Gender-specific effects of capsiate supplementation on body weight and bone mineral density: a randomized, double-blind, placebo-controlled study in slightly overweight women.

INTRODUCTION: Overweight and obesity are highly prevalent conditions associated with premature morbidity and mortality worldwide. Capsiate, a nonpungent analogue of capsaicin, binds to TRP vanilloid 1 (TRPV1) receptor, which is involved in adipogenesis, and could be effective as a weight-lowering agent. METHODS: Eighteen slightly overweight women were enrolled in this randomized, double-blind, placebo-controlled study. Nine patients were included in the capsiate intervention group and received 9 mg/day of capsinoids and 9 patients received placebo for 8 weeks. All patients underwent weight and waist circumference assessment before and after treatment. Body composition and bone mineral density (BMD) were also detected by dual-energy X-ray absorptiometry (DXA). RESULTS: Fourteen patients completed the study. The treatment with capsiate or placebo for 8 weeks was not associated with significant changes in weight or waist circumference. After treatment, there was a significant improvement in BMD values measured at the spine in the capsiate group (1.158 vs 1.106 g/cm2, + 4.7%; p = 0.04), but not in the group treated with placebo. Similarly, the capsiate group showed a 9.1% increase (p = 0.05) in the adipose tissue and an 8.5% decrease in lean mass measured at the supraclavicular level, whereas these changes were not statistically significant in the placebo group. CONCLUSIONS: Treatment with capsiate for 8 weeks led to negligible changes in body weight in a small sample of slightly overweight women, but our findings suggest a potential effect of capsaicin on bone metabolism in humans.

The Adipose Organ Is a Unitary Structure in Mice and Humans.

Obesity is the fifth leading cause of death worldwide. In mice and humans with obesity, the adipose organ undergoes remarkable morpho-functional alterations. The comprehension of the adipose organ function and organization is of paramount importance to understand its pathology and formulate future therapeutic strategies. In the present study, we performed anatomical dissections, magnetic resonance imaging, computed axial tomography and histological and immunohistochemical assessments of humans and mouse adipose tissues. We demonstrate that most of the two types of adipose tissues (white, WAT and brown, BAT) form a large unitary structure fulfilling all the requirements necessary to be considered as a true organ in both species. A detailed analysis of the gross anatomy of mouse adipose organs in different pathophysiological conditions (normal, cold, pregnancy, obesity) shows that the organ consists of a unitary structure composed of different tissues: WAT, BAT, and glands (pregnancy). Data from autoptic dissection of 8 cadavers, 2 females and 6 males (Age: 37.5 ± 9.7, BMI: 23 ± 2.7 kg/m2) and from detailed digital dissection of 4 digitalized cadavers, 2 females and 2 males (Age: 39 ± 14.2 years, BMI: 22.8 ± 4.3 kg/m2) confirmed the mixed (WAT and BAT) composition and the unitary structure of the adipose organ also in humans. Considering the remarkable endocrine roles of WAT and BAT, the definition of the endocrine adipose organ would be even more appropriate in mice and humans.

Noradrenergic fibers are associated with beta-cell dedifferentiation and impaired beta-cell function in humans.

AIMS/HYPOTHESIS: Type 2 diabetes (T2D) is characterized by a progressive loss of beta-cell function, and the "disappearance" of beta-cells in T2D may also be caused by the process of beta -cell dedifferentiation. Since noradrenergic innervation inhibits insulin secretion and density of noradrenergic fibers is increased in type 2 diabetes mouse models, we aimed to study the relation between islet innervation, dedifferentiation and beta-cell function in humans. METHODS: Using immunohistochemistry and electron microscopy, we analyzed pancreata from organ donors and from patients undergoing pancreatic surgery. In the latter, a pre-surgical detailed metabolic characterization by oral glucose tolerance test (OGTT) and hyperglycemic clamp was performed before surgery, thus obtaining in vivo functional parameters of beta-cell function and insulin secretion. RESULTS: The islets of diabetic subjects were 3 times more innervated than controls (0.91 ±â€¯0.21 vs 0.32 ±â€¯0.10, n.fibers/islet; p = 0.01), and directly correlated with the dedifferentiation score (r = 0.39; p = 0.03). In vivo functional parameters of insulin secretion, assessed by hyperglycemic clamp, negatively correlated with the increase in fibers [beta-cell Glucose Sensitivity (r = -0.84; p = 0.01), incremental second-phase insulin secretion (r = -0.84, p = 0.03) and arginine-stimulated insulin secretion (r = -0.76, p = 0.04)]. Moreover, we observed a progressive increase in fibers, paralleling worsening glucose tolerance (from NGT through IGT to T2D). CONCLUSIONS/INTERPRETATION: Noradrenergic fibers are significantly increased in the islets of diabetic subjects and this positively correlates with beta-cell dedifferentiation score. The correlation between in vivo insulin secretion parameters and the density of pancreatic noradrenergic fibers suggests a significant involvement of these fibers in the pathogenesis of the disease, and indirectly, in the islet dedifferentiation process.

Origami multiple paper-based electrochemical biosensors for pesticide detection.

Herein, we propose the first three-dimensional origami paper-based device for the detection of several classes of pesticides by combining different enzyme-inhibition biosensors. This device was developed by integrating two different office paper-based screen-printed electrodes and multiple filter paper-based pads to load enzymes and enzymatic substrates. The versatile analysis of different pesticides was carried by folding and unfolding the filter paper-based structure, without any addition of reagents and any sample treatment (i.e. dilution, filtration, pH adjustment). The paper-based platform was employed to detect paraoxon, 2,4-dichlorophenoxyacetic acid, and atrazine by exploiting the capability of these different types of pesticides (i.e. organophosphorus insecticides, phenoxy-acid herbicides, and triazine herbicide) to inhibit butyrylcholinesterase, alkaline phosphatase, and tyrosinase, respectively. The degree of inhibition correlating to the quantity of pesticides was evaluated by chronoamperometrically monitoring the enzymatic activity in the absence and in the presence of pesticides by using a portable potentiostat. To improve the sensitivity, the paper-based electrodes were modified with carbon black alone in the case of platforms for 2,4-dichlorophenoxyacetic acid and atrazine detection, or decorated with Prussian blue nanoparticles for the detection of paraoxon. The paper-based device was applied for the detection of paraoxon, 2,4-dichlorophenoxyacetic acid, and atrazine at ppb level in both standard solutions and river water sample. The accuracy of this origami multiple paper-based electrochemical biosensor was evaluated in river water by recovery studies, obtaining satisfactory values (e.g. for paraoxon 90 ±â€¯1% and 88 ±â€¯2%, for 10 and 20 ppb, respectively). The proposed three-dimensional origami paper device allows for rapid, cost-effective and accurate pesticide detection in surface water as a result of combining filter and office papers, screen-printing, wax-printing and nanomaterial technology.

Yield of Image-Guided Needle Biopsy for Infectious Discitis: A Systematic Review and Meta-Analysis.

BACKGROUND: Image-guided biopsy is routinely conducted in patients with suspected discitis, though the sensitivity reported in the literature ranges widely. PURPOSE: We applied a systematic review and meta-analysis to estimate the yield of image-guided biopsy for infectious discitis. DATA SOURCES: We performed a literature search of 4 data bases: PubMed, Cochrane CENTRAL Register of Controlled Trials, Embase.com, and Scopus from data base inception to March 2016. STUDY SELECTION: A screen of 1814 articles identified 88 potentially relevant articles. Data were extracted for 33 articles, which were eligible if they were peer-reviewed publications of patients with clinical suspicion of discitis who underwent image-guided biopsy. DATA ANALYSIS: Patients with positive cultures out of total image-guided biopsy procedures were pooled to estimate yield with 95% confidence intervals. Hypothesis testing was performed with an inverse variance method after logit transformation. DATA SYNTHESIS: Image-guided biopsy has a yield of approximately 48% (793/1763), which is significantly lower than the open surgical biopsy yield of 76% (152/201; P < .01). Biopsy in patients with prior antibiotic exposure had a yield of 32% (106/346), which was not significantly different from the yield of 43% (336/813; P = .08) in patients without prior antibiotic exposure. LIMITATIONS: The conclusions of this meta-analysis are primarily limited by the heterogeneity of the included studies. CONCLUSIONS: Image-guided biopsy has a moderate yield for the diagnosis of infectious discitis, which is significantly lower than the yield of open surgical biopsy. This yield is not significantly affected by prior antibiotic use.

Crosstalk Between Muscle and Bone Via the Muscle-Myokine Irisin.

Several lines of evidence have recently established that skeletal muscle is an endocrine organ producing and releasing myokines acting in a paracrine or endocrine fashion. Among these, the newly identified myokine Irisin, produced by skeletal muscle after physical exercise, was originally described as molecule able to promote energy expenditure in white adipose tissue. Recently, it has been shown that the myokine Irisin affects skeletal metabolism in vivo. Thus, mice treated with a micro-dose of r-Irisin displayed improved cortical bone mass, geometry and strength, resembling the effect of physical activity in developing an efficient load-bearing skeleton. Further studies highlighted the autocrine effect of Irisin on skeletal muscle, and research performed in humans has definitively established that Irisin is a circulating hormone-like myokine, increased by physical activity. Albeit there are still few, since Irisin has been very recently discovered, herein are summarized the most relevant research findings published on this topic.

Omental adipose tissue fibrosis and insulin resistance in severe obesity.

BACKGROUND/OBJECTIVES: The unresolved chronic inflammation of white adipose tissue (WAT) in obesity leads to interstitial deposition of fibrogenic proteins as reparative process. The contribution of omental adipose tissue (oWAT) fibrosis to obesity-related complications remains controversial. The aim of our study was to investigate whether oWAT fibrosis may be related to insulin resistance in severely obese population. SUBJECTS/METHODS: Forty obese subjects were studied by glucose clamp before undergoing bariatric surgery and thus stratified according to insulin resistance severity (M-value). From the first (Group B: n=13; M=1.9±0.7 mg kg(-1) min(-1)) and the highest (Group A: n=14; M=4.5±1.4 mg kg(-1) min(-1)) M-value tertiles, which were age-, waist- and body mass index-matched, oWAT samples were then obtained.Gene expression of collagen type I, III and VI, interleukin-6, profibrotic mediators (transforming growth factor (TGF)-ß1, activin A, connective tissue growth factor), hypoxia inducible factor-1α (HIF-1α) and macrophage (CD68, monocyte chemotactic protein (MCP)-1, CD86, CD206, CD150) markers were analyzed by quantitative reverse transcription PCR. Adipocyte size and total fibrosis were assessed by histomorphometry techniques. RESULTS: Fibrosis at morphological level resulted significantly greater in Group B compared with Group A, although collagens gene expression did not differ. Notably, collagen VI messenger RNA significantly correlated with collagen I, collagen III, HIF-1α, TGF-ß1, CD68, MCP-1 and CD86 transcription levels, supporting their relation with fibrosis development. CONCLUSIONS: In conclusion, we show for the first time that human oWAT fibrosis in severe obesity is consistent with a higher degree of insulin resistance measured by glucose clamp. Therefore, collagen deposition could represent a maladaptive mechanism contributing to obesity-related metabolic complications.

Multiple symmetric lipomatosis: a rare disease and its possible links to brown adipose tissue.

AIM: Aim of this study is an updated review of our case series (72 patients) as well as available literature on the Multiple Symmetric Lipomatosis (MSL), a rare disease primarily involving adipose tissue, characterized by the presence of not encapsulated fat masses, symmetrically disposed at characteristic body sites (neck, trunk, proximal parts of upper and lower limbs). DATA SYNTHESIS: The disease is more frequent in males, associated to an elevated chronic alcohol consumption, mainly in form of red wine. Familiarity has been reported and MSL is considered an autosomic dominant inherited disease. MSL is associated to severe clinical complications, represented by occupation of the mediastinum by lipomatous tissue with a mediastinal syndrome and by the presence of a somatic and autonomic neuropathies. Hyper-alphalipoproteinemia with an increased adipose tissue lipoprotein-lipase activity, a defect of adrenergic stimulated lipolysis and a reduction of mitochondrial enzymes have been described. The localization of lipomatous masses suggests that MSL lipomas could originate from brown adipose tissue (BAT). Moreover, studies on cultured pre-adipocytes demonstrate that these cells synthetize the mitochondrial inner membrane protein UCP-1, the selective marker of BAT. Surgical removal of lipomatous tissue is to date the only validated therapeutic approach. CONCLUSIONS: MSL is supposed to be the result of a disorder of the proliferation and differentiation of human BAT cells.

Increased density of inhibitory noradrenergic parenchymal nerve fibers in hypertrophic islets of Langerhans of obese mice.

BACKGROUND AND AIM: We sought to identify mechanisms of beta cell failure in genetically obese mice. Little is known about the role of pancreatic innervation in the progression of beta cell failure. In this work we studied adrenergic innervation, in view of its potent inhibitory effect on insulin secretion. We analyzed genetically obese ob/ob and db/db mice at different ages (6- and 15-week-old), corresponding to different compensatory stages in the course of beta cell dysfunction. 15 week-old HFD mice were also studied. METHODS AND RESULTS: All mice were characterized by measures of plasma glucose, insulin, and HOMA. After perfusion, pancreata were dissected and studied by light microscopy, electron microscopy, and morphometry. Insulin, Tyrosine Hydroxylase-positive fibers and cells and Neuropeptide Y-positive cells were scored by immunohistochemistry. Islets of obese mice showed increased noradrenergic fiber innervation, with significant increases of synaptoid structures contacting beta cells compared to controls. Noradrenergic innervation of the endocrine area in obese db/db mice tended to increase with age, as diabetes progressed. In ob/ob mice, we also detected an age-dependent trend toward increased noradrenergic innervation that, unlike in db/db mice, was unrelated to glucose levels. We also observed a progressive increase in Neuropeptide Y-immunoreactive elements localized to the islet core. CONCLUSIONS: Our data show increased numbers of sympathetic nerve fibers with a potential to convey inhibitory signals on insulin secretion in pancreatic islets of genetically obese animals, regardless of their diabetic state. The findings suggest an alternative interpretation of the pathogenesis of beta cell failure, as well as novel strategies to reverse abnormalities in insulin secretion.

Low FasL levels promote proliferation of human bone marrow-derived mesenchymal stem cells, higher levels inhibit their differentiation into adipocytes.

Mesenchymal stem cells (MSCs) are multipotent progenitor cells that can differentiate into several cell types. Bone marrow (BM)-MSCs mainly differentiate into osteoblasts or adipocytes. MSC interactions with their microenvironment directly affect their self-renewal/differentiation program. Here, we show for the first time that Fas ligand (FasL), a well-explored proapoptotic cytokine, can promote proliferation of BM-derived MSCs in vitro and inhibits their differentiation into adipocytes. BM-MSCs treated with a low FasL dose (0.5 ng/ml) proliferated more rapidly than untreated cells without undergoing spontaneous differentiation or apoptosis, whereas higher doses (25 ng/ml) induced significant though not massive BM-MSC death, with surviving cells maintaining a stem cell phenotype. At the molecular level, 0.5 ng/ml FasL induced ERK1/2 phosphorylation and survivin upregulation, whereas 25 ng/ml FasL induced caspase activation. Importantly, 25 ng/ml FasL reversibly prevented BM-MSC differentiation into adipocytes by modulating peroxisome proliferator-activated receptor gamma (PPARγ) and FABP4/aP2 expression induced by adipogenic medium. All such effects were inhibited by anti-Fas neutralizing antibody. The in vitro data regarding adipogenesis were confirmed using Fas(lpr) mutant mice, where higher PPARγ and FABP4/aP2 mRNA and protein levels were documented in whole tibia. These data show for the first time that the FasL/Fas system can have a role in BM-MSC biology via regulation of both proliferation and adipogenesis, and may have clinical relevance because circulating Fas/FasL levels decline with age and several age-related conditions, including osteoporosis, are characterized by adipocyte accumulation in BM.

Time course of histomorphological changes in adipose tissue upon acute lipoatrophy.

BACKGROUND AND AIMS: Crown-like structures (CLS) are characteristic histopathology features of inflamed adipose tissues in obese mice and humans. In previous work, we suggested that these cells derived from macrophages primarily involved in the reabsorption of dead adipocytes. Here, we used a well-characterized transgenic mouse model in which the death of adipocytes in adult mice is inducible and highly synchronized. In this "FAT ATTAC" model, apoptosis is induced through forced dimerization of a caspase-8 fusion protein. METHODS AND RESULTS: 0, 0.5, 1, 2, 3 and 10 days post induction of adipocyte cell death, we analyzed mesenteric and epididymal adipose depots by histology, immunohistochemistry and electron microscopy. Upon induction of caspase-8 dimerization, numerous adipocytes lost immunoreactivity for perilipin, a marker for live adipocytes. In the same areas, we found adipocytes with hypertrophic mitochondria and signs of organelle degeneration. Neutrophils and lymphocytes were the main inflammatory cells present in the tissue, and the macrophages were predominantly Mac-2 negative. Over the course of ablation, Mac-2 positive macrophages substituted for Mac-2 negative macrophages, followed by CLS formation. All perilipin negative, dead adipocytes were surrounded by CLS structures. The time course of histopathology was similar in both fat pads studied, but occurred at earlier stages and was more gradual in mesenteric fat. CONCLUSION: Our data demonstrate that CLS formation results as a direct consequence of adipocyte death, and that infiltrating macrophages actively uptake remnant lipids of dead adipocytes. Upon induction of adipocyte apoptosis, inflammatory cells infiltrate adipose tissue initially consisting of neutrophils followed by macrophages that are involved in CLS formation.

Exercise as a new physiological stimulus for brown adipose tissue activity.

BACKGROUND AND AIM: Brown adipose tissue (BAT) plays a major role in body energy expenditure counteracting obesity and obesity-associated morbidities. BAT activity is sustained by the sympathetic nervous system (SNS). Since a massive activation of the SNS was described during physical activity, we investigated the effect of endurance running training on BAT of young rats to clarify the role of exercise training on the activity and recruitment state of brown cells. METHODS AND RESULTS: Male, 10-week-old Sprague Dawley rats were trained on a motor treadmill (approximately 60% of VO2max), 5 days/week, both for 1 and 6 weeks. The effect of endurance training was valuated using morphological and molecular approaches. Running training affected on the morphology, sympathetic tone and vascularization of BAT, independently of the duration of the stimulus. Functionally, the weak increase in the thermogenesis (no difference in UCP-1), the increased expression of PGC-1α and the membrane localization of MCT-1 suggest a new function of BAT. Visceral fat increased the expression of the FOXC2, 48 h after last training session and some clusters of UCP-1 paucilocular and multilocular adipocytes appeared. CONCLUSION: Exercise seemed a weakly effective stimulus for BAT thermogenesis, but surprisingly, without the supposed metabolically hypoactive effects. The observed browning of the visceral fat, by a supposed white-to-brown transdifferentiation phenomena suggested that exercise could be a new physiological stimulus to counteract obesity by an adrenergic-regulated brown recruitment of adipocytes.

The adipose organ: white-brown adipocyte plasticity and metabolic inflammation.

White adipocytes can store energy, whereas brown adipocytes dissipate energy for thermogenesis. These two cell types with opposing functions are contained in multiple fat depots forming the adipose organ. In this review, we outline the plasticity of this organ in physiological (cold exposure, physical exercise and lactation) and pathological conditions (obesity). We also highlight molecules and signalling pathways involved in the browning phenomena of white adipose tissue. This phenotypic change has proved to be effective in the protection against the metabolic disorders associated to obesity and diabetes, not only because brown adipocytes are more 'healthy' than white adipocytes, but also because the simple size reduction of white adipocytes that characterizes the first steps of transdifferentiation can be useful in determining how to avoid triggering death based on critical size and the consequent chronic low-grade inflammation due to macrophage infiltration. Thus, a better understanding of the molecular mechanisms at the basis of white-brown transdifferentiation can be extremely useful to exploit new therapeutic strategies to combat the increasing incidence of metabolic diseases.

Mdm2 controls CREB-dependent transactivation and initiation of adipocyte differentiation.

The role of the E3 ubiquitin ligase murine double minute 2 (Mdm2) in regulating the stability of the p53 tumor suppressor is well documented. By contrast, relatively little is known about p53-independent activities of Mdm2 and the role of Mdm2 in cellular differentiation. Here we report a novel role for Mdm2 in the initiation of adipocyte differentiation that is independent of its ability to regulate p53. We show that Mdm2 is required for cAMP-mediated induction of CCAAT/enhancer-binding protein δ (C/EBPδ) expression by facilitating recruitment of the cAMP regulatory element-binding protein (CREB) coactivator, CREB-regulated transcription coactivator (Crtc2)/TORC2, to the c/ebpδ promoter. Our findings reveal an unexpected role for Mdm2 in the regulation of CREB-dependent transactivation during the initiation of adipogenesis. As Mdm2 is able to promote adipogenesis in the myoblast cell line C2C12, it is conceivable that Mdm2 acts as a switch in cell fate determination.

The adipose organ of obesity-prone C57BL/6J mice is composed of mixed white and brown adipocytes.

White and brown adipocytes are believed to occupy different sites in the body. We studied the anatomical features and quantitative histology of the fat depots in obesity and type 2 diabetes-prone C57BL/6J mice acclimated to warm or cold temperatures. Most of the fat tissue was contained in depots with discrete anatomical features, and most depots contained both white and brown adipocytes. Quantitative analysis showed that cold acclimation induced an increase in brown adipocytes and an almost equal reduction in white adipocytes; however, there were no significant differences in total adipocyte count or any signs of apoptosis or mitosis, in line with the hypothesis of the direct transformation of white into brown adipocytes. The brown adipocyte increase was accompanied by enhanced density of noradrenergic parenchymal nerve fibers, with a significant correlation between the density of these fibers and the number of brown adipocytes. Comparison with data from obesity-resistant Sv129 mice disclosed a significantly different brown adipocyte content in C57BL/6J mice, suggesting that this feature could underpin the propensity of the latter strain to develop obesity. However, the greater C57BL/6J browning capacity can hopefully be harnessed to curb obesity and type 2 diabetes in patients with constitutively low amounts of brown adipose tissue.

Adipocyte metabolism and cellularity are related to differences in adipose tissue maturity between Holstein and Charolais or Blond d'Aquitaine fetuses.

This paper reports the metabolic and morphological characteristics of bovine adipose tissue (AT) at end of fetal life and its variability with breed and anatomical site of AT. Our hypothesis was that, in cattle, end-of-fetal-life differences in adipocyte number, size, and histology may account for differences in AT maturity. To address this question, perirenal and intermuscular AT were sampled from Charolais, Blond d'Aquitaine, and Holstein fetuses at 260 d postconception. Holstein fetuses showed greater leptin mRNA abundance, which is consistent with the greater perirenal AT weight (P = 0.03) than Blond d'Aquitaine fetuses. Compared with Blond d'Aquitaine or Charolais fetuses, Holstein fetuses had larger (P < 0.001) adipocytes, greater (P < 0.05) activities of enzymes involved in de novo fatty acid (FA) synthesis (FA synthase, glucose-6-phosphate dehydrogenase, malic enzyme) and FA esterification (glycerol-3-phosphate dehydrogenase), and greater (P = 0.06, P = 0.10, P < 0.001) mRNA abundance for lipolytic enzymes (hormone-sensitive lipase and adipose triglyceride lipase) and uncoupling protein 1 in both perirenal and intermuscular AT. This indicates increased FA turnover in Holstein adipocytes through FA storage, mobilization, and oxidation pathways. Whatever the breed, adipocytes were smaller in perirenal AT than intermuscular AT. Whatever the breed or anatomical site, bovine AT at 260 d postconception contained predominantly unilocular adipocytes believed to be white adipocytes together with a few multilocular brown adipocytes. We conclude that the greater metabolic and morphologic maturity of adipocytes from Holstein than Blond d'Aquitaine and Charolais fetuses may contribute to the greater thermogenic aptitude of Holstein newborns. Moreover, the presence of both white and brown adipocytes at the end of fetal life highlights the complexity of AT structure and may indicate that the cellular and functional heterogeneity of AT repeatedly observed postnatally has a developmental origin.

Lipoatrophy induced by subcutaneous insulin infusion: ultrastructural analysis and gene expression profiling.

CONTEXT AND OBJECTIVE: Subcutaneous adipose tissue (SAT) lipoatrophy (LA) is a rare complication of insulin therapy. We aimed to analyze the ultrastructural and molecular aspects of LA lesions. SETTING AND PATIENTS: Macroscopic and microscopic morphology of SAT beneath the LA areas from patients with type 1 diabetes treated with Lispro insulin by continuous sc insulin infusion was studied using magnetic resonance imaging, immunohistochemistry, electron microscopy, and quantitative PCR for adipose tissue-specific genes. RESULTS: SAT was present in LA lesions characterized by: 1) smaller, unilocular perilipin-positive adipocytes, with lipofuscin granules; 2) some "slimmed cells" losing lipid droplets as those we observed during starvation; and 3) numerous perivascular preadipocytes. We did not identify inflammatory cells. SAT in LA areas displayed a strong leptin down-regulation and an increase of AEBP1, a preadipocyte marker. CONCLUSIONS: Our results clearly indicate that the remarkable reduction in fat cell lipid droplets and adipocyte size justifies the decrease of SAT without a reduction in adipocyte number because of necrosis or apoptosis. Thus, immune cells and any other toxic damaging fat cells were not involved in the generation of LA. We speculate that adipocytes chronically exposed to high local insulin concentrations could become severely insulin resistant, dramatically increasing lipolysis and giving rise to "slimmed cells." Clinical LA regression could be explained by the active recruitment of preadipocytes, even if they were unable to differentiate and regenerate adipose tissue unless the insulin injection was removed.

The emergence of cold-induced brown adipocytes in mouse white fat depots is determined predominantly by white to brown adipocyte transdifferentiation.

The origin of brown adipocytes arising in white adipose tissue (WAT) after cold acclimatization is unclear. Here, we demonstrate that several UCP1-immunoreactive brown adipocytes occurring in WAT after cold acclimatization have a mixed morphology (paucilocular adipocytes). These cells also had a mixed mitochondrioma with classic "brown" and "white" mitochondria, suggesting intermediate steps in the process of direct transformation of white into brown adipocytes (transdifferentiation). Quantitative electron microscopy disclosed that cold exposure (6 degrees C for 10 days) did not induce an increase in WAT preadipocytes. beta(3)-adrenoceptor-knockout mice had a blunted brown adipocyte occurrence upon cold acclimatization. Administration of the beta(3)-adrenoceptor agonist CL316,243 induced the occurrence of brown adipocytes, with the typical morphological features found after cold acclimatization. In contrast, administration of the beta(1)-adrenoceptor agonist xamoterol increased only the number of preadipocytes. These findings indicate that transdifferentiation depends on beta(3)-adrenoceptor activation, whereas preadipocyte recruitment is mediated by beta(1)-adrenoceptor. RT-qPCR experiments disclosed that cold exposure induced enhanced expression of the thermogenic genes and of genes expressed selectively in brown adipose tissue (iBAT) and in both interscapular BAT and WAT. beta(3)-adrenoceptor suppression blunted their expression only in WAT. Furthermore, cold acclimatization induced an increased WAT expression of the gene coding for C/EBPalpha (an antimitotic protein), whereas Ccna1 expression (related to cell proliferation) was unchanged. Overall, our data strongly suggest that the cold-induced emergence of brown adipocytes in WAT predominantly reflects beta(3)-adrenoceptor-mediated transdifferentiation.

Morphological and immunohistochemical features of brown adipocytes and preadipocytes in a case of human hibernoma.

BACKGROUND AND AIM: The role of brown adipose tissue physiology and pathology in humans is debated. A greater knowledge of its developmental aspects could play a pivotal role in devising treatments for obesity and diabetes. METHODS AND RESULTS: Tissue from a rare case of hibernoma, removed from a 17-year-old boy, was examined by light and electron microscopy, morphometry and immunohistochemistry. The tumour was well vascularised and innervated and contained mature adipocytes with the characteristics of both brown and white adipocytes. Numerous, poorly differentiated cells resembling brown adipocyte precursors were seen in a pericytic position in close association with the capillary wall. On immunohistochemistry mature brown adipocytes were seen to express the marker protein UCP1. On morphometry the intensity of uncoupling protein 1 (UCP1) immunostaining varied in relation to the morphological features of adipocytes: the "whiter" their appearance, the weaker their UCP1 immunoreactivity. CONCLUSIONS: Our data suggest that in humans, as in rodents, brown adipocyte precursors arise in close association with vessel walls and that intermediate forms between white and brown adipocytes can also be documented in human adults.