The effects of blueberry and strawberry serum metabolites on age-related oxidative and inflammatory signaling in vitro

Authors: Rutledge, Grant; Fisher, Derek; MILLER, MARSHALL - Former ARS Employee; KELLY, MEGAN - Former ARS Employee; BIELINSKI, DONNA - Tufts University; Shukitt-Hale, Barbara

Submitted to: Food and Function
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2019
Publication Date: 12/11/2019
Citation: Rutledge, G.A., Fisher, D.R., Miller, M.G., Kelly, M.E., Bielinski, D.F., Shukitt Hale, B. 2019. The effects of blueberry and strawberry serum metabolites on age-related oxidative and inflammatory signaling in vitro. Food and Function. 10(12):7707-7713. https://doi.org/10.1039/C9FO01913H.
DOI: https://doi.org/10.1039/C9FO01913H

Interpretive Summary: Age-related decreases in brain function are thought to result from oxidative stress and inflammation. Berry fruits contain a variety of compounds that are antioxidant and anti-inflammatory. We have shown that eating freeze-dried berries can improve brain function in healthy, older adults. Because the compounds in foods are different than those found in the blood after eating, we were interested in whether pre-treatment of cultured cells with serum from the blood of people fed these foods may be a better model system than treating cells with extracts of the foods. We investigated whether serum from BB- or SB-supplemented older adults (60-75yo), taken before and after 45 or 90 days of supplementation, would reduce inflammation, compared to a placebo group, in cultured rat brain cells which had been subjected to an inflammatory stressor. Serum from both BB- and SB-supplemented participants significantly reduced the levels of four inflammatory markers relative to serum from placebo controls. Protection was greatest with serum from the 90-day time-point. These results suggest that berry-derived substances produced by metabolism, present in the circulating blood, may be causing the anti-inflammatory effects of berry fruit, and that continual supplementation may provide the most health benefits.

Technical Abstract: Age-related decrements in cognition are thought to result from the increased susceptibility to and accumulating effects of oxidative stress and inflammation. Berry fruits contain a variety of bioactive polyphenolic compounds that exhibit potent antioxidant and anti-inflammatory activities. We have shown that consumption of freeze-dried whole berry powder, equivalent to 1 cup/day of blueberry (BB) or 2 cups/day of strawberry (SB), can differentially improve some aspects of cognition in healthy, older adults, compared to placebo-supplemented controls. Because the bioactive compounds in foods are different than those found in circulation following consumption, we were interested in whether pre-treatment of stressed cells with serum from people fed these foods may be a more valid model system than treating with extracts of the foods themselves for assessing their anti-inflammatory effects. We investigated whether fasting and postprandial serum from BB- or SB-supplemented older adults (60-75yo), taken at baseline or after 45 or 90 days of supplementation, would reduce the production of inflammatory and oxidative stress signals, as measured by western blot and ELISA techniques, compared to a placebo group, in LPS-stressed HAPI rat microglial cells, in vitro. Serum from both blueberry- and strawberry-supplemented participants reduced nitrite production, iNOS and COX-2 expression, and TNF-alpha release relative to serum from placebo controls (p < 0.05). Protection was greatest with serum from the 90-day time-point, suggesting that ongoing supplementation may provide the most health benefits. Serum was protective in both fasted and postprandial conditions, suggesting that the effects are not acute and that the meal did not challenge subjects’ ability to regulate oxidative and inflammatory stress. These results suggest that berry metabolites, present in the circulating blood, may be mediating the anti-inflammatory effects of dietary berry fruit.