Short-term high-fat diet favors the appearances of apoptosis and gliosis by activation of ERK1/2/p38MAPK pathways in brain

Comparative mathematical modeling reveals the differential effects of high-fat diet and ketogenic diet on the PI3K-Akt signaling pathway in heart

BACKGROUND

Obesity is a global health concern associated with increased risk of diseases like cardiovascular conditions including ischemic heart disease, a leading cause of mortality. The ketogenic diet (KD) has potential therapeutic applications in managing obesity and related disorders. However, the intricate effects of KD on diverse physiological conditions remain incompletely understood. The PI3K-Akt signaling pathway is critical for heart health, and its dysregulation implicates numerous cardiac diseases.

METHODS

We developed comprehensive mathematical models of the PI3K-Akt signaling pathway under high-fat diet (HFD) and KD conditions to elucidate their differential impacts and quantify apoptosis. Simulations and sensitivity analysis were performed.

RESULTS

Simulations demonstrate that KD can reduce the activation of key molecules like Erk and Trp53 to mitigate apoptosis compared to HFD. Findings align with experimental data, highlighting the potential cardiac benefits of KD. Sensitivity analysis identifies regulators like Trp53 and Bcl2l1 that critically influence apoptosis under HFD.

CONCLUSIONS

Mathematical modeling provides quantitative insights into the contrasting effects of HFD and KD on cardiac PI3K-Akt signaling and apoptosis. Findings have implications for precision nutrition and developing novel therapeutic strategies to address obesity-related cardiovascular diseases.

Palmitic Acid Modulation of the Insulin-Like Growth Factor System in Hypothalamic Astrocytes and Neurons

INTRODUCTION

Insulin-like growth factor (IGF)1 and IGF2 have neuroprotective effects, but less is known regarding how other members of the IGF system, including IGF binding proteins (IGFBPs) and the regulatory proteinase pappalysin-1 (PAPP-A) and its endogenous inhibitor stanniocalcin-2 (STC2) participate in this process. Here, we analyzed whether these members of the IGF system are modified in neurons and astrocytes in response to palmitic acid (PA), a fatty acid that induces cell stress when increased centrally.

METHODS

Primary hypothalamic astrocyte cultures from male and female PND2 rats and the pro-opiomelanocortin (POMC) neuronal cell line, mHypoA-POMC/GFP-2, were treated with PA, IGF1 or both. To analyze the role of STC2 in astrocytes, siRNA assays were employed.

RESULTS

In astrocytes of both sexes, PA rapidly increased cell stress factors followed by increased Pappa and Stc2 mRNA levels and then a decrease in Igf1, Igf2, and Igfbp2 expression and cell number. Exogenous IGF1 did not revert these effects. In mHypoA-POMC/GFP-2 neurons, PA reduced cell number and Pomc and Igf1 mRNA levels, and increased Igfbp2 and Stc2, again with no effect of exogenous IGF1. PA increased STC2 expression, but no effects of decreasing its levels by interference assays or exogenous STC2 treatment in astrocytes were found.

CONCLUSIONS

The response of the IGF system to PA was cell and sex specific, but no protective effects of the IGFs were found. However, the modifications in hypothalamic PAPP-A and STC2 indicate that further studies are required to determine their role in the response to fatty acids and possibly in metabolic control.

Dietary Marine Oils Selectively Decrease Obesogenic Diet-Derived Carbonylation in Proteins Involved in ATP Homeostasis and Glutamate Metabolism in the Rat Cerebellum

The regular intake of diets high in saturated fat and sugars increases oxidative stress and has been linked to cognitive decline and premature brain aging. The cerebellum is highly vulnerable to oxidative stress and thus, obesogenic diets might be particularly detrimental to this tissue. However, the precise molecular mechanisms behind obesity-related brain damage are still not clear. Since protein carbonylation, a biomarker of oxidative stress, influences protein functions and is involved in metabolic control, the current investigation addressed the effect of long-term high-fat and high-sucrose diet intake on the cerebellum of Sprague-Dawley rats by deciphering the changes caused in the carbonylated proteome. The antioxidant effects of fish oil supplementation on cerebellar carbonylated proteins were also investigated. Lipid peroxidation products and carbonylated proteins were identified and quantified using immunoassays and 2D-LC-MS/MS in the cerebellum. After 21 weeks of nutritional intervention, the obesogenic diet selectively increased carbonylation of the proteins that participate in ATP homeostasis and glutamate metabolism in the cerebellum. Moreover, the data demonstrated that fish oil supplementation restrained carbonylation of the main protein targets oxidatively damaged by the obesogenic diet, and additionally protected against carbonylation of several other proteins involved in amino acid biosynthesis and neurotransmission. Therefore, dietary interventions with fish oils could help the cerebellum to be more resilient to oxidative damage. The results could shed some light on the effect of high-fat and high-sucrose diets on redox homeostasis in the cerebellum and boost the development of antioxidant-based nutritional interventions to improve cerebellum health.

Sex differences of microglia in the healthy brain from embryonic development to adulthood and across lifestyle influences

Microglia, the central nervous system innate immune cells, play a critical role in maintaining a homeostatic environment in the brain throughout life. These cells exhibit an impressive range of functions and characteristics that help to ensure proper functioning of the brain. Notably, microglia can present differences in their genetic and physical traits, which can be influenced by a range of factors, including age, environmental exposures, disease, and sex. Remarkably, microglia have been found to express receptors for sex hormones, suggesting that these hormones may play a role in modulating microglial behavior and potentially contribute to sex differences. Additionally, sex-chromosomal factors were shown to impact microglial genetics and functioning. In this review, we will examine how microglial responses in homeostasis are impacted by their interaction with sex hormones and sex chromosomes. Specifically, our investigation will focus on examining this interaction from embryonic development to adulthood, and the influence of lifestyle elements on various microglial features, including density and distribution, morphology, transcriptome, and proteome.

Cognitive Functions, Neurotransmitter Alterations, and Hippocampal Microstructural Changes in Mice Caused by Feeding on Western Diet

Metabolic Dysfunction Associated Steatotic Liver Disease (MASLD) is the most common chronic liver disease in Western countries. It is becoming increasingly evident that peripheral organ-centered inflammatory diseases, including liver diseases, are linked with brain dysfunctions. Therefore, this study aims to unravel the effect of MASLD on brain histology, cognitive functions, and neurotransmitters. For this purpose, mice fed for 48 weeks on standard (SD) or Western diet (WD) were evaluated by behavioral tests, followed by sacrifice and analysis of the liver-brain axis including histopathology, immunohistochemistry, and biochemical analyses. Histological analysis of the liver showed features of Metabolic Dysfunction-Associated Steatohepatitis (MASH) in the WD-fed mice including lipid droplet accumulation, inflammation, and fibrosis. This was accompanied by an elevation of transaminase and alkaline phosphatase activities, increase in inflammatory cytokine and bile acid concentrations, as well as altered amino acid concentrations in the blood. Interestingly, compromised blood capillary morphology coupled with astrogliosis and microgliosis were observed in brain hippocampus of the WD mice, indicating neuroinflammation or a disrupted neurovascular unit. Moreover, attention was impaired in WD-fed mice along with the observations of impaired motor activity and balance, enhanced anxiety, and stereotyped head-twitch response (HTR) behaviors. Analysis of neurotransmitters and modulators including dopamine, serotonin, GABA, glutamate, and acetylcholine showed region-specific dysregulation in the brain of the WD-fed mice. In conclusion, the induction of MASH in mice is accompanied by the alteration of cellular morphology and neurotransmitter expression in the brain, associated with compromised cognitive functions.

Research progress of p38 as a new therapeutic target against morphine tolerance and the current status of therapy of morphine tolerance

With the development of the medical industry, new painkillers continue to appear in people's field of vision, but so far no painkiller can replace morphine. While morphine has a strong analgesic effect, it is also easy to produce pain sensitivity and tolerance. Due to the great inter-individual differences in patient responses, there are few clear instructions on how to optimise morphine administration regimens, which complicates clinicians' treatment strategies and limits the effectiveness of morphine in long-term pain therapy. P38MAPK is a key member of the MAPK family. Across recent years, it has been discovered that p38MAPK rises dramatically in a wide range of morphine tolerance animal models. Morphine tolerance can be reduced or reversed by inhibiting p38MAPK. However, the role and specific mechanism of p38MAPK are not clear. In this review, we synthesise the relevant findings, highlight the function and potential mechanism of p38MAPK in morphine tolerance, as well as the present status and efficacy of morphine tolerance therapy, and underline the future promise of p38MAPK targeted morphine tolerance treatment.

The Role of ERK1/2 Pathway in the Pathophysiology of Alzheimer's Disease: An Overview and Update on New Developments

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide. Several findings suggest that correcting the dysregulated signaling pathways may offer a potential therapeutic approach in this disease. Extracellular signal-regulated kinase 1/2 (ERK1/2), a member of the mitogen-activated protein kinase family, plays a major role in regulation of cell proliferation, autophagy process, and protein synthesis. The available literature suggests dysregulated ERK1/2 in AD patients with potential implications in the multifaceted underlying pathologies of AD, including amyloid-β plaque formation, tau phosphorylation, and neuroinflammation. In this regard, in the current review, we aim to summarize the reports on the potential roles of ERK1/2 in AD pathophysiology.

Short-term high-fat diet alters the mouse brain magnetic resonance imaging parameters consistently with neuroinflammation on males and metabolic rearrangements on females. A pre-clinical study with an optimized selection of linear mixed-effects models

Introduction

High-fat diet (HFD) consumption is known to trigger an inflammatory response in the brain that prompts the dysregulation of energy balance, leads to insulin and leptin resistance, and ultimately obesity. Obesity, at the same, has been related to cerebral magnetic resonance imaging (MRI) alterations, but the onset of HFD-induced neuroinflammation, however, has been principally reported on male rodents and by ex vivo methods, with the effects on females and the origin of MRI changes remaining unassessed.

Methods

We characterized the onset and evolution of obesity on male and female mice during standard or HFD administration by physiological markers and multiparametric MRI on four cerebral regions involved in appetite regulation and energy homeostasis. We investigated the effects of diet, time under diet, brain region and sex by identifying their significant contributions to sequential linear mixed-effects models, and obtained their regional neurochemical profiles by high-resolution magic angle spinning spectroscopy.

Results

Male mice developed an obese phenotype paralleled by fast increases in magnetization transfer ratio values, while females delayed the obesity progress and showed no MRI-signs of cerebral inflammation, but larger metabolic rearrangements on the neurochemical profile.

Discussion

Our study reveals early MRI-detectable changes compatible with the development of HFD-induced cerebral cytotoxic inflammation on males but suggest the existence of compensatory metabolic adaptations on females that preclude the corresponding detection of MRI alterations.

Immunohistochemical analysis of caspase expression in the brains of individuals with obesity or overweight

Mechanisms underlying the negative effects of obesity on the brain are still unknown. Obesity is associated with oxidative stress in the brain and neuroinflammation that promotes neurodegenerative diseases. Chronic low-grade neuroinflammation in obesity could be associated with lower volumes of gray matter and lower neuronal density. If neuroinflammation mediated by the expression of cytokines and chemokines leads to apoptosis, this can be assessed by examining caspase expression. The aim of this study was to compare the expression of caspases in the 16 brains of donors with obesity/overweight (n = 8; Body Mass Index [BMI] = 31.6 ± 4.35 kg/m²; 2 females; Age = 52.9 ± 4.76 years) and normal weight (n = 8; BMI = 21.8 ± 1.5 kg/m²; 3 females; Age = 37.8 ± 19.2 years). Sixteen human brain samples were processed. Serial paraffin sections were examined by anti-caspase immunochemistry (caspase-3, caspase-4, caspase-6, caspase-1, caspase-8, and caspase-9 antibodies). Postmortem samples of cerebral cortex tissue were captured as photomicrographs and the images obtained were analyzed using ImageJ software to obtain the percentage of positive caspase expression. Nonparametric Mann-Whitney U tests were performed to compare caspase expression between samples from donors with obesity/overweight and normal weight. Taking into consideration the immunohistochemistry results, the Search Tool for the Retrieval of Interacting Genes was used to model molecular interactions. Results showed that brain samples from individuals with obesity/overweight exhibited significantly greater values of positive expression for Caspase-1 (U = 16.5, p = 0.05, Cohen d = 0.89) and -8 (U = 15, p = 0.03, Cohen d = 0.99) than those from donors with normal weight. This study contributes to the knowledge about the inflammatory effects of obesity/overweight on brain, suggesting the activation of the alternative inflammasome pathway in which interact caspase-1 and -8.