Diet-induced effects on reproduction

Hi, my name is Monika Kaczmarek and I would like to tell you about the diet induced effects on reproduction involving brain. Let’s start with reproduction. Why do we need it? We need to reproduce to provide for the continues maintenance of the species. Every living organism owes its existence to the reproductive activity of other organism, no matter whether it is sexual or asexual reproduction. Unfortunately, nowadays there is an increasing problem with a fertility and reproductive performance in animals and humans. World Health Organization has calculated that over 10% of couples are inflicted and the overall burden of subfertility or infertility is significant. On the other hand, global malnutrition rates remain alarming.

Under-, over-nutrition and obesity are affecting health of the populations around the globe. Lifestyle changes occurring globally, although not necessarily associated with an improvement of available diet, are often accompanied by corresponding increase of diet-related chronic non-communicable diseases such as infertility. So, where do we find connections between reproduction, diet and the brain? They can be find in reproductive axis, known as hypothalamus-pituitary-gonadal axis, HPG axis, coordinating brain and reproductive system performance in both females and males. But how it works? When we can observe diet related effects on reproduction involving brain? Well, all depends on time and the window of susceptibility. Timing of the dietary experience matter.

For sure parental investment is one of the environmental conditions that can directly influence development of offspring and their further performance, including reproductive capacity. In 90’ of the past century the British epidemiologist David Barker suggested that intrauterine growth retardation, low birth weight, and preterm birth have a causal relationship to the origins of hypertension, coronary heart disease, and non-insulin-dependent diabetes, in middle age. Since the original observation of Barker, it has become apparent that environmental factors, including diet, during prenatal and postnatal life, a window of developmental susceptibility, can have profound effect on the programming of intracellular signals, cell-to-cell communication, and metabolic pathways. These adaptations affect the onset of childhood and adulthood disorders, involving among others reproductive system.

Just how important is diet in governing reproduction, can show some studies on animals and humans. An evolutionary adaptation that allows an individual or species to survive when food is scarce is hypothalamic hypogonadism, resulting from deficient release of gonadotropin releasing hormone from hypothalamus. This phenotype is representative of a negative energy balance and can be reversible when energy supplies are restored. It is especially important to female reproduction. For example, undernutrition, caused by anorexia or calorie restriction, delays the onset of puberty and disrupts ovarian cycle in humans, because HPG axis malfunction. On the other hand, obese individuals share the same phenotype through childhood obesity cause precocious puberty in girls.

Recent mouse studies showed that neonates exposed to undernutrition during lactation acquire gender-specific delays in puberty attainment, caused by programming of the hypothalamus over at least two generations. It is due to the fact that morphological and functional development of the reproductive system as well as the HPG axis occurs both pre- and postnatally. To conclude, diet is crucial for prenatal and postnatal development determining future health of next generations. This phenomenon includes reproductive system development and function in adulthood, and seems to be programmed over generations. What mother, child and each individual eats matters, since it can significantly affect different systems of the human body.

And it can occur via brain, the steering center for several systems in our body, such as the one governing reproduction.