High fructose and streptozotocin induced diabetic impairments are mitigated by Indirubin-3-hydrazone via downregulation of PKR pathway in Wistar rats.

Metabolic disorders are becoming more common in young population due to increased consumption of carbohydrate rich diet, lack of physical activity and stress. Fructose is used as a sweetener in many carbonated beverages and is a known inducer of oxidative stress and hypertension. Up-regulation of the double-stranded RNA-dependent protein kinase (PKR) causes impairment in insulin signaling pathway and metabolic dysfunctions in type 2 diabetes mellitus. In the present study we investigated the role of PKR and associated pathways in high fructose (HF) and streptozotocin (STZ) induced diabetes and whether indirubin-3-hydrazone (IHZ), a novel PKR inhibitor can reverse the HF and STZ induced diabetic impairments in Wistar rats. Diabetes was induced by feeding rats 20% high fructose in drinking water for 6 weeks and by giving a single dose of STZ (35 mg/kg., i.p) at the end of week 5. Glucose and lipid levels were measured by using assay kits. Expression of PKR and its downstream genes were determined by immunohistochemistry, qRT-PCR and western blotting techniques. Histo-pathological studies were performed using H&E staining. Fibrosis was detected in insulin sensitive tissues and organs using Sirius red and Masson's trichrome staining and apoptosis by TUNEL assay. HF and STZ induced hyperglycemia, fibrosis, oxidative stress, and inflammation in liver, pancreas, skeletal muscle and adipose tissue are mediated via PKR pathway and its downstream effectors, and these effects were attenuated by PKR inhibitor IHZ. Thus, inhibition of PKR can protect insulin sensitive organs and tissues from HF induced diabetic impairments via the inhibition of c-Jun N-terminal kinase (JNK) pathway.

SGLT1 inhibition boon or bane for diabetes-associated cardiomyopathy.

Chronic hyperglycaemia is a peculiar feature of diabetes mellitus (DM). Sequential metabolic abnormalities accompanying glucotoxicity are some of its implications. Glucotoxicity most likely corresponds to the vascular intricacy and metabolic alterations, such as increased oxidation of free fatty acids and reduced glucose oxidation. More than half of those with diabetes also develop cardiac abnormalities due to unknown causes, posing a major threat to the currently available marketed preparations which are being used for treating these cardiac complications. Even though impairment in cardiac functioning is the principal cause of death in individuals with type 2 diabetes (T2D), reducing plasma glucose levels has little effect on cardiovascular disease (CVD) risk. In vitro and in vivo studies have demonstrated that inhibitors of sodium glucose transporter (SGLT) represent a putative therapeutic intervention for these pathological conditions. Several clinical trials have reported the efficacy of SGLT inhibitors as a novel and potent antidiabetic agent which along with its antihyperglycaemic activity possesses the potential of effectively treating its associated cardiac abnormalities. Thus, hereby, the present review highlights the role of SGLT inhibitors as a successful drug candidate for correcting the shifts in deregulation of cardiac energy substrate metabolism together with its role in treating diabetes-related cardiac perturbations.

Pharmacological evaluation of novel PKR inhibitor indirubin-3-hydrazone in-vitro in cardiac myocytes and in-vivo in wistar rats.

AIMS: Double stranded protein kinase R cellular response is associated with various stress signals such as nutrients, endoplasmic stress, cytokines and mechanical stress. Increased PKR activity has been observed under diabetic and cardiovascular disease conditions. Most of the currently available PKR inhibitors are non-specific and have other effects as well. Thus, the aim of the present study was to examine the effect of novel PKR inhibitor indirubin-3-hydrazone (IHZ) in cultured rat H9C2 cardiomyocytes and wistar rats. MATERIALS AND METHODS: PKR expression was determined by Q-PCR, immunofluorescence and immunoblotting. The expression of different gene markers for apoptosis was measured by RT-PCR. Apoptosis and oxidative stress were determined by flow cytometry. KEY FINDINGS: High glucose (HG) treated H9C2 cardiomyocytes and high fructose (HF) treated wistar rats developed a significant increase in PKR expression. A significant increase in apoptosis and generation of reactive oxygen species was also observed in HG treated H9C2 cells and HF treated rats. Reduced vacuole formation and prominent nuclei were also observed in high glucose treated cells. Cardiac hypertrophy and increased fibrosis were observed in HF treated rats. All these effects of HG and HF were attenuated by novel PKR inhibitor, indirubin-3-hydrazone. SIGNIFICANCE: Our results indicate IHZ as an effective inhibitor of PKR in vitro and in-vivo, thus it may prove very useful in blocking the multiple harmful effects of PKR.

Pharmacological evaluation of novel alagebrium analogs as methylglyoxal scavengers in vitro in cardiac myocytes and in vivo in SD rats.

BACKGROUND: Methylglyoxal (MG) is a byproduct of glucose metabolism and an inducer of advanced glycation end products (AGEs). AGEs are implicated in the pathogenesis of diabetes as well as hypertension. Most of the currently available MG scavengers are non-specific and have other effects as well. Alagebrium (ALA), developed by Alteon Corporation is a MG scavenger. Thus the aim of the present study was to investigate the potential of novel ALA analogs as possible MG scavengers and whether they could prevent any deleterious effects of MG. METHODS AND RESULTS: MG levels were measured by HPLC. The different biochemical and molecular parameters were measured by assay kits, RT-PCR and immunocytochemistry. Out of the 15 ALA analogs tested in vitro, compound no. 13 was found to be an effective inhibitor of MG in a concentration and time dependent manner. Compound no. 13 significantly attenuated the MG levels in vitro in MG treated cultured H9C2 cardiomyocytes as well as in vivo in MG treated SD rats. MG induced oxidative stress and apoptosis were attenuated by pretreatment of H9C2 cardiac myocytes with compound no. 13. MG induced cardiac hypertrophy and apoptosis were also attenuated by treating MG treated SD rats with compound no. 13. CONCLUSION: Our results indicate compound 13 as an effective inhibitor of MG in vitro in cultured cardiomyocytes and in vivo in SD rats and thus it may prove very useful in blocking the multiple deleterious effects of MG, including AGEs and vascular complications of diabetes.