Hypothesis: Peptide-mediated attenuation of CD38-driven NAD+ depletion synergizes with NAD+ precursors to reverse age-related tissue dysfunction\n\n## Rationale\n\n- BPC-157 upregulates growth hormone receptor and activates NO/eNOS, ERK1/2, FAK-paxillin pathways, exerting anti‑inflammatory effects that lower TNF‑α and IL‑6 (see ). Chronic inflammation drives CD38 upregulation, which consumes NAD+ ([2]). Thus BPC‑157‑mediated inflammation reduction should decrease CD38 expression.\n- TB‑500, a thymosin β‑4 fragment, promotes actin polymerization, enhancing cell migration and matrix remodeling. Improved tissue perfusion and macrophage clearance further dampen local inflammatory cues, reinforcing the drop in CD38 activity.\n- Lower CD38 preserves NAD+ pools, allowing SIRT1 and SIRT3 to deacetylate metabolic and DNA‑repair targets, improving mitochondrial function and genome stability.\n- Providing NAD+ precursors (NMN or NR) supplies the substrate needed for NAD+ synthesis; when CD38 activity is suppressed, more of the precursor is converted to functional NAD+ rather than being degraded.\n- The combined action predicts a greater NAD+ restoration and downstream benefits than either approach alone.\n\n## Testable Predictions\n\n1. In aged mice, BPC‑157 + TB‑500 co‑administration will reduce tissue CD38 mRNA and protein levels by ≥30 % versus vehicle (qPCR/Western blot).\n2. The same regimen will increase muscle NAD+ concentration by ≥20 % over baseline, surpassing the ~10 % rise seen with NMN monotherapy ([3]).\n3. Functional readouts (fore‑limb grip strength, treadmill endurance to exhaustion) will show significant improvement only in the combination‑plus‑NMN group, indicating a synergistic effect.\n4. Senescence biomarkers (p16^INK4a mRNA, SA‑β‑gal staining) will be lowest in the triple‑treatment group, reflecting enhanced senolysis.\n\n## Falsifiability\n\nIf CD38 levels are not lowered, NAD+ does not rise beyond that achieved by NMN alone, or functional and senescence outcomes fail to show additive improvement in the peptide‑plus‑precursor groups, the hypothesis is falsified.\n\n## Experimental Design (brief)\n\n- Groups: young control, aged vehicle, aged BPC‑157, aged TB‑500, aged NMN, aged BPC‑157+TB‑500, aged BPC‑157+TB‑500+NMN (n=10 per group).\n- Treatment duration: 12 weeks, with peptides administered intraperitoneally three times weekly and NMN via drinking water.\n- Endpoints: tissue CD38 (mRNA, protein), NAD+ levels (enzymatic assay), SIRT activity, histologic scoring of fibrosis/inflammation, grip strength, treadmill performance, senescence markers.\n- Statistical analysis: two‑way ANOVA with post‑hoc Tukey test; synergy assessed via interaction term.