The Role of AMPK Signaling in Brown Adipose Tissue Activation

Anti‑obesity and immunostimulatory activity of Chrysosplenium flagelliferum in mouse preadipocytes 3T3‑L1 cells and mouse macrophage RAW264.7 cells

Chrysosplenium flagelliferum (CF) is known for its anti-inflammatory, antioxidant and antibacterial activities. However, there is a lack of research on its other pharmacological properties. In the present study, the bifunctional roles of CF in 3T3-L1 and RAW264.7 cells were investigated, focusing on its anti-obesity and immunostimulatory effects. In 3T3-L1 cells, CF effectively mitigated the accumulation of lipid droplets and triacylglycerol. Additionally, CF downregulated the peroxisome proliferator-activated receptor (PPAR)-γ and CCAAT/enhancer-binding protein α protein levels; however, this effect was impeded by the knockdown of β-catenin using β-catenin-specific small interfering RNA. Consequently, CF-mediated inhibition of lipid accumulation was also decreased. CF increased the protein levels of adipose triglyceride lipase and phosphorylated hormone-sensitive lipase, while decreasing those of perilipin-1. Moreover, CF elevated the protein levels of phosphorylated AMP-activated protein kinase and PPARγ coactivator 1-α. In RAW264.7 cells, CF enhanced the production of pro-inflammatory mediators, such as nitric oxide (NO), inducible NO synthase, interleukin (IL)-1β, IL-6 and tumor necrosis factor-α, and increased their phagocytic capacities. Inhibition of Toll-like receptor (TLR)-4 significantly reduced the effects of CF on the production of pro-inflammatory mediators and phagocytosis, indicating its crucial role in facilitating these effects. CF-induced increase in the production of pro-inflammatory mediators was controlled by the activation of c-Jun N-terminal kinase (JNK) and nuclear factor (NF)-κB pathways, and TLR4 inhibition attenuated the phosphorylation of these kinases. The results of the pesent study suggested that CF inhibits lipid accumulation by suppressing adipogenesis and inducing lipolysis and thermogenesis in 3T3-L1 cells, while stimulating macrophage activation via the activation of JNK and NF-κB signaling pathways mediated by TLR4 in RAW264.7 cells. Therefore, CF simultaneously exerts both anti-obesity and immunostimulatory effects.

Mitochondrial UCP1: Potential thermogenic mechanistic switch for the treatment of obesity and neurodegenerative diseases using natural and epigenetic drug candidates

BACKGROUND

Brown fat is known to provide non-shivering thermogenesis through mitochondrial uncoupling mediated by uncoupling protein 1 (UCP1). Non-shivering is not dependent on UCP2, UCP4, and BMCP1/UCP5 genes, which are distinct from UCP1 in a way that they are not constitutive uncouplers. Although they are susceptible to free fatty acid and free radical activation, their functioning has a significant impact on the performance of neurons.

METHODOLOGY

Using subject-specific keywords (Adipose tissue; Adipocytes; Mitochondria; Obesity; Thermogenesis; UCP's in Neurodegeneration; Alzheimer's disease; Parkinson's disease), research articles and reviews were retrieved from Web of Science, ScienceDirect, Google Scholar, and PubMed. This article includespublications published between 2018 and 2023. The drugs that upregulate UCP1 are included in the study while the drugs that do not impact UCP1 are were not included.

RESULTS

Neuronal UCPs have a direct impact on synaptic plasticity, neurodegenerative processes, and neurotransmission, by modulating calcium flux, mitochondrial biogenesis, local temperature, and free radical generation. Numerous significant advances in the study of neuronal UCPs and neuroprotection are still to be made. Identification of the tissue-dependent effects of UCPs is essential first. Pharmacologically targeting neuronal UCPs is a key strategy for preventing both neurodegenerative diseases and physiological aging. Given that UCP2 has activities that are tissue-specific, it will be essential to develop treatments without harmful side effects. The triggering of UCPs by CoQ, an essential cofactor, produces nigral mitochondrial uncoupling, reduces MPTP-induced toxicity, and may even decrease the course of Parkinson's disease, according to early indications.

CONCLUSION

Herein, we explore the potential of UCP1 as a therapeutic target for treating obesity, neurodegenerative diseases as well as a potential activator of both synthetic and natural drugs. A deeper knowledge of synaptic signaling and neurodegeneration may pave the way to new discoveries regarding the functioning and controlling of these genes.

Novel perspectives on autophagy-oxidative stress-inflammation axis in the orchestration of adipogenesis

Adipose tissue, an indispensable organ, fulfils the pivotal role of energy storage and metabolism and is instrumental in maintaining the dynamic equilibrium of energy and health of the organism. Adipocyte hypertrophy and adipocyte hyperplasia (adipogenesis) are the two primary mechanisms of fat deposition. Mature adipocytes are obtained by differentiating mesenchymal stem cells into preadipocytes and redifferentiation. However, the mechanisms orchestrating adipogenesis remain unclear. Autophagy, an alternative cell death pathway that sustains intracellular energy homeostasis through the degradation of cellular components, is implicated in regulating adipogenesis. Furthermore, adipose tissue functions as an endocrine organ, producing various cytokines, and certain inflammatory factors, in turn, modulate autophagy and adipogenesis. Additionally, autophagy influences intracellular redox homeostasis by regulating reactive oxygen species, which play pivotal roles in adipogenesis. There is a growing interest in exploring the involvement of autophagy, inflammation, and oxidative stress in adipogenesis. The present manuscript reviews the impact of autophagy, oxidative stress, and inflammation on the regulation of adipogenesis and, for the first time, discusses their interactions during adipogenesis. An integrated analysis of the role of autophagy, inflammation and oxidative stress will contribute to elucidating the mechanisms of adipogenesis and expediting the exploration of molecular targets for treating obesity-related metabolic disorders.

Adipose tissue plasticity mediated by the counterregulatory axis of the renin-angiotensin system: Role of Mas and MrgD receptors

The renin-angiotensin system (RAS) is an endocrine system composed of two main axes: the classical and the counterregulatory, very often displaying opposing effects. The classical axis, primarily mediated by angiotensin receptors type 1 (AT1R), is linked to obesity-associated metabolic effects. On the other hand, the counterregulatory axis appears to exert antiobesity effects through the activation of two receptors, the G protein-coupled receptor (MasR) and Mas-related receptor type D (MrgD). The local RAS in adipose organ has prompted extensive research into white adipose tissue and brown adipose tissue (BAT), with a key role in regulating the cellular and metabolic plasticity of these tissues. The MasR activation favors the brown plasticity signature in the adipose organ by improve the thermogenesis, adipogenesis, and lipolysis, decrease the inflammatory state, and overall energy homeostasis. The MrgD metabolic effects are related to the maintenance of BAT functionality, but the signaling remains unexplored. This review provides a summary of RAS counterregulatory actions triggered by Mas and MrgD receptors on adipose tissue plasticity. Focus on the effects related to the morphology and function of adipose tissue, especially from animal studies, will be given targeting new avenues for treatment of obesity-associated metabolic effects.

Discovery of Oral AMP-Activated Protein Kinase Activators for Treating Hyperlipidemia

Activation of AMP-activated protein kinase (AMPK) is proposed to alleviate hyperlipidemia. With cordycepin and N6-(2-hydroxyethyl) adenosine (HEA) as lead compounds, a series of adenosine-based derivatives were designed, synthesized, and evaluated on activation of AMPK. Finally, compound V1 was identified as a potent AMPK activator with the lipid-lowering effect. Molecular docking and circular dichroism indicated that V1 exerted its activity by binding to the γ subunit of AMPK. V1 markedly decreased the serum low-density lipoprotein cholesterol levels in C57BL/6 mice, golden hamsters, and rhesus monkeys. V1 was selected as the clinical compound and concluded Phase 1 clinical trials. A single dose of V1 (2000 mg) increased AMPK activation in human erythrocytes after 5 and 12 h of treatment. RNA sequencing data suggested that V1 downregulated expression of genes involved in regulation of apoptotic process, lipid metabolism, endoplasmic reticulum stress, and inflammatory response in liver by activating AMPK.

Polyphenol Compound 18a Modulates UCP1-Dependent Thermogenesis to Counteract Obesity

Recent studies increasingly suggest that targeting brown/beige adipose tissues to enhance energy expenditure offers a novel therapeutic approach for treating metabolic diseases. Brown/beige adipocytes exhibit elevated expression of uncoupling protein 1 (UCP1), which is a thermogenic protein that efficiently converts energy into heat, particularly in response to cold stimulation. Polyphenols possess potential anti-obesity properties, but their pharmacological effects are limited by their bioavailability and distribution within tissue. This study discovered 18a, a polyphenol compound with a favorable distribution within adipose tissues, which transcriptionally activates UCP1, thereby promoting thermogenesis and enhancing mitochondrial respiration in brown adipocytes. Furthermore, in vivo studies demonstrated that 18a prevents high-fat-diet-induced weight gain and improves insulin sensitivity. Our research provides strong mechanistic evidence that UCP1 is a complex mediator of 18a-induced thermogenesis, which is a critical process in obesity mitigation. Brown adipose thermogenesis is triggered by 18a via the AMPK-PGC-1α pathway. As a result, our research highlights a thermogenic controlled polyphenol compound 18a and clarifies its underlying mechanisms, thus offering a potential strategy for the thermogenic targeting of adipose tissue to reduce the incidence of obesity and its related metabolic problems.

Dapagliflozin promotes browning of white adipose tissue through the FGFR1-LKB1-AMPK signaling pathway

BACKGROUND

Obesity is associated with a wide variety of metabolic disorders that impose significant burdens on patients and society. The "browning" phenomenon in white adipose tissue (WAT) has emerged as a promising therapeutic strategy to combat metabolic disturbances. However, though the anti-diabetic drug dapagliflozin (DAPA) is thought to promote "browning," the specific mechanism of this was previously unclear.

METHODS

In this study, C57BL/6 J male mice were used to establish an obesity model by high-fat diet feeding, and 3T3-L1 cells were used to induce mature adipocytes and to explore the role and mechanism of DAPA in "browning" through a combination of in vitro and in vivo experiments.

RESULTS

The results show that DAPA promotes WAT "browning" and improves metabolic disorders. Furthermore, we discovered that DAPA activated "browning" through the fibroblast growth factor receptors 1-liver kinase B1-adenosine monophosphate-activated protein kinase signaling pathway.

CONCLUSION

These findings provide a rational basis for the use of DAPA in treating obesity by promoting the browning of white adipose tissue.

Endoplasmic reticulum stress: bridging inflammation and obesity-associated adipose tissue

Obesity presents a significant global health challenge, increasing the susceptibility to chronic conditions such as diabetes, cardiovascular disease, and hypertension. Within the context of obesity, lipid metabolism, adipose tissue formation, and inflammation are intricately linked to endoplasmic reticulum stress (ERS). ERS modulates metabolism, insulin signaling, inflammation, as well as cell proliferation and death through the unfolded protein response (UPR) pathway. Serving as a crucial nexus, ERS bridges the functionality of adipose tissue and the inflammatory response. In this review, we comprehensively elucidate the mechanisms by which ERS impacts adipose tissue function and inflammation in obesity, aiming to offer insights into targeting ERS for ameliorating metabolic dysregulation in obesity-associated chronic diseases such as hyperlipidemia, hypertension, fatty liver, and type 2 diabetes.

Anthocyanins and their metabolites promote white adipose tissue beiging by regulating mitochondria thermogenesis and dynamics

High-fat diet (HFD) consumption and excess nutrient availability can cause alterations in mitochondrial function and dynamics. We previously showed that anthocyanins (AC) decreased HFD-induced body weight gain and fat deposition. This study investigated: i) the capacity of AC to mitigate HFD-induced alterations in mitochondrial dynamics, biogenesis, and thermogenesis in mouse subcutaneous white adipose tissue (sWAT), and ii) the underlying mechanisms of action of cyanidin-3-O-glucoside (C3G), delphinidin-3-O-glucoside (D3G), and their gut metabolites on mitochondria function/dynamics in 3T3-L1 adipocytes treated with palmitate. Mice were fed control or HFD diets, added or not with 40 mg AC/kg body weight (BW). Compared to control and AC-supplemented mice, HFD-fed mice had fewer sWAT mitochondria that presented alterations of their architecture. AC supplementation prevented HFD-induced decrease of proteins involved in mitochondria biogenesis (PPARγ, PRDM16 and PGC-1α), and thermogenesis (UCP-1), and decreased AMPK phosphorylation. AC supplementation also restored the alterations in sWAT mitochondrial dynamics (Drp-1, OPA1, MNF-2, and Fis-1) and mitophagy (BNIP3L/NIX) caused by HFD consumption. In mature 3T3-L1, C3G, D3G, and their metabolites protocatechuic acid (PCA), 4-hydroxybenzaldehyde (HB), and gallic acid (GA) differentially affected palmitate-mediated decreased cAMP, PKA, AMPK, and SIRT-1 signaling pathways. C3G, D3G, and metabolites also prevented palmitate-mediated decreased expression of PPARγ, PRDM16, PGC-1α, and UCP1. Results suggest that consumption of select AC, i.e. cyanidin and delphinidin, could promote sWAT mitochondriogenesis and improve mitochondria dynamics in the context of HFD/obesity-induced dysmetabolism in part by regulating PKA, AMPK, and SIRT-1 signaling pathways.

Mulberry leaf flavonoids activate BAT and induce browning of WAT to improve type 2 diabetes via regulating the AMPK/SIRT1/PGC-1α signaling pathway

Mulberry (Morus alba L.) leaf is a well-established traditional Chinese botanical and culinary resource. It has found widespread application in the management of diabetes. The bioactive constituents of mulberry leaf, specifically mulberry leaf flavonoids (MLFs), exhibit pronounced potential in the amelioration of type 2 diabetes (T2D). This potential is attributed to their ability to safeguard pancreatic β cells, enhance insulin resistance, and inhibit α-glucosidase activity. Our antecedent research findings underscore the substantial therapeutic efficacy of MLFs in treating T2D. However, the precise mechanistic underpinnings of MLF's anti-T2D effects remain the subject of inquiry. Activation of brown/beige adipocytes is a novel and promising strategy for T2D treatment. In the present study, our primary objective was to elucidate the impact of MLFs on adipose tissue browning in db/db mice and 3T3-L1 cells and elucidate its underlying mechanism. The results manifested that MLFs reduced body weight and food intake, alleviated hepatic steatosis, improved insulin sensitivity, and increased lipolysis and thermogenesis in db/db mice. Moreover, MLFs activated brown adipose tissue (BAT) and induced the browning of inguinal white adipose tissue (IWAT) and 3T3-L1 adipocytes by increasing the expressions of brown adipocyte marker genes and proteins such as uncoupling protein 1 (UCP1) and beige adipocyte marker genes such as transmembrane protein 26 (Tmem26), thereby promoting mitochondrial biogenesis. Mechanistically, MLFs facilitated the activation of BAT and the induction of WAT browning to ameliorate T2D primarily through the activation of AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1)/peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) signaling pathway. These findings highlight the unique capacity of MLF to counteract T2D by enhancing BAT activation and inducing browning of IWAT, thereby ameliorating glucose and lipid metabolism disorders. As such, MLFs emerge as a prospective and innovative browning agent for the treatment of T2D.

Rabbit Meat Extract Induces Browning in 3T3-L1 Adipocytes via the AMP-Activated Protein Kinase Pathway

The browning of white adipocytes may be an innovative approach to address obesity. This study investigated the effects of rabbit meat extract on 3T3-L1 adipocytes, with a specific emphasis on inducing browning. The browning effects of rabbit meat extract were evaluated by analyzing genes specifically expressed in 3T3-L1 adipocytes using quantitative PCR and immunoblotting. Rabbit meat extract increased the expression of brown adipocyte-specific markers, UCP1 and PGC1α, and mitochondrial biogenesis factors, TFAM and NRF1, without affecting cell viability in fully differentiated 3T3-L1 adipocytes. Moreover, adipocyte differentiation and the triglyceride content were decreased; hormone-sensitive lipase activity was promoted. Rabbit meat extract activated the AMPK pathway in the differentiated 3T3-L1 cells. However, in adipocytes treated with rabbit meat extract, the expression of genes related to browning was reduced by the AMP-activated protein kinase (AMPK) inhibitor, dorsomorphin dihydrochloride. To the best of our knowledge, this is the first study to demonstrate that rabbit meat extract induces the browning of white adipocytes via the activation of the AMPK pathway, thereby demonstrating its therapeutic potential in preventing obesity.

High levels of uric acid inhibit BAT thermogenic capacity through regulation of AMPK

Hyperuricemia (HUA) is strongly associated with the increasing prevalence of obesity, but the underlying mechanism remains elusive. Dysfunction of brown adipose tissue (BAT) could lead to obesity. However, studies on the role of HUA on BAT are lacking. Our retrospective clinical analysis showed that serum uric acid (UA) is significantly associated with BAT in humans. To investigate the role of UA in regulating BAT function, we used UA to treat primary brown adipocytes (BACs) in vitro and established HUA mice. In vitro results showed that HUA suppressed thermogenic gene expression and oxygen consumption rate. Accordingly, HUA mice exhibited lower energy expenditure and body temperature, with larger lipid droplets and lower thermogenic gene expression. These results demonstrate that HUA inhibits BAT thermogenic capacity in vitro and in vivo. To further elucidate the mechanism of UA on adipocytes, mRNA-sequencing analysis was performed and screened for "AMP-activated protein kinase (AMPK) signaling pathway" and "mitochondrial biogenesis." Further tests in vivo and in vitro showed that the phosphorylation of AMPK was suppressed by HUA. Activation of AMPK alleviated the inhibition of AMPK phosphorylation by HUA and increased mitochondrial biogenesis, subsequently restoring the impaired BAT thermogenic capacity in vitro and vivo. Thus, we confirmed that HUA suppresses mitochondrial biogenesis by regulating AMPK, thereby inhibiting BAT thermogenic capacity. Taken together, our study identifies UA as a novel regulator of BAT thermogenic capacity, providing a new strategy to combat obesity.NEW & NOTEWORTHY To investigate the effect and mechanism of UA on BAT thermogenic capacity, we established HUA models in vitro and in vivo, and performed RNA sequencing analysis. Our results revealed that HUA suppresses mitochondrial biogenesis by regulating AMPK, thereby inhibiting BAT thermogenic capacity. Taken together, our study identifies UA as a novel regulator of BAT thermogenic capacity, providing a new strategy to combat obesity.

Hydrogen Sulfide Regulates Glucose Uptake in Skeletal Muscles via S-Sulfhydration of AMPK in Muscle Fiber Type-Dependent Way

BACKGROUND

The effect of hydrogen sulfide (H2S) on glucose homeostasis remains to be elucidated, especially in the state of insulin resistance.

OBJECTIVES

In the present study, we aimed to investigate H2S-regulated glucose uptake in the M. pectoralis major (PM) muscle (which mainly consists of fast-twitch glycolytic fibers) and M. biceps femoris (BF) muscle (which mainly consists of slow-twitch oxidative fibers) of the chicken, a potential model of insulin resistance.

METHODS

Chicks were subjected to intraperitoneal injection of sodium hydrosulfide (NaHS, 50 μmol/kg body mass/day) twice a day to explore glucose homeostasis. In vitro, myoblasts from PM and BF muscles were used to detect glucose uptake and utilization. Effects of AMP-activated protein kinase (AMPK) phosphorylation, AMPK S-sulfhydration, and mitogen-activated protein kinase (MAPK) pathway induction by NaHS were detected.

RESULTS

NaHS enhanced glucose uptake and utilization in chicks (P < 0.05). In myoblasts from PM muscle, NaHS (100 μM) increased glucose uptake by activating AMPK S-sulfhydration, AMPK phosphorylation, and the AMPK/p38 MAPK pathway (P < 0.05). However, NaHS decreased glucose uptake in myoblasts from BF muscle by suppressing the p38 MAPK pathway (P < 0.05). Moreover, NaHS increased S-sulfhydration and, in turn, the phosphorylation of AMPK (P < 0.05).

CONCLUSIONS

This study reveals the role of H2S in enhancing glucose uptake and utilization in chicks. The results suggest that NaHS is involved in glucose uptake in skeletal muscle in a fiber type-dependent way. The AMPK/p38 pathway and protein S-sulfhydration promote glucose uptake in fast-twitch glycolytic muscle fibers, which provides a muscle fiber-specific potential therapeutic target to ameliorate glucose metabolism.

Effects of Weight Loss and Aerobic Exercise Training on Adi-Pose Tissue Zinc α2-Glycoprotein and Associated Genes in Obesity

Zinc α2-glycoprotein (ZAG) has been implicated in fatty acid metabolism and utilization and is lower in obese and higher in cachexic adults compared to those of normal weight. Previous studies suggest that ZAG binds to the beta3-adrenergic receptor (β3AR) to influence fatty acid metabolism in adipose tissue by regulating hormone sensitive lipase (HSL). The purpose of this study is to investigate the effects of a six-month weight loss (WL) or aerobic exercise (AEX) intervention on adipose tissue and skeletal muscle ZAG mRNA levels and protein expression, as well as the expression of β3AR, and HSL. Abdominal adipose tissue (AB) and gluteal adipose tissue (Glut) and vastus lateralis muscle biopsies were performed before and after WL (n = 13) or AEX (n = 13). ZAG, HSL, and β3AR expressions were determined by RT-PCR, and ZAG and HSL plasma levels by ELISA. Body weight decreased by 9.69% (p < 0.001) in WL and did not change with AEX. Maximal oxygen consumption (VO2max) increased by 7.1% (p < 0.005) after WL and by 16.69% (p < 0.001) after AEX. WL significantly decreased body weight with a reduction of percentage of fat, fat mass, fat-free mass (FFM). AEX decreased percent fat and increased VO2max, but did not change fat mass and FFM. Abdominal ZAG and HSL mRNA levels did not change significantly after WL or AEX. There were no changes in plasma ZAG, HSL and adipose tissue β3AR mRNA levels after WL and AEX. ZAG, HSL and β3AR mRNA expressions in adipose tissue are positively associated each other. Adipose tissue abdominal and gluteal HSL are negatively associated with HOMA-IR (Homeostatic Model Assessment for Insulin Resistance), and both ZAG and HSL adipose tissue are negatively associated with fasting glucose and the glucose area under the curve. Further work is needed to elucidate the role of ZAG and HSL in the propensity for weight gain and the ability of exercise to mitigate these responses.

UCP1 activation: Hottest target in the thermogenesis pathway to treat obesity using molecules of synthetic and natural origin

Uncoupling protein 1 (UCP1) has been discovered as a possible target for obesity treatment because of its widespread distribution in the inner mitochondrial membrane of brown adipose tissue (BAT) and high energy expenditure capabilities to burn calories as heat. UCP1 is dormant and does not produce heat without activation as it is inhibited by purine nucleotides. However, activation of UCP1 via either direct interaction with the UCP1 protein, an increase in the expression of UCP1 genes or the physiological production of fatty acids can lead to a rise in the thermogenesis phenomenon. Hence, activation of UCP1 through small molecules of synthetic and natural origin can be considered as a promising strategy to mitigate obesity.

Mitochondria-associated programmed cell death as a therapeutic target for age-related disease

Mitochondria, ubiquitous double-membrane-bound organelles, regulate energy production, support cellular activities, harbor metabolic pathways, and, paradoxically, mediate cell fate. Evidence has shown mitochondria as points of convergence for diverse cell death-inducing pathways that trigger the various mechanisms underlying apoptotic and nonapoptotic programmed cell death. Thus, dysfunctional cellular pathways eventually lead or contribute to various age-related diseases, such as neurodegenerative, cardiovascular and metabolic diseases. Thus, mitochondrion-associated programmed cell death-based treatments show great therapeutic potential, providing novel insights in clinical trials. This review discusses mitochondrial quality control networks with activity triggered by stimuli and that maintain cellular homeostasis via mitohormesis, the mitochondrial unfolded protein response, and mitophagy. The review also presents details on various forms of mitochondria-associated programmed cell death, including apoptosis, necroptosis, ferroptosis, pyroptosis, parthanatos, and paraptosis, and highlights their involvement in age-related disease pathogenesis, collectively suggesting therapeutic directions for further research.

Inhibition of lipid droplet accumulation by Solanum nigrum by suppressing adipogenesis and inducing lipolysis, thermogenesis and autophagy in 3T3‑L1 cells

It has been reported that Solanum nigrum exhibits anti-obesity effects in animal models induced by a high-fat diet. However, research on how Solanum nigrum exerts its anti-obesity effects is currently limited. Thus, the present study focused on identifying the mechanism of action associated with the anti-obesity activity of Solanum nigrum aerial part (SNAP), which significantly inhibited the accumulation of lipid droplets in differentiating 3T3-L1 cells. Intracellular lipid accumulation in 3T3-L1 cells was analyzed by Oil-Red O staining and glycerol content was analyzed using an ELISA kit. In addition, changes in protein expression within 3T3-L1 cells were analyzed using western blot analysis. It decreased the expression level of adipogenic proteins such as CCAAT/enhancer-binding protein α, Peroxisome proliferator-activated receptor γ, fatty acid binding protein 4, and adiponectin. In addition, SNAP increased the expression levels of lipolytic proteins, such as adipose triglyceride lipase and hormone-sensitive lipase, while decreasing perilipin-1. The treatment of fully differentiated 3T3-L1 cells increased the free glycerol levels. SNAP treatment resulted in increased AMP-activated protein kinase phosphorylation and the expression levels of thermogenic proteins (peroxisome proliferator-activated receptor-γ coactivator 1-α, PR domain containing 16 and uncoupling protein 1) and an autophagic protein (LC3-II). Overall, these results suggested that SNAP inhibited lipid droplet accumulation by suppressing adipogenesis and promoting lipolysis, thermogenesis and autophagy.

Knocking Down CDKN2A in 3D hiPSC-Derived Brown Adipose Progenitors Potentiates Differentiation, Oxidative Metabolism and Browning Process

Human induced pluripotent stem cells (hiPSCs) have the potential to be differentiated into any cell type, making them a relevant tool for therapeutic purposes such as cell-based therapies. In particular, they show great promise for obesity treatment as they represent an unlimited source of brown/beige adipose progenitors (hiPSC-BAPs). However, the low brown/beige adipocyte differentiation potential in 2D cultures represents a strong limitation for clinical use. In adipose tissue, besides its cell cycle regulator functions, the cyclin-dependent kinase inhibitor 2A (CDKN2A) locus modulates the commitment of stem cells to the brown-like type fate, mature adipocyte energy metabolism and the browning of adipose tissue. Here, using a new method of hiPSC-BAPs 3D culture, via the formation of an organoid-like structure, we silenced CDKN2A expression during hiPSC-BAP adipogenic differentiation and observed that knocking down CDKN2A potentiates adipogenesis, oxidative metabolism and the browning process, resulting in brown-like adipocytes by promoting UCP1 expression and beiging markers. Our results suggest that modulating CDKN2A levels could be relevant for hiPSC-BAPs cell-based therapies.

A Novel Mix of Polyphenols and Micronutrients Reduces Adipogenesis and Promotes White Adipose Tissue Browning via UCP1 Expression and AMPK Activation

Background: Obesity is a pandemic disease characterized by excessive severe body comorbidities. Reduction in fat accumulation represents a mechanism of prevention, and the replacement of white adipose tissue (WAT) with brown adipose tissue (BAT) has been proposed as one promising strategy against obesity. In the present study, we sought to investigate the ability of a natural mixture of polyphenols and micronutrients (A5⁺) to counteract white adipogenesis by promoting WAT browning. Methods: For this study, we employed a murine 3T3-L1 fibroblast cell line treated with A5⁺, or DMSO as control, during the differentiation in mature adipocytes for 10 days. Cell cycle analysis was performed using propidium iodide staining and cytofluorimetric analysis. Intracellular lipid contents were detected by Oil Red O staining. Inflammation Array, along with qRT-PCR and Western Blot analyses, served to measure the expression of the analyzed markers, such as pro-inflammatory cytokines. Results: A5⁺ administration significantly reduced lipids' accumulation in adipocytes when compared to control cells (p < 0.005). Similarly, A5⁺ inhibited cellular proliferation during the mitotic clonal expansion (MCE), the most relevant stage in adipocytes differentiation (p < 0.0001). We also found that A5⁺ significantly reduced the release of pro-inflammatory cytokines, such as IL-6 and Leptin (p < 0.005), and promoted fat browning and fatty acid oxidation through increasing expression levels of genes related to BAT, such as UCP1 (p < 0.05). This thermogenic process is mediated via AMPK-ATGL pathway activation. Conclusion: Overall, these results demonstrated that the synergistic effect of compounds contained in A5⁺ may be able to counteract adipogenesis and then obesity by inducing fat browning.

Synergistic activation of AMPK by AdipoR1/2 agonist and inhibitor of EDPs-EBP interaction recover NAFLD through enhancing mitochondrial function in mice

Nonalcoholic fatty liver disease (NAFLD), especially nonalcoholic steatohepatitis (NASH), is a common hepatic manifestation of metabolic syndrome. However, there are no effective therapy to treat this devastating disease. Accumulating evidence suggests that the generation of elastin-derived peptides (EDPs) and the inhibition of adiponectin receptors (AdipoR)1/2 plays essential roles in hepatic lipid metabolism and liver fibrosis. We recently reported that the AdipoR1/2 dual agonist JT003 significantly degraded the extracellular matrix (ECM) and ameliorated liver fibrosis. However, the degradation of the ECM lead to the generation of EDPs, which could further alter liver homeostasis negatively. Thus, in this study, we successfully combined AdipoR1/2 agonist JT003 with V14, which acted as an inhibitor of EDPs-EBP interaction to overcome the defect of ECM degradation. We found that combination of JT003 and V14 possessed excellent synergistic benefits on ameliorating NASH and liver fibrosis than either alone since they compensate the shortage of each other. These effects are induced by the enhancement of the mitochondrial antioxidant capacity, mitophagy, and mitochondrial biogenesis via AMPK pathway. Furthermore, specific suppression of AMPK could block the effects of the combination of JT003 and V14 on reduced oxidative stress, increased mitophagy and mitochondrial biogenesis. These positive results suggested that this administration of combination of AdipoR1/2 dual agonist and inhibitor of EDPs-EBP interaction can be recommended alternatively for an effective and promising therapeutic strategy for the treatment of NAFLD and NASH related fibrosis.

Anti-Obesity Effects of Metformin: A Scoping Review Evaluating the Feasibility of Brown Adipose Tissue as a Therapeutic Target

Brown adipose tissue (BAT) is increasingly recognized as the major therapeutic target to promote energy expenditure and ameliorate diverse metabolic complications. There is a general interest in understanding the pleiotropic effects of metformin against metabolic complications. Major electronic databases and search engines such as PubMed/MEDLINE, Google Scholar, and the Cochrane library were used to retrieve and critically discuss evidence reporting on the impact of metformin on regulating BAT thermogenic activity to ameliorate complications linked with obesity. The summarized evidence suggests that metformin can reduce body weight, enhance insulin sensitivity, and improve glucose metabolism by promoting BAT thermogenic activity in preclinical models of obesity. Notably, this anti-diabetic agent can affect the expression of major thermogenic transcriptional factors such as uncoupling protein 1 (UCP1), nuclear respiratory factor 1 (NRF1), and peroxisome-proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α) to improve BAT mitochondrial function and promote energy expenditure. Interestingly, vital molecular markers involved in glucose metabolism and energy regulation such as AMP-activated protein kinase (AMPK) and fibroblast growth factor 21 (FGF21) are similarly upregulated by metformin treatment in preclinical models of obesity. The current review also discusses the clinical relevance of BAT and thermogenesis as therapeutic targets. This review explored critical components including effective dosage and appropriate intervention period, consistent with the beneficial effects of metformin against obesity-associated complications.

Inhibition Effect of Adipogenesis and Lipogenesis via Activation of AMPK in Preadipocytes Treated with Canavalia gladiata Extract

The aim of this study was to investigate the effect of Canavalia gladiata extract (CGE) on the regulation of AMP-activated protein kinase (AMPK) in 3T3-L1 preadipocytes and evaluate the adipogenesis and lipogenesis mechanisms. In 3T3-L1 preadipocytes, lipid accumulation and differentiation were suppressed by 1.1, 1.3, and 1.4 times under the CGE treatment at 0.25, 0.5, and 1.0 mg/mL, respectively. The expression of the main genes involved in the inhibition of adipogenesis was evaluated at the mRNA level via a transcription-polymerase chain reaction. The extract at 1.0 mg/mL increased the mRNA expressions of AMPK and carnitine palmitoyl transferase-1 (CPT-1) by 1.9 and 1.2 times, respectively, while it decreased the expression of sterol regulatory element binding proteins-1c (SREBP-1c), peroxisome proliferator activated receptor-γ (PPAR-γ), CCAAT enhancer binding protein-α (C/EBP-α), and fatty acid synthase (FAS) by 1.1, 1.2, 1.8, and 1.5 times, respectively, indicating inhibition of the adipogenesis and lipogenesis potential of CGE. Gallic acid (4.02 mg/g) was identified as the main component of the CGE via LC-MS/MS and HPLC analysis. The results of this study suggested that CGE can be utilized as an anti-obesity food additive or medication by activating the AMPK-induced regulation and suppressing adipogenesis transcription factors.

New Insights into the Basic and Translational Aspects of AMPK Signaling

5'-adenosine monophosphate (AMP)-activated protein kinase (AMPK) is an enzyme regulating numerous cellular processes involved in cell survival as well as health- and lifespan [...].

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.

Effects of allicin on human Simpson-Golabi-Behmel syndrome cells in mediating browning phenotype

INTRODUCTION

Obesity is a major health problem because it is associated with increased risk of cardiovascular disease, diabetes, hypertension, and some cancers. Strategies to prevent or reduce obesity focus mainly on the possible effects of natural compounds that can induce a phenotype of browning adipocytes capable of releasing energy in the form of heat. Allicin, a bioactive component of garlic with numerous pharmacological functions, is known to stimulate energy metabolism.

METHODS

In the present study, the effects of allicin on human Simpson-Golabi-Behmel Syndrome (SGBS) cells were investigated by quantifying the dynamics of lipid droplets (LDs) and mitochondria, as well as transcriptomic changes after six days of differentiation.

RESULTS

Allicin significantly promoted the reduction in the surface area and size of LDs, leading to the formation of multilocular adipocytes, which was confirmed by the upregulation of genes related to lipolysis. The increase in the number and decrease in the mean aspect ratio of mitochondria in allicin-treated cells indicate a shift in mitochondrial dynamics toward fission. The structural results are confirmed by transcriptomic analysis showing a significant arrangement of gene expression associated with beige adipocytes, in particular increased expression of T-box transcription factor 1 (TBX1), uncoupling protein 1 (UCP1), PPARG coactivator 1 alpha (PPARGC1A), peroxisome proliferator-activated receptor alpha (PPARA), and OXPHOS-related genes. The most promising targets are nuclear genes such as retinoid X receptor alpha (RXRA), retinoid X receptor gamma (RXRG), nuclear receptor subfamily 1 group H member 3 (NR1H3), nuclear receptor subfamily 1 group H member 4 (NR1H4), PPARA, and oestrogen receptor 1 (ESR1).

DISCUSSION

Transcriptomic data and the network pharmacology-based approach revealed that genes and potential targets of allicin are involved in ligand-activated transcription factor activity, intracellular receptor signalling, regulation of cold-induced thermogenesis, and positive regulation of lipid metabolism. The present study highlights the potential role of allicin in triggering browning in human SGBS cells by affecting the LD dynamics, mitochondrial morphology, and expression of brown marker genes. Understanding the potential targets through which allicin promotes this effect may reveal the underlying signalling pathways and support these findings.

LSD1 for the Targeted Regulation of Adipose Tissue

White and thermal (brown and beige) adipose tissue energy storage and oxidative regulation pathways play a central role in maintaining the energy balance throughout the body, and the dysregulation of these pathways is closely related to glucose and lipid metabolism disorders and adipose tissue dysfunction, including obesity, chronic inflammation, insulin resistance, mitochondrial dysfunction, and fibrosis. Recent epigenetic studies have identified the novel regulatory element LSD1, which controls the above parameters, and have provided new mechanistic possibilities for re-encoding the fate and function of adipocytes. In this review, we outline the current advances in adipocyte metabolism in physiology and disease and discuss possible strategies for LSD1 to alter the phenotype of adipose tissue and thus influence energy utilization to improve metabolic health.

Anmyungambi Decoction Ameliorates Obesity through Activation of Non-Shivering Thermogenesis in Brown and White Adipose Tissues

Obesity is a burden to global health. Non-shivering thermogenesis of brown adipose tissue (BAT) and white adipose tissue (WAT) is a novel strategy for obesity treatment. Anmyungambi (AMGB) decoction is a multi-herb decoction with clinical anti-obesity effects. Here, we show the effects of AMGB decoction using high-fat diet (HFD)-fed C57BL6/J mice. All four versions of AMGB decoction (100 mg/kg/day, oral gavage for 28 days) suppressed body weight gain and obesity-related blood parameters in the HFD-fed obese mice. They also inhibited adipogenesis and induced lipolysis in inguinal WAT (iWAT). Especially, the AMGB-4 with 2:1:3:3 composition was the most effective; thus, further studies were performed with the AMGB-4 decoction. The AMGB-4 decoction displayed a dose-dependent body weight gain suppression. Serum triglyceride, total cholesterol, and blood glucose decreased as well. In epididymal WAT, iWAT, and BAT, the AMGB-4 decoction increased lipolysis markers. Additionally, the AMGB-4 decoction-fed mice showed an increased non-shivering thermogenic program in BAT and iWAT. Excessive reactive oxygen species (ROS) and suppressed antioxidative factors induced by the HFD feeding were also altered to normal levels by the AMGB-4 decoction treatment. Overall, our study supports the clinical use of AMGB decoction for obesity treatment by studying its mechanisms. AMGB decoction alleviates obesity through the activation of the lipolysis-thermogenesis program and the elimination of pathological ROS in thermogenic adipose tissues.

Salvianolic acid A promotes mitochondrial biogenesis and mitochondrial function in 3T3-L1 adipocytes through regulation of the AMPK-PGC1α signalling pathway

Mitochondrial dysfunction is associated with insulin resistance and type 2 diabetes (T2DM). Decreased mitochondrial abundance and function were found in white adipose tissue (WAT) of T2DM patients. Therefore, promoting WAT mitochondrial biogenesis and improving adipocyte metabolism may be strategies to prevent and reverse T2DM. Salvianolic acid A (SAA) has been found to exert anti-diabetic and lipid disorder-improving effects. However whether SAA benefits mitochondrial biogenesis and function in adipose tissue is unclear. Here, we evaluated SAA's effect on mitochondrial biogenesis and function in 3T3-L1 adipocytes and investigated its potential regulatory mechanism. Results showed that SAA treatment significantly promoted the transcription and expression of peroxisome proliferator-activated receptor γ coactivator- 1α (PGC-1α), nuclear respiratory factor 1 (NRF1) and mitochondrial transcription factor A (TFAM). Meanwhile, SAA treatment significantly promoted mitochondrial biogenesis by increasing mitochondrial DNA (mtDNA) quantity, mitochondrial mass, and expression of mitochondrial respiratory chain enzyme complexes III and complex IV. These enhancements were accompanied by enhanced phosphorylation of AMPK and ACC and were suppressed by Compound C, a specific AMPK inhibitor. Furthermore, SAA treatment improved adipocytes mitochondrial respiration and stimulated ATP generation. These findings indicate that SAA exerts a potential therapeutic capacity against adipocytes mitochondrial dysfunction in diabetes by activating the AMPK-PGC-1α pathway.

Metformin and vitamin D modulate adipose-derived stem cell differentiation towards the beige phenotype

Adipose-derived stem cells (ADSCs) represent an ideal stem cell population for regenerative medicine. ADSC adipogenic differentiation is controlled by the activation of a specific transcriptional program, including epigenetic factors and key adipogenic genes. Under certain conditioned media, ADSCs can differentiate into several phenotypes. We previously demonstrated that bioactive molecules could counteract lipid accumulation and regulate adipogenesis, acting on inflammation and vitamin D metabolism. In the present paper, we aimed at evaluating the effect of metformin and vitamin D in targeting ADSC differentiation towards an intermediate phenotype, as beige adipocytes. We exposed ADSCs to different conditioned media and then we evaluated the levels of expression of main markers of adipogenesis, aP2, LPL and ACOT2. We also analysed the gene and protein expression of thermogenic UCP1 protein, and the expression of PARP1 and the beige specific marker TMEM26. Our results showed a novel effect of metformin and vitamin D not only in inhibiting adipogenesis, but also in inducing a specific ‘brown-like’ phenotype. These findings pave the way for their possible application in the control of de novo lipogenesis useful for the prevention of obesity and its related metabolic disorders.

Cooling down with Entresto. Can sacubitril/valsartan combination enhance browning more than coldness?

BACKGROUND

It is a growing importance to induce a new treatment approach to encourage weight loss but also to improve maintenance of lost weight. It has been shown that promotion of brown adipose tissue (BAT) function or acquisition of BAT characteristics in white adipose tissue (terms referred as "browning") can be protective against obesity.

MAIN TEXT

Amongst numerous established environmental influences on BAT activity, cold exposure is the best interested technique due to its not only effects on of BAT depots in proliferation process but also de novo differentiation of precursor cells via β-adrenergic receptor activation. A novel combination drug, sacubitril/valsartan, has been shown to be more efficient in reducing cardiovascular events and heart failure readmission compared to conventional therapy. Also, this combination of drugs increases the postprandial lipid oxidation contributing to energy expenditure, promotes lipolysis in adipocytes and reduces body weight. To date, there is no research examining potential of combined sacubitril/valsartan use to promote browning or mechanisms in the basis of this thermogenic process.

CONCLUSION

Due to the pronounced effects of cold and sacubitril/valsartan treatment on function and metabolism of BAT, the primary goal of further research should focused on investigation of the synergistic effects of the sacubitril/valsartan treatment at low temperature environmental conditions.

Comprehensive Transcriptome Analysis Reveals the Role of lncRNA in Fatty Acid Metabolism in the Longissimus Thoracis Muscle of Tibetan Sheep at Different Ages

Long noncoding RNA (lncRNA) plays an important regulatory role in mammalian adipogenesis and lipid metabolism. However, their function in the longissimus thoracis (LT) muscle of fatty acid metabolism of Tibetan sheep remains undefined. In this study, fatty acid and fat content in LT muscle of Tibetan sheep were determined, and RNA sequencing was performed to reveal the temporal regularity of lncRNA expression and the effect of lncRNA-miRNA-mRNA ceRNA regulatory network on lipid metabolism of LT muscle in Tibetan sheep at four growth stages (4-month-old, 4 m; 1.5-year-old, 1.5 y; 3.5-year-old, 3.5 y; 6-year-old, 6 y). The results indicated that the intramuscular fat (IMF) content was highest at 1.5 y. Moreover, the monounsaturated fatty acid (MUFA) content in 1.5 y of Tibetan sheep is significantly higher than those of the other groups (P < 0.05), and it was also rich in a variety of polyunsaturated fatty acids (PUFA). A total of 360 differentially expressed lncRNAs (DE lncRNAs) were identified from contiguous period transcriptome comparative groups of 4 m vs. 1.5 y, 1.5 y vs. 3.5 y, 3.5 y vs. 6 y, and 4 m vs. 6 y, respectively. Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis found that the target genes in lncRNA trans-mRNA were significantly related to the protein digestion, absorption, and fatty acid biosynthesis pathways (P < 0.05), which demonstrated that DE lncRNA trans-regulated the target genes, and further regulated the growth and development of the LT muscle and intramuscular fatty acid metabolism in Tibetan sheep. We further analyzed the role of the lncRNA-miRNA-mRNA regulatory network in the lipid metabolism of Tibetan sheep. Additionally, GPD2, LIPE (lipase E hormone-sensitive enzyme), TFDP2, CPT1A, ACACB, ADIPOQ, and other mRNA related to fatty acid and lipid metabolism and the corresponding lncRNA-miRNA regulatory pairs were identified. The enrichment analysis of mRNA in the regulatory network found that the AMPK signaling pathway was the most significantly enriched (P = 0.0000112361). Comprehensive transcriptome analysis found that the LIPE, ADIPOQ, ACACB, and CPT1A that were regulated by lncRNA might change the formation of energy metabolism in Tibetan sheep muscle through the AMPK signaling pathway, and oxidized muscle fibers are transformed into glycolytic muscle fibers, reduced IMF content, and the fatty acid profile also changed.

Ejection of damaged mitochondria and their removal by macrophages ensure efficient thermogenesis in brown adipose tissue

Recent findings have demonstrated that mitochondria can be transferred between cells to control metabolic homeostasis. Although the mitochondria of brown adipocytes comprise a large component of the cell volume and undergo reorganization to sustain thermogenesis, it remains unclear whether an intercellular mitochondrial transfer occurs in brown adipose tissue (BAT) and regulates adaptive thermogenesis. Herein, we demonstrated that thermogenically stressed brown adipocytes release extracellular vesicles (EVs) that contain oxidatively damaged mitochondrial parts to avoid failure of the thermogenic program. When re-uptaken by parental brown adipocytes, mitochondria-derived EVs reduced peroxisome proliferator-activated receptor-γ signaling and the levels of mitochondrial proteins, including UCP1. Their removal via the phagocytic activity of BAT-resident macrophages is instrumental in preserving BAT physiology. Depletion of macrophages in vivo causes the abnormal accumulation of extracellular mitochondrial vesicles in BAT, impairing the thermogenic response to cold exposure. These findings reveal a homeostatic role of tissue-resident macrophages in the mitochondrial quality control of BAT.

Anti-Obesity and Anti-Hyperglycemic Effects of Meretrix lusoria Protamex Hydrolysate in ob/ob Mice

Meretrix lusoria (M. lusoria) is an economically important shellfish which is widely distributed in South Eastern Asia that contains bioactive peptides, proteins, and enzymes. In the present study, the extracted meat content of M. lusoria was enzymatic hydrolyzed using four different commercial proteases (neutrase, protamex, alcalase, and flavourzyme). Among the enzymatic hydrolysates, M. lusoria protamex hydrolysate (MLPH) fraction with MW ≤ 1 kDa exhibited the highest free radical scavenging ability. The MLPH fraction was further purified and an amino acid sequence (KDLEL, 617.35 Da) was identified by LC-MS/MS analysis. The purpose of this study was to investigate the anti-obesity and anti-hyperglycemic effects of MLPH containing antioxidant peptides using ob/ob mice. Treatment with MLPH for 6 weeks reduced body and organ weight and ameliorated the effects of hepatic steatosis and epididymal fat, including a constructive effect on hepatic and serum marker parameters. Moreover, hepatic antioxidant enzyme activities were upregulated and impaired glucose tolerance was improved in obese control mice. In addition, MLPH treatment markedly suppressed mRNA expression related to lipogenesis and hyperglycemia through activation of AMPK phosphorylation. These findings suggest that MLPH has anti-obesity and anti-hyperglycemic potential and could be effectively applied as a functional food ingredient or pharmaceutical.

AMP-activated protein kinase activation in skeletal muscle modulates exercise-induced uncoupled protein 1 expression in brown adipocyte in mouse model

Abstract

Aerobic exercise is an effective intervention in preventing obesity and is also an important factor associated with thermogenesis. There is an increasing interest in the factors and mechanisms induced by aerobic exercise that can influence the metabolism and thermogenic activity in an individual. Recent studies suggest that exercise induced circulating factors (known as ‘exerkines’), which are able to modulate activation of brown adipose tissue (BAT) and browning of white adipose tissue. However, the underlying molecular mechanisms associated with the effect of exercise‐induced peripheral factors on BAT activation remain poorly understood. Furthermore, the role of exercise training in BAT activation is still debatable. Hence, the purpose of our study is to assess whether exercise training affects the expression of uncoupled protein 1 (UCP1) in brown adipocytes via release of different blood factors. Four weeks of exercise training significantly decreased the body weight gain and fat mass gain. Furthermore, trained mice exhibit higher levels of energy expenditure and UCP1 expression than untrained mice. Surprisingly, treatment with serum from exercise‐trained mice increased the expression of UCP1 in differentiated brown adipocytes. To gain a better understanding of these mechanisms, we analysed the conditioned media obtained after treating the C2C12 myotubes with an AMP‐activated protein kinase (AMPK) activator (AICAR; 5‐aminoimidazole‐4‐carboxamide ribonucleotide), which leads to an increased expression of UCP1 when added to brown adipocytes. Our observations suggest the possibility of aerobic exercise‐induced BAT activation via activation of AMPK in skeletal muscles.

Key points

Exercise promotes thermogenesis by activating uncoupling protein 1 (UCP1), which leads to a decrease in the body weight gain and body fat content. However, little is known about the role of exerkines in modulating UCP1 expression and subsequent brown adipose tissue (BAT) activation.

Four weeks of voluntary wheel‐running exercise reduces body weight and fat content.

Exercise induces the increase in AMP‐activated protein kinase (AMPK) and slow‐type muscle fibre marker genes in skeletal muscles and promotes UCP1 expression in white and brown adipose tissues.

Incubation of brown adipocytes with serum isolated from exercise‐trained mice significantly increased their UCP1 gene and protein levels; moreover, conditioned media of AMPK‐activator‐treated C2C12 myotubes induces increased UCP1 expression in brown adipocytes.

These results show that aerobic exercise‐induced skeletal muscle AMPK has a significant effect on UCP1 expression in BAT.

AMPK/PPAR-γ/NF-κB axis participates in ROS-mediated apoptosis and autophagy caused by cadmium in pig liver

The experiment was conducted to investigate the effects of Cadmium (Cd) on growth performance, blood biochemical parameters, oxidative stress, hepatocyte apoptosis and autophagy of weaned piglets. A total of 12 healthy weaned piglets were randomly assigned to the control and the Cd group, which were fed with a basal diet and the basal diet supplemented with 15 ± 0.242 mg/kg CdCl₂ for 30 d, respectively. Our results demonstrated that Cd significantly decreased final body weight, average daily feed intake (ADFI), average daily gain (ADG) and increased feed-to-gain (F/G) ratio (P < 0.05). For blood biochemical parameters, Cd treatment significantly decreased the red blood cell (RBC), hemoglobin (HGB), hematocrit (HCT), total protein, albumin, copper content and iron content (P < 0.05). In addition, liver injury was observed in the Cd-exposed group. Our results also demonstrated that Cd exposure contributed to the production of ROS, activated the AMPK/PPAR-γ/NF-κB pathway (increasing the expressions of P-AMPK/AMPK, NF-κB, I-κB-β, COX-2, and iNOS, decreasing the expressions of PPAR-γ and I-κB-α), finally induced autophagy (increasing the expressions of Beclin-1, the ratio of LC3-II/LC3-I and p62), and apoptosis (increasing the expressions of Bax, Bak, Caspase-9, and Caspase-3, decreasing the expression of Bcl-2). Overall, these findings revealed the vital role of AMPK/PPAR-γ/NF-κB pathway in Cd-induced liver apoptosis and autophagy, which provided deeper insights into a better understanding of Cd-induced hepatotoxicity.

The New Role of AMP-Activated Protein Kinase in Regulating Fat Metabolism and Energy Expenditure in Adipose Tissue

Obesity is characterized by excessive accumulation of fat in the body, which is triggered by a body energy intake larger than body energy consumption. Due to complications such as cardiovascular diseases, type 2 diabetes (T2DM), obstructive pneumonia and arthritis, as well as high mortality, morbidity and economic cost, obesity has become a major health problem. The global prevalence of obesity, and its comorbidities is escalating at alarming rates, demanding the development of additional classes of therapeutics to reduce the burden of disease further. As a central energy sensor, the AMP-activated protein kinase (AMPK) has recently been elucidated to play a paramount role in fat synthesis and catabolism, especially in regulating the energy expenditure of brown/beige adipose tissue and the browning of white adipose tissue (WAT). This review discussed the role of AMPK in fat metabolism in adipose tissue, emphasizing its role in the energy expenditure of brown/beige adipose tissue and browning of WAT. A deeper understanding of the role of AMPK in regulating fat metabolism and energy expenditure can provide new insights into obesity research and treatment.

AMPK Activity: A Primary Target for Diabetes Prevention with Therapeutic Phytochemicals

Diabetes is a metabolic syndrome characterized by inadequate blood glucose control and is associated with reduced quality of life and various complications, significantly shortening life expectancy. Natural phytochemicals found in plants have been traditionally used as medicines for the prevention of chronic diseases including diabetes in East Asia since ancient times. Many of these phytochemicals have been characterized as having few side effects, and scientific research into the mechanisms of action responsible has accumulated mounting evidence for their efficacy. These compounds, which may help to prevent metabolic syndrome disorders including diabetes, act through relevant intracellular signaling pathways. In this review, we examine the anti-diabetic efficacy of several compounds and extracts derived from medicinal plants, with a focus on AMP-activated protein kinase (AMPK) activity.

Astragalus polysaccharide regulates brown adipocytes differentiation by miR-6911 targeting Prdm16

Brown adipose tissue (BAT) is a specialized tissue in mammals related to thermogenesis. The Astragalus polysaccharide (APS) is the major natural active component of Astragalus membranaceus, which has been recognized as one of the most popular herbal medicines worldwide. The role and possible mechanisms of APS on brown adipocytes differentiation is not well defined. Here, we explored the effect of APS on the differentiation of brown adipocytes in C3H10T 1/2 cells. The results showed that APS promoted the differentiation of brown adipocytes and improved insulin sensitivity along with significant increases in the expression of brown adipogenic marker proteins (C/EBPα, C/EBPβ, and PPARγ), thermogenesis marker proteins (UCP1, PRDM16, and PGC-1α), and insulin sensitivity marker protein (GLUT4). Meanwhile, the results showed that the amount of the phosphorylation of insulin receptor substrate 1 (p-IRS1) and phospho-AKT (p-AKT) which are critical factors in the insulin signaling pathway was increased without changing the total amount of IRS and AKT. Furthermore, the results of RNA-seq showed that APS altered the expression profiles of various miRNAs, and among which the expression of miR-6911 as a universal regulatory factor was significantly decreased. Importantly, we found that miR-6911 regulated the differentiation of brown adipocytes by targeting PR domain-containing 16 (Prdm16). In addition, after transfection of miR-6911 mimics, compared with the control and inhibitor group, PRDM16 protein expression significantly decreased, which was accompanied by the decrease of PPARγ, UCP1, and PGC-1α. Collectively, our results indicated that APS regulated brown adipocytes differentiation in C3H10T 1/2 cells via miRNA-6911 targeting Prdm16.

Fruit of Gardenia jasminoides Induces Mitochondrial Activation and Non-Shivering Thermogenesis through Regulation of PPARγ

The extract of the Gardenia jasminoides fruit (GJFE) can been consumed as an herbal tea or used as a yellow dye. Recently, studies report that GFJE exerts inhibitory effects on lipid accumulation and adipogenesis in white adipocytes. We evaluated the thermogenic actions of GJFE by focusing on mitochondrial activation and studying the underlying mechanisms. To investigate the role of GJFE on thermogenesis in mice, we used an acute cold exposure model. After 2 weeks of feeding, the cold tolerance of GJFE-fed mice was notably increased compared to PBS-fed mice. This was due to an increase in thermogenic proteins in the inguinal white adipose tissue of the cold-exposed mice. Moreover, GJFE significantly increased thermogenic factors such as peroxisome proliferator-activated receptor gamma (PPARγ), uncoupling protein 1 (UCP1), and PPARγ coactivator 1 alpha (PGC1α) in vitro as well. Factors related to mitochondrial abundance and functions were also induced by GJFE in white and beige adipocytes. However, the treatment of PPARγ inhibitor abolished the GJFE-induced changes, indicating that activation of PPARγ is critical for the thermogenic effect of GJFE. In conclusion, GJFE induces thermogenic action by activating mitochondrial function via PPARγ activation. Through these findings, we suggest GJFE as a potential anti-obesity agent with a novel mechanism involving thermogenic action in white adipocytes.