endocrinology 3

Comprehensive practice questions based on Dr. David Petrik's lecture on the physiology of ghrelin, covering its discovery, structure, biological actions, and regulation.

What is the name of the G-protein coupled receptor that acts as the specific receptor for Growth Hormone Secretagogues (GHSs)?

GHS-R1a

In which two primary locations is GHS-R1a mRNA expressed?

1. Hypothalamus and 2. Pituitary

Which orally active GHS is described as a potential "pill for growth" and induces GH release in humans?

MK0677

What unique structural modification is essential for ghrelin to bind to GHS-R1a?

Octanoylation (n-Octanoyl group, $C8:0$)

Which enzyme converts unacylated ghrelin (UAG) into ghrelin?

GOAT (ghrelin O-acyltransferase)

What is the major circulating form of the hormone ghrelin?

Des-octanoyl ghrelin

Where is the main site of ghrelin production in the body?

The stomach

What impact does fasting have on circulating ghrelin levels?

Circulating ghrelin is increased by fasting.

How does acute ghrelin administration affect GH secretion?

It stimulates GH secretion via the activation of GRF neurones.

What is the effect of chronic, continuous exposure to ghrelin on GH secretion compared to pulsed release?

Continuous ghrelin exposure suppresses GH secretion, while pulsed release promotes it

Which specific neurones in the arcuate nucleus are activated by ghrelin to stimulate feeding (orexigenesis)?

NPY neurones

Is ghrelin-induced orexigenesis (stimulation of feeding) pattern-dependent?

No, it is not pattern dependent.

What effect do ghrelin and UAG have on the secretion of LH and FSH?

They suppress LH and FSH secretion.

According to the transcript, how does ghrelin affect fat mass?

Ghrelin elevates fat mass by inducing adipogenesis

In which type of fat is ghrelin-induced fat accumulation mediated specifically by the GHS-R1a receptor?

Intra-abdominal fat

What were the findings regarding skeletal growth and food intake in mice with a deleted ghrelin gene (ghrelin-knockout)?

They showed normal skeletal growth, normal food intake, and normal fat deposition.

What are the major functions of ghrelin in relation to pancreatic secretion?

Decrease insulin secretion and increase glucagon secretion.

Which second messenger molecules are shown in the GHS-R1a signaling pathway diagram on Page 6?

DAG, IP3, PIP2 and Ca2+

What term is used to describe the method of discovering ghrelin through the GHS-R cellular screen?

Reverse Pharmacology

What physiological effect does ghrelin have on appetite regulation?

Ghrelin stimulates appetite and signals hunger to the brain.

How does ghrelin influence energy balance in the body?

Ghrelin promotes fat storage and decreases energy expenditure.

What is the relationship between ghrelin levels and sleep?

Ghrelin levels typically increase during periods of sleep deprivation.

How does obesity affect ghrelin levels in the body?

Baseline ghrelin levels decrease and reduced post meal suppression

What happens to ghrelin levels after bariatric surgery?

Ghrelin levels typically decrease significantly after bariatric surgery, contributing to reduced appetite.

What is the role of ghrelin in hunger signaling?

informs the brain of the body's energy deficit and stimulating food intake.

How does ghrelin affect fat storage in the body?

Ghrelin promotes adipogenesis, leading to increased fat storage, particularly in intra-abdominal fat.

What is the interaction between ghrelin and insulin?

Ghrelin decreases insulin secretion, which helps to control blood sugar levels and energy availability.

What happens to ghrelin levels during weight loss?

Ghrelin levels tend to increase during weight loss, which can stimulate appetite and counteract weight loss efforts.

In what conditions are ghrelin levels found to be elevated?

fasting, sleep deprivation, and certain metabolic disorders.

How does ghrelin influence the hypothalamus?

Ghrelin activates neurons in the hypothalamus that are responsible for stimulating appetite and food intake.

What genetic factors influence ghrelin levels?

Polymorphisms in the gene that encodes ghrelin can affect its levels and influence appetite and weight regulation.