Proinflammatory and Metabolic Changes Facilitate Renal Crystal Deposition in an Obese Mouse Model of Metabolic Syndrome

New insight into oxidative stress and inflammatory responses to kidney stones: Potential therapeutic strategies with natural active ingredients

Kidney stones, a prevalent urological disorder, are closely associated with oxidative stress (OS) and the inflammatory response. Recent research in the field of kidney stone treatment has indicated the potential of natural active ingredients to modulate OS targets and the inflammatory response in kidney stones. Oxidative stress can occur through various pathways, increasing the risk of stone formation, while the inflammatory response generated during kidney stone formation further exacerbates OS, forming a detrimental cycle. Both antioxidant systems related to OS and inflammatory mediators associated with inflammation play roles in the pathogenesis of kidney stones. Natural active ingredients, abundant in resources and possessing antioxidative and anti-inflammatory properties, have the ability to decrease the risk of stone formation and improve prognosis by reducing OS and suppressing pro-inflammatory cytokine expression or pathways. Currently, numerous developed natural active ingredients have been clinically applied and demonstrated satisfactory therapeutic efficacy. This review aims to provide novel insights into OS and inflammation targets in kidney stones as well as summarize research progress on potential therapeutic strategies involving natural active ingredients. Future studies should delve deeper into exploring efficacy and mechanisms of action of diverse natural active ingredients, proposing innovative treatment strategies for kidney stones, and continuously uncovering their potential applications.

The association between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and prevalence of urinary stones in US adults: a cross-sectional NHANES study

BACKGROUND

This study examines the association between the non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and urinary stones in American adults.

METHODS

We conducted a cross-sectional study utilizing the 2007-2018 National Health and Nutrition Examination Survey (NHANES) data set. The prevalence of urinary stones was determined based on patient-reported experiences of renal colic. We converted NHHR to natural logarithm (ln-NHHR) to align it better with our statistical analyses. Our analysis methods included weighted multivariate logistic regression, generalized additive model (GAM), and application of smoothed curves to better elucidate the association between ln-NHHR and the prevalence of urinary stones. In addition, we conducted subgroup analyses and employed multiple imputation for sensitivity analyses.

RESULTS

This study involved a total of 30,903 participants, with a 9.97% prevalence of urinary stones and reported colic experience. Elevated ln-NHHR levels were linked with a higher likelihood of urinary stones (OR = 1.20, 95% CI 1.07-1.35). Smooth curve fitting revealed an inverted U-shaped relationship, pinpointing a significant increase in urinary stone risk at ln-NHHR levels below 1.43 (OR = 1.40, 95% CI 1.19-1.64, p < 0.001). Notably, this correlation was stronger among Non-Hispanic Whites and those married or living with a partner. Multiple imputation analyses strengthened the confidence in our results.

CONCLUSIONS

Our findings suggest a reverse U-shaped association between urinary stone occurrence and NHHR level, with a positive association at ln-NHHR < 1.43. This correlation was more pronounced in the Non-Hispanic White population and among those married or living with a partner.

Association between non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) and kidney stone: evidence from NHANES 2007-2018

BACKGROUND

As an innovative lipid parameter, NHHR (the ratio of non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol) can serve as a valuable tool for assessing cardiovascular disease risk. Nevertheless, the relationship between NHHR and the risk of kidney stones remains unexplored.

METHODS

A cross-sectional survey utilized data from the National Health and Population Survey (NHANES) database in the United States spanning from 2007 to 2018. Distinct statistical analyses were applied, including weighted logistic regression, stratified and interaction analysis and restricted cubic spline curve (RCS) models, to examine the correlation between NHHR and the incidence of kidney stones.

RESULTS

This analysis encompassed 24,664 participants, with 9.63% reporting incidents of kidney stones. Following multivariate logistic regression and comprehensive adjustments, participants in NHHR quartile 4 (OR 1.34; 95% CI 1.12, 1.60, P < 0.01) exhibited a significantly increased risk of kidney stones compared to those in NHHR quartile 1 (Q1). The RCS result further illustrated a non-linear correlation between NHHR and the incidence of kidney stones. The result of subgroup analysis manifested that participants without diabetes had a higher risk of kidney stones when measured high NHHR levels compared those with diabetes (p for interaction < 0.05).

CONCLUSION

Elevated NHHR levels were found to be associated with an increased risk of kidney stones. Based on these findings, NHHR appears to be a promising predictive indicator for the occurrence of kidney stones.

Analysis of metabolic syndrome in bilateral upper urinary tract stones: A retrospective study of 3905 cases

Bilateral upper urinary tract stones are significantly related to renal function damage. However, few studies characterized the risk factors of bilateral upper urinary tract stones. We retrospectively enrolled 3905 patients with urinary tract stones from March 2019 to March 2022 at the Second Hospital of Tianjin Medical University. Patients were divided into two groups according to the location of the stones, and the related data were evaluated. In this study, 2485 unilateral and 1420 bilateral stone patients were included. Multivariate logistic regression analysis showed that BMI, gout, hyperparathyroidism, uric acid stone, urine PH, 24-h urinary calcium, blood uric acid, and metabolic syndrome (Mets) were independent risk factors for bilateral stone formation(P < 0.05). Based on these results, we construct a discrimination model. This model revealed good discrimination with an area under the receiver operating characteristic curves of 0.617, and the sensitivity and specificity were 0.592 and 0.586, respectively. Furthermore, the number of Mets components increased the risk of bilateral upper urinary tract stones. Hypertension, hyperglycemia, and low HDL level were strongly associated with bilateral upper urinary tract stones (P < 0.05). Patients with 5 components Mets had 1.89-fold higher risk of bilateral upper urinary tract stones than those with 1 component Mets (OR 3.381; 95 % CI 1.221-9.360; P = 0.013). Additionally, male patients with Mets had higher risk of bilateral upper urinary tract stones than female patients. Our analysis revealed that eight clinical factors were associated with the formation of bilateral upper urinary tract stones, namely BMI, gout, hyperparathyroidism, uric acid stone, urine PH, 24-h urinary calcium, blood uric acid, and Mets. This study could help clinicians adjust treatment strategies for high-risk patients with bilateral upper urinary tract stones.

Role of miRNAs in macrophage-mediated kidney injury

Macrophages, crucial components of the human immune system, can be polarized into M1/M2 phenotypes, each with distinct functions and roles. Macrophage polarization has been reported to be significantly involved in the inflammation and fibrosis observed in kidney injury. MicroRNA (miRNA), a type of short RNA lacking protein-coding function, can inhibit specific mRNA by partially binding to its target mRNA. The intricate association between miRNAs and macrophages has been attracting increasing interest in recent years. This review discusses the role of miRNAs in regulating macrophage-mediated kidney injury. It shows how miRNAs can influence macrophage polarization, thereby altering the biological function of macrophages in the kidney. Furthermore, this review highlights the significance of miRNAs derived from exosomes and extracellular vesicles as a crucial mediator in the crosstalk between macrophages and kidney cells. The potential of miRNAs as treatment applications and biomarkers for macrophage-mediated kidney injury is also discussed.

Associations between the platelet/high-density lipoprotein cholesterol ratio and likelihood of nephrolithiasis: a cross-sectional analysis in United States adults

Aims

The primary objective of this study was to investigate the relationship between the platelet/high-density lipoprotein cholesterol ratio (PHR) and the prevalence of nephrolithiasis within the adult population of the United States.

Methods

The data used in this study were obtained from the National Health and Nutrition Examination Survey (NHANES) conducted between 2007 and 2018. The analysis included a non-pregnant population aged 20 years or older, providing proper PHR index and nephrolithiasis data. The research utilized subgroup analyses and weighted univariate and multivariable logistic regression to evaluate the independent association between the PHR and the susceptibility to nephrolithiasis.

Results

The study comprised 30,899 participants with an average PHR value of 19.30 ± 0.11. The overall prevalence rate of nephrolithiasis was estimated at 9.98% with an increase in the higher PHR tertiles (T1, 8.49%; T2, 10.11%; T3, 11.38%, P < 0.0001). An elevated PHR level was closely linked with a higher susceptibility to nephrolithiasis. Compared with patients in T1, and after adjusting for potential confounders in model 2, the corresponding odds ratio for nephrolithiasis in T3 was 1.48 (95% CI: 1.06 to 2.08), with a P-value = 0.02. The results of the interaction tests revealed a significant impact of chronic kidney disease on the relationship between PHR and nephrolithiasis. Furthermore, the restricted cubic spline analyses exhibited a positive, non-linear correlation between PHR and the risk of nephrolithiasis.

Conclusion

A convenient biomarker, the PHR, was independently associated with nephrolithiasis and could be a novel biomarker in predicting occurrence in clinical decision.

The association of dyslipidemia with kidney stone: result from the NHANES 2007-2020

OBJECTIVE

To examine the association between dyslipidemia and kidney stone disease (KSD).

METHODS

A cross-sectional study data from 2007 to 2020 National Health and Nutrition Examination Survey (NHANES) were analyzed. Multivariate logistic regression was conducted with serum lipid levels as the exposure and presence of KSD as the outcome, and included adjustment for confounders and subgroup analysis.

RESULTS

A total of 38,617 participants were enrolled and classified into two groups according to whether they ever had (n = 3689) or did not have (n = 34,928) KSD. After multivariate logistic regression models, compared to quartile 1 (Q1) of lipid profile, the participants in Q3 (OR 0.8380; 95 CI 0.7380, 0.9515, P < 0.01) and Q4 (OR 0.7373; 95 CI 0.6377, 0.8525, P < 0.01) of high-density lipoprotein cholesterol (HDL) had a significantly lower risk of KSD in adjusted model 3. Results remained stable after stratified by age, gender, and body mass index (BMI) in subgroup analysis. No association was observed between low-density lipoprotein cholesterol (LDL), total cholesterol (TC) and triglycerides (TG) levels, and KSD.

CONCLUSIONS

Low HDL was associated with a higher risk of kidney stones in the USA adult population.

The association of visceral adiposity index with the risk of kidney stone and kidney stone recurrence

AIM

Our aim in this study was primarily to assess the relationship between visceral adiposity index (VAI) and the risk of kidney stones and kidney stone recurrence in US adults.

METHODS

We used data from the National Health and Nutrition Examination Survey (NHANES) 2007-2014 for our analysis. VAI was calculated from waist circumference (WC), body mass index (BMI), triglycerides (TG), and high-density lipoprotein-cholesterol (HDL-C). Kidney stones and recurrence of kidney stones were obtained from questionnaire interview data. We used multivariate logistic regression analysis to explore the correlation between VAI and the risk of kidney stone and kidney stone recurrence. In addition, we performed subgroup analysis, interaction tests, and restricted cubic spline (RCS) analysis.

RESULTS

A total of 9886 participants were included in this study, with a prevalence of 9.24% for kidney stones and 2.97% for recurrence of kidney stones. The prevalence of kidney stones and kidney stone recurrence increased with higher quartiles of VAI. We observed a significantly positive correlation between VAI and the risk of kidney stone and kidney stone recurrence. Participants with the highest VAI quartiles had a 48% (OR: 1.48, 95%CI: 1.08-2.02) and 52% (OR: 1.52, 95%CI: 0.86-2.71) increased risk of kidney stones and kidney stone recurrence, respectively, compared to participants with the lowest VAI quartiles. Subgroup analysis and interaction tests demonstrated this positive association independent of different subgroup factors.

CONCLUSION

Visceral fat accumulation may be associated with an increased risk of kidney stones and kidney stone recurrence.

Prognostic value of total body muscle-fat ratio in patients with kidney stone disease: A US population-based study

Purpose

To examine the relationship between the muscle-fat ratio (MFR) and kidney stone disease (KSD) in the adult population of the United States between 2011 and 2018, and whether it can be used as a predictor of KSD prognosis.

Materials and methods

We conducted a cross-sectional study analysing 9326 patients from the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2018. We analyzed all participants by sex, age, race, level of education, marital status, household income-to-poverty ratio, hypertension, diabetes, vigorous physical activity, moderate physical activity, blood urea nitrogen, creatinine, uric acid, cotinine, and MFR. Dose-response curves with a restricted cubic spline function, univariate and multifactorial logistic regression were used for the analysis of the correlation between MFR and KSD. Finally, we created predictive models based on age, race, hypertension, diabetes mellitus, cotinine and MFR. The prediction model was evaluated using calibration curves, receiver operating characteristic curves and clinical decision curves from the training and test sets.

Results

Of the 9326 participants, 8582 (92%) self-reported that they did not have KSD and 744 (8%) self-reported that they had KSD. Univariate and multifactorial logistic regression showed that MFR was negatively associated with the prevalence of KSD (odds ratio [OR]: 0.770, 95% CI: 0.703-0.843; OR: 0.815, 95% CI: 0.738-0.897). Similarly, the risk of developing KSD decreased with increasing MFR as shown by the dose curves in the restricted cubic bar graphs. Furthermore, there is some accuracy (AUC = 0.652) and clinical applicability to the model we constructed based on the results of multifactorial logistic regression.

Conclusion

The MFR is protective factor against the developing KSD in adults in the USA.

Hormonal and molecular characterization of calcium oxalate stone formers predicting occurrence and recurrence

The purpose of the study is to investigate the role of sex hormones, androgen receptors (ARs) and miRNA/CSF-1 in occurrence and recurrence of calcium oxalate (CaOx) renal urolithiasis. In this prospective study, 74 patients with CaOx stones; stone formers group (SFG) and 40 healthy subjects; control group were compared. SFG includes both de novo and recurrent cases. Steroid sex hormone plasma assay including testosterone, free testosterone, dihydrotestosterone, estradiol, and sex hormone binding globulin was analyzed. ARs, miRNA-185-5p and CSF-1 expression were compared between the groups. SFG showed significant higher ARs and miRNA-185-5p expression (3.7 ± 1.3, 1.8 ± 0.4, respectively) than control group (1 ± 0.08 and 1 ± 0.07, respectively) (p < 0.05). However, CSF-1 expression was significantly lower in stone formers than control group (0.4 ± 0.19 vs 1 ± 0.1, respectively) (p < 0.05). No differences were detected between de novo and recurrent SFG regarding sex hormones, AR, miRNA or CSF-1 expression. Our data suggest the important role of AR, miRNA and CSF-1 signaling in human nephrolithiasis pathogenesis.

Bioinformatics analysis reveals the potential role of matrix metalloproteinases in immunity and urolithiasis

Background

The pathogenesis of urolithiasis remains unclear, making the development of medications for treatment and prevention stagnant. Randall’s plaques (RPs) begin as interstitial calcium phosphate crystal deposits, grow outward and breach the renal papillary surface, acting as attachment for CaOx stones. Since matrix metalloproteinases (MMPs) can degrade all components of extracellular matrix (ECM), they might participate in the breach of RPs. Besides, MMPs can modulate the immune response and inflammation, which were confirmed to be involved in urolithiasis. We aimed to investigate the role of MMPs in the development of RPs and stone formation.

Methods

The public dataset GSE73680 was mined to identify differentially expressed MMPs (DEMMPs) between normal tissues and RPs. WGCNA and three machine learning algorithms were performed to screen the hub DEMMPs. In vitro experiments were conducted for validation. Afterwards, RPs samples were classified into clusters based on the hub DEMMPs expression. Differentially expressed genes (DEGs) between clusters were identified and functional enrichment analysis and GSEA were applied to explore the biological role of DEGs. Moreover, the immune infiltration levels between clusters were evaluated by CIBERSORT and ssGSEA.

Results

Five DEMMPs, including MMP1, MMP3, MMP9, MMP10, and MMP12, were identified between normal tissues and RPs, and all of them were elevated in RPs. Based on WGCNA and three machine learning algorithms, all of five DEMMPs were regarded as hub DEMMPs. In vitro validation found the expression of hub DEMMPs also increased in renal tubular epithelial cells under lithogenic environment. RPs samples were divided into two clusters and cluster A exhibited higher expression of hub DEMMPs compared to cluster B. Functional enrichment analysis and GSEA found DEGs were enriched in immune-related functions and pathways. Moreover, increased infiltration of M1 macrophages and enhanced levels of inflammation were observed in cluster A by immune infiltration analysis.

Conclusion

We assumed that MMPs might participate in RPs and stone formation through ECM degradation and macrophages-mediated immune response and inflammation. Our findings offer a novel perspective on the role of MMPs in immunity and urolithiasis for the first time, and provide potential biomarkers to develop targets for treatment and prevention.

Ghrelin and Leptin among Patients with Urolithiasis with Concomitant Hyperuricemia and Metabolic Syndrome

Introduction: The study evaluated the selected appetite hormones (ghrelin, leptin) and inflammatory parameters (tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6)) in patients with urolithiasis, metabolic syndrome (MetS), and hyperuricemia. Materials: 57 patients with urolithiasis, MetS and hyperuricemia (UP group) and 29 healthy people as the control group (CG group) were recruited to the study. All persons were 22-60 age. Methods: After preliminary testing, the qualified participants were evaluated for fasting serum levels of ghrelin, leptin, IL-6, and TNF-α. Results: Our results revealed differences between average values of leptin (p = 0.045), ghrelin (p < 0.001), IL-6 (p < 0.001), and TNF-α (p < 0.001) in the studied groups. Moreover, in the UP group, significant correlations were found between ghrelin and leptin; between these hormones and IL-6, and between leptin and uric acid (UA). Besides, leptin concentration increased significantly along with the changes in the body mass index (BMI) categories in the UP group. Conclusions: This study showed that patients with urolithiasis, concomitant MetS, and high UA levels may have problems managing appetite hormones.

A pilot dynamic analysis of formative factors of nephrolithiasis related to metabolic syndrome: evidence in a rat model

Introduction and objective

To examine the dynamic changes in the formative factors of nephrolithiasis and the final micromorphological changes in an obesity-initiated metabolic syndrome (MS) rat model.

Methods

Forty five-week-old male Sprague–Dawley (SD) rats were randomly divided into four groups: the regular diet group (RD), high-fat diet group (HFD), regular diet with drug (ethylene glycol and ammonium chloride) group (RDD), and high-fat diet with drug group (HFDD). A dynamic assessment of MS components (body weight (BW), body length (BL), Lee’s index (LI), blood glucose (BG), total cholesterol (TC), and triglycerides (TGs)) and stone-forming factors (urinary pH, urinary calcium, and urinary oxalate acid) was carried out. In addition, the levels of oxidative stress (OS) markers (CAT, SOD, TAC, GSH-PX, and MDA) were measured, and histological analysis was carried out at the end of 16 weeks.

Results

MS-related parameters, such as BW, LI, BG, TC, and TG, were significantly higher in HFD-fed rats than in RD-fed rats (p < 0.001). In the HFDD group, significantly lower urinary pH, hyperoxaluria, and hypocalciuria were noted in the dynamic assessment of stone-forming factors (p < 0.001). CAT, TAC, and MDA were notably changed in the HFD-fed groups, particularly the HFDD rats. Histological analysis showed that the renal tubules of HFDD rats had the highest scores for both inflammation and renal crystallization deposition (p < 0.05).

Conclusions

Our results suggest that male SD rats with MS are prone to developing nephrolithiasis. Validation in an in vivo model may lead to an understanding of the underlying pathophysiological mechanisms of action of MS-related nephrolithiasis in humans.

Key messages

Male SD rats with metabolic syndrome are more prone to developing calcium oxalate nephrolithiasis after treatment with ethylene glycol and ammonium chloride compared to control lean rats.

MS-related nephrolithiasis in rats induced by ethylene glycol and ammonium chloride is mainly related to increased hyperoxaluria and inflammation and decreased antioxidant levels.

High-fat diet-fed SD rats treated with ethylene glycol and ammonium chloride are a stable and valid in vivo model for understanding the potential mechanism of action of MS-related nephrolithiasis.

Osteopontin: An important protein in the formation of kidney stones

The incidence of kidney stones averages 10%, and the recurrence rate of kidney stones is approximately 10% at 1 year, 35% at 5 years, 50% at 10 years, and 75% at 20 years. However, there is currently a lack of good medicines for the prevention and treatment of kidney stones. Osteopontin (OPN) is an important protein in kidney stone formation, but its role is controversial, with some studies suggesting that it inhibits stone formation, while other studies suggest that it can promote stone formation. OPN is a highly phosphorylated protein, and with the deepening of research, there is growing evidence that it promotes stone formation, and the phosphorylated protein is believed to have adhesion effect, promote stone aggregation and nucleation. In addition, OPN is closely related to immune cell infiltration, such as OPN as a pro-inflammatory factor, which can activate mast cells (degranulate to release various inflammatory factors), macrophages (differentiated into M1 macrophages), and T cells (differentiated into T1 cells) etc., and these inflammatory cells play a role in kidney damage and stone formation. In short, OPN mainly exists in the phosphorylated form in kidney stones, plays an important role in the formation of stones, and may be an important target for drug therapy of kidney stones.

Association between visceral adiposity index and kidney stones in American adults: A cross-sectional analysis of NHANES 2007–2018

Objective

To explore the association between Visceral Adiposity Index (VAI) and kidney stones in an American adult population.

Materials and methods

National Health and Nutrition Examination Survey (NHANES) datasets from 2007 to 2018 were used. Participants aged ≥20 years who reported kidney stone history and VAI were included. Weighted proportions, multivariable analysis, generalized additive model (GAM), and spline smoothing were used to evaluate the associations between VAI and kidney stones by adjusting gender, age, race, education, marital status, poverty income ratio, smoking, alcohol, high blood pressure, diabetes, congestive heart failure, cancer, vigorous activity, moderate activity, HEI2015 total score, and energy.

Results

Totally 13,871 American adults were included. All the participants were divided by the VAI into four groups according to the quartile: Q1 (11.96–42.89), Q2 (42.90–74.45), Q3 (74.45–131.43), and Q4 (131.45–611.34). The mean ± standard deviation of the VAI in the four groups were Q1 (29.07 ± 8.22), Q2 (57.53 ± 8.81), Q3 (99.52 ± 16.25), and Q4 (225.92 ± 95.83). In the fully adjusted multivariable model, VAI was positively correlated with urolithiasis [odds ratio (OR) = 1.001; 95% confidence interval (CI) 1.000–1.001]. Compared with the first quartile of VAI, the population in the fourth quartile of VAI had a higher prevalence of kidney stones (OR = 1.329; 95% CI 1.104–1.600). Subgroup analysis detected no significant interaction effect after adjusting for covariates.

Conclusion

The value of VAI is positively correlated with the prevalence of kidney stones, which suggest VAI can be used to assess the potential risk of the prevalence of kidney stones.

Nephrolithiasis: A Red Flag for Cardiovascular Risk

Epidemiological evidence shows that nephrolithiasis is associated with cardiovascular (CV) morbidities. The association between nephrolithiasis and CV disease is not surprising because both diseases share conditions that facilitate their development. Metabolic conditions, encompassed in the definition of metabolic syndrome (MS), and habits that promote nephrolithiasis by altering urine composition also promote clinical manifestations of CV disease. By inducing oxidative stress, these conditions cause endothelial dysfunction and increased arterial stiffness, which are both well-known predictors of CV disease. Furthermore, the subtle systemic metabolic acidosis observed in stone formers with CV disease may have a pathogenic role by increasing bone turnover and leading to reduced mineral content and osteoporosis/osteopenia. Heart valves and/or coronary artery and aortic calcifications are frequently associated with reduced mineral density. This is known as the 'calcification paradox' in osteoporosis and has also been observed in subjects with calcium nephrolithiasis. Evidence supports the hypothesis that osteoporosis/osteopenia is an independent risk factor for the development of CV calcifications. In the long term, episodes of renal stones may occur from the onset of metabolic derangements/MS to arterial stiffness/atherosclerosis and CV morbidities. These episodes should be considered a warning sign of an ongoing and silent atherosclerotic process. The evaluation of cardiometabolic risk factors and MS components should be routine in the assessment of renal stone formers. This would allow for treatment and prevention of the development of CV complications, which are much more severe for the patient and for public health.

Ample dietary fat reduced the risk of primary vesical calculi by inducing macrophages to engulf budding crystals in mice

Although primary vesical calculi is an ancient disease, the mechanism of calculi formation remains unclear. In this study, we established a novel primary vesical calculi model with d,l-choline tartrate in mice. Compared with commonly used melamine and ethylene glycol models, our model was the only approach that induced vesical calculi without causing kidney injury. Previous studies suggest that proteins in the daily diet are the main contributors to the prevention of vesical calculi, yet the effect of fat is overlooked. To assay the relationship of dietary fat with the formation of primary vesical calculi, d,l-choline tartrate-treated mice were fed a high-fat, low-fat, or normal-fat diet. Genetic changes in the mouse bladder were detected with transcriptome analysis. A high-fat diet remarkably reduced the morbidity of primary vesical calculi. Higher fatty acid levels in serum and urine were observed in the high-fat diet group, and more intact epithelia in bladder were observed in the same group compared with the normal- and low-fat diet groups, suggesting the protective effect of fatty acids on bladder epithelia to maintain its normal histological structure. Transcriptome analysis revealed that the macrophage differentiation-related gene C–X–C motif chemokine ligand 14 (Cxcl14) was upregulated in the bladders of high-fat diet-fed mice compared with those of normal- or low-fat diet-fed mice, which was consistent with histological observations. The expression of CXCL14 significantly increased in the bladder in the high-fat diet group. CXCL14 enhanced the recruitment of macrophages to the crystal nucleus and induced the transformation of M2 macrophages, which led to phagocytosis of budding crystals and prevented accumulation of calculi. In human bladder epithelia (HCV-29) cells, high fatty acid supplementation significantly increased the expression of CXCL14. Dietary fat is essential for the maintenance of physiological functions of the bladder and for the prevention of primary vesical calculi, which provides new ideas for the reduction of morbidity of primary vesical calculi.

Identification of the pivotal role of SPP1 in kidney stone disease based on multiple bioinformatics analysis

Background

Kidney stone disease (KSD) is a multifactorial disease involving both environmental and genetic factors, whose pathogenesis remains unclear. This study aims to explore the hub genes related to stone formation that could serve as potential therapeutic targets.

Methods

Based on the GSE73680 dataset with 62 samples, differentially expressed genes (DEGs) between Randall’s plaque (RP) tissues and normal tissues were screened and weighted gene co-expression network analysis (WGCNA) was applied to identify key modules associated with KSD. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis were performed to explore the biological functions. The protein–protein interaction (PPI) network was constructed to identify hub genes. Meanwhile, CIBERSORT and ssGSEA analysis were used to estimate the infiltration level of the immune cells. The correlations between hub genes and immune infiltration levels were also investigated. Finally, the top hub gene was selected for further GSEA analysis.

Results

A total of 116 DEGs, including 73 up-regulated and 43 down-regulated genes, were screened in the dataset. The red module was identified as the key module correlated with KSD. 53 genes were obtained for functional enrichment analysis by taking the intersection of DEGs and genes in the red module. GO analysis showed that these genes were mainly involved in extracellular matrix organization (ECM) and extracellular structure organization, and others. KEGG analysis revealed that the pathways of aldosterone-regulated sodium reabsorption, cell adhesion molecules, arachidonic acid (AA) metabolism, and ECM-receptor interaction were enriched. Through PPI network construction, 30 hub genes were identified. CIBERSORT analysis revealed a significantly increased proportion of M0 macrophages, while ssGSEA revealed no significant differences. Among these hub genes, SPP1, LCN2, MMP7, MUC1, SCNN1A, CLU, SLP1, LAMC2, and CYSLTR2 were positively correlated with macrophages infiltration. GSEA analysis found that positive regulation of JNK activity was enriched in RP tissues with high SPP1 expression, while negative regulation of IL-1β production was enriched in the low-SPP1 subgroup.

Conclusions

There are 30 hub genes associated with KSD, among which SPP1 is the top hub gene with the most extensive links with other hub genes. SPP1 might play a pivotal role in the pathogenesis of KSD, which is expected to become a potential therapeutic target, while its interaction with macrophages in KSD needs further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12920-022-01157-4.

Obesity-related indices and its association with kidney stone disease: a cross-sectional and longitudinal cohort study

Obesity increases the risk of several diseases, including kidney stone disease (KSD). The study aimed to explore the relationship between KSD and various obesity-related indices. A total of 121,605 participants in the Taiwan Biobank from December 2008 to February 2020 were analyzed. The association between self-reported history of KSD and eight obesity-related indices, including body mass index (BMI), waist circumference (WC), waist-to-height ratio (WHtR), waist-to-hip ratio (WHR), abdominal volume index (AVI), body roundness index (BRI), conicity index, and triglyceride glucose index was examined in cross-sectional analysis; additionally, the risk of developing kidney stones was analyzed in a longitudinal cohort of 25,268 participants without KSD at baseline, which was a subset of the main cohort. Of all participants, 77,904 (64.1%) were female. Overall, 10.7% of males and 4.0% of females had KSD. Multivariate-adjusted logistic regression showed that all obesity-related indices were significantly associated with KSD. During a mean follow-up of 47 months, kidney stones occurred in 642 (2.5%) participants, and after adjusting for confounders, the risk of developing kidney stones was higher in participants with higher BMI, WC, WHtR, WHR, AVI and BRI. BMI, WC, WHtR, WHR, AVI, and BRI were found to be associated with a higher prevalence of kidney stones as well as development of incident kidney stones, which could be used as predictive factors for development of KSD in clinical practice.

Rosiglitazone Suppresses Renal Crystal Deposition by Ameliorating Tubular Injury Resulted from Oxidative Stress and Inflammatory Response via Promoting the Nrf2/HO-1 Pathway and Shifting Macrophage Polarization

Oxidative stress and inflammatory response are closely related to nephrolithiasis. This study is aimed at exploring whether rosiglitazone (ROSI), a regulator of macrophage (Mp) polarization, could reduce renal calcium oxalate (CaOx) deposition by ameliorating oxidative stress and inflammatory response. Male C57 mice were equally and randomly divided into 7 groups. Kidney sections were collected on day 5 or day 8 after treatment. Pizzolato staining and polarized light optical microscopy were used to detect crystal deposition. PAS staining and TUNEL assay were performed to assess the tubular injury and cell apoptosis, respectively. Gene expression was assessed by immunohistochemistry, immunofluorescence, ELISA, qRT-PCR, and Western blot. The reactive oxygen species (ROS) level was assessed using a fluorescence microplate and fluorescence microscope. Hydrogen peroxide (H₂O₂), malonaldehyde (MDA), and glutathione (GSH) were evaluated to determine oxidative stress. Lactic dehydrogenase (LDH) activity was examined to detect cell injury. Adhesion of CaOx monohydrate (COM) crystals to HK-2 cells was detected by crystal adhesion assay. HK-2 cell death or renal macrophage polarization was assessed by flow cytometry. In vivo, renal crystal deposition, tubular injury, crystal adhesion, cell apoptosis, oxidative stress, and inflammatory response were significantly increased in the 7-day glyoxylic acid- (Gly-) treated group but were decreased in the ROSI-treated groups, especially in the groups pretreated with ROSI. Moreover, ROSI significantly reduced renal Mp aggregation and M1Mp polarization but significantly enhanced renal M2Mp polarization. In vitro, ROSI significantly suppressed renal injury, apoptosis, and crystal adhesion of HK-2 cells and markedly shifted COM-stimulated M1Mps to M2Mps, presenting an anti-inflammatory effect. Furthermore, ROSI significantly suppressed oxidative stress by promoting the Nrf2/HO-1 pathway in HK-2 cells. These findings indicate that ROSI could ameliorate renal tubular injury that resulted from oxidative stress and inflammatory response by suppressing M1Mp polarization and promoting M2Mp polarization. Therefore, ROSI is a potential therapeutic and preventive drug for CaOx nephrolithiasis.

Macrophage Function in Calcium Oxalate Kidney Stone Formation: A Systematic Review of Literature

Background

The global prevalence and recurrence rate of kidney stones is very high. Recent studies of Randall plaques and urinary components in vivo, and in vitro including gene manipulation, have attempted to reveal the pathogenesis of kidney stones. However, the evidence remains insufficient to facilitate the development of novel curative therapies. The involvement of renal and peripheral macrophages in inflammatory processes offers promise that might lead to the development of therapeutic targets. The present systematic literature review aimed to determine current consensus about the functions of macrophages in renal crystal development and suppression, and to synthesize evidence to provide a basis for future immunotherapy.

Methods

We systematically reviewed the literature during February 2021 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Articles investigating the relationship between macrophages and urolithiasis, particularly calcium oxalate (CaOx) stones, were extracted from PubMed, MEDLINE, Embase, and Scopus. Study subjects, languages, and publication dates were unrestricted. Two authors searched and screened the publications.

Results

Although several studies have applied mixed modalities, we selected 10, 12, and seven (total, n = 29) of 380 articles that respectively described cultured cells, animal models, and human samples.

The investigative trend has shifted to macrophage phenotypes and signaling pathways, including micro (m)-RNAs since the discovery of macrophage involvement in kidney stones in 1999. Earlier studies of mice-associated macrophages with the acceleration and suppression of renal crystal formation. Later studies found that pro-inflammatory M1- and anti-inflammatory M2-macrophages are involved. Studies of human-derived and other macrophages in vitro and ex vivo showed that M2-macrophages (stimulated by CSF-1, IL-4, and IL-13) can phagocytose CaOx crystals, which suppresses stone development. The signaling mechanisms that promote M2-like macrophage polarization toward CaOx nephrocalcinosis, include the NLRP3, PPARγ-miR-23-Irf1/Pknox1, miR-93-TLR4/IRF1, and miR-185-5p/CSF1 pathways.

Proteomic findings have indicated that patients who form kidney stones mainly express M1-like macrophage-related proteins, which might be due to CaOx stimulation of the macrophage exosomal pathway.

Conclusions

This systematic review provides an update regarding the current status of macrophage involvement in CaOx nephrolithiasis. Targeting M2-like macrophage function might offer a therapeutic strategy with which to prevent stones via crystal phagocytosis.

Higher Triglyceride-Glucose Index Is Associated With Increased Likelihood of Kidney Stones

AIMS

We aimed to assess the association between triglyceride-glucose (TyG) index and kidney stones in US adults.

METHODS

Data were obtained from the 2007-2014 National Health and Nutrition Examination Survey (NHANES). Participants aged ≥18 years who were not pregnant and provided complete data about TyG index and kidney stones were included in the analysis. Weighted multivariable regression analysis and subgroup analysis were preformed to estimate the independent relationship between TyG index and nephrolithiasis and recurrence.

RESULTS

A total of 20,972 participants were included with the mean TyG index of 8.71 ± 0.72. The prevalence rates of nephrolithiasis and recurrence were 9.30% and 3.17% overall and increased with the higher TyG index tertiles (Nephrolithiasis: Tertile 1, 6.98%; Tertile 2, 9.15%; Tertile 3, 11.98%, p < 0.01; Recurrence: Tertile 1, 1.84%; Tertile 2, 3.27%; Tertile 3, 4.50%, p < 0.01). Each unit increase in TyG index was associated with 12% and 26% higher odds of nephrolithiasis [odds ratio (OR) = 1.12; 95% CI: 1.02-1.22; p = 0.02] and recurrence (OR = 1.26; 95% CI: 1.08-1.46; p < 0.01). Interaction tests indicated no significant effect of gender, age, body mass index, hypertension, and diabetes on this association between TyG index and kidney stones.

CONCLUSIONS

Higher TyG index was associated with an increased likelihood of nephrolithiasis and recurrence. Considering TyG index is a reliable indicator of insulin resistance (IR). Treatment and management of IR at a younger age may improve or alleviate the occurrence and recurrence of kidney stones.

AhR activation attenuates calcium oxalate nephrocalcinosis by diminishing M1 macrophage polarization and promoting M2 macrophage polarization

Calcium oxalate (CaOx) crystal can trigger kidney injury, which contributes to the pathogenesis of nephrocalcinosis. The phenotypes of infiltrating macrophage may impact CaOx-mediated kidney inflammatory injury as well as crystal deposition. How aryl hydrocarbon receptor (AhR) regulates inflammation and macrophage polarization is well understood; however, how it modulates CaOx nephrocalcinosis remains unclear.

Methods: Mice were intraperitoneally injected with glyoxylate to establish CaOx nephrocalcinosis model with or without the treatment of AhR activator 6-formylindolo(3,2-b)carbazole (FICZ). Positron emission tomography computed tomography (PET-CT) imaging, Periodic acid-Schiff (PAS) staining, and polarized light optical microscopy were used to evaluate kidney injury and crystal deposition in mice kidney. Western blotting, immunofluorescence, chromatin immunoprecipitation, microRNA-fluorescence in situ hybridization, and luciferase reporter assays were applied to analyze polarization state and regulation mechanism of macrophage.

Results: AhR expression was significantly upregulated and negatively correlated with interferon-regulatory factor 1 (IRF1) and hypoxia inducible factor 1-alpha (HIF-1α) levels in a murine CaOx nephrocalcinosis model following administration of FICZ. Moreover, AhR activation suppressed IRF1 and HIF-1α levels and decreased M1 macrophage polarization in vitro. In terms of the mechanism, bioinformatics analysis and chromatin immunoprecipitation assay confirmed that AhR could bind to miR-142a promoter to transcriptionally activate miR-142a. In addition, luciferase reporter assays validated that miR-142a inhibited IRF1 and HIF-1α expression by directly targeting their 3'-untranslated regions.

Conclusions: Our results indicated that AhR activation could diminish M1 macrophage polarization and promote M2 macrophage polarization to suppress CaOx nephrocalcinosis via the AhR-miR-142a-IRF1/HIF-1α pathway.

Sulforaphane elicts dual therapeutic effects on Renal Inflammatory Injury and crystal deposition in Calcium Oxalate Nephrocalcinosis

Intrarenal calcium oxalate (CaOx) crystals induce renal tubular epithelial cells (TECs) injury and inflammation, which involve Toll-like receptor 4 (TLR4)/interferon regulatory factor 1 (IRF1) signaling. Additionally, infiltrating macrophages (Mϕs) might influence intrarenal CaOx crystals and CaOx-induced renal injury. Although the roles of nuclear factor erythroid 2-related factor 2 (Nrf2) in regulating inflammation and macrophage polarization are well characterized, its potential mechanisms in regulating CaOx nephrocalcinosis remain undefined.

Methods: We used a Gene Expression Omnibus dataset to analyze gene-expression profiles. Luciferase reporter, western blot, quantitative polymerase chain reaction, immunofluorescence staining, fluorescence in situ hybridization, positron emission tomography computed tomography imaging, flow cytometry, and chromatin immunoprecipitation assays were employed to study the mechanism of miR-93-TLR4/IRF1 regulation by Nrf2. Anti-inflammatory activity and regulation of macrophage polarization by Nrf2 were investigated in vitro and in vivo.

Results: We found that stone-mediated kidney inflammation significantly affected stone growth, and that sulforaphane attenuated CaOx nephrocalcinosis-induced kidney injury and renal CaOx crystals deposition. Additionally, Nrf2 levels significantly increased and negatively correlated with TLR4 and IRF1 levels in a mouse model of CaOx nephrocalcinosis following sulforaphane treatment. Moreover, Nrf2 suppressed TLR4 and IRF1 levels and decreased M1-macrophage polarization which induced by supernatants from COM-stimulated TECs in vitro. In terms of mechanism, transcription factor analyses, microRNA microarray, and chromatin immunoprecipitation assays showed that Nrf2 exhibited positive transcriptional activation of miR-93-5p. In addition, Luciferase reporter, qRT-PCR, and western blot validated that miR-93-5p targets TLR4 and IRF1 mRNA. Furthermore, suppressed miR-93-5p expression partially reversed Nrf2-dependent TLR4/IRF1 downregulation.

Conclusions: The results suggested that sulforaphane might promote M2Mϕ polarization and inhibit CaOx nephrocalcinosis-induced inflammatory injury to renal tubular epithelial cells via the Nrf2-miR-93-TLR4/IRF1 pathway in vitro and in vivo.

Metabolic syndrome and the composition of urinary calculi: is there any relation?

Introduction

Epidemiologic studies demonstrate that obesity and diabetes increase the prevalence of urinary lithiasis. Most of these studies did not stratify the chemical composition of calculi and the physiological mechanisms responsible for this increased risk are not well understood. This study aims to investigate the relation between the metabolic syndrome and the composition of the urinary calculi.

Material and methods

Observational and retrospective study of all urinary calculi analysis performed at the Centro Hospitalar do Tâmega e Sousa, Portugal – from January 2009 to September 2015. Calculi were analyzed by infrared spectroscopy.

Results

302 analyses of urinary calculi were identified. Metabolic syndrome was diagnosed in 20.5% of patients. A total of 7 different mineral compounds were identified: 51.6% (N = 156) contained calcium oxalate, 41% (N = 124) calcium phosphate, 37.7% (N = 114) uric acid, 22.1% (N = 67) ammonium urate, 9.6% (N = 29) ammonium magnesium phosphate, 6.3% (N = 19) sodium urate and 1.3% (N = 4) contained cystine. Patients with metabolic syndrome presented a higher proportion of uric acid calculi (66.1% vs. 0%, p <0.001) and ammonium urate calculi (38.7% vs. 17%, p = 0.001). Patients without metabolic syndrome had a higher proportion of calcium oxalate calculi (58.8% vs. 24.2%, p <0.001) and calcium phosphate (46.7% vs. 19.4%, p <0.001).

Conclusions

There is a statistically significant relation between metabolic syndrome and uric acid and ammonium urate calculi. Metabolic syndrome may be considered risk factor for this calculi and the diagnosis and treatment of this syndrome must be considered for urolithiasis prevention. Further studies are needed to better the understanding of physiological mechanisms underlying this relationship to improve our strategy of prevention of urinary lithiasis.

Active Phagocytosis and Diachronic Processing of Calcium Oxalate Monohydrate Crystals in an in vitro Macrophage Model

BACKGROUND

We previously discovered that renal macrophages (Mφs) phagocytose renal calcium oxalate monohydrate (COM) crystals. This study investigated the processing of engulfed crystals using in vitro models.

METHODS

J774.1 mouse Mφs were exposed to COM crystals and observed for 24 h using polarized light microscopy with/without cytochalasin B (CB), an inhibitor of phagocytosis, to confirm active crystal phagocytosis. LysoTracker and immunohistochemical staining using transmission electron microscopy for lysosomal-associated membrane protein 1 were used to confirm engulfed COM crystal uptake into lysosomes. Diachronic tracking of specific Mφs was performed to capture the entire course of engulfed COM crystal processing using polarized light microscopy. Follow-up studies of fluorescent COM (f-COM) crystals using imaging cytometry were performed in the presence and absence of nigericin to dissipate the pH gradient in acidic organelles.

RESULTS

Phagocytosis rates increased with COM density and were significantly lower in cells treated with CB (p < 0.01). We observed that engulfed crystals colocalized within lysosomes of the Mφs; moreover, diachronic observation indicated that the engulfed COM crystals were subdivided during Mφ division and eliminated by the 7th day of culture. Additionally, imaging cytometry showed that the fluorescence level of f-COM crystals in the nigericin (-) group after 48 h was significantly lower than that in the nigericin (+) group.

CONCLUSIONS

This study confirmed active phagocytosis and lysosomal processing of engulfed COM crystals by Mφs. This discovery is expected to contribute to the development of future drugs that enhance the COM crystal phagocytic ability of Mφs.

Pioglitazone decreased renal calcium oxalate crystal formation by suppressing M1 macrophage polarization via the PPAR-γ-miR-23 axis

Interaction of pioglitazone (PGZ) and macrophages (Mps) in renal crystal formation remains unclear. In the present study, we investigated the possible mechanisms involved with Mps of PGZ in suppressing renal crystal formation. Crystal formation in the mouse kidney was detected using polarized light optical microscopy and Pizzolato staining. Gene expression was detected by Western blot analysis, quantitative RT-PCR, immunohistochemistry, immunofluorescence, and ELISA. Mp phenotypes were identified by flow cytometric analysis. Cell apoptosis was detected with TUNEL assay, and tubular injury was detected with periodic acid-Schiff staining. Interaction of peroxisome proliferator-activated receptor (PPAR)-γ and promoter was determined by chromatin immunoprecipitation assay. Luciferase reporter assay was performed to authenticate target genes of miRNA-23 (miR-23). Recombinant adenovirus was used to elucidate the role of miR-23 in vivo. Renal crystal formation, inflammation, tubular injury, and cell apoptosis were significantly marked in glyoxylic acid-treated groups and significantly decreased in PGZ-treated groups. PGZ significantly reduced Mp infiltration and M1 Mp polarization in the kidney. In vitro, PGZ shifted crystal-stimulated M1-predominant Mps to M2-predominant Mps, which were anti-inflammatory. PPAR-γ could directly bind to one PPAR-γ regulatory element in the promoter of pre-miR-23 to promote expression of miR-23 in Mps. We identified two downstream target genes of miR-23, interferon regulatory factor 1 and Pknox1. Moreover, miR-23 decreased crystal deposition, M1 Mp polarization, and injury in the kidney. This study has proven that PGZ decreased renal calcium oxalate crystal formation and renal inflammatory injury by suppressing M1 Mp polarization through a PPAR-γ-miR-23-interferon regulatory factor 1/Pknox1 axis. PGZ is liable to be a potential therapeutic medicine for treating urolithiasis.

Helper T-cell signaling and inflammatory pathway lead to formation of calcium phosphate but not calcium oxalate stones on Randall's plaques

OBJECTIVES

To elucidate the difference in the lithogenesis of calcium oxalate and calcium phosphate stones.

METHODS

Renal papillary tissues were obtained from 23 idiopathic calcium oxalate and seven calcium phosphate stone patients who had undergone endoscopic lithotripsy. Samples were individually collected from two different regions in each patient: the papillary mucosa containing Randall's plaque and mucosa not containing Randall's plaque. A microarray analysis was carried out on those tissues to compare their gene expression patterns. Furthermore, a causal pathway analysis comparing their differences was carried out.

RESULTS

Cluster analysis showed that gene expression profiles of calcium phosphate stone patients markedly differed from those of calcium oxalate stone patients. Disease and function analysis showed that Randall's plaque-containing tissues of calcium phosphate stone-forming patients had significantly higher movement and migration of mononuclear leukocytes, and lower tendency toward infection and lymph node formation than Randall's plaque-containing tissues of calcium oxalate stone formers. Additional pathway analysis showed increased immune cell signaling in calcium phosphate formers, such as the helper T cell 1 and 2 pathways, which was confirmed by their messenger ribonucleic acid expression.

CONCLUSIONS

The present results show the upregulation of helper T-cell signaling pathways in Randall's plaque-containing papillae in calcium phosphate, but not in calcium oxalate stone formers. Thus, helper T-cell immune responses and the related inflammatory processes seem to lead to the formation of calcium phosphate stones on Randall's plaques.

Loss of the androgen receptor suppresses intrarenal calcium oxalate crystals deposition via altering macrophage recruitment/M2 polarization with change of the miR-185-5p/CSF-1 signals

Crystals can trigger a wide range of kidney injuries that may link to the development of kidney stones. Infiltrating macrophages may influence hyperoxaluria-induced intrarenal calcium oxalate (CaOx) crystals deposition, yet their linkage to sex hormones remains unclear. Here we demonstrated that suppressing the androgen receptor (AR) expression in renal tubular epithelial cells increased the macrophage recruitment/M2 polarization that may result in enhancing the phagocytosis of intrarenal CaOx crystals. Mechanism dissection suggested that AR can suppress macrophage colony-stimulating factor 1 (CSF-1) expression via increasing miRNA-185-5p expression to suppress the M2 macrophage polarization-mediated intrarenal CaOx crystals phagocytosis. The preclinical study using glyoxylate-induced intrarenal CaOx crystals deposition mouse model revealed that renal tubule-specific AR knockout mice have less intrarenal CaOx crystals deposition with more recruited M2 macrophages in the kidney compared with the wild-type mice. Results from the in vivo rat model using hydroxy-L-proline-induced CaOx crystals deposition also demonstrated that targeting the AR with ASC-J9® suppressed the intrarenal CaOx crystals deposition via increasing the renal macrophage recruitment/M2 polarization. Together, results from multiple preclinical studies using multiple in vitro cell lines and in vivo mouse/rat models all demonstrated that targeting the AR with a small molecule ASC-J9® may function via altering macrophage recruitment/M2 polarization to decrease the intrarenal CaOx crystals deposition, a key phenotype seen in many kidney stone disease patients with hyperoxaluria.

Metformin prevents nephrolithiasis formation by inhibiting the expression of OPN and MCP-1 in vitro and in vivo

Treatment targeting osteopontin (OPN) and monocyte chemoattractant protein 1 (MCP-1) has been recognized as a novel approach in renal crystal formation. The present study was designed to investigate the suppressive effects of metformin on nephrolithiasis formation and its potential mechanism. The cytotoxicity of metformin on MDCK and HK-2 cells was determined using a Cell Counting Kit-8 assay in vitro. Subsequently, the mRNA transcription and protein expression levels of MCP-1 and OPN were detected by reverse transcription-quantitative-polymerase chain reaction analysis, western blot analysis and ELISA. Male Sprague-Dawley rats were divided into a control group, ethylene glycol (EG) group and EG + metformin group. The expression levels of MCP-1 and OPN and crystal formations were evaluated in renal tissues following an 8-week treatment period. In vitro, metformin significantly inhibited the production of MCP-1 and OPN induced by oxalate at the mRNA and protein expression levels. In vivo, increased expression levels of MCP-1 and OPN were detected in the EG group compared with the controls, and this upregulation was reversed in the EG + metformin group. Renal crystal deposition in the EG + metformin group was markedly decreased compared with that in the EG group. Therefore, the results of the study suggest that metformin suppressed urinary crystal deposit formation, possibly by mediating the expression of inflammatory mediators OPN and MCP-1.

Hatano rats are a suitable metabolic syndrome model for studying feeding behavior, blood pressure levels, and percent body fat

Currently, metabolic syndrome is a worldwide concern. Thus, it is imperative to understand the mechanism of metabolic syndrome by establishing various metabolic syndrome models. In this study, we used Hatano high-avoidance animals (HAA) and low-avoidance animals (LAA), both derived from Sprague–Dawley rats by selective breeding to determine high- or low-avoidance rates in shuttle-box active avoidance tests. HAA and LAA rats have some strain differences related to eating and appetite. Therefore, we determined whether Hatano rats could be used as a metabolic syndrome model. We compared food intake, body weights, blood pressure levels, plasma component levels, and fat contents between HAA and LAA rats. The HAA rats showed more active eating, higher blood pressure, higher percentage fat, and higher triglyceride levels than the LAA rats—these features correspond to some of the risk factors associated with metabolic syndrome. Our study suggests that HAA rats can be considered as a metabolic syndrome model by focusing on their feeding behavior, blood pressure levels, and percent body fat.

Identification of new urinary risk markers for urinary stones using a logistic model and multinomial logit model

BACKGROUND

Risk assessment for urinary stones has been mainly based on urinary biochemistry. We attempted to identify the risk factors for urinary stones by statistically analyzing urinary biochemical and inflammation-related factors.

METHODS

Male participants (age, 20-79 years) who visited Nagoya City University Hospital were divided into three groups: a control group (n = 48) with no history of stones and two stone groups with calcium oxalate stone experience (first-time group, n = 22; recurring group, n = 40). Using 25-µL spot urine samples, we determined the concentrations of 18 candidate urinary proteins, using multiplex analysis on a MagPix® system.

RESULTS

In univariate logistic regression models classifying the control and first-time groups, interleukin (IL)-1a and IL-4 were independent factors, with significantly high areas under the receiver operating characteristic curve (1.00 and 0.87, respectively, P < 0.01 for both). The multivariate models with IL-4 and granulocyte-macrophage colony-stimulating factor (GM-CSF) showed higher areas under the receiver operating characteristic curve (0.93) compared to that for the univariate model with IL-4. In the classification of control, first-time, and recurrence groups, accuracy was the highest for the multinomial logit model with IL-4, GM-CSF, IL-1b, IL-10, and urinary magnesium (concordance rate 82.6%).

CONCLUSIONS

IL-4, IL-1a, GM-CSF, IL-1b, and IL-10 were identified as urinary inflammation-related factors that could accurately distinguish control individuals from patients with urinary stones. Thus, the combined analysis of urinary biochemical data could provide an index that more clearly evaluates the risk of urinary stone formation.

Impact of Statin Intake on Kidney Stone Formation

OBJECTIVE

To determine whether statin intake affects nephrolithiasis risk, and whether higher lipid levels correlate with stone risk. Dyslipidemia is a known independent risk factor for urolithiasis, and emerging evidence suggests common biological pathways. Previous work has suggested that statins protect against new stone formation, but these findings have not been verified by other investigators.

METHODS

We queried our Institution's Electronic Data Warehouse for all patients who were newly diagnosed with hyperlipidemia between 2009 and 2011, and had never taken a statin drug. These patients' clinical outcomes were followed until 2015, to assess whether they had been newly prescribed statins and whether they had developed symptomatic urolithiasis. Patient demographics, stone risk factors, prescription data, and serum lipid values were collected.

RESULTS

A total of 101,259 patients met inclusion criteria, 47.8% of whom received a statin prescription during the study period. Patients prescribed statins were significantly older, had a greater likelihood of osteoporosis, hemiplegia, immobility, and more likely to take a thiazide diuretic. Patients without a history of urolithiasis who were started on statin therapy were significantly less likely to develop new stones than patients not taking statins. This protective effect was even greater in patients with a history of stone disease. Lipid parameters (low-density lipoprotein, triglyceride, cholesterol) were lower in the statin-treated group, suggesting overall compliance with these medications.

CONCLUSION

Our data confirm previous work that statins protect against urinary stone formation; however, the underlying mechanism seems to be distinct from statins' lipid-lowering effect.

M1/M2-macrophage phenotypes regulate renal calcium oxalate crystal development

In our previous report, M2-macrophage (Mφs) deficient mice showed increased renal calcium oxalate (CaOx) crystal formation; however, the role of Mφs-related-cytokines and chemokines that affect kidney stone formation remains unknown. Here, we investigated the role of M1/M2s in crystal development by using in vitro and in vivo approaches. The crystal phagocytic rate of bone marrow-derived M2Mφs was higher than that of bone marrow-derived Mφs and M1Mφs and increased on co-culture with renal tubular cells (RTCs). However, the amount of crystal attachment on RTCs reduced on co-culture with M2Mφs. In six hyperoxaluric C57BL/6J mice, M1Mφ transfusion and induction by LPS and IFN-γ facilitated renal crystal formation, whereas M2Mφ transfusion and induction by IL-4 and IL-13 suppressed renal crystal formation compared with the control. These M2Mφ treatments reduced the expression of crystal-related genes, such as osteopontin and CD44, whereas M1Mφ treatment increased the expression of pro-inflammatory and adhesion-related genes such as IL-6, inducible NOS, TNF-α, C3, and VCAM-1. The expression of M2Mφ-related genes was lower whereas that of M1Mφ-related genes was higher in papillary tissue of CaOx stone formers. Overall, our results suggest that renal crystal development is facilitated by M1Mφs, but suppressed by M2Mφs.

Differential Roles of Peroxisome Proliferator-Activated Receptor-α and Receptor-γ on Renal Crystal Formation in Hyperoxaluric Rodents

Peroxisome proliferator-activated receptors (PPARs) and related inflammatory and oxidative molecule expression were investigated in a hyperoxaluric rodent model to evaluate the in vivo efficacy of PPAR agonists in preventing renal crystal formation. PPAR expression was examined in a mouse hyperoxaluria kidney stone model induced by daily intra-abdominal glyoxylate injection. Therapeutic effects of the PPARα agonist fenofibrate and PPARγ agonist pioglitazone were also assessed in a 1% ethylene glycol-induced rat model of hyperoxaluria. Crystal formation, inflammation, cell injury, apoptosis, and oxidative stress were compared to those of vehicle-treated controls. Quantitative reverse transcription-polymerase chain reaction revealed that PPARα and PPARγ expression decrease and increase, respectively, during crystal formation in hyperoxaluric kidneys. In addition, PPARα localized to the cytoplasm of both proximal and distal tubular cells, whereas PPARγ accumulated in the nucleus of proximal tubular cells. Furthermore, renal crystal formation was significantly less prevalent in pioglitazone-treated rats but higher in the fenofibrate-treated and fenofibrate/pioglitazone-cotreated groups compared to controls, thus indicating that pioglitazone, but not fenofibrate, markedly decreased cell inflammation, oxidative stress, and apoptosis. Collectively, the results demonstrated that PPARγ suppressed renal crystal formation via its antioxidative and anti-inflammatory effects; however, the renotoxicity of PPARα may elicit the opposite effect.