Brain
insulin-stimulated glucose uptake (GU) is increased in obese and insulin
resistant subjects but normalizes after weight loss along with improved
whole-body insulin sensitivity. Our aim was to study whether short-term
exercise training (moderate intensity continuous training (MICT) or sprint
interval training (SIT)) alters substrates for brain energy metabolism in insulin
resistance.

Sedentary subjects
(n=21, BMI 23.7-34.3kg/m², age 43-55y) with insulin resistance were
randomized into MICT (n=11, intensity≥60% of VO_2peak) or SIT (n=10, all-out)
groups for a two week training intervention. Brain GU during insulin
stimulation and fasting brain free fatty acid uptake (FAU) were measured using PET.

At baseline, brain GU
was positively associated with the fasting insulin level and negatively with the
whole-body insulin sensitivity. The whole-body insulin sensitivity improved
with both training modes (20%, p=0.007) while only SIT led to an increase in
aerobic capacity (5%, p=0.03). SIT also reduced insulin-stimulated brain GU
both in global cortical grey matter uptake (12%, p=0.03) and in specific
regions (p<0.05, all areas except the occipital cortex), whereas no changes were
observed after MICT. Brain FAU remained unchanged after the training in both
groups.

These findings show that
short-term SIT effectively decreases insulin-stimulated brain GU in sedentary subjects
with insulin resistance.