Soybean meal-dependent intestinal inflammation induces different patterns of bone-loss in adult zebrafish scale.

Inflammatory bowel disease have been linked to several health issues, including high risk of low bone mineral density. Danio rerio (zebrafish) is a good model to verify the effects of intestinal inflammation since gastrointestinal and immune systems are closely related to that of mammalians. Zebrafish is also a powerful model to study bone metabolism using the scale as read-out model. Food strongly impacts zebrafish gut physiology and it’s well known that soybean meal induces intestinal inflammation. Adult zebrafish fed with defatted soybean meal (SBM) exhibited an intestinal inflammation evidentiated by morphological alterations, inflammatory infiltrate and increased mRNA expression of inflammatory cytokines (IL-1β, IL-6, IL-8, IL-10, TGFβ, TNF-α). The pick of acute intestinal inflammation, spanning between 2^nd and 3^rd week, correlates with a transitory osteoporosis-like phenotype in the scale border. Later, a chronic inflammatory condition, associated with persistent IL-8 expression, correlates with the progression of resorption lacunae in the scale center. Both type of resorption lacunae were associated with intense osteoclastic tartrate-resistant acid phosphatase (TRAP) activity. After 3 weeks of SBM treatment, osteoclast activity decreased in scale border but not in the center. At the same time, alkaline phosphatase (ALP) is activated in the border to repair the bone matrix. This model can contribute to elucidate in vivo the molecular mechanisms that links intestinal inflammation and bone metabolism in IBD.