Gene expression is modulated by lifestyle and environmental factors. ~ Mexican toxicologist Jorge Alejandro Alegría-Torres
A man contributes to its offspring’s genetic inheritance, but a fetus develops within a woman’s womb, which strongly influences fetal gene regulation and expression.
A fetus is not the only one genetically affected. Fetal DNA can persist in its mother for the rest of her life. That DNA may benefit a mother’s health or stir adversity.
All mammal mothers undergo a range of hormonal change prior to and after birthing. Stimulating the hypothalamus, oxytocin promotes affection. In healthy animals, these and other changes combine to engender maternal behaviors.
Most furred mammal mothers, including rodents and dogs, lick their pups. Pups mothered by generous lickers fare better under stress than those stingily succored. Neglected rat pups who don’t get loving licks become neglectful mothers.
The psychological effects of parenting can be profound and lifelong. The quality of parenting, especially mothering, creates a perpetuating generational cycle. This has been repeatedly observed in rodents and primates, including people.
A foster pup, going from a poor licker of a mother to a good one, develops a better stress response; one more like that of its foster upbringing than its biological mother.
While epigenetic effects tend to persist, the permanence of methylation is in flux during early development. The earlier methylation goes unabated, the more pronounced and pervasive its impact. Epigenetic alterations account for differences in stress response in identical twins.
Social interactions of every sort affect gene regulation, as they are a form of stress. From fish to humans, competitive interactions influence testosterone levels with consequential impact on gene activity.
Altered genetic expression from stress is passed to the next generation. Chronically stressed pregnant women bear children with greater proclivity to physical, psychological, and behavioral disorders owing to greater sensitivity to stress.
Fathers as well as mothers pass the effects of their diet, temperament, and lifestyle to their offspring.
Epigenetically inherited stress increases the risk of depression, obesity, and autoimmune diseases. Dampened glucocorticoid-receptor-gene activity renders people more aggressive and impulsive. This makes men particularly inclined to abusiveness that perpetuates through generations.
It makes no difference the source of stress – physical or psychological – for parent or offspring; such distinction is clinical anyway. Existence is holistic; so too health and illness.
Methylation patterns vary with diet. Early malnutrition can create a host of problems, such as hyperactive stress response, with wide-ranging effects that last throughout life.
Exposure to pollutants, including alcohol and tobacco, can have lasting epigenetic effects which may be passed to offspring who are never exposed to the triggering pollutant. Such effects can last for generations.
Many chronic diseases are epigenetically endowed as a culmination of lifestyle. Autoimmune diseases, such as rheumatoid arthritis, are exemplary.
Common diseases are due to many changes with small effects on a handful of genes. ~ American geneticist Peter Scacher
The speed at which the epigenome changes relates to lifespan, both in individuals and across species. For animals, eating less slows the rate of epigenomic change.