Module 4 - Hunger and Satiety Hormones

Hunger

A physiologic sensation that prompts us to eat. Our body senses the need to eat which may be nonspecifc (not driven by appetite) rather physiologic in low blood glucose affecting regulatory hormones.

Satiety

The state reached in which there is no longer the desire to eat. Can refer to the feeling of fullness between meals.

Satiation

The feeling of fullness during a meal which may influence the action of stoping a meal.

Appetite

A psychological desire to consume specific foods. It is aroused by environmental cues such as sight, smell, and/or sound which prompts emotions or memories.

Metabolic Factors Influencing Weight Loss and Gain

Relatively low metabolic rate, low level of spontaneous physical activity, low sympathetic nervous system activity, and low fat oxidation

Hypothalamus

Feeding and hunger centers part of the central nervous system

First division of the human nervous system

Central nervous system (CNS) and peripheral nervous system (PNS)

Division of the peripheral nervous system

Autonomic and somatic

Divison of the autonomic nervous system

Sympathetic and parasympathetic

Division of the central nervous system

Brain and spinal chord

Division of the Brain

Forebrain, midbrain, and hindbrain

Division of the forebrain

Cerebral cortex and hypothalamus

What are the two regions in the hypothalamus that dramatically influence feeding behavior?

Satiety (fullness) center

Feeding (hunger) center

**these two centers have opposite effects

GI Tract

the largest endocrine organ in the body

What do gut hormones do?

function to optimize the process of digestion and absorption of nutrients by the gut; play a role in hunger and satiety; underlie the regulation of energy balance

Hormone Ghrelin regulated:

Hunger; in Stomach

Hormone Leptin regulates…

Satiety; in Adipose

Hormone PYY regulates…

Satiety; in small intestine

Hormone CCK regulates…

Satiety; in small intestine

Hormone GLP-1 regulates…

Satiety; in small intestine

Hormone insulin regulates…

Satiety; in pancreas

What are NTs?

Chemical messengers which carry chemical messages from one neuron (Nerve cell) to a target cell. They can influence a neuron in one of three ways: enxitatory, inhibitory, or modulatory

Serotonin

A neurotransmitter involved in eating;

therefore playing a role in our eating

behaviors.

• Can be synthesized from tryptophan

by two enzymatic steps.

• Serotonin is an inhibitory

neurotransmitter.

POMC

Promotes response of satiety and controlled in hypothalamic circuits (ARC)

MC4R

Promotes response in appetite and energy control under control in brain regulates

AgRP

Promotes response in food intake and under control in hypothalamus

What are hormones?

Chemical messengers coordinate various functions throughout the

body. They act as regulators of physiologic processes.

How many hormones are in the human body and where?

Roughly, 50 hormones are identified in the human body with various

regulatory processes.

Various organs, glands, and tissues release hormones (hypothalamus,

pituitary gland, adrenal glands, adipose tissue, gut, and placenta).

Leptin

A protein produced by the adipose cells.

• Primary role is to reduce food intake and cause a decrease in body weight/fat.

• Coded for by the ob gene (Obesity gene)

When gene reduces the ability of adipose cells to synthesize leptin in sufficient amounts….

Food intake increased and energy output reduced = weight gain

Ghrelin

A protein synthesized in the stomach; ghrelin

regulates appetite and storage of body fat.

• Regulations through actions by the

hypothalamus.

What does Ghrelin stimulate?

he appetite and increases the amount of food one may eat

Why do Shrelin levels increase?

before a meal and fall about 1-hour postprandial/meal

What is Ghrelin’s relationship to obesity?

Research shows ghrelin levels may increase after weight loss perhaps resulting in recurrent weight gain after weight loss.

Peptide YY or PYY

A protein produced in the GI tract. Released postprandial/meal related to the energy content of the meal.

• Decreases appetite and inhibits food

intake.

What is PYY in obese individuals?

Obese individuals may have lower levels of PYY when fasting and show less increase postprandial.

Brain Gut Axis

The gastrointestinal system is highly linked with the central nervous system.

• Gut microbiota aids in the regulation of neurotransmitters such as serotonin, GABA, and dopamine.

• A decrease in diversity results in GI or mood distress.

• Stress increased inflammation in the gut and can shift the diversity of bacteria.

The IIeal Brake and Satiety

Food lipids (dietary fats) that are not digested pass on to the distal portion of the small intestine (ileum) this slows digestion and triggers satiety hormone communication in the brain.

How do we measure satiety and hunger in humans?

• How hungry do you feel?

• How full do you feel?

• How satisfied do you feel?

• How much do you think you can eat now?