Effect of triglyceride structure on fecal excretion of 13C-labeled triglycerides.
OBJECTIVE
The aim of this work was to determine the effects of specific changes in the structure of (13)C-labeled triglyceride (TG*) on its fecal excretion relative to total stool fat excretion determined simultaneously in patients with reduced exocrine pancreatic function.


METHODS
A series of 47 studies were conducted in 26 young cystic fibrosis (CF) patients and 11 adult patients with chronic pancreatitis over a five year period. Each test consisted of ingesting a single high fat test meal containing both (13)C-labeled triglyceride (TG*) and dysprosium chloride (DyCl(3)) a nonabsorbable marker of intestinal transit; in most studies the food colorant brilliant blue (FD&C blue #1) was administered along with the DyCl(3). The TG*s tested were: P*P*P* = TRIPALMITIN-1,1,1-(13)C(3); SO*S = 2-OCTANOYL-1,3-DISTEARIN-2-octanoyl-1,2-(13)C(2); and P*LP* = 2-LAURYL-1,3-DIPALMITIN-dipalmitoyl-1,1,2,2-(13)C(4). Ingestion of the test meal was followed by collection of individual stools for at least 72 hours. Stools were analyzed for (13)C-Excess ((13)C*), total fat, and Dy.


RESULTS
Excretion of P*LP* showed a high degree of linear correlation with stool fat (r(2) = 0.924) over a wide-range of fecal fat values. Excretion of SO*S was also significantly correlated with stool fat, but its excretion was less than 10% at all levels of steatorrhea and the slope of the regression line relating TG* excretion to stool fat was some four to five times smaller than observed for P*LP*. Fecal excretion of P*P*P* was highly correlated with stool fat (r(2) = 0.941) in patients with moderate steatorrhea (<25 g fat/24 hours) and the slope of the regression line (3.20) was considerably greater than for P*LP*. Only results from those studies in which stool collections were complete (Dy excretion >90%) were utilized in the statistical comparisons (36 of 47 studies).


CONCLUSIONS
The observed highly significant linear correlation between P*LP* and stool fat over the entire range of steatorrhea suggests that P*LP* excretion may be a suitable surrogate for fecal fat in patients with reduced exocrine pancreatic function. Because fecal excretion of TG* administered as described can be accurately determined by sampling only two visually marked stools, development of a noninvasive test to replace the current 72-hour stool fat test using this approach is possible. Use of other engineered TG*s and/or labeled fatty acids, may provide a method for non-invasive in vivo assessment of the specific defect(s) leading to steatorrhea in other patient groups.
Schuette
Sally A
SA
BioChemAnalysis Corp, 2201 W. Campbell Park Drive, Chicago, IL 60612-3501, USA.
Janghorbani
Morteza
M
Cohen
Mitchell B
MB
Krug
Susan
S
Schindler
Terri
T
Wagner
David A
DA
DiMagno
Eugene P
EP
D000293:Adolescent; D000328:Adult; D000368:Aged; D002247:Carbon Isotopes / Q000378:metabolism; D002648:Child; D002675:Child, Preschool; D002908:Chronic Disease; D003550:Cystic Fibrosis / Q000378:metabolism; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism; D005243:Feces / Q000737:chemistry*; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009820:Ohio; D010195:Pancreatitis / Q000378:metabolism; D012720:Severity of Illness Index; D045602:Steatorrhea / Q000378:metabolism; D013997:Time Factors; D014280:Triglycerides / Q000008:administration & dosage / Q000378:metabolism*
D002247:Carbon Isotopes; D004041:Dietary Fats; D014280:Triglycerides