Type 1 Diabetes mellitus (T1D) is characterized by βcell destruction and a long life
requirement of exogenous insulin. The bolus basal insulin regimen is a widely accepted
therapy concept to treat hyperglycaemia in patients with T1D. This concept requires a very
good knowledge of the individuals prandial and basal insulin requirements. However, insulin
requirement depends on insulin absorption from the injection site and the individual's
insulin sensitivity which relies on a number of effects including body composition,
inflammatory processes and environmental factors. Climatic factors such as differences in air
temperature could affect both, insulin absorption and insulin sensitivity as suggested by
recent reports. For instance, it is reported that hot baths can accelerate the absorption of
short acting but not of long acting insulin formulations from the subcutaneous depot. In
addition, local warming of the injection site by a novel device (InsuPatch) results as well
in an accelerated insulin action profile of short acting insulins. Moreover, Berglund et al.
reported seasonal variations in insulin sensitivity in elderly men with increased insulin
sensitivity during summer time.
Although an effect of temperature on insulin absorption and action can be assumed and was
subject to current clinical trials, there is only little knowledge on the effect of humidity
and the cumulative effect of humidity and temperature on insulin pharmacodynamics and
pharmacokinetics. For subjects with type 2 diabetes it was reported that accommodation to
high temperatures and moist air of more than 75% is impaired compared to healthy subjects as
determined by skin blood flow, temperature and moisture. Although it can be estimated that
changes in blood flow due to hot and moist air affect the pharmacokinetics and
pharmacodynamics of subcutaneous prandial insulins, to our knowledge no such study in
subjects with T1D using the euglycaemic clamp technique was carried out yet. In order to
assess the effect of temperature and humidity on insulin action, subjects with type 1
diabetes will be administered a single dose of short acting insulin in an environmental
chamber either at 15°C or a warm environment of 40°C with either a low or high humidity (10%
vs. 90%). Moreover, an exploratory part of the trial will evaluate the measurement
performance of several blood glucose meters under the experimental climatic situations.