title: Abnormal hepatic energy homeostasis in type 2 diabetes.
abstract: Increased hepatocellular lipids relate to insulin resistance and are typical for individuals with type 2 diabetes mellitus (T2DM). Steatosis and T2DM have been further associated with impaired muscular adenosine triphosphate (ATP) turnover indicating reduced mitochondrial fitness. Thus, we tested the hypothesis that hepatic energy metabolism could be impaired even in metabolically well-controlled T2DM. We measured hepatic lipid volume fraction (HLVF) and absolute concentrations of gammaATP, inorganic phosphate (Pi), phosphomonoesters and phosphodiesters using noninvasive (1)H/ (31)P magnetic resonance spectroscopy in individuals with T2DM (58 +/- 6 years, 27 +/- 3 kg/m (2)), and age-matched and body mass index-matched (mCON; 61 +/- 4 years, 26 +/- 4 kg/m (2)) and young lean humans (yCON; 25 +/- 3 years, 22 +/- 2 kg/m (2), P < 0.005, P < 0.05 versus T2DM and mCON). Insulin-mediated whole-body glucose disposal (M) and endogenous glucose production (iEGP) were assessed during euglycemic-hyperinsulinemic clamps. Individuals with T2DM had 26% and 23% lower gammaATP (1.68 +/- 0.11; 2.26 +/- 0.20; 2.20 +/- 0.09 mmol/L; P < 0.05) than mCON and yCON individuals, respectively. Further, they had 28% and 31% lower Pi than did individuals from the mCON and yCON groups (0.96 +/- 0.06; 1.33 +/- 0.13; 1.41 +/- 0.07 mmol/L; P < 0.05). Phosphomonoesters, phosphodiesters, and liver aminotransferases did not differ between groups. HLVF was not different between those from the T2DM and mCON groups, but higher (P = 0.002) than in those from the yCON group. T2DM had 13-fold higher iEGP than mCON (P < 0.05). Even after adjustment for HLVF, hepatic ATP and Pi related negatively to hepatic insulin sensitivity (iEGP) (r =-0.665, P = 0.010, r =-0.680, P = 0.007) but not to whole-body insulin sensitivity.
  
  
  CONCLUSIONS
  These data suggest that impaired hepatic energy metabolism and insulin resistance could precede the development of steatosis in individuals with T2DM.
authors.affiliation: Institute for Clinical Diabetology, German Diabetes Center, Leibniz Center for Diabetes Research, Heinrich Heine University Düsseldorf, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Szendroedi
authors.forename: Marek
authors.initials: M
authors.lastname: Chmelik
authors.forename: Albrecht Ingo
authors.initials: AI
authors.lastname: Schmid
authors.forename: Peter
authors.initials: P
authors.lastname: Nowotny
authors.forename: Attila
authors.initials: A
authors.lastname: Brehm
authors.forename: Martin
authors.initials: M
authors.lastname: Krssak
authors.forename: Ewald
authors.initials: E
authors.lastname: Moser
authors.forename: Michael
authors.initials: M
authors.lastname: Roden
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000368:Aged; D016022:Case-Control Studies; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000503:physiopathology; D004734:Energy Metabolism / Q000502:physiology*; D005234:Fatty Liver / Q000209:etiology / Q000378:metabolism; D005260:Female; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D050356:Lipid Metabolism / Q000502:physiology; D008099:Liver / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000378:metabolism; D010758:Phosphorus / Q000378:metabolism
chemical_list: D010710:Phosphates; D010758:Phosphorus; D000255:Adenosine Triphosphate