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Life Extension Magazine July 2011


Differentiation of adipose stem cells.

The broad definition of a stem cell is a cell that has the ability to self-renew and differentiate into one or more specialized terminally differentiated cell types. It has become evident that stem cells persist in, and can be isolated from, many adult tissues. Adipose tissue has been shown to contain a population of cells that retain a high proliferation capacity in vitro and the ability to undergo extensive differentiation into multiple cell lineages. These cells are referred to as adipose stem cells and are biologically similar, although not identical, to mesenchymal stem cells derived from the bone marrow. Differentiation causes stem cells to adopt the phenotypic, biochemical, and functional properties of more terminally differentiated cells. This chapter will provide investigators with some background on stem cells derived from adipose tissue and then provide details on adipose stem cell multilineage differentiation along osteogenic, adipogenic, chondrogenic, and neurogenic lineages.

Methods Mol Biol. 2008;456:155-71

Adipose tissue development - Impact of the early life environment.

Increasing experimental and observational evidence in both animals and humans suggests that early life events are important in setting later fat mass. This includes both the number of adipocytes and the relative distribution of both brown and white adipose tissue. Brown adipose tissue is characterised as possessing a unique uncoupling protein (UCP)1 which enables the rapid generation of large amounts of heat and is most abundant in the newborn. In large mammals such as sheep and humans, brown fat that is located around the major internal organs, is largely lost during the postnatal period. However, it is retained in small and discrete areas into adulthood when it is sensitive to environmental cues such as changes in ambient temperature or day length. The extent to which brown adipose tissue is lost or replaced by white adipose tissue and/or undergoes a process of transdifferentiation remains controversial. Small amounts of UCP1 can also be present in skeletal muscle which now appears to share the same common precursor cell as brown adipose tissue. The functional consequences of UCP1 in muscle remain to be confirmed but it could contribute to dietary induced thermogenesis. Challenges in elucidating the primary mechanisms regulating adipose tissue development include changes in methylation status of key genes during development in different species, strains and adipose depots. A greater understanding of the mechanisms by which early life events regulate adipose tissue distribution in young offspring are likely to provide important insights for novel interventions that may prevent excess adiposity in later life.

Prog Biophys Mol Biol. 2010 Dec 14

Inhibition of adipocyte differentiation and adipogenesis by the traditional Chinese herb Sibiraea angustata.

Obesity has become a major health concern due to its strong association with the metabolic syndrome. Inhibition of adipocyte differentiation represents a key strategy to inhibit obesity. Sibiraea angustata (SA), a traditional Chinese herb, has a wide range of pharmacological effects, such as improving digestive functions. Here, we report a novel antiadipogenic effect of SA. By using the SA water extract (SAW), SA acetic ether extract (SAA) and the 3T3-L1 model of adipocyte differentiation and adipogenesis, we showed that both SAW and SAA impaired the proliferation and adipo-differentiation of 3T3-L1 in a dose- and time-dependent manner. At the molecular level, treatment of 3T3-L1 cells with SAW or SAA inhibited the expression of the key adipocyte differentiation regulator CCAAT enhancer binding protein β (C/EBPβ), as well as peroxisome proliferator activated receptor γ, adipocyte protein-2, lipoprotein lipase and glucose transporter 4. Cell cycle analysis showed that both SAW and SAA blocked cell cycle at the G1-S transition phase, causing cells to remain in the preadipocyte state. The expression of CyclinA and cyclin-dependent kinase 2 was also inhibited by SAW and SAA. Treatment with SAW also prevented the localization of C/EBPβ to the centromeres. Taken together, our results show that SA has a potent antiadipogenic effect in 3T3-L1 cells due to the inhibition of adipocyte differentiation and adipogenesis. We propose that SA may be used as a safe and effective neutraceutical to manage obesity.

Exp Biol Med (Maywood). 2010 Dec;235(12):1442-9

Xanthones from mangosteen inhibit inflammation in human macrophages and in human adipocytes exposed to macrophage-conditioned media.

Obesity-associated inflammation is characterized by recruitment of macrophages (MPhi) into white adipose tissue (WAT) and production of inflammatory cytokines, leading to the development of insulin resistance. The xanthones, alpha- and gamma-mangostin (MG), are major bioactive compounds found in mangosteen that are reported to have antiinflammatory and antioxidant properties. Thus, we examined the efficacy of MG to prevent lipopolysaccharide (LPS)-mediated inflammation in human MPhi (differentiated U937 cells) and cross-talk with primary cultures of newly differentiated human adipocytes. We found that alpha- and gamma-MG attenuated LPS-induced expression of inflammatory genes, including tumor necrosis factor-alpha, interleukin-6, and interferon gamma-inducible protein-10 in a dose-dependent manner in MPhi. We also found that alpha- and gamma-MG attenuated LPS-activated mitogen-activated protein kinases (MAPK) and activator protein (AP)-1, but only gamma-MG reduced nuclear factor-kappaB (NF-kappaB). In addition, alpha- and gamma-MG attenuated LPS suppression of PPARgamma gene expression in a dose-dependent manner. Notably, the ability of MPhi-conditioned media to cause inflammation and insulin resistance in primary cultures of human adipocytes was attenuated by pretreating MPhi with gamma-MG. Taken together, these data demonstrate that MG attenuates LPS-mediated inflammation in MPhi and insulin resistance in adipocytes, possibly by preventing the activation of MAPK, NF-kappaB, and AP-1, which are central to inflammatory cytokine production in WAT.

J Nutr. 2010 Apr;140(4):842-7

St. John’s Wort inhibits adipocyte differentiation and induces insulin resistance in adipocytes.

Adipocytes are insulin sensitive cells that play a major role in energy homeostasis. Obesity is the primary disease of fat cells and a major risk factor for the development of Type II diabetes, cardiovascular disease, and metabolic syndrome. Obesity and its related disorders result in dysregulation of the mechanisms that control adipocyte gene expression and function. To identify potential novel therapeutic modulators of adipocytes, we screened 425 botanical extracts for their ability to modulate adipogenesis and insulin sensitivity. We observed that less than 2% of the extracts had substantial effects on adipocyte differentiation of 3T3-L1 cells. Two of the botanical extracts that inhibited adipogenesis were extracts from St. John’s Wort (SJW). Our studies revealed that leaf and flower, but not root, extracts isolated from SJW inhibited adipogenesis as judged by examining PPARgamma and adiponectin levels. We also examined the effects of these SJW extracts on insulin sensitivity in mature 3T3-L1 adipocytes. Both leaf and flower extracts isolated from SJW substantially inhibited insulin sensitive glucose uptake. The specificity of the observed effects was demonstrated by showing that treatment with SJW flower extract resulted in a time and dose dependent inhibition of insulin stimulated glucose uptake. SJW is commonly used in the treatment of depression. However, our studies have revealed that SJW may have a negative impact on adipocyte related diseases by limiting differentiation of preadipocytes and significantly inducing insulin resistance in mature fat cells.

Biochem Biophys Res Commun. 2009 Oct 9;388(1):146-9

Adipose tissue fatty acid metabolism and cardiovascular disease.

Fatty acid and triacylglycerol metabolism in adipose tissue may be involved in the generation of risk factors for cardiovascular disease and type 2 diabetes. Pharmaceutical companies are targeting adipocyte metabolism in their search for drugs for treating, or reducing the risk of, these conditions. We review new developments in adipose tissue fatty acid metabolism and how that might relate to cardiovascular disease. Fatty acid release from human adipose tissue is oscillatory, with a period of about 12 min. Remarkably, oscillatory fatty acid release is also seen in isolated adipocytes. Further evidence has emerged that not all adipose depots are equal, and that lower-body adipose tissue may exert protective effects against cardiovascular disease. There have been a number of developments in the area of fatty acid handling by adipocytes. Fatty acid binding proteins are clearly important in regulating fatty acid metabolism, with striking protection against atherosclerosis in mice deficient in both the binding proteins expressed in adipocytes. The demonstration that adipocytes lacking hormone-sensitive lipase still display lipolysis has led to the identification of novel lipases that may play crucial roles in adipose tissue fatty acid metabolism. Further evidence has accrued of the interaction between hormone-sensitive lipase and perilipin, the protein that coats the adipocyte lipid droplet. Recent developments in our understanding of adipose tissue fatty acid metabolism open up the possibility of new pharmaceutical targets. However, interference with adipose tissue fatty acid metabolism is not to be undertaken lightly and needs a clear understanding of the normal role of adipocyte lipolysis.

Curr Opin Lipidol. 2005 Aug;16(4):409-15

Anti-adipogenesis by 6-thioinosine is mediated by downregulation of PPAR gamma through JNK-dependent upregulation of iNOS.

Adipocyte dysfunction is associated with the development of obesity. This study shows that 6-thioinosine inhibits adipocyte differentiation. The mRNA levels of PPAR gamma and C/EBPalpha, but not C/EBPbeta and delta, were reduced by 6-thioinosine. Moreover, the mRNA levels of PPAR gamma target genes (LPL, CD36, aP2, and LXRalpha) were down-regulated by 6-thioinosine. We also demonstrated that 6-thioinosine inhibits the transactivation activity and the mRNA level of PPAR gamma. Additionally, attempts to elucidate a possible mechanism underlying the 6-thioinosine-mediated effects revealed that 6-thioinosine induced iNOS gene expression without impacting eNOS expression, and that this was mediated through activation of AP-1, especially, JNK. In addition, 6-thioinosine was found to operate upstream of MEKK-1 in JNK activation signaling. Taken together, these findings suggest that the inhibition of adipocyte differentiation by 6-thioinosine occurs primarily through the reduced expression of PPAR gamma, which is mediated by upregulation of iNOS via the activation of JNK.

Cell Mol Life Sci. 2010 Feb;67(3):467-81

Molecular mechanisms of adipocyte differentiation and inhibitory action of pref-1.

Commitment and differentiation of adipocytes is governed by transcription factors that are under the control of the combinatorial effects of hormonal and cell-cell and cell-matrix interaction. Established preadipocyte cell lines, such as 3T3-L1, 3T3-F442A, and Ob 17, have made it possible to examine the molecular details of the differentiation process. Differentiation is accompanied by dramatic increases in adipocyte genes, including adipocyte fatty acid-binding protein and lipid-metabolizing enzymes. Transcription factors PPAR gamma and C/EBP have been shown to transactivate some of the adipocyte-expressed genes. By integrating hormonal and metabolic cues, these nuclear factors may synergistically function in adipocyte lineage determination and differentiation. Adipocyte differentiation involves drastic cell shape alterations that are accompanied by changes in expression of cytoskeletal and extracellular matrix proteins, including decreases in actin and tubulin levels. Pref-1, an EGF-repeat containing transmembrane protein, is highly expressed in preadipocytes; this expression is totally abolished after differentiation to adipocytes. Pref-1 is inhibitory for adipocyte differentiation and processing of transmembrane pref-1 generates a biologically active soluble from corresponding to the ectodomain. Interaction of the EGF-repeats of pref-1 with an as yet unidentified receptor may mediate the inhibitory effects of pref-1 in adipocyte differentiation, thereby affecting nuclear events accompanying adipogenesis.

Crit Rev Eukaryot Gene Expr. 1997;7(4):281-98

The relationship between adipocyte fatty acid binding protein-4, retinol binding protein-4 levels and early diabetic nephropathy in patients with type 2 diabetes.

Adipocyte fatty acid binding protein-4 (A-FABP4) and retinol binding protein-4 (RBP4) have recently been linked to type 2 diabetes mellitus (DM). Serum A-FABP4 and RBP4 levels and their relationships with early diabetic nephropathy were examined in 87 type 2 diabetic patients. The patients with diabetic nephropathy showed high A-FABP4 levels compared to the patients without diabetic nephropathy (p=0.0001). Log A-FABP4 correlated positively with age (p=0.02), log duration of diabetes (p=0.04), log body mass index (BMI) (p=0.0001), log creatinine (p=0.007), log C-reactive protein (CRP) (p=0.01), log albumin excretion rate (AER) (p=0.001), and negatively with MDRD-GFR (p=0.0001). Serum RBP4 levels were similar between the patients with and without diabetic nephropathy. RBP4 correlated positively with triglycerides (p=0.001), log creatinine (p=0.009), and negatively with MDRD-GFR (p=0.04). In regression analysis, log A-FABP4 was associated with age, sex, log BMI, and log AER (r(2)=0.43) and RBP4 was associated with triglycerides and log creatinine (r(2)=0.22). In conclusion, we found high serum A-FABP4 but unchanged RBP4 concentrations and their associations with renal function and early diabetic nephropathy in type 2 DM.

Diabetes Res Clin Pract. 2011 Feb;91(2):203-7

Momordica charantia (bitter melon) inhibits primary human adipocyte differentiation by modulating adipogenic genes.

Escalating trends of obesity and associated type 2 diabetes (T2D) has prompted an increase in the use of alternative and complementary functional foods. Momordica charantia or bitter melon (BM) that is traditionally used to treat diabetes and complications has been demonstrated to alleviate hyperglycemia as well as reduce adiposity in rodents. However, its effects on human adipocytes remain unknown. The objective of our study was to investigate the effects of BM juice (BMJ) on lipid accumulation and adipocyte differentiation transcription factors in primary human differentiating preadipocytes and adipocytes. METHODS: Commercially available cryopreserved primary human preadipocytes were treated with and without BMJ during and after differentiation. Cytotoxicity, lipid accumulation, and adipogenic genes mRNA expression was measured by commercial enzymatic assay kits and semi-quantitative RT-PCR (RT-PCR). RESULTS: Preadipocytes treated with varying concentrations of BMJ during differentiation demonstrated significant reduction in lipid content with a concomitant reduction in mRNA expression of adipocyte transcription factors such as, peroxisome proliferator-associated receptor gamma (PPARgamma) and sterol regulatory element-binding protein 1c (SREBP-1c) and adipocytokine, resistin. Similarly, adipocytes treated with BMJ for 48 h demonstrated reduced lipid content, perilipin mRNA expression, and increased lipolysis as measured by the release of glycerol. CONCLUSION: Our data suggests that BMJ is a potent inhibitor of lipogenesis and stimulator of lipolysis activity in human adipocytes. BMJ may therefore prove to be an effective complementary or alternative therapy to reduce adipogenesis in humans.

BMC Complement Altern Med. 2010 Jun 29;10:34

Signalling role of adipose tissue: adipokines and inflammation in obesity.

White adipose tissue (WAT) is a major endocrine and secretory organ, which releases a wide range of protein signals and factors termed adipokines. A number of adipokines, including leptin, adiponectin, tumour necrosis factor alpha, IL-1beta (interleukin 1beta), IL-6, monocyte chemotactic protein-1, macrophage migration inhibitory factor, nerve growth factor, vascular endothelial growth factor, plasminogen activator inhibitor 1 and haptoglobin, are linked to inflammation and the inflammatory response. Obesity is characterized by a state of chronic mild inflammation, with raised circulating levels of inflammatory markers and the expression and release of inflammation-related adipokines generally rises as adipose tissue expands (adiponectin, which has anti-inflammatory action is an exception). The elevated production of inflammation-related adipokines is increasingly considered to be important in the development of diseases linked to obesity, particularly Type II diabetes and the metabolic syndrome. WAT is involved in extensive cross-talk with other organs and multiple metabolic systems through the various adipokines.

Biochem Soc Trans. 2005 Nov;33(Pt 5):1078-81

Inhibition of Irvingia gabonensis seed extract (OB131) on adipogenesis as mediated via down regulation of the PPARgamma and leptin genes and up-regulation of the adiponectin gene.

BACKGROUND: Endeavors to manage obesity have been heavily reliant on controlling energy intake and expenditure equilibrium, but have failed to curtail the overweight and obesity epidemic. This dynamic equilibrium is more complex than originally postulated and is influenced by lifestyle, calorie and nutrient intake, reward cravings and satiation, energy metabolism, stress response capabilities, immune metabolism and genetics. Fat metabolism is an important indicator of how efficiently and to what extent these factors are competently integrating. We investigated whether an Irvingia gabonensis seed extract (IGOB131) would provide a more beneficial comprehensive approach influencing multiple mechanisms and specifically PPAR gamma, leptin and adiponectin gene expressions, important in anti-obesity strategies. METHODS: Using murine 3T3-L1 adipocytes as a model for adipose cell biology research, the effects of IGOB131 were investigated on PPAR gamma, adiponectin, and leptin. These adipocytes were harvested 8 days after the initiation of differentiation and treated with 0 to 250 microM of IGOB131 for 12 and 24 h at 37 degree C in a humidified 5 percent CO2 incubator. The relative expression of PPAR gamma, adiponectin, and leptin in 3T3-L1 adipocytes was quantified densitometrically using the software LabWorks 4.5, and calculated according to the reference bands of beta-actin. RESULTS: The IGOB131 significantly inhibited adipogenesis in adipocytes. The effect appears to be mediated through the down-regulated expression of adipogenic transcription factors (PPAR gamma) [P less than 0.05] and adipocyte-specific proteins (leptin) [P less than 0.05], and by up-regulated expression of adiponectin [P less than 0.05]. CONCLUSION: IGOB131 may play an important multifaceted role in the control of adipogenesis and have further implications in in-vivo anti obesity effects by targeting the PPAR gamma gene, a known contributory factor to obesity in humans.

Lipids Health Dis. 2008 Nov 13;7:44

Ethanolic extracts of Brassica campestris spp. rapa roots prevent high-fat diet-induced obesity via beta(3)-adrenergic regulation of white adipocyte lipolytic activity.

The influence of ethanolic extracts of Brassica campestris spp. rapa roots (EBR) on obesity was examined in imprinting control region (ICR) mice fed a high-fat diet (HFD) and in 3T3-L1 adipocytes. The ICR mice used were divided into regular diet, HFD, EBR (50 mg/kg/day EBR administered orally), and orlistat (10 mg/kg/day orlistat administered orally) groups. The molecular mechanism of the anti-obesity effect of EBR was investigated in 3T3-L1 adipocytes as well as in HFD-fed ICR mice. In the obese mouse model, both weight gain and epididymal fat accumulation were highly suppressed by the daily oral administration of 50 mg/kg EBR for 8 weeks, whereas the overall amount of food intake was not affected. EBR treatment induced the expression in white adipocytes of lipolysis-related genes, including beta(3)-adrenergic receptor (beta(3)-AR), hormone-sensitive lipase (HSL), adipose triglyceride lipase, and uncoupling protein 2. Furthermore, the activation of cyclic AMP-dependent protein kinase, HSL, and extracellular signal-regulated kinase was induced in EBR-treated 3T3-L1 cells. The lipolytic effect of EBR involved beta(3)-AR modulation, as inferred from the inhibition by the beta(3)-AR antagonist propranolol. These results suggest that EBR may have potential as a safe and effective anti-obesity agent via the inhibition of adipocyte lipid accumulation and the stimulation of beta(3)-AR-dependent lipolysis.

J Med Food. 2010 Apr;13(2):406-14

Adiponectin: a link between excess adiposity and associated comorbidities?

Adiponectin is a novel polypeptide that is highly specific to adipose tissue. In contrast to other adipocytokines, adiponectin levels are decreased in obesity and associated comorbidities, such as type 2 diabetes. Decreased expression of adiponectin is correlated with insulin resistance. It has been suggested that several agents, such as tumor necrosis factor alpha, could mediate their effects on insulin metabolism through modulating adiponectin secretion from adipocytes. The mechanisms for the development of atherosclerotic vascular disease in obese individuals are largely unknown. Several findings support the interesting hypothesis that adiponectin could be a link between obesity and related atherosclerosis. First, adiponectin levels are lower in patients with coronary artery disease. Second, adiponectin modulates endothelial function and has an inhibitory effect on vascular smooth muscle cell proliferation. Moreover, adiponectin is accumulated more preferably to the injured vascular wall than intact vessels and has been shown to suppress macrophage-to-foam cell transformation. Adiponectin may also be involved in the modulation of inflammation. Thiazolidinediones, antiatherogenic and other effects have been explained by their direct enhancing effect on adiponectin. In conclusion, adiponectin has anti-inflammatory and antiatherogeneic effects as well as multiple beneficial effects on metabolism. Therefore it is not a surprise that adiponectin therapy has been tested in animal models of obesity, and it has been shown to ameliorate hyperglycemia and hyperinsulinemia without inducing weight gain or even inducing weight loss in some studies. Unlike agents that exert their effects centrally, adiponectin’s effects seem to be peripherally mediated. The evidence of an association between adiponectin and the metabolic and cardiovascular complications of obesity is growing all the time.

J Mol Med. 2002 Nov;80(11):696-702

Visceral adiposity, not abdominal subcutaneous fat area, is associated with high blood pressure in Japanese men: the Ohtori study.

Visceral adiposity is considered to have a key role in cardiometabolic diseases. The purpose of this study is to investigate cross-sectionally the association between intra-abdominal fat area (IAFA) measured by computed tomography (CT) and high blood pressure independent of abdominal subcutaneous fat area (ASFA) and insulin resistance. Study participants included 624 Japanese men not taking oral hypoglycemic medications or insulin. Abdominal, thoracic and thigh fat areas were measured by CT. Total fat area (TFA) was calculated as the sum of abdominal, thoracic and thigh fat area. Total subcutaneous fat area (TSFA) was defined as TFA minus IAFA. Hypertension and high normal blood pressure were defined using the 1999 criteria of the World Health Organization. Multiple-adjusted odds ratios of hypertension for tertiles of IAFA were 2.64 (95% confidence interval, 1.35-5.16) for tertile 2, and 5.08 (2.48-10.39) for tertile 3, compared with tertile 1 after adjusting for age, fasting immunoreactive insulin, diabetes status, ASFA, alcohol consumption, regular physical exercise and smoking habit. IAFA remained significantly associated with hypertension even after adjustment for ASFA, TSFA, TFA, body mass index or waist circumference, and no other measure of regional or total adiposity was associated with the odds of hypertension in models, which included IAFA. Similar results were obtained for the association between IAFA and the prevalence of high normal blood pressure or hypertension. In conclusion, greater visceral adiposity was associated with a higher odds of high blood pressure in Japanese men.

Hypertens Res. 2011 May;34(5):565-72

Visceral adiposity and the severity of coronary artery disease in middle-aged subjects with normal waist circumference and its relation with lipocalin-2 and MCP-1.

OBJECTIVE: Visceral adipose tissue has emerged as a key organ contributing to the development of coronary artery disease (CAD). However, defining central obesity by waist circumference (WC) may underestimate visceral adiposity in lean patients. The aim of this study was to investigate the relationship between visceral adiposity and severity of CAD in subjects with normal WC. METHODS: Among 365 patients with documented CAD, 90 male subjects with normal WC (<90 cm) were selected and their visceral fat areas (VFA) were examined using computed tomography. Lipid profiles and levels of adipokines including lipocalin-2, high molecular weight adiponectin, and monocyte chemoattractant protein (MCP)-1 were measured. Patients were divided into tertiles based on VFA at the L4 vertebra level. RESULTS: Patients with single-vessel disease had significantly lower VFA than those with multi-vessel disease (P<0.05; 86.0 vs. 97.5 vs. 99.6 cm(2) for single- , double- , and triple-vessel diseases, respectively). Positive association between the extent of CAD and VFA was clearly demonstrated and logistic regression analysis showed that subjects in the upper tertile for VFA had a 4.5-fold higher risk of having multi-vessel disease compared with those in the lowest tertile (P<0.05; odds ratio=4.51; 95% confidence interval=1.10-18.45). Circulating levels of lipocalin-2 and MCP-1 were significantly higher in the upper tertiles of VFA. CONCLUSION: Increased visceral adiposity is significantly associated with the severity of CAD, even in subjects without central obesity as determined by WC measurements. Abnormalities in adipokine regulation may provide a novel mechanistic connection between visceral adiposity and associated cardiovascular complications.

Atherosclerosis. 2010 Dec;213(2):592-7