Journal Article

Protection against lipoapoptosis of beta cells through leptin-dependent maintenance of Bcl-2 expression

Zhou, Y.T, Newgard, C.B, Wang, M.Y, Unger, R.H, Shimabukuro, M. (University of Texas Southwestern Medical Center, Dallas, TX.)

1998

Overview

Obesity causes its complications through functional and morphologic damage to remotely situated tissues via undetermined mechanisms. In one rodent model of obesity, the Zucker diabetic fatty fa/fa rat, overaccumulation of triglycerides in the pancreatic islets may be responsible for a gradual depletion of beta cells, leading to the most common complication of obesity, non-insulin, dependent diabetes mellitus. At the onset of non-insulin-dependent diabetes mellitus, the islets from fa/fa rats contain up to 100 times the fat content of islets from normal lean rats. Ultimately, about 75% of the beta cells disappear from these fat-laden islets as a consequence of apoptosis induced by long-chain fatty acids (FA). Here we quantify Bcl-2, the anti-apoptosis factor in these islets, and find that Bcl-2 mRNA and protein are, respectively, 85% and 70% below controls. In normal islets cultured in 1 mM FA, Bcl-2 mRNA declined by 68% and completely disappeared in fa/fa islets cultured in FA. In both groups, suppression was completely blocked by the fatty acyl-CoA synthetase inhibitor, triacsin C, evidence of its mediation by fatty acyl-CoA. To determine whether leptin action blocked FA-induced apoptosis, we cultured normal and fa/fa islets in 1 mM FA with or without leptin. Leptin completely blocked FA-induced Bcl-2 suppression in normal islets but had no effect on islets from fa/fa rats, which are unresponsive to leptin because of a mutation in their leptin receptors (OB-R). However, when wild-type OB-R is overexpressed in fa/fa islets, leptin completely prevented FA-induced Bcl-2 suppression and DNA fragmentation

• Publisher: National Academy of Sciences of the United States of America,National Acad Sciences,National Academy of Sciences,The National Academy of Sciences
• Subject: ACIDE OLEIQUE / ACIDE PALMITIQUE / ACIDO OLEICO / ACIDO PALMITICO / Adipose Tissue / Adipose Tissue - pathology / ADN / Amino Acid Substitution / ANIMAL MODELS / ANIMAL PROTEINS / Animals / ANTI-APOPTOSIS FACTOR / APOPTOSE / APOPTOSIS / Apoptosis - physiology / ARN MENSAJERO / ARN MESSAGER / Base Sequence / Biological Sciences / Carrier Proteins / Carrier Proteins - chemistry / Carrier Proteins - genetics / Ceramides / chemistry / DIABETE / DIABETES / Diabetes complications / Diabetes mellitus / DNA / DNA FRAGMENTATION / DNA MODIFICATION / DNA Primers / ENZYME INHIBITORS / EXPRESION GENICA / EXPRESSION DES GENES / Fatty Acids / Fatty Acids - metabolism / FATTY ACYL-COA SYNTHETASE / GENE EXPRESSION / Gene Expression Regulation / Gene Expression Regulation - physiology / genetics / HORMONAS / HORMONE / HORMONE RECEPTORS / HORMONES / INHIBIDORES DE ENZIMAS / INHIBITEUR D'ENZYME / islets of Langerhans / Islets of Langerhans - pathology / Leptin / LIGASAS / LIGASE / LIGASES / Male / MESSENGER RNA / metabolism / MODELE ANIMAL / MODELOS ANIMALES / MUTANT / MUTANTES / MUTANTS / Obesity / OLEIC ACID / OVERWEIGHT / PALMITIC ACID / PANCREAS / PANCREAS ISLETS / pathology / PEPTIDE / PEPTIDES / PEPTIDOS / physiology / POLYPEPTIDES / PROTEINAS / PROTEINE / PROTEINS / Proteins - physiology / Proto-Oncogene Proteins c-bcl-2 / Proto-Oncogene Proteins c-bcl-2 - genetics / RAT / RATA / RATS / Rats, Zucker / RECEPTEUR D'HORMONE / RECEPTORES DE HORMONAS / Receptors, Cell Surface / Receptors, Leptin / Reverse transcriptase polymerase chain reaction / Ribonucleic acid / RNA / Rodents / SOBREPESO / SURPOIDS / TRIACSIN