title: Net carbon flux across subcutaneous adipose tissue after a standard meal in normal-weight and insulin-resistant obese subjects.
abstract: OBJECTIVE
  To elucidate the alterations in subcutaneous adipose tissue metabolism in obesity which affect substrate storage in the fed state, by describing as completely as possible the 'metabolic balance sheet' for adipose tissue.
  
  
  METHODS
  13 lean people (age: 24-64 years, BMI: 19.3-29.4 kg/m2) and 9 insulin-resistant obese subjects (age: 38-57 years, BMI: 32.4-56.0 kg/m2).
  
  
  METHODS
  Net flux of eight major substrates and CO2 across subcutaneous adipose tissue in vivo before and after eating a standard mixed meal (3.1 MJ, 41% from fat).
  
  
  RESULTS
  The net flux of total carbon atoms in the 8 substrates and CO2 was negative (net export from the tissue) in both groups in the fasting state. After the meal it changed rapidly to a positive balance (net substrate storage) in the control group and remained positive until 5 h, whereas in the obese group it remained negative throughout. The overall carbon balance in adipose tissue reflected predominantly the movement of fatty acids in and out of the tissue.
  
  
  CONCLUSIONS
  The fact that fat storage failed to occur despite elevated plasma concentrations of triacylglycerol, glucose and insulin indicates an alteration in metabolic regulation at the cellular level which might be called insulin resistance. Insulin resistance of fat metabolism may be an adaptation which limits further fat deposition, but is maladaptive in terms of risk factors for atherosclerosis.
authors.affiliation: Nuffield Department of Clinical Medicine, Radcliffe Infirmary, Oxford, U.K.
authors.forename: K N
authors.initials: KN
authors.lastname: Frayn
authors.forename: S M
authors.initials: SM
authors.lastname: Humphreys
authors.forename: S W
authors.initials: SW
authors.lastname: Coppack
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D002244:Carbon / Q000378:metabolism*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005502:Food; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D007700:Kinetics; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism*; D014280:Triglycerides / Q000097:blood
chemical_list: D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D014280:Triglycerides; D002244:Carbon