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Aims Cardiac autonomic neuropathy is currently an untreatable progressive complication of type 1 diabetes (T1D). Impaired microcirculation is a suspected cause of nerve degeneration in TID. We investigated whether cardiovascular autonomic reflexes often used as indices of nerve functions, are associated with indices of microcirculatory function in young adults with T1D compared with non-diabetic controls. Methods In a cross-sectional study, 15 adults with T1D and 15 age-matched controls (20-40 years) underwent standardized cardiovascular autonomic reflex tests. Continuous recordings of electrocardiogram, cardiac vagal tone, beat-to-beat blood pressure and transcutaneous tissue oxygen (tcpO₂) and carbon dioxide partial pressures (tcpCO2) were done. Results Despite preserved baroreflex, parasympathetic, and sympathetic functions assessed using cardiovascular reflex tests, the individuals with T1D exhibited reduced baseline tcpO2 compared to the controls (37.5±3.75 vs. 49.6 mmHg). During the Valsalva manoeuvre, individuals with T1D exhibited a reduced systolic blood pressure response in phase I (31±10 vs. 43±18 mmHg) and early phase II (-1±15 vs. -18±17 mmHg), and an increased systolic (31±15 vs. 18±14 mmHg) and diastolic (45±11 vs. 33±16 mmHg) response in late phase II compared to controls. The early phase II diastolic response was inversely associated with baseline tcpO2. Conclusion The altered hemodynamic response to the Valsalva manoeuvre is suggestive of possible reduced arterial elasticity, higher vascular resistance, and splanchnic sympatho-vagal imbalance in T1D despite normal autonomic reflex ratios. The concomitant evidence of reduced tissue oxygenation and altered hemodynamics may represent early signs of dysautonomia but require longitudinal validation.
Objective We aimed to evaluate β-cell function of type 1 diabetic patients (T1DP)s based on fasting and stimulated C-peptide levels. Material and methods Study included 135 T1DPs and 31 healthy subjects. Fasting C-peptide levels were measured in healthy subjects and T1DPs. The Mixed-meal tolerance test (MMTT) was performed in T1DPs. Fasting and stimulated (90 minute post MMTT) C-peptide levels were measured via electrochemiluminescence assay. Two categorizations were made according to fasting (the first categorization ) and at 90th minute MMTT (the second categorization) C-peptide levels. For the first categorization; the groups were classified as follows: patients with undetectable ≤0.1ng/mL(group1); minimal 0.1-0.8ng/mL(group2); and sustained ≥0.8ng/mL (group3) C-peptide levels. For the second categorization, groups were as follows: patients with undetectable ≤0.1 ng/mL(group1); minimal 0.1-0.8 ng/ml (group2); and sustained ≥0.8ng/mL (group3) in which C peptide levels were increased to ≥150% of fasting C-peptide levels at the 90th minute after MMTT. Results For the first category; 41.5%, 40% and 18.5% of T1DPs were in group1, group2 and group3, respectively. For the second category; 34.8%, 20.7% and 44.4% were in group1, group2 and group3, respectively. In first categorization 58.5% and in second categorization 65.1% of T1DPs had detectable C-peptide levels. 44,4%of the T1DPs had a response to MMTT with C-peptide levels ≥0.8 ng/mL which increased to ≥150% of fasting C-peptide level at the 90th minute after MMTT as it is seen in non-diabetics. Conclusion The present study suggests the presence of functioning β-cells in T1DPs and 44.4 % of T1DPs have a response to MMTT as seen in non-diabetics. (ClinicalTrials.gov number: NCT02199470.)