Dietary carbohydrates modify cardiac myosin isoenzyme profiles of semistarved rats.
Although food restriction reduces the relative expression of the rodent cardiac myosin isoenzyme V1, the contribution of accompanying metabolic changes to the induction and maintenance of this isoenzyme shift remains unknown. Hence, this study was undertaken to determine the role of carbohydrate (CHO) utilization in the regulation of cardiac myosin isoenzyme distribution in food-restricted rats. Female Sprague-Dawley rats received either a mixed diet (55% of calories as CHO, M) or a high-carbohydrate diet (75% of calories as CHO, HC). Additional animals in each dietary group received daily injections of triiodothyronine (T3; 0.075 microgram/100 microM + T3, HC + T3). Three weeks of food restriction reduced left ventricular Ca2+-activated myofibrillar adenosinetriphosphatase activity by 24% and the relative amount of the myosin V1 isoenzyme by 57% in the M group relative to free-eating controls (P less than 0.05). In contrast, these measures were reduced by only 9 and 21%, respectively, in the HC group. Administration of T3 exerted no apparent effect on V1 expression, regardless of diet. Furthermore, the increased expression of V1 in both HC and HC + T3 groups occurred independently of changes in several measures of thyroid status including serum T3 levels, O2 consumption, heart rate, and systemic blood pressure. These results further suggest that metabolic factors, specifically those associated with CHO utilization, can influence cardiac myosin isoenzyme expression.
Morris
G S
GS
Department of Physiology and Biophysics, University of California, Irvine 92717.
Herrick
R E
RE
Baldwin
K M
KM
D000818:Animals; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D005260:Female; D005508:Food Deprivation / Q000502:physiology*; D009206:Myocardium / Q000201:enzymology*; D009218:Myosins / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D004040:Dietary Carbohydrates; D009218:Myosins