Adjustment of Whey:Casein Ratio from 20:80 to 60:40 in Milk Formulation Affects Food Intake and Brainstem and Hypothalamic Neuronal Activation and Gene Expression in Laboratory Mice.

ABSTRACT

Adjustment of protein content in milk formulations modifies protein and energy levels, ensures amino acid intake and affects satiety. The shift from the natural wheycasein ratio of ~2080 in animal milk is oftentimes done to reflect the 6040 ratio of human milk. Studies show that 2080 versus 6040 wheycasein milks differently affect glucose metabolism and hormone release; these data parallel animal model findings. It is unknown whether the adjustment from the 2080 to 6040 ratio affects appetite and brain processes related to food intake. In this set of studies, we focused on the impact of the 2080 vs. 6040 wheycasein content in milk on food intake and feeding-related brain processes in the adult organism. By utilising laboratory mice, we found that the 2080 wheycasein milk formulation was consumed less avidly and was less preferred than the 6040 formulation in short-term choice and no-choice feeding paradigms. The relative PCR analyses in the hypothalamus and brain stem revealed that the 2080 wheycasein milk intake upregulated genes involved in early termination of feeding and in an interplay between reward and satiety, such as melanocortin 3 receptor (MC3R), oxytocin (OXT), proopiomelanocortin (POMC) and glucagon-like peptide-1 receptor (GLP1R). The 2080 versus 6040 wheycasein formulation intake differently affected brain neuronal activation (assessed through c-Fos, an immediate-early gene product) in the nucleus of the solitary tract, area postrema, ventromedial hypothalamic nucleus and supraoptic nucleus. We conclude that the shift from the 2080 to 6040 wheycasein ratio in milk affects short-term feeding and relevant brain processes.