Exhaled breath metabolites reveal postmenopausal gut-bone cross-talk and non-invasive markers for osteoporosis

Abstract

Menopause driven decline in estrogen exposes women to risk of osteoporosis. Detection of early onset and silent progression are keys to prevent fractures and associated burdens. In a discovery cohort of 120 postmenopausal women, we combined repeated quantitative pulse-echo ultrasonography of bone, assessment of grip strength and serum bone markers with mass-spectrometric analysis of exhaled metabolites to find breath volatile markers and quantitative cutoff levels for osteoporosis. Obtained markers and cutoffs were validated in an independent cohort of 49 age-matched women with six months apart seasonal follow-ups. Here, within the discovery cohort, concentrations of exhaled end-tidal dimethyl sulfide (DMS), allyl-methyl sulfide, butanethiol and butyric acid are increased (p ≤ 0.005) pronouncedly in subjects with bone mineral density (BMD) at high-risk of osteoporosis and fracture, when compared to subjects with normal BMD. Increased age and decreased grip strength are concomitant. All changes are reproduced during independent validation and seasonal follow-ups. Exhaled metabolite expressions remain age independent. Serum markers show random expressions without reproducibility. DMS exhalations differs between patients with recent, old and without fractures. Metabolite exhalations and BMDs are down-regulated during winter. ROC analysis in discovery cohort yields high classification accuracy of DMS with a cutoff for osteoporosis, which predicts subjects at high-risk within the independent validation cohort with >91% sensitivity and specificity. Non-invasive analysis of exhaled DMS allowed more reliable classification of osteoporosis risk than conventional serum markers. We identified associations of exhaled organosulfur and short-chain fatty acids to bone metabolism in postmenopausal osteoporosis via a gut-bone axis. It is estimated globally that one-third of women aged >50 years old experience fractures (breaks in their bones) from osteoporosis (bone weakening and brittleness). It is difficult to diagnose this condition which makes it hard to put in place measures to help prevent fractures. Here, we investigate links between volatile organic chemicals detectable in exhaled breath, blood bone markers and the risk of osteoporosis (tested by measuring bone strength). We discover that chemicals coming from the gut are strongly associated to postmenopausal bone health. Our non-invasive analysis is faster and more reliable than standard blood markers currently used in diagnosing osteoporosis and identifies a connection between the gut and bones not previously shown. These findings offer easier assessment of osteoporosis risk and paths towards new therapeutic targets. Sukul et al. analyze exhaled metabolites to find endogenous volatile markers indicative of postmenopausal osteoporosis. The non-invasive breath analysis serves as more rapid and reliable classification of osteoporosis risk when compared to conventional serum bone markers and includes markers of gut-bone axis.