Modulação colinergica da secreção de insulina em presença de leucina em ilhotas de ratos submetidos a restrição proteica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

The aim of the present work was to study the effect of low protein diet (LP), m particular the role of reduced intake of the amino acid leucine (L) m the mechanism of pancreatic islet insulin secretion. Male Wistar rats submitted to LP (6% protem) were compared to age and gender matched controls maintamed with normal protein diet (NP) (17% protein). Pancreatic islets isolated from NL and LP groups were submitted to various glucose concentrations and stimulatory drugs to compare the amount of the insulin secretion. The insulin was measured by radioimunoassay. The level of leucine oxidation and 45Ca outflow were also compared by 14(:02 output and 45Ca efflux, respectively. Western Blottillg was applied to compare the levels of p70S6k.l and Akt and RT- PCR to evaluate the levels ofp70S6k.1 mRNA in both groups. LP rats presented with significantly lower body weight, serum protein and albumin, but higher glycogen and liver fat. No differences in serum glucose levels were observed. The aminogram analysis from serum demonstrated that LP groups either fasted or fed had significantly lower levels of leucine, valine, arginine, taurine compared to NP. In vitro insulin secretion in the LP group was significantly lower in the basal situation and in response to stimulation with carbachol, potassium, gliceraldeid, PMS, KIC, IBMX. The addition of the amino acids leucine in the media did not elevated the insulin secretion in the LP group to levels comparable to NP group. In addition, leucine oxidation and calcium out flow from pancreatic islets of LP group were significantly lower. The p70S6k-l and Akt protein expression and p70S6k-1 mRNA levels were lower in LP group as revealed by Westem Blotting and RT-PCR analysis, respectively. These findings indicate that LP diet let to pancreatic islets dysfunction and that correlated with reduced calcium outflow and decreased leucine oxidation in those cells. The mechanisms may involve lower systemic leucine levels, and lower expression of the signaling elements p70S6k.1 and Akt

ASSUNTO(S)

insulina ilhotas de langerhans desnutrição

ACESSO AO ARTIGO

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