Ranjan Chakrabarti

Ragaglitazar: a novel PPARα & PPARγ agonist with potent lipid‐lowering and insulin‐sensitizing efficacy in animal models

Ragaglitazar [(−) DRF 2725; NNC 61‐0029] is a coligand of PPARα and PPARγ. In ob/ob mice, ragaglitazar showed significant reduction in plasma glucose, triglyceride and insulin (ED50 values <0.03, 6.1 and <0.1 mg kg−1). These effects are three‐fold better than rosiglitazone and KRP‐297. In Zucker fa/fa rats, ragaglitazar showed dose‐dependent reduction in triglyceride and insulin, hepatic triglyceride secretion and triglyceride clearance kinetics (maximum of 74, 53, 32 and 50% at 3 mg kg−1), which are better than rosiglitazone and KRP‐297. In a high‐fat‐fed hyperlipidaemic rat model, the compound showed an ED50 of 3.95, 3.78 mg kg−1 for triglyceride and cholesterol lowering, and 0.29 mg kg−1 for HDL‐C increase. It also showed improvement in clearance of plasma triglyceride and hepatic triglyceride secretion rate. All these effects are 3–10‐fold better than fenofibrate and KRP‐297. Ragaglitazar treatment showed significant reduction in plasma Apo B and Apo CIII levels, and increase in liver CPT1 and CAT activity and ACO mRNA. Significant increase of both liver and fat LPL activity and fat aP2 mRNA was also observed. In a high‐fat‐fed hamster model, ragaglitazar at 1 mg kg−1 showed 83 and 61% reduction in triglyceride and total cholesterol, and also 17% reduction in fat feed‐induced body weight increase. In these hyperlipidaemic animal models, PPARγ ligands failed to show any significant efficacy. Taken together, ragaglitazar shows better insulin‐sensitizing and lipid‐lowering potential, as compared to the standard compounds.

Novel Coumarin Derivatives of Heterocyclic Compounds as Lipid-Lowering Agents §

Coumarin derivatives of different heterocycles (5,7a-i, 10 and 11) were designed based on cyclisation of 2-ethoxy-3-phenylpropanoic acid and 2-benzylmalonic acid as novel lipid-lowering agents and their preliminary in vivo screening indicates 7c has moderate triglyceride-lowering activity.

Antidiabetic and hypolipidemic activity of Helicteres isora in animal models

Helicteres isora (Sterculiaceae) root juice has been used in the treatment of diabetes by several ethnic groups in different parts of India. A program was initiated to elucidate the scientific basis for the antidiabetic activity of H. isora. Ethanolic extract of H. isora root caused significant reduction in plasma glucose, triglyceride and insulin levels at 300 mg/kg dose after 9 days of administration to insulin resistant and diabetic C57BL/KsJdb/db mice. In normoglycemic and mildly hypertriglyceridemic Swiss albino mice, the extract also showed significant reduction in plasma triglyceride and insulin levels, without affecting plasma glucose level. An ethanolic extract showed activity distinctly different from glybenclamide and acarbose but similar to troglitazone in these models. In high fat fed hamster model, the extract showed significant reduction in plasma lipid levels. In order to identify the active pharmacophore, the ethanolic extract was further subjected to sequential partitioning with low, medium and high polarity solvents, which yielded a semipurified fraction having both euglycemic and lipid-lowering activity. Our study suggests that the extract of H. isora has insulin-sensitizing and hypolipidemic activity and has the potential for use in the treatment of type-2 diabetes.

Novel phthalazinone and benzoxazinone containing thiazolidinediones as antidiabetic and hypolipidemic agents

We report here the synthesis of a series of 5-[4-[2-[substituted phthalazinones-2(or 4)yl]ethoxy]phenylmethyl]thiazolidine-2,4-diones and 5-[4-[2-[2,3-benzoxazine-4-one-2-yl]ethoxy]phenylmethyl]thiazolidine-2,4-diones and their plasma glucose and plasma triglyceride lowering activity in db/db mice. In vitro PPARgamma transactivation assay was performed in HEK 293T cells. In vitro and in vivo pharmacological studies showed that the phthalazinone analogue has better activity. PHT46 (compound 5a), the best compound in this series, showed better in vitro PPARgamma transactivation potential than troglitazone and pioglitazone. In insulin resistant db/db mice, PHT46 showed better plasma glucose and triglyceride lowering activity than the standard drugs. Pharmacokinetic study in Wistar rats showed good systemic exposure of PHT46. Subchronic toxicity study in Wistar rats did not show any treatment-related adverse effect.

Synthesis and biological activity of novel pyrimidinone containing thiazolidinedione derivatives

A series of pyrimidinone derivatives of thiazolidinediones were synthesized. Their biological activity were evaluated in insulin resistant, hyperglycemic and obese db/db mice. In vitro PPARgamma transactivation assay was performed in HEK 293T cells. PMT13 showed the best biological activity in this series. PMT13 (5-[4-[2-[2-ethyl-4-methyl-6-oxo-1,6-dihydro-1-pyrimidinyl]ethoxy]phenylmethyl]thiazolidine-2,4-dione) showed better plasma glucose, triglyceride and insulin-lowering activity in db/db mice than rosiglitazone and pioglitazone. PMT13 showed better PPARgamma transactivation than the standard compounds. Pharmacokinetic study in Wistar rats showed good systemic exposure of PMT13. Twenty-eight day oral toxicity study in Wistar rats did not show any treatment-related adverse effects.

Role of PPAR in Cardiovascular Diseases

Cardiovascular disease (CVD) is the most critical global health threat, which contributes more than one third of global morbidity. CVD includes heart disease, vascular disease, atherosclerosis, stroke and hypertension. The most important independent risk factors for CVD include dyslipidemia along with hypertension, obesity, sedentary lifestyle, diabetes and chronic inflammation. These factors are directly regulated by diet, metabolism and physical activity. Diets rich in fat and carbohydrate coupled to sedentary lifestyles have contributed to the increase in dyslipidemia, type 2 diabetes, obesity and CVD in the world. Discovery of Peroxisome Proliferator Activated Receptors (PPARs) as a key regulator of metabolic pathways has led to significant insight into the mechanisms regulating these processes. Three PPAR subtypes, encoded by distinct genes, are designated as PPAR-alpha, PPAR-delta (also know as beta) and PPAR-gamma. PPARs act as nutritional sensors that regulate a variety of homeostatic functions including metabolism, inflammation and development. PPAR-alpha is the main metabolic regulator for catabolism whereas PPAR-gamma regulates anabolism or storage. PPARs are expressed in the cardiovascular system such as endothelial cells, vascular smooth muscle cells and monocytes/macrophages. It has been shown that they play an important role in the modulation of inflammatory, fibrotic and hypertrophic responses. In 1997, a Glaxo patent described that Troglitazone (first PPAR-gamma ligand to reach market) reduced TNF-induced VCAM1 expression in HUVECs indicating the potential benefit in atherosclerosis. A series of patents from Eli Lilly and Dr. Reddys Laboratories Ltd. between 1999 and 2005 described a variety of PPAR-alpha and -alpha,gamma dual ligands in a number of patents having glucose, triglyceride, cholesterol lowering, HDL elevating and body weight reducing activity. Patents from Metabolex and Tularik in 2001 and 2002 described the beneficial effects of SPPARM molecules for insulin resistance and diabetes, without showing concern on PPAR-gamma related side effects such as edema and body weight. GSK and Takeda described the potential effects of PPAR-delta modulators during 2001 to 2004 in few patents. Several clinical and preclinical studies have demonstrated the beneficial effects of PPAR ligands on various cardiovascular risk factors. This review intends to capture some of the key studies in this area as is described in some recent patents and literature.

Novel indole containing thiazolidinedione derivatives as potent euglycemic and hypolipidaemic agents

Abstract Several thiazolidinediones having indol as heterocyclic moiety have been synthesized and evaluated for euglycemic properties. A few of them have been found to be superior to troglitazone.

Novel pyrazole-3-carboxamide derivatives as cannabinoid-1 (CB1) antagonists: Journey from non-polar to polar amides

The synthesis and biological evaluation of novel pyrazole-3-carboxamide derivatives as CB1 antagonists are described. As a part of eastern amide SAR, various chemically diverse motifs were introduced. In general, a range of modifications were well tolerated. Several molecules with high polar surface area were also identified as potent CB1 receptor antagonists. The in vivo proof of principle for weight loss is exemplified with a lead compound from this series.

Non-insulin dependent diabetes mellitus: present therapies and new drug targets.

Type 2 Diabetes Mellitus (DM) or Non-Insulin Dependent Diabetes Mellitus (NIDDM) accounts for 90-95% of all diabetes cases and has become a major health concern over the years. This disease has assumed frightening proportions due to unhealthy food habits and sedentary life style. About a decade ago, due to the absence of defined molecular targets or an understanding of disease pathophysiology, treatment of this disease was mostly focused on insulin secretion or administration of external insulin. During the past decade however, advent of genomics and proteomics has helped in understanding the molecular alteration characteristics of NIDDM. Untreated type 2 diabetes leads to several complications such as hyperlipidemia, hypertension and atherosclerosis--collectively known as Syndrome X. Though United Kingdom Prospective Diabetes Study (UKPDS) showed that normalization of hyperglycemia could prevent majority of diabetes complications, the available treatment regime does not adequately normalize the blood glucose level in type 2 diabetic patients. Currently, four distinct classes of oral hypoglycemic agents are available, some of which can act as lipid lowering agents as well. The efficacy and side effect profiles of these drugs are still to be optimized, so there is an unmet need for better candidates. Several new targets as well as better drugs for old targets are under investigation across the world. Availability of such drugs, based on the validated targets, may lead to a new therapeutic paradigm for the prevention of diabetes as well as complications arising out of it. The current review will deal with existing oral therapies for type 2 diabetes as well as the emerging therapeutic targets.

Novel euglycemic and hypolipidemic agents: Part-2. Antioxidant moiety as structural motif.

Several thiazolidinediones having antioxidant moities in their structural motif have been synthesised and evaluated for their euglycemic and hypolipidemic activities. A few of them have been found to be superior to troglitazone.