Causal link between childhood obesity and adult osteoporosis: An investigation through Mendelian randomization

The intricate link between childhood obesity and adult osteoporosis has been a subject of numerous clinical inquiries, yet the genetic underpinnings of this association remain enigmatic. Our research aims to unravel the association between adult osteoporosis and childhood obesity using genome-wide association study data for Mendelian randomization (MR) analysis. Utilizing a pool of single-nucleotide polymorphism data associated with childhood obesity obtained from a previous genome-wide association study report involving a study population of 13,848 people in Europe, alongside data of adult osteoporosis sourced from Neale Lab (5266 cases and 331,893 controls). Various methods for MR were used in our research, including weighted mode, simple mode, weighted median, MR-Egger, and the inverse-variance weighted (IVW). We also used Cochran Q test of IVW to assess for heterogeneity, MR-Egger intercept and MR-Pleiotropy RESidual Sum and Outlier (MR-PRESSO) analysis for pleiotropy, and leave-one-out analysis for the result stability. The instrumental variables associated with 11 single-nucleotide polymorphisms were selected. MR analyses unveiled a noteworthy link between genetically forecasted childhood obesity and the onset of adult osteoporosis based on the odds ratio, 95% confidence interval, and P-value from the results of IVW, MR-Egger, weighted median: simple mode, and weighted mode analyses. No significant heterogeneity was found by the assessment using MR-Egger and IVW. Similarly, there was no indication of pleiotropy based on the MR-PRESSO and MR-Egger analyses. Leave-one-out analysis confirmed the stability of the results. Our research suggests that childhood obesity, as predicted by genetic factors, may pose a significant risk for the development of osteoporosis in adulthood.