Portal de Periódicos da CAPES

Reduced contractile response to insulin and IGF-I in ventricular myocytes from genetically obese Zucker rats

2000; American Physical Society; Volume: 279; Issue: 4 Linguagem: Inglês

10.1152/ajpheart.2000.279.4.h1708

1522-1539

Jun Ren, James R. Sowers, Mary F. Walsh, Ricardo A. Brown,

Diet and metabolism studies

Obesity plays a pivotal role in the pathophysiology of metabolic and cardiovascular diseases. Resistance to insulin is commonly seen in metabolic disorders such as obesity and diabetes. Insulin-like growth factor-I (IGF-I) mimics insulin in many tissues and has been shown to enhance cardiac contractile function and growth. Because IGF-I resistance often accompanies resistance to insulin, we sought to determine whether IGF-I-induced myocardial contractile was elevated and whether heart and kidney size were enlarged in obese compared with lean rats. The myocyte contraction profile in the obese rats showed a decreased peak shortening associated with prolonged relengthening and normal shortening duration, a pattern similar to that observed in diabetes. IGF-I (1–500 ng/ml) caused a dose-dependent increase in peak shortening in lean but not obese animals, but it did not alter the duration of shortening and relengthening. Consistent with contractile data, IGF-I induced a dose-dependent increase in Ca 2+ transients only in myocytes of lean rats. IGF-I receptor mRNA levels were significantly reduced in obese rat hearts. These results suggest that the IGF-I-induced cardiac contractile responses are attenuated in the Zucker model of obesity. The mechanisms underlying this alteration may be related to the decreased receptor number and/or changes in intracellular Ca 2+ handling in these animals.