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Adipokines, adipocyte-derived protein, have important roles in various kinds of physiology including energy homeostasis. Chemerin, one of adipocyte-derived adipokines, is highly expressed in differentiated adipocytes and is known to induce macrophage chemotaxis and glucose intolerance. The objective of the present study was to investigate the changes of chemerin and the chemokine-like-receptor 1 (CMKLR1) gene expression levels during differentiation of the bovine adipocyte and in differentiated adipocytes treated with tumor necrosis factor-α (TNF-α), adiponectin, leptin, and chemerin (peptide analog). The expression levels of the chemerin gene increased at d 6 and 12 of the differentiation period accompanied by increased cytoplasm lipid droplets. From d 6 onward, peroxisome proliferator-activated receptor-γ2 (PPAR-γ2) gene expression levels were significantly higher than that of d 0 and 3. In contrast, CMKLR1 expression levels decreased at the end of the differentiation period. In fully differentiated adipocytes (i.e. at d 12), the treatment of TNF-α and adiponectin upregulated both chemerin and CMKLR1 gene expression levels, although leptin did not show such effects. Moreover, chemerin analog treatment was shown to upregulate chemerin gene expression levels regardless of doses. These results suggest that the expression of chemerin in bovine adipocyte might be regulated by chemerin itself and other adipokines, which indicates its possible role in modulating the adipokine secretions in adipose tissues.

No abstract

Journal of Cellular Biochemistry Cover: The cover image, by Tomokazu Fukuda et al., is based on the Article

Chemerin, originally known as a chemoattractant derived from adipose tissue and the liver, has been reported to have regulatory functions in gluconeogenesis, peripheral insulin sensitivity, and insulin secretion. This study was conducted to assess the postweaning changes in expression of this cytokine and its physiological role in the modification of glucose metabolism associated with weaning. Eighteen tissue samples were collected from Holstein calves (90 d of age; n = 4) to investigate the tissue distributions of chemerin and its receptors genes. was highly expressed in the liver, and secreted chemerin protein was found in the plasma. Among the receptors of chemerin, and were ubiquitously expressed whereas was predominantly expressed in the liver. The changes in glucose metabolism and expression of these genes after weaning were assessed by comparing suckling calves (n = 6) and weaned calves (n = 8) of Japanese Black cattle. No significant difference was observed in plasma glucose levels between suckling and weaned calves (P = 0.22), whereas the plasma level of total ketone bodies was significantly higher in weaned calves (P < 0.01). Plasma levels of insulin and cortisol did not differ between suckling and weaned calves. The mRNA levels of certain key enzymes involved in hepatic gluconeogenesis were also altered; for instance, level was lower in postweaning calves (P < 0.05) and () level tended to be higher after weaning (P = 0.08). However, was not altered after weaning. The plasma levels of hepatic stress indicators were also changed, with aspartate transaminase, alanine transaminase, and lactate dehydrogenase being significantly elevated in postweaning calves (P < 0.05). Chemerin protein in liver tissue was less abundant in weaned calves (P < 0.05), although there were no changes in its transcript levels. The abundance of plasma chemerin protein did not change after weaning (P = 0.95). In summary, these data indicate that as a consequence of weaning, which causes physiological stress and alters hepatic metabolism, chemerin protein expression within the liver is downregulated, indicating that chemerin plays a role in the upregulation of hepatic expression via its inhibitory effect on hepatic gluconeogenesis.