Hikari Suzuki

Treatment with SRT1720, a SIRT1 activator, ameliorates fatty liver with reduced expression of lipogenic enzymes in MSG mice

Nonalcoholic fatty liver disease (NAFLD) is an abnormal liver metabolism often observed with insulin resistance and metabolic syndrome. Calorie restriction is a useful treatment for NAFLD and reportedly prolongs the life spans of several species in which sirtuin plays an important role. In this study, we examined whether the activation of SIRT1, a mammalian ortholog of sirtuin, may ameliorate the development of NAFLD. Monosodium glutamate (MSG) mice, which exhibited obesity and insulin resistance, were treated with SRT1720, a specific SIRT1 activator from the age of 6-16 wk. Sixteen-week-old MSG mice exhibited increased liver triglyceride content and elevated levels of aminotransferase. SRT1720 treatment significantly reduced these levels without affecting body weight or food intake. These results suggested that the administration of SRT1720 ameliorated the development of NAFLD in MSG mice. The expressions of lipogenic genes, such as sterol regulatory element-binding protein-1c, acetyl-CoA carboxylase, and fatty acid synthase, and the serum lipid profiles, including free fatty acids, were elevated in MSG mice and were reduced by SRT1720 treatment. SRT1720 treatment also reduced the expressions of lipogenic genes in cultured HepG2 cells. Furthermore, SRT1720 treatment decreased the expressions of marker genes for oxidative stress and inflammatory cytokines in the liver of MSG mice. Taken together, SRT1720 treatment may reduce liver lipid accumulation, at least in part, by directly reducing the expressions of lipogenic genes. The reduction of oxidative stress and inflammation may also be involved in the amelioration of NAFLD.

Telmisartan improves insulin resistance and modulates adipose tissue macrophage polarization in high-fat-fed mice.

Diet-induced obesity is reported to induce a phenotypic switch in adipose tissue macrophages from an antiinflammatory M2 state to a proinflammatory M1 state. Telmisartan, an angiotensin II type 1 receptor blocker and a peroxisome proliferator-activated receptor-γ agonist, reportedly has more beneficial effects on insulin sensitivity than other angiotensin II type 1 receptor blockers. In this study, we studied the effects of telmisartan on the adipose tissue macrophage phenotype in high-fat-fed mice. Telmisartan was administered for 5 wk to high-fat-fed C57BL/6 mice. Insulin sensitivity, macrophage infiltration, and the gene expressions of M1 and M2 markers in visceral adipose tissues were then examined. An insulin- or a glucose-tolerance test showed that telmisartan treatment improved insulin resistance, decreasing the body weight gain, visceral fat weight, and adipocyte size without affecting the amount of energy intake. Telmisartan reduced the mRNA expression of CD11c and TNF-α, M1 macrophage markers, and significantly increased the expressions of M2 markers, such as CD163, CD209, and macrophage galactose N-acetyl-galactosamine specific lectin (Mgl2), in a quantitative RT-PCR analysis. A flow cytometry analysis showed that telmisartan decreased the number of M1 macrophages in visceral adipose tissues. In conclusion, telmisartan improves insulin sensitivity and modulates adipose tissue macrophage polarization to an antiinflammatory M2 state in high-fat-fed mice.

Angiotensin II enhances the increase in monocyte chemoattractant protein-1 production induced by tumor necrosis factor-α from 3T3-L1 preadipocytes

Monocyte chemoattractant protein-1 (MCP-1) and angiotensin II (Ang II) in adipose tissue are thought to induce systemic insulin resistance in rodents; but the precise mechanism is not fully clarified. We examined the mechanism of Ang II-induced and/or tumor necrosis factor-alpha (TNF-alpha)-induced MCP-1 production from 3T3-L1 preadipocytes. The MCP-1 protein and MCP-1 mRNA expression in 3T3-L1 preadipocytes were increased significantly by stimulation with TNF-alpha. We found no significant increase in MCP-1 concentrations by Ang II alone; but it enhanced the TNF-alpha-induced MCP-1 mRNA expression in a dose-dependent manner. Then, we examined the effect of Ang II and/or TNF-alpha on phosphorylation of extracellular signal-regulated kinase (ERK), p38MAPK, and IkappaB-alpha. Ang II and TNF-alpha clearly enhanced ERK and p38MAPK phosphorylation. IkappaB-alpha phosphorylation was enhanced by TNF-alpha, but not by Ang II. The MCP-1 mRNA expression induced by TNF-alpha and co-stimulation with Ang II was inhibited by either ERK inhibitor, p38MAPK inhibitor or NF-kappaB inhibitor. Moreover, Ang II enhanced the activation of AP-1 (c-fos) induced by TNF-alpha. Our results suggest that Ang II may serve as an additional stimulus on the TNF-alpha-induced MCP-1 production through the ERK-and p38MAPK-dependent pathways probably due to AP-1 activation.

Secretory units of islets in transplantation index is a useful predictor of insulin requirement in Japanese type 2 diabetic patients

The objective of the present study was to clarify the validity of β‐cell function‐related parameters for predicting the insulin requirement of Japanese type 2 diabetic patients.

A novel model of insulin-dependent diabetes with renal and retinal lesions by transgenic expression of CaMKIIα (Thr286Asp) in pancreatic β-cells

The activation of Ca2+/calmodulin‐dependent protein kinase II (CaMKII) in pancreatic β‐cells has been thought to play a central role in Ca2+‐mediated insulin secretion. However, the physiological and pathological significance of CaMKII activation in pancreatic β‐cells has never been investigated in vivo.

A cluster randomized trial on the effect of a multifaceted intervention improved the technical quality of diabetes care by primary care physicians: The Japan Diabetes Outcome Intervention Trial-2 (J-DOIT2).

To evaluate the effect of multifaceted interventions using the Achievable Benchmark of Care (ABC) method for improving the technical quality of diabetes care in primary care settings.

Depressive symptoms, not completing a depression screening questionnaire, and risk of poor compliance with regular primary care visits in patients with type 2 diabetes: the Japan Diabetes Outcome Intervention Trial 2 (J-DOIT2) study group.

OBJECTIVES To explore the association between depressive symptoms as measured by the Center for Epidemiologic Studies Depression Scale or not completing the questionnaire and subsequent risk of poor compliance with regular visits to primary care physician in patients with type 2 diabetes. METHODS Using data from patients with type 2 diabetes who participated in the Japan Diabetes Outcome Intervention Trial 2 (J-DOIT2) Pilot Study, which was conducted at primary care settings, we examined the association between depressive symptoms or not completing the questionnaire and risk of poor compliance with regular visits as an event. RESULTS Among 1 584 patients who participated in the J-DOIT2 Pilot Study, we excluded 140 who did not meet inclusion criteria or who declined participation after randomization, leaving 1 444 for entry in the present analysis. During 1 409 person-years of follow-up (median 1 year), 90 events were observed (incidence rate 63.9/1 000 person-years). The multivariable-adjusted hazard ratio of poor compliance with regular visits in those having depressive symptoms was 1.23 (95% CI: 0.46-3.31). In contrast, the multivariable-adjusted hazard ratio of poor compliance in those not completing the questionnaire was 2.26 (95% CI: 1.94-2.63). CONCLUSION Not completing a questionnaire was significantly associated with an increased risk of poor compliance with the maintenance of regular visits to a primary care physician in patients with type 2 diabetes. Patients who do not comply with questionnaire surveys require increased attention to ensure their compliance with regular visits, and thereby ensure better diabetes outcomes.

Characterization of diabetic nephropathy in CaM kinase IIα (Thr286Asp) transgenic mice

Detailed studies were performed on diabetic kidneys derived from transgenic mice overexpressing the mutant form (Thr286Asp) of Ca(2+)/calmodulin-dependent protein kinase IIalpha (CaM kinase IIalpha) in pancreatic beta-cells. Kidney weight/body weight ratio, urinary albumin/creatinine ratio, serum BUN level, and mesangial/glomerular area ratio were all significantly higher in transgenic mice than in wild-type mice. cDNA microarray analysis revealed 17 up-regulated genes and 12 down-regulated genes in transgenic kidney. Among up-regulated genes, cyclin D2 (6.70-fold) and osteopontin (2.35-fold) were thought to play important roles in the progression of diabetic nephropathy. Transgenic glomeruli and tubular epithelial cells were strongly stained for osteopontin, a molecule which induces immune response. In quantitative real-time RT-PCR analyses, expressions of not only M1 macrophage marker genes but also M2 macrophage marker genes were elevated in renal cortex of transgenic mice. Overall results indicate that CaM kinase IIalpha (Thr286Asp) transgenic mice serve as an excellent model for diabetic nephropathy.