Chemokine-like receptor 1 deficiency does not affect the development of insulin resistance and nonalcoholic fatty liver disease in mice

The adipokine chemerin and its receptor, chemokine-like receptor 1 (Cmklr1), are associated with insulin resistance and nonalcoholic fatty liver disease (NAFLD), which covers a broad spectrum of liver diseases, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). It is possible that chemerin and/or Cmklr1 exert their effects on these disorders through inflammation, but so far the data have been controversial. To gain further insight into this matter, we studied the effect of whole-body Cmklr1 deficiency on insulin resistance and NAFLD. In view of the primary role of macrophages in hepatic inflammation, we also transplanted bone marrow from Cmklr1 knock-out (Cmklr1-/-) mice and wild type (WT) mice into low-density lipoprotein receptor knock-out (Ldlr-/-) mice, a mouse model for NASH. All mice were fed a high fat, high cholesterol diet containing 21% fat from milk butter and 0.2% cholesterol for 12 weeks. Insulin resistance was assessed by an oral glucose tolerance test, an insulin tolerance test, and by measurement of plasma glucose and insulin levels. Liver pathology was determined by measuring hepatic inflammation, fibrosis, lipid accumulation and the NAFLD activity score (NAS). Whole-body Cmklr1 deficiency did not affect body weight gain or food intake. In addition, we observed no differences between WT and Cmklr1-/- mice for hepatic inflammatory and fibrotic gene expression, immune cell infiltration, lipid accumulation or NAS. In line with this, we detected no differences in insulin resistance. In concordance with whole-body Cmklr1 deficiency, the absence of Cmklr1 in bone marrow-derived cells in Ldlr-/- mice did not affect their insulin resistance or liver pathology. Our results indicate that Cmklr1 is not involved in the pathogenesis of insulin resistance or NAFLD. Thus, we recommend that the associations reported between Cmklr1 and insulin resistance or NAFLD should be interpreted with caution

Chemokine-like receptor 1 deficiency does not affect the development of insulin resistance and nonalcoholic fatty liver disease in mice

The adipokine chemerin and its receptor, chemokine-like receptor 1 (Cmklr1), are associated with insulin resistance and nonalcoholic fatty liver disease (NAFLD), which covers a broad spectrum of liver diseases, ranging from simple steatosis to nonalcoholic steatohepatitis (NASH). It is possible that chemerin and/or Cmklr1 exert their effects on these disorders through inflammation, but so far the data have been controversial. To gain further insight into this matter, we studied the effect of whole-body Cmklr1 deficiency on insulin resistance and NAFLD. In view of the primary role of macrophages in hepatic inflammation, we also transplanted bone marrow from Cmklr1 knock-out (Cmklr1-/-) mice and wild type (WT) mice into low-density lipoprotein receptor knock-out (Ldlr-/-) mice, a mouse model for NASH. All mice were fed a high fat, high cholesterol diet containing 21% fat from milk butter and 0.2% cholesterol for 12 weeks. Insulin resistance was assessed by an oral glucose tolerance test, an insulin tolerance test, and by measurement of plasma glucose and insulin levels. Liver pathology was determined by measuring hepatic inflammation, fibrosis, lipid accumulation and the NAFLD activity score (NAS). Whole-body Cmklr1 deficiency did not affect body weight gain or food intake. In addition, we observed no differences between WT and Cmklr1-/- mice for hepatic inflammatory and fibrotic gene expression, immune cell infiltration, lipid accumulation or NAS. In line with this, we detected no differences in insulin resistance. In concordance with whole-body Cmklr1 deficiency, the absence of Cmklr1 in bone marrow-derived cells in Ldlr-/- mice did not affect their insulin resistance or liver pathology. Our results indicate that Cmklr1 is not involved in the pathogenesis of insulin resistance or NAFLD. Thus, we recommend that the associations reported between Cmklr1 and insulin resistance or NAFLD should be interpreted with caution

NAFLD progression is not affected by ablation of <i>Cmklr1</i>.

<p>To investigate the progression of NAFLD, hepatic triglyceride (A) and cholesterol (B) accumulation were measured in mice fed a high fat, high cholesterol diet for 12 weeks. (C) To determine the amount of inflammation and fibrosis in the liver, the inflammatory and pro-fibrotic gene expression were measured in WT mice (white bars) and <i>Cmklr1^-/-</i> mice (black bars). (D) In addition, a staining for the macrophage markers CD68 and CD11b was performed on frozen-cut liver sections. (E) NAFLD Activity Score (NAS) was determined by pathological examination of Hematoxylin-Eosin (HE) stained liver sections. Abbreviations: WT, wild type; <i>Cmklr1^-/-</i>, chemokine-like receptor 1 knock-out; <i>Cd68</i>, cluster of differentiation 68; <i>Cd11b</i>, alpha M integrin (<i>Mac1</i>); <i>Mcp-1</i>, monocyte chemo-attractant protein 1; <i>Tnfα</i>, tumor necrosis factor α; <i>Il1-β</i>, interleukin 1β; <i>αSma</i>, α-smooth muscle actin; <i>Col1a1</i>, collagen type 1 alpha 1; <i>Timp1</i>, tissue inhibitor of metalloproteinase 1; <i>Mmp9</i>, matrix metallopeptidase 9. N = 7–8 for all experiments. Data are expressed as mean ± SEM. * p<0.05 vs WT.</p

<i>Cmklr1</i> deficiency does not affect body weight, food intake or plasma lipid levels.

<p>Body weight (A) and food intake (B) were measured throughout the 12-week high fat, high cholesterol diet period. Food intake was expressed as average food intake per day. (C) Representative pictures were taken of Hematoxylin-Eosin (HE) stained visceral and subcutaneous adipose tissue (VAT and SAT) sections. Blood obtained by a heart puncture at the time of euthanasia was used to determine plasma triglycerides (D), plasma cholesterol (E) and plasma free fatty acids (F). (G) Chemerin levels were determined in blood obtained from the tail vein of mice that had fasted for 6 hours at the end of the diet period. Abbreviations: WT, wild type; <i>Cmklr1^-/-</i>, chemokine-like receptor 1 knock-out. N = 7–8 for all experiments. Data are expressed as mean ± SEM. * p<0.05 vs WT.</p

<i>Cmklr1</i> deficiency does not affect insulin resistance.

<p>To determine insulin resistance, glucose (A) and insulin levels (B) were measured in mice that had fasted for 6 hours at the end of the 12-week high fat, high cholesterol diet period. In addition, an oral glucose tolerance test (C) and an insulin tolerance test (D) were performed. Abbreviations: WT, wild type; <i>Cmklr1^-/-</i>, chemokine-like receptor 1 knock-out. N = 7–8 for all experiments. Data are expressed as mean ± SEM. * p<0.05 vs WT.</p

Hematopoietic deletion of <i>Cmklr1</i> does not affect NASH development in <i>Ldlr^-/-</i> mice.

<p>(A) Body weight of <i>Ldlr</i>-BMT<i>^WT</i> and <i>Ldlr</i>-BMT<i>^Cmklr1-/-</i> mice was measured during the high fat, high cholesterol diet period of 12 weeks. Insulin resistance was assessed by an oral glucose tolerance test (B) and an insulin tolerance test (C). NASH progression was investigated by measuring hepatic triglyceride (D) and cholesterol (E) accumulation and by determining hepatic inflammatory and pro-fibrotic gene expression (F) in <i>Ldlr</i>-BMT^WT mice (white bars) and <i>Ldlr</i>-BMT<i>^Cmklr1-/-</i> mice (black bars). Abbreviations: <i>Ldlr</i>-BMT<i>^WT</i>, low-density lipoprotein receptor knock-out mice transplanted with wild type bone marrow cells; <i>Ldlr</i>-BMT<i>^Cmklr1-/-</i>, low-density lipoprotein receptor knock-out mice transplanted with chemokine-like receptor 1 knock-out bone marrow cells; <i>Cd68</i>, cluster of differentiation 68; <i>Mcp-1</i>, monocyte chemo-attractant protein 1; <i>Tnfα</i>, tumor necrosis factor α; <i>Il1-β</i>, interleukin 1β; <i>αSma</i>, α-smooth muscle actin; <i>Col1a1</i>, collagen type 1 alpha 1; <i>Timp1</i>, tissue inhibitor of metalloproteinase 1; <i>Mmp9</i>, matrix metallopeptidase 9. N = 5–7 for all experiments. Data are expressed as mean ± SEM. * p<0.05 vs WT.</p