1. Bioactive cyclic dipeptides
C Prasad Peptides. 1995;16(1):151-64. doi: 10.1016/0196-9781(94)00017-z.
Cyclic dipeptides are among the simplest peptide derivatives commonly found in nature. Most cyclic dipeptides found to date appear to have emerged as by-products of fermentation and food processing. However, many are endogenous to members of animal and plant kingdoms; these include cyclo(Pro-Leu), cyclo(Pro-Val), cyclo(Pro-Phe), cyclo(Ala-Leu), cyclo(Pro-Tyr), cyclo(Pro-Trp), and cyclo(His-Pro). Although the five cyclic dipeptides--cyclo(His-Pro), cyclo(Leu-Gly), cyclo(Tyr-Arg), cyclo(Asp-Pro), and cyclo(Pro-Phe)--exhibit interesting physiological and/or pharmacological activities in mammals, only one of these, cyclo(His-Pro), has been conclusively shown to be endogenous to mammals. On the other hand, cyclo(Leu-Gly), cyclo(Tyr-Arg), and cyclo(Asp-Pro) are structurally related to endogenous peptides Pro-Leu-Gly-NH2 (melanocyte-stimulating hormone release inhibiting factor), Tyr-Arg (kyotorphin), and Val-Pro-Asp-Pro-Arg (enterostatin), respectively, which may serve as precursor peptides. It needs to be determined, however, whether these peptides can indeed result from the processing of their respective precursors. In conclusion, it appears that cyclic dipeptides are a relatively unexplored class of bioactive peptides that may hold great promise for the future.
2. Afferent signals regulating food intake
G A Bray Proc Nutr Soc. 2000 Aug;59(3):373-84. doi: 10.1017/s0029665100000422.
Food intake is a regulated system. Afferent signals provide information to the central nervous system, which is the centre for the control of satiety or food seeking. Such signals can begin even before food is ingested through visual, auditory and olfactory stimuli. One of the recent interesting findings is the demonstration that there are selective fatty acid taste receptors on the tongue of rodents. The suppression of food intake by essential fatty acids infused into the stomach and the suppression of electrical signals in taste buds reflect activation of a K rectifier channel (K 1.5). In animals that become fat eating a high-fat diet the suppression of this current by linoleic acid is less than that in animals that are resistant to obesity induced by dietary fat. Inhibition of fatty acid oxidation with either mercaptoacetate (which blocks acetyl-CoA dehydrogenase) or methylpalmoxirate will increase food intake.
3. Novel hormone "receptors"
Ilka Nemere, Korry Hintze J Cell Biochem. 2008 Feb 1;103(2):401-7. doi: 10.1002/jcb.21437.
Our concepts of hormone receptors have, until recently, been narrowly defined. In the last few years, an increasing number of reports identify novel proteins, such as enzymes, acting as receptors. In this review we cover the novel receptors for the hormones atrial naturetic hormone, enterostatin, hepcidin, thyroid hormones, estradiol, progesterone, and the vitamin D metabolites 1,25(OH)(2)D(3) and 24,25(OH)(2)D(3).
