Effects of interesterified lipid design on the short/medium chain fatty acid hydrolysis rate and extent (in vitro).

Short/medium chain fatty acids have well known health effects such as gut immune regulation and ketogenesis. The ability to realise these health effects is potentially limited by their rapid gastro-intestinal lipolysis. It was proposed that synthesising novel interesterified lipids via an interesterification reaction to generate a combination of short/medium and long chain fatty acids would modulate their gastrointestinal digestion. Using in vitro gastric and gastro-intestinal digestion models, the effect of the fatty acid chain length and interesterification on the rate and extent of lipolysis was analysed. Overall, "pure" (consisting of a single fatty acid) lipids of <= C8 underwent rapid lipolysis releasing three fatty acids after intestinal hydrolysis while lipids of >= C10 released two fatty acids after intestinal hydrolysis. The most interesting observation is that the extent of gastric lipolysis of C4 fatty acids was much lower when they were interesterified with longer chain fatty acids compared to that with the pure C4 triglyceride. Tributyrin underwent similar to 60% lipolysis by gastric lipase as indicated by a decrease in total fatty acid release during SIF lipolysis after pre-exposure to rabbit gastric lipase (RGL) in SGF. In comparison, the C4-C8 interesterified lipid exhibited only a 18.1% decrease, and the C4-C18:1 interesterified lipid a 6.1% decrease in total fatty acid release in SGF-SIF. These results suggest that interesterification modulates the digestion of butyric acid from within the stomach to later in the intestine. This study reveals that the design of interesterified lipids alters the timing, but not the extent of short chain fatty acid delivery in the gastrointestinal tract. Such understanding has likely benefits for designing novel interesterified lipids which may have unique applications in various dietary and therapeutic modalities.