title: Protein metabolism in human obesity: relationship with glucose and lipid metabolism and with visceral adipose tissue.
abstract: It is controversial whether metabolic disorders of human obesity include protein metabolism. Even less information is available concerning the effect of fat distribution on protein metabolism. Therefore, a comprehensive evaluation of glucose, lipid, and protein metabolism was performed in 11 obese nondiabetic and 9 normal women whose body composition and regional fat distribution were determined. [1-14C]Leucine and [3-3H]glucose were infused in the postabsorptive state and during an euglycemic hyperinsulinemic (35-40 microU/mL) clamp combined with indirect calorimetry for assessment of leucine flux, oxidation, and nonoxidative disposal, glucose turnover and oxidation, and lipid oxidation. Fat-free mass (FFM) was estimated by a bolus of 3H2O. Subcutaneous abdominal and visceral adipose tissues were determined by nuclear magnetic resonance imaging. During the clamp, obese women had lower glucose turnover (4.51 +/- 0.41 vs. 6.63 +/- 0.40 mg/min.kg FFM; P < 0.05), with a defect in both oxidation (3.27 +/- 0.22 vs. 3.89 +/- 0.21) and nonoxidative disposal (1.24 +/- 0.27 vs. 2.74 +/- 0.41; P < 0.005), whereas lipid oxidation was higher during the clamp (0.49 +/- 0.15 vs. 0.17 +/- 0.09 mg/min.kg FFM). There was no difference in leucine flux (basal, 2.23 +/- 0.17 vs. 2.30 +/- 0.29; clamp, 2.06 +/- 0.19 vs. 2.10 +/- 0.24 mumol/min.kg FFM), oxidation (basal, 0.37 +/- 0.04 vs. 0.36 +/- 0.05; clamp, 0.34 +/- 0.04 vs. 0.39 +/- 0.06) and nonoxidative leucine disposal (basal, 1.86 +/- 0.17 vs. 1.94 +/- 0.26; clamp, 1.72 +/- 0.20 vs. 1.71 +/- 0.19) in the two groups. In obese women, basal leucine oxidation was directly related with glucose oxidation and inversely to lipid oxidation (both P < 0.05), whereas visceral adipose tissue was inversely related to leucine flux both in the basal state and during the clamp (P < 0.05). In conclusion, in human obesity, 1) rates of protein metabolism in the basal state and in the range of insulin concentrations encountered after a meal are normal; 2) protein oxidation is positively related to glucose oxidation and negatively related to lipid oxidation; and 3) visceral adipose tissue is inversely related to all parameters of protein metabolism.
authors.affiliation: Department of Internal Medicine, University of Ferrara, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Solini
authors.forename: E
authors.initials: E
authors.lastname: Bonora
authors.forename: R
authors.initials: R
authors.lastname: Bonadonna
authors.forename: P
authors.initials: P
authors.lastname: Castellino
authors.forename: R A
authors.initials: RA
authors.lastname: DeFronzo
mesh_terms: D000273:Adipose Tissue; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D001823:Body Composition; D002153:Calorimetry, Indirect; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005502:Food; D005947:Glucose / Q000378:metabolism; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000097:blood; D007930:Leucine / Q000378:metabolism; D015227:Lipid Peroxidation; D008055:Lipids / Q000097:blood*; D009765:Obesity / Q000378:metabolism*; D010084:Oxidation-Reduction; D011506:Proteins / Q000378:metabolism*
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008055:Lipids; D011506:Proteins; D007930:Leucine; D005947:Glucose