Abstract
OBJECTIVE: To use quantitative magnetic resonance imaging (MRI) to test whether mediobasal hypothalamic (MBH) gliosis is associated with obesity and insulin resistance in humans. METHODS: Sixty-seven participants underwent a fasting blood draw and MRI. Cases with radiologic evidence of MBH gliosis (N = 22) were identified as the upper tertile of left MBH T2 relaxation time and were compared to controls (N = 23) from the lowest tertile. In a separate postmortem study, brain slices (N = 10) through the MBH were imaged by MRI and stained for glial fibrillary acidic protein (GFAP). RESULTS: In all participants, longer T2 relaxation time in the left MBH was associated with higher BMI (P = 0.01). Compared with controls, cases had longer T2 relaxation times in the right MBH (P < 0.05), as well as higher BMI (P < 0.05), fasting insulin concentrations (P < 0.01), and HOMA-IR values (P < 0.01), adjusted for sex and age. Elevations in insulin and HOMA-IR were also independent of BMI. In the postmortem study, GFAP staining intensity was positively associated with MBH T2 relaxation time (P < 0.05), validating an MRI-based method for the detection of MBH gliosis in humans. CONCLUSIONS: These findings link hypothalamic gliosis to insulin resistance in humans and suggest that the link is independent of the level of adiposity.