Structured Docosahexaenoic Acid (DHA) Enhances Motility and Promotes the Antioxidant Capacity of Aged C. elegans

Abstract

The human lifespan has increased over the past century; however, healthspans have not kept up with this trend, especially cognitive health. Among nutrients for brain function maintenance, long-chain omega-3 polyunsaturated fatty acids (ω-3 LCPUFA): DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) must be highlighted, particularly structured forms of EPA and DHA which were developed to improve bioavailability and bioactivity in comparison with conventional ω-3 supplements. This study aims to elucidate the effect of a structured triglyceride form of DHA (DHA-TG) on the healthspan of aged C. elegans. Using a thrashing assay, the nematodes were monitored at 4, 8, and 12 days of adulthood, and DHA-TG improved its motility at every age without affecting lifespan. In addition, the treatment promoted antioxidant capacity by enhancing the activity and expression of SOD (superoxide dismutase) in the nematodes. Lastly, as the effect of DHA-TG was lost in the DAF-16 mutant strain, it might be hypothesized that the effects of DHA need DAF-16/FOXO as an intermediary. In brief, DHA-TG exerted a healthspan-promoting effect resulting in both enhanced physical fitness and increased antioxidant defense in aged C. elegans. For the first time, an improvement in locomotive function in aged wild-type nematodes is described following DHA-TG treatment.

Keywords: C. elegans; DAF-16/FOXO; PUFA; aging; antioxidant; cognitive decline; docosahexaenoic acid; healthspan; nematode; omega-3; oxidative stress; physical decline; structured lipids.

Figure 1

Confocal images of worms grown on agar containing nanoemulsions of DHA-TG oil stained with Nile Red. Images (A–C) show decreasing concentrations of DHA. Pictures I and II show different nematodes treated with the same dosage of DHA. Green arrows in the dark pictures C are pointing to the nematode’s fluorescence in the pharynx.

Figure 2

Effects of vehicle, Oleic-TG, and DHA-TG on the lifespan of N2 C. elegans at 20 °C. The graphic on the left (A) shows the lifespan without FUdR. On the right (B), it is represented the lifespan with the use of FUdR.

Figure 3

Motility improvements in WT nematodes treated with DHA-TG. The locomotive function was assessed without FUdR (A) and with FUdR (B). In three independent repeats, a total of at least 30 nematodes per condition and age were analyzed. Data are represented as mean ± SEM, and statistical differences compared to the vehicle were considered significant at p < 0.05 (*), p < 0.01 (**), and p < 0.005 (***) after two-way ANOVA followed by Dunnett’s post-test.

Figure 4

Sensorial response in WT nematodes treated with DHA-TG. Chemotaxis Index (CI) determined in three independent repeats, a total of at least 50 nematodes per condition and age were analyzed. Data are represented as mean ± SEM.

Figure 5

Lipid peroxidation (A), glutathione quantification (B), and SOD activity (C) after Oleic and DHA-TG treatment. Results are presented as mean ±SEM. Statistical differences compared to vehicle of each age are expressed with (*), and statistical differences between ages are expressed as (#). Differences were considered significant at p < 0.05 (*), p < 0.01 (##), and p < 0.005 (***) (###) after two-way ANOVA followed by Dunnett’s post-test.

Figure 6

Levels of gene expression of WT nematodes at 4th (A), 8th (B), and 12th (C) days of adulthood after treatment with Oleic and DHA-TG. Relative mRNA levels are expressed as percentages vs. vehicle for each gene and age. Results are presented as mean ±SEM of at least 3 biological replicates in triplicate for each one. Statistical differences compared to the vehicle of each gene are expressed with (*), and differences were considered significant at p < 0.05 (*) and p < 0.01 (**) after T-Student comparison.

Figure 7

Motility in WT (N2) and DAF-16 deficient (CF1038) nematodes treated with Oleic and DHA-TG. The locomotive function of N2 vs. CF1038 in basal conditions was assessed (A), and the effect of DHA-TG in CF1038 was monitored (B). In three independent repeats, a total of at least 30 nematodes per condition and age were analyzed. Data are represented as mean ± SEM, and statistical differences were considered significant at p < 0.01 (**), and p < 0.005 (***) after two-way ANOVA followed by Dunnett’s post-test.