Leptin production by the stomach is up-regulated in obese (fa/fa) Zucker rats.
OBJECTIVE
Genetically obese (fa/fa) Zucker rats display markedly elevated circulating leptin levels compared with their lean counterparts; this is expected because of the lack of a LepR-mediated feedback inhibition. The aim of this study was to determine the effect of the leptin receptor mutation in the Zucker rat on gastric leptin production and on the response to 14 hours of starvation. The response to a short-term period of food intake (20 minutes) on gastric leptin release was also analyzed.


METHODS
Leptin mRNA expression in the gastric mucosa and in adipose tissue depots (epididymal, retroperitoneal, mesenteric, and inguinal) was assessed by reverse transcriptase-polymerase chain reaction and serum and stomach leptin content by enzyme-linked immunosorbent assay.


RESULTS
Obese Zucker rats overexpressed leptin in the stomach. They overexpress leptin in the inguinal adipose tissue but not in visceral adipose tissue depots, indicating tissue-specific obesity-dependent differences. Gastric leptin expression is regulated by feeding conditions in lean but not in obese (fa/fa) rats. In lean animals, leptin mRNA levels decrease in fasting conditions and increase rapidly with a short period of food intake. Obese Zucker rats also overdisplay stomach leptin levels. Feeding acutely stimulates leptin secretion by the stomach in lean, and to a lesser extent, in obese rats.


CONCLUSIONS
These results indicate impaired regulation of leptin expression in the stomach of obese (fa/fa) Zucker rats. However, there is still an effect of the nutritional status on gastric leptin levels despite the lack of a functional leptin receptor.
Picó
Catalina
C
Department of Fundamental Biology and Health Sciences, University of Balearic Islands, Cra. Valldemossa, Km 7.5, E-07071 Palma de Mallorca, Spain.
Sánchez
Juana
J
Oliver
Paula
P
Palou
Andreu
A
D000273:Adipose Tissue / Q000737:chemistry; D000818:Animals; D001835:Body Weight; D004797:Enzyme-Linked Immunosorbent Assay; D004822:Epididymis; D005502:Food; D005753:Gastric Mucosa / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation; D006119:Groin; D020738:Leptin / Q000096:biosynthesis* / Q000097:blood / Q000235:genetics*; D008297:Male; D008643:Mesentery; D009765:Obesity / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D011924:Rats, Zucker; D012187:Retroperitoneal Space; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013217:Starvation
D020738:Leptin; D012333:RNA, Messenger