The supramolecular structure of milk fat influences plasma triacylglycerols and fatty acid profile in the rat

Effect of Gum Acacia on the Intestinal Bioavailability of n-3 Polyunsaturated Fatty Acids in Rats

Lipid emulsification is a technique that is being explored for improving the bioavailability of omega 3 (n-3) long chain (LC) fatty acid (FA). The nature of the emulsifiers can differently impact the lipid bioavailability via a modification of the lipolysis step. Among natural emulsifiers, gum acacia (GA), an indigestible polysaccharide, provides protective encapsulation of n-3 by forming a specifically crown-like shape around lipid drops, which could also impact the digestion step. Despite the interest in lipolysis rate, the impact of GA on lipid bioavailability has never been explored in a complete physiological context. Thus, we followed in a kinetics study the n-3 bioavailability in rat lymph, orally administered DHA-rich oil, formulated based on GA compared to the bulk phase form of the oil. The AUC values were significantly improved by +121% for total TG and by 321% for n-3 PUFA, specifically for EPA (+244%) and for DHA (+345%). Benefits of GA have also been related to the transport of FA in lymph, which was 2 h earlier (Tmax = 4 h), compared to the Tmax (6 h) obtained with the bulk phase oil. All the data showed that GA is one of the most favorable candidates of natural emulsifiers to improve n-3 bioavailability and their rate of absorption for health targets.

Roles of Milk Fat Globule Membrane on Fat Digestion and Infant Nutrition

Milk fats are present as globules emulsified in the aqueous phase of milk and stabilized by a delicate membrane architecture called milk fat globule membrane (MFGM). The unique structure and composition of the MFGM play an important role in fat digestion and the metabolic programming of neonates. The objective of this review is to compare the structure, composition, and physicochemical characteristics of fat globules in human milk, bovine milk, and infant formula. It provides an overview of the fat digestion process and enzymes in healthy infants, and describes the possible roles of the MFGM in association with factors affecting fat digestion. Lastly, the health benefits of the MFGM on infant nutrition and future perspectives are discussed with a focus on brain development, metabolic response, and gut health.

An Infant Formula with Large, Milk Phospholipid-Coated Lipid Droplets Supports Adequate Growth and Is Well-Tolerated in Healthy, Term Asian Infants: A Randomized, Controlled Double-Blind Clinical Trial

Lipids are essential for healthy infant growth and development. The structural complexity of lipids in human milk is not present in infant milk formula (IF). A concept IF was developed mimicking more closely the structure and composition of human milk fat globules. The current study evaluates whether a concept IF with large, milk phospholipid-coated lipid droplets (mode diameter 3 to 5 μm) is equivalent to standard IF with regard to growth adequacy and safety in healthy, term Asian infants. In this randomized, double-blind, controlled trial, infants were randomized after parents decided to introduce formula. Infants received a standard IF with (Control) or without the specific prebiotic mixture scGOS/lcFOS (9:1 ratio; Control w/o prebiotics), or a Concept IF with large, milk phospholipid-coated lipid droplets and the prebiotic mixture. A group of 67 breastfed infants served as a reference. As a priori defined, only those infants who were fully intervention formula-fed ≤28 days of age were included in the equivalence analysis (Control n = 29; Control w/o prebiotics n = 28; Concept n = 35, per-protocol population). Primary outcome was daily weight gain during the first four months of life, with the difference between the Concept and Control as the key comparison of interest. Additionally, adverse events, growth and tolerance parameters were evaluated. Equivalence of daily weight gain was demonstrated between the Concept and Control group after additional correction for ethnicity and birthweight (difference in estimated means of 0.1 g/d, 90%CI [-2.30, 2.47]; equivalence margin +/- 3 g/d). No clinically relevant group differences were observed in secondary growth outcomes, tolerance outcomes or number, severity or relatedness of adverse events. This study corroborates that an infant formula with large, milk phospholipid-coated lipid droplets supports adequate growth and is well tolerated and safe for use in healthy infants.

Triacylglycerol Composition of Butterfat Fractions Determines Its Gastrointestinal Fate and Postprandial Effects: Lipidomic Analysis of Tri-, Di-, and Mono-acylglycerols and Free Fatty Acids

The lipolytic behaviors and postprandial effects of butterfat and its fractions (30L and 30S) procured by dry fractionation at 30 °C were investigated using in vivo digestion. A total of 142 triacylglycerols (TAGs), 64 diacylglycerols (DAGs), 14 monoacylglycerols (MAGs), and 7 free fatty acids (FFAs) in the butterfat fractions and their hydrolysates were identified by combining high-performance liquid chromatography coupled with electrospray ionization-tandem quadrupole time-of-flight mass spectrometry with solid-phase extraction. The first-step hydrolysis from TAGs to sn-1,2 DAGs occurred slower in the high-melting-temperature solid fat (30S) fraction, which is rich in long-chain FAs compared to that of the low-melting-temperature liquid oil (30L) fraction, which is rich in short-chain unsaturated FAs (the hydrolysis rates were 39.22% vs 60.11%, respectively, in the 30 min gastric phase), and these differences were also reflected in the delayed and relatively flat postprandial lipemia levels in rats force-fed with 30S fraction. This study revealed the importance of TAG composition and lipid physical state in regulating digestion and absorption, which is related to nutrition science and the dairy or pharmaceutical industry.

Influence of Dietary Polar Lipid Supplementation on Memory and Longitudinal Brain Development

Polar lipids, which are found in human milk, serve essential functions within biological membranes, hence their importance in brain development and cognition. Therefore, we aimed to evaluate the longitudinal effects on brain macrostructural and microstructural development and recognition memory of early-life polar lipid supplementation using the translational pig model. Twenty-eight intact (i.e., not castrated) male pigs were provided either a control diet (n = 14) or the control diet supplemented with polar lipids (n = 14) from postnatal day 2 until postnatal week 4. After postnatal week 4, all animals were provided the same nutritionally-adequate diets until postnatal week 24. Pigs underwent magnetic resonance imaging at 8 longitudinal time-points to model brain macrostructural and microstructural developmental trajectories. The novel object recognition task was implemented at postnatal weeks 4 and 8 to evaluate recognition memory. Subtle differences were observed between groups in hippocampal absolute brain volumes and fractional anisotropy, and no differences in myelin water fraction developmental patterns were noted. Behavioral outcomes did not differ in recognition memory, and only minimal differences were observed in exploratory behaviors. Our findings suggest that early-life dietary supplementation of polar lipids has limited effect on brain developmental patterns, object recognition memory, and exploratory behaviors.

Variation in milk fat globule size and composition: A source of bioactives for human health

Milk fat globules (MFGs) are secreted from the mammalian gland and are composed of a triacylglycerol core surrounded by a triple membrane structure, the milk fat globule membrane (MFGM). The MFGM contains complex lipids and proteins reported to have nutritional, immunological, neurological and digestive functions. Human and ruminant milk are shown to share a similar MFG structure but with different size, profile and abundance of protein and polar lipids. This review summarizes the reported data on human, bovine, caprine and ovine MFG composition and concentration of bioactive components in different MFG-size fractions. A comprehensive understanding of compositional variations between milk from different species and MFG size fractions may help promote various milk sources as targeted supplements to improve human development and health. MFG size and MFGM composition are species-specific and affected by lactation, diet and breed (or maternal origin). Purification and enrichment methods for some bioactive proteins and lipids present in the MFGM have yet to be established or are not scaled sufficiently to be used to supplement human diets. To overcome this problem, MFG size selection through fractionation or herd selection may provide a convenient way to pre-enrich the MFG fraction with specific protein and lipid components to fulfill human dietary and health requirements.

New insights into the digestion and bioavailability of a high-melting-temperature solid triacylglycerol fraction in bovine milk fat

Clarifying the health risks associated with the consumption of high-melting-temperature solid triacylglycerol (TAG) from milk fat has profound significance for the nutritional evaluation and development of new dairy products. Our previous work effectively separated butterfat into solid/liquid fractions (30S and 30L) at 30 °C and successfully reconstituted milk fat globules (MFGs) with these fractions. The current study examined the postprandial digestive and daily metabolic properties of a high-melting-temperature solid TAG fraction by performing animal experiments (rats) with 30S-reconstituted MFG emulsion gavage for 240 min and 30S-containing diet administration for 4 weeks. Compared to the consumption of whole butterfat, 30S consumption altered apolipoprotein levels and did not lead to dyslipidaemia in the rats. Conversely, 30S administration induced significant body weight loss by enhancing satiety signals (glucagon-like peptide 1, GLP-1; cholecystokinin, CCK; and peptide YY, PYY), increasing faecal losses, and upregulating the level of hepatic lipolysis-associated enzymes (hormone-sensitive lipase, HSL; adipose triglyceride lipase, ATGL; and protein kinase A, PKA). The 30S diet efficiently improved adipocyte hypertrophy and reduced fat accumulation by downregulating the level of acetyl-CoA carboxylase (ACC) in adipose tissue. This study is of relevance to nutrition science and the dairy industry.

Influence of Dairy Emulsifier Type and Lipid Droplet Size on Gastrointestinal Fate of Model Emulsions: In Vitro Digestion Study

Human breast milk is a natural emulsion containing relatively large triacylglycerol droplets coated by a distinct interfacial layer known as the milk fat globule membrane (MFGM). The unique properties of the MFGM impact the release of nutrients from breast milk in an infant's gastrointestinal tract (GIT), but the membrane architecture is susceptible to disruption by industrial processes. To formulate infant formula that simulates the gastrointestinal behavior of breast milk, food manufacturers require knowledge of the impact of the interfacial properties on the gastrointestinal fate of fat globules. In this study, a simulated GIT was utilized to monitor the gastrointestinal fate of emulsified corn oil with different dairy emulsifiers, including sodium caseinate, lactoferrin (LF), whey protein isolate (WPI), and milk phospholipids (MPL) isolated from MFGM. The influence of droplet size on the gastrointestinal fate of the MPL-stabilized emulsions was also examined. Our findings provide valuable information for the optimization of infant formula and dairy-based nutritional beverages.

Infant milk fat droplet size and coating affect postprandial responses in healthy adult men: a proof-of-concept study

BACKGROUND/OBJECTIVES

Fat droplets in human milk (HM) are larger and surrounded by a phospholipid membrane compared with infant milk formulas (IMF). Since the physical structure of fat droplets might affect digestion and postprandial metabolism, an IMF was developed more mimicking HM lipid structure than current IMF.

SUBJECTS/METHODS

A randomised, double-blind, crossover study was performed in 29 fasted healthy men (aged 18-25 years, BMI: 18-25 kg/m²) to compare 5-hour postprandial responses after consumption of an experimental IMF (Concept, Nuturis) with a current IMF (Control).

RESULTS

Postprandial triacylglycerol (TAG) concentrations tended to increase faster after intake of Concept IMF (P=0.054), but peaked 3 h after intakes at similar concentrations. ApoB48 increased steadily and peaked 3 h after consumption. Increases in plasma glucose concentrations were comparable, but peak concentrations were reached faster after consumption of Concept IMF (P<0.05). Peak insulin concentrations were higher and reached earlier after intake of Concept IMF, causing a sharper decremental glucose rebound (P<0.05) and an earlier time to nadir in non-esterified fatty acid (NEFA) concentrations (P<0.01). Changes in plasma amino acids (AA), apoB100 and apoA1 were comparable. The incremental or decremental areas under-the-curve did not differ between Concept and Control IMF. Satiety scores and changes in the satiety hormones ghrelin and peptide YY were comparable, while cholecystokinin responses were earlier and higher after consumption of Control IMF (P<0.05).

CONCLUSIONS

This proof-of-concept study suggests that fats and carbohydrates from the Concept IMF with larger and phospholipid-coated fat droplets are more rapidly absorbed than those from the current IMF.

Differences in Postprandial Lipid Response to Breast- or Formula-feeding in 8-Week-Old Infants

OBJECTIVE

Lipids play important roles in infant growth and development. In this exploratory observational single-center study, we investigated postmeal responses of infants to dietary lipids and differences between breast-feeding (BF) and formula-feeding (FF).

METHODS

Two capillary blood samples were collected from each subject, before and randomly assigned at either 30, 60, 90, 120, 180, or 240 minutes after their respective feeding, followed by measurement of lipid-related plasma parameter concentrations using enzyme-linked immunosorbent assay-based or combined enzymatic and colorimetric methods.

RESULTS

The intermeal interval before testing was shorter in the BF (182.91 ± 22.85 minutes, n = 33) versus FF group (214.1 ± 30.76 minutes, n = 34); BF subjects fed 5 minutes longer (BF 20.27 ± 7.7 minutes; FF 14.82 ± 3.57 minutes). Composite postmeal concentration profiles were generated from 59 plasma sample pairs with sufficient volume (BF = 30): triglyceride (TG) baselines were not different. A TG difference was indicated for BF over FF subjects at 30 minutes, for FF over BF subjects at 60 minutes when corrected for baseline. TG responses in both groups appeared and seemed to clear much faster than those reported for adults. The TG:apolipoprotein B48 (ApoB48) ratio suggests that chylomicrons in BF subjects may carry a higher fat load (P < 0.05), compensated by a higher chylomicron number in FF subjects (P < 0.05). Cholesterol in BF subjects was higher and showed an increase after feeding when corrected for baseline.

CONCLUSIONS

Our results indicate that lipids from either BF or FF may be handled differently in young healthy infants.

A Postnatal Diet Containing Phospholipids, Processed to Yield Large, Phospholipid-Coated Lipid Droplets, Affects Specific Cognitive Behaviors in Healthy Male Mice

BACKGROUND

Infant cognitive development can be positively influenced by breastfeeding rather than formula feeding. The composition of breast milk, especially lipid quality, and the duration of breastfeeding have been linked to this effect.

OBJECTIVE

We investigated whether the physical properties and composition of lipid droplets in milk may contribute to cognitive development.

METHODS

From postnatal day (P) 16 to P44, healthy male C57BL/6JOlaHsd mice were fed either a control or a concept rodent diet, in which the dietary lipid droplets were large and coated with milk phospholipids, resembling more closely the physical properties and composition of breast milk lipids. Thereafter, all mice were fed an AIN-93M semisynthetic rodent diet. The mice were subjected to various cognitive tests during adolescence (P35-P44) and adulthood (P70-P101). On P102, mice were killed and brain phospholipids were analyzed.

RESULTS

The concept diet improved performance in short-term memory tasks that rely on novelty exploration during adolescence (T-maze; spontaneous alternation 87% in concept-fed mice compared with 74% in mice fed control diet; P < 0.05) and adulthood (novel object recognition; preference index 0.48 in concept-fed mice compared with 0.05 in control-fed mice; P < 0.05). Cognitive performance in long-term memory tasks, however, was unaffected by diet. Brain phospholipid composition at P102 was not different between diet groups.

CONCLUSIONS

Exposure to a diet with lipids mimicking more closely the structure and composition of lipids in breast milk improved specific cognitive behaviors in mice. These data suggest that lipid structure should be considered as a relevant target to improve dietary lipid quality in infant milk formulas.

Milk fat globule membrane coating of large lipid droplets in the diet of young mice prevents body fat accumulation in adulthood

Epidemiological studies have demonstrated protective effects of breast-feeding on childhood obesity. Differences between human milk and infant milk formula (IMF) in dietary lipid structure may contribute to this effect. In our mouse model, feeding a diet containing large lipid droplets coated with phospholipids (PL) (Nuturis^®; PL of milk fat globule membrane (MFGM) fraction origin) in early life protected against excessive body fat accumulation following a diet challenge in adult life. We now set out to determine the relevance of increased droplet size and/or MFGM lipid droplet coating to the observed anti-obesogenic effects in adult life. From day 16 to 42, male mouse pups were exposed to diets with small (S) or large (L) lipid droplets (0·3 v. 2·9 µm average mode diameter, respectively), either without MFGM or with MFGM coating around the lipid droplet, resulting in four groups: S (control diet), L, S^coating and L^coating (Nuturis^® IMF diet). Mice were subsequently challenged with a Western-style diet until dissection at postnatal day 98. A non-challenged group served as reference (REF). We repeatedly determined body composition between postnatal day 42 and 98. At day 98 plasma and gene expression measurements were performed. Only the Nuturis^® IMF diet (L^coating) in early life containing MFGM-coated large lipid droplets reduced body fat mass to a level comparable with the REF group. These data support the notion that the structural aspects of lipids in human milk, for example, both lipid droplet size as well as the MFGM coating, may contribute to its reported protective effect against obesity in later life.

Impact of various emulsifiers on ALA bioavailability and chylomicron synthesis through changes in gastrointestinal lipolysis

Formulating healthy food rich in omega 3 fatty acids requires prior knowledge of the parameters influencing their bioavailability and their metabolic fate. In this context, we studied the effects of various emulsifiers widely used in the food industry, on the gastrointestinal lipolysis of flaxseed oil emulsions in an in vitro model and on the intestinal absorption and lymphatic secretion of alpha-linolenic acid (ALA) in rats. In vitro data showed that the emulsification of flaxseed oil with soya lecithin improved the gastric lipolysis of the oil (+30%), while the presence of Tween 80 or of sodium caseinate decreased it (-80% and -40%, respectively). The in vivo data demonstrated that the intestinal absorption and the lymphatic secretion of ALA were improved with soya lecithin (Cmax = 24 mg mL(-1)) and reduced in the presence of sodium caseinate (Cmax = 7 mg mL(-1)) compared to unemulsified flaxseed oil (Cmax = 16 mg mL(-1)); Tween 80 had no effect. In addition, the synthesized chylomicrons were notably larger and more numerous with soya lecithin whereas they were smaller in the presence of sodium caseinate (p < 0.05). This study shows that the intestinal bioavailability of ALA was increased by the emulsification of flaxseed oil with soya lecithin via an improved lipolysis, favouring the intestinal absorption of ALA and the secretion of many large chylomicrons in lymph.

Structure-function relationship of the milk fat globule

PURPOSE OF REVIEW

The complex biochemical composition and physical structure of the milk fat globule (MFG) are presented as a basis for its paradoxical metabolic fate: MFG is a rapid conveyor of energy through its triacylglycerol (TAG) core but contains some low-digestible bioactive complex lipids and proteins, which influence lipid metabolism and contribute to intestinal and systemic health.

RECENT FINDINGS

MFG structure modulates gastrointestinal lipolysis, postprandial lipemia and even the postprandial fate of ingested fatty acids. Proof-of-concept of the nutritional programming induced by early consumption of an emulsion biomimetic of MFG compared with a typical infant formula was published in an animal model (mice). The metabolic response to a high-fat diet during adulthood was improved following neonatal exposure to the biomimetic emulsion.

SUMMARY

MFG TAG are tailored with a unique regiodistribution delivering in priority short to medium-chain fatty acids in gastric phase, an important amount of quickly metabolizable oleic acid and protecting palmitic acid in sn-2 position. MFG digestion may not only trigger rapid TAG and chylomicron plasma peaks with fast clearance but also the luminal release of nonhydrolysable bioactive compounds (glycosylated compounds and sphingomyelin), which contribute to intestinal and systemic health by shaping the microbiota and modulating the immune system. These bioactive compounds form self-assembled structures, protect specific micronutrients and lower cholesterol absorption. The health benefits of MFG consumption or of some of its fractions (MFGM) under specific structures are steadily being demonstrated with still much unsolved questions especially for populations with high nutritional needs (e.g. elderly, infants).

In vivo digestion of bovine milk fat globules: effect of processing and interfacial structural changes. I. Gastric digestion

The aim was to study the in vivo gastric digestion of fat globules in bovine cream from raw, pasteurised or pasteurised and homogenised milk. Fasted rats were gavaged once and chyme samples were collected after 30, 120 and 180 min post-gavage. Proteins from raw (RC) and pasteurised (PC) creams appeared to be digested faster and to a greater extent. Free fatty acids (FAs) increased throughout the 3h postprandial period. Short and medium chain FAs were released more rapidly than long chain FAs which were hydrolysed to a greater degree from PC. The size of the fat globules of all creams increased in the stomach. Protein aggregates were observed in pasteurised and homogenised cream chyme. Protrusions, probably caused by the accumulation of insoluble lipolytic products, appeared at the surface of the globules in RC and PC chyme. Overall, PC proteins and lipids appeared to be digested to a greater extent.

Effect of dietary lipid structure in early postnatal life on mouse adipose tissue development and function in adulthood

Obese individuals have more (hyperplastic) and larger (hypertrophic) adipocytes in their white adipose tissue (WAT) than normal-weight individuals. The difference in cell number emerges early in childhood, suggesting that this is a critical period for being susceptible to obesity. Breast-feeding has been shown to be protective against obesity, and we have previously shown in mice that the physical structure of lipids in human milk may contribute to this protective effect. In the present study, we investigated how differences in the physical structure of lipids in the early diet may modulate adipose tissue development. Male mice were fed a diet containing control infant milk formula (Control IMF; Danone Research) or Nuturis® (Concept IMF with large phospholipid-coated lipid droplets; Danone Research) from postnatal day (PN)16 to 42. Subsequently, mice were challenged with a moderate Western-style diet (WSD) until PN98, and body composition was monitored by dual-energy X-ray absorptiometry. Epididymal WAT was analysed for adipocyte size, number and gene expression of metabolic transcription factors. Early Concept IMF exposure reduced fat accumulation during the WSD challenge by 30 % compared with the Control IMF. It reduced adipocyte size without affecting adipocyte number in adult mice. The Concept IMF decreased the expression of PPARγ, CCAAT/enhancer-binding protein and retinoid X receptor α in WAT in adulthood, key regulators of metabolic activity. In conclusion, Concept IMF exposure in early life reduced susceptibility to obesity in adult life, by preventing adipocyte hypertrophia upon adult dietary challenge without affecting adipogenesis. These data emphasise the importance of the physical properties of dietary lipids in early life in obesity risk later in life.

In vivo digestion of bovine milk fat globules: effect of processing and interfacial structural changes. II. Upper digestive tract digestion

The aim of this research was to study the effect of milk processing on the in vivo upper digestive tract digestion of milk fat globules. Fasted rats were serially gavaged over a 5h period with cream from raw, pasteurised, or pasteurised and homogenised milk. Only a few intact dietary proteins and peptides were present in the small intestinal digesta. Significantly (P<0.05) more longer chain (C≥10) fatty acids were present in the digesta of rats gavaged with raw (448 mg g(-1) digesta dry matter (DDM)) and homogenised creams (528 mg g(-1) DDM), as compared to pasteurised and homogenised cream (249 mg g(-1) DDM). Microscopy techniques were used to investigate the structural changes during digestion. Liquid-crystalline lamellar phases surrounding the fat globules, fatty acid soap crystals and lipid-mucin interactions were evident in all small intestinal digesta. Overall, the pasteurised and homogenised cream appeared to be digested to a greater extent.

Multiscale structures of lipids in foods as parameters affecting fatty acid bioavailability and lipid metabolism

On a nutritional standpoint, lipids are now being studied beyond their energy content and fatty acid (FA) profiles. Dietary FA are building blocks of a huge diversity of more complex molecules such as triacylglycerols (TAG) and phospholipids (PL), themselves organised in supramolecular structures presenting different thermal behaviours. They are generally embedded in complex food matrixes. Recent reports have revealed that molecular and supramolecular structures of lipids and their liquid or solid state at the body temperature influence both the digestibility and metabolism of dietary FA. The aim of the present review is to highlight recent knowledge on the impact on FA digestion, absorption and metabolism of: (i) the intramolecular structure of TAG; (ii) the nature of the lipid molecules carrying FA; (iii) the supramolecular organization and physical state of lipids in native and formulated food products and (iv) the food matrix. Further work should be accomplished now to obtain a more reliable body of evidence and integrate these data in future dietary recommendations. Additionally, innovative lipid formulations in which the health beneficial effects of either native or recomposed structures of lipids will be taken into account can be foreseen.

Modulating absorption and postprandial handling of dietary fatty acids by structuring fat in the meal: a randomized crossover clinical trial

BACKGROUND

Prolonged postprandial hypertriglyceridemia is a potential risk factor for cardiovascular diseases. In the context of obesity, this is associated with a chronic imbalance of lipid partitioning oriented toward storage and not toward β-oxidation.

OBJECTIVE

We tested the hypothesis that the physical structure of fat in a meal can modify the absorption, chylomicron transport, and further metabolic handling of dietary fatty acids.

DESIGN

Nine normal-weight and 9 obese subjects were fed 40 g milk fat (+[(13)C]triacylglycerols), either emulsified or nonemulsified, in breakfasts of identical composition. We measured the postprandial triacylglycerol content and size of the chylomicron-rich fraction, plasma kinetics of [(13)C]fatty acids, exogenous lipid oxidation with breath-test/indirect calorimetry, and fecal excretion.

RESULTS

The emulsified fat resulted in earlier (>1 h) and sharper chylomicron and [(13)C]fatty acid peaks in plasma than in spread fat in both groups (P < 0.0001). After 2 h, the emulsified fat resulted in greater apolipoprotein B-48 concentrations (9.7 ± 0.7 compared with 7.1 ± 0.9 mg/L; P < 0.05) in the normal-weight subjects than did the spread fat. In the obese subjects, emulsified fat resulted in a 3-fold greater chylomicron size (218 ± 24 nm) compared with the spread fat (P < 0.05). The emulsified fat induced higher dietary fatty acid spillover in plasma and a sharper (13)CO(2) appearance, which provoked increased exogenous lipid oxidation in each group: from 45% to 52% in normal-weight subjects (P < 0.05) and from 40% to 57% in obese subjects (P < 0.01).

CONCLUSION

This study supports a new concept of "slow vs fast fat," whereby intestinal absorption can be modulated by structuring dietary fat to modulate postprandial lipemia and lipid β-oxidation in humans with different BMIs. This trial was registered at clinicaltrials.gov as NCT01249378.

Development of the Digestive System-Experimental Challenges and Approaches of Infant Lipid Digestion

At least during the first 6 months after birth, the nutrition of infants should ideally consist of human milk which provides 40–60 % of energy from lipids. Beyond energy, human milk also delivers lipids with a specific functionality, such as essential fatty acids (FA), phospholipids, and cholesterol. Healthy development, especially of the nervous and digestive systems, depends fundamentally on these. Epidemiological data suggest that human milk provides unique health benefits during early infancy that extend to long-lasting benefits. Preclinical findings show that qualitative changes in dietary lipids, i.e., lipid structure and FA composition, during early life may contribute to the reported long-term effects. Little is known in this respect about the development of digestive function and the digestion and absorption of lipids by the newborn. This review gives a detailed overview of the distinct functionalities that dietary lipids from human milk and infant formula provide and the profound differences in the physiology and biochemistry of lipid digestion between infants and adults. Fundamental mechanisms of infant lipid digestion can, however, almost exclusively be elucidated in vitro. Experimental approaches and their challenges are reviewed in depth.

Size and phospholipid coating of lipid droplets in the diet of young mice modify body fat accumulation in adulthood

BACKGROUND

In addition to contemporary lifestyle factors that contribute to the increased obesity prevalence worldwide, early nutrition is associated with sustained effects on later life obesity. We hypothesized that physical properties of dietary lipids contribute to this nutritional programming. We developed a concept infant formula (IMF) with large, phospholipid-coated lipid droplets (Nuturis; Danone Research, Paris, France) and investigated its programming effect on metabolic phenotype later in life.

METHODS

Male C57Bl/6j mice were fed a control formula (Control IMF) or Nuturis (Concept IMF) diet between postnatal day (PN)16 and PN42. All mice were subsequently fed a Western-style diet (WSD) until PN126. Body composition was monitored repeatedly by dual-energy X-ray absorptiometry between PN42 and PN126.

RESULTS

Concept IMF slightly increased lean body mass as compared with Control IMF at PN42 but did not affect fat mass. Upon 84 d of WSD feeding, the Concept IMF group showed reduced fat accumulation as compared with Control IMF. In addition, fasting plasma leptin, resistin, glucose, and lipids were significantly lower in the Concept IMF group.

CONCLUSION

Large phospholipid-coated lipid droplets in young mice reduced fat accumulation and improved metabolic profile in adulthood. These data emphasize that physical properties of early dietary lipids contribute to metabolic programming.

Oil composition of high-fat diet affects metabolic inflammation differently in connection with endotoxin receptors in mice

Low-grade inflammation observed in obesity is a risk factor for cardiovascular disease. Recent studies revealed that this would be linked to gut-derived endotoxemia during fat digestion in high-fat diets, but nothing is known about the effect of lipid composition. The study was designed to test the impact of oil composition of high-fat diets on endotoxin metabolism and inflammation in mice. C57/Bl6 mice were fed for 8 wk with chow or isocaloric isolipidic diets enriched with oils differing in fatty acid composition: milk fat, palm oil, rapeseed oil, or sunflower oil. In vitro, adipocytes (3T3-L1) were stimulated or not with lipopolysaccharide (LPS; endotoxin) and incubated with different fatty acids. In mice, the palm group presented the highest level of IL-6 in plasma (P < 0.01) together with the highest expression in adipose tissue of IL-1β and of LPS-sensing TLR4 and CD14 (P < 0.05). The higher inflammation in the palm group was correlated with a greater ratio of LPS-binding protein (LBP)/sCD14 in plasma (P < 0.05). The rapeseed group resulted in higher sCD14 than the palm group, which was associated with lower inflammation in both plasma and adipose tissue despite higher plasma endotoxemia. Taken together, our results reveal that the palm oil-based diet resulted in the most active transport of LPS toward tissues via high LBP and low sCD14 and the greatest inflammatory outcomes. In contrast, a rapeseed oil-based diet seemed to result in an endotoxin metabolism driven toward less inflammatory pathways. This shows that dietary fat composition can contribute to modulate the onset of low-grade inflammation through the quality of endotoxin receptors.

Proteome profile and biological activity of caprine, bovine and human milk fat globules

Upon combining bidimensional electrophoresis with monodimensional separation, a more comprehensive analysis of the milk fat globule membrane has been obtained. The proteomic profile of caprine milk fat globules revealed the presence of butyrophilin, lactadherin and perilipin as the major proteins, they were also associated to bovine and human milk fat globule membranes. Xanthine dehydrogenase/oxidase has been detected only in monodimensional gels. Biological activity of milk fat globules has been evaluated in Caco2-cells, as a representative model of the intestinal barrier. The increase of cell viability was indicative of a potential nutraceutical role for the whole milk fat globule, suggesting a possible employment in milk formula preparation.

Lymphatic absorption of α-linolenic acid in rats fed flaxseed oil-based emulsion

The bioavailability of α-linolenic acid (ALA) from flaxseed oil in an emulsified form v. a non-emulsified form was investigated by using two complementary approaches: the first one dealt with the characterisation of the flaxseed oil emulsion in in vitro gastrointestinal-like conditions; the second one compared the intestinal absorption of ALA in rats fed the two forms of the oil. The in vitro study on emulsified flaxseed oil showed that decreasing the pH from 7·3 to 1·5 at the physiological temperature (37°C) induced instantaneous oil globule coalescence. Some phase separation was observed under acidic conditions that vanished after further neutralisation. The lecithin used to stabilise the emulsions inhibited TAG hydrolysis by pancreatic lipase. In contrast, lipid solubilisation by bile salts (after lipase and phospholipase hydrolysis) was favoured by preliminary oil emulsification. The in vivo absorption of ALA in thoracic lymph duct-cannulated rats fed flaxseed oil, emulsified or non-emulsified, was quantified. Oil emulsification significantly favoured the rate and extent of ALA recovery as measured by the maximum ALA concentration in the lymph (Cmax = 14 mg/ml at 3 h in the emulsion group v. 9 mg/ml at 5 h in the oil group; P < 0·05). Likewise, the area under the curve of the kinetics was significantly higher in the emulsion group (48 mg × h/ml for rats fed emulsion v. 26 mg × h/ml for rats fed oil; P < 0·05). On the whole, ALA bioavailability was improved with flaxseed oil ingested in an emulsified state. Data obtained from the in vitro studies helped to partly interpret the physiological results.

Complex links between dietary lipids, endogenous endotoxins and metabolic inflammation

Metabolic diseases such as obesity are characterized by a subclinical inflammatory state that contributes to the development of insulin resistance and atherosclerosis. Recent reports also indicate that (i) there are alterations of the intestinal microbiota in metabolic diseases and (ii) absorption of endogenous endotoxins (namely lipopolysaccharides, LPS) can occur, particularly during the digestion of lipids. The aim of the present review is to highlight recently gained knowledge regarding the links between high fat diets, lipid digestion, intestinal microbiota and metabolic endotoxemia & inflammation.

Emulsified lipids increase endotoxemia: possible role in early postprandial low-grade inflammation

Low-grade inflammation is a risk factor for the onset of atherosclerosis. Little is known about the involvement of endotoxin absorption from the gut during the digestion of lipids. In the present study, we first investigated in humans the impact of a mixed meal containing dispersed lipids on postprandial endotoxemia and inflammation. We then investigated the effect of (i) oil emulsification in vivo in rats and (ii) fatty acid amounts in vitro using Caco-2 cells on postprandial endotoxemia. In humans, postprandial endotoxemia increased early after the meal. Moreover, we evidenced that the endotoxin receptor sCD14 increased during digestion and that chylomicrons could contribute to absorbed endotoxin transport. This could explain the significant peak of inflammatory cytokine IL-6 that we observed 2 h after the mixed meal. Interestingly, in rats, the emulsion led to both higher endotoxemia and hypertriglyceridemia than oil and compared to a control saline load. In vitro, incubation of Caco-2 cells with increasing fatty acid concentrations enhanced epithelial absorption of endotoxin. To our knowledge, this is the first study evidencing in healthy humans that, following a mixed meal containing lipids, increased endotoxemia is associated with raised sCD14 and a peak of IL-6. On a repeated basis, this may thus be a triggering cascade for the onset of atherosclerosis. In this respect, optimizing both dietary fat amount and structure could be a possible strategy to limit such low-grade endotoxemia and inflammation by the control of postprandial lipemia.

Milk Fat Globule structure & function; nanosciece comes to milk production

The biological process of fat globule assembly and secretion produces highly complex globule compositions and structures with many properties now recognized to be the direct result of these structures. During homogenization, fat globules are broken down and subsequently structures and surfaces different than the native state are formed. This process alters the milk fat globule unique macrostructure and the effects associated to their structure would be expected to be lost. In the present overview, the need for continued research of the fundamental aspects of the mechanism involved in milk fat globules synthesis secretion and size distribution, as well as establishing ways to regulate those processes are highlighted. Ultimately these insights will guide food technology to developing a new generation of structure based functional foods and as highlighted in this overview, dairy functional products should be the pioneering commodity.

On the supposed influence of milk homogenization on the risk of CVD, diabetes and allergy

Commercial milk is homogenized for the purpose of physical stability, thereby reducing fat droplet size and including caseins and some whey proteins at the droplet interface. This seems to result in a better digestibility than untreated milk. Various casein peptides and milk fat globule membrane (MFGM) proteins are reported to present either harmful (e.g. atherogenic) or beneficial bioactivity (e.g. hypotensive, anticarcinogenic and others). Homogenization might enhance either of these effects, but this remains controversial. The effect of homogenization has not been studied regarding the link between early cow's milk consumption and occurrence of type I diabetes in children prone to the disease and no link appears in the general population. Homogenization does not influence milk allergy and intolerance in allergic children and lactose-intolerant or milk-hypersensitive adults. The impact of homogenization, as well as heating and other treatments such as cheesemaking processes, on the health properties of milk and dairy products remains to be fully elucidated.

Microfiltration of Raw Whole Milk to Select Fractions with Different Fat Globule Size Distributions: Process Optimization and Analysis

We present an extensive description and analysis of a microfiltration process patented in our laboratory to separate different fractions of the initial milk fat globule population according to the size of the native milk fat globules (MFG). We used nominal membrane pore sizes of 2 to 12 microm and a specially designed pilot rig. Using this process with whole milk [whose MFG have a volume mean diameter (d43) = 4.2 +/- 0.2 microm] and appropriate membrane pore size and hydrodynamic conditions, we collected 2 extremes of the initial milk fat globule distribution consisting of 1) a retentate containing large MFG of d43 = 5 to 7.5 microm (with up to 250 g/kg of fat, up to 35% of initial milk fat, and up to 10% of initial milk volume), and 2) a permeate containing small MFG of d43 = 0.9 to 3.3 microm (with up to 16 g/kg of fat, up to 30% of initial milk fat, and up to 83% of initial milk volume and devoid of somatic cells). We checked that the process did not mechanically damage the MFG by measuring their zeta-potential. This new microfiltration process, avoiding milk aging, appears to be more efficient than gravity separation in selecting native MFG of different sizes. As we summarize from previous and new results showing that the physico-chemical and technological properties of native milk fat globules vary according to their size, the use of different fat globule fractions appears to be advantageous regarding the quality of cheeses and can lead to new dairy products with adapted properties (sensory, functional, and perhaps nutritional).