Hypoglycemic effects of brassinosteroid in diet-induced obese mice.
The prevalence of obesity is increasing globally, and obesity is a major risk factor for metabolic diseases such as type 2 diabetes. Previously, we reported that oral administration of homobrassinolide (HB) to healthy rats triggered a selective anabolic response that was associated with lower blood glucose. Therefore, the aim of this study was to evaluate the effects of HB administration on glucose metabolism, insulin sensitivity, body composition, and gluconeogenic gene expression profiles in liver of C57BL/6J high-fat diet-induced obese mice. Acute oral administration of 50-300 mg/kg HB to obese mice resulted in a dose-dependent decrease in fasting blood glucose within 3 h of treatment. Daily chronic administration of HB (50 mg/kg for 8 wk) ameliorated hyperglycemia and improved oral glucose tolerance associated with obesity without significantly affecting body weight or body composition. These changes were accompanied by lower expression of two key gluconeogenic enzymes, phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G-6-Pase), and increased phosphorylation of AMP-activated protein kinase in the liver and muscle tissue. In vitro, HB treatment (1-15 μM) inhibited cyclic AMP-stimulated but not dexamethasone-stimulated upregulation of PEPCK and G-6-Pase mRNA levels in H4IIE rat hepatoma cells. Among a series of brassinosteroid analogs related to HB, only homocastasterone decreased glucose production in cell culture significantly. These results indicate the antidiabetic effects of brassinosteroids and begin to elucidate their putative cellular targets both in vitro and in vivo.
Biotech Center, School of Environmental and Biological Sciences, Rutgers University, New Brunswick, New Jersey, USA.
Debora
D
Esposito
Pablo
P
Kizelsztein
Slavko
S
Komarnytsky
Ilya
I
Raskin
D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D060406:Brassinosteroids / Q000008:administration & dosage / Q000627:therapeutic use*; D002460:Cell Line; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism; D059305:Diet, High-Fat / Q000009:adverse effects; D019587:Dietary Supplements; D005786:Gene Expression Regulation; D005952:Glucose-6-Phosphatase / Q000235:genetics / Q000378:metabolism; D006943:Hyperglycemia / Q000517:prevention & control; D007004:Hypoglycemic Agents / Q000627:therapeutic use*; D007333:Insulin Resistance; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009765:Obesity / Q000097:blood / Q000178:diet therapy* / Q000209:etiology; D019764:Phosphoenolpyruvate Carboxykinase (ATP) / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D011499:Protein Processing, Post-Translational; D012333:RNA, Messenger / Q000378:metabolism; D011897:Random Allocation
D060406:Brassinosteroids; D007004:Hypoglycemic Agents; D012333:RNA, Messenger; D000242:Cyclic AMP; D055372:AMP-Activated Protein Kinases; D005952:Glucose-6-Phosphatase; D019764:Phosphoenolpyruvate Carboxykinase (ATP)