Mechanical adaptations of skinned cardiac muscle in response to dietary-induced obesity during adolescence in rats

Childhood obesity is a major risk factor for heart disease during adulthood, independent of adulthood behaviours. Therefore, it seems that childhood obesity leads to partly irreversible decrements in cardiac function. Little is known about how obesity during maturation affects the mechanical properties of the heart. The purpose of this study was to evaluate contractile properties in developing hearts from animals with dietary-induced obesity (high-fat high-sucrose diet). We hypothesized that obesity induced during adolescence results in decrements in cardiac contractile function. Three-week-old rats (n = 16) were randomized into control (chow) or dietary-induced obesity (high-fat high-sucrose diet) groups. Following 14 weeks on the diet, skinned cardiac trabeculae fibre bundle testing was performed to evaluate active and passive force, maximum shortening velocity, and calcium sensitivity. Rats in the high-fat high-sucrose diet group had significantly larger body mass and total body fat percentage. There were no differences in maximal active or passive properties of hearts between groups. Hearts from the high-fat high-sucrose diet rats had significantly slower maximum shortening velocities and lower calcium sensitivity than controls. Decreased shortening velocity and calcium sensitivity in hearts of obese animals may constitute increased risk of cardiac disease in adulthood. Novelty Cardiac muscle from animals exposed to an obesogenic diet during development had lower shortening velocity and calcium sensitivity than those from animals fed a chow diet. These alterations in mechanical function may be a mechanism for the increased risk of cardiac disease observed in adulthood.