Reduced Food Intake is the Major Contributor to the Protective Effect of Rimonabant on Islet in Established Obesity-Associated Type 2 Diabetes

PURPOSE: Although the presence of cannabinoid type 1 (CB1) receptor in islets has been reported, the major contributor to the protective effect of rimonabant on islet morphology is unknown. We determined whether the protective effect of rimonabant on pancreatic islet morphology is valid in established diabetes and also whether any effect was independent of decreased food intake. MATERIALS AND METHODS: After diabetes was confirmed, Otsuka Long-Evans Tokushima Fatty rats, aged 32 weeks, were treated with rimonabant (30 mg/kg/d, rimonabant group) for 6 weeks. Metabolic profiles and islet morphology of rats treated with rimonabant were compared with those of controls without treatment (control group), a pair-fed control group, and rats treated with rosiglitazone (4 mg/kg/d, rosiglitazone group). RESULTS: Compared to the control group, rats treated with rimonabant exhibited reduced glycated albumin levels (p<0.001), islet fibrosis (p<0.01), and improved glucose tolerance (p<0.05), with no differences from the pair-fed control group. The retroperitoneal adipose tissue mass was lower in the rimonabant group than those of the pair-fed control and rosiglitazone groups (p<0.05). Rimonabant, pair-fed control, and rosiglitazone groups showed decreased insulin resistance and increased adiponectin, with no differences between the rimonabant and pair-fed control groups. CONCLUSION: Rimonabant had a protective effect on islet morphology in vivo even in established diabetes. However, the protective effect was also reproduced by pair-feeding. Thus, the results of this study did not support the significance of islet CB1 receptors in islet protection with rimonabant in established obesity-associated type 2 diabetes.

Isolation of Density Enrichment Fraction of Adipose-Derived Stem Cells from Stromal Vascular Fraction by Gradient Centrifugation Method

BACKGROUND: Adipose tissues include multipotent cells, the same as bone marrow-derived mesenchymal stem cells. The stromal vascular fractions (SVFs) from adipose tissues represent a heterogeneous cell population. The purpose of this study was to isolate and purify adipose-derived stem cells (ASCs) in SVFs by the density gradient method. METHODS: SVFs were extracted from the subcutaneous, epididymal, mesenteric and retroperitoneal adipose tissue of 8 weeks old male Sprague-Dawley rats (n = 15) and these were separated into 4 layers according to a Nycodenz gradient (Fx-1: < 11%, Fx-2: 11-13%, Fx-3: 13-19% and Fx-4: 19-30%). The post-confluent SVFs were cultured in adipogenic medium for 2 days, in insulin medium for 2 days and in 10% fetal bovine serum medium for 5 days. To observe lipid droplets in SVFs, we performed Oil Red O staining. RESLTS: The SVFs' cellular fractions (Fx-1, Fx-2, Fx-3 and Fx-4) were isolated by density gradient centrifugation from the adipose tissues of rats. The SVFs extracted to fraction 3 (Fx-3) had the most abundant cells compared to that of the other fractions. However fraction 1 (Fx-1) or 2 (Fx-2) had a superior ability to make lipid droplets. The adipogenic differentiation of Fx-1 or 2 was higher than that of the unfractionated cells. The SVFs extracted from retroperitoneal adipose tissue had the highest efficiency for adipogenic differentiation, whereas the SVFs from mesenteric adipose tissue did not differentiate. CONCLUSION: This density gradient fractionated method leads to efficient isolation and purification of cells with the characteristics of ASCs.