Source comparison
Somatopause Research: Restoring vs Replacing the Axis
In aged animal somatopause research, the distinction between Sermorelin and exogenous GH produces meaningful biological differences relevant to longevity research. In 20-22 month Wistar rats, Sermorelin (200µg/kg/day × 12 weeks) restored pulsatile GH architect
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- In aged animal somatopause research, the distinction between Sermorelin and exogenous GH produces meaningful biological differences relevant to longevity research. In 20-22 month Wistar rats, Sermorelin (200µg/kg/day × 12 weeks) restored pulsatile GH architecture (GH pulse frequency 1.2±0.3→2.8±0.4 pulses/12h; amplitude restoration as above), resulting in IGF-1 +34-42%, lean body mass +8-12% (EchoMRI), grip strength +22-28%, and bone mineral density improvement (DXA +6-8%). Notably, IGFBP-1 (an IGF-1 binding protein upregulated in somatopause indicating reduced pulsatile GH tone) normalised with Sermorelin, confirming axis restoration rather than simple IGF-1 supplementation.
- In matched aged rats receiving exogenous GH (0.3mg/kg/day, producing comparable mean IGF-1 elevation), lean mass and grip strength improvements were similar (+9-13% and +20-26% respectively), but GH pulse architecture was abolished (constant GH receptor occupancy suppressed endogenous GH to undetectable), and IGFBP-1 paradoxically increased (continuous IGF-1 elevation with suppressed GH pulsatility altered the STAT5b-mediated IGFBP-1 regulation). IGF-1 receptor desensitisation was evident at 8 weeks in exogenous GH animals (IGF-1-stimulated Akt phosphorylation ex vivo: −18-24% compared to Sermorelin animals), suggesting that supraphysiological continuous IGF-1 from exogenous GH produced partial IGF-1R desensitisation relevant to long-duration research designs.