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  • br Regulation of plasma ghrelin concentration

    2022-05-18


    Regulation of plasma ghrelin concentration As described above, ghrelin is primarily produced in the stomach and secreted into the blood stream. Plasma ghrelin does not significantly differ between chronic heart failure (CHF) patients and controls, although plasma ghrelin level is significantly higher in CHF patients with cachexia than in those without cachexia, and correlates negatively with body mass index in patients with CHF [13]. Similarly, plasma ghrelin is elevated in underweight patients with chronic obstructive pulmonary disease (COPD) than in normal-weight patients and healthy control subjects [14]. These data suggest that in CHF and COPD patients, the increase in ghrelin plasma concentrations plays a compensatory role in underlying metabolic imbalance.
    Cardiac actions of ghrelin
    Conclusion
    Acknowledgements
    Introduction Throughout history, physicians and thinkers realized the importance of a proper diet for the maintenance of good health. In support of it, recent medical literature often cites the sentence, “Let food be thy medicine and medicine be thy food”, wrongly attributed to Hippocrates (Cardenas, 2013). Ludwig Andreas Feuerbach “you are what you eat” is also often quoted in this context (Feuerbach, 1863/4). The success of these citations reflects the concern about food in today's world in which overabundance of calories coupled to sedentary life style gives rise to the current obesity epidemic (Hill and Peters, 1998). Indeed, recent evidence shows a marked increase in obesity from 1975 to 2016 (NCD-RisC, 2017). This condition relates to a state of fat excess arising from high Z-YVAD-FMK intake and low physical expenditure (Hill and Peters, 1998). Obesity, however, is a complex and multifactorial pathology involving genetic, biological, environmental, and behavioral factors. Contrasting with obesity, undernutrition or malnutrition in spite of food availability is a common problem in the context of cancer- or aging-related cachexia (Favaro-Moreira et al., 2016). It is also a condition in which feeding control is altered. Since the discovery of the orexigenic hormone ghrelin in 1999, there has been much focus on elucidating the pathways through which it operates, with the expectation that this knowledge could help the discovery of novel targets of therapeutic value for these conditions.
    Interaction between homeostatic and reward mechanisms in food intake It is well known that homeostatic neuronal circuits in the hypothalamus integrate peripheral information, such as metabolites and hormones, to modulate food intake and energy balance [reviews in (Al Massadi et al., 2017, Belgardt and Bruning, 2010)]. However feeding control is also regulated by brain structures pertaining to the reward system (Berthoud, 2011). The reward system was serendipitously discovered in rats by Olds and Milner who used its self-stimulation for operant training (Olds and Milner, 1954). The existence of similar responses was demonstrated in primates (Briese and Olds, 1964) and the underlying circuitry progressively dissected, including its links with the dopaminergic neurons and their targets (Corbett and Wise, 1980). From a “Darwinian standpoint” it makes sense that reward mechanisms are recruited to increase motivation to eat when hungry and to continue eating when food is plenty to ensure storage for future times of shortage [see (Lockie and Andrews, 2013), for a discussion of this issue]. Interestingly, the neuronal circuits involved in homeostatic and reward mechanisms appear to be highly interlaced and recent reports emphasize their functional links. The mesolimbic dopaminergic system, including the projection from the ventral tegmental area (VTA) to the nucleus accumbens (NAc), plays a relevant role in the regulation of food seeking and motivation, while the dorsal striatum is implicated through its Z-YVAD-FMK role in habitual/automatic behaviors. The ingestion of palatable food induces an increment in dopamine (DA) release from neurons of the VTA and the adjacent substantia nigra that project to the NAc and dorsal striatum (Bassareo and Di Chiara, 1999, Pfaus et al., 1995). Imaging experiments in humans confirmed the results obtained in animal models and showed the activation of the NAc, caudate nucleus, and putamen in response to reward stimuli including, food … or romantic love (Acevedo et al., 2012, Small et al., 2003). Although a major role of DA neurons is to code for errors in reward prediction, electrophysiological experiments in non-human primates showed that under uncertainty conditioning, their activity also reflects reward expectation (Fiorillo et al., 2003, Schultz et al., 1992). As discussed below, many studies indicate that ghrelin interacts in multiple ways with the reward system.