JTT-654, an 11-beta hydroxysteroid dehydrogenase type 1 inhibitor, improves hypertension and diabetic kidney injury by suppressing angiotensinogen production.

11ß-Hydroxysteroid dehydrogenase type 1 (11ß-HSD1) plays an important role in regulating the expression of glucocorticoid actions in target tissues. Overexpression of 11ß-HSD1 in mouse adipose tissue causes a metabolic syndrome-like phenotype, leading to hypertension. Although, many 11ß-HSD1 inhibitors have been studied, few have shown a clear ameliorative effect against hypertension. We investigated whether JTT-654, a novel 11ß-HSD1 inhibitor, ameliorated hypertension and elucidated the underlying mechanisms. JTT-654 showed inhibitory effects on angiotensinogen production in cortisone-treated 3T3-L1 adipocytes and in a rat model. JTT-654 improved hypertension not only in cortisone-treated rats and spontaneously hypertensive rats (SHR), but also in SHR/NDmcr-cp rats. In the SHR study, JTT-654 and losartan showed the same degree of antihypertensive efficacy. In addition, JTT-654 ameliorated diabetic nephropathy by suppressing renal angiotensinogen production in SHR/NDmcr-cp rats. These effects of JTT-654 were independent of its insulin-sensitizing effects, and similar effects were not observed for pioglitazone, an insulin sensitizer. Moreover, JTT-654 did not affect normotension or hypothalamus-pituitary-adrenal (HPA) axis function in normal Sprague-Dawley rats. Our results indicate that JTT-654 ameliorates hypertension and diabetic nephropathy by inhibiting 11ß-HSD1 in the adipose tissue, liver, and kidney.

Characterization of hepatic glucose metabolism disorder with the progress of diabetes in male Spontaneously Diabetic Torii rats.

The Spontaneously Diabetic Torii (SDT) rat has recently been established as a new model of non-obese type 2 diabetes. In this study, we examined changes in hepatic glucose metabolism in prediabetic and diabetic SDT rats compared with age-matched control rats. The prediabetic state was confirmed at 16 weeks of age, and the diabetic state was confirmed at 24 and 32 weeks of age. Decreases in glucokinase mRNA levels and activity were observed in the prediabetic state. In this state, glycogen synthase activity and glycogen content were also decreased in the SDT rat. In addition to the above changes, glycogen phosphorylase mRNA and activity were decreased and gluconeogenetic enzyme mRNA levels were significantly increased in the diabetic state. These results indicate there is a great potential that abnormalities in hepatic glucose metabolism play a role in the progression to onset of diabetes. We suggest that the SDT rat is a valuable diabetic model for investigations into mechanisms or causes of progression to diabetes.

Discovery of potent liver-selective stearoyl-CoA desaturase-1 (SCD1) inhibitors, thiazole-4-acetic acid derivatives, for the treatment of diabetes, hepatic steatosis, and obesity.

SCD1 is a rate-limiting enzyme in the conversion of saturated fatty acids to monounsaturated fatty acids. SCD1 inhibitors have potential effects on obesity, diabetes, acne, and cancer, but the adverse effects associated with SCD1 inhibition in the skin and eyelids are impediments to clinical development. To avoid mechanism-based adverse effects, we explored the compounds that selectively inhibit SCD1 in the liver in an ex vivo assay. Starting from a systemically active lead compound, we focused on the physicochemical properties tPSA and cLogP to minimize exposure in the off-target tissues. This effort led to the discovery of thiazole-4-acetic acid analog 48 as a potent and liver-selective SCD1 inhibitor. Compound 48 exhibited significant effects in rodent models of diabetes, hepatic steatosis, and obesity, with sufficient safety margins in a rat toxicology study with repeated dosing.

Increased fat absorption and impaired fat clearance cause postprandial hypertriglyceridemia in Spontaneously Diabetic Torii rat.

In diabetes, postprandial hyperlipidemia is recognized as a risk factor for premature atherosclerosis and following cardiovascular disease. In the present study, features of fat absorption and clearance were examined to clarify the lipid metabolism of Spontaneously Diabetic Torii (SDT) rats. Olive oil was orally administered to evaluate increase of blood triglyceride (TG) level. Mesenteric lymph chylomicron TG was also measured. mRNAs of enzymes and transfer protein related to TG metabolism and histopathological changes were evaluated. In an oil loading test, elevation of TG in plasma and lymph chylomicron was increased in SDT rats. Interestingly, SDT rats showed elevation of plasma TG after oil loading and relatively low epididymal fat lipoprotein lipase (LPL) mRNA expression even at the pre-diabetic state without increase of TG absorption from intestine. In the diabetic state, intestines of SDT rats were hypertrophic and expressed mRNAs of enzymes and transfer protein related to TG absorption highly. From these results, it seems that intestinal abnormalities related to hypoinsulinemia/hyperglycemia cause postprandial hypertriglyceridemia in SDT rats. In addition, our findings suggest that SDT rats have impaired lipid catabolism antecedent to hypoinsulinemia/hyperglycemia. These characteristics of SDT rats can be useful in studies of diabetic hypertriglyceridemia and TG metabolism.

Pharmacological effects of JTT-551, a novel protein tyrosine phosphatase 1B inhibitor, in diet-induced obesity mice.

Protein tyrosine phosphatase 1B (PTP1B) is a negative regulator of leptin signaling as well as insulin signaling. JTT-551 is a new PTP1B inhibitor, which is reported to improve glucose metabolism by enhancement of insulin signaling. We have evaluated an antiobesity effect of JTT-551 using diet-induced obesity (DIO) mice. A single administration of JTT-551 was provided to DIO mice with or without leptin, and DIO mice were given food containing JTT-551 for six weeks. A single administration of JTT-551 with leptin treatment enhanced the food inhibition and the signal transducer and activator of transcription 3 (STAT3) phosphorylation in hypothalamus. Moreover, chronic administration of JTT-551 showed an antiobesity effect and an improvement of glucose and lipid metabolism in DIO mice. JTT-551 shows an antiobesity effect possibly by enhancement of leptin signaling and could be useful in the treatment of type 2 diabetes and obesity.

Pathophysiological analysis of female Spontaneously Diabetic Torii fatty rats.

Obesity, hyperglycemia, hyperlipidemia, and diabetes-associated complications appear at younger ages (6-8 weeks) in the male Spontaneously Diabetic Torii-Lepr(fa) (SDT-fa/fa) rat than in the male original SDT (SDT-+/+) rat. However, the incidence and progression of diabetes mellitus and diabetic complications in the female SDT-fa/fa rat have not been reported in detail. In the present study, the pathophysiological features of the female SDT-fa/fa rat were examined, and compared with those of the female SDT-+/+ rat. Female SDT-fa/fa rats showed hyperphagia, obesity, hyperglycemia, and hyperlipidemia from 5 or 6 weeks of age, and hyperinsulinemia was observed from 5 to 12 weeks. Pathological changes pancreatic islets were observed from 8 weeks. Renal function parameters, such as urine volume and urinary protein, increased from 16 weeks, and pathological findings in the renal tubule, and cataracts were also observed from 16 weeks. Increases of visceral and subcutaneous fats were obvious during the observation period. In pair-feeding with SDT-+/+ rats, SDT-fa/fa rats showed improved hyperglycemia and hypertriglycemia, but hypercholesterolemia was not entirely improved during the study period. Female SDT-fa/fa rats showed diabetes mellitus and diabetes-associated complications at young ages, and fat accumulation was remarkable. Suppression of hyperphagia in SDT-fa/fa rats was effective at improving hyperglycemia and hypertriglycemia. In conclusion, the female SDT-fa/fa rat has the potential to become an important animal model of type 2 diabetes mellitus with obesity, especially for women, for which few models currently exist.

A high-fat diet inhibits the progression of diabetes mellitus in type 2 diabetic rats.

It is well known that rats and mice, when fed a high-fat diet, develop obesity associated with abnormal glycolipid metabolism. In this study, we investigated the effects of a high-fat diet on a diabetic rat model, Spontaneously Diabetic Torii (SDT), which develops diabetes due to decreased insulin production and secretion with age. We hypothesized that a high-fat diet would accelerate the induction of diabetes in this model. The SDT rats were divided into 2 groups, which were fed a high-fat diet or standard diet for 16 weeks. The group fed a high-fat diet developed obesity, hyperinsulinemia, and hyperlipidemia until 16 weeks of age. Before 16 weeks of age, hyperglycemia accompanied by hypoinsulinemia developed in the group on a standard diet, but serum glucose levels were comparable in both groups. After 16 weeks of age, the group on a standard diet showed an increase in serum glucose levels and a decrease in serum insulin levels. Unexpectedly, in the group on the high-fat diet, we observed a suppressed of the progression of hyperglycemia/hypoinsulinemia. Histopathological observation revealed more pancreatic beta cells in the group on the high-fat diet. This study suggests that feeding SDT rats a high-fat diet induces obesity, hyperinsulinemia, and hyperlipidemia, but not hyperglycemia, until 16 weeks of age. Thereafter, age-dependent progress of hyperglycemia and hypoinsulinemia was delayed by a high-fat diet. The hyperfunction of pancreatic beta cells induced by a high-fat diet before the onset of hyperglycemia appears to suppress development of hyperglycemia/hypoinsulinemia.

Effect of food restriction on adipose tissue in spontaneously diabetic Torii fatty rats.

Spontaneously Diabetic Torii-fa/fa (SDT fatty) rat is a new model of obese type 2 diabetes. SDT fatty rat exhibits obesity associated with hyperphagia. In this study, SDT fatty rats were subjected to pair-feeding with SDT-+/+ (SDT) rats from 6 to 22 weeks of age. The ratio of visceral fat weight to subcutaneous fat weight (V/S) decreased at 12 weeks of age in the pair-feeding rats. The intraperitoneal fat weight such as epididymal and retroperitoneal fat weight decreased, whereas mesenteric fat weight had no change. Cell size of the epididymal fat in the pair-feeding rats tended to decrease. Glucose oxidation level in epididymal fat in the pair-feeding rats at 12 weeks of age was recovered to a similar level with that in SDT rats. These results indicated that SDT fatty rat is a useful model to evaluate the functional or the morphological features in adipose tissue and develop a novel drug for antiobesity.