Lipid droplet remodelling and reduced muscle ceramides following sprint interval and moderate-intensity continuous exercise training in obese males

Background/Objectives:In obesity, improved muscle insulin sensitivity following exercise training has been linked to the lowering of diacylglycerol (DAG) and ceramide concentrations. Little is known, however, about how improved insulin action with exercise training in obese individuals relates to lipid droplet (LD) adaptations in skeletal muscle. In this study we investigated the hypothesis that short-term sprint interval training (SIT) and moderate-intensity continuous training (MICT) in obese individuals would increase perilipin (PLIN) expression, increase the proportion of LDs in contact with mitochondria and reduce muscle concentrations of DAGs and ceramides.Methods:Sixteen sedentary obese males performed 4 weeks of either SIT (4-7 × 30 s sprints at 200% W(max), 3 days week) or MICT (40-60 min cycling at ~65% VO(2peak), 5 days per week), and muscle biopsies were obtained pre- and post-training.Results:Training increased PLIN2 (SIT 90%, MICT 68%) and PLIN5 (SIT 47%, MICT 34%) expression in type I fibres only, and increased PLIN3 expression in both type I (SIT 63%, MICT 67%) and type II fibres (SIT 70%, MICT 160%) (all P < 0.05). Training did not change LD content but increased the proportion of LD in contact with mitochondria (SIT 12%, MICT 21%, P < 0.01). Ceramides were reduced following training (SIT -10%, MICT -7%, P < 0.05), but DAG was unchanged. No training × group interactions were observed for any variables.Conclusions:These results confirm the hypothesis that SIT and MICT results in remodelling of LDs and lowers ceramide concentrations in skeletal muscle of sedentary obese males.