Lower serum osteocalcin concentrations are associated with brain microstructural changes and worse cognitive performance

OBJECTIVE

Rodent models have found that osteocalcin crosses the blood-brain barrier and regulates behaviour. No data are available on osteocalcin's effects on brain microstructure and cognitive performance in humans. We evaluated the association between serum osteocalcin concentrations and (i) brain microstructural changes on magnetic resonance imaging (MRI) and (ii) neuropsychological performance.

DESIGN, PATIENTS AND MEASUREMENTS

We studied 24 consecutive obese subjects (13 women; age, 49·8 ± 8·1 years; body mass index [BMI], 43·9 ± 4·54 kg/m(2) ) and 20 healthy volunteers (10 women; age, 48·8 ± 9·5 years; BMI, 24·3 ± 3·54 kg/m(2) ) in a cross-sectional study within the multicentre FLORINASH Project. FLAIR signal intensity and DTI-metrics (primary (λ1 ), secondary (λ2 ) and tertiary (λ3 ) eigenvalues; fractional anisotropy (FA); and mean diffusivity) in the caudate, hypothalamus, thalamus and putamen, and in subcortical white matter were assessed. Cognitive performance evaluated by neuropsychological test battery.

RESULTS

Lower osteocalcin concentrations were associated with BMI, higher λ1, λ2 and λ3 values at the caudate and lower FLAIR signal intensity at the caudate and putamen. Obese patients with lower osteocalcin concentrations had higher FA at putamen and thalamus. Lower osteocalcin concentrations were associated with higher Iowa Gambling Task (IGT) scores. FLAIR signal intensity at the caudate <601·832 yielded 85·7% sensitivity, 64·3% specificity, 70·6% negative predictive value and 81·8% positive predictive value for IGT score. Lower osteocalcin was an independent predictor of worse cognitive performance on multivariate analysis (F = 3·551, P = 0·01343; R(2) = 0·103). Bayesian information criterion demonstrated that osteocalcin had the predominant role in predicting IGT score.

CONCLUSIONS

Lower serum osteocalcin concentrations are associated with brain microstructural changes and worse cognitive performance.

Gut Microbiota Interacts With Brain Microstructure and Function

CONTEXT

Evidence from animals suggests that gut microbiota affects brain structure and function but evidence in humans is scarce.

OBJECTIVE

This study sought to evaluate potential interactions among gut microbiota composition, brain microstructure, and cognitive tests in obese and nonobese subjects.

DESIGN, SETTING, AND PARTICIPANTS

This was a cross-sectional study at a tertiary hospital including 20 consecutive obese and 19 nonobese subjects similar in age and sex.

MAIN OUTCOME MEASURES

Gut microbiota (16S bacterial gene pyrosequencing), brain microstructure (diffusion tensor imaging of brain white and gray matter and R2* sequences in magnetic resonance imaging) and cognitive tests.

RESULTS

Hierarchical clustering revealed a specific gut microbiota-brain map profile for obese individuals who could be discriminated from nonobese subjects (accuracy of 0.81). Strikingly, Shannon index was linked to R2* and fractional anisotropy of the hypothalamus, caudate nucleus, and hippocampus, suggesting sparing of these brain structures with increased bacterial biodiversity. Microbiota profile also clustered with cognitive function. The relative abundance of Actinobacteria phylum was linked not only to magnetic resonance imaging diffusion tensor imaging variables in the thalamus, hypothalamus, and amygdala but also to cognitive test scores related to speed, attention, and cognitive flexibility.

CONCLUSIONS

In sum, obesity status affects microbiota-brain microstructure and function crosstalk.

Magnetic resonance imaging biomarkers of ischemic stroke: criteria for the validation of primary imaging biomarkers

Ischemic stroke is associated with a high rate of disability and death. Establishing valid biomarkers could help accelerate the approval of promising new therapies for stroke. Whereas many serum biomarkers have been evaluated, possible imaging biomarkers of stroke lack validation. Magnetic resonance imaging (MRI) is a very sensitive technique to study acute stroke and MRI parameters have been established to assess the outcome of acute stroke. This review reassesses the criteria for the validation of MRI biomarkers of acute ischemic stroke (MRI-BAS). Seven criteria were used to review the validity of the main MRI-BAS: vascular status, lesion volume, reversibility on diffusion-weighted imaging, perfusion alteration, penumbra studied with diffusion-perfusion mismatch, clinical-diffusion mismatch, diffusion-angiography mismatch and hemorrhagic transformation. We analyzed the definitions of these biomarkers and the extent to which each fulfills the criteria for validation and found that few MRI-BAS have been fully validated. Further studies should help to improve the validation of current MRI-BAS and develop new biomarkers.