Sterol regulatory element binding protein 1c (SREBP-1c) expression in human obesity

Objective: Investigation of the expression of sterol regulatory element binding protein-1c (SREBP-1c) in different adipose tissue depots in morbidly obese subjects before and after 1 year of weight loss induced by gastric banding operation. Research Methods and Procedures: SREBP-1c expression was studied in 20 massively obese subjects (6 men and 14 women; age: 41 +/- 9 years; weight: 148 +/- 34 kg; percentage of body fat: 42 +/- 4; mean +/- SD) using reverse transcription competitive polymerase chain reaction. Adipose tissue biopsies were taken from omental, subcutaneous abdominal, and femoral depots before weight loss, and from subcutaneous depots after weight loss. Subcutaneous samples were taken also from 6 normal weight subjects. Results: The level of SREBP-1c mRNA was significantly lower in omental (1.8 +/- 0.2 amol/mug of total RNA) than in subcutaneous abdominal (3.7 +/- 0.4 amol/mug of total RNA) or femoral (3.9 +/- 0.4 amol/mug of total RNA; p < 0.001, mean SEM) depots. The values in subcutaneous depots were about twice as high in normal weight (7.4 +/- 2.5 for abdominal and 6.5 +/- 1.5 for femoral, p < 0.01) as in obese subjects. After weight loss, the mRNA levels of SREBP-1c increased in obese subjects, both in subcutaneous abdominal (5.3 +/- 0.7, p < 0.01) and in femoral (4.8 +/- 0.8, p < 0.05) tissue. Discussion: SREBP-1c mRNA expression was lower in omental adipose tissue than in subcutaneous depots in obese subjects before weight loss. Furthermore, the expression of SREBP-Ic in obese subjects was clearly lower than in normal weight subjects, but mRNA levels increased along with weight reduction. Weight reduction was associated with increased mRNA levels of SREBP-1c in obese subjects. The reduced expression of SREBP-1c in obesity could be ascribed to lowered action or concentration of insulin, changeable along, with weight reduction. However, changes in SREBP-1c expression after weight reduction could also be ascribed to the changes in calorie intake or nutritional habits after castric banding operation.