Background/Purpose: Systemic autoimmune rheumatic diseases (SARDs) such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA) are characterized by chronic systemic inflammation and often require immunomodulatory therapies, both of which may affect lipid metabolism and influence breast milk composition, However, data on milk lipidomics in SARDs are scarce. We aimed to characterize and compare fatty acid (FA) profiles in breast milk of mothers with and without SARDs.

Methods: We analyzed archived milk samples from 29 breastfeeding women with SARDs (15 RA, 11 SLE, 3 both) and 15 healthy controls in the UCSD Human Milk Biorepository (HMB). FA (pmol/ml of milk) was assessed using liquid chromatography-mass spectrometry, and median FA levels compared between groups using the Wilcoxon rank-sum test. To estimate the association between FAs and SARDs, FAs were log-transformed to approximate normality and multivariable linear regression was performed. Modela adjusted for maternal and child age, maternal body mass index, parity, gestational age at delivery, infant sex, frequency of feeds, time of milk collection, and hours since last feed. Modelb incorporated variables in Modela plus the milk storage length, and Modelc also accounted for SARD therapies. In subgroup analyses, median FA levels were evaluated by SARD type (RA and SLE) and sample storage length.

Results: Baseline characteristics were comparable, except for earlier gestational age at delivery (38.40 vs. 39.72 weeks) and markedly longer storage duration (40.42 months vs 3.24 months) among SARDs versus controls. Conventional DMARDs (55.17%) and biologic DMARDs (41.38%) were exclusive to SARDs, and corticosteroid use (34.48% vs 6.67%, p=0.07) was more common. Milk macronutrient content did not differ by SARD status. Individual FAs, specifically, medium and long-chain saturated FAs [lauric acid (12:0) and myristic acid (14:0), palmitic acid (16:0)], and long-chain monounsaturated FA oleic acid (18:1) were significantly higher in SARDs. Very-long-chain saturated FA – cerotic acid (26:0) was lower (Table 1). Compared to controls, those with SLE, but not RA, had significantly higher levels of lauric, myristic, oleic, and linoleic acids. Most FAs showed peak levels at ~ 12-24 months storage duration. In multivariable regression analysis, SARD remained associated with higher levels of many of the FAs studied. Furthermore, the magnitude of associations generally increased with sequential model adjustments (Figure 1).

Conclusion: Breast milk in SARDs, particularly SLE, showed higher levels of several medium and long-chain FAs compared to controls. The associations persisted and generally became stronger after sequential adjustments for maternal and infant characteristics, milk storage length, and SARD therapies, providing some indication that inflammatory diseases and therapies may affect the milk FA environment. However, given the marked difference in storage length in our sample and the observed impact of prolonged storage on milk FAs, future studies should match controls on storage length to reduce bias and improve data interpretability.

Table 1. Comparison of fatty acids (pmol/ml of milk) in archived milk samples from 44 women with and without systemic autoimmune rheumatic diseases (SARDs)

Figure 1. Impact of systemic autoimmune rheumatic diseases (SARDs) on human milk fatty acid composition: results from multivariable regression models

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/human-milk-fatty-acid-profiles-among-breastfeeding-mothers-with-and-without-systemic-autoimmune-rheumatic-diseases/