Brown Adipose Tissue: an Update on Recent Findings

Metformin delays the decline in thermogenic function of brown adipose tissue in a mouse model of Hutchinson-Gilford progeria syndrome

Brown adipose tissue (BAT) is the primary site for non-shivering thermogenesis in the body and plays a crucial role in maintaining core body temperature. However, its function gradually declines with age. To mitigate the age-related decline in BAT thermogenic capacity, we treated progeroid mice with metformin to investigate the potential mechanisms by which metformin can slow the reduction in BAT thermogenic function. We found that progeroid mice, after receiving metformin treatment, showed significant improvement in the senescent state of brown adipocytes through the activation of SIRT1, and effectively reduced mitochondrial oxidative stress. Additionally, metformin slowed the age-related decline in UCP1 expression levels in brown adipose tissue, thereby maintaining the thermogenic capacity of the progeroid mice. Moreover, metformin reduced inflammatory responses around senescent cells, further improving the overall senescent state of the tissue. These findings suggest that metformin can slow down the aging process in brown adipose tissue by targeting SIRT1, thereby enhancing its thermogenic capacity.

Berberine-induced browning and energy metabolism: mechanisms and implications

Obesity has become a global pandemic. The approaches researched to prevent it include decreasing energy intake and/or enhancing energy expenditure. Therefore, research on brown adipose tissue is of great importance. Brown adipose tissue is characterized by its high mitochondrial content. Mitochondrial uncoupling protein 1 (UCP1) releases energy as heat instead of chemical energy. Thermogenesis increases energy expenditure. Berberine, a phytochemical widely used in Asian countries, has positive effects on body weight control. While the precise mechanisms behind this effect remain unclear, the adenosine monophosphate-activated protein kinase (AMPK) pathway is known to play a crucial role. Berberine activates AMPK through phosphorylation, significantly impacting brown adipose tissue by enhancing lipolytic activity and increasing the expression of UCP1, peroxisome proliferator-activated receptor γ-co-activator-1α (PGC1α), and PR domain containing 16 (PRDM16). While investigating the mechanism of action of berberine, both the AMPK pathway is being examined in more detail and alternative pathways are being explored. One such pathway is growth differentiation factor 15 (GDF15), known for its appetite-suppressing effect. Berberine's low stability and bioavailability, which are the main obstacles to its clinical use, have been improved through the development of nanotechnological methods. This review examines the potential mechanisms of berberine on browning and summarizes the methods developed to enhance its effect.

Superoxide dismutase 2 deficiency in mesenchymal stromal cells induces sympathetic denervation and functional impairment of brown adipose tissue

Brown adipose tissue (BAT) is an energy-consuming organ, and its functional dysregulation contributes to the development of metabolic diseases and obesity. BAT function is regulated by the sympathetic nervous system but declines with age, which is partly caused by reduced sympathetic nerve fibers innervating BAT. Thus far, the role of mesenchymal stromal/stem cells in age-related BAT dysfunction remains unknown. Here, we show that BAT dysfunction may be induced by a defect in the antioxidant capacity of stromal cells that localize in and around the nerve fibers (perineurial cells) of BAT. These cells express Meflin, a marker of mesenchymal stromal/stem cells. Specific deletion of the antioxidant enzyme superoxide dismutase 2 in Meflin-lineage cells caused sympathetic denervation and whitening of BAT and its functional impairment, as exemplified by a decline in the fat oxidation rate during the daytime. This phenotype was accompanied by overexpression of the neurorepulsive factor semaphorin 3A in perineurial cells. Notably, Meflin-deficient mice exhibited resistance to doxorubicin-induced BAT dysfunction. These results highlight the role of Meflin+ stromal cells, including perineurial cells, in maintaining BAT function and suggest that targeting BAT stromal cells provides a new avenue for improving BAT function.

Research progress on FSH-FSHR signaling in the pathogenesis of non-reproductive diseases

Follicle-stimulating hormone (FSH), a glycoprotein hormone synthesized and secreted by the anterior pituitary gland, plays a critical role in reproductive development and regulation by binding to FSH receptor (FSHR). Beyond reproductive tissue, FSHRs have been identified in various non-reproductive tissues, indicating broader functions. FSH levels chronically rise during menopause and remain elevated in postmenopausal life. This increase in FSH level has been indicated to be associated with heightened risk of several non-reproductive diseases, including osteoporosis, hypercholesterolemia, type 2 diabetes mellitus, obesity, cardiovascular disease, Alzheimer's disease, and certain cancers. In this review, we will examine the role of FSH-FSHR signaling in the pathogenesis of these non-reproductive diseases and explore therapeutic strategies targeting FSH-FSHR signaling pathways.

The anti-obesity effects of polyphenols: a comprehensive review of molecular mechanisms and signal pathways in regulating adipocytes

Excess weight gain is a growing concern worldwide, fueled by increased consumption of calorie-dense foods and more sedentary lifestyles. Obesity in China is also becoming increasingly problematic, developing into a major public health concern. Obesity not only increases the risk of associated disease but also imposes a burden on health care systems, and it is thus imperative that an effective intervention approach be identified. Recent studies have demonstrated that the polyphenol-rich Mediterranean diet has considerable potential in this regard. Polyphenols can inhibit the production of adipocytes and reduce adverse reactions, such as inflammation, insulin resistance, and gut microflora imbalance. In this review, we examine four polyphenols (curcumin, ellagic acid, ferulic acid, and quercetin) in terms of their potential as interventions targeting obesity. The mechanisms that help promote adipocyte browning, increase thermogenic factors, increase thermogenesis, and regulate adipocyte differentiation are summarized, and key signaling pathways, including PPARγ, C/EBP-, and others, are reviewed.

Two Regions with Different Expression of Lipogenic Enzymes in Rats' Posterior Subcutaneous Fat Depot

Lipid metabolism in various adipose tissue depots can differ vastly. This also applies to lipogenesis, the process of synthesizing fatty acids from acetyl-CoA. This study compared the expression of some lipogenic enzymes: fatty acid synthase (FASN), ATP-citrate lyase (ACLY), and malic enzyme 1 (ME1) in different regions of the posterior subcutaneous adipose tissue in rats. Methods and Results: Posterior subcutaneous adipose tissue collected from twelve-month-old Wistar rats was divided into six parts (A-F). The expression of genes encoding lipogenic enzymes was assessed by measuring their activity and mRNA levels using real-time PCR. In the gluteal region of the fat pad, there were much higher levels of activity and mRNA for these lipogenic enzymes compared to the dorsolumbar region. The mRNA level of FASN increased by more than twentyfold, whereas the level of ME1 and ACLY increased eight- and fivefold respectively. This phenomenon was observed in both old and young animals. Furthermore, the lack of uncoupling protein one (Ucp1) expression suggests that neither the presence of brown adipocytes in the gluteal part nor the transformation of white adipocytes into beige contributed to the observed differences. Conclusion: These results indicate that the gluteal white adipose tissue appears to be a unique and separate subcutaneous fat depot.

Butyrate attenuates cold-induced hypertension via gut microbiota and activation of brown adipose tissue

OBJECTIVE

Chronic exposure to cold temperature is known to elevate blood pressure, leading to a condition known as cold-induced hypertension (CIH). Our previous research suggested correlations between alterations in gut microbiota, decrease in butyrate level, and the onset and progression of CIH. However, the role of butyrate in CIH and the underlying mechanisms need further investigation.

METHODS

We exposed Specific Pathogen Free (SPF) rats to continuous cold temperature (4 ± 1 °C) for 6 weeks to establish a CIH rat model. Rats were divided into different groups by dose and duration, and the rats under cold were administered with butyrate (0.5 or 1 g/kg/day) daily. We assessed hypertension-associated phenotypes, pathological morphological changes, and endocrine-related phenotypes of brown adipose tissue (BAT). The effects of butyrate on gut microbiota and intestinal content metabolism were evaluated by 16s RNA sequencing and non-targeted metabolomics, respectively.

RESULTS

The systolic blood pressure (SBP) of rats exposed to cold after supplemented with butyrate were significantly lower than that of the Cold group. Butyrate may increase the species, abundance, and diversity of gut microbiota in rats. Specifically, butyrate intervention enriched beneficial bacterial genera, such as Lactobacillaceae, and decreased the levels of harmful bacteria genera, such as Actinobacteriota and Erysipeiotrichaceae. Cold exposure significantly increased BAT cells and the number of mitochondria. After butyrate supplementation, the levels of peroxisome proliferator-activated receptor gamma coactivator 1a and fibroblast growth factor 21 in BAT were significantly elevated (P < 0.05), and the volume and number of lipid droplets increased. The levels of ANG II and high-density lipoprotein were elevated in the Cold group but decreased after butyrate supplementation.

CONCLUSION

Butyrate may attenuate blood pressure in CIH by promoting the growth of beneficial bacteria and the secretion of beneficial derived factors produced by BAT, thus alleviating the elevation of blood pressure induced by cold. This study demonstrates the anti-hypertensive effects of butyrate and its potential therapeutic mechanisms, offering novel insights to the prevention and treatment of CIH in populations living or working in cold environments.

Sodium Houttuybonate Promotes the Browning of White Adipose Tissue by Inhibiting Ferroptosis via the AMPK-NRF2-HO1 Pathway

The rising prevalence of obesity has resulted in an increased demand for innovative and effective treatment strategies. Houttuynia cordata Thunb. (H. cordata) has demonstrated promising potential in preventing obesity. However, the mechanism underlying the anti-obesity effects of H. cordata and its bioactive component, sodium houttuybonate (SH), remains unclear. Our study reveals that SH treatment promotes the browning of inguinal white adipose tissue (iWAT) and prevents the obesity induced by a high-fat diet. SH significantly mitigates ferroptosis by upregulating glutathione peroxidase 4 (Gpx4) and decreasing malondialdehyde (MDA) levels, while also enhancing superoxide dismutase (SOD) levels. Furthermore, SH promotes the phosphorylation of AMP-activated protein kinase (AMPK), which subsequently increases the expression of nuclear factor erythroid 2-related factor 2 (NRF2) and heme oxygenase-1 (HO-1) in the iWAT. However, the effects of SH were attenuated by ML385, an Nrf2 inhibitor. Collectively, our findings suggest that SH induces iWAT browning and prevents diet-induced obesity primarily through the AMPK/NRF2/HO-1 pathway by inhibiting ferroptosis.

Adipocyte deletion of the oxygen-sensor PHD2 sustains elevated energy expenditure at thermoneutrality

Enhancing thermogenic brown adipose tissue (BAT) function is a promising therapeutic strategy for metabolic disease. However, predominantly thermoneutral modern human living conditions deactivate BAT. We demonstrate that selective adipocyte deficiency of the oxygen-sensor HIF-prolyl hydroxylase (PHD2) gene overcomes BAT dormancy at thermoneutrality. Adipocyte-PHD2-deficient mice maintain higher energy expenditure having greater BAT thermogenic capacity. In human and murine adipocytes, a PHD inhibitor increases Ucp1 levels. In murine brown adipocytes, antagonising the major PHD2 target, hypoxia-inducible factor-(HIF)-2a abolishes Ucp1 that cannot be rescued by PHD inhibition. Mechanistically, PHD2 deficiency leads to HIF2 stabilisation and binding of HIF2 to the Ucp1 promoter, thus enhancing its expression in brown adipocytes. Serum proteomics analysis of 5457 participants in the deeply phenotyped Age, Gene and Environment Study reveal that serum PHD2 associates with increased risk of metabolic disease. Here we show that adipose-PHD2-inhibition is a therapeutic strategy for metabolic disease and identify serum PHD2 as a disease biomarker.

Energy Expenditure in Humans: Principles, Methods, and Changes Throughout the Life Course

Humans require energy to sustain their daily activities throughout their lives. This narrative review aims to (a) summarize principles and methods for studying human energy expenditure, (b) discuss the main determinants of energy expenditure, and (c) discuss the changes in energy expenditure throughout the human life course. Total daily energy expenditure is mainly composed of resting energy expenditure, physical activity energy expenditure, and the thermic effect of food. Total daily energy expenditure and its components are estimated using variations of the indirect calorimetry method. The relative contributions of organs and tissues determine the energy expenditure under different physiological conditions. Evidence shows that energy expenditure varies along the human life course, at least in part due to changes in body composition, the mass and specific metabolic rates of organs and tissues, and levels of physical activity. This information is crucial to estimate human energy requirements for maintaining health throughout the life course.

Sex-specific associations of environmental exposures with prevalent diabetes and obesity - Results from the KORA Fit study

Promising evidence suggests a link between environmental factors, particularly air pollution, and diabetes and obesity. However, it is still unclear whether men and women are equally susceptible to environmental exposures. Therefore, we aimed to assess sex-specific long-term effects of environmental exposures on metabolic diseases. We analyzed cross-sectional data from 3,034 participants (53.7% female, aged 53-74 years) from the KORA Fit study (2018/19), a German population-based cohort. Environmental exposures, including annual averages of air pollutants [nitrogen oxides (NO2, NOx), ozone, particulate matter of different diameters (PM10, PMcoarse, PM2.5), PM2.5abs, particle number concentration], air temperature and surrounding greenness, were assessed at participants' residences. We evaluated sex-specific associations of environmental exposures with prevalent diabetes, obesity, body-mass-index (BMI) and waist circumference using logistic or linear regression models with an interaction term for sex, adjusted for age, lifestyle factors and education. Further effect modification, in particular by urbanization, was assessed in sex-stratified analyses. Higher annual averages of air pollution, air temperature and greenness at residence were associated with diabetes prevalence in men (NO2: Odds Ratio (OR) per interquartile range increase in exposure: 1.49 [95% confidence interval (CI): 1.13, 1.95], air temperature: OR: 1.48 [95%-CI: 1.15, 1.90]; greenness: OR: 0.78 [95%-CI: 0.59, 1.01]) but not in women. Conversely, higher levels of air pollution, temperature and lack of greenness were associated with lower obesity prevalence and BMI in women. After including an interaction term for urbanization, only higher greenness was associated with higher BMI in rural women, whereas higher air pollution was associated with higher BMI in urban men. To conclude, we observed sex-specific associations of environmental exposures with metabolic diseases. An additional interaction between environmental exposures and urbanization on obesity suggests a higher susceptibility to air pollution among urban men, and higher susceptibility to greenness among rural women, which needs corroboration in future studies.

Rose Petal Extract Ameliorates Obesity in High Fat Diet-Induced Obese Mice

In Asia, Rosa spp. has been used in traditional medicine for the treatment of osteoarthritis, rheumatoid arthritis, and edema. In this study, we investigated the effect of rose petal extract (RPE) on high fat diet (HFD)-induced obesity in mice. C57BL/6J mice were fed with either an AIN-93G diet (normal control), a 60% HFD, or a HFD plus supplementation with RPE at 100 or 200 mg/kg body weight (HFD+R100, HFD+R200) for 14 weeks. The HFD increased the body weight gain, liver and fat weight, lipid profiles (total cholesterol, triglyceride, high density lipoprotein cholesterol, and low density lipoprotein cholesterol), and the serum aspartate aminotransferase and alanine aminotransferase levels of mice, while RPE supplementation significantly decreased these parameters compared with the HFD group. Furthermore, the HFD increased the protein expressions of adipogenesis- and lipogenesis-related factors and decreased the protein expression of lipolysis- and energy metabolism-related factors. Conversely, RPE supplementation significantly decreased the protein expression of adipogenesis- and lipogenesis-related factors and increased the protein expression of lipolysis- and energy metabolism-related factors compared to the HFD group. Taken together, the results provide preliminary evidence for the potential protective effects of the RPE against obesity.

Osmanthus fragrans Flavonoid Extract Inhibits Adipogenesis and Induces Beiging in 3T3-L1 Adipocytes

Osmanthus fragrans has a long history of cultivation in Asia and is widely used in food production for its unique aroma, which has important cultural and economic values. It is rich in flavonoids with diverse pharmacological properties, such as antioxidant, anti-tumor, and anti-lipid activities. However, little is known regarding the effects of Osmanthus fragrans flavonoid extract (OFFE) on adipogenesis and pre-adipocyte transdifferentiation. Herein, this research aimed to investigate the effect of OFFE on the differentiation, adipogenesis, and beiging of 3T3-L1 adipocytes and to elucidate the underlying mechanism. Results showed that OFFE inhibited adipogenesis, reduced intracellular reactive oxygen species levels in mature adipocytes, and promoted mitochondrial biogenesis as well as beiging/browning in 3T3-L1 adipocytes. This effect was accompanied by increased mRNA and protein levels of the brown adipose-specific marker gene Pgc-1a, and the upregulation of the expression of UCP1, Cox7A1, and Cox8B. Moreover, the research observed a dose-dependent reduction in the mRNA expression of adipogenic genes (C/EBPα, GLUT-4, SREBP-1C, and FASN) with increasing concentrations of OFFE. Additionally, OFFE activated the AMPK signaling pathway to inhibit adipogenesis. These findings elucidate that OFFE has an inhibitory effect on adipogenesis and promotes browning in 3T3-L1 adipocytes, which lays the foundation for further investigation of the lipid-lowering mechanism of OFFE in vivo in the future.

Depletion of JunB increases adipocyte thermogenic capacity and ameliorates diet-induced insulin resistance

Adipose tissue is a crucial metabolic organ in the human body. It stores and exerts distinct physiological functions in different body regions. Fat not only serves as a cushion and insulator but also stores energy and conveys endocrine signals within the body. There is a growing recognition that adipose tissue is an organ that is misunderstood and underestimated in contribution to human health and disease progression by regulating its size and functionality. In mammals, the adipose tissue reservoir consists of three functionally distinct types of fat: white adipose tissue (WAT), brown adipose tissue (BAT), and beige or inducible brown adipose tissue (iWAT), which exhibits thermogenic capabilities intermediate between the other two. Fat in different depots exhibits considerable differences in origin, characteristics, and functions. They vary not only in adipocyte lineage, properties, thermogenesis, and endocrine functions but also in their immunological functions. In a recent study published in Nature Metabolism, Zhang et al. investigated the role of JunB in the thermogenic capacity of adipocytes and its significance in obesity and metabolic disorders. The study revealed that JunB expression in BAT coexists with both low and high thermogenic adipocytes, indicating a fundamental feature of heterogeneity and plasticity within BAT. In summary, this article demonstrates that research targeting JunB holds promise for improving diet-induced obesity and insulin resistance, offering new avenues for treating metabolic disorders.

Unveiling the Potential of Natural Compounds: A Comprehensive Review on Adipose Thermogenesis Modulation

The process of adipocyte browning has recently emerged as a novel therapeutic target for combating obesity and obesity-related diseases. Non-shivering thermogenesis is the process of biological heat production in mammals and is primarily mediated via brown adipose tissue (BAT). The recruitment and activation of BAT can be induced through chemical drugs and nutrients, with subsequent beneficial health effects through the utilization of carbohydrates and fats to generate heat to maintain body temperature. However, since potent drugs may show adverse side effects, nutritional or natural substances could be safe and effective as potential adipocyte browning agents. This review aims to provide an extensive overview of the natural food compounds that have been shown to activate brown adipocytes in humans, animals, and in cultured cells. In addition, some key genetic and molecular targets and the mechanisms of action of these natural compounds reported to have therapeutic potential to combat obesity are discussed.

A Narrative Review on Adipose Tissue and Overtraining: Shedding Light on the Interplay among Adipokines, Exercise and Overtraining

Lifestyle factors, particularly physical inactivity, are closely linked to the onset of numerous metabolic diseases. Adipose tissue (AT) has been extensively studied for various metabolic diseases such as obesity, type 2 diabetes, and immune system dysregulation due to its role in energy metabolism and regulation of inflammation. Physical activity is increasingly recognized as a powerful non-pharmacological tool for the treatment of various disorders, as it helps to improve metabolic, immune, and inflammatory functions. However, chronic excessive training has been associated with increased inflammatory markers and oxidative stress, so much so that excessive training overload, combined with inadequate recovery, can lead to the development of overtraining syndrome (OTS). OTS negatively impacts an athlete's performance capabilities and significantly affects both physical health and mental well-being. However, diagnosing OTS remains challenging as the contributing factors, signs/symptoms, and underlying maladaptive mechanisms are individualized, sport-specific, and unclear. Therefore, identifying potential biomarkers that could assist in preventing and/or diagnosing OTS is an important objective. In this review, we focus on the possibility that the endocrine functions of AT may have significant implications in the etiopathogenesis of OTS. During physical exercise, AT responds dynamically, undergoing remodeling of endocrine functions that influence the production of adipokines involved in regulating major energy and inflammatory processes. In this scenario, we will discuss exercise about its effects on AT activity and metabolism and its relevance to the prevention and/or development of OTS. Furthermore, we will highlight adipokines as potential markers for diagnosing OTS.

Global gene expression profiling of perirenal brown adipose tissue whitening in goat kids reveals novel genes linked to adipose remodeling

BACKGROUND

Brown adipose tissue (BAT) is known to be capable of non-shivering thermogenesis under cold stimulation, which is related to the mortality of animals. In the previous study, we observed that goat BAT is mainly located around the kidney at birth, and changes to white adipose tissue (WAT) in the perirenal adipose tissue of goats within one month after birth. However, the regulatory factors underlying this change is remain unclear. In this study, we systematically studied the perirenal adipose tissue of goat kids in histological, cytological, and accompanying molecular level changes from 0 to 28 d after birth.

RESULTS

Our study found a higher mortality rate in winter-born goat kids, with goat birthing data statistics. Then we used thermal imaging revealing high temperature in goat hips at postnatal 0 d and gradually decrease during 28 d. This is consistent with the region of perirenal BAT deposition and highlights its critical role in energy expenditure and body temperature regulation in goat kids. Additionally, we found a series of changes of BAT during the first 28 d after birth, such as whitening, larger lipid droplets, decreased mitochondrial numbers, and down-regulation of key thermogenesis-related genes (UCP1, DIO2, UCP2, CIDEA, PPARGC1a, C/EBPb, and C/EBPa). Then, we used RNA-seq found specific marker genes for goat adipose tissue and identified 12 new marker genes for BAT and 10 new marker genes for WAT of goats. Furthermore, 12 candidate genes were found to potentially regulate goat BAT thermogenesis. The mechanism of the change of this biological phenomenon does not involve a large-scale death of brown adipocytes and subsequent proliferation of white adipocytes. While apoptosis may play a limited role, it is largely not critical in this transition process.

CONCLUSIONS

We concluded that perirenal BAT plays a crucial role in thermoregulation in newborn goat kids, with notable species differences in the expression of adipose tissue marker genes, and we highlighted some potential marker genes for goat BAT and WAT. Additionally, the change from BAT to WAT does not involve a large-scale death of brown adipocytes and subsequent proliferation of white adipocytes.

Potential therapies for obesity management: Exploring novel frontiers

Humans are becoming less active in the current age of technological advancement, which leads to poor health. Many factors, including unregulated diet, lack of exercise, environmental pollution and genetic factors are contributing to an increase in overweight. Obesity is a chronic condition that disturbs the physical health of a person, resulting in various other complications including cardiac, respiratory, and psychosocial issues. According to WHO, the current trend of obesity has shown a sharp increase in recent years. Methods ranging from as simple as regulating the diet to as complex as surgery are available. There are many approved drugs to treat the obesity majority of them works as suppressing the appetite and making the patient satisfy. Some of other agents works by insulinotropic activity. However, these agents need to be taken for longer period of time thus are associated with significant adverse drug reactions. Thus, the motive of this study is to understand obesity and the various methods available to manage it using the recent pharmacological and non-pharmacological approaches.

Spermidine activates adipose tissue thermogenesis through autophagy and fibroblast growth factor 21

Spermidine exerts protective roles in obesity, while the mechanism of spermidine in adipose tissue thermogenesis remains unclear. The present study first investigated the effect of spermidine on cold-stimulation and β3-adrenoceptor agonist-induced thermogenesis in lean and high-fat diet-induced obese mice. Next, the role of spermidine on glucose and lipid metabolism in different types of adipose tissue was determined. Here, we found that spermidine supplementation did not affect cold-stimulated thermogenesis in lean mice, while significantly promoting the activation of adipose tissue thermogenesis under cold stimulation and β3-adrenergic receptor agonist treatment in obese mice. Spermidine treatment markedly enhanced glucose and lipid metabolism in adipose tissues, and these results were associated with the activated autophagy pathway. Moreover, spermidine up-regulated fibroblast growth factor 21 (FGF21) signaling and its downstream pathway, including PI3K/AKT and AMPK pathways in vivo and in vitro. Knockdown of Fgf21 or inhibition of PI3K/AKT and AMPK pathways in brown adipocytes abolished the thermogenesis-promoting effect of spermidine, suggesting that the effect of spermidine on adipose tissue thermogenesis might be regulated by FGF21 signaling via the PI3K/AKT and AMPK pathways. The present study provides new insight into the mechanism of spermidine on obesity and its metabolic complications, thereby laying a theoretical basis for the clinical application of spermidine.

Adipose tissue as a therapeutic target for vascular damage in Alzheimer's disease

Adipose tissue has recently been recognized as an important endocrine organ that plays a crucial role in energy metabolism and in the immune response in many metabolic tissues. With this regard, emerging evidence indicates that an important crosstalk exists between the adipose tissue and the brain. However, the contribution of adipose tissue to the development of age-related diseases, including Alzheimer's disease, remains poorly defined. New studies suggest that the adipose tissue modulates brain function through a range of endogenous biologically active factors known as adipokines, which can cross the blood-brain barrier to reach the target areas in the brain or to regulate the function of the blood-brain barrier. In this review, we discuss the effects of several adipokines on the physiology of the blood-brain barrier, their contribution to the development of Alzheimer's disease and their therapeutic potential. LINKED ARTICLES: This article is part of a themed issue From Alzheimer's Disease to Vascular Dementia: Different Roads Leading to Cognitive Decline. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v181.6/issuetoc.

Pheochromocytoma With Brown Adipose Tissue Stimulation: A Case Report

Brown adipose tissue represents about 1% of the adult body mass and decreases with age. Under variable circumstances, this amount changes, for example, with age or environmental conditions. Pathological states with hypersecretion of catecholamines can induce hypertrophy and hyperplasia in mature brown adipocytes. Consequently, this response can have imaging representation as pseudonodules, a pitfall in imaging interpretation, and may be confused with neoplastic involvement. A case of pheochromocytoma with brown fat stimulation and catecholamine cardiomyopathy is presented.

Auricularia auricula-judae Attenuates the Progression of Metabolic Syndrome in High-Fat Diet-Induced Obese Rats: Enzymatic Pre-Digestion Technology Is Superior to Superfine Grinding Method

Auricularia auricula-judae (AAJ) has been cultivated for food in China for centuries, and is also used as a folk medicine for the regulation of glucose and lipid metabolism. However, there are few studies on the effects of different processing technologies on the therapeutic efficacy of AAJ to date. This study investigated the effectiveness of the AAJ made by using superfine grinding and enzymatic pre-digestion technologies, respectively, in a high-fat diet obese rat model. It was found that oral administrations of two AAJ products significantly alleviated dyslipidemia by decreasing serum lipid levels and restoring liver functions. AAJ products made by using pre-digestion technology have appreciable potential to ameliorate lipid metabolic disorders over other products, possibly due to the higher levels of dietary fiber, crude polysaccharides, and total flavonoids released from AAJ during processing. By analysis of transcriptome sequencing and protein expression, it was clear that starch and sucrose metabolism and glycerolipid metabolism-related factors involved in fatty acid synthesis and metabolism in the liver of obese rats were significantly improved. This study gives further evidence that AAJ significantly ameliorates the progression of glucose and lipid metabolism in obese rats. Moreover, this study demonstrated for the first time that the pre-digestion method may be a better and more efficient processing approach for the improvement of AAJ bioavailability.

Extracellular vesicle therapy for obesity-induced NAFLD: a comprehensive review of current evidence

Non-alcoholic fatty liver disease (NAFLD) as a chronic disease especially in Western countries, is still a tough question in the clinical therapy. With the rising prevalence of various chronic diseases, liver transplantation is expected to be the most common therapy after the next 10 years. However, there is still no approved drug for NAFLD, and targeted therapy for NAFLD is urgent. Exosomes as a kind of extracellular vesicle are cell-derived nanovesicles, which play an essential role in intercellular communication. Due to complex cell-cell interactions in the liver, exosomes as therapeutic drugs or drug delivery vesicles may be involved in physiological or pathological processes in NAFLD. Compared with other nanomaterials, exosomes as a cell-free therapy, are not dependent on cell number limitation, which means can be administered safely in high doses. Apart from this, exosomes with the advantages of being low-toxic, high stability, and low-immunological are chosen for targeted therapy for many diseases. In this review, firstly we introduced the extracellular vesicles, including the biogenesis, composition, isolation and characterization, and fundamental function of extracellular vesicles. And then we discussed the modification of extracellular vesicles, cargo packing, and artificial exosomes. Finally, the extracellular vesicles for the therapies of NAFLD are summarized. Moreover, we highlight therapeutic approaches using exosomes in the clinical treatment of NAFLD, which provide valuable insights into targeting NAFLD in the clinical setting.

Tumor Microenvironment: A Niche for Cancer Stem Cell Immunotherapy

Tumorigenic Cancer Stem Cells (CSCs), often called tumor-initiating cells (TICs), represent a unique subset of cells within the tumor milieu. They stand apart from the bulk of tumor cells due to their exceptional self-renewal, metastatic, and differentiation capabilities. Despite significant progress in classifying CSCs, these cells remain notably resilient to conventional radiotherapy and chemotherapy, contributing to cancer recurrence. In this review, our objective is to explore novel avenues of research that delve into the distinctive characteristics of CSCs within their surrounding tumor microenvironment (TME). We will start with an overview of the defining features of CSCs and then delve into their intricate interactions with cells from the lymphoid lineage, namely T cells, B cells, and natural killer (NK) cells. Furthermore, we will discuss their dynamic interplay with myeloid lineage cells, including macrophages, neutrophils, and myeloid-derived suppressor cells (MDSCs). Moreover, we will illuminate the crosstalk between CSCs and cells of mesenchymal origin, specifically fibroblasts, adipocytes, and endothelial cells. Subsequently, we will underscore the pivotal role of CSCs within the context of the tumor-associated extracellular matrix (ECM). Finally, we will highlight pre-clinical and clinical studies that target CSCs within the intricate landscape of the TME, including CAR-T therapy, oncolytic viruses, and CSC-vaccines, with the ultimate goal of uncovering novel avenues for CSC-based cancer immunotherapy.

Body Composition Evaluation and Clinical Markers of Cardiometabolic Risk in Patients with Phenylketonuria

Cardiovascular diseases are the main cause of mortality worldwide. Patients with phenylketonuria (PKU) may be at increased cardiovascular risk. This review provides an overview of clinical and metabolic cardiovascular risk factors, explores the connections between body composition (including fat mass and ectopic fat) and cardiovascular risk, and examines various methods for evaluating body composition. It particularly focuses on nutritional ultrasound, given its emerging availability and practical utility in clinical settings. Possible causes of increased cardiometabolic risk in PKU are also explored, including an increased intake of carbohydrates, chronic exposure to amino acids, and characteristics of microbiota. It is important to evaluate cardiovascular risk factors and body composition in patients with PKU. We suggest systematic monitoring of body composition to develop nutritional management and hydration strategies to optimize performance within the limits of nutritional therapy.

Revealing the contribution of iron overload-brown adipocytes to iron overload cardiomyopathy: Insights from RNA-seq and exosomes coculture technology

Iron overload has been demonstrated to be associated with insulin resistance, iron overload cardiomyopathy (IOC). Brown adipose tissue (BAT) is emerging as a novel therapeutic target for the treatment of various diseases, not only because of its capacity for dissipating excess energy via non-shivering thermogenesis, but also because of its implication in physiological and pathophysiological processes. However, little attention has been devoted to the precise alterations and impacts of iron overload-BAT. We conducted RNA-Seq analysis on BAT samples obtained from mice subjected to a high iron diet (HID) or a normal chow diet (CON), respectively. The RNA-seq transcriptomic analysis revealed that 1,289 differentially expressed RNAs (DEGs) were identified, with a higher number of the downregulated genes (910 genes) compared to the upregulated genes (379 genes). The results of Gene Ontology (GO) and The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that the downregulated DEGs were primarily involved in hypertrophic cardiomyopathy, dilated cardiomyopathy, which were defined as IOC under the iron overload condition. The association between iron overload-BAT with cardiomyopathy was further investigated using exosome coculture technology. Our results demonstrated that the exosomes derived from ferric citrate treated-mature HIB 1B brown adipocytes, could be internalized by HL-1 cardiomyocytes, and contributed to the dysfunction in these cells. The present study has revealed the alterations and impacts of iron overload-BAT, particularly on the onset of IOC via not only RNA-seq but also exosomes coculture technology. The outputs might shed light on the novel therapeutic strategies for the treatment of IOC.

Off the Beaten Path in Oncology: Active Brown Adipose Tissue by Virtue of Molecular Imaging

Brown Adipose Tissue (BAT) is considered beneficial in diabetes and obesity, but it can also have negative effects such as its implication in tumours' pathogenesis and the development of Cancer-induced Cachexia. Since 18F-FDG PET/CT is a common molecular imaging modality used in cancer assessment, we aim to study the 18F-FDG BAT biodistribution in oncological patients and look for possible correlations between BAT activity and different malignancies as well as the patient's weight status. After analysing the total number of oncological 18F-FDG PET/CT scans between 2017 and 2021, we selected patients with active BAT. Based on their BMI, the selected patients were divided into nonobese (NO) vs. overweight and obese (OOB). OOB SUVmaxlean body mass(LBM) had the highest mean values in supraclavicular, latero-cervical, and paravertebral vs. mediastinal and latero-thoracic localisations in NO. BMI was positively correlated with latero-cervical and supraclavicular SUVmax(LBM) but negatively correlated with latero-thoracic and abdominal SUVmax(LBM). Considering the age of the patients, SUVmax(LBM) decreases in the latero-cervical, paravertebral, and abdominal regions. In addition, the males presented lower SUVmax(LBM) values. SUVmax(LBM) was not affected by the treatment strategy or the oncological diagnosis. To conclude, it is mandatory to take into consideration the BAT particularities and effects on weight status in order to optimise the clinical management of oncological patients.

Linking Adiposity to Interstitial Lung Disease: The Role of the Dysfunctional Adipocyte and Inflammation

Adipose tissue has functions beyond its principal functions in energy storage, including endocrine and immune functions. When faced with a surplus of energy, the functions of adipose tissue expand by mechanisms that can be both adaptive and detrimental. These detrimental adipose tissue functions can alter normal hormonal signaling and promote local and systemic inflammation with wide-ranging consequences. Although the mechanisms by which adipose tissue triggers metabolic dysfunction and local inflammation have been well described, little is known about the relationship between adiposity and the pathogenesis of chronic lung conditions, such as interstitial lung disease (ILD). In this review, we detail the conditions and mechanisms by which adipose tissue becomes dysfunctional and relate this dysfunction to inflammatory changes observed in various forms of ILD. Finally, we review the existing basic and clinical science literature linking adiposity to ILD, highlighting the need for additional research on the mechanisms of adipocyte-mediated inflammation in ILD and its clinical implications.

Peppers and their constituents against obesity

Phytotherapy can be an efficient tool for prevention and treatment of disorders including obesity. The purpose of this narrative review is to summarize the available knowledge concerning the positive effects of peppers (Capsicum spp.) and their alkaloid capsaicin on human health, in particular on fat and obesity. Search for literature was performed in Medline/Pubmed, Web of Science and SCOPUS databases between the year 2000 and 2023. Words used to search were pepper, Capsicum, capsaicin, review, obesity, fat, weight loss and mechanisms. The available data demonstrate that both pepper extract and capsaicin can positively influence human health and treat several disorders. Moreover, they can reduce fat storage affecting brain centres responsible for the sensation of hunger, nutrient uptake by gastrointestinal tract, state of adipocytes, increase in carbohydrate and fat oxidation, metabolism and thermogenesis and other mechanisms. Therefore, despite some possible limitations, these substances could be useful for treatment of obesity.

Opportunities and challenges: interleukin-22 comprehensively regulates polycystic ovary syndrome from metabolic and immune aspects

Polycystic ovary syndrome (PCOS) is known as a prevalent but complicated gynecologic disease throughout the reproductive period. Typically, it is characterized by phenotypic manifestations of hyperandrogenism, polycystic ovary morphology, and persistent anovulation. For now, the therapeutic modality of PCOS is still a formidable challenge. Metabolic aberrations and immune challenge of chronic low-grade inflammatory state are significant in PCOS individuals. Recently, interleukin-22 (IL-22) has been shown to be therapeutically effective in immunological dysfunction and metabolic diseases, which suggests a role in the treatment of PCOS. In this review, we outline the potential mechanisms and limitations of IL-22 therapy in PCOS-related metabolic disorders including its regulation of insulin resistance, gut barrier, systemic inflammation, and hepatic steatosis to generate insights into developing novel strategies in clinical practice.

Black Wheat Extracts (Arriheuk) Regulate Adipogenesis and Lipolysis via Adenosine Monophosphate (AMP) Activated Protein Kinase (AMPK)/Sirtuin 1 (SIRT1) Signaling Pathways

Polyphenols and other compounds with antioxidant properties are found in plants and are one of the main antioxidants proven to reduce body weight and the risk of insulin resistance. Still, the mechanism behind the protective effects against obesity remains unclear. Thus, the study aims to assess the impact of flavonoid-rich arriheuk extract, a purple wheat extract, on mitochondrial function using 3T3-L1 adipocytes and investigate the molecular mechanism behind its protective effects against adipogenesis and lipolysis. The study findings strongly indicate that arriheuk significantly suppressed triglyceride levels and inhibited the expression of transcription factors like C/EBPα and PPARγ in 3T3-L1 adipocytes. Furthermore, treatment with arriheuk suppressed the expression of SREBP1c and FAS proteins linked to lipogenesis. In addition, treatment with arriheuk extract decreased the mRNA levels of adipogenic transcription factors, increased glycerol release, and inhibited adipocyte differentiation. Interestingly, the arriheuk-mediated PGC-1α expression triggered mitochondrial biogenesis by promoting the AMPK phosphorylation and SIRT1 expression in adipocytes. Also, arriheuk suppressed adipogenesis and elicited browning through the AMPK- and SIRT1-associated pathways. Collectively, these findings strongly suggest that arriheuk extract regulates browning in 3T3-L1 white adipocytes by triggering the AMPK/SIRT1 pathway, indicating the prospective applications of arriheuk as a functional food to control obesity.

18F-FDG PET/CT technology for the assessment of brown adipose tissue: an updated review

INTRODUCTION

This review provides an update of 18 F-fluorodeoxyglucose ([18F] FDG) for Brown adipose tissue (BAT) activity quantification, whose role is not completely understood.

AREAS COVERED

We conducted an unstructured search of the literature for any studies employing the [18F] FDG PET in BAT assessment. We explored BAT quantification both in healthy individuals and in different pathologies, after cold exposure and as a metabolic biomarker. The assessment of possible BAT modulators by using [18F] FDG PET is shown. Further PET tracers and novel developments for BAT assessments are also described.

EXPERT OPINION

Further PET tracers and imaging modalities are under investigation, but the [18F] FDG PET is currently the method of choice for the evaluation of BAT and further multicentric trials are needed for a better understanding of the BAT physiopathology, also after cold stimuli. The modulation of BAT activity, assessed by [18F] FDG PET imaging, seems a promising tool for the management of conditions such as obesity and type 2 diabetes. Moreover, an interesting possible correlation of BAT activation with prognostic [18F] FDG PET indices in cancer patients should be assessed with further multicentric trials.

Proline hydroxylase 2 (PHD2) promotes brown adipose thermogenesis by enhancing the hydroxylation of UCP1

OBJECTIVE

Brown adipose tissue (BAT) plays a crucial role in regulating non-shivering thermogenesis under cold exposure. Proline hydroxylases (PHDs) were found to be involved in adipocyte differentiation and lipid deposition. However, the effects of PHDs on regulatory mechanisms of BAT thermogenesis are not fully understood.

METHODS

We detected the expression of PHDs in different adipose tissues by using immunoblotting and real-time PCR. Further, immunoblotting, real-time PCR, and immunostaining were performed to determine the correlation between proline hydroxylase 2 (PHD2) and UCP1 expression. Inhibitor of PHDs and PHD2-sgRNA viruses were used to construct the PHD2-deficiency model in vivo and in vitro to investigate the impacts of PHD2 on BAT thermogenesis. Afterward, the interaction between UCP1 and PHD2 and the hydroxylation modification level of UCP1 were verified by Co-IP assays and immunoblotting. Finally, the effect of specific proline hydroxylation on the expression/activity of UCP1 was further confirmed by site-directed mutation of UCP1 and mass spectrometry analysis.

RESULTS

PHD2, but not PHD1 and PHD3, was highly enriched in BAT, colocalized, and positively correlated with UCP1. Inhibition or knockdown of PHD2 significantly suppressed BAT thermogenesis under cold exposure and aggravated obesity of mice fed HFD. Mechanistically, mitochondrial PHD2 bound to UCP1 and regulated the hydroxylation level of UCP1, which was enhanced by thermogenic activation and attenuated by PHD2 knockdown. Furthermore, PHD2-dependent hydroxylation of UCP1 promoted the expression and stability of UCP1 protein. Mutation of the specific prolines (Pro-33, 133, and 232) in UCP1 significantly mitigated the PHD2-elevated UCP1 hydroxylation level and reversed the PHD2-increased UCP1 stability.

CONCLUSIONS

This study suggested an important role for PHD2 in BAT thermogenesis regulation by enhancing the hydroxylation of UCP1.

Transcriptomic Analysis Reveals Fibroblast Growth Factor 11 (FGF11) Role in Brown Adipocytes in Thermogenic Regulation of Goats

Brown adipose tissue (BAT) is the main site of adaptive thermogenesis, generates heat to maintain body temperature upon cold exposure, and protects against obesity by promoting energy expenditure. RNA-seq analysis revealed that FGF11 is enriched in BAT. However, the functions and regulatory mechanisms of FGF11 in BAT thermogenesis are still limited. In this study, we found that FGF11 was significantly enriched in goat BAT compared with white adipose tissue (WAT). Gain- and loss-of-function experiments revealed that FGF11 promoted differentiation and thermogenesis in brown adipocytes. However, FGF11 had no effect on white adipocyte differentiation. Furthermore, FGF11 promoted the expression of the UCP1 protein and an EBF2 element was responsible for UCP1 promoter activity. Additionally, FGF11 induced UCP1 gene expression through promoting EBF2 binding to the UCP1 promoter. These results revealed that FGF11 promotes differentiation and thermogenesis in brown adipocytes but not in white adipocytes of goats. These findings provide evidence for FGF11 and transcription factor regulatory functions in controlling brown adipose thermogenesis of goats.

Combination of Panax ginseng and Diospyros kaki Leaf Inhibits White Adipocyte Differentiation and Browning Process through AMP-Activated Protein Kinase (AMPK) Activation In Vitro and In Vivo

Activating brown adipose tissue (BAT) and stimulating white adipose tissue (WAT) browning is a prospective obesity treatment method. Dietary components derived from plants are the most effective approach to activate BAT and promote WAT browning in rodents. This study investigated the synergistic effects of Panax ginseng (PG) and Diospyros kaki leaf (DKL) extract on adipocyte differentiation and browning, as well as the molecular mechanism underlying their beneficial effects. The administration of PG and DKL to HFD-induced obese mice significantly decreased body weight and epididymal and abdominal adipose tissue mass. In in vitro, PG inhibited the adipogenesis of 3T3-L1 adipocytes by regulating the expression of key adipogenic regulators, such as peroxisome proliferator-activated receptor (PPAR)γ and CCAAT/enhancer-binding protein (C/EBP)-α. In contrast, DKL negligibly influenced the adipogenesis of 3T3-L1 adipocytes but greatly increased the protein expression of UCP-1, PGC-1α, and PPARα in BAT and/or WAT. Moreover, PG and DKL inhibited adipogenesis synergistically and activated white adipocyte browning via AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) pathways. These results suggest that a combination of PG and DKL regulates adipogenesis in white adipocytes and browning in brown adipocytes by activating AMPK/SIRT1 axis. The potential use of PG and DKL may represent an important strategy in obesity management that will be safer and more effective.

CCE and EODF as two distinct non-shivering thermogenesis models inducing weight loss

Increasing energy expenditure and reducing energy intake are considered two classical methods to induce weight loss. Weight loss through physical methods instead of drugs has been a popular research topic nowadays, but how these methods function in adipose and cause weight loss in body remains unclear. In this study, we set up chronic cold exposure (CCE) and every-other-day fasting (EODF) as two distinct models in long-term treatment to induce weight loss, recording their own characteristics in changes of body temperature and metabolism. We investigated the different types of non-shivering thermogenesis induced by CCE and EODF in white and brown adipose tissue through sympathetic nervous system (SNS), creatine-driven pathway, and fibroblast growth factor 21 (FGF21)-adiponectin axis. CCE and EODF could reduce body weight, lipid composition, increase insulin sensitivity, promote the browning of white fat, and increase the expression of endogenous FGF21 in adipose tissue. CCE stimulated the SNS and increased the thermogenic function of brown fat, and EODF increased the activity of protein kinase in white fat. In this study, we further explained the thermogenic mechanism function in adipose and metabolic benefits of the stable phenotype through physical treatments used for weight loss, providing more details for the literature on weight loss models. The influence on metabolism, non-shivering thermogenesis, endogenous FGF21, and ADPN changes in the long-term treatment of distinct methods (increasing energy expenditure and decreasing energy intake) to induce weight loss.

Brown Adipose Tissue: A New Potential Target for Glucagon-like Peptide 1 Receptor Agonists in the Treatment of Obesity

Adipose tissue can be divided into white adipose tissue (WAT), brown adipose tissue (BAT), and beige adipose tissue, according to the differences in morphology. WAT acts as a buffer for increased energy intake and decreased energy expenditure during the development of obesity, resulting in visceral and ectopic WAT accumulation. These WAT depots are strongly associated with chronic systemic inflammation, insulin resistance, and cardiometabolic risk related to obesity. They represent a primary weight loss target in anti-obesity management. Second-generation anti-obesity medications glucagon-like peptide-1 receptor agonists (GLP-1RAs) cause weight loss and improve body composition by reducing visceral and ectopic fat depots of WAT, resulting in improved cardiometabolic health. Recently, the understanding of the physiological significance of BAT beyond its primary function in generating heat through non-shivering thermogenesis has been expanded. This has raised scientific and pharmaceutical interest in the manipulation of BAT to further enhance weight reduction and body weight maintenance. This narrative review focuses on the potential impact of GLP-1 receptor agonism on BAT, particularly in human clinical studies. It provides an overview of the role of BAT in weight management and highlights the need for further research to elucidate the mechanisms by which GLP-1RAs affect energy metabolism and weight loss. Despite encouraging preclinical data, limited clinical evidence supports the notion that GLP-1RAs contribute to BAT activation.

Glucagon and energy expenditure; Revisiting amino acid metabolism and implications for weight loss therapy

Glucagon receptor (GCGR)-targeted multi-agonists are being developed for the treatment of obesity and metabolic disease. GCGR activity is utilised for its favourable weight loss and metabolic properties, including increased energy expenditure (EE) and hepatic lipid metabolism. GLP1R and GIPR activities are increasingly present in a multi-agonist strategy. Due to the compound effect of increased satiety, reduced food intake and increased energy expenditure, the striking weight loss effects of these multi-agonists has been demonstrated in pre-clinical models of obesity. The precise contribution and mechanism of GCGR activity to enhanced energy expenditure and weight loss in both rodents and humans is not fully understood. In this review, our understanding of glucagon-mediated EE is explored, and an amino acid-centric paradigm contributing to this phenomenon is presented. The current progress of GCGR-targeted multi-agonists in development is also highlighted with a focus on the implications of glucagon-stimulated hypoaminoacidemia.

The Role of Oxidative Stress Enhanced by Adiposity in Cardiometabolic Diseases

Cardiometabolic diseases (CMDs), including cardiovascular disease (CVD), metabolic syndrome (MetS), and type 2 diabetes (T2D), are associated with increased morbidity and mortality. The growing prevalence of CVD is mostly attributed to the aging population and common occurrence of risk factors, such as high systolic blood pressure, elevated plasma glucose, and increased body mass index, which led to a global epidemic of obesity, MetS, and T2D. Oxidant–antioxidant balance disorders largely contribute to the pathogenesis and outcomes of CMDs, such as systemic essential hypertension, coronary artery disease, stroke, and MetS. Enhanced and disturbed generation of reactive oxygen species in excess adipose tissue during obesity may lead to increased oxidative stress. Understanding the interplay between adiposity, oxidative stress, and cardiometabolic risks can have translational impacts, leading to the identification of novel effective strategies for reducing the CMDs burden. The present review article is based on extant results from basic and clinical studies and specifically addresses the various aspects associated with oxidant–antioxidant balance disorders in the course of CMDs in subjects with excess adipose tissue accumulation. We aim at giving a comprehensive overview of existing knowledge, knowledge gaps, and future perspectives for further basic and clinical research. We provide insights into both the mechanisms and clinical implications of effects related to the interplay between adiposity and oxidative stress for treating and preventing CMDs. Future basic research and clinical trials are needed to further examine the mechanisms of adiposity-enhanced oxidative stress in CMDs and the efficacy of antioxidant therapies for reducing risk and improving outcome of patients with CMDs.

What is the role of brown adipose tissue in metabolic health: lessons learned and future perspectives in the long COVID?

Metabolic physiology plays a key role in maintaining our health and resilience. Metabolic disorders can lead to serious illnesses, including obesity. The pathogenesis of the new long COVID syndrome in individuals with long-term recovery after SARS-Co-2 infection is still incomplete. Thus there is growing attention in the study of adipose tissue activities, especially brown adipose tissue (BAT) and associated resilience which plays a crucial role in different types of obesity as potential targets for pharmacologic and nutritional interventions in the context of obesity and long COVID. The number of studies examining mechanisms underlying BAT has grown rapidly in the last 10 years despite of role of BAT in individuals with COVID-19 and long COVID is modest. Therefore, this review aims to sum up data examining BAT activities, its resilience in health, obesity, and the possible link to long COVID. The search was conducted on studies published in English mostly between 2004 and 2022 in adult humans and animal models. Database searches were conducted using PubMed, Scopus, and Google Scholar for key terms including adipose tissue, BAT, adipokines, obesity, VPF/VEGF, and pathogenesis. From the initial search through the database were identified relevant articles that met inclusion and exclusion criteria and our data regarding adipose tissues were presented in this review. It will discuss adiposity tissue activities. Current literature suggests that there are BAT integral effects to whitening and browning fat phenomena which reflect the homeostatic metabolic adaptive ability for environmental demand or survival/adaptive mechanisms. We also review neural and vascular impacts in BAT that play a role in resilience and obesity. Finally, we discuss the role of BAT in the context of long COVID in basic research and clinical research.

What is the role of brown adipose tissue in metabolic health: lessons learned and future perspectives in the long COVID?

Metabolic physiology plays a key role in maintaining our health and resilience. Metabolic disorders can lead to serious illnesses, including obesity. The pathogenesis of the new long COVID syndrome in individuals with long-term recovery after SARS-Co-2 infection is still incomplete. Thus there is growing attention in the study of adipose tissue activities, especially brown adipose tissue (BAT) and associated resilience which plays a crucial role in different types of obesity as potential targets for pharmacologic and nutritional interventions in the context of obesity and long COVID. The number of studies examining mechanisms underlying BAT has grown rapidly in the last 10 years despite of role of BAT in individuals with COVID-19 and long COVID is modest. Therefore, this review aims to sum up data examining BAT activities, its resilience in health, obesity, and the possible link to long COVID. The search was conducted on studies published in English mostly between 2004 and 2022 in adult humans and animal models. Database searches were conducted using PubMed, Scopus, and Google Scholar for key terms including adipose tissue, BAT, adipokinins, obesity, VPF/VEGF, and pathogenesis. From the initial search through the database were identified relevant articles that met inclusion and exclusion criteria and our data regarding adipose tissues were presented in this review. It will discuss adiposity tissue activities. Current literature suggests that there are BAT integral effects to whitening and browning fat phenomenons which reflect the homeostatic metabolic adaptive ability for environmental demand or survival/adaptive mechanisms. We also review neural and vascular impacts in BAT that play a role in resilience and obesity. Finally, we discuss the role of BAT in the context of long COVID in basic research and clinical research.

Unveiling the Role of the Proton Gateway, Uncoupling Proteins (UCPs), in Cancer Cachexia

Uncoupling proteins (UCPs) are identified as carriers of proton ions between the mitochondrial inner membrane and the mitochondrial matrix. ATP is mainly generated through oxidative phosphorylation in mitochondria. The proton gradient is generated across the inner mitochondrial membrane and the mitochondrial matrix, which facilitates a smooth transfer of electrons across ETC complexes. Until now, it was thought that the role of UCPs was to break the electron transport chain and thereby inhibit the synthesis of ATP. UCPs allow protons to pass from the inner mitochondrial membrane to the mitochondrial matrix and decrease the proton gradient across the membrane, which results in decreased ATP synthesis and increased production of heat by mitochondria. In recent years, the role of UCPs in other physiological processes has been deciphered. In this review, we first highlighted the different types of UCPs and their precise location across the body. Second, we summarized the role of UCPs in different diseases, mainly metabolic disorders such as obesity and diabetes, cardiovascular complications, cancer, wasting syndrome, neurodegenerative diseases, and kidney complications. Based on our findings, we conclude that UCPs play a major role in maintaining energy homeostasis, mitochondrial functions, ROS production, and apoptosis. Finally, our findings reveal that mitochondrial uncoupling by UCPs may treat many diseases, and extensive clinical studies are required to meet the unmet need of certain diseases.

Fatty Acids as Potent Modulators of Autophagy Activity in White Adipose Tissue

A high-fat diet is one of the causative factors of obesity. The dietary profile of fatty acids is also an important variable in developing obesity, as saturated fatty acids are more obesogenic than monounsaturated and polyunsaturated fatty acids. Overweight and obesity are inseparably connected with the excess of adipose tissue in the body, characterized by hypertrophy and hyperplasia of fat cells, which increases the risk of developing metabolic syndrome. Changes observed within hypertrophic adipocytes result in elevated oxidative stress, unfolded protein accumulation, and increased endoplasmic reticulum (ER) stress. One of the processes involved in preservation of cellular homeostasis is autophagy, which is defined as an intracellular lysosome-dependent degradation system that serves to recycle available macromolecules and eliminate damaged organelles. In obesity, activation of autophagy is increased and the process appears to be regulated by different types of dietary fatty acids. This review describes the role of autophagy in adipose tissue and summarizes the current understanding of the effects of saturated and unsaturated fatty acids in autophagy modulation in adipocytes.

5-Heptadecylresorcinol Regulates the Metabolism of Thermogenic Fat and Improves the Thermogenic Capacity of Aging Mice via a Sirtuin 3-Adenosine Monophosphate-Activated Protein Kinase Pathway

5-Heptadecylresorcinol (AR-C17), a well-known biomarker for whole grain rye consumption, is a primary homolog of alkylresorcinols. In this study, the effects of AR-C17 on the thermogenesis of brown adipocytes and 3T3-L1 adipocytes were investigated. The results showed that AR-C17 increased sirtuin 3 (Sirt3) expression, and the expressions of specific thermogenic genes in adipocytes were increased. Furthermore, AR-C17 increased the mitochondrial functions during the thermogenic activation of adipocytes. In in vivo study, AR-C17 increased the cold tolerance and thermogenic capacity of adipose tissues in aging mice. In addition, Sirt3 activity was required for AR-C17-induced thermogenesis. Meanwhile, AR-C17 increased adenosine monophosphate-activated protein kinase (AMPK) phosphorylation, and AMPK was involved in the regulation of AR-C17 on thermogenic adipocytes. Mechanically, AR-C17 upregulated a Sirt3-AMPK positive-feedback loop in adipocytes and further increased the expression of uncoupling protein 1 to activate thermogenesis. This study indicated that AR-C17 could be a promising thermogenic activator of adipocytes to alleviate obesity and aging-associated metabolic diseases.

Cinnamon: an aromatic condiment applicable to chronic kidney disease

Cinnamon, a member of the Lauraceae family, has been widely used as a spice and traditional herbal medicine for centuries and has shown beneficial effects in cardiovascular disease, obesity, and diabetes. However, its effectiveness as a therapeutic intervention for chronic kidney disease (CKD) remains unproven. The bioactive compounds within cinnamon, such as cinnamaldehyde, cinnamic acid, and cinnamate, can mitigate oxidative stress, inflammation, hyperglycemia, gut dysbiosis, and dyslipidemia, which are common complications in patients with CKD. In this narrative review, we assess the mechanisms by which cinnamon may alleviate complications observed in CKD and the possible role of this spice as an additional nutritional strategy for this patient group.

Comprehensive Analysis of circRNA Expression Profiles in Human Brown Adipose Tissue

PURPOSE

Brown adipose tissue (BAT) can rapidly generate heat and improve energy metabolism. Circular RNAs (circRNAs) are cellular endogenous non-coding RNAs, which can regulate the development and progress of different diseases. However, the role of circRNAs in human BAT is not fully understood. Here, we analyzed the differentially expressed circRNAs (DECs) in human BAT, as well as in white adipose tissue (WAT), and identified new biomarkers of BAT.

PATIENTS AND METHODS

Three human BAT and three human subcutaneous WAT samples were selected, and circRNA microarray was performed. Additionally, quantitative real-time polymerase chain reaction (qRT-PCR) was applied to determine the expression of six circRNAs. Finally, the functional analysis was performed by bioinformatics.

RESULTS

Compared to WAT, 152 upregulated circRNAs and 201 downregulated circRNAs were identified in BAT. The DECs were further subjected to GO and KEGG enrichment analysis. Several circRNAs, for example, hsa_circ_0006168, hsa_circ_26337 and hsa_circ_0007507 were found upregulated and hsa_circ_0030162 was found downregulated in human BAT compared to WAT.

CONCLUSION

This study profiles the circRNA expression in human BAT and WAT, and suggests hsa_circ_0006168, hsa_circ_26337, hsa_circ_0007507, and hsa_circ_0030162 as novel biomarkers for human BAT.

Tea Plant (Camellia sinensis): A Current Update on Use in Diabetes, Obesity, and Cardiovascular Disease

The tea plant (C. sinensis) has traditionally been consumed worldwide as "tea" for its many health benefits, with the potential for the prevention and therapy of various conditions. Regardless of its long history, the use of tea plants in modern times seems not to have changed much, as the beverage remains the most popular form. This review aimed to compile scientific information about the role and action of tea plants, as well as their status concerning clinical applications, based on the currently available evidence, with a focus on metabolic syndrome, mainly covering obesity, diabetes, and cardiovascular disease. It has been recognized that these diseases pose a significant threat to public health, and the development of effective treatment and prevention strategies is necessary but still challenging. In this article, the potential benefits of tea plants and their derived bioactive components (such as epigallocatechin-3-gallate) as anti-obesity, anti-diabetic, and anti-cardiovascular agents are clearly shown and emphasized, along with their mechanisms of action. However, according to the status of the clinical translation of tea plants, particularly in drug development, more substantial efforts in well-designed, randomized, controlled trials are required to expand their applications in treating the three major metabolic disorders and avoiding the toxicity caused by overconsumption.

Nutraceuticals in Brown Adipose Tissue Activation

Obesity and its associated comorbidities have become pandemic, and challenge the global healthcare system. Lifestyle changes, nutritional interventions and phamaceuticals should be differently combined in a personalized strategy to tackle such a public health burden. Altered brown adipose tissue (BAT) function contributes to the pathophysiology of obesity and glucose metabolism dysfunctions. BAT thermogenic activity burns glucose and fatty acids to produce heat through uncoupled respiration, and can dissipate the excessive calorie intake, reduce glycemia and circulate fatty acids released from white adipose tissue. Thus, BAT activity is expected to contribute to whole body energy homeostasis and protect against obesity, diabetes and alterations in lipid profile. To date, pharmacological therapies aimed at activating brown fat have failed in clinical trials, due to cardiovascular side effects or scarce efficacy. On the other hand, several studies have identified plant-derived chemical compounds capable of stimulating BAT thermogenesis in animal models, suggesting the translational applications of dietary supplements to fight adipose tissue dysfunctions. This review describes several nutraceuticals with thermogenic properties and provides indications, at a molecular level, of the regulation of the adipocyte thermogenesis by the mentioned phytochemicals.

Brown adipocytes promote epithelial mesenchymal transition of neuroblastoma cells by inducing PPAR-γ/UCP2 expression

Neuroblastoma (NB) is an embryonic malignant tumour of the sympathetic nervous system, and current research shows that activation of brown adipose tissue accelerates cachexia in cancer patients. However, the interaction between brown adipose tissues and NB remains unclear. The study aimed to investigate the effect of brown adipocytes in the co-culture system on the proliferation and migration of NB cells. Brown adipocytes promoted the proliferation and migration of Neuro-2a, BE(2)-M17, and SH-SY5Y cells under the co-culture system, with an increase of the mRNA and protein levels of UCP2 and PPAR-γ in NB cells. The UCP2 inhibitor genipin or PPAR-γ inhibitor T0090709 inhibited the migration of NB cells induced by brown adipocytes. Genipin or siUCP2 upregulated the expression of E-cadherin, and downregulated the expression of N-cadherin and vimentin in NB cells. We suggest that under co-cultivation conditions, NB cells can activate brown adipocytes, which triggers changes in various genes and promotes the proliferation and migration of NB cells. The PPAR-γ/UCP2 pathway is involved in the migration of NB cells caused by brown adipocytes.