Brown and Beige Adipose Tissue: Therapy for Obesity and Its Comorbidities?

A comparison of five methods to maximize RNA and DNA isolation yield from adipose tissue

Adipose tissue in the human body occurs in various forms with different functions. It is an energy store, a complex endocrine organ, and a source of cells used in medicine. Many molecular analyses require the isolation of nucleic acids, which can cause some difficulties connected with the large amount of lipids in adipocytes. Ribonucleic acid isolation is particularly challenging due to its low stability and easy degradation by ribonucleases. The study aimed to compare and evaluate five RNA and DNA isolation methods from adipose tissue. The tested material was subcutaneous porcine adipose tissue subjected to different homogenization methods and RNA or DNA purification. A mortar and liquid nitrogen or ceramic beads were used for homogenization. The organic extraction (TriPure Reagent), spin columns with silica-membrane (RNeasy Mini Kit or High Pure PCR Template Preparation Kit), and the automatic MagNA Pure system were used for the purification. Five combinations were compared for RNA and DNA isolation. Obtained samples were evaluated for quantity and quality. The methods were compared in terms of yield (according to tissue mass), purity (A260/280 and A260/230), and nucleic acid degradation (RNA Integrity Number, RIN; DNA Integrity Number, DIN). The results were analyzed statistically. The average RNA yield was highest in method I, which used homogenization with ceramic beads and organic extraction. Low RNA concentration didn't allow us to measure degradation for all samples in method III (homogenization with ceramic beads and spin-column purification). The highest RNA quality was achieved with method IV using homogenization in liquid nitrogen and spin column purification, which makes it the most effective for RNA isolation from adipose tissue. Required values of DNA yield, purity, and integrity were achieved only with spin column-based methods (III and IV). The most effective method for DNA isolation from adipose tissue is method III, using spin-columns without additional homogenization.

Antibiotic induced adipose tissue browning in C57BL/6 mice: An association with the metabolic profile and the gut microbiota

AIMS

The use of antibiotics affects health. The gut microbial dysbiosis by antibiotics is thought to be an essential pathway to influence health. It is important to have optimized energy utilization, in which adipose tissues (AT) play crucial roles in maintaining health. Adipocytes regulate the balance between energy expenditure and storage. While it is known that white adipose tissue (WAT) stores energy and brown adipose tissue (BAT) produces energy by thermogenesis, the role of an intermediate AT plays an important role in balancing host internal energy. In the current study, we tried to understand how treating an antibiotic cocktail transforms WAT into BAT or, more precisely, into beige adipose tissue (BeAT).

METHODS

Since antibiotic treatment perturbs the host microbiota, we wanted to understand the role of gut microbial dysbiosis in transforming WAT into BeAT in C57BL/6 mice. We further correlated the metabolic profile at the systemic level with this BeAT transformation and gut microbiota profile.

KEY FINDINGS

In the present study, we have reported that the antibiotic cocktail treatment increases the Proteobacteria and Actinobacteria while reducing the Bacteroidetes phylum. We observed that prolonged antibiotic treatment could induce the formation of BeAT in the inguinal and perigonadal AT. The correlation analysis showed an association between the gut microbiota phyla, beige adipose tissue markers, and serum metabolites.

SIGNIFICANCE

Our study revealed that the gut microbiota has a significant role in regulating the metabolic health of the host via microbiota-adipose axis communication.

The Effect of an Innovative Combination of Bergamot Polyphenolic Fraction and Cynara cardunculus L. Extract on Weight Gain Reduction and Fat Browning in Obese Mice

Obesity is one of the world's most serious public health issues, with a high risk of developing a wide range of diseases. As a result, focusing on adipose tissue dysfunction may help to prevent the metabolic disturbances commonly associated with obesity. Nutraceutical supplementation may be a crucial strategy for improving WAT inflammation and obesity and accelerating the browning process. The aim of this study was to perform a preclinical "proof of concept" study on Bergacyn®, an innovative formulation originating from a combination of bergamot polyphenolic fraction (BPF) and Cynara cardunculus (CyC), for the treatment of adipose tissue dysfunction. In particular, Bergacyn® supplementation in WD/SW-fed mice at doses of 50 mg/kg given orally for 12 weeks, was able to reduce body weight and total fat mass in the WD/SW mice, in association with an improvement in plasma biochemical parameters, including glycemia, total cholesterol, and LDL levels. In addition, a significant reduction in serum ALT levels was highlighted. The decreased WAT levels corresponded to an increased weight of BAT tissue, which was associated with a downregulation of PPARγ as compared to the vehicle group. Bergacyn® was able to restore PPARγ levels and prevent NF-kB overexpression in the WAT of mice fed a WD/SW diet, suggesting an improved oxidative metabolism and inflammatory status. These results were associated with a significant potentiation of the total antioxidant status in WD/SW mice. Finally, our data show, for the first time, that Bergacyn® supplementation may be a valuable approach to counteract adipose tissue dysfunction and obesity-associated effects on cardiometabolic risk.

Adipose Tissue Dynamics: Cellular and Lipid Turnover in Health and Disease

The alarming increase in obesity and its related metabolic health complications, such as type 2 diabetes, has evolved into a global pandemic. Obesity is mainly characterized by excessive accumulation of adipose tissue, primarily due to an imbalance between energy intake and expenditure. Prolonged positive energy balance leads to the expansion of existing adipocytes (hypertrophy) and/or an increase in preadipocyte and adipocyte number (hyperplasia) to accommodate excess energy intake. However, obesity is not solely defined by increases in adipocyte size and number. The turnover of adipose tissue cells also plays a crucial role in the development and progression of obesity. Cell turnover encompasses the processes of cell proliferation, differentiation, and apoptosis, which collectively regulate the overall cell population within adipose tissue. Lipid turnover represents another critical factor that influences how adipose tissue stores and releases energy. Our understanding of adipose tissue lipid turnover in humans remains limited due to the slow rate of turnover and methodological constraints. Nonetheless, disturbances in lipid metabolism are strongly associated with altered adipose tissue lipid turnover. In obesity, there is a decreased rate of triglyceride removal (lipolysis followed by oxidation), leading to the accumulation of triglycerides over time. This review provides a comprehensive summary of findings from both in vitro and in vivo methods used to study the turnover of adipose cells and lipids in metabolic health and disease. Understanding the mechanisms underlying cellular and lipid turnover in obesity is essential for developing strategies to mitigate the adverse effects of excess adiposity.

The quantity and quality of cardiovascular fat at mid-life and future cognitive performance among women: The SWAN cardiovascular fat ancillary study

INTRODUCTION

Cardiovascular fat is a novel risk factor that may link to dementia. Fat volume and radiodensity are measurements of fat quantity and quality, respectively. Importantly, high fat radiodensity could indicate healthy or adverse metabolic processes.

METHODS

The associations of cardiovascular fat (including epicardial, paracardial, and thoracic perivascular adipose tissue [PVAT]) quantity and quality assessed at mean age of 51 with subsequent cognitive performance measured repeatedly over 16 years of follow-up were examined using mixed models among 531 women.

RESULTS

Higher thoracic PVAT volume was associated with a higher future episodic memory (β[standard error (SE)] = 0.08 [0.04], P = 0.033), while higher thoracic PVAT radiodensity with lower future episodic (β[SE] = -0.06 [0.03], P = 0.045) and working (β[SE] = -0.24 [0.08], P = 0.003) memories. The latter association is prominent at higher volume of thoracic PVAT.

DISCUSSION

Mid-life thoracic PVAT may have a distinct contribution to future cognition possibly due to its distinct adipose tissue type (brown fat) and anatomical proximity to the brain circulation.

HIGHLIGHTS

Higher mid-life thoracic perivascular adipose tissue (thoracic PVAT) volume is related to a better future episodic memory in women. Higher mid-life thoracic PVAT radiodensity is related to worse future working and episodic memories. Negative association of high thoracic PVAT radiodensity with working memory is prominent at higher thoracic PVAT volume. Mid-life thoracic PVAT is linked to future memory loss, an early sign of Alzheimer's disease. Mid-life women's epicardial and paracardial fat are not related to future cognition.

The Developmental Implications of Muscle-Targeted Magnetic Mitohormesis: A Human Health and Longevity Perspective

Muscle function reflects muscular mitochondrial status, which, in turn, is an adaptive response to physical activity, representing improvements in energy production for de novo biosynthesis or metabolic efficiency. Differences in muscle performance are manifestations of the expression of distinct contractile-protein isoforms and of mitochondrial-energy substrate utilization. Powerful contractures require immediate energy production from carbohydrates outside the mitochondria that exhaust rapidly. Sustained muscle contractions require aerobic energy production from fatty acids by the mitochondria that is slower and produces less force. These two patterns of muscle force generation are broadly classified as glycolytic or oxidative, respectively, and require disparate levels of increased contractile or mitochondrial protein production, respectively, to be effectively executed. Glycolytic muscle, hence, tends towards fibre hypertrophy, whereas oxidative fibres are more disposed towards increased mitochondrial content and efficiency, rather than hypertrophy. Although developmentally predetermined muscle classes exist, a degree of functional plasticity persists across all muscles post-birth that can be modulated by exercise and generally results in an increase in the oxidative character of muscle. Oxidative muscle is most strongly correlated with organismal metabolic balance and longevity because of the propensity of oxidative muscle for fatty-acid oxidation and associated anti-inflammatory ramifications which occur at the expense of glycolytic-muscle development and hypertrophy. This muscle-class size disparity is often at odds with common expectations that muscle mass should scale positively with improved health and longevity. Brief magnetic-field activation of the muscle mitochondrial pool has been shown to recapitulate key aspects of the oxidative-muscle phenotype with similar metabolic hallmarks. This review discusses the common genetic cascades invoked by endurance exercise and magnetic-field therapy and the potential physiological differences with regards to human health and longevity. Future human studies examining the physiological consequences of magnetic-field therapy are warranted.

Obesity-Related Atrial Fibrillation: Cardiac Manifestation of a Systemic Disease

Atrial fibrillation (AF) is the most common arrhythmia worldwide and is associated with increased morbidity and mortality. The mechanisms underlying AF are complex and multifactorial. Although it is well known that obesity is a strong risk factor for AF, the mechanisms underlying obesity-related AF are not completely understood. Current evidence proposes that in addition to overall hemodynamic changes due to increased body weight, excess adiposity raises systemic inflammation and oxidative stress, which lead to adverse atrial remodeling. This remodeling includes atrial fibrosis, atrial dilation, decreased electrical conduction between atrial myocytes, and altered ionic currents, making atrial tissue more vulnerable to both the initiation and maintenance of AF. However, much remains to be learned about the mechanistic links between obesity and AF. This knowledge will power the development of novel diagnostic tools and treatment options that will help combat the rise of the global AF burden among the obesity epidemic.

New insights into the role of adipocytes in pancreatic cancer progression: paving the way towards novel therapeutic targets

Pancreatic cancer (PC) remains one of the most lethal malignancies across the world, which is due to delayed diagnosis and resistance to current therapies. The interactions between pancreatic tumor cells and their tumor microenvironment (TME) allow cancer cells to escape from anti-cancer therapies, leading to difficulties in treating PC. With endocrine function and lipid storage capacity, adipose tissue can maintain energy homeostasis. Direct or indirect interaction between adipocytes and PC cells leads to adipocyte dysfunction characterized by morphological change, fat loss, abnormal adipokine secretion, and fibroblast-like transformation. Various adipokines released from dysfunctional adipocytes have been reported to promote proliferation, invasion, metastasis, stemness, and chemoresistance of PC cells via different mechanisms. Additional lipid outflow from adipocytes can be taken into the TME and thus alter the metabolism in PC cells and surrounding stromal cells. Besides, the trans-differentiation potential enables adipocytes to turn into various cell types, which may give rise to an inflammatory response as well as extracellular matrix reorganization to modulate tumor burden. Understanding the molecular basis behind the protumor functions of adipocytes in PC may offer new therapeutic targets.

Collagens Regulating Adipose Tissue Formation and Functions

The globally increasing prevalence of obesity is associated with the development of metabolic diseases such as type 2 diabetes, dyslipidemia, and fatty liver. Excess adipose tissue (AT) often leads to its malfunction and to a systemic metabolic dysfunction because, in addition to storing lipids, AT is an active endocrine system. Adipocytes are embedded in a unique extracellular matrix (ECM), which provides structural support to the cells as well as participating in the regulation of their functions, such as proliferation and differentiation. Adipocytes have a thin pericellular layer of a specialized ECM, referred to as the basement membrane (BM), which is an important functional unit that lies between cells and tissue stroma. Collagens form a major group of proteins in the ECM, and some of them, especially the BM-associated collagens, support AT functions and participate in the regulation of adipocyte differentiation. In pathological conditions such as obesity, AT often proceeds to fibrosis, characterized by the accumulation of large collagen bundles, which disturbs the natural functions of the AT. In this review, we summarize the current knowledge on the vertebrate collagens that are important for AT development and function and include basic information on some other important ECM components, principally fibronectin, of the AT. We also briefly discuss the function of AT collagens in certain metabolic diseases in which they have been shown to play central roles.

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.

Sex Differences in Adiposity and Cardiovascular Diseases

Body fat distribution is a well-established predictor of adverse medical outcomes, independent of overall adiposity. Studying body fat distribution sheds insights into the causes of obesity and provides valuable information about the development of various comorbidities. Compared to total adiposity, body fat distribution is more closely associated with risks of cardiovascular diseases. The present review specifically focuses on the sexual dimorphism in body fat distribution, the biological clues, as well as the genetic traits that are distinct from overall obesity. Understanding the sex determinations on body fat distribution and adiposity will aid in the improvement of the prevention and treatment of cardiovascular diseases (CVD).

Seabuckthorn Reverses High-Fat-Diet-Induced Obesity and Enhances Fat Browning via Activation of AMPK/SIRT1 Pathway

Seabuckthorn possesses various bioactive compounds and exhibits several positive pharmacological activities. The present trial aims to determine the effect of seabuckthorn powder intake on high-fat diet (HFD)-induced obesity prevention in mice. The results suggest that seabuckthorn powder intake decreased body weight, fat mass, and circulating lipid levels, and improved insulin sensitivity in HFD-fed mice. Moreover, dietary seabuckthorn powder alleviated hepatic steatosis and hepatic lipid accumulation induced by the HFD. Furthermore, seabuckthorn exhibited obvious anti-inflammatory capacity in white adipose tissue (WAT) by regulating the abundance of inflammation-related cytokines, such as interleukins 4, 6, and 10; tumor necrosis factor α; and interferon-γ. More importantly, dietary seabuckthorn powder promoted a thermogenic program in BAT and induced beige adipocyte formation in iWAT in HFD-fed mice. Interestingly, we found that seabuckthorn powder effectively restored AMPK and SIRT1 activities in both BAT and iWAT in HFD-fed mice. Collectively, these results potentiate the application of seabuckthorn powder as a nutritional intervention strategy to prevent obesity and related metabolic diseases by promoting thermogenesis in BAT and improving beige adipocyte formation in WAT.

Obesity, Weight Gain, and Fluid Overload in Peritoneal Dialysis

Obesity is a global epidemic that has a complicated pathogenesis as well as impact on the outcome of peritoneal dialysis (PD) patients. In this review, the prevalence of obesity in incident PD patients as well as the phenomenon of new-onset glucose intolerance after PD will be reviewed. Published literature on the effect of obesity on the survival and incidence of cardiovascular disease in PD patients will be discussed. Particular emphasis would be put on literature that compared the impact of obesity on the outcome of hemodialysis and PD, and the confounding effect of dialysis adequacy. Next, the complex concept of obesity and its relevance for PD will be explored. The focus would be put on the methods of assessment and clinical relevance of central versus general obesity, as well as visceral versus subcutaneous adipose tissue. The relation between obesity and systemic inflammation, as well as the biological role of several selected adipokines will be reviewed. The confounding effects of metabolic syndrome and insulin resistance will be discussed, followed by the prevalence and prognostic impact of weight gain during the first few years of PD. The differences between weight gain due to fluid overload and accumulation of adipose tissue will be discussed, followed by the current literature on the change in body composition after patients are put on chronic PD. The methods of body composition will be reviewed, and the clinical relevance of individual body component (fluid, fat, muscle, and bone) will be discussed. The review will conclude by highlighting current gaps of knowledge and further research directions in this area.

Exercise-induced beige adipogenesis of iWAT in Cidea reporter mice

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

Lytic cocktail: An effective method to alleviate severe burn induced hyper-metabolism through regulating white adipose tissue browning

Background

Browning of white adipose tissue is associated with elevated resting metabolic rates and is considered to be one of the indispensable causes of hypermetabolism in burn patients. Hypermetabolism means increased resting energy expenditure, raised body temperature and acute-phase proteins. Persistently elevated levels of circulating stress hormones have been reported to induce browning of subcutaneous white adipose tissue. The lytic cocktail is a combination of medicines pethidine, chlorpromazine, and promethazine that has been used clinically in sedation for the management of patients. As reported this sedative treatment can reduce the expression of catecholamines in major burn rats. Thus, in this paper we focused on the effects of lytic cocktail in the regulation of white adipose tissue browning and hypermetabolism and we further investigated the underlying mechanism.

Methods

A 30% total body surface area (TBSA) Ⅲ degree scald rat model was used for this study. The rats were randomly divided into a sham scald group, a scalding with immediate resuscitation group, and a group of scalding with immediate resuscitation and lytic cocktail treatment. The levels of norepinephrine and epinephrine in plasma were dynamically detected. Changes of the rat body weight and food intake were recorded and compared as indexes of metabolism responses after post-scalding. For the study of white adipose tissue browning, inguinal adipose tissue was used. Metabolic changes, while indicatives of white fat browning were measured by PET/CT. The expression of white adipose browning related proteins and the changes of mitochondria number were used to assess browning of inguinal adipose.

Results

The level of plasma catecholamines norepinephrine and epinephrine in the lytic cocktail-treated group was significantly lower than the other two groups. Morphology and PET/CT showed that the inguinal white adipose browning was inhibited in the lytic cocktail treated group, whereas scalding with immediate resuscitation group showed browning of white adipose. The number of mitochondria, the expressions of white adipose browning related proteins in the lytic cocktail group were also significantly lower than that of the group of scalding with immediate resuscitation.

Conclusion

By reducing expression of heat-related proteins, the application of lytic cocktail medicines inhibits the white adipose tissue browning, which suppresses hypermetabolism in scalded rats. The mechanism might be related to decreased expression levels of stress hormones induced by lytic cocktail. This research suggests that lytic cocktails may be an effective treatment for hypermetabolism after severe burn injury.

White, beige and brown adipose tissue: structure, function, specific features and possibility formation and divergence in pigs

Introduction. Traditionally, mammalian adipose tissue is divided into white (white adipose tissue – WAT) and brown (brown adipose tissue – BAT). While the functions of WAT are well known as the triglyceride depot, the role of BAT in mammalian physiology has been under close investigation. The first description of the role of BAT in maintaining thermogenesis dates back to 1961. This article offers a review of structural and functional specificity of white, beige and brown adipose tissue. Results and discussion. The differences and descriptions of adipocytes and their impact on the maintenance of the main functions of the mammalian body are described in this manuscript. In particular, thermogenesis, stress response, obesity, type II diabetes. In addition to WAT and BAT, an intermediate form was also detected in the body – beige fat (BeAT or Brite). The opposite opinions regarding the presence of three types of adipose tissue in the human and animal bodies are presented. Studies on the identification of uncoupling proteins 1 and 3 and their role in the transformation of white fat into beige/brown are considered. Basically, the data on the factors of endogenous and exogenous nature on their formation are given on the example of the human body. Conclusion. With an abundance of publications on the keywords: “white, brown fat”, these studies, in the overwhelming majority, are devoted to the role of these fats in the formation of human thermogenesis, the assessment of the impact on obesity. Pigs have also been suggested to lack functional BAT, which is a major cause of neonatal death in the swine industry, therefore the focus on investigating role of different types of adipose tissue in pigs seems very promising in order to understand whether there is a compensating mechanism of thermogenesis.

Engineering Functional Vascularized Beige Adipose Tissue from Microvascular Fragments of Models of Healthy and Type II Diabetes Conditions

Engineered beige adipose tissues could be used for screening therapeutic strategies or as a direct treatment for obesity and metabolic disease. Microvascular fragments are vessel structures that can be directly isolated from adipose tissue and may contain cells capable of differentiation into thermogenic, or beige, adipocytes. In this study, culture conditions were investigated to engineer three-dimensional, vascularized functional beige adipose tissue using microvascular fragments isolated from both healthy animals and a model of type II diabetes (T2D). Vascularized beige adipose tissues were engineered and exhibited increased expression of beige adipose markers, enhanced function, and improved cellular respiration. While microvascular fragments isolated from both lean and diabetic models were able to generate functional tissues, differences were observed in regard to vessel assembly and tissue function. This study introduces an approach that could be employed to engineer vascularized beige adipose tissues from a single, potentially autologous source of cells.

Exercise and/or Cold Exposure Alters the Gene Expression Profile in the Fat Body and Changes the Heart Function in Drosophila

The major reason of human morbidity and mortality is obesity and related diseases. Brown adipose tissue (BAT) is associated with low total adipose tissue content and a lower risk of type 2 diabetes mellitus. Studies have shown that exercise and cold expose may induce browning. In this study, we verified (1) whether exercise and/or cold exposure can improve the expression level of ucp4c, serca, ampkα, camkII, sirt1, octβ3r, and hamlet; (2) if these interventions can save cardiac dysfunction induced by a high-fat diet (HFD) in Drosophila. w1118 (wild-type) virgin female flies collected within 8 h after eclosion were divided into eight groups: the normal feed control group (NFD-C), the normal feed exercise group (NFD-E), the normal feed cold exposure group (NFD-CA), the normal feed exercise/cold exposure group (NFD-EC), the HFD control group (HFD-C), the HFD exercise group (HFD-E), the HFD cold exposure group (HFD-CA), and the HFD exercise/cold exposure group (HFD-EC). After exercise and/or cold exposure for 7 days, the mRNA expression levels of ucp4c, serca, ampkα, camk II, sirt1, octβ3r, and hamlet were tested by qRT-PCR, and m-mode was used to assess cardiac function. In addition, we assessed the triacylglycerol (TAG) levels, motor ability, fat mass (by Oil Red O [ORO] staining), and morphological features. The results of TAG, ORO staining, and morphological features all indicate that after interventions, body size of Drosophila was smaller compared with the control group, irrespective of the feeding patterns. The mRNA expression levels of ucp4c, serca, octβ3r, hamlet, ampkα, camkII, and sirt1 were changed to varying degrees under different intervention states (exercise and/or cold exposure). Cold exposure and exercise/cold exposure partly improved cardiac function and the normal fruit flies' cardiac function and exercise ability. However, after exercise intervention, exercise ability and heart function were improved in both HFD and normal-fat diet (NFD) fruit flies. In conclusion, different intervention states (exercise and/or cold exposure) can change the mRNA expression levels of ucp4c, serca, octβ3r, hamlet, ampkα, camkII, and sirt1. Exercise is the most effective way to restore HFD-induced cardiac dysfunction.

Short histological kaleidoscope - recent findings in histology. Part I

This article is a review of new advances in histology, concerning either classification or structure of different tissular elements (basement membrane, hemidesmosomes, urothelium, glandular epithelia, adipose tissue, astrocytes), and various organs' constituents (blood-brain barrier, human dental cementum, tubarial salivary glands, hepatic stellate cells, pineal gland, fibroblasts of renal interstitium, Leydig testicular cells, ovarian hilar cells), as well as novel biotechnological techniques (tissue engineering in angiogenesis), recently introduced.

Insight Into Rho Kinase Isoforms in Obesity and Energy Homeostasis

Obesity and associated complications increasingly jeopardize global health and contribute to the rapidly rising prevalence of type 2 diabetes mellitus and obesity-related diseases. Developing novel methods for the prevention and treatment of excess body adipose tissue expansion can make a significant contribution to public health. Rho kinase is a Rho-associated coiled-coil-containing protein kinase (Rho kinase or ROCK). The ROCK family including ROCK1 and ROCK2 has recently emerged as a potential therapeutic target for the treatment of metabolic disorders. Up-regulated ROCK activity has been involved in the pathogenesis of all aspects of metabolic syndrome including obesity, insulin resistance, dyslipidemia and hypertension. The RhoA/ROCK-mediated actin cytoskeleton dynamics have been implicated in both white and beige adipogenesis. Studies using ROCK pan-inhibitors in animal models of obesity, diabetes, and associated complications have demonstrated beneficial outcomes. Studies via genetically modified animal models further established isoform-specific roles of ROCK in the pathogenesis of metabolic disorders including obesity. However, most reported studies have been focused on ROCK1 activity during the past decade. Due to the progress in developing ROCK2-selective inhibitors in recent years, a growing body of evidence indicates more attention should be devoted towards understanding ROCK2 isoform function in metabolism. Hence, studying individual ROCK isoforms to reveal their specific roles and principal mechanisms in white and beige adipogenesis, insulin sensitivity, energy balancing regulation, and obesity development will facilitate significant breakthroughs for systemic treatment with isoform-selective inhibitors. In this review, we give an overview of ROCK functions in the pathogenesis of obesity and insulin resistance with a particular focus on the current understanding of ROCK isoform signaling in white and beige adipogenesis, obesity and thermogenesis in adipose tissue and other major metabolic organs involved in energy homeostasis regulation.

Physical Activity Attenuates the Obesity-Induced Dysregulated Expression of Brown Adipokines in Murine Interscapular Brown Adipose Tissue

In recent years, brown adipose tissue (BAT), which has a high heat-producing capacity, has been confirmed to exist even in adults, and it has become a focal point for the prevention and the improvement of obesity and lifestyle-related diseases. However, the influences of obesity and physical activity (PA) on the fluid factors secreted from BAT (brown adipokines) are not well understood. In this study, therefore, we focused on brown adipokines and investigated the effects of obesity and PA. The abnormal expressions of gene fluid factors such as galectin-3 (Lgals3) and Lgals3 binding protein (Lgals3bp), whose proteins are secreted from HB2 brown adipocytes, were observed in the interscapular BAT of obese mice fed a high-fat diet for 4 months. PA attenuated the abnormalities in the expressions of these genes. Furthermore, although the gene expressions of factors related to brown adipocyte differentiation such as peroxisome proliferator-activated receptor gamma coactivator 1-α were also down-regulated in the BAT of the obese mice, PA suppressed the down-regulation of these factors. On the other hand, lipogenesis was increased more in HB2 cells overexpressing Lgals3 compared with that in control cells, and the overexpression of Lgals3bp decreased the mitochondrial mass. These results indicate that PA attenuates the obesity-induced dysregulated expression of brown adipokines and suggests that Lgals3 and Lgals3bp are involved in brown adipocyte differentiation.

Estrogen-Receptor-Positive Breast Cancer in Postmenopausal Women: The Role of Body Composition and Physical Exercise

Breast cancer (BC) is the most commonly diagnosed cancer among women worldwide and the most common cause of cancer-related death. To date, it is still a challenge to estimate the magnitude of the clinical impact of physical activity (PA) on those parameters producing significative changes in future BC risk and disease progression. However, studies conducted in recent years highlight the role of PA not only as a protective factor for the development of ER+ breast cancer but, more generally, as a useful tool in the management of BC treatment as an adjuvant to traditional therapies. In this review, we focused our attention on data obtained from human studies analyzing, at each level of disease prevention (i.e., primary, secondary, tertiary and quaternary), the positive impact of PA/exercise in ER+ BC, a subtype representing approximately 70% of all BC diagnoses. Moreover, given the importance of estrogen receptors and body composition (i.e., adipose tissue) in this subtype of BC, an overview of their role will also be made throughout this review.

CXCL5 secreted from macrophages during cold exposure mediates white adipose tissue browning

Adipose tissue affects metabolic-related diseases because it consists of various cell types involved in fat metabolism and adipokine release. CXC ligand 5 (CXCL5) is a member of the CXC chemokine family and is highly expressed by macrophages in white adipose tissue (WAT). In this study, we generated and investigated the function of CXCL5 in knockout (KO) mice using CRISPR/Cas9. The male KO mice did not show significant phenotype differences in normal conditions. However, proteomic analysis revealed that many proteins involved in fatty acid beta-oxidation and mitochondrial localization were enriched in the inguinal WAT (iWAT) of Cxcl5 KO mice. Cxcl5 KO mice also showed decreased protein and transcript expression of genes associated with thermogenesis, including uncoupling protein 1 (UCP1), a well-known thermogenic gene, and increased expression of genes associated with inflammation. The increase in UCP1 expression in cold conditions was significantly retarded in Cxcl5 KO mice. Finally, we found that CXCL5 treatment increased the expression of transcription factors that mediate Ucp1 expression and Ucp1 itself. Collectively, our data show that Ucp1 expression is induced in adipocytes by CXCL5, which is secreted upon β-adrenergic stimulation by cold stimulation in M1 macrophages. Our data indicate that CXCL5 plays a crucial role in regulating energy metabolism, particularly upon cold exposure. These results strongly suggest that targeting CXCL5 could be a potential therapeutic strategy for people suffering from disorders affecting energy metabolism.

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

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

TM4SF5 Knockout Protects Mice From Diet-Induced Obesity Partly by Regulating Autophagy in Adipose Tissue

Transmembrane 4 L six family member 5 (TM4SF5) functions as a sensor for lysosomal arginine levels and activates the mammalian target of rapamycin complex 1 (mTORC1). While the mTORC1 signaling pathway plays a key role in adipose tissue metabolism, the regulatory function of TM4SF5 in adipocytes remains unclear. In this study we aimed to establish a TM4SF5 knockout (KO) mouse model and investigated the effects of TM4SF5 KO on mTORC1 signaling-mediated autophagy and mitochondrial metabolism in adipose tissue. TM4SF5 expression was higher in inguinal white adipose tissue (iWAT) than in brown adipose tissue and significantly upregulated by a high-fat diet (HFD). TM4SF5 KO reduced mTORC1 activation and enhanced autophagy and lipolysis in adipocytes. RNA sequencing analysis of TM4SF5 KO mouse iWAT showed that the expression of genes involved in peroxisome proliferator-activated receptor α signaling pathways and mitochondrial oxidative metabolism was upregulated. Consequently, TM4SF5 KO reduced adiposity and increased energy expenditure and mitochondrial oxidative metabolism. TM4SF5 KO prevented HFD-induced glucose intolerance and inflammation in adipose tissue. Collectively, the results of our study demonstrate that TM4SF5 regulates autophagy and lipid catabolism in adipose tissue and suggest that TM4SF5 could be therapeutically targeted for the treatment of obesity-related metabolic diseases.

Polygonum multiflorum Thunb. Hot Water Extract Reverses High-Fat Diet-Induced Lipid Metabolism of White and Brown Adipose Tissues in Obese Mice

The purpose of the present study was to determine whether an anti-obesity effect of a Polygonum multiflorum Thunb. hot water extract (PW) was involved in the lipid metabolism of white adipose tissue (WAT) and brown adipose tissue (BAT) in high-fat diet (HFD)-induced C57BL/6N obese mice. Mice freely received a normal diet (NCD) or an HFD for 12 weeks; HFD-fed mice were orally given PW (100 or 300 mg/kg) or garcinia cambogia (GC, 200 mg/kg) once a day. After 12 weeks, PW (300 mg/kg) or GC significantly alleviated adiposity by reducing body weight, WAT weights, and food efficiency ratio. PW (300 mg/kg) improved hyperinsulinemia and enhanced insulin sensitivity. In addition, PW (300 mg/kg) significantly down-regulated expression of carbohydrate-responsive element-binding protein (ChREBP) and diacylglycerol O-acyltransferase 2 (DGAT2) genes in WAT compared with the untreated HFD group. HFD increased BAT gene levels such as adrenoceptor beta 3 (ADRB3), peroxisome proliferator-activated receptor γ (PPARγ), hormone-sensitive lipase (HSL), cluster of differentiation 36 (CD36), fatty acid-binding protein 4 (FABP4), PPARγ coactivator 1-α (PGC-1α), PPARα, and carnitine palmitoyltransferase 1B (CPT1B) compared with the NCD group; however, PW or GC effectively reversed those levels. These findings suggest that the anti-obesity activity of PW was mediated via suppression of lipogenesis in WAT, leading to the normalization of lipid metabolism in BAT.

Towards an understanding of the mechanoreciprocity process in adipocytes and its perturbation with aging

Adipose tissue (AT) is a complex organ, with multiple functions that are essential for maintaining metabolic health. A feature of AT is its capability to expand in response to physiological challenges, such as pregnancy and aging, and during chronic states of positive energy balance occurring throughout life. AT grows through adipogenesis and/or an increase in the size of existing adipocytes. One process that is required for healthy AT growth is the remodeling of the extracellular matrix (ECM), which is a necessary step to restore mechanical homeostasis and maintain tissue integrity and functionality. While the relationship between mechanobiology and adipogenesis is now well recognized, less is known about the role of adipocyte mechanosignaling pathways in AT growth. In this review article, we first summarize evidence linking ECM remodelling to AT expansion and how its perturbation is associated to a metabolically unhealthy phenotype. Subsequently, we highlight findings suggesting that molecules involved in the dynamic, bidirectional process (mechanoreciprocity) enabling adipocytes to sense changes in the mechanical properties of the ECM are interconnected to pathways regulating lipid metabolism. Finally, we discuss processes through which aging may influence the ability of adipocytes to appropriately respond to alterations in ECM composition.

Chronic stress, epigenetics, and adipose tissue metabolism in the obese state

In obesity, endocrine and metabolic perturbations, including those induced by chronic activation of the hypothalamus-pituitary-adrenal axis, are associated with the accumulation of adipose tissue and inflammation. Such changes are attributable to a combination of genetic and epigenetic factors that are influenced by the environment and exacerbated by chronic activation of the hypothalamus-pituitary-adrenal axis. Stress exposure at different life stages can alter adipose tissue metabolism directly through epigenetic modification or indirectly through the manipulation of hypothalamic appetite regulation, and thereby contribute to endocrine changes that further disrupt whole-body energy balance. This review synthesizes current knowledge, with an emphasis on human clinical trials, to describe metabolic changes in adipose tissue and associated endocrine, genetic and epigenetic changes in the obese state. In particular, we discuss epigenetic changes induced by stress exposure and their contribution to appetite and adipocyte dysfunction, which collectively promote the pathogenesis of obesity. Such knowledge is critical for providing future directions of metabolism research and targets for treating metabolic disorders.

Stimulation of brown adipose tissue by polyphenols in extra virgin olive oil

Obesity is one of the main public health problems of the 21^st century resulting from an imbalance between calorie intake and energy expenditure. Currently, the search for new treatments against this pathology has become a priority. One of the therapeutic strategies against obesity could be the activation of brown adipose tissue through different molecules such as the phenolic compounds of extra virgin olive oil (EVOO). The objective of this review was to provide an update of scientific knowledge on the relationship between EVOO phenolic compounds and brown adipose tissue.According to this review, it has been demonstrated that extra virgin olive oil phenolic compounds can have beneficial effects on obesity by activating brown adipose tissue and enhance thermogenesis through different signaling pathways mediated by molecules such as AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor γ coactivator-1α (PGC1α) or sirtuin 1 (Sirt1).

Vitamin D repletion ameliorates adipose tissue browning and muscle wasting in infantile nephropathic cystinosis-associated cachexia

BACKGROUND

Ctns-/- mice, a mouse model of infantile nephropathic cystinosis, exhibit hypermetabolism with adipose tissue browning and profound muscle wasting. Ctns-/- mice are 25(OH)D3 and 1,25(OH)2 D3 insufficient. We investigated whether vitamin D repletion could ameliorate adipose tissue browning and muscle wasting in Ctns-/- mice.

METHODS

Twelve-month-old Ctns-/- mice and wild-type controls were treated with 25(OH)D3 and 1,25(OH)2 D3 (75 μg/kg/day and 60 ng/kg/day, respectively) or an ethylene glycol vehicle for 6 weeks. Serum chemistry and parameters of energy homeostasis were measured. We quantitated total fat mass and studied expression of molecules regulating adipose tissue browning, energy metabolism, and inflammation. We measured lean mass content, skeletal muscle fibre size, in vivo muscle function (grip strength and rotarod activity), and expression of molecules regulating muscle metabolism. We also analysed the transcriptome of skeletal muscle in Ctns-/- mice using RNAseq.

RESULTS

Supplementation of 25(OH)D3 and 1,25(OH)2 D3 normalized serum concentration of 25(OH)D3 and 1,25(OH)2 D3 in Ctns-/- mice, respectively. Repletion of vitamin D partially or fully normalized food intake, weight gain, gain of fat, and lean mass, improved energy homeostasis, and attenuated perturbations of uncoupling proteins and adenosine triphosphate content in adipose tissue and muscle in Ctns-/- mice. Vitamin D repletion attenuated elevated expression of beige adipose cell biomarkers (UCP-1, CD137, Tmem26, and Tbx1) as well as aberrant expression of molecules implicated in adipose tissue browning (Cox2, Pgf2α, and NF-κB pathway) in inguinal white adipose tissue in Ctns-/- mice. Vitamin D repletion normalized skeletal muscle fibre size and improved in vivo muscle function in Ctns-/- mice. This was accompanied by correcting the increased muscle catabolic signalling (increased protein contents of IL-1β, IL-6, and TNF-α as well as an increased gene expression of Murf-2, atrogin-1, and myostatin) and promoting the decreased muscle regeneration and myogenesis process (decreased gene expression of Igf1, Pax7, and MyoD) in skeletal muscles of Ctns-/- mice. Muscle RNAseq analysis revealed aberrant gene expression profiles associated with reduced muscle and neuron regeneration, increased energy metabolism, and fibrosis in Ctns-/- mice. Importantly, repletion of 25(OH)D3 and 1,25(OH)2 D3 normalized the top 20 differentially expressed genes in Ctns-/- mice.

CONCLUSIONS

We report the novel findings that correction of 25(OH)D3 and 1,25(OH)2 D3 insufficiency reverses cachexia and may improve quality of life by restoring muscle function in an animal model of infantile nephropathic cystinosis. Mechanistically, vitamin D repletion attenuates adipose tissue browning and muscle wasting in Ctns-/- mice via multiple cellular and molecular mechanisms.

Nanotechnology advances towards development of targeted-treatment for obesity

Obesity through its association with type 2 diabetes (T2D), cancer and cardiovascular diseases (CVDs), poses a serious health threat, as these diseases contribute to high mortality rates. Pharmacotherapy alone or in combination with either lifestyle modification or surgery, is reliable in maintaining a healthy body weight, and preventing progression to obesity-induced diseases. However, the anti-obesity drugs are limited by non-specificity and unsustainable weight loss effects. As such, novel and improved approaches for treatment of obesity are urgently needed. Nanotechnology-based therapies are investigated as an alternative strategy that can treat obesity and be able to overcome the drawbacks associated with conventional therapies. The review presents three nanotechnology-based anti-obesity strategies that target the white adipose tissues (WATs) and its vasculature for the reversal of obesity. These include inhibition of angiogenesis in the WATs, transformation of WATs to brown adipose tissues (BATs), and photothermal lipolysis of WATs. Compared to conventional therapy, the targeted-nanosystems have high tolerability, reduced side effects, and enhanced efficacy. These effects are reproducible using various nanocarriers (liposomes, polymeric and gold nanoparticles), thus providing a proof of concept that targeted nanotherapy can be a feasible strategy that can combat obesity and prevent its comorbidities.

Identification of a natural beige adipose depot in mice

Beige fat is a potential therapeutic target for obesity and other metabolic diseases due to its inducible brown fat-like functions. Inguinal white adipose tissue (iWAT) can undergo robust brown remodeling with appropriate stimuli and is therefore widely considered as a representative beige fat depot. However, adipose tissues residing in different anatomic depots exhibit a broad range of plasticity, raising the possibility that better beige fat depots with greater plasticity may exist. Here we identified and characterized a novel, naturally-existing beige fat depot, thigh adipose tissue (tAT). Unlike classic WATs, tAT maintains beige fat morphology at room temperature, whereas high-fat diet (HFD) feeding or aging promotes the development of typical WAT features, namely unilocular adipocytes. The brown adipocyte gene expression in tAT is consistently higher than in iWAT under cold exposure, HFD feeding, and rosiglitazone treatment conditions. Our molecular profiling by RNA-Seq revealed up-regulation of energy expenditure pathways and repressed inflammation in tAT relative to eWAT and iWAT. Furthermore, we demonstrated that the master fatty acid oxidation regulator peroxisome proliferator-activated receptor α is dispensable for maintaining and activating the beige character of tAT. Therefore, we have identified tAT as a natural beige adipose depot in mice with a unique molecular profile that does not require peroxisome proliferator-activated receptor α.

No evidence of white adipocyte browning after endurance exercise training in obese men

BACKGROUND/OBJECTIVES

The phenomenon of adipocyte 'beiging' involves the conversion of non-classic brown adipocytes to brown-like adipose tissue with thermogenic, fat-burning properties, and this phenomenon has been shown in rodents to slow the progression of obesity-associated metabolic diseases. Rodent studies consistently report adipocyte beiging after endurance exercise training, indicating that increased thermogenic capacity in these adipocytes may underpin the improved health benefits of exercise training. The aim of this study was to determine whether prolonged endurance exercise training induces beige adipogenesis in subcutaneous adipose tissues of obese men.

SUBJECTS/METHODS

Molecular markers of beiging were examined in adipocytes obtained from abdominal subcutaneous (AbSC) and gluteofemoral (GF) subcutaneous adipose tissues before and after 6 weeks of endurance exercise training in obese men (n=6, 37.3±2.3 years, 30.1±2.3 kg m^-2).

RESULTS

The mRNAs encoding the brown or beige adipocyte-selective proteins were very lowly expressed in AbSC and GF adipose tissues and exercise training did not alter the mRNA expression of UCP1, CD137, CITED, TBX1, LHX8 and TCF21. Using immunohistochemistry, neither multilocular adipocytes, nor UCP1 or CD137-positive adipocytes were detected in any sample. MicroRNAs known to regulate brown and/or beige adipose development were highly expressed in white adipocytes but endurance exercise training did not impact their expression.

CONCLUSIONS

The present study reaffirms emerging data in humans demonstrating no evidence of white adipose tissue beiging in response to exercise training, and supports a growing body of work demonstrating divergence of brown/beige adipose location, molecular characterization and physiological function between rodents and humans.

Differential effects of diet composition and timing of feeding behavior on rat brown adipose tissue and skeletal muscle peripheral clocks

The effects of feeding behavior and diet composition, as well as their possible interactions, on daily (clock) gene expression rhythms have mainly been studied in the liver, and to a lesser degree in white adipose tissue (WAT), but hardly in other metabolic tissues such as skeletal muscle (SM) and brown adipose tissues (BAT). We therefore subjected male Wistar rats to a regular chow or free choice high-fat-high sugar (fcHFHS) diet in combination with time restricted feeding (TRF) to either the light or dark phase. In SM, all tested clock genes lost their rhythmic expression in the chow light fed group. In the fcHFHS light fed group rhythmic expression for some, but not all, clock genes was maintained, but shifted by several hours. In BAT the daily rhythmicity of clock genes was maintained for the light fed groups, but expression patterns were shifted as compared with ad libitum and dark fed groups, whilst the fcHFHS diet made the rhythmicity of clock genes become more pronounced. Most of the metabolic genes in BAT tissue tested did not show any rhythmic expression in either the chow or fcHFHS groups. In SM Pdk4 and Ucp3 were phase-shifted, but remained rhythmically expressed in the chow light fed groups. Rhythmic expression was lost for Ucp3 whilst on the fcHFHS diet during the light phase. In summary, both feeding at the wrong time of day and diet composition disturb the peripheral clocks in SM and BAT, but to different degrees and thereby result in a further desynchronization between metabolically active tissues such as SM, BAT, WAT and liver.

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Both timing of feeding and diet composition affect clock genes in BAT and SM.

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Light phase time-restricted feeding abolishes SM clock gene rhythms.

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A fcHSHS diet strengthens rhythmic expression of several clock genes in BAT and SM.

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Metabolic genes PDK4 and UCP1/3 are affected by both timing of feeding and diet.

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Light phase time-restricted feeding causes desynchronization of BAT and SM clocks.

Cinnamaldehyde in diabetes: A review of pharmacology, pharmacokinetics and safety

Cinnamaldehyde, one of the active components derived from Cinnamon, has been used as a natural flavorant and fragrance agent in kitchen and industry. Emerging studies have been performed over the past decades to evaluate its beneficial role in management of diabetes and its complications. This review highlights recent advances of cinnamaldehyde in its glucolipid lowering effects, its pharmacokinetics, and its safety by consulting the Pubmed, China Knowledge Resource Integrated, China Science and Technology Journal, National Science and Technology Library, Wanfang Data, and the Web of Science Databases. For the inquiries, keywords such as Cinnamon, cinnamaldehyde, property, synthesis, diabetes, obesity, pharmacokinetics, and safety were used in various combinations. Accumulating evidence supports the notion that cinnamaldehyde exhibits glucolipid lowering effects in diabetic animals by increasing glucose uptake and improving insulin sensitivity in adipose and skeletal muscle tissues, improving glycogen synthesis in liver, restoring pancreatic islets dysfunction, slowing gastric emptying rates, and improving diabetic renal and brain disorders. Cinnamaldehyde exerts these effects through its action on multiple signaling pathways, including PPARs, AMPK, PI3K/IRS-1, RBP4-GLUT4, and ERK/JNK/p38MAPK, TRPA1-ghrelin and Nrf2 pathways. In addition, cinnamaldehyde seems to regulate the activities of PTP1B and α-amylase. Furthermore, cinnamaldehyde has the potential of metalizing into cinnamyl alcohol and methyl cinnamate and cinnamic acid in the body. Finally, there is a potential toxicity concern about this compound. In summary, cinnamaldehyde supplementation is shown to improve glucose and lipid homeostasis in diabetic animals, which may provide a new option for diabetic intervention. To this end, further scientific evidences are required from clinical trials on its glucose regulating effects and safety.

Dietary Factors Promoting Brown and Beige Fat Development and Thermogenesis

Brown adipose tissue (BAT) is a specialized fat tissue that has a high capacity to dissociate cellular respiration from ATP utilization, resulting in the release of stored energy as heat. Adult humans possess a substantial amount of BAT in the form of constitutively active brown fat or inducible beige fat. BAT activity in humans is inversely correlated with adiposity, blood glucose concentrations, and insulin sensitivity; this suggests that strategies aimed at BAT-mediated bioenergetics are an attractive therapeutic target in combating the continuing epidemic of obesity and diabetes. Despite advances in knowledge regarding the developmental lineage and transcriptional regulators of brown and beige adipocytes, our current understanding of environmental modifiers of BAT thermogenesis, such as diet, is limited. In this review, we consolidated the latest research on dietary molecules that may serve to promote BAT thermogenesis. Here, we summarized the thermogenic function of selected phytochemicals (e.g., capsaicin, resveratrol, curcumin, green tea, and berberine), dietary fatty acids (e.g., fish oil and conjugated linoleic acids), and all-trans retinoic acid, a vitamin A metabolite. We also delineated the proposed mechanisms whereby these dietary molecules promote BAT activity and/or browning of white adipose tissue. Characterizing thermogenic dietary factors may offer novel insight into revising nutritional intervention strategies aimed at obesity and diabetes prevention and management.

Sedentary lifestyle related exosomal release of Hotair from gluteal-femoral fat promotes intestinal cell proliferation

Pioneering epidemiological work has established strong association of sedentary lifestyle and obesity with the risk of colorectal cancer, while the detailed underlying mechanism remains unknown. Here we show that Hotair (HOX transcript antisense RNA) is a pro-adipogenic long non-coding RNA highly expressed in gluteal-femoral fat over other fat depots. Hotair knockout in adipose tissue results in gluteal-femoral fat defect. Squeeze of the gluteal-femoral fat induces intestinal proliferation in wildtype mice, while not in Hotair knockout mice. Mechanistically, squeeze of the gluteal-femoral fat induces exosomal Hotair secretion mainly by transcriptional upregulation of Hotair via NFκB. And increased exosomal Hotair in turn circulates in the blood and is partially endocytosed by the intestine, finally promoting the stemness and proliferation of intestinal stem/progenitor cells via Wnt activation. Clinically, obese subjects with sedentary lifestyle have much higher exosomal HOTAIR expression in the serum. These findings establish that sedentary lifestyle promotes exosomal Hotair release from the gluteal-femoral fat, which in turn facilitates intestinal stem and/or progenitor proliferation, raising a possible link between sedentary lifestyle with colorectal tumorigenesis.

Molecular implications of adenosine in obesity

Adenosine has broad activities in organisms due to the existence of multiple receptors, the differential adenosine concentrations necessary to activate these receptors and the presence of proteins able to synthetize, degrade or transport this nucleoside. All adenosine receptors have been reported to be involved in glucose homeostasis, inflammation, adipogenesis, insulin resistance, and thermogenesis, indicating that adenosine could participate in the process of obesity. Since adenosine seems to be associated with several effects, it is plausible that adenosine participates in the initiation and development of obesity or may function to prevent it. Thus, the purpose of this review was to explore the involvement of adenosine in adipogenesis, insulin resistance and thermogenesis, with the aim of understanding how adenosine could be used to avoid, treat or improve the metabolic state of obesity. Treatment with specific agonists and/or antagonists of adenosine receptors could reverse the obesity state, since adenosine receptors normalizes several mechanisms involved in obesity, such as lipolysis, insulin sensitivity and thermogenesis. Furthermore, obesity is a preventable state, and the specific activation of adenosine receptors could aid in the prevention of obesity. Nevertheless, for the treatment of obesity and its consequences, more studies and therapeutic strategies in addition to adenosine are necessary.