The
metabolic syndrome is a constellation of metabolic disorders including
obesity,
hypertension, and
insulin resistance, components which are risk factors for the development of diabetes,
hypertension, cardiovascular, and renal disease. Pathophysiological abnormalities that contribute to the development of the
metabolic syndrome include impaired mitochondrial oxidative phosphorylation and mitochondrial biogenesis, dampened
insulin metabolic signaling, endothelial dysfunction, and associated myocardial functional abnormalities. Recent evidence suggests that impaired myocardial mitochondrial biogenesis,
fatty acid metabolism, and
antioxidant defense mechanisms lead to diminished cardiac substrate flexibility, decreased cardiac energetic efficiency, and diastolic dysfunction. In addition, enhanced activation of the renin-angiotensin-aldosterone system and associated increases in oxidative stress can lead to mitochondrial apoptosis and degradation, altered bioenergetics, and accumulation of
lipids in the heart. In addition to impairments in metabolic signaling and oxidative stress, genetic and environmental factors, aging, and
hyperglycemia all contribute to reduced mitochondrial biogenesis and
mitochondrial dysfunction. These mitochondrial abnormalities can predispose a metabolic
cardiomyopathy characterized by diastolic dysfunction.
Mitochondrial dysfunction and resulting
lipid accumulation in skeletal muscle, liver, and pancreas also impede
insulin metabolic signaling and
glucose metabolism, ultimately leading to a further increase in
mitochondrial dysfunction. Interventions to improve mitochondrial function have been shown to correct
insulin metabolic signaling and other metabolic and
cardiovascular abnormalities. This review explores mechanisms of
mitochondrial dysfunction with a focus on impaired oxidative phosphorylation and mitochondrial biogenesis in the pathophysiology of metabolic
heart disease.