8.A.106.  The Caltrin/Peptide YY (Caltrin/PYY) Family  

Caltrin (calcium transport inhibitor) is a family of small and basic proteins of the mammalian seminal plasma which bind to sperm cells during ejaculation and inhibit the extracellular Ca²⁺ uptake, preventing the premature acrosomal exocytosis and hyperactivation when sperm cells ascend through the female reproductive tract. The binding of caltrin proteins to specific areas of the sperm surface suggests the existence of caltrin receptors, or precise protein-phospholipid arrangements in the sperm membrane, distributed in the regions where Ca²⁺ influx may take place (Grasso and Coronel 2017). 

Ghrelin and peptide YY (PYY) are brain-gut peptides that have a variety of physiological functions and are involved in energy regulation (Li et al. 2011). Abnormalities in the expression and secretion of ghrelin and PYY are known to occur in lifestyle-related diseases including obesity, and the improvement of these abnormalities has become an important challenge. Exercise influences ghrelin and PYY concentrations by increasing PYY secretion although ghrelin levels vary with the study subject, timing of exercise, and duration of exercise (Li et al. 2011).  Metformin, the cornerstone of the pharmacological therapy for type 2 diabetes mellitus (T2DM), belongs to the biguanide class of drugs and improves hepatic insulin resistance possibly by enhancing glucagon like peptide-1 (GLP-1) and peptide YY (PYY) secretion (Tavares Bello et al. 2018). GLP-1- and peptide-YY (PYY)-secreting L cells potentially have antidiabetic and antiobesity effects (Christiansen et al. 2018).