Caffeine Ameliorates AKT-Driven Nonalcoholic Steatohepatitis by Suppressing De Novo Lipogenesis and MyD88 Palmitoylation

SR-A3 suppresses AKT activation to protect against MAFLD by inhibiting XIAP-mediated PTEN degradation

Scavenger receptor class A member 3 (SR-A3) is implicated in metabolic diseases; however, the relationship between SR-A3 and metabolic dysfunction-associated fatty liver disease (MAFLD) has not been documented. Here, we show that hepatic SR-A3 expression is significantly reduced in human and animal models in the context of MAFLD. Genetic inhibition of SR-A3 in hamsters elicits hyperlipidemia, hyperglycemia, insulin resistance, and hepatic steatosis under chow-diet condition, yet escalates in diet-induced MAFLD. Mechanistically, SR-A3 ablation enhances E3 ligase XIAP-mediated proteasomal ubiquitination of PTEN, leading to AKT hyperactivation. By contrast, hepatic overexpression of human SR-A3 is sufficient to attenuate metabolic disorders in WT hamsters fed a high-fat-high-cholesterol diet and ob/ob mice via suppressing the XIAP/PTEN/AKT axis. In parallel, pharmacological intervention by PTEN agonist oroxin B or lipid lowering agent ezetimibe differentially corrects MAFLD in hamsters.

Regulation of pattern recognition receptor signaling by palmitoylation

Pattern recognition receptors (PRRs), consisting of Toll-like receptors, RIG-I-like receptors, cytosolic DNA sensors, and NOD-like receptors, sense exogenous pathogenic molecules and endogenous damage signals to maintain physiological homeostasis. Upon activation, PRRs stimulate the sensitization of nuclear factor κB, mitogen-activated protein kinase, TANK-binding kinase 1-interferon (IFN) regulatory factor, and inflammasome signaling pathways to produce inflammatory factors and IFNs to activate Janus kinase/signal transducer and activator of transcription signaling pathways, resulting in anti-infection, antitumor, and other specific immune responses. Palmitoylation is a crucial type of post-translational modification that reversibly alters the localization, stability, and biological activity of target molecules. Here, we discuss the available knowledge on the biological roles and underlying mechanisms linked to protein palmitoylation in modulating PRRs and their downstream signaling pathways under physiological and pathological conditions. Moreover, recent advances in the use of palmitoylation as an attractive therapeutic target for disorders caused by the dysregulation of PRRs were summarized.

Sex differences in the neuroinflammatory signaling pathway: effect of miRNAs on fatty acid synthesis in microglia

BACKGROUND

Significant sex differences exist in the prevalence and incidence of Alzheimer's disease (AD). Notably, testosterone has been reported to regulate cognitive functions in the brain, with low serum testosterone levels correlating with increased AD risk. However, the specific mechanisms underlying this relationship remain unclear. Recent studies have demonstrated that microglia, the primary innate immune cells in the brain, play a crucial role in AD development. Therefore, this study aimed to explore sex differences in microglial function, specifically focusing on the role of testosterone in miRNA-mediated regulation of microglial gene expression.

METHODS

Microglia were isolated from pooled hippocampal tissue of five 8-month-old male and female mice. Total RNA was extracted and subjected to miRNA microarray analysis. The mouse microglial cell line MG6 was used for in vitro experiments. Following testosterone treatment, miRNA, gene, and protein expression levels were investigated. An inflammatory response was induced using lipopolysaccharide (LPS) stimulation, and subsequent p65 phosphorylation was assessed.

RESULTS

Sex-dependent differences were observed in miRNA-mediated biological processes, with males exhibiting greater changes. Male-enriched miRNAs were associated with fatty acid synthesis and metabolism pathways. In MG6 cells, testosterone treatment upregulated the expression of several miRNAs enriched in male microglia, particularly those targeting genes related to fatty acid synthesis. Additionally, testosterone significantly reduced the gene expression of fatty acid synthase (FASN). This testosterone-induced inhibition of FASN expression attenuated NF-κB/p65 phosphorylation. Consequently, the suppression of FASN expression led to reduced expression and secretion of tumor necrosis factor-alpha following LPS stimulation in MG6 cells.

CONCLUSIONS

These findings suggest that testosterone modulates inflammation in male microglia by regulating fatty acid synthesis, potentially contributing to the observed sex differences in AD pathogenesis.

Protein palmitoylation in hepatic diseases: Functional insights and therapeutic strategies

BACKGROUND

Liver pathologies represent a spectrum of conditions ranging from fatty liver to the aggressive hepatocellular carcinoma (HCC), as well as parasitic infections, which collectively pose substantial global health challenges. S-palmitoylation (commonly referred to as palmitoylation), a post-translational modification (PTM) characterized by the covalent linkage of a 16-carbon palmitic acid (PA) chain to specific cysteine residues on target proteins, plays a pivotal role in diverse cellular functions and is intimately associated with the liver's physiological and pathological states.

AIM OF REVIEW

This study aims to elucidate how protein palmitoylation affects liver disease pathophysiology and evaluates its potential as a target for diagnostic and therapeutic interventions.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Recent studies have identified the key role of protein palmitoylation in regulating the development and progression of liver diseases. This review summarizes the intricate mechanisms by which protein palmitoylation modulates the pathophysiological processes of liver diseases and explores the potential of targeting protein palmitoylation modifications or the enzymes regulating this modification as prospective diagnostic biomarkers and therapeutic targets.

Effect of virgin olive oil as spreadable preparation on atherosclerosis compared to dairy butter in Apoe-deficient mice

Olive oil is the main source of lipid energy in the Mediterranean diet and there is strong evidence of its health benefits. The effect of extra virgin olive oil (EVOO) in the form of a preparation of spreadable virgin olive oil (S-VO) on the progression of atheroma plaques was investigated in Apoe-deficient mice, a model of accelerated atherosclerosis.

METHODS

Two isocaloric Western purified diets containing 20% fat, either as S-VO or as dairy butter, were used to feed 28 males and 16 females of two-month-old Apoe-deficient mice for 12 weeks. S-VO was prepared by blending more than 75% virgin olive oil with other vegetal natural fat to obtain a solid fat. Plasma total cholesterol, triglycerides and HDL cholesterol were measured. Hepatic lipid droplets were analyzed. Areas of atherosclerotic aortic lesions were quantified in cross-sectional images of the proximal aorta and en face analysis of the whole aorta.

RESULTS

Total plasma cholesterol was increased in mice on the butter-supplemented diet in both female and male mice compared to S-VO, and the ratio of TC/HDL-cholesterol was significantly lower in S-VO than in the butter diet, although only in males, and no differences in plasma triglycerides were observed. No significant differences in hepatic lipid droplets were observed between diets in either sex. Aortic lesion areas were significantly higher in mice consuming the butter versus the S-VO diet in both sexes.

CONCLUSION

Extra virgin olive oil prepared in spreadable form maintained the delay in atheroma plaque progression compared to butter.

Examining the Pathogenesis of MAFLD and the Medicinal Properties of Natural Products from a Metabolic Perspective

Metabolic-associated fatty liver disease (MAFLD), characterized primarily by hepatic steatosis, has become the most prevalent liver disease worldwide, affecting approximately two-fifths of the global population. The pathogenesis of MAFLD is extremely complex, and to date, there are no approved therapeutic drugs for clinical use. Considerable evidence indicates that various metabolic disorders play a pivotal role in the progression of MAFLD, including lipids, carbohydrates, amino acids, and micronutrients. In recent years, the medicinal properties of natural products have attracted widespread attention, and numerous studies have reported their efficacy in ameliorating metabolic disorders and subsequently alleviating MAFLD. This review aims to summarize the metabolic-associated pathological mechanisms of MAFLD, as well as the natural products that regulate metabolic pathways to alleviate MAFLD.

Caffeine in Hepatocellular Carcinoma: Cellular Assays, Animal Experiments, and Epidemiological Investigation

The use of caffeine in treating various liver diseases has made substantial progress in the past decade owing to advances in science, technology, and medicine. However, whether caffeine has a preventive effect on hepatocellular carcinoma (HCC) and its mechanism are still worth further investigation. In this review, we summarize and analyze the efficacy and safety of caffeine in the prevention of HCC. We conducted a review of articles published in PubMed and Web of Science in the past 2 decades until December 6, 2023, which were searched for using the terms "Caffeine" and "Hepatocellular Carcinoma." Studies have found that coffee intake is negatively correlated with HCC risk, especially caffeinated coffee. Recent studies have found that caffeine has beneficial effects on liver health, decreasing levels of enzymes responsible for liver damaging and slowing the progression of hepatic fibrosis and cirrhosis. Caffeine also acts against liver fibrosis through adenosine receptors (ARs), which promote tissue remodeling by inducing fibrin and collagen production. Additionally, new studies have found that moderate consumption of caffeinated beverages can decrease various the levels of various collagens in patients with chronic hepatitis C. Furthermore, polyphenolic compounds in coffee can improve fat homeostasis, reduce oxidative stress, and prevent liver steatosis and fibrosis. Moreover, many in vitro studies have shown that caffeine can protect liver cells and inhibit the activation and proliferation of hepatic stellate cells. Taken together, we describe the benefits of caffeine for liver health and highlight its potential values as a drug to prevent various hepatic diseases. As a protective agent of liver inflammation, non-selective AR inhibitor caffeine can inhibit the growth of HCC cells by inhibiting adenosine and AR binding to initiate immune response, providing a basis for the future development of caffeine as an adjuvant drug against HCC.

Metabolic Insights into Caffeine's Anti-Adipogenic Effects: An Exploration through Intestinal Microbiota Modulation in Obesity

Obesity, a chronic condition marked by the excessive accumulation of adipose tissue, not only affects individual well-being but also significantly inflates healthcare costs. The physiological excess of fat manifests as triglyceride (TG) deposition within adipose tissue, with white adipose tissue (WAT) expansion via adipocyte hyperplasia being a key adipogenesis mechanism. As efforts intensify to address this global health crisis, understanding the complex interplay of contributing factors becomes critical for effective public health interventions and improved patient outcomes. In this context, gut microbiota-derived metabolites play an important role in orchestrating obesity modulation. Microbial lipopolysaccharides (LPS), secondary bile acids (BA), short-chain fatty acids (SCFAs), and trimethylamine (TMA) are the main intestinal metabolites in dyslipidemic states. Emerging evidence highlights the microbiota's substantial role in influencing host metabolism and subsequent health outcomes, presenting new avenues for therapeutic strategies, including polyphenol-based manipulations of these microbial populations. Among various agents, caffeine emerges as a potent modulator of metabolic pathways, exhibiting anti-inflammatory, antioxidant, and obesity-mitigating properties. Notably, caffeine's anti-adipogenic potential, attributed to the downregulation of key adipogenesis regulators, has been established. Recent findings further indicate that caffeine's influence on obesity may be mediated through alterations in the gut microbiota and its metabolic byproducts. Therefore, the present review summarizes the anti-adipogenic effect of caffeine in modulating obesity through the intestinal microbiota and its metabolites.

High Gamma-Aminobutyric Acid (GABA) Oolong Tea Alleviates High-Fat Diet-Induced Metabolic Disorders in Mice

Obesity and overweight are associated with an increasing risk of developing health conditions and chronic non-communicable diseases, including cardiovascular diseases, cancer, musculoskeletal problems, respiratory problems, and mental health, and its prevalence is rising. Diet is one of three primary lifestyle interventions. Many bioactive components in tea especially oolong tea, including flavonoids, gamma-aminobutyric acid (GABA), and caffeine were reported to show related effects in reducing the risk of obesity. However, the effects of GABA oolong tea extracts (OTEs) on high-fat diet (HFD)-induced obesity are still unclear. Therefore, this study aims to explore whether the intervention of GABA OTEs can prevent HFD-induced obesity and decipher its underlying mechanisms using male C57BL/6 J mice. The result indicated that GABA OTEs reduced leptin expression in epididymal adipose tissue and showed a protective effect on nonalcoholic fatty liver disease. It promoted thermogenesis-related protein of uncoupling protein-1 and peroxisome proliferator-activated receptor-gamma coactivator (PGC-1α), boosted lipid metabolism, and promoted fatty acid oxidation. It also reduced lipogenesis-related protein levels of sterol regulatory element binding protein, acetyl-CoA carboxylase, and fatty acid synthase and inhibited hepatic triglyceride (TG) levels. These data suggest that regular drinking of GABA oolong tea has the potential to reduce the risk of being overweight, preventing obesity development through thermogenesis, lipogenesis, and lipolysis.

Sex Related Differences in the Complex Relationship between Coffee, Caffeine and Atrial Fibrillation

This literature review aims to explore the data of articles published on the association between coffee, caffeine and atrial fibrillation and to analyze any differences between the two sexes. Several factors influence this complex relationship; genetic, environmental and psychosocial factors come into play in the pathophysiology of atrial fibrillation. These factors are expressed differently in women and men. However, the analysis of the literature has shown that comparison works between the two sexes are extremely rare. Most population-based and prospective studies either analyze aggregated data or focus on exclusively male or female populations. This results in a lack of information that could be useful in the prevention of and treatment approach to atrial fibrillation. It is necessary to deepen this issue with dedicated studies.