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Physio > Adipose Tissue > Flashcards

Adipose Tissue Flashcards

1
Q

Locations of adipose

A

. SubQ
. Visceral
. Bone marrow
. Structural

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2
Q

Brown adipose tissue

A

. Contains cells w/ multiple lipid droplets interspersed among abundant mitochondria
. Completes non-shivering thermogenesis
. In adults it is located in upper chest and neck
. Becomes more active w/ cold exposure via adrenergic stimulation
. Plays functional role in temperature control

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3
Q

White adipose tissue

A

. Contain 1 very large droplet of white fat in cytoplasm
. Main function is long-term energy storage
. Fibroblasts, macrophages, and other cells make up about half the total number of cells

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4
Q

Regulation of adipogenesis

A

. Retains ability to grow in adulthood
. Inc. in size occurs through precursor proliferation, maturation, lipid storage/release from adult adipocytes and apoptosis
. Adipocyte precursors derived from pericytes located just outside the capillaries, transform into preadipocytes or stromatolites cells that can differentiate into white or brown adipocytes

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5
Q

Activators of adipogenesis

A 
. GH
. IGF-1
. insulin
. Cortisol
. Thyroid hormone
. Retinoic acids
. Endogenous peroxisome proliferator-activated receptor-gamma ligand (PPAR-gamma)
. Prostaglandin PGJ2
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6
Q

Inhibitors of adipogenesis

A 
. Tumor necrosis factor 
. Interferon y
. Preadipocyte factor pref-1
. Resistin
. Transforming growth factor beta
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7
Q

PPAR-gamma

A

. Inc. expression of genes for glucose uptake, lipid uptake, and lipid synthesis pathways

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8
Q

How triglycerides are stored in adipocyte

A

. Cytoplasmic droplets coated by layer of phospholipids and proteins
. Coat sequesters the lipids from cytosol and regulate the access of lipases to the surface of the droplet
. One coated proteins (perilipin) can be phosphorylated by PKA and PKG initiating the process of lipolysis

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9
Q

Glucocorticoid signals to adipose tissue

A

. High levels ACTH and glucocorticoids result in obesity
. Enzyme 11HSD-1 present in human adipose tissue and converts inactive cortisone into active cortisol
. Strong positive correlation btw adipocytes size and activity of 11 HDS-1 in converting cortisone into cortisol

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10
Q

Growth hormone/insulin-like growth factor-1 (IGF-1)

A

. Potent lipolysis hormone through activation of cAMP pathways
. Inc. IGF-1 production in adipose
. IGF-1 greatly activates preadipocyte proliferation and differentiation of precursors into mature lipid-storing adipocytes
. Deficiency of GH assoc. w/ central obesity and replacement of GH dec. visceral adipocyte

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11
Q

Estrogens as endocrine signals to adipose tissue

A

. Lipoprotein lipase activity is inc. in gluteal-femoral region of women compared w/ more abdominal in men
. Treatment w/ estradiol inc. LPL in gluteal-femoral region
. Causes adipocyte precursor proliferation and regulating lipid storage in region-specific manner

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12
Q

Neutrals signals to adipose

A

. SubQ and visceral adipose have different rates of lipid synthesis and lipolysis reflecting differences in hormonal exposure and sympathetic innervation
. Catecholamines inc. lipolysis and inhibit adipose tissue hyperplasia from preadipocytes

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13
Q

Rate limiting steps of adipocyte lipolysis

A

. HSL and perilipin

. Both enzymes need to be phosphorylated to be active and allow the breakdown of triglycerides into glycerol and FFAs

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14
Q

Regulation of lipolysis

A

. Adrenergic systems (beta and alpha2 receptors) are major regulators of lipolysis via cAMP pathways
. Beta receptors stimulate lipolysis and alpha2 receptors inhibit lipolysis
.cAMP inc. activity of PKA that in turn phosphorylates the HSL and perilipin
. Insulin inhibits lipolysis via stimulate of phosphodiesterase (PDE) dec. cAMP and lipolysis

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15
Q

Adipose tissue hormones

A

. Sex steroids
. Lepton
. Wide variety of bioactive peptides (adipokines)
. Hormones act at local (autocrine/paracrine) and systemic (endocrine) level
. Affects energy homeostasis, insulin sensitivity, and nutrient-sensing pathways

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16
Q

Leptin

A

. Cross BBB and acts through different brain circuits to induce adaptive responses affecting appetite, energy expenditure, and neuroendocrine function
. Serves as metabolic signal of energy insufficiency
. Levels reduce w/ caloric restriction and weight loss
. Inc. in nutrient intake can inc. plasma leptin levels leading to activation of melanocortin receptors
. Results in dec. in glucose-stimulated insulin secretion

17
Q

How leptin regulates neuroendocrine functions

A

. Dec. hypocortisolemia
. Inhibits stress-induced secretion of CRH
. Inhibits cortisol secretion from adrenocorical cells
. Normalizes reduced thyroid hormone levels in hypothyroid patients via TRH stimulation
. Accelerates puberty and restores normal gonadotropin secretion

18
Q

Main biological function of leptin

A

. Maintenance of minimum level of energy stores during periods of caloric restriction

19
Q

Leptin effect on immune response

A

. Contributes to regulation of immune response, hematopoietic, angiogenesis, bone development, and accelerates wound healing

20
Q

How leptin seems to exert its peripheral metabolic effects

A

. Activates PKA in muscle and liver
. As consequence of PKA activation, ATP-consuming anabolic pathways are inhibited whereas ATP-producing catabolic pathways are activated
. Activated mechanisms include glucose transport, beta oxidation, glycolysis, and mitochondrial biogenesis

21
Q

Adiponectin receptors

A

. AdipoR1: expressed primarily in mm.
. AdipoR2 express primarily in liver
. Biological effects of adiponectin depend on relative circulating conc. And properties of different adiponectin isoforms but also tissue-specific expression of adiponectin receptor subtypes

22
Q

Adiponectin role in vasculature

A

. Binds to collagen types I, III, and V in vascular intima of injured vessels
. Role in vascular repair

23
Q

Adiponectin relationship w/ body fat

A

. Concentration correlates neg. w/ BMI and body fat

. Inverse correlation w/ insulin resistance and obesity

24
Q

Metabolic effects of adiponectin in liver

A

. Enhances insulin sensitivity, dec. influx of non-esterified FAs (NEFAs), inc. FA oxidation, reduces hepatic glucose output

25
Q

Metabolic effects of adiponectin in muscle

A

. Stimulates glucose use and FA oxidation
. W/in vascular wall, adiponectin inhibits monocyte adhesion by dec. expression of adhesion molecules
. Inhibits macrophage transformation to foam cells by inhibiting expression of scavenger receptors
. Dec. proliferation of migrating smooth m. Cells in response of growth factors
. Inc. NO production in endothelial cells and stimulate angiogenesis
. Effects mediated via inc. phosphorylation of insulin receptor, activation of PKA, modulation of nuclear factor KB pathway

26
Q

Adipocyte role in insulin resistance

A

. Adipocyte hypertrophy assoc. w/ it
. Flux of FFAs out of adipose tissue is uncontrolled in obesity w/ adipocyte hypertrophy
. Hypoxia, inflammation and ER stress are mechanistic links btw obesity and insulin resistance
. Hypertrophy of adipocytes causes dec. blood flow per unit of adipose leading to tissue hypoxia inducing inflammation
. Local cytokine conc. Then insulin resistance occurs
. Adipose hypoxia therefore is a signal for remodeling of adipose tissue

27
Q

Cardiovascular diseases assoc. w/ obesity

A

. LV hypertrophy
. CHF
. Hypertension
. Coronary heart disease

28
Q

Primary event in development of atherosclerotic disease

A

. Impaired flow-mediated dilation

. Enlarged vascular tone is caused by atherosclerosis-induced endothelial dysfunction

29
Q

Obesity and reproductive disorders

A

. Irregular menses, amenorrhea, and infertility
. Inc. risk for gestational diabetes, hypertension, and delivery complications
. Higher risk of urinary incontinence

30
Q

Obesity and restrictive lung disease

A

. Inc. pressure placed on chest wall and thoracic cage
. Restricts pulmonary function by dec. respiratory compliance, inc. work of breathing, restricting ventilation, and limiting ventilation of lung bases

31
Q

Hypoventilation syndrome

A

. Partial pressure of CO2 is less than 50 mmHg due to dec. ventilator responsiveness to hypercapnea or hypoxia and inability of respiratory mm. To meet the inc. ventilatory demand imposed by mechanical effects of obesity
. Reduced alveolar ventilation bc of shallow and inefficient ventilation related to dec. tidal volume, inadequate inspiratory strength, and elevation of diaphragm
. Symptoms inc. when lying down from inc. abdominal pressure inc. intrathoracic pressure compromising lung capacity

32
Q

Pickwickian syndrome

A

. Severe form of obesity-hypoventilation syndrome

. Involves extreme obesity, irregular breathing, somnolence, cyanosis, secondary polycythemia, and RV dysfunction

33
Q

Obstructive sleep apnea

A

. Excessive episodes of apnea caused by partial or complete upper airway obstruction

Physio (62 decks)

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