Glucagon dose-response curve for hepatic glucose production and glucose disposal in type 2 diabetic patients and normal individuals.

This study sought to examine whether enhanced hepatic sensitivity to glucagon contributes to impaired glucose homeostasis in subjects with type 2 diabetes mellitus (T2DM). Eight T2DM and 9 age-, weight-, and gender-matched nondiabetic subjects received a 4-hour glucagon infusion at the rates of 0.2, 0.5, 2, 6, and 8 ng. kg(-1). min(-1) while maintaining the plasma insulin concentration constant at the basal level with exogenous infusions of somatostatin and insulin. On the evening prior to study, diabetic subjects received a low-dose insulin infusion at a rate designed to maintain euglycemia and this infusion rate was continued until the end of the glucagon infusion study on the following day. Each glucagon infusion study was performed on a separate day and in random order. 3-(3)H-glucose was infused in all studies to measure endogenous glucose production (EGP) and the rate of whole body glucose disposal. During the first 2 hours (0 to 120 minutes) of glucagon infusion, EGP increased sharply in both groups, and the initial rate of rise in EGP was higher in control versus diabetic subjects. During the last 2 hours (120 to 240 minutes) of glucagon infusion, EGP in the diabetics tended to be higher than controls during the 3 lower glucagon infusion rates and this difference reached statistical significance (P <.05 to.01) during the 6 and 8 ng. kg(-1). min(-1) infusions. During the 2 hours following cessation of glucagon (240- to 360-minute time period), the stimulation of glucose disappearance from plasma was impaired (P <.05) during all 5 glucagon infusion rates in the diabetics compared to controls. We conclude that in T2DM patients, the initial (0 to 120 minutes) stimulation of hepatic glucose output (which primarily reflects glycogenolysis) by glucagon is not enhanced in T2DM patients. The late (120 to 240 minutes) stimulation of hepatic glucose output (which primarily reflects gluconeogenesis) by glucagon tends to be increased, especially at supraphysiologic plasma glucagon concentrations.

Regulation of the HIV promoter/enhancer.

This unit describes adaptations of two molecular techniques that can be used to study the regulation of HIV expression. The first two protocols describe the chloramphenicol acetyltransferase (CAT) assay, in which the CAT reporter gene is attached to an HIV-1 promoter and CAT activity is measured as an indication of the promoter's activity. The basic protocol is rapid, simple, and suited to analyzing multiple samples. An alternate protocol describes an assay for CAT function that involves separating the reaction products by thin-layer chromatography (TLC). The second basic protocol describes an electrophoretic mobility shift assay for detecting proteins present in cell extracts that can bind to the HIV-1 LTR (long terminal repeat). Such studies are central to current HIV research because it is important to know what agents induce and inhibit (or "down-regulate") HIV transcription.