Beneficial effects of oral insulin on intestinal recovery following ischemia-reperfusion injury in rat

Metabolic Conditions Including Obesity, Diabetes, and Polycystic Ovary Syndrome: Implications for Breastfeeding and Breastmilk Composition

Breastfeeding is internationally recognized as the recommended standard for infant nutrition, informed by evidence of its multiple benefits for both mother and baby. In the context of common metabolic conditions such as polycystic ovary syndrome, diabetes (type 1, type 2, and gestational), and obesity, breastfeeding may be particularly beneficial for both mother and infant. However, there is evidence of delayed lactogenesis and reduced breastfeeding rates and duration in women with these conditions, and the effects of altered maternal metabolic environments on breastmilk composition (and potentially infant outcomes) are incompletely understood. In this review, we explore the relationships between maternal metabolic conditions, lactogenesis, breastfeeding, and breastmilk composition. We examine relevant potential mechanisms, including the central role of insulin both in lactogenesis and as a milk-borne hormone. We also describe the bioactive and hormonal components of breastmilk and how these may link maternal and infant health.

Effect of Oral Insulin on the Severity and Recovery of Methotrexate-Induced Gastrointestinal Mucositis in the Rat

OBJECTIVES

Gastrointestinal (GI) mucositis is an adverse-effect of chemo- and radiotherapy. Oral insulin has been suggested as possible intestinal growth factor and possible intervention for GI mucositis. We aimed to determine the effect of oral insulin on the severity and recovery of mucositis in a methotrexate (MTX)-induced GI mucositis rat model.

METHODS

Male Wistar rats (n = 24) received a single injection of 60 mg/kg MTX intravenously at day 0. From day -3 oral insulin was added to the drinking water. Group MTX received normal drinking water, group MTX+INS0.5 received 0.5 U/mL insulin, and group MTX+INS1 received 1 U/mL insulin in drinking water. The severity of mucositis was determined by intake, bodyweight, illness, and plasma citrulline. In the recovery phase, the function of the gut was tested with an oral glucose tolerance test, and villus and crypt length of the small intestine were measured.

RESULTS

MTX-induced mucositis in all 3 groups and oral insulin did not cause a change in the severity of mucositis, with comparable bodyweight, food intake, and water intake. Oral insulin did not alter the enterocyte mass, determined with plasma citrulline. The glucose level after bolus was higher in the MTX group than the MTX+INS1 group (P < 0.05). Histology was not significant different between all groups.

CONCLUSIONS

Oral insulin does not alter the severity or the acceleration of recovery of mucositis. Therefore, we conclude that it is not useful to further study oral insulin as possible intervention to prevent or treat chemotherapy-induced GI mucositis.

Pretreatment with Panax notoginseng saponins protects against small intestinal ischemia-reperfusion injury in rats

AIM: To explore the mechanism underlying the protective effect of Panax notoginseng saponins (PNS) against intestinal ischemia-reperfusion injury in rats.

METHODS: A rat model of intestinal ischemia-reperfusion injury was generated. Rats were divided into four groups: sham-operation group, model control group, low- (200 mg/kg) and high-dose (400 mg/kg) PNS groups. After pretreatment with PNS, plasma levels of D-lactate and lipopolysaccharide (LPS) were determined.Samples of the liver, spleen, mesenteric lymph nodes and blood were taken for culturing aerobic bacteria. The expression of NF-κB and TNF-α in the intestine was detected by immunohistochemistry. Cell apoptosis in the intestine was detected by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay.

RESULTS: The number of positive bacterial cultures in the liver, spleen, mesenteric lymph nodes and blood was significantly lower in the PNS group than in the model control group (all P < 0.05). Plasma levels of D-lactate and LPS were significantly lower in the PNS group (200 mg/kg, 400 mg/kg) than in the model control group (LPS: 461 EU/L, 320 EU/L vs 570 EU/L; D-lactate: 0.37 mmol/L, 0.31 mmol/L vs 0.44 mmol/L, both P < 0.05). Treatment with PNS reduced the expression of NF-κB and TNF-α and the number of apoptotic cells in intestinal tissue (all P < 0.05).

CONCLUSION: Pretreatment with PNS protects against intestinal ischemia-reperfusion injury in rats possibly by reducing mucosal cell apoptosis and down-regulating NF-κB and TNF-α expression in the small intestine.

Effect of oral insulin on diabetes-induced intestinal mucosal growth in rats

BACKGROUND

To evaluate the intestinal response to the induction of diabetes and to oral insulin (OI) administration in a rat.

METHODS

Male Sprague-Dawley rats were divided into four experimental groups: control rats, CONTR-INS rats that were treated with OI given in drinking water for 7 days, diabetic rats that were injected with one dose of streptozotocin, and diabetic rats treated with OI. Intestinal structural changes, enterocyte proliferation and enterocyte apoptosis, bax and bcl-2 mRNA and protein levels, insulin receptor expression and ERK protein levels were determined at sacrifice. A one-way ANOVA for comparison, followed by Tukey's test for pair-wise comparison, were used for statistical analysis.

RESULTS

Induction of diabetes resulted in a significant increase in bowel and mucosal weight (P < 0.05), mucosal protein (P < 0.05), villus height and crypt depth in jejunum and ileum (P < 0.05), and mucosal DNA in ileum (P < 0.05) (vs. control animals). Diabetes also enhances ERK-induced cell proliferation (P < 0.05) and concomitant bax/bcl-2 induced cell apoptosis (P < 0.05). Treatment of diabetic rats with OI resulted in a significant decrease in jejunal protein content (P < 0.05), jejunal and ileal villus height (P < 0.05), and jejunal crypt depth (P < 0.05), as well as an inhibition of ERK-related cell proliferation in ileum (P < 0.05). Expression of insulin receptor was down-regulated following OI administration in both control and diabetic animals.

CONCLUSIONS

Experimental STZ-induced diabetes causes intestinal mucosal growth and enhances enterocyte turnover in a rat model. OI administration diminishes diabetes-accelerated cell turnover and diabetes-induced mucosal hyperplasia.

Oral insulin enhances cell proliferation and decreases enterocyte apoptosis during methotrexate-induced mucositis in the rat

OBJECTIVE

Oral insulin (INS) has been shown to protect intestinal epithelial cells from injury caused by ischemia-reperfusion and endotoxemia. In the present study, we tested whether oral insulin can protect gut epithelial cells from methotrexate (MTX)-induced intestinal damage.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were divided into 3 experimental groups. Control rats were treated with normal saline given intraperitoneally (CONTR), MTX rats were treated with a single dose (20 microg/kg) of MTX given intraperitoneally, and MTX-INS rats were treated with oral insulin given in drinking water (1 U/mL) 72 hours after IP injection of a single dose of MTX (similar to MTX rats). Three days after either MTX or saline injection, rats were killed. Intestinal mucosal damage (Park injury score), mucosal structural changes, enterocyte proliferation, and enterocyte apoptosis were measured. Reverse transcription polymerase chain reaction was used to determine the level of bax and bcl-2 mRNA expression.

RESULTS

MTX-INS rats demonstrated a greater jejunal and ileal mucosal weight, ileal mucosal DNA, greater jejunal villus height, greater jejunal and ileal crypt depth, greater enterocyte proliferation index in ileum, and lower enterocyte apoptosis in ileum than did MTX-nontreated animals. Treatment with insulin did not change the injury score grade in comparison with MTX animals. A significant decrease in cell apoptosis was observed in MTX-INS rats (vs MTX) and also a decrease in a bax mRNA expression and decrease in a bax/bcl-2 ratio.

CONCLUSIONS

In a rat model of MTX-induced mucositis, oral insulin supplementation does not prevent mucosal injury but improves intestinal recovery and enhances enterocyte survival.

Oral insulin up-regulates Toll-like receptor 4 expression and enhances intestinal recovery following lipopolysaccharide-induced gut injury in a rat

In the present study, we evaluated the protective effect of oral insulin (OI) on intestinal mucosa following lipopolysaccharide-induced intestinal damage in a rat. Male Sprague-Dawley rats were divided into three experimental groups: Sham rats, LPS-rats that were treated with lipopolysaccharide (LPS), and LPS-INS rats that were treated with OI given in drinking water 72 h before and following injection of LPS. Intestinal structural changes, enterocyte proliferation, enterocyte apoptosis, and mucosal expression of Toll-like receptor 4 (TLR4) were determined 24 h after the last LPS injection. LPS-INS animals showed a significantly greater bowel and mucosal weight in jejunum and ileum, mucosal DNA and protein in jejunum and ileum, villus height in ileum, crypt depth in jejunum and ileum, cell proliferation rates in jejunum, and significantly lower apoptotic index in ileum compared to LPS- animals. LPS rats demonstrated 50% increase in TLR4 expression in jejunum compared to sham animals. Treatment with OI resulted in a three-fold increase in TLR4 expression in jejunum, compared to LPS animals. In conclusion, OI improves intestinal recovery after LPS endotoxemia in a rat.

Effect of 100% oxygen on E-selectin expression, recruitment of neutrophils and enterocyte apoptosis following intestinal ischemia-reperfusion in a rat

Recent evidence suggests that neutrophil recruitment may initiate cell apoptosis in ischemic tissues. We have recently shown that enterocyte apoptosis is increased following intestinal ischemia-reperfusion (IR) injury. The purpose of the present study was to examine the effect of hyperoxia on E-selectin expression, neutrophil recruitment and enterocyte apoptosis following intestinal IR in a rat. Male Sprague-Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy without vascular occlusion and were ventilated with air (Sham) (2) IR rats underwent occlusion of both the superior mesenteric artery and portal vein for 30 min and were ventilated with air (IR), and (3) IR-O2 rats underwent IR and were ventilated with 100% started 10 min before reperfusion and continued for 6 h (IR-O2). Intestinal structural changes were determined 24 h following IR. Immunohistochemistry for E-selectin (using E-selectin cleaved concentrated polyclonal antibody) was performed to identify E-selectin immunoreactivity localized to the endothelium of venules. The recruitment of neutrophils was calculated per 100 venules. Immunohistochemistry for Caspase-3 was performed for identification of apoptotic cells. Non-parametric one-way ANOVA test was used for statistical analysis with p less than 0.05 considered statistically significant. A significant increase in E-selectin expression in the jejunum (6.1 +/- 2.2 vs. 2.5 +/- 1.0 E-selectin positive vessels/100 vessels, p < 0.05) and ileum (12.1 +/- 2.7 vs. 3.3 +/- 1.2 E-selectin positive vessels/100 vessels, p < 0.05) and a concomitant increase in neutrophil recruitment in the ileum (5.5 +/- 1.6 vs. 1.3 +/- 0.6 adhered PMN's per 100 venules) were observed in IR rats compared to sham animals and were accompanied by increased cell apoptosis (p < 0.05). Treatment with 100% oxygen resulted in a significant attenuation in E-selectin expression in the ileum (2.7 +/- 1.1 vs. 12.1 +/- 2.7 E-selectin positive vessels/100 vessels, p < 0.05), and neutrophil recruitment in the jejunum (2.5 +/- 1.4 vs. 7.7 +/- 1.9 adhered PMN's per 100 venules, p < 0.05) and ileum (1.5 +/- 0.7 vs. 5.5 +/- 1.6 adhered PMN's per 100 venules, p < 0.05) compared to IR animals, and was accompanied by decreased cell apoptosis (p < 0.05). Hyperoxia inhibits enterocyte apoptosis following intestinal ischemia-reperfusion. Down-regulation of E-selectin expression with subsequent decrease in neutrophil recruitment may be responsible for this effect.

The effect of leptin on intestinal recovery following ischemia-reperfusion injury in a rat

Recent evidence suggests that the adipose tissue derived cytokine leptin (LEP) is involved in the modulation of growth and differentiation of normal small intestine. The purpose of the present study was to examine the effect of leptin on enterocyte turnover and intestinal recovery after ischemia-reperfusion (IR) injury in a rat. Male Sprague-Dawley rats were divided into three experimental groups: (1) sham rats underwent laparotomy, (2) IR-rats underwent occlusion of both superior mesenteric artery and portal vein for 30 min followed by 24 h of reperfusion, and (3) IR-LEP rats underwent IR and were treated with leptin given subcutaneously at a dose of 50 microg/kg once a day for 48 h before and 24 h following IR. Intestinal structural changes, enterocyte proliferation and enterocyte apoptosis were determined 24 h following IR. A non-parametric Kruskal-Wallis ANOVA test was used for statistical analysis with P < 0.05 considered statistically significant. Treatment with leptin resulted in a significant increase in bowel weight in ileum, mucosal weight in jejunum and ileum, mucosal DNA content in ileum, mucosal protein content in jejunum and ileum, villus height in jejunum and ileum, and crypt depth in jejunum compared to IR-animals. IR-LEP rats also had a significantly lower intestinal injury score as well as lower apoptotic index and higher cell proliferation index in jejunum and ileum compared to the IR-animals. In conclusion, pre-treatment with leptin prevents gut mucosal damage and improves intestinal rehabilitation following intestinal IR in a rat.

Gastrointestinal tract as a target organ for orally administered insulin

The intestine is not considered to be a classic target tissue for insulin. Recent in vitro and in vivo experiments suggest that intestinal as well as systemic effects are observed following oral administration of insulin. Local effects include enhancement of intestinal growth, cell maturation, enzyme expression, gut adaptation after intestinal resection and reduction of intestinal permeability. Systemic effects, at least in animal models, include favorable effects on blood glucose and lipid profile and on the prevention of autoimmunity and attenuating the atherosclerotic process.

Evaluation of intestinal trophism: review of current methods and techniques

PURPOSE OF REVIEW

This review aims to cover the methods and techniques currently used by researchers to evaluate intestinal trophism.

RECENT FINDINGS

Although subjected to criticisms, conventional gut trophism evaluation by both morphological and histological parameters continues to be largely reported. The metaphase arrest technique and the detection of H-tymidine have been used less frequently in recent years due to increasing interest in the immunohistochemical methods such as 5-bromo-2'deoxy-uridine, Ki-67, and proliferating cell nuclear antigen. Along with common techniques for the evaluation of intestinal trophism, the combination of methods that includes a measurement of cell proliferation and an apoptotic index in the same study are most valuable and are increasing in the current literature.

SUMMARY

Evaluation of intestinal trophism is an important issue for both clinical and experimental nutritional studies. The immunohistochemical techniques are the gold standard to access cell proliferation. Evaluation of proliferation and apoptosis at the same time may offer a more reliable evaluation of the actual status of gut trophism.