Characterization of sucrose-induced changes in cardiac phenotype.

The neuroendocrine factors responsible for long-term regulation of cardiac contractile performance remain ill defined. We examined influences of diet on the expression of myosin isozymes, sarcoplasmic reticulum (SR) Ca(2+) uptake and serum parameters. Dietary regimens (ad libitum feeding, intermittent fasting and 32% sucrose feeding) were used to alter the neurohumoral status of rats. Intermittent fasting decreased serum insulin levels ( P<0.05) and was associated with decreased SR Ca(2+) uptake and myosin V1 proportion ( P<0.05). Sucrose (32%) feeding increased myosin V1 of fasted and ad libitum fed rats ( P<0.05) but had no effect on insulin or SR Ca(2+) uptake. Expression of the alpha-myosin heavy chain correlated with serum insulin. Treatment of sucrose-fed rats with the sympatholytic compound moxonidine and the hypoglycaemic compounds BM13.907 and ciglitazone partially prevented the increase in myosin V1 ( P<0.05) but had no effect on SR Ca(2+) uptake and insulin. The data show that adrenergic activity and metabolic signals are important for an increase in myosin V1 in sucrose-fed rats, which can be associated with an unaltered SR Ca(2+) uptake rate.