Association of breast milk gamma-linolenic acid with infant anthropometric outcomes in urban, low-income Bangladeshi families: a prospective, birth cohort study

γ-Linolenic acid in maternal milk drives cardiac metabolic maturation

Birth presents a metabolic challenge to cardiomyocytes as they reshape fuel preference from glucose to fatty acids for postnatal energy production1,2. This adaptation is triggered in part by post-partum environmental changes3, but the molecules orchestrating cardiomyocyte maturation remain unknown. Here we show that this transition is coordinated by maternally supplied γ-linolenic acid (GLA), an 18:3 omega-6 fatty acid enriched in the maternal milk. GLA binds and activates retinoid X receptors4 (RXRs), ligand-regulated transcription factors that are expressed in cardiomyocytes from embryonic stages. Multifaceted genome-wide analysis revealed that the lack of RXR in embryonic cardiomyocytes caused an aberrant chromatin landscape that prevented the induction of an RXR-dependent gene expression signature controlling mitochondrial fatty acid homeostasis. The ensuing defective metabolic transition featured blunted mitochondrial lipid-derived energy production and enhanced glucose consumption, leading to perinatal cardiac dysfunction and death. Finally, GLA supplementation induced RXR-dependent expression of the mitochondrial fatty acid homeostasis signature in cardiomyocytes, both in vitro and in vivo. Thus, our study identifies the GLA-RXR axis as a key transcriptional regulatory mechanism underlying the maternal control of perinatal cardiac metabolism.

Breast Milk Lipidome Is Associated With Maternal Diet and Infants' Growth

Objectives

The fatty acid (FA) composition of breast milk is a relevant aspect related to the development of the lactating infant. The present study aimed at exploring correlations between dietary intake of macro- and micronutrients with the FA profile in breast milk, and the possible implication for infants' growth.

Study Design

Breast milk samples from a cohort of lactating women were collected 7–15 days postpartum. The FA profiles in triacylglycerol (TAG) and phospholipid (PL)-rich fractions were analyzed by gas chromatography. Diet was registered during the third trimester of pregnancy by means of a food frequency questionnaire (FFQ). In addition, anthropometric measurements of infants were collected from gestation and up to 12 months postpartum.

Results

The FA profile in breast milk was characterized by a median of 37.4, 41.3 and 16.8% of saturated, monounsaturated, and polyunsaturated FAs, respectively. From the dietary components, zinc, iron, and B group vitamins were correlated positively with the proportion of total n-3 FAs in TAG and C20:5 n-3 in PL. Lycopene, vitamin E, zinc, and vitamin B2 showed a similar correlation with total polyunsaturated fatty acid (PUFA), total n-6 FAs, C20:4 n-6, and C18:2 n-6 in TAG. Regarding food groups, nuts showed the strongest association with several PUFA both in TAG and PL, while the vegetable group was also positively associated with C18:3 n-3. Furthermore, the concentration of linolenic acid (C18:3 n-3) and palmitic acid (C16:0) were positively associated with increased length for age (LFA) and weight for age (WFA) at 12 months compared with birth [ΔLFA −0.16 (−0.85, 0.37); ΔWFA −0.26 (−0.77, 0.21)].

Conclusions

Mothers' intake of nuts, dietary sources of zinc, iron, and B group vitamins were identified as potential predictors of a high-unsaturated FA profile in breast milk. In addition, linolenic and palmitic acids in breast milk were positively associated with infants' growth in the first year of life.