Abstract
The central nervous system (CNS) is a major player in the regulation of feeding. Gut-derived hormones, such as glucagon- like peptide-1 (GLP-1), may relay information about the nutritional status to the CNS. Treatment with GLP-1 agonists, such as liraglutide, is associated with reduced appetite and weight loss. We hypothesized that these effects are mediated by effects on the CNS. We performed a randomized cross-over study in patients with type 2 diabetes (n = 20, mean ± SD, age 59.3 ± 4.1 yr, BMI 32 ± 4.7 kg/m2). Each individual underwent 2 periods of 12 week treatment with either liraglutide or insulin glargine with a 12 week wash-out period. Using fMRI, we determined the effects of treatment on CNS activation to food vs. nonfood pictures in areas regulating reward when fasted and 30 min. after a standardized meal. FMRI scans were performed at baseline, after 10 days and 12 weeks of treatment. After 12 weeks, the decrease in HbA1c was larger with liraglutide vs. insulin (Δ -0.7% vs. -0.2%, p difference < 0.001). Body weight decreased during liraglutide vs insulin (Δ -3.3 kg vs. +0.8 kg, p difference < 0.001). After 10 days, before weight changes had occurred, patients treated with liraglutide, compared to insulin, showed decreased activation to food pictures in left putamen in the postprandial condition. After 10 days, in comparison with insulin, liraglutide enhanced the reducing effect of the meal intake on CNS activation to food pictures in left putamen and amygdala. These differences between liraglutide and insulin were not observed after 12 weeks. Compared to insulin, liraglutide decreased CNS activations in response to food pictures in reward areas after short term, but not after longer term treatment. Our findings suggest that the GLP-1 mediated altered CNS activation may contribute to the induction of weight loss. However the absence of effects after longer term treatment might explain why weight loss does not proceed after the initial treatment period with liraglutide.
Published Version
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