The effects of short-chain fatty acid acetate on brown adipocytes differentiation and metabolism

Short-chain fatty acids (SCFA) are a sub-group of fatty acids including formic acid, acetic acid, propionic acid, isobutyric acid, butyric acid, isovaleric acid and valeric acid. Acetate, propionate and butyrate are three major shortchain fatty acids, which are mainly formed in the gastrointestinal tract via colonic bacteria fermentation of carbohydrates, especially resistant starches and dietary fibre. There has been increasing interest in the idea that the short-chain fatty acids play crucial roles in a range of physiological functions. Recently, increasing evidence suggested there is a strong link between short-chain fatty acids and energy homeostasis. Several studies highlighted the protective effects of the short-chain fatty acids on high-fat diet induced obesity and other harmful metabolic disorders in mice. However, the coherent understanding of the multi-level network in which short-chain fatty acids exert their effects still needs to be elucidated. Up to date, it has been demonstrated that short-chain fatty acids can mediate energy balance via affecting appetite control in brain, increasing adipogenesis in white adipocyte, and regulating insulin sensitivities in white adipose tissue and muscle, etc. However, the effects of short-chain fatty acids on brown adipocytes have not been fully investigated. In this study, we examined the roles of short-chain fatty acid acetate and its receptor(s) in the regulation of brown adipocyte differentiation and metabolism. Firstly, we identified the expression of short-chain fatty acids sensing GPR43 in brown adipose tissue and immortalized brown adipocytes by real-time PCR, Western blots and immunohistochemistry. Moreover, GPR43 expression was found to increase during the adipogenesis of cultured brown adipocytes. Pro-adipogenic reagent PPARγ agonist stimulation led to a further augment of GPR43 expression while antiadipogenic reagents such as PPARγ antagonist, RXR antagonist and STAT5 inhibitor played the opposite role on GPR43 expression. Transcription factors such as XBP1 and STAT5 were identified to be involved in GPR43 expression regulation in brown adipocytes. Furthermore, we also examined the role of acetate in the regulation of brown adipogenesis. Our results showed that acetate treatment during adipogenesis up-regulated AP2, PGC-1α and UCP1 expression and affected the morphological changes of brown adipocytes. Moreover, an increase in mitochondrial biogenesis was observed after acetate treatment. Acetate also elicited the activation of ERK and CREB, and these responses were sensitive to G(i/o)-type G-protein inactivator, Gβγ-subunit inhibitor, PLC inhibitor and MEK inhibitor, indicating a role for the G(i/o)βγ/PLC/PKC/MEK signalling pathway in these responses. These effects of acetate were mimicked by treatment with 4-CMTB, a synthetic GPR43 agonist, and were impaired in GPR43 knock-down cells, further supported the hypothesis that GPR43 mediates the pro-adipogenic effects of acetate in brown adipocytes. Furthermore, the effects of acetate treatment on brown adipose tissue were also measured in vivo. Mice fed with acetate demonstrated increased PGC-1α in brown adipose tissue, which was in agreement with the results obtained from immortalized brown adipocytes. In addition, we also measured the effects of acetate on lipid metabolism in differentiated brown adipocytes. The results showed effects of acetate treatment on lipolysis were different in white adipocytes and brown adipocytes. Acetate treatment significantly decreased the lipolysis in white adipocytes while had little effects on lipolysis in brown adipocytes. Besides, acetate treatment was also found to decrease TF2-C12 fatty acid uptake in differentiated IM-BAT cells, suggesting acetate may affect many aspects of lipid metabolism in brown adipocytes. Collectively, our results indicated that acetate might have important physiological roles in brown adipocytes. Short-chain fatty acids may serve to regulate brown adipose tissue functions and therefore improve metabolic health

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Anti-Aging Effects of R-Phycocyanin from <i>Porphyra haitanensis</i> on HUVEC Cells and <i>Drosophila melanogaster</i>

Aging has become a global public health challenge. Many studies have revealed that the excessive generation of ROS and oxidative stress could be the major causative factors contributing to aging. In this study, R-phycocyanin (R-PC) was isolated from Porphyra haitanensis, and its anti-aging ability was explored by natural aging Drosophila melanogaster and H2O2-induced HUVEC cells as the aging model. Results showed that R-PC α and β subunits expressed have antioxidant activity and can inhibit the generation of radicals, exhibiting a protective effect against H2O2-induced apoptotic HUVEC cells death. R-PC prevented the H2O2-induced HUVEC cell cycle phase arrest by regulating cell cycle-related protein. Furthermore, R-PC prevented the H2O2-induced HUVEC cell cycle phase arrest by regulating cell-cycle-related protein expression. In vivo study also indicated that R-PC significantly increased the survival time and alleviated the oxidative stress of Drosophila melanogaster. Moreover, R-PC notably decreased levels of ROS in natural aging flies and inhibited lipid peroxidation by enhancing the expressions of the endogenous stress marker genes (SOD1, SOD2, CAT of Drosophila melanogaster). Taken together, a study on the antioxidation extract from Porphyra haitanensis, such as R-PC, may open a new window for the prevention of anti-aging

Endocrine disruptors in foods: Overlooked factors contributing to the prevalence of obesity

Endocrine disruptors, also known as endocrine-disrupting chemicals, could mimic or interfere with the body's hormones. Indeed, naturally occurring endocrine disruptors have been widely identified in daily foods. Moreover, industrialisation has resulted in increasing synthetic endocrine disruptors being produced and used as food additives or in food package materials, which makes exposure to endocrine disruptors become more common. Although the safety of synthetic chemicals has been extensively evaluated before entering into the food industry, increasing evidence has also highlighted that long-lasting exposure might influence long-term metabolic outcomes and be associated with the prevalence of obesity. Therefore, this review summarised the sources, detection methods, obesogenic effects and possible mechanisms of endocrine disruptors commonly found in foods, as well as discussed possible underlying mechanisms by which endocrine disruptors contribute to the increased risk of obesity. In conclusion, the review may provide useful information for understanding the association between endocrine disruptors and obesity, which could provide a new angle of view for preventing obesity prevalence

Expression of GPR43 in Brown Adipogenesis Is Enhanced by Rosiglitazone and Controlled by PPAR γ

GPR43, a G-protein coupled receptor recognizing short-chain fatty acids, has been reported to participate in many biological functions of white adipocytes, such as adipogenesis and lipolysis. However, the functional role of GPR43 in brown adipocytes is still not clear. In this study, we investigated the effects of the PPARγ agonist rosiglitazone on GPR43 expression in brown adipogenesis. The results demonstrated that GPR43 was expressed during the late phase of brown adipocyte differentiation, which could be further augmented by adipogenic agent rosiglitazone treatment. The PPARγ/RXR heterodimerization was found to be the key transcription factor for this enhancing effect of rosiglitazone on GPR43 expression. Taken together, these results suggested GPR43 levels might be regulated by PPARγ-activated events during brown adipocytes differentiation and reflect the adipogenesis status of brown adipocytes

Prokaryotic Expression, Purification, and Antibacterial Activity of the Hepcidin Peptide of Crescent Sweetlips (<i>Plectorhinchus cinctus</i>)

The hepcidin peptide of crescent sweetlips (Plectorhinchus cinctus) is a cysteine-rich, cationic antimicrobial peptide that plays a crucial role in the innate immune system’s defense against invading microbes. The aim of this study was to identify the optimal parameters for prokaryotic expression and purification of this hepcidin peptide and characterize its antibacterial activity. The recombinant hepcidin peptides were expressed in Escherichia coli strain Arctic Express (DE3), with culture and induction conditions optimized using response surface methodology (RSM). The obtained hepcidin peptides were then purified before tag cleavage, and their antibacterial activity was determined. The obtained results revealed that induction temperature had the most significant impact on the production of soluble recombinant peptides. The optimum induction conditions were determined to be an isopropylthio-β-galactoside (IPTG) concentration of 0.21 mmol/L, induction temperature of 18.81 °C, and an induction time of 16.01 h. Subsequently, the recombinant hepcidin peptide was successfully purified using Ni-IDA affinity chromatography followed by SUMO protease cleavage. The obtained hepcidin peptide (without His-SUMO tag) demonstrated strong antimicrobial activity in vitro against V. parahaemolyticus, E. coli, and S. aureus. The results showed prokaryotic (E. coli) expression is a feasible way to produce the hepcidin peptide of crescent sweetlips in a cost-effective way, which has great potential to be used as an antimicrobial agent in aquaculture

Proteomics Studies in Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

Gestational Diabetes Mellitus (GDM) is the most common metabolic complication during pregnancy and is associated with serious maternal and fetal complications such as pre-eclampsia and stillbirth. Further, women with GDM have approximately 10 times higher risk of diabetes later in life. Children born to mothers with GDM also face a higher risk of childhood obesity and diabetes later in life. Early prediction/diagnosis of GDM leads to early interventions such as diet and lifestyle, which could mitigate the maternal and fetal complications associated with GDM. However, no biomarkers identified to date have been proven to be effective in the prediction/diagnosis of GDM. Proteomic approaches based on mass spectrometry have been applied in various fields of biomedical research to identify novel biomarkers. Although a number of proteomic studies in GDM now exist, a lack of a comprehensive and up-to-date meta-analysis makes it difficult for researchers to interpret the data in the existing literature. Thus, we undertook a systematic review and meta-analysis on proteomic studies and GDM. We searched MEDLINE, EMBASE, Web of Science and Scopus from inception to January 2022. We searched Medline, Embase, CINHAL and the Cochrane Library, which were searched from inception to February 2021. We included cohort, case-control and observational studies reporting original data investigating the development of GDM compared to a control group. Two independent reviewers selected eligible studies for meta-analysis. Data collection and analyses were performed by two independent reviewers. The PROSPERO registration number is CRD42020185951. Of 120 articles retrieved, 24 studies met the eligibility criteria, comparing a total of 1779 pregnant women (904 GDM and 875 controls). A total of 262 GDM candidate biomarkers (CBs) were identified, with 49 CBs reported in at least two studies. We found 22 highly replicable CBs that were significantly different (nine CBs were upregulated and 12 CBs downregulated) between women with GDM and controls across various proteomic platforms, sample types, blood fractions and time of blood collection and continents. We performed further analyses on blood (plasma/serum) CBs in early pregnancy (first and/or early second trimester) and included studies with more than nine samples (nine studies in total). We found that 11 CBs were significantly upregulated, and 13 CBs significantly downregulated in women with GDM compared to controls. Subsequent pathway analysis using Database for Annotation, Visualization and Integrated Discovery (DAVID) bioinformatics resources found that these CBs were most strongly linked to pathways related to complement and coagulation cascades. Our findings provide important insights and form a strong foundation for future validation studies to establish reliable biomarkers for GDM

Preparation and Characterization of Biodegradable &kappa;-Carrageenan Based Anti-Bacterial Film Functionalized with Wells-Dawson Polyoxometalate

In the present study, an anti-bacterial film (Carr/POM film) was prepared through the incorporation of Wells-Dawson polyoxometalate K6[Mo18O62P2] into &kappa;-carrageenan-based polymers using the tape-casting method. The mechanical properties, thermal stability, and morphology of the prepared film were characterized. The obtained results showed that incorporation of K6[Mo18O62P2] significantly affected the morphology and structure of the films. Moreover, the polyoxometalate-based film demonstrated desirable bactericidal activity against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive). Carr/POM (@8 mg/mL) film resulted in an obvious inhibition zone around the film in Kirby-Bauer disk diffusion test, which could also remove 99% of S. aureus and E. coli on plastic, glass, and stainless steel. In addition, this anti-bacterial film also demonstrated good biodegradability, which could be decomposed in soil in around 1 week. In conclusion, the polyoxometalate-based film showed good anti-bacterial property against food-borne pathogenic microbes, suggesting the prepared film has great potential to be developed as promising food packaging