familial adenomatous polyposis   account for 1% of colorectal cancers , and provides a model of apc inactivation as an early genetic event for the approximately 80%85% of cancers that develop from sporadic polyps .
colorectal cancers arising in patients with familial adenomatous polyposis can be largely prevented by polyp surveillance and prophylactic colectomy .
total proctocolectomy with construction of a conventional ileostomy or ileoanal anastomosis with preparation of an ileal pouch , has various effects on the function of the terminal ileum and the intestinal bacterial flora .
this may deteriorate cholesterol metabolism , as absorption of cholesterol in duodenum and jejunum requires micellar solubilization with bile acids , fatty acids , monoglycerides , and phospholipids .
hypothetically , ileal - pouch - anal anastomosis and ileostomy patients might differ with regard to the presence of various fatty acids in feces and their relationship to other reflections of lipoprotein metabolism , but we found no previous study focusing upon this issue .
dietary fatty acids are incorporated into blood and tissues , and the fatty acid composition in these tissues are often used as biomarkers of fat intake .
furthermore , the fecal amount and composition of fatty acids reflect fat ingestion , intestinal fatty acid absorption , and the activity of colonic bacteria .
although some of the discrepancies between studies may be due to the use of different methods to analyze fatty acids , differences in diet , or the fact that assessments have been performed in different body compartments , modifications in the metabolism of fatty acids have been suggested in cancer patients [ 5 , 6 ] .
it is not clear at what steps in the multistage carcinogenesis process a possible distorted fatty acid metabolism occurs .
notably , if such alterations occur in the development of carcinogenesis , this may affect the biological functions of essential fatty acids and their derivates .
very little is known about fatty acid metabolism in familial adenomatous polyposis , although chemoprevention affecting the fatty acid derivates and the cyclooxygenase enzymes is often administered to familial adenomatous polyposis patients .
deregulation of the cyclooxygenase-2 pathway appears to affect tumorigenesis via a number of distinct mechanisms : promoting tumour maintenance and progression , encouraging metastatic spread , and perhaps even participating in tumour initiation .
cyclooxygenase-1 and -2 are the rate limiting enzymes in the synthesis of prostaglandins and thromboxanes .
arachidonic acid is the main substrate for these enzymes , leading to the synthesis of prostaglandins which have growth promoting effects . substituting arachidonic acid with omega-3 fatty acids has been shown to lead to the production of less potent prostaglandins .
since cyclooxygenase-2 is a fatty acid metabolising enzyme , the relationships between cyclooxygenase-2 and fatty acid composition of different tissues is of interest .
colectomized familial adenomatous polyposis patients had a deviant fatty acid profile with high levels of arachidonic acid and docosahexaenoic acid and low levels of linoleic acid and alpha - linolenic acid in serum phospholipids , which is in accordance with studies in patients with other types of cancers [ 5 , 1013 ] .
in a previous familial adenomatous polyposis study , comparable treatment effects of a cyclooxygenase-2 inhibitor were observed on the fatty acid composition in serum phospholipids and duodenal lesions , presumably and most importantly the nonbeneficial effects involving essential fatty acids .  
the results describe the content of fatty acids in feces , and relate this to the proportions of fatty acids and levels of cyclooxygenase mrna expression in duodenal biopsies , diet , and levels of serum lipoproteins . because the effects of ileostomy construction may differ from that of ileal - pouch - anal anastomosis because of scarcity of the bacterial flora and different surface area of the terminal ileum , we did separate analyses for these two groups .
previous familial adenomatous polyposis studies have focused upon faecal sterols and bile acids [ 1517 ] , but none has to the best of our knowledge analysed the content of fatty acids in feces , including very long chained fatty acids .
data from the present study are taken from a randomized double - blind placebo - controlled intervention study with a cyclooxygenase-2 inhibitor [ 12 , 14 , 18 ] .
the main aim was to compare the effect of rofecoxib treatment on duodenal lesions ( data in preparation ) .
the present study comprises data from baseline for only the patients operated with ileal - pouch - anal anastomosis and ileostomy ( 77% of total study group ) .
all of them had been colectomized , and duodenal lesions had been verified by endoscopy and histology .
rikshospitalet university hospital is a highly specialized university hospital with national responsibilities in the area of complicated treatments , such as follow - ups on the norwegian familial adenomatous polyposis patients .
inclusion criteria were verified familial adenomatous polyposis , colectomy , 1870 years of age , and documented duodenal lesions graded as spigelman i , ii , or iii and the largest adenoma10  mm .
exclusion criteria were indications for surgical treatment , suspected or documented intestinal obstruction or stenosis , patients unwilling or unable to adhere to protocol , known cardiac failure requiring medical treatment , and pregnancy .
as for the adenomas sampled , they were all assessed histologically as mild / moderate dysplasia , all below 10  mm and all flat , located in the descending part of the duodenum .
samples of feces were transferred to tubes and mixed to make a homogeneous mass of which 100200  ul were used for lipid extraction by adding 50  ul butanol , 100  l h2o , 1  ml methanol , and 1  ml chloroform .
after 10  min under n2 , the mixture was filtered and the filter washed   with 1  ml chloroform   + 1  ml chloroform / methanol ( 2  :  1 ) + 0.8  ml 0.73% nacl . after mixing for 15  s ,
the tubes were centrifuged for 30  min at 1000  g. the upper phase was discarded and the lower phase transferred to new tubes and evaporated under n2 at 65c using a heat block .
then 0.4  ml 0.5  n naoh in methanol was added and the solution kept for 7  min at 100c under nitrogen . after cooling to room temperature , 0.5  ml 12%
bf3 was added and the solution kept for 10  min at 100c under nitrogen . after cooling to room temperature , 1  ml heptan was added under nitrogen , and mixing for 30  s , 1 ml of saturated nacl solution was added . after mixing ,
the solution was centrifuged for 10  min at 1000  g , and the upper phase transferred to new tubes .
finally , the heptan was evaporated and 300  l hexan added before continuing with the gas chromatography procedure referred to earlier .
dietary intake was assessed by a validated food frequency questionnaire , designed to cover as much of the total habitual diet as possible .
questions were related to habitual frequency of consumption and the amount of foods eaten during the last year .
they were asked to identify their habitual choices of edible fats by pointing at specially prepared pictures , in order to increase the validity of the estimate of dietary fat .
each biopsy was put into a tube containing 600  l trizol and immediately mixed on a mixermill ( retsch gmbh , germany ) .
gene expression analyses were carried out on a 7900  ht real - time pcr machine from applied biosystems .
based on the results from running a housekeeping gene test (  taqman human endogenous control plate ,  applied biosystems ) with rna from isolated human leucocytes ( data not shown ) .
the primers and probes were initially designed as three assays per gene and validated for efficiency and specificity .
the primers and probes for the cox-1 assay were : forward primer : 5-cttccaggagctcgtagga-3 , probe : 5-agaaggagatggcagcagagttggag-3 , and reverse primer : 5-acgcatcaatgtctccatacaat-3. cox-2 forward primer : 5-tggaacatggaattacccagt-3 , probe : 5-tgttgaatcattcaccaggcaaattgct-3 ,   and reverse primer : 5-tcctaccaccagcaaccct-3. gus forward primer : 5-gaaaatatgtggttggagagctcatt-3 , probe : 5-ccagcactctcgtcggtgactgttca-3 ,   and reverse primer : 5-ccgagtgaagatccccttttta-3.
tbp forward primer : 5-ctggaaaagttgtattaacaggtgc-3 , probe : 5-agcagaaatttatgaagcatttgaaaacatctaccctatt-3 ,   and reverse primer : 5-cattacgtcgtcttcctgaatc-3.   taqman universal pcr master mix ( applied biosystems ) was added as reaction mix .
the reaction conditions were initiated by a step of 2  min . at 50c and 10  min . at 95c , followed by 40 cycles of denaturation at 95c for 15 sec . and annealing at 60c for 1  min .
a combination of cdna from several samples were made and diluted in order to make a dilution curve that was included on each plate .
the average of the three values for each gene was divided by the average of the corresponding tbp values , generating a normalized value of the gene expression which is a unit less value used to compare the relative amount of mrna for each gene in the different samples .
patients were informed by a physician , and in addition thoroughly written information was given to all patients .
the protocol was explained to the subjects that had to give their consent before inclusion .
was approved by the norwegian health authorities and the regional committee of medical ethics 20/06/2002 ( reference : s-02127 ) .
nonparametrical statistical methods were chosen , as some of the variables were skewed and the number of observations limited .
age and fecal content of palmitolic acid , linoleic acid , and arachidonic acid differed between the ileostomy and the ileal - pouch - anal anastomosis patients ( table 1 ) .
the content of linoleic acid in feces correlated negatively to the proportion of eicosaenoic acid in duodenal biopsies ( r = 0.6 , p < .05 ) .
the content of arachidonic acid in feces was correlated negatively to the proportions of eicosapentaenoic acid ( r = 0.7 , p = .02 ) and docosahexaenoic acid ( r = 0.7 , p = .008 ) in duodenal biopsies .
total cholesterol were negatively correlated to the content of palmitic acid ( r = 0.7 , p = .03 ) , palmitoleic acid ( r = 0.7 , p = .02 ) , stearic acid ( r = 0.7 , p = .02 ) , oleic acid ( r = 0.7 , p = .02 ) , linoleic acid ( r = 0.8 , p = .002 ) , and monounsaturated fatty acids ( r = 0.7 , p = .02 ) in feces .
the levels of triglycerides was negatively correlated to the content of linoleic acid ( r = 0.8 , p = .003 ) and eicosaenoic acid ( r = 0.7 , p = .03 ) in feces .
no significant correlations were found between the content of different fatty acids in feces and the fatty acid dietary intake ( data not shown ) .   with the exception of the palmitoleic acid / palmitic acid ratio and levels of cyclooxygenase-2 expression in duodenal biopsies ( r = 0.8 , p = .003 ) , no relationships were found between fatty acids in feces and the levels of cyclooxygenase mrna expression ( figure 1 ) .
significant correlations were found between the content of oleic acid in feces and the proportion of myristic acid ( r = 0.8 , p < .001 ) , oleic acid ( r = 0.5 , p <
.05 ) , and eicosaenoic acid ( r = 0.5 , p = .03 ) in duodenal biopsies .
moreover , the content of linoleic acid in feces correlated significantly to the proportion of myristic acid ( r = 0.8 , p < .001 ) in duodenal biopsies , whereas the content of alpha - linolenic acid in feces correlated inversely to eicosaenoic acid ( r = 0.6 , p <
the content of palmitic acid in feces was positively correlated to levels of ldl - cholesterol ( r = 0.05 , p = .05 ) .
no significant correlations were found between the content of different fatty acids in feces and the levels of cyclooxygenase mrna expression in duodenal biopsies ( data not shown ) .   several different fatty acids in feces correlated positively to dietary intake of fatty acids , most predominantly monounsaturated fatty acids ( table 2 ) .
as expected , we found a difference between ileal - pouch - anal anastomosis and ileostomy patients concerning associations between fecal fatty acid composition and other variables involved in lipoprotein metabolism .
possibly , our results relate to metabolic differences caused by the different intestinal reconstructions , but the data are not suitable to explain the findings .
we found no significant relationships between the levels of cyclooxygenase mrna expression in duodenal biopsies and the content of fatty acids in feces , except for the estimates of the content of delta-9-desaturase ( stearoyl - coa desaturase , scd ) activity , namely the ratio of palmitolic acid / palmitic acid [ 19 , 20 ] in the ileostomy group .
stearoyl - coa desaturase is the central lipogenic enzyme catalyzing in vivo reactions in the synthesis of monounsaturated fatty acids , particularly oleic acid and palmitoleic acid , which are the major monounsaturated fatty acids of membrane phospholipids , triglycerides , wax esters , and cholesteryl esters .
both delta-9-desaurase and cyclooxygenase-2 are ppar alpha regulated , although this possible link is only a speculation .
a study in healthy subjects showed that human fecal water contains components can affect both the cyclooxygenase-2 protein level and enzymatic activity .
one recent study claims that it is possible to detect cyclooxygenase-2 mrna in feces of colorectal cancer patients irrespective of clinical stage .
notably , increased cyclooxygenase-2 expression in duodenal compared with colonic tissues in familial adenomatous polyposis was recently reported .  
the significant negative correlation between content of arachidonic acid in the feces and amounts of omega-3 fatty acids in duodenal biopsies which was found in the ileostomy group is interesting , since substitution of arachidonic acid with omega-3 fatty acids has been shown to lead to the production of less potent prostaglandins .
a previous familial adenomatous polyposis study established a positive correlation between the reduction in tissue prostanoid levels and clinical response , as measured by the reduction in size and number of adenomas , when patients were treated with sulindac .
however , this correlation only became consistently significant when prostanoids were assayed after tissue homogenates were first incubated with arachidonic acid .
we may suspect transformation of linoleic acid   to arachidonic acid in feces , but data are limited as with regard to feces from colectomized familial adenomatous polyposis subjects .
however , the dietary assessment showed that the intake of such foods was normal among these familial adenomatous polyposis patients .  
dietary controlled intervention studies on ileostomy subjects have shown that dietary manipulation with fat and fiber may modify cholesterol absorption and sterol excretion . in the ileostomy group
, levels of total cholesterol were negatively correlated to the content of palmitic acid , palmitolic acid , stearic acid , oleic acid , linoleic acid , and monounsaturated fatty acids ( < 18  c atoms ) in feces , which is interesting since the present levels of total cholesterol are lower than those among a healthy reference group . in the ileal - pouch - anal anastomosis group separately , the content of monounsaturated fatty acid in feces was positively correlated to dietary intake of monounsaturated fatty acids in particular . moreover
, positive correlations were found between the content of oleic acid in feces and the proportion of myristic acid , oleic acid , and eicosaenoic acid in duodenal biopsies .
the precise role of monounsaturated fatty acids synthesis in cell proliferation and programmed cell death remains unknown .
the strong correlation of high levels of monounsaturated fatty acids and neoplastic phenotype may suggest that the regulation of stearoyl - coa desaturase must play a role in cancer development .    
this was an observational study , and not a metabolic balance study that was designed to investigate the metabolism of fatty acids in familial adenomatous polyposis patients .  
although some studies have found that the absorption rate of fatty acids are unaffected by age [ 26 , 27 ] , we can not exclude the possibility that some of the observed differences between the ileal - pouch - anal anastomosis and ileostomy patients might be due to age , rather than type of surgery , since lipoprotein clearance has been shown to be altered by age , and that might affect the relationship between dietary fatty acids and the fatty acid profiles found in tissues .
moreover , no conclusions can be drawn from the present study because this is an observational study .
. however , the study addresses the need to learn more about the dietary and lifestyle habits of this subset of at - risk patients .
the present study includes a number of patients close to the maximum possible number of eligible norwegian familial adenomatous polyposis patients .
we may , however , suspect that the low sample size and use of a food frequency questionnaire , may have weakened any associations between the content of fatty acids in feces and dietary intake .
notably , these data do not contradict that the nutrient intake among these patients should at least meet the recommendations for healthy subjects .
nevertheless , we suggest that these data are compelling enough to suggest that future familial adenomatous polyposis studies should investigate overall fatty acid metabolism , molecular mechanisms relevant to fatty acid metabolism , inflammation , and angiogenesis , in addition to nutrition requirements . in conclusion , we found a difference between ileal - pouch - anal anastomosis and ileostomy patients concerning associations between fecal fatty acid composition and other variables involved in lipoprotein metabolism .
we may suggest that fatty acid content in feces is related to dietary intake , serum lipids , and fatty acid composition in duodenal biopsies , even in colectomized familial adenomatous polyposis patients .
this observational study may represent hypothesis - generating suggestions for future familial adenomatous polyposis studies .
 a few familial adenomatous polyposis studies have focused upon faecal sterols and bile acids but none has analysed the fecal content of fatty acids . 
 we report here findings of an observational study on 29 colectomized familial adenomatous polyposis patients that describe the fecal content of fatty acids , and relate this to the proportions of fatty acids and levels of cyclooxygenase mrna expression in duodenal biopsies , levels of serum lipoproteins , and diet . in the ileostomy group separately ( n = 12 ) , the fecal content of arachidonic acid was correlated negatively to the proportions of eicosapentaenoic acid and docosahexaenoic acid in duodenal biopsies . 
 total serum - cholesterol was negatively correlated to the fecal content of saturates and monounsaturates . 
 the fecal palmitoleic acid / palmitic acid ratio was positively correlated to the levels of cyclooxygease-2 expression in duodenal biopsies.in the ileal - pouch - anal anastomosis group separately ( n = 17 ) , significant correlations were found between the fecal contents of oleic acid , linoleic acid , and alpha - linolenic acid , and the proportions of myristic acid , oleic acid and eicosaenoic acid in duodenal biopsies . 
 dietary monounsaturates were positively correlated to different fecal fatty acids . 
 future studies should focus on molecular mechanisms relevant to fatty acid metabolism , inflammation , and angiogenesis , in addition to nutrition . 
1. Introduction
2. Material and Methods
3. Results
4. Discussion