Obesity is associated with alterations in brain structure and cognitive impairment. The mechanisms underlying obesity related decline in cognitive function are not well understood. Obesity related chronic systemic inflammation is postulated to be one of the potential mechanisms leading to cognitive dysfunction. It is unknown whether inflammation impacts brain areas important for higher level cognition such as the anterior cingulate cortex (ACC). Elevated myo-inositol (Ins), as measured by magnetic resonance spectroscopy (MRS), may be a marker of neuroinflammation and reflects activated astrocytes and microglia. We hypothesized that obese subjects (OB) will have higher ACC Ins compared to normal weight controls (CON) and that higher Ins will be associated with elevated blood inflammatory markers and reduced cognitive performance. We examined neurochemical profile from a 24x24x12mm3 voxel over the ACC using 1H MRS at 3 and 7 Tesla (T), in 5 nondiabetic OB (age 33 ± 5 years, BMI 43 ± 6 kg/m2) and 4 CON (age 36 ± 3 years, BMI 23 ± 3 kg/m2). Subjects also underwent cognitive testing and measurement of blood inflammatory markers. MR spectra were quantified using LCModel and the concentrations are expressed as a ratio to total creatine (tCr). There was a strong trend of higher Ins/tCr in ACC in OB compared to CON both at 3T (0.96 ± 0.06 vs. 0.88 ± 0.05, p =0.07) and 7T (0.91 ± 0.07 vs. 0.83 ± 0.08, p =0.17). Pearson correlations were used to test the relationship between Ins/tCr and markers of inflammation among all subjects. Higher blood inflammatory markers were associated with higher Ins/tCr (3T) in ACC (CRP, r=.74, p= 0.04; TNF α, r=.89, p=0.003) and with low levels of crystallized ability as measured by the NIH Toolbox Cognition Battery (CRP, r=-.73, p=0.03). Higher ACC Ins/tCr was also associated with poorer performance on a measure of fine motor coordination (r=.93, p=0.001). These data support the hypothesis that inflammation may contribute to the pathogenesis of brain and cognitive alterations in obesity.
A. Khan: None. J.M. Joers: None. M. Luciana: None. N. Rubin: None. Y. Siddiqui: None. S. Mangia: None. L.E. Eberly: None. S. Ikramuddin: Research Support; Self; Medtronic. E.R. Seaquist: Advisory Panel; Self; Eli Lilly and Company, Zucara Therapeutics Inc. Consultant; Self; 360 Consulting, MannKind Corporation. Research Support; Self; Eli Lilly and Company, JDRF, National Institutes of Health. Other Relationship; Self; American Diabetes Association, Sanofi, WebMD. G. Oz: None. A. Moheet: None.
National Institutes of Health