Hypothesis

Targeting resveratrol to mitochondria via a triphenylphosphonium (TPP)-conjugated zein nanoparticle will increase SIRT1-mediated deacetylation of mitochondrial SOD2 in aged muscle, improving oxidative phosphorylation efficiency. This effect will be separable from nonspecific proton leak because SIRT1 inhibition with EX-527 will abolish the deacetylation and rescue leak respiration, whereas uncoupler‑induced leak will remain unchanged.

Rationale

• Oral resveratrol bioavailability is <1% due to rapid glucuronidation/sulfonation [1].
• Nanocarriers such as zein nanoparticles raise rodent bioavailability ~50% [1].
• SIRT1 deacetylates substrates like SOD2, HIF1α, and PGC‑1α, linking NAD+ status to redox homeostasis [2].
• Current assays cannot easily separate SIRT1‑specific redox signaling from general mitochondrial proton leak or uncoupling [2].
• Mitochondrial targeting vectors (e.g., TPP) accumulate compounds in the matrix with high specificity, allowing organelle‑restricted polyphenol delivery.

Prediction

1. Aged mice receiving TPP‑zein‑resveratrol will show higher mitochondrial resveratrol levels than free resveratrol or non‑targeted nanocarriers.
2. SIRT1 activity, measured by SOD2 deacetylation, will rise significantly only in the TPP‑zein group.
3. Oxygen consumption assays will reveal increased coupling efficiency (lower leak respiration, higher ATP‑linked OXPHOS) in TPP‑zein‑treated mitochondria.
4. Adding the SIRT1 inhibitor EX‑527 will revert SOD2 acetylation and leak respiration to baseline levels, confirming SIRT1 dependence.
5. Uncoupler‑driven leak (e.g., FCCP) will be unaffected by EX‑527, demonstrating assay specificity.

Experimental Design

• Groups (n=8 per group, aged 24‑month C57BL/6 mice): vehicle, free resveratrol, zein‑resveratrol (non‑targeted), TPP‑zein‑resveratrol, TPP‑zein‑resveratrol + EX‑527.
• Dosing: oral gavage daily for 4 weeks; resveratrol dose 100 mg/kg adjusted for encapsulation efficiency.
• Tissue harvest: isolate gastrocnemius mitochondria; measure resveratrol content by LC‑MS/MS.
• SIRT1 read‑out: western blot for acetylated SOD2 and total SOD2; calculate acetylation ratio.
• Respirometry: high‑resolution Oxygraph‑2k; assess LEAK (oligomycin), OXPHOS (ADP), ET capacity (FCCP), and ROX (antimycin A/rotenone). Repeat LEAK measurement after EX‑527 addition.
• Controls: include PARP inhibitor to ensure NAD+ pool not confounded; measure hepatic glucuronide metabolites to confirm reduced first‑pass loss.

Potential Outcomes and Interpretation

• If hypothesis holds: TPP‑zein group shows ↑ mitochondrial resveratrol, ↓ SOD2 acetylation, ↓ LEAK respiration, and ↑ ATP‑linked flux; EX‑527 abolishes these changes. This would confirm that nanocarrier‑mediated mitochondrial delivery yields SIRT1‑specific bioactivity separable from proton leak.
• If hypothesis fails: No difference in SOD2 acetylation or LEAK between TPP‑zein and controls, or EX‑527 does not rescue leak. This would suggest either insufficient mitochondrial targeting, overwhelming glucuronidation despite encapsulation, or that observed benefits stem from non‑SIRT1 mechanisms (e.g., direct antioxidant effects).

This framework provides a falsifiable, mechanistic test that couples advanced polyphenol nanodelivery with refined respirometric discrimination, addressing the key gap between enhanced bioavailability and validated SIRT1‑specific anti‑aging action.