AUTHOR=Pierce Joseph R. , Martin Brian J. , Rarick Kevin R. , Alemany Joseph A. , Staab Jeffery S. , Kraemer William J. , Hymer Wesley C. , Nindl Bradley C.
TITLE=Growth Hormone and Insulin-like Growth Factor-I Molecular Weight Isoform Responses to Resistance Exercise Are Sex-Dependent
JOURNAL=Frontiers in Endocrinology
VOLUME=11
YEAR=2020
URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2020.00571
DOI=10.3389/fendo.2020.00571
ISSN=1664-2392
ABSTRACT=Purpose: To determine if acute resistance exercise-induced increases in growth hormone (GH) and insulin-like growth factor-I (IGF-I) were differentially responsive for one or more molecular weight (MW) isoforms and if these responses were sex-dependent.
Methods: College-aged men (n = 10) and women (n = 10) performed an acute resistance exercise test (ARET; 6 sets, 10 repetition maximum (10-RM) squat, 2-min inter-set rest). Serum aliquots from blood drawn Pre-, Mid-, and Post-ARET (0, +15, and +30-min post) were processed using High Performance Liquid Chromatography (HPLC) fractionation and pooled into 3 MW fractions (Fr.A: >60; Fr.B: 30–60; Fr.C: <30 kDa).
Results: We observed a hierarchy of serum protein collected among GH fractions across all time points independent of sex (Fr.C > Fr.A > Fr.B, p ≤ 0.03). Sex × time interactions indicated that women experienced earlier and augmented increases in all serum GH MW isoform fraction pools (p < 0.05); however, men demonstrated delayed and sustained GH elevations (p < 0.01) in all fractions through +30-min of recovery. Similarly, we observed a sex-independent hierarchy among IGF-I MW fraction pools (Fr.A > Fr.B > Fr.C, p ≤ 0.01). Furthermore, we observed increases in IGF-I Fr. A (ternary complexes) in men only (p ≤ 0.05), and increases in Fr.C (free/unbound IGF-I) in women only (p ≤ 0.05) vs. baseline, respectively.
Conclusions: These data indicate that the processing of GH and IGF-I isoforms from the somatotrophs and hepatocytes are differential in their response to strenuous resistance exercise and reflect both temporal and sex-related differences.