#2717 Fermentable and viscous dietary fiber types improve cortical bone in a rat model of chronic kidney disease-mineral and bone disorder

Abstract

Abstract Background and Aims Renal osteodystrophy is highly prevalent among people with chronic kidney disease (CKD). We recently showed that inulin, a prebiotic fermentable dietary fiber, improved cortical bone parameters in rats with moderate-to-severe CKD. Our objective was to evaluate if this effect was unique to the prebiotic fibers or if other fiber properties, such as viscosity, could be beneficial to bone in a rat model of CKD-mineral and bone disorder (CKD-MBD). Method 22-week-old Cy/+ male rats (50% kidney function compared to normal; CKD hereafter) were randomly assigned to receive one of four fiber treatments (10% w/w each) based on fermentability and viscosity: 1) Cellulose (−fermentability, −viscosity), 2) Inulin (+fermentability, −viscosity), 3) Psyllium husk (−fermentability, +viscosity), or 4) Pectin (+ fermentability, +viscosity). These diets were formulated with a semi-purified, casein-based background diet with 0.7% calcium and 0.7% phosphorus. Treatments lasted 10 weeks, and rats were euthanized at 32 weeks of age (kidney failure; ∼15% of normal). Micro-computed tomography (μCT) at 12-μm resolution was performed on the proximal tibia. Serum creatinine, plasma phosphorus, and plasma calcium were analyzed using colorimetric assays. One-way ANOVA was used to test the effect of dietary fiber types on outcome measures. Results At 32 weeks of age, serum creatinine was lower in the inulin, psyllium, and pectin-treated CKD rats (<0.04). Plasma calcium concentrations were similar between treatments, but phosphorus was lower in the psyllium and pectin-treated CKD rats (p < 0.02). Bone cortical area was higher in the inulin and psyllium-treated CKD rats compared to cellulose-treated rats (p < 0.007). Cortical thickness was higher in the inulin, psyllium, and pectin-treated CKD rats compared to cellulose-treated rats (p < 0.02). There was less cortical porosity in the inulin, psyllium, and pectin-treated rats (p < 0.02). Fermentable or viscous fibers did not impact trabecular bone volume, thickness, spacing, and number (p < 0.05). Plasma phosphorus was negatively associated with cortical area (r = −0.56; p < 0.0001) and cortical thickness (r = −0.75; p < 0.0001), and positively associated with cortical porosity (r = 0.74; p < 0.0001). Conclusion Fermentable and viscous fibers improved cortical bone but had no effect on trabecular bone. This effect may be, at least in part, due to the fiber's ability to lower plasma phosphorus and likely parathyroid hormone.