Evaluation of absorption kinetics and bioavailability of palmitic acid and 2-palmitoylglycerol, a metabolite of interesterified fat, radiolabeled with 99m-technetium.

Interesterified fat (IF) has replaced partially hydrogenated fats because it does not generate trans isomers, but it may affect lipid metabolism due to structural changes in triacylglycerols (TAGs). Since chemical interesterification alters TAG configuration and influences digestion and absorption, methodological approaches capable of tracking lipid metabolites are needed. In this study, we investigated the absorption kinetics and systemic distribution of IF metabolites using a radiolabeling strategy. Eight-week-old Swiss mice received via gavage: PA group-3.7 MBq of 99mTc-palmitic acid (99mTc-PA); 2-PG group-3.7 MBq of 99mTc-2-palmitoylglycerol (99mTc-2PG); and TC group-3.7 MBq of free technetium (99mTcO4-). Scintigraphic imaging was performed in vivo at 1-, 3-, and 6-h post-administration to verify complex stability, while ex vivo imaging assessed absorption kinetics and biodistribution. The data indicated that radiolabeling was stable and efficient. Compared with PA, 2-PG exhibited shorter digestion time, faster intestinal transit until fecal excretion, and more efficient absorption. Once absorbed, 2-PG reached the systemic circulation and was preferentially detected in organs such as mesenteric lymph nodes, spleen, heart, liver, kidneys, and the brain, where it remained detectable throughout the experimental period. Beyond these findings, the use of technetium radiolabeling represents a methodological innovation, providing a powerful tool to track the metabolic fate of lipid molecules. This approach adds a new dimension to the study of lipid bioavailability and supports future investigations into the biological relevance of sn-2 monoacylglycerols.