Background: Muscle wasting prevails in numerous diseases (e.g. diabetes, cardiovascular and kidney diseases, COPD,…) and increases healthcare costs. A major clinical issue is to devise new strategies preventing muscle wasting. We hypothesized that 8-week docosahexaenoic acid (DHA) supplementation prior to fasting may preserve muscle mass in vivo.
Methods: Six-week-old C57BL/6 mice were fed a DHA-enriched or a control diet for 8 weeks and then fasted for 48 h.
Results: Feeding mice a DHA-enriched diet prior to fasting elevated muscle glycogen contents, reduced muscle wasting, blocked the 55% decrease in Akt phosphorylation, and reduced by 30-40% the activation of AMPK, ubiquitination, or autophagy. The DHA-enriched diet fully abolished the fasting induced-messenger RNA (mRNA) over-expression of the endocannabinoid receptor-1. Finally, DHA prevented or modulated the fasting-dependent increase in muscle mRNA levels for Rab18, PLD1, and perilipins, which determine the formation and fate of lipid droplets, in parallel with muscle sparing.
Conclusions: These data suggest that 8-week DHA supplementation increased energy stores that can be efficiently mobilized, and thus preserved muscle mass in response to fasting through the regulation of Akt- and AMPK-dependent signalling pathways for reducing proteolysis activation. Whether a nutritional strategy aiming at increasing energy status may shorten recovery periods in clinical settings remains to be tested.
Keywords: Akt and AMPK signalling; Autophagy; Lipid droplets; Protein turnover; Ubiquitin–proteasome system.