Effects of sprint interval training on ectopic lipids and tissue-specific insulin sensitivity in men with non-alcoholic fatty liver disease

Purpose: This study examined the feasibility of sprint interval exercise training (SIT) for men with non-alcoholic fatty liver disease (NAFLD) and its effects on intrahepatic triglyceride (IHTG), insulin sensitivity (hepatic and peripheral), visceral (VAT) and subcutaneous adipose tissue (ScAT). Methods: Nine men with NAFLD (age 41±8 years; BMI 31.7±3.1 kg·m-2; IHTG 15.6±8.3%) were assessed at: 1) baseline 2) after a control phase of no intervention (pre-training) and 3) after six weeks of SIT (4-6 maximal 30 s cycling intervals, three times per week). IHTG, VAT and ScAT were measured using magnetic resonance spectroscopy or imaging and insulin sensitivity was assessed via dual-step hyperinsulinaemic-euglycaemic clamp with [6,6-D2] glucose tracer. Results: Participants adhered to SIT, completing ≥96.7% of prescribed intervals. SIT increased peak oxygen uptake (V̇O2 peak: +13.6% [95% CI: 8.8 to 18.2%]) and elicited a relative reduction in IHTG (-12.4% [-31.6 to 6.7%]) and VAT (-16.9% [-24.4 to -9.4%]; n=8), with no change in body weight or ScAT. Peripheral insulin sensitivity increased throughout the study (n=8; significant main effect of phase) but changes from pre- to post-training were highly variable (range: -18.5 to +58.7%) and not significant (P=0.09), despite a moderate effect size (g*=0.63). Hepatic insulin sensitivity was not influenced by SIT. Conclusions: SIT is feasible for men with NAFLD in a controlled laboratory setting and is able to reduce IHTG and VAT in the absence of weight loss.