Overview of Breath Testing in Clinical Practice in North America

Human breath is an easily, noninvasively obtained substance. It offers insight into metabolism and is used to diagnose disaccharide malabsorption, infection, small bowel bacterial over growth, and transit times. Herein, we discuss the readily available clinical breath tests, how they function, how they are administered and interpreted and some pitfalls in their use.

New insights into in vivo gastroduodenal digestion of oil-in-water emulsions: gastric stability and in vitro digestion modeling

In this paper, effect of emulsion stability on gastroduodenal emptying/secretion was reviewed and differentiated. Moreover, novel perspectives on physiology of gastric lumen, duodenum, and gall bladder were achieved using mathematical models, being useful for designing artificial digestive systems. In this regard, numerical data for dynamic gastric emptying/secretion were offered for gastric-stable and gastric-unstable emulsion intakes. It was shown that alterations in human gastric and duodenal volume follow, respectively, linear and sinusoidal curves, with high correlation coefficients (r² > 0.93). For both emulsions, about 30-40 mL ingesta discharged rapidly from stomach upon ingestion; However, further gastric emptying was regulated for the rest of digestion period, so that 0.1 mL/min oil was passing through duodenum. Intragastric evacuation of both emulsions started with a lag phase during which stomach stored secretions incrementally by slow gastric discharge. Lag phase ended with fat layering, when emptying considerably enhanced. This reduction was gradual for stable emulsion while unstable emulsion experienced a rapid emptying before slow declining trend. Along with initial gastric emptying, 87% of gallbladder content discharged into duodenum, prolonged up to the gradual reduction phase of stomach. Supplementary investigations are needed to quantify gastroduodenal secretions, particularly pepsin and pancreas in response to emulsion ingesta.

Development of Analytical Methods and Nutritional Studies Using Synthetic Fatty Acids and Triacylglycerols

The metabolism of fatty acids or triacylglycerol (TAG) is affected by their molecular structures. Several methods to separate and quantify TAG isomers in natural fats and oils were developed. For instance, an analytical method of TAG molecular species using a gas chromatograph-flame ionization detector and the analytical method to separate and quantify TAG positional isomers and enantiomers using a high performance liquid chromatograph-mass spectrometer were established. Furthermore, using these analytical methods, the relationship between molecular structure and metabolism of fatty acid and TAG were investigated. Using the CO2 breath test in ddY mice revealed that saturated fatty acids such as palmitic acid bound to the sn-2 (β) position of TAG were highly catabolized in the presence of calcium, whereas saturated fatty acids bound to the sn-1, 3 (α) position of TAG were not well catabolized. Recently, the distribution of dietary fatty acids in the body were visualized by combining a stable isotope labeling technique with imaging mass spectrometry, which revealed that the administered arachidonic and docosahexaenoic acid accumulated as phospholipid in the mouse brain. The methods developed can assess food quality and create new functional foods.

Effect of Calcium Treatment on Catabolic Rates of 13C-Labeled Fatty Acids Bound to the α and β Positions of Triacylglycerol

The absorption efficacies and catabolic rates of fatty acids are affected by their binding position on triacylglycerol (TAG). However, the kind of effect calcium treatment has on the catabolism of fatty acids is unclear. In this study, the catabolic rates of ¹³C-labeled palmitic acid, oleic acid, and linoleic acid bound to sn-1, 3 (α) and sn-2 (β) position of TAG in the presence of calcium were compared using isotope ratio mass spectrometry. The catabolic rates of ¹³C-labeled fatty acids were evaluated using the ratio of ¹³C to ¹²C in the carbon dioxide expired by mice. The catabolic rate of palmitic acid bound to the α position was significantly lower than that of palmitic acid bound to the β position of TAG. The rates of ¹³CO₂ formation from palmitic acid at the β position remained higher for a long time. In contrast, oleic and linoleic acids at the α position were as well catabolized as those at the β position. These results indicate that in the presence of calcium, the saturated fatty acid bound to the β position is highly catabolized, whereas that bound to the α position is not well catabolized. Saturated fatty acid at the α position is hydrolyzed by pancreatic lipase to promptly form insoluble complexes with calcium, which are excreted from the body, and thereby reducing the catabolic rate of these fatty acids.