Impaired glucose-stimulated insulin secretion is coupled with exocrine pancreatic lesions in the Cohen diabetic rat.
OBJECTIVE
The Cohen diabetes-sensitive rat develops postprandial hyperglycemia when fed a high-sucrose, copper-poor diet, whereas the Cohen diabetes-resistant rat maintains normoglycemia. The pathophysiological basis of diabetes was studied in the Cohen diabetic rat centering on the interplay between the exocrine and endocrine compartments of the pancreas.


METHODS
Studies used male Cohen diabetes-sensitive and Cohen diabetes-resistant rats fed 1-month high-sucrose, copper-poor diet. Serum insulin and glucose levels were measured during glucose and insulin tolerance tests. The pancreas was evaluated for weight, insulin content, macrophage, and fat infiltration. Glucose-stimulated insulin secretion (GSIS) was determined in isolated perfused pancreas and in islets.


RESULTS
Hyperglycemic Cohen diabetes-sensitive rats exhibited reduced pancreatic weight with lipid deposits and interleukin-1beta-positive macrophage infiltration in the exocrine pancreas. Islet morphology was preserved, and total pancreatic insulin content did not differ from that of Cohen diabetes-resistant rats. Lipids did not accumulate in skeletal muscle, nor was insulin resistance observed in hyperglycemic Cohen diabetes-sensitive rats. Intravenous glucose-tolerance test revealed markedly elevated glucose levels associated with diminished insulin output. Insulin release was induced in vivo by the non-nutrient secretagogues arginine and tolbutamide, suggesting a selective unresponsiveness to glucose. Decreased GSIS was observed in the isolated perfused pancreas of the hyperglycemic Cohen diabetes-sensitive rat, whereas islets isolated from these rats exhibited glucose-dependent insulin secretion and proinsulin biosynthesis.


CONCLUSIONS
The association of the in vivo insulin secretory defect with lipid accumulation and activated macrophage infiltration in the exocrine pancreas suggests that changes in the islet microenvironment are the culprit in the insulin secretory malfunction observed in vivo.
Weksler-Zangen
Sarah
S
The Diabetes Unit, Hadassah-Hebrew University Medical Center, Jerusalem 1200, Israel. sarahz@hadassah.org.il
Raz
Itamar
I
Lenzen
Sigurd
S
Jörns
Anne
A
Ehrenfeld
Shira
S
Amir
Gail
G
Oprescu
Andrei
A
Yagil
Yoram
Y
Yagil
Chana
C
Zangen
David H
DH
Kaiser
Nurit
N
D000821:Animal Feed; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002408:Catheters, Indwelling; D003300:Copper / Q000172:deficiency; D003921:Diabetes Mellitus, Experimental / Q000473:pathology / Q000503:physiopathology*; D003927:Diet, Diabetic; D004040:Dietary Carbohydrates; D005951:Glucose Tolerance Test; D006943:Hyperglycemia / Q000503:physiopathology; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D010179:Pancreas / Q000187:drug effects / Q000473:pathology*; D019518:Postprandial Period; D051381:Rats; D013395:Sucrose / Q000494:pharmacology*
D001786:Blood Glucose; D004040:Dietary Carbohydrates; D007328:Insulin; D013395:Sucrose; D003300:Copper