Time-Course Changes of Hormones and Cytokines by Lipopolysaccharide and Its Relation with Anorexia

• Published in: Journal of Physiological Sciences Vol. 57; no. 3; pp. 159 - 165
• Main Authors: Yong-Woon KIM, Keon-Ho KIM, Dong-Kuk AHN, Hee-Sun KIM, Jong-Yeon KIM, Dong Chul LEE, So-Young PARK
• Format: Journal Article
• Language: Japanese
• Published: The Physiological Society of Japan 2007
• ISSN: 1880-6546; 1880-6562

We assessed the time course effects of lipopolysaccaride (LPS) on food intake, cytokines, and hormones in rats and evaluated the relation between LPS-induced anorexia and its possible causative factors. Food intake was reduced 2h after LPS injection (500μg/kg, intraperitoneally) and remained decreased for 24h. Plasma TNF-α and IL-6 levels increased by LPS administration at 0.5 and 2h, and at 2 and 4h, respectively. Plasma leptin and glucose levels were elevated at 8 and 16h, and insulin levels were elevated at 2, 4, 8, and 16h in the LPS-injected group, as compared to the counterpart controls. IL-6 levels in the CSF were elevated at 2 and 4h. Hypothalamic cytokines tended to increase as early as 0.5h after LPS injection and remained increased until 16h. LPS-induced anorexia was attenuated in insulin-deficient STZ rats and was abolished by insulin treatment. The hypothalamic expression of NPY, a target of insulin's anorexic effect, was decreased 2h after LPS administration, and central NPY injection (3nM) prevented LPS-induced anorexia. In conclusion, cytokines, insulin, and leptin levels evidence different time courses by LPS administration. In LPS-induced anorexia, insulin may constitute a newly found causative factor, whereas leptin appears to be uninvolved in an early period in rats.