MEK6 Overexpression Exacerbates Fat Accumulation and Inflammatory Cytokines in High-Fat Diet-Induced Obesity

Obesity is a state of abnormal fat accumulation caused by an energy imbalance potentially caused by changes in multiple factors. MEK6 engages in cell growth, such as inflammation and apoptosis, as one of the MAPK signaling pathways. The MEK6 gene was found to be related to RMR, a gene associated with obesity. Because only a few studies have investigated the correlation between MEK6 and obesity or the relevant mechanisms, we conducted an experiment using a TgMEK6 model with MEK6 overexpression with non-Tg and chow diet as the control to determine changes in lipid metabolism in plasma, liver, and adipose tissue after a 15-week high-fat diet (HFD). MEK6 overexpression in the TgMEK6 model significantly increased body weight and plasma triglyceride and total cholesterol levels. p38 activity declined in the liver and adipose tissues and lowered lipolysis, oxidation, and thermogenesis levels, contributing to decreased energy consumption. In the liver, lipid formation and accumulation increased, and in adipose, adipogenesis and hypertrophy increased. The adiponectin/leptin ratio significantly declined in plasma and adipose tissue of the TgMEK6 group following MEK6 expression and the HFD, indicating the role of MEK6 expression in adipokine regulation. Plasma and bone-marrow-derived macrophages (BMDM) of the TgMEK6 group increased MEK6 expression-dependent secretion of pro-inflammatory cytokines but decreased levels of anti-inflammatory cytokines, further exacerbating the results exhibited by the diet-induced obesity group. In conclusion, this study demonstrated the synergistic effect of MEK6 with HFD in fat accumulation by significantly inhibiting the mechanisms of lipolysis in the adipose and M2 associated cytokines secretion in the BMDM.

Metformin Ameliorates Ethanol-Induced Liver Triglyceride Accumulation by LKB1/AMPK/ACC Pathway

Background: Hepatic lipid accumulation is one of the main pathological features of alcoholic liver disease. Metformin is an AMPK activator that has been shown to have lipid lowering effects. The purpose of this study was to investigate whether metformin had a beneficial effect on lipid accumulation in the pathogenesis of ALD.Methods: AML12 cells and male C57BL/6 mice were used to establish ALD models in vitro and in vivo, respectively. The effects of metformin on hepatocyte lipid accumulation and ALD progression in mice were detected. The role of LKB1/AMPK/ACC axis in metformin against ethanol-induced lipid accumulation was evaluated by siRNA and AAV-shRNA interference.Results: Metformin reduced the ethanol-induced lipid accumulation in AML12 cells through activating AMPK/ACC and SREBP1c and inhibiting PPARα. In addition, compared with control mice, metformin treatment inhibited ethanol-induced liver adipose accumulation and the increase of ALT and AST in serum. Interference with LKB1 attenuated the effect of metformin on ethanol-induced lipid accumulation both in vitro and in vivo.Conclusion: Metformin protects against lipid formation in ALD by activating LKB1/AMPK/ACC axis. Thus, metformin has therapeutic potential for the prevention of ALD.

Oleaginous yeasts respond differently to carbon sources present in lignocellulose hydrolysate

Background Microbial oils, generated from lignocellulosic material, have great potential as renewable and sustainable alternatives to fossil-based fuels and chemicals. By unravelling the diversity of lipid accumulation physiology in different oleaginous yeasts grown on the various carbon sources present in lignocellulose hydrolysate (LH), new targets for optimisation of lipid accumulation can be identified. Monitoring lipid formation over time is essential for understanding lipid accumulation physiology. This study investigated lipid accumulation in a variety of oleaginous ascomycetous and basidiomycetous strains grown in glucose and xylose and followed lipid formation kinetics of selected strains in wheat straw hydrolysate (WSH). Results Twenty-nine oleaginous yeast strains were tested for their ability to utilise glucose and xylose, the main sugars present in WSH. Evaluation of sugar consumption and lipid accumulation revealed marked differences in xylose utilisation capacity between the yeast strains, even between those belonging to the same species. Five different promising strains, belonging to the species Lipomyces starkeyi, Rhodotorula glutinis, Rhodotorula babjevae and Rhodotorula toruloides, were grown on undiluted wheat straw hydrolysate and lipid accumulation was followed over time, using Fourier transform-infrared (FTIR) spectroscopy. All five strains were able to grow on undiluted WSH and to accumulate lipids, but to different extents and with different productivities. R. babjevae DVBPG 8058 was the best-performing strain, accumulating 64.8% of cell dry weight (CDW) as lipids. It reached a culture density of 28 g/L CDW in batch cultivation, resulting in a lipid content of 18.1 g/L and yield of 0.24 g lipids per g carbon source. This strain formed lipids from the major carbon sources in hydrolysate, glucose, acetate and xylose. R. glutinis CBS 2367 also consumed these carbon sources, but when assimilating xylose it consumed intracellular lipids simultaneously. Rhodotorula strains contained a higher proportion of polyunsaturated fatty acids than the two tested Lipomyces starkeyi strains. Conclusions There is considerable metabolic diversity among oleaginous yeasts, even between closely related species and strains, especially when converting xylose to biomass and lipids. Monitoring the kinetics of lipid accumulation and identifying the molecular basis of this diversity are keys to selecting suitable strains for high lipid production from lignocellulose.

A Study of the Regulatory Mechanism of the CB1/PPARγ2/PLIN1/HSL Pathway for Fat Metabolism in Cattle

Fat metabolism is closely related to the economic characteristics of beef cattle. Therefore, regulating fat deposition and increasing intramuscular fat deposition are among the main goals of breeders. In this study, we aim to explore the regulatory role of CB1 gene on PPARγ2/PLIN1/HSL pathway in fat metabolism, and to further explore the differential expression of regulatory factors of this pathway in Shandong black cattle and Luxi cattle. In this study, CB1 overexpression stimulated lipid synthesis in adipocytes to some extent by increasing the levels of FASN and ACSL1. CB1 inhibitors reduce the lipid content in adipocytes and reduce the expression of GLUT1 and Insig1. In addition, overexpression of CB1 decreased the expression of PPARγ2 and led to an increase in PLIN1 expression and a decrease in HSL expression in adipocytes. We also found that the CB1/PPARγ2/PLIN1/HSL was differentially expressed in the different breeds of cattle and was involved in the regulation of fat metabolism, which affected the fatty acid content in the longissimus dorsi muscle of the two breeds. In short, CB1 participates in lipid metabolism by regulating HSL in the PPARγ2 and PLIN1 pathways, and improves lipid formation in adipocytes. In conclusion, CB1/PPARγ2/PLIN1/HSL pathway may be involved in the regulation of lipid metabolism.

Circ-140/chi-miR-8516/STC1-MMP1 Regulates αs1-/β-Casein Secretion and Lipid Formation in Goat Mammary Epithelial Cells

MicroRNAs play an essential role in mammary gland development, and involution is a factor that limits lactation. Chi-miR-8516 is one of the validated microRNAs that regulates the expression of STC1 and MMP1, which surge during the involution of the mammary gland. This study aims to explore the direct or indirect regulation of STC1 and MMP1 by chi-miR-8516 and the regulation of chi-miR-8516 by circ-140. In goat mammary epithelial cells, we found that chi-miR-8516 takes circ-140 as a sponge and regulates MMP1 expression by targeting STC1 and promoting the phosphorylation of MAPK. The examination of αs1-/β-casein and lipid showed the modulation of the circ-140/chi-miR-8516/STC1-MMP1 axis in casein secretion and lipid formation, which was regulated by the phosphorylation of mTOR and STAT5. This study illustrates an axis that regulates the synthesis of milk components, and explores the pathways in which the axis participates.

In Vivo Evaluation of Dendropanax morbifera Leaf Extract for Anti-Obesity and Cholesterol-Lowering Activity in Mice

Metabolic syndrome is a worldwide health problem, and obesity is closely related to type 2 diabetes, cardiovascular disease, hypertension, and cancer. According to WHO in 2018, the prevalence of obesity in 2016 tripled compared to 1975. D. morbifera reduces bad cholesterol and triglycerides levels in the blood and provides various antioxidant nutrients and germicidal sub-stances, as well as selenium, which helps to remove active oxygen. Moreover, D. morbifera is useful for treating cardiovascular diseases, hypertension, hyperlipidemia, and diabetes. Therefore, we study in vivo efficacy of D. morbifera to investigate the prevention effect of obesity and cholesterol. The weight and body fat were effectively reduced by D. morbifera water (DLW) extract administration to high-fat diet-fed C57BL/6 mice compared to those of control mice. The group treated with DLW 500 mg∙kg−1∙d−1 had significantly lower body weights compared to the control group. In addition, High-density lipoprotein (HDL) cholesterol increased in the group treated with DLW 500 mg∙kg−1∙d−1. The effect of DLW on the serum lipid profile could be helpful to prevent obesity. DLW suppresses lipid formation in adipocytes and decreases body fat. In conclusion, DLW can be applied to develop anti-obesity functional foods and other products to reduce body fat.

Butyric acid alleviated chronic intermittent hypoxia-induced lipid formation and inflammation through upregulating HuR expression and inactivating AMPK pathways

To investigate whether butyric acid could alleviate chronic intermittent hypoxia (CIH)-induced lipid formation in human preadipocytes-subcutaneous (HPA-s) through accumulation of human antigen R (HuR) and inactivation of AMP-activated protein kinase (AMPK) pathway, human preadipocytes-subcutaneous (HPA-s) were obtained and divided into 3 groups: CIH group: cells were cultured in a three-gas incubator (10% O2); Butyric acid group: 10 mmol/L butyric acid added into cell culture medium. HuR-siRNA was futher transfected into CIH group for verification the function of HuR. Oil red O was implemented for observation of lipid droplets within cells. CCK8 assay was used for detecting cell viability. TUNEL assay as well as flow cytometry analysis was employed for determining cell apoptosis. Western blotting was used for measurement of protein expression levels. RT-qPCR analysis was used for detecting mRNA expression. CIH treatment increased adipocytes proliferation, while butyric acid inhibited cell proliferation and promoted cell apoptosis. The treatment of butyric acid in CIH group downregulated expression of inflammatory factors and increase cell apoptotic rate. Butyric acid treatment increased HuR expression in both cytoplasm and nucleus and decreased the level of p-AMPK and p-ACC, while transfection of AMPK activator or HuR-siRNA would downregulate HuR expression. Moreover, butyric acid alleviated CIH-induced cell proliferation, lipid formation and inflammatory status and promoted cell apoptosis through regulating related genes including p21, PPARγ, C/EBPa, IL-1β, IL-6, TLR4, caspase-8 and caspase-3. In conclusion, butyric acid could alleviate CIH-induced inflammation, cell proliferation and lipid formation through accumulation of HuR and inactivation of AMPK pathway.

Optimisation of microalgal cultivation via nutrient-enhanced strategies: the biorefinery paradigm

Background The production of microalgal biofuels, despite their sustainable and renowned potential, is not yet cost-effective compared to current conventional fuel technologies. However, the biorefinery concept increases the prospects of microalgal biomass as an economically viable feedstock suitable for the co-production of multiple biofuels along with value-added chemicals. To integrate biofuels production within the framework of a microalgae biorefinery, it is not only necessary to exploit multi-product platforms, but also to identify optimal microalgal cultivation strategies maximising the microalgal metabolites from which biofuels are obtained: starch and lipids. Whilst nutrient limitation is widely known for increasing starch and lipid formation, this cultivation strategy can greatly reduce microalgal growth. This work presents an optimisation framework combining predictive modelling and experimental methodologies to effectively simulate and predict microalgal growth dynamics and identify optimal cultivation strategies. Results Microalgal cultivation strategies for maximised starch and lipid formation were successfully established by developing a multi-parametric kinetic model suitable for the prediction of mixotrophic microalgal growth dynamics co-limited by nitrogen and phosphorus. The model’s high predictive capacity was experimentally validated against various datasets obtained from laboratory-scale cultures of Chlamydomonas reinhardtii CCAP 11/32C subject to different initial nutrient regimes. The identified model-based optimal cultivation strategies were further validated experimentally and yielded significant increases in starch (+ 270%) and lipid (+ 74%) production against a non-optimised strategy. Conclusions The optimised microalgal cultivation scenarios for maximised starch and lipids, as identified by the kinetic model presented here, highlight the benefits of exploiting modelling frameworks as optimisation tools that facilitate the development and commercialisation of microalgae-to-fuel technologies.