Relação do magnésio com marcadores de função renal em pacientes com doença renal crônica não-dialítica

Abstract

Introduction: Magnesium plays an important role in numerous physiological functions of the body such as cell signaling, energy production, metabolism, cell growth and proliferation, synthesis of biomacromolecules, among others. Imbalances in magnesium homeostasis are commonly found in kidney diseases and are associated with several comorbidities that are closely linked to chronic kidney disease (CKD). In addition, some researchers have demonstrated that the fraction of magnesium excretion (FEMg) can be a valuable parameter to monitor renal function, and can be used as a potential predictor of CKD progression, however, studies are still scarce. This study aimed to verify the relationship of serum and urinary magnesium with laboratory markers of kidney function in people with non-dialytic chronic kidney disease and to analyze the predictive power of magnesium excretion fraction (FEMg) as a biomarker of kidney disease. Methods: This is an analytical case-control study, carried out on samples of 128 patients with non-dialytic CKD (stages 3A, 3B and 4) undergoing treatment at the Center for Kidney Disease Prevention (CPDR) of the University Hospital from Universidade Federal Maranhão (HU-UFMA) and 110 controls (individuals with eGFR>60 mL/min/1.73 m2). Sociodemographic data (gender, age, skin color, education and marital status), clinical and laboratory determinations (serum cystatin C, serum and urinary creatinine, serum and urinary albumin, serum and urinary magnesium and albumin/creatinine ratio - RAC). Urinary magnesium levels were evaluated through total daily excretion and fraction of excretion

(FEMg) and the estimated Glomerular Filtration Rate (eGFR) was performed using the CKD- EPI formula. Data were analyzed according to groups: Case Group (DCR3A, DRC3B and

DRC4) and Control Group. Results: Among the participants (cases and controls), there was a predominance of females (59.2%) and self-declared non-white skin color (83.2%). Systemic arterial hypertension and diabetes mellitus were present in 89.8% and 46.0% of participants with CKD, respectively. The study showed a statistically significant difference between the case and control groups regarding the values of eGFR, serum creatinine, cystatin C, 24-hour albuminuria, RAC (mg/g of creatinine), 24-hour urine magnesium, isolated urine and FEMg. On the other hand, serum magnesium did not show a statistically significant association between the groups. FEMg was correlated with renal function biomarkers (eGFR, serum creatinine, cystatin C and 24-hour albuminuria), except for the RAC ratio and was significantly higher in the CKD group compared to the control group, in addition, it presented better predictive power (area under the curve 0.933) and sensitivity (88.37%) in the most advanced stage of the disease (CKD 4). The cutoff point > 4.68% determined a more accurate estimate for the reduction of GFR below 60 mL/min/1.73m2. Conclusion: This study demonstrated that magnesium in urine is related to renal function in patients with CKD on non-dialysis treatment and that FEMg can be a useful marker in the investigation of renal system dysfunctions, in addition to other renal markers, especially in the regarding the progression and severity of CKD.