Obesity and Metabolic Syndrome Flashcards by Brandon Craipley

Adipose tissue can be found

Most around visceral organs

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Adipose tissue is made of

adipocytes

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Adipocytes are used

1) to store TAGS (triacyglycerol)
2) For lipid homeostasis and maintenance of energetic metabolism

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Increase of fat mass occurs in 2 ways

1) Hyperplasia: Enlargment of an organ or tissue because of cell proliferation (more cells)
2) Hypertrophy: Enlargment of an organ or tissue from increase in size of its cells

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What two tissues expand through hypertrophy and hyperplasia

1) Subcutaneous adipose tissue (SAT)
2) Vicsceral adipose tissue (VAT)

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T or F: Hyperplasia has a protective effect against obesity-associated metabolic complications.

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What happens to unhealthy individuals in terms of hyperplasia

1) In unhealthy obese individual, hyperplasia of adipocytes in SAT is compromised, limiting the storage capacity of fatty acids.
2) The excess lipids will be stored in VAT as well as ectopic tissues, leading to lipotoxicity.
3) The lipotoxicity will take multiple forms: hypoxia, inflammation, insulin resistance which causes
Metabolic syndrome, type 2 diabetes, heart disease.

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Adipogenesis and obesity (healthy vs unhealthy adipogenesis)

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Energy homeostasis

Maintains amount of adipose tissue at a healthy level

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Energy homeostasis

Maintains amount of adipose tissue at a healthy level

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Purpose of thermic effect of food

Thermic effect of food is the energy necessary to process, digest, absorb and store nutrients in the body

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T or F: Total energy expenditure over a lifetime is constant

True

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Obesity BMI

BMI greater than 30, overweight (25-29.9)

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Obesity (especially visceral obesity) increases the risk of developing other diseases like

-Cardiovascular disease (heart attack, stroke)
-Type II Diabetes
-Sleep apnea
-Fertility problems
-Osteoarthritis
-Cancer (Breast, colon, prostate, endometrium, kidney and gallbladder)

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Adipokines

Signaling molecules important in many physiological and metabolic processes. Mostly produced by adipocytes…but also resident macrophages

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Physiological and metabolic processes regulated by adipokines secreted by adipocytes

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Physiological and metabolic processes regulated by adipokines secreted by adipocytes

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The hypoxia theory

1) As adipose tissue mass expands (obesity), groups of adipocytes will become more and more distant to blood vessels.
2) Increase in adipose tissue does not lead to an increase in blood flow to this tissue
3) Hypertrophic adipocytes (150-200mm in diameter) are larger then the normal diffusion distance of O2 (100-200mm in diameter)
4) Under hypoxic conditions, a variation of expression in adipokines is observed.

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Effects of hypoxia on the secretion of key adipokines by human adipocytes in cell culture

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What is induced by hypoxia/obesity

HIF-1a (hypoxia inducible factor-1a) expression

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HIF1α is linked to Cancer

Rapid growth of tumour and hypoxic conditions found by degradation of HIF1α

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T or F: HIF1α regulated experssion of 1300 genes and decreases the release of which adipokine

Adiponectin

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Effects of hypoxia on adipokine expression

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explain obesity and metabolic syndrom

Metabolic syndrome is a cluster of conditions — increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels — that occur together, increasing your risk of heart disease, stroke and diabetes. (Mayo Clinic)
Group of risk factors that raises your risk for heart disease and other health problems.

What are 3 mdtabolic consequences of obesity

1) Regulation of body weight 2) Inflammation 3) Insulin resistance

T or F: Leptin regulates body weight

True

Leptin

An adipokine secreted by the adipose tissue that is involved in multiple processes including the control of appetite, the rate of of b-oxidation and FA synthesis in the various tissues.

Control of appetite by leptin

What happens if we remove the LEP (Leptin) gene from a mouse genome

Mice become obese Suffer from hyperphagia (abnormal increase in appetite)

What happens if we remove the LEP (Leptin) gene from a mouse genome

Mice become obese Suffer from hyperphagia (abnormal increase in appetite)

t or F: Obese individuals do not develop resistance to leptin

False they do and leptin is a long term response so have increased leptin but stop responding (hyperleptinaemia)

Obesity and inflammation

TNF-α is secreted by

adipose tissue-resident macrophages

Action of TNF-α (pro inflammatory response)

1) Stimulates lipolysis 2) TNF-α counteracts the action of insulin (prevents binding to the receptor and lowers the expression of GLUT4) 3) Block the entry of new free fatty acid. 4)Decrease TAG biosynthesis through inhibition of the peroxisome proliferator-activated receptor gamma (PPARγ)

Summary of Action of TNF-a in regars to Insulin signaling

1) The TNF-α pathway stimulates the expression of proinflammatory genes but also blocks the downstream activation of insulin signalling by inhibiting the kinase activity of IRS1. 2) IRS1 can be destabilized by the Interleukin-6 (IL-6) signaling cascade. 3) Higher concentrations of IL-6, which is an adipokine, are observed in obese individuals.

Explain the interleukin-6 (IL-6) paradox

1) In healthy subjects, 10-35% of the circulating IL-6 is produced by adipose tissue (mainly by adipose resident macrophages).Levels of IL-6 increase in response to acute and low-grade chronic inflammation.It was shown that a transient/acute expression of IL-6 in response to exercise was causing an increase in sensitivity to insulin. 2) On the other hand, multiple studies have also shown that chronic elevated level of IL-6 was leading to a decrease in insulin sensitivity. Obese individuals display a chronic elevated level of IL-6.

Explain obesity and m,etabolic consequences (insulin resistance)

obesity leads to an adipokines imbalance, which in turn causes the body to be in a proinflammatory state. Over time, it will cause cells/organs to become insulin resistant. Insulin resistance will develop into type 2 diabetes.

Effects of insulin

3 consequences of insulin resistance

Adiponectin (Acrp30)

Peptide hormone (adipokine) produced uniquely in adipose tissue.

Function of adiponectin (Acrp30)

When add adiponectin back = decrease gluconeogenesis and can use glucose again

Adiponectin is [blank] in obese indivdiuals and why

Decreased because adiponectin is secreted by visceral fat which obese levels have decreased levels of (VAT and SAT communicate with one another) so if one decreases the other increases

T or F: Adiponectin decreases insulin sensitivity

False, increases

Adiponection can bind to 2 receptors

1) AdipoR1 2)AdipoR2

AdipoR1

-Expressed mainly in the liver, muscle and hypothalamus -Function: Activation of AMPK. -Binds to the globular portion of adiponectin

AdipoR2

-Expressed mainly in the liver, WAT and vasculature. -Function: Activation of PPAR (α, δ, γ) -Binds to the full-length adiponectin

Adiponectin activates

1)AMPK 2)PPAR

Roles of adiponectin

How does adiponectin protect against atherosclerosis

= prevents inflammation

Obesity [blanks] PPARs concentration

decreases

Function of PPARs

These transcription factors respond to change in lipids coming from the diet by regulating the expression of genes involved in fat and carbohydrates.Their translocation to the nucleus requires the binding of a fatty acid (or fatty acids derivatives).

Function of PPARs

3 types of PPAR and function

PPARy is essential for the differentiation of

preadipocytes

Summary of regulation of inflammation, insulin resistance, and atherosclerosis in terms of obesity