PPAR-γ response element activity in intact primary human adipocytes: effects of fatty acids

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.