Circulating chemerin level is associated with metabolic, biochemical and haematological parameters-A population-based study

Vascular chemerin from PVAT contributes to norepinephrine and serotonin-induced vasoconstriction and vascular stiffness in a sex-dependent manner

The adipokine chemerin supports normal blood pressure and contributes to adiposity-associated hypertension, evidenced by falls in mean arterial pressure in Dahl SS rats given an antisense oligonucleotide against chemerin. In humans, circulating chemerin is positively associated with hypertension and aortic stiffness. Mechanisms of chemerin's influence on vascular health and disease remain unknown. We identified chemerin production in the vasculature-the blood vessel and its perivascular adipose tissue (PVAT). Here, using RNAScope, qPCR, isometric contractility, high-frequency ultrasound imaging, and Western blot in the Dahl SS rat, we test the hypothesis that endogenous chemerin amplifies agonist-induced vasoconstriction through the chemerin1 receptor and that chemerin drives aortic stiffness in the thoracic aorta. CMKLR1 (chemerin1) expression was higher in the media, and Rarres2 (chemerin) expression was higher in the PVAT. Chemerin1 receptor antagonism via selective inhibitor CCX832 reduced maximal contraction to norepinephrine (NE) and serotonin (5-HT), but not angiotensin II, in isolated thoracic aorta (PVAT intact) from male Dahl SS rat. In females, CCX832 did not alter contraction to NE or 5-HT. Male, but not female, genetic chemerin knockout Dahl SS rats had lower aortic arch pulse wave velocity than wild types, indicating chemerin's role in aortic stiffness. Aortic PVAT from females expressed less chemerin protein than males, suggesting PVAT as the primary source of active chemerin. We show that chemerin made by the PVAT amplifies NE and 5-HT-induced contraction and potentially induces aortic stiffening in a sex-dependent manner, highlighting the potential for chemerin to be a key factor in blood pressure control and aortic stiffening.NEW & NOTEWORTHY Chemerin1 receptor inhibition reduced norepinephrine (NE) and 5-HT-induced vasoconstriction in males. Genetic chemerin knockout (KO) resulted in lower pulse wave velocity in males. Differences in chemerin abundance in aorta perivascular adipose tissue (APVAT) may explain sex-dependent role of chemerin.

Chemerin Levels in Individuals with Type 2 Diabetes and a Normal Weight versus Individuals with Type 2 Diabetes and Obesity: An Observational, Cross-Sectional Study

Chemerin acts as both a chemotactic agent and an adipokine that undergoes proteolytic cleavage, converting inactive precursors into their active forms before being subsequently inactivated. Elevated chemerin levels are linked to obesity and type 2 diabetes mellitus (T2D). This study aimed to elucidate the effects of T2D and obesity on chemerin levels by comparing plasma samples from individuals with a normal weight and T2D (BMI < 25; NWD group n = 22) with those from individuals who are overweight or obese and have T2D (BMI ≥ 25; OWD group n = 39). The total chemerin levels were similar in the NWD and OWD groups, suggesting that T2D may equalize the chemerin levels irrespective of obesity status. The cleavage of chemerin has been previously linked to myocardial infarction and stroke in NWD, with potential implications for inflammation and mortality. OWD plasma exhibited lower levels of cleaved chemerin than the NWD group, suggesting less inflammation in the OWD group. Here, we showed that the interaction between obesity and T2D leads to an equalization in the total chemerin levels. The cleaved chemerin levels and the associated inflammatory state, however, differ significantly, underscoring the complex relationship between chemerin, T2D, and obesity.

Chemerin in Participants with or without Insulin Resistance and Diabetes

Chemerin is a chemokine/adipokine, regulating inflammation, adipogenesis and energy metabolism whose activity depends on successive proteolytic cleavages at its C-terminus. Chemerin levels and processing are correlated with insulin resistance. We hypothesized that chemerin processing would be higher in individuals with type 2 diabetes (T2D) and in those who are insulin resistant (IR). This hypothesis was tested by characterizing different chemerin forms by specific ELISA in the plasma of 18 participants with T2D and 116 without T2D who also had their insulin resistance measured by steady-state plasma glucose (SSPG) concentration during an insulin suppression test. This approach enabled us to analyze the association of chemerin levels with a direct measure of insulin resistance (SSPG concentration). Participants were divided into groups based on their degree of insulin resistance using SSPG concentration tertiles: insulin sensitive (IS, SSPG ≤ 91 mg/dL), intermediate IR (IM, SSPG 92-199 mg/dL), and IR (SSPG ≥ 200 mg/dL). Levels of different chemerin forms were highest in patients with T2D, second highest in individuals without T2D who were IR, and lowest in persons without T2D who were IM or IS. In the whole group, chemerin levels positively correlated with both degree of insulin resistance (SSPG concentration) and adiposity (BMI). Participants with T2D and those without T2D who were IR had the most proteolytic processing of chemerin, resulting in higher levels of both cleaved and degraded chemerin. This suggests that increased inflammation in individuals who have T2D or are IR causes more chemerin processing.

Chemerin is resident to vascular tunicas and contributes to vascular tone

The adipokine chemerin may support blood pressure, evidenced by a fall in mean arterial pressure after whole body antisense oligonucleotide (ASO)-mediated knockdown of chemerin protein in rat models of normal and elevated blood pressure. Although the liver is the greatest contributor of circulating chemerin, liver-specific ASOs that abolished hepatic-derived chemerin did not change blood pressure. Thus, other sites must produce the chemerin that supports blood pressure. We hypothesize that the vasculature is a source of chemerin independent of the liver that supports arterial tone. RNAScope, PCR, Western blot analyses, ASOs, isometric contractility, and radiotelemetry were used in the Dahl salt-sensitive (SS) rat (male and female) on a normal diet. Retinoic acid receptor responder 2 (Rarres2) mRNA was detected in the smooth muscle, adventitia, and perivascular adipose tissue of the thoracic aorta. Chemerin protein was detected immunohistochemically in the endothelium, smooth muscle cells, adventitia, and perivascular adipose tissue. Chemerin colocalized with the vascular smooth muscle marker α-actin and the adipocyte marker perilipin. Importantly, chemerin protein in the thoracic aorta was not reduced when liver-derived chemerin was abolished by a liver-specific ASO against chemerin. Chemerin protein was similarly absent in arteries from a newly created global chemerin knockout in Dahl SS rats. Inhibition of the receptor Chemerin1 by the receptor antagonist CCX832 resulted in the loss of vascular tone that supports potential contributions of chemerin by both perivascular adipose tissue and the media. These data suggest that vessel-derived chemerin may support vascular tone locally through constitutive activation of Chemerin1. This posits chemerin as a potential therapeutic target in blood pressure regulation.NEW & NOTEWORTHY Vascular tunicas synthesizing chemerin is a new finding. Vascular chemerin is independent of hepatic-derived chemerin. Vasculature from both males and females have resident chemerin. Chemerin1 receptor activity supports vascular tone.

The Role of Chemerin in Metabolic and Cardiovascular Disease: A Literature Review of Its Physiology and Pathology from a Nutritional Perspective

Chemerin is a novel adipokine that plays a major role in adipogenesis and lipid metabolism. It also induces inflammation and affects insulin signaling, steroidogenesis and thermogenesis. Consequently, it likely contributes to a variety of metabolic and cardiovascular diseases, including atherosclerosis, diabetes, hypertension and pre-eclampsia. This review describes its origin and receptors, as well as its role in various diseases, and subsequently summarizes how nutrition affects its levels. It concludes that vitamin A, fat, glucose and alcohol generally upregulate chemerin, while omega-3, salt and vitamin D suppress it. Dietary measures rather than drugs acting as chemerin receptor antagonists might become a novel tool to suppress chemerin effects, thereby potentially improving the aforementioned diseases. However, more detailed studies are required to fully understand chemerin regulation.

Chemerin Forms: Their Generation and Activity

Chemerin is the product of the RARRES2 gene which is secreted as a precursor of 143 amino acids. That precursor is inactive, but proteases from the coagulation and fibrinolytic cascades, as well as from inflammatory reactions, process the C-terminus of chemerin to first activate it and then subsequently inactivate it. Chemerin can signal via two G protein-coupled receptors, chem1 and chem2, as well as be bound to a third non-signaling receptor, CCRL2. Chemerin is produced by the liver and secreted into the circulation as a precursor, but it is also expressed in some tissues where it can be activated locally. This review discusses the specific tissue expression of the components of the chemerin system, and the role of different proteases in regulating the activation and inactivation of chemerin. Methods of identifying and determining the levels of different chemerin forms in both mass and activity assays are reviewed. The levels of chemerin in circulation are correlated with certain disease conditions, such as patients with obesity or diabetes, leading to the possibility of using chemerin as a biomarker.

Divergence of Chemerin Reduction by an ATS9R Nanoparticle Targeting Adipose Tissue In Vitro vs. In Vivo in the Rat

Nanoparticles (NPs) can enable delivery of a drug to a targeted tissue. Previous studies have shown that an NP utilizing an adipose targeting sequence (ATS) peptide in conjunction with a drug can selectively deliver the drug to mouse adipose tissues, using the prohibitin protein expressed in adipose tissue as the target of the ATS. Adipose tissue is a major source of the adipokine chemerin, a prohypertensive protein. Liver-derived chemerin, the largest source of circulating chemerin, is biologically inactive in blood pressure regulation. Our goal is to understand if chemerin produced in adipose tissue contributes to blood pressure/hypertension. We hypothesize the ATS drug delivery system could be used specifically to reduce the levels of adipose tissue-derived chemerin. We created an NP consisting of an antisense oligonucleotide (ASO) against chemerin and a FITC-labeled ATS with a nine arginine sequence (ATS9R). In vitro studies showed that the ASO is functional when incorporated into an NP with ATS9R as it reduced chemerin mRNA expression in isolated epidydimal (Epi) and retroperitoneal (RP) fat adipocytes from Dahl SS rats. This same NP reduced chemerin in isolated whole fats. However, this NP was unable to selectively deliver the ASO to adipose tissue in vivo; liver delivery was dominant. Varying NP doses, administration route, and the concentration of components constituting the NP showed no improvement in ASO delivery to fats vs. the liver. Further studies are therefore needed to develop the ATS9R system to deliver an ASO to adipose beds in rats.

Chemokine-like Receptor 1 in Brain of Spontaneously Hypertensive Rats Mediates Systemic Hypertension

Adipocytokine chemerin is a biologically active molecule secreted from adipose tissue. Chemerin elicits a variety of functions via chemokine-like receptor 1 (CMKLR1). The cardiovascular center in brain that regulates blood pressure (BP) is involved in pathophysiology of systemic hypertension. Thus, we explored the roles of brain chemerin/CMKLR1 on regulation of BP in spontaneously hypertensive rats (SHR). For this aim, we examined effects of intracerebroventricular (i.c.v.) injection of CMKLR1 small interfering (si)RNA on both systemic BP as measured by tail cuff system and protein expression in paraventricular nucleus (PVN) of SHR as determined by Western blotting. We also examined both central and peripheral protein expression of chemerin by Western blotting. Systolic BP of SHR but not normotensive Wistar Kyoto rats (WKY) was decreased by CMKLR1 siRNA. The decrease of BP by CMKLR1 siRNA persisted for 3 days. Protein expression of CMKLR1 in PVN of SHR tended to be increased compared with WKY, which was suppressed by CMKLR1 siRNA. Protein expression of chemerin in brain, peripheral plasma, and adipose tissue was not different between WKY and SHR. In summary, we for the first time revealed that the increased protein expression of CMKLR1 in PVN is at least partly responsible for systemic hypertension in SHR.

Determinants of elevated chemerin as a novel biomarker of immunometabolism: data from a large population-based cohort

OBJECTIVE

Chemerin is a novel inflammatory biomarker suggested to play a role in the development of metabolic disorders, providing new avenues for treatment and prevention. Little is known about the factors that predispose elevated chemerin concentrations. We therefore aimed to explore a range of lifestyle-associated, dietary, and metabolic factors as potential determinants of elevated chemerin concentrations in asymptomatic adults.

DESIGN

We used cross-sectional data from a random subsample of 2433 participants (1494 women and 939 men) aged 42-58 years of the European Prospective Investigation into Cancer and Nutrition-Potsdam cohort.

METHODS

Random forest regression (RFR) was applied to explore the relative importance of 32 variables as statistical predictors of elevated chemerin concentrations overall and by sex. Multivariable-adjusted linear regression was applied to evaluate associations between selected predictors and chemerin concentrations.

RESULTS

Results from RFR suggested BMI, waist circumference, C-reactive protein, fatty liver index, and estimated glomerular filtration rate as the strongest predictors of chemerin concentrations. Additional predictors included sleeping duration, alcohol, red and processed meat, fruits, sugar-sweetened beverages (SSB), vegetables, dairy, and refined grains. Collectively, these factors explained 32.9% variation of circulating chemerin. Multivariable-adjusted analyses revealed linear associations of elevated chemerin with metabolic parameters, obesity, longer sleep, higher intakes of red meat and SSB, and lower intakes of dairy.

CONCLUSIONS

These findings come in support of the role of chemerin as a biomarker characterizing inflammatory and metabolic phenotypes in asymptomatic adults. Modifiable dietary and lifestyle-associated determinants of elevated chemerin concentrations require further evaluation in a prospective study setting.