks of supplementation, only the new nutraceutical group (HFD + Supplemented) experienced reduced fasting glycemia, insulin, HOMA index, HOMA-β, dyslipidemia, ectopic fat deposition, and hepatic fibrosis levels. Additionally, the PPARγ coactivator 1 α (Pgc-1α), interleukin-6 (Il-6), and interleukin-10 (Il-10) gene expression were augmented, while hepatic steatosis decreased and liver parenchyma was recovered. The glutathione-S-transferase activity status was found to be modulated by the supplement. We discovered that the new nutraceutical was able to improve insulin resistance and hepatic steatosis mainly by regulating IL-6, IL-10, and Pgc-1α gene expression.

Non-Centrifugal Sugar (NCS) and Health: A Review on Functional Components and Health Benefits

Non-centrifugal sugar (NCS) is the scientific term the Food and Agriculture Organization (FAO) uses to define a solid product, produced by sugarcane juice evaporation, which is unrefined or minimally refined. NCS is referred to in various names globally, the most significant ones are whole cane sugar, panela (Latin America), jaggery (India) and kokuto (Japan). NCS contains minerals, bioactive compounds, flavonoids and phenolic acids, which have therapeutic potentials from time immemorial. Even though the bioactive property is dependent on the composition, which relies mainly on the agronomic conditions and production process, NCS possesses antioxidant and anti-inflammatory properties. Hence, substituting the consumption of refined sugar with NCS might be helpful in the control of chronic diseases generally connected to oxidative stress and inflammation. Experimental facts from in vitro and in vivo models have proven that NCS plays an essential role in weight management, maintaining insulin sensitivity and preventing neurodegenerative diseases. NCS has also shown hypoglycemic and hypolipidemic effects. This review aims to synopsize the recent literature pertaining to the benefits of NCS in human health. The NCS can be considered a nutraceutical and functional food. However, detailed and regulated studies are important to enhance the beneficial effects in human and animal interventions.

Evaluation of Serum Selenium Status by Age and Gender: A Retrospective Observational Cohort Study in Western Romania

Selenium, residing in a series of selenoproteins, plays an important role in both female and male reproductive function. Of particular significance for reproduction is the antioxidant glutathione peroxidase (GPx), a main selenoenzyme, whose level is regulated by the availability of Se in the body. We hypothesized that changes in Se status, closely related to GPx activity, would result in an increased risk of reproductive dysfunction in individuals. We retrospectively investigated the serum selenium (SeS) concentrations of 1264 apparently healthy people, aged 16–89 years, from Western Romania. The general analysis revealed a non-normal SeS distribution with a median SeS of 100.26 ± 18.32 μg/L and a significant difference in SeS levels between age groups. The analysis of the young group (16–35 years) revealed that up to 50% of individuals did not reach the SeS threshold corresponding to maximum GPx activity (80 μg/L), and a significant imbalance between the genders was apparent when looking at SeS values outside the range. Our results correlated with the general diminished reproductive ability registered in Romania during the last few years. Serum selenium content proves to offer a proper reflection of the fertility competence of the young population, and its monitoring is important for guiding dietary adjustments and attaining normal reproductive function.

Effect of a single, oral administration of selenitetriglycerides, at two dose rates, on blood selenium status and haematological and biochemical parameters in Holstein-Friesian calves

BACKGROUND

Selenitetriglycerides are biologically active, organic forms of selenium formed as a result of the modification of selenic acid and sunflower oil. Studies in rats have shown that they are well absorbed and of low toxicity. There are no published studies on selenitetriglycerides supplementation in calves.

RESULTS

In this study, selenitetriglycerides were administered once orally on the 2nd day of life at a dose of 0.5 or 1 mg Se/kg body weight to each of six Holstein-Friesian calves while six control calves were not supplemented. Blood for determination of selenium concentration, glutathione peroxidase activity, haematological parameters, aspartate aminotransferase, creatine kinase, and lactate dehydrogenase activities and glucose, total protein, albumin, triglycerides, cholesterol, urea, and creatinine concentration was collected before supplementation (day 0) and 1, 2, 5, 10 and 14 days after supplementation. Selenitetriglycerides administration increased (P < 0.01) serum selenium concentration in supplemented calves as early as day1, from a mean of 63.4 to 184.22 µg/l in calves receiving selenium at a dose of 0.5 mg/kg BW, and from 63.17 to 200.33 µg/l in calves receiving 1 mg/kg. Serum selenium concentrations remained significantly higher compared to the control group throughout the experiment. Glutathione peroxidase activity was higher in supplemented than control calves, significantly so in animals receiving the 1 mg/kg dose of Se on the 10th and 14th days (P < 0.05). There were no significant differences in the haematological and biochemical parameters between the groups.

CONCLUSIONS

This experiment showed that supplementation with selenitetriglycerides could significantly improve blood selenium status in calves without adverse effects on haematological or biochemical parameters. These findings are essential prerequisites for future studies on selenitetriglycerides supplementation to manage clinical selenium deficiency in calves.

Effects of dietary antioxidants on glucose and insulin responses to glucose tolerance test in transition dairy cows

Oxidative stress occurs during the transition period and causes insulin resistance, which may be reduced by the use of antioxidants in this period. Twenty-four multiparous Holstein dairy cows, at 8 wk before parturition, were divided into 4 equal groups, namely control (Ctrl), vitamin E (VE), selenium (Se), and vitamin E plus selenium (VE + Se) groups. On a daily basis, VE and Se cows received dietary 1.5 IU vitamin E/kg BW and 0.3 mg/kg DM selenium, respectively, from 8 wk before to 3 wk after parturition. Vitamin E plus selenium group received doses similar to VE and Se groups. Insulin sensitivity was evaluated through intravenous glucose tolerance test (ivGTT) at weekly intervals from 3 wk before to 3 wk after parturition. Serum concentrations of total antioxidant status (TAS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), nonesterified fatty acid (NEFA), and beta-hydroxybutyric acid (BHBA) were assayed weekly before the commencement of ivGTT. Based on the results of ivGTT, the lowest and the highest degrees of insulin sensitivity were detected in Ctrl and VE + Se groups, respectively. The highest and the lowest concentrations of NEFA and BHBA were observed in Ctrl and VE + Se groups, respectively. Total antioxidant status, SOD, and GPx values were significantly lower in Ctrl cows and significantly higher in VE + Se-received cows compared with other groups. However, MDA values in Ctrl and VE + Se cows were significantly higher and lower than the other groups, respectively. Collectively, our results show that dietary administration of vitamin E and selenium ameliorates oxidative stress and lipid mobilization and increases insulin sensitivity in transition cows.

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.

Selenocysteine insertion sequence binding protein 2 (Sbp2) in the sex-specific regulation of selenoprotein gene expression in mouse pancreatic islets

Selenoproteins are a group of selenocysteine-containing proteins with major roles in cellular antioxidant defense and thyroid hormone metabolism. Selenoprotein expression is determined by hierarchical mechanisms that result in tissue-specific levels. Current data inadequately explain the abundance of various selenoproteins under normal and pathological conditions, including in pancreatic β-cells. Selenocysteine insertion sequence binding protein 2 (SBP2) is a critical protein in selenoprotein translation that also plays an essential role in stabilizing selenoprotein transcripts by antagonizing nonsense-mediated decay (NMD). Importantly, dysfunctional SBP2 is associated with endocrine disorders in humans. Here we describe the impact of induced Sbp2 deficiency in pancreatic β-cells on selenoprotein transcript profiles in the pancreatic islets of C57BL/6J mice. Sex differences were noted in control mice, in which female islets showed 5 selenoproteins decreased and one increased versus male islets. Induced Sbp2 deficiency in pancreatic β-cells altered expression of only 3 selenoprotein transcripts in male islets, whereas 14 transcripts were reduced in female islets. In all cases, decreased transcription was observed in genes known to be regulated by NMD. The differential impact of Sbp2 deletion on selenoprotein transcription between sexes suggests sex-specific hierarchical mechanisms of selenoprotein expression that may influence islet biology and consequentially metabolic disease risk.

Sodium Selenite Improves In Vitro Maturation of Bos primigenius taurus Oocytes

Selenium (Se) is an essential trace element with important functions in animals and whose deficiency is associated with reproductive failures. The aim of this study was to investigate the effect of Se concentrations during in vitro maturation (IVM) of Bos taurus oocyte within the reference ranges for Se status in cattle. For this purpose, Aberdeen Angus cumulus-oocyte complexes (COCs) were matured in IVM medium supplemented with 0, 10, 50, and 100 ng/mL Se (control, deficient, marginal, and adequate, respectively). The results demonstrated that marginal and adequate Se concentrations added during IVM increased viability and non-apoptotic cumulus cells (CC). Moreover, the addition of Se to culture media decreased malondialdehyde level in COC with all studied concentrations and increased total glutathione content in CC and oocytes with 10 ng/mL Se. On the other hand, total antioxidant capacity of COC, nuclear maturation, and the developmental capacity of oocytes were not modified by Se supplementation. However, 10 ng/mL Se increased hatching rate. In conclusion, supplementation with 10 ng/mL Se during in vitro maturation of Bos primigenius taurus oocytes should be considered to improve embryo quality.

Ancient wheats: beneficial effects on insulin resistance

Non-alcoholic fatty liver disease and type 2 diabetes mellitus are two conditions that commonly exist together in the context of the metabolic syndrome. Several scientific advances in understanding this association have identified insulin resistance as the key point in the pathogenesis of both diseases. The first line treatment suggested in the management of these diseases is represented by lifestyle changes and in particular the modification of alimentary regimen, with the transition to a healthy diet. In this context, several studies have focused their attention on the identification of food products with beneficial actions, like ancient wheat (AW). AW are defined as the early cereals that were domesticated in their places of origin in the "Fertile Crescent" of the Middle East, and played a central role as a main source of food for the early civilizations in that region. The present narrative review aims to provide a systematic overview of the state of the art on the effects of AW on insulin resistance.

High- and low- selenium diets affect endocrine energy balance during early programming

High- and low- Se diets received by dams during gestation and lactation are related to insulin resistance in their pups. High-Se diet leads to an increase in serum insulin levels, which does not function properly, and an anabolic process. Low-Se diet is related to very low insulin values and an extreme catabolic energy imbalance. Selenoproteins have been implicated directly in the general endocrine regulation of appetite and energy homeostasis. To obtain information concerning how Se intake by dams is involved in regulating endocrine energy balance in progeny, three experimental groups of dam rats were used: control (Se: 0.1 ppm), Se-supplemented (Se: 0.5 ppm) and Se-deficient (Se: 0.01 ppm). At the end of lactation (21d old), the pups' appetite profile, Se levels, peptides from gastrointestinal tract (including pancreas), leptin, thyroid hormones, skeletal growth markers and cytokines in serum were measured. Low-Se diet leads to severe growth retardation, underdeveloped glands, a non-functional pancreas, non-operative high serum leptin levels and low GIT-anorexigenic signals. High-Se diet leads to non-operative high insulin secretion, obesity, inflammation and low leptin levels. These results point to Se as an important marker and a possible dietary supplementation treatment for gestating and lactating mothers in order to avoid metabolic disorders such as gestational diabetes or intrauterine growth retardation which could affect their progeny's future health in adulthood.

Antioxidants and selenocompounds inhibit 3,5-dimethylaminophenol toxicity to human urothelial cells

Exposure to alkyl anilines may lead to bladder cancer, which is the second most frequent cancer of the urogenital tract. 3,5-dimethylaniline is highly used in industry. Studies on its primary metabolite 3,5-dimethylaminophenol (3,5-DMAP) showed that this compound causes oxidative stress, changes antioxidant enzyme activities, and leads to death of different mammalian cells. However, there is no in vitro study to show the direct effects of 3,5-DMAP on human bladder and urothelial cells. Selenocompounds are suggested to decrease oxidative stress caused by some chemicals, and selenium supplementation was shown to reduce the risk of bladder cancer. The main aim of this study was to investigate whether selenocompounds organic selenomethionine (SM, 10 µmol/L) or inorganic sodium selenite (SS, 30 nmol/L) could reduce oxidative stress, DNA damage, and apoptosis in UROtsa cells exposed to 3,5-DMAP. 3,5-DMAP caused a dose-dependent increase in intracellular generation of reactive oxygen species, and its dose of 50 µmol/L caused lipid peroxidation, protein oxidation, and changes in antioxidant enzyme activities in different cellular fractions. The comet assay also showed single-strand DNA breaks induced by the 3,5-DMAP dose of 50 µmol/L, but no changes in double-strand DNA breaks. Apoptosis was also triggered. Both selenocompounds provided partial protection against the cellular toxicity of 3,5-DMAP. Low selenium status along with exposure to alkyl anilines can be a major factor in the development of bladder cancer. More mechanistic studies are needed to specify the role of selenium in bladder cancer.