ESPE Abstracts

Brown adipose tissue (BAT) is a key component of the body's defence against cold challenge and possesses the ability to convert large amounts of chemical energy to heat, conferred by a unique protein, uncoupling protein (UCP)-1, diverting mitochondrial respiration from the production of adenosine triphosphate. In humans, the largest BAT depot is in the supraclavicular region. Sympathetic nervous system stimulation induces glucose uptake into brown adipose tissue, as does insulin. Despite significant improvements in recent years, people with type 1 diabetes mellitus maintain blood glucose levels higher than healthy controls in order to avoid recurrent hypoglycaemia. In addition, insulin is administered into the peripheral circulation, rather than the portal circulation, altering the balance of peripheral and portal levels. Although hyperglycaemia leads to peripheral insulin resistance in muscle and white adipose tissue, it is not known if the same applies to BAT.

BAT is most abundant in children and adolescents and declines with age. The high ionising radiation required for PET-CT, the previous gold standard imaging method, largely excluded children from prospective studies. We have developed a technique to measure the heat signature of supraclavicular BAT using infrared thermography. We used this technique to measure the supraclavicular temperature of 20 children and young people (CYP) with type 1 diabetes (D) and compared them to 20 healthy controls (C). Characteristics (age, gender, height, weight and BMI) were similar between the groups. Following cold stimulation with a cooling blanket around the right forearm, the CYP with type 1 diabetes had a lower absolute supraclavicular temperature (D: 35.0±0.6°C; C: 35.4±0.6°C; P<0.05) which remained significantly lower when compared to a sternal reference point (D: 1.8±0.4°C; C: 2.1±0.5°C; P<0.05). There was no difference in the change from pre-stimulation temperature. Supraclavicular temperatures were not associated with measures of either chronic diabetic control (HbA1C) or acute status (blood glucose level).

The relationship between BAT and insulin is complex. In the physiological state, insulin is strongly suppressed by sympathetic nervous system control. Since exogenous insulin is not responsive to the sympathetic nervous system, it is unable to be suppressed following a cold challenge which could be an explanation for the lower stimulated supraclavicular temperature.