# In Vitro Antioxidant Effects of Coenzyme Q10 on Cellular Metabolism in Aged Mesenchymal Stem Cells
## 4 Discussion
As CoQ10 is abundant in the mitochondrial inner membrane, this inhibitory effect in young cells may represent a protective mechanism to maintain redox balance and prevent excessive antioxidant activity. This is consistent with in vivo findings, where CoQ10 supplementation (1200 mg/kg/day for 60 days) improved oxidative stress markers in transgenic mice [37]. Similarly, in vitro treatment (2.5 uM) reduced mitochondrial superoxide levels in CoQ10-deficient neurons [38]. In aged cells (P16), CoQ10's effects vary by dose. At 10 uM, increased PPARy and CAT expression suggests a compensatory response to oxidative stress. However, at 50 uM, expression levels return to baseline, indicating a dual-phase response. Antioxidant enzymes, such as CAT, play a vital role in neutralizing free radicals and mitigating oxidative stress. CoQ10 not only directly scavenes free radicals, but also enhances the activity of these enzymes by unregulating their gene expression, thereby preserving their function and reinforcing cellular defense mechanisms [39; 40]. Our study offers valuable insights into cellular metabolic processes following CoQ10 supplementation, based on gene expression levels and cellular proliferation, viability, and senescence. However, while CoQ10 is known to regulate antioxidant and chronic inflammatory gene activation or repression, future studies should investigate protein level changes, using proteomic and other protein analysis methods. Also, various other cell types (stem and non-stem cells) should be employed in order to acquire a more comprehensive metabolic profile [41]. CoQ10 differentially regulates sittuin gene expression in MSCs across early (P5) and late (P16) passages, suggesting a nuanced impact on cellular aging and metabolism. In both young and older cells, CoQ10 robustly upregulates SIRT1 in a dose-dependent manner. As a NAD\({}^{+}\)-dependent deacetylase, SIRT1 promotes mitochondrial biogenesis, stress resistance, and metabolic regulation, indicating that CoQ10 enhances cellular resilience and metabolic homeostasis, particularly in aged MSCs [42]. In late passage cells, CoQ10 also strongly increases SIRT3 expression, which is essential for mitochondrial protein deacetylation and oxidative stress reduction. This regulation of SIRT3 is influenced by SIRT1 activity and partially mediated through PPARy-dependent pathways [42; 43]. In late passage MSCs, CoQ10 modestly increases SIRT4 expression, while significantly downregulating this sittuin in early passage MSCs. SIRT4, regulates oxygen consumption and fatty acid metabolism via ANT2-dependent coupling, and shows reduced baseline expression in P16 cells, reflecting mitochondrial dysfunction associated with aging. The modest upregulation of SIRT4 by CoQ10 in older cells suggests a restoration of mitochondrial pathways. In contrast, CoQ10 downregulates the expression of SIRT5, SIRT6, and SIRT7, which are involved in mitochondrial function and cellular stress responses [44]. This suppression may represent a compensatory shift favoring SIRT1-, SIRT3-, and SIRT4-dependent pathways for maintaining mitochondrial health and stress adaptation. The differential regulation of sirtius by CoQ10 underscores its potential as an anti-aging therapeutic, particularly for mitigating mitochondrial dysfunction in aged cells. However, the observed suppression of specific sirtius raises important questions about the balance within the sirtuin network, highlighting the need for further investigation to elucidate potential trade-offs and optimize therapeutic benefits. Fatty acids (FAs) are vital for energy storage, membrane structure, and the synthesis of signaling molecules. They serve as a primary energy source through mitochondrial \(\beta\)-oxidation [45]. CoQ10, in its reduced form, acts as a potent antioxidant, improving lipid packaging and cellular membrane stability. This protection safeguards biological membranes against oxidative damage, enhances resistance to rupture, and slows the release of hydrophilic components [46].