Dietary grape proanthocyanidins modulate gut microbiome and neuroendocrine response in dogs

This research investigates the properties of grape proanthocyanidins (GPAC) in dogs of varying ages and breeds housed in the kennel, with a focus on the interaction between GPAC and gut microbiota. The study also examines the impact of GPAC on endocrine responses measured in saliva and hair. Faecal samples were collected before administration (T0), as well as 14 days (T14) and 28 days (T28) thereafter, with dogs subjected to a control diet (D0), and a diet supplemented with 1 mg/kg body weight (D1), or 3 mg/kg body weight (D3) of GPAC. The alpha diversity, as measured by the Shannon index, remained stable between diets at the study's outset (T0), after 14 days (T14), and 28 days (T28). Differences were observed in the Shannon index between T0 and T14 (P < 0.05), while the variation was lower between T0 and T28 (P < 0.10). In essence, the beta diversity of microbial composition remained unaffected by the variation of GPAC doses at T0, T14, and T28. Instead, specific taxa were affected by the addition of GPAC. The relative abundance (RA, %) of Dorea increased from T14 to T28, with a notable rise in the D1 group (P ≤ 0.05). The RA of the Clostridium genus also increased, particularly in D3 at T28 (P ≤ 0.05). After 28 days, there was a significant increase in the RA of Clostridium perfringens, rising from median of 6.15 at D0 to 10.58 at D1 and further increasing to 11.53 at D3 (P<0.05). GPAC supplementation influenced the RA of the Fusobacteriaceae family at T28, with D3 showing a lower value than D1 and D0 (P ≤ 0.05). The RA of Enterobacteriaceae family varied under different dietary conditions at T14, with a lower value at D3 (P ≤ 0.05). Salivary concentrations of kynurenine varied between diets at T28, with D0 having the highest concentration. The serotonin to cortisol ratios were higher (P<0.05) at T28 for D3, indicating a potentially more favourable balance with this level of supplementation compared to D0 and D1. Our study provides insights into the dynamic interplay between GPAC, faecal microbiota, and endocrine responses in dogs, shedding light on potential effects associated with the supplementation.