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Adipose Tissue Remodeling: Its Role in Energy Metabolism and Metabolic Disorders.

Choe SS, Huh JY, Hwang IJ, Kim JI, Kim JB - Front Endocrinol (Lausanne) (2016)

Bottom Line: In response to changes in the nutritional status, the adipose tissue undergoes dynamic remodeling, including quantitative and qualitative alterations in adipose tissue-resident cells.A growing body of evidence indicates that adipose tissue remodeling in obesity is closely associated with adipose tissue function.This review will discuss current mechanistic understandings of adipose tissue remodeling processes in adaptive energy homeostasis and pathological remodeling of adipose tissue in connection with immune response.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, National Creative Research Initiatives Center for Adipose Tissue Remodeling, Institute of Molecular Biology and Genetics, Seoul National University , Seoul , South Korea.

ABSTRACT
The adipose tissue is a central metabolic organ in the regulation of whole-body energy homeostasis. The white adipose tissue functions as a key energy reservoir for other organs, whereas the brown adipose tissue accumulates lipids for cold-induced adaptive thermogenesis. Adipose tissues secrete various hormones, cytokines, and metabolites (termed as adipokines) that control systemic energy balance by regulating appetitive signals from the central nerve system as well as metabolic activity in peripheral tissues. In response to changes in the nutritional status, the adipose tissue undergoes dynamic remodeling, including quantitative and qualitative alterations in adipose tissue-resident cells. A growing body of evidence indicates that adipose tissue remodeling in obesity is closely associated with adipose tissue function. Changes in the number and size of the adipocytes affect the microenvironment of expanded fat tissues, accompanied by alterations in adipokine secretion, adipocyte death, local hypoxia, and fatty acid fluxes. Concurrently, stromal vascular cells in the adipose tissue, including immune cells, are involved in numerous adaptive processes, such as dead adipocyte clearance, adipogenesis, and angiogenesis, all of which are dysregulated in obese adipose tissue remodeling. Chronic overnutrition triggers uncontrolled inflammatory responses, leading to systemic low-grade inflammation and metabolic disorders, such as insulin resistance. This review will discuss current mechanistic understandings of adipose tissue remodeling processes in adaptive energy homeostasis and pathological remodeling of adipose tissue in connection with immune response.

No MeSH data available.


Related in: MedlinePlus

Adipose tissue functions in energy homeostasis and thermal regulation. (A) In humans, BAT localized around the shoulders and ribs contributes to heat generation. Brown adipocytes exhibit abundant mitochondria and UCP-1 expression related to thermogenesis. It has recently been speculated that BAT efficiency for fat-burning could be harnessed to reduce obesity. Visceral WAT (VAT) and subcutaneous WAT (SAT) possesses considerable capacities for energy storage. VAT surrounds intra-abdominal organs, whereas SAT spreads throughout the body beneath the skin. These fat tissues secrete various adipokines to regulate energy homeostasis. VAT is more strongly associated with obesity-induced metabolic disorders than SAT. (B) In adult mice, BAT is well developed and easily observed compared with that in adult humans. Among WAT depots within the abdominal cavity, the paired gonadal depots located around the ovaries in females and the testes in males are studied as a model of VAT. However, these depots do not exist in humans. The paired inguinal depots in the anterior to the upper part of the hind limbs are representative SATs in mice.
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Figure 1: Adipose tissue functions in energy homeostasis and thermal regulation. (A) In humans, BAT localized around the shoulders and ribs contributes to heat generation. Brown adipocytes exhibit abundant mitochondria and UCP-1 expression related to thermogenesis. It has recently been speculated that BAT efficiency for fat-burning could be harnessed to reduce obesity. Visceral WAT (VAT) and subcutaneous WAT (SAT) possesses considerable capacities for energy storage. VAT surrounds intra-abdominal organs, whereas SAT spreads throughout the body beneath the skin. These fat tissues secrete various adipokines to regulate energy homeostasis. VAT is more strongly associated with obesity-induced metabolic disorders than SAT. (B) In adult mice, BAT is well developed and easily observed compared with that in adult humans. Among WAT depots within the abdominal cavity, the paired gonadal depots located around the ovaries in females and the testes in males are studied as a model of VAT. However, these depots do not exist in humans. The paired inguinal depots in the anterior to the upper part of the hind limbs are representative SATs in mice.

Mentions: Living organisms need to consume energy from their environments to survive. In particular, storage of extra energy obtained during food abundance is an essential physiological activity that enhances survival during food scarcity periods. Multicellular organisms have evolved specialized cells or organs to store excess nutrients as lipids because lipids have higher calories than other nutrients. For example, Caenorhabditis elegans stores surplus energy in the form of lipids in intestinal cells (5), whereas sharks and Drosophila accumulate excess lipids in the liver and fat body, respectively (6, 7). In other organisms, particularly some fishes and higher vertebrates, the adipose tissue functions as a specialized energy reservoir (1). The adipose tissue is distributed throughout the body and is capable of expanding to accommodate excess energy in the form of accumulated lipids, characteristics distinguishing the adipose tissue from other organs and tissues (8). In humans, there are two major types of adipose tissues, white adipose tissue (WAT) and brown adipose tissue (BAT). Anatomically, WAT comprises two major depots, subcutaneous WAT (SAT) and visceral WAT (VAT) around internal organs. VAT, which is concentrated in the abdominal cavity, is further subdivided into mesenteric, omental, perirenal, and peritoneal depots (Figure 1) (8, 9). The key physiological functions of WAT are insulation and energy storage. In obesity, however, excess VAT is closely linked to metabolic complications, such as insulin resistance and type 2 diabetes (8, 9). Mesenteric and omental adipose tissues are particularly important for hepatic insulin resistance and steatosis because liver is directly exposed to releasing factors from these adipose tissues via the portal vein. As an animal model, rodents have gonadal adipose tissue that is considered part of VAT. However, because of lack of gonadal adipose tissue in humans, careful interpretation is required to extrapolate findings in rodents to human. BAT is a specialized form that participates in non-shivering thermogenesis through lipid oxidation (10, 11). The distinct brown color of BAT is attributed to its high mitochondrial density, which is critical for heat generation and lipid oxidation (10, 11). Although BAT is readily observed in both infant and adult rodents, it has been proposed that BAT in humans is limited to neonates and is gradually replaced by WAT with aging. However, recent positron emission tomography/computed tomography studies have shown that BAT is viable and functional in human adults (12, 13). Thus, various adipose tissues act as central regulators of energy homeostasis by storing excess energy as well as by controlling thermogenesis.


Adipose Tissue Remodeling: Its Role in Energy Metabolism and Metabolic Disorders.

Choe SS, Huh JY, Hwang IJ, Kim JI, Kim JB - Front Endocrinol (Lausanne) (2016)

Adipose tissue functions in energy homeostasis and thermal regulation. (A) In humans, BAT localized around the shoulders and ribs contributes to heat generation. Brown adipocytes exhibit abundant mitochondria and UCP-1 expression related to thermogenesis. It has recently been speculated that BAT efficiency for fat-burning could be harnessed to reduce obesity. Visceral WAT (VAT) and subcutaneous WAT (SAT) possesses considerable capacities for energy storage. VAT surrounds intra-abdominal organs, whereas SAT spreads throughout the body beneath the skin. These fat tissues secrete various adipokines to regulate energy homeostasis. VAT is more strongly associated with obesity-induced metabolic disorders than SAT. (B) In adult mice, BAT is well developed and easily observed compared with that in adult humans. Among WAT depots within the abdominal cavity, the paired gonadal depots located around the ovaries in females and the testes in males are studied as a model of VAT. However, these depots do not exist in humans. The paired inguinal depots in the anterior to the upper part of the hind limbs are representative SATs in mice.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4829583&req=5

Figure 1: Adipose tissue functions in energy homeostasis and thermal regulation. (A) In humans, BAT localized around the shoulders and ribs contributes to heat generation. Brown adipocytes exhibit abundant mitochondria and UCP-1 expression related to thermogenesis. It has recently been speculated that BAT efficiency for fat-burning could be harnessed to reduce obesity. Visceral WAT (VAT) and subcutaneous WAT (SAT) possesses considerable capacities for energy storage. VAT surrounds intra-abdominal organs, whereas SAT spreads throughout the body beneath the skin. These fat tissues secrete various adipokines to regulate energy homeostasis. VAT is more strongly associated with obesity-induced metabolic disorders than SAT. (B) In adult mice, BAT is well developed and easily observed compared with that in adult humans. Among WAT depots within the abdominal cavity, the paired gonadal depots located around the ovaries in females and the testes in males are studied as a model of VAT. However, these depots do not exist in humans. The paired inguinal depots in the anterior to the upper part of the hind limbs are representative SATs in mice.
Mentions: Living organisms need to consume energy from their environments to survive. In particular, storage of extra energy obtained during food abundance is an essential physiological activity that enhances survival during food scarcity periods. Multicellular organisms have evolved specialized cells or organs to store excess nutrients as lipids because lipids have higher calories than other nutrients. For example, Caenorhabditis elegans stores surplus energy in the form of lipids in intestinal cells (5), whereas sharks and Drosophila accumulate excess lipids in the liver and fat body, respectively (6, 7). In other organisms, particularly some fishes and higher vertebrates, the adipose tissue functions as a specialized energy reservoir (1). The adipose tissue is distributed throughout the body and is capable of expanding to accommodate excess energy in the form of accumulated lipids, characteristics distinguishing the adipose tissue from other organs and tissues (8). In humans, there are two major types of adipose tissues, white adipose tissue (WAT) and brown adipose tissue (BAT). Anatomically, WAT comprises two major depots, subcutaneous WAT (SAT) and visceral WAT (VAT) around internal organs. VAT, which is concentrated in the abdominal cavity, is further subdivided into mesenteric, omental, perirenal, and peritoneal depots (Figure 1) (8, 9). The key physiological functions of WAT are insulation and energy storage. In obesity, however, excess VAT is closely linked to metabolic complications, such as insulin resistance and type 2 diabetes (8, 9). Mesenteric and omental adipose tissues are particularly important for hepatic insulin resistance and steatosis because liver is directly exposed to releasing factors from these adipose tissues via the portal vein. As an animal model, rodents have gonadal adipose tissue that is considered part of VAT. However, because of lack of gonadal adipose tissue in humans, careful interpretation is required to extrapolate findings in rodents to human. BAT is a specialized form that participates in non-shivering thermogenesis through lipid oxidation (10, 11). The distinct brown color of BAT is attributed to its high mitochondrial density, which is critical for heat generation and lipid oxidation (10, 11). Although BAT is readily observed in both infant and adult rodents, it has been proposed that BAT in humans is limited to neonates and is gradually replaced by WAT with aging. However, recent positron emission tomography/computed tomography studies have shown that BAT is viable and functional in human adults (12, 13). Thus, various adipose tissues act as central regulators of energy homeostasis by storing excess energy as well as by controlling thermogenesis.

Bottom Line: In response to changes in the nutritional status, the adipose tissue undergoes dynamic remodeling, including quantitative and qualitative alterations in adipose tissue-resident cells.A growing body of evidence indicates that adipose tissue remodeling in obesity is closely associated with adipose tissue function.This review will discuss current mechanistic understandings of adipose tissue remodeling processes in adaptive energy homeostasis and pathological remodeling of adipose tissue in connection with immune response.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, National Creative Research Initiatives Center for Adipose Tissue Remodeling, Institute of Molecular Biology and Genetics, Seoul National University , Seoul , South Korea.

ABSTRACT
The adipose tissue is a central metabolic organ in the regulation of whole-body energy homeostasis. The white adipose tissue functions as a key energy reservoir for other organs, whereas the brown adipose tissue accumulates lipids for cold-induced adaptive thermogenesis. Adipose tissues secrete various hormones, cytokines, and metabolites (termed as adipokines) that control systemic energy balance by regulating appetitive signals from the central nerve system as well as metabolic activity in peripheral tissues. In response to changes in the nutritional status, the adipose tissue undergoes dynamic remodeling, including quantitative and qualitative alterations in adipose tissue-resident cells. A growing body of evidence indicates that adipose tissue remodeling in obesity is closely associated with adipose tissue function. Changes in the number and size of the adipocytes affect the microenvironment of expanded fat tissues, accompanied by alterations in adipokine secretion, adipocyte death, local hypoxia, and fatty acid fluxes. Concurrently, stromal vascular cells in the adipose tissue, including immune cells, are involved in numerous adaptive processes, such as dead adipocyte clearance, adipogenesis, and angiogenesis, all of which are dysregulated in obese adipose tissue remodeling. Chronic overnutrition triggers uncontrolled inflammatory responses, leading to systemic low-grade inflammation and metabolic disorders, such as insulin resistance. This review will discuss current mechanistic understandings of adipose tissue remodeling processes in adaptive energy homeostasis and pathological remodeling of adipose tissue in connection with immune response.

No MeSH data available.


Related in: MedlinePlus