Affect Adipose Tissue Research Articles

Abstract 441: Macrophage CD40 in Atherosclerosis, Obesity and Multiple Sclerosis

Introduction: The co-stimulatory dyad CD40-CD40L plays a central role in fine-tuning immune reactions in atherosclerosis, obesity-induced inflammation and multiple sclerosis (MS). Inhibition of CD40 in atherosclerosis and experimental autoimmune encephalomyelitis (EAE) ameliorates disease outcome, whereas CD40-deficiency in a diet induced obesity (DIO) model worsens insulin resistance and induces excessive adipose tissue inflammation. Although inhibition of CD40 has powerful effects, we do not know which CD40 expressing cell-type is responsible for the amelioration/aggravation of disease. As myeloid CD40 is known to play a role in leukocyte trafficking, which is important in atherosclerosis, obesity and neuro-inflammation, we hypothesize that myeloid CD40 is important in these disease modalities. Methods: To investigate the role of myeloid CD40 in atherosclerosis, obesity and EAE we have generated macrophage specific LysM-CD40flfl - (ApoE-/-), and dendritic cell/adipose tissue macrophage specific CD11C-CD40flfl). Atherosclerosis was induced by aging the LysM-CD40flfl - ApoE-/- mice until 30 weeks. EAE was induced in LysM-CD40flfl mice by subjecting them to myelin oligodendrocyte glycoprotein peptide (MOG35-55), and LysM-CD40flfl and CD11c-CD40flfl mice were subjected to a 60% high fat diet for 18 wks. Results: LysM-CD40flfl - ApoE-/- mice showed a significant reduction in atherosclerotic plaque area, with a reduced macrophage accumulation. Loss of macrophage CD40 in EAE results in a significant decrease in the neurological symptoms of EAE, and a majority of the LysM-CD40flfl mice were fully protected against EAE. LysM-CD40flfl mice subjected to DIO showed an increase in macrophage accumulation in the visceral adipose tissue, but did not affect adipose tissue mass, insulin tolerance, or plasma triglyceride concentrations. The CD11CcreCD40flfl mice exhibited a decrease in visceral adipose tissue weight, an increased lipid content in the liver and slightly decreases leukocyte numbers and pro-inflammatory gene expression in the adipose tissue. Conclusions: Macrophage CD40 is an important driver of atherosclerosis and EAE. Macrophage CD40 is protective in obesity-induced inflammation, but is probably not the key player.

Effects of Different Oxygen Concentrations on Human Differentiated Preadipocytes Lipogenic and Lipolytic functions

ContextFat stored in white adipose tissue is the human body's largest energy reservoir. Adipocytes, the predominant cell population in white adipose tissue, play a central role in the clearance of circulating triglyceride (TG) and the delivery of fatty acids for use by peripheral tissues. Impaired regulation of adipose tissue functions is thought to stimulate lipid deposition in non‐adipose tissues, inducing lipotoxic response and the development of metabolic disorders. During weight gain, adipocytes expand in size, decreasing adipose tissue capillary density and creating areas characterized by excessively low oxygen concentrations (hypoxia). It is not clear how hypoxia modulates adipose tissue TG clearance and fatty acid delivery.ObjectiveThe purpose of this study was to investigate the effects of different hypoxia concentrations on lipogenic (store TG) and lipolytic functions (deliver fatty acids) of human differentiated preadipocytes.MethodsDifferentiated human preadipocytes were exposed to different oxygen concentrations (3%, 10%, and 21%) either during differentiation (14d, continuous exposure) or acutely for 24h after differentiation (acute exposure). Gene expression of lipogenic enzymes and regulating factors will be determined by real‐time PCR. Lipoprotein lipase (LPL) activity was measured using the EnzChek Lipase Substrate and lipolytic rate was determined by measuring glycerol release over 3 hours.ResultsIn differentiated human preadipocytes, a dose‐dependent reduction in LPL activity was observed in both acute and continuous hypoxia (6‐fold reduction under 3% O2 p<0.001, 2‐fold reduction under 10% O2, p<0.05, compared to 21% O2). Basal lipolysis was significantly higher during acute hypoxia (3%) session (p<0.05). No differences in isoproterenol‐ and epinephrine‐stimulated lipolytic responses were observed in subcutaneous abdominal preadipocytes between normoxia and acute hypoxia (3%).ConclusionsThese preliminary results suggest that acute and continuous hypoxia strongly inhibits LPL activity and increases basal lipolysis. These observation supports the hypothesis that hypoxia may adversely affect adipose tissue storage functions, which could in turn contribute to ectopic fat storage, lipotoxicity and a greater prevalence of metabolic disorders in individual with excess adiposity.Support or Funding InformationThis study was supported by the Natural Sciences and Engineering Research Council of Canada as well as the University of Ottawa.

Long‐term dietary supplementation with low‐dose nobiletin ameliorates hepatic steatosis, insulin resistance, and inflammation without altering fat mass in diet‐induced obesity

We evaluated the long-term effect of low-dose nobiletin (NOB), a polymethoxylated flavone, on diet-induced obesity and related metabolic disturbances. C57BL/6J mice were fed a high-fat diet (HFD, 45 kcal% fat) with or without NOB (0.02%, w/w) for 16 weeks. NOB did not alter food intake or body weight. Despite increases in fatty acid oxidation-related genes expression and enzymes activity in adipose tissue, NOB did not affect adipose tissue weight due to simultaneous increases in lipogenic genes expression and fatty acid synthase activity. However, NOB significantly decreased not only pro-inflammatory genes expression in adipose tissue but also proinflammatory cytokine levels in plasma. NOB-supplemented mice also showed improved glucose tolerance and insulin resistance, along with decreased levels of plasma insulin, free fatty acids, total cholesterol, non-HDL-cholesterol, and apolipoprotein B. In addition, NOB caused significant decreases in hepatic lipid droplet accumulation and triglyceride content by activating hepatic fatty acid oxidation-related enzymes. Hepatic proinflammatory TNF-α mRNA expression, collagen accumulation, and plasma levels of aminotransferases, liver damage indicators, were also significantly lower in NOB-supplemented mice. These findings suggest that long-term supplementation with low-dose NOB can protect against HFD-induced inflammation, insulin resistance, dyslipidemia, and nonalcoholic fatty liver disease, without ameliorating adiposity.

Seasonal heat stress affects adipose tissue proteome toward enrichment of the Nrf2-mediated oxidative stress response in late-pregnant dairy cows

Environmental heat stress and metabolic stress during transition from late gestation to lactation are main factors limiting production in dairy cattle, and there is a complex interaction between them. Many proteins expressed in adipose tissue are involved in metabolic responses to stress. We aimed to investigate the effects of seasonal heat stress on adipose proteome in late-pregnant cows, and to identify biomarkers of heat stress. Late pregnant cows during summer heat stress (S, n=18), or during the winter season (W, n=12) were used. Subcutaneous adipose tissue biopsies sampled 14days prepartum from S (n=10) and W (n=8) were analyzed by intensity-based, label-free, quantitative shotgun proteomics (nano-LC–MS/MS). Plasma concentrations of malondialdehyde and cortisol were higher in S than in W cows. Proteomic analysis revealed that 107/1495 proteins were differentially abundant in S compared to W (P<0.05 and fold change of at least ±1.5). Top canonical pathways in S vs. W adipose were Nrf2-mediated oxidative stress response, acute-phase response, and FXR/RXR and LXR/RXR activation. Novel biomarkers of heat stress in adipose tissue were found. These findings indicate that seasonal heat stress has a unique effect on adipose tissue in late-pregnant cows. SignificanceThis work shows that seasonal heat stress increases plasma concentrations of the oxidative stress marker malondialdehyde and cortisol in transition dairy cows. As many proteins expressed in the adipose tissue are involved in metabolic responses to stress, we investigated the effects of heat stress on the proteome of adipose tissue from late-pregnant cows during summer or winter seasons. We demonstrated that heat stress enriches several stress-related pathways, such as the Nrf2-mediated oxidative stress response and the acute-phase response in adipose tissues. Thus, environmental heat stress has a unique effect on adipose tissue in late-pregnant cows, as part of the regulatory adaptations to chronic heat load during the summer season. In addition, this study presents the widest available dataset of adipose tissue proteome in dairy cows, and revealed several novel biomarkers of heat stress in adipose tissue of dairy cows, the use of which awaits further validation.

Hedgehog signalling in myeloid cells impacts on body weight, adipose tissue inflammation and glucose metabolism.

Recently, hedgehog (Hh) was identified as a crucial player in adipose tissue development and energy expenditure. Therefore, we tested whether Hh ligands are regulated in obesity. Further, we aimed at identifying potential target cells of Hh signalling and studied the functional impact of Hh signalling on adipose tissue inflammation and glucose metabolism. Hh ligands and receptors were analysed in adipose tissue or serum from lean and obese mice as well as in humans. To study the impact on adipose tissue inflammation and glucose metabolism, Hh signalling was specifically blocked in myeloid cells using a conditional knockout approach (Lys-Smo -/-). Desert Hh (DHH) and Indian Hh (IHH) are local Hh ligands, whereas Sonic Hh is not expressed in adipose tissue from mice or humans. In mice, obesity leads to a preferential upregulation of Hh ligands (Dhh) and signalling components (Ptch1, Smo and Gli1) in subcutaneous adipose tissue. Further, adipose tissue macrophages are Hh target cells owing to the expression of Hh receptors, such as Patched1 and 2. Conditional knockout of Smo (which encodes Smoothened, a mandatory Hh signalling component) in myeloid cells increases body weight and adipose tissue inflammation and attenuates glucose tolerance, suggesting an anti-inflammatory effect of Hh signalling. In humans, adipose tissue expression of DHH and serum IHH decrease with obesity and type 2 diabetes, which might be explained by the intake of metformin. Interestingly, metformin reduced Dhh and Ihh expression in mouse adipose tissue explants. Hh signalling in myeloid cells affects adipose tissue inflammation and glucose metabolism and may be a potential target to treat type 2 diabetes.

Potential Molecular Mechanism of Probiotics in Alcoholic Liver Disease

Alcohol consumption and its abuse are significant prevalent cause for liver diseases and death worldwide. Increased bacterial endotoxin in the portal circulation, the plasma ratio of liver enzymes like alanine aminotransferase (ALT), aspartate aminotransferase (AST) and triglyceride implies the symbiotic relation between the gut and liver plays a key function in alcoholic liver disease (ALD). Consumption of alcohol leads to gut dysbiosis and informalities of the intestinal barrier, hyper gut permeability, oxidative stress, inflammation and adversely affect adipose tissue metabolism, and those are mainly recognized as major factors for progression of alcoholic liver disease. Alteration of gut microbiota is referred to as bacterial overgrowth which leads to the release of bacterial products to change in commercial/pathogenic microbiota equilibrium. Lipopolysaccharide (LPS) derived inflammatory signal renders inflammation in alcoholic liver disease. Increase in concentration of lipopolysaccharide leads to activation of toll-like receptor 4 (TLR4) and alteration in micro RNA (miRNA) expression at the transcription level. Activation of myeloid differentiation factor 88 (MyD88) pathways eventually produces pro inflammatory cytokine activation that is an important mediator of alcoholic liver disease. However, there is no effectual Food and Drug Administration (FDA) approved treatment for any stage of alcoholic liver disease. Thus, the potential therapeutic approach for alcoholic liver disease is restoration and alteration of gut microbiota. With the increasing importance of gut microbiota in the onset and occurrence of a variety of diseases, the potential use of probiotics in ALD is receiving more exploration and clinical attention. Probiotic administration is nontoxic, inexpensive and noninvasive strategy with minimal side effects compared to antibiotic therapy and surgery. Yet, there is no substantial evidence on the efficient molecular mechanism regarding mode of action of probiotics on ALD as therapeutics. This review summarizes the research done on gut liver-axis and potential mechanism of probiotic in alcoholic liver disease.

Controlled dexamethasone delivery via double-walled microspheres to enhance long-term adipose tissue retention

Current materials used for adipose tissue reconstruction have critical shortcomings such as suboptimal volume retention, donor-site morbidity, and poor biocompatibility. The aim of this study was to examine a controlled delivery system of dexamethasone to generate stable adipose tissue when mixed with disaggregated human fat in an athymic mouse model for 6 months. The hypothesis that the continued release of dexamethasone from polymeric microspheres would enhance both adipogenesis and angiogenesis more significantly when compared to the single-walled microsphere model, resulting in long-term adipose volume retention, was tested. Dexamethasone was encapsulated within single-walled poly(lactic-co-glycolic acid) microspheres (Dex SW MS) and compared to dexamethasone encapsulated in a poly(lactic-co-glycolic acid) core surrounded by a shell of poly-l-lactide. The double-walled polymer microsphere system in the second model was developed to create a more sustainable drug delivery process. Dexamethasone-loaded poly(lactic-co-glycolic acid) microspheres (Dex SW MS) and dexamethasone-loaded poly(lactic-co-glycolic acid)/poly-l-lactide double-walled microspheres (Dex DW MS) were prepared using single and double emulsion/solvent techniques. In vitro release kinetics were determined. Two doses of each type of microsphere were examined; 50 and 27 mg of Dex MS and Dex DW MS were mixed with 0.3 mL of human lipoaspirate. Additionally, 50 mg of empty MS and lipoaspirate-only controls were examined. Samples were analyzed grossly and histologically after 6 months in vivo. Mass and volume were measured; dexamethasone microsphere-containing samples demonstrated greater adipose tissue retention compared to the control group. Histological analysis, including hematoxylin and eosin and CD31 staining, indicated increased vascularization (p < 0.05) within the Dex MS-containing samples. Controlled delivery of adipogenic factors, such as dexamethasone via polymer microspheres, significantly affects adipose tissue retention by maintaining healthy tissue formation and vascularization. Dex DW MS provide an improved model to former Dex SW MS, resulting in notably longer release time and, consequently, larger volumes of adipose retained in vivo. The use of microspheres, specifically double-walled, as vehicles for controlled drug delivery of adipogenic factors therefore present a clinically relevant model of adipose retention that has the potential to greatly improve soft tissue repair.

Depot Dependent Effects of Dexamethasone on Gene Expression in Human Omental and Abdominal Subcutaneous Adipose Tissues from Obese Women.

Glucocorticoids promote fat accumulation in visceral compared to subcutaneous depots, but the molecular mechanisms involved remain poorly understood. To identify long-term changes in gene expression that are differentially sensitive or responsive to glucocorticoids in these depots, paired samples of human omental (Om) and abdominal subcutaneous (Abdsc) adipose tissues obtained from obese women during elective surgery were cultured with the glucocorticoid receptor agonist dexamethasone (Dex, 0, 1, 10, 25 and 1000 nM) for 7 days. Dex regulated 32% of the 19,741 genes on the array, while 53% differed by Depot and 2.5% exhibited a Depot*Dex concentration interaction. Gene set enrichment analysis showed Dex regulation of the expected metabolic and inflammatory pathways in both depots. Cluster analysis of the 460 transcripts that exhibited an interaction of Depot and Dex concentration revealed sets of mRNAs for which the responses to Dex differed in magnitude, sensitivity or direction between the two depots as well as mRNAs that responded to Dex only in one depot. These transcripts were also clearly depot different in fresh adipose tissue and are implicated in processes that could affect adipose tissue distribution or functions (e.g. adipogenesis, triacylglycerol synthesis and storage, insulin action). Elucidation of the mechanisms underlying the depot differences in the effect of Dex on the expression of specific genes and pathways that regulate adipose function may offer novel insights into understanding the biology of visceral adipose tissues and their links to metabolic health.

Lamin-B1 contributes to the proper timing of epicardial cell migration and function during embryonic heart development.

Lamin proteins form a meshwork beneath the nuclear envelope and contribute to many different cellular processes. Mutations in lamins cause defective organogenesis in mouse models and human diseases that affect adipose tissue, brain, skeletal muscle, and the heart. In vitro cell culture studies have shown that lamins help maintain nuclear shape and facilitate cell migration. However, whether these defects contribute to improper tissue building in vivo requires further clarification. By studying the heart epicardium during embryogenesis, we show that Lb1-null epicardial cells exhibit in vivo and in vitro migratory delay. Transcriptome analyses of these cells suggest that Lb1 influences the expression of cell adhesion genes, which could affect cell migration during epicardium development. These epicardial defects are consistent with incomplete development of both vascular smooth muscle and compact myocardium at later developmental stages in Lb1-null embryos. Further, we found that Lb1-null epicardial cells have a delayed nuclear morphology change in vivo, suggesting that Lb1 facilitates morphological changes associated with migration. These findings suggest that Lb1 contributes to nuclear shape maintenance and migration of epicardial cells and highlights the use of these cells for in vitro and in vivo study of these classic cell biological phenomena.

Effects of Hydrolyzed Whey versus Other Whey Protein Supplements on the Physiological Response to 8 Weeks of Resistance Exercise in College-Aged Males

Objective: The objective of this study was to compare the chronic effects of different whey protein forms on body composition and performance when supplemented with resistance training.Methods: Resistance-trained men (N = 56, 21.4 ± 0.4 years, 79.5 ± 1.0 kg) participated in an 8-week resistance training regimen (2 upper-body sessions and 2 lower-body sessions per week) and received one of 4 double-blinded treatments: 30 g/serving carbohydrate placebo (PLA) or 30 g/serving protein from either (a) 80% whey protein concentrate (WPC), (b) high-lactoferrin-containing WPC (WPC-L), or (c) extensively hydrolyzed WPC (WPH). All subjects consumed 2 servings of treatment per day; specifically, once immediately before and after training and between meals on nontraining days. Blood collection, one repetition maximum (1RM) testing for bench press and hack squat, and body composition assessment using dual-energy x-ray absorptiometry (DXA) occurred prior to training and 48 hours following the last training session.Results: Total body skeletal muscle mass increased in all groups (p < 0.0125). There were similar between-group increases in upper-body (4%–7%, analysis of covariance [ANCOVA] interaction p = 0.73) and lower-body (24%–35%, ANCOVA interaction p = 0.85) 1RM strength following the intervention. Remarkably, WPH reduced fat mass (−6%), which was significantly different from PLA (+4.4%, p < 0.0125). No time or between-group differences were present for serum markers of health, metabolism, or muscle damage, with the exception of blood urea nitrogen being significantly lower for WPH than WPC (p < 0.05) following the intervention.Conclusions: WPH may augment fat loss but did not provide any other advantages when used in combination with resistance training. More mechanistic research is needed to examine how WPH affects adipose tissue physiology.

Redundant roles of the phosphatidate phosphatase family in triacylglycerol synthesis in human adipocytes.

Aims/hypothesisIn mammals, the evolutionary conserved family of Mg2+-dependent phosphatidate phosphatases (PAP1), involved in phospholipid and triacylglycerol synthesis, consists of lipin-1, lipin-2 and lipin-3. While mutations in the murine Lpin1 gene cause lipodystrophy and its knockdown in mouse 3T3-L1 cells impairs adipogenesis, deleterious mutations of human LPIN1 do not affect adipose tissue distribution. However, reduced LPIN1 and PAP1 activity has been described in participants with type 2 diabetes. We aimed to characterise the roles of all lipin family members in human adipose tissue and adipogenesis.MethodsThe expression of the lipin family was analysed in adipose tissue in a cross-sectional study. Moreover, the effects of lipin small interfering RNA (siRNA)-mediated depletion on in vitro human adipogenesis were assessed.ResultsAdipose tissue gene expression of the lipin family is altered in type 2 diabetes. Depletion of every lipin family member in a human Simpson–Golabi–Behmel syndrome (SGBS) pre-adipocyte cell line, alters expression levels of adipogenic transcription factors and lipid biosynthesis genes in early stages of differentiation. Lipin-1 knockdown alone causes a 95% depletion of PAP1 activity. Despite the reduced PAP1 activity and alterations in early adipogenesis, lipin-silenced cells differentiate and accumulate neutral lipids. Even combinatorial knockdown of lipins shows mild effects on triacylglycerol accumulation in mature adipocytes.Conclusions/interpretationOverall, our data support the hypothesis of alternative pathways for triacylglycerol synthesis in human adipocytes under conditions of repressed lipin expression. We propose that induction of alternative lipid phosphate phosphatases, along with the inhibition of lipid hydrolysis, contributes to the maintenance of triacylglycerol content to near normal levels.Electronic supplementary materialThe online version of this article (doi:10.1007/s00125-016-4018-0) contains peer-reviewed but unedited supplementary material, which is available to authorised users.

Alpha‐Melanocyte Stimulating Hormone (α‐MSH) Affects Adipose Tissue Physiology in Broiler Chicks

The melanocortin system plays an important role in whole‐body energy homeostasis. In mammals, α‐melanocyte stimulating hormone (α‐MSH) induces satiety via the hypothalamus and stimulates lipolysis in adipose tissue. In chickens, it is also highly anorexigenic, but effects on adipose physiology have not been reported in an avian species. The objective of this study was to determine the effects of exogenous α‐MSH on adipose tissue physiology in broiler chicks. We hypothesized that peripheral α‐MSH injection would be associated with changes in transcriptional regulation of the melanocortin system, and lipid metabolism‐associated factors in adipose tissue. At four days post‐hatch, using a randomized complete block design with body weight as the blocking factor, individually caged Cobb‐500 broilers were assigned to receive intraperitoneal injection of 0 (vehicle), 5, 10, or 50 micrograms of α‐MSH (n=10/treatment) and euthanized at 60 minutes post‐injection and feed intake recorded. Subcutaneous and abdominal adipose tissue and Pectoralis major were collected for quantifying mRNA abundance of adipose lipid metabolism‐associated factors, and melanocortin receptors 1–5. Additionally, an in vitro study was conducted where the stromal‐vascular fraction of cells was isolated from the abdominal fat of 14 day‐old Cobb‐500 broilers. At 80% confluence, cells were treated with 0 (control), 1, 10, or 100 nM α‐MSH (n=3 independent experiments) and total RNA isolated at 4 hours to measure mRNA abundance of the same genes. Data were analyzed by ANOVA using the Fit Model platform of JMP (SAS Institute) and the statistical model included the main effect of treatment (sex was non‐significant for all variables and removed from the model), with Dunnett's test used for pairwise comparisons. Food intake was decreased (P &lt; 0.0001) at 60 minutes in chicks that received 50 μg of α‐MSH as compared to vehicle. MC5R mRNA was increased (P &lt; 0.05) in subcutaneous adipose tissue of chicks that received 10 and 50 μg of α‐MSH, but was not affected in the abdominal adipose or Pectoralis major, compared to vehicle‐injected chicks, and increased in vitro in cells receiving 10 and 100 nM α‐MSH, compared to control‐treated cells. The mRNA abundance of fatty acid binding protein 4 (FABP4) was also greater (P = 0.02) in 100 nM α‐MSH‐ than control‐treated cells. In conclusion, α‐MSH injection reduced feed intake, and was associated with increased gene expression of MC5R. Thus, in birds, peripheral α‐MSH may reduce feed intake, and effects in adipose tissue may be depot‐dependent and mediated through melanocortin receptor subtype 5.Support or Funding InformationThis research was supported by a National Science Foundation EAGER grant (IOS 1420285). Funding for this work was also provided in part, by the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture.

Central Injection of Neuropeptide Y Affects Dietary Macronutrient Composition‐Mediated Changes in Broiler Adipose Tissue mRNA Abundance

Neuropeptide Y (NPY) is a potent orexigenic (hunger increasing) factor that also promotes adipose tissue development in birds and mammals. The purpose of this study was to investigate how dietary macronutrient composition and exogenous NPY affect expression of lipid metabolism‐associated factors in different anatomical adipose (fat) depots of chickens. Chicks were fed one of three isocaloric diets (3,000 kcal metabolizable energy (ME)/kg) and isonitrogenous (22% crude protein; CP) corn and soybean meal‐based diets after hatch: high carbohydrate (HC; control), high fat (HF; 30% of ME from soybean oil) or high protein (HP; 27% CP) post hatch. On day 4 post hatch, 0.2 nmol of NPY or vehicle was injected intra cerebroventricularly (into left lateral ventricle) and abdominal and subcutaneous fat were collected at 1‐hour post injection. Total RNA was isolated, reverse transcribed and real‐time PCR performed to quantify expression of genes associated with adipogenesis: Krüppel‐like factor 7 (KLF7), GATA‐binding protein 2 (GATA 2), CCAAT/enhancer‐binding protein alpha (CEBPα), CEBPβ, peroxisome proliferator‐activated receptor gamma (PPARγ), sterol regulatory element‐binding transcription factor 1 (SREBP‐1), and fatty acid binding protein 4 (FABP4). The statistical model (within fat depot) included the main effects of diet and NPY treatment, and the two‐way interaction. There was an effect of diet (P &lt; 0.05) for all of the genes measured in abdominal and subcutaneous fat, except for CEBPβ in subcutaneous fat. Chicks fed the HC diet expressed more (P &lt; 0.0001) KLF7, CEBPα, CEBPβ, PPARγ, SREBP‐1, and FABP4 in abdominal fat than chicks fed the HF or HP diet. There were interactions of diet and NPY treatment on PPARγ (P = 0.04) and FABP4 (P = 0.03) mRNA in abdominal fat, and CEBPα (P = 0.01), PPARγ (P = 0.001), SREBP‐1 (P = 0.001) and FABP4 (P = 0.001) mRNA in subcutaneous fat. Pairwise comparison tests revealed that CEBPα (P &lt; 0.003), PPARγ (P = 0.007), SREBP‐1 (P = 0.008) and FABP4 (P = 0.001) mRNA showed a more pronounced increase in subcutaneous fat of the HF than HC and HP fed chicks after NPY injection. PPARγ (P = 0.01), SREBP‐1 (P = 0.01) and FABP4 (P = 0.04) also showed a more accentuated decrease in subcutaneous fat of HC than HF and HP fed chicks after NPY injection. PPARγ (P = 0.003) and FABP4 (P = 0.003) in abdominal fat increased more in expression in HF than HC and HP fed chicks after NPY injection. These data demonstrate that consumption of diets differing in fat content affect adipose tissue physiology, with differences in gene expression of some adipogenesis‐associated factors during the first week post‐hatch; in general mRNA was greater in chicks fed HC than the HF or HP diet, with similar effects observed in different anatomical fat depots. Injection of NPY affected expression of these factors in an adipose depot‐dependent manner. These results may have implications for understanding how early‐life nutrition and appetite‐regulatory neuropeptides affect development of different adipose tissue depots in birds.Support or Funding InformationFunding for this work was provided in part, by the Virginia Agricultural Experiment Station and the Hatch Program of the National Institute of Food and Agriculture, U.S. Department of Agriculture, and by a John Lee Pratt Undergraduate Research Scholarship awarded to CW.

Adipose tissue macrophages: going off track during obesity.

Inflammation originating from the adipose tissue is considered to be one of the main driving forces for the development of insulin resistance and type 2 diabetes in obese individuals. Although a plethora of different immune cells shapes adipose tissue inflammation, this review is specifically focused on the contribution of macrophages that reside in adipose tissue in lean and obese conditions. Both conventional and tissue-specific functions of adipose tissue macrophages (ATMs) in lean and obese adipose tissue are discussed and linked with metabolic and inflammatory changes that occur during the development of obesity. Furthermore, we will address various circulating and adipose tissue-derived triggers that may be involved in shaping the ATM phenotype and underlie ATM function in lean and obese conditions. Finally, we will highlight how these changes affect adipose tissue inflammation and may be targeted for therapeutic interventions to improve insulin sensitivity in obese individuals. Highlights • Macrophages play a significant role in regulating adipose tissue functioning during health and disease• In addition to conventional functions such as clearing cellular debris and participating in tissue immune surveillance, lipid buffering is an important function of ATMs• Obesity-induced inflammation, characterised by an elevated number of proinflammatory macrophages in adipose tissue, has been suggested to contribute to systemic insulin resistance• Their origin, as well as a combination of peripheral changes and adipose tissue-derived stressors, probably contribute to ATM dysfunction and inflammatory traits during obesity• Identification of transcriptional differences between ATMs from lean vs obese adipose tissue at several key points during the development of obesity and insulin resistance may reveal upstream triggers, regulatory factors and intracellular pathways that shape ATM function• Targeting metabolic capacity rather than the inflammatory phenotype of ATMs may hold potential to restore ATM function and adipose tissue homeostasis in obese individuals

Depot-Specific Changes in Fat Metabolism with Aging in a Type 2 Diabetic Animal Model.

Visceral fat accretion is a hallmark of aging and is associated with aging-induced metabolic dysfunction. PPARγ agonist was reported to improve insulin sensitivity by redistributing fat from visceral fat to subcutaneous fat. The purpose of this study was to investigate the underlying mechanisms by which aging affects adipose tissue remodeling in a type 2 diabetic animal model and through which PPARγ activation modulates aging-related fat tissue distribution. At the ages of 21, 31 and 43 weeks, OLETF rats as an animal model of type 2 diabetes were evaluated for aging-related effects on adipose tissue metabolism in subcutaneous and visceral fat depots. During aging, the ratio of visceral fat weight to subcutaneous fat weight (V/S ratio) increased. Aging significantly increased the mRNA expression of genes involved in lipogenesis such as lipoprotein lipase, fatty acid binding protein aP2, lipin 1, and diacylglycerol acyltransferase 1, which were more prominent in visceral fat than subcutaneous fat. The mRNA expression of adipose triglyceride lipase, which is involved in basal lipolysis and fatty acid recycling, was also increased, more in visceral fat compared to subcutaneous fat during aging. The mRNA levels of the genes associated with lipid oxidation were increased, whereas the mRNA levels of genes associated with energy expenditure showed no significant change during aging. PPARγ agonist treatment in OLETF rats resulted in fat redistribution with a decreasing V/S ratio and improved glucose intolerance. The genes involved in lipogenesis decreased in visceral fat of the PPARγ agonist-treated rats. During aging, fat distribution was changed by stimulating lipid uptake and esterification in visceral fat rather than subcutaneous fat, and by altering the lipid oxidation.

Granulocyte colony-stimulating factor (G-CSF): A saturated fatty acid-induced myokine with insulin-desensitizing properties in humans.

ObjectiveCirculating long-chain free fatty acids (FFAs) are important metabolic signals that acutely enhance fatty acid oxidation, thermogenesis, energy expenditure, and insulin secretion. However, if chronically elevated, they provoke inflammation, insulin resistance, and β-cell failure. Moreover, FFAs act via multiple signaling pathways as very potent regulators of gene expression. In human skeletal muscle cells differentiated in vitro (myotubes), we have shown in previous studies that the expression of CSF3, the gene encoding granulocyte colony-stimulating factor (G-CSF), is markedly induced upon FFA treatment and exercise.Methods and resultsWe now report that CSF3 is induced in human myotubes by saturated, but not unsaturated, FFAs via Toll-like receptor 4-dependent and -independent pathways including activation of Rel-A, AP-1, C/EBPα, Src, and stress kinases. Furthermore, we show that human adipocytes and myotubes treated with G-CSF become insulin-resistant. In line with this, a functional polymorphism in the CSF3 gene affects adipose tissue- and whole-body insulin sensitivity and glucose tolerance in human subjects with elevated plasma FFA concentrations.ConclusionG-CSF emerges as a new player in FFA-induced insulin resistance and thus may be of interest as a target for prevention and treatment of type 2 diabetes.

PKR is not obligatory for high-fat diet-induced obesity and its associated metabolic and inflammatory complications.

Protein kinase R (PKR) has previously been suggested to mediate many of the deleterious consequences of a high-fat diet (HFD). However, previous studies have observed substantial phenotypic variability when examining the metabolic consequences of PKR deletion. Accordingly, herein, we have re-examined the role of PKR in the development of obesity and its associated metabolic complications in vivo as well as its putative lipid-sensing role in vitro. Here we show that the deletion of PKR does not affect HFD-induced obesity, hepatic steatosis or glucose metabolism, and only modestly affects adipose tissue inflammation. Treatment with the saturated fatty acid palmitate in vitro induced comparable levels of inflammation in WT and PKR KO macrophages, demonstrating that PKR is not necessary for the sensing of pro-inflammatory lipids. These results challenge the proposed role for PKR in obesity, its associated metabolic complications and its role in lipid-induced inflammation.

α 1-acid glycoprotein inhibits lipogenesis in neonatal swine adipose tissue

Serum α1-acid glycoprotein (AGP) is elevated during late gestation and at birth in the pig and rapidly declines postnatally. In contrast, the pig is born with minimal lipid stores in the adipose tissue, but rapidly accumulates lipid during the first week. The present study examined if AGP can affect adipose tissue metabolism in the neonatal pig. Isolated cell cultures or tissue explants were prepared from dorsal subcutaneous adipose tissue of preweaning piglets. Porcine AGP was used at concentrations of 0, 100, 1000 and 5000 ng/ml medium in 24 h incubations. AGP reduced the messenger RNA (mRNA) abundance of the lipogenic enzymes, malic enzyme (ME), fatty acid synthase and acetyl coA carboxylase by at least 40% (P<0.001). The activity of ME and citrate lyase were also reduced by AGP (P<0.05). Glucose oxidation was reduced by treatment with 5000 ng AGP/ml medium (P<0.05). The 14C-glucose incorporation into fatty acids was reduced by ~25% by AGP treatment for 24 h with 1000 ng AGP/ml medium (P<0.05). The decrease in glucose metabolism by AGP appears to function through an inhibition in insulin-mediated glucose oxidation and incorporation into fatty acids. This was supported by the analysis of the mRNA abundance for sterol regulatory element-binding protein (SREBP), carbohydrate regulatory element-binding protein (ChREBP) and insulin receptor substrate 1 (IRS1), which all demonstrated reductions of at least 23% in response to AGP treatment (P<0.05). These data demonstrate an overall suppression of lipogenesis due to AGP inhibition of lipogenic gene expression in vitro, which the metabolic data and SREBP, ChREBP and IRS1 gene expression analysis suggest is through an inhibition in insulin-mediated events. Second, these data suggest that AGP may contribute to limiting lipogenesis within adipose tissue during the perinatal period, as AGP levels are highest for any serum protein at birth.

Role of bile acids in carcinogenesis of pancreatic cancer: An old topic with new perspective.

The role of bile acids in colorectal cancer has been well documented, but their role in pancreatic cancer remains unclear. In this review, we examined the risk factors of pancreatic cancer. We found that bile acids are associated with most of these factors. Alcohol intake, smoking, and a high-fat diet all lead to high secretion of bile acids, and bile acid metabolic dysfunction is a causal factor of gallstones. An increase in secretion of bile acids, in addition to a long common channel, may result in bile acid reflux into the pancreatic duct and to the epithelial cells or acinar cells, from which pancreatic adenocarcinoma is derived. The final pathophysiological process is pancreatitis, which promotes dedifferentiation of acinar cells into progenitor duct-like cells. Interestingly, bile acids act as regulatory molecules in metabolism, affecting adipose tissue distribution, insulin sensitivity and triglyceride metabolism. As a result, bile acids are associated with three risk factors of pancreatic cancer: obesity, diabetes and hypertriglyceridemia. In the second part of this review, we summarize several studies showing that bile acids act as cancer promoters in gastrointestinal cancer. However, more question are raised than have been solved, and further oncological and physiological experiments are needed to confirm the role of bile acids in pancreatic cancer carcinogenesis.

Cross-Talk Between Adipose Tissue Health, Myocardial Metabolism and Vascular Function: The Adipose-Myocardial and Adipose-Vascular Axes.

Alterations in myocardial metabolism and blood flow have been described in patients with metabolic disorders, cardiovascular disease and cardiomyopathies, and have been implicated in the pathogenesis or prognosis of cardiac conditions. Adipose tissue dysfunction occurs in the above categories of patients. Adipose tissue plays a fundamental role in the modulation and selection of nutrients reaching the myocardium, and adipocytes secrete adipokines and other molecules affecting myocardial metabolism and regulating vascular function. In turn, the myocardium secretes a series of peptides affecting adipose tissue metabolism, and adipose tissue vascularization and perfusion contribute to the maintenance of adipose tissue health. This review addresses the reciprocal interaction linking adipose tissue to myocardial metabolism and vascular function. We summarize evidence of factors released by adipose tissue that affect cardiac metabolism and vice versa. Then, we address the role of adipose tissue in regulating vascular health, and examine whether adipose tissue hypoperfusion is causative or defensive of adipose tissue dysfunction.