Investigation of the Lipid Changes That Occur in Hypertrophic Muscle due to Fish Protein-feeding Using Mass Spectrometry Imaging

Abstract

Alaska pollack protein (APP) was previously shown to reduce serum triacylglycerol and the atherogenic index and significantly increase gastrocnemius muscle mass in rats. To determine which myofibers are involved in this observed hypertrophy, we stained the gastrocnemius muscle with fast and slow fiber-specific antibodies and measured the muscle fiber diameter. We observed muscle hypertrophy in both the fast and slow fibers of APP-fed rats. Although muscle hypertrophy leads to drastic lipid changes, the amount of lipids did not differ significantly between casein-fed and APP-fed rats. To determine the lipid changes at the molecular species level and their localization, we performed matrix-assisted laser desorption/ ionization mass spectrometry imaging to visualize lipids in the gastrocnemius muscles. We determined that lipid molecules were significantly changed due to APP feeding. Thus, APP feeding changes muscle lipid metabolism, and these metabolic changes might be related to hypertrophy.

Fish Protein Ingestion Induces Neural, but Not Muscular Adaptations, Following Resistance Training in Young Adults

“…Relationships between the stimulation frequency and electrically elicited force are markedly influenced by contractile properties (39), and correlations between motor unit firing patterns and muscle contractile properties (7,8) have been reported in human skeletal muscles. In previous studies using rat muscle, significant increases in the gastrocnemius muscle weight and fiber diameters were observed by ingestions of APP, but not CAS, during 6-or 8-week interventions (10)(11)(12). In a human study, we also showed increases in the muscle volume of older adults with APP ingestion, but not of older adults with CAS ingestion, following 8 weeks of resistance training (9).…”

“…However, another study reported no significant changes in contractile properties in any types of muscle fibers following 12 weeks of resistance training in humans (44). In the present study, although physiological processes cannot be determined, the pathway leading to changes in the motor unit firing pattern following resistance training in the APP group could be alterations in muscle contractile properties caused by a modification of muscle protein synthesis processes due to APP intake (10)(11)(12). Further studies are needed to clarify the effect of APP ingestion on muscle contractile properties and its relationship with motor unit firing patterns.…”

“…During 8 weeks of resistance training intervention, older adults who ingested fish protein showed gains in muscle strength with muscle hypertrophy but without marked motor unit adaptation, while older adults who ingested casein protein showed similar gains in muscle strength with marked motor unit adaptation but without muscle hypertrophy (9). Since previous studies already reported that fish protein intake induced greater muscle hypertrophy when compared with casein intake in rat muscle, enhancements of muscle hypertrophy following resistance training by the ingestion of fish protein in older adults may be likely to be reasonable (10)(11)(12).…”

Novel Insights on Intake of Fish and Prevention of Sarcopenia: All Reasons for an Adequate Consumption

“…Similarly, a recent study using 5-week-old male Sprague-Dawley rats showed that the volume of gastrocnemius increased in the APP-fed rats in comparison to the casein-fed animals. The results indicated a volume increase in both fast and slow fibers [50].…”

“…The fast and slow muscle fibers have different metabolic characteristics and are arranged in a heterogeneous manner in the skeletal muscle. Muscular atrophy and hypertrophy mainly affect fast fibers [50].…”