The prevalence of chronic kidney disease (CKD) is increasing worldwide, and the mortality rate continues to be unacceptably high. The biomarkers currently used in clinical practice are considered relevant when there is already significant renal impairment compromising the early use of potentially successful therapeutic interventions. More sensitive and specific biomarkers to detect CKD earlier on and improve patients’ prognoses are an important unmet medical need. The aim of this review is to summarize the recent literature on new promising early CKD biomarkers of renal function, tubular lesions, endothelial dysfunction and inflammation, and on the auspicious findings from metabolomic studies in this field. Most of the studied biomarkers require further validation in large studies and in a broad range of populations in order to be implemented into routine CKD management. A panel of biomarkers, including earlier biomarkers of renal damage, seems to be a reasonable approach to be applied in clinical practice to allow earlier diagnosis and better disease characterization based on the underlying etiologic process.

Chronic kidney disease (CKD) has been recognized as a global public health problem. Despite the current advances in medicine, CKD-associated morbidity and mortality remain unacceptably high. Several studies have highlighted the contribution of inflammation and inflammatory mediators to the development and/or progression of CKD, such as tumor necrosis factor (TNF)-related biomarkers. The inflammation pathway driven by TNF-α, through TNF receptors 1 (TNFR1) and 2 (TNFR2), involves important mediators in the pathogenesis of CKD. Circulating levels of TNFRs were associated with changes in other biomarkers of kidney function and injury, and were described as predictors of disease progression, cardiovascular morbidity, and mortality in several cohorts of patients. Experimental studies describe the possible downstream signaling pathways induced upon TNFR activation and the resulting biological responses. This review will focus on the available data on TNFR1 and TNFR2, and illustrates their contributions to the pathophysiology of kidney diseases, their cellular and molecular roles, as well as their potential as CKD biomarkers. The emerging evidence shows that TNF receptors could act as biomarkers of renal damage and as mediators of the disease. Furthermore, it has been suggested that these biomarkers could significantly improve the discrimination of clinical CKD prognostic models.

BackgroundWe intended to evaluate the effects of physical activity (PA) programs on renal function in obese boys.MethodsThirty-nine boys participated in one of the following three groups: soccer (SG, n=13), traditional PA (AG, n=13), and sedentary control (CG, n=13). SG and AG were involved in 6-month PA programs, involving three sessions/week for 60-90 min. Anthropometric measurements, body composition, creatinine and cystatin C plasmatic levels, and estimated glomerular filtration rate (eGFR) were evaluated.ResultsAt baseline (n=39), age and lean mass index (LMI) were positively correlated with creatinine levels. After 6 months, both intervention groups decreased the BMI z-score and waist circumference, while the CG increased the body fat percentage (BFP). LMI increased in all the groups. SG presented a small increment in plasma creatinine and a decrease in the eGFR values, using the Schwartz formula. Concerning the cystatin C levels and eGFR values using Filler (cystatin C-based) or Combined Zappitelli (creatinine/cystatin C-based) formulas, no significant changes were observed in any group.ConclusionThe combined Zappitelli formula showed no significant impact of PA on eGFR in obese boys. Although plasma creatinine is significantly influenced by lean body mass, cystatin C is likely to be a more accurate marker of renal function in this population.

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Alport syndrome (AS) is the second most common cause of inherited chronic kidney disease. This disorder is caused by genetic variants on COL4A3, COL4A4 and COL4A5 genes. These genes encode the proteins that constitute collagen type IV of the glomerular basement membrane (GBM). The heterodimer COL4A3A4A5 constitutes the majority of the GBM, and it is essential for the normal function of the glomerular filtration barrier (GFB). Alterations in any of collagen type IV constituents cause disruption of the GMB structure, allowing leakage of red blood cells and albumin into the urine, and compromise the architecture of the GFB, inducing inflammation and fibrosis, thus resulting in kidney damage and loss of renal function. The advances in DNA sequencing technologies, such as next-generation sequencing, allow an accurate diagnose of AS. Due to the important risk of the development of progressive kidney disease in AS patients, which can be delayed or possibly prevented by timely initiation of therapy, an early diagnosis of this condition is mandatory. Conventional biomarkers such as albuminuria and serum creatinine increase relatively late in AS. A panel of biomarkers that might detect early renal damage, monitor therapy, and reflect the prognosis would have special interest in clinical practice. The aim of this systematic review is to summarize the biomarkers of renal damage in AS as described in the literature. We found that urinary Podocin and Vascular Endothelial Growth Factor A are important markers of podocyte injury. Urinary Epidermal Growth Factor has been related to tubular damage, interstitial fibrosis and rapid progression of the disease. Inflammatory markers such as Transforming Growth Factor Beta 1, High Motility Group Box 1 and Urinary Monocyte Chemoattractant Protein- 1 are also increased in AS and indicate a higher risk of kidney disease progression. Studies suggest that miRNA-21 is elevated when renal damage occurs. Novel techniques, such as proteomics and microRNAs, are promising.

The inflammatory pathway driven by TNF-α, through its receptors TNFR1 and TNFR2, is a common feature in the pathogenesis of chronic kidney disease (CKD), regardless of the initial disease cause. Evidence correlates the chronic inflammatory status with decreased renal function. Our aim was to evaluate the potential of TNF receptors as biomarkers for CKD diagnosis and staging, as well as their association with the progression of renal lesions, in rat models of early and moderate CKD. We analyzed the circulating levels of inflammatory molecules—tumor necrosis factor-alpha (TNF-α), tumor necrosis factor receptor 1 (TNFR1) and 2 (TNFR2) and tissue inhibitor of metalloproteinase-1 (TIMP-1)—and studied their associations with TNFR1 and TNFR2 renal expression, glomerular and tubulointerstitial lesions, and with biomarkers of renal (dys)function. An increase in all inflammatory markers was observed in moderate CKD, as compared to controls, but only circulating levels of both TNFR1 and TNFR2 were significantly increased in the early disease; TNFR2 serum levels were negatively correlated with eGFR. However, only TNFR2 renal expression increased with CKD severity and showed correlations with the score of mild and advanced tubular lesions. Our findings suggest that renal TNFR2 plays a role in CKD development, and has potential to be used as a biomarker for the early detection and progression of the disease. Still, the potential value of this biomarker in disease progression warrants further investigation.

Background and Aims Beta trace protein (BTP) is a low molecular weight protein that has been proposed as an earlier biomarker of decreased glomerular filtration rate (GFR) and renal damage, than the traditional biomarkers, particularly in the creatinine blind range. Early biomarkers of renal (dys)function are needed to allow, in due time, the detection and treatment, to prevent worsening of the disease. To the authors’ knowledge, neither urine nor serum BTP has been assessed in animals with kidney disease. In the present study, we aimed to concomitantly evaluate BTP and creatinine circulating levels, to compare their value as early biomarkers of renal dysfunction, by performing the studies in rat models of mild and moderate chronic renal failure (CRF) induced by nephrectomy. Method Male Wistar rats, 12 weeks old, were randomly divided in three groups: Sham (n = 8, subjected to surgical process without kidney mass reduction), Mild CRF (n = 8, subjected to 1/2 nephrectomy), and Moderate CRF (n = 7, subjected to 5/6 nephrectomy). After five weeks, rats were sacrificed, blood and kidneys were collected. We analysed the circulating levels of BTP and creatinine and studied the association of BTP concentration with the glomerular and tubulointerstitial lesions, and with the traditional biomarkers of renal (dys)function, eGFR and creatinine. Results The serum levels of BTP were correlated with serum levels of creatinine (r = 0.575, p = 0.004) and also with eGFR (r = -0.453, p = 0.030); additionally, we found positive correlations with the total score of mild and advanced tubular lesions (r = 0.610, p = 0.02 and r = 0.517, p = 0.011, respectively), observed in kidney sections. The circulating levels of BTP increased with disease severity; Mild CRF showed a higher value of BTP than Sham group, although without statistical significance that was reached in Moderate CRF group, as observed for serum creatinine. The combined use of BTP and creatinine did not improve the discriminatory power in early disease detection. Though, the combination showed stronger correlations with the total score of tubular lesions (r = 0.849, p < 0.001 for mild tubular lesions and r = 0.774, p < 0.01 for advanced tubular lesions). Conclusion In rat models of mild and moderate CRF induced by nephrectomy, serum BTP levels increased with kidney function worsening, and correlated with disease severity, assessed by GFR and the degree of histopathological alterations. However, the earlier diagnostic value of BTP does not outperform serum creatinine in this model.