Measurement of gluconeogenesis by deuterated water: the effect of equilibration time and fasting period

Fasting gluconeogenesis (GNG) is often quantified using the 2H2O technique, which is based on plasma 2H2O enrichment and ensuing enrichment of plasma glucose at the C5 and C2 positions. Fractional (fr)GNG can be calculated using the ratio of C5 to C2 enrichment or the ratio of C5 to plasma 2H2O enrichment. For the latter, equilibration of 2H2O and C2 is required. The optimal equilibration period of 2H2O and C2 remains to be elucidated. In six healthy male subjects fasted for 18 h, we studied the effects of 3-, 5-, and 15-h 2H2O incubation periods on 1) the equilibration of plasma 2H2O and C2 glucose enrichment, 2) the measurement of frGNG, and 3) C5 labeling of hepatic glycogen after 1 mg of glucagon administration. After 3-h 2H2O incubation, plasma 2H2O and C2 were not equilibrated, frGNG C5/2H2O and C5/C2 were also different as was gluconeogenesis calculated with C5/2H2O and C5/C2. After 5- and 15-h 2H2O incubation, plasma 2H2O and C2 were equilibrated, and frGNG C5/2H2O and C5/C2 were similar, as was GNG calculated with C5/2H2O and C5/C2. After glucagon administration, no difference of C5 enrichment was found between 3, 5, and 15 h of 2H2O incubation. In conclusion, for reliable measurement of GNG in healthy subjects with C5/2H2O incubation periods longer than 3 h are required. After 5- and 15-h 2H2O incubation, GNG can be reliably measured with C5/2H2O. Gluconeogenetic labeling of glycogen did not affect the results after 3, 5, or 15 h of 2H2O incubatio

Prolonged fasting induces peripheral insulin resistance, which is not ameliorated by high-dose salicylate

CONTEXT: Elevated plasma free fatty acids, excess reactive oxygen species, inflammation, and gluco-counterregulatory hormones induce insulin resistance (IR) through activation of Jun NH(2)-terminal kinase and nuclear factor-kappaB inhibitor kappaB kinase, which leads to hyperphosphorylation of the insulin receptor substrate type 1. Aspirin blocks nuclear factor-kappaB inhibitor kappaB kinase and improves IR in type 2 diabetes mellitus. OBJECTIVE: We hypothesized that high-dose aspirin would also attenuate fasting-induced IR in healthy lean subjects. DESIGN: Glucose and glutathione (GHS) metabolism was studied after 12 and 60 h of fasting on two occasions: with and without aspirin (6 g/d). SETTING: The study took place at the Academic Medical Center, Metabolic Research Unit. PARTICIPANTS: Six healthy lean men participated. INTERVENTION: Intervention included 60 h of fasting with or without aspirin ( approximately 6 g/d). MAIN OUTCOME MEASURE: Main outcome measures included glucose and GSH metabolism. RESULTS: Fasting decreased insulin-mediated peripheral glucose uptake by 46% after 60 h (P = 0.03). Aspirin did not alter this effect of 60 h of fasting on insulin sensitivity (P = 0.03). GSH concentration decreased during fasting, but the fractional synthetic rate of GSH was unaffected either with or without aspirin. Fasting did not affect inflammatory parameters, although aspirin increased soluble TNF receptors I and II. CONCLUSION: Prolonged fasting induces profound peripheral IR. In contrast to type 2 diabetes mellitus, high-dose salicylate does not affect fasting-induced peripheral I

Markedly diminished lipolysis and partial restoration of glucose metabolism, without changes in fat distribution after extended discontinuation of protease inhibitors in severe lipodystrophic human immunodeficient virus-1-infected patients.

Item does not contain fulltextTreatment for HIV-1 infection is often complicated by a lipodystrophy syndrome associated with insulin resistance and an elevated rate of lipolysis. In eight HIV-1 infected men with lipodystrophy syndrome, we studied the effects of replacement of protease inhibitor (PI) by abacavir on insulin sensitivity and lipolysis by hyperinsulinemic euglycemic clamp and on fat distribution assessed by dual-energy x-ray absorptiometry and computed tomography scan.Glucose metabolism and lipolysis were assessed by tracer dilution employing [6,6-(2)H(2)]glucose and [(2)H(5)]glycerol, respectively. Data are expressed as mean +/- sd or 95% confidence interval (CI), as appropriate.There were no significant changes in fat distribution assessed by dual-energy x-ray absorptiometry and computed tomography scan at wk 36 and wk 96. The fasting total glucose production decreased from 16.1 +/- 2.5 at study entry by 1.1 (range, -2.1 to -0.1) to 15.0 +/- 1.5 micromol/kg.min after PI withdrawal at wk 36 (n = 8). In an analysis restricted to the patients on treatment at wk 96 (n = 6), the decrease was 0.9 (range, -2.1 to 0.3) micromol/kg.min. During insulin infusion, glucose oxidation (as percent of total glucose disposal) increased from 36.8 +/- 12.7% by 11.0% (range, 1.3-20.8) to 47.9 +/- 13.9% in the wk 36 analysis. In the analysis restricted to the patients on treatment at wk 96 (n = 6) the increase was 7.7 (-4.0 to 19.4)%. Fasting lipolysis decreased from 2.7 +/- 0.6 micromol/kg.min by 0.9 (-1.6 to -0.2) to 1.8 +/- 0.3 micromol/kg.min in the wk-96 analysis (n = 6).The replacement of the studied PIs by abacavir in severe lipodystrophic HIV-1-infected patients results in a marked reduction of lipolysis. In contrast, fasting glucose production and insulin-stimulated glucose oxidation improve moderately, whereas insulin-stimulated glucose disposal and fat distribution do not change