title: Progressive alterations in lipid and glucose metabolism during short-term fasting in young adult men.
abstract: Stable isotope tracers and indirect calorimetry were used to evaluate the progressive alterations in lipid and glucose metabolism after 12, 18, 24, 30, 42, 54, and 72 h of fasting in six healthy male volunteers. The rates of appearance (Ra) of glycerol and palmitic acid in plasma doubled from 2.08 +/- 0.22 and 1.63 +/- 0.20 mumol.kg-1 x min-1, respectively, after 12 h to 4.36 +/- 0.36 and 3.26 +/- 0.40 mumol.kg-1 x min-1, respectively, after 72 h of fasting (P < 0.01). Of the total increase in lipid kinetics, 60% occurred between 12 and 24 h of fasting; the greatest interval change occurred between 18 and 24 h of fasting. Glucose Ra and plasma concentration decreased by approximately 25% between 12 h (11.0 +/- 0.4 mumol.kg-1 x min-1 and 5.58 +/- 0.08 mmol/l, respectively) and 72 h (8.3 +/- 0.3 mumol.kg-1 x min-1 and 4.14 +/- 0.10 mmol/l, respectively) of fasting (P < 0.01), but no statistically significant changes occurred between 18 and 24 h of fasting. Plasma insulin decreased by approximately 50% between 12 h (64.6 +/- 12.9 pmol/l) and 72 h (30.1 +/- 7.9 pmol/l) of fasting (P < 0.001). Of the total decline in plasma insulin, 70% occurred within the first 24 h of fasting. These results demonstrate that the mobilization of adipose tissue triglycerides increases markedly between 18 and 24 h of fasting in young adult men. The early alterations in lipid metabolism are associated with a decline in circulating insulin but do not seem to be regulated by changes in glucose kinetics or plasma glucose concentrations.
authors.affiliation: Department of Internal Medicine, University of Texas Medical Branch, Galveston 77555.
authors.forename: S
authors.initials: S
authors.lastname: Klein
authors.forename: Y
authors.initials: Y
authors.lastname: Sakurai
authors.forename: J A
authors.initials: JA
authors.lastname: Romijn
authors.forename: R M
authors.initials: RM
authors.lastname: Carroll
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D003903:Deuterium; D004734:Energy Metabolism; D005215:Fasting / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000097:blood*; D006801:Humans; D007553:Isotope Labeling / Q000379:methods; D008066:Lipolysis; D008297:Male; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000097:blood*; D012044:Regression Analysis; D013997:Time Factors; D014280:Triglycerides / Q000378:metabolism
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D010169:Palmitic Acids; D014280:Triglycerides; D019308:Palmitic Acid; D003903:Deuterium; D005947:Glucose; D005990:Glycerol