7138 Testosterone Modulation of Muscle Transcriptome Profile During Intensive Lifestyle Intervention in Older Men With Obesity and Hypogonadism

Abstract Disclosure: V. Viola: None. T. Samanta: None. M. Duremdes Nava: None. A. Celli: None. R.C. Villareal: None. N.H. Nguyen: None. G. Colleluori: None. Y. Barnouin: None. N. Napoli: None. C. Qualls: None. B.A. Kaipparettu: None. D.T. Villareal: None. Background: We reported that testosterone replacement added to lifestyle therapy can mitigate weight loss-induced reduction of muscle mass and bone mineral density (BMD) in older men with obesity and hypogonadism (Barnouin et al., J Clin Endocrinol Metab, 2021). Objective: To investigate the molecular mechanisms underlying the mitigation of muscle and BMD loss in response to testosterone replacement therapy during intensive lifestyle intervention in this at-risk population. Materials and Methods: Among the 83 older (≥ 65 y) men with obesity (BMI ≥ 30 kg/m2) and hypogonadism (early AM testosterone persistently <300 ng/dl) associated with frailty (PPT score ≤ 31) who were randomized into 26-week lifestyle therapy plus testosterone (LT+Test) or placebo (LT+Pbo), 38 underwent serial muscle biopsies for the muscle transcriptomics substudy. Results: Despite a similar 9% weight loss, lean body mass and thigh muscle volume decreased less in LT+Test than LT+Pbo (both -2% vs -4%, respectively; p=0.04). Hip BMD was preserved in LT+Test compared with LT+Pbo (0.4% vs -1.1%; p=0.03). Muscle strength increased similarly in LT+Test and LT+Pbo (23% vs 24%; p=0.95). Total testosterone increased more in LT+Test than LT+Pbo (133% vs 32%; p=0.01). Based on Next Generation Sequencing, of the 39,160 and 39,115 genes detected in LT+Test and LT+Pbo, respectively, 151 genes were differentially expressed (DEGs) in LT+Test and 114 in LT+Pbo group. Gene Ontology enrichment analyses revealed that in the LT+Test group, just four muscle-related terms (muscle organ development, muscle organ morphogenesis, regulation of skeletal muscle contraction, muscle atrophy) were downregulated, and one term (muscle system process) was upregulated while in the LT+Pbo, nine terms related to muscle (muscle system process, muscle tissue development, muscle organ development, skeletal muscle tissue development, skeletal muscle organ development, skeletal muscle cell differentiation, muscle organ morphogenesis, response to stimuli involved in regulation of muscle adaptation, muscle atrophy), and one term related to bone (bone mineralization involved in bone maturation) were downregulated. Notably, muscle system process was upregulated in the LT+Test but downregulated in the LT+Pbo. The RT-PCR analyses showed that LT+Test resulted in a higher expression of MYOD1 (p=0.02) and WNT4 (p= 0.08), key genes involved in muscle and bone metabolism, respectively, compared to LT+Pbo. Furthermore, we observed significantly higher mRNA expression of MYBPH (p=0.01), SCN3B (p=0.02), and DSC2 (p=0.01), genes involved in the muscle system process, in response to LT+Test compared to LT+Pbo. Conclusion: The addition of testosterone replacement to lifestyle therapy mitigates the weight loss-induced reduction of muscle mass and BMD via countering the weight loss-induced downregulation of genes involved in muscle and bone anabolism. Presentation: 6/2/2024