Developmental sensitivity of the piglet brain to docosahexanoic acid

Milk fat globule membrane plus milk fat increase docosahexaenoic acid availability in infant formulas

PURPOSE

Milk fat globule membrane (MFGM) has components with emulsifier properties that could affect the provision of substrates to the brain. We evaluated the effects of MFGM plus milk fat addition to infant formulas on docosahexaenoic acid (DHA) availability and gut development.

METHODS

In Experiment 1, suckling piglets were divided into 3 groups: Group L1 (n = 8): fed with a vegetal fat formula with palm oil; L2 (n = 8): canola oil formula and L3 (n = 8): milk fat + canola oil + 1% Lacprodan (3% MFGM of total protein content). In Experiment 2, Group L4 (n = 7): fed with canola oil + 1% Lacprodan (3% MFGM) and Group L5 (n = 5): milk fat + canola oil + 2% Lacprodan (6% MFGM). All formulas contained 0.2% DHA and 0.2% arachidonic acid.

RESULTS

In Experiment 1, DHA was similar among the groups in both total fatty acids and plasma phospholipids (PL). However, 3% MFGM (L3) increased significantly the proportion of DHA and LC-PUFA n-3 in liver total fatty acids, jejunum, and also in jejunum PL respect to the other formulas. There were no changes in gut histology, cell proliferation, apoptosis, or brain DHA content. In Experiment 2, higher MFGM dose was used. Then, higher DHA was not only found in peripheral tissues of 6% MFGM (L5) piglets but also in plasma PL, while a similar trend was observed in cortex PL (p = 0.123).

CONCLUSION

In conclusion, MFGM plus milk fat may increase DHA availability of infant formulas which could contribute to their beneficial health effects.

Critical review evaluating the pig as a model for human nutritional physiology

The present review examines the pig as a model for physiological studies in human subjects related to nutrient sensing, appetite regulation, gut barrier function, intestinal microbiota and nutritional neuroscience. The nutrient-sensing mechanisms regarding acids (sour), carbohydrates (sweet), glutamic acid (umami) and fatty acids are conserved between humans and pigs. In contrast, pigs show limited perception of high-intensity sweeteners and NaCl and sense a wider array of amino acids than humans. Differences on bitter taste may reflect the adaptation to ecosystems. In relation to appetite regulation, plasma concentrations of cholecystokinin and glucagon-like peptide-1 are similar in pigs and humans, while peptide YY in pigs is ten to twenty times higher and ghrelin two to five times lower than in humans. Pigs are an excellent model for human studies for vagal nerve function related to the hormonal regulation of food intake. Similarly, the study of gut barrier functions reveals conserved defence mechanisms between the two species particularly in functional permeability. However, human data are scant for some of the defence systems and nutritional programming. The pig model has been valuable for studying the changes in human microbiota following nutritional interventions. In particular, the use of human flora-associated pigs is a useful model for infants, but the long-term stability of the implanted human microbiota in pigs remains to be investigated. The similarity of the pig and human brain anatomy and development is paradigmatic. Brain explorations and therapies described in pig, when compared with available human data, highlight their value in nutritional neuroscience, particularly regarding functional neuroimaging techniques.

Postnatal neurogenesis in the hippocampal dentate gyrus and subventricular zone of the Göttingen minipig

Postnatal neurogenesis is currently viewed as important for neuroplasticity and brain repair. We are, therefore, interested in animal models for neuroimaging of postnatal neurogenesis. A recent stereological study found an age-dependent increase in the number of neurons and glial cells in the neocortex of Göttingen minipigs, suggesting that this species may be characterized by a prolonged postnatal neurogenesis. Since there is no direct evidence on this issue, the goal of our study was to quantify cell proliferation in the two major neurogenic regions of the postnatal brain - the subventricular zone of the lateral ventricle (SVZ) and the hippocampal dentate gyrus (DG) - at two separate points during the lifespan of the minipig. Göttingen minipigs aged 6-7 and 32 weeks were injected with bromodeoxyuridine (BrdU), a marker of cycling cells, and killed after 2h. We found BrdU-positive cells numbering 165,000 in the SVZ and 35,000 in the DG at 6-7 weeks and 66,000 in the SVZ and 19,000 in the DG at 32 weeks-of-age. Stereology showed a 60% increase in the total number of DG granule cells between 6-7 and 32 weeks-of-age. Our findings show a continued postnatal neurogenesis in the major neurogenic regions of Göttingen minipigs, thereby providing a potential animal model for studies aimed at examining ongoing neurogenesis in the living brain with molecular neuroimaging technology.

Fatty Acid Transfer From Sow to Piglet Differs for Different Polyunsaturated Fatty Acids (PUFA)

Polyunsaturated fatty acids (PUFA) are essential for the development of the nervous system in animals. It is known that pigs are good models for human in many aspects. The aim of the study was to investigate how fat content and FA composition in sows’ diet influence FA composition in brain of newborn and in liver and brain of one-day-old piglets, respectively. High fat (6 %) feeds were designed with regard to saturated or polyunsaturated fat content and n-6/n-3 ratio by adding either oats rich in linoleic acid (LA) or linseed oil rich in α-linolenic acid (ALA). The ratio n-6/n-3 PUFA was 11 in all three diets (the low fat (3 %), high fat saturated and high fat oats diet), while the ratio in the linseed oil diet was 2. Increased proportion of ALA in the diet increased ALA and eicosapentaenoic acid (EPA) in piglets’ neutral and polar liver lipids and the long chain PUFA, EPA, docosapentaenoic and docosahexaenoic acid in piglet brain. The results suggest that transport of n-3 PUFA from sow to piglet was higher via milk than via bloodstream in the uterus and that increased content of ALA in sows’ feed led to an increased accumulation of n-3 FA in piglets’ liver and brain.

Differences in fatty acid composition between cerebral brain lobes in juvenile pigs after fish oil feeding

Very long-chain n-3 PUFA from fish are suggested to play a role in the development of the brain. Fish oil feeding results in higher proportions of n-3 PUFA in the brains of newborn piglets. However, the effect of fish oil on the fatty acid composition of specific cerebral brain lobes in juvenile pigs is largely uninvestigated. This study examined the effect of a fish oil diet on the fatty acid composition of the frontal, parietal, temporal and occipital brain lobes in juvenile pigs (7 weeks old). Pigs were randomly allocated to a semipurified pig diet containing either 4% (w/w) fish oil (n 19) or 4% (w/w) high-oleic acid sunflower oil (HOSF diet, n 18) for a period of 8 weeks. The fish oil diet resulted in significantly higher proportions (%) of DHA in the frontal (10.6 (SD1.2)), parietal (10.2 (SD1.5)) and occipital brain lobes (9.9 (SD 1.3)), but not in the temporal lobe (7.7 (SD1.6)), compared with pigs fed the HOSF diet (frontal lobe, 7.5 (SD1.0); parietal lobe, 8.1 (SD 1.3); occipital lobe, 7.3 (SD1.2), temporal lobe, 6.6 (SD1.2). Moreover, the proportion of DHA was significantly lower in the temporal lobe compared with the frontal, parietal and occipital brain lobes in pigs fed a fish oil diet. In conclusion, the brains of juvenile pigs appear to be responsive to dietary fish oil, although the temporal brain lobe is less responsive compared with the other three brain lobes. The functional consequences of these differences are a challenging focus for future investigation.

The fatty acid profile of buccal cheek cell phospholipids is a noninvasive marker of long-chain polyunsaturated Fatty Acid status in piglets

The fatty acid pattern of cheek cell phospholipids has been proposed as a noninvasive marker of long-chain polyunsaturated fatty acid (PUFA) status. However, the cheek cell phospholipid fatty acid pattern has been compared only with that of plasma and erythrocytes. The objective of this study was to assess the extent to which the fatty acid profile of cheek cell phospholipids reflects that of tissue phospholipids. Piglets (n = 31; 6 d old) were fed five formula diets differing in total fat and fatty acid composition. After 14 d of consuming the assigned diets, cheek cell plasma, erythrocyte, liver, muscle, adipose tissue, retina and brain samples were collected for determination of the phospholipid fatty acid patterns. There were significant correlations between the cheek cell phospholipid content of most PUFA and the content of these fatty acids in tissue phospholipids (r = 0.509-0.951, P < 0.01). The cheek cell phospholipid content of most of the PUFA, except 20:4(n-6), reflected that of other tissue phospholipids as well as, or nearly as well as the contents of plasma and/or erythrocyte phospholipids. The correlations between the 22:6(n-3) contents of cheek cell, plasma, or erythrocyte phospholipids and those of brain and retina phospholipids were relatively poor (r = 0.596-0.737, P < 0.001). We conclude that the fatty acid pattern of cheek cell phospholipid can be used as a noninvasive marker of PUFA status, but it is not a better index than the pattern of plasma or erythrocyte phospholipids, particularly for assessing the fatty acid pattern of organs with slow fatty acid incorporation and/or turnover rates.

Dietary long-chain polyunsaturated fatty acids minimize dexamethasone-induced reductions in arachidonic acid status but not bone mineral content in piglets

The primary objective of this study was to determine whether exogenous arachidonic acid (AA) in a supplemented formula substitute for piglets or sow milk would attenuate reductions in AA status, growth, and bone mineral content (BMC) as a result of exogenous glucocorticoid excess using dexamethasone (DEX). A secondary objective was to confirm a positive effect of exogenous AA on growth and BMC of piglets fed formula and not treated with DEX as well as to determine whether the elevation in BMC was related to greater production of prostaglandin E(2) in bone. Forty-eight 5-d-old male piglets were randomized to be suckled or receive either a standard formula or the same formula, but containing AA (0.5% wt/wt total fat) for 15 d in addition to either treatment with DEX or placebo. Piglets treated with DEX grew slower and had lower BMC of whole body, lumbar spine, and femur in addition to lower proportions of AA, but those fed standard formula had the greatest reductions. Piglets in the supplemented group weighed more than piglets fed standard formula or suckled in both the DEX and placebo groups. Suckled piglets had the highest BMC of whole body and femur compared with standard formula, and the supplemented group was intermediate for whole body but similar to suckled pigs for femur. Release of prostaglandin E(2) was elevated only with supplementation of AA. These data indicate that supplemental AA is associated with elevated whole body and femur BMC but that BMC is not enhanced during glucocorticoid treatment.

Utilization of docosahexaenoic acid from intravenous egg yolk phospholipid

Docosahexaenoic acid (DHA, 22:6n-3) is provided directly to human premature infants during parenteral nutrition from the egg yolk fraction of an intravenous fat emulsion. This study aimed to determine whether the high egg yolk phospholipid content of Intralipid 10% (IL 10%, Pharmacia, Uppsala, Sweden) relative to the standard emulsion Intralipid 20% (IL 20%, Pharmacia) could be a strategy to increase the delivery of DHA to the developing brain. Male, Large White piglets were randomly selected from sows 3 d after birth. Piglets were assigned to receive a 9-d continuous intravenous infusion commencing 5 d after birth of either Intralipid (IL) 10%, IL 20%, or Lipofundin S 20% (LFS; B. Braun, Melsungen, Germany). There were four piglets in each treatment group. IL 10% provides twice as much DHA as IL 20%, while LFS provides no DHA. Protein and other nutrients were provided enterally using a low-fat milk formula. After 9 d, animals were killed, and the fatty acid compositions of blood, liver, and cerebral cortex were analyzed. IL 10% infusion approximately doubled the amount of plasma phospholipid DHA (microg/mL of plasma) in comparison to IL 20%. However, red blood cells, liver, and cerebral cortex phospholipid DHA levels were indistinguishable between these two groups. LFS was associated with reduced levels of DHA in plasma, red blood cell and liver phospholipids in comparison to IL 20%. We conclude that infusion of additional phospholipid is an ineffective strategy for increasing DHA delivery to piglet tissues. This may be due to the formation of inert phospholipid particles in plasma. The data do not support the concept of using IL 10% as a means of providing additional DHA to premature human infants.