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

Abstract

Aims/hypothesis: 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).

Methods: 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 ¹H-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 β-oxidation of fatty acids (β-hydroxybutyrate plasma concentrations) were measured.

Results: LF was reduced by 30% after the MUFA diet, as already reported. Postprandial β-hydroxybutyrate incremental AUC (iAUC) was significantly less suppressed after the MUFA diet (n = 16) (-2504 ± 4488 μmol/l × 360 min vs baseline -9021 ± 6489 μmol/l × 360 min) while it was unchanged after the CHO/fibre diet (n = 17) (-8168 ± 9827 μmol/l × 360 min vs baseline -7206 ± 10,005 μmol/l × 360 min, p = 0.962) (mean ± SD, p = 0.043). In the participants assigned to the MUFA diet, the change in postprandial β-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.

Conclusions/interpretation: 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.

Trial registration: ClinicalTrials.gov NCT01025856 FUNDING : The study was funded by Ministero Istruzione Università e Ricerca and Italian Minister of Health.

Keywords: De novo lipogenesis; Diet; Liver fat; Monounsaturated fatty acids; Stearoyl-coenzyme A desaturase-1 activity; Type 2 Diabetes; β-Hydroxybutyrate; β-Oxidation.