Prenatal cigarette smoke exposure linked to heart disease.

Ng, SP, DJ Conklin, A Bhatnagar, DD Bolanowski, J Lyon and JT Zelikoff. 2009. Prenatal exposure to cigarette smoke induces diet and gender-dependent dyslipidemia and weight gain in adult murine offspring. Environmental Health Perspectives doi:10.1289/ehp.0800193.

Cigarette smoke can change prebirth development in ways that contribute to cardiovascular disease later in life, according to results of this study using mice. Smoking exposure altered body weight and cholesterol levels in the offspring.

This study is the first to directly show that in utero exposure to cigarette smoke contributes to changes that can predispose offspring to weight gain and lipid levels in the blood and lead to heart problems later in life. The effects differ depending on gender. A high fat diet increased weight and risk in male but not in female offspring. In female offspring consuming a normal diet, weight gain increased as did levels of blood lipids.

This research adds to prior studies that have found prebirth exposure to cigarette smoke in rodents leads to changes in artery health and thus affects cardiovascular disease. In human studies, exposure before birth affects growth in the womb, umbilical cord arteries and blood lipid measures in the infants.

The research is part of a rapidly developing field that examines prenatal environmental exposures which can impact health later in life. Although this study did not identify how the changes occurred, scientists believe exposures in the womb can alter gene expression that guide growth, body functions and disease throughout life.

The findings have public health implications because of the prevalence of cardiovascular disease in the United States. Further research is necessary to determine how these findings translate to humans.

It is estimated that 13 percent of the 6 million American women who become pregnant each year continue to smoke during pregnancy.

The researchers say the results "underscore the increased vulnerability of the developing fetus and suggest that prenatal insults during critical stages of fetal development can significantly influence later-life health risk."

These risks increase if people smoke, are overweight, have high levels of certain fats and cholesterol and have low levels of other types of fats. The main illnesses are heart attack, heart failure and stroke – a leading cause of death in the US.

Elevated levels of cholesterol and triglyceride fats and/or low levels of high density lipoproteins in the blood is called dyslipidemia. Combined, these factors contribute to atherosclerosis–a condition where the arteries and vessels surrounding the heart harden and clog. It is the leading cause of heart disease.

In this study, both male and female offspring exposed to cigarette smoke in utero developed dyslipidemia on a normal diet. Consuming a high fat diet worsened the effects on total cholesterol and high-density lipoprotein cholesterol levels in the males, but not the females.

These effects were found at a dose range similar to human exposures when a pregnant woman smokes. The period of mouse development relates to the first two trimesters of pregnancy in people.

The authors acknowledge that some of the observed changes in lipid metabolism and/or body weight may be due to differences in dietary protein between the normal and the high fat diets. Future studies will determine if and which of the dietary differences contributed to the observed differences.