Decreased white fat cell thermogenesis in obese individuals.
OBJECTIVE
To investigate whether white adipocyte thermogenesis and energy metabolism are reduced in obese individuals.


METHODS
Eight lean and 15 obese men and women; BMI 19-41.


METHODS
Isolated subcutaneous adipocytes were maintained in agarose gel for 20h under basal conditions and subsequently for 10h after stimulation with 1 microM isoprenaline. Direct microcalorimetry was performed continuously over 30h while biochemical measures were obtained after 0, 20, 25 and 30h.


METHODS
Total cellular thermogenesis, oxygen consumption, glycolysis, lipolysis, triglyceride/FFA substrate cycle, adenine nucleotides, DNA content as basis of reference.


RESULTS
Under basal and stimulated conditions, thermogenesis (5.6 and 8.6 microW/microgDNA, respectively; P < 0.0001) correlated negatively (P < 0.01 and P < 0.05, respectively) with the BMI and positively with O2 and glucose consumption, lactate, glycerol, FFA release and FFA re-esterification. Reduced basal lactate production with increased BMI (P < 0.05) indicates a more aerobic adipocyte metabolism in obese individuals. Negative correlation between BMI and stimulated triglyceride/FFA substrate cycle activity (P < 0.01) explains the decreased hormone induced adipocyte heat production in the obese.


CONCLUSIONS
The results suggest that a reduction of total body energy expenditure, which is discussed to cause obesity, can be associated with distinct metabolic alterations at a cellular level. However, since the estimated total body fat cell thermogenesis does not exceed 7% of the resting metabolic rate, the observed decrease of adipocyte heat production in the face of augmented BMI can only in part be responsible for the development of obesity.
Böttcher
H
H
University of Hohenheim, Institute for Biological Chemistry and Nutrition, Stuttgart, FRG Germany.
Fürst
P
P
D017667:Adipocytes / Q000378:metabolism*; D001833:Body Temperature Regulation; D002151:Calorimetry; D002478:Cells, Cultured; D005230:Fatty Acids, Nonesterified / Q000378:metabolism; D005260:Female; D005990:Glycerol / Q000378:metabolism; D006019:Glycolysis; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D019344:Lactic Acid / Q000378:metabolism; D008066:Lipolysis; D008297:Male; D009765:Obesity / Q000378:metabolism*; D010101:Oxygen Consumption; D013566:Sympathomimetics / Q000494:pharmacology
D005230:Fatty Acids, Nonesterified; D013566:Sympathomimetics; D019344:Lactic Acid; D007545:Isoproterenol; D005990:Glycerol