Coupling factor 6-induced activation of ecto-F 1F o complex induces insulin resistance, mild glucose intolerance and elevated blood pressure in mice

Abstract

Aims/hypothesis: Despite advances in pharmacological treatments, diabetes with hypertension continues to be a major public health problem with high morbidity and mortality rates. We recently identified a circulating peptide coupling factor 6 (CF6), which binds to the plasma membrane ATP synthase (ecto-F 1F o complex), resulting in intracellular acidosis. We investigated whether overexpression of CF6 contributes to diabetes and hypertension by intracellular acidosis. Methods: Transgenic mice overexpressing CF6 (also known as ATP5J) were generated, and physiological, biochemical and molecular biology studies were performed. Results: CF6 overexpression elicited a sustained decrease in intracellular pH in tissues (aorta, kidney, skeletal muscle and liver, with the exception of adipose tissue) that express its receptor, the β-subunit of ecto-F 1F o complex. Consistent with the receptor distribution, phospho-insulin receptor β, phosphoinositide 3-kinase activity and the phospho-Akt1:total Akt1 ratio were all decreased in the skeletal muscle and the liver in transgenic compared with wild-type mice, resulting in a decrease of plasma membrane-bound GLUT4 and an increase in hepatic glucose production. Under a high-sucrose diet, transgenic mice had insulin resistance and mild glucose intolerance; under a high-salt diet, they had elevated blood pressure with increased renal RAS-related C3 botulinum substrate 1 (RAC1)-GTP, which is an activator of mineralocorticoid receptor. Conclusions/interpretation: Through its action on the β-subunit of ecto-F 1F o complex, which results in intracellular acidosis, CF6 plays a crucial role in the development of insulin resistance and hypertension. This finding might advance our understanding of the mechanisms underlying diabetes and hypertension, possibly also providing a novel therapeutic target against cardiovascular disease. © 2011 Springer-Verlag.