The Efficacy of Polyunsaturated Fatty Acids as Protectors against Calcium Oxalate Renal Stone Formation: A Review

The Multidisciplinary Approach in the Management of Patients with Kidney Stone Disease-A State-of-the-Art Review

Kidney stone disease has a multifactorial etiology, and evolving dietary habits necessitate continuous updates on the impact of dietary components on lithogenesis. The relationship between diseases influenced by lifestyle, such as obesity and diabetes, and kidney stone risk underscores the need for comprehensive lifestyle analysis. Effective management of kidney stones requires a multidisciplinary approach, involving collaboration among nutritionists, urologists, nephrologists, and other healthcare professionals to address the complex interactions between diet, lifestyle, and individual susceptibility. Personalized dietary therapy, based on each patient's unique biochemical and dietary profile, is essential and necessitates comprehensive nutritional assessments. Accurate dietary intake evaluation is best achieved through seven-day, real-time dietary records. Key factors influencing urinary risk include fluid intake, dietary protein, carbohydrates, oxalate, calcium, and sodium chloride. Personalized interventions, such as customized dietary changes based on gut microbiota, may improve stone prevention and recurrence. Current research suggests individualized guidance on alcohol intake and indicates that tea and coffee consumption might protect against urolithiasis. There is potential evidence linking tobacco use and secondhand smoke to increased kidney stone risk. The effects of vitamins and physical activity on kidney stone risk remain unresolved due to mixed evidence. For diseases influenced by lifestyle, conclusive evidence on targeted interventions for nephrolithiasis prevention is lacking, though preliminary research suggests potential benefits. Management strategies emphasize lifestyle modifications to reduce recurrence risks, support rapid recovery, and identify predisposing conditions, highlighting the importance of these changes despite inconclusive data.

Causal effects of gut microbiota on the risk of urinary tract stones: A bidirectional two-sample mendelian randomization study

Background

Recent studies increasingly suggest notable changes in both the quantity and types of gut microbiota among individuals suffering from urinary tract stones. However, the causal relationship between GMB and urinary tract stone formation remains elusive, which we aim to further investigate in this research through Mendelian Randomization (MR) analysis.

Materials and methods

Single nucleotide polymorphisms (SNPs) associated with the human GMB were selected from MiBioGen International Consortium GWAS dataset. Data on urinary tract stone-related traits and associated SNPs were sourced from the IEU Open GWAS database. To investigate the causal relationships between gut microbiota and urinary tract stones, Mendelian Randomization (MR) was applied using genetic variants as instrumental variables, utilizing a bidirectional two-sample MR framework. This analysis incorporated various statistical techniques such as inverse variance weighting, weighted median analysis, MR-Egger, and the maximum likelihood method. To ensure the reliability of the findings, a range of sensitivity tests were conducted, including Cochran's Q test, the MR-Egger intercept, leave-one-out cross-validation, and examination of funnel plots.

Results

The results revealed the causal relationship between the increase in the abundance of 10 microbial taxa, including Genus-Barnesiella (IVW OR = 0.73, 95%CI 0.73-0.89, P = 2.29 × 10-3) and Genus-Flavonifractor (IVW OR = 0.69, 95%CI 0.53-0.91, P = 8.57 × 10-3), and the decreased risk of urinary tract stone formation. Conversely, the development of urinary tract stones was observed to potentially instigate alterations in the abundance of 13 microbial taxa, among which Genus-Ruminococcus torques group was notably affected (IVW OR = 1.07, 95%CI 0.64-0.98, P = 1.86 × 10-3). In this context, Genus-Clostridium sensustricto1 exhibited a bidirectional causal relationship with urinary tract stones, while the remaining significant microbial taxa demonstrated unidirectional causal effects in the two-sample MR analysis. Sensitivity analyses did not identify significant estimates of heterogeneity or pleiotropy.

Conclusion

To summarize, the results of this study suggest a likely causative link between gut microbiota and the incidence of urinary tract stones. This insight opens up potential pathways for discovering biomarkers and therapeutic targets in the management and prevention of urolithiasis. However, further in-depth research is warranted to investigate these associations.

Habitual fish oil supplementation, genetic susceptibility of kidney stones and the risk of new-onset kidney stones

OBJECTIVE

We aimed to assess the association between habitual fish oil use and new-onset kidney stones in participants with different levels of genetic risks of kidney stones.

METHODS

477,311 participants free of kidney stones at baseline from the UK Biobank cohort were included. Fish oil use was collected by both food frequency questionnaires and 24-h dietary recalls. A genetic risk score (GRS) for kidney stones was calculated based on 20 single-nucleotide polymorphisms associated with kidney stones. The primary outcome was new-onset kidney stones.

RESULTS

During a median follow-up of 12.0 years, 5,637 cases of kidney stones were documented. Participants with high genetic risks of kidney stones had a higher risk of new-onset kidney stones (vs. low or intermediate risks; adjusted HR, 1.52; 95 %CI:1.44-1.60). Compared with non-users, habitual use of fish oil was associated with a lower risk of new-onset kidney stones (adjusted HR, 0.84, 95 %CI, 0.78-0.92) in participants with low or intermediate genetic risks, but not in those with high genetic risks of kidney stones (adjusted HR, 1.02, 95 %CI, 0.93-1.12; P-interaction =0.001). Among those with low or intermediate genetic risks of kidney stones, compared with fish oil constant nonusers, the adjusted HRs (95 %CI) for kidney stones were 0.89 (0.75-1.06), 0.72 (0.58-0.90), and 0.79 (0.64-0.97), for fish oil occasional users, modestly constant users, and moderately and highly constant users (P for trend = 0.001), respectively.

CONCLUSIONS

Habitual fish oil use was associated with a lower risk of new-onset kidney stones in participants with low or intermediate genetic risk of kidney stones.

The Association between Dietary Sugar Intake and Nephrolithiasis: Results from National Health and Nutrition Examination Survey 2007-2018

BACKGROUND

Dietary sugar intake is gradually considered a risk factor for many diseases. A sugary diet was positively associated with risk of nephrolithiasis, but the specific relationships remain undefined.

OBJECTIVES

To determine associations between risk of nephrolithiasis and dietary sugar intake.

METHODS

This cross-sectional study involved 21,590 participants based on the National Health and Nutrition Examination Survey from 2007 to 2018. Amounts of dietary sugar intake (g/d) were the main exposure, including total sugar intake, added sugar intake, and food sources. Associations were analyzed by logistic regression models and restricted cubic splines using complex weighted designs.

RESULTS

Weighted mean intake [standard error] of total sugar and added sugar were 111.2 [2.0] g/d and 73.7 [1.9] g/d in participants with nephrolithiasis, respectively. In the fully adjusted regression model, compared to those in quartile 1, the population in quartile 4 of total sugar intake showed a significant risk of nephrolithiasis [odds ratio (OR): 1.23; 95% confidence interval (CI): 1.00-1.51]; OR for added sugar intake was 1.56 (95% CI: 1.25-1.94). The risks of nephrolithiasis increased steadily when total sugar and added sugar intake exceeded ∼150 g/d and 63 g/d in restricted cubic spline analyses, respectively. The highest sugar intake from beverages was associated with an increased risk of nephrolithiasis (OR for total sugar: 1.36; 95% CI: 1.07-1.72; OR for added sugar: 1.37; 95% CI: 1.09-1.73). Added sugar intake from meat, egg, and oil was significantly associated with risk of nephrolithiasis (quartile 4, OR: 1.22; 95% CI: 1.02-1.47), whereas total sugar intake from dairy products was in reverse (quartile 4, OR: 0.67; 95% CI: 0.54-0.82).

CONCLUSIONS

Total and added sugar intake, sugar intake from beverages, and added sugar intake from meat, egg, and oil were associated with an increased risk of nephrolithiasis, whereas total sugar intake from dairy products was negatively associated.

Gut microbiota in patients with kidney stones: a systematic review and meta-analysis

BACKGROUND

Mounting evidence indicates that the gut microbiome (GMB) plays an essential role in kidney stone (KS) formation. In this study, we conducted a systematic review and meta-analysis to compare the composition of gut microbiota in kidney stone patients and healthy individuals, and further understand the role of gut microbiota in nephrolithiasis.

RESULTS

Six databases were searched to find taxonomy-based comparison studies on the GMB until September 2022. Meta-analyses were performed using RevMan 5.3 to estimate the overall relative abundance of gut microbiota in KS patients and healthy subjects. Eight studies were included with 356 nephrolithiasis patients and 347 healthy subjects. The meta-analysis suggested that KS patients had a higher abundance of Bacteroides (35.11% vs 21.25%, Z = 3.56, P = 0.0004) and Escherichia_Shigella (4.39% vs 1.78%, Z = 3.23, P = 0.001), and a lower abundance of Prevotella_9 (8.41% vs 10.65%, Z = 4.49, P < 0.00001). Qualitative analysis revealed that beta-diversity was different between the two groups (P < 0.05); Ten taxa (Bacteroides, Phascolarctobacterium, Faecalibacterium, Flavobacterium, Akkermansia, Lactobacillus, Escherichia coli, Rhodobacter and Gordonia) helped the detection of kidney stones (P < 0.05); Genes or protein families of the GMB involved in oxalate degradation, glycan synthesis, and energy metabolism were altered in patients (P < 0.05).

CONCLUSIONS

There is a characteristic gut microbiota dysbiosis in kidney stone patients. Individualized therapies like microbial supplementation, probiotic or synbiotic preparations and adjusted diet patterns based on individual gut microbial characteristics of patients may be more effective in preventing stone formation and recurrence.

A case-based review of dietary management of calcium oxalate stones

PURPOSE

The purpose of this paper is to help patients with calcium oxalate stones to access prevention and treatment options with dietary management.

METHODS

Typical cases in our hospital and other hospitals were selected for case review; combined with literature review through PubMed search, comprehensive analysis and suggestions were put forward.

RESULTS

By retrieving the literature with sufficient evidence, selecting, and summarizing, analysis of dietary liquid, oxalate and oxalate precursors, calcium, protein, fruits and vegetables, salt, high dietary fiber, and other content with high evidence index was carried out, respectively.

CONCLUSION

Through the retrospective analysis of typical cases and literature review, the importance of diet management in the prevention and treatment of calcium oxalate stones was emphasized again, and suggestions were put forward to promote the prevention and treatment of calcium oxalate stones.

Urinary Microbial and Metabolomic Profiles in Kidney Stone Disease

Background

Kidney stones or nephrolithiasis is a chronic metabolic disease characterized by renal colic and hematuria. Currently, a pathogenetic mechanism resulting in kidney stone formation remains elusive. We performed a multi-omic study investigating urinary microbial compositions and metabolic alterations during nephrolithiasis.

Method

Urine samples from healthy and individuals with nephrolithiasis were collected for 16S rRNA gene sequencing and liquid chromatography-mass spectroscopy. Microbiome and metabolome profiles were analyzed individually and combined to construct interactome networks by bioinformatic analysis.

Results

Distinct urinary microbiome profiles were determined in nephrolithiasis patients compared with controls. Thirty-nine differentially abundant taxa between controls and nephrolithiasis patients were identified, and Streptococcus showed the most significant enrichment in nephrolithiasis patients. We also observed significantly different microbial compositions between female and male nephrolithiasis patients. The metabolomic analysis identified 112 metabolites that were differentially expressed. Two significantly enriched metabolic pathways, including biosynthesis of unsaturated fatty acids and tryptophan metabolism, were also identified in nephrolithiasis patients. Four potentially diagnostic metabolites were also identified, including trans-3-hydroxycotinine, pyroglutamic acid, O-desmethylnaproxen, and FAHFA (16:0/18:2), and could function as biomarkers for the early diagnosis of nephrolithiasis. We also identified three metabolites that contributed to kidney stone size. Finally, our integrative analysis of the urinary tract microbiome and metabolome identified distinctly different network characteristics between the two groups.

Conclusions

Our study has characterized important profiles and correlations among urinary tract microbiomes and metabolomes in nephrolithiasis patients for the first time. These results shed new light on the pathogenesis of nephrolithiasis and could provide early clinical biomarkers for diagnosing the disease.

Diet and Stone Disease in 2022

Diet plays a central role in the development and prevention of nephrolithiasis. Although pharmacologic treatment may be required for some patients who are resistant to dietary measures alone, dietary modification may be sufficient to modulate stone risk for many patients. While there is no single specialized diet for stone prevention, several dietary principles and recommendations for stone prevention are supported by practice guidelines, including adequate fluid intake, modest calcium intake, low dietary sodium, and limited animal protein. In this review, we summarized the evidence supporting these dietary recommendations and reviewed the current literature regarding specific dietary components and comprehensive diets for stone prevention.

Discolored Urine in Horses and Foals

This article describes the most common causes of urine discoloration. The review includes a description of the most common disorders causing hematuria, highlighting clinical presentation, treatments, and pathophysiology. Causes of hemoglobinuria and myoglobinuria together with their mechanisms of renal injury are also reviewed.

Causes and prevention of kidney stones: separating myth from fact

Despite high-level evidence supporting the use of pharmacotherapy therapy for the prevention of kidney stones, adherence to medications is often poor because of side-effects, inconvenience and cost. Furthermore, with a desire for more 'natural' products, patients seek dietary and herbal remedies over pharmacotherapy. However, patients are often unaware of the potential side-effects, lack of evidence and cost of these remedies. Therefore, in the present review we examine the evidence for a few of the commonly espoused non-prescription agents or dietary recommendations that are thought to prevent stone formation, including lemonade, fish oil (omega fatty acids), Phyllanthus niruri and the Dietary Approaches to Stop Hypertension (DASH) diet. While the present review includes only a few of the stone-modulating recommendations available to the lay community, we focussed on these four due to their prevalent use. Our goal is not to only dispel commonly held notions about stone disease, but also to highlight the lack of high-level evidence for many commonly utilised treatments.

Nutrition and Kidney Stone Disease

The prevalence of kidney stone disease is increasing worldwide. The recurrence rate of urinary stones is estimated to be up to 50%. Nephrolithiasis is associated with increased risk of chronic and end stage kidney disease. Diet composition is considered to play a crucial role in urinary stone formation. There is strong evidence that an inadequate fluid intake is the major dietary risk factor for urolithiasis. While the benefit of high fluid intake has been confirmed, the effect of different beverages, such as tap water, mineral water, fruit juices, soft drinks, tea and coffee, are debated. Other nutritional factors, including dietary protein, carbohydrates, oxalate, calcium and sodium chloride can also modulate the urinary risk profile and contribute to the risk of kidney stone formation. The assessment of nutritional risk factors is an essential component in the specific dietary therapy of kidney stone patients. An appropriate dietary intervention can contribute to the effective prevention of recurrent stones and reduce the burden of invasive surgical procedures for the treatment of urinary stone disease. This narrative review has intended to provide a comprehensive and updated overview on the role of nutrition and diet in kidney stone disease.

Cultivation Method Effect on Schizochytrium sp. Biomass Growth and Docosahexaenoic Acid (DHA) Production with the Use of Waste Glycerol as a Source of Organic Carbon

Inexpensive carbon sources offering an alternative to glucose are searched for to reduce costs of docosahexaenoic acid production by microalgae. The use of waste glycerol seems substantiated and prospective in this case. The objective of this study was to determine the production yield of heterotrophic microalgae Schizochytrium sp. biomass and the efficiency of docosahexaenoic acid production in various types of cultures with waste glycerol. Cultivation conditions were optimized using the Plackett–Burman method and Response Surface Methodology. The highest technological performance was obtained in the fed-batch culture, where the concentration of Schizochytrium sp. biomass reached 103.44 ± 1.50 g/dm3, the lipid concentration in Schizochytrium sp. biomass was at 48.85 ± 0.81 g/dm3, and the docosahexaenoic acid concentration at 21.98 ± 0.36 g/dm3. The highest docosahexaenoic acid content, accounting for 61.76 ± 3.77% of total fatty acids, was determined in lipid bodies of the Schizochytrium sp. biomass produced in the batch culture, whereas the lowest one, accounting for 44.99 ± 2.12% of total fatty acids, in those of the biomass grown in the fed-batch culture.

Metabolomics analysis of the serum from children with urolithiasis using UPLC-MS

Pediatric urolithiasis is a common urologic disease with high morbidity and recurrence rates. Recent studies have shown that metabolic dysfunction plays a vital role in the pathogenesis of urolithiasis, especially in children, but the specific mechanism is still unclear. Metabolomics is an ideal technology for exploring the mechanism of metabolic disorders in urolithiasis. In the present study, a serum metabolomics based on ultra‐performance liquid chromatography mass spectrometry was performed. A total of 50 children subjects were recruited for the study, including 30 patients with kidney stones and 20 normal controls (NCs). Principal component analysis and orthogonal partial least‐squares determinant analysis were carried, and 40 metabolites were found to be significantly altered in patients with kidney stones, mainly involving retinol metabolism, steroid hormone biosynthesis, and porphyrin and chlorophyll metabolism. The kidney stone group appeared to have a lower serum level of bilirubin, but a relative higher level of retinal, all‐transretinoic acid, progesterone, and prostaglandin E2 compared with those of the NC group. All the findings suggest that patients with urolithiasis have several metabolic characteristics, which are related to stone formation or compensation. These metabolites and pathways are very likely associated with development of kidney stones and should be considered as potential novel targets for treatment and prevention.