Background Breastfeeding is protective against many long-term diseases, yet the mechanisms involved are unknown. Leptin gene ( LEP ) is reported to be associated with body mass index (BMI). On the other hand, breastfeeding duration has been found to be associated with DNA methylation (DNAm) of the LEP gene. Therefore, epigenetic regulation of LEP may represent the mechanism underlying the protective effect of breastfeeding duration against obesity. Methods In the Isle of Wight Birth Cohort, peripheral blood DNAm at 23 cytosine-phosphate-guanine sites (CpGs) in the LEP locus in 10-year-old ( n = 297) samples and 16 CpGs in 18-year-old ( n = 305) samples, were generated using the Illumina Infinium MethylationEPIC and HumanMethylation450 Beadchips respectively and tested for association with breastfeeding duration (total and exclusive) using linear regression. To explore the association between breastfeeding durations and genome-wide DNAm, epigenome-wide association studies (EWASs) and differential methylation region (DMR) analyses were performed. BMI trajectories spanning the first 18 years of life were used as the outcome to test the association with breastfeeding duration (exposure) using multi-nominal logistic regression. Mediation analysis was performed for significant CpG sites. Results Both total and exclusive breastfeeding duration were associated with DNAm at four LEP CpG sites at 10 years ( P value < 0.05), and not at 18 years. Though no association was observed between breastfeeding duration and genome-wide DNAm, DMR analyses identified five significant differentially methylated regions (Sidak adjusted P value < 0.05). Breastfeeding duration was also associated with the early transient overweight trajectory. Furthermore, DNAm of LEP was associated with this trajectory at one CpG site and early persistent obesity at another, though mediation analysis was not significant. Conclusions Breastfeeding duration is associated with LEP methylation at age 10 years and BMI trajectory. LEP DNAm is also significantly associated with BMI trajectories throughout childhood, though sample sizes were small. However, mediation analysis did not demonstrate that DNAm of LEP explained the protective effect of breastfeeding against childhood obesity. Electronic supplementary material The online version of this article (10.1186/s13148-019-0727-9) contains supplementary material, which is available to authorized users.

Several small studies have shown associations between breastfeeding and genome-wide DNA methylation (DNAm). We performed a comprehensive Epigenome-Wide Association Study (EWAS) to identify associations between breastfeeding and DNAm patterns in childhood. We analysed DNAm data from the Isle of Wight Birth Cohort at birth, 10, 18 and 26 years. The feeding method was categorized as breastfeeding duration >3 months and >6 months, and exclusive breastfeeding duration >3 months. EWASs using robust linear regression were performed to identify differentially methylated positions (DMPs) in breastfed and non-breastfed children at age 10 (false discovery rate of 5%). Differentially methylated regions (DMRs) were identified using comb-p. The persistence of significant associations was evaluated in neonates and individuals at 18 and 26 years. Two DMPs, in genes SNX25 and LINC00840, were significantly associated with breastfeeding duration >6 months at 10 years and was replicated for >3 months of exclusive breastfeeding. Additionally, a significant DMR spanning the gene FDFT1 was identified in 10-year-old children who were exposed to a breastfeeding duration >3 months. None of these signals persisted to 18 or 26 years. This study lends further support for a suggestive role of DNAm in the known benefits of breastfeeding on a child’s future health.

The work leading to the introduction of the Advanced Photo System was extremely complex and required Eastman Kodak Company to manage this work through the application of systems engineering principles. This paper will discuss the complexity of the situation, the principles that were applied and specific methodologies that Eastman Kodak used during system development. The definition of a system provided in MIL‐STD‐499B, “Systems Engineering”, May, 1991 Draft“: A system is a composite of people, products, and processes that provide a capability to satisfy stated needs. A complete system includes the facilities, equipment (hardware and software), material, service, data, skilled personnel, and techniques required to achieve, provide and sustain system effectiveness.” The Advanced Photo System, including all of these attributes, as well as the additional interactions involved in joint development, required Kodak to actively implement system engineering principles. These principles can be defined as the application of scientific and engineering effort to transform an operational need into a defined system configuration using a top‐down, iterative process of requirements definition, functional analysis and allocation, synthesis, optimization, design, test, and evaluation as defined by Blanchard and Fabrycky. This paper will describe the four major accomplishments of this effort: Providing an overall process for development and verification of system requirements, using a top‐down approach that views the system as a whole and provides an orientation towards the life‐cycle of the system Integrating existing development management processes by emphasizing the system environment that these processes exist within Integrating widely scattered technology, design, manufacturing and management efforts using “front‐end” analysis of contributions to system performance Providing a framework for managing system level negotiations with our joint development partners and internal organizations