Relationships of in vivo brain norepinephrine transporter and age, BMI, and gender

Previous research reported an age‐related decline in brain norepinephrine transporter (NET) using (S, S)‐[11C]O‐methylreboxetine ([11C]MRB) as a radiotracer. Studies with the same tracer have been mixed in regard to differences related to body mass index (BMI). Here, we investigated potential age‐, BMI‐, and gender‐related differences in brain NET availability using [11C]MRB, the most selective available radiotracer. Forty‐three healthy participants (20 females, 23 males; age range 18–49 years), including 12 individuals with normal/lean weight, 15 with overweight, and 16 with obesity were scanned with [11C]MRB using a positron emission tomography (PET) high‐resolution research tomograph (HRRT). We evaluated binding potential (BPND) in brain regions with high NET availability using multilinear reference tissue model 2 (MRTM2) with the occipital cortex as a reference region. Brain regions were delineated with a defined anatomic template applied to subjects' structural MR scans. We found a negative association between age and NET availability in the locus coeruleus, raphe nucleus, and hypothalamus, with a 17%, 19%, and 14% decrease per decade, respectively, in each region. No gender or BMI relationships with NET availability were observed. Our findings suggest an age‐related decline, but no BMI‐ or gender‐related differences, in NET availability in healthy adults.