Immunological identification of uncoupling protein in interscapular "brown" adipose tissue of suckling and adult pipistrelle bats (Pipistrellus pipistrellus).

1. Interscapular adipose tissue of suckling and adult pipistrelle bats was examined for the presence of the 32,000 Mr "uncoupling protein" diagnostic of brown adipose tissue. 2. Following separation by SDS-polyacrylamide gel electrophoresis, mitochondrial proteins were blotted onto nitrocellulose and probed for uncoupling protein with an anti-(ground squirrel uncoupling protein) serum. 3. Immunoreactivity consistent with the presence of uncoupling protein was found in all samples of adipose tissue mitochondria from both suckling and adult bats. 4. It is concluded that interscapular adipose tissue in pipistrelle bats exhibits the critical biochemical criterion for being designated functionally "brown".     

Fat mobilization in vitro and in vivo in the genetically obese Zucker rat "fatty"

Fat mobilization was studied in vitro with epididymal fat pad tissue and also with cell suspensions from epididymal, retroperitoneal, and subcutaneous fat from the obese mutant "fatty" (fafa) and control rats of four different ages. Fat mobilization per cell in response to epinephrine was well above normal in young "fatties"; in older "fatties" the output per cell fell to near normal, but the much greater number of fat cells per rat indicated that the fat mobilizing capacity of the older "fatty" is well above normal. The "fatty" showed normal reactions to epinephrine in vivo: hyperglycemia, glycogenolysis, lipolysis with elevated free fatty acids and glycerol, and increased entry of free fatty acids into muscle and liver. Response was at least as great in "fatty" as in control animals. Metabolic indices-levels of circulating free fatty acids, glycerol, and in some cases glucose and lipid-determined at various ages in fed "fatties" and controls, and at intervals during prolonged fasting (70 days), were consistent with a picture of excessive adipose tissue lipolysis, excessive reesterification in the adipose tissue, fat mobilization in excess of need, and return of the excess to the adipose tissue via lipoproteins.     

Nutritional regulation of adipose tissue apolipoprotein E expression

Apolipoprotein E (apoE) is a multifunctional protein that is highly expressed in human and murine adipose tissue. Endogenous adipocyte apoE expression influences adipocyte triglyceride turnover and modulates the expression of genes involved in lipid synthesis and oxidation. We now demonstrate the regulation of adipose tissue apoE expression by nutritional status in lean and obese mice. Obesity induced by high-fat diet, or by hyperphagia in ob/ob mice, produces significant reduction of adipose tissue apoE expression at the protein and messenger RNA level. Fasting in C57BL/6J mice for 24 h significantly increased apoE protein and messenger RNA levels. In ob/ob mice, transplantation of adipose tissue from lean littermate controls to restore circulating leptin levels produced significant weight loss over 12 wk and also produced an increase in adipose tissue apoE expression. The increase in adipose tissue apoE expression in this model, however, did not require leptin. Adipose tissue apoE was also significantly increased in ob/ob mice after a 48-h fast or after 7 days of caloric restriction. In summary, obesity suppresses adipose tissue apoE expression, whereas fasting or weight loss increases it. From our previous observations, these changes in adipose tissue apoE expression will have significant impact on adipose tissue lipid flux and lipoprotein metabolism. Furthermore, these results suggest adipose tissue apoE participates in defending adipose tissue and organismal energy homeostasis in response to nutritional perturbation.     

Different "weight" of cardiac and general adiposity in predicting left ventricle morphology

Excess adiposity has been widely related to cardiac morphological changes. Nevertheless, the mechanistic link between increased adiposity and left ventricular (LV) morphology is controversial and not completely understood. In this context, several authors have recently debated the different "weight" of BMI as an index of general adiposity vs. the importance of the epicardial fat depot as a marker of local visceral adiposity in obesity-related LV changes. Studies in uncomplicated obesity suggest that the role of BMI in predicting LV abnormalities remains rather doubtful. In contrast, several lines of evidence suggest that cardiac adiposity could play an important part in the development of cardiac modifications. Epicardial fat as an index of cardiac adiposity could have a functional and mechanical role in obesity-related LV abnormalities. Epicardial fat is clinically correlated with LV mass, atrial dimensions, and diastolic function, but a causal effect of epicardial adipose tissue on cardiac chamber modifications remains to be demonstrated. Nevertheless, the close anatomical and functional relationship of epicardial adipose tissue to the adjacent myocardium should readily allow local, paracrine interactions between these tissues.     

Haptoglobin release by human adipose tissue in primary culture

Haptoglobin is a putative adiposity marker because its concentration in blood is increased in obese humans. The present studies examined haptoglobin release by explants of adipose tissue in primary culture. Haptoglobin was released by explants of human visceral and subcutaneous adipose tissue at a nearly linear rate over 48 h. Explants of visceral adipose tissue released more haptoglobin than did explants of subcutaneous adipose tissue. The release of haptoglobin was quite variable, but there was a close correlation between haptoglobin release by visceral adipose tissue and that by explants of subcutaneous tissue from the same individual. Dexamethasone and niflumic acid, a cyclooxygenase-2 inhibitor, both inhibited haptoglobin release. There was release of haptoglobin by both isolated adipocytes and the adipose tissue matrix remaining after collagenase digestion of human adipose tissue. However, the amount of haptoglobin released by human adipose tissue explants in primary culture was quite low in relationship to the circulating level of haptoglobin.     

Studies on the pituitary "fettstoffwechselhormon". VI. Preparation of two highly purified lipolytic active peptides from hog pituitary glands.

The preparation of two highly purified lipolytically active hog pituitary peptides, called P-LF II C and P-LF II D is described. The two peptides are free of other pituitary hormone activities. In isolated rat and porcine adipose tissue, both fractions are lipolytically much more active than every other lipolytic active pituitary peptide described to date. By fraction P-LF II D, the first pituitary peptide was isolated which has lipolytic activity in isolated rat adipose tissue than corticotropin, the lipolytically most active pituitary hormone known so far. On isolated porcine adipose tissue, fraction P-LF II D as well as P-LF II C showed without doubt higher activity than corticotropin.     

p53-induced adipose tissue inflammation is critically involved in the development of insulin resistance in heart failure

Several clinical studies have shown that insulin resistance is prevalent among patients with heart failure, but the underlying mechanisms have not been fully elucidated. Here, we report a mechanism of insulin resistance associated with heart failure that involves upregulation of p53 in adipose tissue. We found that pressure overload markedly upregulated p53 expression in adipose tissue along with an increase of adipose tissue inflammation. Chronic pressure overload accelerated lipolysis in adipose tissue. In the presence of pressure overload, inhibition of lipolysis by sympathetic denervation significantly downregulated adipose p53 expression and inflammation, thereby improving insulin resistance. Likewise, disruption of p53 activation in adipose tissue attenuated inflammation and improved insulin resistance but also ameliorated cardiac dysfunction induced by chronic pressure overload. These results indicate that chronic pressure overload upregulates adipose tissue p53 by promoting lipolysis via the sympathetic nervous system, leading to an inflammatory response of adipose tissue and insulin resistance.     

Deletion of natriuretic peptide receptor C alleviates adipose tissue inflammation in hypercholesterolemic Apolipoprotein E knockout mice

The inflammation of adipose tissue is one of the most common secondary pathological changes in atherosclerosis, which in turn influences the process of atherosclerosis. Natriuretic peptides have been revealed important effect in regulating adipose metabolism. However, the relationship between natriuretic peptide receptor C and inflammation of adipose tissue in atherosclerosis remains unknown. This study aims to explore the effect natriuretic peptide receptor C exerts on the regulation of the adipose inflammation in atherosclerotic mice induced by western-type diet and its overlying mechanisms. To clarify the importance of NPRC of adipose inflammation in atherosclerotic mice, NPRC expression was measured in mice fed with chow diet and western-type diet for 12 weeks and we found a considerable increase in adipose tissue of atherosclerotic mice. Global NPRC knockout in mice was bred onto ApoE^−/− mice to generate NPRC^−/−ApoE^−/− mice, which displayed remarked increase in browning of white adipose tissue and lipolysis of adipose tissue and decrease in adipose inflammation manifested by decreased macrophage invasion to form less CLS (crown-like structure), reduced oxidative stress and alleviated expression of TNFα, IL-6, IL-1β and MCP1, but increased expression of adiponectin in adipose tissue. Moreover, our study showed that white adipose tissue browning in NPRC^−/−ApoE^−/− atherosclerotic mice was associated with decreased inflammatory response through cAMP/PKA signalling activation. These results identify NPRC as a novel regulator for adipose inflammation in atherosclerotic mice by modulating white adipose tissue browning.     

结缔组织铺片脂肪组织油红染色在组织学实验教学中的应用

目的在传统结缔组织铺片基础上开展脂肪组织油红染色方法在医学本科生组织学实验教学中的应用。方法学生先进行疏松结缔组织铺片,并施行脂肪组织油红o-甲苯胺兰-伊红三重染色,然后镜下观察。结果油红o染色把结缔组织中的脂肪细胞内脂滴保存下来并染上红色。脂肪组织中央的细胞脂滴均匀红染,充满胞浆,周边的脂肪细胞胞浆中油红染色很少,细胞呈空泡状,显示出脂肪细胞亚群存在。甲苯胺兰染色使得疏松结缔组织中肥大细胞染成紫红色,胞核染色浅,细胞数量多、成群分布。伊红可使得结缔组织内除脂肪细胞、肥大细胞意外的其他细胞的胞浆和胶原纤维染成淡红色。结论传统的组织学平铺片技术基础上引入脂肪油红o-甲苯胺兰-伊红三重染色,可增强学生动手能力,并能很好地了解输送结缔组织中细胞的不同表型和分布,丰富组织学内容,把教学、科研连接一起,达到提高实验教学质量的目的。     

Lack of "immunological fitness" during fasting in metabolically challenged animals

Subclinical inflammation is frequently associated with obesity. Here, we aim to better define the acute inflammatory response during fasting. To do so, we analyzed representatives of immune-related proteins in circulation and in tissues as potential markers for adipose tissue inflammation and modulation of the immune system. Lipopolysaccharide treatment or high-fat diet led to an increase in circulating serum amyloid (SAA) and α1-acid glycoprotein (AGP), whereas adipsin levels were reduced. Mouse models that are protected against diet-induced challenges, such as adiponectin-overexpressing animals or mice treated with PPARγ agonists, displayed lower SAA levels and higher adip-sin levels. An oral lipid gavage, as well as prolonged fasting, increased circulating SAA concurrent with the elevation of free FA levels. Moreover, prolonged fasting was associated with an increased number of Mac2-positive crown-like structures, an increased capillary permeability, and an increase in several M2-type macrophage markers in adipose tissue. This fasting-induced increase in SAA and M2-type macrophage markers was impaired in metabolically challenged animals. These data suggest that metabolic inflexibility is associated with a lack of "immunological fitness."     

The inhibition by cycloheximide of lipid metabolism by rat adipose tissue in vitro

Cycloheximide in rat adipose tissue inhibits lipogenesis, decreases O₂ consumption, CO₂ formation and ATP/ADP ratio and increases the ratio of lactate/pyruvate released. These findings suggest a similar mechanism of cycloheximide action in adipose tissue and liver where this compound has been shown to inhibit the mitochondrial energy transfer at site I.     

Proteome analysis in adipose tissue of <Emphasis Type="Italic">ob/ob</Emphasis> mice in response to chitosan oligosaccharides treatment

Adipose tissue plays a central role in the development of obesity, and thus characterization of the molecular changes related to obesity in this tissue is a main concern. Recently we identified chitosan oligosaccharides (CO) as a potent adipogenic inhibitor in 3T3-L1 cells. In the current study, a proteomic approach was used to investigate the anti-obesity effect of CO in white adipose tissue of ob/ob mice. CO administration significantly lowered body weight gain and epididymal WAT mass compared to control animals. In addition, twenty-five proteins were found to be differentially expressed between the two groups of animals in response to CO treatment. Expression changes in Karyopherin beta 1, indoleamine-pyrrole 2,3-dioxygenase, and retinoic acid binding protein were associated here for the first time with obesity. Immunoblotting studies of adipocyte protein 2 (aP2) and aquaporin-7 also showed amelioration in their levels in WAT. Furthermore, the results of adipose tissue specific gene expressions of aP2, adiponectin, TNF-α, and IL-6 were in good agreement with improved levels of obesity. Gene expression of PPARg and SREBP-1c were also down-regulated by CO treatment. The results suggest that the anti-obesity effect of CO might be mediated by the modulation of adipokines and adipose tissue specific genes.     

The role of the sympathetic nervous system in the regulation of leptin synthesis in C57BL/6 mice

The objectives of this study were to determine whether leptin synthesis is regulated by the sympathetic nervous system and if so whether beta-adrenergic receptors mediate this effect. We show that sympathetic blockade by reserpine increases leptin mRNA levels in brown but not white adipose tissue, while acute cold-exposure decreases leptin expression 10-fold in brown adipose tissue and 2-fold in white adipose tissue. The cold-induced reduction in leptin mRNA can be prevented by a combination of propranolol and SR 59230A but not by either antagonist alone, indicating that beta3-adrenergic receptors and classical beta1/beta2-adrenergic receptors both mediate responses to sympathetic stimulation. Circulating leptin levels reflect synthesis in white adipose tissue but not in brown adipose tissue.     

Fatty acid signatures of stomach oil and adipose tissue of northern fulmars (<Emphasis Type="Italic">Fulmarus glacialis</Emphasis>) in Alaska: implications for diet analysis of Procellariiform birds

Procellariiforms are unique among seabirds in storing dietary lipids in both adipose tissue and stomach oil. Thus, both lipid sources are potentially useful for trophic studies using fatty acid (FA) signatures. However, little is known about the relationship between FA signatures in stomach oil and adipose tissue of individuals or whether these signatures provide similar information about diet and physiology. We compared the FA composition of stomach oil and adipose tissue biopsies of individual northern fulmars (N = 101) breeding at three major colonies in Alaska. Fatty acid signatures differed significantly between the two lipid sources, reflecting differences in dietary time scales, metabolic processing, or both. However, these signatures exhibited a relatively consistent relationship between individuals, such that the two lipid sources provided a similar ability to distinguish foraging differences among individuals and colonies. Our results, including the exclusive presence of dietary wax esters in stomach oil but not adipose tissue, are consistent with the notion that stomach oil FA signatures represent lipids retained from prey consumed during recent foraging and reflect little metabolic processing, whereas adipose tissue FA signatures represent a longer-term integration of dietary intake. Our study illustrates the potential for elucidating short- versus longer-term diet information in Procellariiform birds using different lipid sources.     

Development of the Mouse Dermal Adipose Layer Occurs Independently of Subcutaneous Adipose Tissue and Is Marked by Restricted Early Expression of FABP4

The laboratory mouse is a key animal model for studies of adipose biology, metabolism and disease, yet the developmental changes that occur in tissues and cells that become the adipose layer in mouse skin have received little attention. Moreover, the terminology around this adipose body is often confusing, as frequently no distinction is made between adipose tissue within the skin, and so called subcutaneous fat. Here adipocyte development in mouse dorsal skin was investigated from before birth to the end of the first hair follicle growth cycle. Using Oil Red O staining, immunohistochemistry, quantitative RT-PCR and TUNEL staining we confirmed previous observations of a close spatio-temporal link between hair follicle development and the process of adipogenesis. However, unlike previous studies, we observed that the skin adipose layer was created from cells within the lower dermis. By day 16 of embryonic development (e16) the lower dermis was demarcated from the upper dermal layer, and commitment to adipogenesis in the lower dermis was signalled by expression of FABP4, a marker of adipocyte differentiation. In mature mice the skin adipose layer is separated from underlying subcutaneous adipose tissue by the panniculus carnosus. We observed that the skin adipose tissue did not combine or intermix with subcutaneous adipose tissue at any developmental time point. By transplanting skin isolated from e14.5 mice (prior to the start of adipogenesis), under the kidney capsule of adult mice, we showed that skin adipose tissue develops independently and without influence from subcutaneous depots. This study has reinforced the developmental link between hair follicles and skin adipocyte biology. We argue that because skin adipocytes develop from cells within the dermis and independently from subcutaneous adipose tissue, that it is accurately termed dermal adipose tissue and that, in laboratory mice at least, it represents a separate adipose depot.     

Metabolic Dysregulation and Adipose Tissue Fibrosis: Role of Collagen VI

Adipocytes are embedded in a unique extracellular matrix whose main function is to provide mechanical support, in addition to participating in a variety of signaling events. During adipose tissue expansion, the extracellular matrix requires remodeling to accommodate adipocyte growth. Here, we demonstrate a general upregulation of several extracellular matrix components in adipose tissue in the diabetic state, therefore implicating “adipose tissue fibrosis” as a hallmark of metabolically challenged adipocytes. Collagen VI is a highly enriched extracellular matrix component of adipose tissue. The absence of collagen VI results in the uninhibited expansion of individual adipocytes and is paradoxically associated with substantial improvements in whole-body energy homeostasis, both with high-fat diet exposure and in the ob/ob background. Collectively, our data suggest that weakening the extracellular scaffold of adipocytes enables their stress-free expansion during states of positive energy balance, which is consequently associated with an improved inflammatory profile. Therefore, the disproportionate accumulation of extracellular matrix components in adipose tissue may not be merely an epiphenomenon of metabolically challenging conditions but may also directly contribute to a failure to expand adipose tissue mass during states of excess caloric intake.Adipose tissue is a key regulator of systemic energy homeostasis. The physiological state of adipose tissue is driven by cell-autonomous processes within the adipocyte. In addition to this, the adipocyte itself is subject to major modifications by other cell types that infiltrate adipose tissue, such as macrophages and vascular cells; moreover, adipocytes can be markedly influenced by several hormones and cytokines that circulate systemically.Although all these cellular interactions have been the subject of extensive studies in numerous laboratories, the extracellular matrix of adipose tissue has received limited attention to date, despite evidence suggesting that it is a functionally relevant constituent of adipose tissue physiology.It is currently unknown what consequential effects metabolic stress exerts on the extracellular matrix and vice versa. In other words, what is the impact of dysregulation of the extracellular constituents of adipose tissue on the systemic metabolic state? Here, we approach this subject from two different perspectives. We first assessed the overall level of extracellular matrix components under different metabolic conditions and established that the extracellular constituents are globally upregulated during metabolically challenging conditions. We then selected a specific member of the collagen family, collagen VI (exhibiting predominant expression in adipose tissue), and utilized a genetic model of collagen VI disruption to investigate the effects of disruption of the extracellular matrix of adipose tissue. Remarkably, our studies demonstrated that such weakening of adipose tissue extracellular matrix results in considerable improvement of the metabolic phenotype in the context of both a high-fat diet and a challenge with the ob/ob mutation.Our observations highlight the extracellular matrix of adipose tissue as an important and novel site of modulation of systemic metabolism. Obese adipose tissue displays hallmarks similar to other fibrotic tissues, such as the liver; this suggests that specific constituents of this normally rather rigid extracellular matrix environment may provide possible targets for pharmacological intervention for the treatment of metabolic disorders.