Ramipril increases the protein level of skeletal muscle IRS-1 and alters protein tyrosine phosphatase activity in spontaneously hypertensive rats.
To investigate mechanisms by which angiotensin converting enzyme (ACE)-inhibition increases insulin sensitivity, spontaneously hypertensive (SH) rats were treated with or without ramipril (1 mg/kg per day) for 12 weeks. Insulin binding and protein levels of insulin receptor substrate-1 (IRS-1), p85-subunit of phosphatidylinositol 3'-kinase (p85) and Src homology 2 domain-containing phosphatase-2 (SHP2) were then determined in hindlimb muscle and liver. Additionally, protein tyrosine phosphatase (PTPase) activities towards immobilized phosphorylated insulin receptor or phosphorylated IRS-1 of membrane (MF) and cytosolic fractions (CF) of these tissues were measured. Ramipril treatment increased IRS-1-protein content in muscle by 31+/-9% (P<0.05). No effects were observed on IRS-1 content in liver or on insulin binding or protein expression of p85 or SHP2 in both tissues. Ramipril treatment also increased dephosphorylation of insulin receptor by muscle CF (22.0+/-1.0%/60 min compared to 16.8+/-1.5%/60 min; P<0.05), and of IRS-1 by liver MF (37.2+/-1.7%/7.5 min compared to 33.8+/-1.7%/7.5 min; P<0.05) and CF (36.8+/-1.0%/7.5 min compared to 33.2+/-1.0%/7.5 min; P<0.05). We conclude that the observed effects of ACE-inhibition by ramipril on the protein expression of IRS-1 and on PTPase activity might contribute to its effect on insulin sensitivity.
Medizinische Klinik 1, Medical University of Lübeck, Germany.
J
J
Krützfeldt
W
W
Raasch
H H
HH
Klein
D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance / Q000502:physiology; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism*; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism*; D017257:Ramipril / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011972:Receptor, Insulin / Q000378:metabolism*
D000806:Angiotensin-Converting Enzyme Inhibitors; D055504:Insulin Receptor Substrate Proteins; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases; D017027:Protein Tyrosine Phosphatases; D017257:Ramipril; D011972:Receptor, Insulin; C526296:Irs1 protein, rat; C490205:Sprk protein, rat