Low adipocyte IRS-1 protein expression is associated with an increased arterial stiffness in non-diabetic males.
ABSTRACT Low adipocyte IRS-1 protein expression is a biomarker for insulin resistance and early atherosclerosis. However, whether IRS-1 protein expression is related to systemic arterial stiffness, is unknown.
Ten non-diabetic male subjects with low adipocyte IRS-1 protein expression (LIRS) were matched with 10 non-diabetic males with normal IRS-1 protein expression (NIRS). Augmentation index (AIx) and time for reflection of pulse wave (Tr) were studied with pulse wave analysis, both in the fasting state and during a euglycemic hyperinsulinemic clamp. The LIRS-group showed an increased fasting insulin concentration (fP-insulin 71+/-4 pmol/L versus 58+/-5 pmol/L; p=0.02 (mean+/-S.E.)), whereas glucose disposal rate during the clamp (8.7+/-0.8 mg/kg LBM/min versus 10.3+/-1.3 mg/kg LBM/min; n.s.) did not differ significantly. Blood pressure, lipid parameters, adiponectin, endothelin-1 and CRP concentrations were similar. However, in the basal state, AIx was increased (129+/-4% versus 116+/-2%; p<0.02) and Tr was decreased (150+/-3 ms versus 171+/-5 ms; p<0.01), suggesting stiffer vessels in the LIRS-group. The LIRS-group exhibited an attenuated AIx response to hyperinsulinemia compared to the NIRS-group.
The data suggest that non-obese non-diabetic men with a low adipocyte IRS-1 protein expression have an increased systemic arterial stiffness.
Article: Increased MAPK activation and impaired insulin signaling in subcutaneous microvascular endothelial cells in type 2 diabetes: the role of endothelin-1.[show abstract] [hide abstract]
ABSTRACT: To establish a method for isolation and culture of subcutaneous microvascular endothelial cells (MVEC) from small human tissue biopsies to compare gene and protein expression of insulin signaling molecules in MVEC from insulin-resistant and healthy control subjects. Stromavascular cells from subcutaneous needle biopsies of type 2 diabetic and control subjects were expanded in culture and the endothelial cells selected with magnetic immune separation. Western blots and RT-PCR were used for protein and gene expression assays. At least 99% of the expanded primary MVEC could be characterized as endothelial cells. The expression of insulin receptors was low, but insulin increased tyrosine phosphorylation of both the insulin receptor and insulin receptor substrate (IRS)-1 and activated protein kinase B (PKB). The IRS-1 protein expression was reduced and the serine phosphorylation of PKB in response to insulin attenuated whereas basal and insulin-stimulated phosphorylation of extracellular signal-related kinase (ERK)1/2 was increased in type 2 diabetes MVEC. Endothelin (ET)-1 mRNA levels were significantly higher in type 2 diabetes cells. The addition of ET-1 increased the phosphorylation of mitogen-activated protein kinase (MAPK), an effect antagonized by the MEK-1 inhibitor PD98059. Furthermore, the endothelin ET(A) and ET(B) receptor antagonists BQ123 and BQ788 decreased basal MAPK activity in type 2 diabetes MVEC and prevented the ET-1-induced activation. We developed a system for isolation and culture of human MVEC from small needle biopsies. Our observations support the concept of "selective" insulin resistance, involving IRS-1 and the PI3kinase pathway, as an underlying factor for a dysregulated microvascular endothelium in type 2 diabetes. Our data also support a role of ET-1 for the increased MAPK activity seen in nonstimulated type 2 diabetes MVEC.Diabetes 08/2009; 58(10):2238-45. · 8.29 Impact Factor