Your sex affects your genes for body fat, cancer and birth weight

• Whether we are male or female affects our physiology in profound ways 
• Disease biology may, therefore, remain obscured when males and females are considered as a single group
• Differentiating between the sexes can thus lead to an improved, more personal medicinal approach 

Researchers say your biological sex affects gene expression in nearly every type of tissue – influencing body fat, cancer and birth weight.

Gene expression is the amount of product created by a gene for cell function, the international team of researchers explained.

They said their findings could prove important for personalised medicine, creating new drugs and predicting patient outcomes.

"These discoveries suggest the importance of considering sex as a biological variable in human genetics and genomics studies," said project leader Barbara Stranger, an associate professor of pharmacology at Northwestern University Feinberg School of Medicine in Chicago.

Unreported links

The researchers analysed 44 types of healthy human tissue from 838 people to find out if there were differences between women and men in the average amount of gene expression.

They discovered that 37% of all human genes were expressed at different levels in women and men in at least one type of tissue.

They also identified 369 instances where a genetic variant present in males and females affected gene expression to a different degree in each sex. This led to the discovery of 58 previously unreported links between genes and blood pressure, cholesterol levels, breast cancer and body fat percentage.

Gender differences in gene expression were also found for genes involved in how the body responds to medications, how women control blood sugar levels in pregnancy, how the immune system functions and how cancer develops.

Critical component of personalised medicine

"If specific genes or genetic variants contribute differentially to a given trait in males and females, it could suggest sex-specific biomarkers, therapeutics and drug dosing," Stranger said in a Northwestern news release.

"In the future, such knowledge may form a critical component of personalised medicine or may reveal disease biology that remains obscured when considering males and females as a single group," she said.

The study was published in the journal Science.

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