Connective tissue growth factor (CTGF; CCN2) plays a role in the development of diabetic nephropathy (DN). Urinary CTGF (uCTGF) is elevated in DN patients and has been proposed as a biomarker for disease progression, but it is unknown which pathophysiological factors contribute to elevated uCTGF. We studied renal handling of CTGF by infusion of recombinant CTGF in diabetic mice. In addition, uCTGF was measured in type 1 DN patients and compared with glomerular and tubular dysfunction and damage markers. In diabetic mice, uCTGF was increased and fractional excretion (FE) of recombinant CTGF was substantially elevated indicating reduced tubular reabsorption. FE of recombinant CTGF correlated with excretion of endogenous CTGF. CTGF mRNA was mainly localized in glomeruli and medullary tubules. Comparison of FE of endogenous and recombinant CTGF indicated that 60% of uCTGF had a direct renal source, while 40% originated from plasma CTGF. In DN patients, uCTGF was independently associated with markers of proximal and distal tubular dysfunction and damage. In conclusion, uCTGF in DN is elevated as a result of both increased local production and reduced reabsorption due to tubular dysfunction. We submit that uCTGF is a biomarker reflecting both glomerular and tubulointerstitial hallmarks of diabetic kidney disease.
Despite aggressive treatment of cardiovascular disease (CVD) risk factors individuals with type 2 diabetes (T2D) still have increased risk of cardiovascular morbidity and mortality. The primary aim of this study was to examine the cross-sectional association between total (25-hydroxy vitamin D (25(OH)D)) and risk of CVD in patients with T2D. Secondary objective was to examine the association between 25(OH)D and bone health. A Danish cohort of patients with T2D participating in a randomised clinical trial were analysed. In total 415 patients (68% men, age 60±9 years (mean±s.d.), duration of diabetes 12±6 years), including 294 patients (71%) treated with insulin. Carotid intima–media thickness (IMT) and arterial stiffness (carotid artery distensibility coefficient (DC) and Young's elastic modulus (YEM)) were measured by ultrasound scan as indicators of CVD. Bone health was assessed by bone mineral density and trabecular bone score measured by dual energy X-ray absorptiometry. In this cohort, 214 patients (52%) were vitamin D deficient (25(OH)D <50 nmol/l). Carotid IMT was 0.793±0.137 mm, DC was 0.0030±0.001 mmHg, YEM was 2354±1038 mmHg and 13 (3%) of the patients were diagnosed with osteoporosis. A 25(OH)D level was not associated with carotid IMT or arterial stiffness (P>0.3) or bone health (P>0.6) after adjustment for CVD risk factors. In conclusion, 25(OH)D status was not associated with carotid IMT, arterial stiffness or bone health in this cohort of patients with T2D. To explore these associations and the association with other biomarkers further, multicentre studies with large numbers of patients are required.
carotid intima–media thickness; 25-hydroxyvitamin D; bone structure; cardiovascular disease and type 2 diabetes
Intensive insulin therapy is recommended for the treatment of type 1 diabetes (T1D). Hypoglycaemia and weight gain are the common side effects of insulin treatment and may reduce compliance. In patients with insulin-treated type 2 diabetes, the addition of glucagon-like peptide-1 receptor agonist (GLP-1RA) therapy has proven effective in reducing weight gain and insulin dose. The present publication describes a protocol for a study evaluating the efficacy and safety of adding a GLP-1RA to insulin treatment in overweight patients with T1D in a randomised, double-blinded, controlled design.
Methods and analysis
In total, 100 patients with type 1 diabetes, poor glycaemic control (glycated haemoglobin (HbA1c) >8%) and overweight (body mass index >25 kg/m2) will be randomised to either liraglutide 1.8 mg once daily or placebo as an add-on to intensive insulin therapy in this investigator initiated, double-blinded, placebo-controlled parallel study. The primary end point is glycaemic control as measured by changes in HbA1c. Secondary end points include changes in the insulin dose, hypoglyacemic events, body weight, lean body mass, fat mass, food preferences and adverse events. Glycaemic excursions, postprandial glucagon levels and gastric emptying rate during a standardised liquid meal test will also be studied.
Ethics and dissemination
The study is approved by the Danish Medicines Authority, the Regional Scientific-Ethical Committee of the Capital Region of Denmark and the Data Protection Agency. The study will be carried out under the surveillance and guidance of the good clinical practice (GCP) unit at Copenhagen University Hospital Bispebjerg in accordance with the ICH-GCP guidelines and the Helsinki Declaration.
Trial registration number
In this study we estimate the subcutaneous tissue counter pressure during drug infusion from a series of injections of insulin in type 2 diabetic patients using a non-invasive method. We construct a model for the pressure evolution in subcutaneous tissue based on mass continuity and the flow laws of a porous medium. For equivalent injection forces we measure the change in the infusion rate between injections in air at atmospheric pressure and in tissue. From a best fit with our model, we then determine the flow permeability as well as the bulk modulus of the tissue, estimated to be of the order 10−11–10−10 m2 and 105 Pa, respectively. The permeability is in good agreement with reported values for adipose porcine tissue. We suggest our model as a general way to estimate the pressure build-up in tissue during subcutaneous injection.
Heart failure is one of the most common cardiovascular complications of diabetes and the most disabling and deadly complication too. Many antidiabetic agents have been associated with increased morbidity and mortality in a subset of patients with chronic heart failure (CHF); thus, new treatment modalities are warranted. Interestingly, a beneficial effect of the incretin hormone, GLP-1, on cardiac function has been suggested in patients with diabetes and patients without diabetes. Liraglutide (Victoza) is a GLP-1 analogue developed for the treatment of type 2 diabetes (T2D); however, its impact on cardiac function has not previously been investigated in patients with CHF. This prompted us to investigate whether liraglutide treatment for 24 weeks improves left ventricular ejection fraction (LVEF) in patients with CHF with and without T2D compared with placebo treatment.
Methods and analysis
An investigator-initiated, multicentre, randomised, double-blind, parallel, placebo-controlled intervention trial. In total, 240 patients with CHF (with and without T2D) with LVEF≤45% will be randomised to either subcutaneous injection of liraglutide 1.8 mg or matching placebo once daily for 24 weeks. The effect of liraglutide on left ventricular function will be evaluated by advanced echocardiography, including three-dimensional contrast echocardiography.
Ethics and dissemination
The study will be performed and monitored according to the Good Clinical Practice-International Conference on Harmonisation (GCP-ICH) regulations and conducted according to the principles of the Helsinki Declaration. The Danish Medicines Agency, the local Research Ethics Committee and the Danish Data Protection Agency have approved the study.
Trial registration number
ClinicalTrials.gov Identifier: NCT01472640.
An important task in diabetes management is detection of hypoglycemia. Professional continuous glucose monitoring (CGM), which produces a glucose reading every 5 min, is a powerful tool for retrospective identification of unrecognized hypoglycemia. Unfortunately, CGM devices tend to be inaccurate, especially in the hypoglycemic range, which limits their applicability for hypoglycemia detection. The objective of this study was to develop an automated pattern recognition algorithm to detect hypoglycemic events in retrospective, professional CGM.
Continuous glucose monitoring and plasma glucose (PG) readings were obtained from 17 data sets of 10 type 1 diabetes patients undergoing insulin-induced hypoglycemia. The CGM readings were automatically classified into a hypoglycemic group and a nonhypoglycemic group on the basis of different features from CGM readings and insulin injection. The classification was evaluated by comparing the automated classification with PG using sample-based and event-based sensitivity and specificity measures.
With an event-based sensitivity of 100%, the algorithm produced only one false hypoglycemia detection. The sample-based sensitivity and specificity levels were 78% and 96%, respectively.
The automated pattern recognition algorithm provides a new approach for detecting unrecognized hypoglycemic events in professional CGM data. The tool may assist physicians and diabetologists in conducting a more thorough evaluation of the diabetes patient’s glycemic control and in initiating necessary measures for improving glycemic control.
continuous glucose monitoring; diabetes; hypoglycemia; machine learning; retrospective
Cardiac autonomic neuropathy (CAN) is a serious complication of longstanding diabetes and is associated with an increased morbidity and reduced quality of life in patients with diabetes. The present study evaluated the prevalence of CAN diagnosed by reduced heart rate variability (HRV) using a newly developed device in a large, unselected, hospital-based population of patients with diabetes.
The study examined 323 patients consisting of 206 type 1 diabetes (T1DM) patients and 117 type 2 diabetes (T2DM) patients. The new handheld prototype Vagus™ was used to screen for CAN. Three different standardized cardiac reflex tests were performed to calculate HRV: 30:15 ratio, E:I ratio, and the Valsalva maneuver. An abnormal HRV in one test is indicative of early CAN, and if two or more tests show abnormal HRV, the diagnosis of CAN is established.
In total, 86% of examined patients completed all three tests. Each test was completed by more than 90% of the patients. The prevalence of established CAN was 23%, whereas 33% of the patients had early signs of CAN. The prevalence was higher in T2DM patients (27.8%) than in T1DM patients (20.6 %), p = .02. Patients with CAN were older and had a longer duration of diabetes, higher systolic blood pressure, more nephropathy and retinopathy, and a higher vibration threshold.
Cardiac autonomic neuropathy is frequent in both T2DM and T1DM patients, especially in those with other late diabetes complications. Screening for CAN with the new device is feasible.
cardiovascular autonomic neuropathy; cardiovascular reflex tests; diabetes mellitus; diagnostic tests; heart rate variability
The incidence of severe hypoglycemia in type 1 diabetes has not decreased over the past decades. New treatment modalities minimizing the risk of hypoglycemic episodes and attenuating hypoglycemic cognitive dysfunction are needed. We studied if treatment with the neuroprotective hormone erythropoietin (EPO) enhances cognitive function during hypoglycemia.
Materials and Methods
Eleven patients with type 1 diabetes, hypoglycemia unawareness and recurrent severe hypoglycemia completed the study. In a double-blind, randomized, balanced, cross-over study using clamped hypoglycemia they were treated with 40,000 IU of EPO or placebo administered intravenously six days before the two experiments. Cognitive function (primary endpoint), hypoglycemic symptoms, and counter-regulatory hormonal response were recorded.
Compared with placebo, EPO treatment was associated with a significant reduction in errors in the most complex reaction time task (−4.7 (−8.1 to −1.3), p = 0.01) and a less reaction time prolongation (−66 (−117 to −16) msec, p = 0.02). EPO treatment did not change performance in other measures of cognition. Hypoglycemic symptoms, EEG-changes, and counter-regulatory hormone concentrations did not differ between EPO and placebo treatment.
In patients with type 1 diabetes and hypoglycemia unawareness, treatment with EPO is associated with a beneficial effect on cognitive function in a complex reaction time task assessing sustained attention/working memory. Hypoglycemic symptoms and hormonal responses were not changed by EPO treatment.
A large number of nondigitized electrocardiograph (ECG) strips are routinely collected in larger cohort studies such as the ADDITION study (Anglo-Danish-Dutch Study of Intensive Treatment in People with Screen-Detected Diabetes in Primary Care). These ECG strips are routinely read manually but may contain overlooked information revealing cardiac autonomic dysfunction. The aim of this study was to investigate whether clinical information may be lost using manual R wave to R wave (RR) interval measurements in the calculation of heart rate variability (HRV) in patients with type 2 diabetes mellitus (T2DM).
From the Danish part of the ADDITION study, we randomly selected 120 T2DM patients at baseline of the ADDITION study. Analysis of the ECG strips was performed using two different methods: (1) by experienced technicians using rulers and (2) by experienced technicians using a high-resolution computer-assisted method. Calculation of heart rate and time domain HRV [standard deviation of normal-to-normal RR intervals (SDNN) and root mean square of successive differences (RMSSD)] were performed with the same software.
When comparing results from the two methods, the following values of Pearson's r are obtained: 0.98 for heart rate, 0.76 for SDNN, and 0.68 for RMSSD. These results indicate that heart rate and HRV measurements by the computer-assisted and manually based methods correlate. However, Bland-Altman plots and Pitman's test of difference in variance revealed poor agreements (p < .01) for both HRV measurements (SDNN and RMSSD); only heart rate showed substantiated agreement (p = .54) between the two methods. Low HRV was statistically significantly associated to high heart rate, systolic blood pressure, and diastolic blood pressure in these screen-detected T2DM patients.
Paper ECG strips may contain overlooked clinical information on the status of autonomic function in patients with T2DM. In our study, manual measurements of RR intervals were inferior to the computer-assisted method. Based on this study, we recommend cautiousness in the clinical use and interpretation of HRV based on manual or low resolution measurements of RR intervals from ECG strips. High resolution measurements of RR intervals reveal significant associations between low HRV and high heart rate, systolic blood pressure, and diastolic blood pressure among patients with screen-detected T2DM. It is feasible to use a computer-assisted method to determine RR intervals in patients with T2DM.
autonomic dysfunction; complications; diabetes; neuropathy; risk stratification; ultra short-term HRV
Hyperglycemia plays a pivotal role in the development and progression of vascular complications, which are the major sources of morbidity and mortality in diabetes. Furthermore, these vascular complications often persist and progress despite improved glucose control, possibly as a result of prior episodes of hyperglycemia. Epigenetic modifications mediated by histone methyltransferases are associated with gene-activating events that promote enhanced expression of key proinflammatory molecules implicated in vascular injury. In this study, we investigated genetic polymorphisms of the SETD7, SUV39H1, and SUV39H2 methyltransferases as predictors of risk for micro- and macrovascular complications in type 1 diabetes.
RESEARCH DESIGN AND METHODS
In the Finnish Diabetic Nephropathy Study (FinnDiane) cohort, 37 tagging single nucleotide polymorphisms (SNPs) were genotyped in 2,991 individuals with type 1 diabetes and diabetic retinopathy, diabetic nephropathy, and cardiovascular disease. Seven SNPs were genotyped in the replication cohorts from the Steno Diabetes Center and All Ireland/Warren 3/Genetics of Kidneys in Diabetes (GoKinD) U.K. study.
In a meta-analysis, the minor T allele of the exonic SNP rs17353856 in the SUV39H2 was associated with diabetic retinopathy (genotypic odds ratio 0.75, P = 1.2 × 10−4). The same SNP showed a trend toward an association with diabetic nephropathy as well as cardiovascular disease in the FinnDiane cohort.
Our findings propose that a genetic variation in a gene coding for a histone methyltransferase is protective for a diabetic microvascular complication. The pathophysiological implications of this polymorphism or other genetic variation nearby for the vascular complications of type 1 diabetes remain to be investigated.
Diabetic kidney disease, or diabetic nephropathy (DN), is a major complication of diabetes and the leading cause of end-stage renal disease (ESRD) that requires dialysis treatment or kidney transplantation. In addition to the decrease in the quality of life, DN accounts for a large proportion of the excess mortality associated with type 1 diabetes (T1D). Whereas the degree of glycemia plays a pivotal role in DN, a subset of individuals with poorly controlled T1D do not develop DN. Furthermore, strong familial aggregation supports genetic susceptibility to DN. However, the genes and the molecular mechanisms behind the disease remain poorly understood, and current therapeutic strategies rarely result in reversal of DN. In the GEnetics of Nephropathy: an International Effort (GENIE) consortium, we have undertaken a meta-analysis of genome-wide association studies (GWAS) of T1D DN comprising ∼2.4 million single nucleotide polymorphisms (SNPs) imputed in 6,691 individuals. After additional genotyping of 41 top ranked SNPs representing 24 independent signals in 5,873 individuals, combined meta-analysis revealed association of two SNPs with ESRD: rs7583877 in the AFF3 gene (P = 1.2×10−8) and an intergenic SNP on chromosome 15q26 between the genes RGMA and MCTP2, rs12437854 (P = 2.0×10−9). Functional data suggest that AFF3 influences renal tubule fibrosis via the transforming growth factor-beta (TGF-β1) pathway. The strongest association with DN as a primary phenotype was seen for an intronic SNP in the ERBB4 gene (rs7588550, P = 2.1×10−7), a gene with type 2 diabetes DN differential expression and in the same intron as a variant with cis-eQTL expression of ERBB4. All these detected associations represent new signals in the pathogenesis of DN.
The global prevalence of diabetes has reached epidemic proportions, constituting a major health care problem worldwide. Diabetic kidney disease, or diabetic nephropathy (DN)—the major long term microvascular complication of diabetes—is associated with excess mortality among patients with type 1 diabetes. Even though DN has been shown to cluster in families, the underlying genetic and molecular pathways remain poorly defined. We have undertaken the largest genome-wide association study and meta-analysis to date on DN and on its most severe form of kidney disease, end-stage renal disease (ESRD). We identified new loci significantly associated with diabetic ESRD: AFF3 and an intergenic locus on chromosome 15q26 residing between RGMA and MCTP2. Our functional analyses suggest that AFF3 influences renal tubule fibrosis, a pathological hallmark of severe DN. Another locus in ERBB4 was suggestively associated with DN and resides in the same intronic region as a variant affecting the expression of ERBB4. Subsequent pathway analysis of the genes co-expressed with ERBB4 indicated involvement of fibrosis.
Severe hypoglycaemia still represents a significant problem in insulin-treated diabetes. Most patients do not experience severe hypoglycaemia often. However, 20% of patients with type 1 diabetes experience recurrent severe hypoglycaemia corresponding to at least two episodes per year. The effect of insulin analogues on glycaemic control has been documented in large trials, while their effect on the frequency of severe hypoglycaemia is less clear, especially in patients with recurrent severe hypoglycaemia. The HypoAna Trial is designed to investigate whether short-acting and long-acting insulin analogues in comparison with human insulin are superior in reducing the occurrence of severe hypoglycaemic episodes in patients with recurrent hypoglycaemia. This paper reports the study design of the HypoAna Trial.
The study is a Danish two-year investigator-initiated, prospective, randomised, open, blinded endpoint (PROBE), multicentre, cross-over trial investigating the effect of insulin analogues versus human insulin on the frequency of severe hypoglycaemia in subjects with type 1 diabetes. Patients are randomised to treatment with basal-bolus therapy with insulin detemir / insulin aspart or human NPH insulin / human regular insulin in random order. The major inclusion criterion is history of two or more episodes of severe hypoglycaemia in the preceding year.
In contrast to almost all other studies in this field the HypoAna Trial includes only patients with major problems with hypoglycaemia. The HypoAna Trial will elucidate whether basal-bolus regimen with short-acting and long-acting insulin analogues in comparison with human insulin are superior in reducing occurrence of severe hypoglycaemic episodes in hypoglycaemia prone patients with type 1 diabetes. http://www.clinicaltrials.gov: NCT00346996.
Type 1 diabetes; Severe hypoglycaemia; Human insulin; Insulin analogues; PROBE
To investigate the associations of plasma levels of advanced glycation end products (AGEs) with incident cardiovascular disease (CVD) and all-cause mortality in type 1 diabetes and the extent to which any such associations could be explained by endothelial and renal dysfunction, low-grade inflammation, and arterial stiffness.
RESEARCH DESIGN AND METHODS
We prospectively followed 169 individuals with diabetic nephropathy and 170 individuals with persistent normoalbuminuria who were free of CVD at study entry and in whom levels of Nε-(carboxymethyl)lysine, Nε-(carboxyethyl)lysine, pentosidine and other biomarkers were measured at baseline. The median follow-up duration was 12.3 (interquartile range 7.6–12.5) years.
During the course of follow-up, 82 individuals (24.2%) died; 85 (25.1%) suffered a fatal (n = 48) and/or nonfatal (n = 53) CVD event. The incidence of fatal and nonfatal CVD and of all-cause mortality increased with higher baseline levels of AGEs independently of traditional CVD risk factors: hazard ratio (HR) = 1.30 (95% CI = 1.03–1.66) and HR = 1.27 (1.00–1.62), respectively. These associations were not attenuated after further adjustments for markers of renal or endothelial dysfunction, low-grade inflammation, or arterial stiffness.
Higher levels of AGEs are associated with incident fatal and nonfatal CVD as well as all-cause mortality in individuals with type 1 diabetes, independently of other risk factors and of several potential AGEs-related pathophysiological mechanisms. Thus, AGEs may explain, in part, the increased cardiovascular disease and mortality attributable to type 1 diabetes and constitute a specific target for treatment in these patients.
Plasma osteoprotegerin (OPG) is an emerging strong and independent predictor of cardiovascular disease (CVD) in high-risk populations. OPG is a bone-related glycopeptide produced by vascular smooth muscle cells, and increased plasma OPG levels may reflect arterial vascular damage. We aimed to investigate the prognostic value of OPG in relation to all-cause and cardiovascular mortality in a cohort of type 2 diabetic patients.
RESEARCH DESIGN AND METHODS
In a prospective observational follow-up study, 283 type 2 diabetic patients (172 men; aged 53.9 ± 8.8 years) were followed for a median of 16.8 years (range 0.2–23.0). Baseline plasma OPG concentrations were determined by immunoassay.
During follow-up, 193 (68%) patients died. High versus low levels of OPG predicted all-cause mortality (covariate-adjusted for urinary albumin excretion rate [UAER], estimated glomerular filtration rate, and conventional risk factors); hazard ratio (HR) 1.81 [95% CI 1.21–2.69]. The all-cause predictive effect of OPG was independent of NH2-terminal pro-brain natriuretic peptide (NT-proBNP) and was also useful within groups divided according to level of UAER. In total, 103 (73%) patients died because of CVD. High and medium versus low levels of OPG predicted cardiovascular mortality (unadjusted HR 1.86 [95% CI 1.07–3.23] and 3.51 [2.10–5.85], respectively). However, after adjustment for the covariates, HRs were no longer significant.
Elevated plasma OPG is a strong predictor of all-cause mortality in type 2 diabetic patients. The effect of OPG on all-cause mortality was independent of conventional cardiovascular risk factors, UAER, and NT-proBNP levels.
To evaluate vitamin D as a predictor of all-cause and cardiovascular mortality and risk of progression to micro- or macroalbuminuria in type 2 diabetic patients.
RESEARCH DESIGN AND METHODS
In a longitudinal observational follow-up study, 289 type 2 diabetic patients with normoalbuminuria (n = 172), microalbuminuria (n = 73), and macroalbuminuria (n = 44) at baseline were followed for a median (range) of 15.0 (0.2–23) years. Mean ± SD age was 54 ± 9 years. Plasma 25-hydroxyvitamin D3 levels were determined by high-performance liquid chromatography/tandem mass spectrometry on baseline samples. Severe vitamin D deficiency was defined as the lower 10th percentile (<13.9 nmol/l).
Median (range) vitamin D level was 35.7 (5–136.7) nmol/l. Vitamin D levels were not associated with age, sex, estimated glomerular filtration rate, urinary albumin excretion rate (UAER), or A1C at baseline, but low levels were weakly associated with elevated systolic blood pressure (R = 0.13, P = 0.03). During follow-up, 196 (68%) patients died. All-cause mortality was increased in patients with severe vitamin D deficiency (hazard ratio 1.96 [95% CI 1.29–2.98]). The association persisted after adjustment for UAER, A1C, diabetes duration, and conventional cardiovascular risk factors (2.03 [1.31–3.13]). Severe vitamin D deficiency was associated with increased cardiovascular mortality (1.95 [1.11–3.44]), and the association persisted after adjustment (1.90 [1.15–3.10]). Severe vitamin D deficiency at baseline did not predict progression to micro- or macroalbuminuria.
In type 2 diabetic patients, severe vitamin D deficiency predicts increased risk of all-cause and cardiovascular mortality, independent of UAER and conventional cardiovascular risk factors. Whether vitamin D substitution improves prognosis remains to be investigated.
Diabetic nephropathy (DN) affects about 30% of patients with type 1 diabetes (T1D) and contributes to serious morbidity and mortality. So far only the 3q21–q25 region has repeatedly been indicated as a susceptibility region for DN. The aim of this study was to search for new DN susceptibility loci in Finnish, Danish and French T1D families.
Methods and Results
We performed a genome-wide linkage study using 384 microsatellite markers. A total of 175 T1D families were studied, of which 94 originated from Finland, 46 from Denmark and 35 from France. The whole sample set consisted of 556 individuals including 42 sib-pairs concordant and 84 sib-pairs discordant for DN. Two-point and multi-point non-parametric linkage analyses were performed using the Analyze package and the MERLIN software. A novel DN locus on 22q11 was identified in the joint analysis of the Finnish, Danish and French families by genome-wide multipoint non-parametric linkage analysis using the Kong and Cox linear model (NPLpairs LOD score 3.58). Nominal or suggestive evidence of linkage to this locus was also detected when the three populations were analyzed separately. Suggestive evidence of linkage was found to six additional loci in the Finnish and French sample sets.
This study identified a novel DN locus at chromosome 22q11 with significant evidence of linkage to DN. Our results suggest that this locus may be of importance in European populations. In addition, this study supports previously indicated DN loci on 3q21–q25 and 19q13.
To investigate the associations of plasma levels of soluble receptor for advanced glycation end products (sRAGE) with incident cardiovascular disease (CVD) and all-cause mortality in type 1 diabetes and the extent to which any such associations could be explained by endothelial and renal dysfunction, low-grade inflammation, arterial stiffness, and advanced glycation end products (AGEs).
RESEARCH DESIGN AND METHODS
We prospectively followed 169 individuals with diabetic nephropathy and 170 individuals with persistent normoalbuminuria who were free of CVD at study entry and in whom levels of sRAGE and other biomarkers were measured at baseline. The median follow-up duration was 12.3 years (7.6–12.5).
The incidence of fatal and nonfatal CVD and all-cause mortality increased with higher baseline levels of log-transformed sRAGE (Ln-sRAGE) independently of other CVD risk factors: hazard ratio (HR) 1.90 (95% CI 1.13–3.21) and 2.12 (1.26–3.57) per 1-unit increase in Ln-sRAGE, respectively. Adjustments for estimated glomerular filtration rate (eGFRMDRD), but not or to a smaller extent for markers of endothelial dysfunction, low-grade inflammation, arterial stiffness, and AGEs, attenuated these associations to HR 1.59 (95% CI 0.91–2.77) for fatal and nonfatal CVD events and to 1.90 (1.09–3.31) for all-cause mortality. In addition, in patients with nephropathy, the rate of decline of GFR was 1.38 ml/min/1.73 m2 per year greater per 1-unit increase of Ln-sRAGE at baseline (P = 0.036).
Higher levels of sRAGE are associated with incident fatal and nonfatal CVD and all-cause mortality in individuals with type 1 diabetes. sRAGE-associated renal dysfunction may partially explain this association.
Growth deferentiation factor-15 (GDF-15) is involved in inflammation and apoptosis. Expression is induced in the heart in response to ischemia and in atherosclerotic plaques. The aim of this study was to investigate GDF-15 levels in relation to all-cause mortality, cardiovascular mortality and morbidity, decline in glomerular filtration rate (GFR), and progression toward end-stage renal disease (ESRD).
RESEARCH DESIGN AND METHODS
The study was a prospective observational follow-up study including 451 type 1 diabetic patients with diabetic nephropathy (274 men, aged 42.1 ± 0.5 years [means ± SD], diabetes duration 28.3 ± 8.9 years, GFR 76 ± 33 ml/min/1.73 m2) and a control group of 440 patients with longstanding type 1 diabetes and persistent normoalbuminuria (232 men, aged 45.4 ± 11.5 years, duration of diabetes 27.7 ± 10.1 years). The patients were followed for 8.1 (0.0–12.9) years (median [range]).
Among normoalbuminuric patients, GDF-15 above the median predicted an adjusted (age, systolic blood pressure [sBP], and estimated GFR) increased risk of all-cause mortality (hazard ratio [HR] 3.6 [95% CI 1.3–10.3]; P = 0.014). Among patients with diabetic nephropathy, higher (fourth quartile) versus lower (first quartile) GDF-15 levels predict all-cause mortality (covariate-adjusted [sex, age, smoking, blood pressure, A1C, cholesterol, GFR, N-terminal prohormone B-type natriuretic peptide, antihypertensive treatment, and previous cardiovascular events]; HR 4.86 [95% CI 1.37–17.30]) as well as fatal and nonfatal cardiovascular events (adjusted HR 5.59 [1.23–25.43] and 3.55 [1.08–11.64], respectively). In addition, higher GDF-15 levels predict faster decline in GFR (P < 0.001) but not development of ESRD.
Higher levels of GDF-15 are a predictor of all-cause and cardiovascular mortality and morbidity in patients with diabetic nephropathy. Furthermore, higher levels of GDF-15 are associated with faster deterioration of kidney function.
The -945GC polymorphism (rs6918698) in the connective tissue growth factor gene promoter (CTGF/CCN-2) has been associated with end organ damage in systemic sclerosis. Because CTGF is important in progression of diabetic kidney disease, we investigated whether the -945GC polymorphism is associated with plasma CTGF level and outcome in type 1 diabetes.
The study cohort consisted of 448 diabetic nephropathy patients and 419 normoalbuminuric diabetic patients with complete data concerning renal function and cardiovascular characteristics. Genomic DNA was genotyped by a QPCR-based SNP assay. We observed no relation between the -945GC polymorphism and plasma CTGF level, and the genotype frequencies were not different in nephropathy patients vs. normoalbuminuric controls. General and cardiovascular mortality, and renal function decline was similar in patients with CC, CG or GG genotypes.
In conclusion, the -945GC SNP does not affect plasma CTGF levels, incidence and prognosis of diabetic nephropathy, and cardiovascular outcome.
As part of a clinical proteomics programme focused on diabetes and its complications, it was our goal to investigate the proteome of plasma in order to find improved candidate biomarkers to predict diabetic nephropathy.
Proteins derived from plasma from a cross-sectional cohort of 123 type 1 diabetic patients previously diagnosed as normoalbuminuric, microalbuminuric or macroalbuminuric were enriched with hexapeptide library beads and subsequently pooled within three groups. Proteins from the three groups were compared by online liquid chromatography and tandem mass spectrometry in three identical repetitions using isobaric mass tags (iTRAQ). The results were further analysed with ingenuity pathway analysis. Levels of apolipoprotein A1, A2, B, C3, E and J were analysed and validated by a multiplex immunoassay in 20 type 1 diabetic patients with macroalbuminuria and 10 with normoalbuminuria.
A total of 112 proteins were identified in at least two out of three replicates. The global protein ratios were further evaluated by ingenuity pathway analysis, resulting in the recognition of apolipoprotein A2, B, C3, D and E as key nodes in the top-rated network. The multiplex immunoassay confirmed the overall protein expression patterns observed by the iTRAQ analysis.
The candidate biomarkers discovered in this cross-sectional cohort may turn out to be progression biomarkers and might have several clinical applications in the treatment and monitoring of diabetic nephropathy; however, they need to be confirmed in a longitudinal cohort.
Electronic supplementary material
The online version of this article (doi:10.1007/s12014-010-9053-0) contains supplementary material, which is available to authorized users.
Quantitative proteomics; Diabetic nephropathy; iTRAQ; Protein networks; Pathway analysis; Multiplex immunoassay technology
We studied tubular and glomerular damage in type 1 diabetic patients by measuring urinary–liver fatty acid binding protein (U-LFABP) and albuminuria. Subsequently, we evaluated the effect of ACE inhibition on U-LFABP in patients with diabetic nephropathy.
RESEARCH DESIGN AND METHODS
We studied Caucasians with type 1 diabetes: 58 with normoalbuminuria (urinary albumin <30 mg/24 h), 45 with persistent microalbuminuria (30–300 mg/24 h), and 45 with persistent macroalbuminuria (≥300 mg/24 h). A control group consisted of 57 healthy individuals. The groups were matched by sex and duration of diabetes. In addition, U-LFABP was measured in 48 type 1 diabetic patients with diabetic nephropathy in a randomized crossover trial consisting of 2 months of treatment with 20, 40, and 60 mg lisinopril once daily in random order.
In the cross-sectional study, levels of U-LFABP were significantly higher in normoalbuminuric patients versus those in the control group (median 2.6 [interquartile range 1.3–4.1] vs. 19 [0.8–3.0] μg/g creatinine, P = 0.02) and increased with increasing levels of albuminuria (microalbuminuric group 4.2 [1.8–8.3] μg/g creatinine and nephropathy group 71.2 [8.1–123.4], P < 0.05 for all comparisons). U-LFABP correlates with the urinary albumin-to-creatinine ratio (R2 = 0.54, P < 0.001). In the intervention study, all doses of lisinopril significantly reduced urinary albumin excretion rate and U-LFABP from baseline. The reductions in U-LFABP were 43, 46, and 40% with increasing doses of lisinopril (NS).
An early and progressive increase in tubulointerstitial damage as reflected by increased U-LFABP levels occurs in type 1 diabetic patients and is associated with albuminuria. Furthermore, ACE inhibition reduces the tubular and glomerular damage and dysfunction.
The use of carotid intima-media thickness (carotid IMT) as a surrogate marker of cardiovascular disease is increasing and the method has now also been applied in several trials investigating patients with type 2 diabetes (T2D). Even though knowledge about methodology is of highest importance in order to make accurate power calculations and analyses of results, no reproducibility studies have been performed in this group of patients. The aim of this study was to quantify the variability of the measurement of carotid IMT in individuals with and without T2D.
We used B-mode ultrasound and a computerized software programme (MIA vascular tools) for analysis of carotid IMT. Measurement of carotid IMT in the far wall of the common carotid artery (CCA) was done for 30 patients with T2D and 30 persons without T2D. The examinations were done by two different sonographers and two different readers on two separate days in order to quantify sonographer-, reader-, and day-to-day variability.
Comparisons of measurement of carotid IMT in CCA between sonographers (sonographer variability) resulted in limits of agreement (LoA) from -0.18 to 0.13 mm for patients with T2D and -0.12 to 0.10 mm for persons without T2D. This means, that a second scanning of the same person with 95% probability would be within this interval of the first scanning. Comparisons between readers assessing the same scanning (reader variability) resulted in LoA from -0.05 to 0.07 mm and -0.04 to 0.05 mm respectively. LoA of the day-to-day variability was -0.13 to 0.18 mm and -0.09 to 0.18 mm respectively. This corresponds to coefficients of variations (CV) of the sonographer- and day-to-day variability of 10% in patients with T2D and 8% in persons without T2D. The CV of the reader variability was 4% and 3% respectively.
Measurement of carotid IMT in the CCA can be determined with good and comparable reproducibility in both patients with T2D and persons without T2D. These findings support the use of carotid IMT in clinical trials with T2D patients and suggest that the numbers of patients needed to detect a given difference will be the same whether the patients have T2D or not.
Experimental and clinical studies have suggested that uric acid may contribute to the development of hypertension and kidney disease. Whether uric acid has a causal role in the development of diabetic nephropathy is not known. The objective of the present study is to evaluate uric acid as a predictor of persistent micro- and macroalbuminuria.
RESEARCH DESIGN AND METHODS
This prospective observational follow-up study consisted of an inception cohort of 277 patients followed from onset of type 1 diabetes. Of these, 270 patients had blood samples taken at baseline. In seven cases, uric acid could not be determined; therefore, 263 patients (156 men) were available for analysis. Uric acid was measured 3 years after onset of diabetes and before any patient developed microalbuminuria.
During a median follow-up of 18.1 years (range 1.0–21.8), 23 of 263 patients developed persistent macroalbuminuria (urinary albumin excretion rate >300 mg/24 h in at least two of three consecutive samples). In patients with uric acid levels in the highest quartile (>249 μmol/l), the cumulative incidence of persistent macroalbumnuria was 22.3% (95% CI 10.3–34.3) compared with 9.5% (3.8–15.2) in patients with uric acid in the three lower quartiles (log-rank test, P = 0.006). In a Cox proportional hazards model with sex and age as fixed covariates, uric acid was associated with subsequent development of persistent macroalbuminuria (hazard ratio 2.37 [95% CI 1.04–5.37] per 100 μmol/l increase in uric acid level; P = 0.04). Adjustment for confounders did not change the estimate significantly.
Uric acid level soon after onset of type 1 diabetes is independently associated with risk for later development of diabetic nephropathy.
It has been suggested that genetic susceptibility plays an important role in the pathogenesis of diabetic nephropathy. A large-scale genotyping analysis of gene-based single nucleotide polymorphisms (SNPs) in Japanese patients with type 2 diabetes identified the gene encoding acetyl-coenzyme A carboxylase beta (ACACB) as a candidate for a susceptibility to diabetic nephropathy; the landmark SNP was found in the intron 18 of ACACB (rs2268388: intron 18 +4139 C > T, p = 1.4×10−6, odds ratio = 1.61, 95% confidence interval [CI]: 1.33–1.96). The association of this SNP with diabetic nephropathy was examined in 9 independent studies (4 from Japan including the original study, one Singaporean, one Korean, and two European) with type 2 diabetes. One case-control study involving European patients with type 1 diabetes was included. The frequency of the T allele for SNP rs2268388 was consistently higher among patients with type 2 diabetes and proteinuria. A meta-analysis revealed that rs2268388 was significantly associated with proteinuria in Japanese patients with type 2 diabetes (p = 5.35×10−8, odds ratio = 1.61, 95% Cl: 1.35–1.91). Rs2268388 was also associated with type 2 diabetes–associated end-stage renal disease (ESRD) in European Americans (p = 6×10−4, odds ratio = 1.61, 95% Cl: 1.22–2.13). Significant association was not detected between this SNP and nephropathy in those with type 1 diabetes. A subsequent in vitro functional analysis revealed that a 29-bp DNA fragment, including rs2268388, had significant enhancer activity in cultured human renal proximal tubular epithelial cells. Fragments corresponding to the disease susceptibility allele (T) had higher enhancer activity than those of the major allele. These results suggest that ACACB is a strong candidate for conferring susceptibility for proteinuria in patients with type 2 diabetes.
Although cumulative epidemiological findings have suggested that genetic susceptibility plays an important role in the pathogenesis of diabetic nephropathy, no gene conferring susceptibility to diabetic nephropathy has been definitively identified. In a large-scale association study of 1,312 Japanese subjects with type 2 diabetes using SNPs from a Japanese SNP database, we show that the T-allele of ACACB rs2268388 is associated with diabetic nephropathy. We also show that the association is consistently observed in patients with type 2 diabetes and proteinuria across different ethnic groups, including populations of European descent. Because a DNA fragment corresponding to the disease susceptibility allele is shown to have higher enhancer activity, we hypothesize that the increase in the expression and/or activity of the encoded acetyl-coenzyme A carboxylase beta contributes to the development and progression of diabetic nephropathy. Our present analysis provides novel insight into the pathogenesis of diabetic nephropathy. This finding is important because diabetic nephropathy is a leading cause of end-stage renal disease and affects life expectancy in subjects with type 2 diabetes.
As part of a clinical proteomics program focused on diabetes and its complications we are looking for new and better protein biomarkers for diabetic nephropathy. The search for new and better biomarkers for diabetic nephropathy has, with a few exceptions, previously focused on either hypothesis-driven studies or urinary based investigations. To date only two studies have investigated the proteome of blood in search for new biomarkers, and these studies were conducted in sera from patients with type 2 diabetes. This is the first reported in depth proteomic study where plasma from type 1 diabetic patients was investigated with the goal of finding improved candidate biomarkers to predict diabetic nephropathy. In order to reach lower concentration proteins in plasma a pre-fractionation step, either hexapeptide bead-based libraries or anion exchange chromatography, was performed prior to surface enhanced laser desorption/ionization time-of-flight mass spectrometry analysis.
Proteomic analysis of plasma from a cross-sectional cohort of 123 type 1 diabetic patients previously diagnosed as normoalbuminuric, microalbuminuric or macroalbuminuric, gave rise to 290 peaks clusters of which 16 were selected as the most promising biomarker candidates based on statistical performance, including independent component analysis. Four of the peaks that were discovered have been identified as transthyretin, apolipoprotein A1, apolipoprotein C1 and cystatin C. Several yet unidentified proteins discovered by this novel approach appear to have more potential as biomarkers for diabetic nephropathy.
These results demonstrate the capacity of proteomic analysis of plasma, by confirming the presence of known biomarkers as well as revealing new biomarkers for diabetic nephropathy in plasma in type 1 diabetic patients.