Hyperinsulinemia and urinary calcium excretion in calcium stone formers with idiopathic hypercalciuria

Insulin Resistance in Hypercalciuric Calcium Kidney Stone Patients

Rational & Objective

Diabetes and uric acid kidney stones are strongly associated. Patients with calcium kidney stones also have higher risk of developing diabetes compared with nonkidney stone patients yet this has not been further investigated. We aimed to characterize insulin resistance in calcium kidney stone patients.

Study Design

Observational.

Setting & Population

This study was performed in the University of Chicago Clinical Research Center. Kidney stone patients (N = 42) were selected for having idiopathic hypercalciuria and calcium stones with no other medical conditions, and controls (N = 27) were healthy.

Exposures

All participants presented to the Clinical Research Center in a fasting state and at least 2 timed fasting blood and urine collections were collected before a fixed breakfast. Six additional timed blood and urine collections were performed after breakfast.

Outcomes

We compared fasting and fed indices of insulin resistance between the groups.

Analytic Approach

We used t tests and multivariable linear regression models. A sensitivity analysis removing all patients who had ever been on a thiazide diuretic was also performed.

Results

In separate multivariable linear models, kidney stone patients had higher fasting serum insulin levels (24 (3-46 pmol/L), P = 0.03) and higher homeostatic model of insulin resistance (HOMA-IR) (1.0 (0.2-1.8), P = 0.02). In separate multivariable linear models, kidney stone patients had higher fed serum glucose levels (10 (2-18 mg/dL), P = 0.01). Results were similar in a sensitivity analysis removing all patients who had ever been on a thiazide diuretic. There were no differences in urine composition based on HOMA-IR levels.

Limitations

Single institution. Small sample size limited subanalyses by different calcium stone types.

Conclusions

Calcium kidney stone patients without diabetes or other medical conditions demonstrated signs of insulin resistance compared with healthy matched controls.

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.

Contribution of thick ascending limb and distal convoluted tubule to glucose-induced hypercalciuria in healthy controls

Carbohydrates increase kidney stone risk and increase urine calcium and magnesium. We hypothesize that the effects of glucose as an allosteric modulator of calcium-sensing receptors may mediate this effect. Six healthy subjects were on a low-sodium diet before consuming 100 g of glucose beverage. Timed fasting (3) and postglucose (6) urine and blood samples were collected every 30 min. Urine composition and serum markers were measured and microvesicular abundance of tubular transport proteins (NHE3, NKCC2, NCC, and TRPV5) were quantified. Postglucose, serum glucose, and insulin rose rapidly with a parallel increase in calcium and magnesium excretion and no change in fractional excretion of sodium. Both serum parathyroid hormone (PTH) and urine TRPV5 fell in the postglucose periods. The rise in the calcium and magnesium excretion likely occurred primarily in the thick ascending limb where they are both under control of the calcium-sensing receptor. The fall in PTH and TRPV5 support the role of glucose as an allosteric modulator of calcium-sensing receptor.NEW & NOTEWORTHY Sugar increases urine calcium and magnesium as well as kidney stone and bone disease risk. Our study provided new insights into the underlying mechanism as we gave healthy subjects an oral glucose load and used newer tools such as fractional excretion of lithium, serum parathyroid hormone, and microvesicular abundance of tubular transport proteins to characterize the mechanism and identify the thick ascending limb with possible calcium-sensing receptor mediation as a likely contributor to this mechanism.

High Consumption of Sugar-Sweetened Beverages Is Associated with Low Bone Mineral Density in Young People: The Brazilian Birth Cohort Consortium

Sugar-sweetened beverages (SSB) consumption may be associated with a reduction in bone mineral density (BMD). The aim of this study was to evaluate the association between the consumption of SSB and BMD among young people. We performed a cross-sectional study that evaluated 6620 young people (18-23 years of age) from three Brazilian birth cohorts (Ribeirão Preto, Pelotas, and São Luís). We analyzed the daily frequency and the amount and energy contribution of the SSB, which were obtained through a food frequency questionnaire. Total body and lumbar spine BMD (g/cm2), measured by dual-energy X-ray absorptiometry, were the outcomes. Unadjusted linear regression models, adjusted for sex, socioeconomic class, physical activity, smoking, alcohol consumption, and body mass index were used. The highest tertile of SSB consumption frequency (2.1-16.7 times/day) was associated with a lower lumbar spine BMD (β = -0.009; 95% CI: -0.017; -0.001; standardized β = -0.03). This association persisted after adjustment for confounders (β = -0.008; 95% CI: -0.016; -0.001; standardized β = -0.03). No association was observed between SSB consumption frequency and total body BMD or between the amount and energy contribution of SSB and total body or lumbar spine BMD. A high frequency of SSB consumption was associated with a low lumbar spine BMD.

Understanding the link between kidney stones and cancers of the upper urinary tract and bladder

Kidney stones are one of the most common renal pathologies. While emerging evidence has implicated a potential association between kidney stones and upper urinary tract cancers (including renal cancer), there is limited understanding as to the common underlying biological pathways functionally linking the etiology of kidney stone formation and the incidence, development, and progression of urinary tract cancers. From a clinical perspective, kidney stone disease can be a barrier to oncologic care due to renal obstruction. From the epidemiological perspective, risk factors associated with both conditions include smoking, alcohol consumption, diet, and gender. Herein, we review the association between renal calculi and malignancy of the upper urinary tract and discuss the current understanding of (a) potential shared mechanisms, and (b) the impact this has on shared therapeutic management of both conditions.

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.

The Relationship between Modern Fad Diets and Kidney Stone Disease: A Systematic Review of Literature

OBJECTIVES

Kidney stone disease (KSD) has a strong association with diet metabolic syndrome. This review aims at exploring the lithogenic risk posed by the current most popular diets. Our approach was to search for the effect of each diet type on the major urinary risk factors, to try to draw conclusions regarding the association of a specific diet type and KSD.

METHODS

This systematic review searched for the available literature exploring the association between the existing popular fad diets and KSD. Articles in English, French and Spanish were included, without restriction of the search period with the final search done in August 2021.

RESULTS

Total number of studies and studies for each diet type was as follows: 22 articles for the low carbohydrate diet, 20 articles for high protein diets, 26 articles for vegetarian and vegan diets. There exists a substantial variability in different low carbohydrate and high protein diets, and considerable overlap between modern popular fad diets. High carbohydrate intake might increase urine uric acid, calcium and oxalate levels. High protein diets increase urine calcium and uric acid and lower urine pH and citrate. Consumption of fruits and vegetables increases the urinary volume and urinary citrate. In vegan diets, sufficient daily calcium intake is important to avoid possible secondary hyperoxaluria.

CONCLUSIONS

Few studies evaluated the direct relationship between modern fad diets and KSD. In general, the reduction of carbohydrate in the diet, and counterbalancing protein rich diets with sufficient intake of fruits and vegetables, seem to play a protective role against KSD formation. Maintaining sufficient calcium intake in vegan and vegetarian diets is important. Additional research is needed to directly evaluate the link between KSD and each diet type.

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.

Cross-talk between renal lithogenesis and atherosclerosis: an unveiled link between kidney stone formation and cardiovascular diseases

The prevalence of kidney stones and cardiovascular diseases (CVDs) are increasing throughout the world. Both diseases are chronic and characterized by accumulation of oxidized proteins and lipids in the renal tissue and arterial wall, respectively. Emerging studies have revealed a positive association between nephrolithiasis and CVDs. Based on preclinical and clinical evidences, this review discusses: (i) stone forming risk factors, crystal nucleation, aggregation, injury-induced crystal retention, and stone formation, (ii) CVD risk factors such as dyslipidemia, perturbation of gut microbiome, obesity, free radical-induced lipoprotein oxidation, and retention in the arterial wall, subsequent foam cell formation, and atherosclerosis, (iii) mechanism by which stone forming risk factors such as oxalate, calcium, uric acid, and infection contribute toward CVDs, and (iv) how CVD risk factors, such as cholesterol, phospholipids, and uric acid, contribute to kidney stone formation are described.

SaRNA-mediated activation of TRPV5 reduces renal calcium oxalate deposition in rat via decreasing urinary calcium excretion

Hypercalciuria is a main risk factor for kidney stone  formation. TRPV5 is the gatekeeper protein for mediating calcium transport and reabsorption in the kidney. In the present study, we tested the effect of TRPV5 activation with small activating RNA (saRNA), which could induce gene expression by targeting the promoter of the gene, on ethylene glycol (EG)-induced calcium oxalate (CaOx) crystals formation in rat kidney. Five pairs of RNA activation sequences targeting the promoter of rat TRPV5 were designed and synthesized. The synthesized saRNA with the strongest activating effect was selected, and transcellular calcium transportation was tested by Fura-2 analysis. Subsequently, Sprague-Dawley rats were equally divided into three groups and fed with water, 1% EG for 28 days after injecting the negative control saRNA, 1% EG for 28 days after injecting the selected TRPV5-saRNA, respectively. The CaOx crystal formation and the 24-h urine components were assessed. In vitro study, saRNA ds-320 could significantly activate the expression of TRPV5 and transcellular calcium transportation. In vivo study, after 28 days treatment of EG, rats pre-infected with saRNA ds-320 had lower urinary calcium excretion and renal CaOx crystals formation as compared to that pre-infected with negative control saRNA. Activation of TRVP5 with saRNA ds-320 could inhibit EG-induced calcium oxalate crystals formation via promoting urine calcium reabsorption and decreasing urine calcium excretion in rats.

Effect of acute hyperinsulinemia on magnesium homeostasis in humans

BACKGROUND

Insulin may influence magnesium homeostasis through multiple mechanisms. Acutely, it stimulates the shift of magnesium from plasma into red blood cells and platelets, and in vitro, it stimulates the activity of the TRPM6 channel, a key regulator of renal magnesium reabsorption. We investigated the impact of hyperinsulinemia on magnesium handling in participants with a wide range of insulin sensitivity.

METHOD

Forty-seven participants were recruited, including 34 nondiabetic controls and 13 with type 2 diabetes mellitus. After stabilization under fixed metabolic diet, participants underwent hyperinsulinemic-euglycemic clamp. Serum and urine samples were collected before and during hyperinsulinemia. Change in serum magnesium, urinary magnesium to creatinine (Mg²⁺ :Cr) ratio, fractional excretion of urinary magnesium (FEMg²⁺ ), and estimated transcellular shift of magnesium were compared before and during hyperinsulinemia.

RESULTS

Hyperinsulinemia led to a small but statistically significant decrease in serum magnesium, and to a shift of magnesium into the intracellular compartment. Hyperinsulinemia did not significantly alter urinary magnesium to creatinine ratio or fractional excretion of urinary magnesium in the overall population, although a small but statistically significant decline in these parameters occurred in participants with diabetes. There was no significant correlation between change in fractional excretion of urinary magnesium and body mass index or insulin sensitivity measured as glucose disposal rate.

CONCLUSIONS

In human participants, acute hyperinsulinemia stimulates the shift of magnesium into cells with minimal alteration in renal magnesium reabsorption, except in diabetic patients who experienced a small decline in fractional excretion of urinary magnesium. The magnitude of magnesium shift into the intracellular compartment in response to insulin does not correlate with that of insulin-stimulated glucose entry into cells.

Integrative microRNA-gene expression network analysis in genetic hypercalciuric stone-forming rat kidney

Background. MicroRNAs (miRNAs) influence a variety of biological functions by regulating gene expression post-transcriptionally. Aberrant miRNA expression has been associated with many human diseases. Urolithiasis is a common disease, and idiopathic hypercalciuria (IH) is an important risk factor for calcium urolithiasis. However, miRNA expression patterns and their biological functions in urolithiasis remain unknown.

Methods and Results. A multi-step approach combining microarray miRNA and mRNA expression profile and bioinformatics analysis was adopted to analyze dysregulated miRNAs and genes in genetic hypercalciuric stone-forming (GHS) rat kidneys, using normal Sprague-Dawley (SD) rats as controls. We identified 2418 mRNAs and 19 miRNAs as significantly differentially expressed, over 700 gene ontology (GO) terms and 83 KEGG pathways that were significantly enriched in GHS rats. In addition, we constructed an miRNA-gene network that suggested that rno-miR-674-5p, rno-miR-672-5p, rno-miR-138-5p and rno-miR-21-3p may play important roles in the regulatory network. Furthermore, signal-net analysis suggested that NF-kappa B likely plays a crucial role in hypercalciuria urolithiasis.

Conclusions. This study presents a global view of mRNA and miRNA expression in GHS rat kidneys, and suggests that miRNAs may be important in the regulation of hypercalciuria. The data provide valuable insights for future research, which should aim at validating the role of the genes featured here in the pathophysiology of hypercalciuria.

Metabolic Syndrome and Kidney Stone Disease: A Systematic Review of Literature

INTRODUCTION

Worldwide obesity has more than doubled since 1980 with more than 600 million obese patients in 2014. Metabolic syndrome (MetS) is the co-occurrence of metabolic abnormalities, including centrally distributed obesity, hypertension, dyslipidemia, and hyperglycemia. With a concurrent rise in the incidence of kidney stone disease, we wanted to conduct a systematic review focused on the association of MetS to nephrolithiasis.

MATERIALS AND METHODS

A systematic review was performed according to the Cochrane and preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines on all English language articles for the following relevant keywords: association, metabolic syndrome, metabolic syndrome traits, syndrome X, nephrolithiasis, kidney stones, and renal calculi. Our inclusion criteria were studies comparing the prevalence of kidney stone disease in patients with and without MetS.

RESULTS

The initial literature search identified 355 potentially relevant studies. After screening, 22 full text articles were reviewed and 6 (219,255 patients) were included in the final review. All studies displayed increasing odds of nephrolithiasis with increasing number of MetS traits, where patients with three or more MetS traits tended to have a higher prevalence of nephrolithiasis. Studies also showed different significant components of MetS contributing to nephrolithiasis.

CONCLUSIONS

Our review shows a definite association of MetS with kidney stone disease. Although multifactorial in etiology, lifestyle and dietary factors seem to be increasingly important in prevention of stone disease.

The Wnt11 Signaling Pathway in Potential Cellular EMT and Osteochondral Differentiation Progression in Nephrolithiasis Formation

The molecular events leading to nephrolithiasis are extremely complex. Previous studies demonstrated that calcium and transforming growth factor-β1 (TGF-β1) may participate in the pathogenesis of stone formation, but the explicit mechanism has not been defined. Using a self-created genetic hypercalciuric stone-forming (GHS) rat model, we observed that the increased level of serous/uric TGF-β1 and elevated intracellular calcium in primary renal tubular epithelial cells (PRECs) was associated with nephrolithiasis progression in vivo. In the setting of high calcium plus high TGF-β1 in vitro, PRECs showed great potential epithelial to mesenchymal transition (EMT) progression and osteochondral differentiation properties, representing the multifarious increased mesenchymal and osteochondral phenotypes (Zeb1, Snail1, Col2A1, OPN, Sox9, Runx2) and decreased epithelial phenotypes (E-cadherin, CK19) bythe detection of mRNAs and corresponding proteins. Moreover, TGF-β-dependent Wnt11 knockdown and L-type Ca²⁺ channel blocker could greatly reverse EMT progression and osteochondral differentiation in PRECs. TGF-β1 alone could effectively promote EMT, but it had no effect on osteochondral differentiation in NRK cells (Rat kidney epithelial cell line). Stimulation with Ca²⁺ alone did not accelerate differentiation of NRK. Co-incubation of extracellular Ca²⁺ and TGF-β1 synergistically promotes EMT and osteochondral differentiation in NRK control cells. Our data supplied a novel view that the pathogenesis of calcium stone development may be associated with synergic effects of TGF-β1 and Ca²⁺, which promote EMT and osteochondral differentiation via Wnt11 and the L-type calcium channel.

A Single Nucleotide Polymorphism (rs4236480) in TRPV5 Calcium Channel Gene Is Associated with Stone Multiplicity in Calcium Nephrolithiasis Patients

Nephrolithiasis is characterized by calcification of stones in the kidneys from an unknown cause. Animal models demonstrated the functional roles of the transient receptor potential vanilloid member 5 (TRPV5) gene in calcium renal reabsorption and hypercalciuria. Therefore, TRPV5 was suggested to be involved in calcium homeostasis. However, whether genetic polymorphisms of TRPV5 are associated with kidney stone multiplicity or recurrence is unclear. In this study, 365 Taiwanese kidney-stone patients were recruited. Both biochemical data and DNA samples were collected. Genotyping was performed by a TaqMan allelic discrimination assay. We found that a TRPV5 polymorphism (rs4236480) was observed to be associated with stone multiplicity of calcium nephrolithiasis, as the risk of stone multiplicity was higher in patients with the TT+CT genotype than in patients with the CC genotype (p = 0.0271). In summary, despite the complexity of nephrolithiasis and the potential association of numerous calcium homeostatic absorption/reabsorption factors, TRPV5 plays an important role in the pathogenesis of calcium nephrolithiasis.

Calcium ions promote primary renal epithelial cell differentiation into cells with bone-associated phenotypes via transforming growth factor-β1-induced epithelial-mesenchymal transition in idiopathic hypercalciuria patients

The present study aimed to identify the characteristics and cross‑talk between transforming growth factor β1 (TGF‑β1) and calcium ions in nephrolithiasis patients with idiopathic hypercalciuria (IH) in order to elucidate the potential mechanisms underlying changes in cell phenotype induced by bone‑associated factors and their influence on renal nephrolithiasis formation. Blood samples from a total of 29 nephrolithiasis patients with IH, 29 renal stone patients without IH and 29 healthy age‑matched normal controls were subjected to quantification of peripheral serum TGF‑β1, osteopontin (OPN) and bone morphogenetic protein 2 (BMP2) using ELISA. This was followed by detection of BMP2, OPN and 1,25‑dihydroxyvitamin D3 receptor (VDR) mRNA and protein levels in primary renal epithelial cells (PRECs) of IH and HK‑2 human proximal tubular cell lines (control) using reverse transcription quantitative polymerase chain reaction (RT‑qPCR) and western blot analyses. The mRNA expression levels of BMP2, OPN and VDR in PRECs and HK‑2 were evaluated following stimulation with various concentrations of TGF‑β1 (0.5, 2.0 and 5.0 ng/ml), Ca2+ (0.5, 1.5 and 2.5 mM) or TGF‑β1 and Ca2+ combined using RT‑qPCR, respectively. TGF‑β1, BMP2 and OPN expression levels in patients with IH were all significantly higher than those in the control group. The mRNA and protein expression levels of BMP2 and VDR were significantly higher in PRECs than those in HK‑2 cells. Following incubation with TGF‑β1 and/or Ca2+, the mRNA expression levels of BMP2, OPN and VDR in PRECs increased in a dose‑dependent manner; however, no significant differences were observed in HK‑2 cells with increasing TGF‑β1 dosage. Co‑incubation with TGF‑β1 and Ca2+ in PRECs and HK‑2 cell lines resulted in similar effects and the expression of BMP2, OPN and VDR mRNA increased in a time‑dependent manner. In conclusion, the results of the present study demonstrated that TGF‑β1 regulated the expression of BMP2, OPN and VDR in PRECs, but not in HK‑2 cells. Co‑incubation with TGF‑β1 and Ca2+ significantly increased the expression levels of bone‑associated factors in PRECs and HK‑2 cells, which suggested that this process may be partially responsible for the pathogenesis of calcium stone development, and also associated with bone formation and the TGF‑β1‑induced epithelial to mesenchymal transition.

Fad diets and their effect on urinary stone formation

The influence of unhealthy dietary habits on urinary stone formation has been widely recognized in literature. Dietary advice is indeed the cornerstone prescription for prevention of nephrolithiasis as well. However, only a small amount of medical literature has addressed the influence of popular or fad diets, often self-prescribed for the management of obesity and overweight or for cultural beliefs, on the risk of kidney stones. Thereby in this paper we analyze the current knowledge on the effects of some popular diets on overall lithogenic risk. High-protein diets, like Dukan diet, raise some concerns, since animal proteins are able to increase urinary calcium and to decrease urinary citrate excretion, thus leading to a high overall lithogenic risk. Low-carbohydrate diets, like Atkins diet or zone diet, may have a protective role against kidney stone formation, but there are also evidences stating that this dietary approach may rise calciuria and decrease citraturia, since it is generally associated to a relatively high intake of animal proteins. Vegan diet can be harmful for urinary stone disease, especially for the risk of hyperuricemia and micronutrient deficiencies, even if only few studies have addressed this specific matter. On the other side, the benefits of a lacto-ovo-vegetarian diet on kidney stone prevention have been largely emphasized, provided that the intake of calcium and oxalate is balanced. Traditional Mediterranean diet should exert a protective effect on nephrolithiasis as well, even if specific studies have not been carried out yet. High phytate and antioxidant content of this diet have however demonstrated to be beneficial in preventing the formation of new or recurrent calculi. Anyway, at the current state of knowledge, the most effective dietary approach to prevent kidney stone disease is a mild animal protein restriction, a balanced intake of carbohydrates and fats and a high intake of fruit and vegetables. Other fundamental aspects, which are often neglected in fad diets, are a normal intake of milk and dairy products and salt restriction. All these nutritional aspects should be greatly taken into account when patients who are willing to undergo fad or commercial diets ask for dietary advice.