Epigenome-wide analysis of neonatal CD4⁺ T-cell DNA methylation sites potentially affected by maternal fish oil supplementation

Figures & data

Table 1. Population characteristics of the mothers and infants in the cohort (n = 70)

Characteristic	Fish oil (n = 36)	Control (n = 34)	P value
Mothers at recruitment
Age [years (SE)]	31.1 (0.7)	32.6 (0.6)	0.09
BMI at entry [kg/m2 (SE)]	25.5 (0.8)	25.9 (0.7)	0.726
Asthma [n (%)]	15 (42%)	12 (35%)
Allergic rhinitis [n (%)]	21 (58%)	22 (65%)	0.584
Exposed to passive smoke[(%)]	20 (56%)	19 (56%)	0.811
Infants
Male [n(%)]	16 (44%)	21 (62%)	0.147
Gestation [days(SE)]	274.5 (1.4)	273.7 (1.4)	0.687
Delivery method
Vaginal [n(%)]	26 (72%)	27 (79%)
Caesarean section [n(%)]	10 (28%)	7 (21%)	0.483
Neonatal growth parameters
Birth weight [g(SE)]	3491 (57.1)	3481 (63.6)	0.906
Length [cm(SE)]	50.4 (0.3)	49.7 (0.3)	0.117
Head circumference [cm(SE)]	35.2 (0.2)	34.6 (0.2)	0.065
Fatty acid composition in maternal erythrocytes at 37 weeks of gestation
eicosapentaenoic acid, EPA (SE)	2.51 (0.11)	0.68 (0.02)	< 0.001*
docosahexaenoic acid, DHA (SE)	10.75 (0.33)	6.39 (0.15)	< 0.001*
Arachidonic acid, AA (SE)	10.37 (0.28)	13.83 (0.16)	< 0.001*
Total n-3 PUFA (SE)^b	22.31 (0.58)	15.98 (0.29)	< 0.001*
Total n-6 PUFA (SE)^c	21.38 (0.53)	28.44 (0.27)	< 0.001*
Total n-3 to n-6 (SE)^d	1.06 (0.03)	0.57 (0.01)	< 0.001*

Statistical comparisons by Chi square and Man-Whitney U-test.

^aValues for fatty acids are expressed as a percentage of total fatty acids.

^bSum 20:5, 22:5, 22:3.

^cSum 18:2, 20:3, 20:4, 22:3, 22:4.

^dRatio [Sum 20:5, 22:5, 22:3] to [18:2, 20:3, 20:4, 22:3, 22:4].

* indicates significant P-values (P < 0.05)

Figure 1. Cord red blood cell fatty acid measurements in fish oil and control groups. Boxplots represent median and range. Statistical analysis by Man-Whitney U-test. EPA: eicosapentaenoic acid; DHA: docosahexaenoic acid; AA: arachidonic acid; total n-3 PUFAs (Sum 20:5, 22:5, 22:3); total n-6 PUFAs (Sum 18:2, 20:3, 20:4, 22:3, 22:4).

Figure 2. Regression analysis of CpG sites that co-associate with cord red cell total n-3 fatty acid levels. (A) qq plot of P-values from the association test between CpGs and total n-3 fatty acids did not deviate from the null hypothesis. (B) Scatterplots of the top 4 CpGs ranked by P-value for the association with total n-3 fatty acids suggested a dose-response relationship. (C) Histogram of the coefficients from the regression model indicated a small effect size.

Figure 3. Comparative analysis of DNA methylation profiles between treatment and intervention groups. (A) MDS scaling analysis did not discriminate treatment groups. Samples are indicated by open circles and projected along axes of the first 2 principal components of the top 5000 most variable CpG sites. (B) qq plot of P-values from the moderated t-test between intervention and control groups did not deviate from the null hypothesis. (C) Boxplots of data from 6 top-ranked CpG sites for the between-group comparison did not indicate substantive differences in methylation levels. Boxplots show median and range.