Leptin-induced lipolysis opposes the tonic inhibition of endogenous adenosine in white adipocytes

The aim of the present study was to gain insight into the signaling pathway used by leptin to stimulate lipolysis. The lipolytic rate of white adipocytes from sex- and age-matched lean (+/+) and fa/fa rats was determined in the absence or presence of leptin together with a number of agents acting at different levels of the signaling cascade. Leptin did not modify FSK-, dbcAMP-, and IBMX-stimulated lipolysis. Lipolysis can also be maximally stimulated by lowering media adenosine levels with adenosine deaminase (ADA), i.e., in the ligand-free state. Although ADA produced near maximal lipolysis in adipocytes of lean animals, only half of the maximal lipolytic rate (50.9+/-3.2%) was achieved in fat cells from fa/fa rats (P=0.0034). In adipocytes from lean animals preincubated with ADA, leptin caused a concentration-related stimulation of lipolysis (P=0.0001). However, leptin had no effect on the lipolytic activity of adipocytes in the ligand-free state from fa/fa rats. The adenosine A1 receptor agonist CPA effectively inhibited basal lipolysis in both lean and obese adipocytes (P=0.0001 and P=0.0090, respectively). Leptin had no effect on the lipolytic rate of adipocytes isolated from fa/fa rats and preincubated with CPA. When adipocytes were incubated with the A1 receptor antagonist DPCPX, a significant increase in glycerol release was observed in fa/fa fat cells (P=0.009), whereas cells isolated from lean rats showed no differences to ADA-stimulated lipolysis. After pretreatment with PTX, which inactivates receptor-mediated Gi function, adipocytes of obese rats became as responsive to the stimulatory actions of ISO as cells from lean rats (P=0.0090 vs. ISO in fa/fa rats; P=0.2416 vs. lean rats, respectively). PTX treatment of lean cells, however, did not alter their response to this lipolytic agent. It can be concluded that the lipolytic effect of leptin is located at the adenylate cyclase/Gi proteins level and that leptin-induced lipolysis opposes the tonic inhibition of endogenous adenosine in white adipocytes

Nonlinear Transient Field Problems with Phase Change using the Boundary Element Method

Peer reviewe

The impact of a child's chronic illness on hopeful thinking in children and parents

Copyright © Guilford Publications Inc. 2008 All Rights Reserved.The current study investigated the impact of a child's congenital or acquired chronic illness on hope scores reported by children and parents (N= 132). Hope was conceptualised as a cognitive process comprised of a reciprocally derived sense of successful pathways (the ability to visualize goals) and agency (the determination to reach those goals) (Snyder et al., 1991). As expected, children with a chronic illness (congenital or acquired) and their parents reported lower scores than their equivalents without a chronic illness. Moreover, children's hope scores were higher when their illness was congenital, and parents' scores were higher when a child's illness was acquired. Children's hope scores were predicted by self–efficacy and interaction difficulties. Parents' hope scores were predicted by self–efficacy and depression. These results have practical implications for clinicians seeking to inspire hope when a child faces chronic illness, suggesting that hope–based interventions need to be tailored to suit the individual and onset of illness.Anthony J. Venning, Jaklin Eliott, Hayley Whitford and Jill Honno

Blue skies ahead Recapturing the missing generation

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