Adipose tissue browning in mice and humans

Transcriptional profile of the rat cardiovascular system at single-cell resolution

We sought to characterize cellular composition across the cardiovascular system of the healthy Wistar rat, an important model in preclinical cardiovascular research. We performed single-nucleus RNA sequencing (snRNA-seq) in 78 samples in 10 distinct regions, including the four chambers of the heart, ventricular septum, sinoatrial node, atrioventricular node, aorta, pulmonary artery, and pulmonary veins, which produced 505,835 nuclei. We identified 26 distinct cell types and additional subtypes, with different cellular composition across cardiac regions and tissue-specific transcription for each cell type. Several cell subtypes were region specific, including a subtype of vascular smooth muscle cells enriched in the large vasculature. We observed tissue-enriched cellular communication networks, including heightened Nppa-Npr1/2/3 signaling in the sinoatrial node. The existence of tissue-restricted cell types suggests regional regulation of cardiovascular physiology. Our detailed transcriptional characterization of each cell type offers the potential to identify novel therapeutic targets and improve preclinical models of cardiovascular disease.

The Relevance and Potential Role of Orbital Fat in Inflammatory Orbital Diseases: Implications for Diagnosis and Treatment

The orbit is an important structure within the skull that houses the eye, optic nerve, and extraocular muscles. It also contains adipose/fat tissue, which provides a protective cushion for these components. Inflammatory orbital disease can affect any or all components of the orbit, often arising from various underlying pathologic conditions, including autoimmune, infectious, and vascular diseases. Typical signs and symptoms of orbital inflammation include swelling, redness, pain, discomfort, and potential loss of function. The role of orbital fat in the pathogenesis of inflammatory orbital diseases has not been fully explored. This review aims to provide a comprehensive description of orbital fat, its relevance and the potential role in inflammatory diseases of the orbit, and the use of radiologic imaging studies for evaluating this fat depot in cases of as inflammatory orbital diseases. Additionally, this review discusses the various procedures available for the treatment and management of these conditions. A range of interventions, including pharmacotherapy and surgical procedures, will be evaluated as promising therapeutic options. This review also explores the characteristics and potential applications of orbital fat-derived stem cells, with an emphasis on their regenerative abilities and anti-inflammatory effects. Understanding the role of orbital fat and its contribution to inflammatory orbital diseases is essential for optimizing diagnostic and treatment strategies.

Chitooligosaccharide-Epigallocatechin Gallate Conjugate Ameliorates Lipid Accumulation and Promotes Browning of White Adipose Tissue in High Fat Diet Fed Rats

The prevalence of obesity has increased progressively worldwide. Obesity is characterized by excessive accumulation of fat in adipose tissues, leading to metabolic impairment. The anti-obese effects of chitooligosaccharide (COS) and epigallocatechin-3-gallate (EGCG) have been extensively clarified. This study aimed to investigate the effects and potential mechanisms of the COS-EGCG conjugate (CE) on anti-obesity, specifically by alleviating lipid accumulation and promoting the browning of white adipose tissue (WAT) in obese rats. Obesity as a consequence of a high-fat diet (HFD) was induced in male Wistar rats. The HFD was given for 16 weeks and the rats were then randomly subdivided into five groups namely: vehicle (control group), HFD plus CE at 150 mg/kg/day, HFD plus CE at 600 mg/kg/day, HFD plus COS at 600 mg/kg/day, and HFD plus atorvastatin at 10 mg/kg/day for 4 weeks. CE could reduce body weight, improve serum lipid profiles, and promote lipid metabolism via activation of AMP-activated protein kinase (AMPK) in WAT and enhance the processes of WAT browning by activating sirtuin 1 (Sirt 1), peroxisome proliferator-activated receptor-gamma coactivator (PGC1-α), and uncoupling the protein 1 (UCP1) signaling pathway. CE reduced obesity and promoted WAT browning in HFD-fed rats. Therefore, CE might be a new therapy for metabolic syndrome and obesity.

Inflammasomes in chronic liver disease: Hepatic injury, fibrosis progression and systemic inflammation

Chronic liver disease leads to hepatocellular injury that triggers a pro-inflammatory state in several parenchymal and non-parenchymal hepatic cell types, ultimately resulting in liver fibrosis, cirrhosis, portal hypertension and liver failure. Thus, an improved understanding of inflammasomes - as key molecular drivers of liver injury - may result in the development of novel diagnostic or prognostic biomarkers and effective therapeutics. In liver disease, innate immune cells respond to hepatic insults by activating cell-intrinsic inflammasomes via toll-like receptors and NF-κB, and by releasing pro-inflammatory cytokines (such as IL-1β, IL-18, TNF-α and IL-6). Subsequently, cells of the adaptive immune system are recruited to fuel hepatic inflammation and hepatic parenchymal cells may undergo gasdermin D-mediated programmed cell death, termed pyroptosis. With liver disease progression, there is a shift towards a type 2 inflammatory response, which promotes tissue repair but also fibrogenesis. Inflammasome activation may also occur at extrahepatic sites, such as the white adipose tissue in MASH (metabolic dysfunction-associated steatohepatitis). In end-stage liver disease, flares of inflammation (e.g., in severe alcohol-related hepatitis) that spark on a dysfunctional immune system, contribute to inflammasome-mediated liver injury and potentially result in organ dysfunction/failure, as seen in ACLF (acute-on-chronic liver failure). This review provides an overview of current concepts regarding inflammasome activation in liver disease progression, with a focus on related biomarkers and therapeutic approaches that are being developed for patients with liver disease.

A Mixture of Lactobacillus HY7601 and KY1032 Regulates Energy Metabolism in Adipose Tissue and Improves Cholesterol Disposal in High-Fat-Diet-Fed Mice

We aimed to characterize the anti-obesity and anti-atherosclerosis effects of Lactobacillus curvatus HY7601 and Lactobacillus plantarum KY1032 using high-fat diet (HFD)-fed obese C57BL/6 mice. We divided the mice into control (CON), HFD, HFD with 108 CFU/kg/day probiotics (HFD + KL, HY7301:KY1032 = 1:1), and HFD with 109 CFU/kg/day probiotics (HFD + KH, HY7301:KY1032 = 1:1) groups and fed/treated them during 7 weeks. The body mass, brown adipose tissue (BAT), inguinal white adipose tissue (iWAT), and epididymal white adipose tissue (eWAT) masses and the total cholesterol and triglyceride concentrations were remarkably lower in probiotic-treated groups than in the HFD group in a dose-dependent manner. In addition, the expression of uncoupling protein 1 in the BAT, iWAT, and eWAT was significantly higher in probiotic-treated HFD mice than in the HFD mice, as demonstrated by immunofluorescence staining and Western blotting. We also measured the expression of cholesterol transport genes in the liver and jejunum and found that the expression of those encoding liver-X-receptor α, ATP-binding cassette transporters G5 and G8, and cholesterol 7α-hydroxylase were significantly higher in the HFD + KH mice than in the HFD mice. Thus, a Lactobacillus HY7601 and KY1032 mixture with 109 CFU/kg/day concentration can assist with body weight regulation through the management of lipid metabolism and thermogenesis.

The molecular mechanism of macrophage-adipocyte crosstalk in maintaining energy homeostasis

Interactions between macrophages and adipocytes in adipose tissue are critical for the regulation of energy metabolism and obesity. Macrophage polarization induced by cold or other stimulations can drive metabolic reprogramming of adipocytes, browning, and thermogenesis. Accordingly, investigating the roles of macrophages and adipocytes in the maintenance of energy homeostasis is critical for the development of novel therapeutic approaches specifically targeting macrophages in metabolic disorders such as obesity. Current review outlines macrophage polarization not only regulates the release of central nervous system and inflammatory factors, but controls mitochondrial function, and other factor that induce metabolic reprogramming of adipocytes and maintain energy homeostasis. We also emphasized on how the adipocytes conversely motivate the polarization of macrophage. Exploring the interactions between adipocytes and macrophages may provide new therapeutic strategies for the management of obesity-related metabolic diseases.

White adipocyte dysfunction and obesity-associated pathologies in humans

The prevalence of obesity and associated chronic diseases continues to increase worldwide, negatively impacting on societies and economies. Whereas the association between excess body weight and increased risk for developing a multitude of diseases is well established, the initiating mechanisms by which weight gain impairs our metabolic health remain surprisingly contested. In order to better address the myriad of disease states associated with obesity, it is essential to understand adipose tissue dysfunction and develop strategies for reinforcing adipocyte health. In this Review we outline the diverse physiological functions and pathological roles of human white adipocytes, examining our current knowledge of why white adipocytes are vital for systemic metabolic control, yet poorly adapted to our current obesogenic environment.

Role of hydrogen sulfide in the regulation of lipid metabolism: Implications on cardiovascular health

The World Health Organization (WHO) defines obesity as an urgency for health and a social emergency. Today around 39 % of people is overweight, of these over 13 % is obese. It is well-consolidated that the adipose cells are deputy to lipid storage under caloric excess; however, despite the classical idea that adipose tissue has exclusively a passive function, now it is known to be deeply involved in the regulation of systemic metabolism in physiological as well as under obesogenic conditions, with consequences on cardiovascular health. Beside two traditional types of adipose cells (white and brown), recently the beige one has been highlighted as the consequence of the healthy remodeling of white adipocytes, confirming their metabolic adaptability. In this direction, pharmacological, nutraceutical and nutrient-based approaches are addressed to positively influence inflammation and metabolism, thus contributing to reduce the obese-associated cardiovascular risk. In this scenario, hydrogen sulfide emerges as a new mediator that may regulate crucial targets involved in the regulation of metabolism. The current evidence demonstrates that hydrogen sulfide may induce peroxisome proliferator activated receptor γ (PPARγ), a crucial mediator of adipogenesis, inhibit the phosphorylation of perlipin-1 (plin-1), a protein implicated in the lipolysis, and finally promote browning process, through the release of irisin from skeletal muscle. The results summarized in this review suggest an important role of hydrogen sulfide in the regulation of metabolism and in the prevention/treatment of obese-associated cardiovascular diseases and propose new insight on the putative mechanisms underlying the release of hydrogen sulfide or its biosynthesis, delineating a further exciting field of application.

Brown adipose Vanin-1 is required for the maintenance of mitochondrial homeostasis and prevents diet-induced metabolic dysfunction

BACKGROUND

Energy-dissipating brown adipocytes have significant potential for improving systemic metabolism. Vanin-1, a membrane-bound pantetheinase, is involved in various biological processes in mice. However, its role in BAT mitochondrial function is still unclear. In this study, we aimed to elucidate the impact of Vanin-1 on BAT function and contribution during overnutrition-induced obesity.

METHODS

Vanin-1 expression was analyzed in different adipose depots in mice. The cellular localization of Vanin-1 was analyzed by confocal microscopy and western blots. Mice lacking Vanin-1 (Vanin-1-/-) were continuously fed either a chow diet or a high-fat diet (HFD) to establish an obesity model. RNA-seq analysis was performed to identify the molecular changes associated with Vanin-1 deficiency during obesity. BAT-specific Vanin-1 overexpression mice were established to determine the effects of Vanin-1 in vivo. Cysteamine treatment was used to examine the effect of enzymatic reaction products of Vanin-1 on BAT mitochondria function in Vanin-1-/- mice.

RESULTS

The results indicate that the expression of Vanin-1 is reduced in BAT from both diet-induced and leptin-deficient obese mice. Study on the subcellular location of Vanin-1 shows that it has a mitochondrial localization. Vanin-1 deficiency results in increased adiposity, BAT dysfunction, aberrant mitochondrial structure, and promotes HFD induced-BAT whitening. This is attributed to the impairment of the electron transport chain (ETC) in mitochondria due to Vanin-1 deficiency, resulting in reduced mitochondrial respiration. Overexpression of Vanin-1 significantly enhances energy expenditure and thermogenesis in BAT, renders mice resistant to diet-induced obesity. Furthermore, treatment with cysteamine rescue the mitochondrial dysfunction in Vanin-1-/- mice.

CONCLUSIONS

Collectively, these findings suggest that Vanin-1 plays a crucial role in promoting mitochondrial respiration to counteract diet-induced obesity, making it a potential therapeutic target for obesity.

Transcriptional profile of the rat cardiovascular system at single cell resolution

Background

Despite the critical role of the cardiovascular system, our understanding of its cellular and transcriptional diversity remains limited. We therefore sought to characterize the cellular composition, phenotypes, molecular pathways, and communication networks between cell types at the tissue and sub-tissue level across the cardiovascular system of the healthy Wistar rat, an important model in preclinical cardiovascular research. We obtained high quality tissue samples under controlled conditions that reveal a level of cellular detail so far inaccessible in human studies.

Methods and Results

We performed single nucleus RNA-sequencing in 78 samples in 10 distinct regions including the four chambers of the heart, ventricular septum, sinoatrial node, atrioventricular node, aorta, pulmonary artery, and pulmonary veins (PV), which produced an aggregate map of 505,835 nuclei. We identified 26 distinct cell types and additional subtypes, including a number of rare cell types such as PV cardiomyocytes and non-myelinating Schwann cells (NMSCs), and unique groups of vascular smooth muscle cells (VSMCs), endothelial cells (ECs) and fibroblasts (FBs), which gave rise to a detailed cell type distribution across tissues. We demonstrated differences in the cellular composition across different cardiac regions and tissue-specific differences in transcription for each cell type, highlighting the molecular diversity and complex tissue architecture of the cardiovascular system. Specifically, we observed great transcriptional heterogeneities among ECs and FBs. Importantly, several cell subtypes had a unique regional localization such as a subtype of VSMCs enriched in the large vasculature. We found the cellular makeup of PV tissue is closer to heart tissue than to the large arteries. We further explored the ligand-receptor repertoire across cell clusters and tissues, and observed tissue-enriched cellular communication networks, including heightened Nppa - Npr1/2/3 signaling in the sinoatrial node.

Conclusions

Through a large single nucleus sequencing effort encompassing over 500,000 nuclei, we broadened our understanding of cellular transcription in the healthy cardiovascular system. The existence of tissue-restricted cellular phenotypes suggests regional regulation of cardiovascular physiology. The overall conservation in gene expression and molecular pathways across rat and human cell types, together with our detailed transcriptional characterization of each cell type, offers the potential to identify novel therapeutic targets and improve preclinical models of cardiovascular disease.

Effect of 2'-Fucosyllactose on Beige Adipocyte Formation in 3T3-L1 Adipocytes and C3H10T1/2 Cells

2'-Fucosyllactose (2'-FL), the functional oligosaccharide naturally present in milk, has been shown to exert health benefits. This study was aimed to investigate the effect of 2'-fucosyllactose (2'-FL) on the browning of white adipose tissue in 3T3-L1 adipocytes and C3H10T1/2 cells. The results revealed that 2'-FL decreased lipid accumulations with reduced intracellular triglyceride contents in vitro. 2'-FL intervention increased the mitochondria density and the proportion of UCP1-positive cells. The mRNA expressions of the mitochondrial biogenesis-related and browning markers (Cox7a, Cyto C, Tfam, Ucp1, Pgc1α, Prdm16, Cidea, Elovl3, Pparα, CD137, and Tmem26) were increased after 2'-FL intervention to some extent. Similarly, the protein expression of the browning markers, including UCP1, PGC1α, and PRDM16, was up-regulated in the 2'-FL group. Additionally, an adenosine monophosphate-activated protein kinase (AMPK) inhibitor, compound C (1 μM), significantly decreased the induction of thermogenic proteins expressions mediated by 2'-FL, indicating that the 2'-FL-enhanced beige cell formation was partially dependent on the AMPK pathway. In conclusion, 2'-FL effectively promoted the browning of white adipose in vitro.

Polarized macrophages regulate fibro/adipogenic progenitor (FAP) adipogenesis through exosomes

BACKGROUND

Macrophage polarization has been observed in the process of muscle injuries including rotator cuff (RC) muscle atrophy and fatty infiltration after large tendon tears. In our previous study, we showed that fibrogenesis and white adipogenesis of muscle residential fibro/adipogenic progenitors (FAPs) cause fibrosis and fatty infiltration and that brown/beige adipogenesis of FAPs promotes rotator cuff muscle regeneration. However, how polarized macrophages and their exosomes regulate FAP differentiation remains unknown.

METHODS

We cultured FAPs with M0, M1, and M2 macrophages or 2 × 109 exosomes derived from M0, M1 and M2 with and without GW4869, an exosome inhibitor. In vivo, M0, M1, and M2 macrophages were transplanted or purified macrophage exosomes (M0, M1, M2) were injected into supraspinatus muscle (SS) after massive tendon tears in mice (n = 6). SS were harvested at six weeks after surgery to evaluate the level of muscle atrophy and fatty infiltration.

RESULTS

Our results showed that M2 rather than M0 or M1 macrophages stimulates brown/beige fat differentiation of FAPs. However, the effect of GW4869, the exosome inhibitor, diminished this effect. M2 exosomes also promoted FAP Beige differentiation in vitro. The transplantation of M2 macrophages reduced supraspinatus muscle atrophy and fatty infiltration. In vivo injections of M2 exosomes significantly reduced muscle atrophy and fatty infiltration in supraspinatus muscle.

CONCLUSION

Results from our study demonstrated that polarized macrophages directly regulated FAP differentiation through their exosomes and M2 macrophage-derived exosomes may serve as a novel treatment option for RC muscle atrophy and fatty infiltration.

Konjac glucomannan attenuate high-fat diet-fed obesity through enhancing β-adrenergic-mediated thermogenesis in inguinal white adipose tissue in mice

Konjac glucomannan (KGM) has been reported to prevent high-fat diet-induced obesity, and we study investigated whether dietary supplementation with KGM can prevent obesity by increasing energy expenditure in inguinal white adipose tissue (iWAT) of high-fat diet (HF) -fed mice. Weaned mice fed the control diet (Con), HF, or HF plus KGM (8%, w/w, HFK) were divided into three groups. The results showed that 10-week supplementation with KGM significantly reduced partial adipose tissue weight and body weight, and improved glucose tolerance. Compared to the HF group, plasma lipid concentrations in the HFK group were greatly decreased to the control level. Moreover, transcriptomic research has shown that genes that are mainly associated with energy and lipid metabolism are significantly altered in iWAT. Mechanistically, KGM stimulated thermogenesis by promoting the expression of uncoupling protein-1 (UCP1) and the β3-adrenergic receptor (ADR3β). Taken together, our results suggest that dietary supplementation with konjac glucomannan can effectively alleviate obesity induced by a high-fat diet by activating ADR3β-mediated iWAT thermogenesis. Dietary supplementation with KGM can effectively alleviate high fat diet- induced obesity mice by via activating ADR3β-mediated thermogenesis of iWAT.

High-intensity interval training improves fatty infiltration in the rotator cuff through the β3 adrenergic receptor in mice

Aims

Rotator cuff muscle atrophy and fatty infiltration affect the clinical outcomes of rotator cuff tear patients. However, there is no effective treatment for fatty infiltration at this time. High-intensity interval training (HIIT) helps to activate beige adipose tissue. The goal of this study was to test the role of HIIT in improving muscle quality in a rotator cuff tear model via the β3 adrenergic receptor (β3AR).

Methods

Three-month-old C57BL/6 J mice underwent a unilateral rotator cuff injury procedure. Mice were forced to run on a treadmill with the HIIT programme during the first to sixth weeks or seventh to 12th weeks after tendon tear surgery. To study the role of β3AR, SR59230A, a selective β3AR antagonist, was administered to mice ten minutes before each exercise through intraperitoneal injection. Supraspinatus muscle, interscapular brown fat, and inguinal subcutaneous white fat were harvested at the end of the 12th week after tendon tear and analyzed biomechanically, histologically, and biochemically.

Results

Histological analysis of supraspinatus muscle showed that HIIT improved muscle atrophy, fatty infiltration, and contractile force compared to the no exercise group. In the HIIT groups, supraspinatus muscle, interscapular brown fat, and inguinal subcutaneous white fat showed increased expression of tyrosine hydroxylase and uncoupling protein 1, and upregulated the β3AR thermogenesis pathway. However, the effect of HIIT was not present in mice injected with SR59230A, suggesting that HIIT affected muscles via β3AR.

Conclusion

HIIT improved supraspinatus muscle quality and function after rotator cuff tears by activating systemic sympathetic nerve fibre near adipocytes and β3AR.

Magnetic resonance imaging detects white adipose tissue beiging in mice following PDE10A inhibitor treatment

Weight gain is a common harmful side effect of atypical antipsychotics used for schizophrenia treatment. Conversely, treatment with the novel phosphodiesterase-10A (PDE10A) inhibitor MK-8189 in clinical trials led to significant weight reduction, especially in patients with obesity. This study aimed to understand and describe the mechanism underlying this observation, which is essential to guide clinical decisions. We hypothesized that PDE10A inhibition causes beiging of white adipose tissue (WAT), leading to weight loss. Magnetic resonance imaging (MRI) methods were developed, validated, and applied in a diet-induced obesity mouse model treated with a PDE10A inhibitor THPP-6 or vehicle for measurement of fat content and vascularization of adipose tissue. Treated mice showed significantly lower fat fraction in white and brown adipose tissue, and increased perfusion and vascular density in WAT versus vehicle, confirming the hypothesis, and matching the effect of CL-316,243, a compound known to cause adipose tissue beiging. The in vivo findings were validated by qPCR revealing upregulation of Ucp1 and Pcg1-α genes, known markers of WAT beiging, and angiogenesis marker VegfA in the THPP-6 group. This work provides a detailed understanding of the mechanism of action of PDE10A inhibitor treatment on adipose tissue and body weight and will be valuable to guide both the use of MK-8189 in schizophrenia and the potential application of the target for weight loss indication.

Lipid Nanoparticles as a Shuttle for Anti-Adipogenic miRNAs to Human Adipocytes

Obesity and type 2 diabetes are major health burdens for which no effective therapy is available today. One treatment strategy could be to balance the metabolic functions of adipose tissue by regulating gene expressions using miRNAs. Here, we have loaded two anti-adipogenic miRNAs (miR26a and miR27a) into a pegylated lipid nanoparticle (PEG-LNP) formulation by a single-step microfluidic-assisted synthesis step. For the miRNA-loaded LNPs, the following system properties were determined: particle size, zeta potential, miRNA complexation efficiency, and cytotoxicity. We have used a human preadipocyte cell line to address the transfection efficiency and biological effects of the miRNA candidates at the gene and protein level. Our findings revealed that the upregulation of miR27a in preadipocytes inhibits adipogenesis by the downregulation of PPARγ and the reduction of lipid droplet formation. In contrast, miR26a transfection in adipocytes induced white adipocyte browning detected as the upregulation of uncoupling protein 1 (UCP1) as a marker of non-shivering thermogenesis. We conclude that the selective delivery of miRNAs by PEG-LNPs to adipocytes could offer new perspectives for the treatment of obesity and related metabolic diseases.

Effects of multi-organ crosstalk on the physiology and pathology of adipose tissue

In previous studies, adipocytes were found to play an important role in regulating whole-body nutrition and energy balance, and are also important in energy metabolism, hormone secretion, and immune regulation. Different adipocytes have different contributions to the body, with white adipocytes primarily storing energy and brown adipocytes producing heat. Recently discovered beige adipocytes, which have characteristics in between white and brown adipocytes, also have the potential to produce heat. Adipocytes interact with other cells in the microenvironment to promote blood vessel growth and immune and neural network interactions. Adipose tissue plays an important role in obesity, metabolic syndrome, and type 2 diabetes. Dysfunction in adipose tissue endocrine and immune regulation can cause and promote the occurrence and development of related diseases. Adipose tissue can also secrete multiple cytokines, which can interact with organs; however, previous studies have not comprehensively summarized the interaction between adipose tissue and other organs. This article reviews the effect of multi-organ crosstalk on the physiology and pathology of adipose tissue, including interactions between the central nervous system, heart, liver, skeletal muscle, and intestines, as well as the mechanisms of adipose tissue in the development of various diseases and its role in disease treatment. It emphasizes the importance of a deeper understanding of these mechanisms for the prevention and treatment of related diseases. Determining these mechanisms has enormous potential for identifying new targets for treating diabetes, metabolic disorders, and cardiovascular diseases.

Progress and obstacles in transplantation of brown adipose tissue or engineered cells with thermogenic potential for metabolic benefits

Transplantation of brown adipose tissue (BAT), engineered thermogenic progenitor cells, and adipocytes have received much attention for the improvement of obesity and metabolic disorders. However, even though the thermogenic and metabolic potential exists early after transplantation, the whitening of the brown fat graft occurs with metabolic function significantly impaired. In this review, specific experiment designs, graft outcomes, and metabolic benefits for the transplantation of BAT or engineered cells will be discussed. The current advancements will offer guidance to further investigation, and the obstacles appearing in previous studies will require innovation of BAT transplantation methods.

Effect of High-Intensity Interval Training on Fatty Infiltration After Delayed Rotator Cuff Repair in a Mouse Model

Background

Fatty infiltration (FI) of the rotator cuff muscles is correlated with shoulder function and retear rates after rotator cuff repair. High-intensity interval training (HIIT) induces beige adipose tissue to express more uncoupling protein 1 (UCP1) to consume lipids. The beta-3 adrenergic receptor (β3AR) is located on adipocyte membrane and induces thermogenesis.

Purpose

To test the role of HIIT in improving muscle quality and contractility in a delayed rotator cuff repair mouse model via β3AR.

Study Design

Controlled laboratory study.

Methods

Three-month-old C57BL/6J mice underwent a unilateral supraspinatus (SS) tendon transection with a 6-week delayed tendon repair. Mice ran on a treadmill with the HIIT program for 6 weeks after tendon transection or after delayed repair. To study the role of β3AR, SR59230A, a selective β3AR antagonist, was administered to mice 10 minutes before each exercise through intraperitoneal injection. The SS, interscapular brown adipose tissue (iBAT), and subcutaneous inguinal white adipose tissue (ingWAT) were harvested at the end of the 12th week after tendon transection and were analyzed by histology and Western blotting. Tests were performed to assess muscle contractility of the SS.

Results

Histologic analysis of SS showed that HIIT prevented and reversed muscle atrophy and FI. The contractile tests showed higher contractility of the SS in the HIIT groups than in the no-exercise group. In the HIIT groups, SS, iBAT, and ingWAT all showed increased expression of tyrosine hydroxylase, UCP1, and upregulated β3AR thermogenesis pathway. However, SR59230A inhibited HIIT, suggesting that the effect of HIIT depends on β3AR.

Conclusion

HIIT improved SS quality and function after delayed rotator cuff repair through a β3AR-dependent mechanism.

Clinical Relevance

HIIT may serve as a new rehabilitation method for patients with rotator cuff muscle atrophy and FI after rotator cuff repair to improve postoperative clinical outcomes.

A Novel LncRNA MSTRG.310246.1 Promotes Differentiation and Thermogenesis in Goat Brown Adipocytes

Brown adipose tissue (BAT) plays a critical role in maintaining the body temperature in newborn lamb due to its unique non-shivering thermogenesis. Previous studies have found that BAT thermogenesis is regulated by several long non-coding RNAs (lncRNAs). Here, we identified a novel lncRNA, MSTRG.310246.1, which was enriched in BAT. MSTRG.310246.1 was localized in both the nuclear and cytoplasmic compartments. In addition, MSTRG.310246.1 expression was upregulated during brown adipocyte differentiation. Overexpression of MSTRG.310246.1 increased the differentiation and thermogenesis of goat brown adipocytes. On the contrary, the knockdown of MSTRG.310246.1 inhibited the differentiation and thermogenesis of goat brown adipocytes. However, MSTRG.310246.1 had no effect on goat white adipocyte differentiation and thermogenesis. Our results show that MSTRG.310246.1 is a BAT-enriched LncRNA that improves the differentiation and thermogenesis of goat brown adipocytes.

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

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

An Innovative Mei-Gin Formula Exerts Anti-Adipogenic and Anti-Obesity Effects in 3T3-L1 Adipocyte and High-Fat Diet-Induced Obese Rats

BACKGROUND

To investigate the potential anti-obesity properties of an innovative functional formula (called the Mei-Gin formula: MGF) consisting of bainiku-ekisu, Prunus mume (70% ethanol extract), black garlic (water extract), and Mesona procumbens Hemsl. (40% ethanol extract) for reducing lipid accumulation in 3T3-L1 adipocytes in vitro and obese rats in vivo.

MATERIAL AND METHODS

The prevention and regression of high-fat diet (HFD)-induced obesity by the intervention of Japan Mei-Gin, MGF-3 and -7, and positive health supplement powder were investigated in male Wistar rats. The anti-obesity effects of MGF-3 and -7 in rats with HFD-induced obesity were examined by analyzing the role of visceral and subcutaneous adipose tissue in the development of obesity.

RESULTS

The results indicated that MGF-1-7 significantly suppressed lipid accumulation and cell differentiation through the down-regulation of GPDH activity, as a key regulator in the synthesis of triglycerides. Additionally, MGF-3 and MGF-7 exhibited a greater inhibitory effect on adipogenesis in 3T3-L1 adipocytes. The high-fat diet increased body weight, liver weight, and total body fat (visceral and subcutaneous fat) in obese rats, while these alterations were effectively improved by the administration of MGF-3 and -7, especially MGF-7.

CONCLUSION

This study highlights the role of the Mei-Gin formula, particularly MGF-7, in anti-obesity action, which has the potential to be used as a therapeutic agent for the prevention or treatment of obesity.

Transcriptomics Dissection of Calorie Restriction and Exercise Training in Brown Adipose Tissue and Skeletal Muscle

Calorie restriction (CR) and exercise training (EX) are two critical lifestyle interventions for the prevention and treatment of metabolic diseases, such as obesity and diabetes. Brown adipose tissue (BAT) and skeletal muscle are two important organs for the generation of heat. Here, we undertook detailed transcriptional profiling of these two thermogenic tissues from mice treated subjected to CR and/or EX. We found transcriptional reprogramming of BAT and skeletal muscle as a result of CR but little from EX. Consistent with this, CR induced alterations in the expression of genes encoding adipokines and myokines in BAT and skeletal muscle, respectively. Deconvolution analysis showed differences in the subpopulations of myogenic cells, mesothelial cells and endogenic cells in BAT and in the subpopulations of satellite cells, immune cells and endothelial cells in skeletal muscle as a result of CR or EX. NicheNet analysis, exploring potential inter-organ communication, indicated that BAT and skeletal muscle could mutually regulate their fatty acid metabolism and thermogenesis through ligands and receptors. These data comprise an extensive resource for the study of thermogenic tissue molecular responses to CR and/or EX in a healthy state.

COBL, MKX and MYOC Are Potential Regulators of Brown Adipose Tissue Development Associated with Obesity-Related Metabolic Dysfunction in Children

Obesity is already accompanied by adipose tissue (AT) dysfunction and metabolic disease in children and increases the risk of premature death. Due to its energy-dissipating function, brown AT (BAT) has been discussed as being protective against obesity and related metabolic dysfunction. To analyze the molecular processes associated with BAT development, we investigated genome-wide expression profiles in brown and white subcutaneous and perirenal AT samples of children. We identified 39 upregulated and 26 downregulated genes in uncoupling protein 1 (UCP1)-positive compared to UCP1-negative AT samples. We prioritized for genes that had not been characterized regarding a role in BAT biology before and selected cordon-bleu WH2 repeat protein (COBL), mohawk homeobox (MKX) and myocilin (MYOC) for further functional characterization. The siRNA-mediated knockdown of Cobl and Mkx during brown adipocyte differentiation in vitro resulted in decreased Ucp1 expression, while the inhibition of Myoc led to increased Ucp1 expression. Furthermore, COBL, MKX and MYOC expression in the subcutaneous AT of children is related to obesity and parameters of AT dysfunction and metabolic disease, such as adipocyte size, leptin levels and HOMA-IR. In conclusion, we identify COBL, MKX and MYOC as potential regulators of BAT development and show an association of these genes with early metabolic dysfunction in children.

Sesamol promotes browning of white adipocytes through liver-adipose crosstalk signal of hepatic fibroblast growth factor 21

Sesamol (SEM), a lignan from sesame oil, exhibited potential benefits on obesity treatment by promoting browning of adipocytes, and the current study is aimed to explore the molecular mechanisms of SEM from the aspect of systemic liver-adipose crosstalk that mediated by hepatic fibroblast growth factor 21 (FGF21). Our in vivo data showed that SEM induced energy expenditure and white adipose tissue (WAT) browning by increasing the expression level of uncoupling protein-1 in high fat diet induced obese C57BL/6J mice. Elevated levels of circulating FGF21 associated with the increased expression of hepatic FGF21 were observed after SEM intervention. Simultaneously, the increased adipose fibroblast growth factor tyrosine kinase receptor 1/beta-klotho indicated that FGF21 sensitivity was enhanced by SEM in WAT. Furthermore, our in vitro results from HepG2 and 3T3-L1 cell lines confirmed the effects and revealed the mechanism of SEM on the white adipocytes browning. We found that with the specific inhibitors of PPARα, the SEM-mediated hepatic FGF21 expression was decreased, and with the specific inhibitors of PPARγ, the browning effect of adipocytes by SEM combining with FGF21 was significantly suppressed. Taken together, the mechanism of SEM for inducing the WAT browning might be the modulation of SEM on liver-adipose crosstalk mediated by FGF21, and the PPARs family might be the targets of SEM. The novel findings from the present study provided evidence that SEM could be a potent obesity-treating compound.

Beyond Erectile Dysfunction: cGMP-Specific Phosphodiesterase 5 Inhibitors for Other Clinical Disorders

Cyclic guanosine monophosphate (cGMP), an important intracellular second messenger, mediates cellular functional responses in all vital organs. Phosphodiesterase 5 (PDE5) is one of the 11 members of the cyclic nucleotide phosphodiesterase (PDE) family that specifically targets cGMP generated by nitric oxide-driven activation of the soluble guanylyl cyclase. PDE5 inhibitors, including sildenafil and tadalafil, are widely used for the treatment of erectile dysfunction, pulmonary arterial hypertension, and certain urological disorders. Preclinical studies have shown promising effects of PDE5 inhibitors in the treatment of myocardial infarction, cardiac hypertrophy, heart failure, cancer and anticancer-drug-associated cardiotoxicity, diabetes, Duchenne muscular dystrophy, Alzheimer's disease, and other aging-related conditions. Many clinical trials with PDE5 inhibitors have focused on the potential cardiovascular, anticancer, and neurological benefits. In this review, we provide an overview of the current state of knowledge on PDE5 inhibitors and their potential therapeutic indications for various clinical disorders beyond erectile dysfunction.

Potential Involvement of LncRNAs in Cardiometabolic Diseases

Characterized by cardiovascular disease and diabetes, cardiometabolic diseases are a major cause of mortality around the world. As such, there is an urgent need to understand the pathogenesis of cardiometabolic diseases. Increasing evidence suggests that most of the mammalian genome are transcribed as RNA, but only a few percent of them encode for proteins. All of the RNAs that do not encode for proteins are collectively called non-protein-coding RNAs (ncRNAs). Among these ncRNAs, long ncRNAs (lncRNAs) are considered as missing keys to understand the pathogeneses of various diseases, including cardiometabolic diseases. Given the increased interest in lncRNAs, in this study, we will summarize the latest trend in the lncRNA research from the perspective of cardiometabolism and disease by focusing on the major risk factors of cardiometabolic diseases: obesity, cholesterol, diabetes, and hypertension. Because genetic inheritance is unavoidable in cardiometabolic diseases, we paid special attention to the genetic factors of lncRNAs that may influence cardiometabolic diseases.

d-Arabitol Ameliorates Obesity and Metabolic Disorders via the Gut Microbiota-SCFAs-WAT Browning Axis

d-Arabitol, which is typically found in mushrooms, lichens, and higher fungi, might play an effective role in alleviating visceral fat accumulation and insulin resistance particularly for its low calorie and glycemic index. However, the regulatory mechanisms of d-arabitol for alleviating obesity and associated metabolic disorders remain poorly understood. This study aimed to investigate and analyze the underlying relationship between d-arabitol-mediated gut microbiota and obesity. The results showed that d-arabitol dramatically ameliorated body weight gain, fat accumulation, and insulin resistance in HFD-fed rats. Likewise, d-arabitol remarkably increased the relative abundance of the genera Blautia, Anaerostipes, and Phascolarctobacterium and decreased the genera Romboutsia and Clostridium_sensu_stricto_1. Furthermore, these alterations in gut microflora increased SCFAs, which in turn indirectly promoted AMPK-PGC-1α-related white adipose tissue (WAT) browning. Therefore, d-arabitol would have the potential to alleviate obesity through the gut microbiota-SCFAs-WAT browning axis. It could be considered as a sugar substitute for the obese population and diabetic patients.

Imaging Brown Adipose Tissue with TSPO PET Tracers in Preclinical Animal Studies

Brown adipose tissue (BAT) is closely associated with thermogenesis and related to numerous diseases, including type 2 diabetes, nonalcoholic fatty liver disease (NAFLD), and obesity. Using molecular imaging technologies to monitor BAT could facilitate etiology elucidation, disease diagnosis, and therapeutics development. Translocator protein (TSPO), an 18 kDa protein that mainly locates on the outer mitochondrial membrane, has been proven as a promising biomarker for monitoring BAT mass. Here, we lay out the steps for imaging BAT with TSPO PET tracer [¹⁸F]-DPA in mouse studies.

Sex differences in thermoregulation in mammals: Implications for energy homeostasis

Thermal homeostasis is a fundamental process in mammals, which allows the maintenance of a constant internal body temperature to ensure an efficient function of cells despite changes in ambient temperature. Increasing evidence has revealed the great impact of thermoregulation on energy homeostasis. Homeothermy requires a fine regulation of food intake, heat production, conservation and dissipation and energy expenditure. A great interest on this field of research has re-emerged following the discovery of thermogenic brown adipose tissue and browning of white fat in adult humans, with a potential clinical relevance on obesity and metabolic comorbidities. However, most of our knowledge comes from male animal models or men, which introduces unwanted biases on the findings. In this review, we discuss how differences in sex-dependent characteristics (anthropometry, body composition, hormonal regulation, and other sexual factors) influence numerous aspects of thermal regulation, which impact on energy homeostasis. Individuals of both sexes should be used in the experimental paradigms, considering the ovarian cycles and sexual hormonal regulation as influential factors in these studies. Only by collecting data in both sexes on molecular, functional, and clinical aspects, we will be able to establish in a rigorous way the real impact of thermoregulation on energy homeostasis, opening new avenues in the understanding and treatment of obesity and metabolic associated diseases.

Of mice and men: Pinpointing species differences in adipose tissue biology

The prevalence of obesity and metabolic diseases continues to rise, which has led to an increased interest in studying adipose tissue to elucidate underlying disease mechanisms. The use of genetic mouse models has been critical for understanding the role of specific genes for adipose tissue function and the tissue’s impact on other organs. However, mouse adipose tissue displays key differences to human fat, which has led, in some cases, to the emergence of some confounding concepts in the adipose field. Such differences include the depot-specific characteristics of visceral and subcutaneous fat, and divergences in thermogenic fat phenotype between the species. Adipose tissue characteristics may therefore not always be directly compared between species, which is important to consider when setting up new studies or interpreting results. This mini review outlines our current knowledge about the cell biological differences between human and mouse adipocytes and fat depots, highlighting some examples where inadequate knowledge of species-specific differences can lead to confounding results, and presenting plausible anatomic explanations that may underlie the differences. The article thus provides critical insights and guidance for researchers working primarily with only human or mouse fat tissue, and may contribute to new ideas or concepts in the important and evolving field of adipose biology.

Browning of the white adipose tissue regulation: new insights into nutritional and metabolic relevance in health and diseases

Adipose tissues are dynamic tissues that play crucial physiological roles in maintaining health and homeostasis. Although white adipose tissue and brown adipose tissue are currently considered key endocrine organs, they differ functionally and morphologically. The existence of the beige or brite adipocytes, cells displaying intermediary characteristics between white and brown adipocytes, illustrates the plastic nature of the adipose tissue. These cells are generated through white adipose tissue browning, a process associated with augmented non-shivering thermogenesis and metabolic capacity. This process involves the upregulation of the uncoupling protein 1, a molecule that uncouples the respiratory chain from Adenosine triphosphate synthesis, producing heat. β-3 adrenergic receptor system is one important mediator of white adipose tissue browning, during cold exposure. Surprisingly, hyperthermia may also induce beige activation and white adipose tissue beiging. Physical exercising copes with increased levels of specific molecules, including Beta-Aminoisobutyric acid, irisin, and Fibroblast growth factor 21 (FGF21), which induce adipose tissue browning. FGF21 is a stress-responsive hormone that interacts with beta-klotho. The central roles played by hormones in the browning process highlight the relevance of the individual lifestyle, including circadian rhythm and diet. Circadian rhythm involves the sleep-wake cycle and is regulated by melatonin, a hormone associated with UCP1 level upregulation. In contrast to the pro-inflammatory and adipose tissue disrupting effects of the western diet, specific food items, including capsaicin and n-3 polyunsaturated fatty acids, and dietary interventions such as calorie restriction and intermittent fasting, favor white adipose tissue browning and metabolic efficiency. The intestinal microbiome has also been pictured as a key factor in regulating white tissue browning, as it modulates bile acid levels, important molecules for the thermogenic program activation. During embryogenesis, in which adipose tissue formation is affected by Bone morphogenetic proteins that regulate gene expression, the stimuli herein discussed influence an orchestra of gene expression regulators, including a plethora of transcription factors, and chromatin remodeling enzymes, and non-coding RNAs. Considering the detrimental effects of adipose tissue browning and the disparities between adipose tissue characteristics in mice and humans, further efforts will benefit a better understanding of adipose tissue plasticity biology and its applicability to managing the overwhelming burden of several chronic diseases.

The metabolic and molecular mechanisms of α‑mangostin in cardiometabolic disorders (Review)

α‑mangostin is a xanthone predominantly encountered in Garcinia mangostana. Extensive research has been carried out concerning the effects of this compound on various diseases, including obesity, cancer and metabolic disorders. The present review suggests that α‑mangostin exerts promising anti‑obesity, hepatoprotective, antidiabetic, cardioprotective, antioxidant and anti‑inflammatory effects on various pathways in cardiometabolic diseases. The anti‑obesity effects of α‑mangostin include the reduction of body weight and adipose tissue size, the increase in fatty acid oxidation, the activation of hepatic AMP‑activated protein kinase and Sirtuin‑1, and the reduction of peroxisome proliferator‑activated receptor γ expression. Hepatoprotective effects have been revealed, due to reduced fibrosis through transforming growth factor‑β 1 pathways, reduced apoptosis and steatosis through reduced sterol regulatory‑element binding proteins expression. The antidiabetic effects include decreased fasting blood glucose levels, improved insulin sensitivity and the increased expression of GLUT transporters in various tissues. Cardioprotection is exhibited through the restoration of cardiac functions and structure, improved mitochondrial functions, the promotion of M2 macrophage populations, reduced endothelial and cardiomyocyte apoptosis and fibrosis, and reduced acid sphingomyelinase activity and ceramide depositions. The antioxidant effects of α‑mangostin are mainly related to the modulation of antioxidant enzymes, the reduction of oxidative stress markers, the reduction of oxidative damage through a reduction in Sirtuin 3 expression mediated by phosphoinositide 3‑kinase/protein kinase B/peroxisome proliferator‑activated receptor‑γ coactivator‑1α signaling pathways, and to the increase in Nuclear factor‑erythroid factor 2‑related factor 2 and heme oxygenase‑1 expression levels. The anti‑inflammatory effects of α‑mangostin include its modulation of nuclear factor‑κB related pathways, the suppression of mitogen‑activated protein kinase activation, increased macrophage polarization to M2, reduced inflammasome occurrence, increased Sirtuin 1 and 3 expression, the reduced expression of inducible nitric oxide synthase, the production of nitric oxide and prostaglandin E2, the reduced expression of Toll‑like receptors and reduced proinflammatory cytokine levels. These effects demonstrate that α‑mangostin may possess the properties required for a suitable candidate compound for the management of cardiometabolic diseases.

Sexual Dimorphism in Brown Adipose Tissue Activation and White Adipose Tissue Browning

The present narrative review gathers the studies reported so far, addressing sex differences in the effects of cold exposure, feeding pattern and age on brown adipose tissue (BAT) thermogenesis and white adipose tissue (WAT) browning. In rodents, when exposed to decreasing temperatures, females activate thermogenesis earlier. Results obtained in humans go in the same line, although they do not provide results as solid as those obtained in rodents. Regarding the effects of overfeeding, interesting sex differences on BAT thermogenic capacity have been reported, and the greater or lower sensitivity of each sex to this dietary situation seems to be dependent on the type of feeding. In the case of energy restriction, females are more sensitive than males. In addition, sex differences have also been observed in thermogenesis changes induced by phenolic compound administration. During sexual development, an increase in BAT mass and BAT activity takes place. This phenomenon is greater in boys than in girls, probably due to its relation to muscle-mass growth. The opposite situation takes place during ageing, a lifespan period where thermogenic capacity declines, this being more acute in men than in women. Finally, the vast majority of the studies have reported a higher susceptibility to developing WAT browning amongst females. The scarcity of results highlights the need for further studies devoted to analysing this issue, in order to provide valuable information for a more personalised approach.

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.

Weighted Gene Co-expression Network Analysis Revealed That CircMARK3 Is a Potential CircRNA Affects Fat Deposition in Buffalo

Background

Buffalo meat is increasingly widely accepted for consumption as it shares several quality attributes with cattle meat (beef). Hence, there is a huge opportunity for growth in the buffalo meat industry. However, buffalo meat has relatively low intramuscular fat (IMF) content, affecting its flavor, tenderness and juiciness. As there is a dearth of information on factors that control fat deposition, this study was undertaken to provide new candidate factor associated with buffalo fat deposition. Circular RNA (circRNA) is a novel class of non-coding RNA with a closed-loop structure, and play an important role in fat deposition.

Methods

In this study, weighted gene co-expression network analysis (WGCNA) was used to construct a circRNA co-expression network and revealed a candidate circRNA that may affect the IMF deposition of buffalo as determined by RT-qPCR, semiquantitative PCR and gain-of-function experiments.

Results

Herein, WGCNA determined that one module (turquoise module) is significantly associated with the growth and development stages of buffalo. Further analysis revealed a total of 191 overlapping circRNAs among differentially expressed (DE) circRNAs and the co-expression module. A candidate circRNA was found, 21:6969877|69753491 (circRNA_ID), with a reported involvement in lipid metabolism. This circRNA is stably expressed and originates from the MARK3 gene, hence the name circMARK3. circMARK3 is highly expressed in adipose tissue and mature adipocytes and is located in the cytoplasm. Gain-of-function experiments demonstrated that circMARK3 promoted adipogenic differentiation of buffalo adipocytes and 3T3-L1 cells by up-regulating the expression levels of adipogenic marker genes PPARG, C/EBPα and FABP4.

Conclusion

These results indicate that circMARK3 is a potential factor that promotes fat deposition by regulating adipocyte differentiation and adipogenesis in buffalo.

Physical exercise and the functions of microRNAs

MicroRNAs (miRNAs) control RNA translation and are a class of small, tissue-specific, non-protein-coding RNAs that maintain cellular homeostasis through negative gene regulation. Maintenance of the physiological environment depends on the proper control of miRNA expression, as these molecules influence almost all genetic pathways, from the cell cycle checkpoint to cell proliferation and apoptosis, with a wide range of target genes. Dysregulation of the expression of miRNAs is correlated with several types of diseases, acting as regulators of cardiovascular functions, myogenesis, adipogenesis, osteogenesis, hepatic lipogenesis, and important brain functions. miRNAs can be modulated by environmental factors or external stimuli, such as physical exercise, and can eventually induce specific and adjusted changes in the transcriptional response. Physical exercise is used as a preventive and non-pharmacological treatment for many diseases. It is well established that physical exercise promotes various benefits in the human body such as muscle hypertrophy, mental health improvement, cellular apoptosis, weight loss, and inhibition of cell proliferation. This review highlights the current knowledge on the main miRNAs altered by exercise in the skeletal muscle, cardiac muscle, bone, adipose tissue, liver, brain, and body fluids. In addition, knowing the modifications induced by miRNAs and relating them to the results of prescribed physical exercise with different protocols and intensities can serve as markers of physical adaptation to training and responses to the effects of physical exercise for some types of chronic diseases. This narrative review consists of randomized exercise training experiments with humans and/or animals, combined with analyses of miRNA modulation.

Silk Hydrogel-Mediated Delivery of Bone Morphogenetic Protein 7 Directly to Subcutaneous White Adipose Tissue Increases Browning and Energy Expenditure

Objective: Increasing the mass and/or activity of brown adipose tissue (BAT) is one promising avenue for treating obesity and related metabolic conditions, given that BAT has a high potential for energy expenditure and is capable of improving glucose and lipid homeostasis. BAT occurs either in discrete "classical" depots, or interspersed in white adipose tissue (WAT), termed "inducible/recruitable" BAT, or 'beige/brite' adipocytes. We and others have demonstrated that bone morphogenetic protein 7 (BMP7) induces brown adipogenesis in committed and uncommitted progenitor cells, resulting in increased energy expenditure and reduced weight gain in mice. BMP7 is therefore a reliable growth factor to induce browning of WAT. Methods: In this study, we sought to deliver BMP7 specifically to subcutaneous (sc)WAT in order to induce tissue-resident progenitor cells to differentiate into energy-expending recruitable brown adipocytes, without off-target effects like bone formation, which can occur when BMPs are in the presence of bone progenitor cells (outside of WAT). BMP7 delivery directly to WAT may also promote tissue innervation, or directly activate mitochondrial activity in brown adipocytes, as we have demonstrated previously. We utilized silk protein in the form of an injectable hydrogel carrying BMP7. Silk scaffolds are useful for in vivo delivery of substances due to favorable material properties, including controlled release of therapeutic proteins in an active form, biocompatibility with minimal immunogenic response, and prior FDA approval for some medical materials. For this study, the silk was engineered to meet desirable release kinetics for BMP7 in order to mimic our prior in vitro brown adipocyte differentiation studies. Fluorescently-labeled silk hydrogel loaded with BMP7 was directly injected into WAT through the skin and monitored by non-invasive in vivo whole body imaging, including in UCP1-luciferase reporter mice, thereby enabling an approach that is translatable to humans. Results: Injection of the BMP7-loaded silk hydrogels into the subcutaneous WAT of mice resulted in "browning", including the development of multilocular, uncoupling protein 1 (UCP1)-positive brown adipocytes, and an increase in whole-body energy expenditure and skin temperature. In diet-induced obese mice, BMP7-loaded silk delivery to subcutaneous WAT resulted in less weight gain, reduced circulating glucose and lower respiratory exchange ratio (RER). Conclusions: In summary, BMP7 delivery via silk scaffolds directly into scWAT is a novel translational approach to increase browning and energy expenditure, and represents a potential therapeutic avenue for delivering substances directly to adipose depots in pursuit of metabolic treatments.

Preoperative Short-Term High Carbohydrate Diet Provides More High-Quality Transplantable Fat and Improves the Outcome of Fat Grafts in Mice

BACKGROUND

Patients with a low body mass index may have inadequate high-quality adipose tissue for transplantation. The influence of high-energy diets on adipose tissue and graft retention remains unknown.

OBJECTIVES

We explored inguinal fat pad alternation in mice fed on a short-time high-fat diet (HFD) or a high-carbohydrate diet (HCD) preoperatively and the morphological and histological differences after transplantation.

METHODS

Mice were fed HFD (60% kilocalories from fat, 20% from carbohydrate), HCD (9.3% kilocalories from fat, 80.1% from carbohydrate), or normal (12% kilocalories from fat, 67% kilocalories from carbohydrate) diets for 2 or 4 weeks. Histological analyses were carried out following hematoxylin and eosin staining, and CD34 and proliferating cell nuclear antigen immunostaining. The uncoupling protein-1 (UCP-1) expression was determined by western blotting. Fat pads from each group were grafted into the dorsal region of the recipient mice and morphological and histological changes were determined 4, 8, and 12 weeks post-transplantation. Vascular endothelial growth factor α and platelet-derived growth factor α expression were determined using quantitative polymerase chain reaction.

RESULTS

The inguinal fat pad volume increased in the HFD and HCD groups. The presence of multilocular adipocytes in inguinal fat of HCD-fed mice, combined with the increased UCP-1 content, suggested adipocyte browning. HCD grafts showed higher volume retention and reduced oil cyst formation, possibly attributed to better angiogenesis and adipogenesis.

CONCLUSIONS

HCD enlarged adipose tissue and improved grafts survival rates, which may be due to the browning of fat before grafting and enhanced angiogenesis after grafting.

Extract of Ephedra sinica Stapf Induces Browning of Mouse and Human White Adipocytes

Browning of adipocytes using herbal extracts is an attractive and realistic strategy for obesity treatment. Ephedra sinica Stapf (E. sinica) is an Asian traditional medicine known to activate brown adipocytes. To evaluate the effect of E. sinica (EEs) on the browning of white adipocytes, expression levels of browning markers, including uncoupling protein 1 (UCP1), were determined using qPCR, Western blot, and immunocytochemistry after mature mouse inguinal preadipocyte (mIPA) and human adipose-derived stem cells (hADSCs) were treated with EEs. In addition, mitochondrial activity was determined by analyzing MitoTracker staining, mtDNA copy number, and oxygen consumption rate (OCR). Treatment with EEs suppressed lipid accumulation and expression levels of adipogenic markers, including Pparg, during mIPA differentiation. In mature mIPA and hADSCs browning markers, including Ucp1, were up-regulated by EEs. In addition, EEs increased expression of mitochondrial genes, mtDNA copy number, and OCR. EEs showed a dual function: inhibiting adipogenesis in immature preadipocytes, and promoting thermogenesis via browning in mature white adipocytes. Therefore, E. sinica is a potential herb for regulating energy metabolism by inducing the browning process.

Hypothalamic control of energy expenditure and thermogenesis

Energy expenditure and energy intake need to be balanced to maintain proper energy homeostasis. Energy homeostasis is tightly regulated by the central nervous system, and the hypothalamus is the primary center for the regulation of energy balance. The hypothalamus exerts its effect through both humoral and neuronal mechanisms, and each hypothalamic area has a distinct role in the regulation of energy expenditure. Recent studies have advanced the understanding of the molecular regulation of energy expenditure and thermogenesis in the hypothalamus with targeted manipulation techniques of the mouse genome and neuronal function. In this review, we elucidate recent progress in understanding the mechanism of how the hypothalamus affects basal metabolism, modulates physical activity, and adapts to environmental temperature and food intake changes.

The hypothalamus is a key regulator of metabolism, controlling resting metabolism, activity levels, and responses to external temperature and food intake. The balance between energy intake and expenditure must be tightly controlled, with imbalances resulting in metabolic disorders such as obesity or diabetes. Obin Kwon at Seoul National University College of Medicine and Ki Woo Kim at Yonsei University College of Dentistry, Seoul, both in South Korea, and coworkers reviewed how metabolism is regulated by the hypothalamus, a small hormone-producing brain region. They report that hormonal and neuronal signals from the hypothalamus influence the ratio of lean to fatty tissue, gender-based differences in metabolism, activity levels, and weight gain in response to food intake. They note that further studies to untangle cause-and-effect relationships and other genetic factors will improve our understanding of metabolic regulation.

Endocrine Disruptors and Obesity: an Overview

Obesity is a growing pandemic. Endocrine-disrupting chemicals are widespread in the environment. In this perspective, the authors examine the issue related to the exposure to several chemicals with endocrine-disrupting properties as promoting factors to obesity. Data show that Phthalates, Bisphenol compounds, Persistent Organic Pollutants (POPs), solvents, and personal care products can modify metabolic properties in a dose-response and sex-specific manner. Phthalates and bisphenol compounds increase body mass index, waist circumference, waist to height ratio, and the sum of skinfold thicknesses in women and not in men. Low-dose exposure to Persistent Organic Pollutants is strongly associated with increased body mass index in men and decreased this parameter in women. The mechanism through which these compounds act on anthropometric parameters is not entirely understood. Several studies suggest a possible interference in gonadotropin secretion and the thyroid axis. These inspire a decrease of both total and free testosterone levels in men and FT3 and FT4 levels in women, particularly after a pregnancy. The impact of endocrine disruptor chemicals on adipose tissue inflammation and future cardio-metabolic disorders remains to be elucidated. Therefore, studies involving both healthy and obese individuals are needed to unambiguously confirm results from in vitro and animal models.

Adipose tissue: a neglected organ in the response to severe trauma?

Despite the manifold recent efforts to improve patient outcomes, trauma still is a clinical and socioeconomical issue of major relevance especially in younger people. The systemic immune reaction after severe injury is characterized by a strong pro- and anti-inflammatory response. Besides its functions as energy storage depot and organ-protective cushion, adipose tissue regulates vital processes via its secretion products. However, there is little awareness of the important role of adipose tissue in regulating the posttraumatic inflammatory response. In this review, we delineate the local and systemic role of adipose tissue in trauma and outline different aspects of adipose tissue as an immunologically active modifier of inflammation and as an immune target of injured remote organs after severe trauma.

WT1 in Adipose Tissue: From Development to Adult Physiology

Much of the fascination of the Wilms tumor protein (WT1) emanates from its unique roles in development and disease. Ubiquitous Wt1 deletion in adult mice causes multiple organ failure including a reduction of body fat. WT1 is expressed in fat cell progenitors in visceral white adipose tissue (WAT) but detected neither in energy storing subcutaneous WAT nor in heat producing brown adipose tissue (BAT). Our recent findings indicate that WT1 represses thermogenic genes and maintains the white adipose identity of visceral fat. Wt1 heterozygosity in mice is associated with molecular and morphological signs of browning including elevated levels of uncoupling protein 1 (UCP1) in epididymal WAT. Compared to their wild-type littermates, Wt1 heterozygous mice exhibit significantly improved whole-body glucose tolerance and alleviated hepatic steatosis under high-fat diet. Partial protection of heterozygous Wt1 knockout mice against metabolic dysfunction is presumably related to browning of their epididymal WAT. In the light of recent advancements, this article reviews the role of WT1 in the development of visceral WAT and its supposed function as a regulator of white adipose identity.

Bioenergetic Aspects of Mitochondrial Actions of Thyroid Hormones

Much is known, but there is also much more to discover, about the actions that thyroid hormones (TH) exert on metabolism. Indeed, despite the fact that thyroid hormones are recognized as one of the most important regulators of metabolic rate, much remains to be clarified on which mechanisms control/regulate these actions. Given their actions on energy metabolism and that mitochondria are the main cellular site where metabolic transformations take place, these organelles have been the subject of extensive investigations. In relatively recent times, new knowledge concerning both thyroid hormones (such as the mechanisms of action, the existence of metabolically active TH derivatives) and the mechanisms of energy transduction such as (among others) dynamics, respiratory chain organization in supercomplexes and cristes organization, have opened new pathways of investigation in the field of the control of energy metabolism and of the mechanisms of action of TH at cellular level. In this review, we highlight the knowledge and approaches about the complex relationship between TH, including some of their derivatives, and the mitochondrial respiratory chain.

Browning Epicardial Adipose Tissue: Friend or Foe?

The epicardial adipose tissue (EAT) is the visceral fat depot of the heart which is highly plastic and in direct contact with myocardium and coronary arteries. Because of its singular proximity with the myocardium, the adipokines and pro-inflammatory molecules secreted by this tissue may directly affect the metabolism of the heart and coronary arteries. Its accumulation, measured by recent new non-invasive imaging modalities, has been prospectively associated with the onset and progression of coronary artery disease (CAD) and atrial fibrillation in humans. Recent studies have shown that EAT exhibits beige fat-like features, and express uncoupling protein 1 (UCP-1) at both mRNA and protein levels. However, this thermogenic potential could be lost with age, obesity and CAD. Here we provide an overview of the physiological and pathophysiological relevance of EAT and further discuss whether its thermogenic properties may serve as a target for obesity therapeutic management with a specific focus on the role of immune cells in this beiging phenomenon.

Wt1 haploinsufficiency induces browning of epididymal fat and alleviates metabolic dysfunction in mice on high-fat diet

AIMS/HYPOTHESIS

Despite a similar fat storing function, visceral (intra-abdominal) white adipose tissue (WAT) is detrimental, whereas subcutaneous WAT is considered to protect against metabolic disease. Recent findings indicate that thermogenic genes, expressed in brown adipose tissue (BAT), can be induced primarily in subcutaneous WAT. Here, we investigate the hypothesis that the Wilms tumour gene product (WT1), which is expressed in intra-abdominal WAT but not in subcutaneous WAT and BAT, suppresses a thermogenic program in white fat cells.

METHODS

Heterozygous Wt1 knockout mice and their wild-type littermates were examined in terms of thermogenic and adipocyte-selective gene expression. Glucose tolerance and hepatic lipid accumulation in these mice were assessed under normal chow and high-fat diet conditions. Pre-adipocytes isolated from the stromal vascular fraction of BAT were transduced with Wt1-expressing retrovirus, induced to differentiate and analysed for the expression of thermogenic and adipocyte-selective genes.

RESULTS

Expression of the thermogenic genes Cpt1b and Tmem26 was enhanced and transcript levels of Ucp1 were on average more than tenfold higher in epididymal WAT of heterozygous Wt1 knockout mice compared with wild-type mice. Wt1 heterozygosity reduced epididymal WAT mass, improved whole-body glucose tolerance and alleviated severe hepatic steatosis upon diet-induced obesity in mice. Retroviral expression of WT1 in brown pre-adipocytes, which lack endogenous WT1, reduced mRNA levels of Ucp1, Ppargc1a, Cidea, Prdm16 and Cpt1b upon in vitro differentiation by 60-90%. WT1 knockdown in epididymal pre-adipocytes significantly lowered Aldh1a1 and Zfp423 transcripts, two key suppressors of the thermogenic program. Conversely, Aldh1a1 and Zfp423 mRNA levels were increased approximately five- and threefold, respectively, by retroviral expression of WT1 in brown pre-adipocytes.

CONCLUSION/INTERPRETATION

WT1 functions as a white adipocyte determination factor in epididymal WAT by suppressing thermogenic genes. Reducing Wt1 expression in this and other intra-abdominal fat depots may represent a novel treatment strategy in metabolic disease.

Helminth and Host Crosstalk: New Insight Into Treatment of Obesity and Its Associated Metabolic Syndromes

Obesity and its associated Metabolic Syndromes (Mets) represent a global epidemic health problem. Metabolic inflammation, lipid accumulation and insulin resistance contribute to the progression of these diseases, thereby becoming targets for drug development. Epidemiological data have showed that the rate of helminth infection negatively correlates with the incidence of obesity and Mets. Correspondingly, numerous animal experiments and a few of clinic trials in human demonstrate that helminth infection or its derived molecules can mitigate obesity and Mets via induction of macrophage M2 polarization, inhibition of adipogenesis, promotion of fat browning, and improvement of glucose tolerance, insulin resistance and metabolic inflammation. Interestingly, sporadic studies also uncover that several helminth infections can reshape gut microbiota of hosts, which is intimately implicated in the pathogenesis of obesity and Mets. Overall, these findings indicate that the crosstalk between helminth and hosts may be a novel direction for obesity and Mets therapy. The present article reviews the molecular mechanism of how helminth masters immunity and metabolism in obesity.

Delivery of miRNAs to the adipose organ for metabolic health

Despite the increasing prevalence of obesity and diabetes, there is no efficient treatment to combat these epidemics. The adipose organ is the main site for energy storage and plays a pivotal role in whole body lipid metabolism and energy homeostasis, including remodeling and dysfunction of adipocytes and adipose tissues in obesity and diabetes. Thus, restoring and balancing metabolic functions in the adipose organ is in demand. MiRNAs represent a novel class of drugs and drug targets, as they are heavily involved in the regulation of many cellular and metabolic processes and diseases, likewise in adipocytes. In this review, we summarize key regulatory activities of miRNAs in the adipose organ, discuss various miRNA replacement and inhibition strategies, promising delivery systems for miRNAs and reflect the future of novel miRNA-based therapeutics to target adipose tissues with the ultimate goal to combat metabolic disorders.

Withaferin A Promotes White Adipose Browning and Prevents Obesity Through Sympathetic Nerve-Activated Prdm16-FATP1 Axis

The increasing prevalence of obesity has resulted in demands for the development of new effective strategies for obesity treatment. Withaferin A (WA) shows a great potential for prevention of obesity by sensitizing leptin signaling in the hypothalamus. However, the mechanism underlying the weight- and adiposity-reducing effects of WA remains to be elucidated. In this study, we report that WA treatment induced white adipose tissue (WAT) browning, elevated energy expenditure, decreased respiratory exchange ratio, and prevented high-fat diet-induced obesity. The sympathetic chemical denervation dampened the WAT browning and also impeded the reduction of adiposity in WA-treated mice. WA markedly upregulated the levels of Prdm16 and FATP1 (Slc27a1) in the inguinal WAT (iWAT), and this was blocked by sympathetic denervation. Prdm16 or FATP1 knockdown in iWAT abrogated the WAT browning-inducing effects of WA and restored the weight gain and adiposity in WA-treated mice. Together, these findings suggest that WA induces WAT browning through the sympathetic nerve-adipose axis, and the adipocytic Prdm16-FATP1 pathway mediates the promotive effects of WA on white adipose browning.