Alterations Of Leptin And Orexin-A In Hepatic And Enteric Injuries-induced Internal Disorders And Their Effects On Organ Functions

Leptin is an active protein with a primary function of inhibiting food intake and stimulating energy expenditure,while orexin-A is a short peptide which primarily stimulates food intake and inhibits energy expenditure.Recent researches have revealed that leptin inhibits synthesis of glycogen and promotes oxidation of fatty acids through pathways such as adenosine monophosphateactivated protein kinase and peroxisome proliferators-activated receptor-α,while orexin-A exerts opposite roles in energy metabolism and its expression levels are contrary to leptin under certain conditions.Leptin and orexin-A associate with glucocorticoids,sympathetic excitability and inflammatory mediators,suggesting that they may participate in modulating the internal disorders after trauma, inflammation and infection.As liver and enteric tract are vital organs involved in nutritional absorption and energy metabolism,we investigated the alterations of leptin and orexin-A expressions in hepatic and enteric injuries,analyzed the association of these alterations with the structural impairments and functional changes of vital organs,and explored the effects of post-traumatic nutritious support and hormonal intervention on their expression levels and organ functions.1.Alterations of leptin and orexin-A expressions after hepatic ischemia/ reperfusion injury and their association with organ functionsA rat model of 70%hepatic ischemia/reperfusion injury was established, setting groups of sham-operation and those that had 60 min ischemia but different times of reperfusion.Protein levels of leptin and orexin-A in peripheral blood and respective central secretory organs(adipose and hypothalamus)were detected by radioimmunoassays;damaged situations in peripheral organs(lung and liver)that associate closely with free radical injury and energy metabolism were investigated by hematoxylin-eosin staining,serum myeloperoxidase and alanine transaminase were detected by kits to represent functional markers for lung and liver,serum total anti-oxidation capacity and glucose were measured to represent metabolic markers for anti-free radical injury and energy reserve;protein expressions of leptin and orexin-A in lung and liver were detected by immunohistochemistry; mRNA expressions of leptin,orexin-A and their receptors in hypothalamus, adipose,lung and liver were detected by reverse transcription-polymerase chain reaction.We aimed to investigate the association of their expression alterations with organ functions from an angle of longitudinal temporal variation.Results showed that serum leptin,total anti-oxidation capacity and glucose increased significantly at the later phase of reperfusion,protein levels of adipose leptin were significantly higher at the early phase of reperfusion,while protein levels of plasma and hypothalamus orexin-A showed no significant change. Damaged situations and functional markers of lung and liver improved significantly at the later phase of reperfusion.Protein expressions of leptin and orexin-A in lung decreased significantly,protein expressions of leptin in liver were significantly higher at the early and later phases of reperfusion but the levels of orexin-A in liver varied contrarily.Alterative trends of leptin and orexin-A mRNA expressions in each organ are extremely similar with each other,and mRNA expressions of their receptors changed accordingly to them.2.Effects of nutritious support and hormonal intervention on leptin and orexin-A expressions and organ functions during sepsisExperimental results of the first section suggest that expression levels of leptin and orexin-A are regulated by energy metabolism,and they have significant relationship with the functional hypothalamus-adipose-lung/liver axis.As intralipid,insulin and estradiol all associate with energy metabolism and wound repair,we hypothesized that using them to intervene post-traumatic fatty acids metabolism,glucose metabolism and hormonal secretion might affect expression levels of leptin and orexin as well as organ functions.A rat sepsis model induced by cecal ligation and perforation(CLP)was established,setting groups of sham-operation,CLP model and three drug intervention groups.Protein levels of leptin and orexin-A in peripheral blood,lung and liver as well as their mRNA expressions in hypothalamus,adipose,lung and liver were detected at 12 h after CLP.Damaged situations in lung and liver and changes of organ functional and metabolic markers were checked.We aimed to investigate the association of their expression alterations with organ functions from an angle of transverse intervention diversity.Results showed that there was no significant change of serum leptin,total anti-oxidation capacity and glucose in each group,while plasma orexin-A in CLP model and CLP+intralipid increased significantly.Serum myeloperoxidase in CLP model and CLP+insulin were significantly higher,and serum alanine transaminase in CLP+insulin decreased significantly.Distinct injuries of lung and liver were confirmed in CLP model and CLP+estradiol,while significant improvements were found in CLP+intralipid and CLP+insulin.Protein expressions of leptin and orexin-A in lung and liver and their mRNA expressions in each organ were found different in each group.Hypothalamus and adipose leptin mRNA expressions increased significantly in CLP+intralipid,but its leptin mRNA and protein expressions in lung and liver were significantly lower.Experimental results in the aboved two researches indicate that leptin and orexin-A undergo different alterations in hepatic and enteric injuries-induced internal disorders,associate closely with the structural impairments and functional changes of vital organs.Intralipid and insulin significantly attenuate lung and liver injuries,while estradiol has no distinct ameliorative role.Although the three intervention drugs have different influences on leptin and orexin-A expressions,it suggests that leptin and orexin-A participate in the effective pathways of the three intervention drugs on organs,which is worthy of further investigation.To explore the neuroendocrine regulatory mechanisms centrally involved by leptin and orexin-A will benefit the development of endogenous intervention methods on relative diseases.