Structure-function of CD36 and importance of fatty acid signal transduction in fat metabolism

Cluster of Differentiation 36 (CD36) Preferentially Mediates Intestinal Absorption of Dietary Z-Astaxanthin and Especially 9-Z-Isomer via Higher Binding Affinity

Variances in the biological functions of astaxanthin geometric isomers (i.e., all-E, Z) are related to their intestinal absorption, but the mechanism of isomer absorption mediated by transporters remains unclear. Here, models of in vitro cell overexpression, in situ intestinal perfusion, and in vivo mouse inhibition were employed to investigate the impact of cluster of differentiation 36 (CD36) on the absorption of astaxanthin isomers. Cells overexpressing CD36 notably enhanced the uptake of Z-astaxanthin, particularly the 9-Z-isomer (47.76%). The absorption rate and permeability of Z-astaxanthin surpassed that of the all-E-isomer by the in situ model. Furthermore, the addition of the CD36-specific inhibitor sulfo-N-succinimidyl oleate significantly reduced the absorption of Z-astaxanthin in the mouse duodenum and jejunum, especially the 9-Z-isomer (57.66%). Molecular docking and surface plasmon resonance techniques further validated that 9-Z-astaxanthin binds to more amino acids of CD36 with higher affinity and in a fast-binding, fast-dissociating mode, thus favoring transport. Our findings elucidate, for the first time, the mechanism of the CD36-mediated transmembrane transport of astaxanthin geometric isomers.

Combined UPLC-QqQ-MS/MS and AP-MALDI Mass Spectrometry Imaging Method for Phospholipidomics in Obese Mouse Kidneys: Alleviation by Feeding Sea Cucumber Phospholipids

Sea cucumber phospholipids have ameliorative effects on various diseases related to lipid metabolism. However, it is unclear whether it can ameliorate obesity-associated glomerulopathy (ORG) induced by a high-fat diet (HFD). The present study applied UPLC-QqQ-MS/MS and atmospheric pressure matrix-assisted laser desorption ionization mass spectrometry imaging (AP-MALDI MSI) to investigate the effects of sea cucumber phospholipids, including plasmalogen PlsEtn and plasmanylcholine PakCho, on phospholipid profiles in the HFD-induced ORG mouse kidney. Quantitative analysis of 135 phospholipids revealed that PlsEtn and PakCho significantly modulated phospholipid levels. Notably, PlsEtn modulated kidney overall phospholipids better than PakCho. Imaging the "space-content" of 9 phospholipids indicated that HFD significantly increased phospholipid content within the renal cortex. Furthermore, PlsEtn and PakCho significantly decreased the expression of transport-related proteins CD36, while elevating the expression of fatty acid β-oxidation-related protein PPAR-α in the renal cortex. In conclusion, sea cucumber phospholipids reduced renal lipid accumulation, ameliorated renal damage, effectively regulated the content and distribution of renal phospholipids, and improved phospholipid homeostasis, exerting an anti-OGR effect.

CXCL16-dependent scavenging of oxidized lipids by islet macrophages promotes differentiation of pathogenic CD8+ T cells in diabetic autoimmunity

The pancreatic islet microenvironment is highly oxidative, rendering β cells vulnerable to autoinflammatory insults. Here, we examined the role of islet resident macrophages in the autoimmune attack that initiates type 1 diabetes. Islet macrophages highly expressed CXCL16, a chemokine and scavenger receptor for oxidized low-density lipoproteins (OxLDLs), regardless of autoimmune predisposition. Deletion of Cxcl16 in nonobese diabetic (NOD) mice suppressed the development of autoimmune diabetes. Mechanistically, Cxcl16 deficiency impaired clearance of OxLDL by islet macrophages, leading to OxLDL accumulation in pancreatic islets and a substantial reduction in intra-islet transitory (Texint) CD8+ T cells displaying proliferative and effector signatures. Texint cells were vulnerable to oxidative stress and diminished by ferroptosis; PD-1 blockade rescued this population and reversed diabetes resistance in NOD.Cxcl16-/- mice. Thus, OxLDL scavenging in pancreatic islets inadvertently promotes differentiation of pathogenic CD8+ T cells, presenting a paradigm wherein tissue homeostasis processes can facilitate autoimmune pathogenesis in predisposed individuals.

CD36: a promising therapeutic target in hematologic tumors

Cluster of differentiation 36 (CD36) is a multiligand receptor with important roles in lipid metabolism, angiogenesis and innate immunity, and its diverse effects may depend on the binding of specific ligands in different contexts. CD36 is expressed not only on immune cells in the tumor microenvironment (TME) but also on some hematopoietic cells. CD36 is associated with the growth, metastasis and drug resistance in some hematologic tumors, such as leukemia, lymphoma and myelodysplastic syndrome. Currently, some targeted therapeutic agents against CD36 have been developed, such as anti-CD36 antibodies, CD36 antagonists (small molecules) and CD36 expression inhibitors. This paper not only innovatively addresses the role of CD36 in some hematopoietic cells, such as erythrocytes, hematopoietic stem cells and platelets, but also pays special attention to the role of CD36 in the development of hematologic tumors, and suggests that CD36 may be a potential cancer therapeutic target in hematologic tumors.

SNMP1 is critical for sensitive detection of the desert locust aromatic courtship inhibition pheromone phenylacetonitrile

BACKGROUND

Accurate detection of pheromones is crucial for chemical communication and reproduction in insects. In holometabolous flies and moths, the sensory neuron membrane protein 1 (SNMP1) is essential for detecting long-chain aliphatic pheromones by olfactory neurons. However, its function in hemimetabolous insects and its role for detecting pheromones of a different chemical nature remain elusive. Therefore, we investigated the relevance of SNMP1 for pheromone detection in a hemimetabolous insect pest of considerable economic importance, the desert locust Schistocerca gregaria, which moreover employs the aromatic pheromone phenylacetonitrile (PAN) to govern reproductive behaviors.

RESULTS

Employing CRISPR/Cas-mediated gene editing, a mutant locust line lacking functional SNMP1 was established. In electroantennography experiments and single sensillum recordings, we found significantly decreased electrical responses to PAN in SNMP1-deficient (SNMP1-/-) locusts. Moreover, calcium imaging in the antennal lobe of the brain revealed a substantially reduced activation of projection neurons in SNMP1-/- individuals upon exposure to PAN, indicating that the diminished antennal responsiveness to PAN in mutants affects pheromone-evoked neuronal activity in the brain. Furthermore, in behavioral experiments, PAN-induced effects on pairing and mate choice were altered in SNMP1-/- locusts.

CONCLUSIONS

Our findings emphasize the importance of SNMP1 for chemical communication in a hemimetabolous insect pest. Moreover, they show that SNMP1 plays a crucial role in pheromone detection that goes beyond long-chain aliphatic substances and includes aromatic compounds controlling reproductive behaviors.

Protein-energy restriction-induced lipid metabolism disruption causes stable-to-progressive disease shift in Mycobacterium avium-infected female mice

BACKGROUND

Disease susceptibility and progression of Mycobacterium avium complex pulmonary disease (MAC-PD) is associated with multiple factors, including low body mass index (BMI). However, the specific impact of low BMI on MAC-PD progression remains poorly understood. This study aims to examine the progression of MAC-PD in the context of low BMI, utilising a disease-resistant mouse model.

METHODS

We employed a MAC infection-resistant female A/J mouse model to compare the progression of MAC-PD under two dietary conditions: one group was fed a standard protein diet, representing protein-energy unrestricted conditions, and the other was fed a low protein diet (LPD), representing protein-energy restriction.

FINDINGS

Our results reveal that protein-energy restriction significantly exacerbates MAC-PD progression by disrupting lipid metabolism. Mice fed an LPD showed elevated fatty acid levels and related gene expressions in lung tissues, similar to findings of increased fatty acids in the serum of patients who exhibited the MAC-PD progression. These mice also exhibited increased CD36 expression and lipid accumulation in macrophages upon MAC infection. In vitro experiments emphasised the crucial role of CD36-mediated palmitic acid uptake in bacterial proliferation. Importantly, in vivo studies demonstrated that administering anti-CD36 antibody to LPD-fed A/J mice reduced macrophage lipid accumulation and impeded bacterial growth, resulting in remarkable slowing disease progression.

INTERPRETATION

Our findings indicate that the metabolic status of host immune cells critically influences MAC-PD progression. This study highlights the potential of adequate nutrient intake in preventing MAC-PD progression, suggesting that targeting CD36-mediated pathways might be a host-directed therapeutic strategy to managing MAC infection.

FUNDING

This research was funded by the National Research Foundation of Korea, the Korea Research Institute of Bioscience and Biotechnology, and the Korea National Institute of Health.

O-GlcNAcylation promotes the progression of nonalcoholic fatty liver disease by upregulating the expression and function of CD36

BACKGROUND AND AIMS

Nonalcoholic fatty liver disease (NAFLD) and its progressive variant, nonalcoholic steatohepatitis (NASH), constitute a burgeoning worldwide epidemic with no FDA-approved pharmacotherapies. The multifunctional immunometabolic receptor, fatty acid translocase CD36 (CD36), plays an important role in the progression of hepatic steatosis. O-GlcNAcylation is a crucial posttranslational modification that mediates the distribution and function of CD36, but its involvement in NAFLD remains poorly understood.

METHODS

O-GlcNAcylation and CD36 expression were evaluated in human liver tissues obtained from NASH patients and normal control. Mice with hepatocyte-specific CD36 knockout were administered adeno-associated viral vectors expressing wild-type CD36 (WT-CD36) or CD36 O-GlcNAcylation site mutants (S468A&T470A-CD36) and were provided with a high-fat/high-cholesterol (HFHC) diet for 3 months. RT-qPCR analysis, immunoblotting, dual-luciferase reporter assays, chromatin immunoprecipitation, and coimmunoprecipitation were performed to explore the mechanisms by which O-GlcNAcylation regulates CD36 expression. Membrane protein extraction, immunofluorescence analysis, site-directed mutagenesis, and fatty acid uptake assays were conducted to elucidate the impact of O-GlcNAcylation on CD36 function.

RESULTS

O-GlcNAcylation and CD36 expression were significantly increased in patients with NASH, mouse models of NASH, and palmitic acid-stimulated hepatocytes. Mechanistically, the increase in O-GlcNAcylation facilitated the transcription of CD36 via the NF-κB signalling pathway and stabilized the CD36 protein by inhibiting its ubiquitination, thereby promoting CD36 expression. On the other hand, O-GlcNAcylation facilitated the membrane localization of CD36, fatty acid uptake, and lipid accumulation. However, site-directed mutagenesis of residues S468 and T470 of CD36 reversed these effects. Furthermore, compared with their WT-CD36 counterparts, HFHC-fed S468A&T470A-CD36 mice exhibited decreases in systemic insulin resistance, steatosis severity, inflammation and fibrosis. Pharmacological inhibition of O-GlcNAcylation and CD36 also mitigated the progression of NASH.

CONCLUSIONS

O-GlcNAcylation promotes the progression of NAFLD by upregulating CD36 expression and function. Inhibition of CD36 O-GlcNAcylation protects against NASH, highlighting a potentially effective therapeutic approach for individuals with NASH.

Cross-species transcriptomics identifies obesity associated genes between human and mouse studies

BACKGROUND

Fundamentally defined by an imbalance in energy consumption and energy expenditure, obesity is a significant risk factor of several musculoskeletal conditions including osteoarthritis (OA). High-fat diets and sedentary lifestyle leads to increased adiposity resulting in systemic inflammation due to the endocrine properties of adipose tissue producing inflammatory cytokines and adipokines. We previously showed serum levels of specific adipokines are associated with biomarkers of bone remodelling and cartilage volume loss in knee OA patients. Whilst more recently we find the metabolic consequence of obesity drives the enrichment of pro-inflammatory fibroblast subsets within joint synovial tissues in obese individuals compared to those of BMI defined 'health weight'. As such this present study identifies obesity-associated genes in OA joint tissues which are conserved across species and conditions.

METHODS

The study utilised 6 publicly available bulk and single-cell transcriptomic datasets from human and mice studies downloaded from Gene Expression Omnibus (GEO). Machine learning models were employed to model and statistically test datasets for conserved gene expression profiles. Identified genes were validated in OA tissues from obese and healthy weight individuals using quantitative PCR method (N = 38). Obese and healthy-weight patients were categorised by BMI > 30 and BMI between 18 and 24.9 respectively. Informed consent was obtained from all study participants who were scheduled to undergo elective arthroplasty.

RESULTS

Principal component analysis (PCA) was used to investigate the variations between classes of mouse and human data which confirmed variation between obese and healthy populations. Differential gene expression analysis filtered on adjusted p-values of p < 0.05, identified differentially expressed genes (DEGs) in mouse and human datasets. DEGs were analysed further using area under curve (AUC) which identified 12 genes. Pathway enrichment analysis suggests these genes were involved in the biosynthesis and elongation of fatty acids and the transport, oxidation, and catabolic processing of lipids. qPCR validation found the majority of genes showed a tendency to be upregulated in joint tissues from obese participants. Three validated genes, IGFBP2 (p = 0.0363), DOK6 (0.0451) and CASP1 (0.0412) were found to be significantly different in obese joint tissues compared to lean-weight joint tissues.

CONCLUSIONS

The present study has employed machine learning models across several published obesity datasets to identify obesity-associated genes which are validated in joint tissues from OA. These results suggest obesity-associated genes are conserved across conditions and may be fundamental in accelerating disease in obese individuals. Whilst further validations and additional conditions remain to be tested in this model, identifying obesity-associated genes in this way may serve as a global aid for patient stratification giving rise to the potential of targeted therapeutic interventions in such patient subpopulations.

Penthorum chinense Pursh extract ameliorates alcohol-related fatty liver disease in mice via the SIRT1/AMPK signaling axis

Penthorum chinense Pursh (P. chinense), a functional food, has been applied to protect the liver against alcohol-related fatty liver disease (ALD) for a long history in China. This study was designed to evaluate the ameliorative activity of the polyphenolic fraction in P. chinense (PGF) depending on the relief of ALD. The ALD mouse model was established by exposing the mice to a Lieber-DeCarli alcohol liquid diet. We found that PGF administration significantly ameliorated alcohol-induced liver injury, steatosis, oxidative stress, and inflammation in mice. Furthermore, alcohol-increased levels of the critical hepatic lipid synthesis proteins sterol regulatory element binding transcription factor (SREBP-1) and diacylglycerol o-acyltransferase 2 (DGAT2) were attenuated by PGF. Similarly, PGF inhibited the expression of the lipid transport protein very low-density lipoprotein receptor (VLDLR). Interestingly, PGF restored alcohol-inhibited expression of carnitine palmitoyltransferase 1 (CPT1) and peroxisome proliferator-activated receptor alpha (PPARα), essential fatty acid β-oxidation proteins. Mechanistic studies revealed that PGF protects against alcohol-induced hepatocyte injury and lipid deposition via the SIRT1/AMPK signaling pathway. In sum, this research clearly demonstrated the protective effects of PGF against ALD, which was mediated by activating SIRT1/AMPK pathways in hepatocytes. We provide a new theoretical basis for using P. chinense as a functional food in ALD.

Molecular mechanism of renal lipid accumulation in diabetic kidney disease

Diabetic kidney disease (DKD) is a leading cause of end stage renal disease with unmet clinical demands for treatment. Lipids are essential for cell survival; however, renal cells have limited capability to metabolize overloaded lipids. Dyslipidaemia is common in DKD patients and renal ectopic lipid accumulation is associated with disease progression. Unveiling the molecular mechanism involved in renal lipid regulation is crucial for exploring potential therapeutic targets. In this review, we focused on the mechanism underlying cholesterol, oxysterol and fatty acid metabolism disorder in the context of DKD. Specific regulators of lipid accumulation in different kidney compartment and TREM2 macrophages, a lipid-related macrophages in DKD, were discussed. The role of sodium-glucose transporter 2 inhibitors in improving renal lipid accumulation was summarized.

Interplay of CD36, autophagy, and lipid metabolism: insights into cancer progression

CD36, a scavenger receptor B2 that is dynamically distributed between cell membranes and organelle membranes, plays a crucial role in regulating lipid metabolism. Abnormal CD36 activity has been linked to a range of metabolic disorders, such as obesity, nonalcoholic fatty liver disease, insulin resistance and cardiovascular disease. CD36 undergoes various modifications, including palmitoylation, glycosylation, and ubiquitination, which greatly affect its binding affinity to various ligands, thereby triggering and influencing various biological effects. In the context of tumors, CD36 interacts with autophagy to jointly regulate tumorigenesis, mainly by influencing the tumor microenvironment. The central role of CD36 in cellular lipid homeostasis and recent molecular insights into CD36 in tumor development indicate the applicability of CD36 as a therapeutic target for cancer treatment. Here, we discuss the diverse posttranslational modifications of CD36 and their respective roles in lipid metabolism. Additionally, we delve into recent research findings on CD36 in tumors, outlining ongoing drug development efforts targeting CD36 and potential strategies for future development and highlighting the interplay between CD36 and autophagy in the context of cancer. Our aim is to provide a comprehensive understanding of the function of CD36 in both physiological and pathological processes, facilitating a more in-depth analysis of cancer progression and a better development and application of CD36-targeting drugs for tumor therapy in the near future.

The developmental pattern related to fatty acid uptake and oxidation in the yolk sac membrane and jejunum during embryogenesis in Muscovy duck

This study aimed to investigate the developmental change of body growth and gene expression related to fatty acid uptake and oxidation in the yolk sac membrane (YSM) and jejunum during embryogenesis in Muscovy ducks. The weights of embryos and yolk sac (YS) (5 embryos per replicate, n = 6) were recorded on embryonic days (E)16, E19, E22, E25, E28, E31, and the day of hatch (DOH). The fat and fatty acid contents in YSM, jejunal histology, and gene expression related to fatty acid metabolism in YSM and jejunum were determined in each sampling time. Among the nonlinear models, the maximum growth is estimated at 2.83 (E22.5), 2.67 (E22.1), and 2.60 (E21.3) g/d using logistic, Gompertz, and Von Bertalanffy models, respectively. The weight of YS, and ether extract-free YS as well as the amounts of fat and fatty acids in YS decreased (P < 0.05) linearly, whereas the villus height, crypt depth, villus height/crypt depth, and musculature thickness in jejunum increased (P < 0.05) linearly during embryogenesis. The mRNA expression of CD36, SLC27A4, and FABP1 related to fatty acid uptake as well as the mRNA and protein expressions of PPARα and CPT1 related to fatty acid oxidation increased in a quadratic manner (P < 0.05) in both YS and jejunum, and the maximum values were achieved during E25 to E28. In conclusion, the maximum growth rate of Muscovy duck embryos was estimated at 2.60 to 2.83 g/d on E21.3 to E23.5, while the accumulations of lipid and fatty acid in YS were decreased in association with the increased absorptive area of morphological structures in jejunum. The gene and protein expression involved in fatty acid metabolism displayed a similar enhancement pattern between YSM and jejunum during E25 to E28, suggesting that fatty acid utilization could be strengthened to meet the energy demand for embryonic development.

The function of CD36 in Mycobacterium tuberculosis infection

CD36 is a scavenger receptor that has been reported to function as a signaling receptor that responds to pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) and could integrate metabolic pathways and cell signaling through its dual functions. Thereby influencing activation to regulate the immune response and immune cell differentiation. Recent studies have revealed that CD36 plays critical roles in the process of lipid metabolism, inflammatory response and immune process caused by Mycobacterium tuberculosis infection. This review will comprehensively investigate CD36's functions in lipid uptake and processing, inflammatory response, immune response and therapeutic targets and biomarkers in the infection process of M. tuberculosis. The study also raised outstanding issues in this field to designate future directions.

Thbs1 regulates skeletal muscle mass in a TGFβ-Smad2/3-ATF4-dependent manner

Loss of muscle mass is a feature of chronic illness and aging. Here, we report that skeletal muscle-specific thrombospondin-1 transgenic mice (Thbs1 Tg) have profound muscle atrophy with age-dependent decreases in exercise capacity and premature lethality. Mechanistically, Thbs1 activates transforming growth factor β (TGFβ)-Smad2/3 signaling, which also induces activating transcription factor 4 (ATF4) expression that together modulates the autophagy-lysosomal pathway (ALP) and ubiquitin-proteasome system (UPS) to facilitate muscle atrophy. Indeed, myofiber-specific inhibition of TGFβ-receptor signaling represses the induction of ATF4, normalizes ALP and UPS, and partially restores muscle mass in Thbs1 Tg mice. Similarly, myofiber-specific deletion of Smad2 and Smad3 or the Atf4 gene antagonizes Thbs1-induced muscle atrophy. More importantly, Thbs1-/- mice show significantly reduced levels of denervation- and caloric restriction-mediated muscle atrophy, along with blunted TGFβ-Smad3-ATF4 signaling. Thus, Thbs1-mediated TGFβ-Smad3-ATF4 signaling in skeletal muscle regulates tissue rarefaction, suggesting a target for atrophy-based muscle diseases and sarcopenia with aging.

Lutein supplementation for early-life health and development: current knowledge, challenges, and implications

Macular carotenoids, which consist of lutein, zeaxanthin, and meso-zeaxanthin, are dietary antioxidants and macular pigments in the eyes, protecting the macula from light-induced oxidative stress. Lutein is also the main carotenoid in the infant brain and is involved in cognitive development. While a few articles reviewed the role of lutein in early health and development, the current review is the first that focuses on the outcomes of lutein supplementation, either provided to mothers or to infants. Additionally, lutein status and metabolism during pregnancy and lactation, factors that limit the potential application of lutein as a nutritional intervention, and solutions to overcome the limitation are also discussed. In brief, the lutein intake in pregnant and lactating women in the United States may not be optimal. Furthermore, preterm and formula-fed infants are known to have compromised lutein status compared to term and breast-fed infants, respectively. While lutein supplementation via both maternal and infant consumption improves lutein status in infants, the application of lutein as a nutritional intervention may be compromised by its low bioavailability. Various encapsulation techniques have been developed to enhance the delivery of lutein in adult animals or human but should be further evaluated in neonatal models.

Microcystin-RR promote lipid accumulation through CD36 mediated signal pathway and fatty acid uptake in HepG2 cells

Microcystins (MC)-RR is a significant analogue of MC-LR, which has been identified as a hepatotoxin capable of influencing lipid metabolism and promoting the progression of liver-related metabolic diseases. However, the toxicity and biological function of MC-RR are still not well understood. In this study, the toxic effects and its role in lipid metabolism of MC-RR were investigated in hepatoblastoma cells (HepG2cells). The results demonstrated that MC-RR dose-dependently reduced cell viability and induced apoptosis. Additionally, even at low concentrations, MC-RR promoted lipid accumulation through up-regulating levels of triglyceride, total cholesterol, phosphatidylcholines and phosphatidylethaolamine in HepG2 cells, with no impact on cell viability. Proteomics and transcriptomics analysis further revealed significant alterations in the protein and gene expression profiles in HepG2 cells treated with MC-RR. Bioinformatic analysis, along with subsequent validation, indicated the upregulation of CD36 and activation of the AMPK and PI3K/AKT/mTOR in response to MC-RR exposure. Finally, knockdown of CD36 markedly ameliorated MC-RR-induced lipid accumulation in HepG2 cells. These findings collectively suggest that MC-RR promotes lipid accumulation in HepG2 cells through CD36-mediated signal pathway and fatty acid uptake. Our findings provide new insights into the hepatotoxic mechanism of MC-RR.

6-Gingerol alleviates ectopic lipid deposition in skeletal muscle by regulating CD36 translocation and mitochondrial function

Ectopic lipid deposition (ELD) and mitochondrial dysfunction are common causes of metabolic disorders in humans. Consuming too much fructose can result in mitochondrial dysfunction and metabolic disorders. 6-Gingerol, the main component of ginger (Zingiber officinale Roscoe), has been proven to alleviate metabolic disorders. This study seeks to examine the effects of 6-gingerol on metabolic disorders caused by fructose and uncover the underlying molecular mechanisms. In this study, the results showed that 6-Gingerol ameliorated high-fructose-induced metabolic disorders. Moreover, it inhibited CD36 membrane translocation, increased CD36 expression in the mitochondria, and decreased the O-GlcNAc modification of CD36 and OGT expression in vitro and vivo. In addition, 6-Gingerol enhanced the performance of mitochondria in the skeletal muscle and boosted the respiratory capability of L6 myotubes. This study provides a theoretical basis and new insights for the development of lipid-lowering drugs in clinical practice.

Inhibition of Crif1 protects fatty acid-induced POMC neuron-like cell-line damage by increasing CPT-1 function

Hypothalamic proopiomelanocortin (POMC) neurons are sensors of signals that reflect the energy stored in the body. Inducing mild stress in proopiomelanocortin neurons protects them from the damage promoted by the consumption of a high-fat diet, mitigating the development of obesity; however, the cellular mechanisms behind these effects are unknown. Here, we induced mild stress in a proopiomelanocortin neuron cell line by inhibiting Crif1. In proopiomelanocortin neurons exposed to high levels of palmitate, the partial inhibition of Crif1 reverted the defects in mitochondrial respiration and ATP production; this was accompanied by improved mitochondrial fusion/fission cycling. Furthermore, the partial inhibition of Crif1 resulted in increased reactive oxygen species production, increased fatty acid oxidation, and reduced dependency on glucose for mitochondrial respiration. These changes were dependent on the activity of CPT-1. Thus, we identified a CPT-1-dependent metabolic shift toward greater utilization of fatty acids as substrates for respiration as the mechanism behind the protective effect of mild stress against palmitate-induced damage of proopiomelanocortin neurons.NEW & NOTEWORTHY Saturated fats can damage hypothalamic neurons resulting in positive energy balance, and this is mitigated by mild cellular stress; however, the mechanisms behind this protective effect are unknown. Using a proopiomelanocortin cell line, we show that under exposure to a high concentration of palmitate, the partial inhibition of the mitochondrial protein Crif1 results in protection due to a metabolic shift warranted by the increased expression and activity of the mitochondrial fatty acid transporter CPT-1.

PROSTATE CELL HETEROGENEITY AND CXCL17 UPREGULATION IN MOUSE STEROID HORMONE IMBALANCE

Benign prostatic hyperplasia (BPH) is a prevalent age-related condition often characterized by debilitating urinary symptoms. Its etiology is believed to stem from hormonal imbalance, particularly an elevated estradiol-to-testosterone ratio and chronic inflammation. Our previous studies using a mouse steroid hormone imbalance model identified a specific increase in macrophages that migrate and accumulate in the prostate lumen where they differentiate into lipid-laden foam cells in mice implanted with testosterone and estradiol pellets, but not in sham animals. The current study focused on further characterizing the cellular heterogeneity of the prostate in this model as well as identifying the specific transcriptomic signature of the recruited foam cells. Moreover, we aimed to identify the epithelia-derived signals that drive macrophage infiltration and luminal translocation. Male C57BL/6J mice were implanted with slow-release testosterone and estradiol pellets (T+E2) and harvested the ventral prostates two weeks later for scRNA-seq analysis, or performed sham surgery. We identified Ear2+ and Cd72+ macrophages that were elevated in response to steroid hormone imbalance, whereas a Mrc1+ resident macrophage population did not change. In addition, an Spp1+ foam cell cluster was almost exclusively found in T+E2 mice. Further markers of foam cells were also identified, including Gpnmb and Trem2, and GPNMB was confirmed as a novel histological marker with immunohistochemistry. Foam cells were also shown to express known pathological factors Vegf, Tgfb1, Ccl6, Cxcl16 and Mmp12. Intriguingly, a screen for chemokines identified the upregulation of epithelial-derived Cxcl17, a known monocyte attractant, in T+E2 prostates suggesting that it might be responsible for the elevated macrophage number as well as their translocation to the lumen. Our study identified macrophage subsets that respond to steroid hormone imbalance as well as further confirmed a potential pathological role of luminal foam cells in the prostate. These results underscore a pathological role of the identified prostate foam cells and suggests CXCL17-mediated macrophage migration as a critical initiating event.

Vitamin D3 Regulates Energy Homeostasis under Short-Term Fasting Condition in Zebrafish (Danio Rerio)

Vitamin D3 (VD3) is a steroid hormone that plays pivotal roles in pathophysiology, and 1,25(OH)2D3 is the most active form of VD3. In the current study, the crucial role of VD3 in maintaining energy homeostasis under short-term fasting conditions was investigated. Our results confirmed that glucose-depriving pathways were inhibited while glucose-producing pathways were strengthened in zebrafish after fasting for 24 or 48 h. Moreover, VD3 anabolism in zebrafish was significantly suppressed in a time-dependent manner under short-fasting conditions. After fasting for 24 or 48 h, zebrafish fed with VD3 displayed a higher gluconeogenesis level and lower glycolysis level in the liver, and the serum glucose was maintained at higher levels, compared to those fed without VD3. Additionally, VD3 augmented the expression of fatty acids (FAs) transporter cd36 and lipogenesis in the liver, while enhancing lipolysis in the dorsal muscle. Similar results were obtained in cyp2r1-/- zebrafish, in which VD3 metabolism is obstructed. Importantly, it was observed that VD3 induced the production of gut GLP-1, which is considered to possess a potent gluconeogenic function in zebrafish. Meanwhile, the gene expression of proprotein convertase subtilisin/kexin type 1 (pcsk1), a GLP-1 processing enzyme, was also induced in the intestine of short-term fasted zebrafish. Notably, gut microbiota and its metabolite acetate were involved in VD3-regulated pcsk1 expression and GLP-1 production under short-term fasting conditions. In summary, our study demonstrated that VD3 regulated GLP-1 production in zebrafish by influencing gut microbiota and its metabolite, contributing to energy homeostasis and ameliorating hypoglycemia under short-term fasting conditions.

Propofol and salvianolic acid A synergistically attenuated cardiac ischemia-reperfusion injury in diabetic mice via modulating the CD36/AMPK pathway

Background

Prevention of diabetic heart myocardial ischemia-reperfusion (IR) injury (MIRI) is challenging. Propofol attenuates MIRI through its reactive oxygen species scavenging property at high doses, while its use at high doses causes hemodynamic instability. Salvianolic acid A (SAA) is a potent antioxidant that confers protection against MIRI. Both propofol and SAA affect metabolic profiles through regulating Adenosine 5'-monophosphate-activated protein kinase (AMPK). The aim of this study was to investigate the protective effects and underlying mechanisms of low doses of propofol combined with SAA against diabetic MIRI.

Methods

Diabetes was induced in mice by a high-fat diet followed by streptozotocin injection, and MIRI was induced by coronary artery occlusion and reperfusion. Mice were treated with propofol at 46 mg/kg/h without or with SAA at 10 mg/kg/h during IR. Cardiac origin H9c2 cells were exposed to high glucose (HG) and palmitic acid (PAL) for 24 h in the absence or presence of cluster of differentiation 36 (CD36) overexpression or AMPK gene knockdown, followed by hypoxia/reoxygenation (HR) for 6 and 12 h.

Results

Diabetes-exacerbated MIRI is evidenced as significant increases in post-ischemic infarction with reductions in phosphorylated (p)-AMPK and increases in CD36 and ferroptosis. Propofol moderately yet significantly attenuated all the abovementioned changes, while propofol plus SAA conferred superior protection against MIRI to that of propofol. In vitro, exposure of H9c2 cells under HG and PAL decreased cell viability and increased oxidative stress that was concomitant with increased levels of ferroptosis and a significant increase in CD36, while p-AMPK was significantly reduced. Co-administration of low concentrations of propofol and SAA at 12.5 μM in H9c2 cells significantly reduced oxidative stress, ferroptosis and CD36 expression, while increasing p-AMPK compared to the effects of propofol at 25 μM. Moreover, either CD36 overexpression or AMPK silence significantly exacerbated HR-induced cellular injuries and ferroptosis, and canceled propofol- and SAA-mediated protection. Notably, p-AMPK expression was downregulated after CD36 overexpression, while AMPK knockdown did not affect CD36 expression.

Conclusions

Combinational usage of propofol and SAA confers superior cellular protective effects to the use of high-dose propofol alone, and it does so through inhibiting HR-induced CD36 overexpression to upregulate p-AMPK.

Extracellular vesicles-coupled miRNAs from oviduct and uterus modulate signaling pathways related to lipid metabolism and bovine early embryo development

BACKGROUND

Extracellular vesicles (EVs) present in oviductal (OF) and uterine fluid (UF) have been shown to enhance bovine embryo quality during in vitro culture by reducing lipid contents and modulating lipid metabolism-related genes (LMGs), while also influencing cell proliferation, suggesting their involvement on the regulation of different biological pathways. The regulation of signaling pathways related to cell differentiation, proliferation, and metabolism is crucial for early embryo development and can determine the success or failure of the pregnancy. Bioactive molecules within EVs in maternal reproductive fluids, such as microRNAs (miRNAs), may contribute to this regulatory process as they modulate gene expression through post-transcriptional mechanisms.

RESULTS

From the 20 differentially expressed miRNAs, 19 up-regulated in UF-EVs (bta-miR-134, bta-miR-151-3p, bta-miR-155, bta-miR-188, bta-miR-181b, bta-miR-181d, bta-miR-224, bta-miR-23b-3p, bta-miR-24-3p, bta-miR-27a-3p, bta-miR-29a, bta-miR-324, bta-miR-326, bta-miR-345-3p, bta-miR-410, bta-miR-652, bta-miR-677, bta-miR-873 and bta-miR-708) and one (bta-miR-148b) in OF-EVs. These miRNAs were predicted to modulate several pathways such as Wnt, Hippo, MAPK, and lipid metabolism and degradation. Differences in miRNAs found in OF-EVs from the early luteal phase and UF-EVs from mid-luteal phase may reflect different environments to meet the changing needs of the embryo. Additionally, miRNAs may be involved, particularly in the uterus, in the regulation of embryo lipid metabolism, immune system, and implantation. This study evaluated miRNA cargo in OF-EVs from the early luteal phase and UF-EVs from the mid-luteal phase, coinciding with embryo transit within oviduct and uterus in vivo, and its possible influence on LMGs and signaling pathways crucial for early embryo development. A total of 333 miRNAs were detected, with 11 exclusive to OF, 59 to UF, and 263 were common between both groups.

CONCLUSIONS

Our study suggests that miRNAs within OF- and UF-EVs could modulate bovine embryo development and quality, providing insights into the intricate maternal-embryonic communication that might be involved in modulating lipid metabolism, immune response, and implantation during early pregnancy.

Whole-body deletion of Endospanin 1 protects from obesity-associated deleterious metabolic alterations

The importance of the proper localization of most receptors at the cell surface is often underestimated, although this feature is essential for optimal receptor response. Endospanin 1 (Endo1) (also known as OBRGRP or LEPROT) is a protein generated from the same gene as the human leptin receptor and regulates the trafficking of proteins to the surface, including the leptin receptor. The systemic role of Endo1 on whole-body metabolism has not been studied so far. Here, we report that general Endo1-KO mice fed a high-fat diet develop metabolically healthy obesity with lipid repartitioning in organs and preferential accumulation of fat in adipose tissue, limited systematic inflammation, and better controlled glucose homeostasis. Mechanistically, Endo1 interacts with the lipid translocase CD36, thus regulating its surface abundance and lipid uptake in adipocytes. In humans, the level of Endo1 transcripts is increased in the adipose tissue of patients with obesity, but low levels rather correlate with a profile of metabolically healthy obesity. We suggest here that Endo1, most likely by controlling CD36 cell surface abundance and lipid uptake in adipocytes, dissociates obesity from diabetes and that its absence participates in metabolically healthy obesity.

Targeting the lipid metabolic reprogramming of tumor-associated macrophages: A novel insight into cancer immunotherapy

BACKGROUND

Tumor-associated macrophages, as the major immunocytes in solid tumors, show divided loyalty and remarkable plasticity in tumorigenesis. Once the M2-to-M1 repolarization is achieved, they could be switched from the supporters for tumor development into the guardians for host immunity. Meanwhile, Lipid metabolic reprogramming is demonstrated to be one of the most important hallmarks of tumor-associated macrophages, which plays a decisive role in regulating their phenotypes and functions to promote tumorigenesis and immunotherapy resistance. Therefore, targeting the lipid metabolism of TAMs may provide a new direction for anti-tumor strategies.

CONCLUSION

In this review, we first summarized the origins, classifications and general lipid metabolic process of TAMs. Then we discussed the currently available drugs and interventions that target lipid metabolic disorders of TAMs, including those targeting lipid uptake, efflux, lipolysis, FAO and lipid peroxidation. Besides, based on the recent research status, we summarized the present challenges for this cancer immunotherapy, including the precise drug delivery system, the lipid metabolic heterogeneity, and the intricate lipid metabolic interactions in the TME, and we also proposed corresponding possible solutions. Collectively, we hope this review will give researchers a better understanding of the lipid metabolism of TAMs and lead to the development of corresponding anti-tumor therapies in the future.

Pioglitazone, a peroxisome proliferator‑activated receptor γ agonist, induces cell death and inhibits the proliferation of hypoxic HepG2 cells by promoting excessive production of reactive oxygen species

Hypoxia is a hallmark of solid tumors. Hypoxic cancer cells adjust their metabolic characteristics to regulate the production of cellular reactive oxygen species (ROS) and facilitate ROS-mediated metastasis. Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor that regulates the transcription of fatty acid metabolism-related genes that have a key role in the survival and proliferation function of hypoxic cancer cells. In the present study, mRNA expression in HepG2 cells under chemically induced hypoxia was assessed. The protein expression levels of hypoxia-inducible factor 1α (HIF-1α) were measured using western blotting. Following treatment with the PPARγ agonist pioglitazone, cell viability was assessed using a Cell Counting Kit-8 assay, whilst cell proliferation and death were determined using 5-ethynyl-2'-deoxyuridine incorporation staining, and calcein-acetoxymethyl ester and propidium iodide staining, respectively. Cellular ROS production was assessed using dihydroethidium staining. Cobalt chloride was used to induce hypoxia in HepG2 cells, which was evaluated using HIF-1α expression. The results revealed that the mRNA expression of PPARγ, CD36, acetyl-co-enzyme A dehydrogenase (ACAD) medium chain (ACADM) and ACAD short-chain (ACADS) was downregulated in hypoxic HepG2 cells. The PPARγ agonist pioglitazone decreased the cell viability of hypoxic HepG2 cells by inhibiting cell proliferation and inducing cell death. Following treatment with the PPARγ agonist pioglitazone, hypoxic HepG2 cells produced excessive ROS. ROS-mediated cell death induced by the PPARγ agonist pioglitazone was rescued with the antioxidant N-acetyl-L-cysteine. The downregulated mRNA expression of PPARγ, CD36, ACADM and ACADS was not reverted by a PPARγ agonist in hypoxic HepG2 cells. By contrast, the PPARγ agonist suppressed the mRNA expression of BCL2, which was upregulated in hypoxic HepG2 cells. In summary, the PPARγ agonist stimulated excessive ROS production to inhibit cell proliferation and increase the death of hypoxic HepG2 cells by decreasing BCL2 mRNA expression, suggesting a negative association between PPARγ and BCL2 in the regulation of ROS production in hypoxic HepG2 cells.

Proteomics study of bone tissue around ameloblastoma and the potential mechanism of CD36 in bone remodelling

Ameloblastoma (AM) is characterised by local aggressiveness and bone resorption. To our knowledge, the proteomic profile of bone adjacent to AM has not previously been explored. We therefore looked at the differential proteins in cancellous bone (CB) adjacent to AM and normal CB from the mandible. CB proteins were extracted, purified, quantified, and analysed by liquid chromatography-mass spectrometry (LC-MS) using samples from five patients with AM. These proteins were further investigated using gene ontology for additional functional annotation and enrichment. Proteins that met the screening requirements of expression difference ploidy > 1.5-fold (upregulation and downregulation) and p < 0.05 were subsequently deemed differential proteins. Immunohistochemical staining was performed to confirm the above findings. Compared with normal mandibular CB, 151 differential proteins were identified in CB adjacent to the mandibular AM. These were mainly linked to cellular catabolic processes, lipid metabolism, and fatty acids (FA) metabolism. LC-MS and immunohistochemistry showed that CD36 was one of the notably decreased proteins in CB bordering the AM compared with normal mandibular CB (p = 0.0066 and p = 0.0095, respectively). CD36 expression in CB correlates with bone remodelling in AM, making CD36 a viable target for therapeutic approaches.

Impacts of the vegetable Urtica dioica on the intestinal T and B cell phenotype and macronutrient absorption in C57BL/6J mice with diet-induced obesity

In two previous studies, we showed that supplementing a high-fat (HF) diet with 9% w/w U. dioica protects against fat accumulation, insulin resistance, and dysbiosis. This follow-up study in C57BL6/J mice aimed at testing: (i) the efficacy of the vegetable at lower doses: 9%, 4%, and 2%, (ii) the impact on intestinal T and B cell phenotype and secretions, (iii) impact on fat and glucose absorption during excess nutrient provision. At all doses, the vegetable attenuated HF diet induced fat accumulation in the mesenteric, perirenal, retroperitoneal fat pads, and liver but not the epididymal fat pad. The 2% dose protected against insulin resistance, prevented HF diet-induced decreases in intestinal T cells, and IgA+ B cells and activated T regulatory cells (Tregs) when included both in the LF and HF diets. Increased Tregs correlated with reduced inflammation; prevented increases in IL6, IFNγ, and TNFα in intestine but not expression of TNFα in epididymal fat pad. Testing of nutrient absorption was performed in enteroids. Enteroids derived from mice fed the HF diet supplemented with U. dioica had reduced absorption of free fatty acids and glucose compared to enteroids from mice fed the HF diet only. In enteroids, the ethanolic extract of U. dioica attenuated fat absorption and downregulated the expression of the receptor CD36 which facilitates uptake of fatty acids. In conclusion, including U. dioica in a HF diet, attenuates fat accumulation, insulin resistance, and inflammation. This is achieved by preventing dysregulation of immune homeostasis and in the presence of excess fat, reducing fat and glucose absorption.

Lipid Droplets: Formation, Degradation, and Their Role in Cellular Responses to Flavivirus Infections

Lipid droplets (LDs) are cellular organelles derived from the endoplasmic reticulum (ER), serving as lipid storage sites crucial for maintaining cellular lipid homeostasis. Recent attention has been drawn to their roles in viral replication and their interactions with viruses. However, the precise biological functions of LDs in viral replication and pathogenesis remain incompletely understood. To elucidate the interaction between LDs and viruses, it is imperative to comprehend the biogenesis of LDs and their dynamic interactions with other organelles. In this review, we explore the intricate pathways involved in LD biogenies within the cytoplasm, encompassing the uptake of fatty acid from nutrients facilitated by CD36-mediated membranous protein (FABP/FATP)-FA complexes, and FA synthesis via glycolysis in the cytoplasm and the TCL cycle in mitochondria. While LD biogenesis primarily occurs in the ER, matured LDs are intricately linked to multiple organelles. Viral infections can lead to diverse consequences in terms of LD status within cells post-infection, potentially involving the breakdown of LDs through the activation of lipophagy. However, the exact mechanisms underlying LD destruction or accumulation by viruses remain elusive. The significance of LDs in viral replication renders them effective targets for developing broad-spectrum antivirals. Moreover, considering that reducing neutral lipids in LDs is a strategy for anti-obesity treatment, LD depletion may not pose harm to cells. This presents LDs as promising antiviral targets for developing therapeutics that are minimally or non-toxic to the host.

The role of vitamin E in polyunsaturated fatty acid synthesis and alleviating endoplasmic reticulum stress in sub-adult grass carp (Ctenopharyngodon idella)

Vitamin E (VE) is an essential lipid-soluble vitamin that improves the fish flesh quality. However, the underlying molecular mechanisms remain unclear. This study aimed to investigate the effects of VE on growth performance and flesh quality in sub-adult grass carp (Ctenopharyngodon idella). A total of 450 fish (713.53 ± 1.50 g) were randomly divided into six treatment groups (three replicates per treatment) and fed for nine weeks with different experimental diets (dietary lipid 47.8 g/kg) that contained different levels of VE (5.44, 52.07, 96.85, 141.71, 185.66, and 230.12 mg/kg diet, supplemented as dl-α-tocopherol acetate). Notably, the treatment groups that were fed with dietary VE ranging from 52.07 to 230.12 mg/kg diet showed improvement in the percent weight gain, special growth rate, and feed efficiency of grass carp. Moreover, the treatment groups supplemented with dietary VE level of 141.71, 185.66, and 230.12 mg/kg diet showed enhancement in crude protein, lipid, and α-tocopherol contents in the muscle, and the dietary levels of VE ranging from 52.07 to 141.71 mg/kg diet improved muscle pH24h and shear force but reduced muscle cooking loss in grass carp. Furthermore, appropriate levels of VE (52.07 to 96.85 mg/kg diet) increased the muscle polyunsaturated fatty acid content in grass carp. Dietary VE also increased the mRNA levels of fatty acid synthesis-related genes, including fas, scd-1, fad, elovl, srebp1, pparγ, and lxrα, and up-regulated the expression of SREBP-1 protein. However, dietary VE decreased the expression of fatty acid decomposition-related genes, including hsl, cpt1, acox1, and pparα, and endoplasmic reticulum stress-related genes, including perk, ire1, atf6, eif2α, atf4, xbp1, chop, and grp78, and down-regulated the expression of p-PERK, p-IRE1, ATF6, and GRP78 proteins. In conclusion, dietary VE increased muscle fatty acid synthesis, which may be partly associated with the alleviation of endoplasmic reticulum stress, and ultimately improves fish flesh quality. Moreover, the VE requirements for sub-adult grass carp (713.53 to 1590.40 g) were estimated to be 124.9 and 122.73 mg/kg diet based on percentage weight gain and muscle shear force, respectively.

The regulatory role of CD36 in hematopoiesis beyond fatty acid uptake

CD36 is a transmembrane glycoprotein, located on surface of numerous cell types. This review is aimed to explore regulatory role of CD36 in hematopoiesis beyond fatty acid uptake. CD36 acts as a pattern recognition receptor, regulates cellular fatty acid homeostasis, and negatively monitors angiogenesis. CD36 also mediates free fatty acid transportation to hematopoietic stem cells in response to infections. During normal physiology and pathophysiology, CD36 significantly participates in the activation and metabolic needs of platelets, macrophages, monocytes, T cells, B cells, and dendritic cells. CD36 has shown a unique relationship with Plasmodium falciparum-infected erythrocytes (PfIEs) as a beneficiary for both parasite and host. CD36 actively participates in pathogenesis of various hematological cancers as a significant prognostic biomarker including AML, HL, and NHL. CD36-targeting antibodies, CD36 antagonists (small molecules), and CD36 expression inhibitors/modulators are used to target CD36, depicting its therapeutic potential. Many preclinical studies or clinical trials were performed to assess CD36 as a therapeutic target; some are still under investigation. This review reflects the role of CD36 in hematopoiesis which requires more consideration in future research.

Dynamic palmitoylation of STX11 controls injury-induced fatty acid uptake to promote muscle regeneration

Different types of cells uptake fatty acids in response to different stimuli or physiological conditions; however, little is known about context-specific regulation of fatty acid uptake. Here, we show that muscle injury induces fatty acid uptake in muscle stem cells (MuSCs) to promote their proliferation and muscle regeneration. In humans and mice, fatty acids are mobilized after muscle injury. Through CD36, fatty acids function as both fuels and growth signals to promote MuSC proliferation. Mechanistically, injury triggers the translocation of CD36 in MuSCs, which relies on dynamic palmitoylation of STX11. Palmitoylation facilitates the formation of STX11/SNAP23/VAMP4 SANRE complex, which stimulates the fusion of CD36- and STX11-containing vesicles. Restricting fatty acid supply, blocking fatty acid uptake, or inhibiting STX11 palmitoylation attenuates muscle regeneration in mice. Our studies have identified a critical role of fatty acids in muscle regeneration and shed light on context-specific regulation of fatty acid sensing and uptake.

The Molecular and Functional Characterization of Sensory Neuron Membrane Protein 1b (SNMP1b) from Cyrtotrachelus buqueti (Coleoptera: Curculionidae)

Sensory neuron membrane proteins (SNMPs) play important roles in insect chemoreception and SNMP1s have been reported to be essential in detecting sex pheromones in Drosophila and some lepidopteran species. However, SNMPs for Cyrtotrachelus buqueti (Coleoptera: Curculionidae), a major insect pest of bamboo plantations, remain uncharacterized. In this study, a novel SNMP gene, CbuqSNMP1b, from C. buqueti was functionally characterized. The expression of CbuqSNMP1b was significantly higher in antennae than in other tissues of both sexes and the expression level was significantly male-biased. Additionally, CbuqSNMP1b showed significantly higher transcription levels in the adult stage and very low transcription levels in other stages, suggesting that CbuqSNMP1b is involved in the process of olfaction. Fluorescence binding assays indicated that CbuqSNMP1b displayed the strongest binding affinity to dibutyl phthalate (Ki = 9.03 μM) followed by benzothiazole (Ki = 11.59 μM) and phenol (Ki = 20.95 μM) among fourteen C. buqueti volatiles. Furthermore, molecular docking revealed key residues in CbuqSNMP1b that interact with dibutyl phthalate, benzothiazole, and phenol. In conclusion, these findings will lay a foundation to further understand the olfactory mechanisms of C. buqueti and promote the development of novel methods for controlling this pest.

Metabolism-related signalling pathways involved in the pathogenesis and development of metabolic dysfunction-associated steatotic liver disease

Metabolic dysfunction-associated steatotic liver disease (MASLD) which formerly known as non-alcoholic fatty liver disease (NAFLD) is one of the causes of liver cirrhosis. Currently, a growing number of liver cirrhosis cases develop on the basis of MASLD, and the pathogenesis of MASLD remains unclear. This paper reviews the research progress on the involvement of different metabolism-related signalling pathways in the pathogenesis and development of MASLD.

Nrf2 inhibition regulates intracellular lipid accumulation in mouse insulinoma cells and improves insulin secretory function

High amount of fat in the pancreas is linked to poor functioning of β-cells and raises the risk of type 2 diabetes. Here we report the putative role of a circulatory glycoprotein Fetuin-A, a known obesity marker, in promoting lipid accumulation in β-cells and its association with Fatty acid translocase/CD36 for lipid storage culminate in β-cell dysfunction. Additionally, this work reveals regulation of CD36 via Nrf2, a key regulator of oxidative stress, and reduction of lipid accumulation by suppression of Nrf2 that restores β-cell function. Palmitate (0.50 mM) and Fetuin-A (100 μg/mL) exposure showed high levels of intracellular lipid in MIN6 (mouse insulinoma cells) with a concomitant decrease in insulin secretion. This also increased the expression of important lipogenic factors, like CD36, PGC1α, PPARγ, and SREBP1. Flow cytometry analysis of CD36 membrane localization has been corroborated with an increased accumulation of lipids as indicated by Oil-Red-O staining. Immunoblotting and immunofluorescence of Nrf2 indicated its high expression in palmitate-fetuin-A incubation and translocation in the nucleus. Suppression of Nrf2 by siRNA showed a reduced expression of lipogenic genes, ablation of lipid droplets, decrease in the number of apoptotic cells, and restoration of insulin secretion with a corresponding increase of Pdx1, BETA2, and Ins1 gene expression. Our study thus suggested an important aspect of lipid accumulation in the pancreatic β-cells contributing to β-cell dysfunction and demonstrated the role of Fetuin-A in CD36 expression, with a possible way of restoring β-cell function by targeting Nrf2.

CD36 polymorphism, sugary drinks, and sedentarism are associated with hypertriglyceridemic waist phenotype

Background: The hypertriglyceridemic waist (HTGW) phenotype is characterized by concomitant increases in waist circumference (WC) and blood triglyceride levels (TG), which have been identified as a predictor of metabolic disorders. This study aimed to analyze associations between food consumption, exercise, and the CD36 gene rs1761667 G>A polymorphism with the HTGW phenotype in adult Mexicans. Methods: This cross-sectional study included a total of 255 participants (both genders, between 18-64 years of age). The HTGW phenotype was defined as WC >88 cm in women, WC >102 cm in men, and TG >150 mg/dL. Body composition was analyzed by electrical bioimpedance. Dietary intakes (macro and micronutrients) were evaluated through a validated 64-item food frequency questionnaire and a 24-h recall. Physical exercise was subjectively recorded asking the participants if they regularly performed some systematic exercise or sport of moderate intensity at least 150-300 minutes a week. Biochemical tests were determined by an automated system. A Taqman real-time assay was used to detect the rs1761667 (G>A) polymorphism of the CD36 gene. A multivariate logistic regression model was performed to analyze the variables potentially associated with the HTGW phenotype (adjusted for age, energy intake, and total fat mass). Results: Overall, 21.6% of the population presented the HTGW phenotype; compared to the HTGW-, also, they were older, had more body fat, higher glucose, cholesterol and insulin levels, and high blood pressure. Female sex (OR=2.92, 95% CI: 1.12-7.60, p=0.028), body mass index (OR=1.19, 95% CI: 1.07-1.32, p=0.001), total cholesterol (OR=1.01, 95% CI:1.00-1.02, p=0.039), daily consumption of sugary drinks (OR=6.94, 95% CI: 1.80-26.8, p=0.005), and the CD36 AG genotype (OR=3.81, 95% CI: 1.08-13.4, p=0.037) were positively associated with the HTGW phenotype, while performing exercise played a protective role (OR=0.23, 95% CI: 0.08-0.62, p=0.004). Overall, the model predicted the HTGW phenotype in 47% (R2=0.47, p≤0.001). Conclusion: The CD36 AG genotype, daily consumption of sugary drinks and sedentarism are risk factors for the HTGW phenotype in Mexicans.

Image-guided metabolomics and transcriptomics reveal tumour heterogeneity in luminal A and B human breast cancer beyond glucose tracer uptake

BACKGROUND

Breast cancer is a metabolically heterogeneous disease, and although the concept of heterogeneous cancer metabolism is known, its precise role in human breast cancer is yet to be fully elucidated.

METHODS

We investigated in an explorative approach a cohort of 42 primary mamma carcinoma patients with positron emission tomography/magnetic resonance imaging (PET/MR) prior to surgery, followed by histopathology and molecular diagnosis. From a subset of patients, which showed high metabolic heterogeneity based on tracer uptake and pathology classification, tumour centre and periphery specimen tissue samples were further investigated by a targeted breast cancer gene expression panel and quantitative metabolomics by nuclear magnetic resonance (NMR) spectroscopy. All data were analysed in a combinatory approach.

RESULTS

[18 F]FDG (2-deoxy-2-[fluorine-18]fluoro-d-glucose) tracer uptake confirmed dominance of glucose metabolism in the breast tumour centre, with lower levels in the periphery. Additionally, we observed differences in lipid and proliferation related genes between luminal A and B subtypes in the centre and periphery. Tumour periphery showed elevated acetate levels and enrichment in lipid metabolic pathways genes especially in luminal B. Furthermore, serine was increased in the periphery and higher expression of thymidylate synthase (TYMS) indicated one-carbon metabolism increased in tumour periphery. The overall metabolic activity based on [18 F]FDG uptake of luminal B subtype was higher than that of luminal A and the difference between the periphery and centre increased with tumour grade.

CONCLUSION

Our analysis indicates variations in metabolism among different breast cancer subtypes and sampling locations which details the heterogeneity of the breast tumours. Correlation analysis of [18 F]FDG tracer uptake, transcriptome and tumour metabolites like acetate and serine facilitate the search for new candidates for metabolic tracers and permit distinguishing luminal A and B. This knowledge may help to differentiate subtypes preclinically or to provide patients guide for neoadjuvant therapy and optimised surgical protocols based on individual tumour metabolism.

Biochemical Aspects That Lead to Abusive Use of Trimetazidine in Performance Athletes: A Mini-Review

Trimetazidine (TMZ), used for treating stable angina pectoris, has garnered attention in the realm of sports due to its potential performance-enhancing properties, and the World Anti-Doping Agency (WADA) has classified TMZ on the S4 list of prohibited substances since 2014. The purpose of this narrative mini-review is to emphasize the biochemical aspects underlying the abusive use of TMZ among athletes as a metabolic modulator of cardiac energy metabolism. The myocardium's ability to adapt its energy substrate utilization between glucose and fatty acids is crucial for maintaining cardiac function under various conditions, such as rest, moderate exercise, and intense effort. TMZ acts as a partial inhibitor of fatty acid oxidation by inhibiting 3-ketoacyl-CoA thiolase (KAT), shifting energy production from long-chain fatty acids to glucose, reducing oxygen consumption, improving cardiac function, and enhancing exercise capacity. Furthermore, TMZ modulates pyruvate dehydrogenase (PDH) activity, promoting glucose oxidation while lowering lactate production, and ultimately stabilizing myocardial function. TMZs role in reducing oxidative stress is notable, as it activates antioxidant enzymes like glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD). In conclusion, TMZs biochemical mechanisms make it an attractive but controversial option for athletes seeking a competitive edge.

Inside anticancer therapy resistance and metastasis. Focus on CD36

Despite recent advances in targeted cancer therapies, drug resistance remains an important setback in tumor control. Understanding the complex mechanisms involved in both innate and acquired drug resistance represents the first step in discovering novel therapeutic agents. Because of its importance in tumorigenesis, progression, and metastasis, lipid metabolism is increasingly garnering attention. CD36 is a membrane receptor at the top of the signaling cascade that transports lipids. Its expression has been repeatedly presented as an unfavorable prognostic factor for various tumor types, raising the question: could CD36 be a critical factor in cancer treatment resistance? In our review, we set out to explore the most prominent studies on the implication of CD36 in resistance to platinum-based drugs and other adjuvant cancer therapies in solid and haematological neoplasia. Moreover, we provide an overview of the latest anti-CD36 cancer therapies, thus opening new perspectives for future personalized medicine.

CD36: The Bridge between Lipids and Tumors

It has been found that the development of some cancers can be attributed to obesity, which is associated with the excessive intake of lipids. Cancer cells undergo metabolic reprogramming, shifting from utilizing glucose to fatty acids (FAs) for energy. CD36, a lipid transporter, is highly expressed in certain kinds of cancer cells. High expressions of CD36 in tumor cells triggers FA uptake and lipid accumulation, promoting rapid tumor growth and initiating metastasis. Meanwhile, immune cells in the tumor microenvironment overexpress CD36 and undergo metabolic reprogramming. CD36-mediated FA uptake leads to lipid accumulation and has immunosuppressive effects. This paper reviews the types of FAs associated with cancer, high expressions of CD36 that promote cancer development and progression, effects of CD36 on different immune cells in the tumor microenvironment, and the current status of CD36 as a therapeutic target for the treatment of tumors with high CD36 expression.

p53 suppresses lipid droplet-fueled tumorigenesis through phosphatidylcholine

Choline deficiency causes disorders including hepatic abnormalities and is associated with an increased risk of multiple types of cancer. Here, by choline-free diet-associated RNA-Seq analyses, we found that the tumor suppressor p53 drives the Kennedy pathway via PCYT1B to control the growth of lipid droplets (LDs) and their fueling role in tumorigenesis. Mechanistically, through upregulation of PCYT1B, p53 channeled depleted choline stores to phosphatidylcholine (PC) biosynthesis during choline starvation, thus preventing LD coalescence. Cells lacking p53 failed to complete this response to choline depletion, leading to hepatic steatosis and tumorigenesis, and these effects could be reversed by enforcement of PCYT1B expression or restoration of PC abundance. Furthermore, loss of p53 or defects in the Kennedy pathway increased surface localization of hormone-sensitive lipase on LDs to release specific fatty acids that fueled tumor cells in vivo and in vitro. Thus, p53 loss leads to dysregulation of choline metabolism and LD growth and couples perturbed LD homeostasis to tumorigenesis.

Role of Natural Compounds Modulating Heme Catabolic Pathway in Gut, Liver, Cardiovascular, and Brain Diseases

The crucial physiological process of heme breakdown yields biliverdin (BV) and bilirubin (BR) as byproducts. BV, BR, and the enzymes involved in their production (the "yellow players-YP") are increasingly documented as endogenous modulators of human health. Mildly elevated serum bilirubin concentration has been correlated with a reduced risk of multiple chronic pro-oxidant and pro-inflammatory diseases, especially in the elderly. BR and BV per se have been demonstrated to protect against neurodegenerative diseases, in which heme oxygenase (HMOX), the main enzyme in the production of pigments, is almost always altered. HMOX upregulation has been interpreted as a tentative defense against the ongoing pathologic mechanisms. With the demonstration that multiple cells possess YP, their propensity to be modulated, and their broad spectrum of activity on multiple signaling pathways, the YP have assumed the role of an adjustable system that can promote health in adults. Based on that, there is an ongoing effort to induce their activity as a therapeutic option, and natural compounds are an attractive alternative to the goal, possibly requiring only minimal changes in the life style. We review the most recent evidence of the potential of natural compounds in targeting the YP in the context of the most common pathologic condition of adult and elderly life.

Cultured meat with enriched organoleptic properties by regulating cell differentiation

Research on cultured meat has primarily focused on the mass proliferation or differentiation of muscle cells; thus, the food characteristics of cultured meat remain relatively underexplored. As the quality of meat is determined by its organoleptic properties, cultured meat with similar sensory characteristics to animal-derived meat is highly desirable. In this study, we control the organoleptic and nutritional properties of cultured meat by tailoring the 2D differentiation of primary bovine myoblasts and primary bovine adipose-derived mesenchymal stem cells on gelatin/alginate scaffolds with varying stiffness. We assess the effect of muscle and adipose differentiation quality on the sensory properties of cultured meat. Thereafter, we fabricate cultured meat with similar sensory profiles to that of conventional beef by assembling the muscle and adipose constructs composed of highly differentiated cells. We introduce a strategy to produce cultured meat with enriched food characteristics by regulating cell differentiation with scaffold engineering.

BDE-47 induces metabolic dysfunction-associated steatotic liver disease (MASLD) through CD36-mediated increased fatty acid uptake and PPARα-induced abnormal fatty acid oxidation in BALB/c mice

The widespread existence of 2,2',4,4'-tetra-bromodiphenyl ether (BDE-47) in the environment has aroused great concern. BDE-47 induces the occurrence of metabolic dysfunction-associated steatotic liver disease (MASLD), but the mechanism has not been fully elucidated. Here, we further investigate the underlying mechanism using BALB/c mice. After BDE-47 exposure, the livers of mice enlarged, the serum levels of ALT, ALP, TG and TC enhanced, and hepatic steatosis occurred. Transcriptome sequencing identifies 2250 differentially expressed genes (DEGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis reveals that down-regulated DEGs are mainly enriched in pathways associated with lipid metabolism, particularly in fatty acid (FA) degradation. And up-regulated DEGs are mainly enriched in pathways related to lipid and FA transport. The expression levels of AhR, Pparγ and Cd36 involved in FA uptake are up-regulated, and those of PPARα and target genes including Cpt1 and Cyp4a1 related to β and ω-oxidation are inhibited. These results reveal BDE-47 could lead to metabolic dysfunction-associated steatotic liver disease (MASLD) by promoting FA uptake via upregulating Cd36 and hindering oxidative utilization by downregulating PPARα.

Evidence for a role of SNMP2 and antennal support cells in sensillum lymph clearance processes of moth pheromone-responsive sensilla

In insect antenna, following the activation of olfactory sensory neurons, odorant molecules are inactivated by enzymes in the sensillum lymph. How the inactivation products are cleared from the sensillum lymph is presently unknown. Here we studied the role of support cells (SCs) and the so-called sensory neuron membrane protein 2 (SNMP2), a member of the CD36 family of lipid transporters abundantly expressed in SCs, in sensillum lymph clearance processes in the moths Heliothis virescens and Bombyx mori. In these species, the sex pheromone components are inactivated to long-chain fatty acids. To approach a role of SNMP2 in the removal of such inactivation products, we analyzed the uptake of a fluorescent long-chain fatty acid analog into a newly generated HvirSNMP2-expressing cell line. We found an increased uptake of the analog into SNMP2-cells compared to control cells, which could be blocked by the CD36 protein inhibitor, SSO. Furthermore, analyses of sensilla from antenna treated with the fatty acid analog indicated that SNMP2-expressing SCs are able to take up fatty acids from the sensillum lymph. In addition, sensilla from SSO-pretreated antenna of B. mori showed reduced removal of the fluorescent analog from the sensillum lymph. Finally, we revealed that SSO pretreatment of male silkmoth antenna significantly prolonged the duration of the female pheromone-induced wing-fluttering behavior, possibly as a result of impaired lymph clearance processes. Together our findings in H. virescens and B. mori support a pivotal role of olfactory SCs in sensillum lymph maintenance processes and suggest an integral role of SNMP2 in the removal of lipophilic "waste products" such as fatty acids resulting from sex pheromone inactivation.

Targeting metabolic reprogramming in hepatocellular carcinoma to overcome therapeutic resistance: A comprehensive review

Hepatocellular carcinoma (HCC) poses a heavy burden on human health with high morbidity and mortality rates. Systematic therapy is crucial for advanced and mid-term HCC, but faces a significant challenge from therapeutic resistance, weakening drug effectiveness. Metabolic reprogramming has gained attention as a key contributor to therapeutic resistance. Cells change their metabolism to meet energy demands, adapt to growth needs, or resist environmental pressures. Understanding key enzyme expression patterns and metabolic pathway interactions is vital to comprehend HCC occurrence, development, and treatment resistance. Exploring metabolic enzyme reprogramming and pathways is essential to identify breakthrough points for HCC treatment. Targeting metabolic enzymes with inhibitors is key to addressing these points. Inhibitors, combined with systemic therapeutic drugs, can alleviate resistance, prolong overall survival for advanced HCC, and offer mid-term HCC patients a chance for radical resection. Advances in metabolic research methods, from genomics to metabolomics and cells to organoids, help build the HCC metabolic reprogramming network. Recent progress in biomaterials and nanotechnology impacts drug targeting and effectiveness, providing new solutions for systemic therapeutic drug resistance. This review focuses on metabolic enzyme changes, pathway interactions, enzyme inhibitors, research methods, and drug delivery targeting metabolic reprogramming, offering valuable references for metabolic approaches to HCC treatment.

miR-889-3p Facilitates the Browning Process of White Adipocyte Precursors by Targeting the SON Gene

It is well-established that beige/brown adipose tissue can dissipate stored energy through thermogenesis; hence, the browning of white adipocytes (WAT) has garnered significant interest in contemporary research. Our preceding investigations have identified a marked downregulation of miR-889-3p concurrent with the natural maturation of brown adipose tissue. However, the specific role and underlying molecular mechanisms of miR-889-3p in the browning process of white adipose tissue warrant further elucidation. In this research, we initially delved into the potential role of miR-889-3p in preadipocyte growth via flow cytometry and CCK-8 assay, revealing that miR-889-3p can stimulate preadipocyte growth. To validate the potential contribution of miR-889-3p in the browning process of white adipose tissue, we established an in vitro rabbit white adipocyte browning induction, which exhibited a significant upregulation of miR-889-3p during the browning process. RT-qPCR and Western blot analysis indicated that miR-889-3p overexpression significantly amplified the mRNA levels of UCP1, PRDM16, and CIDEA, as well as UCP1 protein levels. Furthermore, miR-889-3p overexpression fostered intracellular triglyceride accumulation. Conversely, the downregulation of miR-889-3p hindered the browning of rabbit preadipocytes. Subsequently, based on target gene prediction and luciferase reporter gene determination, we demonstrated that miR-889-3p directly targets the 3'-UTR region of SON. Lastly, we observed that inhibiting SON could facilitate the browning of rabbit preadipocytes. In conclusion, our findings suggest that miR-889-3p facilitates the browning process of white adipocyte precursors by specifically targeting the SON gene.

Ligand-dependent CD36 functions in cancer progression, metastasis, immune response, and drug resistance

CD36, a multifunctional glycoprotein, has been shown to play critical roles in tumor initiation, progression, metastasis, immune response, and drug resistance. CD36 serves as a receptor for a wide range of ligands, including lipid-related ligands (e.g., long-chain fatty acid (LCFA), oxidized low-density lipoprotein (oxLDL), and oxidized phospholipids), as well as protein-related ligands (e.g., thrombospondins, amyloid proteins, collagens I and IV). CD36 is overexpressed in various cancers and may act as an independent prognostic marker. While it was initially identified as a mediator of anti-angiogenesis through its interaction with thrombospondin-1 (TSP1), recent research has highlighted its role in promoting tumor growth, metastasis, drug resistance, and immune suppression. The varied impact of CD36 on cancer is likely ligand-dependent. Therefore, we focus specifically on the ligand-dependent role of CD36 in cancer to provide a critical review of recent advances, perspectives, and challenges.

Targeting dysregulated lipid metabolism in the tumor microenvironment

The reprogramming of lipid metabolism and its association with oncogenic signaling pathways within the tumor microenvironment (TME) have emerged as significant hallmarks of cancer. Lipid metabolism is defined as a complex set of molecular processes including lipid uptake, synthesis, transport, and degradation. The dysregulation of lipid metabolism is affected by enzymes and signaling molecules directly or indirectly involved in the lipid metabolic process. Regulation of lipid metabolizing enzymes has been shown to modulate cancer development and to avoid resistance to anticancer drugs in tumors and the TME. Because of this, understanding the metabolic reprogramming associated with oncogenic progression is important to develop strategies for cancer treatment. Recent advances provide insight into fundamental mechanisms and the connections between altered lipid metabolism and tumorigenesis. In this review, we explore alterations to lipid metabolism and the pivotal factors driving lipid metabolic reprogramming, which exacerbate cancer progression. We also shed light on the latest insights and current therapeutic approaches based on small molecular inhibitors and phytochemicals targeting lipid metabolism for cancer treatment. Further investigations are worthwhile to fully understand the underlying mechanisms and the correlation between altered lipid metabolism and carcinogenesis.

Mapping the immunological battlefield in gastric cancer: prognostic implications of an immune gene expression signature

BACKGROUND

Gastric cancer (GC) is a heterogeneous malignancy with variable clinical outcomes. The immune system has been implicated in GC development and progression, highlighting the importance of immune-related gene expression patterns and their prognostic significance.

OBJECTIVE

This study aimed to identify differentially expressed immune-related genes (DEIRGs) and establish a prognostic index for GC patients using comprehensive bioinformatic analyses.

METHODS

We integrated RNA sequencing data from multiple databases and identified DEIRGs by overlapping differentially expressed genes with immune-related genes. Functional enrichment analysis was performed to uncover the biological processes and signaling pathways associated with DEIRGs. We conducted a Weighted Gene Co-expression Network Analysis (WGCNA) to identify key gene modules related to with GC. Cox regression analysis was conducted to determine independent prognostic DEIRGs for overall survival prediction. Based on these findings, we developed an immune-related gene prognostic index (IRGPI) based on these findings. The prognostic value of the IRGPI was validated using survival analysis and an independent validation cohort. Functional enrichment analysis, gene mutation analysis, and immune cell profiling were performed to gain insights into the biological functions and immune characteristics associated with the IRGPI-based subgroups.

RESULTS

We identified 493 DEIRGs significantly enriched in immune-related biological processes and signaling pathways associated with GC. WGCNA analysis revealed a significant module (turquoise module) associated with GC, revealing potential therapeutic targets. Cox regression analysis identified RNASE2, CGB5, CTLA4, and DUSP1 as independent prognostic DEIRGs. The IRGPI, incorporating the expression levels of these genes, demonstrated significant prognostic value in predicting overall survival. The IRGPI-based subgroups exhibited distinct biological functions, genetic alterations, and immune cell compositions.

CONCLUSION

Our study identified DEIRGs and established a prognostic index (IRGPI) for GC patients. The IRGPI exhibited promising prognostic potential and provided insights into GC tumor biology and immune characteristics. These findings have implications for guiding therapeutic strategies.

The cluster of differentiation 36 (CD36) rs1761667 polymorphism interacts with dietary patterns to affect cardiometabolic risk factors and metabolic syndrome risk in apparently healthy individuals

Several studies have examined the association between CD36 rs1761667 polymorphism with cardiometabolic risk factors and metabolic syndrome (MetS). This study aimed to investigate the interactions between rs1761667 polymorphism and dietary patterns on the cardiometabolic risk factors and the risk of MetS in apparently healthy individuals aged 20-70 years. Food consumption data were acquired using a validated semi-quantitative FFQ. Dietary patterns were identified by factor analysis. CD36 rs1761667 was genotyped by PCR-restriction fragment length polymorphism. The gene-diet interaction was detected by the general linear model or logistic regression. Significant or marginally significant interactions were observed between healthy dietary pattern (HDP) and CD36 rs1761667 on weight (P = 0·006), BMI (P = 0·009), waist circumference (P = 0·005), hip circumference (P = 0·06), body muscle percentage (P = 0·02), body fat percentage (P = 0·09), TAG-glucose index (P = 0·057), atherogenic index of plasma (P = 0·07), the risk of MetS (P = 0·02), risk of abdominal obesity (P = 0·02) and elevated blood pressure (P = 0·07). Besides, a gene-diet interaction was detected between the traditional dietary pattern and rs1761667 variants on odds of hypertriglyceridaemia (P = 0·02). The adherence to HDP was associated with a lower weight, BMI and higher odds of HDL-cholesterol only in A-allele carriers. In conclusion, adherence to HDP (a diet with high fibre, fish and dairy products) can be more effective on some cardiometabolic risk factors and risk of MetS components in the A-allele carrier than the GG genotype of rs1761667 polymorphism. However, future studies are required to shed light on this issue.