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Expression1
Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brasil;
*
Departamento de Nutrição e Dietética, Faculdade de Enfermagem e Nutrição, Universidade Federal de Mato Grosso, Cuiabá, MT, Brasil; and
Departamento de Bioquímica, Instituto de Biologia, Universidade Estadual de Campinas (UNICAMP), Campinas, SP, Brasil
2To whom correspondence should be addressed. E-mail: emc{at}unicamp.br.
Undernutrition has been shown to affect the autonomic nervous system, leading to permanent alterations in insulin secretion. To understand these interactions better, we investigated the effects of carbamylcholine (CCh) and phorbol 12-myristate 13-acetate (PMA) on insulin secretion in pancreatic islets from rats fed a normal (17%; NP) or low (6%; LP) protein diet for 8 wk. Isolated islets were incubated for 1 h in Krebs-bicarbonate solution containing 8.3 mmol glucose/L, with or without PMA (400 nmol/L) and CCh. Increasing concentrations of CCh (0.1–1000 µmol/L) dose dependently increased insulin secretion by islets from both groups of rats. However, insulin secretion by islets from rats fed the NP diet was significantly higher than that of rats fed the LP diet, and the dose-response curve to CCh was shifted to the right in islets from rats fed LP with a 50% effective concentration (EC50) of 2.15 ± 0.7 and 4.64 ± 0.1 µmol CCh/L in islets of rats fed NP and LP diets, respectively (P < 0.05). PMA-induced insulin secretion was higher in islets of rats fed NP compared with those fed LP. Western blotting revealed that the protein kinase (PK)C
and phospholipase (PL)Cß1 contents of islets of rats fed LP were 30% lower than those of islets of rats fed NP (P < 0.05). In addition, PKC mRNA expression was reduced by 50% in islets from rats fed LP. In conclusion, a reduced expression of PKC and PLCß1 may be involved in the decreased insulin secretion by islets from LP rats after stimulation with CCh and PMA.
KEY WORDS: • low protein diet • carbamylcholine • insulin secretion • protein kinase C • phospholipase Cß1.
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