New-onset metabolic risk factors and the incidence of kidney stones: a prospective cohort study

Blood Calcium, Genetic Risk, and Risk of Incident Kidney Stone: A Population-Based Cohort Study

OBJECTIVE

To investigate the association between blood calcium concentration and incident kidney stone as well as to assess the role played by genetic susceptibility.

METHODS

We performed a population-based cohort study based on participants from the UK Biobank. A multivariable Cox proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% CIs of incident kidney stone for blood calcium level and polygenic risk score (PRS). In addition, the potential interaction was explored. The study was conducted from January 28, 2023, through June 4, 2023.

RESULTS

During the follow-up of 423,301 participants with a total of 5,490,332 person-years (median follow-up of 13.4 years), 4502 cases of kidney stone were recorded. Compared with the low blood calcium concentration group (first tertile), individuals in the high (third tertile) and moderate (second tertile) concentration groups had higher risks of kidney stone with HRs of 1.24 (95% CI, 1.15 to 1.33) and 1.11 (1.04 to 1.20), respectively. The PRS for kidney stone contained 40 independent single-nucleotide polymorphisms and was used to assign individuals to 3 groups according to the quintile. Participants with high (Q5) and moderate (Q2 to Q4) genetic risks had increased risks of kidney stone compared with low (Q1) genetic risk with HRs of 1.70 (1.53 to 1.89) and 1.31 (1.20 to 1.44), respectively. There was a joint cumulative risk of incident kidney stone between blood calcium concentration and genetic susceptibility.

CONCLUSIONS

Blood calcium concentration and PRS are significantly associated with incident kidney stone risk. Excessive blood calcium concentration might bring additional stone risk in populations at high genetic risk. A nonlinear correlation between blood calcium concentration and kidney stone risk was indicated.

Basal metabolic rate and the risk of urolithiasis: a two-sample Mendelian randomization study

OBJECTIVE

Few studies have investigated the impact of basal metabolic rate (BMR) on the development of urolithiasis, and the causal relationship is yet to be established. In this study, a two-sample Mendelian randomization (MR) analysis was utilized to identify the causal relationship between BMR and risk of urolithiasis.

METHOD

Genetic instruments for BMR were drawn from a public genome-wide association study (GWAS). Summary dates on BMR and urolithiasis were obtained from a GWAS meta-analysis with sample sizes of 454,874 and 212,453, respectively. The inverse-variance weighted (IVW) method was provided as the main approach to estimate the causal relationship. The weighted-median method and the MR-Egger method were used as supplements to the IVW method. In addition, we conducted sensitivity analyses, including heterogeneity tests, pleiotropy tests and leave-one-out analysis, to assess the robustness of the outcomes. Furthermore, the funnel plot asymmetry was visually inspected to evaluate possible bias.

RESULTS

The inverse-variance weighted data revealed that genetically predicted BMR significantly decreased the risk of urolithiasis [beta coefficient (beta): - 0.2366, odds ratio (OR): 0.7893, 95% confidence interval (CI) 0.6504-0.9579, p = 0.0166].

CONCLUSIONS

BMR has causal effects on urolithiasis in an MR study, and the risk of urolithiasis in patients with lower levels of BMR is higher.

Central Adiposity Increases Risk of Kidney Stone Disease through Effects on Serum Calcium Concentrations

SIGNIFICANCE STATEMENT

Kidney stone disease is a common disorder with poorly understood pathophysiology. Observational and genetic studies indicate that adiposity is associated with an increased risk of kidney stone disease. However, the relative contribution of general and central adipose depots and the mechanisms by which effects of adiposity on kidney stone disease are mediated have not been defined. Using conventional and genetic epidemiological techniques, we demonstrate that general and central adiposity are independently associated with kidney stone disease. In addition, one mechanism by which central adiposity increases risk of kidney stone disease is by increasing serum calcium concentration. Therapies targeting adipose depots may affect calcium homeostasis and help to prevent kidney stone disease.

BACKGROUND

Kidney stone disease affects approximately 10% of individuals in their lifetime and is frequently recurrent. The disease is linked to obesity, but the mechanisms mediating this association are uncertain.

METHODS

Associations of adiposity and incident kidney stone disease were assessed in the UK Biobank over a mean of 11.6 years/person. Genome-wide association studies and Mendelian randomization (MR) analyses were undertaken in the UK Biobank, FinnGen, and in meta-analyzed cohorts to identify factors that affect kidney stone disease risk.

RESULTS

Observational analyses on UK Biobank data demonstrated that increasing central and general adiposity is independently associated with incident kidney stone formation. Multivariable MR, using meta-analyzed UK Biobank and FinnGen data, established that risk of kidney stone disease increases by approximately 21% per one standard deviation increase in body mass index (BMI, a marker of general adiposity) independent of waist-to-hip ratio (WHR, a marker of central adiposity) and approximately 24% per one standard deviation increase of WHR independent of BMI. Genetic analyses indicate that higher WHR, but not higher BMI, increases risk of kidney stone disease by elevating adjusted serum calcium concentrations (β=0.12 mmol/L); WHR mediates 12%-15% of its effect on kidney stone risk in this way.

CONCLUSIONS

Our study indicates that visceral adipose depots elevate serum calcium concentrations, resulting in increased risk of kidney stone disease. These findings highlight the importance of weight loss in individuals with recurrent kidney stones and suggest that therapies targeting adipose depots may affect calcium homeostasis and contribute to prevention of kidney stone disease.

Critical role of VHL/BICD2/STAT1 axis in crystal-associated kidney disease

Nephrolithiasis is highly prevalent and associated with the increased risk of kidney cancer. The tumor suppressor von Hippel-Lindau (VHL) is critical for renal cancer development, however, its role in kidney stone disease has not been fully elucidated until now. Here we reported VHL expression was upregulated in renal epithelial cells upon exposure to crystal. Utilizing Vhl+/mu mouse model, depletion of VHL exacerbated kidney inflammatory injury during nephrolithiasis. Conversely, overexpression of VHL limited crystal-induced lipid peroxidation and ferroptosis in a BICD2-depdendent manner. Mechanistically, VHL interacted with the cargo adaptor BICD2 and promoted itsd K48-linked poly-ubiquitination, consequently resulting in the proteasomal degradation of BICD2. Through promoting STAT1 nuclear translocation, BICD2 facilitated IFNγ signaling transduction and enhanced IFNγ-mediated suppression of cystine/glutamate antiporter system Xc-, eventually increasing cell sensitivity to ferroptosis. Moreover, we found that the BRAF inhibitor impaired the association of VHL with BICD2 through triggering BICD2 phosphorylation, ultimately causing severe ferroptosis and nephrotoxicity. Collectively, our results uncover the important role of VHL/BICD2/STAT1 axis in crystal kidney injury and provide a potential therapeutic target for treatment and prevention of renal inflammation and drug-induced nephrotoxicity.

Ae index is an independent predictor of kidney stone recurrence in overweight and obese patients

BACKGROUND

Finding some convenient and economical indicators to initially screen overweight and obese patients at high risk of kidney stone recurrence can help them prevent stone recurrence with lower medical cost. The purpose of this article is to determine the clinical value of Ae index (Apo B × 1000/eGFR) as an independent predictor for kidney stone recurrence in overweight and obese populations.

METHODS

We queried the electronic medical records of patients with kidney stone operated at our hospital from March 2016 to March 2022, and selected BMI ≥ 25 kg/m2 as the study population and divided the patients into stone recurrence group and non-recurrence group. Relevant parameters of routine blood and biochemical test, glycated serum protein (GSP), and history of hypertension and hyperglycemia were collected. Then the Chi-square test, independent samples t-test or Wilcoxon rank-sum test were used to calculate the differences between the two groups of data. Next, we performed univariate and multivariate logistic regression analysis to screen out the most significant variables Apo B and eGFR, and then we calculated the Ae index using the formula Apo B × 1000/eGFR, and analyzed the relationship between Ae index and kidney stone recurrence.

RESULTS

Univariate analysis found that Apo B (OR:8.376,95%CI:3.093-22.680), Creatinine (OR:1.012,95%CI:1.003-1.021), Cystatin C(OR:2.747,95%CI:1.369-5.508), LDL-C (OR:1.588,95%CI:1.182-2.134), TC (OR:1.543,95%CI:1.198-1.988) were positively associated, eGFR (OR:0.980,95%CI:0.970-0.991) was negatively associated with kidney stone recurrence. And multivariate logistic regression analysis suggested that Apo B (OR:11.028, 95%CI:3.917-31.047) and eGFR (OR:0.976, 95%CI:0.965-0.988) were the most significant factors. Then we calculated Ae index and analyzed it, the sensitivity was 74.26% and the specificity was 60.00%, higher than either individual variable. Its smoothed curve revealed a non-linear relationship between them with the inflection point of 9.16. And the OR on the left side of the inflection point was 1.574 (95% CI: 1.228-2.018), whereas the OR on the right side of the inflection point was 1.088 (95% CI: 1.007-1.177).

CONCLUSIONS

Ae index is an easily calculated and obtained index that has some predictive value for kidney stone recurrence in overweight and obese patients, which is of interest.

Lifestyle factors, serum parameters, metabolic comorbidities, and the risk of kidney stones: a Mendelian randomization study

Background and objective

The early identification of modifiable risk factors is important for preventing kidney stones but determining causal associations can be difficult with epidemiological data. We aimed to genetically assess the causality between modifiable factors (lifestyle factors, serum parameters, and metabolic comorbidities) and the risk of kidney stones. Additionally, we aimed to explore the causal impact of education on kidney stones and its potential mediating pathways.

Methods

We conducted a two-sample Mendelian randomization (MR) study to explore the causal association between 44 modifiable risk factors and kidney stones. The FinnGen dataset initially explored the causal relationship of risk factors with kidney stones and the UK Biobank dataset was used as the validation set. Then, a meta-analysis was conducted by combining discovery and validation datasets. We used two-step MR to assess potential mediators and their mediation proportions between education and kidney stones.

Results

The combined results indicated that previous exposures may increase the risk of kidney stones, including sedentary behavior, urinary sodium, the urinary sodium/potassium ratio, the urinary sodium/creatinine ratio, serum calcium, 25-hydroxyvitamin D (25OHD), the estimated creatinine-based glomerular filtration rate (eGFRcrea), GFR estimated by serum cystatin C (eGFRcys), body mass index (BMI), waist circumference, type 2 diabetes mellitus (T2DM), fasting insulin, glycated hemoglobin, and hypertension. Coffee intake, plasma caffeine levels, educational attainment, and the urinary potassium/creatinine ratio may decrease the risk of kidney stones. Ranked by mediation proportion, the effect of education on the risk of kidney stones was mediated by five modifiable risk factors, including sedentary behavior (mediation proportion, 25.7%), smoking initiation (10.2%), BMI (8.2%), T2DM (5.8%), and waist circumference (3.2%).

Conclusion

This study provides MR evidence supporting causal associations of many modifiable risk factors with kidney stones. Sedentary lifestyles, obesity, smoking, and T2DM are mediating factors in the causal relationship between educational attainment and kidney stones. Our results suggest more attention should be paid to these modifiable factors to prevent kidney stones.

Short-term effects of ambient air pollution on emergency department visits for urolithiasis: A time-series study in Wuhan, China

Background

Previous studies have explored the correlation between short-term exposure to air pollution and urinary system diseases, but lack of evidence on the correlation between air pollution and urolithiasis.

Methods

Daily data of emergency department visits (EDVs), concentrations of six air pollutants (SO₂, NO₂, PM_2.5, PM₁₀, CO, and O₃) and meteorological variables were collected in Wuhan, China, from 2016 to 2018. And a time-series study was conducted to investigate short-term effects of air pollutants on urolithiasis EDVs. In addition, stratified analyses by season, age and gender were also conducted.

Results

A total of 7,483 urolithiasis EDVs were included during the study period. A 10-μg/m³ increase of SO₂, NO₂, PM_2.5, CO, PM₁₀, and O₃ corresponded to 15.02% (95% confidence interval [CI]: 1.69%, 30.11%), 1.96% (95% CI: 0.19%, 3.76%), 1.09% (95% CI:-0.24%, 2.43%), 0.14% (95% CI: 0.02%, 0.26%), 0.72% (95% CI: 0.02%, 1.43%), and 1.17% (95% CI: 0.40%, 1.94%) increases in daily urolithiasis EDVs. Significant positive correlations were observed between SO₂, NO₂, CO, and O₃ and urolithiasis EDVs. The correlations were mainly among females (especially PM_2.5 and CO) and younger people (especially SO₂, NO₂, and PM₁₀) but the effect of CO was more obvious in elders. Furthermore, the effects of SO₂ and CO were stronger in warm seasons, while the effects of NO₂ were stronger in cool seasons.

Conclusion

Our time-series study indicates that short-term exposure to air pollution (especially SO₂, NO₂, CO, and O₃) was positively correlated with EDVs for urolithiasis in Wuhan, China, and the effects varied by season, age and gender.

Effect of Two Different Dietary Weight Loss Strategies on Risk Factors for Urinary Stone Formation and Cardiometabolic Risk Profile in Overweight Women

Overweight has been suggested to increase the risk of kidney stone formation. Although weight reduction might affect risk factors for urolithiasis, findings on the impact of different dietary weight loss strategies are limited. This randomized, controlled study evaluated the effect of a conventional energy-restricted modified diet with (MR group) or without meal replacement (C group) on risk factors for stone formation in overweight women without a history of urolithiasis. Of 105 participants, 78 were included into the per-protocol analysis. Anthropometric, clinical, biochemical, and 24 h urinary parameters were collected at baseline and after 12 weeks. Although both dietary interventions resulted in a significant weight reduction, relative weight loss and rate of responders were higher in the MR group. Weight loss improved cardiometabolic risk profile in both groups. Unfortunately, the benefit of decreased GPT activity in the C group was offset by a significant increase in homocysteine and a decline in GFR. While the relative supersaturation of calcium oxalate decreased significantly in both groups, a significant decline in serum uric acid concentration and relative supersaturation of uric acid was observed only in the MR group. Finally, the energy-restricted modified diet with meal replacement showed significant advantages over the energy-restricted modified diet alone.

Gender Differences in Kidney Stone Disease (KSD): Findings from a Systematic Review

Purpose of Review

The prevalence of kidney stones is rising and historically carries a preponderance for males. However, recent evidence has questioned whether this gender gap is closing. The aim of this systematic review was to examine this further as well as evaluate possible underlying causes.

Recent Findings

Recent evidence confirms the disparity in kidney stone disease between genders is closing. In the modern era, the rise in prevalence among females has been greater, especially in adolescence. Quality of life is also more adversely affected by kidney stone events among females who are also more likely to develop sepsis after endourological surgery. Males, however, are more likely to present with stone events during periods of high ambient temperatures

Summary

Recent literature demonstrates a temporal change in the disease burden of KSD among men and women. The latter, especially adolescent females, are more likely to develop KSD in their lifetime compared to previous eras. Determining causation is complex and continued research is warranted.

Assessing causal associations of obesity and diabetes with kidney stones using Mendelian randomization analysis

BACKGROUND

Obesity and type 2 diabetes have been associated with an increased risk of kidney stones in observational studies, but the causality of these associations remains unestablished. We conducted a Mendelian randomization study to determine these associations.

METHODS

Independent single nucleotide polymorphisms at the genome-wide significance threshold (p < 5 × 10^-8) were selected as instrumental variables and were identified from meta-analyses of genome-wide association studies on body mass index (up to 806,834 individuals) and type 2 diabetes (228,499 cases and 1,178,783 non-cases). Summary-level data for the associations of exposure-associated SNPs with kidney stones were obtained from the UK Biobank study (3540 cases and 357,654 non-cases) and the FinnGen consortium (3856 cases and 172,757 non-cases). Causal estimates from two sources were combined using the meta-analysis method.

RESULTS

Higher genetically predicted body mass index and genetic liability to type 2 diabetes were associated with an increased risk of kidney stones in both the UK Biobank study and FinnGen consortium. In the meta-analysis of results from the two data sources, the odds ratios of kidney stones were 1.33 (95% confidence interval, 1.17, 1.51; p < 0.001) per one standard deviation increase in genetically predicted body mass index (~4.8 kg/m²) and 1.15 (95% confidence interval, 1.10, 1.20; p < 0.001) for one unit increase in genetically predicted log-transformed odds of type 2 diabetes.

INTERPRETATION

This study based on genetic data suggests that a high body mass index and type 2 diabetes may be causal risk factors for kidney stone formation.

Associations between nephrolithiasis and diabetes mellitus, hypertension and gallstones: A meta-analysis of cohort studies

AIM

To review and clarify the strengths and directions of associations between nephrolithiasis and hypertension (HTN), diabetes mellitus (DM) and gallstones (GS) given the inconsistent results reported in cohort studies.

METHODS

Relevant literature was searched in PubMed and EMBASE from inception to July 2019, for cohort studies that examined the relationships between kidney stones and these three diseases among adults. Pooled relative risks (RRs) were calculated by maximally adjusted risk estimates using a random effect model. Subgroup analysis, meta-regression and sensitivity analysis were conducted whenever appropriate.

RESULTS

Of 3537 papers, 21 articles with each including 1 to 3 cohorts were identified. In this meta-analysis, nephrolithiasis was reciprocally linked to HTN, DM and GS. Kidney stones were significantly associated with 31%, 33% and 46% higher risks of incident HTN, DM and GS whereas GS was associated with a significantly higher risk of nephrolithiasis (RR: 1.49; 95% CI, 1.28-1.73), followed by HTN (RR: 1.30; 95% CI, 1.11-1.52) and DM (RR: 1.18; 95% CI, 1.07-1.29). Also, females with DM (RR: 1.29; 95% CI, 1.08-1.55) were more likely to develop kidney stones than diabetic male patients (RR: 0.91; 95% CI, 0.75-1.10).

CONCLUSION

Although additional studies are needed to confirm these findings and elucidate the mechanisms, this study revealed possible bidirectional associations between nephrolithiasis and HTN, diabetes and GS, which reinforced the notion of nephrolithiasis as a systemic disease that requires comprehensive investigations.

Sex Differences in Kidney Stone Disease in Chinese Patients with Type 2 Diabetes Mellitus

Objectives

To investigate the characteristics of kidney stone disease (KSD) among the Chinese population with type 2 diabetes mellitus (T2DM) and identify sex-specific factors associated with KSD.

Methods

A single-center, cross-sectional analysis was performed among Chinese patients with T2DM. KSD was identified by ultrasonography or computed tomography results. Demographic data, physical measurements, laboratory measurements, comorbidities, and related medication data were collected and analyzed. Binary logistic regression was used to explore the associated factors.

Results

A total of 7,257 patients with T2DM were included in the study, of which 56.1% were male and 15.0% were diagnosed with KSD. The male-to-female ratio for KSD among T2DM patients was 1.35. Among all the T2DM patients, male gender, HOMA2-IR, uric acid, and renal cysts were independent risk factors for KSD development, whereas serum phosphorus and the use of angiotensin-converting enzyme inhibitors (ACEIs) were independent protective factors for KSD. Among male diabetic patients, triglycerides, HOMA2-IR, renal cysts, and urinary tract infections were all associated with a greater risk of KSD. In contrast, serum phosphorus was associated with a lower risk of KSD. Among female diabetic patients, systolic blood pressure and HOMA2-B were both contributing factors, and ACEIs acted as a protective factor for KSD.

Conclusion

Among Chinese patients with T2DM, approximately 1 in 7 patients was affected by KSD, and the prevalence was twice as high as that in the general Chinese population. The factors associated with KSD varied by sex among T2DM patients. Focusing on these factors is beneficial for reducing the risk of KSD and delaying kidney damage in diabetic patients.