Resistance exercise, skeletal muscle FOXO3A, and 85-year-old women

Abstract

This investigation examined Akt-FOXO3A signaling in young women (YW) and old women (OW) before and after 12 weeks of high-intensity resistance training. Muscle biopsies were taken from the vastus lateralis before and immediately after resistance exercise (RE) in the untrained and trained states. In response to RE in YW and OW, phospho Akt Thr308 increased in untrained and trained states, with no change on Ser473 site. FOXO3A-Ser253 site was dephosphorylated in untrained state among YW and OW, and nuclear phospho-FOXO3A increased mainly in YW in trained state. In the basal state, OW displayed lower cytosolic phospho-FOXO3A before training, higher total nuclear FOXO3A, and a trend for higher nuclear-to-cytosolic FOXO3A ratio versus YW after 12 weeks. Basal level MuRF-1 and myostatin mRNA decreased in YW, while OW increased myostatin mRNA after 12-weeks. These data suggest that FOXO3A signaling and FOXO3A-related target gene expression are altered in OW and may partially explain the attenuated training adaptations previously reported in these octogenarian women.

Figure 1.

Study design schematic. 1-RM; one-repetition maximum; PRT = progressive resistance training.

Figure 2.

A bout of resistance exercise (RE), before and after 12 weeks of progressive resistance training (PRT), increases Akt Threonine 308 phosphorylation from skeletal muscle of young and old women. Prior to (untrained) and following (trained) PRT, muscle biopsies were obtained from the vastus lateralis before (Pre) and immediately after (Post) a bout of RE under fasting conditions. Equal protein from cytosolic samples was analyzed for phospho Akt Thr308 (A), phospho-Akt Ser473 (B), and total Akt by Western blot analysis. Values are means ± SE. Representative Western blots are shown. *p < .05 from Pre. AU = arbitrary units.

Figure 3.

Age- and exercise-related alterations in cytosolic and nuclear FOXO3A before and after 12 weeks of progressive resistance training (PRT) from skeletal muscle of young and old women. Prior to (untrained) and following (trained) PRT, muscle biopsies were obtained from the vastus lateralis before (Pre) and immediately after (Post) a bout of resistance exercise under fasting conditions. Equal protein from cytosolic- and nuclear-enriched fractions was analyzed for (A) β-tubulin and Histone H3 protein expression, respectively, (B) cytosolic, and (C) nuclear phospho-FOXO3A Ser253 and total FOXO3A by Western blot analysis. Values are means ± SE. Representative Western blots are shown. *p < .05 from Pre, †p < .05 from young women Pre untrained, **p < .05 from Pre trained. AU = arbitrary units.

Figure 4.

Training-related alterations in the messenger RNA (mRNA) of FOXO3A and transcriptional targets of FOXO3A from skeletal muscle of young and old women. Muscle biopsies were obtained from the vastus lateralis before and after 12 weeks of progressive resistance training under fasting conditions. Samples were analyzed for relative mRNA expression of FOXO3A, MuRF-1, myostatin, and atrogin-1 by real time reverse transcription–polymerase chain reaction, then normalized to glyceraldehyde 3-phosphate dehydrogenase, and calculated using 2^-DCT method. Values are means ± SE. *p < .05 from untrained, †p < .05 from trained young women.

Figure 5.

Altered FOXO3A signaling as a potential mechanism contributing to limited skeletal muscle growth and plasticity in octogenarians. The current data show that 85-year-old skeletal muscle has elevated nuclear FOXO3A protein expression versus the young participants, which promotes proteolytic gene expression (eg, FOXO3A, MuRF-1, and atrogin-1) (41). Increased proteolytic activity may contribute to an inhibition of myogenesis and muscle size, which limits muscle plasticity and muscle function at the level of the whole-muscle and single-muscle fiber (13). Larger bold text within the cell cytosol and nuclear domains indicates more of an increase in protein expression and/or activation or a cellular process. Smaller unbold text (except domain designates) within the cell cytosol and nuclear domains indicates more of a decrease in protein expression and/or activation or a cellular process. RE = resistance exercise.