Abstract
ABSTRACTIntroduction:Obesity and Metabolic Syndrome (MS) are associated with low urinary pH and represent risk factors for nephrolithiasis, especially composed by uric acid. Acidogenic diets may also contribute to a reduction of urinary pH. Propensity for calcium oxalate precipitation has been shown to be higher with increasing features of the MS.Objective:A retrospective evaluation of anthropometric and body composition parameters, MS criteria and the dietary patterns of overweight and obese calcium stone formers and their impact upon urinary pH and other lithogenic parameters was performed.Methods:Data regarding anthropometry, body composition, serum and urinary parameters and 3-days dietary records were obtained from medical records of 102(34M/68F) calcium stone formers.Results:A negative correlation was found between urinary pH, waist circumference and serum uric acid levels (males). The endogenous production of organic acids (OA) was positively correlated with triglycerides levels and number of features of MS (males), and with glucose, uric acid and triglycerides serum levels, and number of features of MS (females). No significant correlations were detected between Net Acid Excretion (NAE) or Potential Renal Acid Load of the diet with any of the assessed parameters. A multivariate analysis showed a negative association between OA and urinary pH.Conclusion:The endogenous production of OA and not an acidogenic diet were found to be independently predictive factors for lower urinary pH levels in calcium stone formers. Hypercalciuric and/or hyperuricosuric patients presented higher OA levels and lower levels of urinary pH.
Highlights
Obesity and Metabolic Syndrome (MS) are associated with low urinary pH and represent risk factors for nephrolithiasis, especially composed by uric acid
The production of organic acids (OA) was significantly higher among obese and overweight patients when compared to their eutrophic counterparts (48 ± 5, 44 ± 3 versus 40 ± 2 p = < 0.001 and 43 ± 2, 41 ± 2 versus 37 ± 2 p = < 0.001) for men and women, respectively
Their obese and overweight counterparts did not present significant differences in potencial de carga ácida renal (PRAL) (37 ± 4, 16 ± 4 versus 27 ± 5 p = 0.603), and the same was true for women (34 ± 5, 17 ± 4 vs. 27 ± 4 p = 0.785)
Summary
Obesity and Metabolic Syndrome (MS) are associated with low urinary pH and represent risk factors for nephrolithiasis, especially composed by uric acid. Conclusion: The endogenous production of OA and not an acidogenic diet were found to be independently predictive factors for lower urinary pH levels in calcium stone formers. Metabolic Syndrome (MS) and obesity have been reported as risk factors for renal diseases, including nephrolithiasis.[1,2,3] Individuals with MS tend to have a more acidic urinary pH, which is considered the most important factor in the precipitation of uric acid crystals.[3,4,5,6,7,8] Likewise, weight and BMI are inversely associated with urinary pH.[3] The mechanisms by which obesity and metabolic syndrome lead to a reduction in urinary pH and, an increased risk of uric lithiasis appear to be mediated by insulin resistance, lower ammonium excretion, and H+ ions buffering.[8]. Preliminary studies have demonstrated an inverse correlation between body weight and net renal acid excretion (NAE) with urinary pH in uric acid stone formers. Sakhaee et al[12] reported that the likelihood of calcium oxalate precipitation in healthy subjects was higher, but not independently associated with the number of criteria for MS
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