A Mouse Model Suggests How an Industrialized Diet Alters Jaw Form

Abstract

Food texture affects jaw form by creating biomechanical stress during chewing. Chewing prompts remodelling via increased bone cell activities, including cell signalling, differentiation, proliferation, and matrix secretion. Vitamin D may influence jaw form via regulation of these bone cell activities. Modern, post-Industrialized human diets are characterized by soft textured food with low levels of vitamin D, but how these two factors affect mandible shape and size is unclear. Via a mouse model and specialized diets, we tested the effects of dietary texture and vitamin D on mandibular form. We hypothesized that vitamin D intake is: 1) imperative for normal mandibular form, and; 2) a greater influence on mandibular form than diet texture. C57BL/6J mice weaned at 7 weeks were raised on a soft or hard diet with vitamin D (n=40; n=48), or on a soft diet without vitamin D (n=39). Post-sacrifice, adult mice were scanned with a Skyscan1172 micro-CT system and landmarked using Amira software. Landmark datasets underwent Generalized Procrustes Analysis followed by Principal Component Analysis (PCA) in Morphologika. Mice fed soft diets had shorter mandibles with diminutive alveolar bone, gentler masseteric crests, a wider angle between dentary bones, and larger bicondylar breadth. Diet groups occupied distinct but overlapping regions of shape space, with diet texture accounting for 30.8% (PC1) of total shape variance. Presence/absence of vitamin D accounted for 13.8% (PC2) of total shape variance between soft diet groups. Mice fed a soft diet with vitamin D had mandibles with more flaring angular processes, more robust masseteric crests, and elevated alveolar bone. Our results indicate that vitamin D influenced dentary bone shape less than diet texture did, and that diet had a greater role in mandibular bone remodelling, including increased variation at muscle attachment sites. Future work will explore whether vitamin D also influences muscle form and function.