To analyze B-cell mechanisms in obesity, we measured the relationship (slope of potentiation) between glucose levels and acute insulin responses (AIR) to isoproterenol or arginine in nondiabetic subjects ranging from lean to markedly obese. Obese men (n = 9) had higher AIRs to isoproterenol than lean men (n = 11) at basal glucose levels [52 +/- 9 (SEM) vs. 32 +/- 5 microU/mL; P less than 0.05], and the difference increased as the ambient glucose level was raised (at 230 mg/dL; 263 +/- 22 vs. 140 +/- 21 microU/mL; P less than 0.0008). The individuals' slopes of glucose potentiation of AIR to isoproterenol were positively correlated with their excess weight (r = 0.72; P less than 0.001). Similar results were found when arginine was used as the secretagogue in other men and in women; the slope of potentiation was positively correlated with excess weight in both men and women (both P less than 0.005), although the effect of excess weight on slope was 51% greater among men (P less than 0.03). An independent measurement of insulin sensitivity (the Bergman SI) was made in the women. The potentiation slope was inversely correlated with SI (P less than 0.0001), indicating that the effect of obesity on insulin secretion is correlated with insulin resistance. These results characterize one mechanism contributing to the hyperinsulinemia of obesity and highlight the importance of considering the prevailing insulin sensitivity when assessing islet function.
It is not clear whether diabetic patients can learn accurate self-monitoring of blood glucose (SMBG) by use of written package instructions. In addition, it is unclear whether the improvement in accuracy of monitoring that results from professional training is due to the professional intervention or to a personal practice effect. For these reasons, improvement in accuracy of SMBG (using Chemstrip bG, Biodynamics Division, Boehringer-Mannheim, Indianapolis, Indiana) after a 30-min session of professional instruction in one group of diabetic patients was compared with improvement after 30 min of practice and study of package instructions in another group. After initial reading of package instructions in both groups, and after the practice session in the control group, mean percent error was 22-37%. In contrast, mean percent error declined to 9% after a professional training session. We conclude that learning SMBG solely by reading package instructions leads to unacceptable inaccuracy. However, by use of short, intensive instruction sessions, a diabetes educator can reduce such errors and teach highly accurate monitoring to most diabetic patients.
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