Decrease in plasma GLP-1 immunoreactivity in starved rats.
To determine whether starvation affects the metabolism of glucagon-like peptide-1 (GLP-1), we measured the plasma levels of proglucagon-derived peptides and the biosynthesis and posttranslational processing of proglucagon in groups of six rats starved for 1, 3 and 5 days. The plasma levels of GLP-1 immunoreactivity (GLP-1 IR) and glucagon-like immunoreactivity (GLI) decreased during starvation reaching 79 and 56% of the respective control values by day 5 (P less than 0.05 and less than 0.01 vs control). The same is true of the plasma IRI level. The ileal contents of GLP-1 IR and GLI were 50.8 +/- 3.8 pmol/g wet weight and 161.8 +/- 13.2 pmol/g wet weight, respectively, on day 5 of starvation, which were significantly lower (P less than 0.01) than the respective values of 94.8 +/- 16.6 pmol/g wet weight and 262.7 +/- 28.1 pmol/g wet weight in control rats. However, the pancreatic contents of proglucagon-derived peptides tended to increase during starvation, although their increases were not statistically significant. No significant change in the posttranslational processing of proglucagon was detected during starvation. The decrease in the ileal proglucagon-derived peptides content was not associated with a decrease in intestinal proglucagon mRNA transcripts. These results suggested that decreased synthesis of proglucagon-derived peptides by the intestine was largely responsible for the reductions in their circulating levels in starved rats.
Takahashi
J
J
Department of Medical Technology, School of Allied Medical Sciences, Kobe University, Japan.
Noma
Y
Y
Yoshimoto
S
S
Fujita
C
C
Shima
K
K
D000704:Analysis of Variance; D000818:Animals; D001835:Body Weight; D002851:Chromatography, High Pressure Liquid; D005215:Fasting; D005934:Glucagon / Q000097:blood* / Q000235:genetics; D052216:Glucagon-Like Peptide 1; D007082:Ileum / Q000503:physiopathology; D007328:Insulin / Q000097:blood; D008297:Male; D010446:Peptide Fragments / Q000097:blood*; D052336:Proglucagon; D011498:Protein Precursors / Q000097:blood* / Q000235:genetics; D011499:Protein Processing, Post-Translational; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D013217:Starvation / Q000503:physiopathology*; D013997:Time Factors
D007328:Insulin; D010446:Peptide Fragments; D011498:Protein Precursors; D052336:Proglucagon; D012313:RNA; D052216:Glucagon-Like Peptide 1; D005934:Glucagon