Evidence for Impaired Gluconeogenesis in Very Long-chain Acyl-CoA Dehydrogenase-deficient Mice

Abstract

Hypoketotic hypoglycaemia is a characteristic feature of fatty acid oxidation (FAO) defects. Although the underlying pathogenic mechanism is unknown, one hypothesis points to an impairment in gluconeogenesis. To study hepatic glucose production in FAO defects, we used the knockout mouse model of very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency presenting with stress-induced hypoglycaemia. We analysed metabolites of hepatic glucose production under non-stressed conditions and after stress in comparison to wildtype controls. Analysis included glycogen, glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), glycerol-3-phosphate (G3P) and dihydroxyacetone-phosphate (DHAP). We also measured the activity of the key enzyme glucose-6-phosphatase. Blood and liver glucose were found to be low after stress, and liver glycogen was depleted. In addition, hepatic G6P and F6P were significantly reduced, especially during hypoglycaemia. Importantly, the activity of the enzyme converting G6P into glucose was not impaired. These data indicate a reduced rate of gluconeogenesis. The levels of DHAP and G3P were significantly lower suggesting decreased availability of glucose precursors from glycerol. This study gives biochemical evidence of impaired gluconeogenesis as one of the causes for hypoglycaemia observed in VLCAD deficiency. Whether this is due to lack of a substrate, inhibitory effects on other gluconeogenic enzymes or impaired transcription of gluconeogenic enzymes needs to be resolved in the future.

Key words

Fatty acid β-oxidation - hypoketotic hypoglycaemia - glycerol - hepatic glucose production

References

• 1 Wilcken B, Wiley V, Hammond J, Carpenter K. Screening newborns for inborn errors of metabolism by tandem mass spectrometry.  N Engl J Med. 2003;  348 2304-2312
• 2 Gregersen N, Andresen BS, Corydon MJ, Corydon TJ, Olsen R, Bolund L, Bross P. Mutation analysis in mitochondrial fatty acid oxidation defects: exemplified by acyl-CoA dehydrogenase deficiencies, with special focus on genotype-phenotype relationship.  Hum Mutat. 2001;  18 169-189
• 3 Gregersen N, Bross P, Andresen BS. Genetic defects in fatty acid β-oxidation and acyl-CoA dehydrogenases. Molecular pathogenesis and genotype-phenotype relationships.  Eur J Biochem. 2004;  271 470-482
• 4 Spiekerkoetter U, Khuchua Z, Yue Z, Bennett MJ, Strauss AW. General mitochondrial trifunctional protein (TFP) deficiency as a result of either alpha- or beta-subunit mutations exhibits similar phenotypes because mutations in either subunit alter TFP complex expression and subunit turnover.  Pediatr Res. 2004;  55 190-196
• 5 Spiekerkoetter U, Tokunaga C, Wendel U, Mayatepek E, Exil V, Duran M, Wijburg FA, Wanders RJA, Strauss AW. Changes in blood carnitine and acylcarnitine profiles of very long-chain acyl-CoA dehydrogenase-deficient mice subjected to stress.  Eur J Clin Invest. 2004;  34 191-196
• 6 Spiekerkoetter U, Tokunaga C, Wendel U, Mayatepek E, IJlst L, Vaz FM, van Vlies N, Overmars H, Duran M, Wijburg FA, Wanders RJ, Strauss AW. Tissue carnitine homeostasis in very long-chain acyl-CoA dehydrogenase-deficient mice.  Pediatr Res. 2005;  57 760-764
• 7 Xu J, Xiao G, Trujillo C, Chang V, Blanco L, Joseph SB, Bassilian S, Saad MF, Tontonoz P, Lee WN, Kurland IJ. Peroxisome proliferator-activated receptor α (PPARα) influences substrate utilization for hepatic glucose production.  J Biol Chem. 2002;  277 50237-50244
• 8 Bergmeyer HU. Methods of enzymatic analysis VI. 3rd ed. VCH Publishers 1986 pp 11, 163, 191, 342, 525, 582
• 9 Groen AK, Vervoorn RC, Van der Meer R, Tager JM. Control of gluconeogenesis in rat liver cells. I. Kinetics of the individual enzymes and the effect of glucagon.  J Biol Chem. 1983;  258 14346-14353
• 10 Exton JH, Park CR. Control of gluconeogenesis in liver. I. General features of gluconeogenesis in the perfused livers of rats.  J Biol Chem. 1967;  242 2622-2636
• 11 Kersten S, Seydoux J, Peters JM, Gonzalez FJ, Desvergne B, Wahli W. Peroxisome proliferator-activated receptor α mediates the adaptive response to fasting.  J Clin Invest. 1999;  103 1489-1498
• 12 Lee WN, Byerley LO, Bergner EA, Edmond J. Mass isotopomer analysis: theoretical and practical considerations.  Biol Mass Spectrom. 1991;  20 451-458
• 13 Podolin DA, Wei Y, Pagliassotti MJ. Effects of a high fat diet and voluntary wheel running on gluconeogenesis and lipolysis in rats.  J Appl Physiol. 1999;  86 1374-1380
• 14 Bizeau ME, Hazel JR. Dietary fat type alters glucose metabolism in isolated rat hepatocytes.  J Nutr Biochem. 1999;  10 709-715
• 15 Bizeau ME, Short C, Thresher JS, Commerford SR, Willis WT, Pagliassotti MJ. Increased pyruvate flux capacities account for diet-induced increase in gluconeogenesis in vitro.  Am J Physiol Regul Integr Comp Physiol. 2001;  281 R427-R433
• 16 Andrikopoulos S, Proietto J. The biochemical basis of increased hepatic glucose-production in a mouse model of type 2 (noninsulin-dependent) diabetes mellitus.  Diabetologia. 1996;  38 1389-1396
• 17 Rhee J, Inoue Y, Yoon JC, Puigserver P, Fan M, Gonzalez FJ, Spiegelman BM. Regulation of hepatic fasting response by PPARgamma coactivator-1alpha (PGC-1): requirement for hepatocyte nuclear factor 4alpha in gluconeogenesis.  Proc Natl Acad Sci USA. 2003;  100 4012-4017
• 18 Roe CR, Sweetman L, Roe DS, David F, Brunengraber H. Treatment of cardiomyopathy and rhabdomyolysis in long-chain fat oxidation disorders using an anaplerotic odd-chain triglyceride.  J Clin Invest. 2002;  110 259-269

Correspondence