Soybean diet improves insulin secretion through activation of cAMP/PKA pathway in rats

Maternal malnutrition leads to permanent alterations in insulin secretion of offspring and the soybean diet contributes to improve insulin release. At least a soy component, genistein, seems to increase the insulin secretion by activating the cAMP/PKA and PLC/PKC pathways. Here, we investigated the effect of the soybean diet on the expression of PKAalpha and PKCalpha, and insulin secretion in response to glucose and activators of adenylate cyclase and PKC in adult pancreatic rat islets. Rats from mothers fed with 17% or 6% protein (casein) during pregnancy and lactation were maintained with 17% casein (CC and CR groups) or soybean (SC and SR groups) diet until 90 days of life. The soybean diet improved the insulin response to a physiological concentration of glucose in control islets, but only in the presence of supra-physiological concentrations of glucose in islets from CR and SR groups. PMA also improved the insulin response in islets of SC and SR groups. The expression of PKCalpha was similar in all groups. Forskolin increased the insulin secretion; however, the magnitude of the increment was lower in islets from CR and SR groups than in control animals and in those from rats maintained with soybean diet than in rats fed with casein diet. The PKAalpha expression was similar between SR and CR groups and lower in SC than in CC islets. Thus, soybean diet improved the secretory pattern of beta cells, at least in part, by activating the cAMP/PKA-signaling cascade.