Valproic acid reduces insulin-resistance, fat deposition and FOXO1-mediated gluconeogenesis in type-2 diabetic rat

Alterations in salivary biochemical composition and redox state disruption induced by the anticonvulsant valproic acid in male rat salivary glands

OBJECTIVE

To investigate the effects of the anticonvulsant valproic acid (VPA) on salivary glands in male rat using biochemical, functional, histomorphometric, and redox state parameters.

MATERIALS AND METHODS

Twenty-four male Wistar rats were randomly distributed into three groups (n = 8 per group): Control (0.9% saline solution), VPA100 (100 mg/kg), and VPA400 (400 mg/kg). After 21 consecutive days of treatment with by intragastric gavage. Pilocarpine-induced saliva was collected to determine salivary flow rate, pH, buffering capacity, and biochemical composition. Analyses of histomorphometric parameters and redox balance markers were performed on the parotid and submandibular glands.

RESULTS

Salivary flow rate, pH, buffering capacity, total protein, potassium, sodium, and chloride were similar between groups. However, phosphate and calcium were reduced in VPA400, while amylase was increased in both VPA100 and VPA400. We did not detect significant differences in the areas of acini, ducts, and connective tissue in the salivary glands between the groups. There were no significant changes in the redox status of the submandibular glands. In turn, in the parotid glands we detected reduced total oxidizing capacity and lipid peroxidation, measured as thiobarbituric acid reactive substances (TBARs) and higher uric acid concentration in both the VPA100 and VPA400 groups, and increased superoxide dismutase (SOD) in the VPA400 group.

CONCLUSION

Chronic treatment with VPA modified the salivary biochemical composition and caused disruption in the redox state of the parotid gland in rats.

Valproate-Induced Metabolic Syndrome

Valproic acid (VPA) and its salts (sodium calcium magnesium and orotic) are psychotropic drugs that are widely used in neurology and psychiatry. The long-term use of VPA increases the risk of developing adverse drug reactions (ADRs), among which metabolic syndrome (MetS) plays a special role. MetS belongs to a cluster of metabolic conditions such as abdominal obesity, high blood pressure, high blood glucose, high serum triglycerides, and low serum high-density lipoprotein. Valproate-induced MetS (VPA-MetS) is a common ADR that needs an updated multidisciplinary approach to its prevention and diagnosis. In this review, we consider the results of studies of blood (serum and plasma) and the urinary biomarkers of VPA-MetS. These metabolic biomarkers may provide the key to the development of a new multidisciplinary personalized strategy for the prevention and diagnosis of VPA-MetS in patients with neurological diseases, psychiatric disorders, and addiction diseases.

The role of histone deacetylases in cardiac energy metabolism in heart diseases

Heart diseases are associated with substantial morbidity and mortality worldwide. The underlying mechanisms and pathological changes associated with cardiac diseases are exceptionally complex. Highly active cardiomyocytes require sufficient energy metabolism to maintain their function. Under physiological conditions, the choice of fuel is a delicate process that depends on the whole body and organs to support the normal function of heart tissues. However, disordered cardiac metabolism has been discovered to play a key role in many forms of heart diseases, including ischemic heart disease, cardiac hypertrophy, heart failure, and cardiac injury induced by diabetes or sepsis. Regulation of cardiac metabolism has recently emerged as a novel approach to treat heart diseases. However, little is known about cardiac energy metabolic regulators. Histone deacetylases (HDACs), a class of epigenetic regulatory enzymes, are involved in the pathogenesis of heart diseases, as reported in previous studies. Notably, the effects of HDACs on cardiac energy metabolism are gradually being explored. Our knowledge in this respect would facilitate the development of novel therapeutic strategies for heart diseases. The present review is based on the synthesis of our current knowledge concerning the role of HDAC regulation in cardiac energy metabolism in heart diseases. In addition, the role of HDACs in different models is discussed through the examples of myocardial ischemia, ischemia/reperfusion, cardiac hypertrophy, heart failure, diabetic cardiomyopathy, and diabetes- or sepsis-induced cardiac injury. Finally, we discuss the application of HDAC inhibitors in heart diseases and further prospects, thus providing insights into new treatment possibilities for different heart diseases.

Drug-induced mitochondrial toxicity: Risks of developing glucose handling impairments

Mitochondrial impairment has been associated with the development of insulin resistance, the hallmark of type 2 diabetes mellitus (T2DM). However, the relationship between mitochondrial impairment and insulin resistance is not fully elucidated due to insufficient evidence to support the hypothesis. Insulin resistance and insulin deficiency are both characterised by excessive production of reactive oxygen species and mitochondrial coupling. Compelling evidence states that improving the function of the mitochondria may provide a positive therapeutic tool for improving insulin sensitivity. There has been a rapid increase in reports of the toxic effects of drugs and pollutants on the mitochondria in recent decades, interestingly correlating with an increase in insulin resistance prevalence. A variety of drug classes have been reported to potentially induce toxicity in the mitochondria leading to skeletal muscle, liver, central nervous system, and kidney injury. With the increase in diabetes prevalence and mitochondrial toxicity, it is therefore imperative to understand how mitochondrial toxicological agents can potentially compromise insulin sensitivity. This review article aims to explore and summarise the correlation between potential mitochondrial dysfunction caused by selected pharmacological agents and its effect on insulin signalling and glucose handling. Additionally, this review highlights the necessity for further studies aimed to understand drug-induced mitochondrial toxicity and the development of insulin resistance.

Does diabetes mellitus affect the safety profile of valproic acid for the treatment of status epilepticus? A retrospective cohort study

Background

In the treatment of status epilepticus less is known about the influence of comorbidities on the safety profile of anticonvulsive drugs. Especially patients with diabetes mellitus may be predisposed to certain adverse events that have been related to therapy with valproic acid. In this single-center retrospective cohort study we examined if the complications of the intravenous treatment with valproic acid is different in patients with or without diabetes.

Methods

Patients who were treated for status epilepticus with intravenous valproic acid between 2008 and 2020 were identified. Primary endpoint was the discontinuation of therapy with valproic acid due to adverse events. Relevant secondary endpoints were the functional status at the time of discharge from hospital in comparison to the premorbid state and the in-hospital mortality. Both groups (patients with or without diabetes) were compared by Mann–Whitney U-Test or Pearson´s Chi² test. To identify therapy with valproic acid as a risk factor of in-hospital mortality, a binary regression model was used.

Results

During the study period 408 patients and 482 episodes of status epilepticus were treated with intravenous valproic acid. Group comparisons did not reveal a significant difference in the rates of discontinuation of therapy. A difference was found in the rate of thrombocytopenia (p = 0.015), which occurred more often in patients with diabetes. In total, 36 hypoglycemic episodes could be identified, two occurred spontaneously under intravenous valproic acid. After correction for potential confounders, continuous therapy with valproic acid could not be confirmed as an independent risk factor for in-hospital mortality (p = 0.079). In patients with diabetes, the proportion of patients with a good functional state, indicated by the modified Rankin Scale, was significantly lower in both times (premorbid: 55% vs. 69%, p = 0.008; at discharge: 22% vs. 36%, p = 0.004).

Conclusions

Tolerability of the treatment with valproic acid was similar in patients with or without diabetes. Diabetes as a relevant comorbidity can signal a potentially increased risk of a poor outcome after status epilepticus.

Trial registration: The study was registered at the German Clinical Trials Register on 8 April 2022 (DRKS 00,027,836).

Supplementary Information

The online version contains supplementary material available at 10.1186/s42466-022-00212-w.

Amelioration of high-fat diet (HFD) + CCl4 induced NASH/NAFLD in CF-1 mice by activation of SIRT-1 using cinnamoyl sulfonamide hydroxamate derivatives: in-silico molecular modelling and in-vivo prediction

Non-alcoholic fatty liver disease (NAFLD) is one of the major hepatic metabolic disorders that occurs because of the accumulation of lipids in hepatocytes in the form of free fatty acids (FFA) and triglycerides (TG) which become non-alcoholic steatohepatitis (NASH). NOTCH-1 receptors act as novel targets for the development of NAFLD/NASH, where overexpression of NOTCH-1 receptor alters the lipid metabolism in hepatocytes leading to NAFLD. SIRT-1 deacetylates the NOTCH-1 receptor and inhibits NAFLD. Hence, computer-aided drug design (CADD) was used to check the SIRT-1 activation ability of cinnamic sulfonyl hydroxamate derivatives (NMJ 1–8), resveratrol, and vorinostat. SIRT-1 (PDB ID: 5BTR) was docked with eight hydroxamate derivatives and vorinostat using Schrödinger software. Based on binding energy obtained (– 26.31 to – 47.34 kcal/mol), vorinostat, NMJ-2, NMJ-3, NMJ-5 were selected for induced-fit docking (IFD) and results were within – 750.70 to – 753.22 kcal/mol. Qikprop tool was used to analyse the pre pharmacokinetic parameters (ADME analysis) of all hydroxamate compounds. As observed in the molecular dynamic (MD) study, NMJ-2, NMJ-3 were showing acceptable results for activation of SIRT-1. Based on these predictions, in-vivo studies were conducted in CF1 mice, where NMJ-3 showed significant (p < 0.05) changes in lipid profile and anti-oxidant parameters (Catalase, SOD, GSH, nitrite, and LPO) and plasma insulin levels. NMJ-3 treatment also reduced inflammation, fibrosis, and necrosis in liver samples.

Integrated Metabolomics and Proteomics Dynamics of Serum Samples Reveals Dietary Zeolite Clinoptilolite Supplementation Restores Energy Balance in High Yielding Dairy Cows

Dairy cows can suffer from a negative energy balance (NEB) during their transition from the dry period to early lactation, which can increase the risk of postpartum diseases such as clinical ketosis, mastitis, and fatty liver. Zeolite clinoptilolite (CPL), due to its ion-exchange property, has often been used to treat NEB in animals. However, limited information is available on the dynamics of global metabolomics and proteomic profiles in serum that could provide a better understanding of the associated altered biological pathways in response to CPL. Thus, in the present study, a total 64 serum samples were collected from 8 control and 8 CPL-treated cows at different time points in the prepartum and postpartum stages. Labelled proteomics and untargeted metabolomics resulted in identification of 64 and 21 differentially expressed proteins and metabolites, respectively, which appear to play key roles in restoring energy balance (EB) after CPL supplementation. Joint pathway and interaction analysis revealed cross-talks among valproic acid, leucic acid, glycerol, fibronectin, and kinninogen-1, which could be responsible for restoring NEB. By using a global proteomics and metabolomics strategy, the present study concluded that CPL supplementation could lower NEB in just a few weeks, and explained the possible underlying pathways employed by CPL.

The role of FoxO1 and its modulation with small molecules in the development of diabetes mellitus: A review

Diabetes mellitus type 2 (T2D) is one of the metabolic disorders suffered by a global human being. Certain factors, such as lifestyle and heredity, can increase a person's tendency for T2D. Various genes and proteins play a role in the development of insulin resistance and ultimately diabetes in which one central protein that is discussed in this review is FoxO1. In this review, we regard FoxO1 activation as detrimental, promote high plasma glucose level, and induce insulin resistance. Indeed, many contrasting studies arise since FoxO1 is an important protein to alleviate oxidative stress and promote cell survival, for example, also by preventing hyperglycemic-induced cell death. Inter-relation to PPARG, another important protein in metabolism, is also discussed. Ultimately, we discussed contrasting approaches of targeting FoxO1 to combat diabetes mellitus by small molecules.

Hidden pharmacological activities of valproic acid: A new insight

Valproic acid (VPA) is an approved drug for managing epileptic seizures, bipolar disorders, and migraine. VPA has been shown to elevate the level of gamma-aminobutyric acid (GABA) in the brain through competitive inhibition of GABA transaminase, thus promoting the availability of synaptic GABA and facilitating GABA-mediated responses. VPA, which is a small chain of fatty acids, prevents histone deacetylases (HDACs). HDACs play a crucial role in chromatin remodeling and gene expression through posttranslational changes of chromatin-associated histones. Recent studies reported a possible effect of VPA against particular types of cancers. This effect was partially attributed to its role in regulating epigenetic modifications through the inhibition of HDACs, which affect the expression of genes associated with cell cycle control, cellular differentiation, and apoptosis. In this review, we summarize the current information on the actions of VPA in diseases such as diabetes mellitus, kidney disorders, neurodegenerative diseases, muscular dystrophy, and cardiovascular disorders.

Potential repurposing of the HDAC inhibitor valproic acid for patients with COVID-19

There is a need for therapeutic approaches to prevent and mitigate the effects of Coronavirus Disease (2019) (COVID-19). The histone deacetylase (HDAC) inhibitor valproic acid, which has been available for the therapy of epilepsy for many years, is a drug that could be repurposed for patients with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. This article will review the reasons to consider valproic acid as a potential therapeutic to prevent severe COVID-19. Valproic acid could reduce angiotensin-converting enzyme 2 and transmembrane serine protease 2 expression, required for SARS-CoV-2 viral entry, and modulate the immune cellular and cytokine response to infection, thereby reducing end-organ damage. The combined anti-thrombotic, anti-platelet, and anti-inflammatory effects of valproic acid suggest it could be a promising therapeutic target for COVID-19.

FoxO1 signaling as a therapeutic target for type 2 diabetes and obesity

Glucose production and the consumption of high levels of carbohydrate increase the chance of insulin resistance, especially in cases of obesity. Therefore, maintaining a balanced glucose homeostasis might form a strategy to prevent or cure diabetes and obesity. The activation and inhibition of glucose production is complicated due to the presence of many interfering pathways. These pathways can be viewed at the downstream level because they activate certain transcription factors, which include the Forkhead-O1 (FoxO1). This has been identified as a significant agent in the pancreas, liver, and adipose tissue, which is significant in the regulation of lipids and glucose. The objective of this review is to discuss the intersecting portrayal of FoxO1 and its parallel cross-talk which highlights obesity-induced insulin susceptibility in the discovery of a targeted remedy. The review also analyses current progress and provides a blueprint on therapeutics, small molecules, and extracts/phytochemicals which are explored at the pre-clinical level.

Roles of Epigenetic Modifications in the Differentiation and Function of Pancreatic β-Cells

Diabetes, a metabolic disease with multiple causes characterized by high blood sugar, has become a public health problem. Hyperglycaemia is caused by deficiencies in insulin secretion, impairment of insulin function, or both. The insulin secreted by pancreatic β cells is the only hormone in the body that lowers blood glucose levels and plays vital roles in maintaining glucose homeostasis. Therefore, investigation of the molecular mechanisms of pancreatic β cell differentiation and function is necessary to elucidate the processes involved in the onset of diabetes. Although numerous studies have shown that transcriptional regulation is essential for the differentiation and function of pancreatic β cells, increasing evidence indicates that epigenetic mechanisms participate in controlling the fate and regulation of these cells. Epigenetics involves heritable alterations in gene expression caused by DNA methylation, histone modification and non-coding RNA activity that does not result in DNA nucleotide sequence alterations. Recent research has revealed that a variety of epigenetic modifications play an important role in the development of diabetes. Here, we review the mechanisms by which epigenetic regulation affects β cell differentiation and function.

Nimbolide abrogates cerulein-induced chronic pancreatitis by modulating β-catenin/Smad in a sirtuin-dependent way

Chronic pancreatitis (CP) is one of the leading causes of mortality worldwide with no clinically approved therapeutic interventions. The present study was designed to investigate the protective effect of nimbolide (NB), an active constituent of neem tree (Azadirachta indica), by targeting β-catenin/Smad/SIRT1 in cerulein-induced CP model. The effects of NB was investigated on cerulein (50 μg/kg/hr*6 exposures /day, 3 days a week for 3 weeks) induced CP in mice. Amylase and lipase activity were measured and histopathological evaluation was performed. Collagen deposition in the pancreatic tissue was estimated by hydroxyproline assay, and collagen specific staining picrosirius red and Masson's trichrome. Cerulein-induced CP was significantly controlled by NB treatment, as shown by the downregulation of β-catenin/Smad signaling in a SIRT1 dependent manner. NB treatment significantly decreased α-SMA, MMP-2, collagen1a, fibronectin, TGF-β1, p-Smad-2/3 expression and extracellular matrix (ECM) deposition in pancreatic tissue. However, the protective effects of NB on cerulein-induced CP were undermined by nicotinamide (NMD) or splitomicin, sirtuin 1 (SIRT1) inhibitors treatment. NB treatment modulated protein expression by activating SIRT1 and decreasing the expression of β-catenin/Smad proteins in CP mice. However, the expression of SIRT1 in pancreatic tissue was elevated by NB treatment and it was decreased by NMD or splitomicin treatment. In summary, our results strongly suggest that NB exerted promising protective effects in cerulein-induced CP model by inhibiting β-catenin/Smad in a sirtuin-dependent manner, which could be attributed to its anti-inflammatory and antifibrotic effects. Our study suggests that NB could be an effective therapeutic intervention for the treatment of CP.

HDAC inhibitors rescue multiple disease-causing CFTR variants

Understanding the role of the epigenome in protein-misfolding diseases remains a challenge in light of genetic diversity found in the world-wide population revealed by human genome sequencing efforts and the highly variable response of the disease population to therapeutics. An ever-growing body of evidence has shown that histone deacetylase (HDAC) inhibitors (HDACi) can have significant benefit in correcting protein-misfolding diseases that occur in response to both familial and somatic mutation. Cystic fibrosis (CF) is a familial autosomal recessive disease, caused by genetic diversity in the CF transmembrane conductance regulator (CFTR) gene, a cyclic Adenosine MonoPhosphate (cAMP)-dependent chloride channel expressed at the apical plasma membrane of epithelial cells in multiple tissues. The potential utility of HDACi in correcting the phenylalanine 508 deletion (F508del) CFTR variant as well as the over 2000 CF-associated variants remains controversial. To address this concern, we examined the impact of US Food and Drug Administration-approved HDACi on the trafficking and function of a panel of CFTR variants. Our data reveal that panobinostat (LBH-589) and romidepsin (FK-228) provide functional correction of Class II and III CFTR variants, restoring cell surface chloride channel activity in primary human bronchial epithelial cells. We further demonstrate a synergistic effect of these HDACi with Vx809, which can significantly restore channel activity for multiple CFTR variants. These data suggest that HDACi can serve to level the cellular playing field for correcting CF-causing mutations, a leveling effect that might also extend to other protein-misfolding diseases.

Regulation of Thermogenic Adipocyte Differentiation and Adaptive Thermogenesis Through Histone Acetylation

Over the past decade, the increasing prevalence of obesity and its associated metabolic disorders constitutes one of the most concerning healthcare issues for countries worldwide. In an effort to curb the increased mortality and morbidity derived from the obesity epidemic, various therapeutic strategies have been developed by researchers. In the recent years, advances in the field of adipocyte biology have revealed that the thermogenic adipose tissue holds great potential in ameliorating metabolic disorders. Additionally, epigenetic research has shed light on the effects of histone acetylation on adipogenesis and thermogenesis, thereby establishing the essential roles which histone acetyltransferases (HATs) and histone deacetylases (HDACs) play in metabolism and systemic energy homeostasis. In regard to the therapeutic potential of thermogenic adipocytes for the treatment of metabolic diseases, herein, we describe the current state of knowledge of the regulation of thermogenic adipocyte differentiation and adaptive thermogenesis through histone acetylation. Furthermore, we highlight how different HATs and HDACs maintain the epigenetic transcriptional network to mediate the pathogenesis of various metabolic comorbidities. Finally, we provide insights into recent advances of the potential therapeutic applications and development of HAT and HDAC inhibitors to alleviate these pathological conditions.

Histone Deacetylase Inhibitors Reduce Cysts by Activating Autophagy in Polycystic Kidney Disease

Background

Histone deacetylase inhibitors (HDACi) have therapeutic effects on various models of renal diseases including autosomal dominant polycystic kidney disease (ADPKD), but the molecular mechanism is unclear.

Objectives

Here, we studied the role of trichostatin A (TSA), a specific HDACi, in regulating cyst growth to test the possibility that HDACi might help manage ADPKD by enhancing autophagy.

Results

Autophagy protein expression was higher in cultured Pkd1 knockout (Pkd1^-/-) cells, an in vitro model of cystogenesis, compared with control cells. TSA prevented cyst formation in Pkd1^-/- cells. We further tested whether TSA could not reduce the size of an already established cyst after inhibition of autophagy by chloroquine in Pkd1^-/- cells. In vivo, treatment with TSA significantly slowed cyst growth in Pkd1^-/- mice. Moreover, TSA treatment stimulated AMPK and inactivated mTOR during cyst growth in Pkd1^-/- cells and kidneys in mice.

Conclusions

Our results suggest that HDACi may prevent cyst formation by activation of the AMPK pathway and autophagy. They also imply that HDACi could have therapeutic potential for ADPKD treatment.

A long noncoding RNA LOC103690121 promotes hippocampus neuronal apoptosis in streptozotocin-induced type 1 diabetes

Diabetes related cognitive impairment is a severe complication. The diabetes-induced cognitive impairment is associated with insulin resistance and glucose-induced neuron apoptosis in the brain. We intended to investigate the association of long non-coding RNAs with diabetes-induced cognitive impairment in rats. Here, Type 1diabetes (T1D) rat model was induced using streptozotocin (STZ). The diabetic rats showed significant cognitive dysfunction, with increased latency period to find the hidden platform during morris water maze test. The brain injury and reduced neuronsin STZ-induced diabetic rats was determined using hematoxylin and eosin staining and Nissl's staining. We performed the LncRNA microarray analysis and identified 101 differentially expressed lncRNAs in streptozotocin (STZ)-induced type 1 diabetes (T1D) comparing with control. Among these lncRNA, LOC103690121 was upregulated. in vitro glucose treatment in hippocampal neurons showed LOC103690121 and neuron apoptosis was increased by glucose treatment. Transfection experiments showed LOC103690121 overexpression promoted neuron apoptosis, and its inhibition suppressed glucose-induced apoptosis. Western blot analysis showed that the expression profiles of apoptosis related proteins (cleaved-caspase-3, -8, -9, and Bax) were in line with LOC103690121 expression, while the profiles of Bcl-2 and PI3K/Akt signaling pathway was contrast to LOC103690121 expression. In conclusion, the results of our study confirmed lncRNA LOC103690121 promoted STZ-induced cognitive impairment in diabetic rats by promoting neuron apoptosis through PI3K/Akt signaling pathway.

Effects of Resveratrol on FOXO1 and FOXO3a Genes Expression in Adipose Tissue, Serum Insulin, Insulin Resistance and Serum SOD Activity in Type 2 Diabetic Rats

Induced oxidative stress in diabetes mellitus (DM) plays a critical role in insulin resistance. Fork head-related transcription factor (FOXO) proteins are important transcriptional factors involved in oxidative stress and insulin resistance. Resveratrol (RSV) is a polyphenol with hypoglycemic and antioxidant properties. The aims of the present study were to examine the effects of RSV on FOXO gene expression, serum superoxide dismutase (SOD) activity, insulin level, and insulin resistance in type 2 diabetic (T2DM) rats. Thirty male Wistar rats were used in this study. DM was induced in rats (n=24) using streptozotocin (STZ) and nicotinamide; then, they were divided into 4 groups of 6 rats each. Six untreated normal rats were used as normal control group; diabetic rats in groups 2 to 5 were treated with 0, 1, 5 and 10 mg /kg body weight of RSV, respectively for 30 days. At the end of the experimental period, the rats were sacrificed, their sera were separated, and adipose tissues were obtained and stored at −80 °C. Serum glucose and SOD activity levels were determined biochemically, and serum insulin level was determined by ELISA method. Gere expression in FOXO1 and FOXO3a in adipose tissue was evaluated using real‐time PCR. Results indicated that RSV significantly reduced blood glucose level, increased insulin level and improved insulin sensitivity. RSV resulted in an increased serum SOD activity and caused decreased FOXO1 and FOXO3a expression in adipose tissue of rats with T2DM. Therefore, by attenuation of FOXO expression in adipose tissue of T2DM rats, RSV showed a hypoglycemic potential and antioxidant properties, and consequently ameliorated insulin resistance.

Sodium valproate ameliorates memory impairment and reduces the elevated levels of apoptotic caspases in the hippocampus of diabetic mice

Learning and memory deficits appear in chronic diabetes and valproic acid has been proved to be beneficial in neurodegenerative diseases. Hence, the current study investigated the effectiveness of chronic valproate treatment for diabetes-induced memory impairment and increased levels of hippocampal apoptotic caspases. This study was conducted in adult male C57B15/J mice. Diabetes, which was induced by alloxan (150 mg/kg; i.p.), was confirmed when fasting blood sugar (FBS) was > 200 mg/dl. Sodium valproate (100 mg/kg; i.p.) was administrated to the diabetic and non-diabetic groups, every 72 h for 2 months. Next, all groups were evaluated for memory performance using the radial maze and shuttle box. After FBS measurement, animals were killed and the hippocampus was extracted and prepared for ELISA to assess caspase levels. Diabetic animals had significantly high FBS and memory impairment 2 months after the alloxan injection. Hippocampal levels of caspases 3, 6, and 8 were significantly higher in the diabetic group than in the control group. However, valproate treatment of diabetic animals significantly improved memory performance in both the radial maze and shuttle box and reduced the elevated levels of hippocampal apoptotic caspases, in comparison with diabetic animals. Chronic administration of valproate seems to have beneficial effects on diabetic neuropathy.

Repurposing of sodium valproate in colon cancer associated with diabetes mellitus: Role of HDAC inhibition

BACKGROUND AND PURPOSE

Diabetic patients are at greater risk for colon cancer. Histone deacetylases (HDACs) serve as common target for both. The key objective of the study was to evaluate the effect of sodium valproate in type 2 diabetes mellitus associated colon cancer.

EXPERIMENTAL APPROACH

High fat diet and streptozotocin were used to induce type 2 diabetes. Following this, after diabetes confirmation, colon cancer was induced using 1,2 dimethylhydrazine (25 mg/kg, s.c.) once weekly from 7th week to 20th weeks. Sodium valproate (200 mg/kg) treatment was given from 20th to 24th week. At the end of 24 weeks, several enzymatic and biochemical parameters, were estimated. MTT, clonogenic and scratch wound healing assay were carried out in HCT-15 cell line.

KEY RESULTS

Hyperglycemia, hyperinsulinemia, increase in cytokines (TNF-α and IL-1β) and carcinoembryonic antigen and presence of proliferating cells was seen in disease control animals which was prevented by sodium valproate treatment. Overexpression of relative HDAC2 mRNA levels was found in diseased control animals, which was reduced by sodium valproate treatment. IC₅₀ of sodium valproate was found to be 3.40 mM and 3.73 mM at 48 h and 72 h respectively on HCT-15 cell line. Sodium valproate also dose dependently prevented colony formation and cell migration.

CONCLUSION AND IMPLICATIONS

Sodium valproate can be considered for repurposing in colon cancer associated with diabetes mellitus.

Histone deacetylase inhibitors protect against cisplatin-induced acute kidney injury by activating autophagy in proximal tubular cells

Histone deacetylase inhibitors (HDACi) have therapeutic effects in models of various renal diseases including acute kidney injury (AKI); however, the underlying mechanism remains unclear. Here we demonstrate that two widely tested HDACi (suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA)) protect the kidneys in cisplatin-induced AKI by enhancing autophagy. In cultured renal proximal tubular cells, SAHA and TSA enhanced autophagy during cisplatin treatment. We further verified the protective effect of TSA against cisplatin-induced apoptosis in these cells. Notably, inhibition of autophagy by chloroquine or by autophagy gene 7 (Atg7) ablation diminished the protective effect of TSA. In mice, TSA increased autophagy in renal proximal tubules and protected against cisplatin-induced AKI. The in vivo effect of TSA was also abolished by chloroquine and by Atg7 knockout specifically from renal proximal tubules. Mechanistically, TSA stimulated AMPK and inactivated mTOR during cisplatin treatment of proximal tubule cells and kidneys in mice. Together, these results suggest that HDACi may protect kidneys by activating autophagy in proximal tubular cells.

Histone deacetylase inhibition ameliorates hypertension and hyperglycemia in a model of Cushing's syndrome

Cushing's syndrome (CS) caused by hypercortisolism is occasionally accompanied by metabolic disorders such as hypertension, diabetes mellitus (DM), dyslipidemia, and central obesity. Thus morbidity and mortality, observed in cardiovascular disease, are elevated in patients with CS. We hypothesized that HDAC inhibition (HDACi) decreased transcriptional activity of glucocorticoid receptor (GR), which ameliorates hypertension and hyperglycemia in patients with CS. To establish an animal model of hypercortisolism, Sprague-Dawley rats were infused with adrenocorticotropic hormone (ACTH, 40 ng/day) or dexamethasone (Dex, 10 μg/day) via osmotic minipumps for 4 wk. Expression of GR target genes was determined by quantitative real-time PCR (qRT-PCR). GR enrichment on specific loci, and across the whole genome, was analyzed by chromatin immunoprecipitation (ChIP) and ChIPseq, respectively. HDACi decreased blood pressure and expression of ion regulators in the kidneys of ACTH-infused rats. Additionally, HDACi reduced deposition of polysaccharide, fasting blood glucose level, glucose intolerance, and expression of gluconeogenesis genes in the livers and kidneys of ACTH- and Dex-infused rats. Among class I HDACs, HDAC1 and HDAC3 interacted with GR. HDAC1 knockdown resulted in increased level of acetylation and decreased transcriptional activity of GR. GR recruitment on the promoters of 2,754 genes, which include ion transporters, channels, and gluconeogenic genes, was significantly decreased by MS-275, a class I HDAC inhibitor. These results indicate that HDACi ameliorates hypertension and hyperglycemia in a model of CS by decreasing the transcriptional activity of GR via elevating its level of acetylation.

Histone deacetylase inhibition attenuates hepatic steatosis in rats with experimental Cushing's syndrome

Cushing's syndrome (CS) is a collection of symptoms caused by prolonged exposure to excess cortisol. Chronically elevated glucocorticoid (GC) levels contribute to hepatic steatosis. We hypothesized that histone deacetylase inhibitors (HDACi) could attenuate hepatic steatosis through glucocorticoid receptor (GR) acetylation in experimental CS. To induce CS, we administered adrenocorticotropic hormone (ACTH; 40 ng/kg/day) to Sprague-Dawley rats by subcutaneous infusion with osmotic mini-pumps. We administered the HDACi, sodium valproate (VPA; 0.71% w/v), in the drinking water. Treatment with the HDACi decreased steatosis and the expression of lipogenic genes in the livers of CS rats. The enrichment of GR at the promoters of the lipogenic genes, such as acetyl-CoA carboxylase (Acc), fatty acid synthase (Fasn), and sterol regulatory element binding protein 1c (Srebp1c), was markedly decreased by VPA. Pan-HDACi and an HDAC class I-specific inhibitor, but not an HDAC class II a-specific inhibitor, attenuated dexamethasone (DEX)-induced lipogenesis in HepG2 cells. The transcriptional activity of Fasn was decreased by pretreatment with VPA. In addition, pretreatment with VPA decreased DEX-induced binding of GR to the glucocorticoid response element (GRE). Treatment with VPA increased the acetylation of GR in ACTH-infused rats and DEX-induced HepG2 cells. Taken together, these results indicate that HDAC inhibition attenuates hepatic steatosis hrough GR acetylation in experimental CS.

CD36 mediates lipid accumulation in pancreatic beta cells under the duress of glucolipotoxic conditions: Novel roles of lysine deacetylases

The cluster of differentiation 36 (CD36) is implicated in the intake of long-chain fatty acids and fat storage in various cell types including the pancreatic beta cell, thus contributing to the pathogenesis of metabolic stress and diabetes. Recent evidence indicates that CD36 undergoes post-translational modifications such as acetylation-deacetylation. However, putative roles of such modifications in its functional activation and onset of beta cell dysregulation under the duress of glucolipotoxicity (GLT) remain largely unknown. Using pharmacological approaches, we validated, herein, the hypothesis that acetylation-deacetylation signaling steps are involved in CD36-mediated lipid accumulation and downstream apoptotic signaling in pancreatic beta (INS-1832/13) cells under GLT. Exposure of these cells to GLT resulted in significant lipid accumulation without affecting the CD36 expression. Sulfo-n-succinimidyl oleate (SSO), an irreversible inhibitor of CD36, significantly attenuated lipid accumulation under GLT conditions, thus implicating CD36 in this metabolic step. Furthermore, trichostatin A (TSA) or valproic acid (VPA), known inhibitors of lysine deacetylases, markedly suppressed GLT-associated lipid accumulation with no discernible effects on CD36 expression. Lastly, SSO or TSA prevented caspase 3 activation in INS-1832/13 cells exposed to GLT conditions. Based on these findings, we conclude that an acetylation-deacetylation signaling step might regulate CD36 functional activity and subsequent lipid accumulation and caspase 3 activation in pancreatic beta cells exposed to GLT conditions. Identification of specific lysine deacetylases that control CD36 function should provide novel clues for the prevention of beta-cell dysfunction under GLT.

Valproate hampers podocyte acquisition of immune phenotypes via intercepting the GSK3β facilitated NFkB activation

Glomerular podocytes are able to transdifferentiate under disease conditions, acquire de novo immune phenotypes and behave as immunocompetent cells, like phagocytes or antigen-presenting cells. Upon stimulation with lipopolysaccharide (LPS), a prototypical pathogen-associated molecular pattern, podocytes demonstrated de novo expression of a variety of NFkB-dependent immune molecules that are pivotal for immune response, including major histocompatibility complex (MHC) class II, costimulatory molecule CD80, lysosomal protease cathepsin L as well as CC chemokine ligand 2 and 5, ultimately resulting in podocyte dysfunction, characterized by cellular shrinkage, a spindle-like or asterlike cell shape and impairment of actin cytoskeleton integrity. The LPS-elicited podocyte phenotypic changes were concurrent with nuclear factor (NF) kB phosphorylation, which was associated with glycogen synthase kinase (GSK) 3β overactivity, marked by a diminished inhibitory phosphorylation of GSK3β. In contrast, valproate, an anticonvulsant and mood stabilizer, offset GSK3β overactivity in LPS-injured podocytes and mitigated NFkB activation and podocyte acquisition of immune phenotypes as well as the ensuing cytopathic changes, podocyte cytoskeleton disorganization and dysfunction. The protective effect of valproate was strikingly blunted in podocytes expressing the constitutively active GSK3β, suggesting an essential role of inhibitory phosphorylation of GSK3β. In vivo in LPS-injured mice, valproate therapy abolished GSK3β overactivity in glomeruli and attenuated podocyte injury and albuminuria, concomitant with a lessened NFkB activation and diminished induction of diverse podocytopathic immune molecules in podocytes and glomeruli. Taken together, valproate directly protects against podocyte injury and hampers podocyte acquisition of de novo immune phenotypes via intercepting the GSK3β facilitated NFkB activation.

Inhibition of exendin-4-induced steatosis by protein kinase A in cultured HepG2 human hepatoma cells

Nonalcoholic fatty liver is characterized by the abnormal accumulation of triglycerides within hepatocytes, resulting in a steatotic liver. Glucagon-like peptide 1 and its analog exendin-4 can ameliorate certain aspects of this syndrome by inducing weight loss and reducing hepatic triglyceride accumulation, but it is unclear whether these effects result from the effects of glucagon-like peptide 1 on the pancreas, or from direct action on the liver. This study investigated the direct action and putative cellular mechanism of exendin-4 on steatotic hepatocytes in culture. Steatosis was induced in cultured HepG2 human hepatoma cells by incubation in media supplemented with 2 mM each of linoleic acid and oleic acid. Steatotic hepatocytes were then pre-incubated in the protein kinase A inhibitor H89 for 30 min, then treated with exendin-4 over a period of 24 h. Cell viability and triglyceride content were characterized by a TUNEL assay and AdipoRed staining, respectively. Our results showed that steatotic cells maintained high levels of intracellular triglycerides (80%) compared to lean controls (25%). Exendin-4 treatment caused a significant reduction in intracellular triglyceride content after 12 h that persisted through 24 h, while protein kinase A inhibitors abolished the effects of exendin-4. The results demonstrate the exendin-4 induces a partial reduction in triglycerides in steatotic hepatocytes within 12 h via the GLP-1 receptor-mediated activation of protein kinase A. Thus, the reduction in hepatocyte triglyceride accumulation is likely driven primarily by downregulation of lipogenesis and upregulation of β-oxidation of free fatty acids.

Phenylbutyrate and β-cell function: contribution of histone deacetylases and ER stress inhibition

Incidences of diabetes are increasing globally due to involvement of genetic and epigenetic factors. Phenylbutyrate (PBA) is a US FDA approved drug for treatment of urea cycle disorder in children. PBA reduces endoplasmic reticulum (ER) stress and is proven as a potent histone deacetylases (HDACs) inhibitor. Chronic ER stress results in unfolding protein response, which triggers apoptosis. Abnormal ER homoeostasis is responsible for defective processing of several genes/proteins and contributes to β-cell death/failure. Accumulated evidences indicated that HDACs modulate key biochemical pathways and HDAC inhibitors improve β-cell function and insulin resistance by modulating multiple targets. This review highlights the role of PBA on β-cell functions, insulin resistance for possible treatment of diabetes through inhibition of ER stress and HDACs.

Anti-fibrotic effects of valproic acid: role of HDAC inhibition and associated mechanisms

Tissue injuries and pathological insults produce oxidative stress, genetic and epigenetic alterations, which lead to an imbalance between pro- and anti-fibrotic molecules, and subsequent accumulation of extracellular matrix, thereby fibrosis. Various molecular pathways play a critical role in fibroblasts activation, which promotes the extracellular matrix production and accumulation. Recent reports highlighted that histone deacetylases (HDACs) are upregulated in various fibrotic disorders and play a central role in fibrosis, while HDAC inhibitors exert antifibrotic effects. Valproic acid is a first-line anti-epileptic drug and a proven HDAC inhibitor. This review provides the current research and novel insights on antifibrotic effects of valproic acid in various fibrotic conditions with an emphasis on the possible strategies for treatment of fibrosis.

Sodium butyrate reduces insulin-resistance, fat accumulation and dyslipidemia in type-2 diabetic rat: A comparative study with metformin

Recent evidences highlighted that histone deacetylases (HDACs) can deacetylate the histone, various transcription factors and regulatory proteins, which directly or indirectly affect glucose metabolism. The present study aimed to evaluate the comparative effects of sodium butyrate (NaB) and metformin on the glucose homeostasis, insulin-resistance, fat accumulation and dyslipidemia in type-2 diabetic rat. Diabetes was developed in Sprague-Dawley rats by the combination of high-fat diet (HFD) and low dose streptozotocin (STZ, 35 mg/kg). NaB at the doses of 200 and 400 mg/kg twice daily as well as metformin (as a positive control) 150 mg/kg twice daily for 10 consecutive weeks were administered by i.p. and oral route, respectively. NaB treatment significantly reduced the plasma glucose, HbA1c, insulin-resistance, dyslipidemia and gluconeogenesis, which are comparable to metformin treatment. Further, NaB treatment ameliorated the micro- and macro-vesicular steatosis in liver and fat deposition in brown adipose tissue, white adipose tissue (adipocytes hypertrophy) as well as pancreatic beta-cell damage. In the present study, both NaB and metformin inhibited the diabetes-associated increased HDACs activity, thereby increased the acetylation of histone H3 in liver. The present findings demonstrated that NaB and metformin reduced insulin-resistance, dyslipidemia, fat accumulation and gluconeogenesis thereby improved the glucose homeostasis in rat. Thus, NaB might be a promising molecule for the prevention and treatment of type-2 diabetes and dyslipidemia.

Role of autophagy and histone deacetylases in diabetic nephropathy: Current status and future perspectives

The prevalence of diabetes and its complications is increasing at an alarming rate in both developed and deve1oping nations. The emerging evidences highlighted that both genetic and epigenetic mechanisms including histone modifications play a significant role in the pathogenesis of diabetic nephropathy (DN). Histone deacetylases (HDACs) and acetylation are involved in the regulation of autophagy as well as pathogenesis of DN. Both HDACs and histone acetyltransferases (HATs) play a key role in chromatin remodeling and affect the transcription of various genes involved in the cellular homeostasis, apoptosis, immunity and angiogenesis. Further, HDAC inhibitors are exert the renoprotective effects in DN and other diabetic complications. Thus, the cellular acetylation plays a crucial role in the regulation of autophagy and can be explored as a new therapeutic target for the treatment of DN. This review aimed to delineate the role of HDACs and associated molecular signaling/pathways in the regulation of autophagy with an emphasis on promising targets for the treatment of DN.

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.