Brown Fat and Browning for the Treatment of Obesity and Related Metabolic Disorders

Molecular dissection of the role of ACE2 in glucose homeostasis

Angiotensin-converting enzyme 2 (ACE2) was discovered 25 years ago as a negative regulator of the renin-angiotensin system, opposing the effects of angiotensin II. Beyond its well-demonstrated roles in cardiovascular regulation and COVID-19 pathology, ACE2 is involved in a plethora of physiopathological processes. In this review, we summarize the latest discoveries on the role of ACE2 in glucose homeostasis and regulation of metabolism. In the endocrine pancreas, ACE2 is expressed at low levels in β-cells, but loss of its expression inhibits glucose-stimulated insulin secretion and impairs glucose tolerance. Conversely, overexpression of ACE2 improved glycemia, suggesting that recombinant ACE2 might be a future therapy for diabetes. In the skeletal muscle of ACE2-deficient mice a progressive triglyceride accumulation was observed, whereas in diabetic kidney the initial increase in ACE2 is followed by a chronic reduction of expression in kidney tubules and impairment of glucose metabolism. At the intestinal level dysregulation of the enzyme alters the amino acid absorption and intestinal microbiome, whereas at the hepatic level ACE2 protects against diabetic fatty liver disease. Not least, ACE2 is upregulated in adipocytes in response to nutritional stimuli, and administration of recombinant ACE2 decreased body weight and increased thermogenesis. In addition to tissue-specific regulation of ACE2 function, the enzyme undergoes complex cellular posttranslational modifications that are changed during diabetes evolution, with at least proteolytic cleavage and ubiquitination leading to modifications in ACE2 activity. Detailed characterization of ACE2 in a cellular and tissue-specific manner holds promise for improving therapeutic outcomes in diabetes and metabolic disorders.

Myriocin Restores Metabolic Homeostasis in dAGE-Exposed Mice via AMPK-PGC1α-Mediated Mitochondrial Activation and Systemic Lipid/Glucose Regulation

Background: Diet-derived advanced glycation end products (dAGEs) are closely associated with obesity and metabolic disorders. This study investigates the therapeutic potential of myriocin (Myr), a sphingolipid synthesis inhibitor, in counteracting dAGE-induced obesity and its underlying mechanisms. Methods: Male C57BL/6J wild-type mice were randomly assigned to receive either a low-AGE diet or a high-AGE diet with or without the administration of myriocin for a duration of 24 weeks. At the end of the experimental period, blood samples, whole livers, and adipose tissues were harvested for subsequent biochemical, histological, and molecular analyses. Results: Using a 24-week high-AGE diet mouse model, we demonstrate that Myr significantly reduces body weight gain (by 76%) and adipose tissue accumulation, while alleviating hepatic steatosis. Myr improves glucose homeostasis by lowering fasting blood glucose (a 44.5% reduction), enhancing oral glucose tolerance, and restoring hepatic glycolysis/gluconeogenesis balance via upregulating glucokinase and suppressing G6pc. Notably, Myr reduces serum LDL-C, TG, and TC levels by 52.3%, 51.8%, and 48.8%, respectively, and ameliorates liver dysfunction as evidenced by normalized ALT/AST activities. Metabolomics reveal Myr reshapes amino acid, carbohydrate, and lipid metabolism pathways. Mechanistically, Myr suppresses lipogenesis by downregulating Srebp1, Fasn, and Acc, while activating AMPK-PGC1α signaling to enhance mitochondrial biogenesis (a 2.1-fold increase in mtDNA) and thermogenesis via Ucp1 upregulation in brown and white adipose tissues. Conclusions: Our findings unveil Myr as a novel dual regulator of lipid and glucose metabolism through AMPK-PGC1α-mediated mitochondrial activation, providing the first evidence of sphingolipid inhibition as a therapeutic strategy against dAGE-induced metabolic syndrome. This study establishes a multifaceted mechanism involving hepatic lipid regulation, adipose browning, and systemic metabolic reprogramming, advancing potential clinical applications for obesity-related disorders.

Anti-Obesity Effects of LB-GABA

Obesity is characterized by an excessive imbalance in energy metabolism and is associated with metabolic syndrome. Mammals have two types of adipose tissue: white adipose tissue (WAT) and brown adipose tissue (BAT). These are key factors in regulating the energy balance. Strategies aimed at reducing obesity should encompass not only the prevention of lipid accumulation but also the stimulation of browning in both WAT and BAT, with the aim of enhancing energy expenditure. In this study, the mechanism by which Lactobacillus brevis-fermented gamma-aminobutyric acid (LB-GABA) prevents obesity was investigated, as well as whether it induces lipolysis and browning in WAT using 3T3-L1 adipocytes. The expression of proteins involved in signaling pathways regulating lipid accumulation and degradation, as well as browning, was measured using Western blotting analysis. We demonstrated that LB-GABA significantly inhibited lipid accumulation by suppressing adipogenesis and lipogenesis. In addition, the microscopic analysis of WAT demonstrated that LB-GABA reduced the adipocyte size and the number of lipid droplets. Moreover, Western blot analysis revealed that GABA increased lipolysis and activated the protein kinase A (PKA) signaling pathway, which promotes uncoupling protein 1 (UCP1)-mediated WAT browning. In conclusion, these results suggest that LB-GABA activates energy expenditure through lipid metabolism regulation and exerts anti-obesity effects.

Daily brief whole-body immersion in 14 °C water temporarily decreases glucose tolerance and insulin sensitivity

Despite growing popularity, experimental evidence regarding the impact of daily cold exposure as an intervention for metabolic health has been lacking, especially with brief cold exposures. Thus, we aimed to investigate the effects of brief repeated whole-body immersion in 14 °C water on glucose tolerance, insulin sensitivity, and resting energy expenditure (REE) in young, nonobese adults. Twelve participants completed sixteen daily 10-min sessions involving whole-body immersion in 14 °C water. Changes in resting catecholamines, REE, and substrate oxidation were assessed in the overnight fasting state, while changes in glucose and insulin were assessed both in the overnight fasting state and during an oral glucose tolerance test before and 24 h after the intervention, and 1 week after the end of the intervention. The findings showed that daily brief cold water immersion (CWI) did not affect adrenaline, noradrenaline, REE, and substrate oxidation rate. However, daily CWI significantly decreased (p < 0.05) glucose tolerance as indicated by increased glucose area under the curve and insulin sensitivity as indicated by decreased Matsuda insulin sensitivity index. However, these effects were temporary and, after 1 week, the values returned to baseline. In conclusion, 16 daily sessions of brief 10-min whole-body immersion in 14 °C water temporarily decreased insulin sensitivity and glucose tolerance.

Neurobiological role and therapeutic potential of exercise-induced irisin in Alzheimer's disease management

Alzheimer's disease (AD) poses a significant obstacle in today's healthcare landscape, with limited effective treatments. Recent studies have revealed encouraging findings about how exercise-triggered irisin might help slow down the advancement of AD. Irisin, a myokine, released during physical activity, has garnered significant attention for its pleiotropic effects, extending beyond its traditional role in metabolic regulation. This review explores irisin's multifaceted potential in combating AD. Research indicates that irisin enhances synaptic plasticity, crucial for learning and memory, and exhibits neuroprotective properties that may slow AD progression by safeguarding neurons from degeneration. Additionally, irisin's ability to modulate inflammatory responses is significant, as neuroinflammation is a key feature of AD pathology. Irisin may also influence the metabolism and clearance of amyloid-beta plaques and tau tangles, hallmark pathological markers of AD. Furthermore, irisin boosts brain-derived neurotrophic factor expression, vital for neuronal health, and improves insulin glucose regulation, addressing impaired brain insulin signaling observed in AD. Exercise-induced irisin presents a non-pharmacological strategy, leveraging physical activity's brain health benefits. Future research should focus on elucidating irisin's mechanisms and conducting clinical trials to assess its therapeutic efficacy and safety in AD patients. Overall, irisin therapy offers a promising avenue for AD treatment, potentially slowing disease progression and enhancing cognitive function, paving the way for innovative therapeutic strategies in the fight against AD.

4-hydroxybenzoic acid induces browning of white adipose tissue through the AMPK-DRP1 pathway in HFD-induced obese mice

BACKGROUND

Beige adipocytes have physiological functions similar to brown adipocytes, which are available to increase energy expenditure through uncoupling protein 1 (UCP1) within mitochondria. Recently, many studies showed white adipocytes can undergo remodeling into beige adipocytes, called "browning", by increasing fusion and fission events referred to as mitochondrial dynamics.

PURPOSE

In this study, we aimed to investigate the browning effects of 4-hydroxybenzoic acid (4-HA), one of the major compounds of black raspberries.

METHODS

We examined the mechanism underlying the browning properties of 4-HA focusing on UCP1-dependent non-shivering thermogenesis in 3T3-L1 white adipocytes, high-fat diet (HFD)-induced obese male C57BL/6J mice, and cold-exposed male C57BL/6J mice.

RESULTS

4-HA treatment elevates browning markers such as UCP1, T-Box transcription factor 1, and PR domain containing 16, mitochondrial function factors like oxidative phosphorylation complex as well as mitochondrial dynamic-related factors like phosphorylated dynamin-related protein 1 (p-DRP1), DRP1, and mitofusin 1 in 3T3-L1 white adipocytes, which were also confirmed in inguinal white adipose tissue (iWAT) of HFD-induced obese mice. Mdivi-1 blocked the increased DRP1-mediated mitochondrial fission by 4-HA, and even the browning effect of 4-HA was abolished. Furthermore, 4-HA increased AMP-activated protein kinase (AMPK) in both the 3T3-L1 white adipocytes and iWAT of HFD-induced obese mice. Inhibition of AMPK with Compound C also blocked the 4-HA-induced mitochondrial fission and browning effect.

CONCLUSIONS

4-HA induces the browning of white adipocytes into beige adipocytes by regulating the DRP1-mediated mitochondrial dynamics through AMPK. These findings suggest that 4-HA could serve as a therapeutic candidate for obesity and related metabolic disorders.

Wu-Mei-Wan enhances brown adipose tissue function and white adipose browning in obese mice via upregulation of HSF1

BACKGROUND

This research aims to explore the anti-obesity potential of Wu-Mei-Wan (WMW), particularly its effects on adipose tissue regulation in obese mice induced by a high-fat diet (HFD). The study focuses on understanding the role of heat shock factor 1 (HSF1) in mediating these effects.

METHODS

HFD-induced obese mice were treated with WMW. Body weight, food intake, and histopathological analysis of adipose tissue were conducted. Brown adipose tissue (BAT) activity was evaluated using Positron Emission Tomography, and ultrastructural changes were examined via transmission electron microscopy. Proteomic analysis identified targets of WMW in obesity treatment. HSF1 expression was inhibited to confirm its role. Molecular docking studied interactions between WMW and HSF1. Short-chain fatty acids (SCFAs) in the intestines were measured to determine if WMW's effects on HSF1 are mediated through SCFAs. Protein expression was assessed using western blot, immunohistochemistry, immunofluorescence and RT-qPCR were employed to detect the mRNA levels. Statistical analyses included t-tests, ANOVA, and non-parametric tests like the Mann-Whitney U test or Kruskal-Wallis test.

RESULTS

WMW significantly mitigates the adverse effects of a HFD on body weight and glucose metabolism in obese mice. Both low-dose WMW and high-dose WMW treatments led to reduced weight gain and improved glucose tolerance, with low-dose WMW showing more pronounced effects. WMW also reversed structural damage in BAT, enhancing mitochondrial integrity and thermogenic function, particularly at the low dose. Additionally, WMW treatment promoted the browning of WAT, evidenced by increased expression of key thermogenic proteins such as UCP1 and PGC-1α. The increase in HSF1 expression in both BAT and WAT, observed with WMW treatment, was crucial for these beneficial effects, as inhibition of HSF1 negated the positive outcomes. Furthermore, WMW treatment led to elevated levels of short-chain fatty acids SCFAs in the intestines, which are associated with increased HSF1 expression.

CONCLUSIONS

WMW represents a potent therapeutic strategy for obesity, promoting metabolic health and beneficial modulation of adipose tissue through an HSF1-dependent pathway.

Effects of Capsicum Oleoresin on the Energy Expenditure and Mitochondrial Content of Brown Adipose Tissue in Mice Fed a High-Fat Diet

Capsicum oleoresin (CO) is a concentrated extract derived from peppers (Capsicum annum L.) containing capsaicin (the active compound responsible for its pungency) and other bioactive components. The present study aimed to determine whether CO affects the energy expenditure and mitochondrial content of brown adipose tissue (BAT) in diet-induced obese mice. Four-week-old C57BL/6J mice were divided into three groups and fed with a normal chow diet, 45% high-fat diet (HF), or HF supplemented with 0.01% CO (HF+CO) for 16 weeks. The results showed that CO supplementation significantly suppressed weight gain and improved serum lipid profiles compared with HF feeding. The energy expenditure was significantly higher in the HF+CO group than in the HF group. Compared with the HF group, the HF+CO group had significantly upregulated the messenger RNA expression levels of uncoupling protein 1 (UCP1) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) in BAT. The mitochondrial DNA content, which was reduced by HF intake, was significantly restored in the HF+CO group. Furthermore, the mitochondrial size and number were restored in the HF+CO group than in in the HF group. The activity of adenosine monophosphate-activated protein kinase (AMPK) in BAT was significantly increased in the HF+CO group than in the HF group. In conclusion, CO potentially inhibits weight gain by increasing energy expenditure in diet-induced obese mice. This beneficial effect is likely associated with the enhancement of mitochondrial content by upregulating key markers, including UCP1, PGC-1α, and AMPK, in BAT.

Nicotinamide Riboside Ameliorates Fructose-Induced Lipid Metabolism Disorders in Mice by Activating Browning of WAT, and May Be Also Related to the Regulation of Gut Microbiota

OBJECTIVES

This study aims to observe the preventive effect of nicotinamide riboside (NR) on fructose-induced lipid metabolism disorders and explore its mechanism.

METHODS

Male C57BL/6J mice were fed a 20% fructose solution and given 400 mg/kg NR daily by gavage for 10 weeks.

RESULTS

The results indicated that NR supplementation significantly reduced the body weight, liver weight, white adipose tissue (WAT) weight, serum, and hepatic lipid levels. NR upregulated the protein expression levels of sirtuin-1 (SIRT1), AMP-activated protein kinase (AMPK), PR domain containing 16 (PRDM16), uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor-gamma coactiva-tor-1-alpha (PGC-1α), nuclear respiratory factor 1-encoding gene (NRF1), mitochondrial transcription factor A (TFAM), cluster of differentiation 137 (CD137), transmembrane protein 26 (TMEM26), and T-box 1 (TBX1). Moreover, NR enhanced the Actinobacteria and Enterorhabdus abundance. Spearman's correlation analysis revealed that significant correlations exist between Firmicutes, Bacteroidetes, and Erysipelotrichaceae with browning-related indicators.

CONCLUSIONS

In conclusion, NR could alleviate lipid metabolic abnormalities induced by fructose through activating SIRT1/AMPK-mediated browning of WAT. The mechanism by which NR improves fructose-induced lipid metabolism disorders may also be associated with the modulation of intestinal flora.

Polyelectrolyte nanofilms on cell surface can induce brown adipogenic differentiation of DFATs

Obesity and its related health issues significantly burden public health systems. Brown adipose tissue holds promise for addressing metabolic disorders and balancing the body's energy, making it a key research focus. Stimulating brown adipogenesis from stem cells could advance regenerative medicine and healthcare. In our previous research, we discovered that poly-l-lysine (PLL) significantly stimulates brown adipogenesis in three-dimensional differentiation of dedifferentiated fat cells (DFATs) within fibrin gels. In this study, we evaluated polyelectrolyte (PE) nanofilms made of PLL and dextran sulfate, applied directly to DFAT surfaces to improve brown adipogenic differentiation through an innovative approach. This approach involved coating the DFAT surfaces with PE nanofilms, forming a multilayer structure that not only provided a supportive matrix but also facilitated the adsorption of essential molecules like T3 and insulin for brown adipogenesis. DFATs coated with three PE layers and encapsulated in fibrin gel showed a significant increase in the adipogenic marker UCP1 gene expression and content. This PLL-based PE nanofilm coating on DFAT surfaces can be a novel and crucial technology for promoting brown adipogenesis in regenerative medicine and healthcare.

Taraxacum Mongolicum Polysaccharides Reverses Mice Obesity via Activation of AKT/mTOR Pathway

BACKGROUND/OBJECTIVES

The global prevalence of obesity and its associated health complications represent significant public health concerns. Plant polysaccharides have been demonstrated to possess a range of beneficial pharmacological effects. This experiment was designed to elucidate the mechanisms of dietary Taraxacum mongolicum polysaccharides involved in the regulation of obesity and fat browning.

METHODS

Male C57BL/6J mice were randomly divided into three groups: a control group, a high-fat diet (HFD) group, and an HFD group supplemented with 0.3% TMPs. The mice were fed their respective diets for 10 weeks, after which their body weight, food consumption, and serum lipid levels were measured. Histological analysis was performed to assess lipid deposition in adipose tissue and liver. Western blot was used to assess the expression of proteins involved in the AKT/mTOR pathway.

RESULTS

The results show that compared with the HFD group, the TMP supplementation group's body-weight gain (12.17 ± 1.77) significantly decreased. TMPs also reduced serum levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol. Histological analysis showed that TMPs reduced lipid deposition in both adipose tissue and the liver.

CONCLUSIONS

In addition, TMPs increased the expression of phosphorylated AKT and the mechanistic target of rapamycin (mTOR), indicating that TMPs exert their beneficial effects on lipid metabolism via the AKT/mTOR pathway.

Dopamine in the regulation of glucose and lipid metabolism: a narrative review

OBJECTIVE

Owing to the global obesity epidemic, understanding the regulatory mechanisms of glucose and lipid metabolism has become increasingly important. The dopaminergic system, including dopamine, dopamine receptors, dopamine transporters, and other components, is involved in numerous physiological and pathological processes. However, the mechanism of action of the dopaminergic system in glucose and lipid metabolism is poorly understood. In this review, we examine the role of the dopaminergic system in glucose and lipid metabolism.

RESULTS

The dopaminergic system regulates glucose and lipid metabolism through several mechanisms. It regulates various activities at the central level, including appetite control and decision-making, which contribute to regulating body weight and energy metabolism. In the pituitary gland, dopamine inhibits prolactin production and promotes insulin secretion through dopamine receptor 2. Furthermore, it can influence various physiological components in the peripheral system, such as pancreatic β cells, glucagon-like peptide-1, adipocytes, hepatocytes, and muscle, by regulating insulin and glucagon secretion, glucose uptake and use, and fatty acid metabolism.

CONCLUSIONS

The role of dopamine in regulating glucose and lipid metabolism has significant implications for the physiology and pathogenesis of disease. The potential therapeutic value of dopamine lies in its effects on metabolic disorders.

Neuronostatin regulates proliferation and differentiation of rat brown primary preadipocytes

Neuronostatin suppresses the differentiation of white preadipocytes. However, the role of neuronostatin in brown adipose tissue remains elusive. Therefore, we investigated the impact of neuronostatin on the proliferation and differentiation of isolated rat brown preadipocytes. We report that neuronostatin and its receptor (GPR107) are synthesized in brown preadipocytes and brown adipose tissue. Furthermore, neuronostatin promotes the replication of brown preadipocytes via the AKT pathway. Notably, neuronostatin suppresses the expression of markers associated with brown adipogenesis (PGC-1α, PPARγ, PRDM16, and UCP1) and reduces cellular mitochondria content. Moreover, neuronostatin impedes the differentiation of preadipocytes by activating the JNK signaling pathway. These effects were not mimicked by somatostatin. Our results suggest that neuronostatin is involved in regulating brown adipogenesis.

Genipin improves obesity through promoting bile secretion and changing bile acids composition in diet-induced obese rats

OBJECTIVES

Bile acids (BAs), as signaling molecules to regulate metabolism, have received considerable attention. Genipin is an iridoid compound extracted from Fructus Gradeniae, which has been shown to relieve adiposity and metabolic syndrome. Here, we investigated the mechanism of genipin counteracting obesity and its relationship with BAs signals in diet-induced obese (DIO) rats.

METHODS

The DIO rats were received intraperitoneal injections of genipin for 10 days. The body weight, visceral fat, lipid metabolism in the liver, thermogenic genes expressions in brown fat, BAs metabolism and signals, and key enzymes for BAs synthesis were determined.

KEY FINDINGS

Genipin inhibited fat synthesis and promoted lipolysis in the liver, and upregulated thermogenic gene expressions in brown adipose tissue of DIO rats. Genipin increased bile flow rate and upregulated the expressions of aquaporin 8 and the transporters of BAs in liver. Furthermore, genipin changed BAs composition by promoting alternative pathways and inhibiting classical pathways for BAs synthesis and upregulated the expressions of bile acid receptors synchronously.

CONCLUSIONS

These results suggest that genipin ameliorate obesity through BAs-mediated signaling pathways.

Role of micro-RNAs associated with adipose-derived extracellular vesicles in metabolic disorders

Micro-RNAs have emerged as important actors in the onset of metabolic disorders including obesity or type 2 diabetes. Particularly, several micro-RNAs are known to be key modulators of lipid metabolism, glucose homeostasis, or feeding behavior. Interestingly, the role of extracellular vesicles containing micro-RNAs, especially adipose-derived extracellular vesicles, are well-documented endocrine signals and disease biomarkers. However, the role of adipose-derived extracellular vesicles on the different tissues is different and highly related to the micro-RNA content. This review provides recent data about the potential involvement of adipose-derived extracellular vesicle-containing micro-RNAs in metabolic diseases.

Walnut supplementation increases levels of UCP1 and CD36 in brown adipose tissue independently of diet type

Dietary interventions that modulate the brown adipose tissue (BAT) thermogenic activity could represent a promising therapy for metabolic disorders. In order to examine if dietary walnuts intake regulates the expression of BAT thermogenic markers levels in healthy and metabolically challenged (fructose fed) animals, rats were initially divided into the control and fructose-fed groups. After nine weeks, these groups were subdivided into the one kept on the original regimens and the other supplemented with walnuts. High-fructose diet resulted in an increased relative BAT mass and no change in UCP1 content, while the walnut supplementation increased the amount of UCP1 in BAT, but did not affect 5-HT, NA, DHPG content and DHPG/NA ratio regardless of the diet. Moreover, the CD36 levels were increased following the walnut consumption, unlike FATP1, GLUT1, GLUT4, and glycogen content which remained unchanged. Additionally, the BAT levels of activated IR and Akt were not affected by walnut consumption, while ERK signaling was decreased. Overall, we found that walnut consumption increased UCP1 and CD36 content in the BAT of both control and metabolically challenged rats, suggesting that FFAs represent the BAT preferred substrate under the previously described circumstances. This further implies that incorporating walnuts into the everyday diet may help to alleviate some symptoms of the metabolic disorder.

Development of Recombinant High-Density Lipoprotein Platform with Innate Adipose Tissue-Targeting Abilities for Regional Fat Reduction

As an escalating public health issue, obesity and overweight conditions are predispositions to various diseases and are exacerbated by concurrent chronic inflammation. Nonetheless, extant antiobesity pharmaceuticals (quercetin, capsaicin, catecholamine, etc.) manifest constrained efficacy alongside systemic toxic effects. Effective therapeutic approaches that selectively target adipose tissue, thereby enhancing local energy expenditure, surmounting the limitations of prevailing antiobesity modalities are highly expected. In this context, we developed a temperature-sensitive hydrogel loaded with recombinant high-density lipoprotein (rHDL) to achieve targeted delivery of resveratrol, an adipose browning activator, to adipose tissue. rHDL exhibits self-regulation on fat cell metabolism and demonstrates natural targeting toward scavenger receptor class B type I (SR-BI), which is highly expressed by fat cells, thereby achieving a synergistic effect for the treatment of obesity. Additionally, the dispersion of rHDL@Res in temperature-sensitive hydrogels, coupled with the regulation of their degradation and drug release rate, facilitated sustainable drug release at local adipose tissues over an extended period. Following 24 days' treatment regimen, obese mice exhibited improved metabolic status, resulting in a reduction of 68.2% of their inguinal white adipose tissue (ingWAT). Specifically, rHDL@Res/gel facilitated the conversion of fatty acids to phospholipids (PA, PC), expediting fat mobilization, mitigating triglyceride accumulation, and therefore facilitating adipose tissue reduction. Furthermore, rHDL@Res/gel demonstrated efficacy in attenuating obesity-induced inflammation and fostering angiogenesis in ingWAT. Collectively, this engineered local fat reduction platform demonstrated heightened effectiveness and safety through simultaneously targeting adipocytes, promoting WAT browning, regulating lipid metabolism, and controlling inflammation, showing promise for adipose-targeted therapy.

Spexin ameliorated obesity-related metabolic disorders through promoting white adipose browning mediated by JAK2-STAT3 pathway

BACKGROUND

Spexin, a 14 amino acid peptide, has been reported to regulate obesity and its associated complications. However, little is known about the underlying molecular mechanism. Therefore, this study aimed to investigate the effects of spexin on obesity and explore the detailed molecular mechanisms in vivo and in vitro.

METHODS

Male C57BL/6J mice were fed a high-fat diet (HFD) for 12 weeks to induce obesity, and mice fed a standard fat diet were used as controls. Then, these mice were treated with SPX or Vehicle by intraperitoneal injection for an additional 12 weeks, respectively. The metabolic profile, fat-browning specific markers and mitochondrial contents were detected. In vitro, 3T3-L1 cells were used to investigate the molecular mechanisms.

RESULTS

After 12 weeks of treatment, SPX significantly decreased body weight, serum lipid levels, and improved insulin sensitivity in HFD-induced obese mice. Moreover, SPX was found to promote oxygen consumption in HFD mice, and it increased mitochondrial content as well as the expression of brown-specific markers in white adipose tissue (WAT) of HFD mice. These results were consistent with the increase in mitochondrial content and the expression of brown-specific markers in 3T3-L1 mature adipocytes. Of note, the spexin-mediated beneficial pro-browning actions were abolished by the JAK2/STAT3 pathway antagonists in mature 3T3-L1 cells.

CONCLUSIONS

These data indicate that spexin ameliorates obesity-induced metabolic disorders by improving WAT browning via activation of the JAK2/STAT3 signaling pathway. Therefore, SPX may serve as a new therapeutic candidate for treating obesity.

Au@16-pH-16/miR-21 mimic nanosystem: An efficient treatment for obesity through browning and thermogenesis induction

Despite the abundance of registered clinical trials worldwide, the availability of effective drugs for obesity treatment is limited due to their associated side effects. Thus, there is growing interest in therapies that stimulate energy expenditure in white adipose tissue. Recently, we demonstrated that the delivery of a miR-21 mimic using JetPEI effectively inhibits weight gain in an obese mouse model by promoting metabolism, browning, and thermogenesis, suggesting the potential of miR-21 mimic as a treatment for obesity. Despite these promising results, the implementation of more advanced delivery system techniques for miR-21 mimic would greatly enhance the advancement of safe and efficient treatment approaches for individuals with obesity in the future. Our objective is to explore whether a new delivery system based on gold nanoparticles and Gemini surfactants (Au@16-ph-16) can replicate the favorable effects of the miR-21 mimic on weight gain, browning, and thermogenesis. We found that dosages as low as 0.2 μg miR-21 mimic /animal significantly inhibited weight gain and induced browning and thermogenic parameters. This was evidenced by the upregulation of specific genes and proteins associated with these processes, as well as the biogenesis of beige adipocytes and mitochondria. Significant increases in miR-21 levels were observed in adipose tissue but not in other tissue types. Our data indicates that Au@16-ph-16 could serve as an effective delivery system for miRNA mimics, suggesting its potential suitability for the development of future clinical treatments against obesity.

Anti-Obesity Effects of GABA in C57BL/6J Mice with High-Fat Diet-Induced Obesity and 3T3-L1 Adipocytes

Obesity is the excessive accumulation of body fat resulting from impairment in energy balance mechanisms. In this study, we aimed to investigate the mechanism whereby GABA (γ-aminobutyric acid) prevents high-fat diet-induced obesity, and whether it induces lipolysis and browning in white adipose tissue (WAT), using high-fat diet (HFD)-fed obese mice and 3T3-L1 adipocytes. We demonstrated that GABA substantially inhibits the body mass gain of mice by suppressing adipogenesis and lipogenesis. Consistent with this result, histological analysis of WAT demonstrated that GABA decreases adipocyte size. Moreover, we show that GABA administration decreases fasting blood glucose and improves serum lipid profiles and hepatic lipogenesis in HFD-fed obese mice. Furthermore, Western blot and immunofluorescence analyses showed that GABA activates protein kinase A (PKA) signaling pathways that increase lipolysis and promote uncoupling protein 1 (UCP1)-mediated WAT browning. Overall, these results suggest that GABA exerts an anti-obesity effect via the regulation of lipid metabolism.

Citrus aurantium L. and synephrine improve brown adipose tissue function in adolescent mice programmed by early postnatal overfeeding

Introduction and aims

Obesity is a multifactorial condition with high health risk, associated with important chronic disorders such as diabetes, dyslipidemia, and cardiovascular dysfunction. Citrus aurantium L. (C. aurantium) is a medicinal plant, and its active component, synephrine, a β-3 adrenergic agonist, can be used for weight loss. We investigated the effects of C. aurantium and synephrine in obese adolescent mice programmed by early postnatal overfeeding.

Methods

Three days after birth, male Swiss mice were divided into a small litter (SL) group (3 pups) and a normal litter (NL) group (9 pups). At 30 days old, SL and NL mice were treated with C. aurantium standardized to 6% synephrine, C. aurantium with 30% synephrine, isolated synephrine, or vehicle for 19 days.

Results

The SL group had a higher body weight than the NL group. Heart rate and blood pressure were not elevated. The SL group had hyperleptinemia and central obesity that were normalized by C. aurantium and synephrine. In brown adipose tissue, the SL group showed a higher lipid droplet sectional area, less nuclei, a reduction in thermogenesis markers related to thermogenesis (UCP-1, PRDM16, PGC-1α and PPARg), and mitochondrial disfunction. C. aurantium and synephrine treatment normalized these parameters.

Conclusion

Our data indicates that the treatment with C. aurantium and synephrine could be a promising alternative for the control of some obesity dysfunction, such as improvement of brown adipose tissue dysfunction and leptinemia.

Modulation of angiogenic switch in reprogramming browning and lipid metabolism in white adipocytes

Thermogenic activation via trans-and de novo browning of white adipocytes is a promising strategy to accelerate lipid metabolism for regulating obesity-related disorders. In this study, we investigated the intricate interplay between angiogenic regulation and browning in white adipocytes using the bioactive compound, resveratrol (Rsv). Rsv has previously been documented for its regulatory influence on the trans and de novo browning of white adipocytes. Our findings revealed that concurrent activation of angiogenesis is prerequisite for inducing browning within the microenvironment of white adipocytes when exposed to browning activators. Additionally, we observed a significant browning effect on white adipocytes when the local adipose tissue environment was prompted to undergo angiogenesis, notably facilitated by a proangiogenic molecule known as Vascular endothelial growth factor (VEGF). Intriguingly, this effect was reversed when angiogenesis was inhibited by treatment with the antiangiogenic agent thalidomide. Furthermore, the study revealed the role of VEGF in paracrine activation of white adipocytes resulting in the induction of browning in both 3T3-L1 cell lines and primary mouse white adipocytes. The cross-talk between angiogenesis and browning was found to be initiated via the transcriptional activation of Estrogen receptor α (ERα) triggering the VEGF/VEGFR2 signaling pathway leading to browning and a reconfiguration of lipid metabolism within adipocytes. In conclusion, this study sheds light on the intricate cross-talk between angiogenesis and browning of white adipocytes. Notably, the findings underscore the reciprocal relationship between these processes, wherein inhibition of one process exerts discernible effects on the other.

Metabolic Syndrome: A Narrative Review from the Oxidative Stress to the Management of Related Diseases

Metabolic syndrome (MS) is a growing disorder affecting thousands of people worldwide, especially in industrialised countries, increasing mortality. Oxidative stress, hyperglycaemia, insulin resistance, inflammation, dysbiosis, abdominal obesity, atherogenic dyslipidaemia and hypertension are important factors linked to MS clusters of different pathologies, such as diabesity, cardiovascular diseases and neurological disorders. All biochemical changes observed in MS, such as dysregulation in the glucose and lipid metabolism, immune response, endothelial cell function and intestinal microbiota, promote pathological bridges between metabolic syndrome, diabesity and cardiovascular and neurodegenerative disorders. This review aims to summarise metabolic syndrome's involvement in diabesity and highlight the link between MS and cardiovascular and neurological diseases. A better understanding of MS could promote a novel strategic approach to reduce MS comorbidities.

Short-duration cold exposure decreases fasting-induced glucose intolerance but has no effect on resting energy expenditure

The aim of the present study was to investigate whether brief cold exposure can reverse fasting-induced glucose intolerance and insulin resistance, and improve resting energy expenditure (REE). Twelve young non-obese women were randomly assigned to undergo the following conditions: 2 days of fasting with two 10-min whole-body cold-water immersions on separate days (FAST-COLD), 2 days of fasting without cold-water immersions (FAST), 2 days of usual diet with two 10-min whole-body cold-water immersions on separate days (COLD), or 2 days of usual diet without cold-water immersions (CON) in a randomised crossover fashion. Changes in REE and substrate utilisation, and glucose tolerance and insulin sensitivity from the oral glucose tolerance test were examined. The results showed that FAST-COLD and FAST trials increased (P < 0.05) REE and decreased (P < 0.05) respiratory quotient, but these variables did not differ significantly between the FAST-COLD and FAST trials. The glucose and insulin area under the curves (AUCs) were higher (P < 0.05) in the FAST-COLD and FAST trials than in the CON and COLD trials, and these AUCs were lower (P < 0.05) in the FAST-COLD than in the FAST trial. Matsuda index was lower in the FAST trial than in the CON trial (P < 0.05), and tended to be greater after the FAST-COLD trial than after the FAST trial (P = 0.060). In conclusion, cold exposure had no effect on REE but decreased fasting-induced glucose intolerance which was accompanied by a maintained insulin sensitivity.

A Newly Synbiotic Combination Alleviates Obesity by Modulating the Gut Microbiota-Fat Axis and Inhibiting the Hepatic TLR4/NF-κB Signaling Pathway

SCOPE

Obesity has been recognized as a worldwide public health crisis, this is accompanied by dysregulation of the intestinal microbiota and upregulation of liver steatosis and adipose inflammation. Synbiotic as a novel alternative therapy for obesity have recently gained much attention.

METHODS

This study innovatively research the anti-obesity properties of a newly synbiotic composed of Lactobacillus acidophilus, Bifidobacterium infantis and konjac glucomannan oligosaccharides.

RESULTS

The synbiotic treatment can reduce body weight, fat mass, blood sugar, liver steatosis and adipose inflammation in obesity mice fed by high-fat diet (HFD). Meanwhile, synbiotic treatment activated brown adipose tissue and improve energy, glucose and lipid metabolism. In addition, synbiotic treatment not solely enhanced the protection of intestinal barrier, but also ameliorated gut microbiota dysbiosis directly by enhancing beneficial microbes and reducing potentially harmful bacteria. Furthermore, the microbiome phenotype and functional prediction showed that synbiotic treatment can improve the gut microbiota functions involving inflammatory state, immune response, metabolism and pathopoiesia.

CONCLUSION

The synbiotic may be an effective candidate treatment strategy for the clinical prevention and treatment of obesity and other associated metabolic diseases such as hyperlipidemia, nonalcoholic fatty liver diseases by alleviating inflammatory response, regulating energy metabolism and maintaining the balance of intestinal microecology.

Thermogenic Modulation of Adipose Depots: A Perspective on Possible Therapeutic Intervention with Early Cardiorenal Complications of Metabolic Impairment

Cardiovascular complications of diabetes and obesity remain a major cause for morbidity and mortality worldwide. Despite significant advances in the pharmacotherapy of metabolic disease, the available approaches do not prevent or slow the progression of complications. Moreover, a majority of patients present with significant vascular involvement at early stages of dysfunction prior to overt metabolic changes. The lack of disease-modifying therapies affects millions of patients globally, causing a massive economic burden due to these complications. Significantly, adipose tissue inflammation was implicated in the pathogenesis of metabolic syndrome, diabetes, and obesity. Specifically, perivascular adipose tissue (PVAT) and perirenal adipose tissue (PRAT) depots influence cardiovascular and renal structure and function. Accumulating evidence implicates localized PVAT/PRAT inflammation as the earliest response to metabolic impairment leading to cardiorenal dysfunction. Increased mitochondrial uncoupling protein 1 (UCP1) expression and function lead to PVAT/PRAT hypoxia and inflammation as well as vascular, cardiac, and renal dysfunction. As UCP1 function remains an undruggable target so far, modulation of the augmented UCP1-mediated PVAT/PRAT thermogenesis constitutes a lucrative target for drug development to mitigate early cardiorenal involvement. This can be achieved either by subtle targeted reduction in UCP-1 expression using innovative proteolysis activating chimeric molecules (PROTACs) or by supplementation with cyclocreatine phosphate, which augments the mitochondrial futile creatine cycling and thus decreases UCP1 activity, enhances the efficiency of oxygen use, and reduces hypoxia. Once developed, these molecules will be first-in-class therapeutic tools to directly interfere with and reverse the earliest pathology underlying cardiac, vascular, and renal dysfunction accompanying the early metabolic deterioration. SIGNIFICANCE STATEMENT: Adipose tissue dysfunction plays a major role in the pathogenesis of metabolic diseases and their complications. Although mitochondrial alterations are common in metabolic impairment, it was only recently shown that the early stages of metabolic challenge involve inflammatory changes in select adipose depots associated with increased uncoupling protein 1 thermogenesis and hypoxia. Manipulating this mode of thermogenesis can help mitigate the early inflammation and the consequent cardiorenal complications.

Metabolic-Dysfunction-Associated Steatotic Liver Disease-Its Pathophysiology, Association with Atherosclerosis and Cardiovascular Disease, and Treatments

Metabolic-dysfunction-associated steatotic liver disease (MASLD) is a chronic liver disease that affects more than a quarter of the global population and whose prevalence is increasing worldwide due to the pandemic of obesity. Obesity, impaired glucose metabolism, high blood pressure and atherogenic dyslipidemia are risk factors for MASLD. Therefore, insulin resistance may be closely associated with the development and progression of MASLD. Hepatic entry of increased fatty acids released from adipose tissue, increase in fatty acid synthesis and reduced fatty acid oxidation in the liver and hepatic overproduction of triglyceride-rich lipoproteins may induce the development of MASLD. Since insulin resistance also induces atherosclerosis, the leading cause for death in MASLD patients is cardiovascular disease. Considering that the development of cardiovascular diseases determines the prognosis of MASLD patients, the therapeutic interventions for MASLD should reduce body weight and improve coronary risk factors, in addition to an improving in liver function. Lifestyle modifications, such as improved diet and increased exercise, and surgical interventions, such as bariatric surgery and intragastric balloons, have shown to improve MASLD by reducing body weight. Sodium glucose cotransporter 2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1RAs) have been shown to improve coronary risk factors and to suppress the occurrence of cardiovascular diseases. Both SGLT2i and GLP-1 have been reported to improve liver enzymes, hepatic steatosis and fibrosis. We recently reported that the selective peroxisome proliferator-activated receptor-alpha (PPARα) modulator pemafibrate improved liver function. PPARα agonists have multiple anti-atherogenic properties. Here, we consider the pathophysiology of MASLD and the mechanisms of action of such drugs and whether such drugs and the combination therapy of such drugs could be the treatments for MASLD.

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.

Brown Fat and Nutrition: Implications for Nutritional Interventions

Brown and beige adipocytes are renowned for their unique ability to generate heat through a mechanism known as thermogenesis. This process can be induced by exposure to cold, hormonal signals, drugs, and dietary factors. The activation of these thermogenic adipocytes holds promise for improving glucose metabolism, reducing fat accumulation, and enhancing insulin sensitivity. However, the translation of preclinical findings into effective clinical therapies poses challenges, warranting further research to identify the molecular mechanisms underlying the differentiation and function of brown and beige adipocytes. Consequently, research has focused on the development of drugs, such as mirabegron, ephedrine, and thyroid hormone, that mimic the effects of cold exposure to activate brown fat activity. Additionally, nutritional interventions have been explored as an alternative approach to minimize potential side effects. Brown fat and beige fat have emerged as promising targets for addressing nutritional imbalances, with the potential to develop strategies for mitigating the impact of metabolic diseases. Understanding the influence of nutritional factors on brown fat activity can facilitate the development of strategies to promote its activation and mitigate metabolic disorders.

Meteorin-like Protein and Asprosin Levels in Children and Adolescents with Obesity and Their Relationship with Insulin Resistance and Metabolic Syndrome

OBJECTIVE

Two newly discovered adipokines, including Meteorin-like protein (Metrnl) and asprosin, have been implicated in glucose and insulin metabolism. This study aimed to investigate the associations of these adipokines with obesity in children and adolescents.

METHODS

This study was performed on 35 normal-weight children and 35 children with obesity. Anthropometric and biochemical parameters were determined. Serum concentrations of Metrnl, asprosin, and insulin were measured using enzyme-linked immunosorbent assay.

RESULTS

Metrnl level was significantly lower in obese children than normal-weight children. Additionally, Metrnl was negatively correlated with body mass index (BMI), insulin, waist-to-hip ratio, and homeostatic model assessment of insulin resistance (HOMA-IR). Our results also revealed that circulating asprosin levels were significantly increased in obese children compared to the control subjects and were positively correlated with BMI, insulin, HOMA-IR, cholesterol, and LDL-C.

CONCLUSION

Obesity is accompanied by significant alterations in Metrnl and asprosin and therefore these adipokines, especially Metrnl, are suggested as new promising therapeutic targets for obesity and its associated metabolic imbalances.

Current Role and Potential of Polymeric Biomaterials in Clinical Obesity Treatment

The rise of obesity and associated fatal diseases has taken a massive toll worldwide. Despite the existing pharmaceuticals and bariatric surgeries, these approaches manifest limited efficacy or accompany various side effects. Therefore, researchers seek to facilitate the prolonged and specific delivery of therapeutics. Or else, to mimic the essential part of "gastric bypass" by physically blocking excessive absorption via less invasive methods. To achieve these goals, polymeric biomaterials have gained tremendous interest recently. They are known for synthesizing hydrogels, microneedle patches, mucoadhesive coatings, polymer conjugates, and so forth. In this Review, we provide insights into the current studies of polymeric biomaterials in the prevention and treatment of obesity, inspiring future improvements in this regime of study.

Effects of caffeoylquinic acid analogs derived from aerial parts of Artemisia iwayomogi on adipogenesis

Artemisia iwayomogi (AI) is a perennial herb found in Korea. Its ground parts are dried and used in food and traditional medicine for treating hepatitis, inflammation, cholelithiasis, and jaundice. In this study, the anti-obesity effects of single compounds isolated from AI extracts on adipose tissue were investigated. Results demonstrated that caffeoylquinic acid analogs strongly inhibited adipocyte differentiation from 3T3-L1 preadipocytes and reduced neutral lipids in differentiated adipocytes. Accordingly, lipid accumulation in adipocytes decreased, and lipid droplets became granulated. Caffeoylquinic acid analogs suppressed the expression of adipocyte differentiation marker genes, namely, Cebpa, Lep, and Fabp4, but it induced the expression of Ucp1, Ppargc1a, and Fgf21, which are browning biomarkers. Therefore, caffeoylquinic acid analogs from AI inhibited preadipocyte differentiation and induced adipose tissue browning, suggesting that these compounds could be promising therapeutic agents for obesity.

Thromboxane A2-TP axis promotes adipose tissue macrophages M1 polarization leading to insulin resistance in obesity

Aberrant arachidonic acid metabolism has been implicated in multiple pathophysiological conditions, and the downstream prostanoids levels are associated with adipocyte dysfunction in obesity. However, the role of thromboxane A₂ (TXA₂) in obesity remains unclear. We observed that TXA₂, through its receptor TP, is a candidate mediator in obesity and metabolic disorders. Obese mice with upregulated TXA₂ biosynthesis (TBXAS1) and TXA₂ receptor (TP) expression in caused insulin resistance and macrophage M1 polarization in white adipose tissue (WAT), which can be prevented by treatment with aspirin. Mechanistically, the activation of TXA₂-TP signaling axis leads to accumulation of protein kinase Cɛ (PKCɛ), thereby enhancing free fat acid (FFA) induced Toll-like receptor4 (TLR4) proinflammatory macrophage activation and the tumor necrosis factor-a (TNF-a) production in adipose tissues. Importantly, TP knockout mice reduced the accumulation of proinflammatory macrophages and adipocyte hypertrophy in WAT. Thus, our findings demonstrate that TXA₂-TP axis plays a crucial role in obesity-induced adipose macrophage dysfunction, and rational targeting TXA₂ pathway may improve obesity and its associated metabolic disorders in future. In this work, we establish previously unknown role of TXA₂-TP axis in WAT. These findings might provide new insight into the molecular pathogenesis of insulin resistance, and indicate rational targeting TXA₂ pathway to improve obesity and its associated metabolic disorders in future.

Green Tea Epigallocatechin Gallate Inhibits Preadipocyte Growth via the microRNA-let-7a/HMGA2 Signaling Pathway

SCOPE

This study investigates the effect of epigallocatechin gallate (EGCG) on white and beige preadipocyte growth and explores the involvement of the miR-let-7a/HMGA2 pathway.

METHODS AND RESULTS

3T3-L1 and D12 cells are treated with EGCG. The effect of EGCG on cell proliferation and viability is evaluated, as well as microRNA (miRNA)-related signaling pathways. EGCG inhibits 3T3-L1 and D12 preadipocyte growth, upregulates miR-let-7a expression, and downregulates high-mobility group AT-hook 2 (HMGA2) mRNA and protein levels in a time- and dose-dependent manner. In addition, overexpression of miR-let-7a significantly inhibits the growth of 3T3-L1 and D12 cells and decreases HMGA2 mRNA and protein levels. MiR-let-7a inhibitor antagonizes the inhibitory effects of EGCG on the number and viability of 3T3-L1 and D12 cells. Furthermore, miR-let-7a inhibitor reverses the EGCG-induced increase in miR-let-7a expression levels and decrease in HMGA2 mRNA and protein levels. HMGA2 overexpression induces an increase in cell number and viability and antagonizes EGCG-suppressed cell growth and HMGA2 expression in 3T3-L1 and D12 preadipocytes.

CONCLUSION

EGCG inhibits the growth of 3T3-L1 and D12 preadipocytes by modulating the miR-let-7a and HMGA2 pathways.

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.

Three-Dimensional Culture of Vascularized Thermogenic Adipose Tissue from Microvascular Fragments

Engineering thermogenic adipose tissue (e.g., beige or brown adipose tissues) has been investigated as a potential therapy for metabolic diseases or for the design of personalized microtissues for health screening and drug testing. Current strategies are often quite complex and fail to accurately fully depict the multicellular and functional properties of thermogenic adipose tissue. Microvascular fragments, small intact microvessels comprised of arteriole, venules, and capillaries isolated from adipose tissue, serve as a single autologous source of cells that enable vascularization and adipose tissue formation. This article describes methods for optimizing culture conditions to enable the generation of three-dimensional, vascularized, and functional thermogenic adipose tissues from microvascular fragments, including protocols for isolating microvascular fragments from adipose tissue and culture conditions. Additionally, best practices are discussed, as are techniques for characterizing the engineered tissues, and sample results from both rodent and human microvascular fragments are provided. This approach has the potential to be utilized for the understanding and development of treatments for obesity and metabolic disease.

Anti-obesity effects of Lactiplantibacillus plantarum SKO-001 in high-fat diet-induced obese mice

PURPOSE

Previous reports showed that some probiotics provide beneficial effects on various diseases including metabolic disorders. This study aimed to investigate the anti-obesity effects of Lactiplantibacillus (L.) plantarum SKO-001 (SKO-001), a probiotic strain newly isolated from Angelica gigas.

METHODS

C57BL/6J mice were fed with high-fat diet (HFD, 60% fat) for four weeks, and then different doses of SKO-001 (n = 10 each group) were orally given for 12 weeks. Following treatment, body weight, fat weight, serum parameters and adipose and liver tissues were analyzed.

RESULTS

SKO-001 (2 × 10¹⁰ CFU/day, per os) reduced body weight gain after 10th week of administration, accompanied by a reduction in body fat mass of mice. In the SKO-001-fed group, increased serum adiponectin, decreased leptin, insulin, total cholesterol, low-density lipoprotein cholesterol, free fatty acids, and triglyceride levels were observed. Hematoxylin and eosin staining of various fat depots showed that increased adipocyte size caused by HFD intake was markedly reduced and correlated with reduced mRNA levels of lipogenesis genes, including sterol regulatory element-binding protein-1c, peroxisome proliferator-activated receptor gamma, and CCAAT/enhancer binding protein alpha, and increased uncoupling protein 1 levels. Similarly, SKO-001 reduced lipid accumulation, decreased the mRNA levels of lipogenic genes, and reduced α-smooth muscle actin and collagen type 1 alpha 1 levels in the liver.

CONCLUSIONS

SKO-001 ameliorates obesity and related metabolic abnormalities in adipose and liver tissues, possibly via the regulation of lipid metabolism. Based on the results of the present study, SKO-001 may be applicable as an anti-obesity therapeutic or functional food.

Adrenoceptors and SCD1 in adipocytes/adipose tissues: The expression and variation in health and obesity

Obesity, considered a metabolic disorder, is one of the most significant health issues that the community has to cope with today. A rising number of studies have been conducted to find out promising genetic targets for obese treatment. The sympathetic nervous system was proven to possess remarkable roles in energy metabolism, including the stimulation of lipolysis as well as thermogenesis, via distinct adrenoceptors appearing on the membrane of adipocyte. A decrease of β-adrenoceptor expression has been observed in obese individuals, which is related to reducing energy expenditure and developing obesity. While that the deficiency of stearoyl-CoA desaturase-1 (SCD1), which is a promising target for treatments of metabolic diseases, decreases oxidation and promotes the synthesis of fatty acids. Here, we emphasized several differences between distinct adrenoceptor subtypes, including their mRNA expression level and function in white adipose tissue and brown adipose tissue. We also highlighted SCD1's roles related to the progression of adipocytes and its changing expression under the obese condition in both rodents and humans, and furthermore, tried to figure out the interaction between adrenoceptors and SCD1 in adipose tissue.

Isolation and Characterization of Brown Adipose Tissue T Cells

Brown adipose tissue (BAT) is a specialized fat depot that can dissipate energy through uncoupled respiration and thermogenesis. Various immune cells such as macrophages, eosinophils, type 2 innate lymphoid cells, and T lymphocytes were recently found to have an unexpected involvement in controlling the thermogenic activity of brown adipose tissue. Here, we describe a protocol for isolation and characterization of T cells from brown adipose tissue.

Modulation of hypothalamic AMPK phosphorylation by olanzapine controls energy balance and body weight

BACKGROUND

Second-generation antipsychotics (SGAs) are a mainstay therapy for schizophrenia. SGA-treated patients present higher risk for weight gain, dyslipidemia and hyperglycemia. Herein, we evaluated the effects of olanzapine (OLA), widely prescribed SGA, in mice focusing on changes in body weight and energy balance. We further explored OLA effects in protein tyrosine phosphatase-1B deficient (PTP1B-KO) mice, a preclinical model of leptin hypersensitivity protected against obesity.

METHODS

Wild-type (WT) and PTP1B-KO mice were fed an OLA-supplemented diet (5 mg/kg/day, 7 months) or treated with OLA via intraperitoneal (i.p.) injection or by oral gavage (10 mg/kg/day, 8 weeks). Readouts of the crosstalk between hypothalamus and brown or subcutaneous white adipose tissue (BAT and iWAT, respectively) were assessed. The effects of intrahypothalamic administration of OLA with adenoviruses expressing constitutive active AMPKα1 in mice were also analyzed.

RESULTS

Both WT and PTP1B-KO mice receiving OLA-supplemented diet presented hyperphagia, but weight gain was enhanced only in WT mice. Unexpectedly, all mice receiving OLA via i.p. lost weight without changes in food intake, but with increased energy expenditure (EE). In these mice, reduced hypothalamic AMPK phosphorylation concurred with elevations in UCP-1 and temperature in BAT. These effects were also found by intrahypothalamic OLA injection and were abolished by constitutive activation of AMPK in the hypothalamus. Additionally, OLA i.p. treatment was associated with enhanced Tyrosine Hydroxylase (TH)-positive innervation and less sympathetic neuron-associated macrophages in iWAT. Both central and i.p. OLA injections increased UCP-1 and TH in iWAT, an effect also prevented by hypothalamic AMPK activation. By contrast, in mice fed an OLA-supplemented diet, BAT thermogenesis was only enhanced in those lacking PTP1B. Our results shed light for the first time that a threshold of OLA levels reaching the hypothalamus is required to activate the hypothalamus BAT/iWAT axis and, therefore, avoid weight gain.

CONCLUSION

Our results have unraveled an unexpected metabolic rewiring controlled by hypothalamic AMPK that avoids weight gain in male mice treated i.p. with OLA by activating BAT thermogenesis and iWAT browning and a potential benefit of PTP1B inhibition against OLA-induced weight gain upon oral treatment.

Omega-3 Polyunsaturated Fatty Acids Protect against High-Fat Diet-Induced Morphological and Functional Impairments of Brown Fat in Transgenic Fat-1 Mice

The role of omega-3 polyunsaturated fatty acids (n-3 PUFAs) in the regulation of energy homeostasis remains poorly understood. In this study, we used a transgenic fat-1 mouse model, which can produce n-3 PUFAs endogenously, to investigate how n-3 PUFAs regulate the morphology and function of brown adipose tissue (BAT). We found that high-fat diet (HFD) induced a remarkable morphological change in BAT, characterized by “whitening” due to large lipid droplet accumulation within BAT cells, associated with obesity in wild-type (WT) mice, whereas the changes in body fat mass and BAT morphology were significantly alleviated in fat-1 mice. The expression of thermogenic markers and lypolytic enzymes was significantly higher in fat-1 mice than that in WT mice fed with HFD. In addition, fat-1 mice had significantly lower levels of inflammatory markers in BAT and lipopolysaccharide (LPS) in plasma compared with WT mice. Furthermore, fat-1 mice were resistant to LPS-induced suppression of UCP1 and PGC-1 expression and lipid deposits in BAT. Our data has demonstrated that high-fat diet-induced obesity is associated with impairments of BAT morphology (whitening) and function, which can be ameliorated by elevated tissue status of n-3 PUFAs, possibly through suppressing the effects of LPS on inflammation and thermogenesis.

Atractylenolide III from Atractylodes macrocephala Koidz promotes the activation of brown and white adipose tissue through SIRT1/PGC-1α signaling pathway

BACKGROUND

Hypothermia is a complex pathophysiological response that can be life-threatening in low-temperature environment because of impaired thermoregulation. However, there is currently no clinically effective drugs that can prevent or treat this disease. Brown adipose tissue (BAT) activation or browning of white adipose tissue (WAT) is a promising therapeutic strategy to prevent or treat hypothermia. Atractylodes macrocephala Koidz extract (AE) and its active compound Atractylenolide III (AIII) has been reported to regulate glycolipid metabolism, which might be relevant to BAT activation. However, the thermogenic effect and mechanism of AE and AIII on adipose tissues have not been explored yet. Therefore, this study firstly investigated the role of AE and AIII on hypothermia by promoting heat production of BAT and WAT.

PURPOSE

To explore the anti-cold effect of AE and AIII in cold exposure model and explore their biological function and mechanism underlying thermogenesis.

METHODS

The effect of thermogenesis and anti-hypothermia of AE and AIII on C57BL/6J mice were evaluated with several experiment in cold environment, such as toxicity test, cold exposure test, metabolism estimation, histology and immunohistochemistry, and protein expression. Additionally, BAT, inguinal WAT (iWAT) and brown adipocytes were utilized to explore the mechanism of AE and AIII on thermogenesis in vivo and in vitro. Finally, SIRT1 agonist and inhibitor in brown adipocytes to verify that AIII activated BAT through SIRT1/PGC-1α pathway.

RESULTS

Both AE and AⅢ could significantly maintain the core body temperature and body surface temperature of mice during cold exposure. Besides, AE and AⅢ could significantly improve the capacity of total antioxidant and glucose, lipid metabolism of mice. In addition, AE and AIII reduced mitochondrial membrane potential and ATP content both in BAT and brown adipocytes, and decreased the size of lipid droplets. Moreover, AE and AⅢ promoted the expression of proteins related to heat production in BAT and iWAT. And AIII might activate BAT via SIRT1/PGC-1α pathway.

CONCLUSION

AE and AⅢ were potential candidate drugs that treated hypothermia by improving the heat production capacity of the mice. Mechanistically, they may activate SIRT1/PGC-1α pathway, thus enhancing the function of BAT, and promoting the browning of iWAT, to act as anti-hypothermia candidate medicine.

Of mice and men: Considerations on adipose tissue physiology in animal models of obesity and human studies

The ever-increasing burden of obesity demands a better pathophysiological understanding, especially regarding adipose tissue pathophysiology. Animal models of obesity are of great importance in investigating potential mechanisms and implications of obesity. Many issues should be considered while interpreting the preclinical results as anatomical and pathophysiological differences exist among species. Importantly, the natural history of obesity development differs considerably. An important example of conflicting results among preclinical models and human physiological studies is that of adipose tissue oxygenation, where rodent models almost unanimously have shown the presence of hypoxia in the adipose tissue of obese animals while human studies have yielded conflicting results to date. Other issues which require further clarification before generalizing preclinical data in humans include adipose tissue browning, endocrine function and fibrosis. The aim of this mini-review is to synopsize similarities and differences between rodent models and humans, which should be taken into consideration in obesity studies.

RNA-Binding Proteins in the Regulation of Adipogenesis and Adipose Function

The obesity epidemic represents a critical public health issue worldwide, as it is a vital risk factor for many diseases, including type 2 diabetes (T2D) and cardiovascular disease. Obesity is a complex disease involving excessive fat accumulation. Proper adipose tissue accumulation and function are highly transcriptional and regulated by many genes. Recent studies have discovered that post-transcriptional regulation, mainly mediated by RNA-binding proteins (RBPs), also plays a crucial role. In the lifetime of RNA, it is bound by various RBPs that determine every step of RNA metabolism, from RNA processing to alternative splicing, nucleus export, rate of translation, and finally decay. In humans, it is predicted that RBPs account for more than 10% of proteins based on the presence of RNA-binding domains. However, only very few RBPs have been studied in adipose tissue. The primary aim of this paper is to provide an overview of RBPs in adipogenesis and adipose function. Specifically, the following best-characterized RBPs will be discussed, including HuR, PSPC1, Sam68, RBM4, Ybx1, Ybx2, IGF2BP2, and KSRP. Characterization of these proteins will increase our understanding of the regulatory mechanisms of RBPs in adipogenesis and provide clues for the etiology and pathology of adipose-tissue-related diseases.

The pathobiology of perivascular adipose tissue (PVAT), the fourth layer of the blood vessel wall

The perivascular adipose tissue (PVAT) is an adipose tissue depot which surrounds most human blood vessels. It is metabolically active and has both a protective and a pathogenic role in vascular biology and pathobiology. It regulates vascular homeostasis and promotes vascular dysfunction. The purpose of this review is to consider the origin, structure, function, and dysfunction of this unique adipose depot consisting of white (WAT), brown (BAT) and beige adipose tissue, to support the concept that PVAT may be considered the fourth layer of the normal arterial wall (tunica adiposa), in which dysfunction creates a microenvironment that regulates, in part, the initiation and growth of the fibro-inflammatory lipid atherosclerotic plaque. Experimental in-vivo and in-vitro studies and human investigations show that the adipocytes, extracellular matrix, nerve fibers and vasa vasorum found in PVAT form a functional adipose tissue unit adjacent to, but not anatomically separated from, the adventitia. PVAT maintains and regulates the structure and function of the normal arterial wall through autocrine and paracrine mechanisms, that include modulation of medial smooth muscle cell contractility and secretion of anti-inflammatory molecules. PVAT shows regional phenotypic heterogeneity which may be important in its effect on the wall of specific sections of the aorta and its muscular branches during perturbations and various injuries including obesity and diabetes. In atherosclerosis, a pan-vascular microenvironment is created that functionally links the intima-medial atherosclerotic plaque to the adventitia and PVAT beneath the plaque, highlighting the local impact of PVAT on atherogenesis. PVAT adipocytes have inflammatory effects which in response to injury show activation and phenotypic changes, some of which are considered to have direct and indirect effects on the intima and media during the initiation, growth, and development of complicated atherosclerotic plaques. Thus, it is important to maintain the integrity of the full vascular microenvironment so that design of experimental and human studies include investigation of PVAT. The era of discarding PVAT tissue in both experimental and human research and clinical vascular studies should end.

Historical and cultural aspects of obesity: From a symbol of wealth and prosperity to the epidemic of the 21st century

World Health Organization defines obesity as abnormal or excess adipose tissue accumulation. Nowadays, this condition is a serious threat to the public health in most countries around the world. Obesity adversely affects physical, mental, and in most cultures, social well-being. However, throughout the ages-from ancient times to the 21st century-this condition has been subject to various interpretations. As a matter of fact, obesity has not always been regarded as a disease. For many decades, excessive body weight has been considered rather a symbol of health. It was a marker of wealth and prosperity, as well as a sign of high social status. The centuries that passed on the development of science and medicine have gradually changed its face, but significant progress in understanding the causes and consequences of obesity has been made in the last 30 years. This paper presents the historical outline of obesity and its treatment from ancient times to the present-from its affirmation to the epidemic in the late 20th and 21st century.

Thermogenic T cells: a cell therapy for obesity?

Obesity is a widespread public health problem with profound medical consequences and its burden is increasing worldwide. Obesity causes significant morbidity and mortality and is associated with conditions including cardiovascular disease and diabetes mellitus. Conventional treatment options are insufficient, or in the case of bariatric surgery, quite invasive. The etiology of obesity is complex, but at its core is often a caloric imbalance with an inability to burn off enough calories to exceed caloric intake, resulting in storage. Interventions such as dieting often lead to decreased resting energy expenditure (REE), with a rebound in weight ("yo-yo effect" or weight cycling). Strategies that increase REE are attractive treatment options. Brown fat tissue engages in nonshivering thermogenesis whereby mitochondrial respiration is uncoupled from ATP production, increasing REE. Medications that replicate brown fat metabolism by mitochondrial uncoupling (e.g., 2,4-dinitrophenol) effectively promote weight loss but are limited by toxicity to a narrow therapeutic range. This review explores the possibility of a new therapeutic approach to engineer autologous T cells into acquiring a thermogenic phenotype like brown fat. Engineered autologous T cells have been used successfully for years in the treatment of cancers (chimeric antigen receptor T cells), and the principle of engineering T cells ex vivo and transferring them back to the patient is established. Engineering T cells to acquire a brown fat-like metabolism could increase REE without the risks of pharmacological mitochondrial uncoupling. These thermogenic T cells may increase basal metabolic rate and are therefore a potentially novel therapeutic strategy for obesity.

Adapalene induces adipose browning through the RARβ-p38 MAPK-ATF2 pathway

Adipose browning has recently been reported to be a novel therapeutic strategy for obesity. Because the retinoic acid receptor (RAR) is a potential target involved in browning, adapalene (AD), an anti-acne agent with RAR agonism, was examined in detail for its effects on adipose browning and the underlying mechanisms in vitro and in vivo. AD upregulated the expression of adipose browning-related markers in a concentration-dependent manner, promoted mitochondrial biogenesis, increased oxygen consumption rates, and lowered lipid droplet sizes in differentiated 3T3/L1 white adipocytes. Among the three retinoic acid receptors (RARα, RARβ, and RARγ), knockdown of the gene encoding RARβ mitigated AD-induced adipose browning. Similarly, LE135 (a selective RARβ antagonist) attenuated AD action, suggesting that AD promotes adipose browning through RARβ. Sequential phosphorylation of p38 mitogen-activated protein kinase (MAPK) and activating transcription factor 2 (ATF2) was critical for AD-induced adipose browning, based on the observations that either SB203580 (a p38 MAPK inhibitor) or ATF2 siRNA reduced the effects of AD. In vivo browning effects of AD were confirmed in C57BL/6J mice and high-fat diet-induced obese (DIO) mice after oral administration of AD either acutely or chronically. This study identifies new actions of AD as an adipose browning agent and demonstrates that RARβ activation followed by increased phosphorylation of p38 MAPK and ATF2 appears to be a key mechanism of AD action.

TRPC5 deletion in the central amygdala antagonizes high-fat diet-induced obesity by increasing sympathetic innervation

Transient receptor potential channel 5 (TRPC5) is predominantly distributed in the brain, especially in the central amygdala (CeA), which is closely associated with pain and addiction. Although mounting evidence indicates that the CeA is related to energy homeostasis, the possible regulatory effect of TRPC5 in the CeA on metabolism remains unclear. Here, we reported that the expression of TRPC5 in the CeA of mice was increased under a high-fat diet (HFD). Specifically, the deleted TRPC5 protein in the CeA of mice using adeno-associated virus resisted HFD-induced weight gain, accompanied by increased food intake. Furthermore, the energy expenditure of CeA-specific TRPC5 deletion mice (TRPC5 KO) was elevated due to augmented white adipose tissue (WAT) browning and brown adipose tissue (BAT) activity. Mechanistically, deficiency of TRPC5 in the CeA boosted nonshivering thermogenesis under cold stimulation by stimulating sympathetic nerves, as the β3-adrenoceptor (Adrb3) antagonist SR59230A blocked the effect of TRPC5 KO on this process. In summary, TRPC5 deletion in the CeA alleviated the metabolic deterioration of mice fed a HFD, and these phenotypic improvements were correlated with the increased sympathetic distribution and activity of adipose tissue.