International Business Department           Liu Bojia           June 11, 2023

  The period before and after pregnancy is a crucial time to lay the groundwork for the birth of a healthy baby. Often mums-to-be make all sorts of preparations, including dietary adjustments, folic acid supplements, quitting smoking and alcohol, and even losing weight. However, preparing for pregnancy is not just for mums-to-be; the physical state of fathers-to-be has a significant impact on the health of the next generation.

  A growing body of research evidence suggests that the dietary profile and weight of the father-to-be affects the quality of sperm and, by extension, the health of the child throughout its life. For example, a study published not long ago in Nature Communications showed through animal experiments that the pre-mating dietary profile of males affects the risk of disease in the next generation. For example, male mice that were chronically low in protein and high in carbon water tended to have sons with higher levels of anxiety, and male mice that were chronically high in fat tended to have daughters who were prone to metabolic problems.

  And in the journal Nature, a study published by the Helmholtz Centre in Munich, Germany, re-emphasises that the diet and health of the father during conception is crucial, affecting the child's weight and risk of metabolic disease later in life.

  The researchers first analysed data from a child study cohort, which included information from more than 3,000 families. The results showed that in families where the mum-to-be was of normal weight, an overweight or obese dad-to-be doubled the risk of obesity in the offspring.

  Subsequently, in order to validate this analysis and reveal the mechanisms behind it, the researchers launched an animal experiment. They fed a portion of male mice of childbearing age a high-fat diet for 2 consecutive weeks and then examined the reproductive organs of the mice.

  As a result, they looked at the mice's epididymis - where newly produced sperm develop and mature - and found that the mitochondria of the newborn sperm in them were affected.

  Mitochondria are energy-producing structures within cells, and the ability of sperm to swim quickly is inextricably linked to mitochondrial activity. Mitochondria have their own separate DNA molecules and also produce proteins using transfer RNA (tRNA) as an intermediary. In the past, it was once thought that mitochondria would only be passed on from mother to offspring, and that fathers did not contribute to the mitochondrial genes of their offspring. However, new research in recent years has shown that some tRNA fragments (referred to as mt-tsRNA) in the mitochondria of spermatozoa enter the egg during insemination and act as epigenetic factors to regulate gene expression during the early embryonic stages, thus indirectly affecting embryo development.

  In the current study, the researchers found that these mt-tsRNAs are then affected by diet. There was more mt-tsRNA in the sperm of mice on a high-fat diet than in those on a low-fat diet, which, according to the authors of the study, is most likely due to the fact that a high-fat diet puts a strain on the mitochondria, which then produce more RNA in order to enhance energy supply.

  Subsequent in vitro fertilisation experiments have shown that when these sperm bind to the egg, the mt-tsRNA in them is transferred to the cells of the embryo and is involved in regulating gene expression in the early embryo.

  In their paper, the study authors note that these results emphasise the importance of the father's health at the time of conception for the metabolism of his offspring, and that in order to reduce their children's risk of developing diseases such as obesity and diabetes later in life, fathers-to-be should pay increased attention to preventive health care, especially by planning for their diets.