Insulin-like Growth Factor-1, Bone Mineral Density, and Fracture: A Mendelian Randomization Study.

CONTEXT: The associations of circulating insulin-like growth factor-1 (IGF-1) levels with bone mineral density and fracture risk are inconclusive in observational studies. OBJECTIVE: We conducted a mendelian randomization study to assess the associations of serum IGF-1 levels with estimated bone mineral density (eBMD) and fracture. METHODS: Genetic instruments for IGF-1 were selected at the genome-wide significance level (P < 5 × 10-8) from a genome-wide association study including 358 072 individuals of European ancestry. Summary-level data for eBMD (426 824 individuals) and fracture (53 184 fracture cases and 373 611 noncases) were obtained from the UK Biobank study. Univariable and multivariable mendelian randomization analyses methods were used to estimate the associations of IGF-1 with eBMD and fracture. The main outcome measure included the change of eBMD and odds ratio of fracture per genetically predicted 1-SD increase of serum IGF-1 levels. RESULTS: For 1-SD increase in IGF-1, the change of eBMD levels was 0.04 g/cm2 (95% CI, 0.01-0.07; P = .011) and the odds ratio of fracture was 0.94 (95% CI, 0.91-0.98; P = .003). The associations persisted with similar magnitude after adjustment for height. The association was consistent for fracture but not for eBMD after excluding genetic instruments that might directly influence these outcomes. The association between IGF-1 and fracture was somewhat attenuated after adjustment for eBMD (odds ratio 0.96; 95% CI, 0.92-0.99; P = .012). CONCLUSION: The present study supports a role for IGF-1 in preventing fracture, possibly and partly mediated by greater bone mineral density.

Combined effects of fruit and vegetables intake and physical activity on the risk of metabolic syndrome among Chinese adults.

BACKGROUND: Unbalanced dietary intake and insufficient physical activity (PA) have been recognized as risk factors for metabolic syndrome (MetS). We aimed to examine the independent and combined effects of fruit and vegetables (FV) intake and PA on MetS. METHODS AND FINDINGS: A cross-sectional survey was conducted among residents of China in 2009, with fasting blood samples collected. Participants were divided into sufficient/insufficient FV intake and adequate/ inadequate PA groups according to self-reported questionnaires. MetS was defined using the NCEP-ATPIII criteria. The difference of individual MetS components was compared across different PA or FV groups. Multivariable logistic regression was used to assess association between FV/PA and the risk of MetS. A total of 7424 adults were included in the current study. MetS was prevalent in 28.7% of participants, with 24.7% and 32.9% in male and female, respectively. Compared with those with inadequate PA and insufficient FV intake, participants with the combination of adequate PA and sufficient FV intake had the lowest risk of MetS (OR = 0.69,95%CI: 0.59-0.82), following by the group with adequate PA time but insufficient FV intake (OR = 0.74, 95%CI:0.65-0.83). CONCLUSION: Findings of the current study show that the combination of sufficient FV intake and adequate PA was significantly associated with reduced MetS risk among adult residents of China.