PPAR-γ response element activity in intact primary human adipocytes: effects of fatty acids
Received 10 January 2005; accepted 26 April 2005. published online 13 October 2005.
Abstract
Objective
We studied the activity and regulation of the peroxisome proliferator-activated receptor-γ response element (PPRE) in primary human adipocytes.
Methods
We transfected primary human adipocytes with a plasmid-encoding firefly luciferase cDNA under control of a PPRE from the acyl-coenzyme A oxidase gene by using our newly developed electroporation-based method. Several fatty acids were added to the fat cells to study potential activation of peroxisome proliferator-activated receptor-γ.
Results
Cells responded maximally to 5 μM of rosiglitazone at a 5.1 ± 1.4-fold over basal increase in luciferase activity. There was a positive correlation between body mass index and the response to 5 μM of rosiglitazone (r = 0.36, P = 0.03). Patients with type 2 diabetes had similar basal PPRE activity but responded more strongly to 5 μM of rosiglitazone than did non-diabetic subjects (10.2 ± 5-fold and 5.4 ± 1-fold over basal increase, respectively, P < 0.0001). Among saturated fatty acids, lauric acid was without effect, but 10 μM of palmitic or stearic acid increased PPRE activity 20% to 35% above basal levels. Monounsaturated palmitoleic acid at 1 μM induced a PPRE transcriptional activity that corresponded to half the therapeutic levels of rosiglitazone.
Conclusion
Adipocytes from obese subjects and patients with type 2 diabetes responded particularly strongly to the effect of rosiglitazone on PPRE. Because fatty acids in the diet can affect the transcriptional activity of peroxisome proliferator-activated receptor-γ over decades, the stimulation induced by stearic and palmitoleic acids can affect insulin sensitivity and, hence, cardiovascular morbidity and mortality in humans.
This study was supported by the Swedish Society for Medical Research, the Swedish Research Council (grants 14254 and 12157), the Swedish National Board for Laboratory Animals, the Lions Foundation, the Östergötland County Council, the Swedish Diabetes Association, the Swedish Medical Society, and the University Hospital of Linköping Research Funds.
ABSTRACT