Transforming growth factor beta superfamily regulation of adipose tissue biology in obesity

Identification of key modules in metabolic syndrome induced by second-generation antipsychotics based on co-expression network analysis

Background

Second-generation antipsychotics (SGAs) frequently cause metabolic syndrome (MetS), which raises the risk of heart disease, type 2 diabetes, morbid obesity, atherosclerosis, and hypertension. MetS also impairs cognitive function in patients with schizophrenia. However, the fundamental reasons of MetS caused by SGAs are not yet fully understood. Thus, we aimed to identify potential therapeutic targets for MetS induced by SGAs.

Methods

The serum biochemical parameters and the RNA-sequencing of peripheral blood mononuclear cells were measured in three groups (healthy controls and patients with schizophrenia with and without MetS taking SGAs). The study of the weighted gene co-expression network was utilized to pinpoint modules that were significantly connected to clinical markers.

Results

Statistical analysis showed significant differences in triglyceride and high-density lipoprotein among the three groups. The TNF signaling pathway, TGF-β signaling pathway, fatty acid metabolism, NF-kappa B signaling pathway, MAPK signaling pathway, and Toll-like receptor signaling pathway were the pathways that were primarily enriched in the two unique co-expression network modules that were found. Finally, five specific genes (TNF, CXCL8, IL1B, TIMP1, and ESR1) associated with metabolism and immunity pathways were identified.

Conclusions

This study indicated that SGAs differentially induced MetS of patients with schizophrenia through metabolic and inflammation-related pathways. Therefore, the potential side effects of drugs on inflammatory processes need to be considered when using SGAs for the treatment of schizophrenia.

The signaling pathways in obesity-related complications

Obesity, a rapidly expanding epidemic worldwide, is known to exacerbate many medical conditions, making it a significant factor in multiple diseases and their associated complications. This threatening epidemic is linked to various harmful conditions such as type 2 diabetes mellitus, hypertension, metabolic dysfunction-associated steatotic liver disease, polycystic ovary syndrome, cardiovascular diseases (CVDs), dyslipidemia, and cancer. The rise in urbanization and sedentary lifestyles creates an environment that fosters obesity, leading to both psychosocial and medical complications. To identify individuals at risk and ensure timely treatment, it is crucial to have a better understanding of the pathophysiology of obesity and its comorbidities. This comprehensive review highlights the relationship between obesity and obesity-associated complications, including type 2 diabetes, hypertension, (CVDs), dyslipidemia, polycystic ovary syndrome, metabolic dysfunction-associated steatotic liver disease, gastrointestinal complications, and obstructive sleep apnea. It also explores the potential mechanisms underlying these associations. A thorough analysis of the interplay between obesity and its associated complications is vital in developing effective therapeutic strategies to combat the exponential increase in global obesity rates and mitigate the deadly consequences of this polygenic condition.

Longitudinal analysis of epigenome-wide DNA methylation reveals novel loci associated with BMI change in East Asians

BACKGROUND

Obesity is a global public health concern linked to chronic diseases such as cardiovascular disease and type 2 diabetes (T2D). Emerging evidence suggests that epigenetic modifications, particularly DNA methylation, may contribute to obesity. However, the molecular mechanism underlying the longitudinal change of BMI has not been well-explored, especially in East Asian populations.

METHODS

This study performed a longitudinal epigenome-wide association analysis of DNA methylation to uncover novel loci associated with BMI change in 533 individuals across two Chinese cohorts with repeated DNA methylation and BMI measurements over four years.

RESULTS

We identified three novel CpG sites (cg14671384, cg25540824, and cg10848724) significantly associated with BMI change. Two of the identified CpG sites were located in regions previously associated with body shape and basal metabolic rate. Annotation of the top 20 BMI change-associated CpGs revealed strong connections to obesity and T2D. Notably, these CpGs exhibited active regulatory roles and located in genes with high expression in the liver and digestive tract, suggesting a potential regulatory pathway from genome to phenotypes of energy metabolism and absorption via DNA methylation. Cross-sectional and longitudinal EWAS comparisons indicated different mechanisms between CpGs related to BMI and BMI change.

CONCLUSION

This study enhances our understanding of the epigenetic dynamics underlying BMI change and emphasizes the value of longitudinal analyses in deciphering the complex interplay between epigenetics and obesity.

Targeting Metabolic Syndrome Pathways: Carrot microRNAs As Potential Modulators

Metabolic syndrome is a condition characterized by metabolic alterations that culminate in chronic noncommunicable diseases of high morbidity and mortality, such as cardiovascular diseases, type 2 diabetes, nonalcoholic fatty liver disease, and colon cancer. Developing new therapeutic strategies with a multifactorial approach is important since current therapies focus on only one or two components of the metabolic syndrome. In this sense, plant-based gene regulation represents an innovative strategy to prevent or modulate human metabolic pathologies, including metabolic syndrome. Here, using a computational and systems biology approach, it was found that carrot microRNAs can modulate key BMPs/SMAD signaling members, C/EBPs, and KLFs involved in several aspects associated with metabolic syndrome, including the hsa04350:TGF-beta signaling pathway, hsa04931:insulin resistance, hsa04152:AMPK signaling pathway, hsa04933:AGE-RAGE signaling pathway in diabetic complications, hsa04010:MAPK signaling pathway, hsa04350:TGF-beta signaling pathway, hsa01522:endocrine resistance, and hsa04910:insulin signaling pathway. These data demonstrated the potential applications of carrot microRNAs as effective food-based therapeutics for obesity and associated metabolic diseases.

Pro- and anti-inflammatory cytokines are the game-changers in childhood obesity-associated metabolic disorders (diabetes and non-alcoholic fatty liver diseases)

Childhood obesity is a chronic inflammatory epidemic that affects children worldwide. Obesity affects approximately 1 in 5 children worldwide. Obesity in children can worsen weight gain and raise the risk of obesity-related comorbidities like diabetes and non-alcoholic fatty liver disease (NAFLD). It can also negatively impact the quality of life for these children. Obesity disrupts immune system function, influencing cytokine (interleukins) balance and expression levels, adipokines, and innate and adaptive immune cells. The altered expression of immune system mediators, including interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-17 (IL-17), interleukin-18 (IL-18), transforming growth factor (TGF), tumor necrosis factor (TNF), and others, caused inflammation, progression, and the development of pediatric obesity and linked illnesses such as diabetes and NAFLD. Furthermore, anti-inflammatory cytokines, including interleukin-2 (IL-2), have been shown to have anti-diabetes and IL-1 receptor antagonist (IL-1Ra) anti-diabetic and pro-NAFLFD properties, and interleukin-10 (IL-10) has been shown to have a dual role in managing diabetes and anti-NAFLD. In light of the substantial increase in childhood obesity-associated disorders such as diabetes and NAFLD and the absence of an effective pharmaceutical intervention to inhibit immune modulation factors, it is critical to consider the alteration of immune system components as a preventive and therapeutic approach. Thus, the current review focuses on the most recent information regarding the influence of pro- and anti-inflammatory cytokines (interleukins) and their molecular mechanisms on pediatric obesity-associated disorders (diabetes and NAFLD). Furthermore, we discussed the current therapeutic clinical trials in childhood obesity-associated diseases, diabetes, and NAFLD.

Extracellular matrix hyaluronan modulates fat cell differentiation and primary cilia dynamics

Hyaluronan is an important extracellular matrix component, with poorly documented physiological role in the context of lipid-rich adipose tissue. We have investigated the global impact of hyaluronan removal from adipose tissue environment by in vitro exposure to exogenous hyaluronidase (or heat inactivated enzyme). Gene set expression analysis from RNA sequencing revealed downregulated adipogenesis as a main response to hyaluronan removal from human adipose tissue samples, which was confirmed by hyaluronidase-mediated inhibition of adipocyte differentiation in the 3T3L1 adipose cell line. Hyaluronidase exposure starting from the time of induction with the differentiation cocktail reduced lipid accumulation in mature adipocytes, limited the expression of terminal differentiation marker genes, and impaired the early induction of co-regulated Cebpa and Pparg mRNA. Reduction of Cebpa and Pparg expression by exogenous hyaluronidase was also observed in cultured primary preadipocytes from subcutaneous, visceral or brown adipose tissue of mice. Mechanistically, inhibition of adipogenesis by hyaluronan removal was not caused by changes in osmotic pressure or cell inflammatory status, could not be mimicked by exposure to threose, a metabolite generated by hyaluronan degradation, and was not linked to alteration in endogenous Wnt ligands expression. Rather, we observed that hyaluronan removal associated with disrupted primary cilia dynamics, with elongated cilium and higher proportions of preadipocytes that remained ciliated in hyaluronidase-treated conditions. Thus, our study points to a new link between ciliogenesis and hyaluronan impacting adipose tissue development.

Glycosaminoglycan dermatan sulfate supplementation decreases diet-induced obesity and metabolic dysfunction in mice

Glycosaminoglycans are complex carbohydrates used as nutraceuticals for diverse applications. We studied the potential of the glycosaminoglycan dermatan sulfate (DS) to counteract the development of diet-induced obesity (DIO) using obesity-prone mice fed a high-fat diet (HFD) as a model. Oral DS supplementation protected the animals against HFD-induced increases in whole-body adiposity, visceral fat mass, adipocyte size, blood glucose levels, insulin resistance, and pro-inflammatory lipids levels in brown adipose tissue (BAT) and the liver, where it largely counteracted the HFD-induced changes in the nonpolar metabolome. Protection against DIO in the DS-supplemented mice occurred despite higher energy intake and appeared to be associated with increased energy expenditure, higher uncoupling protein 1 expression in BAT, decreased BAT "whitening," and an enhanced channeling of fuel substrates toward skeletal muscle. This work is the first preclinical study to examine the anti-obesity activity of DS tested individually in vivo. The results support possible uses of DS as an active component in functional foods/supplements to manage obesity and associated metabolic diseases.

Effects of 12 Weeks of Daily Melatonin Administration on Inflammatory Markers and Adipose Tissue Mass of Rats under Hypoestrogenism

Background and Objectives: The hormonal state of hypoestrogenism is associated with the accumulation of white adipose tissue, which can induce an increase in pro-inflammatory markers, leading to progressive health complications. Melatonin can act on adipose tissue mass, promoting its reduction and influencing inflammation, reducing IL-6 and releasing IL-10, pro- and anti-inflammatory markers, respectively. However, the role of melatonin regarding such parameters under the context of hypoestrogenism remains unknown. The aim of this study was to determine the effect of 12 weeks of hypoestrogenism and melatonin on white adipose tissue mass and circulating levels of IL-6, IL-10, TGF-β-1, and leukotriene C4 (LTC4). Materials and Methods: The animals (Wistar rats with sixteen weeks of age at the beginning of the experiment) under hypoestrogenism were submitted to the surgical technique of bilateral ovariectomy. The animals received melatonin (10 mg·kg-1) or vehicles by orogastric gavage every day for 12 weeks and administration occurred systematically 1 h after the beginning of the dark period. White adipose tissue (perigonadal, peritoneal, and subcutaneous) was collected for mass recording, while blood was collected for the serum determination of IL-6, IL-10, TGF-β-1, and LTC4. Results: Hypoestrogenism increased the perigonadal and subcutaneous mass and IL-6 levels. Melatonin kept hypoestrogenic animals in physiological conditions similar to the control group and increased thymus tissue mass. Conclusions: Hypoestrogenism appears to have a negative impact on white adipose tissue mass and IL-6 and although melatonin commonly exerts a significant effect in preventing these changes, this study did not have a sufficiently negative impact caused by hypoestrogenism for melatonin to promote certain benefits.

TGF-β, IL-1β, IL-6 levels and TGF-β/Smad pathway reactivity regulate the link between allergic diseases, cancer risk, and metabolic dysregulations

The risk of cancer is higher in patients with asthma compared to those with allergic rhinitis for many types of cancer, except for certain cancers where a contrasting pattern is observed. This study offers a potential explanation for these observations, proposing that the premalignant levels of circulating transforming growth factor-β (TGF-β), IL-1β, and IL-6 as well as the reactivity of the TGF-β/Smad signaling pathway at the specific cancer site, are crucial factors contributing to the observed disparities. Circulating TGF-β, IL- β and IL-6 levels also help clarify why asthma is positively associated with obesity, Type 2 diabetes, hypertension, and insulin resistance, whereas allergic rhinitis is negatively linked to these conditions. Furthermore, TGF-β/Smad pathway reactivity explains the dual impact of obesity, increasing the risk of certain types of cancer while offering protection against other types of cancer. It is suggested that the association of asthma with cancer and metabolic dysregulations is primarily linked to the subtype of neutrophilic asthma. A binary classification of TGF-β activity as either high (in the presence of IL-1β and IL-6) or low (in the presence or absence of IL-1β and IL-6) is proposed to differentiate between allergy patients prone to cancer and metabolic dysregulations and those less prone. Glycolysis and oxidative phosphorylation, the two major metabolic pathways utilized by cells for energy exploitation, potentially underlie this dichotomous classification by reprogramming metabolic pathways in immune cells.

Adipose tissue depot specific expression and regulation of fibrosis-related genes and proteins in experimental obesity

Transforming growth factor beta (Tgfb) is a well-studied pro-fibrotic cytokine, which upregulates cellular communication network factor 2 (Ccn2), collagen, and actin alpha 2, smooth muscle (Acta2) expression. Obesity induces adipose tissue fibrosis, which contributes to metabolic diseases. This work aimed to analyze the expression of Tgfb, Ccn2, collagen1a1 (Col1a1), Acta2 and BMP and activin membrane-bound inhibitor (Bambi), which is a negative regulator of Tgfb signaling, in different adipose tissue depots of mice fed a standard chow, mice fed a high fat diet (HFD) and ob/ob mice. Principally, these genes were low expressed in brown adipose tissues and this difference was less evident for the ob/ob mice. Ccn2 and Bambi protein as well as mRNA expression, and collagen1a1 mRNA were not induced in the adipose tissues upon HFD feeding whereas Tgfb and Acta2 mRNA increased in the white fat depots. Immunoblot analysis showed that Acta2 protein was higher in subcutaneous and perirenal fat of these mice. In the ob/ob mice, Ccn2 mRNA and Ccn2 protein were upregulated in the fat depots. Here, Tgfb, Acta2 and Col1a1 mRNA levels and serum Tgfb protein were increased. Acta2 protein was, however, not higher in subcutaneous and perirenal fat of these mice. Col6a1 mRNA was shown before to be higher in obese fat tissues. Current analysis proved the Col6a1 protein was induced in subcutaneous fat of HFD fed mice. Notably, Col6a1 was reduced in perirenal fat of ob/ob mice in comparison to the respective controls. 3T3-L1 cells express Ccn2 and Bambi protein, whose levels were not changed by fatty acids, leptin, lipopolysaccharide, tumor necrosis factor and interleukin-6. All of these factors led to higher Tgfb in 3T3-L1 adipocyte media but did not increase its mRNA levels. Free fatty acids induced necrosis whereas apoptosis did not occur in any of the in vitro incubations excluding cell death as a main reason for higher Tgfb in cell media. In summary, Tgfb mRNA is consistently induced in white fat tissues in obesity but this is not paralleled by a clear increase of its target genes. Moreover, discrepancies between mRNA and protein expression of Acta2 were observed. Adipocytes seemingly do not contribute to higher Tgfb mRNA levels in obesity. These cells release more Tgfb protein when challenged with obesity-related metabolites connecting metabolic dysfunction and fibrosis.

The role of zinc finger proteins in the fate determination of mesenchymal stem cells during osteogenic and adipogenic differentiation

Zinc finger proteins (ZFPs) constitute a crucial group of transcription factors widely present in various organisms. They act as transcription factors, nucleases, and RNA-binding proteins, playing significant roles in cell differentiation, growth, and development. With extensive research on ZFPs, their roles in the determination of mesenchymal stem cells (MSCs) fate during osteogenic and adipogenic differentiation processes have become increasingly clear. ZFP521, for instance, is identified as an inhibitor of the Wnt signaling pathway and RUNX2's transcriptional activity, effectively suppressing osteogenic differentiation. Moreover, ZFP217 contributes to the inhibition of adipogenic differentiation by reducing the M6A level of the cell cycle regulator cyclin D1 (CCND1). In addition, other ZFPs can also influence the fate of mesenchymal stem cells (MSCs) during osteogenic and adipogenic differentiation through various signaling pathways, transcription factors, and epigenetic controls, participating in the subsequent differentiation and maturation of precursor cells. Given the prevalent occurrence of osteoporosis, obesity, and related metabolic disorders, a comprehensive understanding of the regulatory mechanisms balancing bone and fat metabolism is essential, with a particular focus on the fate determination of MSCs in osteogenic and adipogenic differentiation. In this review, we provide a detailed summary of how zinc finger proteins influence the osteogenic and adipogenic differentiation of MSCs through different signaling pathways, transcription factors, and epigenetic mechanisms. Additionally, we outline the regulatory mechanisms of ZFPs in controlling osteogenic and adipogenic differentiation based on various stages of MSC differentiation.

Resveratrol promotes the differentiation of human umbilical cord mesenchymal stem cells into esophageal fibroblasts via AKT signaling pathway

Objectives: Resveratrol has been implicated in the differentiation and development of human umbilical cord mesenchymal stem cells. The differentiation of into esophageal fibroblasts is a promising strategy for esophageal tissue engineering. However, the pharmacological effect and underlying mechanism of resveratrol on human umbilical cord mesenchymal stem cells differentiation are unknown. Here, we investigated the effects and mechanism of resveratrol on the differentiation of human umbilical cord mesenchymal stem cells. Methods: Using a transwell-membrane coculture system to culture human umbilical cord mesenchymal stem cells and esophageal fibroblasts, we examined how resveratrol act on the differentiation of human umbilical cord mesenchymal stem cells. Immunocytochemistry, Sirius red staining, quantitative real-time PCR, and Western blotting were performed to examine collagen synthesis and possible signaling pathways in human umbilical cord mesenchymal stem cells. Results: We found that resveratrol promoted collagen synthesis and AKT phosphorylation. However, co-treatment of cells with resveratrol and the PI3K inhibitor LY294002 inhibited collagen synthesis and AKT phosphorylation. We demonstrated that resveratrol down-regulated the expression of IL-6, TGF-β, caspase-9, and Bax by activating the AKT pathway in human umbilical cord mesenchymal stem cell. Furthermore, resveratrol inhibited phosphorylated NF-ĸB in human umbilical cord mesenchymal stem cells. Conclusion: Our data suggest that resveratrol promotes the differentiation of human umbilical cord mesenchymal stem cells into fibroblasts. The underlying mechanism is associated with the downregulation of IL-6 and TGF-β via the AKT pathway and by inhibiting the NF-ĸB pathway. Resveratrol may be useful for esophageal tissue engineering.

Hepatic Activin E mediates liver-adipose inter-organ communication, suppressing adipose lipolysis in response to elevated serum fatty acids

OBJECTIVE

The liver is a central regulator of energy metabolism exerting its influence both through intrinsic processing of substrates such as glucose and fatty acid as well as by secreting endocrine factors, known as hepatokines, which influence metabolism in peripheral tissues. Human genome wide association studies indicate that a predicted loss-of-function variant in the Inhibin βE gene (INHBE), encoding the putative hepatokine Activin E, is associated with reduced abdominal fat mass and cardiometabolic disease risk. However, the regulation of hepatic Activin E and the influence of Activin E on adiposity and metabolic disease are not well understood. Here, we examine the relationship between hepatic Activin E and adipose metabolism, testing the hypothesis that Activin E functions as part of a liver-adipose, inter-organ feedback loop to suppress adipose tissue lipolysis in response to elevated serum fatty acids and hepatic fatty acid exposure.

METHODS

The relationship between hepatic Activin E and non-esterified fatty acids (NEFA) released from adipose lipolysis was assessed in vivo using fasted CL 316,243 treated mice and in vitro using Huh7 hepatocytes treated with fatty acids. The influence of Activin E on adipose lipolysis was examined using a combination of Inhbe knockout mice, a mouse model of hepatocyte-specific overexpression of Activin E, and mouse brown adipocytes treated with Activin E enriched media.

RESULTS

Increasing hepatocyte NEFA exposure in vivo by inducing adipose lipolysis through fasting or CL 316,243 treatment increased hepatic Inhbe expression. Similarly, incubation of Huh7 human hepatocytes with fatty acids increased expression of INHBE. Genetic ablation of Inhbe in mice increased fasting circulating NEFA and hepatic triglyceride accumulation. Treatment of mouse brown adipocytes with Activin E conditioned media and overexpression of Activin E in mice suppressed adipose lipolysis and reduced serum FFA levels, respectively. The suppressive effects of Activin E on lipolysis were lost in CRISPR-mediated ALK7 deficient cells and ALK7 kinase deficient mice. Disruption of the Activin E-ALK7 signaling axis in Inhbe KO mice reduced adiposity upon HFD feeding, but caused hepatic steatosis and insulin resistance.

CONCLUSIONS

Taken together, our data suggest that Activin E functions as part of a liver-adipose feedback loop, such that in response to increased serum free fatty acids and elevated hepatic triglyceride, Activin E is released from hepatocytes and signals in adipose through ALK7 to suppress lipolysis, thereby reducing free fatty acid efflux to the liver and preventing excessive hepatic lipid accumulation. We find that disrupting this Activin E-ALK7 inter-organ communication network by ablation of Inhbe in mice increases lipolysis and reduces adiposity, but results in elevated hepatic triglyceride and impaired insulin sensitivity. These results highlight the liver-adipose, Activin E-ALK7 signaling axis as a critical regulator of metabolic homeostasis.

Cardiac-to-adipose axis in metabolic homeostasis and diseases: special instructions from the heart

Adipose tissue is essential for maintaining systemic metabolic homeostasis through traditional metabolic regulation, endocrine crosstalk, and extracellular vesicle production. Adipose dysfunction is a risk factor for cardiovascular diseases. The heart is a traditional pump organ. However, it has recently been recognized to coordinate interorgan cross-talk by providing peripheral signals known as cardiokines. These molecules include specific peptides, proteins, microRNAs and novel extracellular vesicle-carried cargoes. Current studies have shown that generalized cardiokine-mediated adipose regulation affects systemic metabolism. Cardiokines regulate lipolysis, adipogenesis, energy expenditure, thermogenesis during cold exposure and adipokine production. Moreover, cardiokines participate in pathological processes such as obesity, diabetes and ischemic heart injury. The underlying mechanisms of the cardiac-to-adipose axis mediated by cardiokines will be further discussed to provide potential therapeutic targets for metabolic diseases and support a new perspective on the need to correct adipose dysfunction after ischemic heart injury.

Differential effects of sugar and fat on adipose tissue inflammation

Obese individuals experience low grade inflammation initiated within their adipose tissue. However, the early events that lead to the release of these inflammatory factors from adipose tissue are poorly characterized. To separate glucose effects from lipid effects on adipose tissue, we used an adipose-specific TXNIP knockout model where excess basal glucose influx into adipocytes led to modest increase in adiposity without using high fat diet. We found an uncoupling of two events that are generally presumed to be coregulated: (1) an increase of adipose tissue macrophage (ATM) number; and (2) pro-inflammatory activation of ATMs. These two events are associated with different triggering signals: elevated free fatty acids output and extracellular matrix remodeling with increased ATM number, whereas decreased adiponectin level with activated ATM. This separation reflects non-overlapping pathways regulated by glucose and lipids in adipocytes, and neither group alone is sufficient to elicit the full inflammatory response in adipose tissue.

Extracellular Matrix Expression in Human Pancreatic Fat Cells of Patients with Normal Glucose Regulation, Prediabetes and Type 2 Diabetes

Previously, we found that human pancreatic preadipocytes (PPAs) and islets influence each other and that the crosstalk with the fatty liver via the hepatokine fetuin-A/palmitate induces inflammatory responses. Here, we examined whether the mRNA-expression of pancreatic extracellular matrix (ECM)-forming and -degrading components differ in PPAs from individuals with normal glucose regulation (PPAs-NGR), prediabetes (PPAs-PD), and type 2 diabetes (PPAs-T2D), and whether fetuin-A/palmitate impacts ECM-formation/degradation and associated monocyte invasion. Human pancreatic resections were analyzed (immuno)histologically. PPAs were studied for mRNA expression by real-time PCR and protein secretion by Luminex analysis. Furthermore, co-cultures with human islets and monocyte migration assays in Transwell plates were conducted. We found that in comparison with NGR-PPAs, TIMP-2 mRNA levels were lower in PPAs-PD, and TGF-β1 mRNA levels were higher in PPAs-T2D. Fetuin-A/palmitate reduced fibronectin, decorin, TIMP-1/-2 and TGF-ß1 mRNA levels. Only fibronectin was strongly downregulated by fetuin-A/palmitate independently of the glycemic status. Co-culturing of PPAs with islets increased TIMP-1 mRNA expression in islets. Fetuin-A/palmitate increased MMP-1, usherin and dermatopontin mRNA-levels in co-cultured islets. A transmigration assay showed increased monocyte migration towards PPAs, which was enhanced by fetuin-A/palmitate. This was more pronounced in PPAs-T2D. The expression of distinct ECM components differs in PPAs-PD and PPAs-T2D compared to PPAs-NGR, suggesting that ECM alterations can occur even in mild hyperglycemia. Fetuin-A/palmitate impacts on ECM formation/degradation in PPAs and co-cultured islets. Fetuin-A/palmitate also enhances monocyte migration, a process which might impact on matrix turnover.

In vivo effects of low dose prenatal bisphenol A exposure on adiposity in male and female ICR offspring

BACKGROUND

Bisphenol A (BPA) is known to exhibit endocrine disrupting activities and is associated with adiposity. We examined the obesogenic effect of prenatal BPA exposure in the present study.

METHODS

Pregnant ICR mice were exposed to vehicle or BPA via the drinking water at a dose of 0.5 μg/kg·d throughout the gestation. Obesity-related indexes were investigated in the 12-wk-old offspring. Primary mouse embryonic fibroblasts (MEFs) collected from treated embryos were used to test effects of BPA on adipocyte differentiation.

RESULTS

Offspring presented a significantly higher rate of weight gain than the control, with impaired insulin sensitivity and increased adipocyte size. Differentiation of MEFs from BPA-treated mice showed a higher propensity for the adipocyte commitment as well as up-regulation of genes enriched in lipid biosynthesis. TGF-β signaling pathway was found to modulate obesogenic effect of BPA in MEF model, but estrogen signaling pathway had no effect.

CONCLUSIONS

The present study provides strong evidence of the association between prenatal exposure to low dose of BPA and a significant increase in body weight in the offspring mice with a critical role played by TGF-β signaling pathway. The potential interactions modulating the binding of BPA and TGF-β that activate its obesogenic effects need to be examined.

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.

The Role of Oxidative Stress and Inflammation in Obesity and Its Impact on Cognitive Impairments-A Narrative Review

Obesity is a chronic low-grade inflammatory condition that induces the generation of oxidative stress and inflammation. This oxidative stress and inflammation stimulate brain atrophy and some morphological changes in the brain that eventually result in cognitive impairments. However, there is no exact study that has summarized the role of oxidative stress and inflammation in obesity and its impact on cognitive impairments. Thus, the objective of this review is to recapitulate the current role of oxidative stress and inflammation in cognitive decline based on in vivo evidence. A comprehensive search was performed in Nature, Medline and Ovid, ScienceDirect, and PubMed, and the search was limited to the past 10 years of publication. From the search, we identified 27 articles to be further reviewed. The outcome of this study indicates that a greater amount of fat stored in individual adipocytes in obesity induces the formation of reactive oxygen species and inflammation. This will lead to the generation of oxidative stress, which may cause morphological changes in the brain, suppress the endogenous antioxidant system, and promote neuroinflammation and, eventually, neuronal apoptosis. This will impair the normal function of the brain and specific regions that are involved in learning, as well as memory. This shows that obesity has a strong positive correlation with cognitive impairments. Hence, this review summarizes the mechanism of oxidative stress and inflammation that induce memory loss based on animal model evidence. In conclusion, this review may serve as an insight into therapeutic development focusing on oxidative stress and inflammatory pathways to manage an obesity-induced cognitive decline in the future.

Adipose tissue specific CCL18 associates with cardiometabolic diseases in non-obese individuals implicating CD4+ T cells

AIM

Obesity is linked to cardiometabolic diseases, however non-obese individuals are also at risk for type 2 diabetes (T2D) and cardiovascular disease (CVD). White adipose tissue (WAT) is known to play a role in both T2D and CVD, but the contribution of WAT inflammatory status especially in non-obese patients with cardiometabolic diseases is less understood. Therefore, we aimed to find associations between WAT inflammatory status and cardiometabolic diseases in non-obese individuals.

METHODS

In a population-based cohort containing non-obese healthy (n = 17), T2D (n = 16), CVD (n = 18), T2D + CVD (n = 19) individuals, seventeen different cytokines were measured in WAT and in circulation. In addition, 13-color flow cytometry profiling was employed to phenotype the immune cells. Human T cell line (Jurkat T cells) was stimulated by rCCL18, and conditioned media (CM) was added to the in vitro cultures of human adipocytes. Lipolysis was measured by glycerol release. Blocking antibodies against IFN-γ and TGF-β were used in vitro to prove a role for these cytokines in CCL18-T-cell-adipocyte lipolysis regulation axis.

RESULTS

In CVD, T2D and CVD + T2D groups, CCL18 and CD4+ T cells were upregulated significantly compared to healthy controls. WAT CCL18 secretion correlated with the amounts of WAT CD4+ T cells, which also highly expressed CCL18 receptors suggesting that WAT CD4+ T cells are responders to this chemokine. While direct addition of rCCL18 to mature adipocytes did not alter the adipocyte lipolysis, CM from CCL18-treated T cells increased glycerol release in in vitro cultures of adipocytes. IFN-γ and TGF-β secretion was significantly induced in CM obtained from T cells treated with CCL18. Blocking these cytokines in CM, prevented CM-induced upregulation of adipocyte lipolysis.

CONCLUSION

We suggest that in T2D and CVD, increased production of CCL18 recruits and activates CD4+ T cells to secrete IFN-γ and TGF-β. This, in turn, promotes adipocyte lipolysis - a possible risk factor for cardiometabolic diseases.

Brown adipose tissue transcriptome unveils an important role of the Beta-alanine/alamandine receptor, MrgD, in metabolism

Alamandine is a recently described heptapeptide component of the renin-angiotensin system (RAS), and its effects are mediated by the receptor Mas-related G protein-coupled receptor D (MrgD) RAS represents an important link between obesity and its consequences by directly modulating the thermogenesis and brown adipose tissue (BAT) function. The alamandine/MrgD metabolic effects and signaling remain unexplored. In this context, the main goal of the present study was to assess the metabolic consequences of MrgD genetic ablation in C57BL6/J mice by evaluating brown adipose tissue RNA sequencing. The main results showed that MrgD-KO mice have diminished brown adipose tissue and that a high-glucose diet (HG) decreased both circulating alamandine levels and MrgD expression in BAT from wild-type mice (WT). BAT transcriptome reveals that MrgD-KO HG mice regulated 45 genes, while WT HG mice regulated 1,148 genes. MrgD-KO mice fed a standard diet (ST) compared with WT ST mice regulated 476 genes, of which 445 genes were downregulated. BAT uses the MrgD receptor to display a normal pattern of gene expression and to respond, like WT mice, to an HG diet. In conclusion, the MrgD signaling is important for the metabolic regulation and manutention of BAT functionality.

Fat-to-heart crosstalk in health and disease

According to the latest World Health Organization statistics, cardiovascular disease (CVD) is one of the leading causes of death globally. Due to the rise in the prevalence of major risk factors, such as diabetes mellitus and obesity, the burden of CVD is expected to worsen in the decades to come. Whilst obesity is a major and consistent risk factor for CVD, the underlying pathological molecular communication between peripheral fat depots and the heart remains poorly understood. Adipose tissue (AT) is a major endocrine organ in the human body, with composite cells producing and secreting hormones, cytokines, and non-coding RNAs into the circulation to alter the phenotype of multiple organs, including the heart. Epicardial AT (EAT) is an AT deposit that is in direct contact with the myocardium and can therefore influence cardiac function through both mechanical and molecular means. Moreover, resident and recruited immune cells comprise an important adipose cell type, which can create a pro-inflammatory environment in the context of obesity, potentially contributing to systemic inflammation and cardiomyopathies. New mechanisms of fat-to-heart crosstalk, including those governed by non-coding RNAs and extracellular vesicles, are being investigated to deepen the understanding of this highly common risk factor. In this review, molecular crosstalk between AT and the heart will be discussed, with a focus on endocrine and paracrine signaling, immune cells, inflammatory cytokines, and inter-organ communication through non-coding RNAs.

The impact of adipokines on vascular networks in adipose tissue

Adipose tissue (AT) is a highly active and plastic endocrine organ. It secretes numerous soluble molecules known as adipokines, which act locally to AT control the remodel and homeostasis or exert pleiotropic functions in different peripheral organs. Aberrant production or loss of certain adipokines contributes to AT dysfunction associated with metabolic disorders, including obesity. The AT plasticity is strictly related to tissue vascularization. Angiogenesis supports the AT expansion, while regression of blood vessels is associated with AT hypoxia, which in turn mediates tissue inflammation, fibrosis and metabolic dysfunction. Several adipokines can regulate endothelial cell functions and are endowed with either pro- or anti-angiogenic properties. Here we address the role of adipokines in the regulation of angiogenesis. A better understanding of the link between adipokines and angiogenesis will open the way for novel therapeutic approaches to treat obesity and metabolic diseases.

Mitochondrial Energy Metabolism in the Regulation of Thermogenic Brown Fats and Human Metabolic Diseases

Brown fats specialize in thermogenesis by increasing the utilization of circulating blood glucose and fatty acids. Emerging evidence suggests that brown adipose tissue (BAT) prevents the incidence of obesity-associated metabolic diseases and several types of cancers in humans. Mitochondrial energy metabolism in brown/beige adipocytes regulates both uncoupling protein 1 (UCP1)-dependent and -independent thermogenesis for cold adaptation and the utilization of excess nutrients and energy. Many studies on the quantification of human BAT indicate that mass and activity are inversely correlated with the body mass index (BMI) and visceral adiposity. Repression is caused by obesity-associated positive and negative factors that control adipocyte browning, de novo adipogenesis, mitochondrial energy metabolism, UCP1 expression and activity, and noradrenergic response. Systemic and local factors whose levels vary between lean and obese conditions include growth factors, inflammatory cytokines, neurotransmitters, and metal ions such as selenium and iron. Modulation of obesity-associated repression in human brown fats is a promising strategy to counteract obesity and related metabolic diseases through the activation of thermogenic capacity. In this review, we highlight recent advances in mitochondrial metabolism, thermogenic regulation of brown fats, and human metabolic diseases.

Adipocyte coculture induces a pro-inflammatory, fibrotic, angiogenic, and proliferative microenvironment in uterine leiomyoma cells

OBJECTIVE

Obesity and its consequences are among the biggest challenges facing the healthcare system. Uterine leiomyomas are the most common gynecologic tumors. The risk of leiomyoma increases with obesity, but the underlying mechanisms of this association remain unclear. The aim of the present study to determine the cellular and molecular mechanisms by which adipocyte contributes to both leiomyoma tumor initiation and promotion.

METHODS

Primary myometrium and leiomyoma cells were isolated from patients who underwent a hysterectomy or myomectomy. Pro-inflammatory, fibrotic, and angiogenic factors were measured using a multiplex cytokine array in human primary and immortalized myometrial and leiomyoma cells cocultured with human adipocyte (SW872) cells, or in animal ELT3 leiomyoma cells cocultured with 3 T3-L1 adipocytes. The free fatty acids (FFAs) and fatty acid-binding protein 4 (FABP4) levels were measured using immunofluorescence assays. Other protein abundances were determined using western blots. The expression levels of TNF-α, MCP-1, phospho-NF-κB, TGFβ3 and VEGF-A in lean and obese in different leiomyoma patients were determined by immunofluorescence staining.

RESULTS

Adipocytes promote inflammation, fibrosis, and angiogenesis in uterine leiomyoma cells by upregulating associated factors, such as IL-1β, TNF-α, MCP-1, GM-CSF, TGF-βs, PLGF, VEGF, HB-EGF, G-CSF and FGF2. Coculture led to the transfer of FFAs and FABP4 from adipocytes to leiomyoma cells, suggesting that adipocytes may modulate metabolic activity in these tumor cells. Increased levels of FFA and FABP4 expressions were detected in obese leiomyoma tissue compared to lean. The adipocyte-leiomyoma cell interaction increased the phospho-NF-κB level, which plays a key role in inflammation, restructuring metabolic pathways, and angiogenesis. Obese leiomyoma patients expressed a higher amount of TNF-α, MCP-1, phospho-NF-κB, TGFβ3 and VEGF-A than lean leiomyoma patients, consistent with in vitro findings. Furthermore, we found that adipocyte secretory factors enhance leiomyoma cell proliferation by increasing PCNA abundance. Finally, the inhibition of the inflammatory factors TNF-α, MCP-1, and NF-κB abrogated the adipocyte coculture-induced proliferation of leiomyoma cells.

CONCLUSIONS

Adipocytes release inflammatory, fibrotic, and angiogenic factors, along with FFAs, which contribute to a tumor-friendly microenvironment that may promote leiomyoma growth and can represent a new target for leiomyoma prevention and treatment.

Bta-miR-493 Inhibits Bovine Preadipocytes Differentiation by Targeting BMPR1A via the TGFβ/BMP and p38MAPK Signaling Pathways

Fat deposition significantly impacts the meat yield and the meat quality of beef cattle, which is closely associated with the preadipocyte proliferation and differentiation. Bta-miR-493 is expressed differentially in the backfat of Qinchuan cattle of various ages, and it may be involved in the fat accumulation of beef cattle. However, the role and functional mechanism of bta-miR-493 in fat deposition are still unclear. Tissue-specific expression analysis showed that the level of bta-miR-493 was moderately abundant in the adipose tissues of beef cattle. Moreover, the expression of bta-miR-493 in perirenal fat, subcutaneous fat, and longissimus dorsi muscle of Japanese black cattle was significantly higher than that in Qinchuan cattle. EdU staining, cell counting assay, and Oil Red O staining indicated that bta-miR-493 promoted the proliferation of bovine preadipocytes but inhibited their differentiation. The dual luciferase assay and transcriptomic analysis confirmed that bone morphogenetic protein receptor 1A (BMPR1A) is a target gene of bta-miR-493. Moreover, rescue experiments showed that bta-miR-493 could promote bovine preadipocyte proliferation but inhibit their differentiation by targeting BMPR1A via the TGFβ/BMP and p38MAPK signaling pathways. Overall, our findings revealed a bta-miR-493-BMPR1A-TGFβ/BMP/p38MAPK regulatory axis that will serve as a theoretical foundation for the molecular breeding of beef cattle with high intramuscular fat deposition.

Obesity-Associated ECM Remodeling in Cancer Progression

Adipose tissue, an energy storage and endocrine organ, is emerging as an essential player for ECM remodeling. Fibrosis is one of the hallmarks of obese adipose tissue, featuring excessive ECM deposition and enhanced collagen alignment. A variety of ECM components and ECM-related enzymes are produced by adipocytes and myofibroblasts in obese adipose tissue. Data from lineage-tracing models and a single-cell analysis indicate that adipocytes can transform or de-differentiate into myofibroblast/fibroblast-like cells. This de-differentiation process has been observed under normal tissue development and pathological conditions such as cutaneous fibrosis, wound healing, and cancer development. Accumulated evidence has demonstrated that adipocyte de-differentiation and myofibroblasts/fibroblasts play crucial roles in obesity-associated ECM remodeling and cancer progression. In this review, we summarize the recent progress in obesity-related ECM remodeling, the mechanism underlying adipocyte de-differentiation, and the function of obesity-associated ECM remodeling in cancer progression.

Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity

Late eating has been linked to obesity risk. It is unclear whether this is caused by changes in hunger and appetite, energy expenditure, or both, and whether molecular pathways in adipose tissues are involved. Therefore, we conducted a randomized, controlled, crossover trial (ClinicalTrials.gov NCT02298790) to determine the effects of late versus early eating while rigorously controlling for nutrient intake, physical activity, sleep, and light exposure. Late eating increased hunger (p < 0.0001) and altered appetite-regulating hormones, increasing waketime and 24-h ghrelin:leptin ratio (p < 0.0001 and p = 0.006, respectively). Furthermore, late eating decreased waketime energy expenditure (p = 0.002) and 24-h core body temperature (p = 0.019). Adipose tissue gene expression analyses showed that late eating altered pathways involved in lipid metabolism, e.g., p38 MAPK signaling, TGF-β signaling, modulation of receptor tyrosine kinases, and autophagy, in a direction consistent with decreased lipolysis/increased adipogenesis. These findings show converging mechanisms by which late eating may result in positive energy balance and increased obesity risk.

The comprehensive detection of miRNA and circRNA in the regulation of intramuscular and subcutaneous adipose tissue of Laiwu pig

circRNAs, as miRNA sponges, participate in many important biological processes. However, it remains unclear whether circRNAs can regulate lipid metabolism. This study aimed to explore the competing endogenouse RNA (ceRNA) regulatory network that affects the difference between intramuscular fat (IMF) and subcutaneous fat (SCF) deposition, and to screen key circRNAs and their regulatory genes. In this experiment, we identified 265 differentially expressed circRNAs, of which 187 up-regulated circRNA and 78 down-regulated circRNA in IMF. Subsequently, we annotated the function of DEcircRNA's host genes, and found that DEcircRNA's host genes were mainly involved in GO terms (including cellular response to fatty acids, lysophosphatidic acid acyltransferase activity, R-SMAD binding, etc.) and signaling pathways (fatty acid biosynthesis, Citrate cycle, TGF- β Signal pathway) related to adipogenesis, differentiation and lipid metabolism. By constructing a circRNA-miRNA network, we screened out DEcircRNA that can competitively bind to more miRNAs as key circRNAs (circRNA_06424 and circRNA_08840). Through the functional annotation of indirect target genes and protein network analysis, we found that circRNA_06424 affects the expression of PPARD, MMP9, UBA7 and other indirect target genes by competitively binding to miRNAs such as ssc-miR-339-5p, ssc-miR-744 and ssc-miR-328, and participates in PPAR signaling pathway, Wnt signaling pathway, unsaturated fatty acid and other signaling pathways, resulting in the difference of fat deposition between IMF and SCF. This study provide a theoretical basis for further research investigating the differences of lipid metabolism in different adipose tissues, providing potential therapeutic targets for ectopic fat deposition and lipid metabolism diseases.

Deoxy-sphingolipids, oxidative stress, and vitamin C correlate with qualitative and quantitative patterns of small fiber dysfunction and degeneration

ABSTRACT

Defined by dysfunction or degeneration of Aδ and C fibers, small fiber neuropathies (SFNs) entail a relevant health burden. In 50% of cases, the underlying cause cannot be identified or treated. In 100 individuals (70% female individuals; mean age: 44.8 years) with an idiopathic, skin biopsy-confirmed SFN, we characterized the symptomatic spectrum and measured markers of oxidative stress (vitamin C, selenium, and glutathione) and inflammation (transforming growth factor beta, tumor necrosis factor alpha), as well as neurotoxic 1-deoxy-sphingolipids. Neuropathic pain was the most abundant symptom (95%) and cause of daily life impairment (72%). Despite the common use of pain killers (64%), the painDETECT questionnaire revealed scores above 13 points in 80% of patients. In the quantitative sensory testing (QST), a dysfunction of Aδ fibers was observed in 70% and of C fibers in 44%, affecting the face, hands, or feet. Despite normal nerve conduction studies, QST revealed Aβ fiber involvement in 46% of patients' test areas. Despite absence of diabetes mellitus or mutations in SPTLC1 or SPTLC2 , plasma 1-deoxy-sphingolipids were significantly higher in the sensory loss patient cluster when compared with those in patients with thermal hyperalgesia ( P < 0.01) or those in the healthy category ( P < 0.1), correlating inversely with the intraepidermal nerve fiber density (1-deoxy-SA: P < 0.05, 1-deoxy-SO: P < 0.01). Patients with arterial hypertension, overweight (body mass index > 25 kg/m 2 ), or hyperlipidemia showed significantly lower L-serine (arterial hypertension: P < 0.01) and higher 1-deoxy-sphingolipid levels (arterial hypertension: P < 0.001, overweight: P < 0.001, hyperlipidemia: P < 0.01). Lower vitamin C levels correlated with functional Aβ involvement ( P < 0.05). Reduced glutathione was lower in patients with Aδ dysfunction ( P < 0.05). Idiopathic SFNs are heterogeneous. As a new pathomechanism, plasma 1-deoxy-sphingolipids might link the metabolic syndrome with small fiber degeneration.

Signaling pathways in obesity: mechanisms and therapeutic interventions

Obesity is a complex, chronic disease and global public health challenge. Characterized by excessive fat accumulation in the body, obesity sharply increases the risk of several diseases, such as type 2 diabetes, cardiovascular disease, and nonalcoholic fatty liver disease, and is linked to lower life expectancy. Although lifestyle intervention (diet and exercise) has remarkable effects on weight management, achieving long-term success at weight loss is extremely challenging, and the prevalence of obesity continues to rise worldwide. Over the past decades, the pathophysiology of obesity has been extensively investigated, and an increasing number of signal transduction pathways have been implicated in obesity, making it possible to fight obesity in a more effective and precise way. In this review, we summarize recent advances in the pathogenesis of obesity from both experimental and clinical studies, focusing on signaling pathways and their roles in the regulation of food intake, glucose homeostasis, adipogenesis, thermogenesis, and chronic inflammation. We also discuss the current anti-obesity drugs, as well as weight loss compounds in clinical trials, that target these signals. The evolving knowledge of signaling transduction may shed light on the future direction of obesity research, as we move into a new era of precision medicine.

GDF11 inhibits adipogenesis and improves mature adipocytes metabolic function via WNT/β-catenin and ALK5/SMAD2/3 pathways

Objective

GDF11 is a member of the TGF‐β superfamily that was recently implicated as potential “rejuvenating” factor, which can ameliorate metabolic disorders. The main objective of the presented study was to closely characterize the role of GDF11 signaling in the glucose homeostasis and in the differentiation of white adipose tissue.

Methods

We performed microscopy imaging, biochemical and transcriptomic analyses of adipose tissues of 9 weeks old ob/ob mice and murine and human pre‐adipocyte cell lines.

Results

Our in vivo experiments employing GDF11 treatment in ob/ob mice showed improved glucose/insulin homeostasis, decreased weight gain and white adipocyte size. Furthermore, GDF11 treatment inhibited adipogenesis in pre‐adipocytes by ALK5‐SMAD2/3 activation in cooperation with the WNT/β‐catenin pathway, whose inhibition resulted in adipogenic differentiation. Lastly, we observed significantly elevated levels of the adipokine hormone adiponectin and increased glucose uptake by mature adipocytes upon GDF11 exposure.

Conclusion

We show evidence that link GDF11 to adipogenic differentiation, glucose, and insulin homeostasis, which are pointing towards potential beneficial effects of GDF11‐based “anti‐obesity” therapy.

Differences in Inflammatory Cytokine Profile in Obesity-Associated Asthma: Effects of Weight Loss

Obesity and asthma are associated with systemic inflammation maintained by mediators released by adipose tissue and lung. This study investigated the inflammatory serum mediator profile in obese subjects (O) (n = 35), non-obese asthma (NOA) patients (n = 14), obese asthmatics (OA) (n = 21) and healthy controls (HC) (n = 33). The effect of weight loss after bariatric surgery (BS) was examined in 10 OA and 31 O subjects. We analyzed serum markers including leptin, adiponectin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, ST2, IL-5, IL-9, and IL-18. Compared with HC subjects, the O group showed increased levels of leptin, TGF-β1, TNFR2, MCP-1, ezrin, YKL-40, and ST2; the OA group presented increased levels of MCP-1, ezrin, YKL-40, and IL-18, and the NOA group had increased levels of ezrin, YKL-40, IL-5, and IL-18. The higher adiponectin/leptin ratio in NOA with respect to OA subjects was the only significant difference between the two groups. IL-9 was the only cytokine with significantly higher levels in OA with respect to O subjects. TNFR2, ezrin, MCP-1, and IL-18 concentrations significantly decreased in O subjects after BS. O, OA, and NOA showed distinct patterns of systemic inflammation. Leptin and adiponectin are regulated in asthma by obesity-dependent and -independent mechanisms. Combination of asthma and obesity does not result in significant additive effects on circulating cytokine levels.

AAV-mediated BMP7 gene therapy counteracts insulin resistance and obesity

Type 2 diabetes, insulin resistance, and obesity are strongly associated and are a major health problem worldwide. Obesity largely results from a sustained imbalance between energy intake and expenditure. Therapeutic approaches targeting metabolic rate may counteract body weight gain and insulin resistance. Bone morphogenic protein 7 (BMP7) has proven to enhance energy expenditure by inducing non-shivering thermogenesis in short-term studies in mice treated with the recombinant protein or adenoviral vectors encoding BMP7. To achieve long-term BMP7 effects, the use of adeno-associated viral (AAV) vectors would provide sustained production of the protein after a single administration. Here, we demonstrated that treatment of high-fat-diet-fed mice and ob/ob mice with liver-directed AAV-BMP7 vectors enabled a long-lasting increase in circulating levels of this factor. This rise in BMP7 concentration induced browning of white adipose tissue (WAT) and activation of brown adipose tissue, which enhanced energy expenditure, and reversed WAT hypertrophy, hepatic steatosis, and WAT and liver inflammation, ultimately resulting in normalization of body weight and insulin resistance. This study highlights the potential of AAV-BMP7-mediated gene therapy for the treatment of insulin resistance, type 2 diabetes, and obesity.

Beta-hydroxybutyrate dampens adipose progenitors' profibrotic activation through canonical Tgfβ signaling and non-canonical ZFP36-dependent mechanisms

BACKGROUND/PURPOSE

Adipose tissue contains progenitor cells that contribute to beneficial tissue expansion when needed by de novo adipocyte formation (classical white or beige fat cells with thermogenic potential). However, in chronic obesity, they can exhibit an activated pro-fibrotic, extracellular matrix (ECM)-depositing phenotype that highly aggravates obesity-related adipose tissue dysfunction.

METHODS

Given that progenitors' fibrotic activation and fat cell browning appear to be antagonistic cell fates, we have examined the anti-fibrotic potential of pro-browning agents in an obesogenic condition.

RESULTS

In obese mice fed a high fat diet, thermoneutral housing, which induces brown fat cell dormancy, increases the expression of ECM gene programs compared to conventionally raised animals, indicating aggravation of obesity-related tissue fibrosis at thermoneutrality. In a model of primary cultured murine adipose progenitors, we found that exposure to β-hydroxybutyrate selectively reduced Tgfβ-dependent profibrotic responses of ECM genes like Ctgf, Loxl2 and Fn1. This effect is observed in both subcutaneous and visceral-derived adipose progenitors, as well as in 3T3-L1 fibroblasts. In 30 patients with obesity eligible for bariatric surgery, those with higher circulating β-hydroxybutyrate levels have lower subcutaneous adipose tissue fibrotic scores. Mechanistically, β-hydroxybutyrate limits Tgfβ-dependent collagen accumulation and reduces Smad2-3 protein expression and phosphorylation in visceral progenitors. Moreover, β-hydroxybutyrate induces the expression of the ZFP36 gene, encoding a post-transcriptional regulator that promotes the degradation of mRNA by binding to AU-rich sites within 3'UTRs. Importantly, complete ZFP36 deficiency in a mouse embryonic fibroblast line from null mice, or siRNA knock-down in primary progenitors, indicate that ZFP36 is required for β-hydroxybutyrate anti-fibrotic effects.

CONCLUSION

These data unravel the potential of β-hydroxybutyrate to limit adipose tissue matrix deposition, a finding that might exploited in an obesogenic context.

Beige Adipocyte as the Flame of White Adipose Tissue: Regulation of Browning and Impact of Obesity

Beige adipocyte, the third and relatively new type of adipocyte, can emerge in white adipose tissue (WAT) under thermogenic stimulations that is termed as browning of WAT. Recent studies suggest that browning of WAT deserves more attention and therapies targeting browning of WAT can be helpful for reducing obesity. Beyond the major inducers of browning, namely cold and β 3-adrenergic stimulation, beige adipocytes are affected by several factors, and excess adiposity per se may also influence the browning process. The objective of the present review is to provide an overview of recent clinical and preclinical studies on the hormonal and nonhormonal factors that affect the browning of WAT. This review further focuses on the role of obesity per se on browning process.

The Obese Brain: Mechanisms of Systemic and Local Inflammation, and Interventions to Reverse the Cognitive Deficit

Overweight and obesity are now considered a worldwide pandemic and a growing public health problem with severe economic and social consequences. Adipose tissue is an organ with neuroimmune-endocrine functions, which participates in homeostasis. So, adipocyte hypertrophy and hyperplasia induce a state of chronic inflammation that causes changes in the brain and induce neuroinflammation. Studies with obese animal models and obese patients have shown a relationship between diet and cognitive decline, especially working memory and learning deficiencies. Here we analyze how obesity-related peripheral inflammation can affect central nervous system physiology, generating neuroinflammation. Given that the blood-brain barrier is an interface between the periphery and the central nervous system, its altered physiology in obesity may mediate the consequences on various cognitive processes. Finally, several interventions, and the use of natural compounds and exercise to prevent the adverse effects of obesity in the brain are also discussed.

Exploring the genetic correlation between obesity-related traits and regional brain volumes: Evidence from UK Biobank cohort

OBJECTIVE

To determine whether there is a correlation between obesity-related variants and regional brain volumes.

METHODS

Based on a mixed linear model (MLM), we analyzed the association between 1,498 obesity-related SNPs in the GWAS Catalog and 164 regional brain volumes from 29,420 participants (discovery cohort N = 19,997, validation cohort N = 9,423) in UK Biobank. The statistically significant brain regions in association analysis were classified into 6 major neural networks (dopamine (DA) motive system, central autonomic network (CAN), cognitive emotion regulation, visual object recognition network, auditory object recognition network, and sensorimotor system). We summarized the association between obesity-related variants (metabolically healthy obesity variants, metabolically unhealthy obesity variants, and unclassified obesity-related variants) and neural networks.

RESULTS

From association analysis, we determined that 17 obesity-related SNPs were associated with 51 regional brain volumes. Several single SNPs (e.g., rs13107325-T (SLC39A8), rs1876829-C (CRHR1), and rs1538170-T (CENPW)) were associated with multiple regional brain volumes. In addition, several single brain regions (e.g., the white matter, the grey matter in the putamen, subcallosal cortex, and insular cortex) were associated with multiple obesity-related variants. The metabolically healthy obesity variants were mainly associated with the regional brain volumes in the DA motive system, sensorimotor system and cognitive emotion regulation neural networks, while metabolically unhealthy obesity variants were mainly associated with regional brain volumes in the CAN and total tissue volumes. In addition, unclassified obesity-related variants were mainly associated with auditory object recognition network and total tissue volumes. The results of MeSH (medical subject headings) enrichment analysis showed that obesity genes associated with brain structure pointed to the functional relatedness with 5-Hydroxytryptamine receptor 4 (5-HT4), growth differentiation factor 5 (GDF5), and high mobility group protein AT-hook 2 (HMGA2 protein).

CONCLUSION

In summary, we found that obesity-related variants were associated with different brain volume measures. On the basis of the multiple SNPs, we found that metabolically healthy and unhealthy obesity-related SNPs were associated with different brain neural networks. Based on our enrichment analysis, modifications of the 5-HT4 pathway might be a promising therapeutic strategy for obesity.

BMP2 increases hyperplasia and hypertrophy of bovine subcutaneous preadipocytes via BMP/SMAD signaling

The study aims to characterize functions of bone morphogenetic protein 2 (BMP2) gene in the process of subcutaneous (SQ) fat deposition of bovine, thereby providing insights into mechanisms for the use of BMP2 in fat management. Our results show that BMP2 was extensively expressed in bovine and relatively rich in adipose tissue. Exogenous BMP2 significantly enhanced proliferation of bovine preadipocytes. Consistently, si-BMP2 apparently induced cell cycle arrest at G0/G1 phase and decreased proliferation of preadipocytes. Meanwhile, exogenous BMP2 mildly enhanced preadipocyte differentiation at day 3 of differentiation, as evidenced by accelerated lipid accumulation, as well as increased mRNA and protein expressions of adipogenic key transcription factor PPARγ; contrary results about lipids were found by BMP2 interference treatment. No difference was observed concerning BMP2 or si-BMP2 treatment at day - 2 and day 0 of differentiation. Additionally, LDN-193189 (inhibitor of BMP type I receptor) pretreatment diminished the enhancement of preadipocyte proliferation and differentiation induced by BMP2, as evidenced by constant proliferation rate and PPARγ expressions. Furthermore, BMP2 markedly enhanced phosphorylation level of SMAD1/5/9, and LDN-193189 could diminish the difference caused by BMP2. Thus, our results suggest that BMP2 triggers BMP/SMAD signaling pathway, promoting both hyperplasia and hypertrophy of bovine preadipocytes.

Postnatal deletion of β-catenin in preosteoblasts regulates global energy metabolism through increasing bone resorption and adipose tissue fibrosis

Many studies revealed bone can regulate global energy metabolism and our previous study also showed that Wnt/β-catenin pathway is involved in this process. To better understand the participation of canonical Wnt pathway in energy metabolism, we examined the β-catenin knock-out (β-cat KO) mice by crossing the osterix-cre transgenic mice with β-catenin^flox/flox mice. First, we identified that postnatal deletion of β-catenin in preosteoblasts led to decreased fat mass and increased energy expenditure in mice. Osteoprotegerin administration largely rescued the decreased fat mass and partly normalized the energy expenditure accompanied by the inhibition of bone resorption. Anti-resorption with alendronate or RANKL-antibody could also partly rescued the decreased bone mass, decreased fat mass and increased energy expenditure in β-cat KO mice. We further found that the adipose cells in the inguinal fat tissue were smaller and the extracellular matrix components around adipocytes accumulated more in β-cat KO mice than their controls by histomorphology. Gene analysis by RT-PCR showed that the expression of collagen VI is 4.8 folds in adipose tissue of the β-cat KO mice compared with the control mice. We further detected the expression of cytokines which were related to fibrosis and the data showed that the level of TGF-beta1 was elevated in both of bone marrow serum and adipose tissue derived from the β-cat KO mice. After administration of TGF-beta1 neutralizing antibody, the impaired energy metabolism was partly rescued in β-cat KO mice. Besides, anti-resorption treatment and TGF-beta1 antibody could partly suppress the increased expression of genes related to fat tissue fibrosis. These results indicate that the abnormal global energy metabolism in β-cat KO mice may be attributed to increasing bone resorption and adipose tissue fibrosis.

Excess glucocorticoid exposure contributes to adipose tissue fibrosis which involves macrophage interaction with adipose precursor cells

Chronic exposure to elevated glucocorticoid levels, as seen in patients with Cushing's syndrome, can induce adipose tissue fibrosis. Macrophages play a pivotal role in adipose tissue remodelling. We used the synthetic glucocorticoid analogue dexamethasone to address glucocorticoid effects on adipose tissue fibrosis, in particular involving macrophage to preadipocyte communication. We analysed the direct effects of dexamethasone at a supra-physiological level, 0.3 µM, on gene expression of pro-fibrotic markers in human subcutaneous adipose tissue. The effects of dexamethasone on the differentiation of human SGBS preadipocytes were assessed in the presence or absence of THP1-macrophages or macrophage-conditioned medium. We measured the expression of different pro-fibrotic factors, including α-smooth muscle actin gene (ACTA2) and protein (α-SMA). Dexamethasone increased the expression of pro-fibrotic genes, e.g. CTGF, COL6A3, FN1, in adipose tissue. Macrophages abolished preadipocyte differentiation and increased the expression of the ACTA2 gene and α-SMA protein in preadipocytes after differentiation. Exposure to dexamethasone during differentiation reduced adipogenesis in preadipocytes, and elevated the expression of pro-fibrotic genes. Moreover, dexamethasone added together with macrophages further increased ACTA2 and α-SMA expression in preadipocytes, making them more myofibroblast-like. Cells differentiated in the presence of conditioned media from macrophages pretreated with or without dexamethasone had a higher expression of profibrotic genes compared to control cells. Our data suggest that macrophages promote adipose tissue fibrosis by directly interfering with preadipocyte differentiation and stimulating gene expression of pro-fibrotic factors. Excess glucocorticoid exposure also has pro-fibrotic effect on adipose tissue, but this requires the presence of macrophages.

Obesity and the Development of Lung Fibrosis

Obesity is an epidemic worldwide and the obese people suffer from a range of respiratory complications including fibrotic changes in the lung. The influence of obesity on the lung is multi-factorial, which is related to both mechanical injury and various inflammatory mediators produced by excessive adipose tissues, and infiltrated immune cells. Adiposity causes increased production of inflammatory mediators, for example, cytokines, chemokines, and adipokines, both locally and in the systemic circulation, thereby rendering susceptibility to respiratory diseases, and altered responses. Lung fibrosis is closely related to chronic inflammation in the lung. Current data suggest a link between lung fibrosis and diet-induced obesity, although the mechanism remains incomplete understood. This review summarizes findings on the association of lung fibrosis with obesity, highlights the role of several critical inflammatory mediators (e.g., TNF-α, TGF-β, and MCP-1) in obesity related lung fibrosis and the implication of obesity in the outcomes of idiopathic pulmonary fibrosis patients.

Autophagy: a molecular switch to regulate adipogenesis and lipolysis

Obesity is a complex epidemic disease caused by an imbalance of adipose tissue function that results in hyperglycemia, hyperlipidemia and insulin resistance which further develop into type 2 diabetes, cardiovascular disease and nonalcoholic fatty liver disease/nonalcoholic steatohepatitis. Adipose tissue is responsible for fat storage; white adipose tissue stores excess energy as fat for availability during starvation, whereas brown adipose tissue regulates thermogenesis through fat oxidation using uncoupling protein 1. However, hypertrophic fat storage results in inflammation and increase the chances for obesity which triggers autophagy genes and lipolytic enzymes to regulate lipid metabolism. Autophagy degrades cargo molecule with the help of lysosome and redistributes the energy back to the cell. Autophagy regulates adipocyte differentiation by modulating master regulators of adipogenesis. Adipogenesis is the process which stores excessive energy in the form of lipid droplets. Lipid droplets (LD) are dynamic cellular organelles that store toxic free-fatty acids into neutral triglycerides in adipose tissue. LD activates both lipolysis and lipophagy to degrade excess triglycerides. In obese tissue, autophagy is activated via pro-inflammatory cytokines produced by surplus fat stored in the adipose tissue. This review focused on the process of autophagy and adipogenesis and the transcription factors that regulate lipogenesis and lipolysis in the adipose tissue. We have also discussed about the importance of autophagic regulation within adipose tissue which controls the onset of obesity and its associated diseases.

microRNAs in Human Adipose Tissue Physiology and Dysfunction

In recent years, there has been a large amount of evidence on the role of microRNA (miRNA) in regulating adipose tissue physiology. Indeed, miRNAs control critical steps in adipocyte differentiation, proliferation and browning, as well as lipolysis, lipogenesis and adipokine secretion. Overnutrition leads to a significant change in the adipocyte miRNOME, resulting in adipose tissue dysfunction. Moreover, via secreted mediators, dysfunctional adipocytes may impair the function of other organs and tissues. However, given their potential to control cell and whole-body energy expenditure, miRNAs also represent critical therapeutic targets for treating obesity and related metabolic complications. This review attempts to integrate present concepts on the role miRNAs play in adipose tissue physiology and obesity-related dysfunction and data from pre-clinical and clinical studies on the diagnostic or therapeutic potential of miRNA in obesity and its related complications.

SP-1154, a novel synthetic TGF-β inhibitor, alleviates obesity and hepatic steatosis in high-fat diet-induced mice

OBJECTIVE

Obesity-induced inflamed visceral adipose tissue (VAT) secretes pro-inflammatory cytokines thereby promoting systemic inflammation and insulin resistance which further exacerbate obesity-associated nonalcoholic fatty liver disease (NAFLD). Transforming growth factor (TGF)-β /Smad3 signaling plays a crucial role in the inflammatory events within the VAT. Here, we investigate whether SP-1154, a novel synthetic verbenone derivative, can inhibit TGF-β/Smad3 signaling thereby exhibiting a therapeutic effect against obesity-induced inflamed VAT and subsequent NAFLD in high-fat diet-induced mice.

METHODS

NAFLD was induced by a high-fat diet (60% fat) for 20 weeks using the male C57BL/6 mice. SP-1154 (50 mg/kg) was orally given daily for 20 weeks. In vivo VAT- and systemic inflammation were measured by using ¹⁸F-fluorodeoxyglucose positron emission tomography and C-reactive protein levels. Both insulin tolerance- and glucose tolerance test were performed to assess the status of insulin resistance and glucose intolerance. Histological and molecular analyses were performed on harvested liver and VAT.

KEY FINDINGS

SP-1154 inhibited TGF-β/Smad3 signaling pathway and remarkably suppressed high-fat diet-induced VAT inflammation and its related systemic inflammation. Furthermore, SP-1154 significantly improved insulin sensitivity with glucose homeostasis and reduced hepatic steatosis. SP-1154 significantly improves VAT inflammation and obesity-related NAFLD.

CONCLUSION

Our novel findings support the potential use of SP-1154 as a therapeutic drug for obesity and its related NAFLD by targeting the inflamed VAT.

SMAD2 and SMAD3 differentially regulate adiposity and the growth of subcutaneous white adipose tissue

Adipose tissue is the primary site of energy storage, playing important roles in health. While adipose research largely focuses on obesity, fat also has other critical functions, producing adipocytokines and contributing to normal nutrient metabolism, which in turn play important roles in satiety and total energy homeostasis. SMAD2/3 proteins are downstream mediators of activin signaling, which regulate critical preadipocyte and mature adipocyte functions. Smad2 global knockout mice exhibit embryonic lethality, whereas global loss of Smad3 protects mice against diet-induced obesity. The direct contributions of Smad2 and Smad3 in adipose tissues, however, are unknown. Here, we sought to determine the primary effects of adipocyte-selective reduction of Smad2 or Smad3 on diet-induced adiposity using Smad2 or Smad3 "floxed" mice intercrossed with Adiponectin-Cre mice. Additionally, we examined visceral and subcutaneous preadipocyte differentiation efficiency in vitro. Almost all wild type subcutaneous preadipocytes differentiated into mature adipocytes. In contrast, visceral preadipocytes differentiated poorly. Exogenous activin A suppressed differentiation of preadipocytes from both depots. Smad2 conditional knockout (Smad2cKO) mice did not exhibit significant effects on weight gain, irrespective of diet, whereas Smad3 conditional knockout (Smad3cKO) male mice displayed a trend of reduced body weight on high-fat diet. On both diets, Smad3cKO mice displayed an adipose depot-selective phenotype, with a significant reduction in subcutaneous fat mass but not visceral fat mass. Our data suggest that Smad3 is an important contributor to the maintenance of subcutaneous white adipose tissue in a sex-selective fashion. These findings have implications for understanding SMAD-mediated, depot selective regulation of adipocyte growth and differentiation.

Functionally diverse heteromeric traps for ligands of the transforming growth factor-β superfamily

Ligands of the transforming growth factor-β (TGF-β) superfamily are important targets for therapeutic intervention but present challenges because they signal combinatorially and exhibit overlapping activities in vivo. To obtain agents capable of sequestering multiple TGF-β superfamily ligands with novel selectivity, we generated soluble, heterodimeric ligand traps by pairing the extracellular domain (ECD) of the native activin receptor type IIB (ActRIIB) alternately with the ECDs of native type I receptors activin receptor-like kinase 4 (ALK4), ALK7, or ALK3. Systematic analysis of these heterodimeric constructs by surface plasmon resonance, and comparison with their homodimeric counterparts, revealed that each type I receptor partner confers a distinct ligand-binding profile to the heterodimeric construct. Additional characterization in cell-based reporter gene assays confirmed that the heterodimeric constructs possessed different profiles of signaling inhibition in vitro, which translated into altered patterns of pharmacological activity when constructs were administered systemically to wild-type mice. Our results detail a versatile platform for the modular recombination of naturally occurring receptor domains, giving rise to inhibitory ligand traps that could aid in defining the physiological roles of TGF-β ligand sets or be directed therapeutically to human diseases arising from dysregulated TGF-β superfamily signaling.