Obesity as a Risk Factor for Dementia and Alzheimer's Disease: The Role of Leptin

Amyloid-β and Phosphorylated Tau are the Key Biomarkers and Predictors of Alzheimer's Disease

Alzheimer's disease (AD) is a age-related neurodegenerative disease and is a major public health concern both in Texas, US and Worldwide. This neurodegenerative disease is mainly characterized by amyloid-beta (Aβ) and phosphorylated Tau (p-Tau) accumulation in the brains of patients with AD and increasing evidence suggests that these are key biomarkers in AD. Both Aβ and p-tau can be detected through various imaging techniques (such as positron emission tomography, PET) and cerebrospinal fluid (CSF) analysis. The presence of these biomarkers in individuals, who are asymptomatic or have mild cognitive impairment can indicate an increased risk of developing AD in the future. Furthermore, the combination of Aβ and p-tau biomarkers is often used for more accurate diagnosis and prediction of AD progression. Along with AD being a neurodegenerative disease, it is associated with other chronic conditions such as cardiovascular disease, obesity, depression, and diabetes because studies have shown that these comorbid conditions make people more vulnerable to AD. In the first part of this review, we discuss that biofluid-based biomarkers such as Aβ, p-Tau in cerebrospinal fluid (CSF) and Aβ & p-Tau in plasma could be used as an alternative sensitive technique to diagnose AD. In the second part, we discuss the underlying molecular mechanisms of chronic conditions linked with AD and how they affect the patients in clinical care.

Anorexigenic neuropeptides as anti-obesity and neuroprotective agents: exploring the neuroprotective effects of anorexigenic neuropeptides

Since 1975, the incidence of obesity has increased to epidemic proportions, and the number of patients with obesity has quadrupled. Obesity is a major risk factor for developing other serious diseases, such as type 2 diabetes mellitus, hypertension, and cardiovascular diseases. Recent epidemiologic studies have defined obesity as a risk factor for the development of neurodegenerative diseases, such as Alzheimer's disease (AD) and other types of dementia. Despite all these serious comorbidities associated with obesity, there is still a lack of effective antiobesity treatment. Promising candidates for the treatment of obesity are anorexigenic neuropeptides, which are peptides produced by neurons in brain areas implicated in food intake regulation, such as the hypothalamus or the brainstem. These peptides efficiently reduce food intake and body weight. Moreover, because of the proven interconnection between obesity and the risk of developing AD, the potential neuroprotective effects of these two agents in animal models of neurodegeneration have been examined. The objective of this review was to explore anorexigenic neuropeptides produced and acting within the brain, emphasizing their potential not only for the treatment of obesity but also for the treatment of neurodegenerative disorders.

Adipocentric origin of the common cardiometabolic complications of obesity in the young up to the very old: pathophysiology and new therapeutic opportunities

Obesity is a multifactorial chronic disease characterized by an excess of adipose tissue, affecting people of all ages. In the last 40 years, the incidence of overweight and obesity almost tripled worldwide. The accumulation of "visceral" adipose tissue increases with aging, leading to several cardio-metabolic consequences: from increased blood pressure to overt arterial hypertension, from insulin-resistance to overt type 2 diabetes mellitus (T2DM), dyslipidemia, chronic kidney disease (CKD), and obstructive sleep apnea. The increasing use of innovative drugs, namely glucagon-like peptide-1 receptor agonists (GLP1-RA) and sodium-glucose cotransporter-2 inhibitors (SGLT2-i), is changing the management of obesity and its related cardiovascular complications significantly. These drugs, first considered only for T2DM treatment, are now used in overweight patients with visceral adiposity or obese patients, as obesity is no longer just a risk factor but a critical condition at the basis of common metabolic, cardiovascular, and renal diseases. An adipocentric vision and approach should become the cornerstone of visceral overweight and obesity integrated management and treatment, reducing and avoiding the onset of obesity-related multiple risk factors and their clinical complications. According to recent progress in basic and clinical research on adiposity, this narrative review aims to contribute to a novel clinical approach focusing on pathophysiological and therapeutic insights.

Long-term trends in Alzheimer's disease and other dementias deaths with high body mass index in China from 1990 to 2019, and projections up to 2042

BACKGROUND

In China, the rising prevalence of high Body Mass Index (BMI) is linked to increasing health issues, including Alzheimer's disease (AD). This study analyzes mortality trends related to AD and other dementias associated with high BMI from 1990 to 2019, considering age, period, and birth cohort effects, and forecasts future trends.

METHODS

We analyzed mortality data for AD and other dementias linked to high BMI in Chinese residents from the Global Burden of Disease 2019 database. Using Joinpoint regression, we examined age-standardized mortality rate (ASMR) trends and calculated annual and average annual percentage changes (APC and AAPC). Age-period-cohort models provided deeper insights, with Bayesian models used to project future ASMR trends to 2042.

RESULTS

From 1990 to 2019, the ASMR for AD and other dementias associated with high BMI in China showed an overall increasing trend. Females had a lower increase rate than males, yet their overall levels remained higher. Specifically, the ASMR for males increased by an average of 2.70% per year, peaking between 2006 and 2010, while for females, it increased by an average of 2.29% per year, also peaking in the same period. Age-period-cohort analysis revealed increasing mortality relative risk with age and period, but a decrease with birth cohort. Projections suggest a continued rise in ASMR by 2042, with rates for males and females expected to be 2.48/100,000 and 2.94/100,000, respectively.

CONCLUSION

The increasing mortality trend from AD and other dementias associated with high BMI highlights the urgent need for policy interventions focused on overweight prevention, particularly vital for addressing the health challenges in China's aging population.

Putative Molecular Mechanisms Underpinning the Inverse Roles of Mitochondrial Respiration and Heme Function in Lung Cancer and Alzheimer's Disease

Mitochondria are the powerhouse of the cell. Mitochondria serve as the major source of oxidative stress. Impaired mitochondria produce less adenosine triphosphate (ATP) but generate more reactive oxygen species (ROS), which could be a major factor in the oxidative imbalance observed in Alzheimer's disease (AD). Well-balanced mitochondrial respiration is important for the proper functioning of cells and human health. Indeed, recent research has shown that elevated mitochondrial respiration underlies the development and therapy resistance of many types of cancer, whereas diminished mitochondrial respiration is linked to the pathogenesis of AD. Mitochondria govern several activities that are known to be changed in lung cancer, the largest cause of cancer-related mortality worldwide. Because of the significant dependence of lung cancer cells on mitochondrial respiration, numerous studies demonstrated that blocking mitochondrial activity is a potent strategy to treat lung cancer. Heme is a central factor in mitochondrial respiration/oxidative phosphorylation (OXPHOS), and its association with cancer is the subject of increased research in recent years. In neural cells, heme is a key component in mitochondrial respiration and the production of ATP. Here, we review the role of impaired heme metabolism in the etiology of AD. We discuss the numerous mitochondrial effects that may contribute to AD and cancer. In addition to emphasizing the significance of heme in the development of both AD and cancer, this review also identifies some possible biological connections between the development of the two diseases. This review explores shared biological mechanisms (Pin1, Wnt, and p53 signaling) in cancer and AD. In cancer, these mechanisms drive cell proliferation and tumorigenic functions, while in AD, they lead to cell death. Understanding these mechanisms may help advance treatments for both conditions. This review discusses precise information regarding common risk factors, such as aging, obesity, diabetes, and tobacco usage.

Polypharmacy in psychiatry and weight gain: longitudinal study of 832 patients hospitalized for depression or schizophrenia, along with data of 3180 students from Europe, the U.S., South America, and China

Epidemiologic data indicate that overweight and obesity are on the rise worldwide. Psychiatric patients are particularly vulnerable in this respect as they have an increased prevalence of overweight and obesity, and often experience rapid, highly undesirable weight gain under psychotropic drug treatment. Current treatment strategies in psychiatry are oriented towards polypharmacy, so that the information on drug-induced weight gain from earlier monotherapy studies is of very limited validity. We have analyzed the longitudinal data of 832 inpatients with ICD-10 diagnoses of either F2 (schizophrenia; n = 282) or F3 (major depression; n = 550) with the goal of ranking treatment regimens in terms of weight gain, side effects, and response to treatment. The patient data were complemented by the data of 3180 students aged 18-22 years, with which we aimed to identify factors that enable the early detection and prevention of obesity and mental health problems. After 3 weeks of treatment, 47.7% of F2 patients and 54.9% of F3 patients showed a weight gain of 2 kg and more. Major predictive factors were "starting weight" (r = 0.115), "concurrent medications" (r = 0.176), and "increased appetite"(r = 0.275). Between 11 and 30% of the observed variance in weight gain could be explained by these factors, complemented by sex and age. The comparison between monotherapy (n = 409) and polypharmacy (n = 399) revealed significant drawbacks for polypharmacy: higher weight gain (p = 0.0005), more severe side effects (p = 0.0011), and lower response rates (F2: p = 0.0008); F3: p = 0.0101). The data of 3180 students made it clear that overweight and obesity often begin early in life among those affected, and are interconnected with personality traits, while increasing the risk of developing psychosomatic disturbances, mental health problems, or somatic illnesses. Although the available data did not readily lead to a comprehensive, clinically applicable model of unwanted weight gain, our results have nevertheless demonstrated that there are ways to successfully counteract such weight gain at early stages of treatment.

Neuroprotective effects of gemfibrozil in neurological disorders: Focus on inflammation and molecular mechanisms

BACKGROUND

Gemfibrozil (Gem) is a drug that has been shown to activate PPAR-α, a nuclear receptor that plays a key role in regulating lipid metabolism. Gem is used to lower the levels of triglycerides and reduce the risk of coronary heart disease in patients. Experimental studies in vitro and in vivo have shown that Gem can prevent or slow the progression of neurological disorders (NDs), including cerebral ischemia (CI), Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Neuroinflammation is known to play a significant role in these disorders.

METHOD

The literature review for this study was conducted by searching Scopus, Science Direct, PubMed, and Google Scholar databases.

RESULT

The results of this study show that Gem has neuroprotective effects through several cellular and molecular mechanisms such as: (1) Gem has the ability to upregulate pro-survival factors (PGC-1α and TFAM), promoting the survival and function of mitochondria in the brain, (2) Gem strongly inhibits the activation of NF-κB, AP-1, and C/EBPβ in cytokine-stimulated astroglial cells, which are known to increase the expression of iNOS and the production of NO in response to proinflammatory cytokines, (3) Gem protects dopamine neurons in the MPTP mouse model of PD by increasing the expression of PPARα, which in turn stimulates the production of GDNF in astrocytes, (4) Gem reduces amyloid plaque pathology, reduces the activity of glial cells, and improves memory, (5) Gem increases myelin genes expression (MBP and CNPase) via PPAR-β, and (6) Gem increases hippocampal BDNF to counteract depression.

CONCLUSION

According to the study, Gem was investigated for its potential therapeutic effect in NDs. Further research is needed to fully understand the therapeutic potential of Gem in NDs.

Adipose tissue as a therapeutic target for vascular damage in Alzheimer's disease

Adipose tissue has recently been recognized as an important endocrine organ that plays a crucial role in energy metabolism and in the immune response in many metabolic tissues. With this regard, emerging evidence indicates that an important crosstalk exists between the adipose tissue and the brain. However, the contribution of adipose tissue to the development of age-related diseases, including Alzheimer's disease, remains poorly defined. New studies suggest that the adipose tissue modulates brain function through a range of endogenous biologically active factors known as adipokines, which can cross the blood-brain barrier to reach the target areas in the brain or to regulate the function of the blood-brain barrier. In this review, we discuss the effects of several adipokines on the physiology of the blood-brain barrier, their contribution to the development of Alzheimer's disease and their therapeutic potential. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Identification of IGF-1 Effects on White Adipose Tissue and Hippocampus in Alzheimer's Disease Mice via Transcriptomic and Cellular Analysis

Alzheimer's disease (AD) stands as the most prevalent neurodegenerative disorder, characterized by a multitude of pathological manifestations, prominently marked by the aggregation of amyloid beta. Recent investigations have revealed a compelling association between excessive adiposity and glial activation, further correlating with cognitive impairments. Additionally, alterations in levels of insulin-like growth factor 1 (IGF-1) have been reported in individuals with metabolic conditions accompanied by memory dysfunction. Hence, our research endeavors to comprehensively explore the impact of IGF-1 on the hippocampus and adipose tissue in the context of Alzheimer's disease. To address this, we have conducted an in-depth analysis utilizing APP/PS2 transgenic mice, recognized as a well-established mouse model for Alzheimer's disease. Upon administering IGF-1 injections to the APP/PS2 mice, we observed notable alterations in their behavioral patterns, prompting us to undertake a comprehensive transcriptomic analysis of both the hippocampal and adipose tissues. Our data unveiled significant modifications in the functional profiles of these tissues. Specifically, in the hippocampus, we identified changes associated with synaptic activity and neuroinflammation. Concurrently, the adipose tissue displayed shifts in processes related to fat browning and cell death signaling. In addition to these findings, our analysis enabled the identification of a collection of long non-coding RNAs and circular RNAs that exhibited significant changes in expression subsequent to the administration of IGF-1 injections. Furthermore, we endeavored to predict the potential roles of these identified RNA molecules within the context of our study. In summary, our study offers valuable transcriptome data for hippocampal and adipose tissues within an Alzheimer's disease model and posits a significant role for IGF-1 within both the hippocampus and adipose tissue.

Relationship between cognitive function and weight-adjusted waist index in people ≥ 60 years old in NHANES 2011-2014

BACKGROUND

Widespread attention has been given to the detrimental effects of obesity on cognitive function. However, there is no evidence on the connection between low cognitive performance and the WWI (weight-adjusted waist index). This study looked into the connection between poor cognitive performance and the WWI in senior Americans.

METHODS

A cross-sectional research study was carried out with information from the NHANES 2011-2014. With multivariate linear regression models, the pertinence between the WWI and low cognitive function in persons older than 60 years was examined. The nonlinear link was described using threshold effect analyses and fitted smoothed curves. Interaction tests and subgroup analysis were also conducted.

RESULTS

The study had 2762 individuals in all, and subjects with higher WWI values were at greater risk for low cognitive function. In the completely adjusted model, the WWI was positively connected with low cognitive performance assessed by CERAD W-L (OR = 1.22, 95% CI 1.03-1.45, p = 0.0239), AFT (OR = 1.30, 95% CI 1.09-1.54, p = 0.0029), and DSST (OR = 1.59, 95% CI 1.30-1.94, p < 0.0001). The effect of each subgroup on the positive correlation between the WWI and low cognitive performance was not significant. The WWI and low cognitive performance as determined by CERAD W-L and AFT had a nonlinear connection (log-likelihood ratio < 0.05).

CONCLUSION

Among older adults in the United States, the risk of low cognitive performance may be positively related to the WWI.

TNF-α Levels Are Increased in Patients with Subjective Cognitive Impairment and Are Negatively Correlated with β Amyloid-42

The role of tumor necrosis factor-α (TNF-α) in Alzheimer's disease (AD) has recently become a topic of debate. TNF-α levels increase in the blood of patients with AD, and amyloid beta (Aβ) plaques contain TNF-α deposits. The therapeutic efficacy of blocking TNF-α in patients with AD remains controversial as it is mostly based on preclinical studies. Thus, whether and how TNF-α contributes to amyloidogenic processes in AD is still an open question to be addressed. We analyzed plasma TNF-α and Aβ42 levels in patients with subjective cognitive impairment (SCI), mild cognitive impairment (MCI), and AD, and in healthy volunteers (HLT). In addition, we performed correlation analysis to evaluate whether changes in plasma TNF-α levels correlate with cognitive decline, Aβ42 levels, age, and BMI, which are all factors considered to contribute to or predispose individuals to AD. We found that TNF-α and Aβ42 plasma levels were higher in patients with AD than in HLT individuals. High TNF-α levels were also observed in patients with SCI, in whom TNF-α and Aβ42 levels were negatively correlated. Notably, TNF-α did not affect the amyloidogenic pathway in human microglial cultures exposed to 48 h of incubation, although it did trigger neuroinflammatory processes. These results imply that high TNF-α levels are more likely to be a clinical condition linked to AD than are direct contributors. Nonetheless, elevated levels of TNF-α in early-stage patients, like those with SCI and MCI, may provide a distinguishing feature for identifying clinical profiles that are at risk of having a poorer outcome in AD and could benefit from tailored therapies.

Alzheimer's disease, a metabolic disorder: Clinical advances and basic model studies (Review)

Alzheimer's disease (AD) is a type of neurodegenerative disease characterized by cognitive impairment that is aggravated with age. The pathological manifestations include extracellular amyloid deposition, intracellular neurofibrillary tangles and loss of neurons. As the world population ages, the incidence of AD continues to increase, not only posing a significant threat to the well-being and health of individuals but also bringing a heavy burden to the social economy. There is epidemiological evidence suggesting a link between AD and metabolic diseases, which share pathological similarities. This potential link would deserve further consideration; however, the pathogenesis and therapeutic efficacy of AD remain to be further explored. The complex pathogenesis and pathological changes of AD pose a great challenge to the choice of experimental animal models. To understand the role of metabolic diseases in the development of AD and the potential use of drugs for metabolic diseases, the present article reviews the research progress of the comorbidity of AD with diabetes, obesity and hypercholesterolemia, and summarizes the different roles of animal models in the study of AD to provide references for researchers.

From Liver to Brain: How MAFLD/MASLD Impacts Cognitive Function

Metabolic dysfunction-associated fatty liver disease or metabolic dysfunction-associated steatotic liver disease (MAFLD/MASLD), is a common chronic liver condition affecting a substantial global population. Beyond its primary impact on liver function, MAFLD/MASLD is associated with a myriad of extrahepatic manifestations, including cognitive impairment. The scope of cognitive impairment within the realm of MAFLD/MASLD is a matter of escalating concern. Positioned as an intermediate stage between the normal aging process and the onset of dementia, cognitive impairment manifests as a substantial challenge associated with this liver condition. Insights from studies underscore the presence of compromised executive function and a global decline in cognitive capabilities among individuals identified as being at risk of progressing to liver fibrosis. Importantly, this cognitive impairment transcends mere association with metabolic factors, delving deep into the intricate pathophysiology characterizing MAFLD/MASLD. The multifaceted nature of cognitive impairment in the context of MAFLD/MASLD is underlined by a spectrum of factors, prominently featuring insulin resistance, lipotoxicity, and systemic inflammation as pivotal contributors. These factors interplay within the intricate landscape of MAFLD/MASLD, fostering a nuanced understanding of the links between hepatic health and cognitive function. By synthesizing the available evidence, exploring potential mechanisms, and assessing clinical implications, the overarching aim of this review is to contribute to a more complete understanding of the impact of MAFLD/MASLD on cognitive function.

A Brief History of the Progress in Our Understanding of Genetics and Lifestyle, Especially Diet, in the Risk of Alzheimer's Disease

The two major determining factors for Alzheimer's disease (AD) are genetics and lifestyle. Alleles of the apolipoprotein E (APOE) gene play important roles in the development of late-onset AD, with APOEɛ4 increasing risk, APOEɛ3 being neutral, and APOEɛ2 reducing risk. Several modifiable lifestyle factors have been studied in terms of how they can modify the risk of AD. Among these factors are dietary pattern, nutritional supplements such as omega-3 fatty acids, and B vitamins, physical exercise, and obesity, and vitamin D. The Western diet increases risk of AD, while dietary patterns such as the Mediterranean and vegetarian/vegan diets reduce risk. Foods associated with reduced risk include coffee, fruits and vegetables, whole grains and legumes, and fish, while meat and ultraprocessed foods are associated with increased risk, especially when they lead to obesity. In multi-country ecological studies, the amount of meat in the national diet has the highest correlation with risk of AD. The history of research regarding dietary patterns on risk of AD is emphasized in this review. The risk of AD can be modified starting at least by mid-life. People with greater genetic risk for AD would benefit more by choosing lifestyle factors to reduce and/or delay incidence of AD.

Thirty Risk Factors for Alzheimer's Disease Unified by a Common Neuroimmune-Neuroinflammation Mechanism

One of the major obstacles confronting the formulation of a mechanistic understanding for Alzheimer's disease (AD) is its immense complexity-a complexity that traverses the full structural and phenomenological spectrum, including molecular, macromolecular, cellular, neurological and behavioural processes. This complexity is reflected by the equally complex diversity of risk factors associated with AD. However, more than merely mirroring disease complexity, risk factors also provide fundamental insights into the aetiology and pathogenesis of AD as a neurodegenerative disorder since they are central to disease initiation and subsequent propagation. Based on a systematic literature assessment, this review identified 30 risk factors for AD and then extended the analysis to further identify neuroinflammation as a unifying mechanism present in all 30 risk factors. Although other mechanisms (e.g., vasculopathy, proteopathy) were present in multiple risk factors, dysfunction of the neuroimmune-neuroinflammation axis was uniquely central to all 30 identified risk factors. Though the nature of the neuroinflammatory involvement varied, the activation of microglia and the release of pro-inflammatory cytokines were a common pathway shared by all risk factors. This observation provides further evidence for the importance of immunopathic mechanisms in the aetiopathogenesis of AD.

The Metabolically Obese, Normal-Weight Phenotype in Young Rats Is Associated with Cognitive Impairment and Partially Preventable with Leptin Intake during Lactation

The intake of high-fat diets (HFDs) and obesity are linked to cognitive impairment. Here, we aimed to investigate whether an early metabolically obese, normal-weight (MONW) phenotype, induced with an HFD in young rats, also leads to cognitive dysfunction and to evaluate the potential cognitive benefits of neonatal intake of leptin. To achieve this, Wistar rats orally received physiological doses of leptin or its vehicle during lactation, followed by 11 weeks of pair-feeding with an HFD or control diet post-weaning. Working memory was assessed using a T-maze, and gene expression in the hippocampus and peripheral blood mononuclear cells (PBMCs) was assessed with real-time RT-qPCR to identify cognition biomarkers. Young MONW-like rats showed hippocampal gene expression changes and decreased working memory. Animals receiving leptin during lactation presented similar gene expression changes but preserved working memory despite HFD intake, partly due to improved insulin sensitivity. Notably, PBMC Syn1 expression appears as an accessible biomarker of cognitive health, reflecting both the detrimental effect of HFD intake at early ages despite the absence of obesity and the positive effects of neonatal leptin treatment on cognition. Thus, the MONW phenotype developed at a young age is linked to cognitive dysfunction, which is reflected at the transcriptomic level in PBMCs. Neonatal leptin intake can partly counteract this impaired cognition resulting from early HFD consumption.

Leptin and risk factors for atherosclerosis: A review

Leptin is a hormone secreted primarily by adipose tissue. It regulates an organism's metabolism, energy balance, and body weight through a negative feedback mechanism. When a person or animal has low body fat and little energy, the leptin level in the body decreases, and conversely, when there is an excess of nutrients, the leptin level increases, giving a feeling of satiety. However, when leptin levels are abnormal (too high or too low) for a number of reasons, it can negatively affect your health, inducing inflammatory responses, obesity, and other problems. Many studies have shown that abnormal leptin levels, such as hyperleptinemia, are closely associated with common risk factors for atherosclerosis (AS). This review systematically states the relationship between leptin and common risk factors for AS (inflammation, obesity, diabetes mellitus, hypertension, and sleep disorders) and provides some new thoughts on the future direction of research on both. Because the abnormal level of leptin will have adverse effects on multiple atherosclerotic risk factors, how to regulate the leptin level of patients with AS, and whether we can treat and prevent AS by intervening the leptin level, these may be our new research directions in the future.

Therapeutic potential of flavonoids in the management of obesity-induced Alzheimer's disease: an overview of preclinical and clinical studies

Obesity is a global epidemic that affects people of all ages, genders, and backgrounds. It can lead to a plethora of disorders, including diabetes mellitus, renal dysfunction, musculoskeletal problems, metabolic syndrome, cardiovascular, and neurodegenerative abnormalities. Obesity has also been linked to neurological diseases such as cognitive decline, dementia, and Alzheimer's disease (AD), caused by oxidative stress, pro-inflammatory cytokines, and the production of reactive oxygen free radicals (ROS). Secretion of insulin hormone is impaired in obese people, leading to hyperglycaemia and increased accumulation of amyloid-β in the brain. Acetylcholine, a key neurotransmitter necessary for forming new neuronal connections in the brain, decreases in AD patients. To alleviate acetylcholine deficiency, researchers have proposed dietary interventions and adjuvant therapies that enhance the production of acetylcholine and assist in the management of AD patients. Such measures include dietary intervention with antioxidant and anti-inflammatory flavonoid-rich diets, which have been found to bind to tau receptors, reduce gliosis, and reduce neuroinflammatory markers in animal models. Furthermore, flavonoids like curcumin, resveratrol, epigallocatechin-3-gallate, morin, delphinidins, quercetin, luteolin, and oleocanthal have shown to cause significant reductions in interleukin-1β, increase BDNF levels, stimulate hippocampal neurogenesis and synapse formation, and ultimately prevent the loss of neurons in the brain. Thus, flavonoid-rich nutraceuticals can be a potential cost-effective therapeutic option for treating obesity-induced AD, but further well-designed, randomized, and placebo-controlled clinical studies are needed to assess their optimal dosages, efficacy, and long-term safety of flavonoids in humans. The main objectives of this review are to underscore the therapeutic potential of different nutraceuticals containing flavonoids that can be added in the daily diet of AD patients to enhance acetylcholine and reduce neuronal inflammation in the brain.

The Levels of Leptin, Cystatin C, Neuropilin-1 and Tau Protein in Relation to Dietary Habits in Patients with Alzheimer's Disease

Alzheimer's disease (AD) is the most common form of dementia in older people. Its prevalence is expected to increase, and therefore it poses a serious challenge to the healthcare system. The aim of the study was to assess the concentration of leptin, cystatin C, neuropilin-1 and tau protein, as well as the influence of dietary habits on these parameters, in a group of AD patients (n = 110) compared to 60 healthy people (n = 60). It has been shown that AD patients, compared to healthy people, are characterized by significantly higher median concentrations of leptin (9.97 vs. 3.08), cystatin c (1.53 vs. 0.56) and tau protein (8.46 vs. 4.19), but significantly lower median neuropilin-1 (69.94 vs. 167.28). Multiple regression analyses showed that leptin levels could be explained by dietary habits in 27%, cystatin C in 51%, neuropilin-1 in 41% and tau protein in 25% of cases. Modification of eating habits may contribute to improving the values of the discussed parameters.

Elevated visceral adiposity index linked to improved cognitive function in middle-aged and elderly Chinese: evidence from the China health and retirement longitudinal study

Object

Cognitive decline and obesity are major global public health issues, and their association has been widely acknowledged. The link between the visceral adiposity index (VAI) and cognitive function in the Chinese population remains uncertain. This study aims to investigate the effects of VAI levels on cognitive function in the Chinese middle-aged and elderly population.

Methods

We analyzed longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS) collected in 2011, 2013, 2015, and 2018. VAI levels were divided into three tertiles. Generalized estimating equation (GEE) models were used to explore the relationships between VAI levels and cognitive function, including overall cognitive scores, episodic memory, and mental status. Adjustments were made for potential confounders.

Results

The study consisted of 2,677 participants. Contrary to expectations, higher VAI levels were associated with higher overall cognitive scores and improved episodic memory scores, while no significant effect was observed on mental status. The GEE models consistently indicated that higher VAI levels were associated with higher overall cognitive scores, primarily due to their association with episodic memory. Stratified analyses revealed that the VAI was associated with better cognitive function primarily in males, individuals under 60 years old, those with lower education levels, rural residents, and married individuals, mainly in relation to episodic memory. No significant interactions were observed between VAI and demographic factors.

Conclusion

Our findings suggest that higher visceral adiposity is associated with slower cognitive decline in the Chinese middle-aged and elderly population, especially in its association with episodic memory. These results underline the need to further investigate the potential protective role of visceral fat in cognitive function, potentially offering new insights for interventions to enhance cognitive function and prevent dementia in this population.

Adiponectin and resistin modulate the progression of Alzheimer´s disease in a metabolic syndrome model

Metabolic syndrome (MetS), a cluster of metabolic conditions that include obesity, hyperlipidemia, and insulin resistance, increases the risk of several aging-related brain diseases, including Alzheimer's disease (AD). However, the underlying mechanism explaining the link between MetS and brain function is poorly understood. Among the possible mediators are several adipose-derived secreted molecules called adipokines, including adiponectin (ApN) and resistin, which have been shown to regulate brain function by modulating several metabolic processes. To investigate the impact of adipokines on MetS, we employed a diet-induced model to induce the various complications associated with MetS. For this purpose, we administered a high-fat diet (HFD) to both WT and APP/PSN1 mice at a pre-symptomatic disease stage. Our data showed that MetS causes a fast decline in cognitive performance and stimulates Aβ42 production in the brain. Interestingly, ApN treatment restored glucose metabolism and improved cognitive functions by 50% while decreasing the Aβ42/40 ratio by approximately 65%. In contrast, resistin exacerbated Aβ pathology, increased oxidative stress, and strongly reduced glucose metabolism. Together, our data demonstrate that ApN and resistin alterations could further contribute to AD pathology.

Recent progress in leptin signaling from a structural perspective and its implications for diseases

As a multi-potency cytokine, leptin not only plays a crucial role in controlling weight and energy homeostasis but also participates in the metabolic balance in the human body. Leptin is a small helical protein with a molecular weight of 16 kDa. It can interact with multiple subtypes of its receptors to initiate intracellular signal transduction and exerts physiological effects. Disturbances in leptin signaling may lead to obesity and a variety of metabolic diseases. Leptin was also found to be a critical factor in many diseases of the elderly. In this review, we focus on recent advances in the structural and molecular mechanisms of leptin signaling through its receptors with the aim of a deeper understanding of leptin-related diseases.

Alzheimer's disease-associated complement gene variants influence plasma complement protein levels

BACKGROUND

Alzheimer's disease (AD) has been associated with immune dysregulation in biomarker and genome-wide association studies (GWAS). GWAS hits include the genes encoding complement regulators clusterin (CLU) and complement receptor 1 (CR1), recognised as key players in AD pathology, and complement proteins have been proposed as biomarkers.

MAIN BODY

To address whether changes in plasma complement protein levels in AD relate to AD-associated complement gene variants we first measured relevant plasma complement proteins (clusterin, C1q, C1s, CR1, factor H) in a large cohort comprising early onset AD (EOAD; n = 912), late onset AD (LOAD; n = 492) and control (n = 504) donors. Clusterin and C1q were significantly increased (p < 0.001) and sCR1 and factor H reduced (p < 0.01) in AD plasma versus controls. ROC analyses were performed to assess utility of the measured complement biomarkers, alone or in combination with amyloid beta, in predicting AD. C1q was the most predictive single complement biomarker (AUC 0.655 LOAD, 0.601 EOAD); combining C1q with other complement or neurodegeneration makers through stepAIC-informed models improved predictive values slightly. Effects of GWS SNPs (rs6656401, rs6691117 in CR1; rs11136000, rs9331888 in CLU; rs3919533 in C1S) on protein concentrations were assessed by comparing protein levels in carriers of the minor vs major allele. To identify new associations between SNPs and changes in plasma protein levels, we performed a GWAS combining genotyping data in the cohort with complement protein levels as endophenotype. SNPs in CR1 (rs6656401), C1S (rs3919533) and CFH (rs6664877) reached significance and influenced plasma levels of the corresponding protein, whereas SNPs in CLU did not influence clusterin levels.

CONCLUSION

Complement dysregulation is evident in AD and may contribute to pathology. AD-associated SNPs in CR1, C1S and CFH impact plasma levels of the encoded proteins, suggesting a mechanism for impact on disease risk.

Cognitive behavioural therapy for adults with overweight or obesity

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To assess the effects of cognitive behavioural therapy for weight management in adults with overweight or obesity.

Exercise and Weight Management: The Role of Leptin-A Systematic Review and Update of Clinical Data from 2000-2022

A well-balanced metabolism means a lower risk for metabolism-related neuropsychiatric disorders. Leptin is a secretory adipokine involved in the central control of appetite that appears to play a role in the etiology of feeding-related disorders. Additionally, the influence of exercise on feeding behaviors potentially modulates the circulation of metabolites that signal through the central nervous system. In this systematic review, we collected the recent clinical evidence on the effect of exercise on leptin concentrations in health individuals published from 2000 to 20 September 2022, according to the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA 2020 statement). Six hundred and thirty-eight papers were retrieved and forty-eight papers were included in the qualitative synthesis. Data supports that exercise positively influences appetite via enhancing peripheral and central leptin signaling (reuptake), especially during weight loss. Exercise modulation of leptin signaling through leptin receptors helps to stabilize increases in food intake during periods of negative energy balance, prior to a decrease in the body fat tissue content. At a high intensity, exercise appears to counteract leptin resistance.

Adult-Onset CNS Sulfatide Deficiency Causes Sex-Dependent Metabolic Disruption in Aging

The interconnection between obesity and central nervous system (CNS) neurological dysfunction has been widely appreciated. Accumulating evidence demonstrates that obesity is a risk factor for CNS neuroinflammation and cognitive impairment. However, the extent to which CNS disruption influences peripheral metabolism remains to be elucidated. We previously reported that myelin-enriched sulfatide loss leads to CNS neuroinflammation and cognitive decline. In this study, we further investigated the impact of CNS sulfatide deficiency on peripheral metabolism while considering sex- and age-specific effects. We found that female sulfatide-deficient mice gained significantly more body weight, exhibited higher basal glucose levels, and were glucose-intolerant during glucose-tolerance test (GTT) compared to age-matched controls under a normal diet, whereas male sulfatide-deficient mice only displayed glucose intolerance at a much older age compared to female sulfatide-deficient mice. Mechanistically, we found that increased body weight was associated with increased food intake and elevated neuroinflammation, especially in the hypothalamus, in a sex-specific manner. Our results suggest that CNS sulfatide deficiency leads to sex-specific alterations in energy homeostasis via dysregulated hypothalamic control of food intake.

Uric acid levels and their association with vascular dementia and Parkinson's disease dementia: a meta-analysis

OBJECTIVES

To explore the association between uric acid (UA) levels and vascular dementia (VaD) and Parkinson's disease dementia (PDD), a meta-analysis was conducted.

METHODS

The relevant studies were identified by searching PubMed, Embase, Web of Science, and Cochrane Collaboration Database up to May 2022. Pooled analysis, sensitivity analysis, and publication bias examination were all conducted. All analyses were performed by using STATA 16.

RESULTS

Twelve studies with a total of 2097 subjects were included. The pooled analysis showed that UA levels were not associated with VaD (WMD =  - 10.99 μmol/L, 95% CI (- 48.05, 26.07), P = 0.561) but were associated with PDD (WMD =  - 25.22 μmol/L, 95% CI (- 43.47, - 6.97), P = 0.007). The statistical stability and reliability were evaluated using sensitivity analysis and publication bias outcomes.

CONCLUSION

UA levels are associated with PDD but not with VaD. This study will help to strengthen our knowledge of the pathophysiologies of VaD and PDD, and promote the development of prevention and treatment strategies.

Polyphenol supplementation and executive functioning in overweight and obese adults at risk of cognitive impairment: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Increasing evidence indicates a link between obesity and cognitive impairment. Furthermore, there is limited literature regarding the effect of polyphenols, a plant derived compounds, on executive functioning in an overweight/obese population at-risk of cognitive impairment. The aim of the present systematic review and meta-analysis of randomized controlled trials is to examine the effect of polyphenol supplementation on executive functions in overweight and/or obese populations at risk of cognitive impairment.

METHODS

A comprehensive literature search was conducted from inception to March 2023 using four electronic databases: PubMed/Medline, PsycInfo, Scopus and Cochrane trials library. Published primary research studies in English that compared the effect of polyphenols with placebo on executive function in overweight/obese adults were considered eligible for the meta-analysis. Jadad scale was used for the methodological quality rating of the included studies. Hedges g with 95% confidence intervals (CI) for endpoints were calculated using random effect model where applicable. Rosenthal's Fail-safe N, funnel plots, the Begg and Mazumdar's rank correlation test (Kendall's S statistic P-Q), Egger's linear regression test, and Duval and Tweedie's trim-and-fill test were identified for potential use as appropriate, to examine publication bias. Sensitivity analysis was conducted to examine the robustness of the results.

RESULTS AND CONCLUSION

A total of 23 RCT studies involving N = 1,976 participants were included in the review. The results of the meta-analysis revealed a non-significant effect for polyphenol supplementation on executive function (g = 0.076, CI = -0.018 to 0.170). Observations from primary studies within the meta-analysis showed a potential positive effect of polyphenol supplementation in a younger population at-risk of cognitive impairment and it is recommended to investigate this further in future studies. Moreover, the variability of the tasks used to examine executive functions as well as the adequate reporting of supplement's phenolic composition is a limitation that future work should also consider.

Ghrelin system in Alzheimer's disease

Alzheimer's disease (AD) is the most common type of dementia in seniors. Current efforts to understand the etiopathogenesis of this neurodegenerative disorder have brought forth questions about systemic factors in the development of AD. Ghrelin is a brain-gut peptide that is activated by ghrelin O-acyltransferase (GOAT) and signals via its receptor, growth hormone secretagogue receptor (GHSR). With increasing recognition of the neurotropic effects of ghrelin, the role of ghrelin system deregulation in the development of AD has been accentuated in recent years. In this review, we summarized recent research progress regarding the mechanisms of ghrelin signaling dysregulation and its contribution to AD brain pathology. In addition, we also discussed the therapeutic potential of strategies targeting ghrelin signaling for the treatment of this neurological disease.

Association of Adipokines with Alzheimer's Disease in a Chinese Cohort

BACKGROUND

The correlation between plasma adipose factor levels and Alzheimer's patients is not entirely clear.

OBJECTIVE

We aimed to investigate associations between AD and plasma levels of three adipokines including plasma adiponectin, leptin, and resistin.

METHODS

A single-center, cross-sectional study recruited AD patients (n = 148) and cognitively normal (CN) controls (n = 110). The multivariate logistic regression analysis was applied to determine associations of adiponectin, leptin, and resistin with the presence of AD. The receiver operating characteristic (ROC) analysis was employed to determine the diagnostic power of adiponectin, leptin and resistin for AD.

RESULTS

After adjusted for the conventional risk factors, plasma levels of leptin (OR = 0.417, 95% CI: 0.272-0.638, p < 0.0001) and adiponectin (OR = 1.249, 95% CI: 1.151-1.354, p < 0.0001) were associated with the presence of AD. In total participants, the plasma adiponectin level was negatively correlated with MMSE scores (p < 0.0001) and was positively with CDR scores (p < 0.0001) and age (p < 0.0001). The plasma level of leptin was negatively correlated with CDR scores (p < 0.0001) and positively correlated with MMSE scores (p < 0.0001). Both adiponectin (p < 0. 0001) and leptin (p < 0. 0001) featured higher AUC than the random chance.

CONCLUSIONS

Plasma adiponectin and leptin were associated with the presence, symptomatic severity, and diagnostic power of AD, suggesting a potential role of adipokines in the pathogenesis of AD.

Vitamin D, a Secosteroid Hormone and Its Multifunctional Receptor, Vitamin D Receptor, in Alzheimer's Type Neurodegeneration

Vitamin D is a secosteroid hormone exerting neurosteroid-like properties. Its well-known nuclear hormone receptor, and recently proposed as a mitochondrial transcription factor, vitamin D receptor, acts for its primary functions. The second receptor is an endoplasmic reticulum protein, protein disulfide isomerase A3 (PDIA3), suggested to act as a rapid response. Vitamin D has effects on various systems, particularly through calcium metabolism. Among them, the nervous system has an important place in the context of our subject. Recent studies have shown that vitamin D and its receptors have numerous effects on the nervous system. Neurodegeneration is a long-term process. Throughout a human life span, so is vitamin D deficiency. Our previous studies and others have suggested that the out-come of long-term vitamin D deficiency (hypovitaminosis D or inefficient utilization of vitamin D), may lead neurons to be vulnerable to aging and neurodegeneration. We suggest that keeping vitamin D levels at adequate levels at all stages of life, considering new approaches such as agonists that can activate vitamin D receptors, and utilizing other derivatives produced in the synthesis process with UVB are crucial when considering vitamin D-based intervention studies. Given most aspects of vitamin D, this review outlines how vitamin D and its receptors work and are involved in neurodegeneration, emphasizing Alzheimer's disease.

Bariatric surgery-induced weight loss and associated genome-wide DNA-methylation alterations in obese individuals

BACKGROUND

Obesity is a multifactorial and chronic condition of growing universal concern. It has recently been reported that bariatric surgery is a more successful treatment for severe obesity than other noninvasive interventions, resulting in rapid significant weight loss and associated chronic disease remission. The identification of distinct epigenetic patterns in patients who are obese or have metabolic imbalances has suggested a potential role for epigenetic alterations in causal or mediating pathways in the development of obesity-related pathologies. Specific changes in the epigenome (DNA methylome), associated with metabolic disorders, can be detected in the blood. We investigated whether such epigenetic changes are reversible after weight loss using genome-wide DNA methylome analysis of blood samples from individuals with severe obesity (mean BMI ~ 45) undergoing bariatric surgery.

RESULTS

Our analysis revealed 41 significant (Bonferroni p < 0.05) and 1169 (false discovery rate p < 0.05) suggestive differentially methylated positions (DMPs) associated with weight loss due to bariatric surgery. Among the 41 significant DMPs, 5 CpGs were replicated in an independent cohort of BMI-discordant monozygotic twins (the heavier twin underwent diet-induced weight loss). The effect sizes of these 5 CpGs were consistent across discovery and replication sets (p < 0.05). We also identified 192 differentially methylated regions (DMRs) among which SMAD6 and PFKFB3 genes were the top hypermethylated and hypomethylated regions, respectively. Pathway enrichment analysis of the DMR-associated genes showed that functional pathways related to immune function and type 1 diabetes were significant. Weight loss due to bariatric surgery also significantly decelerated epigenetic age 12 months after the intervention (mean =  - 4.29; p = 0.02).

CONCLUSIONS

We identified weight loss-associated DNA-methylation alterations targeting immune and inflammatory gene pathways in blood samples from bariatric-surgery patients. The top hits were replicated in samples from an independent cohort of BMI-discordant monozygotic twins following a hypocaloric diet. Energy restriction and bariatric surgery thus share CpGs that may represent early indicators of response to the metabolic effects of weight loss. The analysis of bariatric surgery-associated DMRs suggests that epigenetic regulation of genes involved in endothelial and adipose tissue function is key in the pathophysiology of obesity.

Current Insights on the Use of Insulin and the Potential Use of Insulin Mimetics in Targeting Insulin Signalling in Alzheimer's Disease

Alzheimer's disease (AD) and type 2 diabetes (T2D) are chronic diseases that share several pathological mechanisms, including insulin resistance and impaired insulin signalling. Their shared features have prompted the evaluation of the drugs used to manage diabetes for the treatment of AD. Insulin delivery itself has been utilized, with promising effects, in improving cognition and reducing AD related neuropathology. The most recent clinical trial involving intranasal insulin reported no slowing of cognitive decline; however, several factors may have impacted the trial outcomes. Long-acting and rapid-acting insulin analogues have also been evaluated within the context of AD with a lack of consistent outcomes. This narrative review provided insight into how targeting insulin signalling in the brain has potential as a therapeutic target for AD and provided a detailed update on the efficacy of insulin, its analogues and the outcomes of human clinical trials. We also discussed the current evidence that warrants the further investigation of the use of the mimetics of insulin for AD. These small molecules may provide a modifiable alternative to insulin, aiding in developing drugs that selectively target insulin signalling in the brain with the aim to attenuate cognitive dysfunction and AD pathologies.

The Role of Adipokines in Inflammatory Mechanisms of Obesity

Adipokines are currently widely studied cellular signaling proteins produced by adipose tissue and involved in various processes, including inflammation; energy and appetite modulation; lipid and glucose metabolism; insulin sensitivity; endothelial cell functioning; angiogenesis; the regulation of blood pressure; and hemostasis. The current review attempted to highlight the key functions of adipokines in the inflammatory mechanisms of obesity, its complications, and its associated diseases. An extensive search for materials on the role of adipokines in the pathogenesis of obesity was conducted online using the PubMed and Scopus databases until October 2022.

Sex-specific transcriptional rewiring in the brain of Alzheimer’s disease patients

Sex-specific differences may contribute to Alzheimer’s disease (AD) development. AD is more prevalent in women worldwide, and female sex has been suggested as a disease risk factor. Nevertheless, the molecular mechanisms underlying sex-biased differences in AD remain poorly characterized. To this end, we analyzed the transcriptional changes in the entorhinal cortex of symptomatic and asymptomatic AD patients stratified by sex. Co-expression network analysis implemented by SWItchMiner software identified sex-specific signatures of switch genes responsible for drastic transcriptional changes in the brain of AD and asymptomatic AD individuals. Pathway analysis of the switch genes revealed that morphine addiction, retrograde endocannabinoid signaling, and autophagy are associated with both females with AD (F-AD) and males with (M-AD). In contrast, nicotine addiction, cell adhesion molecules, oxytocin signaling, adipocytokine signaling, prolactin signaling, and alcoholism are uniquely associated with M-AD. Similarly, some of the unique pathways associated with F-AD switch genes are viral myocarditis, Hippo signaling pathway, endometrial cancer, insulin signaling, and PI3K-AKT signaling. Together these results reveal that there are many sex-specific pathways that may lead to AD. Approximately 20–30% of the elderly have an accumulation of amyloid beta in the brain, but show no cognitive deficit. Asymptomatic females (F-asymAD) and males (M-asymAD) both shared dysregulation of endocytosis. In contrast, pathways uniquely associated with F-asymAD switch genes are insulin secretion, progesterone-mediated oocyte maturation, axon guidance, renal cell carcinoma, and ErbB signaling pathway. Similarly, pathways uniquely associated with M-asymAD switch genes are fluid shear stress and atherosclerosis, FcγR mediated phagocytosis, and proteoglycans in cancer. These results reveal for the first time unique pathways associated with either disease progression or cognitive resilience in asymptomatic individuals. Additionally, we identified numerous sex-specific transcription factors and potential neurotoxic chemicals that may be involved in the pathogenesis of AD. Together these results reveal likely molecular drivers of sex differences in the brain of AD patients. Future molecular studies dissecting the functional role of these switch genes in driving sex differences in AD are warranted.

Trends in Gliosis in Obesity, and the Role of Antioxidants as a Therapeutic Alternative

Obesity remains a global health problem. Chronic low-grade inflammation in this pathology has been related to comorbidities such as cognitive alterations that, in the long term, can lead to neurodegenerative diseases. Neuroinflammation or gliosis in patients with obesity and type 2 diabetes mellitus has been related to the effect of adipokines, high lipid levels and glucose, which increase the production of free radicals. Cerebral gliosis can be a risk factor for developing neurodegenerative diseases, and antioxidants could be an alternative for the prevention and treatment of neural comorbidities in obese patients.

AIM

Identify the immunological and oxidative stress mechanisms that produce gliosis in patients with obesity and propose antioxidants as an alternative to reducing neuroinflammation.

METHOD

Advanced searches were performed in scientific databases: PubMed, ProQuest, EBSCO, and the Science Citation index for research on the physiopathology of gliosis in obese patients and for the possible role of antioxidants in its management.

CONCLUSION

Patients with obesity can develop neuroinflammation, conditioned by various adipokines, excess lipids and glucose, which results in an increase in free radicals that must be neutralized with antioxidants to reduce gliosis and the risk of long-term neurodegeneration.

Exposure to outdoor and indoor air pollution and risk of overweight and obesity across different life periods: A review

Due to the highly evolved industrialization and modernization, air quality has deteriorated in most countries. As reported by the World Health Organization (WHO), air pollution is now considered as one of the major threats to global health and a principal risk factor for noncommunicable diseases. Meanwhile, the increasing worldwide prevalence of overweight and obesity is attracting more public attentions. Recently, accumulating epidemiological studies have provided evidence that overweight and obesity may be partially attributable to environmental exposure to air pollution. This review summarizes the epidemiological evidence for the correlation between exposure to various outdoor and indoor air pollutants (mainly particulate matter (PM), nitrogen oxides (NO_x), ozone (O₃), and polycyclic aromatic hydrocarbons (PAHs)) and overweight and obesity outcomes in recent years. Moreover, it discusses the multiple effects of air pollution during exposure periods throughout life and sex differences in populations. This review also describes the potential mechanism underlying the increased risk of obesity caused by air pollution, including inflammation, oxidative stress, metabolic imbalance, intestinal flora disorders and epigenetic modifications. Finally, this review proposes macro- and micro-measures to prevent the negative effects of air pollution exposure on the obesity prevalence.