Related Experiment Videos
Decreased white fat cell thermogenesis in obese individuals
1University of Hohenheim, Institute for Biological Chemistry and Nutrition, Stuttgart, FRG Germany.
Objective:
To investigate whether white adipocyte thermogenesis and energy metabolism are reduced in obese individuals.
Subjects:
Eight lean and 15 obese men and women; BMI 19-41.
Design:
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.
Measurements:
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.