The role of endotoxin,TNF-α,and IL-6 in inducing the state of growth hormone insensitivity

AIM: Critical illnesses such as sepsis, trauma, and burns cause a growth hormone insensitivity, which leads to an increased negative nitrogen balance. Endotoxin is generously released into blood under these conditions and stimulates the production of proinflammatory cytokines such as TNF-alpha, IL-6, and IL-1, which may play a very important role in inducing the growth hormone insensitivity. The objective of this current study was to investigate the role of endotoxin, TNF-alpha and IL-6 in inducing the growth hormone insensitivity at the receptor and post-receptor levels. METHODS: Spague-Dawley rats were injected with endotoxin, TNF-alpha, and IL-6, respectively and part of rats injected with endotoxin was treated with exogenous somatotropin simultaneously. All rats were killed at different time points. The expression of IGF-I, GHR, SOCS-3 and beta-actin mRNA in the liver was detected by RT-PCR and the GH levels were measured by radioimmunoassay, the levels of TNF-alpha and IL-6 were detected by ELISA. RESULTS: There was no significant difference in serous GH levels between experimental group and control rats after endotoxin injection, however, liver IGF-I mRNA expression had been obviously down-regulated in endotoxemic rats. Liver GHR mRNA expression also had a predominant down-regulation after endotoxin injection. The lowest regulation of liver IGF-I mRNA expression occurred at 12h after LPS injection, being decreased by 53% compared with control rats. For GHR mRNA expression, the lowest expression occurred at 8h and had a 81% decrease. Although SOCS-3 mRNA was weakly expressed in control rats, it was strongly up-regulated after LPS injection and had a 7.84 times increase compared with control rats. Exogenous GH could enhance IGF-I mRNA expression in control rats, but it did fail to prevent the decline in IGF-I mRNA expression in endotoxemic rats. Endotoxin stimulated the production of TNF-alpha and IL-6, and the elevated IL-6 levels was shown a positive correlation with increased SOCS-3 mRNA expression. The liver GHR mRNA expression was obviously down-regulated after TNF-alpha iv injection and had a 40% decrease at 8h, but the liver SOCS-3 mRNA expression was the 4.94 times up-regulation occurred at 40 min after IL-6 injection. CONCLUSION: The growth hormone insensitivity could be induced by LPS injection, which was associated with down-regulated GHR mRNA expression at receptor level and with up-regulated SOCS-3 mRNA expression at post-receptor level. The in vivo biological activities of LPS were mediated by TNF-alpha and IL-6 indirectly, and TNF-alpha and IL-6 may exert their effects on the receptor and post-receptor levels respectively.

Effect of Acupuncture-moxibustion on the Expression of IGF-1 and SOCS2 in Colonic Mucosa of Rats with Ulcerative Colitis

Objective： To observe the effect of acupuncture-moxibustion on the expression of insulin-like growth factor-I （IGF-I） and suppressor of cytokine signaling-2 （SOCS2） in colonic mucosa of rat models of ulcerative colitis （UC）, and explore the mechanism of acupuncture- moxibustion therapy in treating UC. Methods： The rats were randomized into a normal control （NC） group, a model control （MC） group, an herb-partitioned moxibustion （HPM） group and an electroacupuncture （EA） group, 8 in each group. The rat models of UC were established by immunological methods combined with local stimulation. The rats in the HPM and EA groups were given herb-partitioned moxibustion and electroacupuncture treatments respectively, once every day, lasting for 14 d. The morphological variations of rat＇s colonic mucosa were observed under light microscope; the colonic mucosal mucin was detected by PAS-AB and HID-AB staining methods; the expression of IGF-1 and SOCS2 was assayed by the immunohistochemical method. Results： In the rat models of UC, ulceration and inflammation of the colon were revealed by light microscope. The concentration of colonic mucosal mucin was reduced （P〈0.01）, while the expression of IGF-1 had an increase （P〈0.01）, and the expression of SOCS2 was reduced （P〈0.01）. After HPM or EA treatment, the pathological injuries of colonic mucosa had improved, the concentration of mucin increased （P〈0.01）, the expression of IGF-1 decreased （P〈0.01）, and the expression of SOCS2 increased （P〈0.01）. Conclusion： The secretion of mucosal mucin in rat UC decreased, the expression of IGF-1 was significantly higher, while the expression of SOCS2 was remarkably lower; both HPM and EA can help improve the damage of colonic mucosa in rat UC, and modulate the secretion of mucin, as well as regulate the expression of IGF-1 and SOCS2 in the colonic mucosa.