Human Milk Drives the Intimate Interplay Between Gut Immunity and Adipose Tissue for Healthy Growth.

As the physiological food for the developing child, human milk is expected to be the diet that is best adapted for infant growth needs. There is also accumulating evidence that breastfeeding influences long-term metabolic outcomes. This review covers the potential mechanisms by which human milk could regulate healthy growth. We focus on how human milk may act on adipose tissue development and its metabolic homeostasis. We also explore how specific human milk components may influence the interplay between the gut microbiota, gut mucosa immunity and adipose tissue. A deeper understanding of these interactions may lead to new preventative and therapeutic strategies for both undernutrition and other metabolic diseases and deserves further exploration.

Shaping the Gut Microbiota by Breastfeeding: The Gateway to Allergy Prevention?

Evidence is accumulating that demonstrates the importance of the gut microbiota in health and diseases such as allergy. Recent studies emphasize the importance of the "window of opportunity" in early life, during which interventions altering the gut microbiota induce long-term effects. The neonate's gut microbiota composition and metabolism could therefore play an essential role in allergic disease risk. Breastfeeding shapes the gut microbiota in early life, both directly by exposure of the neonate to the milk microbiota and indirectly, via maternal milk factors that affect bacterial growth and metabolism such as human milk oligosaccharides, secretory IgA, and anti-microbial factors. The potential of breastmilk to modulate the offspring's early gut microbiota is a promising tool for allergy prevention. Here, we will review the existing evidence demonstrating the impact of breastfeeding on shaping the neonate's gut microbiota and highlight the potential of this strategy for allergy prevention.

Early-Life Nutrition and Gut Immune Development.

Gut immune function conditions the development of local and systemic diseases that result from defects in immune regulation, such as inflammatory bowel disease, allergy and obesity. As epidemiological studies support the developmental origin of health and disease, deciphering the critical factors modulating gut immune development should allow the advance of primary prevention strategies specifically adapted to the early-life immune system. Here, we will review gut mucosal immunity development and cover in more detail the recent understanding of the impact of early nutrition on this process. We will emphasize how nutrition can shape microbiota composition and metabolic function and thereby the production of metabolites with immune-modulatory properties. We will also focus on the role of dietary compounds recently demonstrated to be essential in immune development and function, such as dietary antigens, vitamin A, and aryl hydrocarbon receptor ligands. Finally, we will discuss that early-life physiologic food for mammals contains factors capable of compensating for neonatal immune deficiencies, but also factors that are decisive for immune maturation towards a maternal milk-independent and efficient immune system.

Increased intake of vegetable oil rich in n-6 PUFA enhances allergic symptoms and prevents oral tolerance induction in whey-allergic mice.

Increased intake of vegetable oils rich in n-6 PUFA, including soyabean oil, has been associated with an increase in allergic disease. The present study aimed to determine the effect of an increasing dose of dietary vegetable oil on allergic outcomes in mice. To study this, mice received a 7 v. 10 % soyabean oil diet before and during oral sensitisation with whey or whey hyperimmune serum transfer. Another group of mice received partial whey hydrolysate (pWH) while being fed the diets before oral sensitisation. The acute allergic skin response, serum Ig level, mouse mast cell protease-1 (mMCP-1) concentration and/or splenic T-cell percentages were determined upon whey challenge. When the diets were provided before and during oral sensitisation, the acute allergic skin response was increased in mice fed the 10 % soyabean oil diet compared with the 7 % soyabean oil diet. Whey IgE and IgG1 levels remained unaltered, whereas mMCP-1 levels increased in mice fed the 10 % soyabean oil diet. Furthermore, allergic symptoms were increased in naive mice fed the 10 % soyabean oil diet and sensitised with whey hyperimmune serum. In addition to enhancing the mast cell response, the 10 % soyabean oil diet increased the percentage of activated Th1 and Th2 cells as well as increased the ratios of Th2:regulatory T cells and Th2:Th1 when compared with the 7 % soyabean oil diet. Oral tolerance induction by pWH was abrogated in mice fed the 10 % soyabean oil diet compared with those fed the 7 % soyabean oil diet during pretreatment with pWH. In conclusion, increased intake of soyabean oil rich in n-6 PUFA suppresses tolerance induction by pWH and enhances the severity of the allergic effector response in whey-allergic mice. Dietary vegetable oils rich in n-6 PUFA may enhance the susceptibility to develop or sustain food allergy.

Dietary Marine n-3 PUFAs Do Not Affect Stress-Induced Visceral Hypersensitivity in a Rat Maternal Separation Model.

BACKGROUND: Although never evaluated for efficacy, n-3 (ω-3) long-chain polyunsaturated fatty acids (LCPUFAs) are commercially offered as treatment for irritable bowel syndrome (IBS). OBJECTIVE: This study was designed to investigate, in a mast cell-dependent model for visceral hypersensitivity, whether this pathophysiologic mechanism can be reversed by dietary LCPUFA treatment via peroxisome proliferator-activated receptor γ (PPARG) activation. METHODS: Maternally separated rats were subjected to hypersensitivity-inducing acute stress at adult age. Reversal was attempted by protocols with tuna oil-supplemented diets [4% soy oil (SO) and 3% tuna oil (SO-T3) or 3% SO and 7% tuna oil (SO-T7)] and compared with control SO diets (7% or 10% SO) 4 wk after stress. The PPARG agonist rosiglitazone was evaluated in a 1 wk preventive protocol (30 mg · kg⁻¹ · d⁻¹). Erythrocytes were assessed to confirm LCPUFA uptake and tissue expression of lipoprotein lipase and glycerol kinase as indicators of PPARG activation. Colonic mast cell degranulation was evaluated by toluidine blue staining. In vitro, human mast cell line 1 (HMC-1) cells were pretreated with rosiglitazone, eicosapentaenoic acid, or docosahexaenoic acid, stimulated with phorbol 12-myristate 13-acetate (PMA) and calcium ionophore or compound 48/80 and evaluated for tumor necrosis factor α (TNF-α) and ß-hexosaminidase release. RESULTS: Stress led to visceral hypersensitivity in all groups. Hypersensitivity was not reversed by SO-T3 or control treatment [prestress vs. 24 h poststress vs. posttreatment area under the curve; 76 ± 4 vs. 128 ± 12 (P < 0.05) vs. 115 ± 14 and 82 ± 5 vs. 127 ± 16 (P < 0.01) vs. 113 ± 19, respectively]. Comparison of SO-T7 with its control showed similar results [74 ± 6 vs. 103 ± 13 (P < 0.05) vs. 115 ± 17 and 66 ± 3 vs. 103 ± 10 (P < 0.05) vs. 117 ± 11, respectively]. Erythrocytes showed significant LCPUFA uptake in the absence of colonic PPARG activation. Rosiglitazone induced increased PPARG target gene expression, but did not prevent hypersensitivity. Mast cell degranulation never differed between groups. Rosiglitazone and LCPUFAs significantly reduced PMA/calcium ionophore-induced TNF-α release but not degranulation of HMC-1 cells. CONCLUSION: Dietary LCPUFAs did not reverse stress-induced visceral hypersensitivity in maternally separated rats. Although further research is needed, claims concerning LCPUFAs as a treatment option in IBS cannot be confirmed at this point and should be regarded with caution.

Dietary long chain n-3 polyunsaturated fatty acids prevent impaired social behaviour and normalize brain dopamine levels in food allergic mice.

Allergy is suggested to exacerbate impaired behaviour in children with neurodevelopmental disorders. We have previously shown that food allergy impaired social behaviour in mice. Dietary fatty acid composition may affect both the immune and nervous system. The aim of this study was to assess the effect of n-3 long chain polyunsaturated fatty acids (n-3 LCPUFA) on food allergy-induced impaired social behaviour and associated deficits in prefrontal dopamine (DA) in mice. Mice were fed either control or n-3 LCPUFA-enriched diet before and during sensitization with whey. Social behaviour, acute allergic skin response and serum immunoglobulins were assessed. Monoamine levels were measured in brain and intestine and fatty acid content in brain. N-3 LCPUFA prevented impaired social behaviour of allergic mice. Moreover, n-3 LCPUFA supplementation increased docosahexaenoic acid (DHA) incorporation into the brain and restored reduced levels of prefrontal DA and its metabolites 3,4-dihydroxyphenylacetic acid, 3-methoxytyramine and homovanillic acid in allergic mice. In addition to these brain effects, n-3 LCPUFA supplementation reduced the allergic skin response and restored decreased intestinal levels of serotonin metabolite 5-hydroxyindoleacetic acid in allergic mice. N-3 LCPUFA may have beneficial effects on food allergy-induced deficits in social behaviour, either indirectly by reducing the allergic response and restoring intestinal 5-HT signalling, or directly by DHA incorporation into neuronal membranes, affecting the DA system. Therefore, it is of interest to further investigate the relevance of food allergy-enhanced impairments in social behaviour in humans and the potential benefits of dietary n-3 LCPUFA supplementation.

DHA-rich tuna oil effectively suppresses allergic symptoms in mice allergic to whey or peanut.

BACKGROUND: Supplementation with long-chain n-3 polyunsaturated fatty acids (LCPUFAs) has been found to reduce the development of allergic disease. OBJECTIVE: The aim of this study was to compare the effectiveness of fish oil diets rich in eicosapentaenoic acid (20:5n-3; EPA) or docosahexaenoic acid (22:6n-3; DHA) in suppressing food allergic symptoms. METHODS: Mice were fed a control diet (10% soybean oil) or fish oil diet rich in EPA (4% soybean oil + 6% EPA oil containing 28.8% EPA and 13.7% DHA) or DHA (4% soybean oil + 6% DHA oil containing 7% EPA and 27.8% DHA), starting 14 d before and for 5 wk during oral sensitization with peanut extract (PE) or whey. Acute allergic skin responses, serum immunoglobulins (Igs), and mucosal mast cell protease-1 (mmcp-1) were assessed. Hyperimmune serum was transferred to naive recipient mice fed the different diets. RESULTS: The DHA diet effectively reduced the acute allergic skin response compared with the control or EPA diet in PE-allergic mice (control, 159 ± 15, or EPA, 129 ± 8, vs. DHA, 78 ± 7 µm; P < 0.0001 or P < 0.05, respectively). In contrast, both the DHA and EPA diets reduced the allergic skin response in whey allergic mice (control, 169 ± 9, vs. DHA, 91 ± 13, or EPA, 106 ± 14 µm; P < 0.001 or P < 0.01, respectively); however, only the DHA diet reduced mmcp-1 and whey-specific IgE and IgG1. The DHA and EPA diets also reduced the acute skin response in passively immunized mice. CONCLUSIONS: The DHA-rich fish oil diet reduced allergic sensitization to whey and allergic symptoms in both PE- and whey-allergic mice. These data suggest that DHA-rich fish oil is useful as an intervention to prevent or treat food allergy symptoms.

Dietary fish oil improves endothelial function and lowers blood pressure via suppression of sphingolipid-mediated contractions in spontaneously hypertensive rats.

OBJECTIVE: Long-chain n-3 polyunsaturated fatty acids from oily fish reduce blood pressure (BP) in hypertension. Previously, we demonstrated that hypertension is associated with marked alterations in sphingolipid biology and elevated ceramide-induced vasoconstriction. Here we investigated in spontaneously hypertensive rats (SHRs) whether fish oil improves endothelial function including reduced vascular contraction induced via the sphingolipid cascade, resulting in reduced BP. METHODS: Twelve-week-old SHRs were fed a control or fish oil-enriched diet during 12 weeks, and BP was recorded. Plasma sphingolipid levels were quantified by mass spectrometry and the response of isolated carotid arteries towards different stimuli was measured. Furthermore, erythrocyte membrane fatty acid composition, thromboxane A2 formation and cytokine secretion in ex-vivo lipopolysaccharide-stimulated thoracic aorta segments were determined. RESULTS: The fish oil diet reduced the mean arterial BP (P < 0.001) and improved endothelial function, as indicated by a substantially increased relaxation potential towards ex-vivo methacholine exposure of the carotid arteries (P < 0.001). The long-chain n-3 polyunsaturated fatty acid diet resulted in altered levels of specific (glucosyl)ceramide subspecies (P < 0.05), reduced membrane arachidonic acid content (P < 0.001) and decreased thromboxane concentrations in plasma (P < 0.01). Concomitantly, the fish oil diet largely reduced ceramide-induced contractions (P < 0.01), which are predominantly mediated by thromboxane. Furthermore, thromboxane A2 and interleukin-10 were reduced in supernatants of lipopolysaccharide-stimulated thoracic aorta of SHRs fed the fish oil diet while RANTES (regulated on activation, normal T-cell expressed and secreted) was enhanced. This may contribute to reduced vasoconstriction in vivo. CONCLUSIONS: Dietary fish oil lowers BP in SHRs and improves endothelial function in association with suppression of sphingolipid-dependent vascular contraction.

n-3 Long-chain PUFA reduce allergy-related mediator release by human mast cells in vitro via inhibition of reactive oxygen species.

Increased n-6 and reduced n-3 long-chain PUFA (LC-PUFA) intake in Western diets may contribute to the increased prevalence of allergic diseases. Key effector cells in allergy are mast cells (MC). The aim of the present study was to investigate the effects of n-6 v. n-3 LC-PUFA on MC phenotype. Human MC lines (LAD2 and HMC-1) were incubated for 24 h with either arachidonic acid (AA, n-6 LC-PUFA) or the n-3 LC-PUFA EPA or DHA. The effects of these three LC-PUFA on degranulation, mediator secretion and reactive oxygen species (ROS) generation were assessed. ROS, mitogen-activated protein kinase (MAPK) or NF-κB inhibitors were used to unravel signalling pathways involved in cytokine secretion. AA, EPA or DHA did not reduce IgE-mediated degranulation by LAD2 cells. However, AA increased PGD2 and TNF-α secretion by ionomycin/phorbol 12-myristate 13-acetate-stimulated HMC-1, whereas EPA and DHA more prominently inhibited IL-4 and IL-13 secretion. Suppression of IL-4 and IL-13 release by LC-PUFA correlated with reduced ROS generation. IL-4 and IL-13 release by activated HMC-1 was abrogated using ROS inhibitors. Inhibition of MAPK signalling, but not NF-κB, downstream of ROS reduced IL-13 secretion by activated HMC-1. Combined incubation of EPA or DHA with MAPK inhibitors further suppressed IL-13 secretion. In conclusion, the n-6 LC-PUFA AA enhanced pro-inflammatory mediator production by MC, while the n-3 LC-PUFA EPA as well as DHA more effectively suppressed ROS generation and IL-4 and IL-13 release. This suggests that dietary supplementation with EPA and/or DHA may alter the MC phenotype, contributing to a reduced susceptibility to develop and sustain allergic disease.

Salmon consumption by pregnant women reduces ex vivo umbilical cord endothelial cell activation.

BACKGROUND: In vitro exposure of endothelial cells (ECs) to n-3 (omega-3) long-chain PUFAs (LCPUFAs) reduces cell adhesion molecule (CAM) expression. However, to our knowledge, no previous human studies have examined the influence of an altered diet on CAM expression. OBJECTIVE: We assessed whether salmon (rich in n-3 LCPUFAs) consumption twice a week during pregnancy affected offspring umbilical vein EC CAM expression. DESIGN: Women were randomly assigned to maintain their habitual diets or to consume 2 portions of salmon per week during pregnancy months 4-9. ECs were isolated from umbilical cord veins collected at birth and cultured. The cell surface expression of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) was assessed by flow cytometry after the culture of ECs in the presence and absence of bacterial LPS for 24 h. Cytokine and growth factor concentrations in culture supernatant fluid were measured by using a multiplex assay. RESULTS: LPS increased the expression of VCAM-1 and the production of several cytokines and growth factors. The level of ICAM-1 expression per cell [ie, the median fluorescence intensity (MFI)] was increased by LPS stimulation in the control group (16.9 ± 2.4 compared with 135.3 ± 20.2; P < 0.001) and to a lesser extent in the salmon group (14.1 ± 3.8 compared with 65.8 ± 22.4; P = 0.037). The ICAM-1 MFI in the salmon group after LPS stimulation was lower than in the control group (P = 0.006). CONCLUSION: Increased dietary salmon intake in pregnancy dampens offspring EC activation, which implicates a role for n-3 LCPUFAs in the suppression of inflammatory processes in humans. This trial was registered at clinicaltrials.gov as NCT00801502.

Acute allergic skin reactions and intestinal contractility changes in mice orally sensitized against casein or whey.

BACKGROUND: Cow's milk allergy (CMA) is characterized by hypersensitivity against casein or whey, affecting 2.5% of young infants. The pathogenesis of CMA involves IgE as well as non-IgE-mediated reactions and clinical symptoms are found in the skin, lungs and gastrointestinal tract. In this study, local and systemic immunopathology was determined in whey- or casein-allergic mice. METHODS: Mice were orally sensitized with casein or whey using cholera toxin as an adjuvant. Serum immunoglobulins and the acute allergic skin reaction (ear swelling 1 h after intradermal allergen challenge) were determined to reveal systemic hypersensitivity. Furthermore, pathophysiological changes were assessed within the intestine. RESULTS: An acute allergic skin reaction was induced in both whey- and casein-sensitized mice. In these mice, whey-specific IgE, IgG(1), IgG(2a) and casein-specific IgG(1) levels were found to be increased. In addition, the serum mouse mast cell protease-1 (mMCP-1) concentration was enhanced, reflecting mast cell degranulation. Indeed, the number of mMCP-1-positive mast cells within the colon was diminished in both whey- and casein-sensitized mice. Only in casein-sensitized mice isometric contraction of the colon was reduced, reflecting motility alterations. CONCLUSION: Mice, orally sensitized against casein or whey, revealed an allergen-specific acute allergic skin reaction. In casein-sensitized mice, hypocontractility of the colon reflected pathophysiological changes within the intestine. Allergen-induced ear swelling and intestinal contractility changes are novel parameters in animal models of CMA which may add to the search for new therapeutic strategies to relieve symptoms of CMA.