Effect of calcium supplementation on rectal epithelial hyperproliferation in intestinal bypass subjects

The impact of bariatric surgery on colorectal cancer risk

Obesity is considered a risk factor for different types of cancer, including colorectal cancer (CRC). Bariatric surgery has been associated with improvements in obesity-related co-morbidities and reductions in overall cancer risk. However, given the contradictory outcomes of several cohort studies, the impact of bariatric surgery on CRC risk appears controversial. Furthermore, measurement of CRC biomarkers following Roux-en-Y gastric bypass (RYGB) has revealed hyperproliferation and increased pro-inflammatory gene expression in the rectal mucosa. The proposed mechanisms leading to increased CRC risk are alterations of the gut microbiota and exposure of the colorectum to high concentrations of bile acids, both of which are caused by RYGB-induced anatomical rearrangements. Studies in animals and humans have highlighted the similarities between RYGB-induced microbial profiles and the gut microbiota documented in CRC. Microbial alterations common to post-RYGB cases and CRC include the enrichment of pro-inflammatory microbes and reduction in butyrate-producing bacteria. Lower concentrations of butyrate following RYGB may also contribute to an increased risk of CRC, given the anti-inflammatory and anticarcinogenic properties of this molecule. Laparoscopic sleeve gastrectomy appears to have a more moderate impact than RYGB; however, relatively few animal and human studies have investigated its effects on CRC risk. Moreover, evidence regarding the impact of anastomosis gastric bypass on one is even more limited. Therefore, further studies are required to establish whether the potential increase in CRC risk is restricted to RYGB or may also be associated with other bariatric procedures.

Biomarkers of Colorectal Cancer Risk Decrease 6 months After Roux-en-Y Gastric Bypass Surgery

PURPOSE

The impact of weight loss on obesity-related colorectal cancer (CRC) risk is not well defined. Previous studies have suggested that Roux-en-Y gastric bypass (RYGB) surgery may have an unexpected adverse impact on CRC risk. This study aimed to investigate the impact of RYGB on biomarkers of CRC risk.

MATERIALS AND METHODS

Rectal mucosal biopsies and blood were obtained from patients undergoing RYGB (n = 22) and non-obese control participants (n = 20) at baseline and at a median of 6.5 months after surgery. Markers of systemic inflammation and glucose homeostasis were measured. Expression of pro-inflammatory genes and proto-oncogenes in the rectal mucosa was quantified using qPCR. Crypt cell proliferation state of the rectal mucosa was assessed by counting mitotic figures in whole micro-dissected crypts.

RESULTS

At 6.5 months post-surgery, participants had lost 29 kg body mass and showed improvements in markers of glucose homeostasis and in systemic inflammation. Expression of pro-inflammatory genes in the rectal mucosa did not increase and COX-1 expression fell significantly (P = 0.019). The mean number of mitoses per crypt decreased from 6.5 to 4.3 (P = 0.028) after RYGB.

CONCLUSION

RYGB in obese adults led to lower rectal crypt cell proliferation, reduced systemic and mucosal markers of inflammation and improvements in glucose regulation. These consistent findings of reduced markers of tumourigenic potential suggest that surgically induced weight loss may lower CRC risk.

Body mass index, calcium supplementation and risk of colorectal adenomas

Calcium supplementation (1,200 mg/day) did not significantly reduce colorectal adenomas in our recent randomized, controlled trial (Vitamin D/Calcium Polyp Prevention Study, VCPPS, 2004-2013) in contrast to our previous trial (Calcium Polyp Prevention Study, CPPS, 1988-1996). To reconcile these findings, we identified participant characteristics that differed between the study populations and modified the effect of calcium supplementation on adenomas or high-risk findings (advanced or multiple adenomas). Compared to the CPPS, more participants in the VCPPS were obese (body mass index (BMI) ≥30 kg/m² ; 37.5% vs. 24.4%) and fewer had normal BMI (BMI <25 kg/m² ; 18.5% vs. 31%). BMI appeared to modify the effect of calcium supplementation on adenomas and especially on high risk-findings: in the VCPPS, there was a 44% reduction in high-risk findings among individuals whose BMI was normal (RR = 0.56, 95% CI = 0.26-1.23), but not among overweight (RR = 1.09, 95% CI = 0.62-1.91) or obese (RR = 1.54, 95% CI = 0.92-2.57) individuals (p_interaction = 0.03). Similarly, in the CPPS, there was a 56% reduction in high-risk findings among individuals whose BMI was normal (RR = 0.44, 95% CI = 0.26-0.74), but not among overweight (RR = 0.87, 95% CI = 0.55-1.39) or obese (RR = 1.02, 95% CI = 0.57-1.82) individuals (p_interaction = 0.02). Standardization of each trial's findings to the BMI distribution in the other attenuated calcium's protective effect on adenomas in the CPPS but enhanced it in the VCPPS. In conclusion, 1,200 mg/day calcium supplementation may reduce risk of colorectal adenomas among those with normal BMI but not in overweight or obese individuals; and differences in BMI distribution partially account for the apparent difference in calcium efficacy between the two trials.

Nanoparticulate delivery of novel drug combination regimens for the chemoprevention of colon cancer

The purpose of this work was to assess synergistic inhibitory responses of a novel chemopreventive combination regimen of drugs namely, aspirin in combination with calcium and folic acid on two human colon cancer cell lines, HT-29 and SW-480. Subsequently, based on positive responses, nanotechnology-based formulations were developed for the targeted delivery of these combinatorial regimens to the colon for the chemoprevention of colon cancer. Additionally, conventional drug formulations using controlled release polymers chitosan, pectin and hydroxypropyl methylcellulose (HPMC) were tested for release of the drugs, for comparison purposes. Chemopreventive combination regimens demonstrated significant synergistic efficacy in both cell lines from XTT assay studies, when compared to the effects of individual agents. Approximately 45% decrease in cell viability for aspirin (15 mM) and calcium (30 mM) mixtures was observed in HT-29 cell lines, compared to approximately 55% decrease by the same combination in SW-480 cell lines. With combinations of aspirin (5 mM) and folic acid (1.5 mM), HT-29 cells demonstrated a 30% decrease in cell viability compared to approximately 38% decrease in the SW-480 cell line. Overall, all drug combinations demonstrated significant synergistic responses in the cell lines tested with the SW-480 cell line being more significantly affected by the drug regimens than the HT-29 cell line. Drug encapsulated nanoparticles demonstrated a spherical morphology, <125 nm average particle size (aspirin and folic acid) of nanoparticles and encapsulation efficiencies in the range of 80-91%. Drug release from nanoparticles was controlled with approximately 60% of the original amount released over a 96 h period. Conventional formulations exhibited faster kinetics of drug release when compared to the PLGA nanoparticles. Overall, the cell line studies demonstrate, for the first time, the ability of novel chemopreventive combinations to inhibit the growth of colon cancer cells whereas the nanotechnology-based drug delivery system provides valuable evidence for targeted therapy towards colon cancer chemoprevention.

Increased colorectal epithelial cell proliferation and crypt fission associated with obesity and roux-en-Y gastric bypass

BACKGROUND AND AIMS

The relationship between obesity, weight reduction, and future risk of colorectal cancer is not well understood. Therefore, we compared mucosal biomarkers in normal weight individuals [body mass index (BMI), 18.5-24.9 kg/m(2)] with those in morbidly obese patients (BMI >40 kg/m(2)) before and 6 months after Roux-en-Y gastric bypass (RYGB).

METHODS

Rectal epithelial cell mitosis, crypt area, and crypt branching were measured following whole crypt microdissection. Apoptosis was measured by immunohistochemistry for neo-cytokeratin 18 on fixed tissue sections. Serum levels of C-reactive protein and cytokines were assayed in combination with quantification of mucosal proinflammatory gene expression by real-time RT-PCR.

RESULTS

Twenty-six morbidly obese patients (mean BMI, 54.4 kg/m(2)) had significantly increased mitosis, crypt area, and crypt branching (all P < 0.01) compared with 21 age- and sex-matched normal weight individuals (mean BMI, 22.5 kg/m(2)). Morbidly obese patients underwent a mean excess weight loss of 41.7% at a mean of 26 weeks after RYGB. Surprisingly, this was associated with a further increase in mitosis and decreased apoptosis of epithelial cells. At the same time, lower levels of serum C-reactive protein and interleukin-6 following RYGB were accompanied by a reduction in mucosal IL-6 protein content but elevated mucosal expression of other proinflammatory genes such as cyclooxygenase-1 and cyclooxygenase-2.

CONCLUSIONS

Mucosal biomarkers, accepted as indicators of future colorectal cancer risk, are increased in morbidly obese patients compared with normal weight controls. The hyperproliferative state that exists 6 months after RYGB may have important implications for long-term colorectal cancer risk in bariatric surgery patients.

Effect of orlistat on fecal fat, fecal biliary acids, and colonic cell proliferation in obese subjects

BACKGROUND & AIMS

Orlistat is a weight management agent that selectively inhibits gastrointestinal lipase activity. Because of orlistat's mode of action, increased fecal fat is presented to the colonic mucosa, and fecal bile acid and free fatty acid composition may be altered during treatment. Our aim was to assess the effect of treatment of obese subjects with orlistat 120 mg 3 times a day for 6 weeks on fecal lipid and bile acid parameters and colonic mucosal cell proliferation.

METHODS

Twenty-four obese (body mass index, 30-40 kg/m2) but otherwise healthy male and female subjects were enrolled in a single-center, randomized, double-blind, placebo-controlled, parallel-group study. Participants were hospitalized during days 1-3 and 33-42 of treatment and were treated as outpatients for the remaining days.

RESULTS

Treatment with orlistat for 6 weeks resulted in significantly greater increases in fecal weight, total fecal fat, and fecal free fatty acids than placebo. Total fecal bile acid amounts decreased slightly with orlistat, and increased significantly with placebo treatment (P < .05 between-group difference). Orlistat did not alter colonic cell proliferation as assessed by the 3 proliferative indices (5-bromo-2-deoxyuridine, whole crypt mitotic count, and proliferating cell nuclear antigen).

CONCLUSIONS

Biochemical changes in fecal composition related to the pharmacodynamic mode of action of orlistat are not accompanied by altered colonic cell proliferation, a putative biomarker of colon cancer risk.

Epidemiology and prevention of colorectal cancer

CRC, the second-leading cause of cancer death in the United States, is a highly preventable disease. Ironically, available and effective screening technologies are not consistently applied, even as new ones are developed. This discordance between preventive opportunity and practice conveys a sobering message regarding nontechnologic issues that must be addressed if the promise of CRC prevention is to be realized. Our response to this message will determine the public health impact of cancer prevention. In the 1980s, cancer chemoprevention was regarded as scientific speculation. Within the last decade, however, cancer has been recognized as a late, nonobligate stage of carcinogenesis, a chronic process that provides time and targets for preventive intervention. Further advances are emerging out of rigorous clinical testing, which remains the limiting factor in transforming ingenious concepts into useful tools for the prevention of CRC. The challenges and rewards of participation in chemoprevention research--both as patients and health care providers-have never been greater.

Surgery for obesity

As were most types of gastrointestinal surgery, antiobesity surgery was dominated by the development of laparoscopic techniques during the last decade. The feasibility of performing any primary antiobesity operation safely laparoscopically was convincingly demonstrated during the last 2 years. This represents a significant continued improvement in the perioperative safety of "bariatric" surgery. However, antiobesity surgery entails very much more than technique. Unfortunately, little progress has been made in optimizing patient selection, improving follow-up, and devising strategies for reoperative antiobesity surgery. The latest publications in the field are mainly confirmatory, demonstrating durable medically significant weight loss resulting in comorbidity reduction with increased life expectancy. The most interesting contribution of this surgery is provision of "experimental models" using gastrointestinal physiology to study the pathophysiology of obesity and undernutrition by guaranteeing substantial weight loss maintained long-term. It is unfortunate that surgery for obesity is seriously underutilized.

Nutritional strategies in the prevention of colorectal cancer

A variety of dietary factors have been implicated as agents that can modulate the development of malignancies of the gastrointestinal tract, particularly colorectal cancer. The effects of fat, red meat, fruits, vegetables, and alcohol on colorectal carcinogenesis have been examined extensively and appear to play substantial roles. Although fiber may play a protective role, recent studies raise the question of whether the protection is conveyed by other components in fiber-laden foods. Folate, selenium, calcium, and omega-3 fatty acids have emerged as factors more recently but may be equally important agents in nutritional chemoprevention, whereas the role of antioxidant vitamins is less certain. Until more firm data are available, the dietary recommendations provided by the American Cancer Society and the National Cancer Institute are appropriate for use in counseling patients on this issue.

Dietary and chemopreventive strategies

Dietary and chemopreventive strategies may be used to stem the development of human cancer. This emerging field has increasing potential for influencing cancer incidence rates in defined high-risk groups and the general population. Colorectal cancer in particular, although the fourth most common cancer in the world, due to its temporal nature is amenable to both dietary and chemopreventive strategies. This chapter does not attempt to be all-embracing, but to serve its purpose will concentrate on major natural components of the diet and chemical additions that may be added to it, i.e. non-steroidal anti-inflammatory drugs, which by a common mechanism may reduce risk and recurrence of colorectal cancer.

Mechanisms of the intestinal effects of dietary fats and milk products on colon carcinogenesis

Dietary fat may promote colon cancer by increasing fatty acids (FA) and secondary bile acids (BA) in the colonic lumen. These cytotoxic surfactants can damage colonic epithelial cells and thus induce a compensatory hyperproliferation of crypt cells. Our studies show that the hyperproliferative effect of type and amount of dietary fat is not simply due to changes in colonic FA and BA. This indicates that an additional, at present unknown, cytotoxic factor is involved. The hyperproliferative effect of dietary fat is inversely related to the amount of calcium in the diet. In rat and man, dietary calcium precipitates colonic cytotoxic surfactants and thus inhibits luminal cytotoxicity. These inhibitory effects on metabolic risk factors suggest a preventive effect of dietary calcium on colon carcinogenesis.

Effects of acarbose on fecal nutrients, colonic pH, and short-chain fatty acids and rectal proliferative indices

Acarbose, an alpha-glycosidase inhibitor, treats diabetes mellitus by delaying the digestion and intestinal absorption of dietary carbohydrates. In effective doses, acarbose induces some passage of carbohydrates into the colon. The effect of such chronic carbohydrate transfer on colonic structure and function is unknown. We studied the effects of 1 year of acarbose administration in diabetes mellitus on fecal energy, protein, and fat, including short-chain fatty acids (SCFA) output, fecal pH, and several metabolizing bacterial species. Changes in colonic histology and epithelial cell proliferation were investigated in rectal biopsies. Fecal macronutrient output was unaffected by acarbose, but pH decreased and total SCFA, butyrate, and acetate output were markedly greater. Breath hydrogen output increased after acarbose, but digoxin-metabolizing bacteria and diacylglycerol (DAG) production were unaltered. Compared with the control, acarbose did not induce hyperplasia or change rectal proliferation. However, total fecal SCFA and butyrate output correlated inversely with proliferation in the rectal upper crypt-a biomarker of risk for colonic neoplasia. In conclusion, long-term acarbose administration does not adversely affect colonic function or fecal nutrient output. If increased fecal SCFA and butyrate reduces upper-crypt proliferation, then acarbose may reduce the risk of colonic neoplasia.

Nutrition chemoprevention of gastrointestinal cancers: a critical review

Various strategies utilizing specific dietary factors have been investigated for their ability to modulate the development of several cancers of the gastrointestinal tract. The effects of fat, red meat, fiber, fruits and vegetables, and alcohol on colorectal carcinogenesis have been reasonably well defined. Folate, selenium, and omega-3 fatty acids are rapidly emerging as important agents in nutrition chemoprevention, while the role of antioxidant vitamins and calcium is less certain. Although recent intervention studies from China have suggested a protective role of certain vitamins and minerals for esophageal and gastric cancers, further data from prospective randomized intervention studies are needed. Until more firm data are available, the dietary recommendations provided by the American Cancer Society and the National Cancer Institute are appropriate guidelines.

Calcium and vitamin D: possible protective agents against colorectal cancer?

Nutritional factors are important determinants of colorectal cancer risk. Diets high in fat and/or low in fibre are especially recognised to increase risk. Dietary calcium and vitamin D have been suggested to be protective against colorectal cancer. With respect to calcium, its possible effect is thought to be mediated at least in part through intraluminal precipitation of hydrophobic, cytotoxic substances, in particular fatty and bile acids, which can promote colorectal cancer development. Data from studies in vitro and in animals support a protective effect of calcium, but studies in humans, both epidemiological and interventional, have given inconclusive results. With respect to vitamin D, data from only a small number of studies are available. Results suggest a protective effect by inhibition of cell proliferation, mediated through specific receptors. It is concluded that there are currently insufficient reasons to supplement subjects at increased colon cancer risk with calcium or vitamin D, especially when dietary intake of these substances is in agreement with general guidelines.