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1 CENEXA Centre of Experimental and Applied Endocrinology (UNLP-CONICET, PAHO/WHO Collaborating Centre), University of La Plata School of Medicine, La Plata, Argentina
2 Department of Biochemistry, University of Litoral, Santa Fe, Argentina
(Requests for offprints should be addressed to H Del Zotto, CENEXA (UNLP-CONICET), Facultad de Ciencias Médicas, UNLP, 60 y 120 1900 La Plata, Argentina; Email cenexa{at}speedy.com.ar)
This study aimed to determine the relative importance of different functional and morphological pancreatic changes induced by the chronic administration of a sucrose-rich diet (SRD) to maintain normal glucose homeostasis. Male Wistar rats were fed either sucrose (SRD) or starch (CD) for 6 and 12 months. At both periods, serum glucose and triacylglycerol levels were significantly higher (P<0.05; paired and unpaired Students t-test) in SRD rats. Serum insulin levels were significantly lower in SRD only at 12 months. At 6 months, the insulin secretion doseresponse curve in SRD rats showed a shift to the left that was no longer observed at 12 months, when SRD islets decreased their response to 16 mM glucose. At 6 months, SRD rats showed a significant increase in ß-cell volume density (Vvi) and islet cell replication rate, together with a decrease in ß-cell apoptotic rate. Changes were not detected in the percentage of PDX-1- and islet neogenesis associated protein (INGAP)-positive cells. Conversely, at 12 months, there was a significant decrease in ß-cell Vvi and in the percentage of PDX-1-positive cells; the islet cell replication rate was not modified, and the number of apoptotic ß-cells increased significantly. No signs of increased neogenesis or INGAP-positive cells were recorded at any period in SRD rats. Our results show that SRD rats are unable to develop functional and morphological pancreatic reactive changes sufficient to maintain normal glucose and triacylglycerol levels for a long period. Such failure could be ascribed to their inability to increase the rate of neogenesis and of INGAP production.
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