Urinary tubular markers linked to albuminuria in diabetic nephropathy
MedWire News: Urine levels of tubular markers may be associated with albuminuria in the early stage of diabetic nephropathy, report researchers.
"These tubular markers might be useful to assess early diabetic renal damage," write Sang Heon Song (Pusan National University Hospital, Busan, South Korea) and colleagues in Diabetes Research and Clinical Practice.
Several investigations have demonstrated that some markers of tubular damage are associated with diabetic nephropathy, say the researchers. "However, most of these studies have primarily dealt with Type 1 diabetes or the entire spectrum of diabetic nephropathy, including the patients with renal impairment," they explain.
In the current study, the patients measured levels of two urinary tubular markers, namely, kidney injury molecule (KIM)-1 and neutrophil gelatinase-associated lipocalin (NGAL), in 188 Type 2 diabetes patients and 25 nondiabetic controls. All participants had early nephropathy, as defined by an estimated glomerular filtration rate (eGFR) of at least 60 mL/min per 1.73 m2.
The team also investigated the association of the tubular markers with the proinflammatory biomarker interleukin-18 (IL-18) and with the renin-angiotensin system (RAS) biomarker angiotensinogen, which has previously been shown to be increased before the onset of microalbuminuria in patients with Type 2 diabetes, say the authors.
The researchers divided the diabetes patients into three groups according to their albuminuria levels, as determined by their albumin-to-creatinine ratio. Fifty-eight of the patients had normoalbuminuria (<30 mg/g creatinine), 33 had microalbuminuria (30-299 mg/g creatinine), and 27 had macroalbuminuria (≥300 mg/g creatinine).
The researchers report that urinary levels of KIM-1, NGAL, IL-18, and angiotensinogen were all significantly higher in the macroalbuminuria group than in the control, normoalbuminuria, and microalbuminuria groups. However, levels of these markers were not significantly different between the control group and the normoalbuminuria group.
They also found that urinary KIM-1 and NGAL positively correlated with urinary IL-8 and angiotensinogen.
In addition, multivariate analysis showed that all of the urinary markers except for IL-8 were significantly associated with albuminuria.
"The results of this study suggest that urinary tubular markers such as KIM-1 and NGAL may be independent factors associated with albuminuria in patients with conserved eGFR in the early stage of diabetic nephropathy," writes the team.
"These findings may reflect a close relationship between chronic inflammation/intrarenal RAS activation and renal tubular damage in development of diabetic nephropathy," they add.
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By Sally Robertson