Growth Hormone-Releaser Diet Attenuates Cognitive Dysfunction in Klotho Mutant Mice via Insulin-Like Growth Factor-1 Receptor Activation in a Genetic Aging Model

Risk Factors, Pathological Changes, and Potential Treatment of Diabetes-Associated Cognitive Dysfunction

BACKGROUND

Diabetes is a prevalent public health issue worldwide, and the cognitive dysfunction and subsequent dementia caused by it seriously affect the quality of life of patients.

METHODS

Recent studies were reviewed to provide a comprehensive summary of the risk factors, pathogenesis, pathological changes and potential drug treatments for diabetes-related cognitive dysfunction (DACD).

RESULTS

Several risk factors contribute to DACD, including hyperglycemia, hypoglycemia, blood sugar fluctuations, hyperinsulinemia, aging, and others. Among them, modifiable risk factors for DACD include blood glucose control, physical activity, diet, smoking, and hypertension management, while non-modifiable risk factors include age, genetic predisposition, sex, and duration of diabetes. At the present, the pathogenesis of DACD mainly includes insulin resistance, neuroinflammation, vascular disorders, oxidative stress, and neurotransmitter disorders.

CONCLUSIONS

In this review, we provide a comprehensive summary of the risk factors, pathogenesis, pathological changes and potential drug treatments for DACD, providing information from multiple perspectives for its prevention and management.

The Interaction Between Attention Deficit and Hyperactivity Disorder and Nutrition

PURPOSE OF REVIEW

This review aims to explore the relationship between Attention Deficit Hyperactivity Disorder (ADHD) and nutrition. ADHD, a neurodevelopmental disorder, has been examined in relation to dietary factors through various metabolic pathways, with a focus on the role of nutrition in symptom management. Unhealthy dietary patterns, particularly those characteristics of Western diets, are believed to exacerbate ADHD symptoms through these mechanisms. In contrast, dietary interventions such as intermittent fasting, which offer greater flexibility in application, have been proposed as potential strategies to alleviate ADHD symptoms. While further research in this area is expected to contribute significantly to the field, this review also provides researchers with a brief perspective on the challenges and limitations associated with experimental ADHD studies. Therefore, this study aims to offer a comprehensive evaluation of the interaction between ADHD and nutrition, providing researchers with an integrative approach to the topic.

RECENT FINDINGS

Western dietary patterns have been found to negatively impact gut barrier integrity, synaptic plasticity, insulin resistance, and oxidative stress. On the other hand, the intermittent fasting diet model, which offers practical flexibility, is thought to be a potentially supportive treatment in managing ADHD. Furthermore, it has been concluded that various experimental models are available for ADHD research, and researchers must work within these limitations. Western diets, particularly in their negative impact on synaptic plasticity and other key metabolic pathways involved in ADHD, can worsen the disorder's symptoms. Intermittent fasting emerges as a promising dietary alternative that may mitigate these adverse effects.

New insights into the role of Klotho in inflammation and fibrosis: molecular and cellular mechanisms

As the body's defense mechanism against damage and infection, the inflammatory response is a pathological process that involves a range of inflammatory cells and cytokines. A healthy inflammatory response helps the body repair by eliminating dangerous irritants. However, tissue fibrosis can result from an overly intense or protracted inflammatory response. The anti-aging gene Klotho suppresses oxidation, delays aging, and fosters development of various organs. Numerous investigations conducted in the last few years have discovered that Klotho expression is changed in a variety of clinical diseases and is strongly linked to the course and outcome of a disease. Klotho functions as a co-receptor for FGF and as a humoral factor that mediates intracellular signaling pathways such as transforming growth factor β (TGF-β), toll-like receptors (TLRs), nuclear factor-kappaB (NF-κB), renin -angiotensin system (RAS), and mitogen-activated protein kinase (MAPK). It also interferes with the phenotype and function of inflammatory cells, such as monocytes, macrophages, T cells, and B cells. Additionally, it regulates the production of inflammatory factors. This article aims to examine Klotho's scientific advances in terms of tissue fibrosis and the inflammatory response in order to provide novel therapy concepts for fibrotic and inflammatory disorders.

The location, physiology, pathology of hippocampus Melatonin MT2 receptor and MT2-selective modulators

Melatonin, a neurohormone secreted by the pineal gland and regulated by the suprachiasmatic nucleus (SCN) of the hypothalamus, is synthesized and directly released into the cerebrospinal fluid (CSF) of the third ventricle (3rdv), where it undergoes rapid absorption by surrounding tissues to exert its physiological function. The hippocampus, a vital structure in the limbic system adjacent to the ventricles, plays a pivotal role in emotional response and memory formation. Melatonin MT1 and MT2 receptors are G protein-coupled receptors (GPCRs) that primarily mediate melatonin's receptor-dependent effects. In comparison to the MT1 receptor, the widely expressed MT2 receptor is crucial for mediating melatonin's biological functions within the hippocampus. Specifically, MT2 receptor is implicated in hippocampal synaptic plasticity and memory processes, as well as neurogenesis and axogenesis. Numerous studies have demonstrated the involvement of MT2 receptors in the pathophysiology and pharmacology of Alzheimer's disease, depression, and epilepsy. This review focuses on the anatomical localization of MT2 receptor in the hippocampus, their physiological function in this region, and their signal transduction and pharmacological roles in neurological disorders. Additionally, we conducted a comprehensive review of MT2 receptor ligands used in psychopharmacology and other MT2-selective ligands over recent years. Ultimately, we provide an outlook on future research for selective MT2 receptor drug candidates.

Nonlinear relationship between glycated hemoglobin and cognitive impairment after acute mild ischemic stroke

BACKGROUND

Stroke is the second most common cause of morbidity and mortality. Even mild stroke survivors have an increased risk of cognitive impairment. Studies have been conducted on the relationship between glycated hemoglobin (HbA1c) and cognitive decline, but the findings have been inconsistent. Therefore, this study examined the link between HbA1c levels and cognitive impairment following acute mild ischemic stroke.

METHODS

Data from 311 patients with acute mild ischemic stroke admitted to Suining Central Hospital, Sichuan Province, China, from January 1, 2015, to December 31, 2018, were evaluated. Fasting venous blood was taken to assess HbA1c levels on the day after admission. Cognitive function was assessed using the Chinese version of the Montreal Cognitive Assessment Scale (MoCA) 3-6 months after stroke onset. We used a generalized additive model and smooth curve fitting (penalty spline method) to assess the nonlinear relationship between HbA1c and poststroke cognitive impairment (PSCI).

RESULTS

This study included 311 patients aged 23 to 96 years old (mean age: 67.37 ± 11.92 years), of whom 198 (63.67%) were men. Among the 311 stroke patients, 120 (38.59%) had PSCI. After adjusting for potential confounders, there was a nonlinear relationship between HbA1c and PSCI, with an inflection point of 8.2. To the left of the inflection point, the effect size, 95% confidence interval, and P value were 0.87, 0.58 to 1.31, and 0.5095, respectively; however, to the right of the inflection point, these numbers were 1.96, 1.08 to 3.58, and 0.0280.

CONCLUSION

We found a nonlinear relationship between HbA1c and PSCI. When HbA1c was greater than 8.2%, HbA1c was positively correlated with PSCI.

Virgin coconut oil reverses behavioral phenotypes of letrozole-model of PCOS in Wistar rats via modulation of NRF2 upregulation

Objectives

Polycystic ovarian syndrome (PCOS) is an endocrine disorder associated with insulin resistance, hyperandrogenism, and sub-infertility. Virgin coconut oil (VCO) has been reported to have health benefits, such as anti-inflammatory, anti-oxidant, and antiviral properties. This study investigated the effects of dietary VCO supplementation on memory and cognitive impairment in female rats with letrozole induced PCOS.

Methods

Thirty female rats were randomly divided into five groups. All rats except controls were treated with letrozole for 21 days to induce PCOS and were subsequently treated for 14 days with 10% VCO, clomiphene (CLO), or VCO + CLO. Three neurobehavioral tests were conducted: elevated plus maze, Y maze, and novel object recognition tests.

Results

Our results indicated statistically elevated serum concentrations of sex hormones in rats with PCOS, compared with the control and treated groups. In addition, all treated groups showed significant reversal of the low serum concentrations of catalase and down-regulated gene expression of Nrf2 in the hippocampus seen in the PCOS rats. In addition, gene expression of acetylcholine esterase was up-regulated in PCOS rats, and was statistically reverted in the VCO treated groups.

Conclusion

Anxiety-like behavior and impaired short-term memory were observed in PCOS rats; however, VCO supplementation reversed these effects by modulating the gene expression of Nrf2 and AchE.

A conserved klo-1-mpk-1 pathway regulates autophagy and modulates longevity in Caenorhabditis elegans

There are six different longevity models in Caenorhabditis elegans. Previous studies have identified several convergence points, such as hlh-30, daf-16, and klf-3, required for lifespan extension in these longevity models. However, it is not clear whether there other such convergence points. In this study, based on analysis of transcriptome data, we found that the expression of klo-1/klotho was elevated in several longevity models. klo-1 was required for lifespan extension in the glp-1(e2141) and isp-1(qm150) mutants. klo-1 extended the lifespan of glp-1(e2141) and isp-1(qm150) worms by activating extracellular-signal-regulated kinase (ERK). In addition, klo-1 and mpk-1 (the homologous gene encoding ERK) regulated autophagy in glp-1(e2141) mutants, suggesting that klo-1 regulates lifespan by activating autophagy.

Mechanisms of Insulin Resistance at the Crossroad of Obesity with Associated Metabolic Abnormalities and Cognitive Dysfunction

Obesity mediates most of its direct medical sequelae through the development of insulin resistance (IR). The cellular effects of insulin occur through two main postreceptor pathways that are the phosphatidylinositol 3-kinase (PI3-K) and the mitogen-activated protein kinase (MAP-K) pathways. Obesity-related IR implicates the PI3-K pathway that confers the metabolic effects of insulin. Numerous and complex pathogenic pathways link obesity with the development of IR, including chronic inflammation, mitochondrial dysfunction (with the associated production of reactive oxygen species and endoplasmic reticulum stress), gut microbiota dysbiosis and adipose extracellular matrix remodelling. IR itself plays a key role in the development of metabolic dysfunction, including hypertension, dyslipidaemia and dysglycaemia. Furthermore, IR promotes weight gain related to secondary hyperinsulinaemia, with a resulting vicious cycle of worsening IR and its metabolic sequelae. Ultimately, IR underlies obesity-related conditions such as type 2 diabetes mellitus (T2D) and polycystic ovary syndrome (PCOS). IR also underlies many obesity-related malignancies, through the effects of compensatory hyperinsulinaemia on the relatively intact MAP-K insulin pathway, which controls cellular growth processes and mitoses. Furthermore, the emergent data over recent decades support an important role of obesity- and T2D-related central IR in the development of cognitive dysfunction, including effects on hippocampal synaptic plasticity. Importantly, IR is largely reversible through the optimisation of lifestyle factors that include regular engagement in physical activity with the avoidance of sedentariness, improved diet including increased fibre intake and sleep sufficiency. IR lies at the key crossroad between obesity and both metabolic and cognitive dysfunction. Given the importance of IR in the pathogenesis of many 21st century chronic diseases and its eminent reversibility, it is important that we all embrace and facilitate optimised lifestyles to improve the future health and wellbeing of the populace.

Theanine attenuates memory impairments induced by klotho gene depletion in mice

Theanine (γ-glutamylethylamide), an amino acid in tea, is a putative neuroprotective and antioxidant compound capable of improving lifespan and cognitive function.

Molecular and cellular aspects of age-related cognitive decline and Alzheimer's disease

As the population of people aged 60 or older continues to rise, it has become increasingly important to understand the molecular basis underlying age-related cognitive decline. In fact, a better understanding of aging biology will help us identify ways to maintain high levels of cognitive functioning throughout the aging process. Many cellular and molecular aspects of brain aging are shared with other organ systems; however, certain age-related changes are unique to the nervous system due to its structural, cellular and molecular complexity. Importantly, the brain appears to show differential changes throughout the aging process, with certain regions (e.g. frontal and temporal regions) being more vulnerable than others (e.g. brain stem). Within the medial temporal lobe, the hippocampus is especially susceptible to age-related changes. The important role of the hippocampus in age-related cognitive decline and in vulnerability to disease processes such as Alzheimer's disease has prompted this review, which will focus on the complexity of changes that characterize aging, and on the molecular connections that exist between normal aging and Alzheimer's disease. Finally, it will discuss behavioral interventions and emerging insights for promoting healthy cognitive aging.

Secreted and Transmembrane αKlotho Isoforms Have Different Spatio-Temporal Profiles in the Brain during Aging and Alzheimer's Disease Progression

The Klotho protein is a β-glucuronidase, and its overexpression is associated with life extension. Its mechanism of action is not fully understood, although it has been recently reported that αKlotho improves synaptic and cognitive functions, and it may also influence a variety of structures and functions during CNS maturation and aging. The αKlotho gene has two transcripts, one encoding a transmembrane isoform (m-KL), and the other a putative secreted isoform (s-KL). Unfortunately, little is known about the secreted αKlotho isoform, since available antibodies cannot discriminate s-KL from the KL1 domain cleaved from the transmembrane isoform. This study shows, for the first time, that the klotho transcript produced by alternative splicing generates a stable protein (70 kDa), and that in contrast to the transmembrane Klotho isoform, it is ten times more abundant in the brain than in the kidney suggesting that the two isoforms may have different functions. We also studied whether klotho expression in the CNS was influenced by aging, Alzheimer's disease (AD), or a healthy lifestyle, such as voluntary moderate continuous exercise. We observed a strong correlation between high expression levels of the two klotho transcripts and the healthy status of the animals. Expression of Klotho in brain areas decayed more rapidly in the 3xTg-AD model of AD than in healthy animals, whilst moderate continuous exercise in adulthood prevents the decline in expression of both klotho transcripts.

Evaluation of individual aging degree by standard-free, label-free LC-MS/MS quantification of formaldehyde-modified peptides

In this study, a standard-free, label-free LC-MS/MS method is proposed to evaluate aging based on the cross-linkage theory. First, an aging-biomarker screening model was set up in vitro with formaldehyde and the most abundant protein in plasma, human serum albumin (HSA), based on the Maillard reaction. The modification level of peptides cleaved from HSA was investigated using a liquid chromatography tandem mass spectrometry (LC-MS/MS) method with an (18)O-labeling technique. One formaldehyde-insensitive peptide and six formaldehyde-sensitive peptides that would be verified for being putative peptide-biomarkers were screened via the in vitro aging model. These six putative biomarkers were then preliminarily verified by plasma samples with the aldehyde-insensitive peptide serving as the internal standard. The verification results indicated that the peptides LDELRDEGK and VFDEFKPLVEEPQNLIK showed a significant quantitative difference among young/mid-aged/elderly groups of people.

Insulin resistance and cognitive dysfunction

Epidemiologic and biologic studies support a link between type 2 diabetes mellitus and Alzheimer's disease, but the precise mechanism linking the two remains unclear. Growing evidence supports the concept that insulin resistance is important in the pathogenesis of cognitive impairment and neurodegeneration. Insulin plays a profound role in cognitive function. Impaired insulin signaling in the advancement of cognitive dysfunction is relevant to the pathophysiologic mechanisms of cognitive impairment. In this paper we discuss the relationship between insulin resistance and cognitive impairment and review potential mechanisms of this disease process. Evidence, to date, suggests that brain insulin resistance is an independent risk factor for cognitive impairment.