Metabolic syndrome exacerbates amyloid pathology in a comorbid Alzheimer's mouse model

Morusin, a novel inhibitor of ACLY, induces mitochondrial apoptosis in hepatocellular carcinoma cells through ROS-mediated mitophagy

OBJECTIVE

Morusin (Mor), a prenylated flavonoid isolated from the root bark of Morus alba L., exhibits potent anti-tumour effects; however, the molecular target of Mor is still not entirely clear. This study aimed to elucidate the mechanism of Mor against hepatocellular carcinoma (HCC) and identify potential molecular targets.

METHODS

Mitochondrial function was assessed by measuring the mitochondrial membrane potential, mitochondrial ultrastructure, oxygen consumption, and ATP levels. Mor-induced mitophagy was confirmed using western blotting, immunofluorescence, and fluorescent probes. Transcriptomics, flow cytometry, western blotting, qRT-PCR and biochemical assays were used to reveal the molecular mechanisms and targets of Mor against HCC. We further validated the interaction between Mor and the target proteins using molecular docking and biolayer interferometry (BLI). The inhibitory effect of Mor in vivo was evaluated using a Hep3B murine xenograft model.

RESULTS

Mor significantly reduced the ATP citrate lyase (ACLY) expression and inhibited ACLY activity in HCC cells. BLI analysis demonstrated a direct interaction between Mor and the ACLY active domain. Mor-induced ACLY inhibition led to ROS accumulation in HCC cells, which caused mitochondrial damage, triggered PINK1/Parkin-mediated mitophagy, and ultimately induced mitochondrial apoptosis. We further verified that ROS is crucial in the apoptotic action of Mor through experiments regarding an ROS scavenger. Mor also significantly inhibited tumour xenograft growth in vivo. In addition, analysis of human liver cancer clinical samples revealed elevated ACLY levels positively correlated with histologic grade.

CONCLUSION

Collectively, our findings highlight Mor as a potent bioactive inhibitor of ACLY and a promising candidate for HCC therapy.

Targeting Mitochondrial Sirtuins in Age-Related Neurodegenerative Diseases and Fibrosis

Aging is a natural and complex biological process that is associated with widespread functional declines in numerous physiological processes, terminally affecting multiple organs and tissues. Fibrosis and neurodegenerative diseases (NDs) often occur with aging, imposing large burdens on public health worldwide, and there are currently no effective treatment strategies for these diseases. Mitochondrial sirtuins (SIRT3-5), which are members of the sirtuin family of NAD+-dependent deacylases and ADP-ribosyltransferases, are capable of regulating mitochondrial function by modifying mitochondrial proteins that participate in the regulation of cell survival under various physiological and pathological conditions. A growing body of evidence has revealed that SIRT3-5 exert protective effects against fibrosis in multiple organs and tissues, including the heart, liver, and kidney. SIRT3-5 are also involved in multiple age-related NDs, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. Furthermore, SIRT3-5 have been noted as promising targets for antifibrotic therapies and the treatment of NDs. This review systematically highlights recent advances in knowledge regarding the role of SIRT3-5 in fibrosis and NDs and discusses SIRT3-5 as therapeutic targets for NDs and fibrosis.

Mitochondrial SIRT3 Deficiency Results in Neuronal Network Hyperexcitability, Accelerates Age-Related Aβ Pathology, and Renders Neurons Vulnerable to Aβ Toxicity

Aging is the major risk factor for Alzheimer's disease (AD). Mitochondrial dysfunction and neuronal network hyperexcitability are two age-related alterations implicated in AD pathogenesis. We found that levels of the mitochondrial protein deacetylase sirtuin-3 (SIRT3) are significantly reduced, and consequently mitochondria protein acetylation is increased in brain cells during aging. SIRT3-deficient mice exhibit robust mitochondrial protein hyperacetylation and reduced mitochondrial mass during aging. Moreover, SIRT3-deficient mice exhibit epileptiform and burst-firing electroencephalogram activity indicating neuronal network hyperexcitability. Both aging and SIRT3 deficiency result in increased sensitivity to kainic acid-induced seizures. Exposure of cultured cerebral cortical neurons to amyloid β-peptide (Aβ) results in a reduction in SIRT3 levels and SIRT3-deficient neurons exhibit heightened sensitivity to Aβ toxicity. Finally, SIRT3 haploinsufficiency in middle-aged App/Ps1 double mutant transgenic mice results in a significant increase in Aβ load compared with App/Ps1 double mutant mice with normal SIRT3 levels. Collectively, our findings suggest that SIRT3 plays an important role in protecting neurons against Aβ pathology and excitotoxicity.

A Promising Strategy to Treat Neurodegenerative Diseases by SIRT3 Activation

SIRT3, the primary mitochondrial deacetylase, regulates the functions of mitochondrial proteins including metabolic enzymes and respiratory chain components. Although SIRT3's functions in peripheral tissues are well established, the significance of its downregulation in neurodegenerative diseases is beginning to emerge. SIRT3 plays a key role in brain energy metabolism and provides substrate flexibility to neurons. It also facilitates metabolic coupling between fuel substrate-producing tissues and fuel-consuming tissues. SIRT3 mediates the health benefits of lifestyle-based modifications such as calorie restriction and exercise. SIRT3 deficiency is associated with metabolic syndrome (MetS), a precondition for diseases including obesity, diabetes, and cardiovascular disease. The pure form of Alzheimer's disease (AD) is rare, and it has been reported to coexist with these diseases in aging populations. SIRT3 downregulation leads to mitochondrial dysfunction, neuroinflammation, and inflammation, potentially triggering factors of AD pathogenesis. Recent studies have also suggested that SIRT3 may act through multiple pathways to reduce plaque formation in the AD brain. In this review, we give an overview of SIRT3's roles in brain physiology and pathology and discuss several activators of SIRT3 that can be considered potential therapeutic agents for the treatment of dementia.

Alteration of Cognitive Function in Aging and Alzheimer's Disease Mice Is Related to Dysfunction of the Neuroimmune System

BACKGROUND

Both Alzheimer's disease (AD) and aging have aging-related cognitive dysfunction with a high incidence. These neurological diseases cause serious cognitive problems in patients' daily life. But the cognitive dysfunction mechanism in-depth of aging is far less known than that of AD.

OBJECTIVE

To reveal the different mechanisms of AD and aging-related cognitive dysfunction, we compared the mechanisms of aging and AD through analysis of differentially expressed genes.

METHODS

Mice were divided into four groups (3-month C57BL, 16-month C57BL, 3-month 3xTg AD mice, and 16-month 3xTg AD mice) according to genotype and age. The Morris water maze was employed to investigate the spatial cognition of mice. Differential expressions of genes of AD and aging were analyzed through RNA sequencing and GO, KEGG, Reactome analysis, and the dynamic change trend analysis. Microglia was stained with immunofluorescence and its numbers were counted for analysis.

RESULTS

The cognitive function of elderly mice were worse through testing with the Morris water maze. The cognitive function of 16-month 3xTg AD mice were worse than 16-month C57BL mice. The alteration tendencies of DE genes were uncovered, and microglia numbers increased during aging and AD progression through immunofluorescence.

CONCLUSION

These results suggest that immune-related pathways might play a critical role in aging and AD-related cognitive dysfunction. Our research will help to provide some new potential targets for treating cognitive dysfunction in aging and AD.

Metformin inhibits cardiometabolic syndrome associated cognitive deficits in high fat diet rats

Objectives

Glucose intolerance and insulin resistance are hallmarks of metabolic syndrome and lead to Alzheimer's disease (AD). The purpose of this study is to elucidate the neuroprotective effect of metformin through insulin regulation with cardiometabolic and neurotransmitter metabolic enzyme regulation in high-fat, high-sucrose diet and streptozotocin (HFHS-STZ)-induced rats.

Methods

Male Wistar rats were treated with metformin (180 mg/kg and 360 mg/kg). STZ (35 mg/kg i.p.) injection was performed on the 14th day of 42 days of HFHS diet treatment. Brain neurotransmitter metabolic enzymes (acetylcholinesterase and monoamine oxidase) were determined along with sodium-potassium ATPase (Na+K+-ATPase). Plasma lipids and homeostasis model assessment of insulin resistance (HOMA-IR) was performed. Mean arterial blood pressure, heart rate and electrocardiogram (QT, QTc and RR intervals) were analysed with PowerLab.

Results

Metformin treatment significantly (p < 0.001) reduced the HOMA-IR index and decreased neurotransmitter metabolic enzymes such as AChE and MAO (p < 0.01 and p < 0.05). The lipid profile was significantly (p < 0.001) controlled with cardiometabolic functions.

Conclusions

Our investigation revealed that metformin has a remarkable role in regulating brain insulin, vascular system with monoaminergic metabolic enzymes and enhancing synaptic plasticity. Metformin may be a selective early therapeutic agent in metabolic syndrome associated with cognitive decline.

Sirt3 deficiency induced down regulation of insulin degrading enzyme in comorbid Alzheimer's disease with metabolic syndrome

SIRT3 deacetylates mitochondrial proteins, thereby enhancing their function. We have previously demonstrated that Sirt3 gene deletion leads to brain mitochondrial dysfunction and neuroinflammation. We also reported that silencing of Sirt3 gene in APP/PS1 mice results in exacerbation of insulin resistance, neuroinflammation and β amyloid plaque deposition. To further understand how metabolic syndrome and amyloid pathology interact, we performed RNA-seq analysis of the brain samples of APP/PS1/Sirt3^-/- mice. Gene expression patterns were modulated in metabolic and inflammatory pathways by Sirt3 gene deletion, amyloid pathology, and the combination. Following Sirt3 gene deletion, a key finding was the decreased expression of insulin-degrading enzyme (IDE), an enzyme that regulates the levels of insulin and Aβ peptides. Western diet feeding of Sirt3^-/- and APP/PS1 mice resulted in decrease of IDE protein, parallel to Sirt3 downregulation. Conversely, activation of SIRT3 by nicotinamide riboside in vivo and in vitro resulted in IDE upregulation. SIRT3 activation in vivo also increased the levels of neprilysin, another Aβ degrading enzyme and decreased the levels of BACE1 which generates Aβ peptide suggesting SIRT3's role in amyloid plaque reduction. Our findings provide a plausible mechanism linking metabolic syndrome and amyloid pathology. SIRT3 may be a potential therapeutic target to treat AD.

Biological underpinnings of sex differences in neurological disorders

The importance of sex differences in neurological disorders has been increasingly acknowledged in recent clinical and basic research studies, but the complex biology and genetics underlying sex-linked biological heterogeneity and its brain-to-body impact remained incompletely understood. Men and women differ substantially in their susceptibility to certain neurological diseases, in the severity of symptoms, prognosis as well as the nature and efficacy of their response to treatments. The detailed mechanisms underlying these differences, especially at the molecular level, are being addressed in many studies but leave a lot to be further revealed. Here, we provide an overview of recent advances in our understanding of how sex differences in the brain and brain-body signaling contribute to neurological disorders and further present some future prospects entailed in terms of diagnostics and therapeutics.

Targeting Mitochondrial COX-2 Enhances Chemosensitivity via Drp1-Dependent Remodeling of Mitochondrial Dynamics in Hepatocellular Carcinoma

Simple Summary

New therapeutic strategies are urgently needed to improve the anti-cancer effect for hepatocellular carcinoma (HCC). Overexpression of cyclooxygenase-2 (COX-2) is found in several types of cancers and correlates with a poor prognosis. However, it remains unclear how the mitochondrial translocation of COX-2 is involved in mitochondrial dynamics and sensitizes HCC cells to multipattern anti-tumor therapy. We explored the impact of targeting mitochondrial COX-2 (mito-COX-2) intervention toward mitochondrial dynamics on platinum-based chemotherapeutics in HCC cells and xenograft nude mouse models. Our study indicates that the mito-COX-2 represents a candidate predictive biomarker and potential target to regulate anti-cancer sensitization of HCC, and possibly for other types of COX-2-high-expression cancers.

Abstract

Mitochondria are highly dynamic organelles and undergo constant fission and fusion, which are both essential for the maintenance of cell physiological functions. Dysregulation of dynamin-related protein 1 (Drp1)-dependent mitochondrial dynamics is associated with tumorigenesis and the chemotherapeutic response in hepatocellular carcinoma (HCC). The enzyme cyclooxygenase-2 (COX-2) is overexpressed in most cancer types and correlates with a poor prognosis. However, the roles played by the translocation of mitochondrial COX-2 (mito-COX-2) and the interaction between mito-COX-2 and Drp1 in chemotherapeutic responses remain to be elucidated in the context of HCC. Bioinformatics analysis, paired HCC patient specimens, xenograft nude mice, immunofluorescence, transmission electron microscopy, molecular docking, CRISPR/Cas9 gene editing, proximity ligation assay, cytoplasmic and mitochondrial fractions, mitochondrial immunoprecipitation assay, and flow cytometry analysis were performed to evaluate the underlying mechanism of how mito-COX-2 and p-Drp1^Ser616 interaction regulates the chemotherapeutic response via mitochondrial dynamics in vitro and in vivo. We found that COX-2 and Drp1 were frequently upregulated and confer a poor prognosis in HCC. We also found that the proportion of mito-COX-2 and p-Drp1^Ser616 was increased in HCC cell lines. In vitro, we demonstrated that the enhanced mitochondrial translocation of COX-2 promotes its interaction with p-Drp1^Ser616 via PTEN-induced putative kinase 1 (PINK1)-mediated Drp1 phosphorylation activation. This increase was associated with higher colony formation, cell proliferation, and mitochondrial fission. These findings were confirmed by knocking down COX-2 in HCC cells using CRISPR/Cas9 technology. Furthermore, inhibition of Drp1 using pharmacologic inhibitors (Mdivi-1) or RNA interference (siDNM1L) decreased mito-COX-2/p-Drp1^Ser616 interaction-mediated mitochondrial fission, and increased apoptosis in HCC cells treated with platinum drugs. Moreover, inhibiting mito-COX-2 acetylation with the natural phytochemical resveratrol resulted in reducing cell proliferation and mitochondrial fission, occurring through upregulation of mitochondrial deacetylase sirtuin 3 (SIRT3), which, in turn, increased the chemosensitivity of HCC to platinum drugs in vitro and in vivo. Our results suggest that targeting interventions to PINK1-mediated mito-COX-2/p-Drp1^Ser616-dependent mitochondrial dynamics increases the chemosensitivity of HCC and might help us to understand how to use the SIRT3-modulated mito-COX-2/p-Drp1^Ser616 signaling axis to develop an effective clinical intervention in hepatocarcinogenesis.

Toward the Decipherment of Molecular Interactions in the Diabetic Brain

Diabetes mellitus (DM) has been associated with cognitive complications in the brain resulting from acute and chronic metabolic disturbances happening peripherally and centrally. Numerous studies have reported on the morphological, electrophysiological, biochemical, and cognitive changes in the brains of diabetic individuals. The detailed pathophysiological mechanisms implicated in the development of the diabetic cognitive phenotype remain unclear due to intricate molecular changes evolving over time and space. This review provides an insight into recent advances in understanding molecular events in the diabetic brain, focusing on cerebral glucose and insulin uptake, insulin action in the brain, and the role of the brain in the regulation of glucose homeostasis. Fully competent mitochondria are essential for energy metabolism and proper brain function; hence, the potential contribution of mitochondria to the DM-induced impairment of the brain is also discussed.

A Revisit to Etiopathogenesis and Therapeutic Strategies in Alzheimer's Disease

Dementia is a cluster of brain abnormalities that trigger progressive memory deficits and other cognitive abilities such as skills, language, or executive function. Alzheimer's disease (AD) is the foremost type of age-associated dementia that involves progressive neurodegeneration accompanied by profound cognitive deficits in advanced stages that severely hamper social or occupational abilities with or without the involvement of any other psychiatric condition. The last two decades witnessed a sharp increase (~123%) in mortality due to AD type dementia, typically owing to a very low disclosure rate (~45%) and hence, the prophylactic, as well as the therapeutic cure of AD, has been a huge challenge. Although understanding of AD pathogenesis has witnessed a remarkable growth (e.g., tauopathy, oxidative stress, lipid transport, glucose uptake, apoptosis, synaptic dysfunction, inflammation, and immune system), still a dearth of an effective therapeutic agent in the management of AD prompts the quest for newer pharmacological targets in the purview of its growing epidemiological status. Most of the current therapeutic strategies focus on modulation of a single target, e.g., inhibition of acetylcholinesterase, glutamate excitotoxicity (memantine), or nootropics (piracetam), even though AD is a multifaceted neurological disorder. There is an impedance urgency to find not only symptomatic but effective disease-modifying therapies. The present review focuses on the risk / protective factors and pathogenic mechanisms involved in AD. In addition to the existing symptomatic therapeutic approach, a diverse array of possible targets linked to pathogenic cascades have been re-investigated to envisage the pharmacotherapeutic strategies in AD.

Lactobacillus paracasei ameliorates cognitive impairment in high-fat induced obese mice via insulin signaling and neuroinflammation pathways

Long-term consumption of a high-fat diet (HFD) can cause glucose and lipid metabolism disorders, damage the brain and nervous system and result in cognitive impairment. The objective of this study was to investigate the preventative effects of Lactobacillus paracasei (Jlus66, a probiotic extracted from cheese in Northeast China) on cognitive impairment associated with HFD. The water maze was used to compare memory changes in mice fed HFD with or without Jlus66. Hippocampal tissue morphology was examined using H&E staining. The expression of neurotrophic factors BDNF, PSD95 and SNAP25, insulin resistance related proteins IRS-1, AKT and GSK3β, and inflammatory related proteins JNK and p38 were detected using western blotting. The results showed that Jlus66 significantly increased the expression of BDNF, PSD95 and SNAP25 (p < 0.01, respectively), increased expression of p-AKT (p < 0.05), p-IRS-1Y612 and p-GSK3β (p < 0.01, respectively), and reduced the expression of p-IRS-1S307, p-JNK and p-p38 (p < 0.05) compared with the HFD group. We conclude that Jlus66 can ameliorate cognitive impairment via insulin signaling and neuroinflammation pathways.

Effects of Lipotoxicity in Brain Microvascular Endothelial Cells During Sirt3 Deficiency-Potential Role in Comorbid Alzheimer's Disease

Silence information regulator 3 (SIRT3) is an NAD⁺ dependent deacetylase enzyme that enhances the function of key mitochondrial proteins. We have earlier demonstrated that deletion of Sirt3 gene leads to downregulation of metabolic enzymes, mitochondrial dysfunction and neuroinflammation in the brain, the major causes of Alzheimer’s disease (AD). We also reported recently that Sirt3 gene deletion in Alzheimer’s transgenic mice leads to exacerbation of neuroinflammation, amyloid plaque deposition and microglial activation. AD often coexists with other brain lesions caused by comorbidities which can exert their deleterious effects through the neurovascular unit. This unit consists of brain microvascular endothelial cells (BMECs), end feet of astrocytes, and pericytes. BMECs are uniquely different from other vascular endothelial cells because they are glued together by tight-junction proteins. BMECs are in constant contact with circulating factors as they line the luminal side. Therefore, we hypothesized that vascular endothelial injury caused by comorbidities plays a significant role in neuroinflammation. Herein, we investigated the effects of lipotoxicity in BMECs and how Sirt3 deficiency facilitate the deleterious effects of lipotoxicity on them using in vivo and in vitro models. We observed decreases in the levels of SIRT3 and tight junction proteins in the brain samples of western diet-fed APP/PS1 mice. Similar observations were obtained with Alzheimer’s post-mortem samples. Exposure of BEND3 cells, mouse brain-derived Endothelial cells3, to a combination of high glucose and palmitic acid resulted in significant (P < 0.01-P < 0.001) decreases in the levels of SIRT3, claudin-5 and ZO-1. Induction of inflammatory mediators, including Cox-2, CXCL1, RANTES, and GADD45β was also observed in these treated cells. Interestingly, the induction was more with Sirt3-silenced BEND3 cells, suggesting that Sirt3 deficiency exacerbates inflammatory response. Palmitic acid was more potent in inducing the inflammatory mediators. Significant cytotoxicity and changes in microglial morphology were observed when cocultures of Sirt3-silenced BEND3 and Sirt3-silenced BV2 cells were exposed to palmitic acid. Transendothelial electrical resistance measurement with these cocultures suggested decreased barrier integrity. The findings of this study suggest that hyperlipidemia in comorbidities can compromise blood brain barrier integrity by inducing inflammatory mediators and decreasing tight junction proteins in the vascular endothelial cells of the AD brain, leading to activation of microglia.

Enhancement of Insulin/PI3K/Akt Signaling Pathway and Modulation of Gut Microbiome by Probiotics Fermentation Technology, a Kefir Grain Product, in Sporadic Alzheimer's Disease Model in Mice

Sporadic Alzheimer's disease (AD) is the most common neurodegenerative disorder with cognitive dysfunction. Remarkably, alteration in the gut microbiome and resultant insulin resistance has been shown to be connected to metabolic syndrome, the crucial risk factor for AD, and also to be implicated in AD pathogenesis. Thus, this study, we assessed the efficiency of probiotics fermentation technology (PFT), a kefir product, in enhancing insulin signaling via modulation of gut microbiota to halt the development of AD. We also compared its effectiveness to that of pioglitazone, an insulin sensitizer that has been confirmed to substantially treat AD. AD was induced in mice by a single injection of intracerebroventricular streptozotocin (STZ; 3 mg/kg). PFT (100, 200, 400 mg/kg) and pioglitazone (30 mg/kg) were administered orally for 3 weeks. Behavioral tests were conducted to assess cognitive function, and hippocampal levels of acetylcholine (Ach) and β-amyloid (Aβ1-42) protein were assessed along with histological examination. Moreover, the expression of the insulin receptor, insulin degrading enzyme (IDE), and the phosphorylated forms of phosphoinositide 3-kinase (PI3K), protein kinase B (Akt), glycogen synthase kinase-3β (GSK-3β), mammalian target of rapamycin (mTOR), and tau were detected. Furthermore, oxidative stress and inflammatory biomarkers were estimated. Treatment with PFT reversed STZ-induced neurodegeneration and cognitive impairment, enhanced hippocampal Ach levels, and reduced Aβ1-42 levels after restoration of IDE activity. PFT also improved insulin signaling, as evidenced by upregulation of insulin receptor expression and activation of PI3K/Akt signaling with subsequent suppression of GSK-3β and mTOR signaling, which result in the downregulation of hyperphosphorylated tau. Moreover, PFT significantly diminished oxidative stress and inflammation induced by STZ. These potential effects were parallel to those produced by pioglitazone. Therefore, PFT targets multiple mechanisms incorporated in the pathogenesis of AD and hence might be a beneficial therapy for AD.

Propolis in Metabolic Syndrome and Its Associated Chronic Diseases: A Narrative Review

Propolis is a resinous product collected by bees from plants to protect and maintain the homeostasis of their hives. Propolis has been used therapeutically by humans for centuries. This review article attempts to analyze the potential use of propolis in metabolic syndrome (MetS) and its associated chronic diseases. MetS and its chronic diseases were shown to be involved in at least seven out of the top 10 causes of death in 2019. Patients with MetS are also at a heightened risk of severe morbidity and mortality in the present COVID-19 pandemic. Propolis with its antioxidant and anti-inflammatory properties is potentially useful in ameliorating the symptoms of MetS and its associated chronic diseases. The aim of this article is to provide a comprehensive review on propolis and its therapeutic benefit in MetS and its chronic diseases, with an emphasis on in vitro and in vivo studies, as well as human clinical trials. Moreover, the molecular and biochemical mechanisms of action of propolis are also discussed. Propolis inhibits the development and manifestation of MetS and its chronic diseases by inhibiting of the expression and interaction of advanced glycation end products (AGEs) and their receptors (RAGEs), inhibiting pro-inflammatory signaling cascades, and promoting the cellular antioxidant systems.

Crosstalk between Gut and Brain in Alzheimer's Disease: The Role of Gut Microbiota Modulation Strategies

The gut microbiota (GM) represents a diverse and dynamic population of microorganisms and about 100 trillion symbiotic microbial cells that dwell in the gastrointestinal tract. Studies suggest that the GM can influence the health of the host, and several factors can modify the GM composition, such as diet, drug intake, lifestyle, and geographical locations. Gut dysbiosis can affect brain immune homeostasis through the microbiota-gut-brain axis and can play a key role in the pathogenesis of neurodegenerative diseases, including dementia and Alzheimer's disease (AD). The relationship between gut dysbiosis and AD is still elusive, but emerging evidence suggests that it can enhance the secretion of lipopolysaccharides and amyloids that may disturb intestinal permeability and the blood-brain barrier. In addition, it can promote the hallmarks of AD, such as oxidative stress, neuroinflammation, amyloid-beta formation, insulin resistance, and ultimately the causation of neural death. Poor dietary habits and aging, along with inflammatory responses due to dysbiosis, may contribute to the pathogenesis of AD. Thus, GM modulation through diet, probiotics, or fecal microbiota transplantation could represent potential therapeutics in AD. In this review, we discuss the role of GM dysbiosis in AD and potential therapeutic strategies to modulate GM in AD.

Targeting Insulin Resistance to Treat Cognitive Dysfunction

Dementia is a devastating disease associated with aging. Alzheimer's disease is the most common form of dementia, followed by vascular dementia. In addition to clinically diagnosed dementia, cognitive dysfunction has been reported in diabetic patients. Recent studies are now beginning to recognize type 2 diabetes mellitus, characterized by chronic hyperglycemia and insulin resistance, as a risk factor for Alzheimer's disease and other cognitive disorders. While studies on insulin action have remained traditionally in the domain of peripheral tissues, the detrimental effects of insulin resistance in the central nervous system on cognitive dysfunction are increasingly being reported by recent clinical and preclinical studies. The findings from these studies suggest that antidiabetic drugs have the potential to be used to treat dementia. In this review, we discuss the physiological functions of insulin in the brain, studies on the evaluation of cognitive function under conditions of insulin resistance, and reports on the beneficial actions of antidiabetic drugs in the brain. This review covers clinical studies as well as investigations in animal models and will further highlight the emerging link between insulin resistance and neurodegenerative disorders.

Insulin resistance: a connecting link between Alzheimer's disease and metabolic disorder

Recent evidence suggests that Alzheimer's disease (AD) is closely linked with insulin resistance, as seen in type 2 diabetes mellitus (T2DM). Insulin signaling is impaired in AD brains due to insulin resistance, ultimately resulting in the formation of neurofibrillary tangles (NFTs). AD and T2DM are connected at molecular, clinical, and epidemiological levels making it imperative to understand the contribution of T2DM, and other metabolic disorders, to AD pathogenesis. In this review, we have discussed various modalities involved in the pathogenesis of these two diseases and explained the contributing parameters. Insulin is vital for maintaining glucose homeostasis and it plays an important role in regulating inflammation. Here, we have discussed the roles of various contributing factors like miRNA, leptin hormone, neuroinflammation, metabolic dysfunction, and gangliosides in insulin impairment both in AD and T2DM. Understanding these mechanisms will be a big step forward for making molecular therapies that may help maintain or prevent both AD and T2DM, thus reducing the burden of both these diseases.

Lactobacillus paracasei ameliorates cognitive impairment in high-fat induced obese mice via insulin signaling and neuroinflammation pathways

Long-term consumption of a high-fat diet (HFD) can cause glucose and lipid metabolism disorders, damage the brain and nervous system and result in cognitive impairment.