Yang, R. Z. et al. Identification of omentin as a novel depot-specific adipokine in human adipose tissue: possible role in modulating insulin action. Am. J. Physiol. Endocrinol. Metab. 290, E1253-E1261
Central (visceral) obesity is more closely associated with insulin resistance, type 2 diabetes, and cardiovascular disease than is peripheral [subcutaneous (sc)] obesity, but the underlying mechanism for this pathophysiological difference is largely unknown. To understand the molecular basis of this difference, we sequenced 10,437 expressed sequence tags (ESTs) from a human omental fat cDNA library and discovered a novel visceral fat depot-specific secretory protein, which we have named omentin. Omentin ESTs were more abundant than many known adipose genes, such as perilipin, adiponectin, and leptin in the cDNA library. Protein sequence analysis indicated that omentin mRNA encodes a peptide of 313 amino acids, containing a secretory signal sequence and a fibrinogen-related domain. Northern analysis demonstrated that omentin mRNA was predominantly expressed in visceral adipose tissue and was barely detectable in sc fat depots in humans and rhesus monkeys. Quantative real-time PCR showed that omentin mRNA was expressed in stromal vascular cells, but not fat cells, isolated from omental adipose tissue, with >150-fold less in sc cell fractions. Accordingly, omentin protein was secreted into the culture medium of omental, but not sc, fat explants. Omentin was detectable in human serum by Western blot analysis. Addition of recombinant omentin in vitro did not affect basal but enhanced insulin-stimulated glucose uptake in both sc (47%, n = 9, P = 0.003) and omental (approximately 30%, n = 3, P < 0.05) human adipocytes. Omentin increased Akt phosphorylation in the absence and presence of insulin. In conclusion, omentin is a new adipokine that is expressed in omental adipose tissue in humans and may regulate insulin action.
"Omentin, also referred as intelectin-1 and intestinal lactoferrin receptor, is an adipocytokine originally discovered in omental fat  . Omentin is mainly expressed in visceral rather than subcutaneous adipose tissue . Several epidemiological reports demonstrated the negative relationship between blood omentin level and occurrence of obesity, type 2 diabetes and hypertension  . "
[Show abstract][Hide abstract] ABSTRACT: Omentin is a novel adipocytokine mainly expressed in visceral rather than subcutaneous adipose tissue. Several epidemiological studies demonstrated the negative relationship between blood omentin level and occurrence of obesity, type 2 diabetes and hypertension. Increases of inflammatory responses, contractile reactivity and structural remodeling of vascular wall contribute to hypertension development. Our in vitro studies previously demonstrated that omentin inhibited those hypertension-related pathological processes. In addition, our in vivo study demonstrated that intravenously injected omentin acutely inhibited agonists-induced increases of blood pressure in rats. However, the chronic effects of omentin on hypertension development are not determined. In the present study, we tested the hypothesis that chronic omentin treatment may inhibit pulmonary arterial (PA) hypertension (PAH). PAH was induced by a single intraperitoneal injection of monocrotaline (MCT: 60 mg/kg) to rats. Omentin (18 μg/kg/day) was intraperitoneally treated for 14 days. Chronic omentin treatment inhibited MCT-induced increases in PA pressure. Omentin inhibited MCT-induced right ventricular hypertrophy as well as increase of lung to body weight ratio. Histologically, omentin inhibited MCT-induced PA hyperplasia. Further, omentin inhibited the impairment of both endothelium-dependent and -independent relaxations mediated by acetylcholine and sodium nitroprusside, respectively. In conclusion, we for the first time demonstrate that chronic omentin treatment inhibits MCT-induced PAH in rats via inhibiting vascular structural remodeling and abnormal contractile reactivity.
Biochemical and Biophysical Research Communications 09/2014; 452(1). DOI:10.1016/j.bbrc.2014.08.070 · 2.30 Impact Factor
"Omentin was initially found in intestinal cell (called intelectin) and then omental adipose tissue and human adipocytes (especially stromal vascular cells of visceral adipose tissue), but it is also expressed in lung, heart, placenta, and ovary [18, 83]. There are two forms, omentin 1 and omentin 2, which share 83% of amino acid sequences. "
[Show abstract][Hide abstract] ABSTRACT: Obesity becomes pandemic, predisposing these individuals to great risk for lung injury. In this review, we focused on the anti-inflammatories and addressed the following aspects: adipocytokines and obesity, inflammation and other mechanisms, adipocytokines and lung injury in obesity bridged by inflammation, and potential therapeutic targets. To sum up, the majority of evidence supported that adiponectin, omentin, and secreted frizzled-related protein 5 (SFRP5) were reduced significantly in obesity, which is associated with increased inflammation, indicated by increase of TNF α and IL-6, through activation of toll-like receptor (TLR4) and nuclear factor light chain κ B (NF- κ B) signaling pathways. Administration of these adipocytokines promotes weight loss and reduces inflammation. Zinc- α 2-glycoprotein (ZAG), vaspin, IL-10, interleukin-1 receptor antagonist (IL-1RA), transforming growth factor β (TGF- β 1), and growth differentiation factor 15 (GDF15) are also regarded as anti-inflammatories. There were controversial reports. Furthermore, there is a huge lack of studies for obesity related lung injury. The effects of adiponectin on lung transplantation, asthma, chronic obstructive pulmonary diseases (COPD), and pneumonia were anti-inflammatory and protective in lung injury. Administration of IL-10 agonist reduces mortality of acute lung injury in rabbits with acute necrotizing pancreatitis, possibly through inhibiting proinflammation and strengthening host immunity. Very limited information is available for other adipocytokines.
Mediators of Inflammation 05/2014; 2014(1):978463. DOI:10.1155/2014/978463 · 3.24 Impact Factor
"Shibata et al. reported that decreased plasma omentin-1 levels predict the prevalence of coronary artery disease . Yang et al. reported that omentin-1 enhances insulin-stimulated glucose uptake in human adipocytes and may regulate insulin sensitivity . Yamawaki et al. reported that omentin-1 modulates vascular function and attenuates cyclooxygenase-2 expression and c-jun N-terminal kinase (JNK) activation in cytokine-stimulated endothelial cells [35,36]. "
[Show abstract][Hide abstract] ABSTRACT: Various adipokines are reported to be associated with the development of heart failure (HF) through insulin resistance and chronic inflammation. Omentin-1 is a novel adipokine and is associated with incident coronary artery disease. However, it remains unclear whether serum omentin-1 levels are associated with cardiac prognosis in patients with HF.
We measured serum omentin-1 levels at admission in 136 consecutive patients with HF, and 20 control subjects without signs of significant heart disease. We prospectively followed patients with HF to endpoints of cardiac death or re-hospitalization for worsening HF.
Serum omentin-1 levels were markedly lower in HF patients with cardiac events compared with to without. The patients who were in New York Heart Association (NYHA) functional class IV showed significantly lower serum omentin-1 levels compared to those in class II and III, whereas serum omentin-1 levels did not correlate with serum brain natriuretic peptide levels (r = 0.217, P = 0.011). We divided the HF patients into three groups based on the tertiles of serum omentin-1 level (low T1, middle T2, and high T3). Multivariate Cox hazard analysis showed that the lowest serum omentin-1 level (T1) was independently associated with cardiac events after adjustment for confounding factors (hazard ratio 5.78, 95% confidence interval 1.20-12.79). We divided the HF patients into two groups according to the median serum omentin-1 levels. Kaplan-Meier analysis revealed that the patients with low serum omentin-1 levels had a higher risk of cardiac events compared with those with high serum omentin-1 levels (log-rank test p < 0.001).
Decreased serum omentin-1 levels were associated with a poor cardiac outcome in patients with HF.
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