Associations of cardiorespiratory fitness and exercise with brain white matter in healthy adults: A systematic review and meta-analysis.

Magnetic resonance imaging (MRI) studies have revealed positive associations between brain structure and physical activity, cardiorespiratory fitness, and exercise (referred to here as PACE). While a considerable body of research has investigated the effects of PACE on grey matter, much less is known about effects on white matter (WM). Hence, we conducted a systematic review of peer-reviewed literature published prior to 5th July 2021 using online databases (PubMed and Scopus) and PRISMA guidelines to synthesise what is currently known about the relationship between PACE and WM in healthy adults. A total of 60 studies met inclusion criteria and were included in the review. Heterogeneity across studies was calculated using Qochran's q test, and publication bias was assessed for each meta-analysis using Begg and Mazumdar rank correlation test. A meta-regression was also conducted to explore factors contributing to any observed heterogeneity. Overall, we observed evidence of positive associations between PACE and global WM volume (effect size (Hedges's g) = 0.137, p < 0.001), global WM anomalies (effect size = 0.182, p < 0.001), and local microstructure integrity (i.e., corpus callosum: effect size = 0.345, p < 0.001, and anterior limb of internal capsule: effect size = 0.198, p < 0.001). These findings suggest that higher levels of PACE are associated with improved global WM volume and local integrity. We appraise the quality of evidence, and discuss the implications of these findings for the preservation of WM across the lifespan. We conclude by providing recommendations for future research in order to advance our understanding of the specific PACE parameters and neurobiological mechanisms underlying these effects.

Neural correlates of symptom severity in obsessive-compulsive disorder using magnetization transfer and diffusion tensor imaging.

Recent neuroimaging studies in OCD have reported structural alterations in the brain, not limited to frontostriatal regions. While Diffusion Tensor Imaging (DTI) is typically used to interrogate WM microstructure in OCD, additional imaging metric, such as Magnetization Transfer Imaging (MTI), allows for further identification of subtle but important structural changes across both GM and WM. In this study, both MTI and DTI were utilised to investigate the structural integrity of the brain, in OCD in relation to healthy controls. 38 adult OCD patients were recruited, along with 41 age- and gender-matched controls. Structural T1, MTI and DTI data were collected. Case-control differences in Magnetization Transfer Ratio (MTR) and DTI metrics (FA, MD) were examined, along with MTR/DTI-related associations with symptom severity in patients. No significant group differences were found across MTR, FA, and MD. However, OCD symptom severity was positively correlated with MTR in a distributed network of brain regions, including the striatum, cingulate, orbitofrontal area and insula. Within the same regions, OCD symptoms were also positively correlated with FA in WM, and negatively correlated with MD in GM. These results indicate a greater degree of myelination in certain cortical and subcortical regions in the more severe cases of OCD.

Serum Mannose-binding Lectin in Patients on Peritoneal Dialysis Compared With Healthy Individuals.

INTRODUCTION: The increased susceptibility to infection in patients with end-stage renal disease is probably secondary to the impaired immune defense in uremia. Mannose-binding lectin (MBL) has an important role in host defense through activation of the lectin complement pathway. The aim of this study was to measure serum MBL level in peritoneal dialysis patients and compare it with a healthy group. MATERIALS AND METHODS: Seventy peritoneal dialysis patients and 70 healthy individuals were enrolled in this study. Serum MBL levels were measured by an enzyme-linked immunosorbent assay kit using the mannan molecule. In addition, serum C-reactive protein and albumin levels were measured to determine whether there is a correlation between serum MBL level and these two parameters. RESULTS: The mean serum MBL level was 2.32 ± 2.54 µg/mL (range, zero to 6.93 µg/mL) in the patients group and 1.80 ± 2.14 µg/mL (range, zero to 6.97µg/mL) in the control group (P = .19). No significant correlation was detected between age and serum MBL level in either the groups. In the patients group, no significant correlation was found between serum MBL and C-reactive protein levels or MBL and albumin levels. There were no correlation between duration of peritoneal dialysis and MBL or dialysis adequacy and MBL, either. CONCLUSIONS: This study did not find MBL deficiency in peritoneal dialysis patients as compared to the healthy individuals.