Rapid communicationHyperleptinemia prevents increased plasma ghrelin concentration during short-term moderate caloric restriction in rats
Section snippets
Materials and methods
Twenty-four, 6-month-old Fischer 344 male rats were purchased from Harlan Italy (San Pietro al Natisone, Italy). All animals were kept in individual cages in the Animal Facility of the University of Trieste in a controlled environment (t = 22°C, 12:12-hour light:dark cycle) and fed a standard commercial chow diet (Harlan 2018, Harlan; 3.4 kcal/g). Experimental protocol and procedures were approved by the Institutional Review Committee for animal studies as part of a larger protocol to study
Results
Leptin infusion reduced overall spontaneous food intake by 26% compared with control rats and super-imposable changes were induced by design in pair-fed animals (Table 1, Figure 1). As expected, leptin-treated and pair-fed rats lost weight moderately but significantly compared with control animals (Table 1). Plasma leptin concentration increased approximately 3-fold in the leptin-treated group and was reduced in the pair-fed group compared with control animals (both P < 0.05 vs. control,
Discussion
The current study demonstrates negative regulation by circulating leptin of plasma ghrelin concentration in vivo. Physiologic increments in plasma leptin prevent a substantial raise in plasma ghrelin concentration observed following 1 week of moderate caloric restriction in lean adult rats. Because ghrelin is an important gastric orexigenic signal in rodents as well as in humans,1, 2, 3, 4 this leptin effect may contribute to sustained reduction of spontaneous food intake during body weight
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Rikkunshito as a ghrelin enhancer
2012, Methods in EnzymologyCitation Excerpt :We have found that plasma leptin and insulin levels in aged mice are significantly higher than in young ones (Takeda et al., 2010). Leptin and insulin are reported to inhibit ghrelin secretion from the stomach into the circulation (Barazzoni et al., 2003); hence elevated leptin and insulin in the elderly may contribute to the inhibition of secretion of ghrelin during fasting, resulting in prolonged satiety and inhibition of hunger sensation. Moreover, the activation of the phosphoinositide 3-kinase (PI3K)–phosphodiesterase 3 (PDE3) pathway was recently proposed as a mechanism by which leptin blocks ghrelin signaling in neuropeptide Y (NPY) neurons, and it may counteract the adenylate cyclase–cAMP–protein kinase A system implicated in the effect of ghrelin (Kohno et al., 2007).
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The authors thank M. Sturma, A. de Santis, and A. Semolic for skillful technical assistance, and Dr. W. Micheli for invaluable assistance in RIA measurements.