Evaluation of the relationship between circulating omentin-1 concentrations and components of the metabolic syndrome in adults without type 2 diabetes or cardiovascular disease

Evaluation of serum adipokines (omentin-1 and visfatin) in coronary artery disease at a North Indian hospital

Objective. Adipose tissue is considered to be an endocrine organ that secretes bioactive substances known as adipokines that contribute to the pathophysiology of metabolic and coronary diseases related to obesity. In this study, various novel biomarkers, such as inflammatory markers that are pro-inflammatory (visfatin) and anti-inflammatory (omentin-1), as prognostic indicators for people with coronary artery disease (CAD) were investigated. Methods. In this study, 30 diabetic patients with CAD, 30 diabetic patients without CAD, and 30 healthy control counterparts were included. Serum omentin and visfatin concentrations were evaluated by solid-phase enzyme linked immunosorbent assay (ELISA) kit. Patients with established diagnosis of CAD based on angiography, ECG, and elevated cardiac marker level were included into the study. Patients with cardioembolic stroke, cerebral venous sinus thrombosis, CNS vasculitis, and hemorrhage due to trauma, tumor, vascular malformation, and coagulopathy were excluded. Results. The serum omentin-1 levels were significantly higher in the healthy controls in comparison with the diabetic group (p<0.0001) and serum visfatin levels were significantly higher in the diabetic group in comparison with the healthy controls (p<0.0001). The serum omentin levels were significantly higher in the diabetic group in comparison with the cardio-diabetic group (p<0.0001) and serum visfatin levels were significantly higher in the cardio-diabetic group in comparison with the diabetic group (p<0.0001). The serum omentin-1 showed negative correlation with the serum visfatin in the cardio-diabetic group. Conclusion. The adipokines, such as omentin and visfatin, may be good therapeutic candidates in preventing or ameliorating CAD.

Omentin-1: A newly discovered warrior against metabolic related diseases

INTRODUCTION

: Chronic metabolism-related diseases are challenging clinical problems. Omentin-1 is mainly expressed in stromal vascular cells of adipose tissue and can also be expressed in airway goblet cells, mesothelial cells, and vascular cells. Omentin-1 has been found to exert important anti-inflammatory, antioxidative and anti-apoptotic roles and to regulate endothelial dysfunction. Moreover, omentin-1 also has protective effects against cancer, atherosclerosis, type 2 diabetes mellitus, and bone metabolic diseases. The current review will discuss the therapeutic potential of omentin-1.

AREAS COVERED

: This review summarizes the biological actions of omentin-1 and provides an overview of omentin-1 in metabolic-related diseases. The relevant literature was derived from a PubMed search spanning 1998-2021 using these search terms: omentin-1, atherosclerosis, diabetes mellitus, bone, cancer, inflammation, and oxidative stress.

EXPERT OPINION

: As a novel adipocytokine, omentin-1 is a promising therapeutic target in metabolic-related diseases. Preclinical animal studies have shown encouraging results. Moreover, circulating omentin-1 has excellent potential as a noninvasive biomarker. In the future, strategies for regulating omentin-1 need to be investigated further in clinical trials in a large cohort.

Omentin as an Independent Predictor of Metabolic Syndrome and Obesity Among Adolescents in Northeast China

PURPOSE

We investigated the association of omentin with metabolic syndrome (MetS), MetS components, and obesity in adolescents.

METHODS

A total of 742 middle-school students from Liaoyang City were enrolled in this cross-sectional study using the stratified cluster sampling method. Clinical information and blood samples were collected, and serum omentin levels were measured using enzyme-linked immunosorbent assay.

RESULTS

Mean plasma omentin levels were lower in male than in female participants (88.25 (interquartile range 63.02-133.61) vs 99.46 (interquartile range 69.08-188.35) ng/L, P = 0.004). The participants were divided into four groups according to the quartile (Q) values of omentin from low to high. With increasing omentin levels from Q1 to Q4, the age of adolescents and the proportion of males gradually increased (P < 0.05), whereas the body mass index (BMI) (P < 0.05) and prevalence of MetS (P > 0.05) tended to decrease. Omentin levels were significantly and negatively correlated with waist circumference and BMI (correlation coefficients of -0.099 and -0.115, respectively). Regression analysis showed that omentin level was independently associated with the risk of MetS (Odds ratio, OR = 0.639, 95% confidence interval, CI (0.432, 0.945)), which was attributed to the association with central obesity (OR = 0.775, 95% CI (0.605, 0.993)) among MetS components. Increased omentin levels also indicated a reduced risk of obesity (OR = 0.700, 95% CI (0.563, 0.870)).

CONCLUSION

Omentin is an independent predictor of MetS and obesity among adolescents in northeast China.

Relationship between circulating serum omentin-1 levels and nascent metabolic syndrome in patients with hypertension

The prevalence of metabolic syndrome (MetS) is more common in patients with hypertension and is associated with an increased risk of target organ damage and/or cardiovascular disease (CVD). Omentin-1 is a beneficial adipokine considered to play a role in MetS and MetS-related states such as obesity, diabetes, and coronary artery disease. The aim of this study was to determine the relationship between circulating omentin-1 levels and MetS uncomplicated by diabetes or CVD (nascent MetS) in patients with hypertension. In this study, 110 patients (54 men, 49%; average age: 49.72±11.32 years) treated for hypertension but without overt diabetes and/or CVD were enrolled. 66 patients were stratified into MetS (+) (group 1) and 44 patients into MetS (-) (group 2) according to the American Heart Association/National Heart, Lung, and Blood Institute criteria. The triglyceride glucose (TyG) index was used to assess insulin resistance. Circulating omentin-1 levels in venous blood samples were measured by an ELISA kit. Circulating omentin-1 levels in patients with MetS were significantly lower than in patients without MetS (46.35 ng/mL (42.70-57.70 ng/mL) vs 130.95 ng/mL (62.83-236.48 ng/mL), p<0.001). Omentin-1 was inversely correlated with TyG index (r=-0.204, p=0.033). In a multivariate logistic regression analysis, omentin-1, TyG index, and body mass index were independent predictors of MetS. A receiver operating characteristic curve analysis determined that the best cut-off value for omentin-1 in predicting MetS was 62.20 ng/mL and the area under the curve was 0.880 (95% CI 0.817 to 0.942, p<0.001). The findings of this study suggest that circulating omentin-1 levels are inversely related to the presence of MetS and may be a reliable marker to predict the development of MetS in patients with hypertension.

Molecular and Pathophysiological Links between Metabolic Disorders and Inflammatory Bowel Diseases

Despite considerable epidemiological evidence indicating comorbidity between metabolic disorders, such as obesity, type 2 diabetes, and non-alcoholic fatty liver disease, and inflammatory bowel diseases (IBD), such as Crohn’s disease and ulcerative colitis, as well as common pathophysiological features shared by these two categories of diseases, the relationship between their pathogenesis at molecular levels are not well described. Intestinal barrier dysfunction is a characteristic pathological feature of IBD, which also plays causal roles in the pathogenesis of chronic inflammatory metabolic disorders. Increased intestinal permeability is associated with a pro-inflammatory response of the intestinal immune system, possibly leading to the development of both diseases. In addition, dysregulated interactions between the gut microbiota and the host immunity have been found to contribute to immune-mediated disorders including the two diseases. In connection with disrupted gut microbial composition, alterations in gut microbiota-derived metabolites have also been shown to be closely related to the pathogeneses of both diseases. Focusing on these prominent pathophysiological features observed in both metabolic disorders and IBD, this review highlights and summarizes the molecular risk factors that may link between the pathogeneses of the two diseases, which is aimed at providing a comprehensive understanding of molecular mechanisms underlying their comorbidity.

The association between serum omentin level and bodyweight: A systematic review and meta-analysis of observational studies

BACKGROUND AND AIMS

A number of studies have examined the association between omentin and body weight, but the findings have been inconclusive. Here in, we systematically reviewed available observational studies to elucidate the overall relationship between omentin and body weight, by comparison of serum omentin level in overweight/obese and normal weight subjects.

METHODS

PubMed, Science direct, Scopus and ISI web of science databases were searched for all available literature until January 2020 for studies assessing the association between omentin and body weight. The Newcastle-Ottawa Quality Assessment Scale was used to assess the quality of each study.

RESULTS

A total of 27 articles met the inclusion criteria and were included in our systematic review and meta-analysis. There was a significant association between omentin serum level and body weight (Standard Mean Difference (SMD) -0.43; 95% CI, -0.70 to -0.15; P = 0.002; I² = 93.2%). In order to find the probable source of heterogeneity subgroup analysis based on the participants' age (adolescent, adult), gender (male, female, both gender), health status (healthy, unhealthy), geographical location (Asian, non-Asian countries), study quality (low, medium, high), study design (case-control, cross-sectional), participants' health status (healthy, unhealthy) and BMI (obese, overweight) was carried out.

CONCLUSION

According to what was discussed, we found that serum omentin level is significantly lower in overweight subjects but not obese ones. This finding should be interpreted cautiously because of significant heterogeneity among included studies.

Omentin: a biomarker of cardiovascular risk in individuals with axial spondyloarthritis

Cardiovascular (CV) disease is the main cause of mortality in axial spondyloarthritis (axSpA). CV risk is enhanced by dysregulation of adipokines. Low omentin levels were associated with metabolic dysfunction and CV disease in conditions different from axSpA. Accordingly, we evaluated the genetic and functional implication of omentin in CV risk and subclinical atherosclerosis in a cohort of 385 axSpA patients. Subclinical atherosclerosis was evaluated by carotid ultrasound. Omentin rs12409609, in linkage disequilibrium with a polymorphism associated with CV risk, was genotyped in 385 patients and 84 controls. Serum omentin levels were also determined. omentin mRNA expression was assessed in a subgroup of individuals. Serum and mRNA omentin levels were lower in axSpA compared to controls. Low serum omentin levels were related to male sex, obesity, inflammatory bowel disease (IBD) and high atherogenic index. rs12409609 minor allele was associated with low omentin mRNA expression in axSpA. No association was observed with subclinical atherosclerosis at the genetic or functional level. In conclusion, in our study low omentin serum levels were associated with CV risk factors in axSpA. Furthermore, rs12409609 minor allele may be downregulating the expression of omentin. These data support a role of omentin as a CV risk biomarker in axSpA.

Association of serum omentin concentration with anthropometric, physiological, and biochemical parameters in obese individuals

OBJECTIVE

Omentin is a secretory protein produced in visceral adipose tissue. The potential protective action of omentin in metabolic disorders is not yet fully understood. The aim of this study was to determine the association of omentin with anthropometric, physiologic, and biochemical parameters in obese individuals.

METHODS

Sixty obese individuals and 40 normal weight controls were enrolled in the study. Anthropometric measurements were taken, systolic (SBP) and diastolic blood pressures (DBP) were recorded. Serum fasting glucose, insulin, homeostatic model assessment of insulin resistance (HOMA-IR), lipid profile, and serum omentin concentrations were determined.

RESULTS

The concentration of omentin in obese individuals was significantly lower than in controls (145.5 ± 33.3 versus 383.6 ± 92.9; P < 0.001). Omentin correlated negatively with waist circumference (P < 0.01), hip circumference (P < 0.05), percent of adipose tissue (P < 0.001), fasting insulin (P < 0.001), HOMA-IR (P < 0.001), and SBP (P < 0.001) in the patients who were obese. A positive relationship was documented with high-density lipoprotein in both the obese patients (P < 0.01) and the overall population (P < 0.001). Multiple negative omentin correlations with body weight, body mass index, waist and hip circumference and its ratio, percent of adipose tissue, SBP, triacylglycerols, glucose, fasting insulin, and HOMA-IR were demonstrated in the entire population. In the multivariate linear regression model, insulin concentration (β = -0.49; P < 0.001), percent of adipose tissue (β = -0.31; P < 0.001), and waist circumference (β = -0.21; P < 0.01) were independent predictors of omentin concentration in individuals who were obese.

CONCLUSIONS

A concentration of omentin is associated with cardiometabolic risk-related factors in obesity. Fasting insulin, adipose tissue percentage, and waist circumference can be considered candidates for markers of omentin concentration in obese individuals.

Higher circulating omentin is associated with increased risk of primary cardiovascular events in individuals with diabetes

AIMS/HYPOTHESIS

Higher concentrations of the adipokine omentin are associated with lower levels of cardiometabolic risk factors in experimental and cross-sectional studies, but with higher risk of type 2 diabetes and cardiovascular diseases in population-based cohort studies. However, it is unknown whether high omentin concentrations are associated with increased risk of cardiovascular events in people with established diabetes. Therefore, the present study investigated the association between serum omentin concentrations and the risk of cardiovascular events in individuals with diabetes.

METHODS

This prospective study was based on participants of the German ESTHER cohort with diabetes and without previous cardiovascular event. The ESTHER cohort consists of individuals aged 50-75 years at baseline who were recruited by their general practitioners. After exclusion of individuals with serum C-reactive protein ≥10 mg/l (≥95.24 nmol/l), the final analysis population consisted of 933 individuals. At baseline, serum omentin concentrations were measured by ELISA. Cox regression models were fitted to estimate HRs and their corresponding 95% CIs for associations of omentin tertiles with a composite endpoint of cardiovascular events and separately with incident myocardial infarction, stroke and cardiovascular death.

RESULTS

During 14 years of follow-up, 228 individuals experienced a primary cardiovascular event (myocardial infarction, stroke or cardiovascular death). After comprehensive adjustment for age, sex, BMI, metabolic and lifestyle factors and medication use, HRs (95% CIs) for the 2nd and 3rd tertile of omentin compared with the 1st tertile were: 1.24 (95% CI 0.86, 1.79) and 1.63 (1.15, 2.32) (p_trend = 0.005) for the composite cardiovascular endpoint; 1.39 (0.78, 2.47) and 1.71 (0.98, 2.99) (p_trend = 0.065) for incident myocardial infarction; 1.40 (0.78, 2.53) and 2.05 (1.17, 3.58) (p_trend = 0.010) for incident stroke; and 1.43 (0.85, 2.40) and 1.72 (1.04, 2.83) (p_trend = 0.040) for cardiovascular death. Effect estimates and p values were almost unaltered after additional adjustment for adiponectin.

CONCLUSIONS/INTERPRETATION

Higher omentin concentrations are associated with an increased risk for cardiovascular events in individuals with diabetes after adjustment for multiple cardiovascular risk factors. Given data from preclinical studies, it appears possible that this association reflects a compensatory, but insufficient upregulation of omentin concentrations as a response to stimuli that increase cardiovascular risk.

New Insights into Adipokines as Potential Biomarkers for Type-2 Diabetes Mellitus

A large number of studies have been focused on investigating serum biomarkers associated with risk or diagnosis of type-2 diabetes mellitus. In the last decade, promising studies have shown that circulating levels of adipokines could be used as a relevant biomarker for diabetes mellitus progression as well as therapeutic future targets. Here, we discuss the possible use of recently described adipokines, including apelin, omentin-1, resistin, FGF-21, neuregulin-4 and visfatin, as early biomarkers for diabetes. In addition, we also include recent findings of other well known adipokines such as leptin and adiponectin. In conclusion, further studies are needed to clarify the pathophysiological significance and clinical value of these biological factors as potential biomarkers in type-2 diabetes and related dysfunctions.

The association between resting metabolic rate and metabolic syndrome May Be mediated by adipokines in overweight and obese women

AIMS

Adipokines play a major role in developing metabolic syndrome (MetS), and it has been found that there is a significant relationship between MetS and resting metabolic rate (RMR) in obese people. The present study aimed to investigate the mediatory effect of adipokines on the RMR-MetS relationship.

METHODS

This cross-sectional study included 263 obese and overweight women, mean BMI 33.28 (4.93) kg/m, and mean age 39.02 (11.60) who were assessed for RMR using indirect calorimetry. Moreover, using the body composition analyzer the Body composition was measured. Also, Enzyme-linked Immunosorbent Assay (ELISA) test provided a quantitative measurement of biochemical parameters.

RESULTS

The results indicated that women in low RMR group had higher fat mass (P < 0.0001), FFM (P = 0.002), weight (P = 0.006), BMI (P < 0.0001), age (P = 0.01), and hs-CRP (P = 0.001). The results did not confirm any significant mediating roles for RBP4 (P = 0.051, β = -0.28) and Vaspin (P = 0.06, β = 0.32) in the RMR-MetS relationship. Additionally, after a binary regression test, Omentin-1 showed a significant mediating role (P = 0.25, β = 0.04) as an interrelated agent to RMR and MetS.

CONCLUSION

As this study shows, Omentin-1 was found to play a significant mediating role as a mediatory agent in relationship between RMR and MetS.

Omentin-1 ameliorates the attachment of the leukocyte THP-1 cells to HUVECs by targeting the transcriptional factor KLF2

Oxidation of low-density lipoproteins (ox-LDL) plays a critical role in endothelial dysfunction and the pathological progression of atherosclerosis by causing leukocyte attachment to endothelial surfaces. Omentin-1, an important adipokine primarily secreted by stromal vascular cells, has displayed various biological functions in diverse tissues. However, little information regarding the effects of omentin-1 on ox-LDL- induced endothelial dysfunction has been reported before. In the current study, we found that omentin-1 significantly reduced the attachment of the leukocyte THP-1 cells to human umbilical vein endothelial cells (HUVECs) in a dose dependent manner. Additionally, omentin-1 treatment prevented the expression of cell adhesion molecules such as VCAM-1 and E-selectin at both the mRNA level and the protein level. Notably, we found that omentin-1 significantly restored ox-LDL-induced reduction of KLF2, an important transcriptional factor and regulator of endothelial function. Also, omentin-1 promoted the expression of KLF2 target genes eNOS and PAI-1. Mechanistically, our results indicate that the effects of omentin-1 on KLF2 expression are mediated by p53. These results highlight the potential of omentin-1 in preventing endothelial dysfunction and atherosclerosis.

Population-based serum omentin-1 levels: paradoxical association with cardiometabolic disorders primarily in men

AIM

The conflicting relationships of serum omentin with inflammation markers and cardiometabolic disorders were investigated. Results & methods: Unselected 864 population-based middle-aged adults were cross-sectionally studied by sex-specific omentin tertiles. Men in the lowest omentin tertile (T1) had lower systolic blood pressure, HbA1c and glucose values and tended in T3 to higher lipoprotein(a) levels. Logistic regression analysis, adjusted for four covariates, revealed significant independent associations with the presence of hypertension and diabetes only in men. Sex- and age-adjusted odds ratio in gender combined for T2 & T3 versus T1 was 1.34 (95% CI: 1.00-1.79) for metabolic syndrome.

DISCUSSION & CONCLUSION

The elicited adverse relationships of omentin-1 support the notion of oxidative stress-induced proinflammatory conversion of omentin, rendering loss of anti-inflammatory properties.

Role of Omentin, Vaspin, Cardiotrophin-1, TWEAK and NOV/CCN3 in Obesity and Diabetes Development

Adipose tissue releases bioactive mediators called adipokines. This review focuses on the effects of omentin, vaspin, cardiotrophin-1, Tumor necrosis factor-like Weak Inducer of Apoptosis (TWEAK) and nephroblastoma overexpressed (NOV/CCN3) on obesity and diabetes. Omentin is produced by the stromal-vascular fraction of visceral adipose tissue. Obesity reduces omentin serum concentrations and adipose tissue secretion in adults and adolescents. This adipokine regulates insulin sensitivity, but its clinical relevance has to be confirmed. Vaspin is produced by visceral and subcutaneous adipose tissues. Vaspin levels are higher in obese subjects, as well as in subjects showing insulin resistance or type 2 diabetes. Cardiotrophin-1 is an adipokine with a similar structure as cytokines from interleukin-6 family. There is some controversy regarding the regulation of cardiotrophin-1 levels in obese -subjects, but gene expression levels of cardiotrophin-1 are down-regulated in white adipose tissue from diet-induced obese mice. It also shows anti-obesity and hypoglycemic properties. TWEAK is a potential regulator of the low-grade chronic inflammation characteristic of obesity. TWEAK levels seem not to be directly related to adiposity, and metabolic factors play a critical role in its regulation. Finally, a strong correlation has been found between plasma NOV/CCN3 concentration and fat mass. This adipokine improves insulin actions.

Common links between metabolic syndrome and inflammatory bowel disease: Current overview and future perspectives

Metabolic syndrome (MS) features a constellation of central obesity, dyslipidemia, impaired glucose metabolism and often hypertension joined by insulin resistance and chronic inflammation. All these elements greatly raise patient's risk of cardiovascular disease and type 2 diabetes, resulting in an increased mortality. Metabolic syndrome affects approximately 20-25% of the world's adult population and thus it is essential to study its pathophysiology and seek new pharmacological targets. There is a thoroughly studied link between MS and inflammatory diseases of the gastrointestinal (GI) system, i.e. steatohepatitis. However, recent findings also indicate similarities in pathophysiological features between MS and inflammatory bowel disease (IBD), including adipose tissue dysregulation, inadequate immune response, and inflammation. In this review we aim to outline the pathophysiology of MS and emphasize the aspects revealed recently, such as mineralocorticoid activity, involvement of sex hormones and an accompanying increase in prolactin secretion. More importantly, we focus on the common links between MS and IBD. Finally, we describe new strategies and drug targets that may be utilized in MS therapy, namely adiponectin mimetics, GLP-1-based multi agonists, ABCA1 agonists and possible role of miRNA. We also discuss the possible utility of selected agents as adjuvants in IBD therapy.

Differential Effects of Oral and Intravenous Lipid Administration on Key Molecules Related to Energy Homeostasis

CONTEXT

The spectrum of lipid-induced changes in the secretion of hormones important in energy homeostasis has not yet been fully elucidated.

OBJECTIVE

To identify potential incretin-like effects in response to lipid administration, we examined the short-term effect of iv vs oral lipids on key molecules regulating energy homeostasis. Design, Intervention, and Participants: After a 10-hour overnight fast, 26 subjects were randomized to receive an oral lipid load, a 10% iv lipid emulsion, a 20% iv lipid emulsion, or an iv saline infusion. We obtained blood samples at 30-minute intervals for the first 2 hours and hourly thereafter for a total of 6 hours.

MAIN OUTCOME MEASURES

Circulating levels of insulin, glucose, c-peptide, free fatty acids, incretins (glucagon-like peptide-1, gastric inhibitory polypeptide), glucagon, peptide YY, ghrelin, fibroblast growth factor 21, fetuin A, irisin, omentin, and adiponectin were measured.

RESULTS

Oral lipid ingestion resulted in higher glucagon-like peptide-1, gastric inhibitory polypeptide, glucagon, and peptide YY levels, compared with the other three groups (incremental area under the curve P = .003, P < .001, P < .001, P < .001, respectively). The 20% lipid emulsion, leading to higher free fatty acid levels, resulted in greater insulin, c-peptide, and fibroblast growth factor 21 responses compared with placebo and the other two groups (incremental area under the curve P = .002, P = .005, P < .001, P < .001, respectively). Omentin, adiponectin, fetuin A, and irisin levels were not affected by either mode of lipid administration.

CONCLUSIONS

Metabolic responses to lipids depend on the route of administration. Only iv lipids trigger a dose-dependent fibroblast growth factor 21 secretion, which is nonglucagon mediated. Intravenous lipids also induce hyperinsulinemia without concurrent decreases in glucose, a phenomenon observed in insulin-resistant states. Orally administered lipids mostly affect gastrointestinal tract-secreted molecules important in glucose and energy homeostasis such as glucagon, incretins, and peptide YY.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

New Insights into the Role of Metformin Effects on Serum Omentin-1 Levels in Acute Myocardial Infarction: Cross-Sectional Study

Background. Serum omentin-1 level was low in the most types of ischemic heart disease compared to normal subjects; it also dependently correlated with coronary heart disease; thus, omentin-1 is regarded as a novel biomarker in IHD. Objective. The aim of the present study was to establish the links between omentin-1 and acute myocardial infarction in metformin patients. Subjects and Methods. A cross-sectional study was performed on eighty-five patients with type II DM and acute MI. They are divided as follows: Group I, 62 patients with type II DM who received metformin prior to onset of acute MI; Group II, 23 patients with type II DM who did not receive metformin prior to onset of acute MI; and Group III, 30 normal healthy controls. Venous blood was drawn from each participant for determination of lipid profile, plasma omentin-1, cardiac troponin-I (cTn-I) and other routine tests. Results. Patients that presented with acute MI that received metformin show a significant difference in all biochemical parameters (p < 0.001); metformin increases serum omentin-1 level and decreases serum cardiac troponin-I level compared with control subjects and nonmetformin treated patients. Conclusion. Metformin pharmacotherapy increases omentin-1 serum levels and may be regarded as a potential agent in the prevention of the occurrences of acute MI in diabetic patients.

Adiponectin may mediate the association between omentin, circulating lipids and insulin sensitivity: results from the KORA F4 study

OBJECTIVE

Reduced circulating omentin levels have been reported in obesity and type 2 diabetes, but data were mostly derived from univariate analyses in small study samples. This study aimed to investigate the relationship between omentin, abnormal glucose tolerance and related metabolic factors in a large population-based cross-sectional study.

DESIGN AND METHODS

Serum omentin was measured by ELISA in 1092 participants of the German KORA F4 survey (2006-2008). Associations between omentin serum levels, glucose tolerance (assessed with an oral glucose tolerance test) and diabetes-related factors were estimated using logistic and linear regression models respectively.

RESULTS

Serum levels of omentin were not related to categories of glucose tolerance. However, serum omentin was positively associated with whole-body insulin sensitivity index (ISI (composite)) and HDL cholesterol and showed inverse associations with 2-h post-load glucose, fasting insulin, homeostasis model assessment-estimated insulin resistance, BMI and triglycerides (all P≤0.03 after adjustment for age, sex and lifestyle factors). Further adjustment for BMI and/or serum lipids attenuated the associations with parameters of glucose metabolism, whereas adjustment for serum adiponectin virtually abolished all aforementioned associations. In contrast, adjustment for omentin had no effect on the positive association between adiponectin levels and ISI (composite).

CONCLUSIONS

The data from this large population-based cohort show that circulating omentin levels are associated with insulin sensitivity. Our observations further suggest that omentin acts via upregulation of adiponectin, which in turn affects lipid metabolism and thereby also indirectly enhances insulin sensitivity, but mechanistic studies are required to corroborate this hypothesis.

A novel adipocytokine, omentin, inhibits platelet-derived growth factor-BB-induced vascular smooth muscle cell migration through antioxidative mechanism

Omentin is a novel adipocytokine expressed in visceral adipose tissue. Secretion and blood concentration of omentin decrease in the obese subjects. We previously demonstrated that omentin is anti-inflammatory in vascular smooth muscle cells (SMCs). While vascular remodeling via migration of SMCs is also important for hypertension development, it remains to be clarified whether omentin affects this process. Here we examined whether omentin controls SMC migration. Omentin (300 ng/ml, 2 h) significantly inhibited platelet-derived growth factor (PDGF)-BB (10 ng/ml, 6 h)-induced migration of rat mesenteric arterial SMCs, as determined by Boyden chamber assay. Omentin (300 ng/ml, 2 h) significantly inhibited PDGF-BB (10 ng/ml, 30 min)-induced phosphorylation of p38 and heat shock protein (HSP) 27. Omentin (300 ng/ml, 2 h) significantly inhibited PDGF-BB (10 ng/ml, 30 min)-induced NADPH oxidase (NOX) activation as determined by lucigenin assay. Omentin (300 ng/ml, 24 h) significantly inhibited fetal bovine serum (5%, 4 days)-induced SMC outgrowth from rat isolated mesenteric artery. In vivo, omentin significantly inhibited carotid intimal hyperplasia in mouse ligation model. In summary, we for the first time demonstrate that omentin prevents PDGF-BB-induced SMC migration by preventing NOX/O2−/p38/HSP27 pathways, which might be at least partly responsible for the preventive effects on neointimal hyperplasia. Our data suggest that omentin may be protective against hypertension development by inhibiting vascular structural remodeling.