a1 Department of Biochemistry, Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Pondicherry-605 006, India
The aim of this present study was to investigate the effect of bitter gourd extract on insulin sensitivity and proximal insulin signalling pathways in high-fat-fed rats. High-fat feeding of male Wistar rats for 10 weeks decreased the glucose tolerance and insulin sensitivity compared to chow-fed control rats. Bitter gourd extract supplementation for 2 weeks (9th and 10th) of high-fat feeding improved the glucose tolerance and insulin sensitivity. In addition bitter gourd extract reduced the fasting insulin (43 (se 4·4) v. 23 (se 5·2) μU/ml, P < 0·05), TAG (134 (se 12) v. 96 (se 5·5) mg/dl, P < 0·05), cholesterol (97 (se 6·3) v. 72 (se 5·2) mg/dl, P < 0·05) and epidydimal fat (4·8 (se 0·29) v. 3·6 (se 0·24) g, P < 0·05), which were increased by high-fat diet (HFD). High-fat feeding and bitter gourd supplementation did not have any effect on skeletal muscle insulin receptor, insulin receptor subtrate-1 (IRS-1) and insulin- stimulated insulin receptor tyrosine phosphorylation compared to chow-fed control rats. However high-fat feeding for 10 weeks reduced the insulin-stimulated IRS-1 tyrosine phosphorylation compared to control rats. Bitter gourd supplementation together with HFD for 2 weeks improved the insulin-stimulated IRS-1 tyrosine phosphorylation compared to rats fed with HFD alone. Our results show that bitter gourd extract improves insulin sensitivity, glucose tolerance and insulin signalling in HFD-induced insulin resistance. Identification of potential mechanism(s) by which bitter gourd improves insulin sensitivity and insulin signalling in high-fat-fed rats may open new therapeutic targets for the treatment of obesity/dyslipidemia-induced insulin resistance.
(Received March 14 2007)
(Revised August 10 2007)
(Accepted August 13 2007)
Abbreviations: BG, bitter gourd; HFD, high-fat diet; IRS-1, insulin receptor substrate-1