Sinapic acid induces the expression of thermogenic signature genes and lipolysis through activation of PKA/CREB signaling in brown adipocytes

Bioactivity-based molecular networking-guided identification of guttiferone J from Garcinia cambogia as an anti-obesity candidate

BACKGROUND AND PURPOSE

Pharmacological intervention to induce browning of white adipose tissue provides a promising anti-obesity therapy. The fruits of Garcinia cambogia (Clusiaceae) have been widely applied to manage body weight; however, the chemical principles remain unclear. The current study aims to discover browning inducers from the fruits of G. cambogia and investigate the underlying mechanisms.

EXPERIMENTAL APPROACH

The bioactivity-based molecular networking and Oil Red O staining on 3T3-L1 and C3H10T1/2 adipocytes were applied for guided isolation. High-fat diet-induced obese mice were recruited to evaluate the anti-obesity activity.

KEY RESULTS

The bioactivity-based molecular networking-guided isolation yielded several polycyclic polyprenylated acylphloroglucinols from the fruits of G. cambogia with lipid-lowering effect in adipocytes, including guttiferone J (GOJ), garcinol and 14-deoxygarcinol. As the most potent one, GOJ (10 μM) reduced lipid accumulation by 70% and 76% in 3T3-L1 and C3H10T1/2 adipocytes, respectively. Furthermore, GOJ (2.5-10 μM) increased the expression of the deacetylase sirtuin 3 (SIRT3) and activated it, which, in turn, reduced the acetylation level of PPARγ coactivator-1α to boost mitochondrial biogenesis and promoted uncoupling protein 1 expression to enhance thermogenesis, resulting in browning of adipocytes. In high-fat diet-induced-obese mice, GOJ (10 and 20 mg·kg^-1 ·day^-1 for 12 weeks) protected against adiposity, hyperlipidaemia, insulin resistance and liver lipotoxicity, through boosting SIRT3-mediated browning of inguinal adipose tissue.

CONCLUSION AND IMPLICATIONS

GOJ represents a new scaffold of thermogenic inducer, which is responsible for the anti-obesity property of G. cambogia and can be further developed as a candidate for treating obesity and its related disorders.

Acacetin alleviates energy metabolism disorder through promoting white fat browning mediated by AC-cAMP pathway

Acacetin (ACA), a flavone isolated from Chinese traditional medical herbs, has numerous pharmacological activities. However, little is known about the roles in white fat browning and energy metabolism. In the present study, we investigated whether and how ACA would improve energy metabolism in vivo and in vitro. ACA (20 mg/kg) was intraperitoneally injected to the mice with obesity induced by HFD for 14 consecutive days (in vivo); differentiated 3T3-L1 adipocytes were treated with ACA (20 µmol/L and 40 µmol/L) for 24 h (in vitro). The metabolic profile, lipid accumulation, fat-browning and mitochondrial contents, and so on were respectively detected. The results in vivo showed that ACA significantly reduced the body weight and visceral adipose tissue weight, alleviated the energy metabolism disorder, and enhanced the browning-related protein expressions in adipose tissue of rats. Besides, the data in vitro revealed that ACA significantly reduced the lipid accumulation, induced the expressions of the browning-related proteins and cAMP-dependent protein kinase A (PKA), and increased the mitochondrium contents, especially enhanced the energy metabolism of adipocytes; however, treatment with beta-adrenergic receptor blocker (propranolol, Pro) or adenyl cyclase (AC) inhibitor (SQ22536, SQ) abrogated the ACA-mediated effects. The data demonstrate that ACA alleviates the energy metabolism disorder through the pro-browning effects mediated by the AC-cAMP pathway. The findings would provide the experimental foundation for ACA to prevent and treat obesity and related metabolism disorders.

Scytosiphon lomentaria Extract Ameliorates Obesity and Modulates Gut Microbiota in High-Fat-Diet-Fed Mice

Scytosiphon lomentaria (SL) is a brown seaweed with antioxidant and anti-inflammatory properties; however, its effects on obesity are unknown. In this research, we investigated the anti-obesity properties and underlying mechanisms of the SL extract in vitro and in vivo. In 3T3-L1 preadipocytes, SL extract inhibited lipid accumulation, decreased the expression of Acc1, C/ebpa, Pparg mRNA and p-ACC1, and increased the expression of Ucp1 mRNA, UCP1 and p-AMPK. In animal experiments, mice were fed a chow diet, a high-fat diet (HF; 60% of calories as fat), and high-fat diet with SL extract (150 and 300 mg/kg body weight) for eight weeks (n = 10/group). SL extract reduced HF-induced weight gain, epididymal fat weight, fat cell size, LDL-C, leptin, fasting glucose, and glucose tolerance. In addition, SL extract had comparable effects on mRNA expression in WAT and liver to those observed in vitro, thereby inhibiting p-ACC1/ACC1 and increasing p-AMPK/AMPK and UCP1 expression. Furthermore, SL extract decreased HF-induced Firmicutes/Bacteroidetes ratio and reversed HF-reduced Bacteroides spp., Bacteroides vulgatus, and Faecalibacterium prausnitzii. These findings suggest that SL extract can aid in weight loss in mice fed a high-fat diet by altering adipogenic and thermogenic pathways, as well as gut microbiota composition.

Bifidobacterium bifidum DS0908 and Bifidobacterium longum DS0950 Culture-Supernatants Ameliorate Obesity-Related Characteristics in Mice with High-Fat Diet-Induced Obesity

Probiotic supplements have promising therapeutic effects on chronic diseases. In this study, we demonstrated the anti-obesity effects of two potential probiotics, Bifidobacterium bifidum DS0908 (DS0908) and Bifidobacterium longum DS0950 (DS0950). Treatment with DS0908 and DS0950 postbiotics significantly induced the expression of the brown adipocyte-specific markers UCP1, PPARγ, PGC1α, PRDM16 and beige adipocyte-specific markers CD137, FGF21, P2RX5, and COX2 in C3H10T1/2 mesenchymal stem cells (MSCs). In mice with high-fat diet (HFD)-induced obesity, both potential probiotics and postbiotics noticeably reduced body weight and epididymal fat accumulation without affecting food intake. DS0908 and DS0950 also improved insulin sensitivity and glucose use in mice with HFD-induced obesity. In addition, DS0908 and DS0950 improved the plasma lipid profile, proved by reduced triglyceride, low-density lipoprotein, and cholesterol levels. Furthermore, DS0908 and DS0950 improved mitochondrial respiratory function, confirmed by the high expression of oxidative phosphorylation proteins, during thermogenesis induction in the visceral and epididymal fat in mice with HFD-induced obesity. Notably, the physiological and metabolic changes were more significant after treatment with potential probiotic culture-supernatants than those with the bacterial pellet. Finally, gene knockdown and co-treatment with inhibitor-mediated mechanistic analyses showed that both DS0908 and DS0950 exerted anti-obesity-related effects via the PKA/p38 MAPK signaling activation in C3H10T1/2 MSCs. Our observations suggest that DS0908 and DS0950 could potentially alleviate obesity as dietary supplements.

Dietary Sinapic Acid Alleviates Adiposity and Inflammation in Diet-Induced Obese Mice

Sinapic acid (SA), a hydroxycinnamic acid, is known to confer protection against oxidative stress, inflammation, diabetes, and liver disease. However, the effectiveness of SA in improving obesity remains obscure. Therefore, this study evaluated anti-obesity efficacy of SA and to elucidate its mechanism of action. Male mice were maintained for 16 weeks on high-fat diet (HFD) alone or with SA (0.004%, w/w) and bodyweight, fat mass, adipocyte size, food intake, and biochemical and molecular markers were evaluated. SA-supplemented mice demonstrated markedly decreased fat mass and adipocyte size compared to unsupplemented group, without any changes in bodyweight and food intake between the two groups. Plasma adipocytokines levels including leptin, resistin, monocyte chemoattractant protein (MCP)-1 and interleukin-6 were also markedly reduced by SA supplementation. SA tended to lower plasma insulin level and improved homeostatic index of insulin resistance and intraperitoneal glucose tolerance test in HFD-induced obese mice. The anti-adiposity effect of SA was maybe owing to down-regulation of the mRNA expression of lipogenic genes, including acetyl coenzyme A (CoA) carboxylase, fatty acid synthesis, stearoyl-CoA desaturase 1, and phosphatidate phosphatase, and peroxisome proliferator-activated receptor γ, a transcription factor responsible for governing lipid metabolism, in adipose tissues. SA significantly down-regulated pro-inflammatory nuclear factor kappa B, MCP-1, tumor necrosis factor-α, and Toll-like receptor 4 mRNA expression in adipose tissue. Thus, SA could be beneficial for the development of functional foods or herbal medications to combat obesity.

Dietary sinapic acid attenuated high-fat diet-induced lipid metabolism and oxidative stress in male Syrian hamsters

The current study investigated the effects of sinapic acid on high-fat diet (HFD)-induced lipid metabolism and oxidative stress in male Syrian hamsters. Sinapic acid treatment significantly reduced body weight, epididymal fat, and perirenal fat mass in HFD hamsters. Sinapic acid also improved dyslipidemia levels (reducing the serum levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol, and increasing the high-density lipoprotein cholesterol) and increased T-AOC levels to mitigate oxidative stress injury. Moreover, sinapic acid intervention increased the activations of PPAR-γ, CPT-1, and CYP7A1 and decreased the activations of FAS, ACC1, SREBP1, SREBP2, and HMGCR in the livers of HFD hamsters. In addition, sinapic acid intervention also significantly inhibited the intestinal mRNA levels of Srebp2 and Npc1l1 in HFD hamsters. In conclusion, sinapic acid can significantly attenuate abnormal lipid metabolism in the development of HFD-induced obesity and reduce the level of oxidative stress to exert its anti-obesity effect. PRACTICAL APPLICATIONS: Obesity is the main cause of some chronic metabolic syndromes, such as dyslipidemia, nonalcoholic fatty liver disease, diabetes, and hyperuricemia. Searching for new, safe, and effective natural products in weight loss and fat reduction has become one of the hot research topics. As a natural source of simple phenolic acids, sinapic acid is present in fruits, vegetables, and grains and has been indicated to have anti-inflammatory, antioxidant, antihyperuricemic, lipid homeostasis regulation, and anticancer activities. However, the lipid metabolism- and oxidative stress-regulating activities of sinapic acid are not clear. Here, the current study investigated the lipid metabolism and oxidative stress regulating activities of sinapic acid in male Syrian hamsters fed a high-fat diet.

UCP2 KO mice exhibit ameliorated obesity and inflammation induced by high-fat diet feeding

Uncoupling protein 2 (Ucp2) was first introduced as a member of Uncoupling protein family and a regulator of ROS formation; however, its role in adipose tissue is not fully understood. In the present study, we have investigated the role of Ucp2 against high-fat diet (HFD)-induced obesity in epididymal white adipose tissue (eWAT) and browning of inguinal white adipose tissue (iWAT). Diet-induced obesity is closely related to macrophage infiltration and the secretion of pro-inflammatory cytokines. Macrophages surround adipocytes and form a crown-like-structure (CLS). Some reports have suggested that CLS formation requires adipocyte apoptosis. After 12 weeks of HFD challenge, Ucp2 knockout (KO) mice maintained relatively lean phenotypes compared to wild-type (WT) mice. In eWAT, macrophage infiltration, CLS formation, and inflammatory cytokines were reduced in HFD KO mice compared to HFD WT mice. Surprisingly, we found that apoptotic signals were also reduced in the Ucp2 KO mice. Our study suggests that Ucp2 deficiency may prevent diet-induced obesity by regulating adipocyte apoptosis. However, Ucp2 deficiency did not affect the browning capacity of iWAT.

Sinapic acid inhibits pancreatic cancer proliferation, migration, and invasion via downregulation of the AKT/Gsk-3β signal pathway

Among digestive system cancers, the extremely poor prognosis of pancreatic cancer (PC) is a pressing concern. Nonoperative treatments such as targeted and immunotherapy, have improved the current situation, however, the accompanying side effects of these chemicals should not be ignored. Here, we discovered a novel hydroxycinnamic acid named sinapic acid (SA) derived from fruits, vegetables, cereals, and oil crops as an effective anti-PC molecule. Both the in vitro and in vivo models we designed showed that SA exhibited anticancer activities but not apoptosis induction. Research on the underlying mechanisms illustrated that AKT phosphorylation was blocked by SA, and the downstream Gsk-3β was downregulated subsequently. Our study revealed the inhibitory activity and underlying mechanisms of SA, providing evidence that SA is a potential strategy for cancer research and can be a promising option of PC chemotherapy.

Exercise-induced beige adipogenesis of iWAT in Cidea reporter mice

Obesity is caused by an imbalance between energy intake and energy expenditure. Exercise is attracting attention as one of the ways to treat obesity. Exercise induces ‘beige adipogenesis’ in white adipose tissue, increasing total energy expenditure via energy dissipation in the form of heat. Also, beige adipogenesis can be induced by treatment with a beta-adrenergic receptor agonist. We developed a Cidea-dual reporter mouse (Cidea-P2A-Luc2-T2A-tdTomato, Luciferase/tdTomato) model to trace and measure beige adipogenesis in vivo. As a result, both exercise and injection of beta-adrenergic receptor agonist induced beige adipogenesis and was detected through fluorescence and luminescence. We confirmed that exercise and beta-adrenergic receptor agonist induce beige adipogenesis in Cidea-dual reporter mouse, which will be widely used for detecting beige adipogenesis in vivo.

The Use of Bioactive Compounds in Hyperglycemia- and Amyloid Fibrils-Induced Toxicity in Type 2 Diabetes and Alzheimer’s Disease

It has become increasingly apparent that defective insulin signaling may increase the risk for developing Alzheimer’s disease (AD), influence neurodegeneration through promotion of amyloid formation or by increasing inflammatory responses to intraneuronal β-amyloid. Recent work has demonstrated that hyperglycemia is linked to cognitive decline, with elevated levels of glucose causing oxidative stress in vulnerable tissues such as the brain. The ability of β-amyloid peptide to form β-sheet-rich aggregates and induce apoptosis has made amyloid fibrils a leading target for the development of novel pharmacotherapies used in managing and treatment of neuropathological conditions such as AD-related cognitive decline. Additionally, deposits of β-sheets folded amylin, a glucose homeostasis regulator, are also present in diabetic patients. Thus, therapeutic compounds capable of reducing intracellular protein aggregation in models of neurodegenerative disorders may prove useful in ameliorating type 2 diabetes mellitus symptoms. Furthermore, both diabetes and neurodegenerative conditions, such as AD, are characterized by chronic inflammatory responses accompanied by the presence of dysregulated inflammatory biomarkers. This review presents current evidence describing the role of various small bioactive molecules known to ameliorate amyloidosis and subsequent effects in prevention and development of diabetes and AD. It also highlights the potential efficacy of peptide–drug conjugates capable of targeting intracellular targets.

Sinapic Acid Alleviates Acute Pancreatitis in Association with Attenuation of Inflammation, Pyroptosis, and the AMPK/NF-κB Signaling Pathway

Among the diseases of the digestive system, the incidence of acute pancreatitis (AP) has increased. Although the AP is primarily self-limited, mortality remains high when it progressed to severe acute pancreatitis (SAP). Despite significant advances in new drug development, treatments for AP are not ideal. Here, we discovered a novel hydroxycinnamic acid, sinapic acid (SA), which is widely distributed in plants and is an effective treatment for AP. Using in vitro and in vivo models, we demonstrated that pretreatment with SA ameliorated cerulein-induced pancreatic damage and inflammation and inhibited the activation of Caspase-1 and Caspase-11, which mediate pyroptosis of pancreatic acinar cells during AP. These effects may occur through the inhibition of AMPK phosphorylation and downregulation of NF-[Formula: see text]B. Our findings demonstrate the therapeutic effects and reveal the underlying mechanisms of SA, which warrants its further study as an effective treatment for AP.

Butein-Enriched Fractions of Butea monosperma (Lam.) Taub. Flower Decrease Weight Gains and Increase Energy Expenditure in High-Fat Diet-Induced Obese Mice

Butea monosperma (Lam.) Taub. has been applied to treat inflammatory, metabolic, and infectious diseases. However, the antiobesity effects of B. monosperma (Lam.) Taub. flower (BMF) and the underlying mechanisms have not been determined. In this study, we analyzed the various extraction procedures, investigated the antiobesity effects, and identified the main chemical constituents of BMF. The BMF was subjected to acid hydrolysis in 5% H₂SO₄ in methanol at 50°C for 48 h and partitioned with ethyl acetate. The acid-hydrolyzed BMF ethyl acetate extracts (BMFE) strongly induced the expression of uncoupling protein 1 (Ucp1) and other thermogenic genes in C3H10T1/2 adipocytes. Daily oral administration of 70 mg/kg BMFE (BMFE70) to mice with diet-induced obesity resulted in less body weight gain, increased glucose tolerance, higher rectal temperature, and increased oxygen consumption. Qualitative and quantitative analyses along with treatments in Akt1 knockout mouse embryonic fibroblasts indicate that butein is a major active ingredient of BMFE, which stimulates Ucp1 gene expression. These data show the effects of butein-containing B. monosperma flower extract on thermogenesis and energy expenditure, further suggesting the potential role of BMFE as a functional ingredient in obesity and related metabolic diseases.

Adipogenic function of tetranectin mediated by enhancing mitotic clonal expansion via ERK signaling

Tetranectin (TN), an adipogenic serum protein, enhances adipocyte differentiation, however, its functional mechanism has yet to be elucidated. In the present study, we investigated the adipogenic function of TN by using medium containing TN-depleted fetal bovine serum (TN-del-FBS) and recombinant mouse TN (mTN). The adipocyte differentiation of 3T3-L1 cells was significantly enhanced by mTN supplementation essentially at differentiation induction, which indicated a potential role of the protein in the early differentiation phase. The adipogenic effect of mTN was more significant with insulin in the differentiation induction cocktail, implicating their close functional relationship. mTN enhanced not only the proliferation of growing cells, but also mitotic clonal expansion (MCE) that is a prerequisite for adipocyte differentiation in the early phase. Consistently, mTN increased the phosphorylation of ERK in the early phase of adipocyte differentiation. Results of this study demonstrate that the adipogenic function of mTN is mediated by enhancing MCE via ERK signaling.

CREB nuclear transcription activity as a targeting factor in the treatment of diabetes and diabetes complications

Diabetes mellitus is a metabolic disorder diagnosed by elevated blood glucose levels and a defect in insulin production. Blood glucose, an energy source in the body, is regenerated by two fundamental processes: glycolysis and gluconeogenesis. These two processes are the main mechanisms used by humans and many other animals to maintain blood glucose levels, thereby avoiding hypoglycaemia. The released insulin from pancreatic β-cells activates glycolysis. However, the glucagon released from the pancreatic α-cells activates gluconeogenesis in the liver, leading to pyruvate conversion to glucose-6-phosphate by different enzymes such as fructose 1,6-bisphosphatase and glucose 6-phosphatase. These enzymes' expression is controlled by the glucagon/ cyclic adenosine 3',5'-monophosphate (cAMP)/ proteinkinase A (PKA) pathway. This pathway phosphorylates cAMP-response element-binding protein (CREB) in the nucleus to bind it to these enzyme promoters and activate their expression. During fasting, this process is activated to supply the body with glucose; however, it is overactivated in diabetes. Thus, the inhibition of this process by blocking the expression of the enzymes via CREB is an alternative strategy for the treatment of diabetes. This review was designed to investigate the association between CREB activity and the treatment of diabetes and diabetes complications. The phosphorylation of CREB is a crucial step in regulating the gene expression of the enzymes of gluconeogenesis. Many studies have proven that CREB is over-activated by glucagon and many other factors contributing to the elevation of fasting glucose levels in people with diabetes. The physiological function of CREB should be regarded in developing a therapeutic strategy for the treatment of diabetes mellitus and its complications. However, the accessible laboratory findings for CREB activity of the previous research still not strong enough for continuing to the clinical trial yet.

Myonectin inhibits adipogenesis in 3T3-L1 preadipocytes by regulating p38 MAPK pathway

In current times, obesity is a major health problem closely associated with metabolic disease such as diabetes, dyslipidemia, and cardiovascular disease. The direct cause of obesity is known as an abnormal increase in fat cell size and the adipocyte pool. Hyperplasia, the increase in number of adipocytes, results from adipogenesis in which preadipocytes differentiate into mature adipocytes. Adipogenesis is regulated by local and systemic cues that alter transduction pathways and subsequent control of adipogenic transcription factors. Therefore, the regulation of adipogenesis is an important target for preventing obesity. Myonectin, a member of the CTRP family, is a type of myokine released by skeletal muscle cells. Although several studies have shown that myonectin is associated with lipid metabolism, the role of myonectin during adipogenesis is not known. Here, we demonstrate the role of myonectin during adipocyte differentiation of 3T3-L1 cells. We found that myonectin inhibits the adipogenesis of 3T3-L1 preadipocytes with a reduction in the expression of adipogenic transcription factors such as C/EBPα, β and PPARγ. Furthermore, we show that myonectin has an inhibitory effect on adipogenesis through the regulation of the p38 MAPK pathway and CHOP. These findings suggest that myonectin may be a novel therapeutic target for the prevention of obesity.

Sesamol Increases Ucp1 Expression in White Adipose Tissues and Stimulates Energy Expenditure in High-Fat Diet-Fed Obese Mice

Sesamol found in sesame oil has been shown to ameliorate obesity by regulating lipid metabolism. However, its effects on energy expenditure and the underlying molecular mechanism have not been clearly elucidated. In this study, we show that sesamol increased the uncoupling protein 1 (Ucp1) expression in adipocytes. The administration of sesamol in high-fat diet (HFD)-fed mice prevented weight gain and improved metabolic derangements. The three-week sesamol treatment of HFD-fed mice, when the body weights were not different between the sesamol and control groups, increased energy expenditure, suggesting that an induced energy expenditure is a primary contributing factor for sesamol’s anti-obese effects. Consistently, sesamol induced the expression of energy-dissipating thermogenic genes, including Ucp1, in white adipose tissues. The microarray analysis showed that sesamol dramatically increased the Nrf2 target genes such as Hmox1 and Atf3 in adipocytes. Moreover, 76% (60/79 genes) of the sesamol-induced genes were also regulated by tert-butylhydroquinone (tBHQ), a known Nrf2 activator. We further verified that sesamol directly activated the Nrf2-mediated transcription. In addition, the Hmox1 and Ucp1 induction by sesamol was compromised in Nrf2-deleted cells, indicating the necessity of Nrf2 in the sesamol-mediated Ucp1 induction. Together, these findings demonstrate the effects of sesamol in inducing Ucp1 and in increasing energy expenditure, further highlighting the use of the Nrf2 activation in stimulating thermogenic adipocytes and in increasing energy expenditure in obesity and its related metabolic diseases.

Uncovering the Role of p38 Family Members in Adipose Tissue Physiology

The complex functions of adipose tissue have been a focus of research interest over the past twenty years. Adipose tissue is not only the main energy storage depot, but also one of the largest endocrine organs in the body and carries out crucial metabolic functions. Moreover, brown and beige adipose depots are major sites of energy expenditure through the activation of adaptive, non-shivering thermogenesis. In recent years, numerous signaling molecules and pathways have emerged as critical regulators of adipose tissue, in both homeostasis and obesity-related disease. Among the best characterized are members of the p38 kinase family. The activity of these kinases has emerged as a key contributor to the biology of the white and brown adipose tissues, and their modulation could provide new therapeutic approaches against obesity. Here, we give an overview of the roles of the distinct p38 family members in adipose tissue, focusing on their actions in adipogenesis, thermogenic activity, and secretory function.