Sunday, 23 March 2014

Catecholamine resistance in obesity

Inflammation produces catecholamine resistance in obesity via activation of PDE3B by the protein kinases IKK{varepsilon} and TBK1.
Decreased sympathetic activation of adipose tissue due to impaired catecholamine synthesis or sensitivity has been observed in obese patients (Reynisdottir et al., 1994Stallknecht et al., 1997;Horowitz and Klein, 2000Jocken et al., 2008). Obesity is commonly associated with blunted whole-body catecholamine-induced lipolysis (Horowitz and Klein, 2000). This is thought to occur through a number of mechanisms, including leptin resistance (Myers et al., 2010), as well as the reduced expression of β-adrenergic receptors (Reynisdottir et al., 1994) or increased expression of α2-adrenergic receptors (Stich et al., 2002). White adipose tissue and cultured isolated adipocytes from obese human and mouse models exhibit decreased cAMP-stimulated lipolysis and fat oxidation, due to reduced energy expenditure from decreased mitochondrial uncoupling (Yehuda-Shnaidman et al., 2010). This desensitization to adrenergic activation is also a feature of childhood onset obesity (Bougneres et al., 1997Enoksson et al., 2000), and has been observed in adipocytes from first-degree relatives of obese subjects (Hellstrom et al., 1996).

Acute stimulation of white adipocyte respiration by PKA-induced lipolysis.

we present evidence that human white adipocytes can acutely increase aerobic and anaerobic respiration in response to βAR and protein kinase A (PKA)-dependent stimulation of lipolysis.

Lipolysis stimulated by βAR activation or other maneuvers that increase cAMP levels in white adipocytes acutely induces mitochondrial uncoupling and cellular energetics,

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