Nutritional inputs into the reproductive neuroendocrine control system - a multidimensional perspective

Abstract

Evolution has shaped regulatory systems to improve the chance of reproductive success in a somewhat unpredictable environment. One of the more powerful regulators of reproductive function in both sexes is metabolic status, defined as the availability of nutrients and energy to the tissues. Here, we briefly review the basics of the relationship between metabolic status and the activity of the system that controls pulsatile GnRH and LH secretion. We then reflect on these relationships within the framework of a model that comprises four interdependent 'dimensions': 1) genetic, 2) structural, 3) communicational, and 4) temporal. Using two major examples, the male sheep and the post-partum dairy cow, we illustrate aspects of each dimension that seemed to have evolved to limit the risks associated with 'the decision to reproduce'. The results of recent studies have also led us to include in our model the concepts of 'metabolic memory' and 'nutrient sensing' to help explain some aspects of the temporal dimension. Throughout the review, we propose directions for future research that could shed light on pathways that have evolved to ensure that animals are able to take the least risky 'decision'.