Diabetes & Metabolism Journal

Original Article

The long-term effect of ramipril on Gialpha2-protein and Protein Tyrosine Phosphatase 1B in an animal model of type 2 diabetes(OLETF rat).: Jung Min Lee, Ok Ki Hong, Hyuk Sang Kwon, Sung Dae Moon, Sang Ah Chang, Hyun Shik Son, Kun Ho Yoon, Bong Yun Cha, Sung Koo Kang; Korean Diabetes J. 2006;30(1):25-38. Published online January 1, 2006; DOI: https://doi.org/10.4093/jkda.2006.30.1.25

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Abstract PDF: BACKGROUND
The regulation of tyrosine phosphorylation/dephosphorylation is an important mechanism in various intracellular metabolism. Also impaired insulin signal transduction is important in pathogenesis of type 2 diabetes. It has been reported that PTP1B is a negative regulator of insulin action, and Gialpha2-protein is related to the regulation of PTP1B. Herein we investigated the long-term effects of ramipril on PTP1B/insulin signal protein interaction and the relation between Gialpha2 and PTP1B in animal model of type 2 diabetes (OLETF rat). METHODS: OLETF rats and age-matched LETO rats were divided into two groups. One group of rats received ramipril (10 mg/kg body weight) for 12 weeks, and another group did not. Finally, each group was divided into 2 subgroups, with or without insulin injection intravenously, before sacrifice. After sacrifice, tissues extracts of liver, hind limb muscle, and epididymal fat were obtained for quantification of PTP1B, Gialpha2, and several insulin signal proteins by western blotting. RESULTS: In liver and muscle, the levels of basal PTP1B and activated PTP1B of OLETF rats treated with ramipril and insulin were significantly decreased. The levels of Gialpha2, activated IRS-2, and activated p-85alpha were significantly increased in OLETF rats treated with ramipril and insulin. In adipose tissue, the levels of Gialpha2 and activated p-85alpha of OLETF rats treated with ramipril and insulin were slightly increased as in liver and muscle. But, the levels of basal PTP1B and activated PTP1B were significantly increased. And, the levels of activated IRS-1 and activated IRS-2 were decreased. CONCLUSION: These results suggest that the improvement of insulin sensitivity by treatment with ramipril was related to the decreased level of activated PTP1B. Also, we could suggest that the changes of activated PTP1B level was related with the changes of Gialpha2-protein. However, the results of adipose tissue were different from those of liver and muscle. So it seemed likely that there would be various major modulators for regulation of insulin signal pathway according to tissue.

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