Abstract
ABSTRACTLay Summary: This review sets out the hypothesis that life history trade-offs in the maternal generation favour the emergence of similar trade-offs in the offspring generation, mediated by the partitioning of maternal investment between pregnancy and lactation, and that these trade-offs help explain widely reported associations between growth trajectories and NCD risk.Growth patterns in early life predict the risk of non-communicable diseases (NCDs), but adaptive explanations remain controversial. It is widely assumed that NCDs occur either because of physiological adjustments to early constraints, or because early ecological cues fail to predict adult environmental conditions (mismatch). I present an inter-generational perspective on developmental plasticity, based on the over-arching hypothesis that a key axis of variability in maternal metabolism derives from life history trade-offs, which influence how individual mothers partition nutritional investment in their offspring between pregnancy and lactation. I review evidence for three resulting predictions: (i) Allocating relatively more energy to growth during development promotes the capacity to invest in offspring during pregnancy. Relevant mechanisms include greater fat-free mass and metabolic turnover, and a larger physical space for fetal growth. (ii) Allocating less energy to growth during development constrains fetal growth of the offspring, but mothers may compensate by a tendency to attain higher adiposity around puberty, ecological conditions permitting, which promotes nutritional investment during lactation. (iii) Since the partitioning of maternal investment between pregnancy and lactation impacts the allocation of energy to ‘maintenance’ as well as growth, it is expected to shape offspring NCD risk as well as adult size and body composition. Overall, this framework predicts that life history trade-offs in the maternal generation favour the emergence of similar trade-offs in the offspring generation, mediated by the partitioning of maternal investment between pregnancy and lactation, and that these trade-offs help explain widely reported associations between growth trajectories and NCD risk.
Highlights
There is compelling evidence that patterns of nutrition and growth during early life shape diverse components of adult phenotype, as recognized in the developmental origins of adult health and disease (DOHaD) hypothesis [1]
Many researchers consider two ‘adaptive’ models of developmental plasticity—either that it reflects developmental adjustments to resolve effects of early constraints on nutritional supply, or that it adjusts phenotype to current ecological cues in anticipation of experiencing similar conditions in adulthood [2]
Various dimensions of maternal capital may be relevant, here I focus on one aspect by proposing the over-arching hypothesis that variability in maternal investment is shaped by life history trade-offs that emerged during maternal development
Summary
There is compelling evidence that patterns of nutrition and growth during early life shape diverse components of adult phenotype, as recognized in the developmental origins of adult health and disease (DOHaD) hypothesis [1]. A certain threshold maternal fat stores may elevate birth weight, for example maternal obesity is associated with high body fat in the offspring [49], while in one African population, mothers showed a net loss of fat mass during pregnancy, indicating the diversion of energy stores to fund fetal growth [50]. In between these extremes, maternal adiposity appears less important for fetal investment than FFM. The association between maternal phenotype and the capacity for nutritional investment during lactation, is different
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