Early-Life Dietary Protein Source Reshapes Gut Microbiota but Fails to Curtail Diet-Induced Metabolic Syndrome in Young Rats.

OBJECTIVE:Dairy consumption plays a protective role in obesity that may be mediated through the gut microbiota. This study examined the role of dairy proteins, casein, whey, and complete dairy (skim milk powder), and a plant-based alternative, soy, on gut microbiota composition, obesity susceptibility, and insulin sensitivity in early development. METHODS:Following weaning, rat pups were randomized into four isocaloric diets (n = 8-11/sex/diet) for 4 weeks: (1) complete dairy; (2) casein; (3) whey; and (4) soy. Primary outcomes included food intake, growth, body composition, glucose tolerance, and fecal microbiota composition. Animals were then metabolically challenged with a high-fat, high-sucrose diet (HFHS, 40% kilocalories from fat) for 5 weeks. RESULTS:The impacts on gut microbiota and metabolic outcomes were sex and protein dependent. Compared to casein, complete dairy consumption reduced diversity, while early exposure to complete dairy improved body fat percentage but not glucose tolerance or insulin sensitivity. Soy elicited differential effects in males and females. Despite preserved microbial patterns, diets were unable to overcome the detrimental metabolic impacts of HFHS diet exposure. CONCLUSIONS:Results show that complete dairy positively modulates gut microbial profiles and benefits body composition early in life, but it could not curtail the negative metabolic impacts of HFHS feeding.