AniView Supports Infant Nutrition & Lipid Metabolism Research: Digestive and absorptive properties of human milk fat substitute evaluated by in vitro and in vivo models

New progress has been made in the development and evaluation of human milk fat substitutes (HMFS).

Professor Zeyuan Deng and Associate Professor Yong Sun from the College of Food Science, Nanchang University, published their findings in “Food Chemistry”  (IF = 8.5, Q1 top journal).

This study provides new insights into the digestion dynamics and nutritional evaluation of HMFS through near-infrared fluorescence imaging, offering theoretical support and translational strategies for the development of next-generation infant formula lipids.

Human milk fat (HMF) is characterized by the presence of ≥70% palmitic acid esterified at the sn-2 position of triglycerides rather than the sn-1/3 positions, which significantly improves the absorption efficiency of fatty acids and calcium in infants. Human milk contains abundant structured lipids such as OPO (1-oleoyl-2-palmitoyl-3-oleoyl glycerol) and OPL (1-oleoyl-2-palmitoyl-3-linoleoyl glycerol). In contrast, palmitic acid in conventional vegetable oils and bovine milk fat is randomly distributed, potentially causing reduced fat absorption and an increased risk of constipation in infants. Although commercial structured lipids such as Betapol® enrich OPO through enzymatic modification, they still cannot fully reproduce the structural diversity of human milk triglycerides, particularly the highly abundant OPL and LPL species found in Chinese maternal milk.

Human milk fat substitutes (HMFS) aim to mimic the composition and structure of human milk lipids, with optimization of sn-2 palmitic acid content as a key strategy. Previous studies have shown that HMFS synthesized enzymatically from fish oils or plant oils, such as golden pomfret oil and high-oleic sunflower oil, can achieve >90% similarity in total fatty acid composition and >80% similarity in sn-2 fatty acids and triglyceride profiles compared with human milk fat. However, existing studies have mainly focused on compositional simulation and process optimization, while systematic evaluation of HMFS digestion and absorption performance remains limited. Human milk lipids undergo sequential hydrolysis initiated by gastric lipase, followed by pancreatic lipase-mediated generation of sn-2 monoacylglycerols and free fatty acids, a process distinct from conventional plant-oil-based formulas. The lack of knowledge regarding in vitro digestion kinetics and in vivo metabolic trajectories of HMFS has limited its clinical translation potential.

To address this knowledge gap, this study established a multi-level evaluation system. An in vitro infant digestion model was applied to simulate gastrointestinal conditions and quantitatively analyze HMFS lipolysis efficiency (FFA release) and emulsion stability (particle size and zeta potential changes). Acute metabolic experiments in Sprague–Dawley rats were conducted to monitor serum lipid profiles and time-dependent changes in key fatty acids, including C16:0, C18:1, and C18:2. Furthermore, near-infrared fluorescence imaging using DIR dye labeling was introduced for the first time to visualize real-time gastrointestinal emptying kinetics in vivo. Compared with conventional vegetable oil (BVO) and BVO+OPO formulations, this approach aimed to validate the advantages of HMFS in digestion efficiency, nutritional absorption of unsaturated fatty acids, and metabolic benefits.

Experiments using AniView

To directly compare gastrointestinal digestion and emptying dynamics of human milk fat substitutes (HMFS), conventional vegetable oil (BVO), and their emulsified formulations in SD rat models, fluorescence imaging was performed using the AniView multimodal animal imaging system developed by Guangzhou Biolight Biotechnology Following oral administration of different oil emulsions, fluorescence signals were monitored at multiple time points. The results showed that within 1–9 hours after administration, the overall fluorescence intensity of the HMFS and emulsified HMFSE groups was significantly lower than that of the BVO and BVOE groups (p < 0.05), indicating faster gastrointestinal clearance of HMFS. Regional gastrointestinal imaging further demonstrated that fluorescence intensity in the HMFS group was lower than that in the BVO group as early as 1 hour after administration, with a reduction of 38.2%–45.6%. This difference increased over time, and by 6 hours, obvious fluorescence retention remained in the BVO group, whereas the HMFS group was almost completely cleared.

Notably, the emulsification process synergistically improved lipid absorption efficiency. The emptying rates of BVOE and HMFSE were increased by 17.3% and 22.1%, respectively, compared with their non-emulsified counterparts, demonstrating that milk components in infant formulas (such as whey protein and casein) generally promote lipid digestion. These findings directly verified the efficient in vivo digestion characteristics of HMFS through visualization approaches, establishing a mechanistic correlation with its higher in vitro lipolysis rate (78.5% vs. 40.0% for BVO) and enhanced serum unsaturated fatty acid absorption (C18:1 AUC: 2.181 vs. 1.878 for BVO).

DOI: org/10.1016/j.foodchem.2025.145409