Combined exposure of lead and high-fat diet enhanced cognitive decline via interacting with CREB-BDNF signaling in male rats

Maternal high fat diet programs spatial learning and central leptin signaling in mouse offspring in a sex-specific manner

Environmental factors in early life have been demonstrated to increase the risk of neurodevelopmental disorders in offspring, especially the deficiency of the cognitive ability. Leptin has emerged as a key hormone that conveys information on energy stores, but there is growing appreciation that leptin signaling may also play an important role in neurodevelopment. The present study aimed to investigate whether maternal HFD exposure impairs the offspring learning and memory through the programming of central leptin system. We observed that hippocampus-dependent learning and memory were impaired in male but not female offspring from HFD-fed maternal ancestors (C57BL/6 mice), as assessed by novel object recognition and Morris water maze tests. Moreover, the chromatin immunoprecipitation results revealed the maternal HFD consumption led to the increasement in the binding of the histone marker H3K9me3 in male offspring, which mediates gene silencing in the leptin receptor promoter region. Furthermore, there was an increase in the expression of the histone methylase SUV39H1 in male but not female offspring, which regulates H3K9me3. Additionally, it has been observed that IL-6 and IL-1 also could lead to similar alternations when acting on cultured hippocampal neurons in vitro. Taken together, our data suggest that maternal HFD consumption influences male offspring hippocampal cognitive performance in a sex-specific manner, and central leptin signaling may serve as the cross-talk between maternal diet and cognitive impairment in offspring.

Environmental Toxins and Alzheimer's Disease: a Comprehensive Analysis of Pathogenic Mechanisms and Therapeutic Modulation

Alzheimer's disease is a leading cause of mortality worldwide. Inorganic and organic hazards, susceptibility to harmful metals, pesticides, agrochemicals, and air pollution are major environmental concerns. As merely 5% of AD cases are directly inherited indicating that these environmental factors play a major role in disease development. Long-term exposure to environmental toxins is believed to progress neuropathology, which leads to the development of AD. Numerous in-vitro and in-vivo studies have suggested the harmful impact of environmental toxins at cellular and molecular level. Common mechanisms involved in the toxicity of these environmental pollutants include oxidative stress, neuroinflammation, mitochondrial dysfunction, abnormal tau, and APP processing. Increased expression of GSK-3β, BACE-1, TNF-α, and pro-apoptotic molecules like caspases is observed upon exposure to these environmental toxins. In addition, the expression of neurotrophins like BDNF and GAP-43 have been found to be reduced as a result of toxicity. Further, modulation of signaling pathways involving PARP-1, PGC-1α, and MAPK/ERK induced by toxins have been reported to contribute in AD pathogenesis. These pathways are a promising target for developing novel AD therapeutics. Drugs like epigallocatechin-gallate, neflamapimod, salsalate, dexmedetomidine, and atabecestat are in different phases of clinical trials targeting the pathways for possible treatment of AD. This review aims to culminate the correlation between environmental toxicants and AD development. We emphasized upon the signaling pathways involved in the progression of the disease and the therapeutics under clinical trial targeting the altered pathways for possible treatment of AD.

A mechanistic exploration of the metabolome of African mango seeds and its potential to alleviate cognitive impairment induced by high-fat/high-carbohydrate diets: Involvement of PI3K/AKT/GSK-3β/CREB, PERK/CHOP/Bcl-2, and AMPK/SIRT-1/mTOR Axes

ETHNOPHARMACOLOGICAL RELEVANCE

Irvingia gabonensis (Aubry-Lecomte ex O'Rorke) Baill., also known as "African mango" or "bush mango", belonging to family Irvingiaceae, has been mostly used as food and traditional medicine for weight loss and to enhance the health.

AIM OF THE STUDY

The overconsumption of high-fat and high-carbohydrate (HFHC) food induces oxidative stress, leading to neurological and cognitive dysfunction. Consequently, there is an immediate need for effective treatment. Hence, this study explored the efficacy of orlistat, metformin, and I. gabonensis seeds' total aqueous extract (IG SAE) in addressing HFHC-induced cognitive impairment by mitigating oxidative stress and their underlying mechanistic pathways.

MATERIALS AND METHODS

Initially, the secondary metabolite profile of IG SAE is determined using high-performance liquid chromatography coupled with a mass detector (UHPLC/MS). The in vivo study involves two phases: an established model phase with control (10 rats on a standard diet) and HFHC diet group (50 rats) for 3 months. In the study phase, HFHC is divided into 5 groups. The first subgroup receives HFHC diet only, while the remaining groups each receive HFHC diet with either Orlistat, metformin, or IG SAE at doses of 100 mg/kg and 200 mg/kg, respectively, for 28 days.

RESULTS

More than 150 phytoconstituents were characterized for the first holistic approach onto IG metabolome. Characterization of IG SAE revealed that tannins dominate metabolites in the plant. Total phenolics and flavonoids were estimated to standardize our extract (77.12 ± 7.09 μg Gallic acid equivalent/mg extract and 8.039 ± 0.53 μg Rutin equivalent/mg extract, respectively). Orlistat, metformin, and IG SAE successfully reduced the body weight, blood glucose level, lipid profile, oxidative stress and neurotransmitters levels leading to improved behavioral functions as well as histological alternation. Also, IG SAE halted inflammation, apoptosis, and endoplasmic reticulum stress, together with promoting autophagy, via modulation of PI3K/AKT/GSK-3β/CREB, PERK/CHOP/Bcl-2 and AMPK/SIRT-1/m-TOR pathways.

CONCLUSION

Metformin, orlistat, and IG SAE offer a promising multi-target therapy to mitigate HFHC diet-induced oxidative stress, addressing cognitive function. This involves diverse molecular mechanisms, particularly the modulation of inflammation, ER stress, and both PI3K/AKT/GSK-3β/CREB and AMPK/SIRT-1/m-TOR pathways. Furthermore, the higher dose of IG SAE demonstrated effects comparable to orlistat and metformin across most studied parameters.

Thymol as a Potential Neuroprotective Agent: Mechanisms, Efficacy, and Future Prospects

Neurodegenerative diseases pose a growing global health challenge, with limited effective therapeutic options. Mitochondrial dysfunction, oxidative stress, neuroinflammation, apoptosis, and autophagy are common underlying mechanisms in these diseases. Thymol is a phenolic monoterpene compound that has gained attention for its diverse biological properties, including antioxidant, anti-inflammatory, and immunomodulatory activities. Thymol supplementation could provide potential neuroprotection and improve cognitive deficits, depressant-like effects, learning, and memory impairments in rodents. Mechanistic investigations reveal that the neuroprotective effects of thymol involve the improvement of oxidative stress, mitochondrial dysfunction, and inflammatory response. Several signaling pathways, including mitochondrial apoptotic, NF-κB, AKT, Nrf2, and CREB/BDNF pathways are also involved. In this review, the neuroprotective effects of thymol, the potential molecular mechanisms, safety, applications, and current challenges toward development as a neuroprotective agent were summarized and discussed. We hope that this review provides valuable insights for the further development of this promising natural product as a promising neuroprotective agent.

Gut microbiome-based therapies for alleviating cognitive impairment: state of the field, limitations, and future perspectives

Cognitive impairment (CI) is a multifaceted neurological condition that can trigger negative emotions and a range of concurrent symptoms, imposing significant public health and economic burdens on society. Therefore, it is imperative to discover a remedy for CI. Nevertheless, the mechanisms behind the onset of this disease are multifactorial, which makes the search for effective amelioration difficult and complex, hindering the search for effective measures. Intriguingly, preclinical research indicates that gut microbiota by influencing brain function, plays an important role in the progression of CI. Furthermore, numerous preclinical studies have highlighted the potential of probiotics, prebiotics, fecal microbiota transplantation (FMT), and diet in modulating the gut microbiota, thereby ameliorating CI symptoms. This review provides a comprehensive evaluation of CI pathogenesis, emphasizing the contribution of gut microbiota disorders to CI development. It also summarizes and discusses current strategies and mechanisms centered on the synergistic role of gut microbiota modulation in the microbiota-gut-brain axis in CI development. Finally, problems with existing approaches are contemplated and the development of microbial modulation strategies as therapeutic approaches to promote and restore brain cognition is discussed. Further research considerations and directions are highlighted to provide ideas for future CI prevention and treatment strategies.

High-fat diet exacerbated motor dysfunction via necroptosis and neuroinflammation in acrylamide-induced neurotoxicity in mice

Health risks associated with acrylamide (ACR) or high-fat diet (HFD) exposure alone have been widely concerned in recent years. In a realistic situation, ACR and HFD are generally co-existence, and both are risk factors for the development of neurological diseases. The purpose of the present study was to investigate the combined effects of ACR and HFD on the motor nerve function. As a result, neurobehavioral tests and Nissl staining disclosed that long-term HFD exacerbated motor dysfunction and the damage of spinal cord motor neurons in ACR-exposed mice. Co-exposure of ACR and HFD resulted in morphological changes in neuronal mitochondria of the spinal cord, a significantly reduced mitochondrial subunits NDUFS1, UQCRC2, and MTCO1, released the mitochondrial DNA (mtDNA) into the cytoplasm, and promoted the production of reactive oxygen species (ROS). Combined exposure of HFD and ACR activated the calpain/CDK5/Drp1 axis and caused the mitochondrial excessive division, ultimately increasing MLKL-mediated necroptosis in spinal cord motor neurons. Meanwhile, HFD significantly exacerbated ACR-induced activation of NFkB, NLRP3 inflammasome, and cGAS-STING pathway. Taken together, our findings demonstrated that combined exposure of ACR and HFD aggravated the damage of spinal cord motor neurons via neuroinflammation and necroptosis signaling pathway, pointing to additive effects in mice than the individual stress effects.

Combined exposure to lead and high-fat diet induced neuronal deficits in rats: Anti-neuroinflammatory role of SIRT1

INTRODUCTION

Lead (Pb) exposure and high-fat diet (HFD) trigger neurotoxicity, which may involve neuroinflammation. However, the mechanism by which combined Pb and HFD exposure induces nucleotide oligomerization domain-like receptor family pyrin domain 3 (NLRP3) inflammasome activation has not been fully elucidated.

MATERIAL AND METHODS

The Sprague-Dawley (SD) rat model of exposure to Pb and HFD was established to reveal the influence of co-exposure on cognition and identify signaling clues that mediate neuroinflammation and synaptic dysregulation. PC12 cells was treated with Pb and PA in vitro. Silent information regulator 1 (SIRT1) agonist (SRT 1720) was employed as intervention agent.

RESULTS

Our results showed that Pb and HFD exposure induced cognitive impairment and lead to neurological damage in rats. Meanwhile, Pb and HFD could stimulate the NLRP3 inflammasome assembly and activate caspase 1, releasing proinflammatory cytokines interleukin-1β (IL-1β) and interleukin-18 (IL-18), further promoting neuronal cell activation and amplifying neuroinflammatory responses. Additionally, our findings suggest that SIRT1 plays a role in Pb and HFD induced neuroinflammation. However, the use of SRT 1720 agonists showed some potential in alleviating these impairments.

CONCLUSION

Pb exposure and HFD intake could induce neuronal damage through activation of the NLRP3 inflammasome pathway and synaptic dysregulation, while the NLRP3 inflammasome pathway may be rescued via activating SIRT1.

Profile of N6-methyladenosine of Pb-exposed neurons presents epitranscriptomic alterations in PI3K-AKT pathway-associated genes

Lead (Pb) is a pervasive heavy metal with multi-organ toxicity. However, the molecular mechanisms of Pb-induced neurotoxicity are not fully understood. The dynamics of N6-methylademine (m6A) is an emerging regulatory mechanism for gene expression, which is closely related to nervous system diseases. To elucidate the association between m6A modification and Pb-mediated neurotoxicity, primary hippocampal neurons exposed to 5 μM Pb for 48 h were used as the paradigm neurotoxic model in this study. According to the results, Pb exposure reprogrammed the transcription spectrum. Simultaneously, Pb exposure remodeled the transcriptome-wide distribution of m6A while disrupting the overall level of m6A in cellular transcripts. United analysis of MeRIP-Seq and RNA-Seq was applied to further identify the core genes whose expression levels are regulated by m6A in the process of lead-induced nerve injury. GO and KEGG analysis unveiled that the modified transcripts were overrepresented by the PI3K-AKT pathway. Mechanically, we elucidated the regulatory role of the methyltransferase like3 (METTL3) in the process of lead-induced neurotoxicity and the downregulation of the PI3K-AKT pathway. In conclusion, our novel findings shed new light on the functional roles of m6A modification in the expressional alternations of downstream transcripts caused by lead, providing an innovative molecular basis to explain Pb neurotoxicity.

Chronic lead exposure exacerbates hepatic glucolipid metabolism disorder and gut microbiota dysbiosis in high-fat-diet mice

Lead (Pb) and obesity are co-occurring risk factors for metabolic disorders. However, there is still a lack of study on the combined effects of both stressors on metabolism. C57BL/6J mice were exposed to 200 mg/L Pb or/and HFD for 24 weeks and were used to investigate the effects and underlying mechanisms of chronic Pb exposure on obese mice. The results showed that Pb significantly increased body weight, visceral obesity, fasting blood glucose levels, and insulin resistance, and aggravated liver damage, hepatic lipid accumulation and steatosis in HFD-fed mice. Further analysis showed that Pb significantly inhibited insulin signaling pathway PI3K/AKT and fatty acid β-oxidation, and accelerated fatty acid synthesis. Moreover, Pb exacerbated HFD-induced disruption of gut microbiota homeostasis, manifested by increased proportions of pathogenic genera such as Desulfovibrio, Alistipes and Helicobacter, and decreased proportions of beneficial microbes Akkermansia and Barnesiella, which were negatively associated with obesity. These results indicated that Pb exposure exacerbated the disruption of liver glucolipid metabolism in HFD mice possibly by disrupting gut microbiota.