Endocrine Abstracts

JOINT1151

Background: Macrophages play a key role in muscle regeneration following injury, with androgens (testosterone [T] and dihydrotestosterone [DHT]) and glucocorticoids (cortisone [E] and cortisol [F]) influencing anabolic, anti-anabolic, and catabolic muscle metabolism. We have shown that inflammation dynamically regulates glucocorticoid and androgen metabolism in macrophages, and these processes may be dysregulated in inflammatory diseases.

Methods: Primary human macrophages from healthy donors were polarized with TNFα/IFNγ or left unpolarized before treatment with F precursor (E; 100 nmol/l) and DHT precursors (T & A4; 100 nmol/l). Treated macrophages or conditioned media were co-cultured with myotubes and myoblasts derived from healthy human quadriceps. Macrophage F and DHT metabolite synthesis was measured by LC-MS/MS. Myotube thickness (microscopy), muscle metabolism markers (qRT-PCR), cell migration (scratch assay), proliferation (BrdU), and protein synthesis (synthesis assay) were assessed.

Results: Inflammatory-activated macrophages exhibited a distinct regulation of steroid metabolism, increasing cortisol (F) activation from cortisone (E) and dihydrotestosterone (DHT) activation from testosterone (T) and androstenedione (A4). Conditioned media or co-culture with activated macrophages led to reduced myotube fiber size without altering metabolic gene expression. However, conditioned media with T significantly increased fiber thickness (P < 0.001). T treatment also decreased myoblast proliferation after 72 hours (P = 0.0196) without affecting cell viability. In contrast, conditioned media with E did not affect fiber thickness but significantly reduced myoblast proliferation at 72 hours (P = 0.0009). E treatment increased catabolic markers (Foxo1, Fbox32) and decreased the anabolic marker Igf-1. In comparison, T-conditioned media decreased catabolic Foxo1 and anti-anabolic Myostatin (Mstn) and increased the differentiation marker Myod after 24 hours. Direct DHT treatment did not increase protein synthesis rate compared to control and reduced proliferation at 48 hours (P < 0.05). F significantly decreased myoblast proliferation at both 48 and 72 hours (P < 0.0001). Finally, examination of myoblasts revealed that macrophage-conditioned media enhanced cell migration and proliferation, regardless of T precursor treatment.

Conclusions: Inflammatory-activated macrophages dynamically regulate glucocorticoid and androgen metabolism, influencing muscle fiber size and metabolism. These effects may be altered in chronic inflammatory diseases, potentially impairing muscle regeneration. Further investigation is needed to determine if these processes are dysregulated in inflammatory conditions.