Gut-brain communication: how does it stand after bariatric surgery?

Changes in intestinal permeability after Roux-en-Y gastric bypass

BACKGROUND

Roux-en-Y gastric bypass (RYGB) interferes considerably with the anatomy and physiology of the gastrointestinal tract. The study of intestinal permeability can provide important information regarding changes in the structure and function of the mucosal barrier after the procedure.

METHODS

The urinary excretion rates of lactulose and mannitol after oral intake of both substances were evaluated. We also evaluated the lactulose/mannitol excretion ratio. Tests were performed during the preoperative period (T0), at the first postoperative month (T1), and at the sixth postoperative month (T6).

RESULTS

The study included 16 morbidly obese patients. The excretion rate of mannitol was significantly lower at T1 compared with T0 and T6 (p = 0.003). There was no significant difference in the excretion rates of lactulose or in the lactulose/mannitol ratio during the three periods. Six patients (37.5%) exhibited a considerable increase in the excretion rate of lactulose at T6 (4-73 times higher than the preoperative value), accompanied by proportional variations in the lactulose/mannitol ratio.

CONCLUSIONS

The significant increase in mannitol excretion rate from T1 to T6 most likely reflects the occurrence of intestinal adaptation (mucosal hyperplasia), which would tend to minimize the malabsorption of macronutrients. A subgroup of patients who undergo RYGB exhibit pronounced increase in their intestinal permeability (assessed by the lactulose/mannitol ratio and the lactulose excretion rate) at T6.

The mechanism of weight loss with laparoscopic adjustable gastric banding: induction of satiety not restriction

Laparoscopic adjustable gastric banding (LAGB) has rapidly emerged as a popular bariatric procedure because of its safety, efficacy, durability and adjustability. Despite widespread use, there is limited understanding of how it induces weight loss. Previously, it has been classified as a restrictive procedure, physically limiting the patient to a small meal that subsequently slowly empties into the distal stomach. However, the tiny pouch of stomach created above the LAGB appears to be unable to accommodate even the smallest of meals. Therefore, the key mechanism has been hypothesized to be the induction of satiety via, as yet, undefined pathways. The critical question remains: what are the key physiological changes that lead to satiety and weight loss? In successful LAGB patients, a consistent intraluminal pressure at the level of the LAGB of 26.9 ± 19.8 mm Hg is observed. Studies using semi-solid swallows combined with intraluminal pressure recordings have demonstrated that semi-solid transit across the resistance of the LAGB is mediated by repeated esophageal peristaltic contractions (mean 4.5 ± 2.9) that produce episodic flow, interspersed by reflux events. Failed transit results in obstruction and regurgitation, whereas dilatation of the supraband stomach induces severe and intolerable reflux. Overall gastric emptying does not appear to be significantly altered following LAGB. Focused investigations have shown that the supraband stomach is empty of an ingested meal 1-2 min after intake ceases. Considerable progress has been made in understanding the mechanical physiological effects of the LAGB on esophageal and proximal gastric function. These have been correlated with patient outcomes and sensations. On the basis of recent data, it appears that the LAGB activates the peripheral satiety mechanism without physically restricting the meal size. Therefore, it should not be classified as a restrictive procedure. The precise mechanism of weight loss with the LAGB remains to be delineated.

Bariatric surgery and the gut-brain communication--the state of the art three years later

OBJECTIVE

This review analyzes the literature concerning gut peptides and bariatric surgery, from 2005 to July 2009. In particular, we are interested in whether, and how, gastrointestinal peptide alterations following surgery interfere with appetite/satiety, and what role they might play in the resolution of comorbidities.

RESEARCH METHODS AND PROCEDURE

PubMed/MEDLINE and ISI Web of Knowledge were used to search for human studies concerning gut peptides profiles after any bariatric operation technique.

RESULTS

Most of the studies reviewed had longitudinal design, short follow-up, and low statistical power. The diversity of study results may be partially explained by methodological aspects. Glucagon-like peptide-1, gastric inhibitory peptide, and peptide YY alterations may contribute to the excellent results in glycemic control of diabetics. Results do vary depending on bariatric operation technique; this is particularly evident in the case of ghrelin, which has been much studied in recent years. Ghrelin suppression has been linked to increased satiety, alterations in energy homeostasis, and better glucose metabolism.

CONCLUSIONS

There is a lack of long-term data on gastrointestinal hormone profiles after bariatric surgery and the studies have many methodological pitfalls. We still need prospective, long-term, good methodological studies in this area.

Expert panel on weight loss surgery: executive report update

Rapid shifts in the demographics and techniques of weight loss surgery (WLS) have led to new issues, new data, new concerns, and new challenges. In 2004, this journal published comprehensive evidence-based guidelines on WLS. In this issue, we've updated those guidelines to assure patient safety in this fast-changing field. WLS involves a uniquely vulnerable population in need of specialized resources and ongoing multidisciplinary care. Timely best-practice updates are required to identify new risks, develop strategies to address them, and optimize treatment. Findings in these reports are based on a comprehensive review of the most current literature on WLS; they directly link patient safety to methods for setting evidence-based guidelines developed from peer-reviewed scientific publications. Among other outcomes, these reports show that WLS reduces chronic disease risk factors, improves health, and confers a survival benefit on those who undergo it. The literature also shows that laparoscopy has displaced open surgery as the predominant approach; that government agencies and insurers only reimburse procedures performed at accredited WLS centers; that best practice care requires close collaboration between members of a multidisciplinary team; and that new and existing facilities require wide-ranging changes to accommodate growing numbers of severely obese patients. More than 100 specialists from across the state of Massachusetts and across the many disciplines involved in WLS came together to develop these new standards. We expect them to have far-reaching effects of the development of health care policy and the practice of WLS.

The regulation of body mass and its relation to the development of obesity

A testtömeg, ezen belül a zsírtömeg regulálása egy visszacsatolásos rendszerben valósul meg, melyben a zsírtömeg nagyságáról adipositasszignálok (leptin, inzulin, amylin), a pillanatnyi tápláltsági állapotról intestinalis peptidhormonok (ghrelin, PYY, PP, GLP-1, OXM, CCK) és a n. vagus informálják a központi idegrendszert mint központi szabályozót. A hypothalamus nucleus arcuatusának két jól elkülöníthető neuroncsoportja fogadja a zsírtömeg nagyságával arányos mennyiségben termelődő leptin közvetítette afferens információt. A leptinkötődés a sejtek felszínén elhelyezkedő leptinreceptorokhoz intracelluláris szignálmechanizmusokon keresztül a targetgének aktiválódását és anorexigén (POMC, CART) neuropeptidek termelését, majd másodlagos központokon keresztül az energiafelvétel és -leadás folyamatainak efferens regulációs mechanizmusait generálja. A testtömeg-szabályozás összetett és redundáns rendszer, számos más neuroendokrin folyamattal (növekedés, mellékvese- és pajzsmirigyműködés, reproduktív funkciók stb.), memória-, valamint jutalmazási és függőségi mechanizmussal áll kapcsolatban, így a szabályozórendszer egyes elemeinek befolyásolása, pl. gyógyszerekkel, más rendszerek működésére is hatással lehet, mellékhatások felléptére lehet számítani. Az obesitas világméretű epidémiája – mely elsősorban a magas energiasűrűségű élelmiszerek bőségével és a mozgásszegény életmóddal áll összefüggésben, melyhez a testtömeg-szabályozó rendszerünk nem tud megfelelően alkalmazkodni – intenzív kutatásokra ösztönzi az akadémiai és gyógyszeripari kutatóközpontokat annak érdekében, hogy új gyógyszerek, hatékony testsúlycsökkentő kezelési eljárások álljanak rendelkezésre az életmód-változtatási stratégiákon (diéta, fizikai aktivitás, magatartásterápia) túlmenően.