Urinary markers of renal inflammation in adolescents with Type 1 diabetes mellitus and normoalbuminuria

Minireview: Understanding and targeting inflammatory, hemodynamic and injury markers for cardiorenal protection in type 1 diabetes

The coexistence of cardiovascular disease (CVD) and diabetic kidney disease (DKD) is common in people with type 1 diabetes (T1D) and is strongly associated with an increased risk of morbidity and mortality. Hence, it is imperative to explore robust tools that can accurately reflect the development and progression of cardiorenal complications. Several cardiovascular and kidney biomarkers have been identified to detect at-risk individuals with T1D. The primary aim of this review is to highlight biomarkers of injury, inflammation, or renal hemodynamic changes that may influence T1D susceptibility to CVD and DKD. We will also examine the impact of approved pharmacotherapies for type 2 diabetes, including renin-angiotensin-aldosterone system (RAAS) inhibitors, sodium-glucose cotransporter-2 (SGLT2) inhibitors and glucagon-like peptide-1 receptor agonists (GLP-1RAs) on candidate biomarkers for cardiorenal complications in people with T1D and discuss how these changes may potentially mediate kidney and cardiovascular protection. Identifying predictive and prognostic biomarkers for DKD and CVD may highlight potential drug targets to attenuate cardiorenal disease progression, implement novel risk stratification measures in clinical trials, and improve the assessment, diagnosis, and treatment of at-risk individuals with T1D.

Associations Among Biomarkers of Inflammation, Tubular Injury and Lipid Metabolism With Gestational Diabetes Mellitus Status, Microalbuminuria and Retinopathy in the Microalbuminuria and Retinopathy in Gestational Diabetes Study

OBJECTIVES

Pregnancy may be complicated by gestational diabetes mellitus (GDM) and/or microvascular complications like albuminuria, retinopathy and pre-eclampsia. In this study we aimed to identify whether mechanistic pathways associated with microvascular complications are active in pregnant women with GDM or microvascular disease.

METHODS

Urinary albumin excretion and biomarkers of inflammation, lipoprotein metabolism and tubular injury were quantified in 355 pregnant women with and without GDM. Participants underwent fundus photography graded for retinopathy. Adjusted associations between individual biomarkers and each outcome variable of interest, including GDM status, albuminuria and retinopathy, were performed using logistic regression.

RESULTS

After adjusting for age, systolic blood pressure, body mass index and ethnicity, significant associations between GDM status and apolipoprotein A1, interleukin (IL)-6, IL-8, soluble tumour necrosis factor receptor-I and -II (sTNFR-I and -II), vascular endothelial growth factor and von Willebrand factor were observed. Increased high-sensitivity C-reactive protein (hsCRP) and sTNFR-II were associated with higher levels of albuminuria. hsCRP and previous GDM were associated with retinopathy.

CONCLUSION

Mechanistic pathways associated with microvascular complications appear to be active in pregnant women with GDM or microvascular disease.

Urinary interleukin-9 in youth with type 1 diabetes mellitus

AIMS

Interleukin-9 (IL-9) attenuates podocyte injury in experimental kidney disease, but its role in diabetic nephropathy is unknown. We sought to relate urinary IL-9 levels to the release of podocyte-derived extracellular vesicles (EVs) in youth with type 1 diabetes. We related urinary IL-9 levels to clinical variables and studied interactions between urinary IL-9, vascular endothelial growth factor (VEGF), tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) on urinary albumin/creatinine ratio (ACR) a functional measure of podocyte injury.

METHODS

We performed an analysis of urine samples and clinical data from a cohort of youth with type 1 diabetes (n = 53). Cytokines were measured using a Luminex platform (Eve Technologies), and nanoscale flow cytometry was employed to quantify urinary podocyte-derived EVs. All urinary measures were normalized to urinary creatinine.

RESULTS

Mean age was 14.7 ± 1.6 years, and the mean time from diagnosis was 6.7 ± 2.9 years. Mean HbA1c was 70.3 ± 13.9 mmol/mol, mean ACR was 1.3 ± 1.9 mg/mmol, and mean eGFR was 140.3 ± 32.6 ml/min/1.73 m². IL-9 was inversely related to podocyte EVs (r = - 0.56, p = 0.003). IL-9 was also inversely related to blood glucose, HbA1C and eGFR (r = - 0.44, p = 0.002; r = - 0.41, p = 0.003; r = - 0.49, p < 0.001, respectively) and positively correlated with systolic BP (r = 0.30, p = 0.04). There was a significant interaction between IL-9, EVs and ACR (p = 0.0143), and the relationship between IL-9 and ACR depended on VEGF (p = 0.0083), TNFα (p = 0.0231) and IL-6 levels (p = 0.0178).

CONCLUSIONS

IL-9 is associated with podocyte injury in early type 1 diabetes, and there are complex interactions between urinary IL-9, inflammatory cytokines and ACR.

Urinary sediment CCL5 messenger RNA as a potential prognostic biomarker of diabetic nephropathy

Background

Urinary sediment messenger RNAs (mRNAs) have been shown as novel biomarkers of kidney disease. We aimed to identify targeted urinary mRNAs in diabetic nephropathy (DN) based on bioinformatics analysis and clinical validation.

Methods

Microarray studies of DN were searched in the GEO database and Nephroseq platform. Gene modules negatively correlated with estimated glomerular filtration rate (eGFR) were identified by informatics methods. Hub genes were screened within the selected modules. In validation cohorts, a quantitative polymerase chain reaction assay was used to compare the expression levels of candidate mRNAs. Patients with renal biopsy–confirmed DN were then followed up for a median time of 21 months. End-stage renal disease (ESRD) was defined as the primary endpoint. Multivariate Cox proportional hazards regression was developed to evaluate the prognostic values of candidate mRNAs.

Results

Bioinformatics analysis revealed four chemokines (CCL5, CXCL1, CXLC6 and CXCL12) as candidate mRNAs negatively correlated with eGFR, of which CCL5 and CXCL1 mRNA levels were upregulated in the urinary sediment of patients with DN. In addition, urinary sediment mRNA of CXCL1 was negatively correlated with eGFR (r = −0.2275, P = 0.0301) and CCL5 level was negatively correlated with eGFR (r = −0.4388, P &lt; 0.0001) and positively correlated with urinary albumin:creatinine ratio (r = 0.2693, P = 0.0098); also, CCL5 and CXCL1 were upregulated in patients with severe renal interstitial fibrosis. Urinary sediment CCL5 mRNA was an independent predictor of ESRD [hazard ratio 1.350 (95% confidence interval 1.045–1.745)].

Conclusions

Urinary sediment CCL5 and CXCL1 mRNAs were upregulated in DN patients and associated with a decline in renal function and degree of renal interstitial fibrosis. Urinary sediment CCL5 mRNA could be used as a potential prognostic biomarker of DN.

Relationships between inflammation, hemodynamic function and RAAS in longstanding type 1 diabetes and diabetic kidney disease

The renin angiotensin aldosterone system (RAAS) is associated with renal disease and inflammation in a diabetes setting, however, little is known about the implicated mechanisms in individuals with long standing diabetes. Accordingly, our aim was to perform an observational study to quantify urinary excretion of inflammatory biomarkers in participants with long standing type 1 diabetes (T1D) (with and without diabetic kidney disease [DKD]) and controls, at baseline and in response to RAAS activation. GFR_INULIN, ERPF_PAH, and 42 urine inflammatory biomarkers were measured in 74 participants with T1D for ≥50 years (21 with DKD and 44 without DKD [DKD resistors]) and 73 healthy controls. Additionally, inflammatory biomarkers were measured before and after an angiotensin II infusion (ANGII, 1 ng∙kg^-1∙min^-1). Significantly lower urinary excretion of cytokines (IL-18, IL-1RA, IL-8), chemokines (MCP1, RANTES) and growth factors (TGF-α, PDGFAA, PDGFBB, VEGF-A) was observed in participants with T1D at baseline compared to controls. Urinary IL-6 was higher in DKD than in DKD resistors in an exploratory analysis unadjusted for multiple comparisons. In T1D only, lower GFR_INULIN correlated with greater excretion of proinflammatory biomarkers (IL-18, IP-10, & RANTES), growth factors (PDGF-AA & VEGFAA), and chemokines (eotaxin & MCP-1). ANGII increased 31 of 42 inflammatory biomarkers in T1D vs controls (p < 0.05), regardless of DKD resistor status. In conclusion, lower GFR and intra-renal RAAS activation were associated with increased inflammation even after longstanding T1D. The increased urinary IL-6 in patients with DKD requires further investigation to determine whether IL-6 is a candidate protective biomarker for prognostication or targeted therapy in DKD.

Comparison of Clinical and Social Characteristics of Canadian Youth Living With Type 1 and Type 2 Diabetes

OBJECTIVES

Our aim in this study was to describe the clinical and social characteristics of 2 Canadian cohorts of adolescents with diabetes.

METHODS

Participants from the Improving renal Complications in Adolescents with type 2 diabetes through REsearch (iCARE) study (n=322) and the Early Determinants of Cardio-Renal Disease in Youth With Type 1 Diabetes (n=199) study were compared.

RESULTS

Adolescents were 10 to 18 years of age (mean ± standard deviation: 14.8±2.4 years). The T2DM cohort had a shorter duration of diabetes. Both groups had glycated hemoglobin levels above target. The type 2 diabetes (T2D) cohort was comprised of predominantly Indigenous youth. The type 1 diabetes (T1D) cohort was 58.3% European/Caucasian, with a high proportion (41.7%) of visible minority groups (Afro-Caribbean, Asian/Pacific Islander, Hispanic). The prevalence of obesity, hypertension, left ventricular hypertrophy, albuminuria and hyperfiltration was higher in the T2D cohort. The T1D cohort was more socially and economically advantaged in all 4 dimensions of health inequality.

CONCLUSIONS

There are significant differences in clinical and social characteristics of adolescents with T2D and T1D in Canada. Both have inadequate glycemic control with evidence of onset and progression of diabetes-related complications.

The Effect of Lipotoxicity on Renal Dysfunction in a Nonobese Rat Model of Metabolic Syndrome: A Urinary Proteomic Approach

INTRODUCTION

The development of metabolic syndrome-associated renal dysfunction is exacerbated by a number of factors including dyslipidemia, ectopic deposition of lipids and their toxic metabolites, impairment of lipid metabolism, and insulin resistance. Renal dysfunction is also affected by the production of proinflammatory and profibrotic factors secreted from adipose tissue, which can in turn directly impair kidney cells and potentiate insulin resistance. In this study, we investigated the manifestation of renal lipid accumulation and its effect on renal dysfunction in a model of metabolic syndrome-the hereditary hypertriglyceridemic rat (HHTg)-by assessing microalbuminuria and targeted urinary proteomics. Male Wistar control rats and HHTg rats were fed a standard diet and observed over the course of ageing at 3, 12, and 20 months of age.

RESULTS

Chronically elevated levels of triglycerides in HHTg rats were associated with increased levels of NEFA during OGTT and over a period of 24 hours (+80%, P < 0.01). HHTg animals exhibited qualitative changes in NEFA fatty acid composition, represented by an increased proportion of saturated fatty acids (P < 0.05) and a decreased proportion of n-3 PUFA (P < 0.01). Ectopic lipid deposition in the kidneys of HHTg rats-triglycerides (+30%) and cholesterol (+10%)-was associated with markedly elevated microalbuminuria as ageing increased, despite the absence of microalbuminuria at the young age of 3 months in these animals. According to targeted proteomic analysis, 3-month-old HHTg rats (in comparison to age-matched controls) exhibited increased urinary secretion of proinflammatory parameters (MCP-1, IL-6, IL-8, P < 0.01) and decreased urinary secretion of epidermal growth factor (EGF, P < 0.01) before manifestation of microalbuminuria. Elevation in the urinary secretion of inflammatory cytokines can be affected by increased relative expression of MCP-1 in the renal cortex (P < 0.05).

CONCLUSIONS

Our results confirm dyslipidemia and ectopic lipid accumulation to be key contributors in the development of metabolic syndrome-associated renal dysfunction. Assessing urinary secretion of proinflammatory cytokines and epidermal growth factor can help in detecting early development of metabolic syndrome-associated renal dysfunction.

Social Determinants of Health Are Associated with Markers of Renal Injury in Adolescents with Type 1 Diabetes

OBJECTIVE

To examine the relationship between the social determinants of health and markers of early renal injury in adolescent patients with type 1 diabetes (T1D).

STUDY DESIGN

Renal outcomes included estimated glomerular filtration rate (eGFR) and albumin-creatinine excretion ratio (ACR). Differences in urinary and serum inflammatory markers also were assessed in relation to social determinants of health. Regression analysis was used to evaluate the association between the Ontario Marginalization Index (ON-Marg) as a measure of the social determinants of health, patient characteristics, ACR, eGFR, and renal filtration status (hyperfiltration vs normofiltration).

RESULTS

Participants with T1D (n = 199) with a mean age of 14.4 ± 1.7 years and diabetes duration of 7.2 ± 3.1 years were studied. Mean eGFR was 122.0 ± 19.4 mL/min/1.73 m². Increasing marginalization was positively associated with eGFR (P < .0001) but not with ACR (P = .605). Greater marginalization was associated with greater median levels of urinary interleukin (IL)-2, IL-12 (p40), macrophage-derived chemokine, monocyte chemoattractant protein-3, and tumor necrosis factor-β and serum IL-2. ON-Marg was significantly associated with eGFR after we controlled for age, sex, body mass index z score, ethnicity, serum glucose, and hemoglobin A1c in linear regression. A similar association between hyperfiltration and ON-Marg score was observed in multivariable logistic regression.

CONCLUSION

Increasing marginalization is significantly associated with both eGFR and hyperfiltration in adolescents with T1D and is associated with significant changes in urinary inflammatory biomarkers. These findings highlight a potentially important interaction between social and biological determinants of health in adolescents with T1D.

Biomarkers of diabetic kidney disease

Diabetic kidney disease (DKD) remains one of the leading causes of reduced lifespan in diabetes. The quest for both prognostic and surrogate endpoint biomarkers for advanced DKD and end-stage renal disease has received major investment and interest in recent years. However, at present no novel biomarkers are in routine use in the clinic or in trials. This review focuses on the current status of prognostic biomarkers. First, we emphasise that albuminuria and eGFR, with other routine clinical data, show at least modest prediction of future renal status if properly used. Indeed, a major limitation of many current biomarker studies is that they do not properly evaluate the marginal increase in prediction on top of these routinely available clinical data. Second, we emphasise that many of the candidate biomarkers for which there are numerous sporadic reports in the literature are tightly correlated with each other. Despite this, few studies have attempted to evaluate a wide range of biomarkers simultaneously to define the most useful among these correlated biomarkers. We also review the potential of high-dimensional panels of lipids, metabolites and proteins to advance the field, and point to some of the analytical and post-analytical challenges of taking initial studies using these and candidate approaches through to actual clinical biomarker use.

Improvements in peripheral vascular function with vitamin D treatment in deficient adolescents with type 1 diabetes

BACKGROUND

Vitamin D (VitD) deficiency is prevalent in adolescents with type 1 diabetes (T1D) and is associated with diabetes-related vascular complications in adulthood. The objective of this clinical trial was to assess VitD treatment on endothelial function (EF) and markers of renal inflammation, in this patient group.

METHODS

Adolescents with T1D with suboptimal levels of VitD (<37.5 nmol/L) were treated for 12 to 24 weeks with a VitD analog (VitD₃ ) at doses of 1000 or 2000 IU daily. The primary end-point assessed the change in reactive hyperemia index (lnRHI), a measure of EF. Secondary end-points included changes in blood pressure, lipid profile, HbA1c and albumin creatinine ratio (ACR). Urinary cytokine/chemokine inflammatory profile was also assessed in a subset of subjects posttreatment.

RESULTS

Two hundred and seventy-one subjects were screened for VitD status and 31 VitD deficient subjects with a mean age of 15.7 ± 1.4 years were enrolled and completed the study. Mean 25-OH-VitD levels significantly increased (33.0 ± 12.8 vs 67.0 ± 23.2 nmol/L, P < .01) with a significant improvement in EF following VitD supplementation (lnRHI 0.58 ± 0.20 vs 0.68 ± 0.21, P = .03). VitD supplementation did not significantly impact systolic blood pressure/diastolic blood pressure (SBP/DBP), lipids, HbA1c and ACR and no adverse effects were seen. Several urinary inflammatory cytokines/chemokines: MCP-3 (P < .01), epidermal growth factor (EGF) (P < .01) tumor necrosis factor β (TNFβ) (P = .01), interleukin-10 (IL-10) (P = .01), also significantly decreased post-VitD-treatment.

CONCLUSIONS

Treatment with VitD was associated with an improvement in EF and reduced expression of urinary inflammatory markers in adolescents with T1D. This data is suggestive of an additional benefit of VitD supplementation on early markers of microvascular complications.

Aerobic exercise regulates blood lipid and insulin resistance via the toll‑like receptor 4‑mediated extracellular signal‑regulated kinases/AMP‑activated protein kinases signaling pathway

Diabetes mellitus is a complicated metabolic disease with symptoms of hyperglycemia, insulin resistance, chronic damage and dysfunction of tissues, and metabolic syndrome for insufficient insulin production. Evidence has indicated that exercise treatments are essential in the progression of type‑ІІ diabetes mellitus, and affect insulin resistance and activity of islet β‑cells. In the present study, the efficacy and signaling mechanism of aerobic exercise on blood lipids and insulin resistance were investigated in the progression of type‑ІІ diabetes mellitus. Body weight, glucose metabolism and insulin serum levels were investigated in mouse models of type‑ІІ diabetes mellitus following experienced aerobic exercise. Expression levels of inflammatory factors, interleukin (IL)‑6, high‑sensitivity C‑reactive protein, tumor necrosis factor‑α and leucocyte differentiation antigens, soluble CD40 ligand in the serum were analyzed in the experimental mice. In addition, expression levels of toll‑like receptor 4 (TLR‑4) were analyzed in the liver cells of experimental mice. Changes of oxidative stress indicators, including reactive oxygen species, superoxide dismutase, glutathione and catalase were examined in the liver cells of experimental mice treated by aerobic exercise. Expression levels and activity of extracellular signal‑regulated kinases (ERK) and AMP‑activated protein kinase (AMPK) signaling pathways were investigated in the liver cells of mouse models of type‑ІІ diabetes mellitus after undergoing aerobic exercise. Aerobic exercise decreased the expression levels of inflammatory factors in the serum of mouse models of type‑ІІ diabetes mellitus. The results indicated that aerobic exercise downregulated oxidative stress indicators in liver cells from mouse models of type‑ІІ diabetes mellitus. In addition, the ERK and AMPK signaling pathways were inactivated by aerobic exercise in liver cells in mouse models of type‑ІІ diabetes mellitus. The activity of ERK and AMPK, and the function of islet β‑cells were observed to be improved in experimental mice treated with aerobic exercise. Furthermore, blood lipid metabolism and insulin resistance were improved by treatment with aerobic exercise. Body weight and glucose concentration of serology was markedly improved in mouse models of type‑ІІ diabetes mellitus. Furthermore, TLR‑4 inhibition markedly promoted ERK and AMPK expression levels and activity. Thus, these results indicate that aerobic exercise may improve blood lipid metabolism, insulin resistance and glucose plasma concentration in mouse models of type‑ІІ diabetes mellitus. Thus indicating aerobic exercise is beneficial for improvement of blood lipid and insulin resistance via the TLR‑4‑mediated ERK/AMPK signaling pathway in the progression of type‑ІІ diabetes mellitus.

Canadians Seeking Solutions and Innovations to Overcome Chronic Kidney Disease (Can-SOLVE CKD): Form and Function

PURPOSE OF REVIEW

This article serves to describe the Can-SOLVE CKD network, a program of research projects and infrastructure that has excited patients and given them hope that we can truly transform the care they receive.

ISSUE

Chronic kidney disease (CKD) is a complex disorder that affects more than 4 million Canadians and costs the Canadian health care system more than $40 billion per year. The evidence base for guiding care in CKD is small, and even in areas where evidence exists, uptake of evidence into clinical practice has been slow. Compounding these complexities are the variations in outcomes for patients with CKD and difficulties predicting who is most likely to develop complications over time. Clearly these gaps in our knowledge and understanding of CKD need to be filled, but the current state of CKD research is not where it needs to be. A culture of clinical trials and inquiry into the disease is lacking, and much of the existing evidence base addresses the concerns of the researchers but not necessarily those of the patients.

PROGRAM OVERVIEW

The Canadian Institutes of Health Research (CIHR) has launched the national Strategy for Patient-Oriented Research (SPOR), a coalition of federal, provincial, and territorial partners dedicated to integrating research into care. Canadians Seeking Solutions and Innovations to Overcome Chronic Kidney Disease (Can-SOLVE CKD) is one of five pan-Canadian chronic kidney disease networks supported through the SPOR. The vision of Can-SOLVE CKD is that by 2020 every Canadian with or at high risk for CKD will receive the best recommended care, experience optimal outcomes, and have the opportunity to participate in studies with novel therapies, regardless of age, sex, gender, location, or ethnicity.

PROGRAM OBJECTIVE

The overarching objective of Can-SOLVE CKD is to accelerate the translation of knowledge about CKD into clinical research and practice. By focusing on the patient's voice and implementing relevant findings in real time, Can-SOLVE CKD will transform the care that CKD patients receive, and will improve kidney health for future generations.

Urinary inflammatory cytokines as indicators of kidney damage in type 2 diabetic patients

BACKGROUND

The aim of this study was to investigate whether urinary levels of interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ) are altered in normoalbuminuric patients with type 2 diabetes mellitus (T2DM), and whether these cytokines are able to identify diabetic kidney disease (DKD) among these patients.

METHODS

This study included 125 T2DM patients classified into 3 groups according to urinary albumin/creatinine ratio (uACR): uACR <10mg/g creatinine, uACR 10-30mg/g creatinine and uACR >30mg/g creatinine. Urinary inflammatory cytokines were measured.

RESULTS

The urinary IL-6 concentrations increased from uACR <10 (97.2±26.4pg/ml) to uACR 10-30 (113.6±28.0pg/ml) and to uACR >30mg/g creatinine (163.5±25.6pg/ml) (P<0.05 and P<0.001, respectively) patients. The urinary IL-10 concentrations decreased in these uACR ranges [100.0 (58.0-141.0) pg/ml vs. 62.0 (54.5-71.5) pg/ml vs. 42.0 (32.0-48.0) pg/ml] (P<0.05 and P<0.001, respectively). All urinary cytokines demonstrated good ability to identify DKD (areas under curves >0.9).

CONCLUSIONS

Urinary inflammatory cytokines, especially IL-6 and IL-10, may assist in the identification of DKD in T2DM patients, even in the absence of micro- and macroalbuminuria.

The urinary inflammatory profile in gluten free diet-adherent adolescents with type 1 diabetes and celiac disease

AIMS

Our objective was to characterize urinary cytokine/chemokine excretion in adolescents with type 1 diabetes (T1D) and celiac disease (CD) adhering to gluten free diet (GFD) compared to matched T1D patients and healthy control (HC) group from an existing cohort.

METHODS

Eighteen T1D+CD+GFD patients aged 10-16years were identified and matched 2:1 for age, sex, diabetes duration and glycated hemoglobin to 36 T1D subjects and 36 HC. T1D+CD+GFD patients were adherent with a GFD. Urine and serum levels of cytokines/chemokines as well as baseline clinical and laboratory variables were assessed.

RESULTS

T1D+CD+GFD patients exhibited lower levels of urinary IL-1B, IL-4, IL-5 (p<0.05) and IFN-γ, IL-8 and G-CSF levels (p<0.07) compared with T1D patients. Urinary biomarker levels between T1D+CD+GFD and HC were mostly similar. In contrast, urinary FGF-2, Flt-3, IL-1B, IL-1RA, IL-4, IL-5, IL-9, IL-10, IL-12p40, IL-15, MIP-1β, and TNF-β (p<0.05) were higher in T1D patients compared to HC. Similar levels of inflammatory markers were seen in the serum for all 3 groups.

CONCLUSIONS

T1D+CD+GFD patients demonstrated decreased urinary inflammatory cytokine/chemokines compared to T1D and some similar to HC, which is suggestive of a potential modulatory role of treated CD on urinary markers.

Urinary Biomarkers in the Assessment of Early Diabetic Nephropathy

Diabetic nephropathy (DN) is a frequent and severe complication of diabetes mellitus (DM). Its diagnosis in incipient stages may allow prompt interventions and an improved prognosis. Towards this aim, biomarkers for detecting early DN can be used. Microalbuminuria has been proven a remarkably useful biomarker, being used for diagnosis of DN, for assessing its associated condition-mainly cardiovascular ones-and for monitoring its progression. New researches are pointing that some of these biomarkers (i.e., glomerular, tubular, inflammation markers, and biomarkers of oxidative stress) precede albuminuria in some patients. However, their usefulness is widely debated in the literature and has not yet led to the validation of a new "gold standard" biomarker for the early diagnosis of DN. Currently, microalbuminuria is an important biomarker for both glomerular and tubular injury. Other glomerular biomarkers (transferrin and ceruloplasmin) are under evaluation. Tubular biomarkers in DN seem to be of a paramount importance in the early diagnosis of DN since tubular lesions occur early. Additionally, biomarkers of inflammation, oxidative stress, podocyte biomarkers, and vascular biomarkers have been employed for assessing early DN. The purpose of this review is to provide an overview of the current biomarkers used for the diagnosis of early DN.

Markers of endothelial dysfunction and inflammation predict progression of diabetic nephropathy in African Americans with type 1 diabetes

African Americans with early-onset type 1 diabetes mellitus are at a high risk for severe diabetic nephropathy and end-stage renal disease. In order to determine whether baseline plasma levels of inflammatory markers predict incidence of overt proteinuria or renal failure in African Americans with type 1 diabetes mellitus, we re-examined data of 356 participants in our observational follow-up study of 725 New Jersey African Americans with type 1 diabetes. At baseline and 6-year follow-up, a detailed structured clinical interview was conducted to document medical history including kidney dialysis or transplant, other diabetic complications, and renal-specific mortality. Plasma levels of 28 inflammatory biomarkers were measured using a multiplex bead analysis system. After adjusting for baseline age, glycohemoglobin, and other confounders, the baseline plasma levels of soluble intercellular adhesion molecule-1 (sICAM-1) in the upper two quartiles were, respectively, associated with a three- to fivefold increase in the risk of progression from no albuminuria or microalbuminuria to overt proteinuria. Baseline plasma levels of the chemokine eotaxin in the upper quartile were significantly associated with a sevenfold increase in risk of incident renal failure. These associations were independent of traditional risk factors for progression of diabetic nephropathy. Thus, in type 1 diabetic African Americans, sICAM-1 predicted progression to overt proteinuria and eotaxin-predicted progression to renal failure.

The urinary cytokine/chemokine signature of renal hyperfiltration in adolescents with type 1 diabetes

OBJECTIVE

Urinary cytokine/chemokine levels are elevated in adults with type 1 diabetes (T1D) exhibiting renal hyperfiltration. Whether this observation extends to adolescents with T1D remains unknown. Our first objective was to determine the relationship between hyperfiltration and urinary cytokines/chemokines in normotensive, normoalbuminuric adolescents with T1D using GFR(cystatin). Our second aim was to determine the relationship between urine and plasma levels of inflammatory biomarkers, to clarify the origin of these factors.

METHODS

Urine and serum cytokines/chemokines (Luminex platform) and GFR(cystatin) were measured in normofiltering (n = 111, T1D-N, GFR<135 ml/min/1.73 m(2)) and hyperfiltering (n = 31, T1D-H, GFR ≥ 135 ml/min/1.73 m(2)) adolescents with T1D (ages 10-16), and in age and sex matched healthy control subjects (HC, n = 59).

RESULTS

We noted significant step-wise increases in urinary cytokine/chemokine excretion according to filtration status with highest levels in T1D-H, with parallel trends in serum analyte concentrations. After adjusting for serum glucose at the time of sampling, differences in urinary cytokine excretion were not statistically significant. Only serum IL-2 significantly differed between HC and T1D (p = 0.0076).

CONCLUSIONS

Hyperfiltration is associated with increased urinary cytokine/chemokine excretion in T1D adolescents, and parallel trends in serum cytokine concentration. The GFR-associated trends in cytokine excretion may be driven by the effects of ambient hyperglycemia. The relationship between hyperfiltration, glycemia, and variations in serum and urine cytokine expression and their impact on future renal and systemic vascular complications requires further study.

Predictive usefulness of urinary biomarkers for the identification of cyclosporine A-induced nephrotoxicity in a rat model

The main side effect of cyclosporine A (CsA), a widely used immunosuppressive drug, is nephrotoxicity. Early detection of CsA-induced acute nephrotoxicity is essential for stop or minimize kidney injury, and timely detection of chronic nephrotoxicity is critical for halting the drug and preventing irreversible kidney injury. This study aimed to identify urinary biomarkers for the detection of CsA-induced nephrotoxicity. We allocated salt-depleted rats to receive CsA or vehicle for 7, 14 or 21 days and evaluated renal function and hemodynamics, microalbuminuria, renal macrophage infiltration, tubulointerstitial fibrosis and renal tissue and urinary biomarkers for kidney injury. Kidney injury molecule-1 (KIM-1), tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL-6), fibronectin, neutrophil gelatinase-associated lipocalin (NGAL), TGF-β, osteopontin, and podocin were assessed in urine. TNF-α, IL-6, fibronectin, osteopontin, TGF-β, collagen IV, alpha smooth muscle actin (α -SMA) and vimentin were assessed in renal tissue. CsA caused early functional renal dysfunction and microalbuminuria, followed by macrophage infiltration and late tubulointerstitial fibrosis. Urinary TNF-α, KIM-1 and fibronectin increased in the early phase, and urinary TGF-β and osteopontin increased in the late phase of CsA nephrotoxicity. Urinary biomarkers correlated consistently with renal tissue cytokine expression. In conclusion, early increases in urinary KIM-1, TNF-α, and fibronectin and elevated microalbuminuria indicate acute CsA nephrotoxicity. Late increases in urinary osteopontin and TGF-β indicate chronic CsA nephrotoxicity. These urinary kidney injury biomarkers correlated well with the renal tissue expression of injury markers and with the temporal development of CsA nephrotoxicity.

The effect of aliskiren on urinary cytokine/chemokine responses to clamped hyperglycaemia in type 1 diabetes

AIMS/HYPOTHESIS

Acute clamped hyperglycaemia activates the renin-angiotensin-aldosterone system (RAAS) and increases the urinary excretion of inflammatory cytokines/chemokines in patients with uncomplicated type 1 diabetes mellitus. Our objective was to determine whether blockade of the RAAS would blunt the effect of acute hyperglycaemia on urinary cytokine/chemokine excretion, thereby giving insights into potentially protective effects of these agents prior to the onset of clinical nephropathy.

METHODS

Blood pressure, renal haemodynamic function (inulin and para-aminohippurate clearances) and urinary cytokines/chemokines were measured after 6 h of clamped euglycaemia (4-6 mmol/l) and hyperglycaemia (9-11 mmol/l) on two consecutive days in patients with type 1 diabetes mellitus (n = 27) without overt nephropathy. Measurements were repeated after treatment with aliskiren (300 mg daily) for 30 days.

RESULTS

Before aliskiren, clamped hyperglycaemia increased filtration fraction (from 0.188 ± 0.007 to 0.206 ± 0.007, p = 0.003) and urinary fibroblast growth factor-2 (FGF2), IFN-α2 and macrophage-derived chemokine (MDC) (p < 0.005). After aliskiren, the filtration fraction response to hyperglycaemia was abolished, resulting in a lower filtration fraction after aliskiren under clamped hyperglycaemic conditions (p = 0.004), and none of the biomarkers increased in response to hyperglycaemia. Aliskiren therapy also reduced levels of urinary eotaxin, FGF2, IFN-α2, IL-2 and MDC during clamped hyperglycaemia (p < 0.005).

CONCLUSIONS/INTERPRETATION

The increased urinary excretion of inflammatory cytokines/chemokines in response to acute hyperglycaemia is blunted by RAAS blockade in humans with uncomplicated type 1 diabetes mellitus.

The effect of renal hyperfiltration on urinary inflammatory cytokines/chemokines in patients with uncomplicated type 1 diabetes mellitus

AIMS/HYPOTHESIS

High intraglomerular pressure causes renal inflammation in experimental models of diabetes. Our objective was to determine whether renal hyperfiltration, a surrogate for intraglomerular hypertension, is associated with increased excretion of urinary cytokines/chemokines in patients with type 1 diabetes mellitus.

METHODS

Blood pressure, renal haemodynamic function (inulin and para-aminohippurate clearances for glomerular filtration rate (GFR) and effective renal plasma flow (ERPF), respectively) and urine samples were obtained during clamped euglycaemia in individuals with type 1 diabetes with either hyperfiltration (GFR determined using inulin [GFRINULIN] ≥ 135 ml min⁻¹ 1.73 m⁻², n = 28) or normofiltration (n = 21) and healthy control individuals (n = 18).

RESULTS

Baseline clinical characteristics, dietary sodium and protein intake and blood pressure levels were similar in the diabetic and healthy control groups. In addition, HbA1c levels were similar in the two diabetic groups. As expected baseline GFR was higher in hyperfilterers than either normofiltering diabetic patients or healthy control patients (165 ± 9 vs 113 ± 2 and 116 ± 4 ml min⁻¹ 1.73 m⁻², respectively, p < 0.01). ERPF and renal blood flow were also comparatively higher and renal vascular resistance was lower in hyperfiltering patients (p < 0.01). Hyperfiltering diabetic patients had higher excretion rates for eotaxin, IFNα2, macrophage-derived chemokine, platelet-derived growth factor (PDGF)-AA, PDGF-AB/BB and granulocyte-macrophage colony-stimulating factor (p ≤ 0.01). Urinary monocyte chemoattractant protein (MCP)-1 and RANTES (regulated on activation, normal T expressed and secreted) excretion was also higher in hyperfiltering vs normofiltering diabetic individuals (p < 0.01) and fibroblast growth factor-2, MCP-3 and CD40K excretion was elevated in hyperfiltering diabetic individuals vs healthy controls (p < 0.01).

CONCLUSIONS/INTERPRETATION

Renal hyperfiltration is associated with increased urinary excretion of inflammatory cytokines/chemokines in patients with uncomplicated type 1 diabetes.