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Type: Artigo de periódico
Title: Low-protein diets reduce PKA alpha expression in islets from pregnant rats
Author: Milanski, M
Arantes, VC
Ferreira, F
Reis, MAD
Carneiro, EM
Boschero, AC
Collares-Buzato, CB
Latorraca, MQ
Abstract: We investigated the effect of protein restriction on insulin secretion and the expression of protein kinase (PK)A alpha and PKC alpha in islets from control and pregnant rats. Adult control nonpregnant (CN) and control pregnant (CP) rats were fed a normal-protein diet (17%), whereas low-protein nonpregnant (LPN) and low-protein pregnant (LPP) rats were fed a low-protein diet (6%) for 15 d. In the presence of 2.8 and 8.3 mmol glucose/L, insulin secretion by islets of CP rats was higher than that by islets of CN rats. Compared with the CN groups, insulin secretion by islets of LPN rats was lower with 8.3 but not with 2.8 mmol glucose/L. The insulin secretion by islets of LPP rats was higher than by LPN rats at both glucose concentrations. IBMX (1 mmol/L), a phosphodiesterase inhibitor, increased insulin secretion by islets from pregnant rats, and this effect was greater in islets of CP rats than in LPP rats. Forskolin (0.01 -100 mu mol/L), a stimulator of adenylyl cyclase, increased insulin sacretion only in islets of CN and CP rats, with a higher 50% effective concentration in islets of CP rats compared with CN rats. The insulin secretion induced by phorbol 12-myristate 13-acetate (a stimulator of PKC) was higher in islets of LPN and LPP rats than in the respective controls, especially, at 8.3 mmol glucose/L. PKA alpha, but not PKC alpha, expression was lower in islets of rats fed low protein than in the controls, regardless of the physiological status of the rats. All endocrine cells of the islets, including beta-cells, expressed the PKA alpha isoform. The cytoplasmic distribution of this enzyme in beta-cells was not modified by pregnancy and/or protein restriction. In conclusion, our results indicate that the response of islets from rats fed low protein during pregnancy is similar to that of control rats, at least for physiologic glucose concentration. However, the decreased response to IBMX and forskolin indicates decreased production and/or sensitivity to cAMP; this was associated with a decrease in PKA expression, which may result in lower PKA activity.
Subject: low-protein diet
insulin secretion
PKA alpha
PKC alpha
Country: EUA
Editor: Amer Society Nutritional Science
Citation: Journal Of Nutrition. Amer Society Nutritional Science, v. 135, n. 8, n. 1873, n. 1878, 2005.
Rights: fechado
Date Issue: 2005
Appears in Collections:Unicamp - Artigos e Outros Documentos

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