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-cell mass in normal and
-cell-reduced lean and obese Göttingen minipigs in vivo
1Department of Pharmacology Research I and 2Department of Pharmacology Research III, Novo Nordisk A/S, Maaloev; 3Department of Assay and Cell Technology, Novo Nordisk A/S, Bagsvaerd; 4Discovery Management, Novo Nordisk A/S, Bagsvaerd; 5Medical Department C, Aarhus University Hospital, Aarhus; and 6Department of Pharmacology Research IV, Novo Nordisk A/S, Maaloev, Denmark
Submitted 6 June 2005 ; accepted in final form 1 November 2005
At present, the best available estimators of
-cell mass in humans are those based on measurement of insulin levels or appearance rates in the circulation. In several animal models, these estimators have been validated against
-cell mass in lean animals. However, as many diabetic humans are obese, a correlation between in vivo tests and
-cell mass must be evaluated over a range of body weights to include different levels of insulin sensitivity. For this purpose, obese (n = 10) and lean (n = 25) Göttingen minipigs were studied.
-Cell mass had been reduced (n = 16 lean, n = 5 obese) with a combination of nicotinamide (67 mg/kg) and streptozotocin (125 mg/kg), acute insulin response (AIR) to intravenous glucose and/or arginine was tested, pulsatile insulin secretion was evaluated by deconvolution (n = 30), and
-cell mass was determined histologically. AIR to 0.3 (r2 = 0.4502, P < 0.0001) or 0.6 g/kg glucose (r2 = 0.6806, P < 0.0001), 67 mg/kg arginine (r2 = 0.5730, P < 0.001), and maximum insulin concentration (r2 = 0.7726, P < 0.0001) were all correlated to
-cell mass when evaluated across study groups, and regression lines were not different between lean and obese groups except for AIR to 0.3 g/kg glucose. Baseline pulse mass was not significantly correlated to
-cell mass across the study groups (r2 = 0.1036, NS), whereas entrained pulse mass did show a correlation across groups (r2 = 0.4049, P < 0.001). This study supports the use of in vivo tests of insulin responses to evaluate
-cell mass over a range of body weights in the minipig. Extensive stimulation of insulin secretion by a combination of glucose and arginine seems to give the best correlation to
-cell mass.
animal model; streptozotocin; arginine; pulsatile insulin secretion
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