Understanding the Link Between Gut Microbiome and Urinary Stone Disease

Knowledge, attitudes, and practices towards urinary system stones among the Chengdu population

This cross-sectional study aimed to explore the knowledge, attitudes, and practices (KAP) regarding urinary system stones among the general public in Chengdu, China. Conducted between January and June 2023, this research targeted individuals undergoing physical examinations at the Health Management Center of Sichuan Provincial People's Hospital. Structured questionnaires were administered to collect demographic information and assess KAP related to urinary system stones. Following meticulous scrutiny, 1014 valid questionnaires were retained for analysis. The computed scores for knowledge, attitude, and practice were 9.36 ± 4.23 (possible score range 0-17), 37.75 ± 7.20 (possible score range 11-55), and 30.77 ± 4.00 (possible score range 10-50), respectively. These outcomes suggested insufficient knowledge and moderately positive attitudes and practices among the participants. Structural Equation Modeling (SEM) analysis revealed a direct impact of knowledge on attitude (β = 0.967, P < 0.001), with attitude subsequently exerting a direct influence on practice (β = 0.167, P < 0.001). This indicated an indirect impact of knowledge on practice. Additionally, there was a direct effect of knowledge on practice (β = 0.167, P < 0.001). In conclusion, the general populace in Chengdu exhibited insufficient knowledge and moderate attitudes and practices concerning urinary stones. These findings underscore the imperative for targeted educational interventions aimed at enhancing public awareness and fostering positive attitudes and practices toward urinary stone prevention and management.

Update on the Effect of the Urinary Microbiome on Urolithiasis

Microbiota are ecological communities of commensal, symbiotic, and pathogenic microorganisms. The microbiome could be involved in kidney stone formation through hyperoxaluria and calcium oxalate supersaturation, biofilm formation and aggregation, and urothelial injury. Bacteria bind to calcium oxalate crystals, which causes pyelonephritis and leads to changes in nephrons to form Randall's plaque. The urinary tract microbiome, but not the gut microbiome, can be distinguished between cohorts with urinary stone disease (USD) and those without a history of the disease. In the urine microbiome, the role is known of urease-producing bacteria (Proteus mirabilis, Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeruginosa, Providencia stuartii, Serratia marcescens, and Morganella morganii) in stone formation. Calcium oxalate crystals were generated in the presence of two uropathogenic bacteria (Escherichia coli and K. pneumoniae). Non-uropathogenic bacteria (S. aureus and Streptococcus pneumoniae) exhibit calcium oxalate lithogenic effects. The taxa Lactobacilli and Enterobacteriaceae best distinguished the healthy cohort from the USD cohort, respectively. Standardization is needed in urine microbiome research for urolithiasis. Inadequate standardization and design of urinary microbiome research on urolithiasis have hampered the generalizability of results and diminished their impact on clinical practice.

Association of Gut Microbiota and Biochemical Features in a Chinese Population With Renal Uric Acid Stone

Previous studies suggest that patients with nephrolithiasis exhibit dysbiosis in their gut microbiota, but those studies were conducted in calcium oxalate stone patients. We aimed to explore the association of gut microbiota and biochemical features of renal uric acid stone (UAS) patients in a Chinese population and identify the related bacteria that may affect the pathopoiesis of UAS. A case-control study of 117 patients with UAS, 123 patients with gout, and 135 healthy controls were included from January 2014 to October 2020. For each subject, data on demographics, biochemical parameters of blood and urine were analyzed. Fifteen patients with gout, 16 patients with UAS, 17 UAS patients with gout, and 17 healthy subjects were enrolled and provided fecal samples. The characteristics of gut microbiota were explored by using 16S ribosomal RNA (rRNA) gene sequencing and analyzed by using a combination of software mother and R. Hyperuricemia was the main risk factor for the development of gout and UAS. Obesity, dyslipidemia, and aciduria were unique risk factors for UAS patients. The richness, diversity, and relative abundance of dominant bacteria at the phylum and genus levels of gut microbiota in UAS patients were significantly distinct from other subjects. Abundance of Bacteroides and Fusobacterium was significantly positively correlated with the serum uric acid (UA) level of UAS patients. Fusobacteria was involved in the metabolism and degradation of certain short-chain fatty acids, amino acids, and sugars in pathopoiesis of UAS, and inhibited their synthesis pathways. Fusobacteria may be related to the pathogenesis of UAS, and this finding contributes to the personalized treatment of UAS from the perspective of maintaining micro-ecological equilibrium in gut.

Gut microbiota and immunity relevance in eubiosis and dysbiosis

Human gut is colonized by numerous microorganisms, in which bacteria present the highest proportion of this colonization that live in a symbiotic relationship with the host. This microbial collection is commonly known as the microbiota. The gut microbiota can mediate gut epithelial and immune cells interaction through vitamins synthesis or metabolic products. The microbiota plays a vital role in growth and development of the main components of human’s adaptive and innate immune system, while the immune system regulates host-microbe symbiosis. On the other hand, negative alteration in gut microbiota composition or gut dysbiosis, can disturb immune responses. This review highlights the gut microbiota-immune system cross-talk in both eubiosis and dysbiosis.

Intestinal dysbacteriosis leads to kidney stone disease

The formation and physicochemical properties of kidney stones (KSs) are closely associated with diet. In view of the differences in ethnicity and dietary composition between Chinese and Western populations, the present study aimed to investigate the association between intestinal dysbacteriosis and KSs in China. The current study examined the differences in intestinal microbes between the KS disease (KSD) and the healthy control (HLT) groups, and statistically significant differences based on 16s rRNA gene amplicons were identified using a Student's t-test or one-way ANOVA. In addition, the calcium oxalate KS (COKS), uric acid KS (UAKS) and carbonate apatite KS(CCKS) groups were compared with a non-parametric statistical test. Determination of bacterial abundance was performed via the analysis of 16s rRNA marker gene sequences using next-generation sequencing. Firmicutes (F) and Bacteroides (B) levels were significantly higher in the KSD group compared with the HLT group (B/F=0.67 vs. 0.08; P<0.001), as were the overall levels of B (6.19-fold higher compared with the HLT group; 22.2 vs. 3.6%; P<0.001). The Prevotella-9 abundance levels in the KSD group were 4.65-fold higher compared with those in the HLT group (8.8 vs. 1.9%; P<0.001). The levels of Blautia and Lachnoclostridium were significantly decreased in the KSD group (13.3 vs. 6.0%; and 5.0 vs. 7.9%; both P<0.05). Moreover, Prevotella-9 levels were higher in non-calciferous KSs (UAKS) compared with calciferous KSs (COKS and CCKS). Therefore, the findings of the present study indicated a key association between specific KS components and intestinal flora, providing a theoretical basis for new treatment methods for KSs. Moreover, differences and interactions between these bacteria could initially predict specific types of urolithiasis.

The Role of Gut, Vaginal, and Urinary Microbiome in Urinary Tract Infections: From Bench to Bedside

The current paradigm of urinary tract infection (UTI) pathogenesis takes into account the contamination of the periurethral space by specific uropathogens residing in the gut, which is followed by urethral colonization and pathogen ascension to the urinary bladder. Consequently, studying the relationship between gut microbiota and the subsequent development of bacteriuria and UTI represents an important field of research. However, the well-established diagnostic and therapeutic paradigm for urinary tract infections (UTIs) has come into question with the discovery of a multifaceted, symbiotic microbiome in the healthy urogenital tract. More specifically, emerging data suggest that vaginal dysbiosis may result in Escherichia coli colonization and prompt recurrent UTIs, while urinary microbiome perturbations may precede the development of UTIs and other pathologic conditions of the urinary system. The question is whether these findings can be exploited for risk reduction and treatment purposes. This review aimed to appraise the three aforementioned specific microbiomes regarding their potential influence on UTI development by focusing on the recent studies in the field and assessing the potential linkages between these different niches, as well as evaluating the state of translational research for novel therapeutic and preventative approaches.

The Bladder is Not Sterile: an Update on the Urinary Microbiome

Purpose of Review

The article discusses (1) techniques used to study bacterial urinary microbiota; (2) existence of non-bacterial urinary microbiota; (3) associations between changes in urinary microbiota and various benign lower urinary tract disorders.

Recent Findings

Urine harbors a diverse microbial community that resides within it. A multitude of studies have identified differences in these communities associated with urologic conditions, suggesting that microbial communities may maintain normal bladder homeostasis. Technological advances in analytic approaches have improved our understanding of the urinary microbiome. The choice of urine sampling method (voided, catheterized, or aspirated) will significantly influence microbiome findings. Sex and age highly influence urinary microbiota; in addition to rigorous inclusion criteria, microbial studies must be sufficiently powered to overcome the substantial interindividual variability of urinary microbiota. Regardless of these complicating factors, studies have identified microbial patterns correlating with both urologic diagnoses and treatment responses.

Summary

Without a clear understanding of the variability of and exogenous influences on the urinary microbiota in the absence of disease, it has been challenging to reveal the microbial patterns responsible for disease pathophysiology. Host mechanisms in response to the urinary microbiome are also poorly understood. Additional research can address whether the manipulation of urinary microbiota will benefit lower urinary tract health.

[Current concepts on the pathogenesis of urinary stones]

The process of kidney stone formation is complex and still not completely understood. Supersaturation and crystallization are the main drivers for the etiopathogenesis of uric acid, xanthine and cystine stones but this physicochemical concept fails to adequately explain the formation of calcium-based nephrolithiasis, which represents the majority of kidney stones. Contemporary concepts of the pathogenesis of calcium-based nephrolithiasis focus on a nidus-associated stone formation of calcium-based nephrolithiasis on Randall's plaques or on plugs of Bellini's duct. Randall's plaques originate from the interaction of interstitial calcium supersaturation in the renal papilla, vascular and interstitial inflammatory processes and mineral deposits of calcifying nanoparticles on the basal membrane of the thin ascending branch of the loop of Henle; however, plugs of Bellini's duct are assumed to be caused by mineral deposits on the wall of the collecting ducts. Aggregation and overgrowth are influenced by the interaction of matrix proteins with calcium supersaturated urine, by an imbalance between promoters and inhibitors of stone formation in the calyceal urine. Current research has elucidated many factors contributing to stone formation by revealing novel insights into the physiology of nephron and papilla, by analyzing vascular, inflammatory and calcifying processes in the renal medulla, by examining the proteome, the microbiome, promoters and inhibitors of stone formation in the urine and by conducting the first genome-wide association studies; however, more future research is mandatory to fill the gap of knowledge and hopefully, to obtain novel prophylactic, therapeutic and metaphylactic tools beyond the current state of knowledge.