piperidines and ruboxistaurin

Type 2 diabetes is recognised as a major cardiovascular risk factor, and future therapies must therefore address more than just blood glucose levels. Novel approaches to the treatment of type 2 diabetes are now at various stages of development or regulatory approval. Exenatide and pramlintide, analogues of gut-derived hormones glucagon-like peptide-1 (GLP-1) and amylin, respectively, have demonstrated improvements in glycaemic control and bodyweight in clinical studies and have been recently approved for treatment of type 2 diabetes. Initial studies have indicated that agents that activate both peroxisome proliferator-activated receptor (PPAR)alpha and gamma improve glycaemic control and have beneficial effects on lipid profiles. Two dual PPARalpha/gamma agonists, muraglitazar and tesaglitazar, are under regulatory review and in phase III trials, respectively. Modulation of the endogenous endocannabinoid system by rimonabant, which is under regulatory review, has been shown to improve body weight, atherogenic lipid profiles and glycaemic control. In addition, enhanced understanding of the pathophysiology underlying the microvascular complications of type 2 diabetes has led to the development of targeted therapies for conditions such as diabetic retinopathy, including the protein kinase C (PKC)-antagonist ruboxistaurin, now in phase III trials. Such therapies should enable physicians to achieve more for their patients with type 2 diabetes.

Topics: Adamantane; Alkanesulfonates; Amyloid; Diabetes Mellitus, Type 2; Enzyme Inhibitors; Exenatide; Glycine; Humans; Hypoglycemic Agents; Indoles; Islet Amyloid Polypeptide; Maleimides; Nitriles; Oxazoles; Peptides; Phenylpropionates; Piperidines; PPAR alpha; PPAR gamma; Protein Kinase C; Pyrazoles; Pyrrolidines; Receptor, Cannabinoid, CB1; Receptors, Glucagon; Rimonabant; Venoms; Vildagliptin

Elevation of diacylglycerol (DAG) and protein kinase C (PKC) levels in diabetic vascular tissue is associated with abnormalities of retinal and renal hemodynamics. The object of this study was to determine whether direct elevation of retinal DAG levels, in the absence of diabetes or hyperglycemia, can mimic the hemodynamic abnormalities normally observed in diabetic rats. Retinal DAG levels were elevated using an inhibitor of DAG kinase that converts DAG to phosphatidic acid. The effectiveness of a specific PKC-beta isoform inhibitor introduced directly into the retinas of diabetic rats in reversing diabetes-related abnormal retinal hemodynamics was also investigated.. For retinal blood flow studies, diacylglycerol kinase (DGK) inhibitor R59949, at various concentrations, was injected into the vitreous of nondiabetic Sprague-Dawley rats (n = 33), and a PKC-beta isoform-selective inhibitor LY333531 was injected into the vitreous of rats with streptozotocin (STZ)-induced diabetes of 2 weeks' duration (n = 21). Retinal hemodynamic changes were quantitated using video-based fluorescein angiography. Total DAG levels were assayed from five nondiabetic rat retinas after DGK inhibition and retinal PKC activities were assayed from six diabetic rat retinas after PKC-beta inhibition.. DGK inhibitor R59949 injected into the vitreous dose dependently increased the mean circulation time (MCT) and decreased retinal blood flow (EC50 = 10(-8) M). After 30 minutes, 10(-5) M R59949 induced a 1.7-fold increase in total retinal DAG levels, compared with the levels in vehicle-injected eyes, an increase in MCT from 0.87 +/- 0.05 seconds to 1.44 +/- 0.12 seconds (P < 0.01) and a decrease in retinal blood flow from 105.3 +/- 6.5 pixel2/second to 64.1 +/- 5 pixel2/second (P < 0.01). The effect of R59949 was sustained for 60 minutes after injection. These retinal hemodynamic parameters after DGK inhibition were comparable to those measured at baseline in rats with STZ-induced diabetes of 2 weeks' duration (MCT = 1.38 +/- 0.20 seconds; retinal blood flow = 68 +/- 11.2 pixel2/second). Intravitreal injection of the PKC-beta inhibitor (LY333531) at 10(-5) M in diabetic rats decreased by a factor of 1.6 the diabetes-related increased PKC activation, decreased the prolonged MCT (0.98 +/- 0.13 seconds; P < 0.01) and increased retinal blood flow (93.4 +/- 14.2 pixel2/second; P < 0.01). The measured retinal circulatory parameters after PKC inhibition in the retina were comparable to those measured at baseline in the nondiabetic rats.. These results provide direct evidence that DAG elevation and subsequent PKC-beta isoform activation are the primary biochemical sequelae responsible for the development of the abnormal retinal hemodynamics observed in diabetic rats.

Topics: Animals; Blood Flow Velocity; Diabetes Mellitus, Experimental; Diacylglycerol Kinase; Diglycerides; Enzyme Inhibitors; Fluorescein Angiography; Hyperglycemia; Indoles; Isoenzymes; Male; Maleimides; Piperidines; Protein Kinase C; Quinazolines; Quinazolinones; Rats; Rats, Sprague-Dawley; Retina; Retinal Vessels