Molecular Evidence for Differential Long-term Outcomes of Early Life Severe Acute Malnutrition

Abstract

Background: Severe acute malnutrition (SAM) in infants may present as one of two distinct syndromic forms: non-edematous (marasmus), with severe wasting and no nutritional edema; or edematous (kwashiorkor) with moderately severe wasting. These differences may be related to developmental changes prior to the exposure to SAM and phenotypic changes appear to persist into adulthood with differences between the two groups. We examined whether the different response to SAM and subsequent trajectories may be explained by developmentally-induced epigenetic differences.

Methods: We extracted genomic DNA from muscle biopsies obtained from adult survivors of kwashiorkor (n=21) or marasmus (n=23) and compared epigenetic profiles (CpG methylation) between the two groups using the Infinium® 450K BeadChip array.

Findings: We found significant differences in methylation of CpG sites from 63 genes in skeletal muscle DNA. Gene ontology studies showed significant differential methylation of genes in immune, body composition, metabolic, musculoskeletal growth, neuronal function and cardiovascular pathways, pathways compatible with the differences in the pathophysiology of adult survivors of SAM.

Interpretation: These findings suggest persistent developmental influences on adult physiology in survivors of SAM. Since children who develop marasmus have lower birth weights and after rehabilitation have different intermediary metabolism, these studies provide further support for persistent developmentally-induced phenomena mediated by epigenetic processes affecting both the infant response to acute malnutrition and later life consequences.

Funding: Supported by a Grant from the Bill and Melinda Gates Foundation (Global Health OPP1066846), Grand Challenge "Discover New Ways to Achieve Healthy Growth."

Evidence before this study: Previous research has shown that infants who develop either kwashiorkor or marasmus in response to SAM differ in birth weight and subsequently have different metabolic patterns in both infancy and adulthood.

Added value of this study: This study demonstrates epigenetic differences in the skeletal muscle of adult survivors of marasmus versus kwashiorkor and these differences are in genes that may underlie the longer-term consequences.

Implications of all the available evidence: These data are compatible with the different clinical responses to SAM arising from developmentally-induced epigenetic changes laid down largely before birth and provide evidence for the predictive adaptive response model operating in human development.

Keywords: Birthweight; Epigenetic; Jamaica; Muscle; Severe acute malnutrition.

Fig. 1

Methylation variance of dmCpGs from muscle biopsies of adult survivors of kwashiorkor or marasmus. (A) Cluster analysis illustrating subject grouping into K (kwashiorkor) or M (marasmus) groups based on the methylation profile of 133 dmCpGs. Distance measure was calculated using Euclidean method. Clustering was done using complete agglomeration method. Red-black-green: Low to high methylation (row z-score). (B) Absolute methylation change between K and M subjects for the 133 dmCpGs (p < 0.05). (C) Biological processes associated with the differentially methylated genes in adult survivors of severe acute malnutrition.

Fig. 2

Clinical measures used as Hit 1 and Hit 2 proxies for the assessment of the prenatal and postnatal factors on the methylation variance measured in the kwashiorkor (K) and marasmus (M) groups. Boxplots illustrate mean (dot), 25th and 75th percentile (box), and minimum and maximum (tails) values of each clinical measure after adjusting for gender (bwt); gender and age (hfa, wfh, ht., htAd, bmc, lm, tfm, tmm); gender and BMI (i0, gauc). Abbreviations (variable; y-axis unit of measurement): bwt: birth weight (kg); wfh: weight for height on admission (kg); hfa: height for age on admission (cm); htAd: height on admission (cm); ht.: adult height (attained height, cm); lm: total lean mass (kg); tfm: total fat mass (kg); tmm: thigh muscle mass (kg); bmc: bone mineral content (kg); bmd: bone mineral density (kg/m²); i0: insulin concentration at baseline (μIU/ml); gauc: glucose area under the curve; neu: neutrophil count (× 10⁸/L) on admission; lymphocyte count (× 10⁸/L) on admission; nlr: neutrophil to lymphocyte ratio on admission.

Fig. 3

Multiple regression analysis of the dmCpGs associated with (A) overall and bone growth, (B) glucose metabolism and (C) immunity. The heatmap illustrates the level of significance (by p-values) of Hit 1 and Hit 2 variables for each regression model. Regression model: Methylation Y_ij = μ + α_iGender + β₁Hit1_ij + β₂Hit2_ij + ε_ij. Abbreviations: bwt: birth weight; wfh: weight for height; hfa: height for age; htAd: height on admission; ht.: adult height (i.e., attained height); lm: total lean mass; tfm: total fat mass; tmm: thigh muscle mass; bmd: bone mineral density; bmc: bone mineral content; gauc: glucose area under the curve; i0: insulin concentration at baseline; km: subject group (classified as kwashiorkor or marasmus); neu: neutrophil count; lym: lymphocyte count; nlr: neutrophil to lymphocyte ratio. ProbeID_GeneSymbol: Illumina probe identifier (ProbeID) corresponding to a CpG site on the gene of interest.