Dataset Information

Higher Blood Pressure Partially Links Greater Adiposity to Reduced Brain White Matter Integrity.

ABSTRACT:

Background

Adiposity and elevated blood pressure (BP) are associated with brain structure abnormalities, but whether these effects are independent is unknown. We tested whether associations between adiposity and white matter integrity were explained by elevated BP.

Methods

A sample of 209 middle-aged adults underwent diffusion tensor imaging to quantify indirect metrics of white matter structural integrity. These included putative markers of global white matter integrity (fractional anisotropy (FA)), axonal integrity (axial diffusivity), and myelin integrity (radial diffusivity). Participants were either normotensive or prehypertensive.

Results

After adjusting for age and sex, regression analyses showed that waist circumference was associated with FA (? = -0.15, P < 0.05) and axial diffusivity (? = -0.24, P < 0.001), and mean arterial pressure (MAP) was associated with FA (? = -0.21, P < 0.05). Direct and indirect effect analyses showed that waist circumference was indirectly associated with whole brain FA through MAP (? = -0.06), and directly related to whole brain axial diffusivity, independent of MAP (? = -0.24). Examination of specific white matter tracts yielded similar results; waist circumference was indirectly related to FA through MAP and radial diffusivity, and directly related to axial diffusivity, independent of MAP. Supplemental analyses using body mass index, systolic BP, and diastolic BP also yielded similar results.

Conclusion

These findings suggest at least 2 mechanisms explain the adiposity and white matter association: one pathway through elevated BP impacting global white matter integrity and reducing integrity of the myelin sheath, and at least one other adiposity-specific pathway decreasing axonal integrity.

SUBMITTER: Allen B

PROVIDER: S-EPMC5661494 | biostudies-literature | 2016 Sep

REPOSITORIES: biostudies-literature

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Project description:BackgroundThe aim of this study was to investigate whether default mode network (DMN) connectivity and brain white matter integrity at baseline were associated with severe cognitive impairments at baseline and poor cognitive outcomes after shunt placement in patients with idiopathic normal pressure hydrocephalus (iNPH).MethodsTwenty consecutive patients with iNPH whose symptoms were followed for 6 months after shunt placement and 10 healthy controls (HCs) were enrolled. DMN connectivity and brain white matter integrity at baseline in the patients with iNPH and HCs were detected by using resting-state functional magnetic resonance imaging (MRI) with independent component analysis and diffusion tensor imaging, respectively, and these MRI indexes were compared between the patients with iNPH and HCs. Performance on neuropsychological tests for memory and executive function and on the gait test was assessed in the patients with iNPH at baseline and 6 months after shunt placement. We divided the patients with iNPH into the relatively preserved and reduced DMN connectivity groups using the MRI indexes for DMN connectivity and brain white matter integrity, and the clinical measures were compared between the relatively preserved and reduced DMN connectivity groups.ResultsMean DMN connectivity in the iNPH group was significantly lower than that in the HC group and was significantly positively correlated with Rey auditory verbal learning test (RAVLT) immediate recall scores and frontal assessment battery (FAB) scores. Mean fractional anisotropy of the whole-brain white matter skeleton in the iNPH group was significantly lower than that in the HC group. The reduced DMN connectivity group showed significantly worse performance on the RAVLT at baseline and significantly worse improvement in the RAVLT immediate recall and recognition scores and the FAB scores than the preserved DMN connectivity group. Moreover, the RAVLT recognition score highly discriminated patients with relatively preserved DMN connectivity from those with relatively reduced DMN connectivity.ConclusionsOur findings indicated that iNPH patients with reduced DMN connectivity relative to the severity of brain white matter disruption have severe memory deficits at baseline and poorer cognitive outcomes after shunt placement. However, further larger-scale studies are needed to confirm these findings.