Circadian regulation of lipid metabolism

ANA CECILIA ANZULOVICH

Advances in Lipid Metabolism

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Lugar: Kerala (India); Año: 2008;

A wide diversity of biochemical, physiological and behavioral parameters vary rhythmically throughout a day and are called circadian rhythms. Such rhythms which include, among others, heartbeating, blood pressure, and some hormonal secretions, are essencial for anticipating adaptation of individuals to coming environmental changes and activity-rest periods. In mammals, a central clock in the suprachiasmatic nucleus (SCN) of the hypothalamus synchronizes those rhythms through several signals (neural, humoral, etc.), and many peripheral clocks located in most tissues and cells,coordinate their daily activities. Metabolism in general is under circadianregulation. Expression of several genes codifying enzymes or regulator proteins involved in lipid metabolism, such as Acetyl Co-A carboxylase, Fatty acid synthetase, Cholesterol-7α- hydroxylase, SREBP1, PPARα, etc., follow a  circadian pattern. CLOCK and BMAL1 transcription factors are key components of the molecular machinery of the clock. Clock or Bmal (-/-) mutant mice develop obesity and metabolic syndrome evidencing the importance of the circadian clock in the energy metabolism. On the other hand, feeding itself is able to generate and send powerful cues to the peripheral organs which, under certain conditions can override thesynchronizing signals from the central clock in the SCN. In this chapter I summarize the molecular links between the circadian clock mechanism and lipid metabolism as well as the role played by key regulators such SREBPs and PPARs as integrators of circadian and nutritional cues.