Pro-inflammatory gene expression profile in obese adults with high plasma GIP levels.

BACKGROUND: Glucose-dependent insulinotropic peptide (GIP) provides a novel link between the immune system and the gut, although results from different experimental and observational studies are contradictory, ranging from anti-inflammatory, through neutral to pro-inflammatory action of GIP. Thus, the aim of this study was to analyze inflammatory pathways on the level of gene expression and circulating inflammatory markers in relation to plasma GIP level. SUBJECTS/METHODS: The study included 128 obese adults. Two groups of obese subjects were created according to fasting GIP levels, with cutoff point at the 66th percentile and compared in respect with molecular and circulating markers of inflammation. GIP, interleukin (IL)-6 and adipokines: leptin, adiponectin, visfatin were measured by enzyme-linked immunosorbent assay. Inflammatory markers: monocyte chemoattractant protein-1 (MCP-1), sE-Selectin, sVCAM-1, sPECAM-1 were studied at fasting and after nutrient challenges. Gene expression in blood cells was determined by human gene microarray. RESULTS: Obese patients with high GIP levels had elevated fasting glucose (Q2 (Q1-Q3): 5.6 (5.0-6.0) vs 5.0 (4.8-5.4), P<0.001), homeostasis model assessment of insulin resistance (Q2 (Q1-Q3): 3.68 (2.72-5.42) vs 2.70 (2.13-4.33), P=0.021), thus increased markers of insulin resistance as well as elevated inflammatory markers Il-6 (Q2 (Q1-Q3): 1.34 (1.0-2.04) vs 1.12 (0.76-1.64), P=0.045), MCP-1 (Q2 (Q1-Q3): 363 (287-447) vs 323 (263-389), P=0.026). Leptin to adiponectin ratio was significantly associated with fasting plasma GIP levels (ß (95% CI): 0.84 (0.10-1.59)) independently of glucose levels. sE-Selectin was found to be a factor influencing GIP response to oral glucose intake (ß (95% CI): 0.47 (0.14-0.81)) and sVCAM was found to be a factor influencing GIP response to high-fat meal intake (ß (95% CI): 0.19 (0.01-0.37)). We identified 32 genes of inflammatory pathways differentially expressed in subjects with a high plasma GIP level compared to low GIP. Most upregulated genes play a role in leukocyte chemotaxis and tissue infiltration. CONCLUSIONS: These findings support the hypothesis that increased GIP signaling has a role in chronic low-grade inflammation.

Proangiogenic activity of beta-carotene is coupled with the activation of endothelial cell chemotaxis.

Endothelial cells play an important role in angiogenesis (formation of new vessels from preexisting ones), which is essential for organogenesis, tissue remodeling but also inflammatory response, carcinogenesis in all periods of our life. Beta-carotene (BC) in non-toxic concentrations (up to 3 microM) had no detectable effect on HUVECs (human umbilical vein endothelial cells) proliferation or apoptosis, despite significant changes of the expression patterns of pro- and anti-apoptotic genes. However beta-carotene did not change the tubulogenic activity of HUVEC in the in vitro angiogenesis model, it potently accelerated the bFGF-induced development of microcapillaries, as well as the migration of endothelial cells, in matrigel plug injected subcutaneously to mice. Potent activation of endothelial cell migration in the in vitro model of chemotaxis was also observed. According to the microarray data, genes involved in cell/cell and cell/matrix adhesion, matrix reorganization, activation of chemotaxis, the G-protein regulated intracellular signaling as well as genes involved in the rapid remodeling of protein cytoskeleton were the most affected by BC in HUVEC. We conclude that beta-carotene in the physiological concentration range stimulates early steps of angiogenesis by the activation of cellular migration as well as matrix reorganization and decrease of cell adhesion.

Assessment of incretins in oral glucose and lipid tolerance tests may be indicative in the diagnosis of metabolic syndrome aggravation.

Incretins stimulated by oral meals are claimed to be protective for the pancreatic beta cells, to increase insulin secretion, to inhibit glucagon release, slow gastric emptying (glucagon-like peptide-1) and suppress appetite. Recently it has however been suggested that glucagon-like peptide-1 (GLP-1) is putative early biomarker of metabolic consequences of the obesity associated proinflammatory state. The study was aimed to compare the release of incretins and some of early markers of inflammation at the fasting and postprandial period induced by functional oral glucose as well as lipid load in healthy controls and patients with metabolic syndrome (MS) to see if functional tests may be helpful in searching for the inflammatory status of patients. Fifty patients with MS and 20 healthy volunteers (C) participated in this study. The 3-hour oral glucose (OGTT) and the 8-hour oral lipid (OLTT) tolerance tests were performed. At fasting leptin and adiponectin, as well as every 30 minutes of OGTT and every 2 hours of OLTT blood concentration of GLP-1, glucose-dependent insulinotropic polypeptide (GIP), glucose, insulin, triglycerides, free fatty acids, glutathione peroxidase, interleukin-6, sE-selectin, monocyte chemoattractant protein-1 (MCP1) and visfatin were measured. At fasting and during both OGTT and OLTT the level of incretins did not differ between the MS and the C group. Both glucose and lipids reach food activated incretins secretion. Glucose was the main GLP-1 release activator, while the lipid load activated evidently GIP secretion. A significantly larger AUC-GIP after the lipid-rich meal over the carbohydrate meal was observed, while statistically bigger value of AUC-GLP-1 was noticed in OGTT than in OLTT (P < 0.001) within each of the investigated groups. In patients with the highest fasting plasma GIP concentration (3(rd) tertile), IL-6, MCP-1, sE-selectin and visfatin blood levels were increased and correlated with glutathione peroxydase, leptin/adiponectin ratio, higher visfatin and interleukin-6 levels. The fat containing meals stimulate the long-lasting release of incretins, mainly GIP, parallel to the increase of the markers of low grade inflammation associating obesity in metabolic syndrome. The possibility of use of the postprandial (OLTT) GIP release measurement for the low grade inflammation progress in MS patients is suggested.

Modulation of endothelial cell proliferation and capillary network formation by the ox-LDL component: 1-palmitoyl-2-archidonoyl-sn-glycero-3-phosphocholine (ox-PAPC).

Atherosclerotic plaque formation is often associated with pathological angiogenesis. Modified phospholipids, including oxidized lipoproteins such as LDL, are found to induce adhesion of the monocytes to the endothelial cells and to stimulate their chemotaxis. Effects of oxidized 1-palmitoyl-2-archidonoyl-sn-glycero-3-phosphocholine (ox-PAPC) mimic actions of minimally modified LDL in vivo. Interleukin-8 (IL-8) and interleukin-15 (IL-15) are known to induce both inflammation and angiogenesis. The goal of our study was to analyze a potential synergism between ox-PAPC and IL-15 in the in vitro model of angiogenesis carried out in the human endothelial cells (HUVECs). Increasing IL-15 concentrations led to formation of the tube-like structures in the matrigel 3D-model of angiogenesis (P < 0.05), in contrast to ox-PAPC that inhibited this process. HUVECs incubation with ox-PAPC led to reduced IL-15 gene basal expression (P = 0.033) along with parallel increase, however statistically insignificant, of basal gene expression of IL-8 (P = 0.086). Our findings point to the ox-PAPC opposite effects on the IL-8- and IL-15-mediated angiogenic responses that contribute to pathological angiogenesis induced by ox-LDL.

The adipose tissue gene expression in mice with different nitric oxide availability.

Mice with the knockout of endothelial nitric oxide synthase (eNOS ko) demonstrate symptoms resembling the human metabolic syndrome. NO has been recently demonstrated to be deeply involved in regulation of not only blood flow and angiogenesis, but also in modulation of mammalian basal energy substrate metabolism. Asymmetric dimethylarginine (ADMA) is an endogenous competitive inhibitor of NOS. The enzyme dimethylarginine dimethylaminohydrolase (DDAH) catabolizes ADMA, what leads to increase of endogenous NO bioavailability. This study was aimed to compare the brown (BAT) and white (WAT) adipose tissue gene expression of age matched mice with decreased (eNOS ko) and increased (overexpressing DDAH) endogenous NO generation. The 19 week old eNOS ko mice demonstrated significantly lower weight, higher circulating glucose, insulin, leptin and cholesterol concentrations. The adiponectin as well as fasting triglyceride concentrations were not significantly altered. Animals with DDAH knock in, presented significantly increased angiogenic activity than eNOS ko mice. The microarray analysis pointed to activation of adipogenesis-related genes in eNOS ko mice in WAT, what was in contrast with the inhibition observed in the DDAH overexpressing mice. The angiogenesis related gene expression was down-regulated in both models in comparison to WT animals. This study support the multipotential role of endogenous NO in maintaining homeostasis of energy substrate catabolism.

DNA methylation, induced by beta-carotene and arachidonic acid, plays a regulatory role in the pro-angiogenic VEGF-receptor (KDR) gene expression in endothelial cells.

UNLABELLED: DNA methylation is a potent regulator of gene expression. The influence of beta-carotene (BC) and arachidonic acid (AA) on angiogenesis--a new blood vessel formation, was reported. The tyrosine kinase VEGFR-2 receptor (KDR) activation by vascular endothelial growth factor is one of the main angiogenic mechanisms. This study was aimed to investigate a possible role of CpG island methylation on regulation of the pro-angiogenic KDR gene expression after incubation of human endothelial cells with BC and/or AA. METHODS: Human umbilical vein endothelial cells (HUVEC) were incubated with BC (1-10 microM) and/or 3 microM AA for 24 hours. The CpG island methylation was quantified using the COBRA method and restriction enzymes' digestion (NewEngland BioLabs). Intracellular protein concentrations were determined by Western blot analysis using the specific antibodies (Santa Cruz). RESULTS: Incubation with BC and AA, decreased methylation of the KDR promoter region. These results well-correlated with the detected, by qRT-PCR, up-regulation of KDR gene expression by BC (p=0.035) as well as by AA. Incubation with BC (p=0.02) and AA (p=0.0014) increased the KDR protein levels in HUVECs. CONCLUSION: The changes in CpG island methylation of the KDR the pro-angiogenic gene promoter, represents one of the mechanisms involved in regulation of angiogenic response by BC and AA.