Contribution of vitamin A deficiency to calculogenic risk factors of urine: studies in children

Vitamins as regulators of calcium-containing kidney stones - new perspectives on the role of the gut microbiome

Calcium-based kidney stone disease is a highly prevalent and morbid condition, with an often complicated and multifactorial aetiology. An abundance of research on the role of specific vitamins (B6, C and D) in stone formation exists, but no consensus has been reached on how these vitamins influence stone disease. As a consequence of emerging research on the role of the gut microbiota in urolithiasis, previous notions on the contribution of these vitamins to urolithiasis are being reconsidered in the field, and investigation into previously overlooked vitamins (A, E and K) was expanded. Understanding how the microbiota influences host vitamin regulation could help to determine the role of vitamins in stone disease.

Micronutrient inadequacy and urinary stone disease: an analysis of the National Health and Nutrition Examination Survey 2007-2018

Urinary stone disease is common and affects approximately 10% of the American adults. The role of diet in stone formation is well-recognized; however, the literature focus has been on dietary excess rather than micronutrient inadequacy. As patients with stones may be at risk for nutrient inadequacies, we investigated the role of micronutrient inadequacy in stone formation by performing a cross-sectional analysis of the National Health and Nutrition Examination Survey on adults who were not taking dietary supplements. Micronutrient intake was obtained from 24-h dietary recalls, and usual intake was calculated. Survey-weighted, adjusted logistic regression was used for an incident analysis on having any history of stones. An additional analysis on recurrent stone-formers was performed with the outcome being 2 or more stones passed. Finally, a sensitivity analysis using quasi-Poisson regression was performed with the outcome being number of stones passed. There were 9777 respondents representing 81,087,345 adults, of which 9.36% had a stone history. Our incident analysis revealed inadequate vitamin A intake to be associated with stone formation (OR 1.33, 95% CI: 1.03-1.71). Recurrent analysis did not find any significant associations, while our sensitivity analysis revealed inadequate vitamin A (IRR 1.96, 95% CI: 1.28-3.00) and pyridoxine (IRR 1.99, 95% CI: 1.11-3.55) to be associated with a higher number of recurrent stones. Hence, inadequate dietary intake of vitamin A and pyridoxine was associated with nephrolithiasis. Further research is needed to identify the roles of these micronutrients in stone-formers and the potential for evaluation and treatment.

Collecting duct cells show differential retinoic acid responses to acute versus chronic kidney injury stimuli

Retinoic acid (RA) activates RA receptors (RAR), resulting in RA response element (RARE)-dependent gene expression in renal collecting duct (CD). Emerging evidence supports a protective role for this activity in acute kidney injury (AKI) and chronic kidney disease (CKD). Herein, we examined this activity in RARE-LacZ transgenic mice and by RARE-Luciferase reporter assays in CD cells, and investigated how this activity responds to neurotransmitters and mediators of kidney injury. In RARE-LacZ mice, Adriamycin-induced heavy albuminuria was associated with reduced RA/RAR activity in CD cells. In cultured CD cells, RA/RAR activity was repressed by acetylcholine, albumin, aldosterone, angiotensin II, high glucose, cisplatin and lipopolysaccharide, but was induced by aristolochic acid I, calcitonin gene-related peptide, endothelin-1, gentamicin, norepinephrine and vasopressin. Compared with age-matched normal human CD cells, CD-derived renal cystic epithelial cells from patients with autosomal recessive polycystic kidney disease (ARPKD) had significantly lower RA/RAR activity. Synthetic RAR agonist RA-568 was more potent than RA in rescuing RA/RAR activity repressed by albumin, high glucose, angiotensin II, aldosterone, cisplatin and lipopolysaccharide. Hence, RA/RAR  in CD cells is a convergence point of regulation by neurotransmitters and mediators of kidney injury, and may be a novel therapeutic target.

[Unusual case of struvite urolithiasis in a dog. A case report]

A dog was referred for nutrition consultation after surgical removal of struvite uroliths from the bladder. Inspection of the dog's current ration revealed a pronounced vitamin-A deficiency together with a marked deficiency of protein, phosphorus and magnesium. Therefore, a supersaturation of the urine with ammonium, magnesium and phosphate, the three constituents of struvite, as a cause of struvite calculi formation appears rather unlikely. Vitamin-A deficiency can promote urinary infections and consequently struvite stone formation because of the lack of the protective effect of vitamin A on the epithelia of the urinary tract. Not only common causes for struvite urolith formation, including urinary supersaturation with stone-forming constituents and urinary tract infection, but also less common causes, including vitamin-A deficiency, which was the presumed trigger in the present case study, have to be taken into consideration. Dietetic measures appear to be a useful tool in such cases to prevent uroliths from reoccurring.

Retinoic acid receptor-dependent, cell-autonomous, endogenous retinoic acid signaling and its target genes in mouse collecting duct cells

BACKGROUND

Vitamin A is necessary for kidney development and has also been linked to regulation of solute and water homeostasis and to protection against kidney stone disease, infection, inflammation, and scarring. Most functions of vitamin A are mediated by its main active form, all-trans retinoic acid (tRA), which binds retinoic acid receptors (RARs) to modulate gene expression. We and others have recently reported that renal tRA/RAR activity is confined to the ureteric bud (UB) and collecting duct (CD) cell lineage, suggesting that endogenous tRA/RARs primarily act through regulating gene expression in these cells in embryonic and adult kidney, respectively.

METHODOLOGY/PRINCIPAL FINDINGS

To explore target genes of endogenous tRA/RARs, we employed the mIMCD-3 mouse inner medullary CD cell line, which is a model of CD principal cells and exhibits constitutive tRA/RAR activity as CD principal cells do in vivo. Combining antagonism of RARs, inhibition of tRA synthesis, exposure to exogenous tRA, and gene expression profiling techniques, we have identified 125 genes as candidate targets and validated 20 genes that were highly regulated (Dhrs3, Sprr1a, and Ppbp were the top three). Endogenous tRA/RARs were more important in maintaining, rather than suppressing, constitutive gene expression. Although many identified genes were expressed in UBs and/or CDs, their exact functions in this cell lineage are still poorly defined. Nevertheless, gene ontology analysis suggests that these genes are involved in kidney development, renal functioning, and regulation of tRA signaling.

CONCLUSIONS/SIGNIFICANCE

A rigorous approach to defining target genes for endogenous tRA/RARs has been established. At the pan-genomic level, genes regulated by endogenous tRA/RARs in a CD cell line have been catalogued for the first time. Such a catalogue will guide further studies on molecular mediators of endogenous tRA/RARs during kidney development and in relation to renal defects associated with vitamin A deficiency.

Percutaneous cystolithotomy for pediatric endemic bladder stone: experience with 155 cases from 2 developing countries

PURPOSE

The aim of this study was to evaluate retrospectively our experience with percutaneous cystolithotomy (PCCL) in children having endemic urinary bladder stones.

METHODS

Between January 1993 and June 2003, 155 children younger than 14 years underwent PCCL. The patients' age ranged from 8 months to 14 years (average, 4.5 years). One hundred fifteen patients (74.2%) were 5 years or younger, 31 patients (20%) were between 6 and 10 years, and 9 patients (5.8%) were between 11 and 14 years. There were 153 boys and 2 girls. The stone size ranged from 0.7 to 4 (average, 2.3) cm. The procedure was done under general anesthesia. Dilation of the tract was made under fluoroscopy. The instrument was the adult 26F nephroscope, the same that is used for percutaneous nephrolithotomy. Ultrasound disintegration was needed for stones larger than 1 cm. Suprapubic catheter was left for 24 hours. Urethral catheter was kept for 48 hours.

RESULTS

All patients became stone-free. The average operating time was 20 (5-60) minutes. The average hospital stay was 2.7 (2-5) days. No any severe intra- or postoperative complication was observed. The nucleus and/or the main component of the stones were ammonium acid urate in 144 patients (93%).

CONCLUSIONS

Based on our experience, we can conclude that PCCL is a safe and effective method for treatment of endemic bladder stones in children. It reduces morbidity and hospital stay, and thus the cost of treatment. Our series proves the nutritional etiology of the endemic pediatric bladder stones.

Levels of Retinol and Retinyl Esters in Plasma and Urine of Dogs with Urolithiasis

Vitamin A (VA) deficiency and Tamm-Horsfall glycoprotein (THP), a protein that binds retinol and retinyl esters in canine urine, might be involved in the pathogenesis of urolithiasis in dogs. In the present study, we assessed levels of retinol, retinyl esters, retinol-binding protein (RBP) and THP in plasma and urine of dogs with a history of urolithiasis (n = 25) compared with clinically healthy controls (n = 18). Plasma retinol concentrations were higher in dogs with uroliths of struvit (P < 0.01), calcium oxalate (P < 0.05), urate (P < 0.01) and cysteine, but there were no differences in the concentrations of plasma RBP and retinyl esters. Excretion of urinary retinol and retinyl esters were tentatively, but not significantly higher in the stone-forming groups, which was accompanied by increased levels of urinary RBP (P < 0.01) and lower excretions in THP (P < 0.01). The results show that VA deficiency may be excluded as a potential cause for canine urolithiasis. However, the occurrence of RBP and a concomitant reduction of THP in urine indicates a disturbed kidney function as cause or consequence of stone formation in dogs.

Percutaneous suprapubic cystolithotripsy for vesical calculi in children

BACKGROUND

The majority of vesical calculi in adults can now be treated per-urethrally with the use of ultrasonic or pneumatic lithotripsy. However, the use of these devices is restricted in pediatric patients by the narrow caliber of the urethra. A percutaneous suprapubic approach to the bladder circumvents the problem of urethral caliber in these situations.

PATIENTS AND METHODS

Thirty-eight children presenting with bladder stones underwent percutaneous suprapubic cystolithotripsy (PCCL) between November 1989 and April 1996. The age ranged from 1.5 to 7 years. The stone size ranged from 0.8 to 2.4 cm. Seven of these were recurrent stones, and five of the patients were female. The procedure was done under general anesthesia, and the equipment was the same as for upper tract endourology. The bladder was distended with saline and a suprapubic puncture made. The nephroscope was introduced after tract dilation and the stone removed, intact if small or after fragmentation if >1 cm. The procedure was done without fluoroscopy. A suprapubic catheter was left in for 48 hours.

RESULTS

All patients had an uneventful recovery following stone removal. The average hospital stage was 3 days. Here, the access provided by percutaneous suprapubic cystostomy has been combined with the experience gained in upper-tract endourology to perform procedures that would otherwise require open operation because of nonavailability of urethral access.

CONCLUSION

Extension of endourologic procedures to the lower tract reduces morbidity and hospital stay and thus the cost of treatment. Percutaneous suprapubic cystolithotripsy, in our experience, is a safe and cost-effective alternative to open surgery in children.