interrelationships between ghrelin, insulin and glucose homeostasis: physiological relevance

Ghrelin is a 28 amino acid peptide mainly derived from the oxyntic gland of the stomach. Both acylated(AG) and unacylated(UAG) forms of ghrelin are found in the circulation. Initially, AG was considered as the only bioactive form of ghrelin. However, recent advances indicate that both AG and UAG exert distinct and common effects in organisms. Soon after its discovery, ghrelin was shown to promote appetite and adiposity in animal and human models. In response to these anabolic effects, an impressive number of elements have suggested the influence of ghrelin on the regulation of metabolic functions and the development of obesityrelated disorders. However, due to the complexity ofits biochemical nature and the physiological processes it governs, some of the effects of ghrelin are still debated in the literature. Evidence suggests that ghrelin influences glucose homeostasis through the modulation of insulin secretion and insulin receptor signaling. On the other hand, insulin was also shown to influence circulating levels of ghrelin. Here, we review the relationship between ghrelin and insulin and we describe the impact of this interaction on the modulation of glucose homeostasis.

Comparison of total/active ghrelin levels in primary open angle glaucoma,pseudoexfoliation glaucoma and pseudoexfoliation syndrome

AIM：To investigate the levels of ghrelin（Gh）,acylated ghrelin（AGh） and AGh/Gh ratio in the humor aqueous（HA） of cases with pseudoexfoliation syndrome（PXS）,pseudoexfoliation glaucoma（PXG）,primary open angle glaucoma（POAG） and to compare these with control subjects.METHODS：A prospective examination was made of the total Gh,and AGh levels in HA of 67 patients undergoing cataract surgery.Patients were divided into 4 groups.HA samples were aspirated at the beginning of the surgery,stored at -70℃.Gh and AGh quantification was performed with ELISA kits and the AGh/total-Gh ratios were calculated.ANOVA,Kruskal-Wallis,Chi-square and post-hoc tests were used for statistical analysis.RESULTS：Total Gh levels in HA were 189.2±45.6 pg/mL in the control group,199.2±32.9 pg/mL in PXS,180.6±20.9 pg/mL in PXG and 176.8±21.4 pg/mL in POAG groups（P〉0.05）.AGh levels in HA were 23.09±5.01 pg/mL in the control group,24.13±5.22 pg/mL in PXS,22.29±1.55 pg/m L in PXG and 19.69±2.93 pg/mL in POAG groups（P〉0.05）.The ratio of AGh/Gh was 10.3%±2.34% in the control group,13.03%±2.58% in PXS,12.3%±1.54% in PXG and 11.79%±1.41% in POAG groups（P=0.044）.The difference between the PXS and control groups was significant（P=0.03）.CONCLUSION：In spite of statistically insignificant results,the HA total Gh levels were lower than those of the control subjects but not parallel with the AGh levels in glaucoma patients.The relative increase in the AGh/Gh ratio in glaucoma cases supports the view that proportional increases of AGh might play a role in the pathogenesis of glaucoma.

Anti-oxidant and anti-inflammatory effects of hydrogenrich water alleviate ethanol-induced fatty liver in mice

AIM To investigate the effects of hydrogen-rich water(HRW) treatment on prevention of ethanol(Et OH)-induced early fatty liver in mice.METHODS In vitro reduction of hydrogen peroxide by HRW was determined with a chemiluminescence system. Female mice were randomly divided into five groups: control,Et OH,Et OH + silymarin,Et OH + HRW and Et OH + silymarin + HRW. Each group was fed a Lieber-De Carli liquid diet containing Et OH or isocaloric maltose dextrin(control diet). Silymarin was used as a positive control to compare HRW efficacy against chronic Et OH-induced hepatotoxicity. HRW was freshly prepared and given at a dosage of 1.2 m L/mouse trice daily. Blood and liver tissue were collected after chronic-binge liquid-diet feeding for 12 wk.RESULTS The in vitro study showed that HRW directly scavenged hydrogen peroxide. The in vivo study showed that HRW increased expression of acyl ghrelin,which was correlated with food intake. HRW treatment significantly reduced Et OH-induced increases in serum alanine aminotransferase,aspartate aminotransferase,triglycerol and total cholesterol levels,hepatic lipid accumulation and inflammatory cytokines,including tumor necrosis factor-alpha(TNF-α) and interleukin(IL)-6. HRW attenuated malondialdehyde level,restored glutathione depletion and increased superoxide dismutase,glutathione peroxidase and catalase activities in the liver. Moreover,HRW reduced TNF-α and IL-6 levels but increased IL-10 and IL-22 levels.CONCLUSION HRW protects against chronic Et OH-induced liver injury,possibly by inducing acyl ghrelin to suppress the pro-inflammatory cytokines TNF-α and IL-6 and induce IL-10 and IL-22,thus activating antioxidant enzymes against oxidative stress.