Mice Ccrl2 Deficiency Exacerbates Obesity And Insulin Resistance By Increasing Macrophage Infiltration

Background:Obesity is a high-risk factor for the occurrence of metabolic-related diseases such as hypertension,diabetes,atherosclerosis,which seriously endangers the health of modern people.The occurrence of insulin resistance is an important induction of obesity-related diseases.,The inflammatory responses especially macrophages in the adipose tissue play important roles in the process of obesity-related insulin resistance,mainly manifest in the increased macrophages number,the increased proportion of M1 proinflammatory macrophages,decreased proportion of M2 anti-inflammatory macrophages and the up-regulation of pro-inflammatory cytokines such as interleukin-6?IL-6?.Chemokines play important roles in regulating the differentiation and activation of mononuclear phagocytes through their chemokine receptors.Chemokine?C-C motif?receptor-like2?Ccrl2?belongs to the chemokine receptor family and is expressed in various immune cells such as macrophages,dendritic cells and is closely related to the inflammatory response.However,there is no report about the roles of Ccrl2 in obesity and insulin resistance.Objective:To understand the effect of Ccrl2 on obesity and obesity-related insulin resistance and to further explore whether Ccrl2 affects the inflammatory environment especially macrophages to find out the specific mechanism of the Ccrl2.Methods:?1?q RT-PCR was used to detect the expression of ccrl2 in the adipose tissue of male C5BL/6J mice fed with high-fat diet?HFD?and ob/ob,db/db mice fed with normal diet?ND?.?2?Fed ccrl2^-/-mice with HFD,monitored the dynamic changes of body weight of mice and detected related indexes of insulin resistance,including glucose tolerance test?GTT?,insulin tolerance test?ITT?,HOMR-IR,serum insulin concentration in random or fasting situation and used Western blotting to detect kinase B?Akt?and phosphorylation of Protein kinase B?p-Akt?.?3?Flow cytometry/immunofluorescence/q RT-PCR were used to detect the number of macrophages in the adipose tissue of ccrl2^-/-mice,flow cytometry/q RT-PCR were used to detect the ratio of M1 type macrophages and M2 type macrophages and serum mice IL-6 level was detected by ELISA.?4?The proliferation ability of macrophages in adipose tissue of mice was detected by Ki67 immunofluorescence staining.?5?The chemotactic ability of mice macrophages was detected by in vivo and in vitro chemotaxis.Results:?1?The expression of ccrl2 was significantly increased in the adipose tissue of obese mice and diabetic mice?HFD fed mice,ND fed ob/ob mice,db/db mice?.?2?The weight gain value of ccrl2^-/-mice fed with HFD increased significantly.In ccrl2^-/-mice,glucose tolerance test?GTT?,insulin tolerance test?ITT?,and HOMR-IR?insulin resistance indicator?are deteriorated significantly,fasting and random insulin levels were slightly higher and p-Akt protein expression was significantly down-regulated.?3?HFD fed ccrl2^-/-mice manifested increased macrophages infiltration and M1/M2 macrophages ratio.?4?The proliferation marker Ki67 expression in ccrl2^-/-mice was not different from that in control mice.?5?Results of in vitro and in vivo chemotaxis experiments showed that ccrl2^-/-mouse-derived macrophages are more chemotactic.Conclusion:?1?Ccrl2 deficiency deteriorated obesity and insulin sensitivity in mice.?2?The worsening obesity and insulin resistance might be mainly through increased macrophages infiltration in visceral adipose tissue.