title: Relationship between autonomic cardiac activity, beta-cell function, anthropometrics and metabolic indices in type II diabetics.
abstract: OBJECTIVE
  Recent studies have demonstrated that C-peptide exerts beneficial effects on the diabetic state, including improvements in kidney and nerve function. Thus, we investigated the effect of residual pancreatic C-peptide secretion on the cardiac autonomic nervous system in well- and poorly controlled type II diabetic patients.
  
  
  METHODS
  Randomised cross-sectional study.
  
  
  METHODS
  Forty type II diabetic patients free from diabetic neuropathy, with similar anthropometric parameters, volunteered for our study.
  
  
  METHODS
  Insulin action, residual pancreatic C-peptide secretion and the cardiac autonomic nervous system were investigated by euglycaemic hyperinsulinaemic clamp, glucagon bolus test and heart rate variability, respectively. M-values were used as an index of insulin sensitivity. High frequency (HF) and low frequency (LF) oscillations in heart rate were analysed.
  
  
  RESULTS
  The patients were categorized into those with good (HbA1c < or = 7.0) and poor (HbA1c > or = 8.0) metabolic control. The patients with good metabolic control had fasting plasma glucose and C-peptide levels, plasma area under the curve (auc) insulin and C-peptide levels, M-values, LF values and LF/HF ratio significantly lower than patients with poor metabolic control. In contrast, RR interval, total power and HF values had an opposite trend. Basal plasma C-peptide correlated with LF/HF in patients with good (r = -0.42; P < 0.05) and poor metabolic control (r = -0.45; P < 0.05). An even stronger correlation between auc C-peptide and LF/HF in patients with good (r = -0.53, P < 0.002) and poor metabolic control (r = -0.49; P < 0.03), as well as in the whole group (r = -0.83; P < 0.001) was found. By multiple regression analyses performed in all patients, LF/HF were independently associated with auc C-peptide (t = -8.618; P < 0.001) but not basal C-peptide levels (t = -0.137; P < 0.88).
  
  
  CONCLUSIONS
  Our study demonstrated that preserved C-peptide secretion is associated with a well balanced cardiac autonomic activity in type II diabetic patients.
authors.affiliation: Department of Geriatric Medicine and Metabolic Diseases, Second University of Naples, Naples, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Manzella
authors.forename: Marco
authors.initials: M
authors.lastname: Carbonella
authors.forename: Emilia
authors.initials: E
authors.lastname: Ragno
authors.forename: Nicola
authors.initials: N
authors.lastname: Passariello
authors.forename: Rodolfo
authors.initials: R
authors.lastname: Grella
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Paolisso
mesh_terms: D019540:Area Under Curve; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001786:Blood Glucose / Q000032:analysis; D002096:C-Peptide / Q000378:metabolism*; D003430:Cross-Sectional Studies; D003924:Diabetes Mellitus, Type 2 / Q000503:physiopathology*; D015716:Electrocardiography, Ambulatory; D005260:Female; D006329:Heart Conduction System / Q000503:physiopathology*; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged
chemical_list: D001786:Blood Glucose; D002096:C-Peptide