Effects of a Functional Ice Cream Enriched with Milk Proteins on Bone Metabolism: A Feasibility Clinical Study and In Vitro Investigation

Background: Milk proteins (MPs) and their derivative whey proteins (WPs) are important components of human diet that might prevent bone loss. We aimed to investigate the effects of MP on the bones of postmenopausal women, along with the effects of WP on osteoblast cells. Methods: We conducted a feasibility controlled clinical study with 62 postmenopausal women who were asked to consume an MP-enriched ice cream. We also investigated the effect of WP on the ERK1/2 and AKT pathways, RUNX2, alkaline phosphatase, RANKL/OPG ratio, and COL1A of Saos-2. Results: After 12 weeks, we found a greater bone mineral density and bone alkaline phosphatase reduction in women who consumed the MP-enriched ice cream compared to the control group (p = 0.03 and p = 0.02, respectively). In Saos-2 cells, WP upregulated ERK1/2 and AKT pathways (p = 0.002 and p = 0.016), cell proliferation (p = 0.03), and osteoblast differentiation markers, along with downregulating RANKL/OPG (p < 0.001). Moreover, the inhibition of ERK1/2 by PD184253 reverted the effects on both the RUNX2 and ALP mRNA expression and cells proliferation (p = 0.028, p = 0.004, and p = 0.003, respectively) when treated with WP. Conclusions: WP upregulates cell proliferation, RUNX2, and alkaline phosphatase through the activation of the ERK1/2 pathways on Saos-2. These mechanisms probably contribute to preventing bone loss in postmenopausal women.