CW2

Question 1

what is the gap in the paper?

Answer 1

Molecular and cellular hallmarks are needed for understanding age-related brain decline – so don’t know these really
- pattern separation memory and AHN gap knowledge

Question 2

what is the hypothesis?

Answer 2

• hypothesis that 5:2 diet promotes AHN and cognition via ghrelin receptor signalling
• Lots of cellular and molecular mechanisms underlying the beneficial effects of DR
• Ghrelin stimulates neurogenesis

Question 3

what can be used to monitor the molecular and cellular hallmarks which are needed for understanding age-related brain decline?

Answer 3

dietary restriction
- But do this without causing malnutrition, so instead change daily caloric intake each day or macronutrient intake or feeding duration of mix or each
- Seem to delay and prevent age-related disease and metabolic dysfunction in rodents and non-human primates
- Can do DR by daily calorie intake reduced (20-40%) but meal time and frequency not constrained
- Or IF with 16-48hrs of limited food or no food then eating as normal (ad libitum) between those periods

Question 4

what is ad libitum?

Answer 4

eating as much as needed as often as needed

Question 5

how can DR increase brain plasticity?

Answer 5

• Birth of new neurons in adult hippocampus (AHN)
• AHN regulates gives high degree of neuroplasticity and regulates spatial memory function and mood-like behaviours
• AHN declines with age – so need to identify factors that regulate it

Question 6

what is AHN?

Answer 6

adult hippocampus neurogenesis
- AHN regulates gives high degree of neuroplasticity and regulates spatial memory function and mood-like behaviours
- AHN declines with age – so need to identify factors that regulate it

Question 7

what does IF do?

Answer 7

IF with 16-48hrs of limited food or no food then eating as normal (ad libitum) between those periods
- Can promote cell proliferation in neurogenesis and neurone differentiation

Question 8

what are the molecular drivers of neural differentiation?

Answer 8

NGN2 and NED1/2 which are transcription factors to regulate neuronal subtype specification and maturation

Question 9

What do NGN2 and NED1/2 do?

Answer 9

transcription factors to regulate neuronal subtype specification and maturation

Question 10

which signalling pathway is also key in neural differentiation?

Answer 10

Notch signalling
- inhibiting it can promote neuronal differentiation
- when its active, it keeps cells in progenitor state

Question 11

what is neural differentiation?

Answer 11

• Extensive neurite growth and functional synapses established

Question 12

what is the shift in metabolism in neural differentiation?

Answer 12

from relying on glycolysis to using oxidative phosphorylation with newly formed mitochondria

Question 13

what can mature neurons be identified?

Answer 13

specific markers like neurofilament proteins

Question 14

what do neurofilament proteins do?

Answer 14

they help stabilise structure, they are type IV intermediate filaments
- needed for cytoskeleton, help maintain shape and regulate axonal diameter
- maintain proper spacing between parallel NFs, connected by plectins and other plakins
- excess aggregation of NFs are associated with neurodegenerative diseases

Question 15

how is hippocampus dependent cognition improved by CR?

Answer 15

through ghrelin

Question 16

how does ghrelin exist?

Answer 16

Ghrelin exists as acylated and unacylated forms to act as a molecular switch

Question 17

how many peptides is ghrelin?

Answer 17

28-aa pptide

Question 18

what is ghrelin a ligand for?

Answer 18

• It is the only natural endogenous ligand for the growth hormone secretagogue receptor (GHSR)

Question 19

what are the two forms of the GHSR?

Answer 19

• Two forms of the GHSR – GHSR-1a and GHSR-1b

Question 20

which form of the GHSR is mostly the active form?

Answer 20

• GHSR-1a is the active form

Question 21

what is ghrelin acylation catalysed by?

Answer 21

• Ghrelin acylation is catalysed by ghrelin- O-acyltransferase (GOAT) which uses FAs

Question 22

what activates GHSR-1a?

Answer 22

Acetylated Ghrelin (AG)
- Only AG can activate GHSR-1a and exert its activity but also UAG can exhibit activities through a GHSR independent pathway

Question 23

Can AG pass through the BBB?

Answer 23

• AG can pass the BBB and is mainly distributed in the hypothalamus

Question 24

what can ghrelin being over-expressed be associated with?

Answer 24

• Ghrelin being over-expressed may be associated with hepatic lipid deposit and non-alcoholic fatty liver disease and insulin resistance

Question 25

what does AG stimulate?

Answer 25

- Stimulates feeding in fasting - stimulates appetite

Question 26

what can oppose AG?

Answer 26

- UAG can oppose AG and inhibit it and inhibit neurogenesis and memory which AG promotes

Question 27

what does UAG do?

Answer 27

- UAG may play a role in regulating blood glucose and improving insulin sensitivity

Question 28

what converts AG to UAG by?

Answer 28

- AG converted to UAG by paraoxonase (PON)

Question 29

how does ghrelin stimulate?

Answer 29

- Signals to the hypothalamus to stimulate appetite and increase food intake and promote fat storage - Spikes before meals - Regulates energy homeostasis - Stimulates growth hormone release from anterior pituitary gland - Aids in GI motility - It is orexigenic

Question 30

which hormone does ghrelin stimulate release from anterior pituitary gland?

Answer 30

- Stimulates growth hormone release from anterior pituitary gland

Question 31

what does ghrelin do to the pancreas?

Answer 31

- Plays role in glucose metabolism by acting on the pancreas triggering it to release glucagon and inhibits insulin secretion - Stimulates bone formation and muscle growth

Question 32

where is the ghrelin receptor located?

Answer 32

in the neuropeptide Y and agouti-related protein neurons

Question 33

what happens when ghrelin binds to GHSRs?

Answer 33

- Ghrelin binds to GHSRs on NPYs and AGP neurones - Stimulates these and they release NPY which act on receptors on the efferent neuron to increase appetite - This melanocortin system is in the arcuate nucleus in the hypothalamus

Question 34

what can inhibit ghrelin?

Answer 34

- Also leptin receptors on these neurons and inhibits ghrelin response - GLP1 can inhibit NPY and AGRP neurons to suppress appetite

Question 35

what are BrdU+ cells?

Answer 35

- Actively dividing cells that incorporate the synthetic nucleoside 5-bromo-2’-deoxyuridine (BrdU) into DNA instead of thymine - Detected using antibody based stains to identify, track and quantify newborn cells, proliferating tumour cells or neurogenesis in the brain - Detected by immunohistochemistry or flow cytometry - It acts as a birthdate marker for cells so you can track when a cell was born and then its migration and differentiation - So can track neurogenesis

Question 36

what do BrdU+ cells show?

Answer 36

show neurogenesis - marker for new neurons being made

Question 37

how are BrdU+ cells detected?

Answer 37

- Detected by immunohistochemistry or flow cytometry

Question 38

when can BrdU+ cells be bad?

Answer 38

can interfere with DNA replications and potentially causes mutations or alter cell growth

Question 39

what are DCU+ cells?

Answer 39

- Doublecortin- expressing (DCX+) neural progenitor cells - Microtubule associated protein that shows immature neurons (neuroblasts) so signifies ongoing neurogenesis - Help new granule cells form in hippocampus - Also show neural progenitors

Question 40

what do DCU+ cells show?

Answer 40

- shows immature neurons and neural progenitors signifies ongoing neurogenesis

Question 41

what was decreased in ghrelin-knockout mice?

Answer 41

cell proliferation in DG, proportion of new BrdU+ cells (express markers of new immature neurons so shows neurogenesis), neurone differentiation and mature neurons was decreased - but giving ghrelin to these mice restored levels of neuronal differentiation

Question 42

how does stress affect AHN?

Answer 42

it can reduce AHN - it is more severe in mice lacking the ghrelin receptor GHSR

Question 43

can you inject ghrelin to increase neurogenesis?

Answer 43

- Acy-ghrelin needed as cells increased in WT mice with DR but not in GKO mice - Daily injections for 8 days enhanced AHN and acyl-ghrelin treatment rescued abnormal neurogenesis in a mouse model of AD - Don’t know how - Maybe due to non-cell autonomous pathways involving release of pro-neurogenic factors e.g brain-derived neurogenic factor - Acyl-ghrelin increased BDNF mRNA in the granule cell layer of the hippocampus