Normal function of pancreatic lipase needs bile salts, free fatty acids (hydrolysed from dietary triacylglycerol by lingual and gastric lipase) and pH 6.5-8.0 in the duodenum. Cystic fibrosis liver disease (CFLD) lead to cholestasis and decreased intraduodenal bile salt concentration that results in the reduction in the solubilisation and absorption of the products of fat digestion along with depression the activity of pancreatic lipase. The ¹³C-mixed triacylglycerol (MTG) breath test, a non-invasive, is used to indirect determination of intraluminal lipolysis, in which ¹³C-octanoate is released after digestion of ¹³C-MTG whose rapid absorption and oxidation is independent of bile salts and liver disease.

The current study is aimed at evaluating the effect of CFLD on triacylglycerol lipolysis using the ¹³C-MTG breath test. The authors included 40 children with CF who underwent a ¹³C-MTG breath test after an overnight fast. 10-20 mg/kg ¹³C-MTG were administered with a standard breakfast and the childs normal pancreatic enzyme replacement therapy. Breath samples were obtained before and every 30 minutes after ingestion for 6 hours. ¹³C enrichment of breath CO₂ was analyzed by isotope ratio mass spectrometry, and the cumulative percent dose recovered at 6 hours (cPDR) was also measured. CFLD was typified by the presence of hepatic parenchymal abnormalities on ultrasound (patchy echogenicity of the parenchyma or a scalloped liver edge), or clinical hepatosplenomegaly.

          The results suggested that among the total enrolled children, 24 children had CFLD. Lipase dose in CFLD and non-CFLD children were 57167 ± 31151 IU and 49714 ± 35664 IU, respectively. cPDR at 6h was 22.7 ± 8.2% in CFLD and 21.7 ± 11.7% in non-CFLD children.

          Thus, the study concluded that results of ¹³C-MTG breath test evaluation suggest that intestinal lipolysis is not decreased in children with CFLD. These findings substantiates the utility of tests as an indirect measure of fat digestion, which remains unaffected by insufficient bile salts or impaired fatty acid oxidation.

 Source: Ling S, Amarri S, Slater C, Hollman A, Preston T, Weaver L. Does liver disease affect fat digestion, as measured by the 13C-MTG breath test?. Journal of Pediatric Gastroenterology & Nutrition. May1999;28(5):p591. Available at : https://journals.lww.com/jpgn/Fulltext/1999/05000/Does_liver_disease_affect_fat_digestion,_as.212.aspx#:~:text=Conclusion%20%2D%20Intestinal%20lipolysis%20is%20not,or%20impaired%20fatty%20acid%20oxidation.