Beta Cell Function in (Pre)Type 1 Diabetes

Overview

Increased glycemic variability has been proposed as an independent predictor of hypoglycemia in diabetic patients. Likewise, episodes of dysglycemia have been found to be predictive of diabetes in antibodypositive nondiabetic individuals. We hypothesise that an in-depth observational study comparing state-of-the-art measures of functional beta cell mass and glycemic variability will specify the relationship between both variables over a broad range of residual function and will identify treatment goals for functional beta cell mass to be reached in future beta cell therapy trials in order to avoid frequent hypoglycemia in patients and dysglycemia in risk groups. The available expertise and infrastructure (see background and (inter)national context) place the promoters of the present project in a unique position to carry out the planned experiments and support their feasibility.

The established clinical network and the developed dynamic function tests and biological markers provide us with the unique opportunity to identify sufficiently large groups of high-risk first-degree relatives (\> 50% risk of diabetes) of a proband with type 1 diabetes and of recent-onset type 1 diabetic patients with the overall aim to investigate the correlation between functional beta cell mass and glycemic variability in relation to metabolic outcome in order to determine thresholds of residual function below which: 1. glucose tolerance starts to decline sharply in relatives 2. the risk of deteriorating metabolic control and (severe) hypoglycemic events strongly increases in patients To this effect we will: 1. measure and follow over a two-year period 1. the functional beta cell mass of participants as determined by AUC C-peptide release - the preferred outcome measure in type 1 diabetes trials during hyperglycemic clamp test 2. the participants' within- and between-day glycemic variability as determined by seven point selfmonitoring of blood glucose (SMBG) and continuous glucose monitoring (CGM) during 5 days preceding each clamp procedure 2. perform oral glucose tolerance tests (OGTTs; only in relatives), determine HbA1c levels centrally (relatives and patients) and record insulin requirements and hypoglycemic episodes (in patients) Our previous experiments have documented that the selected patients and relatives (see workplan) display large inter-individual differences in functional beta cell mass (ranging anywhere between control values and \< 10% of controls) allowing to study glycemic variability as a function of residual cell function over a large range of values. They also illustrate that the recruitment capacity of the clinical network and the acceptance rate and compliance of the patients and relatives for the clamp procedure is high and sufficient to carry out the planned experiments.