Fasted C-Peptide Distribution and Associated Clinical Factors in Adults With Longstanding Type 1 Diabetes: Analysis of the Canadian Study of Longevity in Type 1 Diabetes.

OBJECTIVE: Although insulin production is reportedly retained in many people with longstanding type 1 diabetes (T1D), the magnitude and relevance of connecting peptide (C-peptide) production are uncertain. In this study, we aimed to define fasted C-peptide distributions and associated clinical factors. METHODS: In a cross-sectional analysis of the Canadian Study of Longevity, fasted serum and urinary C-peptide was measured in 74 patients with longstanding T1D (duration ≥50 years) and 75 age- and sex-matched controls. Extensive phenotyping for complications was performed and patient-reported variables were included. C-peptide distributions were analyzed, and multivariable logistic regression was used to assess the variable association in participants with T1D. RESULTS: The 74 participants with T1D had a mean age of 66±8 years, a disease duration of 54 (interquartile range 52 to 58) years, and a glycated hemoglobin (A1C) of 7.4%±0.8% (56.8±9.15 mmol/mol). The 75 controls had a mean age of 65±8 years and an A1C of 5.7%±0.4% (38.4±4.05 mmol/mol). Participants with T1D had lower fasted serum C-peptide than controls (0.013±0.022 vs 1.595±1.099 nmol/L, p<0.001). Of the participants with T1D, C-peptide was detectable in 30 of 73 (41%) serum samples, 32 of 74 (43%) urine samples, and 48 of 74 (65%) for either serum or urine. The variables independently associated with detectable serum or urinary C-peptide were lower total daily insulin requirement (odds ratio 2.351 [for 1 lower unit/kg], p=0.013) and lower hypoglycemia worry score (odds ratio 1.059 [for 1 point lower on the worry subscore of the Hypoglycemia Fear Survey], p=0.030). CONCLUSIONS: Although detectable C-peptide in longstanding diabetes was common, the magnitude of concentration was extremely low when compared with age- and sex-matched controls. Despite minimal detectability, its presence is validated by lower insulin requirements and strongly associated with lower hypoglycemia worry.

Ketone production and excretion even during mild hyperglycemia and the impact of sodium-glucose co-transporter inhibition in type 1 diabetes.

AIMS: We aimed to determine if ketone production and excretion are increased even at mild fasting hyperglycemia in type 1 diabetes (T1D) and if these are modified by ketoacidosis risk factors, including sodium-glucose co-transporter inhibition (SGLTi) and female sex. METHODS: In secondary analysis of an 8-week single-arm open-label trial of empagliflozin (NCT01392560) we evaluated ketone concentrations during extended fasting and clamped euglycemia (4-6 mmol/L) and mild hyperglycemia (9-11 mmol/L) prior to and after treatment. Plasma and urine beta-hydroxybutyrate (BHB) concentrations and fractional excretion were analyzed by metabolomic analysis. RESULTS: Forty participants (50 % female), aged 24 ± 5 years, HbA1c 8.0 ± 0.9 % (64 ± 0.08 mmol/mol) with T1D duration of 17.5 ± 7 years, were studied. Increased BHB production even during mild hyperglycemia (median urine 6.3[3.5-13.6] vs. 3.5[2.2-7.0] µmol/mmol creatinine during euglycemia, p < 0.001) was compensated by increased fractional excretion (0.9 % [0.3-1.6] vs. 0.4 % [0.2-0.9], p < 0.001). SGLTi increased production and attenuated the increased BHB fractional excretion (decreased to 0.3 % during mild hyperglycemia, p < 0.001), resulting in higher plasma concentrations (increased to 0.21 [0.05-0.40] mmol/L, p < 0.001), particularly in females (interaction p < 0.001). CONCLUSIONS: Even mild hyperglycemia is associated with greater ketone production, compensated by urinary excretion, in T1D. However, SGLTi exaggerates production and partially reduces compensatory excretion, particularly in women.

Estimated glomerular filtration rate calculated by serum creatinine lacks precision and accuracy in adults with type 2 diabetes with preserved renal function.

AIMS: We evaluated the performance of creatinine-based equations that are currently used to estimate glomerular filtration rate (GFR) in people with type 2 diabetes compared to measured GFR using gold-standard methods. METHODS: In this post-hoc analysis, 32 participants underwent repeated measurement of GFR by inulin clearance (mGFR). GFR was estimated by serum creatinine using the MDRD (eGFRMDRD) and CKD-EPI (eGFRCKD-EPI) equations four times over the course of one month. Performance was evaluated using measurements of bias (mean difference), precision (SD), and inaccuracy (proportion of eGFR that differed by >20 % of mGFR). Treatment and time effects on bias were evaluated using linear mixed effects models. RESULTS: At baseline, participants (38 % female) were age 60 ± 8 years, had diabetes duration of 9 ± 7 years, HbA1c 56 ± 9 mmol/mol (7.2 ± 0.8 %), and BMI 31.0 ± 6.2 kg/m2. Mean mGFR was 113 ± 24, mean eGFRMDRD was 93 ± 12, and mean eGFRCKD-EPI was 94 ± 9 mL/min/1.73 m2. When 128 observations (32 participants measured 4 times) were evaluated, both equations substantially underestimated mGFR. For eGFRMDRD, mean bias was -21.5 mL/min/1.73 m2, precision was 22.7 mL/min/1.73 m2, and 46 % of observations differed by >20 %. Results were similar for eGFRCKD-EPI. No time or treatment effects on bias were observed. CONCLUSIONS: In adults with type 2 diabetes and preserved renal function, eGFR equations underestimated mGFR, lacked precision and accuracy, and performance was lower at higher ranges of mGFR. Current eGFR equations by serum creatinine are inaccurate in adults with type 2 diabetes with preserved renal function, highlighting the necessity to develop new methods to measure kidney function at earlier stages of diabetic kidney disease.

Point-of-Care Capillary Blood Ketone Measurements and the Prediction of Future Ketoacidosis Risk in Type 1 Diabetes.

OBJECTIVE: Rather than during illness while diabetic ketoacidosis (DKA) is developing, we aimed to determine if levels of routine point-of-care capillary blood ketones could predict future DKA. RESEARCH DESIGN AND METHODS: We examined previously collected data from placebo-assigned participants in an adjunct-to-insulin medication trial program that included measurement of fasted capillary blood ketone levels twice per week in a 2-month baseline period. The outcome was 6- to 12-month trial-adjudicated DKA. RESULTS: DKA events occurred in 12 of 484 participants at a median of 105 (interquartile range 43, 199) days. Maximum ketone levels were higher in patient cases compared with in control patients (0.8 [0.6, 1.2] vs. 0.3 [0.2, 0.7] mmol/L; P = 0.002), with a nonparametric area under the receiver operating characteristic curve of 0.77 (95% CI 0.66-0.88). Ketone levels ≥0.8 mmol/L had a sensitivity of 64%, a specificity of 78%, and positive and negative likelihood ratios of 2.9 and 0.5, respectively. CONCLUSIONS: This proof of concept that routine capillary ketone surveillance can identify individuals at high risk of future DKA implies a role for future technologies including continuous ketone monitoring.

The association between physical activity time and neuropathy in longstanding type 1 diabetes: A cross-sectional analysis of the Canadian study of longevity in type 1 diabetes.

AIM: Physical activity (PA) is recommended to improve glycemic control in T1D; however, the effect of PA on distal symmetric polyneuropathy (DSPN) and cardiac autonomic function in longstanding T1D is unknown. METHODS: Data from 75 participants were collected as part of the Canadian Study of Longevity in T1D. Participants completed a physical exam, medical history, extensive complications phenotyping and reported their daily PA from the preceding 12-months. Pearson and Spearman correlations were used to assess PA time and complications variables. Linear regression was used to test associations between PA time, neurological and electrophysiological measures. Univariable regression was used to indicate the change in the given independent variables associated with a 30-min increase in PA per week. RESULTS: Participants were 66 ± 8 years old with diabetes duration of 54 [52,58] years, HbA1c was 7.3 ± 0.8, 65(89%) had DSPN. Weekly PA time was 156 ± 132 min, and 35(47%) reported ≧150 min/week. Participants with DSPN reported lower PA time compared to individuals without DSPN (141 ± 124 min/week vs. 258 ± 129 min/week; p = 0.015). PA time was associated with better cooling detection threshold (r = 0.24; p = 0.043), peroneal and sural amplitude (r = 0.36; p = 0.0017, rs = 0.26; p = 0.024) and conduction velocity (rs = 0.28; p = 0.015, r = 0.23; p = 0.050). Linear regression adjusting for age and HbA1c, showed that for each 30-min of PA there was a 0.09mv higher peroneal amplitude (p = 0.032) and 0.048 ms lower peroneal F-wave latency (p = 0.022). CONCLUSION: In longstanding T1D, PA time is associated with superior large nerve fibre function in the lower limbs and some better measures of small nerve fibre function.

Changes in plasma and urine metabolites associated with empagliflozin in patients with type 1 diabetes.

AIM: To examine the impact of the sodium-glucose co-transporter-2 inhibitor, empagliflozin, on plasma and urine metabolites in participants with type 1 diabetes. MATERIAL AND METHODS: Participants (n = 40, 50% male, mean age 24.3 years) with type 1 diabetes and without overt evidence of diabetic kidney disease had baseline assessments performed under clamped euglycaemia and hyperglycaemia, on two consecutive days. Participants then proceeded to an 8-week, open-label treatment period with empagliflozin 25 mg/day, followed by repeat assessments under clamped euglycaemia and hyperglycaemia. Plasma and urine metabolites were first grouped into metabolic pathways using MetaboAnalyst software. Principal component analysis was performed to create a representative value for each sufficiently represented metabolic group (false discovery rate ≤ 0.1) for further analysis. RESULTS: Of the plasma metabolite groups, tricarboxylic acid (TCA) cycle (P < .0001), biosynthesis of unsaturated fatty acids (P = .0045), butanoate (P < .0001), propanoate (P = .0053), and alanine, aspartate and glutamate (P < .0050) metabolites were increased after empagliflozin treatment under clamped euglycaemia. Of the urine metabolite groups, only butanoate metabolites (P = .0005) were significantly increased. Empagliflozin treatment also attenuated the increase in a number of urine metabolites observed with acute hyperglycaemia. CONCLUSIONS: Empagliflozin was associated with increased lipid and TCA cycle metabolites in participants with type 1 diabetes, suggesting a shift in metabolic substrate use and improved mitochondrial function. These effects result in more efficient energy production and may contribute to end-organ protection by alleviating local hypoxia and oxidative stress.

Reducing the need for carbohydrate counting in type 1 diabetes using closed-loop automated insulin delivery (artificial pancreas) and empagliflozin: A randomized, controlled, non-inferiority, crossover pilot trial.

AIM: To assess whether adding empagliflozin to closed-loop automated insulin delivery could reduce the need for carbohydrate counting in type 1 diabetes (T1D) without worsening glucose control. MATERIALS AND METHODS: In an open-label, crossover, non-inferiority trial, 30 adult participants with T1D underwent outpatient automated insulin delivery interventions with three random sequences of prandial insulin strategy days: carbohydrate counting, simple meal announcement (no carbohydrate counting) and no meal announcement. During each sequence of prandial insulin strategies, participants were randomly assigned empagliflozin (25 mg/day) or not, and crossed over to the comparator. Mean glucose for carbohydrate counting without empagliflozin (control) was compared with no meal announcement with empagliflozin (in the primary non-inferiority comparison) and simple meal announcement with empagliflozin (in the conditional primary non-inferiority comparison). RESULTS: Participants were aged 40 ± 15 years, had 27 ± 15 years diabetes duration and HbA1c of 7.6% ± 0.7% (59 ± 8 mmol/mol). The system with no meal announcement and empagliflozin was not non-inferior (and thus reasonably considered inferior) to the control arm (mean glucose 10.0 ± 1.6 vs. 8.5 ± 1.5 mmol/L; non-inferiority p = .94), while simple meal announcement and empagliflozin was non-inferior (8.5 ± 1.4 mmol/L; non-inferiority p = .003). Use of empagliflozin on the background of automated insulin delivery with carbohydrate counting was associated with lower mean glucose, corresponding to a 14% greater time in the target range. While no ketoacidosis was observed, mean fasting ketones levels were higher on empagliflozin (0.22 ± 0.18 vs. 0.13 ± 0.11 mmol/L; p < .001). CONCLUSIONS: Empagliflozin added to automated insulin delivery has the potential to eliminate the need for carbohydrate counting and improves glycaemic control in conjunction with carbohydrate counting, but does not allow for the elimination of meal announcement.

Analysis of Prevalence, Magnitude and Timing of the Dawn Phenomenon in Adults and Adolescents With Type 1 Diabetes: Descriptive Analysis of 2 Insulin Pump Trials.

OBJECTIVES: To better understand the dawn phenomenon in type 1 diabetes, we sought to determine its prevalence, timing and magnitude in studies specifically designed to assess basal insulin requirements in patients using insulin pumps. METHODS: Thirty-three participants from 2 sensor-augmented insulin pump studies were analyzed. Twenty participants were obtained from a methodologically ideal semiautomated basal analysis trial in which basal rates were determined from repeated fasting tests (the derivation set) and 13 from an artificial pancreas trial in which duration of fasting was variable (the "confirmation" set). Prevalence was determined for the total cohort and for individual trials using the standard definition of an increase in insulin exceeding 20% and lasting ≥90 minutes. Among cases, time of onset and percent change in the magnitude of basal delivery were determined. RESULTS: Seventeen participants (52%) experienced the dawn phenomenon (11 of 20 [55%] in the derivation set and 6 of 13 [46%] in the confirmation set). Time of onset was 3 AM (interquartile range [IQR], 3 to 4:15 AM) in the derivation set and 3 AM (IQR, 3 to 4 AM) in the confirmation set. The magnitude of the dawn phenomenon was a 58.1% (IQR, 28.8% to 110.6%) increase in insulin requirements in the derivation set and 65.5% (IQR, 45.6% to 87.4%) in the confirmation set. CONCLUSIONS: The dawn phenomenon occurs in approximately half of patients with type 1 diabetes; when present, it has predictable timing of onset (generally 3 AM) and a substantial, but highly variable, magnitude. These findings imply that optimization of glycemic control requires clinical emphasis on fasted overnight basal insulin assessment.

Estimating GFR by Serum Creatinine, Cystatin C, and ß2-Microglobulin in Older Adults: Results From the Canadian Study of Longevity in Type 1 Diabetes.

INTRODUCTION: Glomerular filtration rate (GFR) is routinely used for clinical assessment of kidney function. However, the accuracy of estimating equations in older adults is uncertain. METHODS: In 66 adults with ≥50 years type 1 diabetes (T1D) duration and 73 nondiabetic controls from age/sex-matched subgroups (65 ± 8 years old and 77[55%] were women) we evaluated the performance of estimated GFR (eGFR) by creatinine (Modification of Diet and Renal Disease [MDRD], Chronic Kidney Disease-Epidemiology [CKD-EPI]cr), cystatin C (CKD-EPIcys, CKD-EPIcr-cys), and ß2-microglobulin (ß2M) compared with measured GFR by inulin clearance (mGFR). Performance was evaluated using metrics of bias (mean difference), precision (SD), and accuracy (proportion of eGFR that differed by >20% of mGFR). RESULTS: Mean mGFR was 104 ± 18 ml/min per 1.73 m2 (range: 70-154 ml/min per 1.73 m2) and was not different between T1D and controls (103 ± 17 vs. 105 ± 19 ml/min per 1.73 m2, P = 0.39). All equations significantly underestimated mGFR (bias: -15 to -30 ml/min per 1.73 m2, P < 0.001 for all comparisons) except for ß2M, which had bias of 1.9 ml/min per 1.73 m2 (P = 0.61). Bias was greatest in cystatin C-based equations. Precision was lowest for ß2M (SD: 43.5 ml/min per 1.73 m2, P < 0.001 for each comparison). Accuracy was lowest for CKD-EPIcysC (69.1%, P < 0.001 for each comparison). Cystatin C-based equations demonstrated greater bias and lower accuracy in older age subgroups (<60, 60-69, ≥70 years). All equations demonstrated greater bias across higher ranges of mGFR (60-89, 90-119, ≥120 ml/min per 1.73 m2). Results were similar between T1D and controls except that ß2M had lower performance in T1D. CONCLUSION: Better estimates of GFR in older adults are needed for research and clinical practice, as this subgroup of the population has an amplified risk for the development of chronic kidney disease (CKD) that requires accurate GFR estimation methods.

Elevated plasma cyclic guanosine monophosphate may explain greater efferent arteriolar tone in adults with longstanding type 1 diabetes: A brief report.

Cyclic guanosine monophosphate (cGMP) influences intrarenal hemodynamics in animal models, but the relationship between cGMP and renal function in adults with type 1 diabetes (T1D) remains unclear. In this study, plasma cGMP correlated with efferent arteriolar resistance, effective renal plasma flow, and renal vascular resistance in adults with T1D.

Bone mineral density in patients with longstanding type 1 diabetes: Results from the Canadian Study of Longevity in Type 1 Diabetes.

AIM: It is currently unclear if longstanding type 1 diabetes (T1D) affects bone mineral density (BMD). METHODS: BMD measured by dual-energy X-ray absorptiometry and history of fragility fracture was determined in 75 T1D participants with ≥50 years of diabetes duration and 75 age- and sex-matched non-diabetic controls. BMD T-scores were determined for the lumbar spine (LS), total hip (TH) and femoral neck (FN). RESULTS: T1D participants had median diabetes duration of 54 [52, 58] years, 41 (55%) were females, and mean A1c was 7.3 ±â€¯0.8%. T1D females had higher LS T-scores compared to female controls (-0.3 ±â€¯1.2 vs. -1.1 ±â€¯1.4, p = 0.014), lower FN T-scores (-1.5 ±â€¯1.0 vs. -1.2 ±â€¯0.9, p = 0.042) and more fragility fractures (7 (17%) vs. 1 (2%), p = 0.021). In T1D, higher A1c was associated with higher adjusted odds of fragility fracture (p = 0.006). T1D males and controls showed no difference in BMD or fractures. CONCLUSIONS: There were no substantial differences in T-score between T1D and matched controls; however, T1D females showed higher BMD at the LS and possibly paradoxically higher fragility fractures compared to matched controls. These findings suggest that lower T-scores may not be associated with a history of fragility fracture in females with longstanding T1D and that other factors should be investigated.

Atherosclerosis and Microvascular Complications: Results From the Canadian Study of Longevity in Type 1 Diabetes.

OBJECTIVE: Type 1 diabetes carries a significant risk for cardiovascular mortality, but it is unclear how atherosclerosis associates with microvascular complications. We aimed to determine the relationships between atherosclerotic burden and neuropathy, retinopathy, and diabetic kidney disease (DKD) in adults with a ≥50-year history of type 1 diabetes. RESEARCH DESIGN AND METHODS: Adults with type 1 diabetes (n = 69) underwent coronary artery calcification (CAC) volume scoring by wide-volume computerized tomography. Microvascular complications were graded as follows: neuropathy by clinical assessment, electrophysiology, vibration and cooling detection thresholds, heart rate variability, and corneal confocal microscopy; retinopathy by ultra-wide-field retinal imaging; and DKD by renal hemodynamic function measured by inulin and para-aminohippurate clearance at baseline and after intravenous infusion of angiotensin II. The cohort was dichotomized to high (≥300 Agatston units [AU]) or low (<300 AU) CAC and was stratified by diabetes status. A comparator group without diabetes (n = 73) matched for age and sex also underwent all study procedures except for retinal imaging. RESULTS: CAC scores were higher in participants with type 1 diabetes (median Agatston score 1,000 [interquartile range = 222, 2,373] AU vs. 1 [0.75] AU in comparators, P < 0.001). In participants with type 1 diabetes, high CAC scores associated with markers of neuropathy and retinopathy, but not with DKD, or renal hemodynamic function at baseline or in response to angiotensin II. CONCLUSIONS: The presence of high CAC in adults with longstanding type 1 diabetes was associated with large nerve fiber neuropathy and retinopathy but not with renal hemodynamic function, suggesting that neuropathy, retinopathy, and macrovascular calcification share common risk factors.

Corneal confocal microscopy for identification of diabetic sensorimotor polyneuropathy: a pooled multinational consortium study.

AIMS/HYPOTHESIS: Small cohort studies raise the hypothesis that corneal nerve abnormalities (including corneal nerve fibre length [CNFL]) are valid non-invasive imaging endpoints for diabetic sensorimotor polyneuropathy (DSP). We aimed to establish concurrent validity and diagnostic thresholds in a large cohort of participants with and without DSP. METHODS: Nine hundred and ninety-eight participants from five centres (516 with type 1 diabetes and 482 with type 2 diabetes) underwent CNFL quantification and clinical and electrophysiological examination. AUC and diagnostic thresholds were derived and validated in randomly selected samples using receiver operating characteristic analysis. Sensitivity analyses included latent class models to address the issue of imperfect reference standard. RESULTS: Type 1 and type 2 diabetes subcohorts had mean age of 42 ± 19 and 62 ± 10 years, diabetes duration 21 ± 15 and 12 ± 9 years and DSP prevalence of 31% and 53%, respectively. Derivation AUC for CNFL was 0.77 in type 1 diabetes (p < 0.001) and 0.68 in type 2 diabetes (p < 0.001) and was approximately reproduced in validation sets. The optimal threshold for automated CNFL was 12.5 mm/mm2 in type 1 diabetes and 12.3 mm/mm2 in type 2 diabetes. In the total cohort, a lower threshold value below 8.6 mm/mm2 to rule in DSP and an upper value of 15.3 mm/mm2 to rule out DSP were associated with 88% specificity and 88% sensitivity. CONCLUSIONS/INTERPRETATION: We established the diagnostic validity and common diagnostic thresholds for CNFL in type 1 and type 2 diabetes. Further research must determine to what extent CNFL can be deployed in clinical practice and in clinical trials assessing the efficacy of disease-modifying therapies for DSP.

Sex differences in neuropathic pain in longstanding diabetes: Results from the Canadian Study of Longevity in Type 1 Diabetes.

AIM: Neuropathy and neuropathic pain are common complications of type 1 diabetes (T1D). We aimed to determine if sex-specific differences in neuropathic pain are present in adults with longstanding T1D. METHODS: Canadians with ≥50 years of T1D (n = 361) completed health history questionnaires that included assessment of neuropathy (defined by Michigan Neuropathy Screening Instrument questionnaire components ≥3; NEUROPATHYMNSI-Q) and neuropathic pain. Multivariable logistic regression was used to determine sex-differences in neuropathic pain controlling for neuropathy. RESULTS: Participants had mean age 66 ±â€¯9 years, median diabetes duration 53[51,58] years, mean HbA1c 7.5 ±â€¯1.0%, and 207(57%) were female. Neuropathic pain was present in 128(36%) of all participants, more prevalent among those with NEUROPATHYMNSI-Q compared to those without [96(63%) vs. 31(15%), p < 0.001], and more prevalent in females compared to males [87(42%) vs. 41(27%), p = 0.003]. Independent of the presence of NEUROPATHYMNSI-Q and other factors, female sex was associated with the presence of neuropathic pain [OR 2.68 (95% CI 1.4-5.0), p = 0.002]. CONCLUSIONS: We demonstrated a novel sex-specific difference in neuropathic pain in females compared to males with longstanding T1D, independent of the presence of neuropathy. Further research using more objective measures of neuropathy than the MNSI is justified to further understand this sex-specific difference.

Validity of a point-of-care nerve conduction device for polyneuropathy identification in older adults with diabetes: Results from the Canadian Study of Longevity in Type 1 Diabetes.

OBJECTIVE: Point-of-care nerve conduction devices (POCD) have been studied in younger patients and may facilitate screening for polyneuropathy in non-specialized clinical settings. However, performance may be impaired with advanced age owing to age-related changes in nerve conduction. We aimed to evaluate the validity of a POCD as a proxy for standard nerve conduction studies (NCS) in older adults with type 1 diabetes (T1D). METHODS: Sural nerve amplitude potential (AMP) and sural nerve conduction velocity (CV) was measured in 68 participants with ≥ 50 years T1D duration and 71 controls (from age/sex-matched subgroups) using POCD and NCS protocols. Agreement was determined by the Bland-Altman method, and validity was determined by receiver operating characteristic curves. RESULTS: T1D were 53% female, aged 66±8yr and had diabetes duration 54yr[52,58]. Controls were 56%(p = 0.69) female and aged 65±8yr(p = 0.36). Mean AMPPOCD and CVPOCD for the 139 participants was 7.4±5.8µV and 45.7±11.2m/s and mean AMPNCS and CVNCS was 7.2±6.1µV and 43.3±8.3m/s. Mean difference of AMPPOCD-AMPNCS was 0.3±3.8µV and was 2.3±8.5m/s for CVPOCD-CVNCS. A AMPPOCD of ≤6µV had 80% sensitivity and 80% specificity for identifying abnormal AMPNCS, while a CVPOCD of ≤44m/s had 81% sensitivity and 82% specificity to identify abnormal CVNCS. Abnormality in AMPPOCD or CVPOCD was associated with 87% sensitivity, while abnormality in both measures was associated with 97% specificity for polyneuropathy identification. CONCLUSIONS: The POCD has strong agreement and diagnostic accuracy for identification of polyneuropathy in a high-risk subgroup and thus may represent a sufficiently accurate and rapid test for routinely detecting those with electrophysiological dysfunction.

Adiposity Impacts Intrarenal Hemodynamic Function in Adults With Long-standing Type 1 Diabetes With and Without Diabetic Nephropathy: Results From the Canadian Study of Longevity in Type 1 Diabetes.

OBJECTIVE: Central adiposity is considered to be an important cardiorenal risk factor in the general population and in type 1 diabetes. We sought to determine the relationship between central adiposity and intrarenal hemodynamic function in adults with long-standing type 1 diabetes with and without diabetic nephropathy (DN). RESEARCH DESIGN AND METHODS: Patients with type 1 diabetes (n = 66, duration ≥50 years) and age-/sex-matched control subjects (n = 73) were studied. The cohort was stratified into 44 DN Resistors (estimated glomerular filtration rate [eGFR] >60 mL/min/1.73 m2 and <30 mg/day urine albumin) and 22 patients with DN (eGFR ≤60 mL/min/1.73 m2 or ≥30 mg/day urine albumin). Intrarenal hemodynamic function (glomerular filtration rate for inulin [GFRINULIN], effective renal plasma flow for p-aminohippuric acid [ERPFPAH]) was measured. Afferent arteriolar resistance, efferent arteriolar resistance, renal blood flow, renal vascular resistance [RVR], filtration fraction, and glomerular pressure were derived from the Gomez equations. Fat and lean mass were quantified by DXA. RESULTS: Whereas measures of adiposity did not associate with GFRINULIN or ERPFPAH in healthy control subjects, trunk fat mass inversely correlated with GFRINULIN (r = -0.46, P < 0.0001) and ERPFPAH (r = -0.31, P = 0.01) and positively correlated with RVR (r = 0.53, P = 0.0003) in type 1 diabetes. In analyses stratified by DN status, greater central adiposity related to lower GFRINULIN values in DN and DN Resistors, but the relationships between central adiposity and ERPFPAH and RVR were attenuated and/or reversed in patients with DN compared with DN Resistors. CONCLUSIONS: The adiposity-intrarenal hemodynamic function relationship may be modified by the presence of type 1 diabetes and DN, requiring further study of the mechanisms by which adiposity influences renal hemodynamic function.

Renin-angiotensin-aldosterone system activation in long-standing type 1 diabetes.

BACKGROUND: In type 1 diabetes (T1D), adjuvant treatment with inhibitors of the renin-angiotensin-aldosterone system (RAAS), which dilate the efferent arteriole, is associated with prevention of progressive albuminuria and renal dysfunction. Uncertainty still exists as to why some individuals with long-standing T1D develop diabetic kidney disease (DKD) while others do not (DKD resistors). We hypothesized that those with DKD would be distinguished from DKD resistors by the presence of RAAS activation. METHODS: Renal and systemic hemodynamic function was measured before and after exogenous RAAS stimulation by intravenous infusion of angiotensin II (ANGII) in 75 patients with prolonged T1D durations and in equal numbers of nondiabetic controls. The primary outcome was change in renal vascular resistance (RVR) in response to RAAS stimulation, a measure of endogenous RAAS activation. RESULTS: Those with DKD had less change in RVR following exogenous RAAS stimulation compared with DKD resistors or controls (19%, 29%, 31%, P = 0.008, DKD vs. DKD resistors), reflecting exaggerated endogenous renal RAAS activation. All T1D participants had similar changes in renal efferent arteroilar resistance (9% vs. 13%, P = 0.37) irrespective of DKD status, which reflected less change versus controls (20%, P = 0.03). In contrast, those with DKD exhibited comparatively less change in afferent arteriolar vascular resistance compared with DKD resistors or controls (33%, 48%, 48%, P = 0.031, DKD vs. DKD resistors), indicating higher endogenous RAAS activity. CONCLUSION: In long-standing T1D, the intrarenal RAAS is exaggerated in DKD, which unexpectedly predominates at the afferent rather than the efferent arteriole, stimulating vasoconstriction. FUNDING: JDRF operating grant 17-2013-312.

Agreement between automated and manual quantification of corneal nerve fiber length: Implications for diabetic neuropathy research.

AIMS: Quantification of corneal nerve fiber length (CNFL) by in vivo corneal confocal microscopy represents a promising diabetic neuropathy biomarker, but applicability is limited by resource-intensive image analysis. We aimed to evaluate, in cross-sectional analysis of non-diabetic controls and patients with type 1 and type 2 diabetes with and without neuropathy, the agreement between manual and automated analysis protocols. METHODS: Sixty-eight controls, 139 type 1 diabetes, and 249 type 2 diabetes participants underwent CNFL measurement (N=456). Neuropathy status was determined by clinical and electrophysiological criteria. CNFL was determined by manual (CNFLManual, reference standard) and automated (CNFLAuto) protocols, and results were compared for correlation and agreement using Spearman coefficients and the method of Bland and Altman (CNFLManual subtracted from CNFLAuto). RESULTS: Participants demonstrated broad variability in clinical characteristics associated with neuropathy. The mean age, diabetes duration, and HbA1c were 53±18years, 15.9±12.6years, and 7.4±1.7%, respectively, and 218 (56%) individuals with diabetes had neuropathy. Mean CNFLManual was 15.1±4.9mm/mm2, and mean CNFLAuto was 10.5±3.7mm/mm2 (CNFLAuto underestimation bias, -4.6±2.6mm/mm2 corresponding to -29±17%). Percent bias was similar across non-diabetic controls (-33±12%), type 1 (-30±20%), and type 2 diabetes (-28±16%) subgroups (ANOVA, p=0.068), and similarly in diabetes participants with and without neuropathy. Levels of CNFLAuto and CNFLManual were both inversely associated with neuropathy status. CONCLUSIONS: Although CNFLAuto substantially underestimated CNFLManual, its bias was non-differential between diverse patient groups and its relationship with neuropathy status was preserved. Determination of diagnostic thresholds specific to CNFLAuto should be pursued in diagnostic studies of diabetic neuropathy.

Reproducibility of In Vivo Corneal Confocal Microscopy Using an Automated Analysis Program for Detection of Diabetic Sensorimotor Polyneuropathy.

OBJECTIVE: In vivo Corneal Confocal Microscopy (IVCCM) is a validated, non-invasive test for diabetic sensorimotor polyneuropathy (DSP) detection, but its utility is limited by the image analysis time and expertise required. We aimed to determine the inter- and intra-observer reproducibility of a novel automated analysis program compared to manual analysis. METHODS: In a cross-sectional diagnostic study, 20 non-diabetes controls (mean age 41.4±17.3y, HbA1c 5.5±0.4%) and 26 participants with type 1 diabetes (42.8±16.9y, 8.0±1.9%) underwent two separate IVCCM examinations by one observer and a third by an independent observer. Along with nerve density and branch density, corneal nerve fibre length (CNFL) was obtained by manual analysis (CNFLMANUAL), a protocol in which images were manually selected for automated analysis (CNFLSEMI-AUTOMATED), and one in which selection and analysis were performed electronically (CNFLFULLY-AUTOMATED). Reproducibility of each protocol was determined using intraclass correlation coefficients (ICC) and, as a secondary objective, the method of Bland and Altman was used to explore agreement between protocols. RESULTS: Mean CNFLManual was 16.7±4.0, 13.9±4.2 mm/mm2 for non-diabetes controls and diabetes participants, while CNFLSemi-Automated was 10.2±3.3, 8.6±3.0 mm/mm2 and CNFLFully-Automated was 12.5±2.8, 10.9 ± 2.9 mm/mm2. Inter-observer ICC and 95% confidence intervals (95%CI) were 0.73(0.56, 0.84), 0.75(0.59, 0.85), and 0.78(0.63, 0.87), respectively (p = NS for all comparisons). Intra-observer ICC and 95%CI were 0.72(0.55, 0.83), 0.74(0.57, 0.85), and 0.84(0.73, 0.91), respectively (p<0.05 for CNFLFully-Automated compared to others). The other IVCCM parameters had substantially lower ICC compared to those for CNFL. CNFLSemi-Automated and CNFLFully-Automated underestimated CNFLManual by mean and 95%CI of 35.1(-4.5, 67.5)% and 21.0(-21.6, 46.1)%, respectively. CONCLUSIONS: Despite an apparent measurement (underestimation) bias in comparison to the manual strategy of image analysis, fully-automated analysis preserves CNFL reproducibility. Future work must determine the diagnostic thresholds specific to the fully-automated measure of CNFL.