Reduction in liver fat by dietary MUFA in type 2 diabetes is helped by enhanced hepatic fat oxidation

The aim of this work was to investigate hepatic lipid metabolic processes possibly involved in the reduction of liver fat content (LF) observed in patients with type 2 diabetes after an isoenergetic diet enriched in monounsaturated fatty acids (MUFAs). This is an ancillary analysis of a published study. In a parallel-group design, 30 men and eight women, aged 35-70 years, with type 2 diabetes and whose blood glucose was controlled satisfactorily (HbA(1c) < 7.5% [58 mmol/mol]) by diet or diet plus metformin, were randomised by MINIM software to follow either a high-carbohydrate/high-fibre/low-glycaemic index diet (CHO/fibre diet, n = 20) or a high-MUFA diet (MUFA diet, n = 18) for 8 weeks. The assigned diets were known for the participants and blinded for people doing measurements. Before and after intervention, LF was measured by H-1-MRS (primary outcome) and indirect indices of de novo lipogenesis (DNL) (serum triacylglycerol palmitic:linoleic acid ratio), stearoyl-CoA desaturase activity (SCD-1) (serum triacylglycerol palmitoleic:palmitic acid ratio) and hepatic beta-oxidation of fatty acids (beta-hydroxybutyrate plasma concentrations) were measured. LF was reduced by 30% after the MUFA diet, as already reported. Postprandial beta-hydroxybutyrate incremental AUC (iAUC) was significantly less suppressed after the MUFA diet (n = 16) (-2504 +/- 4488 mu mol/l x 360 min vs baseline -9021 +/- 6489 mu mol/l x 360 min) while it was unchanged after the CHO/fibre diet (n = 17) (-8168 +/- 9827 mu mol/l x 360 min vs baseline -7206 +/- 10,005 mu mol/l x 360 min, p = 0.962) (mean +/- SD, p = 0.043). In the participants assigned to the MUFA diet, the change in postprandial beta-hydroxybutyrate iAUC was inversely associated with the change in LF (r = -0.642, p = 0.010). DNL and SCD-1 indirect indices did not change significantly after either of the dietary interventions. Postprandial hepatic oxidation of fatty acids is a metabolic process possibly involved in the reduction of LF by a MUFA-rich diet in patients with type 2 diabetes.