Effects of melatonin administration on intestinal adaptive response after massive bowel resection in rats

A protective effect of melatonin on intestinal permeability is induced by diclofenac via regulation of mitochondrial function in mice

AIM

This study investigated the effect of intragastrically administered melatonin on intestinal mucosal permeability induced by diclofenac in mice.

METHODS

Intestinal mucosal permeability was induced in mice by intragastric administration of diclofenac (2.5 mg/kg). Melatonin was given intragastrically (10 mg/kg) once per day for 3 d after diclofenac administration. The small intestine was examined macroscopically and microscopically for pathologic injury to the intestinal mucosa. Intestinal mucosal permeability was evaluated by Evans blue and FITC-dextran methods. Mitochondrial functional parameters, including mitochondrial membrane potential, mitochondrial ATPase and succinate dehydrogenase (SDH) activity, were assessed. The malondialdehyde (MDA) and myeloperoxidase (MPO) levels were determined from small intestinal mucosal homogenates.

RESULTS

As compared with control mice, the permeability, pathologic score, MDA and MPO levels and ulceration of the intestinal mucosa were increased significantly by diclofenac treatment, and a broadened junctional complex and enlarged intercellular space were observed by transmission electron microscopy (TEM). Melatonin treatment significantly reduced the intestinal mucosal permeability, pathologic score, MDA, and MPO levels and ulceration of the intestinal mucosa. By TEM, the small intestine villus morphology and intercellular spaces were nearly normal in melatonin-treated mice. At the level of the mitochondria, melatonin treatment significantly restored the activities of ATPase and SDH.

CONCLUSION

The intestinal damage and increased intestinal permeability induced by diclofenac in mice was limited by melatonin; moreover, melatonin preserved several aspects of mitochondrial function.

Protective effects of melatonin and octreotide against radiation-induced intestinal injury

PURPOSE

To compare the protective effects of the potent antioxidants, melatonin and octreotide, against radiation-induced intestinal injury.

METHODS

A total of 42 male 3-month-old Swiss albino mice (40 ± 10 g) were matched according to body weight and randomly assigned to one of six groups: control; radiation treatment (RT) only; melatonin only (15 mg/kg, i.p.); melatonin + RT; octreotide only (50 μg/kg i.p.); and octreotide + RT. Intestinal damage was induced by exposure to a single whole-body radiation dose of 8 Gy. All mice tolerated the experimental interventions, and no deaths were observed.

RESULTS

Irradiation induced architectural disorganization, including inflammatory mononuclear cell infiltration, villitis, and desquamation with eosinophilic necrosis, and diminished mucosal thickness, crypt height, and villous height. In the melatonin + RT and octreotide + RT groups, the villous pattern was well preserved; desquamation at villous tips and edema was prominent, but necrosis was absent. The radiation-induced decrease in mucosal thickness was significantly reduced by pretreatment with melatonin (p < 0.001) or octreotide (p = 0.01), although the protective effect was significantly greater for melatonin (p = 0.04). Pretreatment with melatonin also preserved villous height (p = 0.009) and crypt height (p = 0.03); although a similar trend was observed for pre-irradiation octreotide, the differences were not significant.

CONCLUSIONS

Melatonin and octreotide potently protected against radiation-induced intestinal injury in mice, but melatonin was significantly more effective in preserving the histological structure of the intestines, a finding that warrants confirmation in clinical studies.

Mechanisms of ileal adaptation for glucose absorption after proximal-based small bowel resection

INTRODUCTION

The hexose transmembrane transporters SGLT1 and GLUT2 are present in low quantities in ileum where little glucose absorption occurs normally; however, glucose uptake in ileum is highly adaptable after small bowel resection.

HYPOTHESIS

Ileal adaptability for glucose absorption after jejunal resection is mediated predominately by upregulation of GLUT2.

METHODS

Rats underwent 70% proximal-based jejunoileal resection. Transporter-mediated glucose uptake was measured in proximal and distal remnant ileum 1 and 4 wk postoperatively (n = 6 rats, each) and in corresponding ileal segments in control and 1 wk sham laparotomy rats (n = 6, each) without and with selective inhibitors of SGLT1 and GLUT2. In separate groups of rats (n = 6, each), protein (Western blots), mRNA (reverse transcriptase polymerase chain reaction [RT-PCR]), and villus height (histomorphology) were measured.

RESULTS

After 70% proximal intestinal resection, there was no dramatic change in protein or mRNA expression per cell of either SGLT1 or GLUT2, but median glucose uptake (nmol/cm/min) increased markedly from 52 (range 28-63) in controls to 118 (range 80-171) at 1 wk, and 203 (range 93-248) at 4 wk (p < or = 0.04 each) correlating with change in villus height (p < or = 0.03).

CONCLUSIONS

Ileal adaptation for glucose transport occurs through cellular proliferation (hyperplasia) and not through cellular upregulation of glucose transporters.

Reactive oxygen species and the hypomotility of the gall bladder as targets for the treatment of gallstones with melatonin: a review

Free radical-mediated damage of the gall bladder epithelium predisposes to the development of both gall bladder inflammation and gallstone formation, which often coexist. Melatonin, a pineal and gut secretory product, due to its antioxidant activity along with its effect on the aging gall bladder myocytes, inhibits gallstone formation. Melatonin reduces the biliary levels of cholesterol by inhibiting cholesterol absorption across the intestinal epithelium and by increasing the conversion of cholesterol to bile acids. The incidence of gallstones is increasing and is expected to rise dramatically with the increase in the longevity and the risk factors such as obesity. The change in the prevalence of cholelithiasis is associated with a proportionate rise in the incidence of cholangiocarcinoma. In an attempt to improve the quality of life of the rapidly increasing aging population, this article reviews up-to-date information on the pathophysiology of the gall bladder function and discusses the development of new therapies with potential good patient compliance and lower cost than the current treatments.