Hyperinsulinemic-euglycemic Clamps in Conscious, Unrestrained Mice

Abstract

Type 2 diabetes is characterized by a defect in insulin action. The hyperinsulinemic-euglycemic clamp, or insulin clamp, is widely considered the "gold standard" method for assessing insulin action in vivo. During an insulin clamp, hyperinsulinemia is achieved by a constant insulin infusion. Euglycemia is maintained via a concomitant glucose infusion at a variable rate. This variable glucose infusion rate (GIR) is determined by measuring blood glucose at brief intervals throughout the experiment and adjusting the GIR accordingly. The GIR is indicative of whole-body insulin action, as mice with enhanced insulin action require a greater GIR. The insulin clamp can incorporate administration of isotopic 2[ 14 C]deoxyglucose to assess tissue-specific glucose uptake and [3-3 H]glucose to assess the ability of insulin to suppress the rate of endogenous glucose appearance (endoRa), a marker of hepatic glucose production, and to stimulate the rate of whole-body glucose disappearance (Rd).

Hemin Improves Insulin Sensitivity in Skeletal Muscle in High Fat–Fed Mice

“…Although hemin increases glucose-stimulated insulin secretion via CO (24), it may be not the case in this study since the high fat-fed hemin-injected mice showed reduced basal and clamp insulin levels. Reduced insulin levels during clamp imply improved insulin sensitivity (25).…”

Insulin Resistance and Metabolic Derangements in Obese Mice Are Ameliorated by a Novel Peroxisome Proliferator-activated Receptor γ-sparing Thiazolidinedione

“…After a 5-6-h fast, hyperinsulinemic clamp studies were performed on conscious mice using the protocol adopted from the Vanderbilt Mouse Metabolic Phenotyping Center (28) by the University of Michigan Animal Phenotyping Core consisting of a 90-min equilibration period followed by a 120-min experimental period (t ϭ 0 -120 min). Insulin was infused at 2.5 milliunits/kg/min.…”

Insulin exits skeletal muscle capillaries by fluid-phase transport

“…ITTs were performed under anesthesia to mimic the conditions of the in vivo imaging experiment. At least 5 days before the day of the study, mice had indwelling catheters implanted in the jugular vein for infusions of insulin, isotopic glucose tracers, and anesthetics (41). After a 5-hour fast, mice were anesthetized with an intravenously administered ketamine/xylazine/ acepromazine (KXA) cocktail (7.9/1.6/0.2 mg/kg).…”

“…Hyperinsulinemic-euglycemic clamps were performed in conscious, unstressed, chronically catheterized mice as described previously (41). Mice were fasted for 5 hours before starting of the insulin clamp.…”