Download Control of blood glucose

Homeostasis
What does that mean?
We will look at….
1. Homeostasis of blood glucose (insulin and
glucagon, diabetes)
2. Homeostasis of basal metabolic rate (thyroid
hormone, goitre and brain development)
3. Homeostasis of appetite (leptin hormone,
obesity and OB gene mutations)
4. Management of growth (growth hormone and
doping)
5. Management of circadian rhythm (melatonin
and jet lag)
1. Control of metabolism
define metabolism?....
What do thyroid hormones do?
• Metabolic rate – raises BMR and increeases
energy metabolism in most tissues
• Reproductive health
• Brain development and general development
in the unborn baby
• thermoregulation
Thyroxine (T3 and
T4) are tyrosine
based
Hormones,
containing iodine
Thyroid hormone release is controlled
by negative feedback…
What happens if we don’t consume
sufficient iodine?
GOITRE (benign
hyperthyroidism)
>90% of cases of goitre
Are due to iodine
deficiency
What happens if we don’t consume
sufficient iodine
2015
How has the world reduced iodine
deficiency?
2. Control of blood glucose
Normal glucose levels are kept within
strict limits
Glucose regulation in healthy people
• Kick-in when blood glucose levels deviate 20%
from set-point
Key players in glucose homeostasis
Pancreas (α and β
cells: Islets of
Langerhans)
ALL tissues…particularly
liver, muscles, fat
• Insulin
• Glucagon
(also epinephrine,
steroids, growth hormone)
Insulin and glucagon are peptide
hormones made in the pancreas
Management of plasma glucose levels
Glucose and insulin act on
all tissues, but especially
• Liver
• Muscle
• Fat
• Brain
Insulin facilitates glucose uptake by cells
NB: The BRAIN
and the LIVER
don’t need
GLUT4 for
glucose uptake
Insulin is an anabolic hormone
• Primary targets of
insulin are liver, fat and
muscle cells (but acts on
all tissues)
• Drives glucose into cells,
promotes glucose uptake
by muscle, fat and other
tissues through
facilitated diffusion
(GLUT4 protein channel)
• Stimulates conversion of
glucose to glycogen in
liver and in muscles
• Inhibits fat breakdown
(promotes fat synthesis)
• Stimulates amino acid
uptake and protein
synthesis
• Insulin receptors in the
hypothalamus promote
satiety: the appetite
centre has an insulindriven ‘off’ button
Glucagon release is stimulated by LOW
plasma glucose
Released from α-cells in
response to:
• Low plasma glucose
• Protein-rich meal (high
levels of aa’s in blood)
• Exercise
Glucose regulation in healthy people
• Kick-in when blood glucose levels deviate 20%
from set-point
Diabetes
Symptoms of diabetes
Type 1
• 10% of diabetes patients
• ‘Childhood diabetes’
1. Toilet
2. Thirst
3. Thinner
4. Tired
•
•
•
•
•
Type 2
90% of diabetes patients
May be influenced by
obesity
May be influenced by
genetic factors
May be slow onset
symptoms
Often undiagnosed for up
to 10 years
Complications of diabetes
There are many serious potential complications
of chronic diabetes, including:
• Chronic skin infections
• Eye problems and potential blindness from
glaucoma (build up of pressure in the eye)
• Nerve damage (often leads to amputations)
• High blood pressure, leading to strokes, heart
attacks, kidney damage…
Management of Type 1 diabetes
• Insulin treatment
• ‘Islet ‘ transplants (stem cell therapy?)
• ‘Vaccine’ to prevent auto-immune destruction
of the pancreas
Management of type 2 diabetes
• The first-line of treatment is WEIGHT LOSS,
dietary control and exercise
• Recommended diets are high fibre, low fat
• …’diabetes superfoods’….
3. Appetite control
Appetite… how?
Genes and appetite
• There are many genes which have been
associated with obesity
• Most are involved with the brain’s regulation
of appetite
Control of appetite
The appetite control centre in the
hypothalamus is influenced by
leptin
Leptin
5. Management of circadian rhythm
Melatonin and circadian rhythm
Melatonin is a derivative of tryptophan
(amine hormone)
Melatonin is a biological marker of
darkness
• Scientists are keen to correct a frequently repeated
misconception. “Melatonin is most emphatically not
a sleep hormone,” says Russell Foster, professor of
circadian neuroscience at the University of Oxford. “It
is a biological marker of darkness.” In humans and
other diurnal animals, the release of melatonin into the
bloodstream helps prepare the body for sleep. In
nocturnal animals, however, it can signal breakfast
time. The duration of melatonin release also helps
animals keep track of the seasons, telling deer when to
grow their winter coat or find a mating partner, for
example.
Jet lag and melatonin
Do melatonin supplements help jet
lag?...
…use the Blog to find out….
4. Management of Growth
Influenced by growth hormone (secreted by the
anterior pituitary gland)
Athletes and growth hormone
How growth hormone ‘helps’ athletes
• Speeds up tissue repair
(recovery from injuries)
• Increases metabolic rate
• Increased muscle mass
and muscle strength
• Increases fat burning
(lipolysis) and
development of muscle
mass (anabolic)
• Improves energy levels
Is growth hormones supplementation
dangerous?
• May cause
diabetes in
prone
individuals
• May exacerbate
heart disease
• May lead to
metabolic
dysfunction