Molecular mechanism of benzo [a] pyrene regulating lipid metabolism via aryl hydrocarbon receptor.

BACKGROUND: Benzo [a] pyrene (BaP), a potent carcinogen, has been proved that it has toxicological effects via activation the aryl hydrocarbon receptor (AhR) pathway. AhR can participate in regulating lipogenesis and lipolysis. This topic will verify whether BaP regulates lipid metabolism via AhR. METHODS: (1) C57BL/6 mice were gavaged with BaP for 12 weeks to detect serum lipids, glucose tolerance, and insulin resistance. Morphological changes in white adipose tissue (WAT) were detected by Hematoxylin and Eosin staining. The mRNA expression levels of adipogenesis-related factors included recombinant human CCAAT/enhancer binding protein alpha (C/EBPα), peroxisome proliferator-activated receptor gamma (PPARγ), and fatty acid binding protein 4 (FABP4) and inflammatory factors included nuclear factor kappa-B (NF-κB), monocyte chemotactic protein-1 (MCP-1), and tumor necrosis factor alpha (TNF-α) were detected using PCR. (2) Neutral lipid content changes in differentiated 3 T3-L1 adipocytes treated with BaP with and w/o AhR inhibitor were detected by Oil red staining. The protein expression levels of adipogenesis- and decomposition-related factors included PPARγ coactivator-1 alpha (PGC-1α), and peroxisome proliferation-activated receptor alpha (PPARα) were detected using western blotting. The mRNA expression levels of inflammatory factors were detected using PCR. RESULTS: (1) BaP inhibited body weight gain, decreased lipid content, increased lipid levels, and decreased glucose tolerance and insulin tolerance in mice; (2) BaP reduced the expressions of C/EBPα, PPARγ, FABP4, PGC-1α, and PPARα and increased the expressions of NF-κB, MCP-1, and TNF-α by activating AhR. CONCLUSION: BaP inhibit fat synthesis and oxidation while inducing inflammation by activating AhR, leading to WAT dysfunction and causing metabolic complications.

Photoperiodic modulation of ovarian metabolic, survival, proliferation and gap junction markers in adult golden hamster, Mesocricetus auratus.

Female reproductive physiology is greatly dependent on tight regulation of metabolic and survival factors. Photoperiod regulates female reproductive rhythms but very less information exists explaining whether photoperiod could modulate thyroid hormone homeostasis, metabolic/energy parameters along with survival, proliferation and gap junction proteins in the ovary of a long-day breeder, Mesocricetus auratus. Adult female hamsters were exposed to different photoperiodic regimes i.e., critical photoperiod (CP; 12.5L:11.5D), short photoperiod (SP; 8L:16D) and long photoperiod (LP; 16L:8D) for 12 weeks. LP upregulated thyroidal and gonadal activity as apparent by histoarchitecture, thyroid hormone profile [triiodothyronine (T3), thyroxin (T4) and thyroid stimulating hormone (TSH)], luteinizing hormone (LH), follicle stimulating hormone (FSH), estradiol (E2) and progesterone (P4) levels when compared with SP exposed hamsters. Further, LP increased thyroid hormone receptor-α/deiodinase-2 (TRα/Dio-2), estrogen receptor-α (ERα)/aromatase and insulin receptor/glucose transporter-4 (IR/GLUT-4) expressions in ovary. Interestingly, ovarian sirtuin-1 (SIRT-1) expression was also upregulated under LP condition along with cell proliferation (proliferating cell nuclear antigen or PCNA), survival (B cell lymphoma-2 or Bcl-2) and gap junction (connexin-43) markers when compared to SP exposed hamsters. We also noted elevated levels of circulatory leptin, insulin along with melatonin and its receptor (MT-1) in ovary under SP condition. Thus, we suggest that photoperiod plays a vital role in regulation of thyroid and reproductive hormone homeostasis along with key metabolic and survival markers in the ovary of adult golden hamsters, M. auratus providing further insight into the regulation of female reproductive seasonality in a long-day breeder.

A comprehensive morphometric study of visceral and subcutaneous adipose tissue depots in mice, hamsters and rats / Un estudio morfométrico completo de los depósitos de tejido adiposo visceral y subcutáneo en ratones, hámsters y ratas

SUMMARY: Adipose tissue morphology of different fat tissue depots can be described using the number of adipocytes and cell surface of adipocytes. This study deals with characteristics and morphometric analysis of white and brown adipose tissue depots in healthy adult laboratory mice, hamsters and rats of both sexes. The number of unilocular adipocytes in white adipose tissue differs from one adipose tissue depot to another, with the largest number of adipocytes in mice and a similar number in hamsters and rats. The smallest surface area and the largest percentage of small unilocular adipocytes were found in mice. White adipose tissue in hamsters and rats was predominantly made out of a larger percentage of medium-sized adipocytes and a smaller percentage of small and medium-sized adipocytes. Uncoupling protein 1 positive multilocular adipocytes were found in classic brown adipose tissue depots with larger percentages in mice (93.20 %) and hamsters (91.30 %), while rats had a smaller percentage (78.10 %). In white and brown adipose tissue, significant differences between species and both sexes within the same species were found, indicating the influence of sexual dimorphism. The presented morphometric results could serve as a basis for further studies concerning experimental animal models of metabolic disorders and obesity.

RESUMEN: La morfología del tejido adiposo de diferentes depósitos de tejido graso se puede describir utilizando el número de adipocitos y la superficie celular de los adipocitos. Este estudio analiza las características y el análisis morfométrico de los depósitos de tejido adiposo blanco y marrón en ratones, hamsters y ratas de laboratorio, adultos sanos de ambos sexos. El número de adipocitos uniloculares en el tejido adiposo blanco difiere de un depósito de tejido adiposo a otro, con el mayor número de adipocitos en ratones y un número similar en hámsteres y ratas. La superficie más pequeña y el mayor porcentaje de adipocitos uniloculares pequeños se encontraron en ratones. El tejido adiposo blanco en hámsteres y ratas estaba compuesto predominantemente por un mayor porcentaje de adipocitos de tamaño mediano y un porcentaje menor de adipocitos de tamaño pequeño y mediano. Los adipocitos multiloculares positivos para la proteína desacopladora 1 se encontraron en depósitos de tejido adiposo marrón clásico con mayores porcentajes en ratones (93,20 %) y hámsters (91,30 %), mientras que las ratas tenían un porcentaje menor (78,10 %). En el tejido adiposo blanco y pardo se encontraron diferencias significativas entre especies y entre ambos sexos dentro de una misma especie, lo que indica la influencia del dimorfismo sexual. Los resultados morfométricos presentados podrían servir como base para futuros estudios sobre modelos animales experimentales de trastornos metabólicos y obesidad.

Mouse model of the adipose organ: the heterogeneous anatomical characteristics.

Adipose tissue plays a pivotal role in energy storage, hormone secretion, and temperature control. Mammalian adipose tissue is largely divided into white adipose tissue and brown adipose tissue, although recent studies have discovered the existence of beige adipocytes. Adipose tissues are widespread over the whole body and each location shows distinctive metabolic features. Mice are used as a representative experimental model system in metabolic studies due to their numerous advantages. Importantly, the adipose tissues of experimental animals and humans are not perfectly matched, and each adipose tissue exhibits both similar and specific characteristics. Nevertheless, the diversity and characteristics of mouse adipose tissue have not yet been comprehensively summarized. This review summarizes diverse information about the different types of adipose tissue being studied in mouse models. The types and characteristics of adipocytes were described, and each adipose tissue was classified by type, and features such as its distribution, origin, differences from humans, and metabolic characteristics were described. In particular, the distribution of widely studied adipose tissues was illustrated so that researchers can comprehensively grasp its location. Also, the adipose tissues misused or confusingly used among researchers were described. This review will provide researchers with comprehensive information and cautions needed to study adipose tissues in mouse models.

Thymic stromal lymphopoietin induces adipose loss through sebum hypersecretion.

Emerging studies indicate that the immune system can regulate systemic metabolism. Here, we show that thymic stromal lymphopoietin (TSLP) stimulates T cells to induce selective white adipose loss, which protects against obesity, improves glucose metabolism, and mitigates nonalcoholic steatohepatitis. Unexpectedly, adipose loss was not caused by alterations in food intake, absorption, or energy expenditure. Rather, it was induced by the excessive loss of lipids through the skin as sebum. TSLP and T cells regulated sebum release and sebum-associated antimicrobial peptide expression in the steady state. In human skin, TSLP expression correlated directly with sebum-associated gene expression. Thus, we establish a paradigm in which adipose loss can be achieved by means of sebum hypersecretion and uncover a role for adaptive immunity in skin barrier function through sebum secretion.

Sex differences on adipose tissue remodeling: from molecular mechanisms to therapeutic interventions.

Sexual dimorphism greatly influences adipose tissue remodeling, which is characterized by changes in the activity, number, and/or size of adipocytes in response to distinct stimuli, including lifestyle and anti-obesity drugs. This sex dependence seems to be due to the anatomical and endocrine disparities between men and women. At the molecular level, sex hormones are believed to mediate such differences and involve estrogen and androgen receptor-induced gene expression. The signaling pathways that regulate adipose tissue metabolism and function include peroxisome proliferator-activated receptor gamma, uncoupling protein 1 (UCP1), 5' adenosine monophosphate-activated protein kinase (AMPK), and mitochondrial oxidative phosphorylation (OXPHOS), among other molecular players. Sex hormone-related pathways also interplay with adrenergic signaling, probably the most well-characterized molecular mechanism implicated in the remodeling of white adipose tissue. This review overviews and integrates the signaling pathways behind sexual dimorphism in adipose tissue remodeling, hoping to increase the knowledge on the pathogenesis of diseases, such as obesity and related comorbidities, and consequently, to drive future studies to investigate the regulation of this tissue homeostasis, either in men or women.

Electroacupuncture Regulates Inguinal White Adipose Tissue Browning by Promoting Sirtuin-1-Dependent PPARγ Deacetylation and Mitochondrial Biogenesis.

Background: Previous studies had suggested that electroacupuncture (EA) can promote white adipose tissue (WAT) browning to counter obesity. But the mechanism was still not very clear. Aim: In this study, we aim to study the effect of EA on promoting inguinal WAT (iWAT) browning and its possible mechanism. Method: Three-week-old rats were randomly divided into a normal diet (ND) group and a high-fat diet (HFD) group. After 10 weeks, the HFD rats were grouped into HFD + EA group and HFD control group. Rats in the EA group were electro-acupunctured for 4 weeks on Tianshu (ST25) acupoint under gas anesthesia with isoflurane, while the rats in HFD group were under gas anesthesia only. Body weight and cumulative food intake were monitored, and H&E staining was performed to assess adipocyte area. The effect of EA on WAT was assessed by qPCR, immunoblotting, immunoprecipitation and Co-immunoprecipitation. Mitochondria were isolated from IWAT to observe the expression of mitochondrial transcription factor A (TFAM). Results: The body weight, WAT/body weight ratio and cumulative food consumption obviously decreased (P < 0.05) in the EA group. The expressions of brown adipose tissue (BAT) markers were increased in the iWAT of EA rats. Nevertheless, the mRNA expressions of WAT genes were suppressed by 4-week EA treatment. Moreover, EA increased the protein expressions of SIRT-1, PPARγ, PGC-1α, UCP1 and PRDM16 which trigger the molecular conversion of iWAT browning. The decrease of PPARγ acetylation was also found in EA group, indicating EA could advance WAT-browning through SIRT-1 dependent PPARγ deacetylation pathway. Besides, we found that EA could activate AMPK to further regulate PGC-1α-TFAM-UCP1 pathway to induce mitochondrial biogenesis. Conclusion: In conclusion, EA can remodel WAT to BAT through inducing SIRT-1 dependent PPARγ deacetylation, and regulating PGC-1α-TFAM-UCP1 pathway to induce mitochondrial biogenesis. This may be one of the mechanisms by which EA affects weight loss.

Duration of a "Brown-Like" Phenotype of White Adipose Tissue Induced by the ß3 Agonist CL-316,243.

"Browning" i. e. the transformation of white adipose tissue into brown-like adipose tissue could induce efficient burning of excess fat reserves via induction of non-shivering thermogenesis. For example, activation of ß3 adrenergic receptors has been show to induce such changes, however, it is still not clear, how long after termination of such a treatment, beneficial effects might be maintained. To address this question, we treated rats s.c. for 2 weeks with the ß3 agonist CL-316,243 at 1 mg/kg and assessed interscapular brown fat and inguinal white fat pads weight, UCP-1 (a marker for the brown-like fat phenotype) using immunohistochemistry and H&E staining, at different intervals after treatment termination.One 1 day after the treatment cessation there was a decrease of inguinal white fat pad weight and increase of interscapular fat pad. This change vanished at 7 days for inguinal pad and at 14 days for interscapular pad. Histological analysis of interscapular pads showed increased UCP-1 staining and brown-like morphology in H&E staining slices at 1 day, but not other time points. In case of inguinal pad there were brown-like features in H&E slices at 1 day and less after 7 days, but absent at 14 days. UCP-1 staining was only detected 1 day after the treatment.In conclusion, the present results indicate that browning-like changes of white fat may be short lasting after treatment termination and could require maintenance treatment of inductor to achieve desired therapeutic effect. This might be a serious shortcoming of potential therapeutic use.

Loss of µ-crystallin causes PPARγ activation and obesity in high-fat diet-fed mice.

The thyroid hormone-binding protein µ-crystallin (CRYM) mediates thyroid hormone action by sequestering triiodothyronine in the cytoplasm and regulating the intracellular concentration of thyroid hormone. As thyroid hormone action is closely associated with glycolipid metabolism, it has been proposed that CRYM may contribute to this process by reserving or releasing triiodothyronine in the cytoplasm. We aimed to clarify the relationship between CRYM and glycolipid metabolism by comparing wild-type and CRYM knockout mice fed a high-fat diet. Each group was provided a high-fat diet for 10 weeks, and then their body weight and fasting blood glucose levels were measured. Although no difference in body weight was observed between the two groups with normal diet, the treatment with a high-fat diet was found to induce obesity in the knockout mice. The knockout group displayed increased dietary intake, white adipose tissue, fat cell hypertrophy, and hyperglycemia in the intraperitoneal glucose tolerance test. In CRYM knockout mice, liver fat deposits were more pronounced than in the control group. Enhanced levels of PPARγ, which is known to cause fatty liver, and ACC1, which is a target gene for thyroid hormone and is involved in the fat synthesis, were also detected in the livers of CRYM knockout mice. These observations suggest that CRYM deficiency leads to obesity and lipogenesis, possibly in part through increasing the food intake of mice fed a high-fat diet.

Gonadectomy in Mito-Ob mice revealed a sex-dimorphic relationship between prohibitin and sex steroids in adipose tissue biology and glucose homeostasis.

BACKGROUND: Recently, we have developed a novel transgenic mouse model by overexpressing prohibitin (PHB) in adipocytes, which developed obesity due to upregulation of mitochondrial biogenesis in adipocytes, hence named "Mito-Ob." Interestingly, only male Mito-Ob mice developed obesity-related impaired glucose homeostasis and insulin sensitivity, whereas female Mito-Ob mice did not. The observed sex differences in metabolic dysregulation suggest a potential involvement of sex steroids. Thus, the main aim of this study is to investigate the role of sex steroids on the overall phenotype of Mito-Ob mice through gonadectomy, as well as direct effect of sex steroids on adipocytes from Mito-Ob mice in vitro. METHODS: Mito-Ob mice and wild-type CD-1 mice were gonadectomized at 12 weeks of age. Age- and sex-matched sham-operated mice were used as controls. Body weight, white adipose tissue, glucose tolerance, and insulin sensitivity were analyzed 3 months post-surgery. Differentiation of adipocytes isolated from female and male Mito-Ob mice were studied with and without sex steroids. RESULTS: Gonadectomy significantly reduced body weight in Mito-Ob mice compared with sham-operated mice, whereas the opposite trend was observed in wild-type mice. These changes occurred independent of food intake. A corresponding decrease in adipose tissue weight was found in gonadectomized Mito-Ob mice, but depot-specific differences were observed in male and female. Gonadectomy improved glucose tolerance in male wild-type and Mito-Ob mice, but the effect was more pronounced in wild-type mice. Gonadectomy did not alter insulin sensitivity in male Mito-Ob mice, but it was improved in male wild-type mice. In primary cell cultures, testosterone inhibited adipocyte differentiation to a lesser extent in male Mito-Ob preadipocytes compared with the wild-type mice. On the other hand, preadipocytes from female wild-type mice showed better differentiation potential than those from female Mito-Ob mice in the presence of 17ß-estradiol. CONCLUSIONS: PHB requires sex steroids for the development of obese phenotype in Mito-Ob mice, which differentially affect glucose homeostasis and insulin sensitivity in male and female. It appears that PHB plays sex- and adipose depot-specific roles and involves additional factors. In vitro studies suggested that PHB differently influenced adipocyte differentiation in the presence and absence of sex steroids. Overall, this study along with available information in the literature indicated that a multifaceted relationship exists between PHB and sex steroids, which may work in a cell/tissue type- and sex-specific manner.

Differential response to caloric restriction of retroperitoneal, epididymal, and subcutaneous adipose tissue depots in rats.

The beneficial actions of caloric restriction (CR) are partially mediated by metabolic remodeling of white adipose tissue (WAT). Recently, we showed that CR enhances de novo fatty acid (FA) biosynthesis and mitochondrial biogenesis, particularly in WAT. Here, to better understand the response of WAT to CR, we compare the effects of CR on three WAT depots in rats: retroperitoneal (rWAT), epididymal (eWAT) and subcutaneous (sWAT). Computed tomography and histological analysis showed that CR reduced the volume and average size of rWAT adipocytes. In all WAT depots, CR markedly upregulated the expression of proteins involved in FA biosynthesis in fed rats. In visceral WAT (rWAT and eWAT), hormone-sensitive lipase (lipolytic form) phosphorylation was increased by CR under fed conditions, and decreased by CR under fasted conditions. Conversely, in sWAT, hormone-sensitive lipase phosphorylation was increased by CR under fasted conditions. CR enhanced the effect of feeding on AKT activity in sWAT (indicative of a positive effect on insulin sensitivity) but not in rWAT or eWAT. These data suggest that CR improves lipid metabolism in an insulin signaling-dependent manner in sWAT only. The effects of CR on adipokine (adiponectin and leptin) expression were also different among rWAT, eWAT and sWAT, and CR reduced the gene expression of M2 macrophage markers in rWAT and sWAT, but not in eWAT. We conclude that CR differentially affects the characteristics of WAT depots in rats, including adipocyte size, lipid metabolism, insulin signaling, adipocytokine profile and macrophage infiltration.

Eccrine sweat glands associate with the human hair follicle within a defined compartment of dermal white adipose tissue.

BACKGROUND: Eccrine sweat glands (ESGs) are critical for thermoregulation and are involved in wound healing. ESGs have traditionally been considered as separate skin appendages without connection to the pilosebaceous unit (PSU). However, recent preliminary evidence has encouraged the hypothesis that the PSU and ESG are more interconnected than previously thought. OBJECTIVES: To re-evaluate the morphology of human skin adnexa with an integrated three-dimensional (3D) perspective in order to explore the possible interconnections that the PSU and the ESG may form. METHODS: A systematic 3D reconstruction method of skin sections, direct visualization of human scalp follicular unit transplant grafts and a scalp strip ex vivo were used to validate and further explore the hypothesis. RESULTS: We demonstrate that the coiled portion of most ESGs is morphologically integrated into the PSU of human scalp skin and forms a structural unit that is embedded into a specific, hair follicle-associated region of dermal white adipose tissue (dWAT). This newly recognized unit is easily accessible and experimentally tractable by organ culture of follicular units and can be visualized intravitally. CONCLUSIONS: We propose a model of functional human skin anatomy in which ESGs are closely associated with the PSU and the dWAT to form a common homeostatic tissue environment, which may best be encapsulated in the term 'adnexal skin unit'. The challenge now is to dissect how each component of this superstructure of human skin functionally cooperates with and influences the other under physiological conditions, during regeneration and repair and in selected skin diseases.

An Adipose Tissue Atlas: An Image-Guided Identification of Human-like BAT and Beige Depots in Rodents.

[18F]Fluorodeoxyglucose-PET/CT (18F-FDG-PET/CT) imaging has been invaluable for visualizing metabolically active adipose tissues in humans with potential anti-diabetic and anti-obesity effects. To explore whether mice display human-like fat depots in anatomically comparable regions, we mapped fat depots using glucose or fatty acid imaging tracers, such as 18F-FDG through PET/CT or [123/125I]-ß-methyl-p-iodophenyl-pentadecanoic acid with SPECT/CT imaging, to analogous depots in mice. Using this type of image analysis with both probes, we define a large number of additional areas of high metabolic activity corresponding to novel fat pads. Histological and gene expression analyses validate these regions as bona fide fat pads. Our findings indicate that fat depots of rodents show a high degree of topological similarity to those of humans. Studies involving both glucose and lipid tracers indicate differential preferences for these substrates in different depots and also suggest that fatty acid-based visualized approaches may reveal additional brown adipose tissue and beige depots in humans.

Arcuate nucleus neurons are not essential for the preprandial peak in plasma ghrelin after neonatal monosodium glutamate treatment.

The aim of the present study was to determine whether arcuate nucleus (ARC) lesions affect the ghrelin level in the plasma and the stomach in monosodium glutamate (MSG)­treated mice. The aim of the present study was to investigate whether the ARC was destroyed in mice treated neonatally with MSG, and whether the ARC lesions affect the ghrelin level in the plasma and lipid mobilization in MSG­treated mice. The results revealed that MSG led to a marked reduction in ARC cresyl violet staining, tyrosine hydroxylase-immunoreactive (IR) neurons and neuropeptide Y­IR fibers, compared with saline controls. MSG­treated mice exhibited significantly increased body mass compared with saline controls, and MSG treatment did not prevent food deprivation­induced decrease in white adipose tissue mass compared with controls. Plasma ghrelin levels were significantly increased in MSG­treated mice that were fasted for 48 h, compared with the levels prior to fasting and re­feeding, and the preprandial peak of plasma ghrelin persisted in MSG­treated mice. In summary, the ARC was not found to be essential for food deprivation­induced lipid mobilization and preprandial peak in MSG­treated mice. However, this finding does not mean that ARC neurons do not contribute to food sensing and lipid mobilization under normal conditions, as compensatory mechanisms may have emerged after the ablation of ARC neurons.

Association of proton density fat fraction in adipose tissue with imaging-based and anthropometric obesity markers in adults.

BACKGROUND/OBJECTIVES: The purpose of this study was to examine the relationship of the proton density fat fraction (PDFF), measured by magnetic resonance imaging (MRI), of supraclavicular and gluteal adipose tissue with subcutaneous and visceral adipose tissue (SAT and VAT) volumes, liver fat fraction and anthropometric obesity markers. The supraclavicular fossa was selected as a typical location where brown adipocytes may be present in humans and the gluteal region was selected as a typical location enclosing primarily white adipocytes. SUBJECTS/METHODS: In this cross-sectional study, 61 adults (44 women, median age 29.3 years, range 21-68 years) underwent an MRI examination of the neck and the abdomen/pelvis (3T, Ingenia, Philips Healthcare). PDFF maps of the supraclavicular and gluteal adipose tissue and the liver were generated. Volumes of SAT and VAT were calculated and supraclavicular and subcutaneous fat were segmented using custom-built post-processing algorithms. Body mass index (BMI), waist circumference and waist-to-height ratio were recorded. Statistical analysis was conducted using the Student's t-test and Pearson correlation analysis. RESULTS: Mean supraclavicular PDFF was 75.3±4.7% (range 65.4-83.8%) and mean gluteal PDFF was 89.7±2.9% (range 82.2-94%), resulting in a significant difference (P<0.0001). Supraclavicular PDFF was positively correlated with VAT (r=0.76, P<0.0001), SAT (r=0.73, P<0.0001), liver PDFF (r=0.42, P=0.0008) and all measured anthropometric obesity markers. Gluteal subcutaneous PDFF also correlated with VAT (r=0.59, P<0.0001), SAT (r=0.63, P<0.0001), liver PDFF (r=0.3, P=0.02) and anthropometric obesity markers. CONCLUSIONS: The positive correlations between adipose tissue PDFF and imaging, as well as anthropometric obesity markers suggest that adipose tissue PDFF may be useful as a biomarker for improving the characterization of the obese phenotype, for risk stratification and for selection of appropriate treatment strategies.

MicroRNAs-361-5p and miR-574-5p associate with human adipose morphology and regulate EBF1 expression in white adipose tissue.

Reduced adipose expression of the transcription factor Early B cell factor 1 (EBF1) is linked to white adipose tissue (WAT) hypertrophy. We aimed to identify microRNAs (miRNAs) associated with WAT hypertrophy and EBF1 regulation. We mapped WAT miRNA expression from 26 non-obese women discordant in WAT morphology and determined EBF1 activity in the non-obese and 30 obese women. Expression of 15 miRNAs was higher in hypertrophy and 10 were predicted to target EBF1. Binding of miR-365-5p/miR-574-5p were validated with 3'-UTR assay. Overexpression of miR-365-5p or miR-574-5p reduced EBF1 while inhibition of miR-574 increased EBF1 expression in human adipocytes in vitro. Additive effects on EBF1 were observed when concomitantly overexpressing both miRNAs. EBF1 targets were affected by over expression/inhibition of either miRNAs. Finally, miR-365-5p/miR-574-5p expression in 56 individuals correlated significantly with EBF1 activity. Our results suggest that miR-365-5p and miR-574-5p may be linked to WAT hypertrophy via effects on EBF1 expression.

Intermittent hypoxia-induced insulin resistance is associated with alterations in white fat distribution.

Sleep apnea syndrome is characterized by repetitive upper airway collapses during night leading to intermittent hypoxia (IH). The latter is responsible for metabolic disturbances that rely, at least in part, on abdominal white fat inflammation. Besides qualitative alterations, we hypothesized that IH could also modify body fat distribution, a key factor for metabolic complications. C57BL6 mice exposed to IH (21-5% FiO2, 60 s cycle, 8 h/day) or air for 6 weeks were investigated for topographic fat alterations (whole-body MRI). Specific role of epididymal fat in IH-induced metabolic dysfunctions was assessed in lipectomized or sham-operated mice exposed to IH or air. Whereas total white fat volume was unchanged, IH induced epididymal adipose tissue (AT) loss with non-significant increase in subcutaneous and mesenteric fat. This was associated with impaired insulin sensitivity and secretion. Epididymal lipectomy led to increased subcutaneous fat in the perineal compartment and prevented IH-induced metabolic disturbances. IH led to reduced epididymal AT and impaired glucose regulation. This suggests that, rather than epididymal AT volume, qualitative fat alterations (i.e. inflammation) could represent the main determinant of metabolic dysfunction. This deterioration of glucose regulation was prevented in epididymal-lipectomized mice, possibly through prevention of IH-induced epididymal AT alterations and compensatory increase in subcutaneous AT.

Caloric Restriction Promotes Structural and Metabolic Changes in the Skin.

Caloric restriction (CR) is the most effective intervention known to enhance lifespan, but its effect on the skin is poorly understood. Here, we show that CR mice display fur coat remodeling associated with an expansion of the hair follicle stem cell (HFSC) pool. We also find that the dermal adipocyte depot (dWAT) is underdeveloped in CR animals. The dermal/vennule annulus vasculature is enlarged, and a vascular endothelial growth factor (VEGF) switch and metabolic reprogramming in both the dermis and the epidermis are observed. When the fur coat is removed, CR mice display increased energy expenditure associated with lean weight loss and locomotion impairment. Our findings indicate that CR promotes extensive skin and fur remodeling. These changes are necessary for thermal homeostasis and metabolic fitness under conditions of limited energy intake, suggesting a potential adaptive mechanism.

Follistatin Targets Distinct Pathways To Promote Brown Adipocyte Characteristics in Brown and White Adipose Tissues.

We previously demonstrated that Fst expression is highest in brown adipose tissue (BAT) and skeletal muscle, but is also present at substantial levels in epididymal and subcutaneous white adipose tissues (WATs). Fst promotes mouse brown preadipocyte differentiation and promotes browning during differentiation of mouse embryonic fibroblasts. Fst-transgenic (Fst-Tg) mice show substantial increases in circulating Fst levels and increased brown adipose mass. BAT of Fst-Tg mice had increased expression of brown adipose-associated markers including uncoupling protein 1 (UCP1), PRDM16, PGC-1α, and Glut4. WATs from Fst-Tg mice show upregulation of brown/beige adipose markers and significantly increased levels of phosphorylated p38 MAPK/ERK1/2 proteins compared with the wild-type (WT) mice. Pharmacological inhibition of pp38 MAPK/pERK1/2 pathway of recombinant mouse Fst (rFst) treated differentiating 3T3-L1 cells led to significant blockade of Fst-induced UCP1 protein expression. On the other hand, BAT from Fst-Tg mice or differentiating mouse BAT cells treated with rFst show dramatic increase in Myf5 protein levels as well as upregulation of Zic1 and Lhx8 gene expression. Myf5 levels were significantly downregulated in Fst knock-out embryos and small inhibitory RNA-mediated inhibition of Myf5 led to significant inhibition of UCP1, Lhx8, and Zic1 gene expression and significant blockade of Fst-induced induction of UCP1 protein expression in mouse BAT cells. Both interscapular BAT and WAT tissues from Fst-Tg mice display enhanced response to CL316,243 treatment and decreased expression of pSmad3 compared with the WT mice. Therefore, our results indicate that Fst promotes brown adipocyte characteristics in both WAT and BAT depots in vivo through distinct mechanisms.

Heterogeneity of white adipose tissue: molecular basis and clinical implications.

Adipose tissue is a highly heterogeneous endocrine organ. The heterogeneity among different anatomical depots stems from their intrinsic differences in cellular and physiological properties, including developmental origin, adipogenic and proliferative capacity, glucose and lipid metabolism, insulin sensitivity, hormonal control, thermogenic ability and vascularization. Additional factors that influence adipose tissue heterogeneity are genetic predisposition, environment, gender and age. Under obese condition, these depot-specific differences translate into specific fat distribution patterns, which are closely associated with differential cardiometabolic risks. For instance, individuals with central obesity are more susceptible to developing diabetes and cardiovascular complications, whereas those with peripheral obesity are more metabolically healthy. This review summarizes the clinical and mechanistic evidence for the depot-specific differences that give rise to different metabolic consequences, and provides therapeutic insights for targeted treatment of obesity.