Immunoinflammatory role of apolipoprotein E4 in malnutrition and enteric infections and the increased risk for chronic diseases under adverse environments

Apolipoprotein E4 and Alzheimer's disease causality under adverse environments and potential intervention by senolytic nutrients

Apolipoprotein E (apoE) has a pivotal role in Alzheimer's Disease (AD) pathophysiology. APOE4 has been recognized as a risk factor for developing late-onset AD. Recently, APOE4 homozygosity was regarded as a new familial genetic trait of AD. In this opinion paper, we summarized the potential pleiotropic antagonism role of APOE4 in children living under early life adversity and afflicted with enteric infection/malnutrition-related pathogenic exposome. APOE4 was found to be neuroprotective early in life despite its increasing risk for AD with aging. We call for awareness of the potential burden this can bring to the public health system when APOE4 carriers, raised under adverse environmental conditions in early life and then aging with unhealthy lifestyles in later life may be at special risk for cognitive impairments and acquired AD. We postulate the importance of anti-senescence therapies to protect these individuals and remediate aging-related chronic illnesses.

Plasma proteome profiling reveals metabolic and immunologic differences between Anorexia Nervosa subtypes

AIMS/HYPOTHESIS

Anorexia Nervosa (AN) is a severe psychiatric disorder of an unknown etiology with a crude mortality rate of about 5 % per decade, making it one of the deadliest of all psychiatric illnesses. AN is broadly classified into two main subtypes, restricting and binge/purging disorder. Despite extensive research efforts during several decades, the underlying pathophysiology of AN remains poorly understood. In this study, we aimed to identify novel protein biomarkers for AN by performing a proteomics analysis of fasting plasma samples from 78 females with AN (57 restrictive and 21 binge/purge type) and 70 healthy controls.

METHODS

Using state-of-the-art mass spectrometry-based proteomics technology in conjunction with an advanced bioinformatics pipeline, we quantify >500 plasma proteins.

RESULTS

Differential expression analysis and correlation of proteomics data with clinical variables led to identification of a panel of novel protein biomarkers with potential pathophysiological significance for AN. Our findings demonstrate evidence of a humoral immune system response, altered lipid metabolism and potential alteration of plasma cells in AN patients. Additionally, we stratified AN patients based on the quantified proteins and suggest a potential autoimmune nature in the restrictive subtype of AN.

CONCLUSIONS/INTERPRETATION

In summary, on top of biomarkers of AN subtypes, this study provides a comprehensive map of plasma proteins that constitute a resource for further studies of the pathophysiology of AN.

Pros and Cons of APOE4 Homozygosity and Effects on Neuroplasticity, Malnutrition, and Infections in Early Life Adversity, Alzheimer's Disease, and Alzheimer's Prevention

Fortea et al.'s. (2024) recent data analysis elegantly calls attention to familial late-onset Alzheimer's disease (AD) with APOE4 homozygosity. The article by Grant (2024) reviews the factors associated with AD, particularly the APOE genotype and lifestyle, and the broad implications for prevention, both for individuals with the lifestyles associated with living in resource-rich countries and for those enduring environmental adversity in poverty settings, including high exposure to enteric pathogens and precarious access to healthcare. Grant discusses the issue of APOE genotype and its implications for the benefits of lifestyle modifications. This review highlights that bearing APOE4 could constitute an evolutionary benefit in coping with heavy enteric infections and malnutrition early in life in the critical formative first two years of brain development. However, the critical issue may be that this genotype could be a health concern under shifts in lifestyle and unhealthy diets during aging, leading to severe cognitive impairments and increased risk of AD. This commentary supports the discussions of Grant and the benefits of improving lifestyle for decreasing the risks for AD while providing further understanding and modelling of the early life benefits of APOE4 amidst adversity. This attention to the pathophysiology of AD should help further elucidate these critical, newly appreciated pathogenic pathways for developing approaches to the prevention and management in the context of the APOE genetic variations associated with AD.

Myeloperoxidase as a biomarker for intestinal-brain axis dysfunction induced by malnutrition and Cryptosporidium infection in weanling mice

Cryptosporidiosis is a waterborne protozoal infection that may cause life-threatening diarrhea in undernourished children living in unsanitary environments. The aim of this study is to identify new biomarkers that may be related to gut-brain axis dysfunction in children suffering from the malnutrition/infection vicious cycle, necessary for better intervention strategies. Myeloperoxidase (MPO) is a well-known neutrophil-related tissue factor released during enteropathy that could drive gut-derived brain inflammation. We utilized a model of environmental enteropathy in C57BL/6 weanling mice challenged by Cryptosporidium and undernutrition. Mice were fed a 2%-Protein Diet (dPD) for eight days and orally infected with 107-C. parvum oocysts. C. parvum oocyst shedding was assessed from fecal and ileal-extracted genomic DNA by qRT-PCR. Ileal histopathology scores were assessed for intestinal inflammation. Prefrontal cortex samples were snap-frozen for MPO ELISA assay and NF-kb immunostaining. Blood samples were drawn by cardiac puncture after anesthesia and sera were obtained for serum amyloid A (SAA) and MPO analysis. Brain samples were also obtained for Iba-1 prefrontal cortex immunostaining. C. parvum-infected mice showed sustained stool oocyst shedding for six days post-infection and increased fecal MPO and inflammation scores. dPD and cryptosporidiosis led to impaired growth and weight gain. C. parvum-infected dPD mice showed increased serum MPO and serum amyloid A (SAA) levels, markers of systemic inflammation. dPD-infected mice showed greater MPO, NF-kB expression, and Iba-1 immunolabeling in the prefrontal cortex, an important brain region involved in executive function. Our findings suggest MPO as a potential biomarker for intestinal-brain axis dysfunction due to environmental enteropathy.

Apolipoprotein ɛ4-Associated Protection Against Pediatric Enteric Infections is a Survival Advantage in Pre-Industrial Populations

Until 300,000 years ago, ancestors of modern humans ubiquitously carried the apolipoprotein E (APOE) ɛ4/ɛ4 genotype, when the ɛ3 allele mutated from the ancestral ɛ4, which elevates the risk of Alzheimer's disease. Modern humans living today predominantly carry the ɛ3 allele, which provides protection against heart disease and dementia in long-lived populations. The ancestral ɛ4 allele has been highly preserved in isolated populations in tropical and Arctic regions with high pathogen burdens, e.g., helminths. Early humans experienced serious enteric infections that exerted evolutionary selection pressure, and factors that mitigate infant and childhood mortality from enteric infections also exert selection pressure. Some bacteria can exploit the host's defensive inflammatory response to colonize and invade the host. Pathogen-induced inflammation associated with infant and childhood diarrhea can damage the gut wall long after the invading organisms are no longer present. Inflammation not only resides in the mucosal wall, but also induces systemic inflammation. Baseline systemic inflammation is lower in ɛ4 carriers, yet ɛ4 carriers display a stronger host inflammatory response that reduces pathogen burdens, increasing infant and early childhood survival. Evolutionary selection of the ɛ3 allele likely occurred after humans moved into temperate zones with lower pathogen burdens, unrelated to protection from Alzheimer's disease.

ApoE Mimetic Peptides to Improve the Vicious Cycle of Malnutrition and Enteric Infections by Targeting the Intestinal and Blood-Brain Barriers

Apolipoprotein E (apoE) mimetic peptides are engineered fragments of the native apoE protein’s LDL-receptor binding site that improve the outcomes following a brain injury and intestinal inflammation in a variety of models. The vicious cycle of enteric infections and malnutrition is closely related to environmental-driven enteric dysfunction early in life, and such chronic inflammatory conditions may blunt the developmental trajectories of children with worrisome and often irreversible physical and cognitive faltering. This window of time for microbiota maturation and brain plasticity is key to protecting cognitive domains, brain health, and achieving optimal/full developmental potential. This review summarizes the potential role of promising apoE mimetic peptides to improve the function of the gut-brain axis, including targeting the blood-brain barrier in children afflicted with malnutrition and enteric infections.