Decreased insulin secretion in islets from rats fed a low protein diet is associated with a reduced PKAalpha expression.
A low protein diet has been shown to affect the amount and activity of several enzymes and to decrease insulin secretion by islets isolated from rats fed such a diet. To understand the mechanisms involved in this phenomenon, we investigated the effects of forskolin, a stimulator of adenylyl cyclase, on insulin secretion by 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 10 micromol forskolin/L. The forskolin-induced insulin secretion was higher in islets from NP rats than in those from LP rats (P<0.05). Western blotting revealed that the amount of the alpha catalytic subunit of protein kinase A (PKAalpha) was 35% lower in islets from LP rats than in islets from NP rats (P<0.05). Moreover, PKAalpha mRNA expression was reduced by 30% in islets from LP rats (P<0.05). Our results indicated a possible relationship between a low protein diet and a reduction in PKAalpha expression. These alterations in PKAalpha may be responsible in part for the decreased insulin secretion by islets from rats fed a low protein diet.
Ferreira
Fabiano
F
Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, Campinas, SP, Brazil.
Barbosa
Helena C L
HC
Stoppiglia
Luiz Fabrizio
LF
Delghingaro-Augusto
Viviane
V
Pereira
Eliana A
EA
Boschero
Antonio C
AC
Carneiro
Everardo M
EM
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics*; D018753:Diet, Protein-Restricted; D015870:Gene Expression; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction
D007328:Insulin; D012333:RNA, Messenger; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases; D000262:Adenylyl Cyclases