Unilaterality of the sympathetic innervation of each pad of rat interscapular brown adipose tissue

Do, Foster; Depocas, Florent; Zaror-Behrens, Gloria

doi:10.1139/y82-018

Cited by 63 publications

(23 citation statements)

References 2 publications

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“…Lipid content before administration of NA was set to 100% (A). Integral values of the (CH 2 ) n peak were converted into milligrams of lipid (B) Supplemental Material can be found at: ( 42,43 ), as has been demonstrated in studies about denervation of BAT (44)(45)(46)(47). The present fi ndings show that the reorganization of BAT during cold acclimation toward an improvement of its thermogenic capacity occurs in the absence of UCP1, although a slightly reduced intensity was observed as compared with WT mice.…”

Section: In Vivo Lipid Oxidation During Na-induced Thermogenesissupporting

confidence: 63%

Brown adipose tissue dynamics in wild-type and UCP1-knockout mice: in vivo insights with magnetic resonance

Grimpo

Völker

Heppe

et al. 2014

Journal of Lipid Research

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This article is available online at http://www.jlr.org body temperature maintenance of small eutherian mammals and newborns during periods of cold exposure. BAT thermogenesis is activated by the release of noradrenaline (NA) from sympathetic innervation. Uncoupling protein 1 (UCP1) in the inner mitochondrial membrane of the brown adipocytes uncouples the respiratory chain from ATP synthesis and thus energy is dissipated as heat ( 1-3 ). Prolonged cold exposure or a short photoperiod induces the recruitment of BAT ( 4-6 ). Brown adipocytes of coldadapted mice, contain small and multilocular lipid vacuoles, which are rich in cytoplasm and have a high content of mitochondrial protein (7)(8)(9). This provides an enhanced thermogenic capacity during cold exposure, and BAT can be considered as the major site of adaptive nonshivering thermogenesis (NST) in rodents and other small mammals ( 4, 10-12 ).The breakdown of lipids via lipoprotein lipase plays an important role during UCP1-mediated heat production ( 13 ). Free fatty acids (FFAs) directly activate UCP1 and feed the respiratory chain, i.e., FFAs are the major substrate for NST ( 14,15 ). Therefore active BAT is considered as a main consumer of lipids and FFAs and its contribution to plasma clearance of administered triglycerides has been shown previously ( 16,17 ). On the other hand a release of fatty acids during thermogenesis from BAT has been assumed, indicating a substrate supply to other tissues ( 18,19 ). Sympathetic activation by cold exposure or injections of NA not only activate BAT but also stimulate sympathetic receptors in general, leading to an increase in heart rate, blood flow, and metabolic responses in other tissues. The contribution of these UCP1-independent processes to total NST remain unclear ( 20, 21 ).Abstract We used noninvasive magnetic resonance imaging (MRI) and magnetic resonance spectroscopy to compare interscapular brown adipose tissue (iBAT) of wild-type (WT) and uncoupling protein 1 (UCP1)-knockout mice lacking UCP1-mediated nonshivering thermogenesis (NST). Mice were sequentially acclimated to an ambient temperature of 30°C, 18°C, and 5°C. We detected a remodeling of iBAT and a decrease in its lipid content in all mice during cold exposure. Ratios of energy-rich phosphates (ATP/ADP, phosphocreatine/ATP) in iBAT were maintained stable during noradrenergic stimulation of thermogenesis in coldand warm-adapted mice and no difference between the genotypes was observed. As free fatty acids (FFAs) serve as fuel for thermogenesis and activate UCP1 for uncoupling of oxidative phosphorylation, brown adipose tissue is considered to be a main acceptor and consumer of FFAs. We measured a major loss of FFAs from iBAT during noradrenergic stimulation of thermogenesis. This mobilization of FFAs was observed in iBAT of WT mice as well as in mice lacking UCP1. The high turnover and the release of FFAs from iBAT suggests an enhancement of lipid metabolism, which in itself contributes to the sympathetically activated NST and which is independent fro...

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Section: In Vivo Lipid Oxidation During Na-induced Thermogenesissupporting

confidence: 63%

Brown adipose tissue dynamics in wild-type and UCP1-knockout mice: in vivo insights with magnetic resonance

Grimpo

Völker

Heppe

et al. 2014

Journal of Lipid Research

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“…Under physiological circumstances, when an animal is exposed to cold, it will attempt to activate whatever brown fat it possesses. This is mediated by activation of the sympathetic nerves that directly innervate the brown adipose tissue depots (Foster et al, 1982). This is thus not a generalized sympathetic activation but a highly localized one .…”

Section: Norepinephrine Injection As a Test To Determine Nonshiveringmentioning

confidence: 99%

Nonshivering thermogenesis and its adequate measurement in metabolic studies

Cannon

Nedergaard

2011

Journal of Experimental Biology

595

610

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SummaryAlterations in nonshivering thermogenesis are presently discussed as being both potentially causative of and able to counteract obesity. However, the necessity for mammals to defend their body temperature means that the ambient temperature profoundly affects the outcome and interpretation of metabolic experiments. An adequate understanding and assessment of nonshivering thermogenesis is therefore paramount for metabolic studies. Classical nonshivering thermogenesis is facultative, i.e. it is only activated when an animal acutely requires extra heat (switched on in minutes), and adaptive, i.e. it takes weeks for an increase in capacity to develop. Nonshivering thermogenesis is fully due to brown adipose tissue activity; adaptation corresponds to the recruitment of this tissue. Diet-induced thermogenesis is probably also facultative and adaptive and due to brown adipose tissue activity. Although all mammals respond to injected/infused norepinephrine (noradrenaline) with an increase in metabolism, in non-adapted mammals this increase mainly represents the response of organs not involved in nonshivering thermogenesis; only the increase after adaptation represents nonshivering thermogenesis. Thermogenesis (metabolism) should be expressed per animal, and not per body mass [not even to any power (0.75 or 0.66)]. A 'cold tolerance test' does not examine nonshivering thermogenesis capacity; rather it tests shivering capacity and endurance. For mice, normal animal house temperatures are markedly below thermoneutrality, and the mice therefore have a metabolic rate and food consumption about 1.5 times higher than their intrinsic requirements. Housing and examining mice at normal house temperatures carries a high risk of identifying false positives for intrinsic metabolic changes; in particular, mutations/treatments that affect the animal's insulation (fur, skin) may lead to such problems. Correspondingly, true alterations in intrinsic metabolic rate remain undetected when metabolism is examined at temperatures below thermoneutrality. Thus, experiments with animals kept and examined at thermoneutrality are likely to yield an improved possibility of identifying agents and genes important for human energy balance.

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“…This can be carried out by surgical denervation and, moreover, can be accomplished using the unilateral surgical denervation model. Specifically, because both the lobes of IBAT have unilateral postganglionic innervation by the SNS in laboratory rats, 36,37 mice 38 and Syrian 39,40 and Siberian hamsters 41 (but see Seydoux et al 42 and Girardier and Seydoux 43 ), one side of the IBAT is surgically denervated and its contralateral side is sham-denervated, yielding a within-animal control. Thus, the beauty of the unilateral denervation model is that, for each animal, all circulating and central (brain) factors, as well as the animal’s nutritional status, genetics and behavior, are identical, with the exception that one lobe of the IBAT is denervated and the other is not (for review see Bartness and Song 26 ).…”

Section: What Is the Functional Evidence For The Sympathetic Neural Cmentioning

confidence: 99%

Sympathetic and sensory innervation of brown adipose tissue

2010

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The innervation of brown adipose tissue (BAT) by the sympathetic nervous system (SNS) is incontrovertible and, with its activation, functions as the principal, if not exclusive, stimulator of BAT thermogenesis. The parasympathetic innervation of BAT only appears in two minor BAT depots, but not in the major interscapular BAT (IBAT) depot. BAT thermogenesis is triggered by the release of norepinephrine from its sympathetic nerve terminals, stimulating β3-adrenoceptors that turns on a cascade of intracellular events ending in activation of uncoupling protein-1 (UCP-1). BAT also has sensory innervation that may function to monitor BAT lipolysis, a response necessary for activation of UCP-1 by fatty acids, or perhaps responding in a feedback manner to BAT temperature changes. The central sympathetic outflow circuits ultimately terminating in BAT have been revealed by injecting the retrograde viral transneuronal tract tracer, pseudorabies virus, into the tissue; moreover, there is a high degree of colocalization of melanocortin 4-receptor mRNA on these neurons across the neural axis. The necessary and sufficient central BAT SNS outflow sites that are activated by various thermogenic stimuli are not precisely known. In a chronic decerebration procedure, IBAT UCP-1 gene expression can be triggered by fourth ventricular injections of melanotan II, the melanocortin 3/4 receptor agonist, suggesting that there is sufficient hindbrain neural circuitry to generate thermogenic responses with this stimulation. The recent recognition of BAT in normal adult humans suggests a potential target for stimulation of energy expenditure by BAT to help mitigate increased body fat storage.

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Unilaterality of the sympathetic innervation of each pad of rat interscapular brown adipose tissue

Cited by 63 publications

References 2 publications

Brown adipose tissue dynamics in wild-type and UCP1-knockout mice: in vivo insights with magnetic resonance

Brown adipose tissue dynamics in wild-type and UCP1-knockout mice: in vivo insights with magnetic resonance

Nonshivering thermogenesis and its adequate measurement in metabolic studies

Sympathetic and sensory innervation of brown adipose tissue

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