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genetics concepts > Lecture 9 > Flashcards

Lecture 9 Flashcards

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1
Q

what are the health conditions that stem from obesity?

A
  • diabetes type II metabolic syndrome
  • cardiovascular disease
  • liver disease (non alcoholic fatty liver disease)
  • PCOS
  • Arthritis
  • depression
  • cancer
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2
Q

obesity and overweight account for how many premature deaths?

A

300,000

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3
Q

obesity would surpass what as the leading cause of death worldwide in the next decade?

A

tobacco

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4
Q

t or f: obesity is not what kills you, diabetes is

A

true, diabetes leads to retinopathy, neuropathy, nephropathy, coronary and cerebrobscular disease

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5
Q

what is the relationship of obesity to CVD?

A

obesity is an independent risk factor to CVD, meaning that without any other factors obesity makes cvd more likely

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6
Q

what are some traits about liver disease and obesity?

A
  • most common of all liver disorders
  • most frequent cause of abnormal liver enzymes
  • affects 3-20% of gen population
  • its present in 75% of people with obesity and diabetes type 2
  • present in 3% of children and more than 50% of obese children
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7
Q

what is liver steatosis?

A

fatty liver

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8
Q

what are the stages of NAFLD (non alcoholic fatty liver disease)?

A
  1. normal liver
  2. steatosis
  3. NASH (non alcoholic steatohepatitis)
  4. cirrhosis
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9
Q

what is the description of steatosis besides fatty liver?

A

retention of lipids within hepatocytes

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10
Q

what is the description of NASH (non alcoholic steatohepatitis)?

A

necroinflammation and fibrosis (progressive scarring)

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11
Q

what is the description for cirrhosis?

A

end stage liver disease and can lead to HCC

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12
Q

what is impaired to NAFLD?

A

coronary flow reserve

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13
Q

what are the symptoms of sleep apnea?

A
  • daytime sleepiness
  • fatigue
  • nightmares
  • snoring
  • intermittent hypoxia
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14
Q

how is sleep apnea described as?

A

pauses in breath while sleeping that can last from a few seconds to minutes, may occur 5-30 times or more an hour

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15
Q

what is a suggestive sign of sleep apnea?

A

intermittent snoring

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16
Q

what is the most obvious consequence of sleep apnea?

A

lack of oxygen to the brain

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17
Q

what are silent strokes?

A

MRI defined silent brain infarcts

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18
Q

what are silent strokes associated with?

A

subtle deficits in physical and cognitive function that commonly go unnoticed, examples are memory loss, difficulties with walking and mood problems

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19
Q

what does the presence of silent stroke increase the risk of?

A

more than doubles the risk of subsequent stroke and dementia

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20
Q

what is the relationship to silent strokes and sleep apnea?

A
  • more than 1/2 of people who had silent stroke had sleep apnea
  • having 25+ episodes of sleep apnea a night is linked with silent stroke
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21
Q

what is depression described as?

A

a mood disorder in which feelings of sadness, loss, anger, or frustration interfere with everyday life for weeks or longer

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22
Q

what is the relationship between bmi and depression?

A

high bmi means higher prevelance of depression

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23
Q

what is the relationship between depression, obesity and stress?

A

people suffering from depression or obesity report higher stress levels than rest of population

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24
Q

what are the stress management strategies for obese adults?

A

watching tv for more than 2 hours a day, listening to music, and eating

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25
Q

what does inflammatory stimuli cause/

A

sickness and depression like behavior

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26
Q

what leads to chronic immune activation?

A
  • inflammatory stimui

- macrophages theory of depression

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27
Q

what is chronic immune activation common in?

A

depression and obesity

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28
Q

what are insulin resistance, inflammation, and metabolic shifts associated with obesity helping?

A

cancer cells

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29
Q

what is the family evidence of genetic influence on obesity?

A
  1. familial aggregation
  2. twin studies
  3. genetic obesity syndrome
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30
Q

how does familial aggregation prove as evidence for genetic obesity?

A

familial clustering of obesity in families

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31
Q

how does twin studies serve as proof for genetic obesity?

A

greater concordance among MZ twins compared to DZ twins

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32
Q

how does genetic obesity syndromes serve as proof for genetic obesity?

A

there are monogenic forms of human obesity, both dominant and recessive

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33
Q

what did the adoption study of human obesity conclude?

A

genetic influences have important role in determining human fatness in adults, whereas the family environment alone has no apparent effect

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34
Q

what are anorexigenic signals?

A
  • suppress food intake
  • increase energy expenditure
  • POMC (pro-opiomelanocortin)
  • CART (cocaine and amphetamine regulated transcript)
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35
Q

what are the orexigenic signals?

A
  • stimulate food intake
  • decrease energy expenditure
  • NPY (neuropeptide Y)
  • AGRP (agouti related protein)
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36
Q

how does the body balance energy?

A

using leptin, its used in long term control, helps regulate weight. low leptin in decreased body fat, increased leptin in increased body fat

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37
Q

what is lipostatic theory?

A

suggested a circulating factor that acts on the brain to inhibit food intake and adiposity then in 1994 leptin was cloned

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38
Q

what is the cycle for leptin?

A

high fat–>high leptin–>binds to receptor in brain–>stimulates metabolism and reduces appetite–>lower fat–>low leptin–>unbinds from receptor in brain–>reduces metabolism and stimulates appetite–> back to high fat and repeat

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39
Q

what is leptin’s effect on anorexigenic and orexigenic signaling?

A

increases anorexigenic signaling in the brain and decreases orexigenic in the brain

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40
Q

what does leptin do to POMC?

A

increases POMC expression, then alpha-MSH is released, that activates MC4 receptors and that leads to decreased appetite

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41
Q

what does leptin do to AgRP?

A

decreases AgRP expression, leads to decrease of MC4 receptor inhibition which leads to decreased appetite

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42
Q

what effect does leptin have on CART and NPY expression?

A

increases CART expression and decreases NPY expression leading to decreased appetite

43
Q

what happens when leptin binds to its receptors?

A

activates JAK/STAT pathway and that turns some genes on or off

44
Q

what are the leptin receptors?

A

LepR and for obesity factor Ob-R

45
Q

what is the relationship between leptin and body fat?

A

since leptin regulates adiposity, leptin and body fat positively correlate in human

46
Q

what are things regulated by leptin?

A
  1. immune function, leptin stimulates immunity
  2. bone density- leptin makes bones thinner
  3. reproduction- leptin initiates puberty
47
Q

human heterozytoes for the G133 mutation in the leptin gene have low what?

A

serum leptin levels and increased body fat percentage relative to controls

48
Q

how is the short term treatment for leptin gene mutations helpful?

A

helps leptin mutant kids reach puberty

49
Q

what does exogenous leptin replacement therapy do for males?

A
  • increases FSH
  • increases testicular and seminal vesicle weights
  • increases sperm count
50
Q

what does exogenous leptin replacement do for females?

A
  • increases LH

- increases ovarian and uterine weight

51
Q

why doesnt leptin therapy work on regular obesity?

A

because they already have alot of leptin and have leptin resistance

52
Q

what are the mechanistic basis of leptin resistance in obese individuals?

A
  1. receptor problems
  2. reduced transport of the leptin through blood brain barrier
  3. feedback inhibition of leptin receptor by SOCS3
  4. increased in PTP1B phosphatase shuts off signals downstream of LepR
53
Q

what exactly are the receptor problems for leptin resistance?

A

mutations in LepR which are rare or decrease in receptors for leptin in the brain

54
Q

what does high levels of fat in the blood do to the blood brain barrier?

A

disrupts transport through BBB

55
Q

what is SOCS3?

A

stimulated by leptin so binds to leptin receptor and shuts it off

56
Q

what does PTP1B do?

A

removes phosphatase from JAK2 and leptin receptor and shuts it off

57
Q

how do obese individuals vary?

A
  • ability of exogenously administered leptin to gain access to CNS
  • degree or type of leptin resistance
58
Q

how does diet induce leptin sensitivity?

A

exogenous leptin may be relatively more effective in subjects in whom endogenous leptin production has first been reduced by dieting

59
Q

what is special about pramlintide?

A
  • amylin derivative
  • augments leptin actin in some individuals
  • approved as addition to insulin therapy in diabetics
60
Q

what are the symptoms of Bardet/Biedle syndrome?

A
  • early blindness
  • kidney cysts
  • polydactily
  • obesity
  • hypogonadism
  • developmental delays/mental retardation
61
Q

what is bardet/biedle syndrome mainly associated with?

A

primary cilia dysfunction

62
Q

what do bardet/biedl complexes contain?

A

variety of coatlike proteins that can bind and transport various receptor molecules into the cilium

63
Q

what do primary cilia do?

A

they protrude from the surface of mammalian cells and localize components of key signal transduction pathways

64
Q

what kind of cells are cilia common in?

A
  • fibroblasts
  • kidney cells (IMCD)
  • POMC expressing neurons
65
Q

what does the large complex of proteins implicated in BBS promote?

A

-cilia formation and movement of membrane proteins from the cell into the cilium

66
Q

what is the relationship between BBS and leptin receptor?

A
  • leptin receptor is located in cilia on POMC neurons
  • BBS proteins deliver leptin recepter up the cilia
  • problem is BBS patients are deficient in leptin signaling
67
Q

which is more common, leptin mutations or melanocortin pathway mutations?

A

melanocortin pathway mutations

68
Q

what do mutations in MC4R receptor do?

A

renders it insensitive to alpha MSH and beta MSH anorexigenic hormones

69
Q

besides symptoms/phenotypes what are some traits of MCR4 mutations

A
  • most common known monogenic cause of human obesity

- greater than 4% morbidly obese children have mutation in one MC4R allele due to haploinsufficiency

70
Q

what are the phenotypes of MC4R mutations

A
  • hyperphagia
  • tendency towards being tall
  • hyperinsulinemia
  • increased bone mineral density
71
Q

t or f: MC4R deficiency also stimulates increase in height

A

true

72
Q

what risk is high for MC4R receptor mutants?

A

risk of obesity is high in infancy

73
Q

for MC4R mutated individuals, some genetic/environmental modifiers prevent obesity like what?

A
  • incomplete penetrance
  • expression is variable
  • exposed to powerful agonsts
74
Q

some non-genetically obese patients have what that work against MC4R receptor?

A

autoantibodies

75
Q

what does MC4R bind to?

A

POMC

76
Q

ablation of what gene in humans also causes obesity

A

POMC

77
Q

what are some of the phenotypes associated with mutations in human POMC with recessive pattern of inheritance

A
  • red hair
  • hyperphagia
  • obesity
78
Q

what POMC derived peptides is associated with melanocytes?

A

-MC1R and leads to red hair and pale skin

79
Q

what POMC derived peptides is associated with adrenal gland?

A

MC2R and that leads to ACTH deficiency

80
Q

what POMC derived peptides is associated with the brain?

A

-MC3R and MC4R and leads to hyperphagia and obesity

81
Q

what POMC derived peptides is associated with skin?

A

MC5R

82
Q

what does α-melanocyte-stimulating hormone (α-MSH) lead to?

A
  • anorexigenic signal

- its cleaved from precursor molecule POMC, binds to melanocortin receptors

83
Q

what does agouti related protein do in humans

A

leads to orexigenic signal, homologous to agouti protein in mouse antagonist of the melanocortin receptor

84
Q

how is action of agouti protein reversible?

A

by extraneous addition of POMC encoded peptide alpha MSH

85
Q

defects of melanocortin receptors MC3R produces obesity in mice but does what in humans

A

unknown

86
Q

what are some conclusions from studies of monogenic obesity?

A
  • defect is in the satiety centers in the brain
  • affects appetite control centers in the brain
  • obesity is not due to slow metabolism
87
Q

what is the influence of the environment and genetics on obesity?

A

most cases of obesity are environmental but some people are more predisposed to obesity than others

88
Q

what is the genetic definition of polymorphism?

A

-a sequence of variant that has an allele frequency of greater than 1% in the population, below that its just a mutation

89
Q

what are the common types of SNP’s

A
  1. coding SNPs (synonymous and non synonymous)
  2. noncoding snps
  3. noncoding silent snps
90
Q

what are the methodological problems in discerning gene environment interactions?

A
  • power
  • replication
  • biological
91
Q

what exactly is the methodological problem with power?

A

-we need to test genetics in a lot of people to increase sample size

92
Q

what exactly is the methodological problem with replication

A

test for association in independent ethnic groups

93
Q

what exactly is the problem for biological validation?

A
  • functional assessment of putative disease causing variants

- evidence for pathophysiological role of the implicated gene

94
Q

what is FTO?

A
  • fat mass and obesity associated transcript

- but function not really related to obesity, nucleic acid demethylation

95
Q

what is significant about where FTO gene is expressed?

A

-expressed in same area of the brain as leptin and POMC act (arcuate nucleus)

96
Q

what kind of diet increased expression of FTO gene in animals?

A

high fat

97
Q

what happens when FTO is expressed by 2.5 fold in the arcuate nucleus?

A

a 14% reduction in average daily food intake

98
Q

what happens when fto expression is knocked down by 40%?

A

increases food intake by 16%

99
Q

what happens on average when a person has both fto and MC4R variants?

A

they are about 8.5 lbs heavier than average

100
Q

what is FTO very close to?

A

RPGRIP1L, it localizes in the primary cilia and centrosomes of ciliated cells

101
Q

subtle differences in what kind of factors cause people to respond differently to the same environmental exposure?

A

genetic ,explains why some individuals have a fairly low risk of developing a disease as a result of an environmental insult, while others are much more vulnerable

102
Q

what are the concepts of the thrifty genotype hypothesis?

A
  • genotypes were selected because of the need to survive inevitable famine
  • carriers of thrifty genes are efficient in the intake and utilization of food
  • sedentary lifestyle and constant food availability have disrupted gene environment interaction resulting in modern obesity
103
Q

how do thrifty genes operate?

A

-cyclically to process fuel sources in a manner that would maximize survival during food shortages

genetics concepts (13 decks)

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