Leukotriene D4 induces cellular senescence in osteoblasts

Network pharmacology and untargeted metabolomic-based investigation of anti-osteoporotic effects of viscozyme-assisted polysaccharide from Portulaca oleracea L

Osteoporosis is a metabolic bone disease closely associated with oxidative stress. We had previously confirmed that the Viscozyme-assisted polysaccharide from Portulaca oleracea L (VPOP1) protects against antioxidant stress and evaluated the structure of VPOP1. In this study, we aimed to explore the anti-osteoporotic effects of VPOP1 on H2O2-induced osteoblast apoptosis. In addition, untargeted zebrafish metabolomics based on UPLC-Q-Orbitrap-HRMS was used to investigate the potential anti-osteoporotic mechanisms of VPOP1. The levels of Bcl-2 decreased significantly and those of caspase-3, Bax, and cytochrome C increased after treatment with H2O2. VPOP1 inhibited apoptosis in H2O2-induced MC3T3 cells. Metabolomic analyses showed that 28 potential biomarkers were gradually restored to normal levels after treatment with VPOP1 compared with that in the model group. Among them, leukotrienes D4 and A4, L-dopa, and L-tyrosine are important biomarkers and therapeutic targets. Pathway analysis revealed that arachidonic acid, tyrosine, phenylalanine, and sphingolipid metabolism were the major intervening pathways. Collectively, these results help us understand the protective activity of large molecular weight compounds, such as VPOP1, against osteoporosis.

Arachidonic acid in aging: New roles for old players

BACKGROUND

Arachidonic acid (AA), one of the most ubiquitous polyunsaturated fatty acids (PUFAs), provides fluidity to mammalian cell membranes. It is derived from linoleic acid (LA) and can be transformed into various bioactive metabolites, including prostaglandins (PGs), thromboxanes (TXs), lipoxins (LXs), hydroxy-eicosatetraenoic acids (HETEs), leukotrienes (LTs), and epoxyeicosatrienoic acids (EETs), by different pathways. All these processes are involved in AA metabolism. Currently, in the context of an increasingly visible aging world population, several scholars have revealed the essential role of AA metabolism in osteoporosis, chronic obstructive pulmonary disease, and many other aging diseases.

AIM OF REVIEW

Although there are some reviews describing the role of AA in some specific diseases, there seems to be no or little information on the role of AA metabolism in aging tissues or organs. This review scrutinizes and highlights the role of AA metabolism in aging and provides a new idea for strategies for treating aging-related diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

As a member of lipid metabolism, AA metabolism regulates the important lipids that interfere with the aging in several ways. We present a comprehensivereviewofthe role ofAA metabolism in aging, with the aim of relieving the extreme suffering of families and the heavy economic burden on society caused by age-related diseases. We also collected and summarized data on anti-aging therapies associated with AA metabolism, with the expectation of identifying a novel and efficient way to protect against aging.

The senescence-associated secretory phenotype and its physiological and pathological implications

Cellular senescence is a state of terminal growth arrest associated with the upregulation of different cell cycle inhibitors, mainly p16 and p21, structural and metabolic alterations, chronic DNA damage responses, and a hypersecretory state known as the senescence-associated secretory phenotype (SASP). The SASP is the major mediator of the paracrine effects of senescent cells in their tissue microenvironment and of various local and systemic biological functions. In this Review, we discuss the composition, dynamics and heterogeneity of the SASP as well as the mechanisms underlying its induction and regulation. We describe the various biological properties of the SASP, its beneficial and detrimental effects in different physiological and pathological settings, and its impact on overall health span. Finally, we discuss the use of the SASP as a biomarker and of SASP inhibitors as senomorphic interventions to treat cancer and other age-related conditions.

A multi-tissue metabolome atlas of primate pregnancy

Pregnancy induces dramatic metabolic changes in females; yet, the intricacies of this metabolic reprogramming remain poorly understood, especially in primates. Using cynomolgus monkeys, we constructed a comprehensive multi-tissue metabolome atlas, analyzing 273 samples from 23 maternal tissues during pregnancy. We discovered a decline in metabolic coupling between tissues as pregnancy progressed. Core metabolic pathways that were rewired during primate pregnancy included steroidogenesis, fatty acid metabolism, and arachidonic acid metabolism. Our atlas revealed 91 pregnancy-adaptive metabolites changing consistently across 23 tissues, whose roles we verified in human cell models and patient samples. Corticosterone and palmitoyl-carnitine regulated placental maturation and maternal tissue progenitors, respectively, with implications for maternal preeclampsia, diabetes, cardiac hypertrophy, and muscle and liver regeneration. Moreover, we found that corticosterone deficiency induced preeclampsia-like inflammation, indicating the atlas's potential clinical value. Overall, our multi-tissue metabolome atlas serves as a framework for elucidating the role of metabolic regulation in female health during pregnancy.

Arachidonic acid metabolism in health and disease

Arachidonic acid (AA), an n-6 essential fatty acid, is a major component of mammalian cells and can be released by phospholipase A2. Accumulating evidence indicates that AA plays essential biochemical roles, as it is the direct precursor of bioactive lipid metabolites of eicosanoids such as prostaglandins, leukotrienes, and epoxyeicosatrienoic acid obtained from three distinct enzymatic metabolic pathways: the cyclooxygenase pathway, lipoxygenase pathway, and cytochrome P450 pathway. AA metabolism is involved not only in cell differentiation, tissue development, and organ function but also in the progression of diseases, such as hepatic fibrosis, neurodegeneration, obesity, diabetes, and cancers. These eicosanoids are generally considered proinflammatory molecules, as they can trigger oxidative stress and stimulate the immune response. Therefore, interventions in AA metabolic pathways are effective ways to manage inflammatory-related diseases in the clinic. Currently, inhibitors targeting enzymes related to AA metabolic pathways are an important area of drug discovery. Moreover, many advances have also been made in clinical studies of AA metabolic inhibitors in combination with chemotherapy and immunotherapy. Herein, we review the discovery of AA and focus on AA metabolism in relation to health and diseases. Furthermore, inhibitors targeting AA metabolism are summarized, and potential clinical applications are discussed.

Age-related alterations in metabolome and microbiome provide insights in dietary transition in giant pandas

We conducted UPLC-MS-based metabolomics, 16S rRNA, and metagenome sequencing on the fecal samples of 44 captive giant pandas (Ailuropoda melanoleuca) from four age groups (i.e., Cub, Young, Adult, and Old) to comprehensively understand age-related changes in the metabolism and gut microbiota of giant pandas. We characterized the metabolite profiles of giant pandas based on 1,376 identified metabolites, with 152 significantly differential metabolites (SDMs) found across the age groups. We found that the metabolites and the composition/function of the gut microbiota changed in response to the transition from a milk-dominant diet in panda cubs to a bamboo-specific diet in young and adult pandas. Lipid metabolites such as choline and hippuric acid were enriched in the Cub group, and many plant secondary metabolites were significantly higher in the Young and Adult groups, while oxidative stress and inflammatory related metabolites were only found in the Old group. However, there was a decrease in the α-diversity of gut microbiota in adult and old pandas, who exclusively consume bamboo. The abundance of bacteria related to the digestion of cellulose-rich food, such as Firmicutes, Streptococcus, and Clostridium, significantly increased from the Cub to the Adult group, while the abundance of beneficial bacteria such as Faecalibacterium, Sarcina, and Blautia significantly decreased. Notably, several potential pathogenic bacteria had relatively high abundances, especially in the Young group. Metagenomic analysis identified 277 CAZyme genes including cellulose degrading genes, and seven of the CAZymes had abundances that significantly differed between age groups. We also identified 237 antibiotic resistance genes (ARGs) whose number and diversity increased with age. We also found a significant positive correlation between the abundance of bile acids and gut bacteria, especially Lactobacillus and Bifidobacterium. Our results from metabolome, 16S rRNA, and metagenome data highlight the important role of the gut microbiota-bile acid axis in the regulation of age-related metabolism and provide new insights into the lipid metabolism of giant pandas. IMPORTANCE The giant panda is a member of the order Carnivora but is entirely herbivorous. The giant panda's specialized diet and related metabolic mechanisms have not been fully understood. It is therefore crucial to investigate the dynamic changes in metabolites as giant pandas grow and physiologically adapt to their herbivorous diet. This study conducted UPLC-MS-based metabolomics 16S rRNA, and metagenome sequencing on the fecal samples of captive giant pandas from four age groups. We found that metabolites and the composition/function of gut microbiota changed in response to the transition from a milk-dominant diet in cubs to a bamboo-specific diet in young and adult pandas. The metabolome, 16S rRNA, and metagenome results highlight that the gut microbiota-bile acid axis has an important role in the regulation of age-related metabolism, and our study provides new insights into the lipid metabolism of giant pandas.

Senescence-associated secretory phenotype and its impact on oral immune homeostasis

The senescence-associated secretory phenotype (SASP), which accumulates over the course of normal aging and in age-related diseases, is a crucial driver of chronic inflammation and aging phenotypes. It is also responsible for the pathogenesis of multiple oral diseases. However, the pathogenic mechanism underlying SASP has not yet been fully elucidated. Here, relevant articles on SASP published over the last five years (2017-2022) were retrieved and used for bibliometric analysis, for the first time, to examine SASP composition. More than half of the relevant articles focus on various cytokines (27.5%), growth factors (20.9%), and proteases (20.9%). In addition, lipid metabolites (13.1%) and extracellular vesicles (6.5%) have received increasing attention over the past five years, and have been recognized as novel SASP categories. Based on this, we summarize the evidences demonstrating that SASP plays a pleiotropic role in oral immunity and propose a four-step hypothetical framework for the progression of SASP-related oral pathology-1) oral SASP development, 2) SASP-related oral pathological alterations, 3) pathological changes leading to oral immune homeostasis disruption, and 4) SASP-mediated immune dysregulation escalating oral disease. By targeting specific SASP factors, potential therapies can be developed to treat oral and age-related diseases.

Bioactive Lipids in Age-Related Disorders

Our own studies and those of others have shown that defects in essential fatty acid (EFA) metabolism occurs in age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, atherosclerosis, coronary heart disease, immune dysfunction and cancer. It has been noted that in all these disorders there could occur a defect in the activities of desaturases, cyclo-oxygenase (COX), and lipoxygenase (LOX) enzymes leading to a decrease in the formation of their long-chain products gamma-linolenic acid (GLA), arachidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA). This leads to an increase in the production of pro-inflammatory prostaglandin E2 (PGE2), thromboxanes (TXs), and leukotrienes (LTs) and a decrease in anti-inflammatory lipoxin A4, resolvins, protectins and maresins. All these bioactive molecules are termed as bioactive lipids (BALs). This imbalance in the metabolites of EFAs leads to low-grade systemic inflammation and at times acute inflammatory events at specific local sites that trigger the development of various age-related disorders such as obesity, type 2 diabetes mellitus, hypertension, coronary heart disease, atherosclerosis, and immune dysfunction as seen in rheumatoid arthritis, lupus, nephritis and other localized inflammatory conditions. This evidence implies that methods designed to restore BALs to normal can prevent age-related disorders and enhance longevity and health.

The senescence-associated secretory phenotype and its regulation

The senescence-associated secretory phenotype (SASP) defines the ability of senescent cells to express and secrete a variety of extracellular modulators that includes cytokines, chemokines, proteases, growth factors and bioactive lipids. The role of the SASP depends on the context. The SASP reinforces the senescent cell cycle arrest, stimulates the immune-mediated clearance of potentially tumorigenic cells, limits fibrosis and promotes wound healing and tissue regeneration. On the other hand, the SASP can mediate chronic inflammation and stimulate the growth and survival of tumor cells. The regulation of the SASP occurs at multiple levels including chromatin remodelling, activation of specific transcription factors such as C/EBP and NF-κB, control of mRNA translation and intracellular trafficking. Several SASP modulators have already been identified setting the stage for future research on their clinical applications.