A practical method to measure GFR in people with type 1 diabetes

Evaluation of the diagnostic performance of the creatinine-based Chronic Kidney Disease Epidemiology Collaboration equation in people with diabetes: A systematic review

AIMS

GFR estimated with the creatinine-based Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI_Cr ) equation is used to screen for diabetic kidney disease and assess its severity. We systematically reviewed the process and outcome of evaluating CKD-EPI_Cr in estimating point GFR or GFR decline over time in adults with type 1 or type 2 diabetes.

METHODS

In this systematic review, MEDLINE, Embase and Cochrane Central Register of Controlled Trials were searched up to August 2019. Observational studies comparing CKD-EPI_Cr with measured GFR (mGFR) in adults with diabetes were included. Studies on people with kidney transplant, non-diabetes related kidney disease, pregnancy, potential kidney donors, and those with critical or other systematic illnesses were excluded. Two independent reviewers extracted data from published papers and disagreements were resolved by consensus. Risk-of-bias was assessed using the Quality Assessment of Diagnostic Accuracy Studies-2 tool. (PROSPERO registration number: CRD42018108776).

RESULTS

From the 2820 records identified, 29 studies (14 704 participants) were included. All studies were at risk of bias. Bias (eight different forms) ranged from -26 to 35 ml min^-1  1.73 m^-2 ; precision (five different forms) ranged between 9 and 63 ml min^-1  1.73 m^-2 ; accuracy (five different forms) ranged between 16% and 96%; the correlation coefficient between CKD-EPI_Cr and mGFR (four different forms) ranged between 0.38 and 0.86; and the reduced major axis regression slope ranged between 0.8 and 1.8.

CONCLUSIONS

Qualitative synthesis of data suggested CKD-EPI_Cr was inaccurate in estimating point GFR or GFR decline over time. Furthermore, a lack of consistency in the methods and processes of evaluating the diagnostic performance of CKD-EPI_Cr limits reliable quantitative assessment. The equation needs to be improved in adults with diabetes.

Estimating glomerular filtration rate in youth with obesity and type 2 diabetes: the iCARE study equation

BACKGROUND

The validity of pediatric estimated glomerular filtration rate equations (eGFRs) in early stages of CKD including hyperfiltration is unknown. The purpose of this study was to develop an eGFR equation for adolescents with obesity and type 2 diabetes (T2D).

METHODS

eGFRs were developed from iohexol-derived GFRs (iGFRs) in 26 overweight/obese (BMI > 85th percentile) youth and 100 with T2D from the iCARE (Improving renal Complications in Adolescents with T2D through REsearch) cohort. Twenty percent of the cohort was withheld as a validation dataset. Linear regression analyses were used to develop the best formula based on body size, sex, creatinine, urea, ± cystatin C. Comparable validity of commonly used eGFR equations was assessed.

RESULTS

Mean age 15.4 + 2.4 years, BMI Z-score 2.5 + 1.2, 61% female, and mean iGFR 129.0 + 27.7 ml/min/ 1.73 m². The best adjusted eGFR formula (ml/min/1.73 m²) was 50.7 × BSA^0.816 × (height (cm)/creatinine)^0.405 × 0.8994 if sex = female | 1 otherwise. It resulted in 53.8% of eGFRs within 10% of measured iGFR and 96.2% within 30%. Bland-Altman 95% limits of agreement in the external dataset were - 37.6 to 45.5 ml/min/1.73m² (bias = 3.96), and the correlation was 0.62. This equation performed better than all previously published creatinine-based eGFRs. cystatin C did not significantly improve results; however, some other cystatin C formulas also performed well.

CONCLUSIONS

The iCARE equation provides a more accurate creatinine-based eGFR in obese youth with and without T2D. Further studies are warranted to evaluate within-subject variability and applicability to lower GFRs and other populations.

Determination of iohexol by capillary blood microsampling and UHPLC-MS/MS

One of the most important tools used to evaluate kidney function in the context of chronic kidney disease or other renal function related pathologies is the exploration of glomerular filtration rate (GFR). Iohexol is up to this moment a good candidate molecule for the GFR assessment since it exhibits minimum protein binding rates and minimum extra-renal clearance, being neither secreted nor reabsorbed at the tubular level. This study proposes and evaluates a new LC-MS/MS method for the iohexol determination from capillary blood, prelevated using volumetric absorbative microsampling (VAMS) systems. As an alternative to VAMS, a brand new HemaPEN^® device for micro-prelevation was also tested. A new high throughput sample preparation protocol adapted for iohexol quantification from whole blood VAMS samples was developed. The medium term stability study of iohexol in dried whole blood VAMS samples that was conducted showed a good stability of this molecule for up to 12 days. By collecting only 10 μL of blood, iohexol can be analyzed from dried whole blood VAMS samples for concentration ranges between 1 and 250 μg/mL. Due to the analyte stability in VAMS for up to 12 days, this approach might be successfully applied for GFR assessment for clinical cases allowing minimum invasiveness and even delayed analysis.

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Successful VAMS-based bioanalytical method for iohexol analysis in whole human blood.

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Proven medium term stability of iohexol in VAMS samples.

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HemaPens as a promising alternative for iohexol analysis using only 2.74 μL of blood.

Performance of Cystatin C-Based Equations for Estimation of Glomerular Filtration Rate in Diabetes Patients: A Prisma-Compliant Systematic Review and Meta-Analysis

The accuracy of estimated glomerular filtration rate (eGFR) equations in diabetes mellitus (DM) patients has been extensively questioned. We evaluated the performance of cystatin C-based equations alone or in combination with creatinine to estimate GFR in DM patients. A PRISMA-compliant systematic review was performed in the MEDLINE and Embase databases, with “diabetes mellitus” and “cystatin C” as search terms. Studies comparing cystatin C-based eGFR equations with measured GFR (mGFR) in DM patients were eligible. Accuracies P10, P15, P20, and P30 indicated the proportion of eGFR results within 10, 15, 20, and 30% of mGFR. Single-arm meta-analyses were conducted, and the Quality of Diagnostic Accuracy Studies-II tool (QUADAS-2) was applied. Twenty-three studies comprising 7065 participants were included, and 24 equations were analyzed in a broad range of GFRs. Meta-analyses were completed for 10 equations. The mean P30 accuracies of the equations ranged from 41% to 87%, with the highest values found with both CKD-EPI equations. Mean P10-P15 achieved 35% in the best scenario. A sensitivity analysis to evaluate different mGFR methods did not change results. In conclusion, cystatin C-based eGFR equations represent measured GFR fairly at best in DM patients, with high variability among the several proposed equations.

Dynamic changes in retinal vessel diameter during acute hyperglycemia in type 1 diabetes

AIMS

To investigate changes in retinal vessel diameter during acute hyperglycemia in patients with type 1 diabetes.

METHODS

We conducted a study on 11 subjects with type 1 diabetes. Euglycemia was maintained for 3h followed by induction of hyperglycemia and simultaneous bolus of rapid acting insulin. Two fundus photos were captured during euglycemia and five fundus photos, blood glucose and blood pressure were taken every 30min for 2.5h post-prandial. Central retinal artery equivalent (CRAE) and central retinal vein equivalent (CRVE) were measured over the study visit and examined using generalized linear mixed models.

RESULTS

In a multivariate mixed model, mean CRAE and CRVE were reduced at 90min post-prandial in both zones B and C. In repeated measures analysis, arterioles exhibited a significant association with change in vessel caliber per change in blood glucose. Inconsistent effects of blood pressure on vessel diameter were also measured.

CONCLUSIONS

We document a change in retinal vessel diameter during acute hyperglycemia in persons with type 1 diabetes. Larger controlled studies are required to further investigate this phenomenon and to more accurately assess if hyperglycemia has direct effects on retinal vessel diameter.

Measured GFR in Routine Clinical Practice-The Promise of Dried Blood Spots

Accurate determination of glomerular filtration rate (GFR) is crucial for the diagnosis of kidney disease. Estimated GFR (eGFR) calculated by serum creatinine and/or cystatin C is a mainstay in clinical practice and epidemiologic research but lacks precision and accuracy until GFR <60 mL/min/1.73 m². Furthermore, eGFR may not precisely and accurately represent changes in GFR longitudinally. The lack of precision and accuracy is of concern in populations at high risk for kidney disease, as the dissociation between changes in eGFR and GFR may lead to missed diagnoses of early kidney disease. Therefore, improved methods to quantify GFR are needed. Whereas direct measures of GFR have been too cumbersome for screening and ambulatory care, a practical method of measuring GFR by iohexol clearance using dried capillary blood spots exists. In this review, we examine the current literature and data addressing GFR measurements by dried capillary blood spots and its potential application in high-risk groups.

Predictors of early renal function decline in adults with Type 1 diabetes: the Coronary Artery Calcification in Type 1 Diabetes and the Pittsburgh Epidemiology of Diabetes Complications studies

AIM

Diabetic kidney disease is one of the leading complications of Type 1 diabetes, but its prediction remains a challenge. We examined predictors of rapid decline in estimated GFR (eGFR) in two Type 1 diabetes cohorts: the Coronary Artery Calcification in Type 1 Diabetes (CACTI) and the Pittsburgh Epidemiology of Diabetes Complications (EDC).

METHODS

A select subset of participants (CACTI: n = 210 and EDC: n = 98) diagnosed before 17 years of age with Type 1 diabetes duration ≥ 7 years, and follow-up data on eGFR by CKD-EPI creatinine for up to 8 years were included in the analyses. Early renal function decline was defined as annual decline in eGFR ≥ 3 ml/min/1.73 m² , and normal age-related decline as eGFR ≤ 1 ml/min/1.73 m² . Parallel logistic regression models were constructed in the two cohorts.

RESULTS

Early renal function decline incidence was 36% in CACTI and 41% in EDC. In both cohorts, greater baseline eGFR (CACTI: OR 3.12, 95% CI 1.97-5.05; EDC: OR 1.92, 95% CI 1.17-3.15 per 10 ml/min/1.73 m² ) and log albumin-to-creatinine (ACR) (CACTI: OR 3.24, 95% CI 1.80-5.83; EDC: OR 1.87, 95% CI 1.18-2.96 per 1 unit) predicted greater odds of early renal function decline in fully adjusted models. Conversely, ACE inhibition predicted lower odds of early renal function decline in women in CACTI, but similar relationships were not observed in women in EDC.

CONCLUSIONS

A substantial proportion of people with Type 1 diabetes in the EDC and CACTI cohorts experienced early renal function decline over time. ACE inhibition appeared to be protective only in women in CACTI where the prevalence of its use was twofold higher compared with the EDC.

Evaluation of various equations for estimating renal function in elderly Chinese patients with type 2 diabetes mellitus

BACKGROUND

The clinical assessment of kidney function based on the estimated glomerular filtration rate (GFR) in older patients remains controversial. This study evaluated the concordance and feasibility of using various creatinine-based equations for estimating GFR in elderly Chinese patients with type 2 diabetes mellitus (T2DM).

METHODS

A cross-sectional analytical study was conducted in 21,723 older diabetic patients (≥60 years) based on electronic health records (EHR) for Minhang District, Shanghai, China. The concordance of chronic kidney disease (CKD) classification among different creatinine-based equations was assessed based on Kappa values, intraclass correlation coefficient (ICC) statistics, and the eGFR agreement between the equations was tested using Bland-Altman plots. The GFR was estimated using the Cockcroft-Gault (CG), Berlin Initiative Study 1 (BIS1), simplified Modification of Diet in Renal Disease (MDRD), MDRD modified for Chinese populations (mMDRD), chronic kidney disease epidemiology collaboration (CKD-EPI), CKD-EPI in Asians (CKD-EPI-Asia), and Ruijin equations.

RESULTS

Overall, the proportion of CKD stages 3-5 (eGFR <60 mL/min/1.73 m²) was calculated as 28.9%, 39.1%, 11.8%, 8.4%, 14.3%, 11.5%, and 12.7% by the eGFR_CG, eGFR_BIS1, eGFR_MDRD, e_GFRmMDRD, e_GFRCKD-EPI, e_{GFRCKD-EPI-Asia}, and e_GFRRuijin equations, respectively. The concordance of albuminuria and decreased eGFR based on the different equations was poor by both the Kappa (<0.2) and ICC (<0.4) statistics. The CKD-EPI-Asia equation resulted in excellent concordance with the CKD-EPI (ICC =0.931), MDRD (ICC =0.963), mMDRD (ICC =0.892), and Ruijin (ICC =0.956) equations for the classification of CKD stages, whereas the BIS1 equation exhibited good concordance with the CG equation (ICC =0.809). In addition, significant differences were observed for CKD stage 1 among all these equations.

CONCLUSION

Accurate GFR values are difficult to estimate using creatinine-based equations in older diabetic patients. Kidney function is complex, and the staff need to be aware of the individualized consideration of other risk factors or markers of reduced renal function in clinical practice.

Establishing the presence or absence of chronic kidney disease: Uses and limitations of formulas estimating the glomerular filtration rate

The development of formulas estimating glomerular filtration rate (eGFR) from serum creatinine and cystatin C and accounting for certain variables affecting the production rate of these biomarkers, including ethnicity, gender and age, has led to the current scheme of diagnosing and staging chronic kidney disease (CKD), which is based on eGFR values and albuminuria. This scheme has been applied extensively in various populations and has led to the current estimates of prevalence of CKD. In addition, this scheme is applied in clinical studies evaluating the risks of CKD and the efficacy of various interventions directed towards improving its course. Disagreements between creatinine-based and cystatin-based eGFR values and between eGFR values and measured GFR have been reported in various cohorts. These disagreements are the consequence of variations in the rate of production and in factors, other than GFR, affecting the rate of removal of creatinine and cystatin C. The disagreements create limitations for all eGFR formulas developed so far. The main limitations are low sensitivity in detecting early CKD in several subjects, e.g., those with hyperfiltration, and poor prediction of the course of CKD. Research efforts in CKD are currently directed towards identification of biomarkers that are better indices of GFR than the current biomarkers and, particularly, biomarkers of early renal tissue injury.

Serum cystatin C in youth with diabetes: The SEARCH for diabetes in youth study

AIMS

We compared cystatin C in youth with versus without diabetes and determined factors associated with cystatin C in youth with type 1 diabetes (T1D) and type 2 diabetes (T2D).

METHODS

Youth (ages 12-19years) without diabetes (N=544) were ascertained from the NHANES Study 2000-2002 and those with T1D (N=977) and T2D (N=168) from the SEARCH for Diabetes in Youth Study. Adjusted means of cystatin C concentrations were compared amongst the 3 groups. Next, we performed multivariable analyses within the T1D and T2D SEARCH samples to determine the association between cystatin C and race, sex, age, diabetes duration, HbA1c, fasting glucose, and BMI.

RESULTS

Adjusted cystatin C concentrations were statistically higher in NHANES (0.85mg/L) than in either the T1D (0.75mg/L) or T2D (0.70mg/L) SEARCH groups (P<0.0001). Fasting glucose was inversely related to cystatin C only in T1D (P<0.001) and BMI positively associated only in T2D (P<0.01) while HbA1c was inversely associated in both groups.

CONCLUSIONS

Cystatin C concentrations are statistically higher in youth without diabetes compared to T1D or T2D, however the clinical relevance of this difference is quite small, especially in T1D. In youth with diabetes, cystatin C varies with BMI and acute and chronic glycemic control, however their effects may be different according to diabetes type.

Adiponectin is associated with early diabetic kidney disease in adults with type 1 diabetes: A Coronary Artery Calcification in Type 1 Diabetes (CACTI) Study

OBJECTIVE

The associations between elevated adiponectin and end-stage renal disease are well recognized and thought to be at least partially explained by reduced renal clearance. Conversely, the relationship between adiponectin and early diabetic kidney disease (DKD) with preserved glomerular filtration rate (GFR), including rapid GFR decline and incident chronic kidney disease (CKD) is unclear. We hypothesized that elevated adiponectin would be associated with early DKD in adults with type 1 diabetes.

METHODS

Adults with type 1 diabetes (n=646 at baseline, n=525 at 6years) had adiponectin and renal function by estimated GFR (eGFR) by CKD-EPI creatinine and albumin-excretion rate (AER) evaluated at baseline and 6years. Linear and logistic models evaluated the associations of baseline adiponectin with AER, macroalbuminuria (AER ≥200μg/min), eGFR, CKD (<60mL/min/1.73m²) and rapid GFR decline (>3mL/min/1.73m²/year). Models adjusted for age, sex, duration, HbA1c, SBP, LDL-C and current smoking.

RESULTS

Compared to non-diabetics, adults with type 1 diabetes had significantly higher adiponectin, and the difference remained significant after adjusting for AER and/or eGFR (p<0.0001). Adiponectin at baseline was positively associated with rapid GFR decline (OR: 1.24, 95% CI 1.00-1.53), incident CKD (OR: 1.75, 1.14-2.70), and persistent macroalbuminuria and CKD (OR: 1.61, 1.10-2.36) over 6years in adjusted models. The associations also remained significant after further adjustments for CRP, estimated insulin sensitivity and ACEi/ARB therapy.

CONCLUSIONS

Adults with type 1 diabetes have higher adiponectin than their non-diabetic peers, and elevated adiponectin at baseline is independently associated with greater odds of developing early DKD over 6years.

The Gomez' equations and renal hemodynamic function in kidney disease research

Diabetic kidney disease (DKD) remains the leading cause of end-stage renal disease. A major challenge in preventing DKD is the difficulty in identifying high-risk patients at an early, pre-clinical stage. Albuminuria and eGFR as measures of renal function in DKD research and clinical practice are limited by regression of one-third of patients with microalbuminuria to normoalbuminuria and eGFR is biased and imprecise in the normal-elevated range. Moreover, existing methods that are used to assess renal function do not give detailed insight into the location of the renal hemodynamic effects of pharmacological agents at the segmental level. To gain additional information about the intrarenal circulation in-vivo in humans, mathematical equations were developed by Gomez et al in the 1950s. These equations used measurements of GFR, renal blood flow (RBF), effective renal plasma flow (ERPF), renal vascular resistance (RVR), hematocrit and serum protein to calculate afferent and efferent arteriolar resistances, glomerular hydrostatic pressure and filtration pressure. Although indirect and based on physiological assumptions, these techniques have the potential to improve researchers' ability to identify early pre-clinical changes in renal hemodynamic function in patients with a variety of conditions including DKD, thereby offering tremendous potential in mechanistic human research studies. In this review, we focus on the application of Gomez' equations and summarize the potential and limitations of this technique in DKD research. We also summarize illustrative data derived from Gomez' equations in patients with type 1 (T1D) and type 2 diabetes (T2D) and hypertension.

Iohexol plasma clearance for measuring glomerular filtration rate in clinical practice and research: a review. Part 1: How to measure glomerular filtration rate with iohexol?

While there is general agreement on the necessity to measure glomerular filtration rate (GFR) in many clinical situations, there is less agreement on the best method to achieve this purpose. As the gold standard method for GFR determination, urinary (or renal) clearance of inulin, fades into the background due to inconvenience and high cost, a diversity of filtration markers and protocols compete to replace it. In this review, we suggest that iohexol, a non-ionic contrast agent, is most suited to replace inulin as the marker of choice for GFR determination. Iohexol comes very close to fulfilling all requirements for an ideal GFR marker in terms of low extra-renal excretion, low protein binding and in being neither secreted nor reabsorbed by the kidney. In addition, iohexol is virtually non-toxic and carries a low cost. As iohexol is stable in plasma, administration and sample analysis can be separated in both space and time, allowing access to GFR determination across different settings. An external proficiency programme operated by Equalis AB, Sweden, exists for iohexol, facilitating interlaboratory comparison of results. Plasma clearance measurement is the protocol of choice as it combines a reliable GFR determination with convenience for the patient. Single-sample protocols dominate, but multiple-sample protocols may be more accurate in specific situations. In low GFRs one or more late samples should be included to improve accuracy. In patients with large oedema or ascites, urinary clearance protocols should be employed. In conclusion, plasma clearance of iohexol may well be the best candidate for a common GFR determination method.

Diabetic Kidney Disease in Adolescents With Type 2 Diabetes: New Insights and Potential Therapies

Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease (ESRD) and dialysis in the Western world. Early DKD, including microalbuminuria and renal hyperfiltration, is common in adolescents with type 2 diabetes (T2D). Furthermore, youth-onset T2D carries a higher risk of progressive DKD than adult-onset T2D of similar diabetes duration. DKD is characterized by a long clinically silent period without signs of disease. Therefore, a major challenge in preventing DKD is the difficulty in identifying high-risk T2D patients at an early stage. The Type 2 Diabetes in Adolescents and Youth (TODAY) study demonstrated a high initial prevalence that increased over time, irrespective of treatment arm. This key observation underscores the importance of discovering new therapeutic targets to supplement conventional management, in order to reduce DKD risk. In this review, we focus on early DKD in T2D and summarize potential novel biomarkers and therapeutic targets.

Update on Estimation of Kidney Function in Diabetic Kidney Disease

The American Diabetes Association recommends annual assessment of glomerular filtration rate (GFR) to screen for diabetic nephropathy. GFR is measured indirectly using markers that, ideally, are eliminated only by glomerular filtration. Measured GFR, although the gold standard, remains cumbersome and expensive. GFR is therefore routinely estimated using creatinine and/or cystatin C and clinical variables. In pediatrics, the Schwartz creatinine-based equation is most frequently used even though combined creatinine and cystatin C-based equations demonstrate stronger agreement with measured GFR. In adults, the CKD Epidemiology Collaboration (CKD-EPI) equations with creatinine and/or cystatin C are the most accurate and precise estimating equations. Despite recent advances, current estimates of GFR lack precision and accuracy before chronic kidney disease stage 3 (GFR < 60 mL/min/1.73 m(2)). There is therefore an urgent need to improve the methods for estimating and measuring GFR. In this review, we examine the current literature and data addressing measurement and estimation of GFR in diabetes.

Rapid GFR decline is associated with renal hyperfiltration and impaired GFR in adults with Type 1 diabetes

BACKGROUND

Rapid glomerular filtration rate (GFR) decline (>3 mL/min/1.73 m(2)) is an increasingly recognized high-risk diabetic nephropathy (DN) phenotype in Type 1 diabetes. Rapid GFR decline is a recognized predictor of impaired GFR (<60 mL/min/1.73 m(2)). However, the association between rapid GFR decline and renal hyperfiltration is not well described in Type 1 diabetes. We hypothesized that renal hyperfiltration (estimated glomerular filtration rate, eGFR ≥ 120 mL/min/1.73 m(2)) would predict rapid GFR decline over 6 years and that rapid GFR decline would predict impaired GFR at 6 years in adults with Type 1 diabetes.

METHODS

GFR was calculated by chronic kidney disease epidemiology (CKD-EPI) creatinine in 646 adults with Type 1 diabetes in the coronary artery calcification in Type 1 diabetes study. Logistic multivariable models were employed to investigate the relationships between renal hyperfiltration and rapid GFR decline, and rapid GFR decline and incident impaired GFR over 6 years.

RESULTS

Renal hyperfiltration predicted greater odds of rapid GFR decline over 6 years [odds ratio (OR): 5.00, 95% confidence interval (CI): 3.03-8.25, P < 0.0001] adjusting for hemoglobin A1c (HbA1c), systolic blood pressure (SBP), low-density lipoprotein cholesterol (LDL-C), sex, duration, log of albumin/creatinine ratio and estimated insulin sensitivity. Furthermore, rapid GFR decline predicted greater odds of incident impaired eGFR (OR: 15.99, 95% CI 2.34-114.37, P = 0.006) in a similarly adjusted model. Sensitivity analyses with GFR calculated by CKD-EPI combined creatinine and cystatin C, and renal hyperfiltration defined as ≥135 mL/min/1.73 m(2) yielded similar results.

CONCLUSIONS

In adults with Type 1 diabetes, rapid GFR decline over 6 years was associated with baseline renal hyperfiltration and incident GFR impairment. These observations may suggest an intermediate and predictive role of rapid GFR decline in the progression of DN.

Diabetes Complications in Childhood Diabetes-New Biomarkers and Technologies

A major challenge in preventing vascular complications in diabetes is the inability to identify high-risk patients at an early stage, emphasizing the importance of discovering new risk factors, technologies and therapeutic targets to reduce the development and progression of complications. Promising biomarkers which may improve risk stratification and serve as therapeutic targets, include: uric acid, insulin sensitivity, copeptin, SGLT-2 and Klotho/FGF-23. Non-invasive measures of macrovasuclar disease in youth, include: 1) pulse wave velocity to examine arterial stiffness; 2) carotid intima-media thickness to evaluate arterial thickness; 3) cardiac MRI to investigate cardiac function and structure. Novel microvascular measures include: GFR by iohexol clearance using filter paper to directly measure GFR, retinal vascular geometry to predict early retinal changes and corneal confocal microscopy to improve detection of early nerve loss to better predict diabetic neuropathy. Herein we will review technologies, novel biomarkers, and therapeutic targets in relation to vascular complications of diabetes.

Renal function is associated with peak exercise capacity in adolescents with type 1 diabetes

OBJECTIVE

Diabetic nephropathy and cardiovascular disease are strongly related in adults with type 1 diabetes, yet little is known about this relationship in adolescents prior to the onset of detectable clinical disease. We hypothesized that cardiopulmonary fitness would be directly associated with albumin-to-creatinine ratio (ACR) and inversely related to estimated glomerular filtration rate (eGFR) in adolescents with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Sixty-nine adolescents with type 1 diabetes and 13 nondiabetic control subjects of similar pubertal stage and BMI had insulin sensitivity (glucose infusion rate [GIR]), measured by hyperinsulinemic-euglycemic clamp, and lean body mass, measured by DEXA. Cardiopulmonary fitness was measured by cycle ergometry to obtain peak volume of oxygen (VO2peak), and renal function was measured by eGFR using the Bouvet equation (measuring creatinine and cystatin C levels) and ACR.

RESULTS

Adolescents (15.5 ± 2.2 years of age) with type 1 diabetes (6.3 ± 3.8 years diabetes duration) had reduced VO2peak (31.5 ± 6.3 vs. 36.2 ± 7.9 mL/kg ⋅ min, P = 0.046) and VO2peak/lean kg (43.7 ± 7.0 vs. 51.0 ± 8.6 mL/lean kg ⋅ min, P = 0.007) compared with nondiabetic control subjects. eGFR was inversely associated with VO2peak and VO2peak/lean kg after adjusting for sex, Tanner stage, GIR, HbA1c level, systolic blood pressure, and LDL cholesterol level (β ± SE, VO2peak: -0.19 ± 0.07, P = 0.02; VO2peak/lean kg: -0.19 ± 0.09, P = 0.048). Moreover, participants in the highest tertile for eGFR had significantly lower sex- and Tanner-adjusted VO2peak and VO2peak/lean kg compared with participants in the lowest tertile.

CONCLUSIONS

Adolescents with type 1 diabetes had reduced exercise capacity, which was strongly associated with renal health, independent of insulin sensitivity. Future studies should examine the underlying interrelated pathophysiology in order to identify probable targets for treatment to reduce cardiovascular and renal complications.