Comparison of cystatin C- and creatinine-based estimated glomerular filtration rates for predicting all-cause mortality in Japanese patients with type 2 diabetes: the Fukuoka Diabetes Registry

Osteopontin as a Biomarker in Chronic Kidney Disease

Osteopontin (OPN) is a ubiquitously expressed protein with a wide range of physiological functions, including roles in bone mineralization, immune regulation, and wound healing. OPN has been implicated in the pathogenesis of several forms of chronic kidney disease (CKD) where it promotes inflammation and fibrosis and regulates calcium and phosphate metabolism. OPN expression is increased in the kidneys, blood, and urine of patients with CKD, particularly in those with diabetic kidney disease and glomerulonephritis. The full-length OPN protein is cleaved by various proteases, including thrombin, matrix metalloproteinase (MMP)-3, MMP-7, cathepsin-D, and plasmin, producing N-terminal OPN (ntOPN), which may have more detrimental effects in CKD. Studies suggest that OPN may serve as a biomarker in CKD, and while more research is needed to fully evaluate and validate OPN and ntOPN as CKD biomarkers, the available evidence suggests that they are promising candidates for further investigation. Targeting OPN may be a potential treatment strategy. Several studies show that inhibition of OPN expression or activity can attenuate kidney injury and improve kidney function. In addition to its effects on kidney function, OPN has been linked to cardiovascular disease, which is a major cause of morbidity and mortality in patients with CKD.

Glomerular filtration rate estimated by differing measures and risk of all-cause mortality among Chinese individuals without or with diabetes: A nationwide prospective study

BACKGROUND

Whether estimated glomerular filtration rates (eGFRs) by differing biomarkers are differentially associated with mortality or whether the associations differ by diabetes status remains unclear, especially in Chinese population.

METHODS

We included 6995 participants without diabetes (mean age: 60.4 years) and 1543 with diabetes (mean age: 61.8 years). Each eGFR measure was divided into normal (≥90 mL/min/1.73 m² ), modestly declined (60 to <90 mL/min/1.73 m² ), and chronic kidney disease (CKD) (<60 mL/min/1.73 m² ) groups. Cox proportional hazards models were used to estimate hazard ratio (HR) of all-cause mortality associated with each eGFR.

RESULTS

Over a follow-up of 7 years, 677 and 215 deaths occurred among individuals without or with diabetes, respectively. Among those without diabetes, all measures of modestly declined eGFR were not associated with mortality, whereas CKD defined by eGFR cystatin C (eGFRcys) and eGFR creatinine (eGFRcr)-cys (HRs were 1.71 and 1.55, respectively) but not by eGFRcr were associated with higher risk of mortality. Among diabetes, all measures of modestly declined eGFR (HRs: 1.53, 1.56, and 2.09 for eGFRcr, eGFRcys, and eGFRcr-cys, respectively) and CKD (HRs: 2.57, 2.99, and 3.92 for eGFRcr, eGFRcys, and eGFRcr-cys, respectively) were associated with higher risk of mortality. Regardless of diabetes status, an addition of eGFRcys or eGFRcr-cys to traditional risk factors lead to a larger improvement in the prediction of all-cause mortality risk than adding eGFRcr.

CONCLUSIONS

The association of eGFR with mortality risk appeared to be varied by its measures and by diabetes status among middle-aged and older Chinese, which needs to be considered in clinical practice.

Review of potential biomarkers of inflammation and kidney injury in diabetic kidney disease

Diabetic kidney disease is expected to increase rapidly over the coming decades with rising prevalence of diabetes worldwide. Current measures of kidney function based on albuminuria and estimated glomerular filtration rate do not accurately stratify and predict individuals at risk of declining kidney function in diabetes. As a result, recent attention has turned towards identifying and assessing the utility of biomarkers in diabetic kidney disease. This review explores the current literature on biomarkers of inflammation and kidney injury focussing on studies of single or multiple biomarkers between January 2014 and February 2020. Multiple serum and urine biomarkers of inflammation and kidney injury have demonstrated significant association with the development and progression of diabetic kidney disease. Of the inflammatory biomarkers, tumour necrosis factor receptor-1 and -2 were frequently studied and appear to hold most promise as markers of diabetic kidney disease. With regards to kidney injury biomarkers, studies have largely targeted markers of tubular injury of which kidney injury molecule-1, beta-2-microglobulin and neutrophil gelatinase-associated lipocalin emerged as potential candidates. Finally, the use of a small panel of selective biomarkers appears to perform just as well as a panel of multiple biomarkers for predicting kidney function decline.

Re-thinking diabetic nephropathy: Microalbuminuria is just a piece of the diagnostic puzzle

The decline of the estimated glomerular filtration rate (eGFR) and the presence of albuminuria are the typical hallmarks of kidney disease arising as one of the most frequent diabetic complications over a long period of time, generally known as diabetic nephropathy or diabetes kidney disease (DKD). However, a decline in the renal function may occur in diabetic patients for other reasons unrelated to glycemic control, and this condition is known as non-diabetic kidney disease (NDKD). In this opinion paper we will review these conditions, and we outline the importance of other investigations, such as kidney biopsy and the measurement of novel biomarkers, in order to identify the disease progression early, and to allow a timely intervention. We will also focus on the actual limits of the quantitative measurements of albumin in urine, especially with regards to potential interferences due to the treatment of patients with statins.

Incidence of end-stage renal disease and risk factors for progression of renal dysfunction in Japanese patients with type 2 diabetes: the Fukuoka Diabetes Registry

BACKGROUND

Epidemiological data regarding diabetic kidney disease are accumulated insufficiently in Japan. We prospectively investigated the incidence of end-stage renal disease (ESRD) and risk factors for progression of renal dysfunction in Japanese patients with type 2 diabetes.

METHODS

4904 participants with type 2 diabetes (mean age 65 years, mean estimated glomerular filtration rate (eGFR) 75 mL/min/1.73 m², proportion of eGFR  < 60 mL/min/1.73 m² 21%) were investigated for the progression to ESRD requiring dialysis in multicenter outpatients registry for 5 years. Risk factors for progression of renal dysfunction (≥ 30% decline in eGFR from the baseline and annual eGFR decline rates) were evaluated.

RESULTS

The incidence rates of ESRD and all-cause mortality were 4.1/1000 person-years and 12.3/1000 person-years, respectively, and increased according to stages of chronic kidney disease (eGFR  < 30 mL/min/1.73 m², incidence of ESRD 176.6/1000 person-years, all-cause mortality 57.4/1000 person-years). Incidence of  ≥ 30% decline in eGFR from the baseline was 16.4% at 5 years, and the mean annual decline rate was -1.84 mL/min/1.73 m²/year. The progression of renal dysfunction was significantly associated with older age, poor glycemic control, blood pressure, albuminuria, eGFR, previous cardiovascular disease, lifestyle factors (body mass index, reduced intake of dietary fiber, increased intake of sodium, no regular exercise), and depressive symptoms.

CONCLUSIONS

This prospective study has emphasized the importance of multifactorial interventions on risk factors to suppress the high incidence of ESRD in Japanese patients with type 2 diabetes.

Cystatin C as a biomarker of chronic kidney disease: latest developments

INTRODUCTION

Chronic kidney disease (CKD) is common, occurring in over 10% of individuals globally, and is increasing in prevalence. The limitations of traditional biomarkers of renal dysfunction, such as serum creatinine, have been well demonstrated in the literature. Therefore, augmenting clinical assessment with newer biomarkers, such as serum cystatin C, has the potential to improve disease monitoring and patient care.

AREAS COVERED

The present paper assesses the utility and limitations of serum cystatin C as a biomarker for CKD in light of the current literature.

EXPERT OPINION

Serum cystatin C has been well established as an early and accurate biomarker of CKD that is particularly helpful in patients for whom creatinine is an inadequate marker or for whom more cumbersome methods of glomerular filtration rate (GFR) measurement are impractical. Current research questions are no longer focused on if, but rather when and how often cystatin C should be used in the evaluation of CKD patients. However, transition of all reagents and estimated GFR equations to the newly established International Standard is critical for developing generalizable data.

Association of circulating cystatin C levels with type 2 diabetes mellitus: a systematic review and meta-analysis

INTRODUCTION

This study aimed to systemically summarize the present literature about circulating cystatin C (Cys C) levels in type 2 diabetes mellitus (T2DM) and provide a more precise evaluation of Cys C levels in T2DM.

MATERIAL AND METHODS

Relevant studies about Cys C concentrations in T2DM were searched in PubMed, EMBASE and the Cochrane Library database (up to Oct 31 2018). We computed the pooled standard mean difference (SMD) with its 95% confidence interval (CI) of Cys C levels through a random-effect model. The Q test and the I² statistic were used to assess and quantify between-study heterogeneity; publication bias was evaluated through a funnel plot and Egger's linear regression test.

RESULTS

After the literature search and screening process, 14 studies with 723 T2DM patients and 473 healthy controls were finally included in the meta-analysis. The results showed that T2DM patients had significantly higher Cys C levels compared to healthy controls (SMD = 1.39, 95% CI: 0.92-1.86, p < 0.001). Publication bias was not detected based on the symmetrical shape of the funnel plot and the results of Egger's test (p = 0.452). Subgroup analyses suggested that variables of human race, age, gender, study sample size and disease duration have a relationship with Cys C level in T2DM patients.

CONCLUSIONS

Overall, our study suggests that patients with T2DM have an elevated circulating Cys C level compared to healthy controls, and it is associated with race, age, gender, study sample size and disease duration. Further investigations are still needed to explore the causal relationship of aberrant Cys C concentrations in T2DM.

Albuminuria Increases All-Cause Mortality in Japanese Patients with Type 2 Diabetes Mellitus

Previous studies have reported that diabetic kidney disease is associated with cardiovascular events and death. Little is known about the independent association of albuminuria and estimated glomerular filtration rate (eGFR), with mortality in Asian patients with type 2 diabetes mellitus (T2DM) without renal failure. We conducted a historical cohort study to clarify this issue in Japanese patients with T2DM. In this study, we recruited 385 patients with T2DM, who never had chronic renal failure (eGFR < 30 mL/min/1.73 m² at baseline) and malignant diseases. With the end point of all-cause mortality, Cox regression analysis was performed. During the observational period of 7 years, 54 patients died. Cox regression analysis adjusted for confounding factors such as age, duration of diabetes, body mass index, and HbA1c, and showed that urinary albumin level was significantly associated with the mortality [hazard ratio (HR) = 1.32, 95% confidence interval (CI) = 1.03–1.70 per standard deviation (SD) increase, p = 0.031]. After additional adjustment for eGFR, the association remained significant (HR = 1.32, 95% CI = 1.02–1.70 per SD increase, p = 0.033). On the other hand, eGFR was not associated with the mortality. The present study showed that higher urinary albumin was associated with increased all-cause mortality in T2DM, independently of eGFR. These findings suggest that, regardless of eGFR, albuminuria is important for the increased risk of mortality in Japanese T2DM patients without chronic renal failure (eGFR < 30 mL/min/1.73 m²). However, because of several limitations, further large-scale longitudinal studies are necessary to confirm the present study.

The Association between Glomerular Filtration Rate Estimated Using Different Equations and Mortality in the Japanese Community-Based Population: The Yamagata (Takahata) Study

Background

To evaluate renal function, the indices of estimated glomerular filtration rate (eGFR) obtained using several equations, including the Japanese versions of the serum creatinine-based MDRD equation (eGFRcreat), Chronic Kidney Disease Epidemiology Collaboration equation (eGFR-EPI), and serum cystatin C-based equation (eGFRcys), are utilized. This study prospectively examined the association between these eGFR values and all-cause mortality during a 12-year observational period in a community-based population.

Methods and Results

The subjects of this study were 1312 participants undergoing a health checkup, aged ≥40 years. In the total population, the mean eGFR values (mL·min⁻¹·1.73 m⁻²) were 81.5 for eGFRcreat, 78.1 for eGFR-EPI, and 76.6 for eGFRcys. There were 141 deaths during the observation period, and the area under the receiver operating characteristic curve for predicting mortality was 0.59 for eGFRcreat, 0.67 for eGFR-EPI, and 0.70 for eGFRcys (all P < 0.01). In the Cox proportional analysis adjusted for age and sex, eGFRcys, but not eGFRcreat and eGFR-EPI, showed a significant association with all-cause mortality (per 15 mL·min⁻¹·1.73 m⁻² decrease: hazard ratio 1.40, 95% confidence interval 1.18–1.67).

Conclusions

This study revealed that eGFRcys showed lower values than eGFRcreat and eGFR-EPI and was significantly associated with all-cause mortality in the Japanese community-based population.