title: Postprandial and fasting hepatic glucose fluxes in long-standing type 1 diabetes.
abstract: OBJECTIVE
  Intravenous insulin infusion partly improves liver glucose fluxes in type 1 diabetes (T1D). This study tests the hypothesis that continuous subcutaneous insulin infusion (CSII) normalizes hepatic glycogen metabolism.
  
  
  METHODS
  T1D with poor glycemic control (T1Dp; HbA(1c): 8.5 ± 0.4%), T1D with improved glycemic control on CSII (T1Di; 7.0 ± 0.3%), and healthy humans (control subjects [CON]; 5.2 ± 0.4%) were studied. Net hepatic glycogen synthesis and glycogenolysis were measured with in vivo (13)C magnetic resonance spectroscopy. Endogenous glucose production (EGP) and gluconeogenesis (GNG) were assessed with [6,6-(2)H(2)]glucose, glycogen phosphorylase (GP) flux, and gluconeogenic fluxes with (2)H(2)O/paracetamol.
  
  
  RESULTS
  When compared with CON, net glycogen synthesis was 70% lower in T1Dp (P = 0.038) but not different in T1Di. During fasting, T1Dp had 25 and 42% higher EGP than T1Di (P = 0.004) and CON (P < 0.001; T1Di vs. CON: P = NS). GNG was 74 and 67% higher in T1Dp than in T1Di (P = 0.002) and CON (P = 0.001). In T1Dp, GP flux (7.0 ± 1.6 μmol ⋅ kg(-1) ⋅ min(-1)) was twofold higher than net glycogenolysis, but comparable in T1Di and CON (3.7 ± 0.8 and 4.9 ± 1.0 μmol ⋅ kg(-1) ⋅ min(-1)). Thus T1Dp exhibited glycogen cycling (3.5 ± 2.0 μmol ⋅ kg(-1) ⋅ min(-1)), which accounted for 47% of GP flux.
  
  
  CONCLUSIONS
  Poorly controlled T1D not only exhibits augmented fasting gluconeogenesis but also increased glycogen cycling. Intensified subcutaneous insulin treatment restores these abnormalities, indicating that hepatic glucose metabolism is not irreversibly altered even in long-standing T1D.
authors.affiliation: Karl-Landsteiner Institute for Endocrinology and Metabolism, Vienna, Vienna, Austria.
authors.forename: Michaela
authors.initials: M
authors.lastname: Kacerovsky
authors.forename: John
authors.initials: J
authors.lastname: Jones
authors.forename: Albrecht I
authors.initials: AI
authors.lastname: Schmid
authors.forename: Cristina
authors.initials: C
authors.lastname: Barosa
authors.forename: Angelika
authors.initials: A
authors.lastname: Lettner
authors.forename: Gertrud
authors.initials: G
authors.lastname: Kacerovsky-Bielesz
authors.forename: Julia
authors.initials: J
authors.lastname: Szendroedi
authors.forename: Marek
authors.initials: M
authors.lastname: Chmelik
authors.forename: Peter
authors.initials: P
authors.lastname: Nowotny
authors.forename: Visvanathan
authors.initials: V
authors.lastname: Chandramouli
authors.forename: Michael
authors.initials: M
authors.lastname: Wolzt
authors.forename: Michael
authors.initials: M
authors.lastname: Roden
mesh_terms: D000328:Adult; D003922:Diabetes Mellitus, Type 1 / Q000378:metabolism*; D005215:Fasting / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism; D006801:Humans; D008099:Liver / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D008297:Male; D019518:Postprandial Period / Q000502:physiology*; D055815:Young Adult
chemical_list: D006003:Glycogen; D005947:Glucose