Association of muscle and visceral adipose tissues with the probability of Alzheimer's disease in healthy subjects

Skeletal muscle TFEB signaling promotes central nervous system function and reduces neuroinflammation during aging and neurodegenerative disease

Skeletal muscle has recently arisen as a regulator of central nervous system (CNS) function and aging, secreting bioactive molecules known as myokines with metabolism-modifying functions in targeted tissues, including the CNS. Here, we report the generation of a transgenic mouse with enhanced skeletal muscle lysosomal and mitochondrial function via targeted overexpression of transcription factor E-B (TFEB). We discovered that the resulting geroprotective effects in skeletal muscle reduce neuroinflammation and the accumulation of tau-associated pathological hallmarks in a mouse model of tauopathy. Muscle-specific TFEB overexpression significantly ameliorates proteotoxicity, reduces neuroinflammation, and promotes transcriptional remodeling of the aged CNS, preserving cognition and memory in aged mice. Our results implicate the maintenance of skeletal muscle function throughout aging in direct regulation of CNS health and disease and suggest that skeletal muscle originating factors may act as therapeutic targets against age-associated neurodegenerative disorders.

Relationship between sarcopenic obesity and cognitive function in patients with mild to moderate Alzheimer's disease

BACKGROUND

Previous research has linked sarcopenic obesity (SO) to cognitive function; however, the relationship between cognitive performance and SO Alzheimer's disease (AD) patients remains unclear. This study aimed to investigate their relationship in AD patients.

METHODS

One hundred and twenty mild to moderate AD patients and 56 normal controls were recruited. According to sarcopenia or obesity status, AD patients were classified into subgroups: normal, obesity, sarcopenia, and SO. Body composition, demographics, and sarcopenia parameters were assessed. Cognitive performance was evaluated using neuropsychological scales.

RESULTS

Among the 176 participants, the prevalence of SO in the moderate AD group was higher than in the normal control group. The moderate AD group had the lowest appendicular skeletal muscle mass index (ASMI) and the highest percentage of body fat (PBF). Hypertension and diabetes were more prevalent in the SO group than in the normal group among the subgroups. The sarcopenia and SO groups exhibited worse global cognitive function compared to the normal and obesity groups. Partial correlation analysis revealed that ASMI, PBF, and visceral fat area were associated with multiple cognitive domains scores. In logistic regression analysis, after adjusting for confounders, obesity was not found to be associated with AD. However, sarcopenia (odds ratio (OR) = 5.35, 95% CI: 1.27-22.46) and SO (OR = 5.84, 95% CI: 1.26-27.11) were identified as independent risk factors for AD.

CONCLUSIONS

SO was associated with cognitive dysfunction in AD patients. Moreover, the impact of SO on cognitive decline was greater than that of sarcopenia. Early identification and intervention for SO may have a positive effect on the occurrence and progression of AD.

White matter hyperintensities: a possible link between sarcopenia and cognitive impairment in patients with mild to moderate Alzheimer's disease

PURPOSE

Alzheimer's disease (AD) has been reported to be associated with sarcopenia. White matter hyperintensities (WMH) are common in AD patients. However, the effect of WMH on sarcopenia in AD remains unclear. We hence aimed to investigate the possible association between regional WMH volumes and sarcopenic parameters in AD.

METHODS

57 mild to moderate AD patients and 22 normal controls (NC) were enrolled. Sarcopenic parameters were assessed, including appendicular skeletal mass index (ASMI), grip strength, 5-times sit-to-stand (5-STS) time, and gait speed. The volumes of periventricular hyperintensities (PVH) and deep white matter hyperintensities (DWMH) were quantified using 3D-slicer software.

RESULTS

AD subjects exhibited a lower ASMI, a slower gait speed, an increased 5-STS time, and larger volumes of PVH and DWMH than those in the NC group. In AD subjects, total WMH and PVH volumes were related to cognitive impairment, particularly executive function decline. Moreover, total WMH volume and PVH volume were negatively correlated with gait speed across various clinical stages of AD. Multiple linear regression analysis showed that PVH volume was independently associated with 5-STS time and gait speed, whereas DWMH volume was only independently associated with gait speed.

CONCLUSION

WMH volume was associated with cognitive decline and various sarcopenic parameters. It thereby suggested that WMH may serve as the connection between sarcopenia and cognitive dysfunction in AD. Further studies are needed to confirm these findings and to determine whether sarcopenia interventions reduce WMH volume and improve cognitive function in AD.

Increase in skeletal muscular adiposity and cognitive decline in a biracial cohort of older men and women

BACKGROUND

Obesity and loss of muscle mass are emerging as risk factors for dementia, but the role of adiposity infiltrating skeletal muscles is less clear. Skeletal muscle adiposity increases with older age and especially among Black women, a segment of the US population who is also at higher risk for dementia.

METHODS

In 1634 adults (69-79 years, 48% women, 35% Black), we obtained thigh intermuscular adipose tissue (IMAT) via computerized tomography at Years 1 and 6, and mini-mental state exam (3MS) at Years 1, 3, 5, 8 and 10. Linear mixed effects models tested the hypothesis that increased IMAT (Year 1-6) would be associated with 3MS decline (Year 5-10). Models were adjusted for traditional dementia risk factors at Year 1 (3MS, education, APOe4 allele, diabetes, hypertension, and physical activity), with interactions between IMAT change by race or sex. To assess the influence of other muscle and adiposity characteristics, models accounted for change in muscle strength, muscle area, body weight, abdominal subcutaneous and visceral adiposity, and total body fat mass (all measured in Years 1 and 6). Models were also adjusted for cytokines related to adiposity: leptin, adiponectin, and interleukin-6.

RESULTS

Thigh IMAT increased by 4.85 cm2 (Year 1-6) and 3MS declined by 3.20 points (Year 6-10). The association of IMAT increase with 3MS decline was statistically significant: an IMAT increase of 4.85 cm2 corresponded to a 3MS decline of an additional 3.60 points (p < 0.0001), indicating a clinically important change. Interactions by race and sex were not significant.

CONCLUSIONS

Clinicians should be aware that regional adiposity accumulating in the skeletal muscle may be an important, novel risk factor for cognitive decline in Black and White participants independent of changes to muscle strength, body composition and traditional dementia risk factors.

The association between regional adiposity, cognitive function, and dementia-related brain changes: a systematic review

Background

Adiposity has been previously associated with cognitive impairment and Alzheimer's disease and related disorders (ADRD). Body mass index (BMI) is the most common measure of global adiposity, but inconsistent results were found since it is a global measurement. BMI does not represent regional fat distribution which differs between sexes, race, and age. Regional fat distribution may contribute differently to cognitive decline and Alzheimer's disease (AD)-related brain changes. Fat-specific targeted therapies could lead to personalized improvement of cognition. The goal of this systematic review is to explore whether regional fat depots, rather than central obesity, should be used to understand the mechanism underlying the association between adiposity and brain.

Methods

This systematic review included 33 studies in the English language, conducted in humans aged 18 years and over with assessment of regional adiposity, cognitive function, dementia, and brain measures. We included only studies that have assessed regional adiposity using imaging technics and excluded studies that were review articles, abstract only or letters to editor. Studies on children and adolescents, animal studies, and studies of patients with gastrointestinal diseases were excluded. PubMed, PsychInfo and web of science were used as electronic databases for literature search until November 2022.

Results

Based on the currently available literature, the findings suggest that different regional fat depots are likely associated with increased risk of cognitive impairment, brain changes and dementia, especially AD. However, different regional fat depots can have different cognitive outcomes and affect the brain differently. Visceral adipose tissue (VAT) was the most studied regional fat, along with liver fat through non-alcoholic fatty liver disease (NAFLD). Pancreatic fat was the least studied regional fat.

Conclusion

Regional adiposity, which is modifiable, may explain discrepancies in associations of global adiposity, brain, and cognition. Specific regional fat depots lead to abnormal secretion of adipose factors which in turn may penetrate the blood brain barrier leading to brain damage and to cognitive decline.

APP in the Neuromuscular Junction for the Development of Sarcopenia and Alzheimer's Disease

Sarcopenia, an illness condition usually characterized by a loss of skeletal muscle mass and muscle strength or function, is often associated with neurodegenerative diseases, such as Alzheimer's disease (AD), a common type of dementia, leading to memory loss and other cognitive impairment. However, the underlying mechanisms for their associations and relationships are less well understood. The App, a Mendelian gene for early-onset AD, encodes amyloid precursor protein (APP), a transmembrane protein enriched at both the neuromuscular junction (NMJ) and synapses in the central nervous system (CNS). Here, in this review, we highlight APP and its family members' physiological functions and Swedish mutant APP (APP_swe)'s pathological roles in muscles and NMJ. Understanding APP's pathophysiological functions in muscles and NMJ is likely to uncover insights not only into neuromuscular diseases but also AD. We summarize key findings from the burgeoning literature, which may open new avenues to investigate the link between muscle cells and brain cells in the development and progression of AD and sarcopenia.

Exploring the relationship between socioeconomic deprivation index and Alzheimer's disease using summary-level data: From genetic correlation to causality

Patients with Alzheimer's disease (AD) are markedly increasing as population aging and no disease-modifying therapies are currently available for AD. Previous studies suggested a broad link between socioeconomic status and a variety of disorders, including mental illness and cognitive abilities. However, the association between socioeconomic deprivation and AD has been unknown. We here employed Townsend deprivation index (TDI) to explore such relation and found a positive genetic correlation (r̂_g=0.211, P = 8.00 × 10^-4) between the two traits with summary statistics data (N = 455,258 for TDI and N = 455,815 for AD). Then, we performed pleiotropy analysis at both variant and gene levels using a powerful method called PLACO and detected 87 distinct pleiotropic genes. Functional analysis demonstrated these genes were significantly enriched in pancreas, liver, heart, blood, brain, and muscle tissues. Using Mendelian randomization methods, we further found that one genetically predicted standard deviation elevation in TDI could lead to approximately 18.5% (95% confidence intervals 1.6- 38.2%, P = 0.031) increase of AD risk, and that the identified causal association was robust against used MR approaches, horizontal pleiotropy, and instrumental selection. Overall, this study provides deep insight into common genetic components underlying TDI and AD, and further reveals causal connection between them. It is also helpful to develop a more suitable plan for ameliorating inequities, hardship, and disadvantage, with the hope of improving health outcomes among economically disadvantaged people.

Relationship Between MicroRNA Signature and Arterial Stiffness in Patients With Ischemic Stroke

BACKGROUND AND PURPOSE

We investigated whether circulating microRNAs (miRNAs) is associated with arterial stiffness in patients with acute ischemic stroke.

METHODS

We recruited patients with acute ischemic stroke who were admitted to a university hospital stroke center and underwent carotid-femoral pulse wave velocity (cfPWV) measurement using SphygmoCor (AtCor Medical, Sydney, Australia) and brachial-ankle PWV using a volume-plethysmography device (VP-1000, Omron Colin, Komaki, Japan). Circulating miRNAs were measured in venous blood samples stored in EDTA. We selected five miRNAs (miR-17, miR-93, miR-450, miR-629, and let-7i) related to atherosclerosis based on a literature review. Pearson's correlation analysis was applied to the correlations between miRNAs and arterial stiffness parameters. Finally, multivariable linear regression analysis was performed to identify the independent factors for cfPWV.

RESULTS

This study included 70 patients (age=71.1±10.3 years [mean±SD], 29 females). The expression levels of miR-93 (r=-0.27, p=0.049) and let-7i (r=-0.27, p=0.039) were inversely correlated with cfPWV. Multivariable linear regression analysis including age, hypertension, and estimated glomerular filtration rate showed that let-7i was independently related with cfPWV (standardized coefficient=-0.262, p=0.036). Correlation analysis indicated that let-7i was positively associated with visceral muscle Hounsfield units on computed tomography (r=0.264, p=0.043).

CONCLUSIONS

The expression level of let-7i was independently related to arterial stiffness in patients with cerebral infarction, suggesting that it plays a pathophysiological role in atherosclerosis.

Association between cognitive performance and sarcopenic obesity in older adults with Alzheimer's disease

Sarcopenic obesity (SO), the co-occurrence of sarcopenia and obesity, is associated with functional loss, frailty, and incapacity in older adults. Recently, SO was associated with reduced cognitive performance in adults. However, no SO studies have been done with older adults with Alzheimer's disease (AD).

Objective

The objective of this study was to verify the occurrence of SO and associated factors in 43 older adults with AD.

Methods

We applied the Mini-Mental State Examination (MMSE) and Clinical Dementia Rating (CDR). SO was verified by using dual-emission X-ray absorptiometry.

Results

We found five women with SO. Women had higher body fat and lower muscle mass compared with men. There was a significant relationship between body fat and cognitive performance only in men (r=0.65; p<0.01) adjusted by age and education. Men with obesity and aged >75 years had better cognitive performance compared with non-obese men aged <75 years (p=0.010) and women with obesity aged >75 years (p=0.033).

Conclusions

Women with AD had higher body fat and lower muscle mass than men. SO occurs in older women with AD. Men with higher body fat showed better cognitive performance, independent of age and education.

Methodology, clinical applications, and future directions of body composition analysis using computed tomography (CT) images: A review

PURPOSE OF THE REVIEW

We aim to review the methods, current research evidence, and future directions in body composition analysis (BCA) with CT imaging.

RECENT FINDINGS

CT images can be used to evaluate muscle tissue, visceral adipose tissue (VAT), and subcutaneous adipose tissue (SAT) compartments. Manual and semiautomatic segmentation methods are still the gold standards. The segmentation of skeletal muscle tissue and VAT and SAT compartments is most often performed at the level of the 3rd lumbar vertebra. A decreased amount of CT-determined skeletal muscle mass is a marker of impaired survival in many patient populations, including patients with most types of cancer, some surgical patients, and those admitted to the intensive care unit (ICU). Patients with increased VAT are more susceptible to impaired survival / worse outcomes; however, those patients who are critically ill or admitted to the ICU or who will undergo surgery appear to be exceptions. The independent significance of SAT is less well established. Recently, the roles of the CT-determined decrease of muscle mass and increased VAT area and epicardial adipose tissue (EAT) volume have been shown to predict a more debilitating course of illness in patients suffering from severe acute respiratory syndrome coronavirus 2 (COVID-19) infection.

SUMMARY

The field of CT-based body composition analysis is rapidly evolving and shows great potential for clinical implementation.

Forgot to Exercise? Exercise Derived Circulating Myokines in Alzheimer's Disease: A Perspective

Regular exercise plays an essential role in maintaining healthy neurocognitive function and central nervous system (CNS) immuno-metabolism in the aging CNS. Physical activity decreases the risk of developing Alzheimer's Disease (AD), is associated with better AD prognosis, and positively affects cognitive function in AD patients. Skeletal muscle is an important secretory organ, communicating proteotoxic and metabolic stress to distant tissues, including the CNS, through the secretion of bioactive molecules collectively known as myokines. Skeletal muscle undergoes significant physical and metabolic remodeling during exercise, including alterations in myokine expression profiles. This suggests that changes in myokine and myometabolite secretion may underlie the well-documented benefits of exercise in AD. However, to date, very few studies have focused on specific alterations in skeletal muscle-originating secreted factors and their potential neuroprotective effects in AD. In this review, we discuss exercise therapy for AD prevention and intervention, and propose the use of circulating myokines as novel therapeutic tools for modifying AD progression.

Skeletal muscle mass is associated with erythropoietin response in hemodialysis patients

Background

Hyporesponsiveness to erythropoietin stimulating agent (ESA) is associated with poor outcomes in patients with chronic kidney disease. Although ESA hyporesponsiveness and sarcopenia have a common pathophysiological background, clinical evidence linking them is scarce. The purpose of the study was to investigate the relationship between ESA responsiveness and skeletal muscle mass in hemodialysis patients.

Methods

This cross-sectional study analyzed 70 patients on maintenance hemodialysis who were treated with ESA. ESA responsiveness was evaluated by erythropoietin resistance index (ERI), calculated as a weekly dose of ESA divided by body weight and hemoglobin (IU/kg/week/dL), and a weekly dose of ESA/hemoglobin (IU/week/dL). A dose of ESA is equivalated to epoetin β. Correlations between ESA responsiveness and clinical parameters including skeletal muscle mass were analyzed.

Results

Among the 70 patients, ERI was positively correlated to age (p < 0.002) and negatively correlated to height (p < 0.001), body weight (p < 0.001), BMI (p < 0.001), skeletal muscle mass (p < 0.001), transferrin saturation (TSAT) (p = 0.049), and zinc (p = 0.006). In the multiple linear regression analysis, TSAT, zinc, and skeletal muscle mass were associated with ERI and weekly ESA dose/hemoglobin.

Conclusions

Skeletal muscle mass was the independent predictor for ESA responsiveness as well as TSAT and zinc. Sarcopenia is another target for the management of anemia in patients with hemodialysis.

Health-related physical indicators and self-rated quality of life in older adults with neurocognitive disorder

PURPOSE

This study aimed to identify the association between health-related physical indicators-sarcopenia-related factors, physical fitness, independence in activities of daily living (ADL) and habitual physical activity-and self-rated quality of life (QoL) in people with neurocognitive disorder (NCD).

METHODS

This cross-sectional study included 115 participants (78.22 ± 7.48 years; 74.8% female) clinically diagnosed with NCD. Self-rated QoL was evaluated using The Quality of Life-Alzheimer's Disease (QoL-AD). Dual energy X-ray Absorptiometry, handgrip strength, Short Physical Performance Battery, and the 6-m Walk test were used to assess sarcopenia-related factors. Senior Fitness Test and One Leg Balance test, Barthel Index, Baecke Modified Habitual Physical Activity Questionnaire were used to determine physical fitness, independence in ADL and physical activity, respectively. Regressions analyses were performed to examine associations between these variables and QoL-AD.

RESULTS

Data from univariable linear regression analysis revealed that self-rated QoL was associated with sarcopenia-related factors (lower body function, handgrip strength, gait speed, and appendicular skeletal muscle mass index-ASMI), physical fitness (upper-and-lower-body strength, agility/dynamic balance, cardiorespiratory fitness and body mass index), habitual physical activity and independence in ADL. Results from multivariable regression analysis showed that ASMI (B = 1.846, 95% CI 0.165-3.527, p = 0.032) and lower body function (B = 0.756, 95% CI 0.269-1.242, p = 0.003) were positively associated with self-rated QoL. These variables explained 20.1% of the variability seen in self-rated QoL, controlling for age, sex, marital status and education.

CONCLUSION

Sarcopenia-related factors, namely lower body function and ASMI, should be acknowledged in future research studies as critical health-related indicators associated with QoL in people with NCD.

TRIAL REGISTRATION

ClinicalTrials.gov-identifier number NCT04095962.

Possible Existence of the Hypothalamic-Pituitary-Hippocampal (HPH) Axis: A Reciprocal Relationship Between Hippocampal Specific Neuroestradiol Synthesis and Neuroblastosis in Ageing Brains with Special Reference to Menopause and Neurocognitive Disorders

The hippocampus-derived neuroestradiol plays a major role in neuroplasticity, independent of circulating estradiol that originates from gonads. The response of hypothalamus-pituitary regions towards the synthesis of neuroestradiol in the hippocampus is an emerging scientific concept in cognitive neuroscience. Hippocampal plasticity has been proposed to be regulated via neuroblasts, a major cellular determinant of functional neurogenesis in the adult brain. Defects in differentiation, integration and survival of neuroblasts in the hippocampus appear to be an underlying cause of neurocognitive disorders. Gonadotropin receptors and steroidogenic enzymes have been found to be expressed in neuroblasts in the hippocampus of the brain. However, the reciprocal relationship between hippocampal-specific neuroestradiol synthesis along neuroblastosis and response of pituitary based feedback regulation towards regulation of estradiol level in the hippocampus have not completely been ascertained. Therefore, this conceptual article revisits (1) the cellular basis of neuroestradiol synthesis (2) a potential relationship between neuroestradiol synthesis and neuroblastosis in the hippocampus (3) the possible involvement of aberrant neuroestradiol production with mitochondrial dysfunctions and dyslipidemia in menopause and adult-onset neurodegenerative disorders and (4) provides a hypothesis for the possible existence of the hypothalamic-pituitary-hippocampal (HPH) axis in the adult brain. Eventually, understanding the regulation of hippocampal neurogenesis by abnormal levels of neuroestradiol concentration in association with the feedback regulation of HPH axis might provide additional cues to establish a neuroregenerative therapeutic management for mood swings, depression and cognitive decline in menopause and neurocognitive disorders.