High-fat diet-induced activation of SGK1 promotes Alzheimer's disease-associated tau pathology.
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ABSTRACT:
SUBMITTER: Elahi M
PROVIDER: S-EPMC8411983 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Alzheimer's disease (AD) is mainly characterized by the accumulation and aggregation of amyloid-β (Aβ) peptides in brain parenchyma and cerebral microvasculature. Unfortunately, the exact causes of the disease are still unclear. However, blood-brain barrier (BBB) dysfunction and activation of inflammatory pathways are implicated in AD pathogenesis. Importantly, advanced age and high fat diet, two major risk factors associated with AD, were shown to deeply affect BBB function and modulate the immune response. As such, this study evaluated the impact of age and high fat diet on AD progression. For this purpose, 3 (i.e. young) and 12 (i.e. aged) months old APPswe/PS1 mice were fed for 4 months with a high fat diet (i.e. Western diet (WD)) or normal diet. Interestingly, neurobehavioral tests revealed that WD accelerates age-associated cognitive decline without affecting parenchymal Aβ. Nonetheless, WD decreases matrix metalloproteinase-9 enzymatic activity and brain-derived neurotrophic factor mRNA and protein levels in brain, suggesting loss of synaptic plasticity. In the periphery, WD promotes systemic inflammation by increasing the levels of blood-circulating monocytes and monocyte chemotactic protein-1 production, which is accompanied by an augmentation of oxidized-low density lipoprotein levels in blood circulation. At the BBB, WD potentiates the age-induced increase of Aβ 1-40 accumulation and exacerbates the oxidative stress, specifically in cerebral microvasculature. These effects were accompanied by the dysfunction of pericytes, thus altering BBB functionality without compromising its integrity. Our study provides new insights into the implication of high fat diet in accelerating the cognitive decline in AD.
| S-EPMC5356521 | biostudies-literature
Project description:BackgroundEpidemiological studies link vascular disease risk factors such as atherosclerosis, hypertension, and diabetes mellitus with Alzheimer's disease (AD). Whether there are direct links between these conditions to β-amyloid (Aβ) aggregation and tau pathology is uncertain.MethodsTo investigate the possible link between atherosclerosis and AD pathology, we subjected triple transgenic (3 × Tg) AD mice to a high-fat diet (HFD) at 3 months of age, which corresponds to early adulthood in humans.ResultsAfter 9 months of treatment, HFD-treated 3 × Tg mice exhibited worse memory deficits accompanied by blood hypercoagulation, thrombocytosis, and chronic platelet activation. Procoagulant platelets from HFD-treated 3 × Tg mice actively induced the conversion of soluble Aβ40 into fibrillar Aβ aggregates, associated with increased expression of integrin αIIbβ3 and clusterin. At 9 months and older, platelet-associated fibrillar Aβ aggregates were observed to obstruct the cerebral blood vessels in HFD-treated 3 × Tg mice. HFD-treated 3 × Tg mice exhibited a greater cerebral amyloid angiopathy (CAA) burden and increased cerebral vascular permeability, as well as more extensive neuroinflammation, tau hyperphosphorylation, and neuron loss. Disaggregation of preexisting platelet micro-clots with humanized GPIIIa49-66 scFv Ab (A11) significantly reduced platelet-associated fibrillar Aβ aggregates in vitro and improved vascular permeability in vivo.ConclusionsThese findings suggest that a major contribution of atherosclerosis to AD pathology is via its effects on blood coagulation and the formation of platelet-mediated Aβ aggregates that compromise cerebral blood flow and therefore neuronal function. This leads to cognitive decline.
| S-EPMC8403418 | biostudies-literature
Project description:Pharmacological treatment of recombinant growth differentiation factor 15 (GDF15) proteins reduces body weight in obese rodents and primates. Paradoxically, circulating GDF15 levels are increased in obesity. To investigate the role of endogenous GDF15 in obesity development, we put GDF15 knockout mice and wildtype controls on high fat diet for the mice to develop diet-induced obesity. Compared to wildtype animals, GDF15 knockout mice were more prone to high fat diet-induced obesity. Male knockout mice showed worse glucose tolerance, lower locomotor activity and lower metabolic rate than wildtype mice. Additionally, GDF15 deficiency increased occurrences of high fat diet-induced skin lesions. Our data suggests that endogenous GDF15 has a protective role in obesity development and lack of GDF15 aggravates the progression of obesity and associated pathological conditions. Elevated GDF15 levels in obesity may have resulted from a response to overcome GDF15 resistance.
| S-EPMC6072047 | biostudies-literature
Project description:P2Y2, a G protein-coupled receptor (R), is expressed in all organs involved in the development of obesity and insulin resistance. To explore the role of it in diet-induced obesity, we fed male P2Y2-R whole body knockout (KO) and wild type (WT) mice (B6D2 genetic background) with regular diet (CNT; 10% calories as fat) or high-fat diet (HFD; 60% calories as fat) with free access to food and water for 16 weeks, and euthanized them. Adjusted for body weights (BW), KO mice consumed modestly, but significantly more HFD vs. WT mice, and excreted well-formed feces with no taint of fat or oil. Starting from the 2nd week, HFD-WT mice displayed significantly higher BW with terminal mean difference of 22% vs. HFD-KO mice. Terminal weights of white adipose tissue (WAT) were significantly lower in the HFD-KO vs. HFD-WT mice. The expression of P2Y2-R mRNA in WAT was increased by 2-fold in HFD-fed WT mice. Serum insulin, leptin and adiponectin levels were significantly elevated in the HFD-WT mice, but not in the HFD-KO mice. When induced in vitro, preadipocytes derived from KO mice fed regular diet did not differentiate and mature as robustly as those from the WT mice, as assessed by cellular expansion and accumulation of lipid droplets. Blockade of P2Y2-R by AR-C118925 in preadipocytes derived from WT mice prevented differentiation and maturation. Under basal conditions, KO mice had significantly higher serum triglycerides and showed slightly impaired lipid tolerance as compared to the WT mice. HFD-fed KO mice had significantly better glucose tolerance (GTT) as compared to HFD-fed WT mice. Whole body insulin sensitivity and mRNA expression of insulin receptor, IRS-1 and GLUT4 in WAT was significantly higher in HFD-fed KO mice vs. HFD-fed WT mice. On the contrary, the expression of pro-inflammatory molecules MCP-1, CCR2, CD68, and F4/80 were significantly higher in the WAT of HFD-fed WT vs. HFD-fed KO mice. These data suggest that P2Y2-R plays a significant role in the development of diet-induced obesity by promoting adipogenesis and inflammation, and altering the production of adipokines and lipids and their metabolism in adipose tissue, and thereby facilitates HFD-induced insulin resistance.
| S-EPMC7283874 | biostudies-literature
Project description:While the main function of white adipose tissue (WAT) is to store surplus of energy as triacylglycerol, that of brown adipose tissue (BAT) is to burn energy as heat. Epigenetic mechanisms participate prominently in both WAT and BAT energy metabolism. We previously reported that the histone demethylase ubiquitously transcribed tetratricopeptide (Utx) is a positive regulator of brown adipocyte thermogenesis. Here, we aimed to investigate whether Utx also regulates WAT metabolism in vivo. We generated a mouse model with Utx deficiency in adipocytes (AUTXKO). AUTXKO animals fed a chow diet had higher body weight, more fat mass and impaired glucose tolerance. AUTXKO mice also exhibited cold intolerance with an impaired brown fat thermogenic program. When challenged with high-fat diet (HFD), AUTXKO mice displayed adipose dysfunction featured by suppressed lipogenic pathways, exacerbated inflammation and fibrosis with less fat storage in adipose tissues and more lipid storage in the liver; as a result, AUTXKO mice showed a disturbance in whole body glucose homeostasis and hepatic steatosis. Our data demonstrate that Utx deficiency in adipocytes limits adipose tissue expansion under HFD challenge and induces metabolic dysfunction via adipose tissue remodeling. We conclude that adipocyte Utx is a key regulator of systemic metabolic homeostasis.
| S-EPMC8773702 | biostudies-literature
Project description:UnlabelledThe intestines of obese humans and mice are enriched with Erysipelotrichi, a class within the Firmicutes. Clostridium ramosum, a member of the Erysipelotrichi, is associated with symptoms of the metabolic syndrome in humans. To clarify the possible obesogenic potential of this bacterial species and to unravel the underlying mechanism, we investigated the role of C. ramosum in obesity development in gnotobiotic mice. Mice were associated with a simplified human intestinal (SIHUMI) microbiota of eight bacterial species, including C. ramosum, with the SIHUMI microbiota except C. ramosum (SIHUMIw/oCra), or with C. ramosum only (Cra) and fed a high-fat diet (HFD) or a low-fat diet (LFD). Parameters related to the development of obesity and metabolic diseases were compared. After 4 weeks of HFD feeding, the mouse groups did not differ in energy intake, diet digestibility, gut permeability, and parameters of low-grade inflammation. However, SIHUMI and Cra mice fed the HFD gained significantly more body weight and body fat and displayed higher food efficiency than SIHUMIw/oCra mice fed the HFD. Gene expression of glucose transporter 2 (Glut2) in jejunal mucosa and of fatty acid translocase (CD36) in ileal mucosa was significantly increased in the obese SIHUMI and Cra mice compared with the less obese SIHUMIw/oCra mice. The data demonstrate that the presence of C. ramosum in SIHUMI and Cra mice enhanced diet-induced obesity. Upregulation of small intestinal glucose and fat transporters in these animals may contribute to their increased body fat deposition.ImportanceObesity is a growing health problem worldwide. Changes in the proportions of Bacteroidetes and Firmicutes, the two dominant phyla in the human and the murine intestinal tract, link the intestinal microbiota to obesity. Erysipelotrichi, a class within the Firmicutes, increase in response to high-fat feeding in mice. Clostridium ramosum, a member of the Erysipelotrichi, has been linked to symptoms of the metabolic syndrome. We hypothesized that C. ramosum promotes obesity development and related pathologies. Our experiments in gnotobiotic mice show that C. ramosum promoted diet-induced obesity, probably by enhancing nutrient absorption. Identification of obesogenic bacteria and understanding their mode of action enable the development of novel strategies for the treatment of this epidemic disease. Pharmaceuticals that target obesogenic bacteria or their metabolism could help to prevent and treat obesity and related disorders in the future.
| S-EPMC4196224 | biostudies-literature
Project description:BackgroundChronic changes caused by a high-fat diet (HFD) may be associated with weakened lung function in obese patients. However, few studies have focused on the role of senescent cells in HFD-induced pulmonary fibrosis. This study aimed to determine whether (i) obesity causes the accumulation of aging cells in the lungs, (ii) p16 accumulation in aging epithelial cells or fibroblasts exacerbates long-term HFD-induced senescence-associated pulmonary fibrosis (SAPF) and (iii) p16 deletion or clearance of aging cells ameliorates HFD-induced SAPF through inactivation of the inflammasome and metabolic remodelling.MethodsTwelve-month old male mice of p16INK4a (hereafter p16) knockout (p16-- ) and wild-type (WT), ApoE knockout (ApoE-- ) and ApoE-- p16-- were fed a HFD to induce obesity, and the effects of treatment with the senolytic drug ABT263 or the SGK1 specific inhibitor EMD638683 on fibrosis, inflammaging, gene expression, integrin-inflammasome signalling and metabolism were examined. A549 and IMR-90 cells were transduced with p16-overexpressing adenovirus, and treated with palmitic and oleic acids (P&O) to induce steatosis in vitro.ResultsWe found that long-term HFD promoted the expression of p16 and the increase of senescent cells in the lung. P16 knockout or ABT263 treatment alleviated pulmonary fibrosis, the increase of senescent cells and senescence-associated secretory phenotype (SASP) in HFD-fed mice, as well as in P&O-treated A549 and IMR-90 cells. RNA sequencing and bioinformatics analyses revealed that p16 knockout inhibited activation of the integrin-inflammasome pathway and cellular glycolysis. Mass spectrometry, co-immunoprecipitation and GST pull-down assays demonstrated that p16 bound to the N-terminal of SGK1, thereby interfering with the interaction between the E3 ubiquitin ligase NEDD4L and SGK1, and subsequently inhibiting K48-polyubiquitin-dependent degradation of SGK1 mediated by the NEDD4L-Ubch5 complex. EMD638683 was found to alleviate HFD-induced pulmonary fibrosis and activation of the integrin-inflammasome pathway.ConclusionP16 accumulation promoted activation of integrin- inflammasome pathway and cell glycolysis by binding to the N- terminal of SGK1, intefering with the interaction between the E3 ubiquitin ligase NEDD4L and SGK1, thereby inhibiting K48- polyubiquitin- dependent degradation of SGK1 mediated by the NEDD4L-Ubch5 complex. ABT263 or EMD638683 could be used as potential drugs to treat pulmonary fibrosis in obese patients.
| S-EPMC10285269 | biostudies-literature
Project description:Defining specific cellular and molecular mechanisms in most obesity-related diseases remains an important challenge. Here we report a serendipitous finding that consumption of a high-fat diet (HFD) greatly increased the occurrence of skin lesions in C57BL/6 mice. We demonstrated that HFD induced the accumulation of a specific type of CD11c(+) macrophages in skin preceding detectable lesions. These cells primed skin to induce IL-1? and IL-18 signaling, which further promoted the cytokines IFN-?- and IL-17-mediated skin inflammation. Mechanistically, epidermal fatty acid binding protein (E-FABP) was significantly upregulated in skin of obese mice, which coupled lipid droplet formation and NLRP3 inflammasome activation. Deficiency of E-FABP in obese mice decreased recruitment of CD11c(+) macrophages in skin tissues, reduced production of IL-1? and IL-18, and consequently dampened activation of effector T cells. Furthermore, E-FABP-deficient mice are completely resistant to HFD-induced skin lesions. Collectively, E-FABP represents a molecular sensor triggering HFD-induced skin inflammation.
| S-EPMC4440244 | biostudies-literature
Project description:With rapid economic development, the prevalence of obesity has increased remarkably worldwide. Obesity can induce a variety of metabolic diseases, such as atherosclerosis, diabetes, hypertension and coronary heart disease, which significantly endanger the health and welfare of individuals. Brown and beige fat tissues play an important role in thermogenesis in mammals. Recent studies have shown that follistatin (FST) can potentially induce the browning of white adipose tissue (WAT). In this study, high-fat diet-induced obese mice were injected with follistatin for one week to explore the effects of follistatin on browning and metabolism and to determine the mechanism. The results showed that follistatin suppressed obesity caused by a high-fat diet and increased insulin sensitivity, energy expenditure, and subcutaneous fat browning. The beneficial effects remained even after a period of withdrawal. Follistatin promoted secretion of irisin from subcutaneous fat via the AMPK-PGC1?-irisin signal pathway, which induces browning of WAT, and activated the insulin pathway in beige fat thereby promoting metabolism.
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Project description:Gut fungi is known to play many important roles in human health regulations. Herein, we investigate the anti-obesity efficacy of the antifungal antibiotics (amphotericin B, fluconazole and 5-fluorocytosine) in the high fat diet-fed (HFD) mice. Supplementation of amphotericin B or fluconazole in water can effectively inhibit obesity and its related disorders, whereas 5-fluorocytosine exhibit little effects. The gut fungus Candida parapsilosis is identified as a key commensal fungus related to the diet-induced obesity by the culture-dependent method and the inoculation assay with C. parapsilosis in the fungi-free mice. In addition, the increase of free fatty acids in the gut due to the production of fungal lipases from C. parapsilosis is confirmed as one mechanism by which C. parapsilosis promotes obesity. The current study demonstrates the gut C. parapsilosis as a causal fungus for the development of diet-induced obesity in mice and highlights the therapeutic strategy targeting the gut fungi.
| S-EPMC8546080 | biostudies-literature