Galacto-oligosaccharides ameliorate dysbiotic Bifidobacteriaceae decline in Japanese patients with type 2 diabetes.

Gut microbiota affects the host's metabolism, and it is suggested that there are differences in gut microbiota composition between patients with type 2 diabetes and healthy individuals. Additionally, dysbiosis may increase the concentration of lipopolysaccharides (LPS), causing metabolic endotoxemia, which induces impaired glucose tolerance. Several studies have reported relationships between metabolic diseases and the gut microbiota; and prebiotics, such as oligosaccharides, are commonly consumed to regulate gut microbiotas in healthy individuals. Galacto-oligosaccharides (GOS) are a major prebiotic, which specifically increase Bifidobacteriaceae abundance. Recent studies have reported that Bifidobacteriaceae improved metabolic endotoxemia or impaired glucose tolerance. However, there are few studies reporting the effects of GOS on patients with type 2 diabetes. In the current study, we compared clinical parameters, faecal gut microbiota, their associated metabolic products and their components such as LPS, and LPS-binding protein (LBP) produced by the host, between patients with diabetes and healthy controls. We then assessed the effects of GOS on glycaemic control, and gut microbiotas and metabolites in patients with type 2 diabetes in a double-blind controlled manner. LBP levels were significantly higher in patients with diabetes than those of healthy subjects, which was consistent with previous reports. The abundance of Bifidobacteriaceae and the diversity of intestinal microbiota were significantly lower in patients with diabetes than in healthy subjects. Interestingly, Bifidobacteriaceae was markedly restored in patients with diabetes after consumption of GOS, whereas LBP and glucose tolerance did not improve during this short-term trial period. In the present study, we demonstrated that GOS can ameliorate dysbiosis in patients with diabetes, and continuous intake of GOS may be a promising method for managing type 2 diabetes.

Glycaemic control and hypoglycaemia with insulin glargine 300 U/mL compared with glargine 100 U/mL in Japanese adults with type 2 diabetes using basal insulin plus oral anti-hyperglycaemic drugs (EDITION JP 2 randomised 12-month trial including 6-month extension).

AIMS: To compare insulin glargine 300 U/mL (Gla-300) with glargine 100 U/mL (Gla-100) in Japanese adults with uncontrolled type 2 diabetes on basal insulin and oral anti-hyperglycaemic drugs over 12 months. METHODS: EDITION JP 2 was a randomised, open-label, phase 3 study. Following a 6-month treatment period, participants continued receiving previously assigned once daily Gla-300 or Gla-100, plus oral anti-hyperglycaemic drugs, in a 6-month extension period. Glycaemic control, hypoglycaemia and adverse events were assessed. RESULTS: The 12-month completion rate was 88% for Gla-300 and 96% for Gla-100, with comparable reasons for discontinuation. Mean HbA1c decrease from baseline to month 12 was 0.3% in both groups. Annualised rates of confirmed (≤3.9mmol/L [≤70mg/dL]) or severe hypoglycaemia were lower with Gla-300 than Gla-100 (nocturnal [00:00-05:59h]: rate ratio 0.41; 95% confidence interval: 0.18 to 0.92; anytime [24h]: rate ratio 0.64; 95% confidence interval: 0.44 to 0.94). Cumulative number of hypoglycaemic events was lower with Gla-300 than Gla-100. Adverse event profiles were comparable between treatments. CONCLUSION: Over 12 months, Gla-300-treated participants achieved sustained glycaemic control and experienced less hypoglycaemia, particularly at night, versus Gla-100, supporting 6-month results.

Impact of renal transplantation on glucose tolerance in Japanese recipients with impaired glucose tolerance.

AIMS: To investigate changes in glucose tolerance, insulin secretion and insulin sensitivity in Japanese recipients before and 1 year after renal transplantation. METHODS: We conducted a study of Japanese recipients without diabetes who underwent renal transplantation at Hokkaido University Hospital. A 75-g oral glucose tolerance test was performed before and 1 year after renal transplantation in these recipients. Insulin sensitivity was estimated using the Matsuda index and homeostasis model assessment of insulin resistance (HOMA-IR). Insulin secretion was evaluated based on the insulin secretion sensitivity index-2 (ISSI-2). RESULTS: Of the 62 renal transplant recipients, 31 were diagnosed as having impaired glucose tolerance before transplantation. Among these 31 recipients, after 1 year, four had developed new-onset diabetes after transplantation, and nine had impaired glucose tolerance. Unexpectedly, 18 changed from impaired to normal glucose tolerance. When these recipients with impaired glucose tolerance were classified into a non-amelioration group and an amelioration group, the ISSI-2 was significantly reduced, with no significant changes in the Matsuda index or HOMA-IR, in the non-amelioration group 1 year after renal transplantation. By contrast, ISSI-2 and Matsuda index values were significantly increased, with no significant changes in HOMA-IR values in the amelioration group. CONCLUSIONS: More than half of Japanese renal transplant recipients with impaired glucose tolerance had normal glucose tolerance 1 year after renal transplantation. These results suggest that an increase in insulin secretion and whole insulin sensitivity was associated with improvement in glucose tolerance in these recipients.

New insulin glargine 300 U/ml versus glargine 100 U/ml in Japanese people with type 2 diabetes using basal insulin and oral antihyperglycaemic drugs: glucose control and hypoglycaemia in a randomized controlled trial (EDITION JP 2).

AIMS: To compare the efficacy and safety of insulin glargine 300 U/ml (Gla-300) with glargine 100 U/ml (Gla-100) in Japanese people with type 2 diabetes using basal insulin plus oral antihyperglycaemic drug(s) [OAD(s)]. METHODS: The EDITION JP 2 study (NCT01689142) was a 6-month, multicentre, open-label, phase III study. Participants (n = 241, male 61%, mean diabetes duration 14 years, mean weight 67 kg, mean body mass index 25 kg/m(2), mean glycated haemoglobin (HbA1c) 8.02 %, mean basal insulin dose 0.24 U/kg/day) were randomized to Gla-300 or Gla-100, while continuing OAD(s). Basal insulin was titrated to target fasting self-monitored plasma glucose 4.4-5.6 mmol/l. The primary efficacy endpoint was HbA1c change over 6 months. Safety endpoints included hypoglycaemia and weight change. RESULTS: Gla-300 was non-inferior to Gla-100 for HbA1c reduction [least squares (LS) mean difference 0.10 (95% confidence interval [CI] -0.08, 0.27) %]. The mean HbA1c at month 6 was 7.56 and 7.52 % with Gla-300 and Gla-100, respectively. Nocturnal confirmed (≤3.9 mmol/l) or severe hypoglycaemia risk was 38% lower with Gla-300 versus Gla-100 [relative risk 0.62 (95% CI 0.44, 0.88)]; annualized rates were 55% lower at night [rate ratio 0.45 (95% CI 0.21, 0.96)] and 36% lower at any time [24 h; rate ratio 0.64 (95% CI 0.43, 0.96)]. Severe hypoglycaemia was infrequent. A significant between-treatment difference in weight change favoured Gla-300 [LS mean difference -1.0 (95% CI -1.5, -0.5) kg; p = 0.0003]. Adverse event rates were comparable between groups. CONCLUSIONS: Japanese people with type 2 diabetes using basal insulin plus OAD(s) experienced less hypoglycaemia with Gla-300 than with Gla-100, while glycaemic control did not differ.

Sitagliptin improves glycaemic excursion after a meal or after an oral glucose load in Japanese subjects with impaired glucose tolerance.

AIMS: To evaluate the efficacy and tolerability of sitagliptin in subjects with impaired glucose tolerance (IGT). METHODS: In a double-blind, parallel-group study, 242 Japanese subjects with IGT, determined by a 75-g oral glucose tolerance test (OGTT) at week -1, were randomized (1 : 1 : 1) to placebo (n = 83), sitagliptin 25 mg (n = 82) or 50 mg (n = 77) once daily for 8 weeks. Glycaemic variables were assessed using another OGTT at week 7 and meal tolerance tests (MTTs) at weeks 0 and 8. Primary and secondary endpoints were percent change from baseline in glucose total area under the curve 0-2 h (AUC(0 -2 h)) during the MTT and OGTT, respectively. RESULTS: Least squares mean percent change from baseline in glucose AUC(0 -2 h) during the MTT were -2.4, -9.5 and -11.5%, and during the OGTT were -3.7, -21.4 and -20.1% with placebo, sitagliptin 25 mg once daily, and 50 mg once daily, respectively (p < 0.001 for either sitagliptin dose vs placebo in both tests). Sitagliptin treatment enhanced early insulin response during the OGTT and decreased total insulin response, assessed as the total AUC(0 -2 h) during the MTT. Sitagliptin treatment also suppressed glucagon response during the MTT. The incidence of adverse events, including hypoglycaemia, was low and generally similar in all treatment groups. CONCLUSIONS: Treatment with sitagliptin significantly reduced glucose excursions during both an MTT and an OGTT; this effect was associated with an increase in early insulin secretion after oral glucose loading as well as a blunted glucagon response during an MTT. Sitagliptin was generally well tolerated in subjects with IGT.

Impact of underlying diabetes and presence of lung cavities on treatment outcomes in patients with pulmonary tuberculosis.

AIMS: We investigated the effects of diabetes and the presence of lung cavities on treatment outcomes in patients with pulmonary tuberculosis. METHODS: We conducted a retrospective review of the clinical records of all consecutive patients admitted to the Kanagawa Cardiovascular and Respiratory Centre with the diagnosis of pulmonary tuberculosis. The study outcomes examined were time to sputum culture conversion and percentage of patients with sputum culture conversion by the time 2 months of treatment, and these outcomes were compared between patients with and without diabetes. RESULTS: Of the 260 patients enrolled in the study, 69 were diagnosed as having diabetes mellitus, while the remaining 191 did not have diabetes. The percentage of patients with cavities was higher in the patients with diabetes (71.0%) than in those without (45.5%; P = 0.0003). The time to sputum culture conversion was significantly longer in the patients with diabetes than in those without (P = 0.0005), and the percentage of patients with a positive sputum culture at 2 months was higher in the patients with diabetes (43.5%) than in those without (18.8%; P = 0.0001). Multivariate analyses revealed that the presence/absence of lung cavities was a more important determinant of treatment outcomes than the presence/absence of diabetes. CONCLUSIONS: The presence of lung cavities was found to be a more important determinant of the treatment outcomes than that of diabetes per se in patients with pulmonary tuberculosis.

Metformin prevents liver tumorigenesis induced by high-fat diet in C57Bl/6 mice.

The prevalence of nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH) is increasing with the growing epidemics of obesity and diabetes. NAFLD encompasses a clinicopathologic spectrum of disease ranging from isolated hepatic steatosis to NASH, which is a more aggressive form of fatty liver disease, to cirrhosis and, finally, hepatocellular carcinoma (HCC). The exact mechanism behind the development of HCC in NASH remains unclear; however, it has been established that hepatic steatosis is the important risk factor in the development of HCC. Metformin has recently drawn attention because of its potential antitumor effect. Here, we investigated the effects of metformin on high-fat diet (HFD)-induced liver tumorigenesis, using a mouse model of NASH and liver tumor. Metformin prevented long-term HFD-induced liver tumorigenesis in C57Bl/6 mice. Of note, metformin failed to protect against liver tumorigenesis in mice that had already begun to develop NAFLD. Metformin improved short-term HFD-induced fat accumulation in the liver, associated with the suppression of adipose tissue inflammation. Collectively, these results suggest that metformin may prevent liver tumorigenesis via suppression of liver fat accumulation in the early stage, before the onset of NAFLD, which seems to be associated with a delay in the development of inflammation of the adipose tissue.

Long-term efficacy and safety of sitagliptin in the treatment of Japanese Type 2 diabetes (ASSET-K1) to a target of HbA1c <7%.

BACKGROUND: Few studies have investigated the factors related to improvement and maintenance of glycemic control with sitagliptin in Type 2 diabetes (T2D) patients. AIM: To identify factors contributing to reaching and maintaining glycated hemoglobin (HbA1c) <7% with sitagliptin in Japanese T2D patients. SUBJECTS AND METHODS: This study included 1327 patients who were: taking sitagliptin as monotherapy; switched to sitagliptin; or taking sitagliptin in combination therapy. At baseline and 1, 3, 6, and 12 months after starting sitagliptin, weight, body mass index (BMI), HbA1c, fasting plasma glucose (FPG), and post-prandial plasma glucose (PPG) were measured. The subjects were divided into a group that achieved HbA1c<7% at 12 months, a poor control group (HbA1c≥8% at 12 months), and a discontinued group. Multiple regression analysis was performed to identify factors contributing to long-term control and maintenance with sitagliptin treatment. RESULTS: HbA1c decreased significantly from 8.0% at baseline to 7.3%, but weight was unchanged. FPG and PPG improved significantly. The HbA1c<7% group had a significantly higher age and a signifi cant ly lower BMI at baseline than the HbA1c≥8% group and the discontinued group. On multivariate regression analysis, baseline HbA1c, baseline BMI, and Δbody weight after 12 months were significantly related to HbA1c reduction. The most common adverse event was hypoglycemia, and the most common adverse event responsible for discontinuation was constipation. CONCLUSIONS: HbA1c<7.0% was achieved in 31% of T2D patients who had poor control with conventional treatment. Weight management is important for maintaining good long-term control with sitagliptin.

Comparative study of sitagliptin with pioglitazone in Japanese type 2 diabetic patients: the COMPASS randomized controlled trial.

AIMS: To compare the efficacy and safety of these two agents and the impact on surrogate markers related to diabetic complications in Japanese type 2 diabetic patients. METHODS: In a multicenter, open-label trial, 130 patients whose diabetes had been inadequately controlled (HbA1c, 6.9-9.5%) with metformin and/or sulphonylurea were randomly assigned to a sitagliptin group (50 mg/day) or a pioglitazone group (15 mg/day) and were followed up for 24 weeks. At 16 weeks, if the patient's HbA1c level was ≥6.5%, the dose of sitagliptin or pioglitazone was increased up to 100 or 30 mg/day, respectively. Main outcome measure was the difference in the mean changes in the HbA1c level from baseline at 24 weeks between these two groups. RESULTS: Of the 130 patients who were enrolled, 115 subjects (sitagliptin group: 58 patients, pioglitazone group: 57 patients) completed this trial. At 0 weeks, the mean HbA1c level was 7.47 ± 0.66% in the sitagliptin group and 7.40 ± 0.61% in the pioglitazone group. At 24 weeks, the mean changes in the HbA1c level from baseline were -0.86 ± 0.63% versus -0.58 ± 0.68% (p = 0.024). Hypoglycaemia (2 patients, 3.4% vs. 2 patients, 3.5%), gastrointestinal symptoms (3 patients, 5.2% vs. 1 patient, 1.8%) and pretibial oedema (0 patients, 0% vs. 39 patients, 68.4%, p < 0.001) were observed for 24 weeks. CONCLUSIONS: Sitagliptin was not only more tolerable, but also more effective than pioglitazone in Japanese type 2 diabetic patients who had been treated with metformin and/or sulphonylurea.

Protection from non-alcoholic steatohepatitis and liver tumourigenesis in high fat-fed insulin receptor substrate-1-knockout mice despite insulin resistance.

AIMS/HYPOTHESIS: Epidemiological studies have revealed that obesity and diabetes mellitus are independent risk factors for the development of non-alcoholic steatohepatitis (NASH) and hepatocellular carcinoma. However, the debate continues on whether insulin resistance as such is directly associated with NASH and liver tumourigenesis. Here, we investigated the incidence of NASH and liver tumourigenesis in Irs1 ( -/- ) mice subjected to a long-term high-fat (HF) diet. Our hypothesis was that hepatic steatosis, rather than insulin resistance may be related to the pathophysiology of these conditions. METHODS: Mice (8 weeks old, C57Bl/6J) were given free access to standard chow (SC) or an HF diet. The development of NASH and liver tumourigenesis was evaluated after mice had been on the above-mentioned diets for 60 weeks. Similarly, Irs1 ( -/- ) mice were also subjected to an HF diet for 60 weeks. RESULTS: Long-term HF diet loading, which causes obesity and insulin resistance, was sufficient to induce NASH and liver tumourigenesis in the C57Bl/6J mice. Obesity and insulin resistance were reduced by switching mice from the HF diet to SC, which also protected these mice against the development of NASH and liver tumourigenesis. However, compared with wild-type mice fed the HF diet, Irs1 ( -/- ) mice fed the HF diet were dramatically protected against NASH and liver tumourigenesis despite the presence of severe insulin resistance and marked postprandial hyperglycaemia. CONCLUSIONS/INTERPRETATION: IRS-1 inhibition might protect against HF diet-induced NASH and liver tumourigenesis, despite the presence of insulin resistance.

Control of beta cell function and proliferation in mice stimulated by small-molecule glucokinase activator under various conditions.

AIMS/HYPOTHESIS: We investigated changes in the expression of genes involved in beta cell function and proliferation in mouse islets stimulated with glucokinase activator (GKA) in order to elucidate the mechanisms by which GKA stimulates beta cell function and proliferation. METHODS: Islets isolated from mice were used to investigate changes in the expression of genes related to beta cell function and proliferation stimulated by GKA. In addition, Irs2 knockout (Irs2 (-/-)) mice on a high-fat diet or a high-fat diet containing GKA were used to investigate the effects of GKA on beta cell proliferation in vivo. RESULTS: In wild-type mice, Irs2 and Pdx1 expression was increased by GKA. In Irs2 (-/-) mice, GKA administration increased the glucose-stimulated secretion of insulin and Pdx1 expression, but not beta cell proliferation. It was particularly noteworthy that oxidative stress inhibited the upregulation of the Irs2 and Pdx1 genes induced by GKA. Moreover, whereas neither GKA alone nor exendin-4 alone upregulated the expression of Irs2 and Pdx1 in the islets of db/db mice, prior administration of exendin-4 to the mice caused GKA to increase the expression of these genes. CONCLUSIONS/INTERPRETATION: GKA-stimulated IRS2 production affected beta cell proliferation but not beta cell function. Oxidative stress diminished the effects of GKA on the changes in expression of genes involved in beta cell function and proliferation. A combination of GKA and an incretin-related agent might therefore be effective in therapy.

Crucial role of insulin receptor substrate-2 in compensatory beta-cell hyperplasia in response to high fat diet-induced insulin resistance.

In type 2 diabetes, there is a defect in the regulation of functional beta-cell mass to overcome high-fat (HF) diet-induced insulin resistance. Many signals and pathways have been implicated in beta-cell function, proliferation and apoptosis. The co-ordinated regulation of functional beta-cell mass by insulin signalling and glucose metabolism under HF diet-induced insulin-resistant conditions is discussed in this article. Insulin receptor substrate (IRS)-2 is one of the two major substrates for the insulin signalling. Interestingly, IRS-2 is involved in the regulation of beta-cell proliferation, as has been demonstrated using knockout mice models. On the other hand, in an animal model for human type 2 diabetes with impaired insulin secretion because of insufficiency of glucose metabolism, decreased beta-cell proliferation was observed in mice with beta-cell-specific glucokinase haploinsufficiency (Gck(+/) (-)) fed a HF diet without upregulation of IRS-2 in beta-cells, which was reversed by overexpression of IRS-2 in beta-cells. As to the mechanism underlying the upregulation of IRS-2 in beta-cells, glucose metabolism plays an important role independently of insulin, and phosphorylation of cAMP response element-binding protein triggered by calcium-dependent signalling is the critical pathway. Downstream from insulin signalling via IRS-2 in beta-cells, a reduction in FoxO1 nuclear exclusion contributes to the insufficient proliferative response of beta-cells to insulin resistance. These findings suggest that IRS-2 is critical for beta-cell hyperplasia in response to HF diet-induced insulin resistance.

Comparison of pre- vs. postmeal administration of miglitol for 3 months in type 2 diabetic patients.

AIM: alpha-Glucosidase inhibitors (alphaGIs) primarily modify postprandial plasma glucose levels and should be taken just before meals. We previously demonstrated that a single administration of miglitol within 30 min after the start of a meal was equally effective as when administered just before a meal. We here compared pre- vs. postmeal administration of miglitol for 3 months in type 2 diabetic patients. METHODS: Thirty-one type 2 diabetic outpatients who had never been treated with insulin injections or alphaGIs were randomized to two groups: patients in group A were asked to take miglitol just before meals, while patients in group B were asked to take miglitol after meals. We measured 1,5-anhydroglucitol (1,5-AG) and HbA(1C) levels in these patients. RESULTS: The administration of miglitol after meals for a 3-month period decreased HbA(1C) and increased 1,5-AG levels to the same extent as when administered just before meals. The incidence of adverse effects seemed to be unrelated to the timing of the miglitol administration. CONCLUSIONS: Our results suggest that if patients have difficulty remembering to take miglitol just before meal, they should be instructed to take the medicine together with other medicine(s) after the meal; this instruction may improve the treatment compliance of diabetic patients.

Hepatitis C virus directly associates with insulin resistance independent of the visceral fat area in nonobese and nondiabetic patients.

Insulin resistance (IR) is known to be associated with the visceral adipose tissue area. Elucidation of the relationship between hepatitis C virus (HCV) and IR is of great clinical relevance, because IR promotes liver fibrosis. In this study, we tested the hypothesis that HCV infection by itself may promote IR. We prospectively evaluated 47 patients with chronic HCV infection who underwent liver biopsy. Patients with obesity, type 2 diabetes mellitus (DM), or a history of alcohol consumption were excluded. IR was estimated by calculation of the modified homeostasis model of insulin resistance (HOMA-IR) index. Abdominal fat distribution was determined by computed tomography. Fasting blood glucose levels were within normal range in all the patients. The results of univariate analysis revealed a significant correlation between the quantity of HCV-RNA and the HOMA-IR (r = 0.368, P = 0.0291). While a significant correlation between the visceral adipose tissue area and the HOMA-IR was also observed in the 97 control, nondiabetic, non-HCV-infected patients (r = 0.398, P < 0.0001), no such significant correlation between the visceral adipose tissue area and the HOMA-IR (r = 0.124, P = 0.496) was observed in the patients with HCV infection. Multiple regression analysis with adjustment for age, gender and visceral adipose tissue area revealed a significant correlation between the HCV-RNA and the HOMA-IR (P = 0.0446). HCV is directly associated with IR in a dose-dependent manner, independent of the visceral adipose tissue area. This is the first report to demonstrate the direct involvement of HCV and IR in patients with chronic HCV infection.

Peroxisome proliferator-activated receptor-gamma haploinsufficiency enhances B cell proliferative responses and exacerbates experimentally induced arthritis.

Peroxisome proliferator-activated receptor-gamma (PPAR gamma) controls adipogenesis and glucose metabolism. It was reported recently that PPAR gamma activation by its agonistic ligands modifies lymphocyte function. Since synthetic ligands are known to exert their effect via PPAR gamma-dependent and -independent pathways, we examined the physiological role of PPAR gamma in lymphocytes by using heterozygote mutant mice in which one allele of PPAR gamma is deleted (PPAR gamma(+/-)). In contrast to T cells, which did not exhibit a significant difference, B cells from PPAR gamma(+/-) showed an enhanced proliferative response to stimulation by either lipopolysaccharide or cross-linking of antigen receptors. Dysregulation of the NF-kappa B pathway in B cells from PPAR gamma(+/-) was indicated by spontaneous NF-kappa B activation, as well as increased I kappa B alpha phosphorylation and gel-shift activity following LPS stimulation. Mice primed with either ovalbumin or methylated BSA also showed enhanced antigen-specific immune response of both T and B cells, an immunological abnormality that exacerbated antigen-induced arthritis. These findings indicate that PPAR gamma plays a critical role in the control of B cell response and imply a role in diseases in which B cell hyperreactivity is involved, such as arthritis and autoimmunity.

Inhibition of RXR and PPARgamma ameliorates diet-induced obesity and type 2 diabetes.

PPARgamma is a ligand-activated transcription factor and functions as a heterodimer with a retinoid X receptor (RXR). Supraphysiological activation of PPARgamma by thiazolidinediones can reduce insulin resistance and hyperglycemia in type 2 diabetes, but these drugs can also cause weight gain. Quite unexpectedly, a moderate reduction of PPARgamma activity observed in heterozygous PPARgamma-deficient mice or the Pro12Ala polymorphism in human PPARgamma, has been shown to prevent insulin resistance and obesity induced by a high-fat diet. In this study, we investigated whether functional antagonism toward PPARgamma/RXR could be used to treat obesity and type 2 diabetes. We show herein that an RXR antagonist and a PPARgamma antagonist decrease triglyceride (TG) content in white adipose tissue, skeletal muscle, and liver. These inhibitors potentiated leptin's effects and increased fatty acid combustion and energy dissipation, thereby ameliorating HF diet-induced obesity and insulin resistance. Paradoxically, treatment of heterozygous PPARgamma-deficient mice with an RXR antagonist or a PPARgamma antagonist depletes white adipose tissue and markedly decreases leptin levels and energy dissipation, which increases TG content in skeletal muscle and the liver, thereby leading to the re-emergence of insulin resistance. Our data suggested that appropriate functional antagonism of PPARgamma/RXR may be a logical approach to protection against obesity and related diseases such as type 2 diabetes.

The mechanisms by which both heterozygous peroxisome proliferator-activated receptor gamma (PPARgamma) deficiency and PPARgamma agonist improve insulin resistance.

Peroxisome proliferator-activated receptor (PPAR) gamma is a ligand-activated transcription factor and a member of the nuclear hormone receptor superfamily that is thought to be the master regulator of fat storage; however, the relationship between PPARgamma and insulin sensitivity is highly controversial. We show here that supraphysiological activation of PPARgamma by PPARgamma agonist thiazolidinediones (TZD) markedly increases triglyceride (TG) content of white adipose tissue (WAT), thereby decreasing TG content of liver and muscle, leading to amelioration of insulin resistance at the expense of obesity. Moderate reduction of PPARgamma activity by heterozygous PPARgamma deficiency decreases TG content of WAT, skeletal muscle, and liver due to increased leptin expression and increase in fatty acid combustion and decrease in lipogenesis, thereby ameliorating high fat diet-induced obesity and insulin resistance. Moreover, although heterozygous PPARgamma deficiency and TZD have opposite effects on total WAT mass, heterozygous PPARgamma deficiency decreases lipogenesis in WAT, whereas TZD stimulate adipocyte differentiation and apoptosis, thereby both preventing adipocyte hypertrophy, which is associated with alleviation of insulin resistance presumably due to decreases in free fatty acids, and tumor necrosis factor alpha, and up-regulation of adiponectin, at least in part. We conclude that, although by different mechanisms, both heterozygous PPARgamma deficiency and PPARgamma agonist improve insulin resistance, which is associated with decreased TG content of muscle/liver and prevention of adipocyte hypertrophy.

Increased expression of the sterol regulatory element-binding protein-1 gene in insulin receptor substrate-2(-/-) mouse liver.

Insulin receptor substrate (IRS)-2(-/-) mice develop diabetes because of insulin resistance in the liver and failure to undergo beta-cell hyperplasia. Here we show by DNA chip microarray analysis that expression of the sterol regulatory element-binding protein (SREBP)-1 gene, a downstream target of insulin, was paradoxically increased in 16-week-old IRS-2(-/-) mouse liver, where insulin-mediated intracellular signaling events were substantially attenuated. The expression of SREBP-1 downstream genes, such as the spot 14, ATP citrate-lyase, and fatty acid synthase genes, was also increased. Increased liver triglyceride content in IRS-2(-/-) mice assures the physiological importance of SREBP-1 gene induction. IRS-2(-/-) mice showed leptin resistance; low dose leptin administration, enough to reduce food intake and body weight in wild-type mice, failed to do so in IRS-2(-/-) mice. Interestingly, high dose leptin administration reduced SREBP-1 expression in IRS-2(-/-) mouse liver. Thus, IRS-2 gene disruption results in leptin resistance, causing an SREBP-1 gene induction, obesity, fatty liver, and diabetes.

The fat-derived hormone adiponectin reverses insulin resistance associated with both lipoatrophy and obesity.

Adiponectin is an adipocyte-derived hormone. Recent genome-wide scans have mapped a susceptibility locus for type 2 diabetes and metabolic syndrome to chromosome 3q27, where the gene encoding adiponectin is located. Here we show that decreased expression of adiponectin correlates with insulin resistance in mouse models of altered insulin sensitivity. Adiponectin decreases insulin resistance by decreasing triglyceride content in muscle and liver in obese mice. This effect results from increased expression of molecules involved in both fatty-acid combustion and energy dissipation in muscle. Moreover, insulin resistance in lipoatrophic mice was completely reversed by the combination of physiological doses of adiponectin and leptin, but only partially by either adiponectin or leptin alone. We conclude that decreased adiponectin is implicated in the development of insulin resistance in mouse models of both obesity and lipoatrophy. These data also indicate that the replenishment of adiponectin might provide a novel treatment modality for insulin resistance and type 2 diabetes.

Simultaneous determination of the histamine H1-receptor antagonist ebastine and its two metabolites, carebastine and hydroxyebastine, in human plasma using high-performance liquid chromatography.

Ebastine (CAS 90729-43-4) is an antiallergic agent which selectively and potently blocks histamine H1-receptors in vivo. A simple and sensitive high-performance liquid chromatography (HPLC) method is described for the simultaneous determination of ebastine and its two oxidized metabolites, carebastine (CAS 90729-42-3) and hydroxyebastine (M-OH), in human plasma. After a pretreatment of plasma sample by solid-phase extraction, ebastine and its metabolites were analyzed on an HPLC system with ultraviolet detection at 254 nm. Chromatography was performed on a cyano column (250x4.0 mm I.D.) at 40 degrees C with the mobile phase of acetonitrile-methanol-0.012 M ammonium acetate buffer (20:30:48, v/v/v) at a flow rate of 1.2 ml/min. Accurate determinations were possible over the concentration range of 3-1000 ng/ml for the three compounds using 1 ml plasma samples. The intra- and inter-day assay accuracy of this method were within 100+/-15% of nominal values and the precision did not exceed 12.4% of relative standard deviation. The lower limits of quantitation were 3 ng/ml for ebastine and its metabolites in human plasma. This method was satisfactorily applied to the determination of ebastine and its two oxidized metabolites in human plasma after oral administration of ebastine.