Decreased liver fatty acid delta-6 and delta-5 desaturase activity in obese patients.

Steatosis in obese nonalcoholic fatty liver disease (NAFLD) patients is a clinicopathological condition associated with depletion of n-3 polyunsaturated fatty acids (PUFA), a feature that may be related to PUFA desaturation. Liver Delta-6 and Delta-5 desaturase (Delta-6D and Delta-5D) activities, homeostasis model assessment of insulin resistance (HOMA(IR)), and ferric reducing ability of plasma (FRAP) were evaluated in 13 obese patients who underwent subtotal gastrectomy with gastro-jejunal anastomosis in Roux-en-Y and 15 nonobese patients who underwent laparoscopic cholecystectomy (controls). Liver Delta-6D and Delta-5D activities in obese patients were 87% and 66% lower than controls (P < 0.001), respectively, with a 62% diminution in the Delta-6D/Delta-5D activity ratio (P < 0.02). Delta-6D inversely correlated with both HOMA(IR) (r = -0.70, P < 0.0001) and oxidative stress assessed as the reciprocal value of FRAP (r = -0.40, P < 0.05). Delta-5D negatively correlated with HOMA(IR) (r = -0.48, P < 0.01) but not with FRAP(-1) (r = -0.13, not significant). In conclusion, liver PUFA desaturation is diminished in obese NAFLD patients, in association with underlying insulin resistance and oxidative stress, which may play a role in altering lipid metabolism favoring fatty infiltration.