# Markers of bone turnover after 12 months of exercise in patients with chronic kidney disease 3–5: a post-hoc analysis of RENEXC – a randomized controlled trial

## TL;DR

A 12-month exercise program in CKD patients did not significantly change bone turnover markers, but showed a possible protective effect on bone resorption.

## Contribution

This study explores the impact of strength and balance exercises on bone turnover markers in CKD patients not on dialysis.

## Key findings

- Exercise did not significantly alter bone turnover markers over 12 months in CKD patients.
- Both exercise groups showed more participants with TRAP5b values indicating low bone turnover.
- No significant differences were found between strength and balance exercise groups for bone markers.

## Abstract

Bone and mineral disorders are common in patients with chronic kidney disease (CKD), leading to poor quality of life, high fracture risk, and increased morbidity and cardiovascular mortality. Parathyroid hormone (PTH) and bone-specific alkaline phosphatase (bALP) are frequently used to assess bone turnover, but markers such as procollagen type I N-terminal propeptide (intact PINP) and tartrate-resistant acid phosphatase isoform 5b (TRAP5b), which reflect bone formation and resorption, may provide more specific insights into bone remodeling. This study aims to investigate the effects of balance and strength exercises on bone turnover markers in patients with CKD not undergoing kidney replacement therapy.

This study is a post-hoc sub-analysis of the RENEXC trial, a randomized controlled exercise intervention lasting 12 months. A total of 151 CKD stage 3–5 patients were randomly assigned to either strength or balance exercise, both combined with endurance exercise. Exercise intensity was monitored using the Borg Rating of Perceived Exertion scale. Bone turnover markers, including intact PINP and TRAP5b, were measured at baseline and after 12 months.

Over 12 months, within-group changes in bone turnover markers were not statistically significant. In the strength group, intact PINP showed a non-significant increase and TRAP5b a slight decrease, while in the balance group intact PINP tended to decrease and TRAP5b remained stable. After adjustment for baseline values, between-group differences at 12 months were small and non-significant for both markers. Overall adjusted means were 78.7 µg/L for intact PINP and 1.87 U/L for TRAP5b, with no significant effects of treatment group, sex, or CKD stage. Additionally, both exercise groups showed an increase in the proportion of patients with TRAP5b values indicative of low bone turnover, suggesting a possible protective effect on bone resorption.

Neither strength nor balance exercise significantly altered bone turnover markers over 12 months in patients with CKD. Nonetheless, both interventions were associated with more participants exhibiting TRAP5b values consistent with low bone turnover, indicating a potential role in mitigating bone resorption. These findings warrant further investigation into the long-term effects of exercise on bone health in CKD, with a particular focus on the mechanisms underlying these responses.

NCT02041156 at http://www.ClinicalTrials.gov. Date of registration January 20, 2014. Retrospectively registered.