Hypercaloric diets cause dyslipidemia, insulin resistance and contribute to the development of type 2 diabetes. Nevertheless, the degree of fatty acid (FA) saturation may differently affect metabolism and risk of cardiovascular diseases, with saturated FA (SAFA) considered to be harmful and polyunsaturated FA (PUFA) considered to be beneficial. Thus, we aimed at characterizing the acute effects of palm oil (POL, SAFA-rich) and safflower oil (SOL, PUFA-rich) on tissue-specific insulin sensitivity and skeletal muscle mitochondrial function in glucose-tolerant volunteers (10 m/6 f; age 24±2 years; BMI 23.1±0.9 kg/m2), who ingested 1.2 g/kg BW of POL, SOL or control (CON, water) on three occasions. Whole-body glucose disposal (Rd) was assessed with [2H2]glucose before and during hyperinsulinemic-euglycemic clamps. Skeletal muscle biopsies were performed to assess protein kinase C (PKC) ԑ and θ translocation and oxygen fluxes by high-resolution respirometry at 1 h before and 2, 4 and 7 h after the interventions. Before the clamp, POL but not SOL ingestion raised plasma palmitic acid levels by 102% (p<0.01) compared to CON. Only POL decreased Rd by 28% and muscle mitochondrial oxidative capacity by 38% from succinate and by 39% from octanoyl-carnitine, but increased PKCɛ activity by 57% (all p<0.05 vs. CON). During insulin stimulation, Rd decreased by 38% after POL and by 26% after SOL (all p<0.05 to CON). Non-oxidative glucose disposal was lower after POL than after SOL (p<0.05).
In conclusion, oral ingestion of palmitate-enriched lipids rapidly induces whole-body insulin resistance, which is likely mediated through skeletal muscle lipid-mediated PKCԑ activation and possibly accelerated by impaired mitochondrial function. Thus, the amount of dietary lipids determines acute insulin resistance, but its composition may differentially regulate skeletal muscle oxidative capacity.
T. Sarabhai: None. C. Koliaki: None. S. Kahl: None. D. Pesta: None. L. Mastrototaro: None. M. Apostolopoulou: None. D.F. Markgraf: None. C. Herder: Research Support; Self; Sanofi-Aventis. M. Roden: Advisory Panel; Self; Servier. Board Member; Self; Poxel SA. Consultant; Self; Eli Lilly and Company, Gilead Sciences, Inc., ProSciento, TARGET PharmaSolutions. Research Support; Self; Boehringer Ingelheim International GmbH, Novartis Pharma K.K., Sanofi US. Speaker’s Bureau; Self; Novo Nordisk A/S.
German Federal Ministry of Health and Ministry of Culture and Science of the State North Rhine-Westphalia; German Federal Ministry of Education and Research by the European Regional Development Fund (KomIT, EFRE-0400191); German Research Foundation (DFG; SFB 1116/2)