No abstract

In the last few years, kisspeptin-KISS1R signaling has appeared as a major regulator of the reproductive function in several vertebrate species. However, KISS1(encoding kisspeptin) and its putative receptor, KISS1R, are expressed in several other tissues. Adipose tissue, which secretes many peptides with diverse functions in normal physiology, expresses KISS1, which is modulated by gonadal steroids as well as by body nutritional status. Similarly, KISS1Rexpression is also found in adipose tissue, but the local role of kisspeptin in adipocyte function is currently unknown. Therefore, in the present study the effects of exogenous human kisspeptin-10 (KP10) were studied on three important adipokines, namely, adiponectin, leptin, and resistin in a set of four chair-restraint habituated intact adult male rhesus monkeys under; 1) normal fed conditions, 2) 24-h fasting conditions, and 3) 48-h fasting conditions. Plasma resistin and leptin levels decreased (p<0.01), whereas adiponectin levels increased (p<0.05) in fasted monkeys. Kisspeptin administration significantly increased (p<0.05) mean plasma adiponectin levels under fed and 24-h fasting conditions as compared to pretreatment or vehicle-treatment levels. A stimulatory effect was also observed on the 48-h fasting stimulated plasma adiponectin levels, but it lacked statistical significance. In contrast, no effect of kisspeptin was observed on mean plasma leptin and resistin levels. Thus, the present study demonstrated a stimulatory effect of peripheral kisspeptin administration on the plasma adiponectin levels under fed and 24-h fasting conditions in the adult male rhesus monkey. These findings, therefore, assign a novel role to kisspeptin, a regulator of adipocyte function in higher primate.

The gut microbiome is comprised of various types of bacteria, fungi, protozoa, and viruses naturally occurring in humans and animals as normal microflora. Gut microorganisms are typically host specific, and their number and type vary according to different host species and environment. Gut microbes contribute directly and/or indirectly to various physiological processes including immune modulation, regulation of various neurotransmitter, and hormones, as well as production of many antioxidants and metabolites. They also play a role as antibiotic, antiinflammatory, anti-diabetic, and anti-carcinogenic agents. Moreover, the ability of gut microbes to attenuate various systemic diseases like coronary heart disease, irritable bowel syndrome, metabolic diseases like diabetes mellitus, and infectious diseases like diarrhea has recently been reported. Current research findings have enough evidence to suggest that gut microbiome is a new organ system mainly due to the microorganisms' specific biochemical interaction with their hosts and their systemic integration into the host biology. Investigations into the potential ability of gut microbiome to influence metabolism inside their host via biochemical interaction with antibiotics and other drugs has recently been initiated. This chapter specifically focuses on the importance of gut microorganisms as a new organ system.

Kisspeptin-Kiss1R signalling in mammals has been implicated as an integral part of the reproductive cascade. Kisspeptinergic neurons upstream of GnRH neurons are involved in the activation of the hypothalamic GnRH pulse generator during pubertal onset. Thus, the major research focus has been on the central effects of kisspeptin. The demonstration of the presence of KissR expression in human testes suggests additional unknown actions of kisspeptin-KISS1R signalling at the distal component of the male reproductive axis. Here we explored the impact of kisspeptin at the testis in the adult male rhesus monkey. We employed the clamped monkey model to assess the intratesticular actions of kisspeptin. Plasma testosterone and LH levels were monitored in four adult male monkeys. The peripheral administration of human kisspeptin-10 (50 μg, iv bolus) caused a single LH pulse, which was followed by a robust increase in plasma testosterone levels sustained for at least 180 min. This response was abolished when kisspeptin was administered to GnRH receptor antagonist (acyline) pre-treated animals. However, kisspeptin administration significantly (P < 0.005) elevated hCG-stimulated testosterone levels in acyline pre-treated monkeys when compared with saline+ hCG treatment. These results revealed a novel peripheral facet of kisspeptin signalling.

Kisspeptin receptor and kisspeptin are localized in the testis of Old World and New World primates.