Evidence from an Avian Embryo Model that Zinc-Inducible MT4 Expression Protects Mitochondrial Function Against Oxidative Stress.

BACKGROUND: Metallothioneins (MTs) have a strong affinity for zinc (Zn) and remain at a sufficiently high level in mitochondria. As the avian embryo is highly susceptible to oxidative damage and relatively easy to manipulate in a naturally closed chamber, it is an ideal model of the effects of oxidative stress on mitochondrial function. However, the protective roles and molecular mechanisms of Zn-inducible protein expression on mitochondrial function in response to various stressors are poorly understood. OBJECTIVES: The study aimed to investigate the mechanisms by which Zn-induced MT4 expression protects mitochondrial function and energy metabolism subjected to oxidative stress using the avian embryo and embryonic primary hepatocyte models. METHODS: First, we investigated whether MT4 expression alters mitochondrial function. Then, we examined the effects of Zn-induced MT4 overexpression and MT4 silencing on embryonic primary hepatocytes from breeder hens fed a normal Zn diet subjected to a tert-butyl hydroperoxide (BHP) oxidative stress challenge during incubation. In vivo, the avian embryos from hens fed the Zn-deficient and Zn-adequate diets were used to determine the protective roles of Zn-induced MT4 expression on the function of mitochondria exposed to oxidative stress induced by in ovo BHP injection. RESULTS: An in vitro study revealed that Zn-induced MT4 expression reduced reactive oxygen species accumulation in primary hepatocytes. MT4 silencing exacerbated BHP-mediated mitochondrial dysfunction whereas Zn-inducible MT4 overexpression mitigated it. Another in vivo study disclosed that maternal Zn-induced MT4 expression protected mitochondrial function in chick embryo hepatocytes against oxidative stress by inhibiting the peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α)/peroxisome proliferators-activated receptor-γ (PPAR-γ) pathway. CONCLUSION: This study underscores the potential protective roles of Zn-induced MT4 expression via the downregulation of the PGC-1α/PPAR-γ pathway on mitochondrial function stimulated by the stress challenge in the primary hepatocytes in an avian embryo model. Our findings suggested that Zn-induced MT4 expression could provide a new therapeutic target and preventive strategy for repairing mitochondrial dysfunction in disease.

Resveratrol ameliorates intestinal lipid metabolism through the PPAR signaling pathway in high-fat diet-fed red tilapia (Oreochromis niloticus).

Feeding high-fat (HF) diets has been shown to cause hepatic and intestinal impairment in fish species, but the mode of action, especially the pathways involved in the intestine, has not been determined yet. In this study, the effects of resveratrol (RES) supplementation on the intestinal structure, microbial flora, and fat metabolism in red tilapia (Oreochromis niloticus) were determined. The results showed RES maintained the structural integrity of the intestine and significantly increased the number of goblet cells in the midgut. RES significantly induced interferon (IL)-1ß, IL-6, IL-10, and tumor necrosis factor (TNF)-α, serumal and fecal trimetlylamine oxide (TMAO) and lipopolysaccharides (LPS), intestinal acetic acid levels. However, the concentrations of bound bile acids increased in HF-fed red tilapia. Atp5fa1 and Pafah1b3 significantly increased, Pmt and Acss2 significantly decreased, respectively, with RES supplementation, which was alleviated and retained at the same level in the selisistat (EX527) group. While for transcriptome and proteomics results, RES was found to promote fatty acid ß-oxidation and arachidonic acid metabolism associated with the peroxisome proliferator-activated receptor (PPAR) signaling pathway. The next validation experiment showed some genes related to apoptosis and fatty acid metabolism pathways were altered by RES supplementation. Namely, sn6, loc100702698, new_14481, and prkaa1 were upregulated, while ffrs1, ap3s1, and loc100705861 were downregulated. RES significantly increased Planctomycetes and Verrucomicrobia while decreased Moonvirus, Citrobacter, and Pseudomonas. Akkermansia and Fusobacterium significantly increased and Aeromonas significantly decreased. Thus, unsaturated fatty acid biosynthesis significantly increased and carbohydrate/energy metabolism decreased. To conclude, RES enabled the body to complete fatty acid ß-oxidation and arachidonic acid metabolism, whereas the addition of inhibitors increased the expression of the phagosome transcriptome and reduced fatty acid ß-oxidative metabolism.

PDK4 inhibits osteoarthritis progression by activating the PPAR pathway.

BACKGROUND: Osteoarthritis (OA) is a degenerative joint disease caused by the deterioration of cartilage. However, the underlying mechanisms of OA pathogenesis remain elusive. METHODS: Hub genes were screened by bioinformatics analysis based on the GSE114007 and GSE169077 datasets. The Sprague-Dawley (SD) rat model of OA was constructed by intra-articular injection of a mixture of papain and L-cysteine. Hematoxylin-eosin (HE) staining was used to detect pathological changes in OA rat models. Inflammatory cytokine levels in serum were measured employing the enzyme-linked immunosorbent assay (ELISA). The reverse transcription quantitative PCR (RT-qPCR) was implemented to assess the hub gene expressions in OA rat models. The roles of PDK4 and the mechanism regulating the PPAR pathway were evaluated through western blot, cell counting kit-8 (CCK-8), ELISA, and flow cytometry assays in C28/I2 chondrocytes induced by IL-1ß. RESULTS: Six hub genes were identified, of which COL1A1, POSTN, FAP, and CDH11 expressions were elevated, while PDK4 and ANGPTL4 were reduced in OA. Overexpression of PDK4 inhibited apoptosis, inflammatory cytokine levels (TNF-α, IL-8, and IL-6), and extracellular matrix (ECM) degradation protein expressions (MMP-3, MMP-13, and ADAMTS-4) in IL-1ß-induced chondrocytes. Further investigation revealed that PDK4 promoted the expression of PPAR signaling pathway-related proteins: PPARA, PPARD, and ACSL1. Additionally, GW9662, an inhibitor of the PPAR pathway, significantly counteracted the inhibitory effect of PDK4 overexpression on IL-1ß-induced chondrocytes. CONCLUSION: PDK4 inhibits OA development by activating the PPAR pathway, which provides new insights into the OA management.

Icariin promotes bone marrow mesenchymal stem cells osteogenic differentiation via the mTOR/autophagy pathway to improve ketogenic diet-associated osteoporosis.

BACKGROUND: Icariin, a traditional Chinese medicine, has demonstrated anti-osteoporotic properties in ovariectomized mice. However, its effectiveness in preventing bone loss induced by ketogenic diet (KD), which mimics osteoporosis in human, remains unexplored. This study aims to investigate icariin's impact on KD-induced bone loss in mice. METHODS: Thirty mice were divided into: sham, KD, and KD + icariin groups. Post a 12-week intervention, evaluation including bone microstructures, serum concentrations of tartrate-resistant acid phosphatase (TRAP) and bone-specific alkaline phosphatase (ALP), and femoral tissue expression levels of osteocalcin (OCN) and TRAP. The expression levels of mammalian target of rapamycin (mTOR), ALP, peroxisome proliferator-activated receptor gamma (PPAR-γ), phosphorylated mTOR (p-mTOR), and the autophagy adaptor protein (p62) were also analyzed. Alizarin granule deposition and cellular ALP levels were measured following the induction of bone marrow mesenchymal stem cells (BMSCs) into osteogenesis. RESULTS: The study found that KD significantly impaired BMSCs' osteogenic differentiation, leading to bone loss. Icariin notably increased bone mass, stimulated osteogenesis, and reduced cancellous bone loss. In the KD + icariin group, measures such as bone tissue density (TMD), bone volume fraction (BV/TV), trabecular number (Tb.N), and trabecular thickness (Tb.Th) were significantly higher than in the KD group. Additionally, bone trabecular separation (Tb.Sp) was markedly lower in the KD + icariin group. Moreover, icariin increased OCN and ALP levels while suppressing PPAR-γ, TRAP, p62, and p-mTOR. In cellular studies, icariin encouraged osteogenic development in BMSCs under KD conditions. CONCLUSIONS: Icariin effectively counteracts bone thinning and improves bone microstructure. Its mechanism likely involves stimulating BMSCs osteogenic differentiation and inhibiting bone resorption, potentially through mTOR downregulation. These findings suggest icariin's potential as an alternative treatment for KD-induced bone loss.

Produtos naturais ativadores de PPAR e marcadores associados ao processo inflamatório na Síndrome Metabólica / The inflammatory process in the metabolic syndrome: PPAR activators of natural products and markers associated with metabolic disorders

O processo inflamatório é o elo entre a síndrome metabólica e as doenças cardiovasculares. Para verificar a presença e o grau da inflamação, vários biomarcadores têm sido propostos e investigados. Este trabalho tem como objetivo revisar as recentes pesquisas que associam alguns marcadores expressos no tecido adiposo, enfatizando, dentre eles, a adiponectina, a resistina, a leptina e o transportador de glicose GLUT-4 na síndrome metabólica, a relação da inflamação decorrente desse conjunto de desordens metabólicas sob os receptores proliferadores peroxissomais (PPARs), bem como o efeito de diferentes extratos vegetais e produtos naturais bioativos na ativação desses receptores.

The inflammatory process is the link between metabolic syndrome and cardiovascular diseases. To verify the presence and degree of inflammation, several biomarkers have been proposed and different receptors have been investigated. This study aims to review recent researches involving some markers expressed in the adipose tissue, emphasizing, among them, adiponectin, resistin, leptin and glucose transporter GLUT-4 in the metabolic syndrome, the relationship of inflammation arising from this set of metabolic disorders on the peroxisome proliferator receptors (PPARs) and the effect of different bioactive compounds in the activation of these receptors.

O endotélio na síndrome metabólica / The endothelium in the metabolic syndrome

O endotélio é responsável pela manutenção da homeostase vascular. Em condições fisiológicas, mantém o tônus vascular, o fluxo sangüíneo laminar, a fluidez da membrana plasmática, o equilíbrio entre coagulação e fibrinólise, a inibição da proliferação e da migração celulares e o controle da resposta inflamatória. A disfunção endotelial é definida como uma alteração do relaxamento vascular por diminuição da biodisponibilidade de fatores de relaxamento derivados do endotélio, principalmente o óxido nítrico (NO). Estas respostas vasomotoras anormais ocorrem na presença de inúmeros fatores de risco para a aterosclerose. A síndrome metabólica é considerada um estado de inflamação crônica que se acompanha de disfunção endotelial e ocasiona aumento na incidência de eventos isquêmicos cardiovasculares e elevada mortalidade. Essa revisão abordará o processo fisiológico de regulação da função vascular pelo endotélio, os métodos disponíveis para avaliação in vivo da disfunção endotelial e as terapias capazes de melhorar a função vascular e conseqüentemente minimizar o risco cardiovascular dessa síndrome tão prevalente no nosso meio.

The endothelium is responsible for the maintenance of vascular homeostasis. In physiological conditions it acts keeping vascular tonus, laminar blood flow, plasmatic membrane fluidity, the balance between coagulation and fibrinolysis and the inhibition of cellular proliferation, migration and the inflammatory response. Endothelial dysfunction is defined as an alteration of vascular relaxation induced by reduction of endothelium-derived relaxing factors (ERRFs), mainly nitric oxide. These abnormal vasomotor responses occur in the presence of various risk factors for atherosclerosis. The metabolic syndrome is considered a state of chronic inflammation accompanied of endothelial dysfunction causing an increased incidence of ischemic cardiovascular events and high mortality. This revision will encompass the physiological process of vascular function regulation, methods for in vivo assessment of endothelial dysfunction and therapies capable to improve vascular function and consequently minimize the cardiovascular risk due to metabolic syndrome.