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Winter 2014 > KIN 404 1 > Flashcards

KIN 404 1 Flashcards

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1
Q

What is diabetes mellitus?

A

A metabolic disorder characterized by the presence of hyperglycemia due to defective insulin secretion, insulin action or both. The chronic hyperglycemia of diabetes is associated with significant long-term damage, dysfunction and failure of various organs – especially the kidneys, eyes, nerves, heart and blood vessels

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2
Q

Characeristics of type I diabetes

A

Absolute deficiency of insulin secretion due to autoimmuno destruction of beta-cells of the pancreas. Also called insulin-dependent diabetes/juvenile onset diabets. Account for only 5-10% of those with diabetes/

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3
Q

Characteristics of Type II diabetes

A

A combination of insulin resistance and relative insulin deficiency. Also called non-insulin-dependent diabetes/adult onset diabetes. No auto-immune destruction of beta-cells. Patients usually obese and particularly in the abdominal region

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4
Q

What is metabolic syndrome?

A

A clustering of chronic disease risk factors, including abdominal obesity, dyslipidemia (elevated TGs and/or low levels of HDL-C), elevated blood pressure and elevated fasting glucose

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5
Q

MetS is associated with substantially elevated risk of…

A

type 2 diabetes (5-fold) and of atherosclerotic cardiovascular disease (2-3 fold)

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6
Q

Neuronal population within the arcuate nucleus (ARC) of the hypothalamus that stimulate food intake?

A

Neurons that co-express neuropeptide Y (NPY) and agouti related peptide (AgRP) stimulate appetite

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7
Q

Neuronal population within the acruate nucleus (ARC) of the hypothalamus that suppress feeding?

A

Neurons co-expressing pro-opiomelanocortin (POMC) and cocaine-amphetamine-regulated transcript (CART) supress feeding

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8
Q

How do POMC neurons stimulate appetite?

A

alpha-melanocyte-stimulating hormone is produced and this binds to melanocortin-4 receptors in the paraventricular nucleus to suppress food intake

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9
Q

What is the orexigenic effect of NPY mediated by?

A

Stimulation of hypothalamic Y1R and Y5R in addition to local inhibition of POMC neurons in the ARC

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10
Q

In relation to food intake, what does BDNF do?

A

suppresses food intake

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11
Q

What is PYY, and what does it do?

A

Peptide tyrosine tyrosine (PYY)…acts in hypothalamus to decrease food intake. It also increases energy expenditure and delays gastric emptying in mice

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12
Q

What is PP, and what does it do?

A

Pancreatic Polypeptide…thought to reduce food intake directly through Y4R in the brainstem and hypothalamus

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13
Q

What is GLP-1, and what does it do?

A

Glucagon-like-peptide-1. …has a potent incretin effect, reduces food intake, supresses glucagon secretion and delays gastric emptying

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14
Q

What is GLP-2, and what does it do?

A

Glucagon-like-peptide-2…no effect on food intake, but stimulates crypt cell proliferation

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15
Q

What is oxyntomoduline, and what does it do?

A

Reduces food intake and increases energy expenditure

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16
Q

What is glucagon, and what does it do?

A

Produced by the alpha-cells of the pancreatic islets…reduces food intake and meal size in addition to reducing body weight gain

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17
Q

What is ghrelin, and what does it do?

A

It’s the only known orexigenic gut hormone…increases food intake and body weight with a reduction in fat utilization in rodents

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18
Q

What is CCK, and what does it do?

A

Cholecystokinin, first gut hormone shown to modualte food intake. May act to reduce food intake.

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19
Q

What is amylin, and what does it do?

A

Stored and released along with insulin in response to food intake. Reduces food intake and body weight and improves glycemic control and causes weight loss in patients with T2DM

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20
Q

What is leptin, and what does it do?

A

Adipokine that exerts its anorectic effect via the ARC. It inhibits NPY/AgRP neurons and activates POMC/CART neurons, resulting in reduced food intake and increased energy expenditure.

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21
Q

How does gastric bypass surgery affect ghrelin levels differently than diet induced weight loss?

A

Gastric bypass actually lowers ghrelin levels, whereas 24-hour diet induced weight loss actually increases ghrelin levels (making weight gain easier)

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22
Q

How does hypothalamic ciliary neurotrophic factor effect food intake?

A

Reduces AMPK signaling, and its effects are maintained in diet-induced obesity

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23
Q

A woman with a BMI of 24 would be classidied _______ and a man with a BMI of 29 would be ________

A

normal, overweight

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24
Q

An unnamed kin prof has undergone a # of tests in your clinic which have produced the following results: a fasting hyperinsulinemia in the highest quartile, normal blood glucose following an OGTT, BMI of 33, low fasting blood glucose, and high plasma TGs. What is your diagnosis?

A

Insulin resistance and obesity (not metabolic syndrome because he only has 1/4 risk factors, with elevated TGs to be the only risk factor)

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25
Energy intake consists of?
Energy consumed and intake efficiency
26
Energy output consists of, the 2 main ones?
physical and resting metabolic rate (highest constituent)
27
What 2 streams of info are integrated to determine behavioural (feeding) and autonomic/endocrine responses?
Internal millieu (hormonal and neural) and environmental/lifestyle
28
What are the individual predispositions/"wiring" that influence both the cognitive and metabolic brain?
Genetics, epigenetics, imprinted, early life events
29
Adiposity signals are what type of satiation regulators?
Long term regulators
30
Hunger and satiety signals are what type of satiation regulators?
Hunger and satiety signals
31
Where is the appetite control center located?
In the hypothalamus and hindbrain (brain stem)
32
What do orixegenic/anabolic regulators of energy homeostasis do?
Signals that increase food intake and decrease energy expenditure through metabolic brain
33
What do anoregenic/catabolic regulators of energy homeostasis do?
Signals that decrease food intake and/or increae energy expenditure through metabolic brain
34
What is the ARC, and where is it located?
The arcuate nucleus located in the hypothalamus...contains both catabolic and anabolic first order neurons
35
What is the PVN and where is it located?
The paraventricular nucleus in the hypothalamus. ..contains second order catabolic neurons
36
What is the PFA/LHA, and where is it located?
Perifornical area/lateral hypothalamus in the hypothalamus...contain second-order anabolic neurons
37
What is the ME?
Median eminence...area in the hypothalamus where there is no blood brain barrier so that peripheral signals can enter and act on higher brain centres
38
What are NPY and AgRP?
Neuropeptide Y and Agouti Related Peptide...First order anabolic neurons located in the ARC that project onto anabolic neurons in the LHA
39
What is alpha-MSH?
First order catabolic neurons in the ARC that activate secondary neurons in the PVN
40
How are peptide hormones synthesized and stored?
Made in advance and stored in secretory vesicles
41
Compare and contrast Ghrelin and Obestatin?
Both hormones derive from the same precursor protein and are predominatly secreted by the stomach and released into the blood. However, each has a different receptor (GHS-R and GPR39 respectively) and has an opposite effect on food intake, body wegiht and GI motility. Obestatin is only biologicallt active when it is methylated, therefore, ghrelin is more biologically active
42
What is POMC?
Pro-opiomelanocortin is the precursor for alpha-melanocyte stimulating hormone (alpha-MSH) -- a neuropeptide that suppresses appetite
43
Effect on food intake and energy expenditure of neuropeptide Y?
increases food intake and decreases energy expenditure...anabolic/orexigenic
44
Effect on food intake and energy expenditure of agouti-related protein?
increases food intake and decreases energy expenditure...anabolic/orexigeneic
45
Effect on food intake and energy expenditure of endocannabinoids?
increase food intake and decreaes energy expenditure...anabolic/orexigenic
46
Effect on food intake and energy expenditure of of melanin concentrating hormone?
increase food intake and decreases energy expenditure...anabolic/orexigenic
47
Effect on food intake and energy expenditure of of hypocretin/orexin
increases food intake and decreases energy expenditure
48
Effect on food intake and energy expenditure of cortiocptropin-releasing hormone
decreases food intake and increases energy expenditure...catabolic/anorexic
49
Effect on food intake and energy expenditure of cocaine amphetamine regulated transcript (CART)
decreases food intake and increases energy expenditure...catabolic/anorexic
50
Effect on food intake and energy expenditure of alpha-melanocyte stimulating hormone?
decreases food intake and increases energy expenditure...catabolic/anorexic
51
Effect on food intake and energy expenditure of gamma-aminobutyric acid (GABA)
increases food intake and decreases energy expenditure...anabolic/orexigenic
52
Effect on food intake and energy expenditure of serotin (5-HT)
Decreases food intake and increases energy expenditure...catabolic.anorexic
53
Increases in circulating ghrelin would result in: a) activation of anabolic neurons in ARC b) inhibition of catabolic neurons in ARC c) activation of orexigenic neurons in ARC d) a and b e) all of the above
e) all of the above
54
All of the following regarding leptin are true except: a) synthesized in ARC b) suppresses appetite c) inhibits orexigenic neurons in hypothalamus d) activates anorexigenic neurons in hypothalamus e) increases energy expendiure
a) synthesized in ARC (synthesized in white adipocytes)
55
What receptor does alpha-MSH bind to to inhibit the Agrp/Npy neuron?
MC3R
56
What receptor does alpha-MSH bind to to activate a secondary catabolic neuron in the PVN?
MC4R
57
What receptor does NPY bind to on a PMC/CAR neuron to inhibit it?
Y1R
58
What receptor does NPY bind to on a catabolic second order neuron in the PVN?
Y1R
59
What receptor does NPY bind to on an anabolic neuron in the LHA?
Y1R
60
What receptor does alpha-MSH bind to on an anabolic neuron in the LHA to inhibit?
MC4R
61
In what way(s) does AgRP stimulate feeding?
It inhibits alpha-MSH from inhibiting LHA (i.e. blocks inhibitory effect of alpha-MSH on the LHA) by acting as an inverse agonist and binding teh MC4R (thus, inhibiting PVN)
62
What receptors does alpha-MSH signal through?
MC3R and MC4R (melanocortin receptors)
63
How does AGRP anatognize alpha-MSH?
Acts as an inverse agonist (decreases PVN activation to the extent that alpha-MSH would increase it) and competes for the MC4R in the presence of alpha-MSH
64
What receptor does NPY signal through?
Y1R
65
What is the name of the ghrelin receptor?
Ghsr
66
What is GABA?
WHen Npy/Agrp neurons are activated by ghrelin, they release GABA. GABA binds to GABAnergic receptors on POMC/CART neurons, which inhibits the neuron, leading decreased PVN activation
67
What neuropeptides do secondary catabolic neurons in the PVN release?
Corticotropin releasing hormone and cocaine-amphetamine regulated transcipt
68
What neuropeptides do secondary anabolic neurons in the LHA release?
Orexin and melanin concentrating hormone
69
What is CB1R?
g-protein coupled cannabinoid-1 receptor
70
Is the CB1R anabolic or catabolic?
Anabolic...the munchies
71
In what ways does activation of NPY/AGRP neuron in the ARC by ghrelin increase feeding behavior?
1) Release of NPY, acting on Y1 receptors on the POMC/CART neurons and the Y1R in the PVN to inhibit the both of them 2) Release of AGRP antagonizes the MC4R in the PVN, inhibiting it. 3) NPY activating MC4R on LHA second order neurons, releasing ORX and MCH, which work on higher cortical areas and reward centers to increase appetite 4) Release of GABA, which inhibits the POMC/CART neuron by binding to a GABAnergic receptor
72
In what ways does activation of a POMC/CART neuron in the ARC by various factors decrease feeding behavior?
1) Activation of the POMC/CART neuron leads to release of alpha-MSH, which binds to MC3R on NPY/AGRP neurons, inhibiting it, and thus relieving its inhibition on catabolic neurons 2)Release of alpha-MSH binds to MC4R on second order neurons in the PVN, leading to release of CRH and CART, which suppress appetite and increase energy expenditure 3) Alpha-MSH binds to MC4R on second order neurons in the LHA, inhibiting them
73
Is serotonin anabolic or catabolic?
Catabolic
74
What is the serotonin receptor?
5-HT receptor
75
What is CRH?
corticotropin releasing hormone
76
What is ORX?
Orexin/hypocretin
77
What is MCH?
melanin concentrating hotmone
78
What neuropeptides do PVN secondary neuron release?
CRH and CART
79
What neuropepetides do LHA secondary neurons release?
ORX and MCH
80
What would a CB1 receptor antagonist do?
An endocannibinoid receptor antagonist. Has an anorexigenic effect on the hypothalamus
81
What genes in the lepton-melanocortin pathways when mutated cause monogenic obesity in humans?
Leptin, Leptin Receptor, POMC, PC1, MC4R or MC3R, SIM1
82
Satiation?
processes that promote meal termination, thereby limiting meal size (rapid and acute)
83
Satiety?
postprandial events that affect the interval to the next meal, thereby limiting meal frequency (also influenced by learned habits)...how long you feel full
84
Satiation factor criteria?
1) Factors should be released during food ingestion 2) Exogenous administration should decrease meal size in a dose-dependent manner -- rapidly, transiently and at physiological concentrations without causing illness
85
Adiposity (negative-feedback) signal criteria?
1) Circulates at levels proportionate to body fat content and enters the brain 2) Promotes weight loss by acting on neuronal systems implicated in energy homeostasis 3) Blockade of the neuronal actions increases food intake and body weight
86
Only adiposity singals?
Leptin and insulin
87
Intestinal peptides that decrease food intake?
CCK, GLP1, oxyntomodulin, PYY
88
Pancreatic peptides that decrease food intake?
Pancreatic peptide and insulin and amylin
89
What cells in the small intestine sense nutritive and non-nutritive properties of luminal food and release satiation peptides from their basolateral aspect in response?
Enteroendocrine cells
90
All of the following are true regarding AgRP except: a) synthesized in the ARC b) stimulates appetite c) inhibits anorexigenic/catabolic neurons in the hpothalamus d) secreted in response to ghrelin e) increases energy expenditure
e) increases energy expenditure
91
Which of the following is false? a) mutation of leptin gene causes monogenic obesity b) mutation of leptin gene would increase feeding c) mutation of leptin gene would increase alpha-MSH d) mutation of leptin gene would increase fasting insulin levels e) mutation of leptin gene would decrease activity of PVN neurons
c) mutation of leptin gene would increase alpha-MSH
92
What receptor do GLP-1 and OXM work on?
GLP1R
93
What receptor does PYY work on?
Y2R
94
What is the site of action for PYY?
Vagus nerve to the NTS and the bloodstream to work on the hypothalamus
95
What is the site of action for oxyntomodulin?
Vagus nerve to the NTS and the bloodstream to work on the hypothalamus
96
What is the site of action for GLP-1?
Vagus nerve to NTS and bloodstream to work on the hypothalamus
97
What is the site of action of CCK?
Vagus nerve to the NTS only
98
Where do cell bodies of afferent fibers of the abdominal vagus nerve project onto?
The NTS of the brainstem
99
What does gastric load in the stomach stimulate?
Stimulates mechanosensitive fibers confined to the stomach dose-dependently which suppresses meal size. Mela suppression by gastric load occurs independently of the nutrient content of the load.
100
What does CCK do?
Directly activates vagal afferent fibers sensitizing them to subsequent distension and results in pyloric contraction and slowing of the gastric emptying
101
What gut satiation hormones are cleaved from proglucagon?
GLP-1 and Oxyntomodulin
102
What are GLP-1 and ocyntomodulin co-secreted with from the intestine?
PYY
103
What do GLP-1 and OXM bind to in the brainstem and hypothalamus?
Bind to GLP-1 receptor
104
What is the PP-fold family, and what are some examples of proteins in this family?
36 aa in length and share a common structural motif known as the PP-fold...NPY, PYY, PP
105
What receptor does PYY bind to, and what does it do?
Binds to Y2 receptor isoform and decreases food intake
106
What does PP do, and how does it differ from other satiation factors?
Acutely reduces food intake but the effect remains for up to 24 h in contrast to other satiation signals (i.e. CCK). Chronic exposure to PP does not diminish the anorectic effects (i.e. no development of PP resistance)
107
What receptor does PP act through?
A Y receptor isoform...Y4
108
Mice with mutation of leptin?
ob/ob mice
109
Mice with mutation in leptin receptor?
db/db mice
110
ob/ob and db/db mice have what characteristics?
Obesity and diabetes. Weigh 3X more than normal mice and have 5X higher body fat content (even when fed the same diet). Display hypothyroidism, decreased growth, infertility and decreased immune function (i.e. neuroendocrine starvation response)
111
When injected centrally, leptin causes weight loss...what does this show?
Shows that leptin isn't crossing the blood brain barrier in obesity
112
Why is leptin efficacious during fasting induced weight loss?
Body still thinks it is fat, so it still suppress feedings (i.e. ghrelin)
113
What is a possible strategy to cirumvent leptin resistance?
Ciliary Neurotrophic Factor
114
What is STAT 3, and what does it do in leptin signaling?
Signal Transducer and Activator of Transcription...decreases transcription of AgRP and increases transcription of POMC
115
What is SOCS3, what does it do, and what activates it?
Suppressor of Cytokine Signaling, negative feedback to turn off the leptin receptor by inhibiting JAK and SHP-2, and it is activated by phosphorylation of Tyr1138 (which activates STAT 3, thus increasing transciption of SOCS3)
116
What is JAK, and what does it do in the leptin signal pathway?
Janus Kinase...physically binds to ObR --? autophosphorylates its own tyrosine residues which activate the enzyme, this activating numerous cascades
117
What is SHP-2, and what does it do in the leptin signaling pathway?
Src homology-containing typrosine phosphatase 2...activated by phosphorylation of Tyr985 and it activates the ERK 1/2 pathways, leading to a decrease in NPY/AgRP neuron firing and an increase in POMC neuron firing
118
What activates the IRS-PI3K pathway in leptin signaling and what does it do?
Activated by phosphorylation of the proximal tyrosine on the leptin domain. Leads to a decreaes in AgRP protein and increased POMC protein and may also increase POMC neuron firing
119
How does leptin regulate POMC and AgRP gene transcription?
They activate STAT3, which decreases AGRP protein expression and increased POMC protein expression
120
How does insulin regulate POMC and AgRP regulate gene transcription?
Activates the IRS/PI3K pathway, leading to activation of PKB. PKB inhibits FOXO1. Because FOXO1 usually increases expression of AgRP and decreases expression of POMC, inhibiting it relieves this inhibition leading to an increase in POMC and a decrease in STAT3
121
In s/s mice (LRb S1138), what are the effects?
Increased feeding and decreased energy expendiure, profound obesity like db/db, decrease in POMC but normal NPY, leptin still decreases AgRP/NPY activity, retain fertility/growth/immune functions
122
What are the effects of a LRb L985 mutation (l/l mice)?
Decreased feeding and adiposity and decreased NPY and AgRP levels
123
Why are l/l mice (LRb L985) resistant to diet induced boesity?
It reduces the activation of SOCS3, and therefore there is less leptin inhibition from JAK = less leptin resistance
124
What is AMPK?
AMP Activated Protein Kinase...important downstream target of leptin signaling that mediates the anorexigenic effects of leptin
125
What receptor family does Lrb?
Belongs to the IL-6 Receptor Family of Class 1 Cytokine Receptors
126
What does AMPK activation do?
Catabolism/energy production to restore energy balance
127
What stimulates AMPK?
Metabolic stress such as hypoxia, glucose deprivation and metformin
128
What does AMPK inhibit?
Increased ATP consumption such as cell growth and division, activation of motor proteins.
129
What is the structure of AMPK?
Hetertrimetric cimplex (alpha, beta and gamma subunits)
130
How is AMPK activated?
Activated by upstream kinases such as LKB1 and CaMKK via phosphorylation of Threonine 172
131
What can acitvate CaMKK?
Anything that causes an increase in intracellular calcium levels
132
What are some things that can increase AMPK activity?
ghrelin, fasting and AICAR...increases AMPK, increases NPY, leading to an increase in food intake and decreased energy expenditure
133
What are some things that can decrease AMPK?
Leptin, fed state, insulin...decreased NPY, leading to a decrease in food intake and increased energy expendiure
134
How does AMPK reduce food intake?
Leptin/insulin/glucose/alpha-linolenic acid bind to their receptors and decrease AMPK activity --> decreased ACC phosphorlyation, which increases its activity --> increased production of malonyl-CoA --> inhibits CPT-1 --> less mitochondrial fatty acid --> less beta-oxidation and accumulation of long chain fatty acid CoA in the cell --> decreased food intake
135
How does ghrelin activate AMPK in the hypothalamus?
Ghrelin binds to its receptor --> phosphorlyates and thereby activates AMPK --> phosphrylation of ACC, which decreases its activity/inhibition of ACC --> decrease in malonyl-CoA --> increased CPT-1 --? increased fatty acid oxidation --> decrased long chain fatty acid CoA in the cell --> increased food intake
136
What is the pulsatile pattern of ghrelin?
Levels rise sharply just before meals or wiht food restriction or starvation and they call rapidly after meals. Circulating ghrelin also plays a role in long term energy balance and body weight regulation because it increases with weight loss and decreases with increased adiposity
137
Hoe does initiate cell depolarization in AgRP/NPY neurons?
It binds to its receptor, which initiates a G-Protein coupled signaling cascade that results in cell depolarization...increases intracellular calcium which also stimulates AMPK and that whole cascade of increases food intake

Winter 2014 (5 decks)

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