Mechanisms involved in the beta-cell mass increase induced by chronic sucrose feeding to normal rats.
The aim of the present study was to clarify the mechanisms by which a sucrose-rich diet (SRD) produces an increase in the pancreatic beta-cell mass in the rat. Normal Wistar rats were fed for 30 weeks either an SRD (SRD rats; 63% wt/wt), or the same diet but with starch instead of sucrose in the same proportion (CD rats). We studied body weight, serum glucose and triacylglycerol levels, endocrine tissue and beta-cell mass, beta-cell replication rate (proliferating cell nuclear antigen; PCNA), islet neogenesis (cytokeratin immunostaining) and beta-cell apoptosis (propidium iodide). Body weight (g) recorded in the SRD rats was significantly (P<0.05) larger than that of the CD group (556.0+/-8.3 vs 470.0+/-13.1). Both serum glucose and triacylglycerol levels (mmol/l) were also significantly higher (P<0.05) in SRD than in CD rats (serum glucose, 8.11+/-0.14 vs 6.62+/-0.17; triacylglycerol, 1.57+/-0.18 vs 0.47+/-0.04). The number of pancreatic islets per unit area increased significantly (P<0.05) in SRD rats (3.29+/-0.1 vs 2.01+/-0.2). A significant increment (2.6 times) in the mass of endocrine tissue was detected in SRD animals, mainly due to an increase in the beta-cell mass (P=0.0025). The islet cell replication rate, measured as the percentage of PCNA-labelled beta cells increased 6.8 times in SRD rats (P<0.03). The number of apoptotic cells in the endocrine pancreas decreased significantly (three times) in the SRD animals (P=0.03). The cytokeratin-positive area did not show significant differences between CD and SRD rats. The increase of beta-cell mass induced by SRD was accomplished by an enhanced replication of beta cells together with a decrease in the rate of beta-cell apoptosis, without any evident participation of islet neogenesis. This pancreatic reaction was unable to maintain serum glucose levels of these rats at the level measured in CD animals.
Del Zotto
H
H
CENEXA, Centre of Experimental and Applied Endocrinology (UNLP-CONICET), University of La Plata School of Medicine, La Plata, Argentina.
Gómez Dumm
C L
CL
Drago
S
S
Fortino
A
A
Luna
G C
GC
Gagliardino
J J
JJ
D000818:Animals; D017209:Apoptosis; D001786:Blood Glucose / Q000032:analysis; D001835:Body Weight; D002452:Cell Count; D002455:Cell Division; D048429:Cell Size; D004032:Diet; D005934:Glucagon / Q000032:analysis; D007515:Islets of Langerhans / Q000473:pathology*; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D013213:Starch / Q000008:administration & dosage; D013395:Sucrose / Q000008:administration & dosage*; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D014280:Triglycerides; D013395:Sucrose; D013213:Starch; D005934:Glucagon