Polyunsaturated fatty acids ameliorate aging via redox-telomere-antioncogene axis

Abstract

Polyunsaturated fatty acids (PUFA), a group of nourishing and health-promoting nutrients, ameliorate age-related chronic diseases. However, how PUFA especially n-3 PUFA exert anti-aging functions remains poorly understood. Here we link fish oil, docosahexaenoic acid (DHA) and arachidonic acid (AA) to the aging etiology via a redox-telomere-antioncogene axis based on D-galactose-induced aging mice. Both fish oil and PUFA enhanced hepatic superoxide dismutase (SOD) and catalase activities and cardiac SOD activities within the range of 18%-46%, 26%-65% and 19%-58%, respectively, whereas reduced cerebral monoamine oxidase activity, plasma F2-isoprostane level and cerebral lipid peroxidation level by 56%-90%, 20%-79% and 16%-54%, respectively. Thus, PUFA improve the in vivo redox and oxidative stress induced aging process, which however does not exhibit a dose-dependent manner. Notably, both PUFA and fish oil effectively inactivated testicular telomerase and inhibited c-Myc-mediated telomerase reverse transcriptase expression, whereas n-3 PUFA rather than n-6 PUFA protected liver and testes against telomere shortening within the range of 13%-25% and 25%-27%, respectively. Therefore, n-3 PUFA may be better at inhibiting the DNA damage induced aging process. Surprisingly, only DHA significantly suppressed cellular senescence pathway evidenced by testicular antioncogene p16 and p53 expression. This work provides evident support for the crosstalk between PUFA especially n-3 PUFA and the aging process via maintaining the in vivo redox homeostasis, rescuing age-related telomere attrition and down-regulating the antioncogene expression.

Keywords: Gerotarget; anti-aging; antioncogene; polyunsaturated fatty acids; redox; telomere protection.

Figure 1. PUFA ameliorate hepatic oxidative stress

Both fish oil and PUFA monomers significantly promoted hepatic A. SOD and B. CAT activities (P < 0.05). However, the improvement in C. GSH-Px activities did not seem significant (P > 0.05). Each column with error bar indicates the data expressed as mean ± standard deviation (SD) (n = 5). Bars marked with different letters indicate significant discrepancies (P < 0.05). AM, aging model group; Con, saline control group; VE, vitamin E positive control; 400FO1, 200FO1, and 100FO1, FO1 (DHA/EPA ratio = 2.28) at high, moderate and low doses, respectively; 400FO2, 200FO2, and 100FO2, FO2 (DHA/EPA ratio = 0.66) at high, moderate and low doses, respectively; 120DHA, 60DHA, and 30DHA, DHA at high, moderate and low doses, respectively; 120AA, 60AA, and 30AA, AA at high, moderate and low doses, respectively.

Figure 2. n-3 rather than n-6 PUFA inhibit excessive telomere length loss in

A. livers and B. testes of aging mice. Each column with error bar indicates the data expressed as mean ± SD (n = 5). Bars marked with different letters indicate significant discrepancies (P < 0.05). The instructions about the group labels were the same as indicated in Figure 1.

Figure 3. PUFA repress testicular telomerase activities through the reduction of

c-Myc-mediated TERT expression in aging mice. A. The effect of PUFA on telomerase activities (n = 5). B. The effect of PUFA on the mRNA expression of testicular TERT (n = 5). C. The effect of PUFA on the protein expression of testicular TERT and c-Myc (n = 3). The TERT and c-Myc primary antibody recognized a single protein band with molecular weights of approximately 126 kDa and 57 kDa, respectively. Each column with error bar indicates the data expressed as mean ± SD. Bars marked with different letters indicate significant discrepancies (P < 0.05). gapdh, glyceraldehyde-3-phosphate dehydrogenase. The instructions about the group labels were the same as indicated in Figure 1.

Figure 4. PUFA reduce the testicular

TERT protein expression confirmed by the immunofluorescence of histological testicular sections. DAPI, 4’,6-diamidino-2- phenylindole. Scale bar, 50 μm.

Figure 5. DHA inhibits testicular

p16 and p53 protein expression and SA-β-gal. A. The effect of PUFA on the protein expression of testicular p16. B. The effect of PUFA on the protein expression of testicular p53. The p16 and p53 primary antibodies recognized a single protein band with molecular weights of approximately 16 kDa and 53 kDa, respectively. C. Representative fields of in situ SA-β-gal staining in testicular cryosections. Arrows indicate foci with high SA-β-gal activities. Each column with error bar indicates the data expressed as mean ± SD (n = 3). Bars marked with different letters indicate significant discrepancies (P < 0.05). The instructions about the group labels were the same as indicated in Figure 1.