Association between Visceral Fat and Brain Structural Changes or Cognitive Function

Associations of the body roundness index with cognitive function in US older adults and the mediating role of depression: a cross-sectional study from the NHANES 2011-2014

The body roundness index (BRI) accurately assesses body composition and visceral fat distribution, but its independent associations with cognitive function and cognitive impairment remain unclear. This study, which is based on data from the 2011-2014 U.S. National Health and Nutrition Examination Survey (NHANES), explores the associations between the BRI and cognitive function as well as cognitive impairment in older adults. Weighted linear regression and weighted logistic regression models were used for data analysis. Restricted cubic spline (RCS) models, subgroup analysis, and mediation analysis were conducted to explore effect modification, nonlinear associations, and the mediating role of depression. The BRI score was negatively correlated with the cognitive function score (DSST score β = -0.63, P = 0.037; Sum Score β = -0.83, P = 0.042) and was not significantly associated with cognitive impairment. As the BRI score increases, both the DSST score (trend P = 0.013) and the Sum Score (trend P = 0.023) show a linear decrease. The mediation effect analysis revealed that depression mediated 39.4% of the association between the BRI score and cognitive function, suggesting that the effect may be indirectly mediated through mental health pathways. Subgroup analysis and RCS models did not reveal significant interaction effects or nonlinear associations.

Role of obesity-related anthropometric indicators on cognitive function in obese older adults: A systematic review and meta-analysis

OBJECTIVES

The association between obesity and cognitive function in older adults remains inconsistent due to the use of various anthropometric indicators, such as body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR). More conclusive evidence is warranted. The aim of this study was to systematically summarize and synthesize the association between specific obesity-related anthropometric indicators (BMI, WC, and WHR) and cognitive function in obese older adults. Higher BMI, WC, or WHR is linked to cognitive decline in this population.

STUDY DESIGN

Systematic review and meta-analysis.

METHODS

A comprehensive literature search was carried out using PubMed, CINAHL, Scopus, Embase, and the Cochrane Library (from their inception to October 2023). Studies investigating the association between obesity indicators, including BMI, WC, WHR, and cognitive performance in older adults were included. The weighted mean difference (WMD), Odds Ratio, and 95 % confidence interval (CI) were used to estimate the pooled effect size. A random-effects model was employed as the main method. Subgroup analyses and the certainty of evidence using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach were assessed (registered number: CRD42023461770).

RESULTS

Thirty-three eligible studies, involving 83,251 participants, were included. Obese older adults, as assessed by WC, had lower Mini-Mental State Examination (MMSE) scores than non-obese counterparts (WMD -0.84, 95 % CI -1.64 to -0.05, very low certainty). Those measured by WHR had a 31 % higher risk of cognitive impairment (OR 1.31, 95 % CI 1.12 to 1.53, moderate certainty). Subgroup analysis revealed a lower Montreal Cognitive Assessment (MoCA) score in obese group classified by WHO criteria compared to controls (WMD -1.67, 95 % CI -2.94 to -0.39).

CONCLUSION

This review suggests an association between obesity, as measured by WHR and WC, and poorer cognitive performance in older adults. WHR is moderately recommended for identifying cognitive impairment-related obesity, while WC recommendations are limited by very low evidence certainty.

Association of body composition with neuroimaging biomarkers and cognitive function; a population-based study of 70-year-olds

BACKGROUND

A better understanding of body-brain links may provide insights on targets for preventing cognitive decline. The aim was to explore associations of body composition with neuroimaging biomarkers and cognitive function among dementia-free 70-year-olds.

METHODS

Dual-energy X-ray absorptiometry body composition measures in relation to neuroimaging measures of cortical thickness, hippocampal volume, small vessel disease, predicted brain age, and cognitive performance were explored in a cross-sectional study of 674 dementia-free 70-year-olds from the Swedish Gothenburg H70 Birth Cohort study. Linear or ordinal regression analyses were performed.

FINDINGS

Higher quantity of muscle mass was associated with lower predicted brain age (β: -0.31 [95% CI: -0.45, -0.16], p: 0.00013). Those with normal level muscle mass (>7.0 men, >5.5 women kg/height m2) had overall thicker cortex (β: 0.043 [95% CI: 0.023, 0.064], p: 0.00016), thicker cortex in Alzheimer's disease signature regions (β: 0.051 [95% CI: 0.025, 0.076], p: 0.00040), and larger hippocampal volume (β: 111.52 [95% CI: 25.28, 197.75], p: 0.030) compared to those with sarcopenic level muscle mass. Higher accumulation of visceral fat was associated with overall thinner cortex (β: -0.017 [95% CI: -0.028, -0.005], p: 0.024). Faster gait speed and higher handgrip strength were associated with indicators of better brain health.

INTERPRETATION

Improving muscle mass fitness and lower visceral fat may be beneficial for brain health. Intervention studies are needed to confirm that targeting body composition can promote healthy brain ageing and reduce the risk of cognitive impairment among older adults.

FUNDING

The Swedish Research Council, Hjärnfonden, and Alzheimerfonden.

Weight trajectories in aging humanized APOE mice with translational validity to human Alzheimer's risk population: A retrospective analysis

Translational validity of mouse models of Alzheimer's disease (AD) is variable. Because change in weight is a well-documented precursor of AD, we investigated whether diversity of human AD risk weight phenotypes was evident in a longitudinally characterized cohort of 1,196 female and male humanized APOE (hAPOE) mice, monitored up to 28 months of age which is equivalent to 81 human years. Autoregressive Hidden Markov Model (AHMM) incorporating age, sex, and APOE genotype was employed to identify emergent weight trajectories and phenotypes. In the hAPOE-AD mouse cohort, five distinct weight trajectories emerged: three trajectories were associated with a weight loss phenotype (36% of mice, n = 426), one with weight gain (13% of mice, n = 152), and one trajectory of no change in weight (34% of mice, n = 403). The AHMM model findings were validated with post-hoc survival analyses, revealing differences in survival rates across the five identified phenotypes. Further validation was performed using body composition and plasma β-amyloid data from mice within the identified gain, loss and stable weight trajectories. Weight gain trajectory was associated with elevated plasma β-amyloid levels, higher body fat composition, lower survival rates and a greater proportion of APOE4/4 carriers. In contrast, weight loss was associated with greater proportion of hAPOE3/4 carriers, better survival rates and was predominantly male. The association between weight change and AD risk observed in humans was mirrored in the hAPOE-AD mouse model. Weight trajectories of APOE3/3 mice were equally distributed across weight gain, loss and stability. Surprisingly, despite genetic uniformity, comparable housing, diet and handling, distinct weight trajectories and divergence points emerged for subpopulations. These data are consistent with the heterogeneity observed in the human population for change in body weight during aging and highlight the importance of longitudinal phenotypic characterization of mouse aging to advance the translational validity of preclinical AD mouse models.

The Association Between Metabolic Score for Visceral Fat and Cognitive Function Among Older Adults in the United States

BACKGROUND

Although several studies have demonstrated a link between obesity and cognitive function, the majority have primarily utilized body mass index (BMI) and waist circumference, ignoring the distribution of body fat. Evidence regarding the association of metabolic score for visceral fat (METS-VF), a proposed measurement for visceral adipose tissue (VAT), with cognitive function remains limited. We mainly aimed to investigate this association in older adults in the United States.

METHODOLOGY

Data were from the National Health and Nutrition Examination Survey (NHANES) 2011 to 2014. Weighted linear regression models were adopted to examine the association of METS-VF and cognitive function scores, with further exploration of these associations across different obesity subgroups. Smoothing curve analysis, along with threshold and saturation effect analysis, were conducted to explore potential non-linear relationships.

RESULTS

In the multivariable-adjusted model, participants in the highest quartile (Quartile 4) of METS-VF exhibited a β coefficient of -1.52 [95% CI (-2.43, -0.62)] for the CERAD score compared with those in the lowest quartile (Quartile 1). Threshold and saturation effect analysis revealed non-linear associations of METS-VF with DSST score and Z-score.

CONCLUSIONS

The findings of this study indicate that elevated METS-VF scores are inversely related to cognitive function, highlighting the importance of considering visceral fat distribution in cognitive health assessments.

A multifactorial lens on risk factors promoting the progression of Alzheimer's disease

The prevalence of Alzheimer's disease (AD) among adults has continued to increase over the last two decades, which has sparked a significant increase in research that focuses on the topic of "brain health." While AD is partially determined by a genetic predisposition, there are still numerous pathophysiological factors that require further research. This research requirement stems from the acknowledgment that AD is a multifactorial disease that to date, cannot be prevented. Therefore, addressing and understanding the potential AD risk factors is necessary to increase the quality of life of an aging population. To raise awareness of critical pathways that impact AD progression, this review manuscript describes AD etiologies, structural impairments, and biomolecular changes that can significantly increase the risk of AD. Among them, a special highlight is given to inflammasomes, which have been shown to bolster neuroinflammation. Alike, the role of brain-derived neurotrophic factor, an essential neuropeptide that promotes the preservation of cognition is presented. In addition, the functional role of neurovascular units to regulate brain health is highlighted and contrasted to inflammatory conditions, such as cellular senescence, vascular damage, and increased visceral adiposity, who all increase the risk of neuroinflammation. Altogether, a multifactorial interventional approach is warranted to reduce the risk of AD.

Rewiring of the glymphatic landscape in metabolic disorders

The incorporation of the glymphatic clearance system in the study of brain physiology aids in the advancement of innovative diagnostic and treatment strategies for neurological disorders. Exploring the glymphatic system across (from) neurological and (to) metabolic diseases may provide a better link between obesity and neurological disorders. Recent studies indicate the role of metabolic dysfunction as a risk factor for cognitive decline and neurological disorders through the disruption of the glymphatic system. Further investigation into how metabolic dysfunction disrupts glymphatic homeostasis and the domino effects on the neurovascular landscape, including neurovascular uncoupling, cerebral blood flow disruptions, blood-brain barrier leakage, and demyelination, can provide mechanistic insights into the link between obesity and neurological disorders.

Visceral adiposity is associated with iron deposition and myelin loss in the brains of aged mice

Iron deposition and myelin loss are observed in the brain with aging, and iron accumulation is suggested to be involved in myelin damage. However, the exact mechanism of iron deposition with aging remains unclear. This study was aimed to determine whether expanded visceral adipose tissue contributes to iron deposition and myelin loss by inducing hepcidin in the brains of aged male mice. Compared with young adult mice, levels of hepcidin in the brain, epididymal adipose tissue, and circulation were increased in aged mice, which had expanded visceral adipose tissue with inflammation. An increase in expressions of ferritin, an indicator of intracellular iron status, was accompanied by decreased levels of proteins related to myelin sheath in the brains of aged mice. These age-related changes in the brain were improved by visceral fat removal. In addition, IL-6 level, activation of microglia/macrophages, and nuclear translocation of phosphorylated Smad1/5 (pSmad1/5) inducing hepcidin expression were reduced in the brains of aged mice after visceral fat removal, accompanied by decreases of pSmad1/5- and ferritin-positive microglia/macrophages and mature oligodendrocytes. These findings indicate that visceral adiposity contributes to hepcidin-mediated iron deposition and myelin loss with inflammation in the aged brain. Our results support the importance of preventing visceral adiposity for maintaining brain health in older individuals.

Association between abdominal adiposity and cognitive decline in older adults: a 10-year community-based study

OBJECTIVES

This study aimed to investigate the association between abdominal adiposity and change in cognitive function in community-dwelling older adults.

DESIGN, SETTING, AND PARTICIPANTS

This longitudinal study included older adults aged ≥60 years without cognitive impairment who participated in the National Institute for Longevity Sciences - Longitudinal Study of Aging.

MEASUREMENTS

Cognitive function was evaluated biennially using the Mini-Mental State Examination (MMSE) over 10 years. Waist circumference (WC) was measured at the naval level, and subcutaneous fat area (SFA) and visceral fat area (VFA) were assessed using baseline computed tomography scans. WC, SFA, and VFA areas were stratified into sex-adjusted tertiles. A linear mixed model was applied separately for men and women.

RESULTS

This study included 873 older adults. In men, the groups with the highest levels of WC, SFA, and VFA exhibited a greater decline in MMSE score than the groups with the lowest levels (β [95% confidence interval]: WC, -0.12 [-0.23 to -0.01]; SFA, -0.13 [-0.24 to -0.02]; VFA, -0.11 [-0.22 to -0.01]). In women, the group with the highest level of WC and SFA showed a greater decline in MMSE score than the group with the lowest level (WC, -0.12 [-0.25 to -0.01]; SFA, -0.18 [-0.30 to -0.06]), but VFA was not associated with cognitive decline.

CONCLUSION

Higher WC, SFA, and VFA in men and higher WC and SFA in women were identified as risk factors for cognitive decline in later life, suggesting that abdominal adiposity involved in cognitive decline may differ according to sex.

Overview of the Current Knowledge and Conventional MRI Characteristics of Peri- and Para-Vascular Spaces

Brain spaces around (perivascular spaces) and alongside (paravascular or Virchow-Robin spaces) vessels have gained significant attention in recent years due to the advancements of in vivo imaging tools and to their crucial role in maintaining brain health, contributing to the anatomic foundation of the glymphatic system. In fact, it is widely accepted that peri- and para-vascular spaces function as waste clearance pathways for the brain for materials such as ß-amyloid by allowing exchange between cerebrospinal fluid and interstitial fluid. Visible brain spaces on magnetic resonance imaging are often a normal finding, but they have also been associated with a wide range of neurological and systemic conditions, suggesting their potential as early indicators of intracranial pressure and neurofluid imbalance. Nonetheless, several aspects of these spaces are still controversial. This article offers an overview of the current knowledge and magnetic resonance imaging characteristics of peri- and para-vascular spaces, which can help in daily clinical practice image description and interpretation. This paper is organized into different sections, including the microscopic anatomy of peri- and para-vascular spaces, their associations with pathological and physiological events, and their differential diagnosis.

Impact of insulin resistance on mild cognitive impairment in type 2 diabetes mellitus patients with non-alcoholic fatty liver disease

AIMS

Insulin resistance (IR) is a pivotal factor in the pathogenesis of type 2 diabetes mellitus (T2DM) and non-alcoholic fatty liver disease (NAFLD). Nevertheless, the impact of IR on cognitive dysfunction in T2DM patients with NAFLD remains inadequately understood. We aim to investigate the effect of IR on mild cognitive impairment (MCI) in T2DM individuals with NAFLD.

MATERIALS AND METHODS

143 T2DM individuals were categorized into Non-MCI and MCI groups, as well as Non-NAFLD and NAFLD groups. Clinical parameters and cognitive preference test outcomes were compared. Correlation and regression analyses were executed to explore the interconnections between IR and cognitive details across all T2DM patients, as well as within the subgroup of individuals with NAFLD.

RESULTS

In comparison to the Non-MCI group, the MCI group displayed elevated HOMA-IR levels. Similarly, the NAFLD group exhibited higher HOMA-IR levels compared to the Non-NAFLD group. Additionally, a higher prevalence of MCI was observed in the NAFLD group as opposed to the Non-NAFLD group. Notably, HOMA-IR levels were correlated with Verbal Fluency Test (VFT) and Trail Making Test-B (TMTB) scores, both related to executive functions. Elevated HOMA-IR emerged as a risk factor for MCI in the all patients. Intriguingly, increased HOMA-IR not only correlated with TMTB scores but also demonstrated an influence on TMTA scores, reflecting information processing speed function in patients with NAFLD.

CONCLUSION

IR emerges as a contributory factor to cognitive dysfunction in T2DM patients. Furthermore, it appears to underlie impaired executive function and information processing speed function in T2DM individuals with NAFLD.

Effects of sleep on brain perivascular space in a cognitively healthy population

The magnetic resonance imaging (MRI) visible perivascular space (PVS) reportedly clears amyloid-β and metabolic waste during sleep. Previous studies reported an association between sleep and the PVS in small vessel disease, traumatic brain injury, and Alzheimer's disease. However, this relationship in a healthy cohort is still unclear. Here, we used the Human Connectome Project Aging dataset to analyze the relationship between sleep and the PVS in cognitively healthy adults across the aging continuum. We measured sleep parameters using the self-reported Pittsburgh Sleep Quality Index questionnaire. We found that older adults who had better sleep quality and sleep efficiency presented with a larger PVS volume fraction in the basal ganglia (BG). However, sleep measures were not associated with PVS volume fraction in the centrum semiovale (CSO). In addition, we found that body mass index (BMI) influenced the BG-PVS across middle-aged and older participants. In the entire cognitively healthy cohort, the effect of sleep quality on PVS volume fraction was mediated by BMI. However, BMI did not influence this effect in the older cohort. Furthermore, there are significant differences in PVS volume fraction across racial/ethnic cohorts. In summary, the effect of sleep on the PVS volume alteration was different in the middle-aged adults and older adults.

Effect of Continuous Ingestion of Bifidobacteria and Dietary Fiber on Improvement in Cognitive Function: A Randomized, Double-Blind, Placebo-Controlled Trial

Bifidobacterium animalis subsp. lactis GCL2505 has been shown to have some positive effects on health, including improved defecation frequency and reduced visceral fat. These effects are thought to be due to GCL2505's unique ability to reach the intestine in a viable form and proliferate after a single intake. This leads to an increased number of intestinal bifidobacteria. This randomized, double-blind, placebo-controlled, parallel-group study was conducted to confirm that intake of GCL2505 and inulin (a prebiotic) improve cognitive function (n = 80). Participants consumed test drinks containing 1 × 1010 colony-forming units of GCL2505 per 100 g and 2.0 g of inulin per 100 g for 12 weeks. The change in cognitive function assessment scores was set as the primary endpoint. There were significant improvements in scores in the neurocognitive index domain, which is an assessment of overall cognitive function, in addition to overall attention, cognitive flexibility, and executive function domains. The intervention significantly increased the number of fecal bifidobacteria and affected the levels of several inflammatory markers. These results suggest that intake of GCL2505 and inulin improves cognitive function by improving the intestinal environment and alleviating inflammation.

Gender-specific factors associated with the Japanese version of the trail making test among Japanese workers

[Purpose] The Trail Making Test is a valuable tool for predicting the transition from mild cognitive impairment to dementia. This cross-sectional study aimed to investigate gender-specific factors associated with the Trail Making Test using body composition and motor function among Japanese workers. [Participants and Methods] Demographic data, body composition, motor function, and cognitive and attentional functions (Trail Making Test, Part B) were analyzed among 627 workers who underwent health assessments during the 2019 fiscal year. After conducting univariate analysis, multiple regression analysis was performed. [Results] The presence of metabolic syndrome risk factors was found to significantly prolonged the performance time of the Trail Making Test-B in male workers. In addition, low fat-free mass and the 30-second chair stand test also significantly prolonged the performance time of the Trail Making Test-B in male workers. Among female workers, the presence of metabolic syndrome risk factors affected the performance time of the Trail Making Test-B. Therefore, MetS risk factors affect the performance times of the Trail Making Test-B in both male and female workers. [Conclusion] As male and female workers exhibit different body composition and motor function items in the Trail Making Test-B, gender differences should be considered when formulating measures to prevent cognitive and attentional decline.

Memory function performance in individuals classified as overweight, obese, and normal weight

Evidence accumulated to date about the relationship between cognitive impairments and adults who are overweight and obese suggests that excess weight has a great impact on memory function. Nevertheless, most of the literature has focused only on studying the influences on working memory and episodic memory. This study aimed to examine the potential associations of clinical and anthropometric measures [body mass index (BMI), WHR, body fat, visceral fat, muscle mass, and hypertension] with six memory domains, including contextual memory, short-term visual memory, short-term memory, non-verbal memory, short-term phonological memory, and working memory, in a sample of 124 individuals classified as overweight (n = 33), obese (n = 53), and normal weight (n = 38). The results obtained showed that, after controlling for employment situations, people classified as obese had poorer short-term phonological memory and working memory than those with normal weights. Bivariate correlations showed that measures of weight, BMI, waist-hip ratio index, body fat, and visceral fat were inversely associated with memory function. However, muscle mass was not a significant predictor of memory function. Higher systolic blood pressure was also associated with worse memory function. The study provides evidence of the importance of adiposity in health and memory function.

Effects of reducing sedentary behaviour duration by increasing physical activity, on cognitive function, brain function and structure across the lifespan: a systematic review protocol

INTRODUCTION

Greater engagement in sedentary behaviours has been related to poorer cognitive functions in epidemiological research. However, the effects of reducing sedentary behaviour duration on cognitive function, brain function, and structure remain poorly understood. This systematic review aims to synthesise the evidence on the effects of reducing sedentary behaviour duration by increasing time spent in physical activity on cognitive function, brain structure and function in apparently healthy children, adolescents and adults.

METHODS AND ANALYSIS

The protocol follows Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The literature search will be conducted (search dates: August-September 2022) across six databases: PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (via EBSCO Host), PsycINFO (via ProQuest), SPORTDiscus and Web of Science (Science and Social Science Citation Index). The inclusion criteria are as follows: randomised and non-randomised experimental studies as defined by the Cochrane Handbook, published in English, in peer-reviewed journals, and as theses or dissertations. References of included papers will be screened for additional studies. Acute and chronic interventions targeting children (≥ 4 years), adolescents, younger adults (≥ 18-40 years), middle-aged (40-64 years) and older adults (65+ years) will be eligible. Methodological quality will be assessed with the Effective Public Health Practice Project quality assessment tool for quantitative studies. Qualitative synthesis will be stratified by intervention type (acute vs chronic), intervention content (reducing sedentary time or interrupting prolonged sitting) and outcome (cognitive, brain structure and function).

ETHICS AND DISSEMINATION

No primary data collection will be conducted as part of this systematic review. Study findings will be disseminated through peer-reviewed publications, conference presentations and social media.

PROSPERO REGISTRATION NUMBER

CRD42020200998.

Effects of 12 weeks of aerobic exercise combined with resistance training on neurocognitive performance in obese women

Background/Objectives

To the best of our knowledge, there have been no previous studies conducted on the long-term effects of an exercise intervention on deficits in inhibitory control in obese individuals. The aim of this study was thus to examine the effect of 12 weeks of a combination of aerobic and resistance exercise on behavioral and cognitive electrophysiological performance involving cognitive interference inhibition in obese individuals.

Methods

Thirty-two qualified healthy obese women were randomly divided into either an exercise group (EG, age: 34.76 ± 5.52 years old; BMI: 29.35 ± 3.52 kg/m2) or a control group (CG, age: 33.84 ± 7.05 years old; BMI: 29.61 ± 4.31 kg/m2). All participants performed the Stroop task, with electrophysiological signals being collected simultaneously before and after a 12-week intervention. The estimated V̇O2max, muscular strength, and body fat percentage (measured with dual-energy X-ray absorptiometry) were also assessed within one week before and after the intervention. Participants in the EG group engaged in 30 min of moderate-intensity aerobic exercise combined with resistance exercise, 5 sessions per week for 12 weeks, while the participants in the CG group maintained their regular lifestyle without engaging in any type of exercise.

Results

The results revealed that although a 12-week exercise intervention did not enhance the behavioral indices [e.g., accuracy rates (ARs) and reaction times (RTs)] in the EG group, significantly shorter N2 and P3 latencies and greater P2 and P3 amplitudes were observed. Furthermore, the fat percentage distribution (e.g. total body fat %, trunk fat %, and leg fat %) and level of physical fitness (e.g. estimated V̇O2max and muscular strength) in the EG group were significantly improved. The changes prior to and after the intervention in the P3 amplitude and trunk fat percentage were significantly negatively correlated in the EG group (r = -0.521, p = 0.039).

Conclusions

These findings suggested that 12 weeks of aerobic exercise combined with resistance exercise in obese women affects cognitive function broadly, but not specifically in terms of inhibitory control. The percentage of decreased trunk fat may play a potential facilitating role in inhibition processing in obesity.

Imaging perivascular space structure and function using brain MRI

In this article, we provide an overview of current neuroimaging methods for studying perivascular spaces (PVS) in humans using brain MRI. In recent years, an increasing number of studies highlighted the role of PVS in cerebrospinal/interstial fluid circulation and clearance of cerebral waste products and their association with neurological diseases. Novel strategies and techniques have been introduced to improve the quantification of PVS and to investigate their function and morphological features in physiological and pathological conditions. After a brief introduction on the anatomy and physiology of PVS, we examine the latest technological developments to quantitatively analyze the structure and function of PVS in humans with MRI. We describe the applications, advantages, and limitations of these methods, providing guidance and suggestions on the acquisition protocols and analysis techniques that can be applied to study PVS in vivo. Finally, we review the human neuroimaging studies on PVS across the normative lifespan and in the context of neurological disorders.

Overnutrition Induced Cognitive Impairment: Insulin Resistance, Gut-Brain Axis, and Neuroinflammation

Overnutrition-related obesity has become a worldwide epidemic, and its prevalence is expected to steadily rise in the future. It is widely recognized that obesity exerts negative impacts on metabolic disorders such as type 2 diabetes mellitus (T2DM) and cardiovascular diseases. However, relatively fewer reports exist on the impairment of brain structure and function, in the form of memory and executive dysfunction, as well as neurogenerative diseases. Emerging evidence indicates that besides obesity, overnutrition diets independently induce cognitive impairments via multiple mechanisms. In this study, we reviewed the clinical and preclinical literature about the detrimental effects of obesity or high-nutrition diets on cognitive performance and cerebral structure. We mainly focused on the role of brain insulin resistance (IR), microbiota-gut-brain axis, and neuroinflammation. We concluded that before the onset of obesity, short-term exposure to high-nutrition diets already blunted central responses to insulin, altered gut microbiome composition, and activated inflammatory mediators. Overnutrition is linked with the changes in protein expression in brain insulin signaling, leading to pathological features in the brain. Microbiome alteration, bacterial endotoxin release, and gut barrier hyperpermeability also occur to trigger mental and neuronal diseases. In addition, obesity or high-nutrition diets cause chronic and low-grade systematic inflammation, which eventually spreads from the peripheral tissue to the central nervous system (CNS). Altogether, a large number of unknown but potential routes interact and contribute to obesity or diet-induced cognitive impairment. The challenge for future research is to identify effective interventions involving dietary shifts and personalized therapy targeting the underlying mechanisms to prevent and improve cognition deficits.

Kefir milk consumption decreases sperm alterations due to the high-fat diet in adult male rats

Over the past decades, an increase of male infertility through the decrease of sperm count has been noted. It has been suggested that environmental factors and lifestyle could a negative impact over sperm quality. Among these factors, the consumption of foods high in fat, which leads to overweight and obesity, can negatively influence fertility. The present study was designed to highlight the protective effect of Kefir, natural probiotic, against the decline in sperm quality related to fat high diet. Thirty adult rats were divided into four groups: Control (1 ml/100 g of body weight (bw) of semi-shimmed cow milk), KM (1 ml/100 g bw of Kefir milk), HFD (1 ml/100 g bw of semi-shimmed cow milk + high-fat diet) and KM/HFD (1 ml/100 g bw Kefir milk + high-fat diet). After 60 days of treatment, sperm quality, biochemical assays of lipids profil, blood cell count and histological examination in testis were assessed. The results described an improved of sperm density (64.28 10⁶  ml vs 54.14 10⁶  ml), viability (70.50% vs 55.33%), mobility (65.40% vs 63.60%) and morphological abnormalities (52% vs 25%) in the KM/HFD group compared to HFD group. In the same group, the lipid profil (Triglycerides (128.39 mg/dl vs 102.85 mg/dl), C-LDL (13.65 mg/dl vs 15.32 mg/dl) and C-HDL (23.21 mg/dl vs 19.15 mg/dl)) was corrected compared to HFD group. The histological observation of testis revealed a normal spermatogenesis compared to seminiferous tubules of HFD group, which showed a serious disruption and damage of testicular epithelium exerted by the high-fat diet. These findings corroborated the previous beneficial effect of Kefir and brought new insights into its beneficial effect against deteriorated spermatogenesis in obese adult rats.