Silver nanoparticles inhibit beige fat function and promote adiposity

Transferrin receptor levels and its rare variant are associated with human obesity

AIM

Iron homeostasis is critical for functional respiratory chain complex of mitochondrial, thus potentially contributing to fat biology and energy homeostasis. Transferrin receptor (Tfrc) binds to transferrin for extracellular iron uptake and is recently reported to be involved in brown fat development and functionality. However, whether TFRC levels and variants are associated with human obesity is unknown.

METHODS

To investigate the association of TFRC levels and variants with human obesity, fat biopsies were obtained from surgery. Exon-sequencing and genetic assessments were conducted of a case-control study. For TFRC levels assessment in fat biopsy, 9 overweight and 12 lean subjects were involved. For genetic study, obese (n = 1271) and lean subjects (n = 1455) were involved. TFRC levels were compared in abdominal mesenteric fat of pheochromocytoma patients versus control subjects, and overweight versus lean subjects. For genetic study, whole-exome sequencing of obese and matched control subjects were conducted and analyzed. In addition, the possible disruption in protein stability of TFRC variant was assessed by structural and molecular analysis.

RESULTS

TFRC levels are increased in human browning adipose tissue and decreased in fat of overweight patients. Besides, TFRC levels are negatively correlated with body mass index and positively correlated with uncoupling protein 1 levels. Furthermore, a rare heterozygous missense variant p.I337V in TFRC shows a tendency to enrich in obese subjects. Structural and functional study reveals impaired protein stability of the TFRC variant compared to wild-type.

CONCLUSIONS

Reduced TFRC levels and its rare variant p.I337V with protein instability are associated with human obesity.

Dual mechanism of silver nanoparticle-mediated upregulation of adipogenesis in mouse fibroblasts (3T3-L1) in vitro

Silver nanoparticles (AgNPs) are widespread in the environment due to the increase in their application e.g. in medicine as part of hard-to-heal wound dressings. Many studies have revealed easy diffusion of AgNPs into deep skin layers through damaged epidermis and contact with e.g. fibroblasts. Therefore, the aim of this study was to evaluate the impact of small-size AgNPs (10 nm) in ppm concentrations on the adipogenesis process in mouse embryo fibroblasts (3T3-L1). The results showed a decrease in the metabolic activity, followed by an increase in the reactive oxygen species (ROS) level in a dose- and time-dependent manner (0-20 ppm). The increased caspase-3 activity was observed only at the highest concentration (20 ppm) of AgNPs. Further analysis showed the ability of the tested NPs to increase the lipid accumulation in adipocytes, similar to ROSI [peroxisome proliferator-activated receptor gamma (PPARγ) agonist], measured by Oil-Red-O staining. Moreover, the analyses evidenced the ability of AgNPs to increase the lipoxygenase activity and malondialdehyde levels, which is probably based on ROS-dependent enhancement of lipid hydroperoxidation. Lastly, a significant increase in the PPARγ, Adiponectin, Resistin, Vegf, and Serpine mRNA expression was shown 6 h after the induction of the differentiation process. Based on the obtained results, it can be concluded that small-size AgNPs increase adipogenesis via ROS- and PPARγ-based mechanisms with potential engagement of crosstalk with the aryl hydrocarbon receptor, which is important due to the widespread application of AgNPs in medicine. However, more studies are needed to elucidate the full mechanism of these NPs in the tested cell model in depth.

Redox Biology in Adipose Tissue Physiology and Obesity

Reactive oxygen species (ROS), a by-product of mitochondrial oxidative phosphorylation and cellular metabolism, is vital for cellular survival, proliferation, damage, and senescence. In recent years, studies have shown that ROS levels and redox status in adipose tissue are strongly associated with obesity and metabolic diseases. Although it was previously considered that excessive production of ROS and impairment of antioxidant capability leads to oxidative stress and potentially contributes to increased adiposity, it has become increasingly evident that an adequate amount of ROS is vital for adipocyte differentiation and thermogenesis. In this review, by providing a systematic overview of the recent understanding of the key factors of redox systems, endogenous mechanisms for redox homeostasis, advanced techniques for dynamic redox monitoring, as well as exogenous stimuli for redox production in adipose tissues and obesity, the importance of redox biology in metabolic health is emphasized.

Histone deacetylase inhibitors inhibit lung adenocarcinoma metastasis via HDAC2/YY1 mediated downregulation of Cdh1

Metastasis is a leading cause of mortality in patients with lung adenocarcinoma. Histone deacetylases have emerged as promising targets for anti-tumor drugs, with histone deacetylase inhibitors (HDACi) being an active area of research. However, the precise mechanisms by which HDACi inhibits lung cancer metastasis remain incompletely understood. In this study, we employed a range of techniques, including qPCR, immunoblotting, co-immunoprecipitation, chromatin-immunoprecipitation, and cell migration assays, in conjunction with online database analysis, to investigate the role of HDACi and HDAC2/YY1 in the process of lung adenocarcinoma migration. The present study has demonstrated that both trichostatin A (TSA) and sodium butyrate (NaBu) significantly inhibit the invasion and migration of lung cancer cells via Histone deacetylase 2 (HDAC2). Overexpression of HDAC2 promotes lung cancer cell migration, whereas shHDAC2 effectively inhibits it. Further investigation revealed that HDAC2 interacts with YY1 and deacetylates Lysine 27 and Lysine9 of Histone 3, thereby inhibiting Cdh1 transcriptional activity and promoting cell migration. These findings have shed light on a novel functional mechanism of HDAC2/YY1 in lung adenocarcinoma cell migration.

Interaction of silver nanoparticles with marine/lake snow in early formation stage

Marine and lake snows play an important ecological role in aquatic systems, and recent researches have also revealed their interactions with various pollutants. In this paper, the interaction of silver nanoparticles (Ag-NPs), a typical nano-pollutant, with marine/lake snow in the early formation stage was investigated by roller table experiments. Results indicated Ag-NPs promoted the accumulation of larger marine snow flocs while inhibited the development of lake snow. The promotion effect of AgNPs might be attributed to their oxidative dissolution into low-toxic silver chloride complexes in seawater, and the subsequent incorporation into marine snow, which would enhance the rigidity and strength of larger flocs and favor the development of biomass. Conversely, Ag-NPs mainly existed in the form of colloidal nanoparticles in lake water and their strong antimicrobial effect suppressed the growths of biomass and lake snow. In addition, Ag-NPs could also affect the microbial community of marine/lake snow, including impact on microbial diversity, and elevation on abundances of extracellular polymeric substances (EPS) synthesis genes and silver resistance genes. This work has deepened our understanding of the fate and ecological effect of Ag-NPs via the interaction with marine/lake snow in aquatic environments.

The progress of research on the application of redox nanomaterials in disease therapy

Redox imbalance can trigger cell dysfunction and damage and plays a vital role in the origin and progression of many diseases. Maintaining the balance between oxidants and antioxidants in vivo is a complicated and arduous task, leading to ongoing research into the construction of redox nanomaterials. Nanodrug platforms with redox characteristics can not only reduce the adverse effects of oxidative stress on tissues by removing excess oxidants from the body but also have multienzyme-like activity, which can play a cytotoxic role in tumor tissues through the catalytic oxidation of their substrates to produce harmful reactive oxygen species such as hydroxyl radicals. In this review, various redox nanomaterials currently used in disease therapy are discussed, emphasizing the treatment methods and their applications in tumors and other human tissues. Finally, the limitations of the current clinical application of redox nanomaterials are considered.

Adipocytolytic Polymer Nanoparticles for Localized Fat Reduction

The demand for body fat reduction is increasing. However, conventional lipolytic approaches fail to control adipose tissue reduction and cause severe side effects in adjacent nonadipose tissues. A strategy to specifically reduce subcutaneous fat using adipocytolytic polymer nanoparticles in a minimally invasive manner is reported here. The polymer nanoparticles are designed to generate carbon dioxide gas when selectively absorbed by adipocytes. The carbon dioxide gas generated within late endosomes/lysosomes induces adipocytolysis, thereby reducing the number of cells. Localized injection of the adipocytolytic nanoparticles substantially reduces subcutaneous fat in a high-fat diet-induced obese mouse model, without significant changes in hematological or serum biochemical parameters. The adipocytolytic efficacy of the nanoparticles is also evaluated in a porcine model. This strategy addresses the need to develop safe and effective adipocytolytic agents using functional polymer nanoparticles.

Quercetin 3-O-glucuronide-rich lotus leaf extract promotes a Brown-fat-phenotype in C3H10T1/2 mesenchymal stem cells

Lotus (Nelumbo nucifera Gaertn.) is an aquatic perennial crop planted worldwide and its leaf (also called "He-Ye") has therapeutic effects on obesity. However, whether the underlying mechanism leads to increased energy expenditure by activation of brown adipocytes has not been clarified. Here, murine C₃H₁₀T_1/2 mesenchymal stem cells (MSCs) were employed to investigate the effects of ethanol extracts from lotus leaf (LLE) on brown adipocytes formation and the underlying molecular mechanisms. The results showed LLE was rich in polyphenols (383.7 mg/g) and flavonoids (178.3 mg/g), with quercetin 3-O-glucuronide (Q3G) the most abundant (128.2 μg/mg). In LLE-treated C₃H₁₀T_1/2 MSCs, the expressions of lipolytic factors (e.g., ATGL, HSL, and ABHD5) and brown regulators (e.g., Sirt1, PGC-1α, Cidea, and UCP1) were significantly upregulated compared to that in the untreated MSCs. Furthermore, LLE promoted mitochondrial biogenesis and fatty acid β-oxidation, as evidenced by increases in the expression of Tfam, Cox7A, CoxIV, Cox2, Pparα, and Adrb3. Likewise, enhanced browning and mitochondrial biogenesis were also observed in Q3G-stimulated cells. Importantly, LLE and Q3G induced phosphorylation of AMPK accompanied by a remarkable increase in the brown fat marker UCP1, while pretreatment with Compound C (an AMPK inhibitor) reversed these changes. Moreover, stimulating LLE or Q3G-treated cells with CL316243 (a beta3-AR agonist) increased p-AMPKα/AMPKα ratio and UCP1 protein expression, indicating β3-AR/AMPK signaling may involve in this process. Collectively, these observations suggested that LLE, especially the component Q3G, stimulates thermogenesis by activating brown adipocytes, which may involve the β3-AR/AMPK signaling pathway.

Antibiotic Azithromycin inhibits brown/beige fat functionality and promotes obesity in human and rodents

Obesity, a metabolic disease caused by multiple factors, has become a global health problem. In addition to nutrient intake and sedentary lifestyle, environmental pollutants exposure has been shown to be involved in obesity epidemics. Antibiotics, a new type of environmental pollutant, have been widely used in animal husbandry, aquaculture and microorganism. However, the effects of antibiotics exposure on fat metabolism and metabolic diseases are largely unknown. Methods: We screened major types of antibiotics to examine their effects on the differentiation capacity and thermogenic functionality of brown and beige adipocytes, and found that azithromycin, one major kind of macrolide antibiotics suppressed brown and beige adipocyte functionality. We thus examined azithromycin accretion in adipose tissues of obese patients that correlates with BMI by high performance liquid chromatography-tandem mass spectrometry and systematically explore the influences of azithromycin on adiposity and metabolic performance in mice under high diet. Results: Azithromycin (macrolides) inhibits the mitochondrial and thermogenic gene programs of brown and beige adipocytes, thus disrupting their mitochondrial function and thermogenic response. Consistently, azithromycin treatment are more prone to diet-induced obesity in mice, and this was associated with impaired energy expenditure. Importantly, azithromycin is more accumulated in adipose tissue of obese patients and correlates with BMI and body weight. Mechanistically, we found that azithromycin inhibits mitochondria respiratory complex I protein levels and increases reactive oxidative species (ROS) levels, which causes damage of mitochondrial function in brown and beige adipocytes. The deleterious effects of azithromycin can be ameliorated by antioxidant N-acetyl-L-cysteine. Conclusions: Taken together, this work highlights the possible role of azithromycin in obesity epidemic and presents strategies for safe applications of antibiotics in the future.

Spatial Regulation of Reactive Oxygen Species via G6PD in Brown Adipocytes Supports Thermogenic Function

Reactive oxygen species (ROS) are associated with various roles of brown adipocytes. Glucose-6-phosphate dehydrogenase (G6PD) controls cellular redox potentials by producing NADPH. Although G6PD upregulates cellular ROS levels in white adipocytes, the roles of G6PD in brown adipocytes remain elusive. Here, we found that G6PD defect in brown adipocytes impaired thermogenic function through excessive cytosolic ROS accumulation. Upon cold exposure, G6PD-deficient mutant (G6PD^mut) mice exhibited cold intolerance and downregulated thermogenic gene expression in brown adipose tissue (BAT). In addition, G6PD-deficient brown adipocytes had increased cytosolic ROS levels, leading to extracellular signal-regulated kinase (ERK) activation. In BAT of G6PD^mut mice, administration of antioxidant restored the thermogenic activity by potentiating thermogenic gene expression and relieving ERK activation. Consistently, body temperature and thermogenic execution were rescued by ERK inhibition in cold-exposed G6PD^mut mice. Taken together, these data suggest that G6PD in brown adipocytes would protect against cytosolic oxidative stress, leading to cold-induced thermogenesis.

ENDOCRINE DISRUPTING CHEMICALS AND OBESITY: THE EVOLVING STORY OF OBESOGENS

Increase in obesity pandemic all over the world consequently leads to the investigation of possible causes. In addition to the traditional explanation using the so-called caloric model, the field of endocrine disruptors (EDs), especially subgroup called obesogens, offered more light on the pathogenetic mechanisms involved. After the Second World War a correlation between an increased production of exogenous pollutants and actual obesity epidemic was suggested. "Obesogen hypothesis" implies that molecules called obesogens inadequately stimulate the development of adipose cells and lipid accumulation in existing adipose cells, as well as change metabolic balance or hormonal control of appetite and satiety, leading to an increase in body fat mass. The list of obesogens includes some industrial chemicals, biocides, pharmaceuticals, pollutants, and smoke. EDs from the group of obesogens may exert their effects by the impairment in the programming development of adipocytes, by an increase in energetic depot in the adipose tissue, and by influencing neuroendocrine control of appetite and satiety. Increased scientific evidence on obesogens and their mechanisms of action may help to prevent obesity and mitigate deleterious effects of the environment on human life and development. New translational studies are needed to explain the possible mechanism proposed.

Impact of Ag Nanoparticles (AgNPs) and Multimicrobial Preparation (EM) on the Carcass, Mineral, and Fatty Acid Composition of Cornu aspersum aspersum Snails

The hygienic practices on farms should reduce pathogenic microorganisms while simultaneously not harming the animals themselves; they must also not degrade the products' quality. We assessed the effect of covering feed tables with paint containing silver nanoparticles (AgNPs) and the periodic spraying of effective microorganisms (EM) on production indicators and basic chemical composition, mineral content and fatty acid profiles in the bodies of Cornu aspersum aspersum snails. The animals were divided into four groups: (1) control, (2) with feed tables covered with AgNPs paint, (3) with EM spray applied and (4) with both factors-AgNP paint and EM spray. The highest increase in Ag, Zn, Fe and Ca retention, and the remodelling of the fatty acid profile in the carcasses of snails was found to be in the group of animals in contact with the feed tables covered with AgNP paint. In the group of animals exposed to the action of EM, an increased retention of Fe, Cu, P, Mg and Zn was found.

In Vivo Study of Entero- and Hepatotoxicity of Silver Nanoparticles Stabilized with Benzyldimethyl-[3-myristoylamine)-propyl]ammonium Chloride (Miramistin) to CBF1 Mice upon Enteral Administration

Silver nanoparticles (AgNPs) are the most widely studied antimicrobial nanomaterials. However, their use in biomedicine is currently limited due to the availability of data that prove the nanosilver toxicity associated primarily with oxidative stress development in mammalian cells. The surface modification of AgNPs is a potent technique of improvement of their biocompatibility. The synthetic or natural compounds that combine zero or low toxicity towards human and animal organisms with inherent antimicrobial properties are the most promising stabilizing agents, their use would also minimize the risks of microorganisms developing resistance to silver-based materials. We used a simple technique to obtain 30–60 nm AgNPs stabilized with benzyldimethyl[3-myristoylamine)-propyl]ammonium chloride monohydrate (BAC)—a well-known active ingredient of many antibacterial drugs. The objective of the study was to assess the AgNPs-BAC entero- and hepatotoxicity to CBF1 mice upon enteral administration. The animals were exposed to 0.8–7.5 mg/kg doses of AgNPs-BAC in the acute and to 0.05–2.25 mg/kg doses of AgNPs-BAC in the subacute experiments. No significant entero- and hepatotoxic effects following a single exposure to doses smaller than 4 mg/kg were detected. Repeated exposure to the doses of AgNPs-BAC below 0.45 mg/kg and to the doses of BAC below 0.5 mg/kg upon enteral administration also led to no adverse effects. During the acute experiment, the higher AgNPs-BAC dose resulted in increased quantities of aminotransferases and urea, as well as the albumin-globulin ratio shift, which are indicative of inflammatory processes. Besides, the relative mass of the liver of mice was smaller compared to the control. During the subacute experiment, the groups treated with the 0.25–2.25 mg/kg dose of AgNPs-BAC had a lower weight gain rate compared to the control, while the groups treated with the 2.25 mg/kg dose of AgNPs-BAC showed statistically significant variations in the blood serum transaminases activity, which indicated hepatosis. It should be noted that the spleen and liver of the animals from the groups treated with the 0.45 and 2.25 mg/kg dose of AgNPs-BAC were more than two times smaller compared to the control. In the intestines of some animals from the group treated with the 2.25 mg/kg dose of AgNPs-BAC small areas of hyperemia and enlarged Peyer’s patches were observed. Histological examination confirmed the initial stages of the liver and intestinal wall inflammation.

Synergistic Treatment of Obesity via Locally Promoting Beige Adipogenesis and Antioxidative Defense in Adipose Tissues

Obesity is a primary risk factor for type 2 diabetes, cardiovascular diseases, cancer, and other chronic diseases. Current antiobesity medications need frequent administration and show limited efficacy with severe side effects. Herein, browning agent rosiglitazone (Rsg) and antioxidant manganese tetroxide nanoparticles (MnNPs, around 250 nm) are integrated into electrospun short fibers (SF@Rsg-Mn) with a 1.5 μm width and a 20 μm length. Upon injection into inguinal adipose tissues, SF@Rsg-Mn are well retained in the local depots to sustainably release Rsg in 30 days for adipose tissue browning, while MnNPs on the fiber surface continuously scavenge adipose reactive oxygen species (ROS) for an extended period of time. Synergistic inhibition of fat accumulation through ROS scavenging and white adipocyte browning has been demonstrated for the first time, and the optimal synergistic ratio of Rsg and MnNPs is determined to be 1/14 via combination index examination. SF@Rsg-Mn inhibit lipid accumulation through downregulation of adipogenic gene PPARγ while promoting energy expenditure through upregulation of brown-specific gene UCP1 and mitochondrial function gene COX7A1. In a diet-induced obesity mouse model, a single injection of SF@Rsg-Mn into inguinal adipose tissues has accomplished a synergistic effect on body weight loss, fat reduction, glucose, and lipid metabolic improvement while minimizing adverse effects on other tissues, thereby paving the way to efficacious, safe, and practical treatment of obesity.

Obesogens: How They Are Identified and Molecular Mechanisms Underlying Their Action

Adult and childhood obesity have reached pandemic level proportions. The idea that caloric excess and insufficient levels of physical activity leads to obesity is a commonly accepted answer for unwanted weight gain. This paradigm offers an inconclusive explanation as the world continually moves towards an unhealthier and heavier existence irrespective of energy balance. Endocrine disrupting chemicals (EDCs) are chemicals that resemble natural hormones and disrupt endocrine function by interfering with the body's endogenous hormones. A subset of EDCs called obesogens have been found to cause metabolic disruptions such as increased fat storage, in vivo. Obesogens act on the metabolic system through multiple avenues and have been found to affect the homeostasis of a variety of systems such as the gut microbiome and adipose tissue functioning. Obesogenic compounds have been shown to cause metabolic disturbances later in life that can even pass into multiple future generations, post exposure. The rising rates of obesity and related metabolic disease are demanding increasing attention on chemical screening efforts and worldwide preventative strategies to keep the public and future generations safe. This review addresses the most current findings on known obesogens and their effects on the metabolic system, the mechanisms of action through which they act upon, and the screening efforts through which they were identified with. The interplay between obesogens, brown adipose tissue, and the gut microbiome are major topics that will be covered.

Transferrin Receptor Functionally Marks Thermogenic Adipocytes

Background

Thermogenic adipocytes, including beige and brown adipocytes, are critical for thermogenesis and energy homeostasis. Identification of functional cell surface markers of thermogenic adipocytes is of significance for potential application in biological and clinical practices.

Methods

With a combination of RNA-sequencing of in vivo and in vitro models, we identified transferrin receptor (Tfr1), a receptor specialized for cellular iron uptake, as a previously unappreciated cell surface molecule for thermogenic adipocytes compared to white adipocytes. The alternation of Tfr1 levels under physiological and pathological stimuli was assessed, and the mitochondria functionality, browning capacity, and iron metabolism of mature adipocytes were examined with Tfr1 knockdown.

Results

Tfr1 was expressed predominantly in thermogenic adipocytes versus white adipocyte, and its expression levels were tightly correlated with the activation or inhibition status of thermogenic adipocytes under external stimuli. Besides, Tfr1 gene deficiency in thermogenic adipocytes led to reduced thermogenic gene programs and mitochondrial integrity.

Conclusion

Tfr1 functionally marks thermogenic adipocytes and could serve as a potential thermogenic adipocyte surface marker.