Endocrine Abstracts

Circadian rhythms are cycles of behaviour and physiology that persist with a period of approximately (circa-) one day (-dian) when an individual is held in temporal isolation. They permeate all levels of biological activity, from gene expression and hormone secretion to cognitive ability. These daily rhythms are co-ordinated by a hypothalamic pacemaker, the suprachiasmatic nuclei (SCN). Individual SCN neurons are competent circadian pacemakers, synchronised to solar time by re...

There is a growing body of literature indicating that circadian mechanisms regulate metabolism in adipose tissues. Genes encoding the core circadian regulatory proteins (CCRP) display a robust oscillatory expression profile in murine adipose tissue depots, as well as the bone, liver, and heart. Temporally restricted food access as well as photic stimuli can entrain the CCRP expression. In murine models, deletion or mutation of the CCRP genes, clock and PPAR gamma coa...

In mammals, a master pacemaker residing in the hypothalamic suprachiasmatic nuclei (SCN) and subordinate clocks found throughout the body coordinate circadian rhythms of behavior and physiology. One prominent physiological rhythm is the release of glucocorticoids (GCs) by the adrenal gland, brought about by the rhythmic activation of the hypothalamus–pituitary–adrenal (hpa) axis and the secretion of ACTH from the pituitary. In humans, blood GC levels peak in the earl...

Life on earth is governed by the continuous 24-hour cycle of light and dark. Organisms have adapted to this environment with clear diurnal rhythms in their physiology and metabolism enabling them to anticipate predictable environmental fluctuations over the day and to optimise the timing of relevant biological processes to this cycle. It is of considerable interest that the normal diurnal variation in these processes is lost in the presence of insulin resistance, obesity and d...