Nutritional Intervention Alleviates Signs of Dermatological Problems in Dogs by Modulating Immune Regulation and Skin Microbiome

Objectives: Atopic dermatitis (AD) is a chronic inflammatory skin disorder in dogs. We show that dietary intervention alleviates AD by modulating immune regulation and skin microbiome. Methods: Positive control food (PC) that has been previously shown to alleviate AD signs and Test food (TF) were formulated to meet or exceed AAFCO recommendations. Both foods had similar nutrient levels as fed basis (fat: 17.1% ±0.04, protein: 16.0% ±0.2, carbohydrate: 54.2% ±0.2, crude fiber: 1.1% ±0.1, dietary fiber: 4.6% ±0, moisture: 7.1% ±0.3 and ash: 4.2% ±0.04) but TF had higher levels of hydroxyproline (73%) and glycine (49%). Dogs with derm disorder (DD, n=15) and pair-matched healthy dogs (HD, n=15) were pre-fed maintenance food for 28 days, randomized into 2 groups based on their age, gender and phenotype, and fed either PC or TF for 42 days followed by a cross-over design without a washout period and fed PC or TF for 42 more days. All dogs were bathed at the end of each phase (pre-fed, phase 1 & 2) after the skin assessment and sample collections. Skin assessment was conducted by a veterinarian for DD dogs. Blood samples were analyzed for gene expression using the NanoString nCounter® platform. Skin swab samples were collected from the inguinal region for microbiome analyses performed by MiDOG LLC. A mixed model analysis was performed using food as a fixed effect and animal as a random effect using JMP Pro v17 followed by Tukey post-hoc analyses. Results: TF improved the response rate of DD reducing pruritus, erythema and alopecia by 42.8%, 57.1% and 28.5% respectively, compared with PC. Dogs fed TF had significantly decreased levels of PLAUR, ITGAX, TSC2 and PRKCE and increased levels of CD83 and S100A4 compared with the baseline but showed a similar non-significant trend compared with PC. These genes are known to be involved in immune regulation, wound healing and hair follicle regeneration processes. Compared to baseline, dogs fed PC or TF show skin microbiome changes and significantly reduced fungal diversity, evenness and abundance levels of pathogenic species (Malassezia pachydermatis, Staphylococcus epidermidis and Streptococcus canis). Conclusions: Nutritional intervention alleviates AD symptoms by modulating immune responses and skin microbiome composition. Funding Sources: Study was funded by Hill's Pet Nutrition, Inc.