Chronic exposure to valproic acid promotes insulin release, reduces KATP channel current and does not affect Ca (2+) signaling in mouse islets

Research Progress on the Effect of Epilepsy and Antiseizure Medications on PCOS Through HPO Axis

Epilepsy is a common chronic neurological disease that manifests as recurrent seizures. The incidence and prevalence of epilepsy in women are slightly lower than those in men. Polycystic ovary syndrome (PCOS), a reproductive endocrine system disease, is a complication that women with epilepsy are susceptible to, and its total prevalence is 8%-13% in the female population and sometimes as high as 26% in female epilepsy patients. The rate of PCOS increased markedly in female patients who chose valproate (VPA), to 1.95 times higher than that of other drugs. In addition, patients receiving other anti-seizure medications (ASMs), such as lamotrigine (LTG), oxcarbazepine (OXC), and carbamazepine (CBZ), also have reproductive endocrine abnormalities. Some scholars believe that the increase in incidence is related not only to epilepsy itself but also to ASMs. Epileptiform discharges can affect the activity of the pulse generator and then interfere with the reproductive endocrine system by breaking the balance of the hypothalamic-pituitary-ovarian (HPO) axis. ASMs may also cause PCOS-like disorders of the reproductive endocrine system through the HPO axis. Moreover, other factors such as hormone metabolism and related signalling pathways also play a role in it.

Small Molecule-Induced Pancreatic β-Like Cell Development: Mechanistic Approaches and Available Strategies

Diabetes is a metabolic disease which affects not only glucose metabolism but also lipid and protein metabolism. It encompasses two major types: type 1 and 2 diabetes. Despite the different etiologies of type 1 and 2 diabetes mellitus (T1DM and T2DM, respectively), the defining features of the two forms are insulin deficiency and resistance, respectively. Stem cell therapy is an efficient method for the treatment of diabetes, which can be achieved by differentiating pancreatic β-like cells. The consistent generation of glucose-responsive insulin releasing cells remains challenging. In this review article, we present basic concepts of pancreatic organogenesis, which intermittently provides a basis for engineering differentiation procedures, mainly based on the use of small molecules. Small molecules are more auspicious than any other growth factors, as they have unique, valuable properties like cell-permeability, as well as a nonimmunogenic nature; furthermore, they offer immense benefits in terms of generating efficient functional beta-like cells. We also summarize advances in the generation of stem cell-derived pancreatic cell lineages, especially endocrine β-like cells or islet organoids. The successful induction of stem cells depends on the quantity and quality of available stem cells and the efficient use of small molecules.

Islet β-cell-produced NUCB2/nesfatin-1 maintains insulin secretion and glycemia along with suppressing UCP-2 in β-cells

Nesfatin-1 is a hypothalamic anorexigenic peptide processed from nucleobindin 2 (NUCB2). Central and peripheral administration of NUCB2/nesfatin-1 enhances glucose metabolism and insulin release. NUCB2/nesfatin-1 is also localized in pancreatic islets, while its function remains unknown. To explore the role of pancreatic β-cell-produced NUCB2/nesfatin-1, we developed pancreatic β-cell-specific NUCB2 knockout (βNUCB2 KO) mice and NUCB2 gene knockdown (shNUCB2) MIN6 β-cell line. In βNUCB2 KO mice, casual blood glucose was elevated from 12 weeks of age. In a glucose tolerance test at 12 weeks, insulin secretion at 15 min was reduced and blood glucose at 2 h increased in βNUCB2 KO mice fasted 8 h. In islets isolated from βNUCB2 KO mice, high glucose-stimulated insulin secretion (GSIS) was impaired. In shNUCB2 MIN6 cells, GSIS was reduced and UCP-2 mRNA expression was elevated. These results show impaired GSIS possibly associated with UCP-2 overexpression in NUCB2-silenced β-cells, suggesting that β-cell-produced NUCB2/nesfatin-1 maintains GSIS and thereby glycemia.

SIRT5 regulates pancreatic β-cell proliferation and insulin secretion in type 2 diabetes

Impaired insulin secretion and insulin resistance are the primary characteristics of type 2 diabetes (T2D). However, the mechanisms underlying insulin secretion failure have yet to be elucidated. The present study demonstrated that sirtuin 5 (SIRT5) is upregulated in patients with T2D and in pancreatic β-cell lines. It was also revealed that elevated SIRT5 expression is positively associated with age and blood glucose levels, and negatively associated with pancreatic and duodenal homeobox 1 (PDX1) expression. Colony formation and Cell Counting Kit-8 assays demonstrated that SIRT5 suppressed the proliferation of pancreatic β-cells in vitro. In addition, downregulation of SIRT5 promoted the secretion of insulin. Additionally, SIRT5 ectopic expression downregulated the expression of PDX1 and the inhibition of SIRT5 upregulated PDX1 expression. Chromatin immunoprecipitation assay analysis demonstrated that SIRT5 may regulate the transcription of PDX1 via H4K16 deacetylation. In conclusion, the results of the present study indicate that SIRT5 may serve an important role in the pathogenesis of T2D, and may present a novel therapeutic target for the treatment of patients with T2D.

Sox5 regulates beta-cell phenotype and is reduced in type 2 diabetes

Type 2 diabetes (T2D) is characterized by insulin resistance and impaired insulin secretion, but the mechanisms underlying insulin secretion failure are not completely understood. Here, we show that a set of co-expressed genes, which is enriched for genes with islet-selective open chromatin, is associated with T2D. These genes are perturbed in T2D and have a similar expression pattern to that of dedifferentiated islets. We identify Sox5 as a regulator of the module. Sox5 knockdown induces gene expression changes similar to those observed in T2D and diabetic animals and has profound effects on insulin secretion, including reduced depolarization-evoked Ca²⁺-influx and β-cell exocytosis. SOX5 overexpression reverses the expression perturbations observed in a mouse model of T2D, increases the expression of key β-cell genes and improves glucose-stimulated insulin secretion in human islets from donors with T2D. We suggest that human islets in T2D display changes reminiscent of dedifferentiation and highlight SOX5 as a regulator of β-cell phenotype and function.

Improvement of oral contraceptive-induced glucose dysregulation and dyslipidemia by valproic acid is independent of circulating corticosterone

CONTEXT

Cardiometabolic disorders are rapidly becoming major public health challenges. Valproic acid (VPA) is a widely prescribed anticonvulsant drug.

OBJECTIVE

We hypothesized that treatment with VPA would improve the regulation of glucose and atherogenic dyslipidemia through reduction in circulating corticosterone.

METHODS

Female Wistar rats recieved (p.o.) combined oral contraceptive (COC) containing 1.0 µg ethinylestradiol plus 5.0 µg levonorgestrel and valproic acid (VPA; 20 mg) for 8 weeks.

RESULTS

Treatment with COC led to elevated fasting blood glucose, insulin, corticosterone, triglycerides (TG), TG/HDL-cholesterol ratio, insulin resistance (IR) and impaired glucose tolerance. VPA significantly attenuated the alterations induced by COC treatment, but did not affect the corticosterone level. However, VPA treatment led to significant increases in plasma insulin, corticosterone, atherogenic lipids and impaired glucose tolerance in rats not treated with COC.

CONCLUSION

The findings in this study suggest that VPA mitigates against the development of COC-induced insulin resistance and dyslipidemia independent of elevated circulating corticosterone.

Valproic Acid Improves Glucose Homeostasis by Increasing Beta-Cell Proliferation, Function, and Reducing its Apoptosis through HDAC Inhibition in Juvenile Diabetic Rat

Recent evidence highlighted that there is a link between type-1 diabetes mellitus and histone deacetylases (HDACs) due to their involvement in beta-cell differentiation, proliferation, and function. The present study aimed to investigate the protective role of valproic acid (VPA) on beta-cell proliferation, function, and apoptosis in juvenile diabetic rat. Diabetes was induced in juvenile Sprague-Dawley rats by streptozotocin (75 mg/kg, i.p.) and VPA was administered at the doses of 150 and 300 mg/kg/day for 3 weeks by oral route. Various biochemical parameters, cellular alterations, and protein expression as well as apoptosis were assessed using different assays. VPA treatment significantly decreased plasma glucose, beta-cell damage, and apoptosis as well as increased the beta-cell function, insulin level/expression. The present study demonstrated that VPA improves beta-cell proliferation and function as well as reduces beta-cell apoptosis through HDAC inhibition. Our findings provide evidence that VPA may be useful for the treatment of juvenile diabetes.

Valproate modulates glucose metabolism in patients with epilepsy after first exposure

Valproate (VPA) treatment has been reported to be associated with weight gain and metabolic changes, such as hyperinsulinemia. The question of whether hyperinsulinemia and other metabolic changes are consequences of increased weight, or are instead direct results of VPA treatment, remains a matter of debate. The aim of the current study was to explore the influence of VPA treatment on glucose and insulin levels during the oral glucose tolerance test (OGTT) directly following the first intravenous (IV) administration. Sixteen patients (18-46 years old) with newly diagnosed epilepsy underwent an OGTT with 75 g glucose prior to the start of VPA treatment, as well as directly following the first IV VPA administration. We observed that plasma glucose levels during the 120 min of OGTT session following infusion of VPA were significantly lower than those measured during OGTT without VPA treatment (mean ± standard deviation [SD] 4.28 ± 0.94 mmol/l vs. 4.75 ± 1.09 mmol/l respectively, p = 0.038). However, blood concentrations of insulin and C-peptide did not differ significantly between the two measurements. This is the first study to show a potential acute glucose-lowering effect of VPA during OGTT in patients with newly diagnosed epilepsy.