Unraveling the gut-brain connection: The association of microbiota-linked structural brain biomarkers with behavior and mental health.

AIM: The gut microbiota can influence human behavior. However, due to the massive multiple-testing problem, research into the relationship between microbiome ecosystems and the human brain faces drawbacks. This problem arises when attempting to correlate thousands of gut bacteria with thousands of brain voxels. METHODS: We performed brain magnetic resonance imaging (MRI) scans on 133 participants and applied machine-learning algorithms (Ridge regressions) combined with permutation tests. Using this approach, we were able to correlate specific gut bacterial families with brain MRI signals, circumventing the difficulties of massive multiple testing while considering sex, age, and body mass index as confounding factors. RESULTS: The relative abundance (RA) of the Selenomonadaceae, Clostridiaceae, and Veillonellaceae families in the gut was associated with altered cerebellar, visual, and frontal T2-mapping and diffusion tensor imaging measures. Conversely, decreased relative abundance of the Eubacteriaceae family was also linked to T2-mapping values in the cerebellum. Significantly, the brain regions associated with the gut microbiome were also correlated with depressive symptoms and attentional deficits. CONCLUSIONS: Our analytical strategy offers a promising approach for identifying potential brain biomarkers influenced by gut microbiota. By gathering a deeper understanding of the microbiota-brain connection, we can gain insights into the underlying mechanisms and potentially develop targeted interventions to mitigate the detrimental effects of dysbiosis on brain function and mental health.

Increased brain fractional perfusion in obesity using intravoxel incoherent motion (IVIM) MRI metrics.

OBJECTIVE: This research seeks to shed light on the associations between brain perfusion, cognitive function, and mental health in individuals with and without obesity. METHODS: In this study, we employed the noninvasive intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) technique to examine brain fractional perfusion (FP) in two groups: individuals with obesity (N = 72) and healthy controls (N = 66). Additionally, we investigated potential associations between FP, cognitive function, and depressive symptoms in the participants with and without obesity. Finally, artificial intelligence algorithms (Boruta analysis) were also used. RESULTS: Participants with obesity exhibited increased FP within dopaminergic brain circuits, particularly involving prefrontal cortex areas, anterior and posterior sections of the cingulate cortex, the right striatum, and the midbrain. Additionally, these individuals demonstrated lower working memory and higher depressive symptoms compared to the control group. Notably, higher FP in the inferior temporal and occipital cortices correlated with greater depressive symptoms, whereas increased FP in the right ventral caudate and the midbrain was associated with better working memory performance. A link between inflammatory and metabolic variables, with a particular emphasis on monocytes, and FP in obesity was also evidenced by Boruta analysis. CONCLUSIONS: Increased brain perfusion in individuals with obesity is associated with cognitive function and mental health through interaction with metabolic and inflammatory factors.

Lower serum ferritin levels are associated with worse cognitive performance in aging.

OBJECTIVES: Iron is important for neurogenesis, synaptic development, and neurotransmitter synthesis. Serum ferritin (SF) is a reliable marker for assessing iron stores. Therefore, we evaluated the cognitive function associated with SF levels. We also assessed brain iron content using R2* Magnetic Resonance Imaging (MRI) and its association with SF levels. DESIGN: Data from three cross-sectional observational studies were used. Aging Imageomics (n = 1030) was conducted on aged subjects. Health Imageomics (n = 971) and IR0NMET (n = 175) were conducted in middle-aged subjects. SETTING AND PARTICIPANTS: Participants were enrolled at Dr. Josep Trueta University Hospital facilities. The three cohorts included a total of 2176 subjects (mean age, 52 years; 48% men). MEASUREMENTS: SF levels were measured by standard laboratory methods. Total Digits Span (TDS), and Phonemic Verbal Fluency (PVF) were used to assess executive function. Language function was assessed by semantic verbal fluency (SVF), attention by the Symbol Digit Modalities Test, and memory by the Memory Binding Tests - Total Free Recall and Total Delayed Free Recall. MRI was used to assess the iron content of the brain by R2*. RESULTS: In subjects aged 65 years or older, SF levels were associated with increased TDS (ß = 0.003, p = 0.02), PVF (ß = 0.004, p = 0.01), and SVF (ß = 0.004, p = 0.002) scores. After stratification by sex, these findings were significant only in men, where SF was associated with increased TDS (ß = 0.003, p = 0.01), PVF (ß = 0.004, p = 0.03), and SVF (ß = 0.004, p = 0.009) scores. In middle-aged subjects, SF was also associated with increased SVF scores (ß = 0.005, p = 0.011). Lastly, in men, SF levels were negatively associated with R2*, a surrogate marker of brain iron content, in both the left frontal inferior opercular area (r = -0.41, p = 0.005) and the right frontal inferior opercular area (r = -0.44, p = 0.002). CONCLUSIONS: SF is significantly and positively associated with cognition. In older people with low SF levels, iron supplementation may be a promising therapy to improve cognition.

Differences in metacognition between multiple sclerosis phenotypes: cognitive impairment and fatigue are key factors.

Background: Cognitive impairment is present in 40-65% of patients with multiple sclerosis (pwMS). Objectively measured cognitive performance often does not match patients' subjective perception of their own performance. Objective: We aimed to compare cognitive performance and subjective perception of cognitive deficits between pwMS and healthy controls (HCs), as well as the accuracy of subjective perception. Methods: In total, 54 HC and 112 pwMS (relapsing-remitting, RRMS, and progressive PMS) underwent neuropsychological evaluation and completed perceived deficit, fatigue, and anxiety-depression scales. Participants were classified according to their consistency between subjective self-evaluation of cognitive abilities and objective cognitive performance to assess accuracy. Regression models were used to compare cognitive performance between groups and explore factors explaining inaccuracy in the estimation of cognitive performance. Results: PMS showed greater and more widespread cognitive differences with HC than RRMS. No differences were found between pwMS and HC in the perception of deficit. PMS had higher ratios of overestimators. In explaining inaccuracy, fatigue and cognitive preservation were found to be risk factors for underestimation, whereas physical disability and cognitive impairment were risk factors for overestimation. Conclusion: PwMS have metacognitive knowledge impairments. This study provides new information about metacognition, data on the prevalence of impairments over a relatively large sample of PwMS, and new insights into factors explaining it. Anosognosia, related to cognitive impairment, may be present in pwMS. Fatigue is a key factor in underestimating cognition.

Adipose tissue coregulates cognitive function.

Obesity is associated with cognitive decline. Recent observations in mice propose an adipose tissue (AT)-brain axis. We identified 188 genes from RNA sequencing of AT in three cohorts that were associated with performance in different cognitive domains. These genes were mostly involved in synaptic function, phosphatidylinositol metabolism, the complement cascade, anti-inflammatory signaling, and vitamin metabolism. These findings were translated into the plasma metabolome. The circulating blood expression levels of most of these genes were also associated with several cognitive domains in a cohort of 816 participants. Targeted misexpression of candidate gene ortholog in the Drosophila fat body significantly altered flies memory and learning. Among them, down-regulation of the neurotransmitter release cycle-associated gene SLC18A2 improved cognitive abilities in Drosophila and in mice. Up-regulation of RIMS1 in Drosophila fat body enhanced cognitive abilities. Current results show previously unidentified connections between AT transcriptome and brain function in humans, providing unprecedented diagnostic/therapeutic targets in AT.

An expert patient program to improve the empowerment and quality of life of people with multiple sclerosis: protocol for a multicenter pre-post intervention study.

Introduction: Multiple sclerosis (MS) causes a progressive disability, which substantially impacts the quality of life (QoL). Health interventions that meet the needs and demands of people with MS are essential to minimize QoL impairment. Expert patient programs (EPPs) facilitate health-related empowerment through peer learning. Based on a previous focus group study, we designed an EPP for MS coordinated by nursing professionals for implementation in the different MS reference units of Catalonia (Southwestern Europe). This study aims to evaluate the effects on quality of life, disease-related knowledge, and self-management related to the health process of the participants of the Expert Patient Program Catalonia™ for people with multiple sclerosis (EPPC-MS). Methods: Pre-post intervention multicenter clinical study involving 12 groups of 12 participants: six groups including relapsing and six groups including progressive MS patients, with 144 participants from 7 MS reference units from all over Catalonia, organized in six teams. The intervention will consist of nine telematic learning peer-led sessions (one weekly session). The expert patient (EP) leading the sessions will be an individual with MS with disease-related knowledge, who will be further trained by nurses to lead the sessions. Study variables will be measured before and immediately after the intervention and 6 and 12 months after the end of the sessions and will include: QoL, emotional impact, activation of the person, MS-related knowledge, fatigue, habits and lifestyles, health services use, and program-related experience. Baseline characteristics considered will be sociodemographic data, date of MS diagnosis and type, family history, and treatment characteristics. Variables related to disease follow-up will be new relapses and characteristics and changes in the ongoing treatment. The number of sessions attended will also be collected. Study variables will be analyzed using a pre-post comparison. Discussion: Peer-led learning programs led by EP help empower people with chronic conditions and offer them tools to improve their autonomy and QoL. This study's intervention will be performed remotely, offering advantages both for people with chronic conditions and the healthcare system regarding the facilitation of family and work conciliation, saving time, simplifying attendance to meetings, lowering costs, and using fewer material resources. Trial registration: NCT04988880 on September 22, 2021.

The nature of memory impairment in multiple sclerosis: understanding different patterns over the course of the disease.

Introduction: Memory deficit is one of the most common and severe cognitive impairments in patients with multiple sclerosis and can greatly affect their quality of life. However, there is currently no agreement as to the nature of memory deficit in multiple sclerosis. Methods: This cross-sectional study, carried out at the Dr. Josep Trueta and Santa Caterina hospitals in Girona (Spain), was designed to determine the semiology of verbal memory deficit in the different stages of the disease. To this end, a modification of Rey's verbal auditory test was created by introducing two recognition trials between the five learning trials, thus monitoring what happens in terms of acquisition versus the retrieval of information during the learning phase. Linear regression models were used to evaluate verbal episodic memory performance between-groups adjusting results by age, sex, educational level, and the presence of anxiety and/or depressive symptoms. Results: 133 patients with multiple sclerosis, clinically isolated syndrome, and radiologically isolated syndrome and 55 healthy controls aged 18-65 years were assessed. It was observed that the memory processes of multiple sclerosis patients worsen with the progression of the disease. In this respect, patients in pre-diagnostic phases (radiologically isolated syndrome and clinically isolated syndrome) show no differences in verbal episodic memory compared to the healthy controls. Patients in the inflammatory stage (relapsing-remitting multiple sclerosis) show a previously learned information retrieval deficit, while patients in progressive stages (secondary progressive multiple sclerosis and primary progressive multiple sclerosis) do not even correctly acquire information. Discussion: These results provide significant information to assist in understanding the nature of memory deficits in multiple sclerosis over the course of the disease. These results are discussed in terms of possible cognitive rehabilitation strategies depending on the evolutive stage and are related to neuropathological mechanisms involved in the progression of the disease.

Oligoclonal IgM bands are a promising biomarker for long-term cognitive outcomes in multiple sclerosis.

BACKGROUND: The presence of lipid-specific oligoclonal IgM bands (LS-OCMB) in cerebrospinal fluid is associated with a more severe clinical multiple sclerosis (MS) course. OBJECTIVE: To investigate LS-OCMB as a prognostic biomarker of cognitive long-term outcomes in MS. METHODS: Ninety-nine patients underwent neuropsychological assessment. Cognitive performance between LS-OCMB- and LS-OCMB+ patients was compared adjusting by age, education, anxiety-depression, disease duration, and disability. RESULTS: LS-OCMB+ patients of ∼13 years of disease duration performed worse on Symbol Digit Modalities Test (SDMT) (p = 0.005). CONCLUSION: LS-OCMB+ perform worse on information processing speed and working memory (SDMT), suggesting that LS-OCMB could be a useful biomarker for long-term cognitive outcomes.

Assessing the presence of oligoclonal IgM bands as a prognostic biomarker of cognitive decline in the early stages of multiple sclerosis.

BACKGROUND: An association has been found between the presence of lipid-specific oligoclonal IgM bands (LS-OCMB) in cerebrospinal fluid and a more severe clinical multiple sclerosis course. OBJECTIVE: To investigate lipid-specific oligoclonal IgM bands as a prognostic biomarker of cognitive impairment in the early stages of multiple sclerosis. METHODS: Forty-four patients underwent neuropsychological assessment at baseline and 4 years. Cognitive performance at follow-up was compared adjusting by age, education, anxiety-depression, and baseline performance. RESULTS: LS-OCMB+ patients only performed worse for Long-Term Storage in the Selective Reminding Test (p = .018). CONCLUSION: There are no remarkable cognitive differences between LS-OCMB- and LS-OCMB+ patients in the early stages of MS.