Abstract
The expression of leptin and leptin receptor (Ob-R) has been partially elucidated in colon of patients with inflammatory bowel diseases (IBDs), even though leptin is involved in angiogenesis and inflammation. We previously reported overexpression of GLUT5 fructose transporter, in aberrant clusters of lymphatic vessels in lamina propria of IBD and controls. Here, we examine leptin and Ob-R expression in the same biopsies. Specimens were obtained from patients with ulcerative colitis (UC), Crohn’s disease (CD) and controls who underwent screening for colorectal cancer, follow-up after polypectomy or with a history of lower gastrointestinal symptoms. Immunohistochemistry revealed leptin in apical and basolateral membranes of short epithelial portions, Ob-R on the apical pole of epithelial cells. Leptin and Ob-R were also identified in structures and cells scattered in the lamina propria. In UC, a significant correlation between leptin and Ob-R in the lamina propria was found in all inflamed samples, beyond non-inflamed samples of the proximal tract, while in CD, it was found in inflamed distal samples. Most of the leptin and Ob-R positive areas in the lamina propria were also GLUT5 immunoreactive in inflamed and non-inflamed mucosa. A significant correlation of leptin or Ob-R expression with GLUT5 was observed in the inflamed distal samples from UC. Our findings suggest that there are different sites of leptin and Ob-R expression in large intestine and those in lamina propria do not reflect the status of mucosal inflammation. The co-localization of leptin and/or Ob-R with GLUT5 may indicate concomitance effects in colorectal lamina propria areas.
Highlights
Leptin is a 16 kDa hormone that is encoded by the ob gene
Immunolocalization of leptin in colorectal samples in inflammatory bowel diseases (IBDs) and control group Distinct expression patterns of leptin staining were observed throughout portions of the large intestine
We identified leptin and Ob-R expression in epithelial cells and in structures within the lamina propria of the large intestine mucosa from IBD and control patients
Summary
Leptin is a 16 kDa hormone that is encoded by the ob gene. Initially believed to be mainly synthesized and secreted by adipocytes, leptin is documented to be present in a variety of human and rodent tissues, including placenta, lung, muscle and kidney tissues, the olfactory system and gastric epithelia (Masuzaki et al 1997; Wang et al 1998).Leptin acts through the leptin receptor (Ob-R) on the hypothalamus to regulate food intake and energy expenditure resulting in control of body weight and fat deposition. Leptin is a 16 kDa hormone that is encoded by the ob gene. Believed to be mainly synthesized and secreted by adipocytes, leptin is documented to be present in a variety of human and rodent tissues, including placenta, lung, muscle and kidney tissues, the olfactory system and gastric epithelia (Masuzaki et al 1997; Wang et al 1998). Leptin acts through the leptin receptor (Ob-R) on the hypothalamus to regulate food intake and energy expenditure resulting in control of body weight and fat deposition. Mice lacking endogenous leptin (ob/ob) are genetically obese and develop hyperglycemia and hyperinsulinemia. Ob-R is a member of the type I cytokine receptor family that is encoded by the db gene. Hypogonadism, delayed onset of puberty, hypothyroidism and immune dysfunction (Mackey-Lawrence and Petri 2012)
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