Kisspeptin, also known as’metastin’, is an incredible complex peptide that has been shown to suppress cancer cell growth and metastasis. It is a pleiotropic protein that acts in many ways, including altering mood and behaviour and modulating hormone signalling during puberty and reproduction.
Interestingly, the gene for this peptide has been linked to the melatonin receptor (MTR1). This makes it possible that sleep cycles influence both the levels of melatonin and kisspeptin. In one experiment, mice kept in darkness had low levels of both melatonin and kisspeptin, whilst those exposed to daylight had high levels of each. The mice with the high levels of kisspeptin and melatonin were found to have suppressed tumour growth and had significantly less spread of the melanoma.
The kisspeptin gene encodes a precursor peptide, with ‘KiSS-1’, which is cleaved into the major mature peptide kisspeptin-54 (also known as metastin). Kisspeptin/GPR54 signaling is central to the neuroendocrine reproductive axis for puberty and fertility. In the hypothalamus, kisspeptins activate GnRH neurons which ultimately stimulate LH secretion. Kisspeptin/GPR54 signaling also controls the onset of puberty by indirectly stimulating gonadotropin (FSH) release from the pituitary gland via regulation of NPY mRNA in a GnRH-secreting cell line.
In zebrafish behavioural studies, kisspeptin administration reduces AS-evoked fear responses (erratic movement and freezing) via direct activation of the GPR54 receptor. This indicates that kisspeptin signalling may have a broader role in sexual processing involving limbic and paralimbic brain structures, sexual appetite and erection generation. Moreover, kisspeptin levels in the blood skyrocket during healthy pregnancy. This suggests that a future goal of kisspeptin research may be to develop a simple blood test to determine whether a woman has the potential for successful conception.