High-fiber diet reduces bone formation but does not affect bone microarchitecture in type 2 diabetes individuals.

Bone fragility is a recognized complication of type 2 diabetes mellitus (T2DM), increasing patient morbidity. Thus, the development of an effective intervention to prevent diabetic bone fragility is urgently needed. As lifestyle intervention represents an effective option for diabetes management, it may have an impact on bone health. While studies have shown a beneficial effect of dietary fiber in T2DM management, its effect on bone health is still unclear. Thus, we investigated the impact of a high-fiber diet on bone and glucose control in men and women with T2DM. Forty-five T2DM patients (HbA1c: 6.5% ± 0.49%, age: 74 ± 7.29 yr) scheduled for hip arthroplasty were randomly assigned to follow a high-fiber diet (38 g/day) or to make no diet changes for 12 wk. Interestingly, BMI decreased by 4% (p <.0001) and HbA1c by 3.4% (p <.0001) in the high-fiber diet group, but did not decrease in the control group. However, serum concentration of the bone formation marker procollagen type 1 amino-terminal propeptide (P1NP) decreased by 8.6 % in the high-fiber diet group (p =.0004), whereas it remained unchanged in the control group. In contrast, similar to the control group, serum concentration of the bone resorption marker C-terminal telopeptide of type I collagen (CTX) concentrations did not change in the high-fiber diet group. Bone microCT analysis revealed no changes in trabecular and cortical bone parameters between the high-fiber diet and control groups. Similarly, real-time (RT)-PCR analysis in bone tissue showed no changes in the gene expression of Wnt pathway-related genes (Sost, Dkk-1, Wnt10b, and Lef-1), bone formation markers (Runx2, Col1a1, and Ocn), and inflammatory cytokines (IL-6, IL-8, TNF-α, and IL-10) between the two groups. Our findings suggest that 12-wk high-fiber diet intervention improves metabolic outcomes in patients with T2DM. However, it may reduce bone formation without affecting bone microarchitecture or Wnt pathway regulation.