JTT-130, a novel intestine-specific inhibitor of microsomal triglyceride transfer protein, ameliorates lipid metabolism and attenuates atherosclerosis in hyperlipidemic animal models.

JTT-130 was developed as an intestine-specific MTP inhibitor designed to rapidly catabolize after absorption to avoid causing hepatotoxicity due to hepatic MTP inhibition. In previous reports, we have demonstrated that JTT-130 suppresses dietary lipid absorption in the small intestine without inducing hepatic steatosis. Thus, in this report, JTT-130 was administered to hyperlipidemic animals fed a Western diet to investigate the effect of intestinal MTP inhibition on lipid metabolism and progression of atherosclerosis. JTT-130 potently lowered plasma non-high density lipoprotein-cholesterol, and elevated plasma high density lipoprotein-cholesterol (HDL-C), indicating improvement in atherogenic index in hamsters. HDL fractions obtained after two weeks treatment with JTT-130 significantly increased the efflux of cholesterol from macrophages, as an index parameter of HDL function. Furthermore, long-term treatment with JTT-130 also improved the plasma lipid profile without inducing hepatic steatosis in rabbits, resulting in the suppression of atherosclerosis formation in aortas. From these results, JTT-130 ameliorates lipid metabolism accompanied with the enhancement of the anti-atherosclerotic function of HDL, and attenuates the progression of atherosclerosis in hyperlipidemic animals. These findings indicate that intestinal MTP inhibition may be atherogenic in vivo and that JTT-130 may be a useful compound for the treatment of dyslipidemia and a potential anti-atherogenic drug.

Mechanism of action of hypoglycemic effects of an intestine-specific inhibitor of microsomal triglyceride transfer protein (MTP) in obese rats.

Diminished insulin sensitivity in the peripheral tissues and failure of pancreatic beta cells to secrete insulin are known major determinants of type 2 diabetes mellitus. JTT-130, an intestine-specific microsomal transfer protein inhibitor, has been shown to suppress high fat-induced obesity and ameliorate impaired glucose tolerance while enhancing glucagon-like peptide-1 (GLP-1) secretion. We investigated the effects of JTT-130 on glucose metabolism and elucidated the mechanism of action, direct effects on insulin sensitivity and glucose-stimulated insulin secretion in a high fat diet-induced obesity rat model. Male Sprague Dawley rats fed a high-fat diet were treated with a single administration of JTT-130. Glucose tolerance, hyperglycemic clamp and hyperinsulinemic-euglycemic testing were performed to assess effects on insulin sensitivity and glucose-stimulated insulin secretion, respectively. Plasma GLP-1 and tissue triglyceride content were also determined under the same conditions. A single administration of JTT-130 suppressed plasma glucose elevations after oral glucose loading and increased the disposition index while elevating GLP-1. JTT-130 also enhanced glucose-stimulated insulin secretion in hyperglycemic clamp tests, whereas increased insulin sensitivity was observed in hyperinsulinemic-euglycemic clamp tests. Single-dose administration of JTT-130 decreased lipid content in the liver and skeletal muscle. JTT-130 demonstrated acute and direct hypoglycemic effects by enhancing insulin secretion and/or insulin sensitivity.

Pharmacological characterization of diethyl-2-({3-dimethylcarbamoyl-4-[(4'-trifluoromethylbiphenyl-2-carbonyl)amino]phenyl}acetyloxymethyl)-2-phenylmalonate (JTT-130), an intestine-specific inhibitor of microsomal triglyceride transfer protein.

Inhibitors of microsomal triglyceride transfer protein (MTP) expressed in the liver and small intestine are potential candidates for lipid-lowering agents. However, inhibition of hepatic MTP could lead to significant safety issues such as fatty liver disease. To develop a specific inhibitor of intestinal MTP, JTT-130 [diethyl-2-({3-dimethylcarbamoyl-4-[(4'-trifluoromethylbiphenyl-2-carbonyl)amino]phenyl}acetyloxymethyl)-2-phenylmalonate], was designed to be rapidly hydrolyzed in the absorption process. Here, we describe JTT-130, an intestine-specific MTP inhibitor, and evaluate its pharmacological properties. In in vitro metabolic stability tests, JTT-130 was readily hydrolyzed during incubation with liver S9 from humans, hamsters, and rats. In an in vitro triglyceride (TG) transfer assay with human intestinal MTP, JTT-130 potently inhibited TG transfer activity with an IC(50) value of 0.83 nM. When orally administered to hamsters, JTT-130 significantly suppressed an increase in chylomicron-TG after olive oil loading at 0.3 mg/kg and above but did not inhibit TG secretion from the liver at doses of up to 1000 mg/kg, indicating an inhibitory action highly specific for the small intestine. In rats orally administered [(14)C]triolein, JTT-130 potently suppressed an increase in blood (14)C radioactivity and increased (14)C radioactivity in the upper small intestine and the intestinal lumen. In hyperlipidemic hamsters fed a high-fat and high-cholesterol diet, repeated dosing with JTT-130 for 2 weeks reduced TG and cholesterol levels in the plasma and TG content in the liver. These results indicated that JTT-130 is a potent inhibitor specific to intestinal MTP and suggested that JTT-130 would be a useful compound for the treatment of dyslipidemia without inducing hepatotoxicity.

JTT-130, a novel intestine-specific inhibitor of microsomal triglyceride transfer protein, suppresses food intake and gastric emptying with the elevation of plasma peptide YY and glucagon-like peptide-1 in a dietary fat-dependent manner.

The microsomal triglyceride transfer protein (MTP) takes part in the mobilization and secretion of triglyceride-rich lipoproteins from enterocytes and hepatocytes. In this study, we investigated the effects of diethyl-2-({3-dimethylcarbamoyl-4-[(4'-trifluoromethylbiphenyl-2-carbonyl) amino] phenyl}acetyloxymethyl)-2-phenylmalonate (JTT-130), a novel intestine-specific MTP inhibitor, on food intake, gastric emptying, and gut peptides using Sprague-Dawley rats fed 3.1% fat, 13% fat, or 35% fat diets. JTT-130 treatment suppressed cumulative food intake and gastric emptying in rats fed a 35% fat diet, but not a 3.1% fat diet. In rats fed a 13% fat diet, JTT-130 treatment decreased cumulative food intake but not gastric emptying. In addition, treatment with orlistat, a lipase inhibitor, completely abolished the reduction of food intake and gastric emptying by JTT-130 in rats fed a 35% fat diet. On the other hand, JTT-130 treatment increased the plasma concentrations of gut peptides, peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) but not cholecystokinin, in the portal vein in rats fed a 35% fat diet. These elevations in PYY and GLP-1 were also abolished by treatment with orlistat. Furthermore, JTT-130 treatment in rats fed a 35% fat diet increased the contents of triglycerides and free fatty acids in the intestinal lumen, which might contribute to the elevation of PYY and GLP-1 levels. The present findings indicate that JTT-130 causes satiety responses, decreased food intake, and gastric emptying in a dietary fat-dependent manner, with enhanced production of gut peptides such as PYY and GLP-1 from the intestine.

Hereditary postprandial hypertriglyceridemic rabbit exhibits insulin resistance and central obesity: a novel model of metabolic syndrome.

OBJECTIVE: We have established a hereditary postprandial hypertriglyceridemic (PHT) rabbit. The present study was designed to define whether this rabbit model represents both insulin resistance and central obesity. METHODS AND RESULTS: Body weight, abdominal circumference, visceral fat weight, and glucose tolerance were compared between PHT and Japanese white (JW) rabbit. Plasma levels of triglycerides (TG), total cholesterol (TC), glucose, and insulin were measured before and after feeding. Abdominal circumference of PHT rabbit was larger than that of JW rabbit, with no difference in body mass index. Visceral fat accumulation was noted as obvious in mesenterium, retroperitoneal space, and epididymal area. Plasma TG and TC levels were high preprandially and markedly increased postprandially in PHT rabbit compared with JW rabbit. Although plasma glucose levels were comparable in both groups, plasma insulin levels were elevated in PHT rabbit. Glucose tolerance tests indicated that plasma insulin levels in PHT rabbit were consistently higher than in JW rabbit. A positive correlation was observed between plasma insulin levels and visceral fat weight in PHT rabbit. CONCLUSIONS: PHT rabbit shows insulin resistance along with central obesity. PHT rabbit will serve as a model for elucidating genetic predisposition and pathophysiology in metabolic syndrome.

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.

Contribution of hyperglycemia on diabetic complications in obese type 2 diabetic SDT fatty rats: effects of SGLT inhibitor phlorizin.

The spontaneously diabetic torii (SDT) fatty rat is a new model of type 2 diabetes showing overt obesity, hyperglycemia and hyperlipidemia. With early onset of diabetes mellitus, diabetic microvascular complications, including nephropathy, peripheral neuropathy and retinopathy, are observed at young ages. In the present study, blood glucose levels of female SDT fatty rats were controlled with phlorizin, a non-selective SGLT inhibitor, to examine whether and how these complications are caused by hyperglycemia. Phlorizin treatment adequately controlled plasma glucose levels during the experiment. At 29 weeks of age, urinary albumin excretion considerably increased in SDT fatty rats. Glomerulosclerosis and tubular pathological findings also indicate diabetic nephropathy. These renal parameters tended to decrease with phlorizin; however, effects were partial. Sciatic nerve conduction velocities were significantly delayed in SDT fatty rats compared with Sprague-Dawley (SD) rats. Intraepidermal nerve fiber density, an indicator of subclinical small nerve fiber neuropathy, significantly decreased in SDT fatty rats. Retinal dysfunction (prolongation of peak latency for oscillatory potential in electroretinograms) and histopathological eye abnormalities, including retinal folding and mature cataracts were also observed. Both nerve and eye disorders were prevented with phlorizin. These findings indicate that severe hyperglycemia mainly causes diabetic complications in SDT fatty rats. However, other factors, such as hyperlipidemia and hypertension, may affect diabetic nephropathy. These characteristics of diabetic complications will become helpful in evaluating new drugs for diabetic complications using SDT fatty rats.

JTT-130, a novel intestine-specific inhibitor of microsomal triglyceride transfer protein, improves hyperglycemia and dyslipidemia independent of suppression of food intake in diabetic rats.

We investigated the effects of JTT-130 on glucose and lipid metabolism independent of the suppression of feeding by comparing with pair-fed animals. Male Zucker diabetic fatty (ZDF) rats were divided into control, JTT-130 treatment, and pair-fed groups. The rats were fed with a regular powdered diet with or without JTT-130 as a food admixture for 6 weeks. We compared the effects on glucose and lipid metabolism in JTT-130 treatment group with those in pair-fed group. RESULTS. Hyperglycemia in ZDF rats was prevented in both JTT-130 treatment and pair-fed groups, but the prevention in pair-fed group became poor with time. Moreover, reduction in plasma cholesterol levels was observed only in JTT-130 treatment group. JTT-130 treatment group showed improved glucose tolerance at 5 weeks after treatment and significant elevation of portal glucagon-like peptide-1 (GLP-1) levels. The hepatic lipid content in JTT-130 treatment group was decreased as compared with pair-fed group. Furthermore, pancreatic protection effects, such as an increase in pancreatic weight and an elevation of insulin-positive area in islets, were observed after JTT-130 treatment. CONCLUSIONS. JTT-130 improves hyperglycemia and dyslipidemia via a mechanism independent of suppression of food intake, which is ascribed to an enhancement of GLP-1 secretion and a reduction of lipotoxicity.

Combination therapy of an intestine-specific inhibitor of microsomal triglyceride transfer protein and peroxisome proliferator-activated receptor γ agonist in diabetic rat.

We investigated effects on glucose and lipid metabolism in combination of JTT-130, a novel intestine-specific microsomal triglyceride transfer protein (MTP) inhibitor, and pioglitazone, peroxisome proliferator-activated receptor (PPAR) γ agonist. Male Zucker diabetic fatty rats were divided into 4 groups: control group, JTT-130 treatment group, pioglitazone treatment group, and combination group. The Zucker diabetic fatty rats were fed a regular powdered diet with JTT-130 and/or pioglitazone as a food admixture for 6 weeks. Effects on glucose and lipid metabolism were compared mainly between JTT-130 treatment group and combination group. JTT-130 treatment showed good glycemic control, while the plasma glucose and glycated hemoglobin levels in combination group were significantly decreased as compared with those JTT-130 treatment group. The reduction in the plasma triglyceride and free fatty acid levels in combination group was higher than that in JTT-130 treatment group, and glucose utilization was significantly elevated in adipose tissues. In Zucker diabetic fatty rats, combination treatment of JTT-130 and pioglitazone showed better glycemic control and a strong hypolipidemic action with an enhancement of insulin sensitivity. Combination therapy of MTP inhibitor and PPAR γ agonist might be more useful in the treatment of type 2 diabetes accompanied with obesity and insulin resistance.

JTT-130, a novel intestine-specific inhibitor of microsomal triglyceride transfer protein, reduces food preference for fat.

Microsomal triglyceride transfer protein (MTP) is involved in the assembly and secretion of triglyceride-rich lipoproteins from enterocytes and hepatocytes. JTT-130 is a novel intestine-specific MTP inhibitor, which has been shown to be useful in the prevention and treatment of dyslipidemia, obesity, and diabetes. JTT-130 has also been shown to suppress food intake in a dietary fat-dependent manner in rats. However, whether JTT-130 enables changes in food preference and nutrient consumption remains to be determined. Therefore, the aim of the present study was to investigate the effects of JTT-130 on food preference in rat under free access to two different diets containing 3.3% fat (low-fat diet, LF diet) and 35% fat (high-fat diet, HF diet). JTT-130 decreased HF diet intake and increased LF diet intake, resulting in a change in ratio of caloric intake from LF and HF diets to total caloric intake. In addition, macronutrient analysis revealed that JTT-130 did not affect carbohydrate consumption but significantly decreased fat consumption (P < 0.01). These findings suggest that JTT-130 not only inhibits fat absorption, but also suppresses food intake and specifically reduces food preference for fat. Therefore, JTT-130 is expected to provide a new option for the prevention and treatment of obesity and obesity-related metabolic disorders.

Diabetic peripheral neuropathy in Spontaneously Diabetic Torii-Lepr(fa) (SDT fatty) rats.

Spontaneously Diabetic Torii (SDT) rat is a hereditary model of diabetes. Although the SDT rat shows severe diabetic complications, the onset of hyperglycemia is late. SDT fatty rat, established by introducing the fa allele of the Zucker fatty rat to SDT rat, develops diabetes much faster than SDT rat. In the present study, diabetic peripheral neuropathy (DPN) was evaluated to show the further usefulness of this animal model. Motor nerve conduction velocity (MNCV) was delayed, and the number of sural nerve fibers was decreased in SDT fatty rat. Treatment of pioglitazone lowered blood glucose level and prevented delay of MNCV in SDT fatty rats. SDT fatty rat is a useful animal model for studies of DPN in type 2 diabetes.