Sesamol protects MIN6 pancreatic beta cells against simvastatin-induced toxicity by restoring mitochondrial membrane potentials

Comparative efficacy, toxicity, and insulin-suppressive effects of simvastatin and pravastatin in fatty acid-challenged mouse insulinoma MIN6 β-cell model

INTRODUCTION

Familial hypercholesterolemia, the highly prevalent form of dyslipidemia, is a well-known risk factor for premature heart disease and stroke worldwide. Statins, which inhibit 3-hydroxy 3-methylglutaryl coenzyme A (HMG-CoA) reductase, are the first-choice treatment for dyslipidemias, and have been effective in reducing the risk of stroke and myocardial infarction. However, emerging evidence indicates that statins may increase the incidence of new-onset type 2 diabetes by reducing β-cell mass and function. Notably, past in vitro reports studying the effects of statins on β-cells were performed without including free fatty acids in the model. This factor should have been addressed since these agents are used to treat individuals with hyperlipidemia.

METHODS

Here, we used a mouse insulinoma MIN6 β-cell culture model to assess the efficacy, cytotoxicity, and insulin-suppressive effects of simvastatin and pravastatin in the presence of palmitic, linoleic, and oleic acids cocktail to mimic mixed lipids challenge in a biologically relevant setting.

RESULTS AND DISCUSSION

Our findings indicate that simvastatin was more effective in lowering intracellular cholesterol but was more cytotoxic as compared to pravastatin. Similarly, simvastatin exhibited a higher suppression of total insulin content and insulin secretion. Both drugs suppressed insulin secretion in phases 1 and 2, dose-dependently. No significant effect was observed on mitochondrial respiration. More importantly, elution experiments showed that insulin content diminution by simvastatin treatment was reversible, while exogenous mevalonate did not improve total insulin content. This suggests that simvastatin's influence on insulin content is independent of its specific inhibitory action on HMG-CoA reductase. In conclusion, our study identified that simvastatin was more effective in lowering intracellular cholesterol, albeit it was more toxic and suppressive of β-cells function. Notably, this suppression was found to be reversible.

Structural characterization of squash polysaccharide and its effect on STZ-induced diabetes mellitus model in MIN6 cells

A novel natural water-soluble acidic polysaccharide (PWESP-3) was isolated from squash with a molecular mass of 140.519 kDa, which was composed of arabinose (Ara, 35.30 mol%), galactose (Gal, 61.20 mol%), glucose (Glc, 1.80 mol%), and Mannuronic acid (ManA, 1.70 mol%) and contained Araf-(1→, →3)-Araf-(1→, →5)-Araf-(1→, Glcp-(1→, Galp-(1→, →3,5)-Araf-(1→, →2)-Glcp-(1→, →2)-Manp-(1→, →3)-Glcp-(1→, →4)-Galp-(1→, →3)-Galp-(1→, →6)-Galp-(1→, →3,4)-Galp-(1→, →4,6)-Galp-(1→ residues in the backbone. Moreover, the structure of PWESP-3 was identified by NMR spectra. The branch chain was connected to the main chain by the O-3 and O-4 atom of Gal. In addition, the effect of PWESP-3 on STZ-induced type I diabetes mellitus model in MIN6 cells was investigated. The results showed that PWESP-3 can increase the viability and insulin secretion of MIN6 cells and reduce the oxidative stress caused by ROS and NO. Meanwhile, PWESP-3 can also reduce the content of ATP, Ca2+, mitochondrial membrane potential and Caspase-3 activity in MIN6 cells. Furthermore, treatment with PWESP-3 can prevent single or double stranded DNA breaking to form DNA fragments and improve DNA damage in MIN6 cells, thereby avoiding apoptosis. Therefore, the above data highlight that PWESP-3 can improve the function of insulin secretion in STZ-induced MIN6 cells in vitro and can be used as an alternative food supplement to diabetes drugs.

Sesamol combats diabetogenic effects of atorvastatin through GLUT-4 expression and improved pancreatic viability

Statin-associated diabetes (SAD) is an issue that has come to light after a series of recent clinical trials that has led to the issue of a black box warning for statins by the US FDA. However, the benefit of statin outweighs its risk. Nevertheless, experiments have been conducted to identify the mechanism by which statins aggravate the risk of diabetes only in a select population who bear the risk factors of obesity, sedentary lifestyle, hypertension, and other associated risk factors of lifestyle disorders. In this study, the possibility of utilization of a phyto-molecule, sesamol, for its ability to combat statin-associated diabetes using atorvastatin as the agent of choice has been explored. MMP assay and western blot was conducted to investigate the effects of atorvastatin on apoptotic cascade with sesamol as a protective agent was conducted in MIN-6 cells. Effect of the combination was tested in L6 cells with 2-NBDG uptake assay and as well as western blot for GLUT-4. A diet-induced hypercholesterolemia model was developed in an in vivo model animals and treated with atorvastatin and sesamol with histopathological analysis being carried out to evaluate the apoptotic markers and GLUT-4 presence. It was found that sesamol can combat pancreatic beta cell apoptosis via the internal apoptotic pathway activated by atorvastatin. With regards to muscle cells, sesamol could improve the GLUT-4 vesical production, but not improve glucose uptake which is inhibited by atorvastatin. These findings are further confirmed by animal studies. These findings indicate that sesamol can serve as a prototype molecule for further development and investigation of similar compounds to tackle SAD.

Sesamol protects the function and structure of rat ovaries against side effects of cyclophosphamide by decreasing oxidative stress and apoptosis

AIM

Chemotherapy with cyclophosphamide can damage ovaries and cause infertility in girls and women. Sesamol is a phenolic antioxidant that can protect various organs from damage. The purpose of this study was to evaluate the effects of sesamol on protecting the function and structure of rat ovaries against the side effects of a chemotherapy model with cyclophosphamide.

METHODS

Twenty-four adult female Wistar rats were randomly divided into three groups: (1) normal group, without any treatment, (2) control group, immediately after receiving cyclophosphamide, 0.5% dimethyl sulfoxide (DMSO) as the solvent of sesamol was intraperitoneally injected for 14 consecutive days, (3) sesamol group, immediately after receiving cyclophosphamide, 50 mg/kg sesamol was intraperitoneally injected for 14 consecutive days. Four weeks after the last injection, superoxide dismutase (SOD) activity and malondialdehyde (MDA) levels in the ovary, anti-Mullerian hormone (AMH) levels in the serum, number of ovarian follicles in different stages, and expression of proteins growth differentiation factor-9 (GDF-9), Bcl-2, and Bax in the ovary were evaluated.

RESULTS

The results of SOD activity and MDA levels in the ovary, AMH levels in the serum, number of ovarian follicles in different stages, and expression of proteins GDF9, Bcl-2, and Bax in the ovary were significantly more favorable in the sesamol group than the control group.

CONCLUSIONS

The results suggest that sesamol may protect function and structure in the rat ovaries against side effects of the chemotherapy model with cyclophosphamide by decreasing oxidative stress and apoptosis in the ovary.

Pleiotropic use of Statins as non-lipid-lowering drugs

Statins, known as HMG-CoA reductase (HMGCR) inhibitors, have primarily been utilized for metabolic and angiographic medical applications because of their cholesterol-lowering effects. Similar to other drugs, statins may also induce a series of potential side effects. Statins inhibit the HMGCR (rate-limiting enzyme) activity in early stages of mevalonate pathway and then indirectly affect a number of intermediate products, including non-sterol isoprenoids (coenzyme Q10, dolichol etc.), which can result in impaired functions of body organs. Recently, scores of studies have uncovered additional functional mechanisms of statins in other diseases, such as diabetes mellitus, nervous system diseases, coronary heart disease, inflammation and cancers. This review aims to summarize the positive and adverse mechanisms of statin therapy. Statin care should be taken in the treatment of many diseases including cancers. Since the underlying mechanisms are not fully elucidated, future studies should spend more time and efforts on basic research to explore the mechanisms of statins.