Protein Kinase C-β Contributes to Impaired Endothelial Insulin Signaling in Humans With Diabetes Mellitus

• Published in: Circulation (New York, N.Y.) Vol. 127; no. 1; pp. 86 - 95
• Main Authors: Tabit, Corey E., Shenouda, Sherene M., Holbrook, Monica, Fetterman, Jessica L., Kiani, Soroosh, Frame, Alissa A., Kluge, Matthew A., Held, Aaron, Dohadwala, Mustali M., Gokce, Noyan, Farb, Melissa G., Rosenzweig, James, Ruderman, Neil, Vita, Joseph A., Hamburg, Naomi M.
• Format: Journal Article
• Language: English
• Published: Hagerstown, MD Lippincott Williams & Wilkins 01.01.2013
• Subjects: Adult; Associated diseases and complications; Biological and medical sciences; Blood and lymphatic vessels; Cardiology. Vascular system; Cells, Cultured; Diabetes Mellitus, Type 2 - metabolism; Diabetes. Impaired glucose tolerance; Diabetic Angiopathies - metabolism; Diseases of the peripheral vessels. Diseases of the vena cava. Miscellaneous; Endocrine pancreas. Apud cells (diseases); Endocrinopathies; Endothelial Cells - drug effects; Endothelial Cells - metabolism; Female; Humans; Hypoglycemic Agents - metabolism; Hypoglycemic Agents - pharmacology; Insulin - metabolism; Insulin - pharmacology; Insulin Resistance - physiology; Male; Medical sciences; Mesylates - pharmacology; Middle Aged; NF-kappa B - metabolism; Nitric Oxide - metabolism; Nitric Oxide Synthase Type III - metabolism; Oxidative Stress - physiology; Protein Kinase C - antagonists & inhibitors; Protein Kinase C - metabolism; Protein Kinase C beta; Pyrroles - pharmacology; Signal Transduction - drug effects; Signal Transduction - physiology; Endocrinopathy; Target tissue resistance; Protein kinase C; Enzyme; Insulin human; Transferases; Diabetes mellitus; Nitric oxide; Metabolic diseases; Insulin resistance; Cardiovascular disease; Endothelium
• ISSN: 0009-7322; 1524-4539; 1524-4539
• DOI: 10.1161/CIRCULATIONAHA.112.127514

Abnormal endothelial function promotes atherosclerotic vascular disease in diabetes. Experimental studies indicate that disruption of endothelial insulin signaling, through the activity of protein kinase C-β (PKCβ) and nuclear factor κB, reduces nitric oxide availability. We sought to establish whether similar mechanisms operate in the endothelium in human diabetes mellitus. We measured protein expression and insulin response in freshly isolated endothelial cells from patients with type 2 diabetes mellitus (n=40) and nondiabetic controls (n=36). Unexpectedly, we observed 1.7-fold higher basal endothelial nitric oxide synthase (eNOS) phosphorylation at serine 1177 in patients with diabetes mellitus (P=0.007) without a difference in total eNOS expression. Insulin stimulation increased eNOS phosphorylation in nondiabetic subjects but not in diabetic patients (P=0.003), consistent with endothelial insulin resistance. Nitrotyrosine levels were higher in diabetic patients, indicating endothelial oxidative stress. PKCβ expression was higher in diabetic patients and was associated with lower flow-mediated dilation (r=-0.541, P=0.02). Inhibition of PKCβ with LY379196 reduced basal eNOS phosphorylation and improved insulin-mediated eNOS activation in patients with diabetes mellitus. Endothelial nuclear factor κB activation was higher in diabetes mellitus and was reduced with PKCβ inhibition. We provide evidence for the presence of altered eNOS activation, reduced insulin action, and inflammatory activation in the endothelium of patients with diabetes mellitus. Our findings implicate PKCβ activity in endothelial insulin resistance.