Aims/hypothesis. An enteral nutritional load augments the glucose gradient which occurs as glucose passes through the arteries and capillaries, into the venous system. This gradient is well described in health but is not well described in T1D (type 1 diabetes). We aimed to determine the magnitude and clinical correlates of this gradient, in free living participants with well controlled T1D.
Methods. In participants taking fast acting mealtime analogue insulin the gradient was assessed by comparing concurrently collected capillary finger stick and antecubital fossa venous samples using two glucose meter systems with different strip enzymes (one utilised a glucose oxidase based system and the second utilised glucose dehydrogenase). Sampling occurred before the administration of an insulin dose and breakfast of the participant’s choosing and was repeated after one and two hours. Demographic, anthropometric and clinical characteristics were documented, including carbohydrate consumption (gm).
Results. There were 43 participants. The magnitude of the capillary-venous glucose gradient measured using the two glucose meters was similar and results were therefore combined. Mean (SD) capillary - venous glucose (mmol/L) gradient was; pre-breakfast 0.21±0.43, one hour 0.87±0.66; two hours 0.52±0.62. Comparison of prandial change in glucose gradient compared to the pre-breakfast gradient was highly significant (P<0.001). The relationship between the magnitude of the gradient and dietary carbohydrate intake (g.kg-1) was also significant (P<0.01) at both the one hour and two hour time points.
Conclusions/interpretation. In the majority of patients, the expected negative glucose gradient was observed between the peripheral capillary and venous systems. The gradient appears to be maximal around one hour after a large carbohydrate load. In type 1 diabetes, post prandial capillary and venous glucose concentrations cannot be assumed to be equivalent.