Fatty acid activation in thermogenic adipose tissue

The cellular and molecular targets of natural products against metabolic disorders: a translational approach to reach the bedside

Metabolic disorders, including obesity, dyslipidemia, diabetes, nonalcoholic fatty liver disease, and metabolic syndrome, are characterized by insulin resistance, abnormalities in circulating cholesterol and lipid profiles, and hypertension. The most common pathophysiologies of metabolic disorders are glucose/lipid metabolism dysregulation, insulin resistance, inflammatory response, and oxidative stress. Although several agents have been approved for the treatment of metabolic disorders, there is still a strong demand for more efficacious drugs with less side effects. Natural products have been critical sources of drug research and discovery for decades. However, the usefulness of bioactive natural products is often limited by incomplete understanding of their direct cellular targets. In this review, we highlight the current understanding of the established and emerging molecular mechanisms of metabolic disorders. We further summarize the therapeutic effects and underlying mechanisms of natural products on metabolic disorders, with highlights on their direct cellular targets, which are mainly implicated in the regulation of glucose/lipid metabolism, insulin resistance, metabolic inflammation, and oxidative stress. Finally, this review also covers the clinical studies of natural products in metabolic disorders. These progresses are expected to facilitate the application of these natural products and their derivatives in the development of novel drugs against metabolic disorders.

Licochalcone D ameliorates lipid metabolism in hepatocytes by modulating lipogenesis and autophagy

Metabolic dysfunction-associated fatty liver disease is a metabolic disease caused by abnormal lipid accumulation in the liver. Excessive lipid accumulation results in liver inflammation and fibrosis. Previous studies have demonstrated that the chalcone licochalcone D, which is isolated from Glycyrrhiza inflata Batal, has anti-tumor and anti-inflammatory effects. The present study explored whether licochalcone D can regulate lipid accumulation in fatty liver cells. FL83B hepatocytes were incubated with oleic acid to establish a fatty liver cell model, and then treated with licochalcone D to evaluate the molecular mechanisms underlying the regulation of lipid metabolism. In addition, male C57BL/6 mice were fed a methionine/choline-deficient diet to induce an animal model of metabolic dysfunction-associated steatohepatitis (MASH) and given 5 mg/kg licochalcone D by intraperitoneal injection. In cell experiments, licochalcone D significantly reduced lipid accumulation in fatty liver cells and reduced sterol regulatory element-binding protein 1c expression, blocking fatty acid synthase production. Licochalcone D increased adipose triglyceride lipase and carnitine palmitoyltransferase 1 expression, enhancing lipolysis and fatty acid β-oxidation, respectively. Licochalcone D also significantly increased SIRT-1 and AMPK phosphorylation, reducing acetyl-CoA carboxylase phosphorylation and inhibiting fatty acid synthesis. Licochalcone D also increased the fusion of autophagosomes and lysosomes to promote autophagy, reducing oil droplet accumulation in fatty liver cells. In the animal experiments, licochalcone D effectively reduced the number of lipid vacuoles and degree of fibrosis in liver tissue and inhibited liver inflammation. Thus, licochalcone D can improve MASH by reducing lipid accumulation, inhibiting inflammation, and increasing autophagy.

Knockdown of ACOT4 alleviates gluconeogenesis and lipid accumulation in hepatocytes

Acyl-CoA thioesterase 4 (ACOT4) has been reported to be related to acetyl-CoA carboxylase activity regulation; However, its exact functions in liver lipid and glucose metabolism are still unclear. Here, we discovered explored the regulatory roles of ACOT4 in hepatic lipid and glucose metabolism in vitro. We found that the expression level of ACOT4 was significantly increased in the hepatic of db/db and ob/ob mice as well as obese mice fed a high fat diet. Adenovirus-mediated overexpression of ACOT4 promoted gluconeogenesis and high-glucose/high-insulin-induced lipid accumulation and impaired insulin sensitivity in primary mouse hepatocytes, whereas ACOT4 knockdown notably suppressed gluconeogenesis and decreased the triglycerides accumulation in hepatocytes. Furthermore, ACOT4 knockdown increased insulin-induced phosphorylation of AKT and GSK-3β in primary mouse hepatocytes. Mechanistically, we found that upregulation of ACOT4 expression inhibited AMP-activated protein kinase (AMPK) activity, and its knockdown had the opposite effect. However, activator A769662 and inhibitor compound C of AMPK suppressed the impact of the change in ACOT4 expression on AMPK activity. Our data indicated that ACOT4 is related to hepatic glucose and lipid metabolism, primarily via the regulation of AMPK activity. In conclusion, ACOT4 is a potential target for the therapy of non-alcoholic fatty liver (NAFLD) and type 2 diabetes.

Extract mixture of plants (OXYLIA) inhibits fat accumulation by blocking FAS-related factors and promoting lipolysis via cAMP-dependent PKA activation

Background

Obesity is characterized by an imbalance between energy intake and expenditure, leading to the excessive accumulation of triglycerides in adipose tissue.

Objective

This study investigated the potential of Oxylia to prevent obesity in mice fed with a high-fat diet (HFD).

Design

C57BL/6J mice were fed with one of the following five diets - AIN93G normal diet (normal control), 60% (HFD; control), HFD containing metformin at 40 mg/kg body weight (b.w.) (Met; positive control), HFD containing Oxylia at 30 mg/kg b.w. (O30), or HFD containing Oxylia at 60 mg/kg b.w. (O60) - for 15 weeks.

Results

Mice under an HFD supplemented with Oxylia had decreased body weight gain, adipose tissue weight, and adipose tissue mass. In addition, triglyceride (TG), total cholesterol, and VLDL/LDL cholesterol levels were lower in the O60 groups than in the HFD-fed control group. Moreover, Oxylia supplementation decreased the expression of adipogenesis-related mRNAs and lipogenesis-related proteins while increasing the expression of lipolysis-related proteins in white adipose tissue and thermogenesis-related proteins in brown adipose tissue.

Conclusions

These findings suggest that Oxylia has potential as a functional food ingredient for the prevention and treatment of obesity and related metabolic disorders.

Investigation of seasonal changes in lipid synthesis and metabolism-related genes in the oviduct of Chinese brown frog (<em>Rana dybowskii</em>)

A peculiar physiological characteristic of the Chinese brown frog (Rana dybowskii) is that its oviduct dilates during pre-brumation rather than during the breeding season. This research aimed to examine the expression of genes connected with lipid synthesis and metabolism in the oviduct of R. dybowskii during both the breeding season and pre-brumation. We observed significant changes in the weight and size of the oviduct between the breeding season and pre-brumation. Furthermore, compared to the breeding season, pre-brumation exhibited significantly lower triglyceride content and a marked increase in free fatty acid content. Immunohistochemical results revealed the spatial distribution of triglyceride synthase (Dgat1), triglyceride hydrolase (Lpl and Hsl), fatty acid synthase (Fasn), and fatty acid oxidases (Cpt1a, Acadl, and Hadh) in oviductal glandular cells and epithelial cells during both the breeding season and pre-brumation. While the mRNA levels of triglycerides and free fatty acid synthesis genes (dgat1 and fasn) did not show a significant difference between the breeding season and pre-brumation, the mRNA levels of genes involved in triglycerides and free fatty acid metabolism (lpl, cpt1a, acadl, acox and hadh) were considerably higher during pre-brumation. Furthermore, the R. dybowskii oviduct's transcriptomic and metabolomic data confirmed differential expression of genes and metabolites enriched in lipid metabolism signaling pathways during both the breeding season and pre-brumation. Overall, these results suggest that alterations in lipid synthesis and metabolism during pre-brumation may potentially influence the expanding size of the oviduct, contributing to the successful overwintering of R. dybowskii.

Acyl-CoA synthase ACSL4: an essential target in ferroptosis and fatty acid metabolism

ABSTRACT

Long-chain acyl-coenzyme A (CoA) synthase 4 (ACSL4) is an enzyme that esterifies CoA into specific polyunsaturated fatty acids, such as arachidonic acid and adrenic acid. Based on accumulated evidence, the ACSL4-catalyzed biosynthesis of arachidonoyl-CoA contributes to the execution of ferroptosis by triggering phospholipid peroxidation. Ferroptosis is a type of programmed cell death caused by iron-dependent peroxidation of lipids; ACSL4 and glutathione peroxidase 4 positively and negatively regulate ferroptosis, respectively. In addition, ACSL4 is an essential regulator of fatty acid (FA) metabolism. ACSL4 remodels the phospholipid composition of cell membranes, regulates steroidogenesis, and balances eicosanoid biosynthesis. In addition, ACSL4-mediated metabolic reprogramming and antitumor immunity have attracted much attention in cancer biology. Because it facilitates the cross-talk between ferroptosis and FA metabolism, ACSL4 is also a research hotspot in metabolic diseases and ischemia/reperfusion injuries. In this review, we focus on the structure, biological function, and unique role of ASCL4 in various human diseases. Finally, we propose that ACSL4 might be a potential therapeutic target.

Salacia reticulata Extract Suppresses Fat Accumulation by Regulating Lipid Metabolism

The excessive storage of triglycerides in adipose tissue is a characteristic feature of obesity, which arises from an imbalance between energy intake and expenditure. In this study, we aimed to explore the potential anti-obesity effects of Salacia reticulata extracts (SC) in a high-fat diet (HFD)-induced in obese mice and 3T3-L1 adipocytes, with a specific focus on understanding the underlying lipid mechanisms. Mice were fed with a normal diet (NC; normal control), HFD (60% high-fat diet), Met (HFD containing metformin 250 mg/kg b.w.), SC25 (HFD containing SC 25 mg/kg b.w.), SC50 (HFD containing SC 50 mg/kg b.w.), or SC 100 (HFD containing SC 100 mg/kg b.w.) for 12 weeks. Notably, SC supplementation led to significant reductions in body weight gain, adipose tissue weight, adipose tissue mass, and adipocyte size in HFD-fed mice. Furthermore, SC supplementation exerted inhibitory effects on the adipogenesis and lipogenesis pathways while promoting lipolysis and thermogenesis pathways in the adipose tissues of HFD-fed mice. In vitro experiments using 3T3-L1 cells demonstrated that SC treatment during the differentiation phase suppressed adipogenesis and lipogenesis, whereas SC treatment after differentiation, activated lipolysis and thermogenesis. Collectively, these findings indicate that SC exhibits a direct influence on the lipid metabolism of adipocytes, making it an effective candidate for weight loss interventions.

Ssu72 phosphatase is essential for thermogenic adaptation by regulating cytosolic translation

Brown adipose tissue (BAT) plays a pivotal role in maintaining body temperature and energy homeostasis. BAT dysfunction is associated with impaired metabolic health. Here, we show that Ssu72 phosphatase is essential for mRNA translation of genes required for thermogenesis in BAT. Ssu72 is found to be highly expressed in BAT among adipose tissue depots, and the expression level of Ssu72 is increased upon acute cold exposure. Mice lacking adipocyte Ssu72 exhibit cold intolerance during acute cold exposure. Mechanistically, Ssu72 deficiency alters cytosolic mRNA translation program through hyperphosphorylation of eIF2α and reduces translation of mitochondrial oxidative phosphorylation (OXPHOS) subunits, resulting in mitochondrial dysfunction and defective thermogenesis in BAT. In addition, metabolic dysfunction in Ssu72-deficient BAT returns to almost normal after restoring Ssu72 expression. In summary, our findings demonstrate that cold-responsive Ssu72 phosphatase is involved in cytosolic translation of key thermogenic effectors via dephosphorylation of eIF2α in brown adipocytes, providing insights into metabolic benefits of Ssu72.

The role of noncoding RNAs in cancer lipid metabolism

Research on noncoding ribonucleic acids (ncRNAs) is mostly and broadly focused on microRNAs (miRNAs), cyclic RNAs (circRNAs), and long ncRNAs (lncRNAs), which have been confirmed to play important roles in tumor cell proliferation, invasion, and migration. Specifically, recent studies have shown that ncRNAs contribute to tumorigenesis and tumor development by mediating changes in enzymes related to lipid metabolism. The purpose of this review is to discuss the characterized ncRNAs involved in the lipid metabolism of tumors to highlight ncRNA-mediated lipid metabolism-related enzyme expression in malignant tumors and its importance to tumor development. In this review, we describe the types of ncRNA and the mechanism of tumor lipid metabolism and analyze the important role of ncRNA in tumor lipid metabolism and its future prospects from the perspectives of ncRNA biological function and lipid metabolic enzyme classification. However, several critical issues still need to be resolved. Because ncRNAs can affect tumor processes by regulating lipid metabolism enzymes, in the future, we can study the unique role of ncRNAs from four aspects: disease prevention, detection, diagnosis, and treatment. Therefore, in the future, the development of ncRNA-targeted therapy will become a hot direction and shoulder a major task in the medical field.

MicroRNA and circular RNA profiling in the deposited fat tissue of Sunite sheep

As the most typical deposited fat, tail fat is an important energy reservoir for sheep adapted to harsh environments and plays an important role as a raw material in daily life. However, the regulatory mechanisms of microRNA (miRNA) and circular RNA (circRNA) in tail fat development remain unclear. In this study, we characterized the miRNA and circRNA expression profiles in the tail fat of sheep at the ages of 6, 18, and 30 months. We identified 219 differentially expressed (DE) miRNAs (including 12 novel miRNAs), which exhibited a major tendency to be downregulated, and 198 DE circRNAs, which exhibited a tendency to be upregulated. Target gene prediction analysis was performed for the DE miRNAs. Functional analysis revealed that their target genes were mainly involved in cellular interactions, while the host genes of DE circRNAs were implicated in lipid and fatty acid metabolism. Subsequently, we established a competing endogenous RNA (ceRNA) network based on the negative regulatory relationship between miRNAs and target genes. The network revealed that upregulated miRNAs play a leading role in the development of tail fat. Finally, the ceRNA relationship network with oar-miR-27a_R-1 and oar-miR-29a as the core was validated, suggesting possible involvement of these interactions in tail fat development. In summary, DE miRNAs were negatively correlated with DE circRNAs during sheep tail fat development. The multiple ceRNA regulatory network dominated by upregulated DE miRNAs may play a key role in this developmental process.

Lipid exposure activates gene expression changes associated with estrogen receptor negative breast cancer

Improved understanding of local breast biology that favors the development of estrogen receptor negative (ER-) breast cancer (BC) would foster better prevention strategies. We have previously shown that overexpression of specific lipid metabolism genes is associated with the development of ER- BC. We now report results of exposure of MCF-10A and MCF-12A cells, and mammary organoids to representative medium- and long-chain polyunsaturated fatty acids. This exposure caused a dynamic and profound change in gene expression, accompanied by changes in chromatin packing density, chromatin accessibility, and histone posttranslational modifications (PTMs). We identified 38 metabolic reactions that showed significantly increased activity, including reactions related to one-carbon metabolism. Among these reactions are those that produce S-adenosyl-L-methionine for histone PTMs. Utilizing both an in-vitro model and samples from women at high risk for ER- BC, we show that lipid exposure engenders gene expression, signaling pathway activation, and histone marks associated with the development of ER- BC.

Lipidomic Profiling in Synovial Tissue

The analysis of synovial tissue offers the potential for the comprehensive characterization of cell types involved in arthritis pathogenesis. The studies performed to date in synovial tissue have made it possible to define synovial pathotypes, which relate to disease severity and response to treatment. Lipidomics is the branch of metabolomics that allows the quantification and identification of lipids in different biological samples. Studies in animal models of arthritis and in serum/plasma from patients with arthritis suggest the involvement of different types of lipids (glycerophospholipids, glycerolipids, sphingolipids, oxylipins, fatty acids) in the pathogenesis of arthritis. We reviewed studies that quantified lipids in different types of tissues and their relationship with inflammation. We propose that combining lipidomics with currently used “omics” techniques can improve the information obtained from the analysis of synovial tissue, for a better understanding of pathogenesis and the development of new therapeutic strategies.

Sirtuin 3: Emerging therapeutic target for cardiovascular diseases

Acetylation is one of the most important methods of modification that lead to a change in the function of proteins. In humans, metabolic enzymes commonly undergo acetylation, which regulates the activities of metabolic enzymes and metabolic pathways. Sirtuin 3 (SIRT3) is a prominent deacetylase that participates in mitochondrial metabolism, redox balance, and mitochondrial dynamics by regulating mitochondrial protein acetylation, thereby protecting mitochondria from damage. Normal mitochondrial function is essential for maintaining the metabolism and function of the heart. Therefore, mitochondrial dysfunction caused by SIRT3 consumption and defects leads to the development of a variety of cardiovascular diseases. A comprehensive understanding of the role of SIRT3 in cardiovascular disease is critical for developing new therapeutic strategies. Herein, we summarize the function of SIRT3 in mitochondria, the complex mechanisms mediating cardiovascular diseases, and the potential value of SIRT3 small-molecule agonists in future clinical treatments.

Signaling Lipidomic Analysis of Thermogenic Adipocytes

Brown adipose tissue is a thermogenic organ that possesses anti-diabetic and anti-obesogenic potential. There has recently been growing interest on the secretory role of brown adipose tissue in regulating whole-body metabolism. Several signaling lipids, including 12-HEPE and 12,13-diHOME, have been shown to be secreted by brown adipose tissue and have demonstrated roles in regulating whole-body energy metabolism. Lipidomics platforms that broadly characterize the signaling lipidome can deconvolute the underlying biology of the lipid metabolites having a broad systemic impact on physiology. Herein, we describe how to perform and analyze LC-MS/MS signaling lipidomics on mature brown adipocytes.

Integrated application of metabolomics and RNA-seq reveals thermogenic regulation in goat brown adipose tissues

Brown adipose tissue (BAT) plays an important role on no shivering thermogenesis during cold exposure to maintain animal body temperature and energy homeostasis. However, knowledge of the cellular transition from white adipose tissue (WAT) to BAT is still limited. In this study, we provided a comprehensive metabolomics and transcriptional signatures of goat BAT and WAT. A total of 157 metabolites were significantly changed, including 81 upregulated and 76 downregulated metabolites. In addition, we identified the citric acid cycle, fatty acid elongation, and degradation pathways as coordinately activated in BAT. Interestingly, five unsaturated fatty acids (Eicosadienoic Acid, C20:2; γ-Linolenic acid, C20:3; Arachidonic Acid, C20:4; Adrenic acid, C22:4; Docosahexaenoic acid, C22:6), Succinate, L-carnitine, and L-palmitoyl-carnitine were found to be abundant in BAT. Furthermore, L-carnitine, an intermediate of fatty acid degradation, is required for goat brown adipocyte differentiation and thermogenesis through activating AMPK pathway. However, L-carnitine decreased lipid accumulation through inducing lipolysis and thermogenesis in white adipocytes. These results revealed that there are the significant alterations in transcriptomic and metabolomic profiles between goat WAT and BAT, which may contribute to better understanding the roles of metabolites in BAT thermogenesis process.

Is brown adipose tissue a new target for obesity therapy?

The rapid increase in the prevalence of obesity and related diseases has prompted researchers to seek novel effective therapeutic targets. Recently, brown adipose tissue has been in the spotlight as a potential target for treatment of metabolic diseases due to its ability to increase energy expenditure and regulate glucose and lipid homeostasis. The review presents the latest data on approaches aimed at activating and expanding brown adipose tissue in order to combat obesity.

Contribution of PGC-1α to Obesity- and Caloric Restriction-Related Physiological Changes in White Adipose Tissue

Peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α) regulates mitochondrial DNA replication and mitochondrial gene expression by interacting with several transcription factors. White adipose tissue (WAT) mainly comprises adipocytes that store triglycerides as an energy resource and secrete adipokines. The characteristics of WAT vary in response to systemic and chronic metabolic alterations, including obesity or caloric restriction. Despite a small amount of mitochondria in white adipocytes, accumulated evidence suggests that mitochondria are strongly related to adipocyte-specific functions, such as adipogenesis and lipogenesis, as well as oxidative metabolism for energy supply. Therefore, PGC-1α is expected to play an important role in WAT. In this review, we provide an overview of the involvement of mitochondria and PGC-1α with obesity- and caloric restriction-related physiological changes in adipocytes and WAT.

Dehydroabietic acid improves nonalcoholic fatty liver disease through activating the Keap1/Nrf2-ARE signaling pathway to reduce ferroptosis

The accumulation of iron-dependent lipid peroxides is one of the important causes of NAFLD. The purpose of this study is to explore the effect of dehydroabietic acid (DA) on ferroptosis in nonalcoholic fatty liver disease (NAFLD) mice and its possible mechanisms. DA improved NAFLD and reduced triglycerides (TG), total cholesterol (TC), and lipid peroxidation level and inhibited ferroptosis in the liver of HFD-induced mice. DA binds with Keap1 to form 3 stable hydrogen bonds at VAL512 and LEU557 and increased nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response elemen (ARE) luciferase activity. DA promoted the expression downstream of Nrf2 such as heme oxygenase-1 (HO-1), glutathione (GSH) and its peroxidase 4 (GPX4), so as to eliminate the accumulation of reactive oxygen species (ROS) and reduce lipid peroxides malondialdehyde (MDA) in the liver. DA inhibited ferroptosis and increased the expression of key genes such as ferroptosis suppressor protein 1 (FSP1) in vitro and vivo. In all, DA may bind with Keap1, activate Nrf2-ARE, induce its target gene expression, inhibit ROS accumulation and lipid peroxidation, and reduce HFD-induced NAFLD.

Plant extracts in prevention of obesity

Obesity has become a worldwide issue and is accompanied by serious complications. Western high energy diet has been identified to be a major factor contributing to the current obesity pandemic. Thus, it is important to optimize dietary composition, bioactive substances, and agents to prevent and treat obesity. To date, extracts from plants, such as vegetables, tea, fruits, and Chinese herbal medicine, have been showed to have the abilities of regulating adipogenesis and attenuating obesity. These plant extracts mainly contain polyphenols, alkaloids, and terpenoids, which could play a significant role in anti-obesity through various signaling pathways and gut microbiota. Those reported anti-obesity mechanisms mainly include inhibiting white adipose tissue growth and lipogenesis, promoting lipolysis, brown/beige adipose tissue development, and muscle thermogenesis. In this review, we summarize the plant extracts and their possible mechanisms responsible for their anti-obesity effects. Based on the current findings, dietary plant extracts and foods containing these bioactive compounds can be potential preventive or therapeutic agents for obesity and its related metabolic diseases.

Phloretin ameliorates hepatic steatosis through regulation of lipogenesis and Sirt1/AMPK signaling in obese mice

Background

Phloretin is isolated from apple trees and could increase lipolysis in 3T3-L1 adipocytes. Previous studies have found that phloretin could prevent obesity in mice. In this study, we investigated whether phloretin ameliorates non-alcoholic fatty liver disease (NAFLD) in high-fat diet (HFD)-induced obese mice, and evaluated the regulation of lipid metabolism in hepatocytes.

Methods

HepG2 cells were treated with 0.5 mM oleic acid to induce lipid accumulation, and then treated with phloretin to evaluate the molecular mechanism of lipogenesis. In another experiment, male C57BL/6 mice were fed normal diet or HFD (60% fat, w/w) for 16 weeks. After the fourth week, mice were treated with or without phloretin by intraperitoneal injection for 12 weeks.

Results

Phloretin significantly reduced excessive lipid accumulation and decreased sterol regulatory element-binding protein 1c, blocking the expression of fatty acid synthase in oleic acid-induced HepG2 cells. Phloretin increased Sirt1, and phosphorylation of AMP activated protein kinase to suppress acetyl-CoA carboxylase expression, reducing fatty acid synthesis in hepatocytes. Phloretin also reduced body weight and fat weight compared to untreated HFD-fed mice. Phloretin also reduced liver weight and liver lipid accumulation and improved hepatocyte steatosis in obese mice. In liver tissue from obese mice, phloretin suppressed transcription factors of lipogenesis and fatty acid synthase, and increased lipolysis and fatty acid β-oxidation. Furthermore, phloretin regulated serum leptin, adiponectin, triglyceride, low-density lipoprotein, and free fatty acid levels in obese mice.

Conclusions

These findings suggest that phloretin improves hepatic steatosis by regulating lipogenesis and the Sirt-1/AMPK pathway in the liver.

SOCS2 Inhibits Mitochondrial Fatty Acid Oxidation via Suppressing LepR/JAK2/AMPK Signaling Pathway in Mouse Adipocytes

Suppressor of cytokine signaling 2 (SOCS2) plays an important role in fat deposition, skeletal muscle, central nervous system development, and mitochondria biogenesis. Nevertheless, the regulatory mechanisms of SOCS2 on mitochondrial fatty acid oxidation (FAO) remain unclear. Leptin could inhibit food intake and increase thermogenesis through leptin receptor (LepR), which was present in the hypothalamus and certain peripheral organs, including adipose tissue. With strong interest, we focused on the connection between leptin and SOCS2 and their effect on FAO in adipocytes. In our study, we found that the mRNA level of SOCS2 and the protein levels of PGC-1α, CPT-1b, FAT, and p-ACC were elevated by leptin in the inguinal adipose tissue of mice. On the contrary, the protein levels of FABP4, FATP1, and FAS were declined. The genes related to fatty acid oxidation such as PGC-1α, NRF-1, TFAM, CPT-1b, AOX1, COX2, and UCP2 were attenuated by SOCS2, but elevated by leptin. Moreover, fatty acid oxidation enzyme MCAD, LCAD, and Cyt C levels were reduced in response to SOCS2. These reductions correspond well with the reduced release of free fatty acid and the reduction of mitochondrial complexes I and III by SOCS2. Furthermore, JAK2/AMPK pathway-specific inhibitors could block the mitochondrial FAO; hence, this pathway was implied to have a potential impact on FAO. Together, these studies suggested that SOCS2 had a negative effect on mitochondrial fatty acid oxidation, and the LepR/JAK2/AMPK pathway played a crucial role in this process.

Ginsenoside Rb1 Induces Beta 3 Adrenergic Receptor-Dependent Lipolysis and Thermogenesis in 3T3-L1 Adipocytes and db/db Mice

Obesity is constantly rising into a major health threat worldwide. Activation of brown-like transdifferentiation of white adipocytes (browning) has been proposed as a promising molecular target for obesity treatment. In this study, we investigated the effect of ginsenoside Rb1 (Rb1), a saponin derived from Panax ginseng Meyer, on browning. We used 3T3-L1 murine adipocytes and leptin receptor mutated db/db mice. The lipid accumulation, AMP-activated protein kinase alpha (AMPKα)-related pathways, lipolytic and thermogenic factors were measured after Rb treatment in 3T3-L1 adipocytes. Body weight change and lipolysis-thermogenesis factors were investigated in Rb1-treated db/db mice. Beta 3 adrenergic receptor activation (β3AR) changes were measured in Rb1-treated 3T3-L1 cells with or without β3AR inhibitor L748337 co-treatment. As a result, Rb1 treatment decreased lipid droplet size in 3T3-L1 adipocytes. Rb1 also induced phosphorylations of AMPKα pathway and sirtuins. Moreover, lipases and thermogenic factors such as uncoupling protein 1 were increased by Rb1 treatment. Through these results, we could expect that the non-shivering thermogenesis program can be induced by Rb1. In db/db mice, 6-week injection of Rb1 resulted in decreased inguinal white adipose tissue (iWAT) weight associated with shrunken lipid droplets and increased lipolysis and thermogenesis. The thermogenic effect of Rb1 was possibly due to β3AR, as L748337 pre-treatment abolished the effect of Rb1. In conclusion, we suggest Rb1 as a potential lipolytic and thermogenic therapeutic agent which can be used for obesity treatment.

Associations between body condition score at parturition and microRNA profile in colostrum of dairy cows as evaluated by paired mapping programs

MicroRNA (miRNA) are abundant in milk, and likely have regulatory activity involving lactation and immunity. The objective of this study was to determine the miRNA profile in colostrum of overconditioned cows compared with cows of more moderate body condition score (BCS) at calving. Multiparous cows with either high (≥4.0 on a scale of 1 to 5; n = 7) or moderate BCS (2.75 to 3.50; n = 9) in the week before parturition were selected from a commercial dairy herd. Blood and colostrum were sampled within 24 h after calving. Blood serum was analyzed for free fatty acid (FFA) concentration. MicroRNA was isolated from colostrum samples after removing milk fat and cells. MicroRNA were sequenced, and reads were mapped to the bovine genome and to the existing database of miRNA at miRBase.org. Two programs, Oasis 2.0 and miRDeep2, were employed in parallel for read alignment, and analysis of miRNA count data was performed using DESeq2. Identification of differentially expressed miRNA from DESeq2 was not affected by the differences in miRNA detected by the 2 mapping programs. Most abundant miRNA included miR-30a, miR-148a, miR-181a, let-7f, miR-26a, miR-21, miR-22, and miR-92a. Large-scale shifts in miRNA profile were not observed; however, colostrum of cows with high BCS contained less miR-486, which has been linked with altered glucose metabolism. Colostrum from cows with elevated serum FFA contained less miR-885, which may be connected to hepatic function during the transition period. Potential functions of abundant miRNA suggest involvement in development and maintenance of cellular function in the mammary gland, with the additional possibility of influencing neonatal tissue and immune system development.

Transcriptional Response of Subcutaneous White Adipose Tissue to Acute Cold Exposure in Mice

Beige adipose tissue has been considered to have potential applications in combating obesity and its related metabolic diseases. However, the mechanisms of acute cold-stimulated beige formation still remain largely unknown. Here, transcriptional analysis of acute cold-stimulated (4 °C for 4 h) subcutaneous white adipose tissue (sWAT) was conducted to determine the molecular signatures that might be involved in beige formation. Histological analysis confirmed the appearance of beige adipocytes in acute cold-treated sWAT. The RNA-sequencing data revealed that 714 genes were differentially expressed (p-value < 0.05 and fold change > 2), in which 221 genes were upregulated and 493 genes were downregulated. Gene Ontology (GO) analyses showed that the upregulated genes were enriched in the GO terms related to lipid metabolic process, fatty acid metabolic process, lipid oxidation, fatty acid oxidation, etc. In contrast, downregulated genes were assigned the GO terms of regulation of immune response, regulation of response to stimulus, defense response, etc. The expressions of some browning candidate genes were validated in cold-treated sWAT and 3T3-L1 cell browning differentiation. In summary, our results illustrated the transcriptional response of sWAT to acute cold exposure and identified the genes, including Acad11, Cyp2e1, Plin5, and Pdk2, involved in beige adipocyte formation in mice.

Phytochemicals as potential candidates to combat obesity via adipose non-shivering thermogenesis

Obesity is a chronic metabolic disease caused by a long-term imbalance between energy intake and expenditure. The discovery of three different shades of adipose tissues has implications in terms of understanding the pathogenesis and potential interventions for obesity and its related complications. Fat browning, as well as activation of brown adipocytes and new beige adipocytes differentiated from adipogenic progenitor cells, are emerging as interesting and promising methods to curb obesity because of their unique capacity to upregulate non-shivering thermogenesis. This capacity is due to catabolism of stored energy to generate heat through the best characterized thermogenic effector uncoupling protein 1 (UCP1). A variety of phytochemicals have been shown in the literature to contribute to thermogenesis by acting as chemical uncouplers, UCP1 inducers or regulators of fat differentiation and browning. In this review, we summarize the mechanisms and strategies for targeting adipose-mediated thermogenesis and highlight the role of phytochemicals in targeting adipose thermogenesis to fight against obesity. We also discuss proposed targets for how these phytochemical molecules promote BAT activity, WAT browning and beige cell development, thereby offering novel insights into interventional strategies of how phytochemicals may help prevent and manage obesity via adipose thermogenesis.