Abstract:
:Ghrelin is produced by the gastrointestinal tract, and its systemic concentrations are mainly regulated by nutritional factors. Our aim was to investigate: 1) endogenous portal and systemic acylated and unacylated ghrelin levels (AG and UAG, respectively); 2) whether an iv glucose tolerance test (IVGTT) modifies AG and UAG; and 3) whether the liver passage plays a role in regulating systemic AG and UAG. To elucidate this, we evaluated the effects of IVGTT or saline injection on endogenous portal and systemic concentrations of glucose, insulin, AG, and UAG in anesthetized fasting rats. Hepatic extraction of insulin, AG, and UAG and the ratio of AG to UAG were also measured. IVGTT suppressed both portal (P < 0.03) and peripheral (P < 0.05) UAG, whereas it only blunted prehepatic, but not peripheral, AG. During fasting, hepatic clearance of UAG was 11%, and it was decreased to 8% by IVGTT. AG was cleared by the liver by 38% but unaffected by glucose. The AG to UAG ratio was higher in the portal than the systemic circulation, both in the saline (P < 0.004) and IVGTT (P < 0.0005) rats. In conclusion, this study shows that: 1) the ratio of AG to UAG is very low in the portal vein and decreases further in the systemic circulation; 2) IVGTT in anesthetized fasting rats inhibits UAG, whereas it only blunts prehepatic, but not systemic, AG; and 3) hepatic clearance of AG is much higher than that of UAG. Thus, our results suggest that peripheral AG metabolic regulation and action are mainly confined within the gastrointestinal tract.
journal_name
Endocrinologyjournal_title
Endocrinologyauthors
Gauna C,Uitterlinden P,Kramer P,Kiewiet RM,Janssen JA,Delhanty PJ,van Aken MO,Ghigo E,Hofland LJ,Themmen AP,van der Lely AJdoi
10.1210/en.2007-0225subject
Has Abstractpub_date
2007-11-01 00:00:00pages
5278-87issue
11eissn
0013-7227issn
1945-7170pii
en.2007-0225journal_volume
148pub_type
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