Background and Purpose: Unstable carotid plaques are a common cause of ischemic strokes. Identifying markers that reflect/contribute to plaque instability has become a prominent focus in cardiovascular research. The adipokines, resistin and chemerin, and ChemR23 (chemerin receptor), may play a role in carotid atherosclerosis, making them potential candidates to assess plaque instability. However, the expression and interrelationship of resistin and chemerin (and ChemR23) protein and mRNA within the carotid atherosclerotic plaque remains elusive. Thus, we investigated herein, the association between plaque mRNA and protein expression of resistin and chemerin (and ChemR23) and carotid plaque instability in humans, and whether sex differences exist in the relationship between these adipokines and plaque instability. Methods: Human carotid plaques were processed for immunohistochemical/mRNA analysis of resistin, chemerin, and ChemR23. Plaque instability was assessed by gold-standard histological classifications. A semi-quantitative scoring system was used to determine the intensity of adipokine expression on macrophages/foam cells, as well as the percentage of inflammatory cells stained positive. Plaque adipokine protein expression was also digitally quantified and mRNA expression was assessed by qRT-PCR. Results: Resistin and chemerin mRNA expression was 80% and 32% lower, respectively, in unstable versus stable plaques ( P <0.05), while no difference in ChemR23 mRNA expression was observed. In contrast, greater resistin staining intensity and percentage of cells stained positive were detected in unstable versus stable plaques ( P <0.01). Similarly, chemerin and ChemR23 staining intensity and percentage of cells stained were positively associated with plaque instability ( P <0.05). No strong sex-specific relationship was observed between adipokines and plaque instability. Conclusions: This study examined the relationship between resistin, chemerin, and ChemR23, and carotid plaque instability, with a specific analysis at the plaque level. We reported a positive association between plaque instability and protein levels of resistin, chemerin, and ChemR23 but a negative association with resistin and chemerin mRNA expression. This suggests these adipokines exert proinflammatory roles in the process of carotid atherosclerosis and may be regulated via a negative feedback regulatory mechanism.

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Introduction: Sex differences in plaque morphology and composition exist; men develop more unstable plaques than women. Yet, stroke kills more women than men. Despite these differences, no sex-specific guidelines for carotid disease management exist. Thus, markers that reflect sex-specific morphological features in the plaque should be explored for better prediction of stroke risk. Pro-inflammatory adipokines, chemerin and resistin, influence vascular function. Herein we are the first to investigate sex differences in the relationship between carotid plaque instability and the expression of these adipokines. Methods: Subjects with ≥50% carotid stenosis scheduled for a carotid endarterectomy were recruited from McGill-affiliated hospitals. Pre-operative plasma chemerin and resistin levels were measured using ELISA. Stability of carotid plaque specimens was assessed by two gold standard histological classifications. Stable and unstable plaques were immunostained for chemerin, chemerin’s receptor (ChemR23), and resistin. Digital and semi-quantifications assessed the % area of expression as well as staining intensity (mild to high) and % of positively stained macrophages/foam cells. Plaque mRNA expression was assessed by quantitative PCR. Sex-hormone analyses are ongoing. Results: Men (n=171) had more unstable plaque features, i.e., greater hemorrhage (P=0.022), lipid core size (P<0.001), inflammation (P=0.007), cap infiltration (P=0.006), and less fibrous tissue (P<0.001) than women (n=79). Circulating chemerin and resistin levels were similar between men and women and no sex differences were observed in relation to plaque instability. The % area of chemerin and resistin staining in the plaque was greater in unstable vs stable plaques in men only (P=0.040; P=0.005, respectively). Similarly, greater intensity in chemerin, ChemR23, and resistin staining was associated with plaque instability in men only (P<0.001; P=0.013; P=0.033, respectively). In contrast, lower resistin plaque mRNA expression was associated with plaque instability in women only (P=0.040). Conclusion: Our results suggest the possibility of a sex-dependent regulatory mechanism underlying the connection between these adipokines and plaque instability.