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Microcalorimetric and biochemical investigations of thermogenesis and metabolic pathways in human white adipocytes
1Institute for Biological Chemistry and Nutrition, University of Hohenheim, Stuttgart, FRG.
Objective:
Validation of a novel culture technique for human white adipocytes, facilitating direct microcalorimetry and simultaneously performed biochemistry for 3 days.
Design:
Subcutaneous adipocytes were cultured in a 3-dimensional matrix of agarose gel. Biochemical measures were obtained every 24 h, while thermogenesis was continuously monitored for 72 h. DNA content of the cultures served as reference.
Subjects:
73 men and women undergoing uncomplicated surgery.
Measurements:
Cell viability (LDH release), total cellular thermogenesis, oxygen consumption, glycolysis, lipolysis (basal, catecholamin-stimulated) triglyceride/free fatty acid substrate cycle, adenine nucleotides, insulin-induced thermogenesis.
Results:
LDH release was 0.4% of total LDH per hour. Cellular ATP, ADP and AMP (3.77, 0.39 and 0.06 nmol/microgramDNA, resp.) were constant. The rates of glucose consumption, lactate and pyruvate production and basal glycerol release (56.4, 43.1, 2.7 and 28.1 nmol/microgramDNA.h, resp.) were stable during 72 h. Isoprenaline (1 microM) enhanced lipolytic rate by the same extent at any time of the study (glycerol release 67.8 nmol/microgramDNA.h). FFA release (initially 26.0 nmol/ microgramDNA.h) declined during the experiment, due to an increase of reesterfication rate. Unstimulated heat production was 6.5 microW/microgramDNA, 68% of which were of oxidative origin. Insulin (0.1 microM) induced thermogenesis was 8.8 microW/ microgramDNA.
Conclusion:
The results were in accordance with data from human white adipocytes in suspensions. However, in contrast to fat cell suspensions, gel cultured adipocytes were viable for 3 days without metabolic alterations.