Small Fat Cells Research Articles

Edible Vitalmelon Fruit Extract Inhibits Adipogenesis and Ameliorates High-Fat Diet-Induced Obesity.

Conventional breeding of wild (Cucumis melo var. makuwa Makino (CM)) and cultivated (Cucumis melo var. reticulatus (CR)) melons is aimed at improving their biological traits. Here, we prepared a nontoxic, bioactive extract of vitalmelon (F1 hybrid) and evaluated its antiadipogenic and antiobesity effects in fully differentiated 3T3-L1 adipocytes and high-fat diet- (HFD-) induced obese C57BL/6 mice. In fully differentiated 3T3-L1 adipocytes, the vitalmelon extract reduced the DMI- (dexamethasone, 3-isobutyl-1-methylxanthine, and insulin-) induced increases in lipid droplet number and intracellular glucose and triglyceride levels. In addition, the extract inhibited 3T3-L1 preadipocyte differentiation by downregulating PPAR-γ and target genes LPL, CD36, HMGCR, and L-FABP. To investigate the inhibitory effects of the vitalmelon extract on lipid metabolism, we measured serum lipid, hormone, and cytokine concentrations; lipolytic activity; lipid accumulation; and adipogenesis in HFD-fed mice treated with the extract. The HFD+vitalmelon-fed mice showed lower blood cholesterol, free fatty acid, sugar, leptin, and insulin concentrations but higher blood adiponectin concentrations than the HFD-fed mice. Moreover, the HFD+vitalmelon-fed mice showed lower abdominal fat levels, smaller fat cells, lower weight, and fewer lipid droplets in the liver tissue than the HFD-fed mice. Therefore, in HFD-fed mice, vitalmelon regulated lipid metabolism through PPAR-γ, highlighting its potential as a promising antiobesity functional food.

ADIPOSE CLC-3 DEFICIENCY PROTECTS AGAINST DIET-INDUCED OBESITY AND INSULIN RESISTANCE BY REGULATING GLUT4 THROUGH THE PI3K/AKT PATHWAY

Obesity is a worldwide medical condition with excess body fat and has negative effects on personal health. Adipocyte hyperplasia or hypertrophy are considered to be accountable for excessive accumulation of adipose tissue. One of the main reasons that induce obesity is high-fat diet (HFD), HFD can also lead to a series of complications such as insulin resistance and type 2 diabetes. GLUT4 is an important glucose transporter regulating blood glucose, it is supervised by a complicated cascade known as PI3K/Akt pathway for sensing the high concentration of glucose in the blood. Upregulation of PI3K/Akt pathway can stimulate GLUT4 to be activated to transport glucose into adipose cells. Here, we identify voltage-gated chloride ion channel family protein ClC-3 has remarkable impact on the PI3K/Akt pathway to regulate glucose uptake mediated by GLUT4. Conditional knockout ClC-3 with CRISPR/Cas9-Cre/Lox method in adipocytes (ClC-3AKO) will decrease size of the adipocytes, which is mainly decreased in epididymal (eWAT), meanwhile, ClC-3AKO can upregulate the PI3K/Akt pathway phosphorylation level, and prompt glucose uptake by GLUT4. Our studies illustrate the important function of ClC-3 in regulating the HFD-induced obesity and provide new insight into treatment for the diabetic associated disease. 1. To generate ClC-3 systemic knockout mice, and measure the size of fat cells with HE staining; 2. To take human omentum tissue, detect ClC-3 protein and mRNA levels, and analyze its relationship with obesity indicators; 3. Use the CRISPR/Cas9-Cre/Lox method to construct ClC-3AKO mice, and measure their obesity, insulin resistance and changes in adipose tissue. And extract the epididymal fat protein and perform Western Blotting to detect the phosphorylation level of key protein molecules. 4. ClC-3 was overexpressed on the 3T3-L1 cell line, and immunofluorescence, glucose uptake experiments and Western Blotting were performed to determine whether the glucose uptake and signal pathways were restored. 1. ClC-3 systemic knockout mice have smaller fat cells, reduced fat tissue and improved obesity. 2. In human omentum fat, the expression of ClC-3 is positively correlated with obesity indicators. 3. We further found that specific fat knockout ClC-3 mice have reduced fat cells, mainly in eWAT, while ClC-3AKO mice can up-regulate the phosphorylation level of PI3K/Akt pathway. And promote GLUT4 uptake of glucose. 4. ClC-3 over-expression reversed the above effects. 1. ClC-3 knockout improves obesity and insulin resistance

Mentha cordifolia Leaf Extract Improves Hepatic Glucose and Lipid Metabolism in Obese Mice Fed with High-Fat Diet.

Mentha cordifolia (MC) is a popular herb used to flavor food in Thailand that exhibits several biological effects. The present study aimed to determine the role of MC in regulating glucose and lipid metabolism in mice fed a high-fat diet (HFD). ICR obese mice were fed an HFD (45 kcal% lard fat) for 12 weeks, with MC (100 and 200 mg/kg/d) treatment from Week 7. After treatment with MC for 6 weeks, mice showed significantly lower rates of hyperglycemia, hyperinsulinemia, hyperleptinemia, and hyperlipidemia, and increased amounts of serum adiponectin. Furthermore, in mice treated with MC, serum interleukin-6 and tumor necrosis factor alpha were significantly inhibited and liver histology results showed decreased lipid accumulation and liver triglyceride content vs. untreated mice. In addition, MC treatment was associated with smaller fat cells and lower gene expression of liver sterol regulatory element binding protein 1c, acetyl-CoA carboxylase, and fatty acid synthase. However, MC treatment was associated with higher carnitine palmitoyltransferase 1a gene expression and significantly higher rates of adenosine monophosphate-activated protein kinase (AMPK) phosphorylation in liver, but lower levels of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. These results indicate MC regulates glucose and lipid metabolism in a HFD-induced obese mouse model, possibly via activation of AMPK signaling pathway.

An RNAi Screening of Clinically Relevant Transcription Factors Regulating Human Adipogenesis and Adipocyte Metabolism.

ContextHealthy hyperplasic (many but smaller fat cells) white adipose tissue (WAT) expansion is mediated by recruitment, proliferation and/or differentiation of new fat cells. This process (adipogenesis) is controlled by transcriptional programs that have been mostly identified in rodents.ObjectiveA systemic investigation of adipogenic human transcription factors (TFs) that are relevant for metabolic conditions has not been revealed previously.MethodsTFs regulated in WAT by obesity, adipose morphology, cancer cachexia, and insulin resistance were selected from microarrays. Their role in differentiation of human adipose tissue-derived stem cells (hASC) was investigated by RNA interference (RNAi) screen. Lipid accumulation, cell number, and lipolysis were measured for all screened factors (148 TFs). RNA (RNAseq), protein (Western blot) expression, insulin, and catecholamine responsiveness were examined in hASC following siRNA treatment of selected target TFs.ResultsAnalysis of TFs regulated by metabolic conditions in human WAT revealed that many of them belong to adipogenesis-regulating pathways. The RNAi screen identified 39 genes that affected fat cell differentiation in vitro, where 11 genes were novel. Of the latter JARID2 stood out as being necessary for formation of healthy fat cell metabolic phenotype by regulating expression of multiple fat cell phenotype-specific genes.ConclusionThis comprehensive RNAi screening in hASC suggests that a large proportion of WAT TFs that are impacted by metabolic conditions might be important for hyperplastic adipose tissue expansion. The screen also identified JARID2 as a novel TF essential for the development of functional adipocytes.

Adult-onset neuronal intranuclear inclusion disease, with both stroke-like onset and encephalitic attacks: a case report

BackgroundNeuronal intranuclear inclusion disease (NIID) is a neurodegenerative disease, the clinical manifestations of which are complex and easily misdiagnosed. NIID clinical characteristics are varied, affecting the central and peripheral nervous systems and autonomic nerves. In this study, we present an NIID case with both stroke-like onset and encephalitic attacks, which is a rare case report.Case presentationA 68-year-old Chinese female presented with sudden aphasia and limb hemiplegia as the first symptoms, as well as fever, cognitive impairment and mental irritability from encephalitic attacks. During hospitalization, a brain magnetic resonance imaging (MRI) examination detected high signal intensity from diffusion-weighted imaging (DWI) of the bilateral frontal grey matter-white matter junction. Electrophysiological tests revealed the main site of injury was at the myelin sheath in the motor nerves. A skin biopsy revealed eosinophilic spherical inclusion bodies in the nuclei of small sweat gland cells, fibroblasts and fat cells, whilst immunohistochemistry revealed that p62 and ubiquitin antibodies were positive. From genetic analyses, the patient was not a carrier of the fragile X mental retardation 1 (FMR1) permutation, but repeated GGC sequences in the NOTCH2NLC gene confirmed an NIID diagnosis. Through antipsychotic and nutritional support therapy, the patient’s symptoms were completely relieved within 3 weeks.ConclusionsThis report of an NIID case with both stroke-like onset and encephalitic attacks provides new information for NIID diagnoses, and a comprehensive classification of clinical characteristics.

Improved metabolism and body composition beyond normal levels following gastric bypass surgery: a longitudinal study.

The cardiometabolic risk profile improves following bariatric surgery. However, the degree of improvement in relation to weight-stable control subjects is unknown. To study the differences in cardiometabolic risk profile between formerly obese patients following Roux-en-Y gastric bypass (RYGB) surgery and control subjects. Subjects undergoing RYGB and reaching a BMI <30kgm-2 2years postsurgery were matched with control subjects regarding age, sex and BMI. The following examinations were performed: insulin sensitivity measured by hyperinsulinaemic-euglycaemic clamp, insulin clearance, homeostatic model assessment of insulin resistance (HOMA-IR), lipid profile, inflammatory marker levels, dual-energy X-ray absorptiometry and subcutaneous adipose tissue cellularity (fat cell size and number). Sixty-nine subjects undergoing RYGB were matched to a control subject. Insulin sensitivity measured by hyperinsulinaemic-euglycaemic clamp, blood pressure, inflammatory status and glucose, triglyceride and HDL cholesterol levels were comparable to values of control subjects. However, HOMA-IR (1.0±0.5 vs. 1.3±0.7, P=0.005), insulin clearance (0.38±0.08 vs. 0.34±0.08μLm-2 min-1 , P<0.0001) and circulating levels of insulin (31±15 vs. 37±17 pmolL-1 , P=0.008), total cholesterol (4.1±0.7 vs. 4.8±0.9mmolL-1 , P<0.0001) and LDL cholesterol (2.1±0.6 vs. 2.9±0.8mmolL-1 , P<0.0001) were improved beyond the levels in matched control subjects. Furthermore, formerly obese subjects had higher lean and lower fat mass as well as a more benign type of adipose cellularity (hyperplasia with many small fat cells) compared to control subjects. Subjects who underwent RYGB and reached a postobese state demonstrated a beneficial body composition, slightly increased insulin sensitivity as indirectly measured by HOMA-IR and higher insulin clearance, lower atherogenic lipid/lipoprotein levels and benign adipocyte morphology compared with control subjects who had never been obese. In line with previous results, our findings may in part explain why RYGB confers long-term protection against metabolic complications.

Adipose cell size: importance in health and disease.

Adipose tissue is necessary to harbor energy. To handle excess energy, adipose tissue expands by increasing adipocyte size (hypertrophy) and number (hyperplasia). Here, we have summarized the different experimental techniques used to study adipocyte cell size and describe adipocyte size in relation to insulin resistance, type 2 diabetes, and diet interventions. Hypertrophic adipocytes have an impaired cellular function, and inherent mechanisms restrict their expansion to protect against cell breakage and subsequent inflammation. Reduction of large fat cells by diet restriction, physical activity, or bariatric surgery therefore is necessary to improve cellular function and health. Small fat cells may also be dysfunctional and unable to expand. The distribution and function of the entire cell size range of fat cells, from small to very large fat cells, are an important but understudied aspect of adipose tissue biology. To prevent dysmetabolism, therapeutic strategies to expand small fat cells, recruit new fat cells, and reduce large fat cells are needed.

The difference in synovitis (synovial membrane) and angiogenesis between young obese, young lean and old lean people with primary knee osteoarthritis

Purpose: OA is a complex disorder with multiple risk factors including obesity. The excess weight and lipids inherent in obesity have been implicated in the development of OA through mechanical and metabolic effects and low-grade inflammation. Furthermore, synovitis and inflammation have gained an enhanced significance in research as a cause of OA. The aim of this laboratory research: 1: To determine the relationship between BMI and synovial vascularity and inflammation among different age groups with advanced OA. 2: To examine the effect of increased lipid stores as indicated by the fat cell size on the vascularity and inflammation. 3: To assess the difference in synovitis among young obese, young lean and old lean people with advanced OA. Methods: A total of 17 patients (matched for gender, the advanced stage of OA requiring total knee arthroplasty, Kellgren-Lawrence score, comorbidities, ASA grade, medications and functional outcome score) were recruited into three groups based on age (young <60, old >70) and BMI (lean <30, obese >30). Group-1: young-obese (N=6) with age and BMI mean (SD) 53.3 (2.33) and 38.53 (1.16) respectively. Group-2: young-lean (N=5) with age and BMI 55.60(4.5) and 27.01(1.59) respectively. Group-3: old-lean (N=6) with age and BMI 75.33 (3.2) and 25.64 (2.5) respectively. Synovial tissues obtained during surgery were examined using H&E staining and Immunohistochemistry (IHC) on 5μm sections. The monoclonal antibodies included vWF and CD34 for angiogenesis, CD68 for macrophage, CD3 for T-lymphocytes, CD20 for B-lymphocytes and vimentin for fibroblast (all Dako Ltd.). Visualization employed DAB. Quantitative assessment of each marker used image J software. Each slide was divided into synovial and fat sectors based on the content. The software measured each marker in the synovial and fat sectors separately and combined. Further analysis followed regrouping patients into two groups based on fat cell diameter, measured as small (< 68 μm) and large (>68 μm) fat cells. The IHC markers were reanalyzed based on the fat cell size. Additional manual counts, vessel diameter and distance to the synovial surface, were undertaken on vessels in the synovial and fat sectors. A synovitis score was determined using the H&E stained sections (Krenn et al., 2006). Results: Using the initial grouping, overall vascularity did not show any significant differences (p=0.468); vimentin positivity was significantly reduced in the old lean group (p=0.006), and inflammatory markers showed a trend of increasing with increase BMI. Regrouping patients based on fat cell size revealed multiple significant differences. Macrophages, T cells, B cells and fibroblasts positivity was significantly higher in the presence of big fat cells (p= 0.035, 0.016, 0.046, 0.014 respectively). The vascular density was significantly higher in the fatty sections with big fat cells (p= 0.028). Inflammatory markers showed positive correlation with BMI and negative correlation with age. An increasing trend of vascular density, the distance to the synovial surface and vascular wall thickness was observed in the young obese group. There was no clear difference between the groups in relation to synovitis but majority of patients showed mild grade synovitis. Conclusions: The synovium of the obese patients showed more inflammatory response but the vascularity was not significantly different. Increased fat cell size attracted significantly more inflammatory cells. Moreover, vascular hyperplasia, which was noticed mainly in the obese people, could be an indication of atherosclerosis in the synovial vessels. Low grade synovitis is common in primary knee OA. This image showed H&E stain of the synovium of an obese person. The vessels has increased wall thickness very close to the intimal surface.

Blubber news: whale fat is active!

In the world of physiology, scientists use model organisms, such as fish, rats and mice, to study how the complex relationship between the body and its environment influences behaviour. Yet, few have the courage to tackle the challenges of working with the largest mammals on Earth. Undeterred, Hope Ball from University of Akron, USA, and her collaborators from several US institutions decided to investigate how bowhead whales (Balaena mysticetus) and belugas (Delphinapterus leucas) tackle the physical challenges of survival in the extreme environment of the Arctic Ocean and their lengthy migrations.Whales have a unique layer of tissue under their skin called blubber, which provides buoyancy and thermal insulation in cold waters in addition to allowing them to store large amounts of fat to fuel migration while fasting. Other animals that undergo long periods of fasting also possess a specialized protein hormone, called leptin, that varies seasonally to suppress appetite and stimulate fat breakdown when the animals have stopped feeding. While whales are known to produce leptin, little was known about production of the hormone and how the levels vary in these animals.Ball and her colleagues partnered with residents of several Inupiat settlements during their annual subsistence hunt, to collect blubber and tissue samples from bowhead and beluga juveniles and adults during the autumn migration and in the spring. In samples collected from the whales in the autumn – following an intense summer feeding period – the authors reported that leptin gene expression was approximately 10- to 50-fold higher than in the spring whales, suggesting that extreme seasonal variation in leptin plays a role in regulating fat breakdown during fasting periods. The authors also reported that the largest amount of leptin was found in the deepest layer of blubber, where fat is actively broken down for energy production when food is unavailable. This suggests that leptin levels, in addition to seasonal cues, may drive the whales’ migration to and from summer feeding grounds.To determine the influence of season on fat utilization, the authors analysed the activity of the enzymes that break down fat. They found that in the autumn, when the whales were well fed, the blubber was composed of large fat cells and the activity of these enzymes was low. However, in winter, following migration from cold waters back to summer feeding grounds, the blubber contained smaller fat cells and more connective tissue, and the activity of the enzymes that break down fat was high. This suggests that the whales break down fat to maintain the energy demands of the body when they migrate. In addition, Ball and colleagues reported low levels of leptin in juveniles, which were similar to those found in the spring fasting adults, suggesting that the metabolism of the young whales is low to minimize energy loss and it is directed at stimulating appetite to ensure maturation.It appears that these extreme seasonal and life stage variations in leptin levels are unique adaptations that Arctic whales have evolved to drive fat utilization, feeding behaviour and initiation of migration in cold waters. In whales, leptin controls appetite and fat breakdown, thus making blubber an active player in a whale's physiology.

The fat cell epigenetic signature in post-obese women is characterized by global hypomethylation and differential DNA methylation of adipogenesis genes.

Obese subjects have increased number of enlarged fat cells that are reduced in size but not in number in post-obesity. We performed DNA methylation profiling in fat cells with the aim of identifying differentially methylated DNA sites (DMS) linked to adipose hyperplasia (many small fat cells) in post-obesity. Genome-wide DNA methylation was analyzed in abdominal subcutaneous fat cells from 16 women examined 2 years after gastric bypass surgery at a post-obese state (body mass index (BMI) 26±2 kg m(-2), mean±s.d.) and from 14 never-obese women (BMI 25±2 kg m(-2)). Gene expression was analyzed in subcutaneous adipose tissue from nine women in each group. In a secondary analysis, we examined DNA methylation and expression of adipogenesis genes in 15 and 11 obese women, respectively. The average degree of DNA methylation of all analyzed CpG sites was lower in fat cells from post-obese as compared with never-obese women (P=0.014). A total of 8504 CpG sites were differentially methylated in fat cells from post-obese versus never-obese women (false discovery rate 1%). DMS were under-represented in CpG islands and surrounding shores. The 8504 DMS mapped to 3717 unique genes; these genes were over-represented in cell differentiation pathways. Notably, 27% of the genes linked to adipogenesis (that is, 35 of 130) displayed DMS (adjusted P=10(-8)) in post-obese versus never-obese women. Next, we explored DNA methylation and expression of genes linked to adipogenesis in more detail in adipose tissue samples. DMS annotated to adipogenesis genes were not accompanied by differential gene expression in post-obese compared with never-obese women. In contrast, adipogenesis genes displayed differential DNA methylation accompanied by altered expression in obese women. Global CpG hypomethylation and over-representation of DMS in adipogenesis genes in fat cells may contribute to adipose hyperplasia in post-obese women.

Animal Obesity - causes, consequences and comparative aspects: meeting abstracts.

The turnover of fat cells and their lipid content is constantly ongoing in adult life. Fat cell turnover has importance for development of adipose tissue consisting of many small fat cells (hyperplasia) or few but large cells (hypertrophy). The latter is linked to metabolic disorders. Variations in lipids turnover in fat cells is also linked to metabolic disease.

Localized Involutional Lipoatrophy in a Child

Dear Editor: Localized loss of adipose tissue without prior clinical or histologic inflammation is usually termed idiopathic lipoatrophy1. Localized involutional lipoatrophy (LIL), which was first described by Peters and Winkelmann2 in 1986, generally appears asymptomatic well-demarcated, depressed lesion on a single or in several sites3. Most of the reported cases occur in adolescence or in adulthood, but there has been only one reported childhood case of LIL2. Thus, we report a rare case of LIL in childhood in which triggering factors are not found and we reviewed the previously published reports. A 5-year-old boy presented with an asymptomatic depressed lesion on his right buttock 1 month ago. The patient denied any history of injury or local injection at that site. He had no other medical problems or any associated drug intake. Physical examination revealed a well-demarcated, 3.0×3.5 cm sized hypopigmented, depressed atrophic patch (Fig. 1). Laboratory examination showed no abnormal findings in the patient's complete blood count, blood chemistry, C-reactive protein level, and autoantibody screening tests for antinuclear, anti-DNA, and anticentromere antibodies. Histopathological examination of a biopsy specimen showed epidermal atrophy and a decrease in the size of subcutaneous fat lobules composed of small adipocytes. There was no significant dermal or subcutaneous inflammation (Fig. 2). Immunohistochemical studies revealed CD68 positive macrophages within the fat lobules. We have followed up this patient without any treatments or procedures for 6 months, but there was no spontaneous regression. Fig. 1 Well-demarcated, hypopigmented, and depressed atrophic patch on the right buttock. Fig. 2 Histological examination of the skin biopsy specimen shows. (A) Epidermal atrophy, compaction of collagen bundle in the dermis without inflammation (H&E, ×40). (B) Diminutive fat lobules composed of variable sizes adipocytes (H&E, ... Peters and Winkelmann2 first reported LIL in 6 patients, most of all patients were adolescence or adult age except one 5-year-old boy. Yamamoto et al.3 reported 6 patients with LIL, all of whom were female, while 4 of the 6 patients had a history of local injections. Dahl et al.1 reported 16 patients with LIL, who had an average age of 32.8 year (range: 13 to 65 year) with female predominance; 9 of 16 patients had a history of antecedent intramuscular or intra-articular injections at the affected sites. Histological examination presented variable sized fat lobules composed of small fat cells embedded in a well-vascularized and hyalinized background. Each adipocyte that resembles fetal fat tissue may vary in size, but are smaller than the normal fat cell3. LIL is also characterized by the presence of CD68-positive and mucin-positive macrophages scattered between the affected lipocytes. Lesional direct immunofluorescence findings are usually negative1,2. The pathophysiology of LIL is still unknown. LIL is associatied with various immunologic disorders, which may suggest a background of immunologic dysregulation that may predispose for the development of LIL lesions after injection of medications such as antibiotics, insulin, or steroids1,3-5. Ultrastructurally, the activated macrophages were shown in close to fat cells. It is believed that these macrophages are activated after injury and secrete many cytokines, such as tumor necrosis factor-α, interleukin 1, platelet-derived growth factor, transforming growth factor-β1, and fibroblast growth factor-2, which may then mediate the involution of the adipose tissue5. In our case, we could not identified any triggering factors. However, we presumed that the cause of our case was any injury that included injection or trauma; most cases of childhood LIL were triggered after injection. In conclusion, most reported cases have occurred in females of adolescent or adult age with a local injection history, but there has been only one report on childhood LIL2. Thus, we think that this case is very interesting in terms of age of onset, gender, and unidentified triggering factor.

Beta-Mecaptoethanol Suppresses Inflammation and Induces Adipogenic Differentiation in 3T3-F442A Murine Preadipocytes

Preadipocytes are present in adipose tissues throughout adult life that can proliferate and differentiate into mature adipocytes in response to environmental cues. Abnormal increase in adipocyte number or size leads to fat tissue expansion. However, it is now recognized that adipocyte hypertrophy is a greater risk factor for metabolic syndrome whereas fat tissue that continues to produce newer and smaller fat cells through preadipocyte differentiation is “metabolically healthy”. Because adipocyte hypertrophy is often associated with increased oxidant stress and low grade inflammation, both are linked to disturbed cellular redox, we tested how preadipocyte differentiation may be regulated by beta-mercaptoethanol (BME), a pharmacological redox regulator and radical scavenger, using murine 3T3-F442A preadipocytes as the cell model. Effects of BME on adipogenesis were measured by microphotography, real-time PCR, and Western analysis. Our data demonstrated that preadipocyte differentiation could be regulated by extracellular BME. At an optimal concentration, BME enhanced expression of adipogenic gene markers and lipid accumulation. This effect was associated with BME-mediated down-regulation of inflammatory cytokine expression during early differentiation. BME also attenuated TNFalpha-induced activation of NFkappaB in differentiating preadipocytes and partially restored TNFalpha-mediated suppression on adipogenesis. Using a non-adipogenic HEK293 cell line transfected with luciferase reporter genes, we demonstrated that BME reduced basal and TNFalpha-induced NFkappaB activity and increased basal and ciglitazone-induced PPARgamma activity; both may contribute to the pro-adipogenic effect of BME in differentiating F442A preadipocytes.

Regulation of Lipolysis in Small and Large Fat Cells of the Same Subject

Large fat cell size is linked to type 2 diabetes risk and may involve an enhanced rate of adipocyte lipolysis causing elevated levels of fatty acids. Our objective was to study the role of fat cell size in the regulation of lipolysis within a subject. Subcutaneous adipose tissue was obtained from 16 healthy subjects. Large and small adipocytes were isolated for each sample. Hormonal regulation of lipolysis and expression of lipolysis-regulating proteins were investigated. No effect of cell size on the rate of lipolysis was observed when lipolysis was expressed per lipid weight of fat cells. However, when expressed per number of fat cells, the lipolysis was significantly higher in large as compared with small adipocytes. This was observed in both the unstimulated (basal) state and in the presence of the major lipolysis-regulating hormones such as catecholamines (stimulating), natriuretic peptides (stimulating), and insulin (inhibiting). The receptor properties (number, affinity, and coupling) for these hormones did not differ between large and small adipocytes. However, the expression of proteins regulating the final steps in hormone signaling to lipolysis (hormone-sensitive lipase, adipose triglyceride lipase, and perilipin) was increased in large adipocytes. Independently of the donor, sc fat cell size per se determines lipolysis rates. Large adipocytes have increased lipolytic capacity, probably due to the enrichment of regulatory proteins distal in the lipolytic cascade, to which all lipolytic signals converge (lipases and perilipin). Enhanced lipolytic capacity may link adipocyte hypertrophy to the risk of developing type 2 diabetes.

Caveolins/caveolae protect adipocytes from fatty acid-mediated lipotoxicity

Mice and humans lacking functional caveolae are dyslipidemic and have reduced fat stores and smaller fat cells. To test the role of caveolins/caveolae in maintaining lipid stores and adipocyte integrity, we compared lipolysis in caveolin-1 (Cav1)-null fat cells to that in cells reconstituted for caveolae by caveolin-1 re-expression. We find that the Cav1-null cells have a modestly enhanced rate of lipolysis and reduced cellular integrity compared with reconstituted cells as determined by the release of lipid metabolites and lactic dehydrogenase, respectively, into the media. There are no apparent differences in the levels of lipolytic enzymes or hormonally stimulated phosphorylation events in the two cell lines. In addition, acute fasting, which dramatically raises circulating fatty acid levels in vivo, causes a significant upregulation of caveolar protein constituents. These results are consistent with the hypothesis that caveolae protect fat cells from the lipotoxic effects of elevated levels fatty acids, which are weak detergents at physiological pH, by virtue of the property of caveolae to form detergent-resistant membrane domains.

Identification of dAven, a Drosophila melanogaster ortholog of the cell cycle regulator Aven

Aven is a regulator of the DNA-damage response and G2/M cell cycle progression. Overexpression of Aven is associated with poor prognosis in patients with childhood acute lymphoblastic leukemia and acute myeloid leukemia, and altered intracellular Aven distribution is associated with infiltrating ductal carcinoma and papillary carcinoma breast cancer subtypes. Although Aven orthologs have been identified in most vertebrate species, no Aven gene has been reported in invertebrates. Here, we describe a Drosophila melanogaster open reading frame (ORF) that shares sequence and functional similarities with vertebrate Aven genes. The protein encoded by this ORF, which we named dAven, contains several domains that are highly conserved among Aven proteins of fish, amphibian, bird and mammalian origins. In flies, knockdown of dAven by RNA interference (RNAi) resulted in lethality when its expression was reduced either ubiquitously or in fat cells using Gal4 drivers. Animals undergoing moderate dAven knockdown in the fat body had smaller fat cells displaying condensed chromosomes and increased levels of the mitotic marker phosphorylated histone H3 (PHH3), suggesting that dAven was required for normal cell cycle progression in this tissue. Remarkably, expression of dAven in Xenopus egg extracts resulted in G2/M arrest that was comparable to that caused by human Aven. Taken together, these results suggest that, like its vertebrate counterparts, dAven plays a role in cell cycle regulation. Drosophila could be an excellent model for studying the function of Aven and identifying cellular factors that influence its activity, revealing information that may be relevant to human disease.

Adipose tissue inflammation: are small or large fat cells to blame?

Adipose tissue inflammation: are small or large fat cells to blame?

Adipose tissue inflammation: are small or large fat cells to blame?

Adipose tissue inflammation: are small or large fat cells to blame?

Characterization of the Proliferated Histiocytes in Acute Leukemia by Performing Immunohistochemistry

Background: The bone marrow biopsy sections of acute leukemia patients occa sionally reveal a pro- liferation of large mononuclear cells that accompany the leukemic blasts, and this proliferation shows a starry sky pattern. We characterized these large mononuclear cells by performing immunohistochemistry with 12 different antibodies. The clinical characteristics were examined and then we determined their difference from hemophagocytic lymphohistiocytosis (HLH) and malignant histiocytic disorders. Methods: Of the 200 acute leukemic bone marrow biopsy samples, 11 ALL and 10 AML cases showed large mononuclear cell proliferations. The panel of antibodies used for immunohistochemistry included those against the mononuclear phagocyte system, and immunohistochemistry was performed on the pa- tients' initial specimens and the complete remission specimens. 10 normal specimens, 4 initial CML speci- mens and their complete hematologic response specimens were included as controls. Results: The large mononuclear cells showed immunohistochemical results consistent with histiocytes. They were negative for the markers of dendritic cells the histiocytes and cytokines that are involved in the pathogenesis of HLH and vascular proliferation. Histiocyte proliferation was not observed in the complete remission specimens and in the initial and complete hematological response specimens of the CML patients and the normal bone marrow specimens. None of the cases fulfilled the criteria of HLH, and all 5 ALL cases, for which the immunophenotype results were available, showed a B cell phenotype. Conclusion: We characterized the large mononuclear cell proliferations as reactive histiocyte pro- liferations and we differentiated these from those of secondary HLH and malignant histiocytic disorders. A proportion of the large mononuclear cells showed negative results for all 12 antibodies and they showed characteristics that were suggestive of small fat cells. The pathophysiology and the prognostic effect of the reactive histiocyte proliferation accompanying acute leukemia require further study. (Korean J

Letters to the Editor

Letters to the Editor