[Show abstract][Hide abstract] ABSTRACT: Prevalence of obesity is increasing to pandemic proportions. However, obese subjects differ in insulin resistance, adipokine production and co-morbidities. Based on fasting plasma analysis, obese subjects were grouped as Low Acylation Stimulating protein (ASP) and Triglyceride (TG) (LAT) vs High ASP and TG (HAT). Subcutaneous (SC) and omental (OM) adipose tissues (n = 21) were analysed by microarray, and biologic pathways in lipid metabolism and inflammation were specifically examined.
LAT and HAT groups were matched in age, obesity, insulin, and glucose, and had similar expression of insulin-related genes (InsR, IRS-1). ASP related genes tended to be increased in the HAT group and were correlated (factor B, adipsin, complement C3, p < 0.01 each). Differences between LAT and HAT group were almost exclusively in SC tissue, with little difference in OM tissue. Increased C5L2 (p < 0.01), an ASP receptor, in HAT suggests a compensatory ASP pathway, associated with increased TG storage.
HAT adipose tissue demonstrated increased lipid related genes for storage (CD36, DGAT1, DGAT2, SCD1, FASN, and LPL), lipolysis (HSL, CES1, perilipin), fatty acid binding proteins (FABP1, FABP3) and adipocyte differentiation markers (CEBPalpha, CEBPbeta, PPARgamma). By contrast, oxidation related genes were decreased (AMPK, UCP1, CPT1, FABP7). HAT subjects had increased anti-inflammatory genes TGFB1, TIMP1, TIMP3, and TIMP4 while proinflammatory PIG7 and MMP2 were also significantly increased; all genes, p < 0.025.
Taken together, the profile of C5L2 receptor, ASP gene expression and metabolic factors in adipose tissue from morbidly obese HAT subjects suggests a compensatory response associated with the increased plasma ASP and TG.
Full-text · Article · Jan 2010 · BMC Medical Genomics
[Show abstract][Hide abstract] ABSTRACT: Acylation stimulating protein (ASP) stimulates triglyceride synthesis and glucose transport via its receptor C5L2. In human studies, ASP is increased in insulin resistant states such as obesity, diabetes, polycystic ovary syndrome and late pregnancy (the latter two associated with altered sex hormones). The aims were (i) to evaluate ASP response and C5L2 expression following treatment with sex steroid hormones and (ii) to identify mechanisms of ASP resistance using 3T3-L1 adipocytes and preadipocytes. Overnight incubation with physiological progesterone (PROG) concentrations induced dose-dependent inhibition of ASP-stimulated glucose transport in adipocytes (188 +/- 11% +ASP, 100 +/- 4% control, 129 +/- 18% to 85 +/- 7% [ASP + PROG 10(-8) to 10(-6) M] and preadipocytes (263 +/- 18% +ASP, 100 +/- 3% control, 170 +/- 11% to 167 +/- 4% [ASP + PROG 10(-8) to 10(-6) M]), while estradiol and testosterone (TEST) were effective only at the highest concentration (10(-6) M). In adipocytes, dose-dependent maximal C5L2 mRNA decreases were 39-75% (P = 0.003), with decreased cell-surface C5L2 of -22% and -27% (10(-6) M PROG and TEST, respectively) with no change in preadipocytes. Adipocytes treated with PROG displayed decreases in G proteins: Gbeta (-55%), Galphaq/11 (-56%) as well as complete inhibition of ASP stimulation. PROG significantly decreased basal levels of phosphorylated PKCalpha (p-PKCalpha) while there was no change in p- PKCzeta. ASP increased p-PKCalpha and PKCzeta to 161% (P < 0.0.001) and 160% (P < 0.01), a stimulation effectively blocked by PROG (10(-8) and 10(-6) M) and TEST (10(-6) M). Sex steroid hormone-induced ASP resistance via C5L2 may contribute to altered adipose tissue function and insulin resistance phenotype in humans.
No preview · Article · Oct 2008 · Journal of Cellular Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Acylation stimulating protein (ASP) stimulates triglyceride synthesis and glucose transport via its receptor C5L2. The aims were (i) to evaluate ASP response under insulin-resistant conditions and (ii) to identify mechanisms of ASP resistance using 3T3-L1 adipocytes and preadipocytes. Overnight incubation with palmitate (PAL) or oleate (OLE) induced dose-dependent inhibition of ASP-stimulated glucose transport in adipocytes (198 +/- 18% +ASP, 100 +/- 4% basal, 131 +/- 14% + ASP + 1 mmol/L PAL) and preadipocytes (287 +/- 21% + ASP, 100 +/- 4% basal, 109 +/- 13% + ASP + 1 mmol/L PAL). In adipocytes, dose-dependent maximal C5L2 mRNA decreases were -41 +/- 15% and -82 +/- 2%, with decreased cell-surface C5L2 of -55 +/- 12% and -39 +/- 9% (1 mmol/L PAL and OLE, respectively) with no change in preadipocytes. Adipocytes treated with PAL or OLE evidenced inhibition of ASP stimulation of G proteins: Gbeta (-50%), Galphaq/11 (-50%) and protein kinase C: PKCalpha-P (-52%), PKCzeta-P (-43%). Fatty acid-induced ASP resistance via C5L2 may contribute to altered adipose tissue function and obesity/insulin resistance phenotype in humans.
No preview · Article · May 2008 · Journal of Cellular Biochemistry
[Show abstract][Hide abstract] ABSTRACT: Obesity, in particular, abdominal obesity, is highly correlated with metabolic disorders and cardiovascular lesions in humans and animal models and may in fact play a role in their pathogenesis. The development of obesity, while partially genetic, is largely affected by environmental and lifestyle factors such as diet. The aim of the present study was to determine the short- and long-term effects of dietary corn oil on the abdominal fat pat morphology and serum lipid and lipoprotein profile. Forty male Wistar rats were randomly separated into two groups. The experimental group was fed a corn oil-rich diet (CRD), which consisted of 32.5% of kilocalories from corn oil and provided a total number of kcal/kg/day similar to the average western diet. The control group received regular chow (6.5% kilocalories from fat source). In each group, eight rats were sacrificed after 3 weeks and the remaining 12 rats in each group were sacrificed after 10 weeks. Adipocyte size, distribution and adipocyte number per gram of abdominal fat pad were determined. The total weight of the abdominal fat pad from the CRD rats was approximately twice the weight of the pad from the control rats at both time points (5.43 ± 0.93 g versus 11.6 ± 1.98 g after 3 weeks and 6.24 ± 1.38 g versus 11.18 ± 2.17 g after 10 weeks). There was a significant increase (P < 0.001) in adipocyte number per gram of fat and in the total triacylglycerol (TAG) content of the fat pad in the CRD group compared to the control at both short-term and long-term time points. However, the adipocyte size distribution showed a similar pattern in both the CRD and control groups. Serum TAG, total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C) and very low-density lipoprotein cholesterol (VLDL-C) were also measured. In the long-term study, higher values of TAG (P = 0.015), TC (P < 0.001), low-density lipoprotein cholesterol (P < 0.001) and VLDL-C (P = 0.005) were seen in the CRD group in comparison with the control. These results suggest that the deleterious effects of a CRD are because of serum changes rather than adipocyte morphology changes.
Although further research is required, corn oil administration may be associated with the development of cardiovascular disorders.
No preview · Article · Feb 2008 · Journal of Food Lipids
[Show abstract][Hide abstract] ABSTRACT: Obesity and insulin resistance are independent risk factors for metabolic syndrome, diabetes, and cardiovascular disease. Adipose tissue samples from nonobese (NO), insulin-sensitive obese (ISO), and insulin-resistant obese (IRO) subjects from subcutaneous (SC) and omental (OM) adipose tissue (n = 28) were analyzed by microarray and confirmed by real-time PCR. Insulin signaling gene expression changes were greater in OM than in SC tissue and were related to insulin resistance rather than to obesity; few genes correlated with body mass index. Insulin receptor and insulin receptor substrate 1 (IRS-1) increased in the IRO versus pooled insulin-sensitive (NO+ISO) subjects. In glucose transport, PI3Kalpha and PDK2 decreased in IRO subjects, whereas PI3Kgamma, Akt2, GLUT4, and GLUT1 increased. IRS-1 regulators Jnk and IKK increased in IRO (P < 0.01 and P < 0.001 respectively). In protein synthesis, most genes examined were downregulated in IRO subjects, including mTor, Rheb, and 4EBP and eIF members (all P < 0.05). In proliferation, SHC, SOS, and Raf1 (P < 0.05) were increased, whereas Ras and MEK1/2 kinase 1 (P < 0.05) were decreased, in IRO subjects. Finally, in differentiation, PPARgamma, CEBPalpha, and CEBPbeta decreased, whereas PPARdelta, CEBPgamma, and CEBPepsilon increased, in IRO subjects (P < 0.05). Together, microarray and real-time PCR data demonstrate that insulin resistance rather than obesity is associated with altered gene expression of insulin signaling genes, especially in OM adipose tissue.
Full-text · Article · Feb 2008 · The Journal of Lipid Research
[Show abstract][Hide abstract] ABSTRACT: There is increasing evidence of close interactions between the adipose and the immune systems. Adipocytes secrete multiple factors, including adipokines such as leptin and adiponectin that have both pro- and anti-inflammatory effects, and influence diseases involving the immune system. Further, adipose tissue also secretes various chemokines and cytokines, derived from either the adipocytes themselves, or the neighbouring cells including both resident and infiltrating macrophages. This close physical and paracrine interaction results in reciprocal actions of adipocytes, preadipocytes and macrophages within the microenvironment of the adipose tissue. Adipose tissue is a source of Acylation Stimulating Protein (ASP)/C3adesArg which interacts with the receptor C5L2 to stimulate triglyceride synthesis and glucose transport. C5L2, present on adipocytes, preadipocytes, macrophages, and numerous other myeloid and non-myeloid cells is also postulated to be a decoy receptor for C5a in immune cells. Several reviews within the past year have recently examined the role of C5L2 in C5a-mediated physiology. The present mini-review is an adipocentric view with emphasis on the role of ASP and C5L2 in lipid metabolism. C5L2 may play a role in mediating, on one hand, ASP stimulation of triglyceride synthesis in adipose, and, on the other hand, a role as mediator of C5a immune function. Both roles remain controversial, and will only be resolved with further studies.
No preview · Article · Feb 2008 · Advances in Experimental Medicine and Biology
[Show abstract][Hide abstract] ABSTRACT: The novel adipokine visfatin has 'insulin-mimicking' effects and is increased in models of diet-induced obesity, but factors that regulate visfatin have not been fully elucidated.
In order to determine visfatin regulation in adipocyte development and metabolism, as well as in pathophysiological conditions related to metabolic syndrome, endogenous visfatin expression was measured in 3T3-L1 pre-adipocytes and adipocytes using real-time reverse transcriptase polymerase chain reaction (real-time RT-PCR).
A marked increase in visfatin expression was observed during differentiation, with a 2.2-fold increase between preconfluent and 2-day confluent cells even before differentiation was initiated. A further 4.1-fold increase was induced from day 0 to day 9 of differentiation (overall ninefold). Overnight incubation with dexamethasone (10(-8) to 10(-2) M) increased visfatin expression in both pre-adipocytes (1.5- to 3.3-fold, p < 0.05) and adipocytes (1.9-fold, p < 0.01). All other treatments decreased visfatin expression. In pre-adipocytes, visfatin expression decreased by 23% at a concentration of 1 microM insulin, 15% at 1-15 nM T3, 15% at 10 nM-1 microM progesterone, 33-44% at 10 nM-1 microM testosterone, 50% with palmitate and 30% with oleate (p < 0.05 for all). In adipocytes, insulin had a much greater effect, decreasing visfatin by 77% at 100 nM (p < 0.01), whereas oleate and sex hormones did not affect visfatin expression. However, tumor necrosis factor alpha, which had no effect on pre-adipocytes, significantly decreased visfatin in adipocytes by 26% at 10 ng/ml (p < 0.05). Interestingly, the thiazolidinedione (TZD) rosiglitizone also decreased visfatin by 28% at a concentration of 1 microM (p < 0.01).
In summary, while the mechanism of visfatin action remains to be elucidated, the clear effects of multiple hormones on visfatin expression support a physiological role.
No preview · Article · Aug 2007 · Diabetes Obesity and Metabolism
[Show abstract][Hide abstract] ABSTRACT: Acylation-stimulating protein (ASP) and interaction with its receptor C5L2 influences adipocyte metabolism. We examined insulin resistance and differentiation-mediated regulation of C5L2 and the mechanistic impact on both C5L2 cell-surface protein and ligand binding to the receptor. C5L2 mRNA increased 8.7-fold with differentiation in 3T3-L1 cells (p < 0.0001) by day 9. In preadipocytes, insulin and dexamethasone increased C5L2 mRNA (1 micromol/L insulin resulted in a 2.6-fold increase, p < 0.01; 10 nmol/L dexamethasone resulted in a 17.9-fold increase, p < 0.01) and C5L2 cell-surface protein (100 nmol insulin resulted in a 2.7-fold increase, p < 0.001; 10 nmol/L dexamethasone resulted in a 2.8-fold increase, p < 0.001). In adipocytes, 100 nmol/L insulin increased C5L2 mRNA and ASP binding (respectively, 1.3-fold, p < 0.01; and 2.4-fold, p < 0.05). Dexamethasone decreased ligand binding (-60%, p < 0.02) without changing mRNA. Tumor necrosis factor alpha decreased C5L2 mRNA (-88% in preadipocytes and -38% in adipocytes, p < 0.001), C5L2 cell-surface protein (-53% in preadipocytes, p < 0.0001), and ASP binding (-60% and -49% in, respectively, preadipocytes and adipocytes, p < 0.05). Conversely, 1 micromol/L and 10 nmol/L rosiglitazone increased, respectively, C5L2 mRNA (9.3-fold, p < 0.0001) and ASP binding (2.4-fold, p < 0.05). Thus, C5L2 mRNA increases with differentiation, insulin, and thiazolidinedione treatment, and decreases with tumor necrosis factor alpha, all of which results in functional changes in ASP-C5L2 response and may have implications for human metabolism.
No preview · Article · Feb 2007 · Biochemistry and Cell Biology
[Show abstract][Hide abstract] ABSTRACT: Lipid storage, particularly in the abdominal cavity, is a major concern in poultry breeding because it affects the net meat yield. The major contributors to lipid storage in the abdominal cavity are hepatic fatty acid synthesis and VLDL secretion. These factors are strongly correlated with the body fatness in the chicken. The aim of our study was to determine if a traditional food supplement, the extract from fig tree leaves (fig tree leaf extract (FTE)), can be used to decrease hepatic triglyceride (TG) content and secretion of TG and cholesterol (TC) from the liver. Livers from 8-week-old roosters (n = 24) with high abdominal fat pad ratios were extracted, sliced, and cultured with increasing concentrations of FTE, insulin and both of them. While insulin significantly increased TG secretion (0.190 ± 0.013 mmol/l), TG content (0.523 ± 0.093 mmol/l) and TC secretion (1.727 ± 0.412 mmol/l) above the basal levels (P < 0.001), when FTE was added these effects were drastically reduced to the basal levels in a concentration-dependent manner (P < 0.001). Furthermore, we showed that in response to 1.7, 2.5 and 3.3 μl of FTE/ml of media hepatic TG content and TG secretion values from the liver significantly decreased in a concentration-dependent manner when compared to the control (P < 0.001). Our results suggest that Ficus carica leaf extract could be a beneficial supplement to modulate TG and TC secretion from the poultry liver.
No preview · Article · Jan 2006 · Turkish Journal of Veterinary and Animal Sciences
[Show abstract][Hide abstract] ABSTRACT: C5L2 binds acylation-stimulating protein (ASP) with high affinity and is expressed in ASP-responsive cells. Functionality
of C5L2 has not yet been demonstrated. Here we show that C5L2 is expressed in human subcutaneous and omental adipose tissue
in both preadipocytes and adipocytes. In mice, C5L2 is expressed in all adipose tissues, at levels comparable with other tissues.
Stable transfection of human C5L2 cDNA into HEK293 cells results in ASP stimulation of triglyceride synthesis (TGS) (193 ±
33%, 5 μm ASP, p < 0.001, where basal = 100%) and glucose transport (168 ± 21%, 10 μm ASP, p < 0.001). C3a similarly stimulates TGS (163 ± 12%, p < 0.001), but C5a and C5a des-Arg have no effect. The ASP mechanism is to increase Vmax of glucose transport (149%) and triglyceride (TG) synthesis activity (165%) through increased diacylglycerolacyltransferase
activity (200%). Antisense oligonucleotide down-regulation of C5L2 in human skin fibroblasts decreases cell surface C5L2 (down
to 54 ± 4% of control, p < 0.001, comparable with nonimmune background). ASP response is coordinately lost (basal TGS = 14.6 ± 1.6, with ASP = 21.0
± 1.4 (144%), with ASP + oligonucleotides = 11.0 ± 0.8 pmol of TG/mg of cell protein, p < 0.001). In mouse 3T3-L1 preadipocytes, antisense oligonucleotides decrease C5L2 expression to 69.5 ± 0.5% of control, p < 0.001 (comparable with nonimmune) with a loss of ASP stimulation (basal TGS = 22.4 ± 2.9, with ASP = 39.6 ± 8.8 (177%),
with ASP + oligonucleotides = 25.3 ± 3.0 pmol of TG/mg of cell protein, p < 0.001). C5L2 down-regulation and decreased ASP response correlate (r = 0.761, p < 0.0001 for HSF and r = 0.451, p < 0.05 for 3T3-L1). In HEK-hC5L2 expressing fluorescently tagged β-arrestin, ASP induced β-arrestin translocation to the
plasma membrane and formation of endocytic complexes concurrently with increased phosphorylation of C5L2. This is the first
demonstration that C5L2 is a functional receptor, mediating ASP triglyceride stimulation.
Full-text · Article · Jun 2005 · Journal of Biological Chemistry