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Diabetologia. 2004 Nov;47(11):2022-31. Epub 2004 Dec 1.

Enhanced glucose cycling and suppressed de novo synthesis of glucose-6-phosphate result in a net unchanged hepatic glucose output in ob/ob mice.

Author information

1
The Centre for Liver, Digestive and Metabolic Diseases, Research Laboratory of Paediatrics, CMC IV/2, University Hospital Groningen, P.O. Box 30.001, 9700 RB Groningen, The Netherlands.

Abstract

AIMS/HYPOTHESIS:

Leptin-deficient ob/ob mice are hyperinsulinaemic and hyperglycaemic; however, the cause of hyperglycaemia remains largely unknown.

METHODS:

Glucose metabolism in vivo in 9-h fasted ob/ob mice and lean littermates was studied by infusing [U-(13)C]-glucose, [2-(13)C]-glycerol, [1-(2)H]-galactose and paracetamol for 6 h, applying mass isotopomer distribution analysis on blood glucose and urinary paracetamol-glucuronide.

RESULTS:

When expressed on the basis of body weight, endogenous glucose production (109+/-23 vs 152+/-27 micromol.kg(-1).min(-1), obese versus lean mice, p<0.01) and de novo synthesis of glucose-6-phosphate (122+/-13 vs 160+/-6 micromol.kg(-1).min(-1), obese versus lean mice, p<0.001) were lower in ob/ob mice than in lean littermates. In contrast, glucose cycling was greatly increased in obese mice (56+/-13 vs 26+/-4 micromol.kg(-1).min(-1), obese versus lean mice, p<0.001). As a result, total hepatic glucose output remained unaffected (165+/-31 vs 178+/-28 micromol.kg(-1).min(-1), obese vs lean mice, NS). The metabolic clearance rate of glucose was significantly lower in obese mice (8+/-2 vs 18+/-2 ml.kg(-1).min(-1), obese versus lean mice, p<0.001). Hepatic mRNA levels of genes encoding for glucokinase and pyruvate kinase were markedly increased in ob/ob mice.

CONCLUSIONS/INTERPRETATION:

Unaffected total hepatic glucose output in the presence of hyperinsulinaemia reflects hepatic insulin resistance in ob/ob mice, which is associated with markedly increased rates of glucose cycling. Hyperglycaemia in ob/ob mice primarily results from a decreased metabolic clearance rate of glucose.

PMID:
15599701
DOI:
10.1007/s00125-004-1571-8
[Indexed for MEDLINE]

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