%0 Journal Article
%T Circadian Rhythms and Obesity in Mammals
%A Oren Froy
%J ISRN Obesity
%D 2012
%R 10.5402/2012/437198
%X Obesity has become a serious public health problem and a major risk factor for the development of illnesses, such as insulin resistance and hypertension. Attempts to understand the causes of obesity and develop new therapeutic strategies have mostly focused on caloric intake and energy expenditure. Recent studies have shown that the circadian clock controls energy homeostasis by regulating the circadian expression and/or activity of enzymes, hormones, and transport systems involved in metabolism. Moreover, disruption of circadian rhythms leads to obesity and metabolic disorders. Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. Feeding regimens, such as restricted feeding (RF), calorie restriction (CR), and intermittent fasting (IF), provide a time cue and reset the circadian clock and lead to better health. In contrast, high-fat (HF) diet leads to disrupted circadian expression of metabolic factors and obesity. This paper focuses on circadian rhythms and their link to obesity. 1. Introduction Obesity has become a serious and growing public health problem [1]. Attempts to develop new therapeutic strategies have mostly focused on energy expenditure and caloric intake. Recent studies link energy homeostasis to the circadian clock at the behavioral, physiological, and molecular levels [2¨C5], emphasizing that certain nutrients and the timing of food intake may play a significant role in weight gain [6]. Therefore, it is plausible that resetting of the circadian clock can be used as a new approach to attenuate obesity. 2. Circadian Rhythms Our planet revolves around its axis causing light and dark cycles of 24 hours. Organisms on our planet evolved to predict these cycles by developing an endogenous circadian (circa: about and dies: day) clock, which is synchronized to external time cues. This way, organisms ensure that physiological processes are carried out at the right time of the circadian cycle [7]. All aspects of physiology, including sleep-wake cycles, cardiovascular activity, endocrine system, body temperature, renal activity, gastrointestinal tract motility, and metabolism, are influenced by the circadian clock [7, 8]. Indeed, 10¨C20% of all cellular transcripts are cyclically expressed, most of which are tissue-specific [2, 9¨C13]. 3. The Circadian Clock The central circadian clock is located in the suprachiasmatic nuclei (SCN) of the brain anterior hypothalamus. The SCN clock is composed of multiple, single-cell oscillators synchronized to generate circadian rhythms [8, 14¨C16]. The
%U http://www.hindawi.com/journals/isrn.obesity/2012/437198/