ABSTRACT
AIM:To investigate the role of peroxisome proliferator-activated receptor β( PPARβ)-nitric oxide (NO) signal pathway in cardiomyocyte hypertrophy induced by high glucose (25.5 mmol/L) and insulin (0.1 μmol/L) ( HGI) .METHODS: The cardiomyocyte hypertrophy was characterized in rat primary cardiomyocytes by measuring the cell surface area, protein content, and the mRNA expression of atrial natriuretic factor (ANF).The mRNA and protein ex-pression were measured by real-time PCR and Western blotting , respectively .The activity of NO synthase ( NOS) and NO content were measured by a reagent kit through ultraviolet spectroscopy .RESULTS:HGI induced profound change of hy-pertrophic morphology , and significantly increased the cell surface area , protein content and mRNA expression of ANF (P<0.01), but decreased the expression of PPARβat mRNA and protein levels (P<0.05).At the same time, the ex-pression of inducible NOS (iNOS) was obviously elevated (P<0.01), which occurred in parallel with the rising NOS ac-tivity and NO concentration (P<0.01).GW0742 (1 μmol/L), a selective PPARβagonist, inhibited the cardiomyocyte hypertrophy induced by HGI ( P<0.01 ) , and up-regulated the expression of PPARβat both mRNA and protein levels . Meanwhile, GW0742 also inhibited the increases in iNOS expression , NOS activity, and NO content induced by HGI , which were abolished by GSK0660 (1 μmol/L), a selective PPARβantagonist (P<0.01).CONCLUSION: PPARβdown-regulation and the following iNOS-NO activation are involved in the cardiomyocyte hypertrophy induced by HGI .
ABSTRACT
AIM The effects of GW501516, a peroxisome proliferator-activated receptor β (PPARβ) agonist, in long term diet induced obesity (DIO, high fat and maltose diet for 4 months) mice were evaluated, and the efficacy of GW501516 against insulin resistance and the involved mechanism was investigated. METHODSMice were divided into 3 groups: normal control, DIO model and DIO model+GW501516. GW501516 (10 mg·kg-1·d-1) was administered by ig once a day for 14 d. During the treatment, body weight and food intake were monitored every other day. The oral glucose tolerance test, and the serum biochemical parameters including the serum triglyceride, total cholesterol and high density lipoprotein cholesterol (HDL-C) levels were measured according to the specifications. To confirm the GW501516-mediated PPARβ activation, the mRNA levels of downstream genes related to glucose, lipid metabolism and energy expenditure was measured. RESULTS GW501516 treatment effectively improved the glucose intolerance, increased the area under the glucose curves[DIO model, (32.4±4.6) mmol·h·L-1 compared with DIO model+GW501516, (23.4±2.5) mmol·h·L-1, n=7-8, P<0.05], normalized the fasted blood glucose, and increased serum HDL-C level, besides, histological analysis revealed the decreased hepatic lipid accumulation and hypertrophy of hepatocyte in DIO mice. Moreover, RT-PCR results indicated that carnitine palmitoyltransferase 1b, uncoupling protein 2, uncoupling protein 3 and glucose transport protein 4 were all upregulated. CONCLUSIONGW501516 significantly ameliorates glucose intolerance, decreases fasted blood glucose and hepatic steatosis, which might be related to ① the enhancement of fatty acid oxidation and energy uncoupling in muscle, and ②the improvement of insulin-stimulated glucose transportation in skeletal muscle in the long term DIO mice.