Monika A. Niewczas

Circulating TNF Receptors 1 and 2 Predict ESRD in Type 2 Diabetes

Levels of proinflammatory cytokines associate with risk for developing type 2 diabetes but whether chronic inflammation contributes to the development of diabetic complications, such as ESRD, is unknown. In the 1990s, we recruited 410 patients with type 2 diabetes for studies of diabetic nephropathy and recorded their characteristics at enrollment. During 12 years of follow-up, 59 patients developed ESRD (17 per 1000 patient-years) and 84 patients died without ESRD (24 per 1000 patient-years). Plasma markers of systemic inflammation, endothelial dysfunction, and the TNF pathway were measured in the study entry samples. Of the examined markers, only TNF receptors 1 and 2 (TNFR1 and TNFR2) associated with risk for ESRD. These two markers were highly correlated, but ESRD associated more strongly with TNFR1. The cumulative incidence of ESRD for patients in the highest TNFR1 quartile was 54% after 12 years but only 3% for the other quartiles (P<0.001). In Cox proportional hazard analyses, TNFR1 predicted risk for ESRD even after adjustment for clinical covariates such as urinary albumin excretion. Plasma concentration of TNFR1 outperformed all tested clinical variables with regard to predicting ESRD. Concentrations of TNFRs moderately associated with death unrelated to ESRD. In conclusion, elevated concentrations of circulating TNFRs in patients with type 2 diabetes at baseline are very strong predictors of the subsequent progression to ESRD in subjects with and without proteinuria.

Circulating TNF Receptors 1 and 2 Predict Stage 3 CKD in Type 1 Diabetes

Elevated plasma concentrations of TNF receptors 1 and 2 (TNFR1 and TNFR2) predict development of ESRD in patients with type 2 diabetes without proteinuria, suggesting these markers may contribute to the pathogenesis of renal decline. We investigated whether circulating markers of the TNF pathway determine GFR loss among patients with type 1 diabetes. We followed two cohorts comprising 628 patients with type 1 diabetes, normal renal function, and no proteinuria. Over 12 years, 69 patients developed estimated GFR less than 60 mL/min per 1.73 m(2) (16 per 1000 person-years). Concentrations of TNFR1 and TNFR2 were strongly associated with risk for early renal decline. Renal decline was associated only modestly with total TNFα concentration and appeared unrelated to free TNFα. The cumulative incidence of estimated GFR less than 60 mL/min per 1.73 m(2) for patients in the highest TNFR2 quartile was 60% after 12 years compared with 5%-19% in the remaining quartiles. In Cox proportional hazards analysis, patients with TNFR2 values in the highest quartile were threefold more likely to experience renal decline than patients in the other quartiles (hazard ratio, 3.0; 95% confidence interval, 1.7-5.5). The risk associated with high TNFR1 values was slightly less than that associated with high TNFR2 values. TNFR levels were unrelated to baseline free TNFα level and remained stable over long periods within an individual. In conclusion, early GFR loss in patients with type 1 diabetes without proteinuria is strongly associated with circulating TNF receptor levels but not TNFα levels (free or total).

High-Normal Serum Uric Acid Increases Risk of Early Progressive Renal Function Loss in Type 1 Diabetes Results of a 6-year follow-up

OBJECTIVE We previously described a cross-sectional association between serum uric acid and reduced glomerular filtration rate (GFR) in nonproteinuric patients with type 1 diabetes. Here, we prospectively investigated whether baseline uric acid impacts the risk of early progressive renal function loss (early GFR loss) in these patients. RESEARCH DESIGN AND METHODS Patients with elevated urinary albumin excretion (n = 355) were followed for 4–6 years for changes in urinary albumin excretion and GFR. The changes were estimated by multiple determinations of albumin-to-creatinine ratios (ACRs) and serum cystatin C (GFRcystatin). RESULTS At baseline, the medians (25th–75th percentiles) for uric acid, ACR, and GFRcystatin values were 4.6 mg/dl (3.8–5.4), 26.2 mg/g (15.1–56.0), and 129 ml/min per 1.73 m2 (111–145), respectively. During the 6-year follow-up, significant association (P < 0.0002) was observed between serum uric acid and development of early GFR loss, defined as GFRcystatin decline exceeding 3.3% per year. In baseline uric acid concentration categories (in mg/dl: <3.0, 3.0–3.9, 4.0–4.9, 5.0–5.9, and ≥6), the risk of early GFR loss increased linearly (9, 13, 20, 29, and 36%, respectively). This linear increase corresponds to odds ratio 1.4 (95% CI 1.1–1.8) per 1 mg/dl increase of uric acid. The progression and regression of urinary albumin excretion were not associated with uric acid. CONCLUSIONS We found a clear dose-response relation between serum uric acid and risk of early GFR loss in patients with type 1 diabetes. Clinical trials are warranted to determine whether uric acid–lowering drugs can halt renal function decline before it becomes clinically significant.

Regression of microalbuminuria in type 1 diabetes is associated with lower levels of urinary tubular injury biomarkers, kidney injury molecule-1, and N-acetyl-β-D-glucosaminidase

Elevated urinary albumin excretion in patients with type 1 diabetes reverts to normoalbuminuria in a majority of patients but advances toward proteinuria in some. In order to gain valuable insights into the early pathophysiology of diabetic nephropathy we evaluated the association of kidney tubular injury biomarkers with changes in albuminuria in patients with type 1 diabetes mellitus. Urine levels of kidney injury molecule-1 (KIM-1), N-acetyl-β-D-glucosaminidase (NAG), and some inflammatory markers were determined in 38 healthy individuals and 659 patients with type 1 diabetes mellitus having varying degrees of albuminuria. Urinary interleukin-6, CXCL10/IP-10, NAG, and KIM-1 levels were very low in healthy individuals, increased in type 1 patients with normoalbuminuria, and were highest in diabetic patients that had microalbuminuria. Low baseline concentrations of urinary KIM-1 and NAG both individually and collectively were significantly associated with the regression of microalbuminuria over the subsequent 2 years; an effect independent of clinical characteristics. Progression and regression of microalbuminuria were unrelated to urinary levels of interleukins 6 and 8, CXCL10/IP-10, and monocyte chemoattractant protein-1. Thus our results show that lower urinary KIM-1 and NAG levels were associated with the regression of microalbuminuria in type 1 diabetes mellitus. Hence, tubular dysfunction is a critical component of the early course of diabetic nephropathy.

Risk for ESRD in Type 1 Diabetes Remains High Despite Renoprotection

Historically, patients with type 1 diabetes and macroalbuminuria had high competing risks: cardiovascular death or renal failure. Here, we assessed these risks in patients receiving therapies implemented during the last 30 years. Between 1991 and 2004, we enrolled 423 white patients with type 1 diabetes who developed macroalbuminuria (albumin excretion rate, ≥300 μg/min). With follow-up for 98% through 2008, ESRD developed in 172 patients (incidence rate, 5.8/100 person-years), and 29 died without ESRD (mortality rate, 1/100 person-years). The majority of these outcomes occurred between ages 36 and 52 years with durations of diabetes of 21 to 37 years. The 15-year cumulative risks were 52% for ESRD and 11% for pre-ESRD death. During the 15 years of follow-up, the use of renoprotective treatment increased from 56 to 82%, and BP and lipid levels improved significantly; however, the risks for both ESRD and pre-ESRD death did not change over the years analyzed. There were 70 post-ESRD deaths, and the mortality rate was very similar during the 1990s and the 2000s (11/100 person-years versus 12/100 person-years, respectively). Mortality was low in patients who received a pre-emptive kidney transplant (1/100 person-years), although these patients did not differ from dialyzed patients with regard to predialysis eGFR, sex, age at onset of ESRD, or duration of diabetes. In conclusion, despite the widespread adoption of renoprotective treatment, patients with type 1 diabetes and macroalbuminuria remain at high risk for ESRD, suggesting that more effective therapies are desperately needed.

High-normal serum uric acid is associated with impaired glomerular filtration rate in nonproteinuric patients with type 1 diabetes.

BACKGROUND AND OBJECTIVES Early renal function decline begins before the onset of proteinuria in patients with type 1 diabetes. The association of elevated serum uric acid with advanced impaired renal function prompts an examination of its role in early renal function decline in patients before proteinuria develops. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS Patients with type 1 diabetes and normoalbuminuria or microalbuminuria were recruited to the Second Joslin Kidney Study. A medical history and measurements of BP, hemoglobin A1c, albumin excretion rate, and serum concentrations of uric acid and cystatin C were obtained. Estimated glomerular filtration rate was measured by a cystatin C-based formula. RESULTS We studied 364 patients with normoalbuminuria and 311 patients with microalbuminuria. Mean glomerular filtration rate in these groups was 119 and 99 ml/min, respectively. Mildly or moderately impaired renal function (<90 ml/min) was present in 10% of those with normoalbuminuria and 36% of those with microalbuminuria. In univariate and multivariate analyses, lower glomerular filtration rate was strongly and independently associated with higher serum uric acid and higher urinary albumin excretion rate, older age, and antihypertensive treatment. CONCLUSIONS Serum uric acid concentration in the high-normal range is associated with impaired renal function in patients with type 1 diabetes. Follow-up studies are needed to confirm that this level of serum uric acid is a risk factor for early renal function decline in type 1 diabetes and to determine whether its reduction would prevent the decline.

High-Normal Serum Uric Acid Increases Risk of Early Declining Renal Function In Type 1 Diabetes: Results of 6-year Follow-up.

OBJECTIVE We previously described a cross-sectional association between serum uric acid and reduced glomerular filtration rate (GFR) in nonproteinuric patients with type 1 diabetes. Here, we prospectively investigated whether baseline uric acid impacts the risk of early progressive renal function loss (early GFR loss) in these patients. RESEARCH DESIGN AND METHODS Patients with elevated urinary albumin excretion (n = 355) were followed for 4–6 years for changes in urinary albumin excretion and GFR. The changes were estimated by multiple determinations of albumin-to-creatinine ratios (ACRs) and serum cystatin C (GFRcystatin). RESULTS At baseline, the medians (25th–75th percentiles) for uric acid, ACR, and GFRcystatin values were 4.6 mg/dl (3.8–5.4), 26.2 mg/g (15.1–56.0), and 129 ml/min per 1.73 m2 (111–145), respectively. During the 6-year follow-up, significant association (P < 0.0002) was observed between serum uric acid and development of early GFR loss, defined as GFRcystatin decline exceeding 3.3% per year. In baseline uric acid concentration categories (in mg/dl: <3.0, 3.0–3.9, 4.0–4.9, 5.0–5.9, and ≥6), the risk of early GFR loss increased linearly (9, 13, 20, 29, and 36%, respectively). This linear increase corresponds to odds ratio 1.4 (95% CI 1.1–1.8) per 1 mg/dl increase of uric acid. The progression and regression of urinary albumin excretion were not associated with uric acid. CONCLUSIONS We found a clear dose-response relation between serum uric acid and risk of early GFR loss in patients with type 1 diabetes. Clinical trials are warranted to determine whether uric acid–lowering drugs can halt renal function decline before it becomes clinically significant.

Serum Concentrations of Markers of TNFα and Fas-Mediated Pathways and Renal Function in Nonproteinuric Patients with Type 1 Diabetes

BACKGROUND AND OBJECTIVES The aim of our study was to examine serum markers of the TNF and Fas pathways for association with cystatin-C based estimated glomerular filtration rate (cC-GFR) in subjects with type 1 diabetes (T1DM) and no proteinuria. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS The study group (the 2nd Joslin Kidney Study) comprised patients with T1DM and normoalbuminuria (NA) (n = 363) or microalbuminuria (MA) (n = 304). Impaired renal function (cC-GFR <90 ml/min) was present in only 10% of patients with NA and 36% of those with MA. We measured markers of the tumor necrosis factor alpha (TNFalpha) pathway [TNFalpha, soluble TNF receptor 1 (sTNFR1), and 2 (sTNFR2)], its downstream effectors [soluble intercellular and soluble vascular adhesion molecules (sICAM-1 and sVCAM-1), interleukin 8 (IL8/CXCL8), monocytes chemoattractant protein-1 (MCP1), and IFNgamma inducible protein-10 (IP10/CXCL10)], the Fas pathway [soluble Fas (sFas) and Fas ligand (sFasL)], CRP, and IL6. RESULTS Of these, TNFalpha, sTNFRs, sFas, sICAM-1, and sIP10 were associated with cC-GFR. However, only the TNF receptors and sFas were associated with cC-GFR in multivariate analysis. Variation in the concentration of the TNF receptors had a much stronger impact on GFR than clinical covariates such as age and albumin excretion. CONCLUSIONS Elevated concentrations of serum markers of the TNFalpha and Fas-pathways are strongly associated with decreased renal function in nonproteinuric type 1 diabetic patients. These effects are independent of those of urinary albumin excretion. Follow-up studies are needed to characterize the role of these markers in early progressive renal function decline.

Early progressive renal decline precedes the onset of microalbuminuria and its progression to macroalbuminuria

OBJECTIVE Progressive decrease in the glomerular filtration rate (GFR), or renal decline, in type 1 diabetes (T1D) is observed in patients with macroalbuminuria. However, it is unknown whether this decline begins during microalbuminuria (MA) or normoalbuminuria (NA). RESEARCH DESIGN AND METHODS The study group (second Joslin Kidney Study) comprises patients with T1D and NA (n = 286) or MA (n = 248) who were followed for 4–10 years (median 8 years). Serial measurements (median 6, range 3–16) of serum creatinine and cystatin C were used jointly to estimate GFR (eGFRcr-cys) and assess its trajectories during follow-up. RESULTS Renal decline (progressive eGFRcr-cys loss of at least 3.3% per year) occurred in 10% of the NA and 35% of the MA (P < 0.001). In both groups, the strongest determinants of renal decline were baseline serum concentrations of uric acid (P < 0.001) and tumor necrosis factor receptor 1 or 2 (TNFR-1 or -2, P < 0.001). Other significant risk factors included baseline HbA1c, age/diabetes duration, and systolic blood pressure. Relative impacts of these determinants were similar in NA and MA. Renal decline was not associated with sex or baseline serum concentration of TNF-α, IL-6, IL-8, IP-10, MCP-1, VCAM, ICAM, Fas, or FasL. CONCLUSIONS Renal decline in T1D begins during NA and it is determined by multiple factors, similar to MA. Thus, this early decline is the primary disease process leading to impaired renal function in T1D. Changes in albumin excretion rate, such as the onset of MA or its progression to macroalbuminuria, are either caused by or develop in parallel to the early renal decline.

Association of Urinary Inflammatory Markers and Renal Decline in Microalbuminuric Type 1 Diabetics

Progressive renal function decline begins in one third of patients with microalbuminuria and type 1 diabetes. This study examined whether this decline is associated with elevated excretion of inflammatory markers in urine. Five inflammatory markers (IL-6, IL-8, monocyte chemoattractant protein-1, interferon-gamma-inducible protein (IP-10), and macrophage inflammatory protein-1delta) were measured in urine samples from the First Joslin Study of the Natural History of Microalbuminuria in Type 1 Diabetes, a cohort recruited in 1991. Samples were obtained from 43 participants with microalbuminuria and stable renal function (nondecliners), from 28 with microalbuminuria and early progressive renal function decline (decliners), and from 74 with normoalbuminuria and stable renal function (reference). Urinary concentrations of all five inflammatory markers were significantly higher in decliners than in nondecliners, who were similar to the reference group. Multivariate analysis revealed that those with more than two markers elevated were more than five times as likely to have early progressive decline of renal function. In contrast, serum concentrations of C-reactive protein, IL-8, and macrophage inflammatory protein-1delta did not differ between decliners and nondecliners. These results support the hypothesis that inflammatory processes in the kidney contribute to the progression of nephropathy in patients with type 1 diabetes.