Adipocyte-derived PGE2 is required for intermittent fasting-induced Treg proliferation and improvement of insulin sensitivity

The transcriptomic profile shows the protective effects of celecoxib on cirrhotic splenomegaly

BACKGROUND

Splenomegaly can exacerbate liver cirrhosis and portal hypertension. We have previously demonstrated that cyclooxygenase-2 (COX-2) inhibitor can attenuate cirrhotic splenomegaly. However, the mechanism of cirrhotic splenomegaly remains unclear, thus becoming the focus of the present study.

MATERIALS AND METHODS

Thioacetamide (TAA) intraperitoneal injection was used to induce cirrhotic splenomegaly. Rats were randomized into the control, TAA and TAA + celecoxib groups. Histological analysis and high-throughput RNA sequencing of the spleen were conducted. Splenic collagen III, α-SMA, Ki-67, and VEGF were quantified.

RESULTS

A total of 1461 differentially expressed genes (DEGs) were identified in the spleens of the TAA group compared to the control group. The immune response and immune cell activation might be the major signaling pathways involved in the pathogenesis of cirrhotic splenomegaly. With its immunoregulatory effect, celecoxib presents to ameliorate cirrhotic splenomegaly and liver cirrhosis. Furthermore, 304 coexisting DEGs were obtained between TAA vs. control and TAA + celecoxib vs. TAA. Gene ontology (GO) and KEGG analyses collectively indicated that celecoxib may attenuate cirrhotic splenomegaly through the suppression of splenic immune cell proliferation, inflammation, immune regulation, and fibrogenesis. The impacts on these factors were subsequently validated by the decreased splenic Ki-67-positive cells, macrophages, fibrotic areas, and mRNA levels of collagen III and α-SMA.

CONCLUSIONS

Celecoxib attenuates cirrhotic splenomegaly by inhibiting splenic immune cell proliferation, inflammation, and fibrogenesis. The current study sheds light on the therapeutic strategy of liver cirrhosis by targeting splenic abnormalities and provides COX-2 inhibitors as a novel medical treatment for cirrhotic splenomegaly.

Depletion of JunB increases adipocyte thermogenic capacity and ameliorates diet-induced insulin resistance

The coexistence of brown adipocytes with low and high thermogenic activity is a fundamental feature of brown adipose tissue heterogeneity and plasticity. However, the mechanisms that govern thermogenic adipocyte heterogeneity and its significance in obesity and metabolic disease remain poorly understood. Here we show that in male mice, a population of transcription factor jun-B (JunB)-enriched (JunB+) adipocytes within the brown adipose tissue exhibits lower thermogenic capacity compared to high-thermogenic adipocytes. The JunB+ adipocyte population expands in obesity. Depletion of JunB in adipocytes increases the fraction of adipocytes exhibiting high thermogenic capacity, leading to enhanced basal and cold-induced energy expenditure and protection against diet-induced obesity and insulin resistance. Mechanistically, JunB antagonizes the stimulatory effects of PPARγ coactivator-1α on high-thermogenic adipocyte formation by directly binding to the promoter of oestrogen-related receptor alpha, a PPARγ coactivator-1α downstream effector. Taken together, our study uncovers that JunB shapes thermogenic adipocyte heterogeneity, serving a critical role in maintaining systemic metabolic health.

Effects of Calorie Restriction and Fasting on Macrophage: Potential Impact on Disease Outcomes?

Energy restriction, including calorie restriction and fasting, has garnered significant attention for its potential therapeutic effects on a range of chronic diseases (such as diabetes, obesity, and cancer) and aging. Since macrophages are critical players in many diseases, their response to energy restriction may impact disease outcomes. However, the diverse metabolic patterns and functions of macrophages can lead to variability in the effects of energy restriction on macrophages across different tissues and disease states. This review outlines the effects of energy restriction on macrophages in several diseases, offering valuable guidance for future studies and insights into the clinical applications of calorie restriction and fasting.

A 2-week time-restricted feeding attenuates psoriasis-like lesions with reduced inflammatory cytokines and immunosenescence in mice

Psoriasis, a well-established T-cell mediated dermatosis, exhibits a robust correlation with obesity and systemic inflammation, manifesting psoriasis skin lesions and premature immunosenescence within the peripheral blood and lesion. Intermittent fasting (IF) has exhibited various beneficial effects in reducing inflammation, resisting oxidative stress and slowing ageing, as well as losing weight. A form of IF known as time-restricted feeding (TRF) restricts daily caloric intake within 4-8 h. Nonetheless, the advantageous impacts of TRF on psoriasis still require further verification. We measured the acanthosis in Imiquimod (IMQ)-induced psoriasis mice and evaluated their pathological phenotypes. Our study examined the effects of a 2-week TRF on body weight and metabolic parameters. The subsets of T cells in spleens and skin lesions were accessed by flow cytometry. Cytokines and senescence-associated genes were evaluated by immunofluorescence and RT-qPCR. RNA sequencing was conducted on skin lesions. According to our findings, a 2-week TRF attenuates psoriasis-like lesions in mice with reduced inflammatory cytokines and mitigated immunosenescence. TRF increased the counts of CD4+ Treg cells in skin lesions while reducing the counts of Th2 and Th17 cells in spleens. Furthermore, the administration of TRF resulted in a decrease in the population of CD4+ senescent T cells in both the dermis and spleens, concomitant with the expression of senescence-associated genes in spleen CD4+ T cells. The outcomes mentioned above provide valuable evidence in support of TRF for the management of psoriasis.

Targeting metabolic pathways: a novel therapeutic direction for type 2 diabetes

Background

Type 2 diabetes mellitus (T2DM) is a prevalent metabolic disease that causes multi-organ complications, seriously affecting patients' quality of life and survival. Understanding its pathogenesis remains challenging, with current clinical treatment regimens often proving ineffective.

Methods

In this study, we established a mouse model of T2DM and employed 16s rDNA sequencing to detect changes in the species and structure of gut flora. Additionally, we used UPLC-Q-TOF-MS to identify changes in urinary metabolites of T2DM mice, analyzed differential metabolites and constructed differential metabolic pathways. Finally, we used Pearman correlation analysis to investigate the relationship between intestinal flora and differential metabolites in T2DM mice, aiming to elucidate the pathogenesis of T2DM and provide an experimental basis for its clinical treatment.

Results

Our findings revealed a reduction in both the species diversity and abundance of intestinal flora in T2DM mice, with significantly decreased levels of beneficial bacteria such as Lactobacillus and significantly increased levels of harmful bacteria such as Helicobacter pylori. Urinary metabolomics results identified 31 differential metabolites between T2DM and control mice, including Phosphatidylcholine, CDP-ethanolamine and Leukotriene A4, which may be closely associated with the glycerophospholipid and arachidonic acid pathways. Pearman correlation analysis showed a strong correlation between dopamine and gonadal, estradiol and gut microbiota, may be a novel direction underlying T2DM.

Conclusion

In conclusion, our study suggests that alterations in gut microbiota and urinary metabolites are characteristic features of T2DM in mice. Furthermore, a strong correlation between dopamine, estradiol and gut microbiota, may be a novel direction underlying T2DM, the aim is to provide new ideas for clinical treatment and basic research.

Adipose tissue-derived lipokines in metabolism

Adipose tissue is a crucial regulator of metabolism with functions that include energy storage and dissipation as well as the secretion of bioactive molecules. As the largest endocrine organ in the body, the adipose tissue produces diverse bioactive molecules, including peptides, metabolites, and extracellular vesicles, which communicate with and modulate the function of other organs. In recent years, lipid metabolites, also known as lipokines, have emerged as key signaling molecules that actively participate in multiple metabolic processes. This review highlights the latest advances in adipose tissue-derived lipokines and their underlying cellular and molecular functions. Furthermore, we offer our perspective on the future directions for adipose-derived bioactive lipids and potential therapeutic implications for obesity and its associated complications.

Physiological Approaches Targeting Cellular and Mitochondrial Pathways Underlying Adipose Organ Senescence

The adipose organ is involved in many metabolic functions, ranging from the production of endocrine factors to the regulation of thermogenic processes. Aging is a natural process that affects the physiology of the adipose organ, leading to metabolic disorders, thus strongly impacting healthy aging. Cellular senescence modifies many functional aspects of adipose tissue, leading to metabolic alterations through defective adipogenesis, inflammation, and aberrant adipocytokine production, and in turn, it triggers systemic inflammation and senescence, as well as insulin resistance in metabolically active tissues, leading to premature declined physiological features. In the various aging fat depots, senescence involves a multiplicity of cell types, including mature adipocytes and immune, endothelial, and progenitor cells that are aging, highlighting their involvement in the loss of metabolic flexibility, one of the common features of aging-related metabolic disorders. Since mitochondrial stress represents a key trigger of cellular senescence, and senescence leads to the accumulation of abnormal mitochondria with impaired dynamics and hindered homeostasis, this review focuses on the beneficial potential of targeting mitochondria, so that strategies can be developed to manage adipose tissue senescence for the treatment of age-related metabolic disorders.

m 6 A mRNA Methylation in Brown Adipose Tissue Regulates Systemic Insulin Sensitivity via an Inter-Organ Prostaglandin Signaling Axis

Brown adipose tissue (BAT) has the capacity to regulate systemic metabolism through the secretion of signaling lipids. N6-methyladenosine (m 6 A) is the most prevalent and abundant post-transcriptional mRNA modification and has been reported to regulate BAT adipogenesis and energy expenditure. In this study, we demonstrate that the absence of m 6 A methyltransferase-like 14 (METTL14), modifies the BAT secretome to initiate inter-organ communication to improve systemic insulin sensitivity. Importantly, these phenotypes are independent of UCP1-mediated energy expenditure and thermogenesis. Using lipidomics, we identified prostaglandin E2 (PGE2) and prostaglandin F2a (PGF2a) as M14 KO -BAT-secreted insulin sensitizers. Notably, circulatory PGE2 and PGF2a levels are inversely correlated with insulin sensitivity in humans. Furthermore, in vivo administration of PGE2 and PGF2a in high-fat diet-induced insulin-resistant obese mice recapitulates the phenotypes of METTL14 deficient animals. PGE2 or PGF2a improves insulin signaling by suppressing the expression of specific AKT phosphatases. Mechanistically, METTL14-mediated m 6 A installation promotes decay of transcripts encoding prostaglandin synthases and their regulators in human and mouse brown adipocytes in a YTHDF2/3-dependent manner. Taken together, these findings reveal a novel biological mechanism through which m 6 A-dependent regulation of BAT secretome regulates systemic insulin sensitivity in mice and humans.

Highlights

Mettl14 KO -BAT improves systemic insulin sensitivity via inter-organ communication; PGE2 and PGF2a are BAT-secreted insulin sensitizers and browning inducers;PGE2 and PGF2a sensitize insulin responses through PGE2-EP-pAKT and PGF2a-FP-AKT axis; METTL14-mediated m 6 A installation selectively destabilizes prostaglandin synthases and their regulator transcripts; Targeting METTL14 in BAT has therapeutic potential to enhance systemic insulin sensitivity.

Abstract Figure

[Adipocytes, adipokines and metabolic alterations in pulmonary fibrosis]

Idiopathic pulmonary fibrosis (IPF) is a fatal respiratory disease characterized by severe remodeling of the lung parenchyma, with an accumulation of activated myofibroblasts and extracellular matrix, along with aberrant cellular differentiation. Within the subpleural fibrous zones, ectopic adipocyte deposits often appear. In addition, alterations in lipid homeostasis have been associated with IPF pathophysiology. In this mini-review, we will discuss the potential involvement of the adipocyte secretome and its paracrine or endocrine-based contribution to the pathophysiology of IPF, via protein or lipid mediators in particular.

Harnessing prostaglandin E2 signaling to ameliorate autoimmunity

The etiology of most autoimmune diseases remains unknown; however, shared among them is a disruption of immunoregulation. Prostaglandin lipid signaling molecules possess context-dependent immunoregulatory properties, making their role in autoimmunity difficult to decipher. For example, prostaglandin E2 (PGE2) can function as an immunosuppressive molecule as well as a proinflammatory mediator in different circumstances, contributing to the expansion and activation of T cell subsets associated with autoimmunity. Recently, PGE2 was shown to play important roles in the resolution and post-resolution phases of inflammation, promoting return to tissue homeostasis. We propose that PGE2 plays both proinflammatory and pro-resolutory roles in the etiology of autoimmunity, and that harnessing this signaling pathway during the resolution phase might help prevent autoimmune attack.

Potential benefits of metformin and pioglitazone combination therapy via gut microbiota and metabolites in high-fat diet-fed mice

Metformin and pioglitazone monotherapy have been proven to alter gut microbiota in diabetes and obesity. The present study aimed to investigated whether the combined administration of pioglitazone and metformin achieved superior protective effects on high-fat diet (HFD)-fed obese mice and elucidated its molecular mechanism via the gut microbiota and its metabolites. C57BL/6 males were randomly divided into five groups: the control group, fed a normal control diet; the HFD group, fed an HFD; the metformin monotherapy group, fed an HFD and treated with metformin; the pioglitazone monotherapy group, fed an HFD and treated with pioglitazone; and the combination therapy group, fed an HFD and treated with metformin and pioglitazone combination therapy. The cecal contents were collected for 16S rDNA amplicon sequencing and untargeted metabolomics analysis. The results showed that the combination therapy of metformin and pioglitazone significantly improved insulin sensitivity and glucolipid metabolism in HFD-fed mice. Combination therapy markedly altered gut microbiota by increasing beneficial bacteria, such as Bifidobacterium, Christensenellaceae_R-7_group, Faecalibacterium and Roseburia, and decreasing harmful bacteria, such as Oscillibacter and Eubacterium_xylanophilum_group. Fecal metabolites were significantly changed in the combination therapy group, including a reduction in amino acid metabolism and augmentation of lipid metabolism, such as citrulline, sarcosine, D-glutamine, lipoxin A4, prostaglandin E2, stearidonic acid and lucidenic acid A. These results revealed that combined metformin and pioglitazone therapy had synergistic effects or at least have an additive effect on modifying gut microbiota and metabolites, closely associated with improved glucolipid metabolic parameters in HFD-fed mice, which provides novel evidence and promising targets for metformin and pioglitazone combination therapy in type 2 diabetes.

A Bibliometric and Visualization Analysis of Intermittent Fasting

CiteSpace software was utilized to visually analyze the literature on intermittent fasting from Web of Science from 2000 to 2020 in order to reveal the current status, research hotspots and emerging trends of intermittent fasting. The results show that: (1) intermittent fasting research results are increasing year by year; (2) the United States is at the core of this field and has a high influence; (3) intermittent fasting research is mainly concentrated in the fields of nutrition, cell biology and kinesiology, which embodies interdisciplinary characteristics; (4) the literature of Sutton, Mattson and Trepanowski that were published in the same period have the highest co-citation frequencies, however, their research perspectives are quite different, reflecting that the research in this field is still in a state of continuous development; (5) from the perspective of citation bursts, the evolution of research hotspots in this field in the last 20 years can be divided into 3 stages; (6) the keyword timeline mapping shows that time restricted feeding is at the forefront of this research field. This study can help researchers explore the field for the first time to quickly grasp the frontiers and obtain more valuable data, thereby providing facilitation for the follow-up research.

COX-2 Deficiency Promotes White Adipogenesis via PGE2-Mediated Paracrine Mechanism and Exacerbates Diet-Induced Obesity

Cyclooxygenase-2 (COX-2) plays a critical role in regulating innate immunity and metabolism by producing prostaglandins (PGs) and other lipid mediators. However, the implication of adipose COX-2 in obesity remains largely unknown. Using adipocyte-specific COX-2 knockout (KO) mice, we showed that depleting COX-2 in adipocytes promoted white adipose tissue development accompanied with increased size and number of adipocytes and predisposed diet-induced adiposity, obesity, and insulin resistance. The increased size and number of adipocytes by COX-2 KO were reversed by the treatment of prostaglandin E2 (PGE2) but not PGI2 and PGD2 during adipocyte differentiation. PGE2 suppresses PPARγ expression through the PKA pathway at the early phase of adipogenesis, and treatment of PGE2 or PKA activator isoproterenol diminished the increased lipid droplets in size and number in COX-2 KO primary adipocytes. Administration of PGE2 attenuated increased fat mass and fat percentage in COX-2 deficient mice. Taken together, our study demonstrated the suppressing effect of adipocyte COX-2 on adipogenesis and reveals that COX-2 restrains adipose tissue expansion via the PGE2-mediated paracrine mechanism and prevents the development of obesity and related metabolic disorders.