Estrella, Michelle M

Key Points Serum glycerol-3-phosphate (G3P) levels were significantly associated with higher fibroblast growth factor 23 levels in ESKD. Pathway and mediation analyses identified the pentose phosphate pathway as the top mediator of the relationship between serum G3P and fibroblast growth factor 23. The role of G3P in ESKD provides new insights into potential therapeutic targets for CKD-mineral and bone disorder. Background Fibroblast growth factor 23 (FGF23) is a key regulator of mineral metabolism that is independently associated with mortality in patients with ESKD. Glycerol-3-phosphate (G3P), a byproduct of glycolysis that can be derived from injured kidneys, stimulates FGF23 production. We aimed to determine if serum G3P is associated with FGF23 levels in patients with ESKD and identify potential molecular pathways that mediate their relationship. Methods We conducted a cross-sectional study of 99 nondiabetic patients with ESKD on hemodialysis. We used linear regression to examine the association between G3P terciles and log-transformed C-terminal FGF23 levels, adjusting for demographics, coronary artery disease, serum calcium, phosphorus, and parathyroid hormone. Mann–Whitney U tests compared 247 serum metabolite levels between the first and third FGF23 terciles; significant metabolites ( P < 0.01) were selected for pathway enrichment analyses. Top pathway scores were used in mediation analyses. Results The median age of participants was 54 years (interquartile range [IQR], 44–63), 38% were women, 71% self-identified as Black, and 27% had coronary artery disease. The median FGF23 level was 777 (interquartile range, 222–1310) RU/ml. In adjusted analyses, compared with participants with the lowest G3P tercile, those with the highest G3P tercile had a 95% higher FGF23 level (95% Confidence Interval, 6% to 260%; P = 0.04). Of the 27 metabolites significantly associated with FGF23 levels, pathway enrichment analysis identified the pentose phosphate pathway as the top hit (impact score=0.33, false discovery rate-adjusted P value = 0.01). The pentose phosphate pathway mediated the relationship between G3P and FGF23, resulting in a 62% change in the β coefficient. Conclusions In nondiabetic patients with ESKD on hemodialysis, serum G3P positively correlated with serum C-terminal FGF23, and this relationship was mediated by the pentose phosphate pathway. Exploring the pentose phosphate pathway could yield critical mechanistic insights into the regulation of FGF23, enhancing our understanding of its broader biologic functions.

Background: Improvement in renal function (IRF) in acute decompensated heart failure is associated with adverse outcomes. The mechanisms driving this paradox remain undefined. Methods: Using the ROSE-AHF study (Renal Optimization Strategies Evaluation–Acute Heart Failure), 277 patients were grouped according to renal function, with IRF defined by a ≥20% increase (N=75), worsening renal function by a ≥20% decline (N=53), and stable renal function (SRF) by a <20% change (N=149) in estimated glomerular filtration rate between baseline and 72 hours. Three well-validated renal tubular injury markers, NGAL (neutrophil gelatinase-associated lipocalin), NAG (N-acetyl-β-d-glucosaminidase), and KIM-1 (kidney injury molecule 1), were evaluated at baseline and 72 hours. Patients were also classified by the pattern of change in these markers. Results: Patients with IRF had the lowest admission estimated glomerular filtration rate (IRF, 37 [28 to 51] mL/min per 1.73 m 2 ; worsening renal function, 43 [35 to 55] mL/min per 1.73 m 2 ; and SRF, 43 [32 to 55] mL/min per 1.73 m 2 ; P trend =0.032) but greater cumulative urine output (IRF, 8780 [7025 to 11 208] mL; worsening renal function, 7860 [5555 to 9765] mL; and SRF, 8150 [6325 to 10 456] mL; P trend =0.024) and weight loss (IRF, –9.0 [–12.4 to –5.3] lb; worsening renal function, –5.1 [–8.1 to –1.3] lb; and SRF, –7.1 [–11.9 to –3.2] lb; P trend <0.001) despite similar diuretic doses ( P trend =0.16). There were no differences in the relative change in NGAL, NAG, or KIM-1 between renal function groups ( P trend >0.19 for all). Patients with IRF had worse survival than patients with SRF (27% versus 54%; hazard ratio, 1.98 [1.10–3.58]; P =0.024). Conclusions: IRF during decongestive therapy for acute decompensated heart failure was not associated with improved markers of renal tubular injury and was associated with worsened survival, likely driven by the presence of greater underlying cardiorenal dysfunction and more severe congestion.