CNS and hormone control of lipid mobilization: interest and limits of comparative physiology

The mobilization of lipids stored in adipose tissue is closely controlled by neuro-humoral signals. The process of lipolysis, i.e. the hydrolysis of triglycerides stored in fat cells (or adipocytes) and release of glycerol and non-esterified fatty acids, is highly specific of the adipose tissue. No other tissue is able to provide notable amounts of non-esterified fatty acids, whether on a short-term or long-term basis. Once they reach the plasma where they bind to albumin, these fatty acids are used as preferred oxidative substrate by skeletal muscle, liver, kidney and myocardium. This article summarises the mechanisms of action of various neuro-humoral mediators (catecholamines,insulin, natriuretic peptides, adenosine, neuropeptide Y, peptide YY, prostaglandins) involved in the control of hormone-sensitive lipase activity and hydrolysis of triglycerides in fat cells in man and in various small mammal models used in laboratories. Species-specific differences and their potential consequences on extrapolation from animal models to man and clinical research are highlighted.Le contrôle de la mobilisation des lipides stockés dans le tissu adipeux est un processus étroitement contrôlé par le système neuro-humoral. La lipolyse, processus assurant l'hydrolyse des triglycérides stockés dans la gouttelette lipidique des adipocytes, et la libération du glycérol et des acides gras non estérifiés, est une fonction très spécifique du tissu adipeux. Il n'existe pas d'autre tissu capable de fournir à court et long terme des quantités notables d'acides gras non-estérifiés. Libérés dans le plasma où ils se lient à l'albumine, ils constituent un substrat oxydatif privilégié pour le muscle squelettique, le foie, le rein et le myocarde. Ce mémoire récapitule les mécanismes d'action des divers signaux neuro-humoraux (catécholamines, insuline, peptides natriurétiques, adénosine, neuropeptide Y, peptide YY, prostaglandines) impliqués dans le contrôle de la lipase hormono-sensible et de l'hydrolyse des triglycérides de l'adipocyte de l'homme et de divers petits mammifères utilisés dans les laboratoires. Nous insistons plus particulièrement sur les disparités interspécifiques et leurs conséquences potentielles pour l'extrapolation des données acquises sur les modèles animaux, à l'homme et à la recherche clinique

Atrial Natriuretic Peptide Induces Postprandial Lipid Oxidation in Humans

OBJECTIVE—Atrial natriuretic peptide (ANP) regulates arterial blood pressure. In addition, ANP has recently been shown to promote human adipose tissue lipolysis through cGMP-mediated hormone-sensitive lipase activation. We hypothesized that ANP increases postprandial free fatty acid (FFA) availability and energy expenditure while decreasing arterial blood pressure

Methodological approaches to assess body-weight regulation and aetiology of obesity

Obesity, which is becoming one of the major health hazards in developed and developing societies, results from a long-term positive energy balance. Body-weight regulation and stability depend on an axis with three interrelated components: food intake, energy expenditure and adipogenesis, although there are still many unknown features concerning fuel homeostasis and energy balance. Biochemical processes are interconnected, and a separate consideration of each component is often useful for methodological purposes and to achieve a better understanding of the whole system. Thus, many different experimental approaches can be applied by using laboratory animals, cell culture or human subjects to unravel the molecular mechanisms which participate in body-weight regulation. Thus, both in vitro (cellular and subcellular models) and in vivo methods have dramatically increased our knowledge of weight control. Several strategies in obesity research are reported here, exploiting the opportunities of the molecular era as well as novel whole-body approaches, which will impact on the development of new targets for obesity management and prevention

Sugar-sweetened beverages and weight gain in children and adults: a systematic review from 2013 to 2015 and a comparison with previous studies

Objective: Partly inconsistent findings from previous reviews have fueled discussions on the impact of sugar-sweetened beverages (SSBs) on obesity development. The aim was to systematically review the recent evidence in children and adults. Methods: Data were retrieved from the databases MEDLINE, EMBASE, and Cochrane library for the period January 2013 to October 2015. A systematic review of prospective cohort studies and randomized controlled trials (RCTs) relating SSBs to weight measures was conducted. Results: 30 publications met the inclusion criteria. Prospective cohort studies (96%; n = 26) showed a positive association between consumption of SSBs and weight/BMI in adults and children (n = 242,352), and only one cohort study in children showed no association. Findings from three RCTs in children demonstrated that SSB consumption had an effect on BMI/BMI z-score. The one RCT in adults showed no significant effect of the intervention. 63% of the studies were of good, 30% of medium quality, and none was funded by industry. Conclusion: Recent evidence suggests that SSB consumption is positively associated with or has an effect on obesity indices in children and adults. By combining the already published evidence with the new one, we conclude that public health policies should aim to reduce the consumption of SSBs and encourage healthy alternatives such as water. (c) 2017 The Author(s) Published by S. Karger GmbH, Freibur

Obésité humaine et système nerveux sympathique

The sympathetic nervous system (SNS) is an important element of the autonomic nervous system which has an essential role in the maintenance of body homeostasis. SNS activation involves norepinephrine release by noradrenergic fibres and epinephrine secretion by adrenal medulla. SNS controls a number of physiological events including metabolic processes, cardiac and vascular activities, gastrointestinal functions and endocrine secretions. The SNS has a major role in the control of adipose tissue function through a direct effect on adipocytes and adipose tissue vessels, and by an indirect effect on pancreatic hormones secretion. Various alterations of SNS effects on metabolism have been implicated in the development and the maintenance of obesity. This review provides an overview of physiological aspects of the SNS involvement in normal and obese subjects. Physiological and pathological changes in SNS activity are summarized. Modifications occurring in adipose tissue function and fat cell responsiveness to norepinephrine and epinephrine are also considered