Signaling proteins associated with diabetic-induced exocrine pancreatic insufficiency in rats.
Diabetes mellitus (DM) is associated with pancreatic atrophy and compromised digestion of carbohydrates as a result of exocrine pancreatic insufficiency and lower alpha-amylase synthesis and secretion. The reduced production of digestive enzymes is likely to be caused by deregulated protein metabolism. The relative concentrations and phosphorylation of signaling proteins associated with protein translation, such as PKB, p70S6K1, 4E-BP1, ERK1/2, and also some of those implicated in protein breakdown, such as ubiquitin and NF-kappaB, in the pancreas of streptozotocin (STZ)-induced type I diabetic pancreas were measured using Western blotting. There were significant decreases in the levels of total PKB, p70S6K, 4E-BP1, ERK1/2, and NF-kappaB in the diabetic pancreas compared to control. In contrast, the phosphorylation of p70S6K1, 4E-BP1, ERK1/2, and protein ubiquitination increased significantly compared to controls. Together, these results indicate that STZ-induced DM leads to reduced levels of enzymes mediating protein synthesis while their phosphorylation is actually increased, perhaps in an attempt to maintain protein homeostasis, which is further compromised by heightened ubiquitin-dependent protein breakdown. It is likely that these factors are responsible for pancreatic atrophy, enzyme synthesis, and net protein loss in DM.
Patel
Rekha
R
Department of Biological Sciences, University of Central Lancashire, Preston, Lancashire, PR1 2HE UK.
Atherton
Philip
P
Wackerhage
Henning
H
Singh
Jaipaul
J
D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D008297:Male; D046790:Pancreas, Exocrine / Q000201:enzymology / Q000503:physiopathology*; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000302:isolation & purification / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012016:Reference Values; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa