Effect of Dietary XOS Supplementation on Systemic Amino Acid Homeostasis

Systemic amino acid (AA) levels are tightly regulated. Homeostasis of certain AAs, such as branched chain AAs (BCAAs), and aromatic AAs are not only associated with impaired glucose control but also important determinants of mood. The health benefits of dietary xylooligosaccharides (XOS) in glucose control have been published. In addition, XOS consumption was reported to increase participant-reported vitality and happiness. Therefore, we hypothesized that dietary XOS supplementation induce changes of AA homeostasis, which contributes to its metabolic and mood benefit. Male db/db BSK mice and their respective lean control db/m BSK mice were used in this study. Mice at age 7 wk were randomized into three groups and fed AIN93M, AIN93M + 2%−, or 7%-XOS (w/w) for 8 weeks (n = 8–10/group). At the end of the intervention, fasting serum samples were collected and processed for glucose, insulin, AA analysis. db/db mice developed obesity, hyperglycemia and hyperinsulinemia compared to db/m mice. We did not detect difference in serum BCAAs and aromatic AAs, including phenylalanine (phe), tryptophan (Trp) and tyrosine (Tyr) between db/db and db/m mice. Serum arginine (Arg), proline (Pro) and methionine (Met) were significantly lower in db/db compared db/m. Dietary XOS supplementation (2 and 7%) did not change body weight and fat depots in db/m and db/db mice. Fasting blood glucose, Met and Pro levels were significantly reduced by 7% XOS in db/m not db/db mice. XOS did not change any other AAs in either db/db or db/m mice. Serum Trp microbial metabolites indole acetate (IAA) was significantly higher while indole propionate (IPA) was lower in db/db mice compared to db/m mice. XOS (both 2 and 7%) decreased IAA in both db/m and db/db mice, while 2% XOS increased IPA only in db/db mice. Tyr was decreased by 7% XOS in db/m mice but not db/db mice, while Tyr metabolite, p-cresol sulfate, was reduced by 2% XOS in db/db mice only. Our data indicate interactions between dietary XOS and Leptin R genotype/or host metabolic status on glucose control and systemic AA homeostasis. The mechanism of how dietary XOS intake modulate AA homeostasis needs further investigation. This project was supported by NIH-R01 and Center for Human Nutrition.