Nutrition and the gastrointestinal tract: Edited by M. Isabel T.D. Correia and Herbert Lochs
The current issue of Nutrition and the gastrointestinal tract offers us very challenging topics that stress the role of this system in the control of endocrine as well as metabolic distinct human body pathways. These subjects are discussed not only in terms of treatment options but also as preventive approaches.
As the number of bariatric operations to treat morbid obesity have increased worldwide , it is of utmost importance to understand how, in a short period, even before weight reduction has markedly been achieved, glycemic control is found in up to 80% of patients with previous diabetes. Saliba et al. (pp. 515–521) have elegantly covered this aspect, focusing on the hormonal changes accompanying Roux-en-Y gastric bypass (RYGB). Incretins, gastrointestinal hormones that stimulate insulin release, such as glucagon like peptide-1 (GLP-1), which is mainly secreted by L cells in the distal ileum and proximal ascending colon, have a key role in such event. Also, ghrelin secreted by the gastric fundus and proximal small intestines interferes in such phenomena.
Another updated topic is the role that Helicobacter pylori infection plays in the hormonal milieu leading to important nutritional regulation mechanisms. Despite its decreasing prevalence in developed countries, H. pylori infects close to one-half of the world's population . H. pylori has been directly linked to gastric adenocarcinoma, especially noncardia, and to gastric mucosal associated lymphoid tissue (MALT) lymphoma. However, Weigt and Malfertheiner's review (pp. 522–525) introduces us to another very challenging concept, which is the impact that H. pylori infection has on obesity. H. pylori leads to a decrease in circulating ghrelin through a reduction in ghrelin-producing cells in the gastric mucosa and increases the amount of gastric leptin with no effect on circulating leptin levels. Eradication of H. pylori reverses the abnormal regulation of gastric hormone secretion. This finding is suggested to favor weight gain after H. pylori eradication and points to the potential effect of H. pylori in the pathophysiology of obesity.
Short bowel syndrome is a life-threatening condition associated with poor quality of life, as most patients with small intestinal remnants rely totally on lifelong parenteral nutrition for life maintenance. Several pharmacological and nutritional options have been tried to improve these patients' conditions. Glucagon-like peptide-2 (GLP-2) is a promising option, as it is an important intestinotrophic growth factor and mediator of intestinal adaptation. IGF-1, so important in the control of diabetes, as previously described (Wallis et al., pp. 526–532), once again appears as a key element. This is co-located with the GLP-2R in subepithelial myofibroblasts and appears to be essential for GLP-2-induced intestinal epithelial proliferation. GLP-2 holds promise as adjuvant therapy in short bowel syndrome by possibly contributing to parenteral nutrition weaning.
Physical exercise, so beneficial to health maintenance, can bring about harm to any organ, and in this sense, the gastrointestinal tract can also be affected under intense activity load. Unfortunately, most athletes and exercise practitioners do not worry much about such potential risk and do not pay attention to these relevant issues. The current literature is also poor, as it is difficult to find articles covering such aspects. Oliveira and Burini (pp. 533–538) have reviewed the role of physical exercise on gastrointestinal distress mainly when it is vigorous and practiced in a hot environment without adequate training and/or proper hydration. The major pathophysiological mechanisms are related to ischemic, mechanic, or neuroendocrine factors.
Finally, colon cancer and the role of specific nutrients in its prevention have been constantly marked by controversies. The ecologic observation that colon cancer risk and mortality tend to track with industrialization and economic development has led many to emphasize diet. Although many offshoots of industrialization other than diet – physical activity, obesity, exposure to electromagnetic fields, radiation, the use of various medications, and fertility – are potentially important, the diet has seemed a plausible candidate. Diet comes into direct contact with the intestinal lumen, and it affects the bowel transit and stool characteristics. Burkitt's observation that a concomitant of the dietary differences between the Bantu and European lineage populations of South Africa were differences in stool characteristics added to interest in diet (Marshall, pp. 539–543). Marshall, in his review (pp. 539–543), discusses all these aspects but adds extra information on the potential combination of diflouromethylornithine and sulindac as options to substantially decrease adenomatous polyp recurrence and thus impact on cancer development.
1 Pories WJ. Bariatric surgery: risks and rewards. J Clin Endocrinol Metab 2008; 93:S89–S96.
2 Mbulaiteye SM, Hisada M, El-Omar EM. Helicobacter pylori
associated global gastric cancer burden. Front Biosci 2009; 14:1490–1504.