Chromium picolinate supplementation improves cardiac metabolism, but not myosin isoenzyme distribution in the diabetic heart

Abstract

Because chromium (Cr) containing compounds are thought to improve glucose homeostasis, we hypothesized that chromium picolinate (CrP) could partially reverse diabetes-induced damage to cardiac tissue. Young, adult female rats were fed either a basal diet (CONT), a basal diet containing no CrP and made diabetic (DIAB-CONT) or a basal diet containing 600 ng/g of CrP (3 times the suggested daily chromium intake) and made diabetic (DIAB-CrP). Diabetes was induced by a single streptozotocin injection, 55 mg/kg i.p. After 8 weeks animals were sacrificed, hearts removed, and spectrophotometrically analyzed for citrate synthase (CS), hexokinase (HK), and beta hydroxyacyl CoA dehydrogenase activity (HOAD). Cardiac myosin isoenzymes were separated from crude myofibril extracts by PAGE electrophoresis. Diabetes did not alter CS activity relative to the CONT group, but did significantly (P < 0.05) reduce HK and HOAD activity and expression of the high ATPase myosin isoenzyme VI. In contrast, DIAB-CrP animals displayed normal HK activity and greater HOAD activity relative to CONT animals. Surprisingly, the addition of CrP to the diet further reduced expression of the VI myosin isoenzyme. These results demonstrate that dietary CrP supplementation has diverse effects on the subcellular properties of the diabetic heart. The functional impact of these CrP-induced changes remains to be defined.