Associations Between Brain Gray Matter Volumes and Adipose Tissue Metabolism in Healthy Adults

Objective Gray matter (GM) volume in different brain loci has been shown to vary in obesity and diabetes, and elevated fasting plasma nonesterified fatty acid (NEFA) levels have been suggested as one potential mechanism. The hypothesis presented in this study is that brown adipose tissue (BAT) activity may correlate with GM volume in areas negatively associated with obesity and diabetes. Methods A total of 36 healthy patients (M/F: 12/24, age 39.7 +/- 9.4 years, BMI 27.5 +/- 5.6 kg/m(2)) were imaged with positron emission tomography using fatty acid analog [F-18]FTHA to measure NEFA uptake and with [O-15]H2O to measure perfusion during cold exposure, at room temperature during fasting, or during a postprandial state. A 2-hour hyperinsulinemic euglycemic clamp was performed to measure whole-body insulin sensitivity (M value, mean 7.6 +/- 3.9 mg/kg/min). T1-weighted magnetic resonance imaging at 1.5 T was performed on all patients. Results BAT NEFA uptake was associated directly with GM volume in anterior cerebellum and occipital lobe (P <= 0.04) when adjusted for age, gender, and intra-abdominal fat volume and with anterior cerebellum, limbic lobe, and temporal lobe GM volumes when adjusted for M value. Conclusions BAT NEFA metabolism may participate in protection from cognitive degeneration associated with cardiometabolic risk factors, such as central obesity and insulin resistance. Potential causal relationships between BAT activity and GM volumes remain to be examined.