title: Time course of the hepatic adaptation to TPN: interaction with glycogen depletion.
abstract: In response to chronic (5 days) TPN, the liver becomes a major site of glucose disposal, removing approximately 45% (4.5 mg.kg(-1).min(-1)) of exogenous glucose. Moreover, approximately 70% of glucose is not stored but released as lactate. We aimed to determine in chronically catheterized conscious dogs the time course of adaptation to TPN and the glycogen depletion impact on early time course. After an 18-h (n = 5) fast, TPN was infused into the inferior vena cava for 8 (n = 5) or 24 h (n = 6). A third group, of 42-h-fasted animals (n = 6), was infused with TPN for 8 h. TPN was infused at a rate designed to match the dog's calculated basal energy and nitrogen requirements. NHGU (-2.3 +/- 0.1 to 2.2 +/- 0.7 to 3.9 +/- 0.6 vs. -1.7 +/- 0.3 to 1.1 +/- 0.5 to 2.9 +/- 0.4 mg.kg(-1).min(-1), basal to 4 to 8 h, 18 vs. 42 h) and net hepatic lactate release (0.7 +/- 0.3 to 0.6 +/- 0.1 to 1.4 +/- 0.2 vs. -0.6 +/- 0.1 to 0.1 +/- 0.1 to 0.8 +/- 0.1 mg.kg(-1).min(-1), basal to 4 to 8 h) increased progressively. Net hepatic glycogen repletion and tracer determined that glycogen syntheses were similar. After 24 h of TPN, NHGU (5.4 +/- 0.6 mg.kg(-1).min(-1)) and net hepatic lactate release (2.6 +/- 0.4 mg.kg(-1).min(-1)) increased further. In summary, 1) most hepatic adaptation to TPN occurs within 24 h after initiation of TPN, and 2) prior glycogen depletion does not augment hepatic adaptation rate.
authors.affiliation: Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA.
authors.forename: Sheng-Song
authors.initials: SS
authors.lastname: Chen
authors.forename: Carlos J
authors.initials: CJ
authors.lastname: Torres-Sanchez
authors.forename: Nadeen
authors.initials: N
authors.lastname: Hosein
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Zhang
authors.forename: D Brooks
authors.initials: DB
authors.lastname: Lacy
authors.forename: Owen P
authors.initials: OP
authors.lastname: McGuinness
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004285:Dogs; D005260:Female; D005934:Glucagon / Q000097:blood; D006003:Glycogen / Q000378:metabolism*; D006614:Hindlimb / Q000378:metabolism; D007328:Insulin / Q000097:blood; D007413:Intestinal Mucosa / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008102:Liver Circulation / Q000502:physiology; D010289:Parenteral Nutrition, Total
chemical_list: D001786:Blood Glucose; D007328:Insulin; D006003:Glycogen; D005934:Glucagon