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Cai Z, Yuan S, Zhong Y, Deng L, Li J, Tan X, Feng J. Amelioration of Endothelial Dysfunction in Diabetes: Role of Takeda G Protein-Coupled Receptor 5. Front Pharmacol 2021; 12:637051. [PMID: 33995040 PMCID: PMC8113688 DOI: 10.3389/fphar.2021.637051] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Accepted: 02/22/2021] [Indexed: 12/25/2022] Open
Abstract
Diabetes mellitus (DM) eventually leads to chronic vascular complications, resulting in cardiovascular diseases. DM-associated endothelial dysfunction (ED) plays an important role in the development of chronic vascular complications. Low endothelial nitric oxide synthase (eNOS) activity, inflammation, and oxidative stress all contribute to ED. The G protein-coupled receptor Takeda G protein-coupled receptor 5 (TGR5) is a membrane receptor for bile acids that plays an important role in the regulation of glucose metabolism. Recent studies have shown that TGR5 is involved in the regulation of various mediators of ED, which suggests that TGR5 may represent a target for the treatment of DM-associated ED. In this review, we summarize the principal mechanisms of DM-associated ED, then propose TGR5 as a novel therapeutic target on the basis of its mechanistic involvement, and suggest potential directions for future research.
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Affiliation(s)
- Zhengyao Cai
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Suxin Yuan
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Yi Zhong
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Li Deng
- Department of Rheumatology, The Affiliated Hospital of Southwest Medical University, Luzhou, China
| | - Jiafu Li
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Xiaoqiu Tan
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
| | - Jian Feng
- Department of Cardiology, The Affiliated Hospital of Southwest Medical University, Key Laboratory of Medical Electrophysiology, Ministry of Education and Medical Electrophysiological Key Laboratory of Sichuan Province, Institute of Cardiovascular Research, Southwest Medical University, Luzhou, China
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Carpentier AC. 100 th anniversary of the discovery of insulin perspective: insulin and adipose tissue fatty acid metabolism. Am J Physiol Endocrinol Metab 2021; 320:E653-E670. [PMID: 33522398 DOI: 10.1152/ajpendo.00620.2020] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Insulin inhibits systemic nonesterified fatty acid (NEFA) flux to a greater degree than glucose or any other metabolite. This remarkable effect is mainly due to insulin-mediated inhibition of intracellular triglyceride (TG) lipolysis in adipose tissues and is essential to prevent diabetic ketoacidosis, but also to limit the potential lipotoxic effects of NEFA in lean tissues that contribute to the development of diabetes complications. Insulin also regulates adipose tissue fatty acid esterification, glycerol and TG synthesis, lipogenesis, and possibly oxidation, contributing to the trapping of dietary fatty acids in the postprandial state. Excess NEFA flux at a given insulin level has been used to define in vivo adipose tissue insulin resistance. Adipose tissue insulin resistance defined in this fashion has been associated with several dysmetabolic features and complications of diabetes, but the mechanistic significance of this concept is not fully understood. This review focusses on the in vivo regulation of adipose tissue fatty acid metabolism by insulin and the mechanistic significance of the current definition of adipose tissue insulin resistance. One hundred years after the discovery of insulin and despite decades of investigations, much is still to be understood about the multifaceted in vivo actions of this hormone on adipose tissue fatty acid metabolism.
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Affiliation(s)
- André C Carpentier
- Division of Endocrinology, Department of Medicine, Centre de recherche du CHUS, Université de Sherbrooke, Sherbrooke, Quebec, Canada
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Association of Gut Hormones and Microbiota with Vascular Dysfunction in Obesity. Nutrients 2021; 13:nu13020613. [PMID: 33668627 PMCID: PMC7918888 DOI: 10.3390/nu13020613] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 01/25/2021] [Accepted: 02/10/2021] [Indexed: 02/08/2023] Open
Abstract
In the past few decades, obesity has reached pandemic proportions. Obesity is among the main risk factors for cardiovascular diseases, since chronic fat accumulation leads to dysfunction in vascular endothelium and to a precocious arterial stiffness. So far, not all the mechanisms linking adipose tissue and vascular reactivity have been explained. Recently, novel findings reported interesting pathological link between endothelial dysfunction with gut hormones and gut microbiota and energy homeostasis. These findings suggest an active role of gut secretome in regulating the mediators of vascular function, such as nitric oxide (NO) and endothelin-1 (ET-1) that need to be further investigated. Moreover, a central role of brain has been suggested as a main player in the regulation of the different factors and hormones beyond these complex mechanisms. The aim of the present review is to discuss the state of the art in this field, by focusing on the processes leading to endothelial dysfunction mediated by obesity and metabolic diseases, such as insulin resistance. The role of perivascular adipose tissue (PVAT), gut hormones, gut microbiota dysbiosis, and the CNS function in controlling satiety have been considered. Further understanding the crosstalk between these complex mechanisms will allow us to better design novel strategies for the prevention of obesity and its complications.
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Emanuel AL, Meijer RI, Muskiet MHA, van Raalte DH, Eringa EC, Serné EH. Role of Insulin-Stimulated Adipose Tissue Perfusion in the Development of Whole-Body Insulin Resistance. Arterioscler Thromb Vasc Biol 2017; 37:411-418. [PMID: 28126826 DOI: 10.1161/atvbaha.116.308670] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Accepted: 01/17/2017] [Indexed: 01/08/2023]
Abstract
After food ingestion, macronutrients are transported to and stored in the skeletal muscle and adipose tissue. They can be subsequently used as an energy source in times of energy deprivation. Uptake of these nutrients in myocytes and adipocytes depends largely on adequate tissue perfusion. Interestingly, insulin is able to dilate skeletal muscle arterioles, which facilitates the delivery of macronutrients and insulin itself to muscle tissue. Insulin-stimulated skeletal muscle perfusion is impaired in several insulin-resistant states and is believed to contribute to impaired skeletal muscle glucose uptake and consequently impaired whole-body glucose disposal. Insulin-resistant individuals also exhibit blunted postprandial adipose tissue perfusion. However, the relevance of this impairment to metabolic dysregulation is less clear. In this review, we provide an overview of adipose tissue perfusion in healthy and insulin-resistant individuals, its regulation among others by insulin, and the possible influences of impaired adipose tissue perfusion on whole-body insulin sensitivity. Finally, we propose a novel hypothesis that acute overfeeding impacts distribution of macronutrients by reducing skeletal muscle perfusion, while adipose tissue perfusion remains intact. VISUAL OVERVIEW An online visual overview is available for this article.
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Affiliation(s)
- Anna L Emanuel
- From the Departments of Internal Medicine (A.L.E., R.I.M., M.H.A.M., D.H.v.R., E.H.S.) and Physiology (E.C.E.), VU University Medical Center, Amsterdam.
| | - Rick I Meijer
- From the Departments of Internal Medicine (A.L.E., R.I.M., M.H.A.M., D.H.v.R., E.H.S.) and Physiology (E.C.E.), VU University Medical Center, Amsterdam
| | - Marcel H A Muskiet
- From the Departments of Internal Medicine (A.L.E., R.I.M., M.H.A.M., D.H.v.R., E.H.S.) and Physiology (E.C.E.), VU University Medical Center, Amsterdam
| | - Daniël H van Raalte
- From the Departments of Internal Medicine (A.L.E., R.I.M., M.H.A.M., D.H.v.R., E.H.S.) and Physiology (E.C.E.), VU University Medical Center, Amsterdam
| | - Etto C Eringa
- From the Departments of Internal Medicine (A.L.E., R.I.M., M.H.A.M., D.H.v.R., E.H.S.) and Physiology (E.C.E.), VU University Medical Center, Amsterdam
| | - Erik H Serné
- From the Departments of Internal Medicine (A.L.E., R.I.M., M.H.A.M., D.H.v.R., E.H.S.) and Physiology (E.C.E.), VU University Medical Center, Amsterdam
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Conde SV, Ribeiro MJ, Melo BF, Guarino MP, Sacramento JF. Insulin resistance: a new consequence of altered carotid body chemoreflex? J Physiol 2017; 595:31-41. [PMID: 27027507 PMCID: PMC5199745 DOI: 10.1113/jp271684] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2015] [Accepted: 03/11/2016] [Indexed: 01/22/2023] Open
Abstract
Metabolic diseases affect millions of individuals across the world and represent a group of chronic diseases of very high prevalence and relatively low therapeutic success, making them suitable candidates for pathophysiological studies. The sympathetic nervous system (SNS) contributes to the regulation of energy balance and energy expenditure both in physiological and pathological states. For instance, drugs that stimulate sympathetic activity decrease food intake, increase resting metabolic rate and increase the thermogenic response to food, while pharmacological blockade of the SNS has opposite effects. Likewise, dysmetabolic features such as insulin resistance, dyslipidaemia and obesity are characterized by a basal overactivation of the SNS. Recently, a new line of research linking the SNS to metabolic diseases has emerged with the report that the carotid bodies (CBs) are involved in the development of insulin resistance. The CBs are arterial chemoreceptors that classically sense changes in arterial blood O2 , CO2 and pH levels and whose activity is known to be increased in rodent models of insulin resistance. We have shown that selective bilateral resection of the nerve of the CB, the carotid sinus nerve (CSN), totally prevents diet-induced insulin resistance, hyperglycaemia, dyslipidaemia, hypertension and sympathoadrenal overactivity. These results imply that the beneficial effects of CSN resection on insulin action and glucoregulation are modulated by target-related efferent sympathetic nerves through a reflex that is initiated in the CBs. It also highlights modulation of CB activity as a putative future therapeutic intervention for metabolic diseases.
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Affiliation(s)
- Silvia V. Conde
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
| | - Maria J. Ribeiro
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
| | - Bernardete F. Melo
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
| | - Maria P. Guarino
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
- UIS‐Unidade de Investigação em Saúde – Escola Superior de Saúde de Leiria – Instituto Politécnico de LeiriaLeiriaPortugal
| | - Joana F. Sacramento
- CEDOC, Centro Estudos Doenças Crónicas, NOVA Medical School, Faculdade de Ciências MédicasUniversidade Nova de LisboaLisboaPortugal
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Abstract
AbstractThe endothelium, a thin single sheet of endothelial cells, is a metabolically active layer that coats the inner surface of blood vessels and acts as an interface between the circulating blood and the vessel wall. The endothelium through the secretion of vasodilators and vasoconstrictors serves as a critical mediator of vascular homeostasis. During the development of the vascular system, it regulates cellular adhesion and vessel wall inflammation in addition to maintaining vasculogenesis and angiogenesis. A shift in the functions of the endothelium towards vasoconstriction, proinflammatory and prothrombic states characterise improper functioning of these cells, leading to endothelial dysfunction (ED), implicated in the pathogenesis of many diseases including diabetes. Major mechanisms of ED include the down-regulation of endothelial nitric oxide synthase levels, differential expression of vascular endothelial growth factor, endoplasmic reticulum stress, inflammatory pathways and oxidative stress. ED tends to be the initial event in macrovascular complications such as coronary artery disease, peripheral arterial disease, stroke and microvascular complications such as nephropathy, neuropathy and retinopathy. Numerous strategies have been developed to protect endothelial cells against various stimuli, of which the role of polyphenolic compounds in modulating the differentially regulated pathways and thus maintaining vascular homeostasis has been proven to be beneficial. This review addresses the factors stimulating ED in diabetes and the molecular mechanisms of natural polyphenol antioxidants in maintaining vascular homeostasis.
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Sotorník R, Baillargeon JP, Gagnon-Auger M, Ménard J, Brassard P, Ardilouze JL. Regulation of blood flow in adipose tissue: involvement of the cholinergic system. Am J Physiol Endocrinol Metab 2015; 309:E55-62. [PMID: 25968573 DOI: 10.1152/ajpendo.00016.2015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 05/08/2015] [Indexed: 01/24/2023]
Abstract
Acetylcholine (Ach) has vasodilatory actions. However, data are conflicting about the role of Ach in regulating blood flow in subcutaneous adipose tissue (ATBF). This may be related to inaccurate ATBF recording or to the responder/nonresponder (R/NR) phenomenon. We showed previously that healthy individuals are R (ATBF increases postprandially by >50% of baseline BF) or NR (ATBF increases ≤50% postprandially). Our objective was to assess the role of the cholinergic system on ATBF in R and NR subjects. ATBF was manipulated by in situ microinfusion of vasoactive agents (VA) in AT and monitored by the (133)Xenon washout technique (both recognized methods) at the VA site and at the control site. We tested incrementally increasing doses of Ach (10(-5), 10(-3), and 10(-1) mol/l; n = 15) and Ach receptor antagonists (Ra) before and after oral administration of 75-g glucose using atropine (muscarinic Ra; 10(-4) mol/l, n = 13; 10(-5) mol/l, n = 22) and mecamylamine (nicotinic Ra; 10(-3) mol/l, n = 15; 10(-4) mol/l, n = 10). Compared with baseline [2.41 (1.36-2.83) ml·100 g(-1)·min(-1)], Ach increased ATBF dose dependently [3.32 (2.80-5.09), 6.46 (4.36-9.51), and 10.31 (7.98-11.52), P < 0.0001], with no difference between R and NR. Compared with control side, atropine (both concentrations) had no effect on fasting ATBF; only atropine 10(-4) mol/l decreased post-glucose ATBF [iAUC: 1.25 (0.32-2.91) vs. 1.98 (0.64-2.94); P = 0.04]. This effect was further apparent in R. Mecamylamine had no impact on fasting and postglucose ATBF in R and NR. Our results suggest that the cholinergic system is implicated in ATBF regulation, although it has no role in the blunting of ATBF response in NR.
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Affiliation(s)
- Richard Sotorník
- Department of Medicine, Division of Endocrinology, University Hospital Center of Sherbrooke, University of Sherbrooke, Sherbrooke, Quebec, Canada; and
| | - Jean-Patrice Baillargeon
- Department of Medicine, Division of Endocrinology, University Hospital Center of Sherbrooke, University of Sherbrooke, Sherbrooke, Quebec, Canada; and Clinical Research Center, University Hospital Center of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Maude Gagnon-Auger
- Department of Medicine, Division of Endocrinology, University Hospital Center of Sherbrooke, University of Sherbrooke, Sherbrooke, Quebec, Canada; and
| | - Julie Ménard
- Department of Medicine, Division of Endocrinology, University Hospital Center of Sherbrooke, University of Sherbrooke, Sherbrooke, Quebec, Canada; and Clinical Research Center, University Hospital Center of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Pascal Brassard
- Department of Medicine, Division of Endocrinology, University Hospital Center of Sherbrooke, University of Sherbrooke, Sherbrooke, Quebec, Canada; and Clinical Research Center, University Hospital Center of Sherbrooke, Sherbrooke, Quebec, Canada
| | - Jean-Luc Ardilouze
- Department of Medicine, Division of Endocrinology, University Hospital Center of Sherbrooke, University of Sherbrooke, Sherbrooke, Quebec, Canada; and Clinical Research Center, University Hospital Center of Sherbrooke, Sherbrooke, Quebec, Canada
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Lambadiari V, Triantafyllou K, Dimitriadis GD. Insulin action in muscle and adipose tissue in type 2 diabetes: The significance of blood flow. World J Diabetes 2015; 6:626-633. [PMID: 25987960 PMCID: PMC4434083 DOI: 10.4239/wjd.v6.i4.626] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 12/03/2014] [Accepted: 02/11/2015] [Indexed: 02/05/2023] Open
Abstract
Under normal metabolic conditions insulin stimulates microvascular perfusion (capillary recruitment) of skeletal muscle and subcutaneous adipose tissue and thus increases blood flow mainly after meal ingestion or physical exercise. This helps the delivery of insulin itself but also that of substrates and of other signalling molecules to multiple tissues beds and facilitates glucose disposal and lipid kinetics. This effect is impaired in insulin resistance and type 2 diabetes early in the development of metabolic dysregulation and reflects early-onset endothelial dysfunction. Failure of insulin to increase muscle and adipose tissue blood flow results in decreased glucose handling. In fat depots, a blunted postprandial blood flow response will result in an insufficient suppression of lipolysis and an increased spill over of fatty acids in the circulation, leading to a more pronounced insulin resistant state in skeletal muscle. This defect in blood flow response is apparent even in the prediabetic state, implying that it is a facet of insulin resistance and exists long before overt hyperglycaemia develops. The following review intends to summarize the contribution of blood flow impairment to the development of the atherogenic dysglycemia and dyslipidaemia.
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Abreu-Vieira G, Hagberg CE, Spalding KL, Cannon B, Nedergaard J. Adrenergically stimulated blood flow in brown adipose tissue is not dependent on thermogenesis. Am J Physiol Endocrinol Metab 2015; 308:E822-9. [PMID: 25738783 DOI: 10.1152/ajpendo.00494.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Accepted: 02/26/2015] [Indexed: 01/24/2023]
Abstract
Brown adipose tissue (BAT) thermogenesis relies on blood flow to be supplied with nutrients and oxygen and for the distribution of the generated heat to the rest of the body. Therefore, it is fundamental to understand the mechanisms by which blood flow is regulated and its relation to thermogenesis. Here, we present high-resolution laser-Doppler imaging (HR-LDR) as a novel method for noninvasive in vivo measurement of BAT blood flow in mice. Using HR-LDR, we found that norepinephrine stimulation increases BAT blood flow in a dose-dependent manner and that this response is profoundly modulated by environmental temperature acclimation. Surprisingly, we found that mice lacking uncoupling protein 1 (UCP1) have fully preserved BAT blood flow response to norepinephrine despite failing to perform thermogenesis. BAT blood flow was not directly correlated to systemic glycemia, but glucose injections could transiently increase tissue perfusion. Inguinal white adipose tissue, also known as a brite/beige adipose tissue, was also sensitive to cold acclimation and similarly increased blood flow in response to norepinephrine. In conclusion, using a novel noninvasive method to detect BAT perfusion, we demonstrate that adrenergically stimulated BAT blood flow is qualitatively and quantitatively fully independent of thermogenesis, and therefore, it is not a reliable parameter for the estimation of BAT activation and heat generation.
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Affiliation(s)
- Gustavo Abreu-Vieira
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden; and
| | - Carolina E Hagberg
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - Kirsty L Spalding
- Department of Cell and Molecular Biology, Karolinska Institute, Stockholm, Sweden
| | - Barbara Cannon
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden; and
| | - Jan Nedergaard
- Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden; and
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Friedmann DP, Avram MM, Cohen SR, Duncan DI, Goldman MP, Weiss ET, Young VL. An evaluation of the patient population for aesthetic treatments targeting abdominal subcutaneous adipose tissue. J Cosmet Dermatol 2015; 13:119-24. [PMID: 24910275 DOI: 10.1111/jocd.12088] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/23/2014] [Indexed: 11/28/2022]
Abstract
A large and growing population of patients currently seeks minimally invasive therapeutic options for the aesthetic treatment of localized, central abdominal subcutaneous adipose tissue (SAT). We sought to evaluate the ideal population for aesthetic treatment of central abdominal SAT, highlight the existing disparities between SAT in obese (body mass index [BMI] ≥ 30; BMI) and nonobese (BMI < 30) patients, and review the available FDA-cleared, minimally invasive treatment options for central abdominal adiposity. The cosmetic issue of localized, central (periumbilical) abdominal adiposity in nonobese individuals is quite distinct from abdominal bulging secondary to obesity. Given the recognized clinical and physiologic differences between obese and nonobese counterparts, the exclusion of obese patients from clinical study by currently available FDA-cleared devices targeting abdominal fat, and the status of obesity as a chronic, systemic disease requiring medical, surgical, and/or lifestyle-altering therapies, minimally invasive therapeutic options for aesthetic reductions in central abdominal SAT must be limited to the nonobese population.
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Affiliation(s)
- Daniel P Friedmann
- Westlake Dermatology Clinical Research Center, Westlake Dermatology & Cosmetic Surgery, Austin, TX, USA
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12
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Frayn KN, Karpe F. Regulation of human subcutaneous adipose tissue blood flow. Int J Obes (Lond) 2013; 38:1019-26. [PMID: 24166067 DOI: 10.1038/ijo.2013.200] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 09/12/2013] [Accepted: 09/21/2013] [Indexed: 12/14/2022]
Abstract
Subcutaneous adipose tissue represents about 85% of all body fat. Its major metabolic role is the regulated storage and mobilization of lipid energy. It stores lipid in the form of triacylglycerol (TG), which is mobilized, as required for use by other tissues, in the form of non-esterified fatty acids (NEFA). Neither TG nor NEFA are soluble to any extent in water, and their transport to and out of the tissue requires specialized transport mechanisms and adequate blood flow. Subcutaneous adipose tissue blood flow (ATBF) is therefore tightly linked to the tissue's metabolic functioning. ATBF is relatively high (in the fasting state, similar to that of resting skeletal muscle, when expressed per 100 g tissue) and changes markedly in different physiological states. Those most studied are after ingestion of a meal, when there is normally a marked rise in ATBF, and exercise, when ATBF also increases. Pharmacological studies have helped to define the physiological regulation of ATBF. Adrenergic influences predominate in most situations, but nevertheless the regulation of ATBF is complex and depends on the interplay of many different systems. ATBF is downregulated in obesity (when expressed per 100 g tissue), and its responsiveness to meal intake is reduced. However, there is little evidence that this leads to adipose tissue hypoxia in human obesity, and we suggest that, like the downregulation of catecholamine-stimulated lipolysis seen in obesity, the reduction in ATBF represents an adaptation to the increased fat mass. Most information on ATBF has been obtained from studying the subcutaneous abdominal fat depot, but more limited information on lower-body fat depots suggests some similarities, but also some differences: in particular, marked alpha-adrenergic tone, which can reduce the femoral ATBF response to adrenergic stimuli.
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Affiliation(s)
- K N Frayn
- Oxford Centre for Diabetes, Endocrinology & Metabolism, University of Oxford, Oxford, UK
| | - F Karpe
- 1] Oxford Centre for Diabetes, Endocrinology & Metabolism, University of Oxford, Oxford, UK [2] National Institute for Health Research, Oxford Biomedical Research Centre, Oxford University Hospitals Trust, Oxford, UK
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Tchkonia T, Thomou T, Zhu Y, Karagiannides I, Pothoulakis C, Jensen MD, Kirkland JL. Mechanisms and metabolic implications of regional differences among fat depots. Cell Metab 2013; 17:644-656. [PMID: 23583168 PMCID: PMC3942783 DOI: 10.1016/j.cmet.2013.03.008] [Citation(s) in RCA: 454] [Impact Index Per Article: 41.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Fat distribution is closely linked to metabolic disease risk. Distribution varies with sex, genetic background, disease state, certain drugs and hormones, development, and aging. Preadipocyte replication and differentiation, developmental gene expression, susceptibility to apoptosis and cellular senescence, vascularity, inflammatory cell infiltration, and adipokine secretion vary among depots, as do fatty-acid handling and mechanisms of enlargement with positive-energy and loss with negative-energy balance. How interdepot differences in these molecular, cellular, and pathophysiological properties are related is incompletely understood. Whether fat redistribution causes metabolic disease or whether it is a marker of underlying processes that are primarily responsible is an open question.
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Affiliation(s)
| | - Thomas Thomou
- Joslin Diabetes Center, Harvard Medical School, Boston, MA 02215, USA
| | - Yi Zhu
- Robert and Arlene Kogod Center on Aging
| | - Iordanes Karagiannides
- Inflammatory Bowel Disease Center, Division of Digestive Diseases, Department of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
| | - Charalabos Pothoulakis
- Inflammatory Bowel Disease Center, Division of Digestive Diseases, Department of Medicine, University of California at Los Angeles, Los Angeles, CA 90095, USA
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