Strontium isotope ratios in kidney stones reveal the environmental implications for humans in Beijing, China

Association of multi-metal exposure with hyperuricemia in middle-aged and older adults: A cross-sectional study in rural Guangxi, China

BACKGROUND

Hyperuricemia constitutes a significant global public health concern, particularly among the elderly, and is associated with environmental factors such as metal exposure. In China, the predominant focus of existing research has been on urban populations, which leaves the relationship between hyperuricemia and ecological exposures in rural populations inadequately explored. This study investigates the association between hyperuricemia and exposure to multiple metals among elderly residents in rural China.

METHODS

Cross-sectional survey data were collected from middle-aged and elderly individuals residing in Yao Autonomous County of Gongcheng, Guangxi, China, from 2018 to 2019. The analytical techniques employed included least absolute shrinkage and selection operator (LASSO) regression, binary logistic regression and Bayesian kernel machine regression (BKMR) to examine the association between exposure to multi-metal mixtures and hyperuricemia.

RESULTS

Logistic regression results indicated a negative association between magnesium (OR=0.634, 95 % CI=0.476-0.867, Q3) and hyperuricemia, while iron, nickel, strontium, molybdenum, and tin were positively associated with hyperuricemia (all P < 0.05). The Bayesian kernel machine regression analysis revealed a significant overall positive correlation between hyperuricemia and plasma polymetallic mixtures, with notable contributions from Sr (PIP=0.991) and Fe (PIP=0.749), particularly when all metals were at their respective 50th percentiles. Exposure-response relationships were consistent with the logistic regression results. Plasma Sr was positively correlated with hyperuricemia at different levels of other metals (p25, p50, p75).

CONCLUSION

This study suggests that exposure to multi-metal mixtures is positively associated with hyperuricemia, with Sr and Fe being the most significant contributors.

Characteristics of heavy metals in the hair of firefighters: concentration dynamics and elemental interactions

Heavy metal pollution poses a major threat to human health. Firefighters, a high-risk occupational group, are regularly exposed to airborne heavy metals and fly ash. Consequently, detailed investigations into their heavy metal exposure levels are essential. This study evaluated the heavy metal exposure of 14 firefighters across five stages before and after firefighting, with a focus on concentration trends and element interactions. The concentration order was Zn > Cu > Fe > Pb > Mn > Cr > As > Ni > Cd > Co. Comparisons with health reference values and other regions indicated that while most metals were within reference ranges, Zn concentrations were elevated. The elevated Zn concentrations may result from its attachment to hair through chemisorption and absorption from airborne particles and fly ash during combustion. Heavy metal concentrations in the hair of firefighters increased after firefighting, and continued firefighting missions may further accumulate heavy metals in the body. However, concentrations decreased after a period of firefighting. Correlation analysis revealed that, except for Zn, metals exhibited synergistic interactions, with correlations strengthening significantly after firefighting. Variation in heavy metals reflects long-term pollutant exposure, and Zn in hair may serve as a biomarker of fire-related exposure.

Deciphering the mineral code of urinary stones: A first look at zinc isotopes

Zinc (Zn) is an essential element for all living organisms, and Zn isotopes play a key role in studying the formation of disease. Despite extensive studies on Zn isotopes in healthy and diseased human tissues, the role of Zn isotopes in urinary stones remains unexplored. This study investigates Zn isotopes in 37 urinary stones using multi-collector inductively coupled plasma mass spectrometry. The δ66Zn values of urinary stones range from -0.15‰ to 0.47‰, with a mean value of 0.11‰. Carbonate apatite (CA) stones exhibit lighter Zn isotopic compositions (δ66Zn = -0.15‰ ∼ -0.03‰) compared to calcium oxalate (CO) stones (δ66Zn = -0.11‰ ∼ 0.47‰). The variation in Zn isotopic compositions between CO and CA stones may result from urinary pH differences during stone formation. At higher urinary pH, CA stones are enriched in lighter Zn isotopes compared to CO stones. Urinary stones are enriched in lighter Zn isotopes compared to blood and urine. This study identifies two steps influencing Zn isotope variations during kidney transport. The first step involves kidney filtration and reabsorption, enriching heavy Zn isotope in the urine. The second step is the deposition process of urinary stones, where light isotopes, due to their lower bond energy, are more prone to breaking. This kinetic fractionation effect leads to an enrichment of light Zn isotope in urinary stones. Overall, this study offers preliminary insights into the geochemical mechanisms that influence the Zn isotopic composition in urinary stones.

Natural variation of magnesium stable isotopes in human kidney stones

Kidney stones, as typical biominerals produced within the human body, pose a significant threat to human health, affecting over 12% of the global population. However, the exact mechanisms underlying their formation are not fully understood. Recent metal isotopic analysis provides a new way to study the roles of metal cations in biological processes within organisms. Here, we report the Mg isotope ratios of human kidney stones for the first time. The total range of measured values for δ26Mg in kidney stones is 1.05‰, from -1.12‰ to -0.07‰. Our data exhibit a significant 24Mg enrichment compared with the values calculated from density functional theory. We suggest that the Mg-isotopic fractionations in vivo are linked to active Mg transport mediated by proteins during intestinal absorption and preferential renal reabsorption of ionized Mg2+ via tight junctional proteins. Our results indicate that the inhibitory effect of Mg on kidney stones is related to the kink-blocking mechanism, and the incorporation of hydrated Mg lessens the extent of inhibition and the magnitude of isotope discrimination. We show that metal isotopes provide new insights into the underlying biological processes and human health.

The key role of major and trace elements in the formation of five common urinary stones

BACKGROUND

Urolithiasis has emerged as a global affliction, recognized as one of the most excruciating medical issues. The elemental composition of stones provides crucial information, aiding in understanding the causes, mechanisms, and individual variations in stone formation. By understanding the interactions between elements in various types of stones and exploring the key role of elements in stone formation, insights are provided for the prevention and treatment of urinary stone disease.

METHODS

This study collected urinary stone samples from 80 patients in Beijing. The chemical compositions of urinary stones were identified using an infrared spectrometer. The concentrations of major and trace elements in the urinary stones were determined using Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS), respectively. The data were processed using correlation analysis and Principal Component Analysis (PCA) methods.

RESULTS

Urinary stones are categorized into five types: the calcium oxalate (CO) stone, carbonate apatite (CA) stone, uric acid (UA) stone, mixed CO and CA stone, and mixed CO and UA stone. Ca is the predominant element, with an average content ranging from 2.64 to 27.68% across the five stone groups. Based on geochemical analysis, the high-content elements follow this order: Ca > Mg > Na > K > Zn > Sr. Correlation analysis and PCA suggested significant variations in the interactions between elements for different types of urinary stones. Trace elements with charges and ionic structures similar to Ca may substitute for Ca during the process of stone formation, such as Sr and Pb affecting the Ca in most stone types except mixed stone types. Moreover, the Mg, Zn and Ba can substitute for Ca in the mixed stone types, showing element behavior dependents on the stone types.

CONCLUSION

This study primarily reveals distinct elemental features associated with five types of urinary stones. Additionally, the analysis of these elements indicates that substitutions of trace elements with charges and ion structures similar to Ca (such as Sr and Pb) impact most stone types. This suggests a dependence of stone composition on elemental behavior. The findings of this study will enhance our ability to address the challenges posed by urinary stones to global health and improve the precision of interventions for individuals with different stone compositions.

Investigating strontium isotope linkage between biominerals (uroliths), drinking water and environmental matrices

This study presents the mineralogy and strontium isotope ratio (87Sr/86Sr) of 21 pathological biominerals (bladder and kidney stones) collected from patients admitted between 2018 and 2020 at the Department of Urology of the San Pio Hospital (Benevento, southern Italy). Urinary stones belong to the calcium oxalate, purine or calcium phosphate mineralogy types. Their corresponding 87Sr/86Sr range from 0.707607 for an uricite sample to 0.709970 for a weddellite one, and seem to be partly discriminated based on the mineralogy. The comparison with the isotope characteristics of 38 representative Italian bottled and tap drinking waters show a general overlap in 87Sr/86Sr with the biominerals. However, on a smaller geographic area (Campania Region), we observe small 87Sr/86Sr differences between the biominerals and local waters. This may be explained by external Sr inputs for example from agriculture practices, inhaled aerosols (i.e., particulate matter), animal manure and sewage, non-regional foods. Nevertheless, biominerals of patients that stated to drink and eat local water/wines and foods every day exhibited a narrower 87Sr/86Sr range roughly matching the typical isotope ratios of local geological materials and waters, as well as those of archaeological biominerals from the same area. Finally, we conclude that the strontium isotope signature of urinary stones may reflect that of the environmental matrices surrounding patients, but future investigations are recommended to ultimately establish the potential for pathological biominerals as reliable biomonitoring proxies, taking into the account the contribution of the external sources of Sr.