Oxalate Formation From Glyoxal in Erythrocytes.

OBJECTIVE: To determine whether glyoxal can be converted to oxalate in human erythrocytes. Glyoxal synthesis is elevated in diabetes, cardiovascular disease, and other diseases with significant oxidative stress. Erythrocytes are a good model system for such studies as they lack intracellular organelles and have a simplified metabolism. MATERIALS AND METHODS: Erythrocytes were isolated from healthy volunteers and incubated with varying concentrations of glyoxal for different amounts of time. Metabolic inhibitors were used to help characterize metabolic steps. The conversion of glyoxal to glycolate and oxalate in the incubation medium was determined by chromatographic techniques. RESULTS: The bulk of the glyoxal was converted to glycolate, but ~1% was converted to oxalate. Inclusion of the pro-oxidant, menadione, in the medium increased oxalate synthesis, and the inclusion of disulfiram, an inhibitor of aldehyde dehydrogenase activity, decreased oxalate synthesis. CONCLUSION: The glyoxalase system, which utilizes glutathione as a cofactor, converts the majority of the glyoxal taken up by erythrocytes to glycolate, but a small portion is converted to oxalate. A reduction in intracellular glutathione increases oxalate synthesis and a decrease in aldehyde dehydrogenase activity lowers oxalate synthesis and suggests that glyoxylate is an intermediate. Thus, oxidative stress in tissues could potentially increase oxalate synthesis.

Fish oil supplementation and urinary oxalate excretion in normal subjects on a low-oxalate diet.

OBJECTIVE: To determine if fish oil supplementation reduces endogenous oxalate synthesis in healthy subjects. MATERIALS AND METHODS: Fifteen healthy non-stone-forming adults participated in this study. Subjects first abstained from using vitamins, medications, or foods enriched in omega-3 fatty acids for 30 days. Next, they collected two 24-hour urine specimens while consuming a self-selected diet. Subjects consumed an extremely low-oxalate and normal-calcium diet for 5 days and collected 24-hour urine specimens on the last 3 days of this diet. Next, the subjects took 2 fish oil capsules containing 650-mg eicosapentaenoic acid and 450-mg docosahexaenoic acid twice daily for 30 days. They consumed a self-selected diet on days 1-25 and the controlled diet on days 26-30. Twenty-four-hour urine samples were collected on days 28-30. Excretion levels of urinary analytes including oxalate and glycolate were analyzed. RESULTS: Although there was a significant reduction in urinary oxalate, magnesium, and potassium excretions and an increase in uric acid excretion during the controlled dietary phases compared with the self-selected diet, there were no significant differences in their excretion during controlled diet phases with and without fish oil supplementation. CONCLUSION: These results suggest that fish oil supplementation does not reduce endogenous oxalate synthesis or urinary oxalate excretion in normal adults during periods of extremely low oxalate intake. However, these results do not challenge the previously described reduction in urinary oxalate excretion demonstrated in normal subjects consuming a moderate amount of oxalate in conjunction with fish oil.

Implantation and persistence of yeast inoculum in Pinot noir fermentations at three Canadian wineries.

Inoculated fermentations are practiced in most wine regions of the world. This type of fermentation involves adding a commercial Saccharomyces cerevisiae strain as an inoculant. It is often assumed that the inoculant maintains dominance throughout the fermentation; however, sometimes commercial or indigenous yeasts, which were not intentionally added, end up as the dominant yeast in the winery fermentation. The aim of this study was to compare implantation/persistence of inoculants among three Canadian wineries (Quails' Gate, Cedar Creek, and Road 13 wineries). In 2010, three inoculated fermentation tanks at each of three wineries were sampled at four stages of fermentation (pre-inoculation, early, mid, and end). In addition, results from the end stage of fermentation, from two of the three wineries, were compared among different vintages (resulting in a 4-year comparison at Quails' Gate winery and a 2-year comparison at Cedar Creek winery). Strains of S. cerevisiae were discriminated by microsatellite analysis and identified using commercial microsatellite databases, whereas DNA sequencing was used to identify non-Saccharomyces. The percent implantation/persistence of the inoculum was significantly lower at Quails' Gate and Cedar Creek wineries as compared with the Road 13 winery in the 2010 vintage. Relatively low persistence of the inoculum at Quails' Gate winery was also found in the 2009 vintage, but low values were not found at Quails' Gate winery in 2011 and 2012 or at Cedar Creek winery in 2012. In all tanks having <80% relative abundance of the inoculant, the commercial strain (Lalvin ICV-D254®/Fermol® Premier Cru) was the dominant or co-dominant yeast. Our findings highlight year-to-year variation in inoculum implantation/persistence and the idea that unless strain typing of S. cerevisiae is conducted at the winery, there are no obvious fermentation factors that would indicate a relatively low inoculum implantation/persistence.

Internet program for facilitating dietary modifications limiting kidney stone risk.

INTRODUCTION: Certain dietary modifications limit the risk of stone recurrence. Compliance is an important component of dietary therapy for stone prevention, and self-efficacy is an important ingredient of compliance. We developed an internet program to facilitate dietary compliance for stone prevention and performed a pilot study to assess its effectiveness. MATERIALS AND METHODS: The internet program provides information regarding dietary modifications including increased fluid consumption, limited animal protein, sodium, and oxalate intake, and adequate calcium consumption. Participants record their daily food and fluid intake and receive immediate feedback as to whether they were compliant or not. Five adult calcium stone formers collected three 24 hour urine specimens on self-selected diets, three 24 hour urine specimens while on a stone preventive metabolic diet, and three 24 hour urine specimens after utilizing the internet program for 1 month. Urinary stone risk parameters were measured, and data were analyzed using repeated measures ANOVA and Student's t test. RESULTS: All participants recorded their meals and snacks for each day and found the program easy to navigate. The mean time in hours from food consumption to log in was 35.25 +/- 70.8 hours. There were no statistically significant differences in stone risk factors between the controlled and internet dietary phases. Oxalate excretion was significantly higher during the self-selected dietary intake (p = 0.03). CONCLUSIONS: This pilot study demonstrates that subjects appear to be compliant with utilization of an interactive internet program for stone prevention with dietary modifications. In addition, improvement in certain stone risk parameters occurred.

Optimizing shock wave lithotripsy: a comprehensive review.

Shock wave lithotripsy is a commonly used procedure for eradicating upper urinary tract stones in patients who require treatment. A number of methods have been proposed to improve the results of this procedure, including proper patient selection, modifications in technique, adjunctive therapy to facilitate elimination of fragments, and changes in lithotripter design. This article assesses the utility of these measures through an analysis of contemporary literature.

The effects of Oxazyme on oxalate degradation: results and implications of in vitro experiments.

UNLABELLED: Abstract Background and Purpose: Urinary oxalate excretion influences the development of calcium oxalate kidney stones. Urinary oxalate is derived from dietary sources and endogenous synthesis. Oxalate decarboxylase metabolizes oxalate and, if consumed, could theoretically accomplish this in the gastrointestinal tract. This study aimed to determine whether a commercially produced form of oxalate decarboxylase (Oxazyme(®)) could degrade oxalate in simulated gastric and intestinal environments. MATERIALS AND METHODS: One buffer (pH 3.6) simulated the gastric environment, while another (pH 6.5), approximated the proximal intestine. Potassium oxalate (soluble form of oxalate) and whole and homogenized spinach (a high oxalate containing food) were incubated in the different buffered solutions, with or without Oxazyme. Oxalate content, after incubation, was measured using established ion chromatographic techniques. RESULTS: Oxazyme resulted in complete degradation of oxalate derived from potassium oxalate in the intestinal buffer; meanwhile, oxalate derived from potassium oxalate in the gastric buffer was profoundly digested by Oxazyme. Adding Oxazyme also substantially reduced the oxalate content of both whole and homogenized spinach preparations, in either buffer. CONCLUSIONS: These in vitro findings demonstrate that Oxazyme can metabolize oxalate in both simulated gastric and small intestinal environments.

Safety and efficacy of removable inferior vena cava filters in anticoagulated patients undergoing percutaneous nephrostolithotomy.

BACKGROUND AND PURPOSE: Increasing numbers of patients are receiving a diagnosis of thrombophilic conditions necessitating chronic anticoagulation therapy. The best management approach for such patients needing percutaneous nephrostolithotomy (PCNL) has not been established. Discontinuing anticoagulation therapy before PCNL is needed to prevent hemorrhage, placing some of these patients at risk for thromboembolic events. We describe the use of removable inferior vena cava filters (RIVCF) in patients undergoing PCNL who are at risk for a venous thromboembolic event. PATIENTS AND METHODS: A retrospective study of outcomes of PCNL with RIVCF placement was conducted. RESULTS: Four patients underwent PCNL with RIVCF placement on the same day of the procedure. The mean age was 49 years (range 35-69 years). PCNL was performed on a total of six renal units with a mean of 2.2 (range 1-3) operations per renal unit. Five of six (83%) renal units were rendered stone free. There were no complications associated with either the PCNL or RIVCF placement. No patient had a thromboembolic event or received blood products. Two of the four patients underwent successful removal of the RIVCF, and one elected to keep the device in place. The device could not be extracted in the other patient. The average length that the filters were in place was 52.5 days. Patients resumed anticoagulation therapy shortly after RIVCF removal. CONCLUSION: RIVCF placement is a safe and effective method of preventing venous thromboembolic complications in thrombophilic patients needing PCNL. Patients should be informed, however, that RIVCF removal is not always possible.

Gas-containing renal stones: findings from five consecutive patients.

OBJECTIVE: To describe the clinical course, microbiology, and metabolic findings of 5 patients presenting to our institution with gas-containing renal stones. MATERIALS AND METHODS: During a 20-month period beginning in 2009, 5 patients were identified by computed tomography scanning to harbor gas-containing renal calculi. Despite similar imaging and referral practice patterns, no such cases had been seen at our institution in the preceding 20 years. The records of these patients were reviewed to better characterize this unique condition. RESULTS: All 5 subjects were premenopausal women. One patient presented with urosepsis and 4 presented with flank pain. All had urinary tract infections, and Escherichia coli was isolated from a voided urine specimen in 3. Stone culture was positive in 2 and was concordant with the voided specimen in 1. The stones were solitary in 4 and multiple in 1 patient. All the stones were composed of calcium phosphate. Of the 5 patients, 3 had pure calcium phosphate stones and 2 had stones with calcium oxalate monohydrate components. Also, 3 subjects had diabetes mellitus, 3 had hypertension, and 1 had a history of gout. Two subjects underwent 24-hour urine metabolic testing, and abnormalities were identified in both. All patients were rendered stone free: 4 with percutaneous nephrostolithotomy and 1 using robotic pyelolithotomy. CONCLUSION: Gas-containing renal stones are rare but might be increasing in prevalence. The pathophysiology is unknown but is most likely influenced by a combination of metabolic and infectious factors.

Sensitivity of human strains of Oxalobacter formigenes to commonly prescribed antibiotics.

OBJECTIVE: To determine the sensitivity of 4 strains of Oxalobacter formigenes (Oxf) found in humans--HC1, Va3, CC13, and OxK--to varying concentrations of commonly prescribed antibiotics. Oxf gut colonization has been associated with a decreased risk of forming recurrent calcium oxalate kidney stones. METHODS: For each strain and each antibiotic concentration, 100 µL of an overnight culture and 100 µL of the appropriate antibiotic were added to a 7-mL vial of oxalate culture medium containing 20 mM oxalate. On the fourth day, vials were visually examined for growth, and a calcium oxalate precipitation test was performed to determine whether Oxf grew in the presence of the antibiotic. RESULTS: All 4 Oxf strains were resistant to amoxicillin, amoxicillin/clavulanate, ceftriaxone, cephalexin, and vancomycin, and they were all sensitive to azithromycin, ciprofloxacin, clarithromycin, clindamycin, doxycycline, gentamicin, levofloxacin, metronidazole, and tetracycline. One strain, CC13, was resistant to nitrofurantoin, and the others were sensitive. Differences in minimum inhibitory concentration between strains were demonstrated. CONCLUSION: Four human strains of Oxf are sensitive to a number of antibiotics commonly used in clinical practice; however, minimum inhibitory concentrations differ between strains.

Glyoxal formation and its role in endogenous oxalate synthesis.

Calcium oxalate kidney stones are a common condition affecting many people in the United States. The concentration of oxalate in urine is a major risk factor for stone formation. There is evidence that glyoxal metabolism may be an important contributor to urinary oxalate excretion. Endogenous sources of glyoxal include the catabolism of carbohydrates, proteins, and fats. Here, we review all the known sources of glyoxal as well as its relationship to oxalate synthesis and crystal formation.

The impact of dietary calcium and oxalate ratios on stone risk.

OBJECTIVE: To determine whether the ratio of dietary calcium and oxalate consumption at mealtime affects gastrointestinal oxalate absorption and urinary oxalate excretion. METHODS: A study was conducted with 10 non-stone-forming adults placed on controlled diets with daily calcium and oxalate contents of 1000 and 750 mg, respectively. Subjects consumed a balanced calcium/oxalate ratio diet for 1 week, observed a minimum 1-week washout period, and subsequently consumed an imbalanced calcium/oxalate ratio diet for one week. Urine specimens were collected on the last 4 days of each diet. Outcome measures included urinary creatinine, calcium, and oxalate as well as the Tiselius index for assessing urinary calcium oxalate supersaturation. RESULTS: Total daily calcium excretion, oxalate excretion, and Tiselius index were similar between balanced and imbalanced dietary phases. There were significant differences in calcium excretion (mg/g creatinine) between balanced and imbalanced diets in the 1-6 PM (83.1 vs 110.2, P <.04), 6-11 PM (71.3 vs 107.2, P <.02), and 11 PM-8 AM collections (55.0 vs 41.8, P <.02). There was significantly higher oxalate excretion on the balanced diet in the 1-6 pm time period (28.1 vs 16.7, P <.01). There were no differences in the Tiselius index in these collections. CONCLUSION: These results demonstrate that the sequence of ingesting relatively large amounts of oxalate does not significantly affect calcium oxalate stone risk if the recommended daily quantity of dietary calcium is consumed.

The association of cardiovascular disease and metabolic syndrome with nephrolithiasis.

PURPOSE OF REVIEW: This review describes the relationship between nephrolithiasis, vascular disease and metabolic syndrome. RECENT FINDINGS: There is increasing evidence that kidney stone formation is associated with a number of systemic problems including cardiovascular disease, metabolic syndrome and its components. Some of these associations are bidirectional. The reasons for these associations are not totally clear, but potential factors include metabolic responses associated with these disorders that promote a stone forming milieu in urine, environmental factors such as diet, oxidative stress and inflammation and molecular changes impacting the transport of certain analytes in urine. SUMMARY: Urologists need to be cognizant of these associations as they may be able to contribute to an early diagnosis of a significant medical problem, or provide counseling to patients to prevent their occurrence.

Multibacterial growth from a surgical renal stone culture: a case report and literature review.

Urinary calculi may harbor bacteria, and this may lead to deleterious events during stone fragmentation and removal. The isolation of such bacteria from surgically extracted calculi allows for the specific tailoring of antimicrobial therapy. Here, we describe a case involving percutaneous stone removal from which the stone culture demonstrated growth of five different microorganisms. The results of this culture prompted a change in the antibiotic coverage, resulting in a more targeted treatment and improved patient care.