Expression of the beacon gene in the rat pancreatic islets: opposite effects of beacon (47-73) protein (ubiquitin-like protein 5) on insulin secretion in vivo and insulin release by isolated islets.
OBJECTIVE
Beacon gene expression is elevated in the hypothalamus of the Israeli sand rat (Psammomys obesus), an animal that is used as a polygenic animal model of obesity and NIDDM. We performed studies aimed at investigating the expression of beacon mRNA and protein in pancreatic islets of the rat and the possible beacon protein effects on insulin secretion.


METHODS
Rat pancreatic islets were isolated by the collagenase digestion technique. Beacon mRNA expression was demonstrated in isolated islets using RT-PCR and beacon-like immunoreactivity using immunocytochemistry (ICC) on a sections of Bouin-fixed pancreas. Isolated islets were incubated with 1-100 nmol/L beacon (47-73) protein in normoglycemic medium. Adult female rats were subcutaneously injected with beacon (47-73) at doses 0.35 or 0.7 nmol/100 g body weight and killed after 30 and 60 minutes.


RESULTS
RT-PCR results indicate the presence of beacon mRNA in isolated rat pancreatic islets. Beacon-like immunoreactivity is present in all cell types of the Langerhans islet. Beacon inhibits insulin secretion from isolated islets. In contrast, a bolus administration of beacon at a lower dose notably stimulates blood insulin concentration at 30 and 60 minutes of the experiment while the higher dose does not change insulinemia. None of the treatment had an effect on blood glucose concentration.


CONCLUSIONS
This study demonstrated the presence of beacon mRNA in isolated rat islets as well as a direct inhibitory effect of beacon protein on insulin secretion by isolated rat pancreatic islets. The data obtained suggest that beacon may be involved in physiologic regulation of insulin secretion.
Nowak
Krzysztof W
KW
Department of Animal Physiology and Biochemistry, August Cieszkowski University of Agriculture, Poznań, Poland. kwnowak@owl.au.poznan.pl
Ruciński
Marcin
M
Kaczmarek
Przemyslaw
P
Szkudelski
Tomasz
T
Malendowicz
Ludwik K
LK
D000818:Animals; D001786:Blood Glucose / Q000032:analysis; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D005260:Female; D005786:Gene Expression Regulation; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007279:Injections, Subcutaneous; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000494:pharmacology / Q000502:physiology; D010446:Peptide Fragments / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014452:Ubiquitins / Q000494:pharmacology
D001786:Blood Glucose; D007328:Insulin; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D012333:RNA, Messenger; D014452:Ubiquitins; C498170:Ubl5 protein, rat; D005947:Glucose