Endocrine Abstracts

Background: Optimal testing of beta-cell dysfunction is still elusive. Oral based solid-food tests could superiorly approximate real-life stimulation by incorporating incretin activation. Increased body fat was recently associated with better preserved beta-cell secretory response, due to gluco-lipotoxicity induced adaptation.

Objective: To assess C-peptide response to standardised test meal (STM) and its dependency on subject characteristics in newly diagnosed type 2 diabetes mellitus (DM2) patients.

Patients and Methods: STM consisted of one 60g white flour bread-roll (24g carbohydrates) and 200 ml 2.8% milk-fat yoghurt (12g carbohydrates), totalling 300 kCal, consumed over 5 minutes after overnight fasting. C-peptide was analysed at baseline and 2h post STM in newly diagnosed DM2 patients (n=80; 30-65 years old; 47 males) with initial HbA1c ≧ 9% and BMI 25-40 kg/m².

Results: Baseline C-peptide of 2.29±0.14 ng/ml, increased after STM by 1.40±0.20 ng/ml (63.6%±7.7%). In women vs. men, there was non-significantly higher baseline C-peptide (2.48±0.26 ng/ml vs. 2.16±0.15 ng/ml, P> 0,05) with a significantly greater C-peptide increase (ΔCP) in STM: 1.92±0.33 ng/ml vs. 1.04±0.14 ng/ml (P 0,05). Average baseline C-peptide (2.29±0.14 ng/ml) correlated significantly with average BMI (29.7±0.5 kg/m2) (P<0.01; Pearson’s r=0.32). Baseline C-peptide was significantly lower in the normally nourished (1.58±0.22ng/ml) compared to overweight (2.41±0.23ng/ml; p<0.05) and obese (2.46±0.22 ng/ml; p<0.05). STM-stimulated ΔCP was significantly lower in the normally nourished (0.68±0.21 ng/ml) compared to twice greater in the overweight (1.40±0.20ng/ml; p<0.05) and obese (1.71±0.44 ng/ml; p<0.05). Average ΔCP in STM (1.40±0.20 ng/ml) correlated significantly with BMI (29.7±0.5 kg/m2) (P 0.05; Pearson’s r=0.23). ΔCP correlation to age was not significant.

Conclusions: Standardised test meal is a promising simple and naturalistic alternative to asses beta-cell function in-vivo through C-peptide response in patients with newly diagnosed DM2, but interpretation should respect its dependency on gender and BMI. Significant positive correlation of baseline C-peptide and its stimulated response to STM with BMI supports the hypothesis of more preserved or better adapted beta-cell reserve in the obese patients.