A botanical containing freeze dried açai pulp promotes healthy aging and reduces oxidative damage in sod1 knockdown flies

Abstract

Superoxide dismutase 1 (SOD1), a critical enzyme against oxidative stress, is implicated in aging and degenerative diseases. We previously showed that a nutraceutical containing freeze-dried açai pulp promotes survival of flies fed a high-fat diet or sod1 knockdown flies fed a standard diet. Here, we investigated the effect of açai supplementation initiated at the early or late young adulthood on lifespan, physiological function, and oxidative damage in sod1 knockdown flies. We found that Açai supplementation extended lifespan even when started at the age of 10 days, which is the time shortly before the mortality rate of flies accelerated. Life-long açai supplementation increased lifetime reproductive output in sod1 knockdown flies. Our molecular studies indicate that açai supplementation reduced the protein levels of genes involved in oxidative stress response, cellular growth, and nutrient metabolism. Açai supplementation also affected the protein levels of ribosomal proteins. In addition, açai supplementation decreased the transcript levels of genes involved in oxidative stress response and gluconeogenesis, while increasing the transcript levels of mitochondrial biogenesis genes. Moreover, açai supplementation reduced the level of 4-hydroxynonenal-protein adducts, a lipid peroxidation marker. Our findings suggest that açai supplementation promotes healthy aging in sod1-deficient flies partly through reducing oxidative damage, and modulating nutrient metabolism and oxidative stress response pathways. Our findings provide a foundation to further evaluate the viability of using açai as an effective dietary intervention to promote healthy aging and alleviate symptoms of diseases with a high level of oxidative stress.

Fig. 1

The effect of a later life supplementation of açai on lifespan. (a) Lifespan curve of sod1RNAi (UAS-sod1IR/+ and da-Gal4/+) female flies. (b) Lifespan curve of the wild-type control flies, UAS-sod1IR/+. Açai supplementation was initiated at 10 days of age. Mean lifespan with standard error is listed in parentheses. ^***p < 0.001 for comparison between açai-supplemented and genotype-matched non-supplemented groups by logrank test (n = 133–147 flies for each treatment)

Fig. 2

The effect of açai supplementation on physiological and behavioral function in sod1RNAi female flies and their wild-type control da-Gal4/+ flies. (a) Lifespan curves of sod1RNAi females fed the 0, 2, and 4 % açai-supplemented diets. (b) Lifespan curves of the wild-type control da-Gal4/+ females fed the 0, 2, and 4 % açai-supplemented diets. Mean lifespan with standard errors is listed in parentheses. ^***p < 0.001 for comparison between açai-supplemented and non-supplemented groups by logrank test (n = ~30 for each treatment). (c) Supplementation of 2 or 4 % açai significantly increased lifetime egg production when compared to the non-supplemented control in sod1RNAi flies. ^*p < 0.05; ^**p < 0.01 by Student’s t test; n = 6 replicates each with five females. (d) Supplementation of 2 or 4 % açai did not increase lifetime egg production relative to the non-supplemented control in the wild-type control da-Gal4/+ flies (n = 6 replicates each with five females). (e) Egg production during each transfer interval per survived fly fed the 0, 2, or 4 % açai-supplemented diet throughout the adult life of sod1RNAi flies. Arrow indicates when the significant difference in egg production showed up between açai-supplemented and non-supplemented control flies.^*p < 0.05 for comparison between açai-supplemented and non-supplemented groups by Student’s t test (n = 6 for each treatment). (f) Egg production during each transfer interval per survived fly fed the 0, 2, or 4 % açai-supplemented diet throughout the adult life of da-Gal4/+ flies. (g) Two percent açai supplementation did not change daily food intake in volume when compared to the non-supplemented control in sod1RNAi flies. (h) Two percent açai supplementation did not change daily food intake in volume when compared to the non-supplemented control for da-Gal4/+ flies. a.u. refers to arbitrary unit

Fig. 3

The effect of açai supplementation on changes in protein levels in sod1RNAi female flies. (a) The effect of açai supplementation on expression changes in 22 proteins. All fold changes in the graph are >1.4-fold and statistically significant at p < 0.05 by Student’s t test (n = 2-3). (b) The changes at the transcript level for four genes, whose expression was altered at the protein level by açai supplementation shown in (a). l(1)G0156 refers to lethal (1) G0156, and Zasp52 represents Z band alternatively spliced PDZ-motif protein 52. All transcript levels were normalized to the internal control RpL32. a.u. refers to arbitrary unit. ^*p < 0.05; ^**p < 0.01 for comparison between açai-supplemented and non-supplemented control groups by Student’s t test (n = 5–6 for each treatment)

Fig. 4

Gene expression changes induced by açai supplementation in sod1RNAi female flies. (a) The transcript levels of eight genes in fly heads from non-supplemented and 2 % açai-supplemented treatments. (b) The transcript levels of the same eight genes in fly bodies from non-supplemented and 2 % açai-supplemented treatments. The full names of all genes are described in the main text. The transcript levels of all genes were normalized to the internal control RpL32. Error bars refer to standard errors. a.u. refers to arbitrary unit. ^*p < 0.05; ^**p < 0.01; ^***p < 0.001 for comparison between açai-supplemented and non-supplemented control groups by Student’s t test (n = 5–6 for each treatment)

Fig. 5

The effect of açai supplementation on lipid oxidation in sod1RNAi female flies. The levels of 4-hydroxynonenal (4-HNE)-protein adducts were detected by Western blot and semi-quantified in protein samples from whole flies fed the diets supplemented or not with 2 % açai. β-actin was used as a loading control. Western blot images from three biological replicates are shown on the left panel. The 4-HNE/actin ratios were calculated from five biological replicates for each treatment. a.u. refers to arbitrary unit. ^***p < 0.001 for comparison between açai-supplemented and non-supplemented control groups by Student’s t test