Post on 24-Feb-2016
description
Stress:Living and Performance,
an Endocrine story
Drew Deppen BSc
Are you stressed yet?
“If you only follow guru’s, you’ll be nothing but
average.”Stu McGill Stress Guru’s
Walter Cannon Hans Seyle Bruce McEwen Robert Sapolsky – Why Zebra’s don’t get Ulcers Peter Sterling Katrina Borer – Exercise Endocrinology
Stress
11 different definitions
“Stress is a specific response by the body to a stimulus that disturbs or interferes with the ‘normal’ physiological equilibrium of an organism.”
Stressor is anything that causes an organism to experience stress.
The Stress Response
Walter Cannon Homeostasis
Constancy in an open system requires mechanisms that act to maintain this constancy.
Steady-state conditions require that any tendency toward change automatically meets with factors that resist change.
The regulating system that determines the homeostatic state consists of a number of cooperating mechanisms acting simultaneously or successively.
Homeostasis does not occur by chance, but is the result of organized self-government
The Stress Response Hans Selye
General Adaptation Syndrome Now called the Stress Response
Injected Rats with ovary extract Peptic ulcers Enlarged adrenals Shrunken immune tissue
Body has a similar set of responses to a broad array of stressors
Sounds counterintuitive to have same physiology when too hot, and too cold Built around the fact that muscles need energy when stressed Chances of you running for food, or from being food are high
If stressors go on for too long, they can make you sick
Types of Stressors
Acute Physical Stress Fight of Flight response
Highly adapted to handle this type Chronic Physical Stress
Drought, famine, parasites, infections Fairly adapted to handle these things
Psychological and Social Stress Western society, traffic jams, depression, anxiety
Fairly recent in evolutionary timeframe Chess players can place metabolic demands on their bodies
equal to high class athletes at peak events
SNS and PSNS
Sympathetic Nervous System 4F’s
Fighting, Flighting, Frighting, and Sexing Adrenals are connected to SNS via a
preganglionic synapse! Stress Response increases SNS tone
Parasympathetic Nervous System Rest and Digest Inhibited with Stress response
Endocrine Review
Hypothalamus Brain control center secreting releasing and
inhibitory hormones, Oxytocin, ADH, Dopamine Pituitary
Releasing ‘trophic’ hormones Adrenals
Glucocorticoids, Mineralcorticoids, Androgens, Estrogens, and Catecholamines
Other endocrine glands as well HPA axis - this is the main ‘axis’
1- Pineal gland 1b - Hypothalamus 2- Pituitary gland 3- Thyroid gland 4- Thymus 5- Adrenal gland 6- Pancreas 7- Ovary 8- Testis
1bEndocrine Anatomy
Glucorticoid functions Metabolism
↑ Protein Degradation ↓ Protein Synthesis ↑ Amino Acids to liver ↓ Amino Acids to muscle ↑ Gluconeogenesis ↑ Glycogen liver synthesis ↑ Lipolysis ↑ Truncal and Facial lipogenesis and fat deposition
Immune ↓ Inflammatory cytokines ↓ Capillary permeability ↓ Phagocytosis ↓ T-lymphocytes
Blood ↑ Vasoconstriction ↑ blood volume ↑ RBC and Leukocyte synthesis
Kidney ↑ GFR ↑ Na retention – blood volume
Brain ↑ ↓ Mood ↑ Senses ↑ Appetite
General Stress Response You get ‘Stressed’
Muscles need energy NOW Glucose, Protein, Fatty Acids
mobilized HR, BP, Respiration increases Vasodilatation in skeletal muscle
and skin Vasoconstriction in kidneys and
GI tract Decrease reproductive stuff
(during physical stress) Sorry boys and girls - ↓ erections and
ovulations Decrease Immunity Secrete Endorphins – POMC
cells Senses Sharpen Cognition actually improves
How did I get out of this one last time?
Acute Physical Stress (Phase 1) Stressor introduced
SNS system activated Anticipation
Even thinking about certain scenarios
Cyclical SNS activity Catecholamines
Positive feedback causing ↑ NE, Epi
Glucagon secreted (insulin inhibited)
Acute Physical Stress (Phase 2)
Hypothalamus activated in minutes CRH, TRH, ADH
Causes the secretion of trophic hormones
HPA axis fast to react CRH, and ADH releases ACTH
which releases glucocorticoids Intra/Intercellular cytokines
released TNF – a, IL-1, IL-4
ADH, PRL, Endorphins, Enkephalins also secreted
Insulin, Estrogen, Testosterone, and GH inhibited during stress After stress GH may increase
Acute Physical Stress (Phase 3)
Nutrient Partitioning Different depending
on type of exercise Mobilize Energy
↑ hepatic glucose production
Lipolysis Proteolysis Gluconeogenesis Glycogenolysis
Energy Mobilisation Non stressful situations
Body will store energy for later times
Stress! ↑ SNS ↓ PSNS (stops energy
storage) Release glucocorticoids, glucagon,
NE/E FFA’s, glycerol released, glycogen
oxidized, GNG Glucocorticoids actually block
energy uptake in muscles and adipocytes Exercising muscle overcomes
this mechisms --? Crazy Energy is shunted from non-
exercising muscle to exercising muscle
Acute Physical Stress (Phase 4) Recovery
PS tone increases and SNS decreases Restores homeostasis, fuel storage, structural repair
Insulin rebound after high intensity followed by a rapid decrease in NE
GH increases along with IGF’s Early and Late Phase recovery may be different
Cellular glucose uptake Adaptation Occurs
Basal Hormonal Conc. changes PS and SNS changes
Smaller NE response to same exercise bouts
Acute Physical Stress
Hormones Secreted CRH ACTH Glucocorticoids Glucagon ADH Prolactin Catecholamines Endorphins IL-1, IL-6, TNF – a
Hormones Inhibited Insulin Testosterone Estrogen GH IGF’s
Immune Response Common misconception that
stress ↓ IR Initially it enhances immunity –
esp innate More inflammatory cells
mobilized, antibodies released in saliva May need to fight infection from
a tiger bite Prolonged stress ↓ IR
Glucocorticoid, NE/E levels start destroying lymphocytes Can be good to get rid of old
cells Chronic stress response can
lead to autoimmunity Constantly ramping up IR may
lead you toward ‘friendly fire’
Psychological Stress Same stress response Body gears up to utilize a huge
amount of energy Never gets to use it Metabolically costly
No tiger to run from when road-raging
Bad deal Metabolic Syndrome Cardiovascular Disease Ulcers Autoimmune Disease Depression Cancer risk not associated!
May be associated with outcomes
Building Blocks for psychological stress Outlets for frustration
Rats shocked with and without block to gnaw on Humans can imagine outlets
Great way to relieve stress is to stress someone else Social Support
Primates may have a decreased response when surrounded by other primates If others are strangers it doesn’t help
Crying on someone’s shoulder physiologically helps! People with spouses live longer
Predictability Rats shocked after a warning have ↓ response Blitzkrieg bombings
London hit every night, suburbs sporadically – who developed greater responses? Control
Rats that can press lever to inhibit a shock then remove level – huge response People afraid of flying but driving is more dangerous – I can control my driving.
Perception of things worsening 2 rats – 1 gets 10 shocks/hour, other 50
Next day both get 25 shocks per hour – stress response is different
Food Consumption
How many people eat more when stressed? CRH ↓ appetite but Glucocoricoids ↑ appetite
Uses leptin secreted from adipocytes to blunt ‘fullness’ Glucocorticoids help mobilize energy, inhibit storage What’s going on? Released at different times
CRH released immediately, glucocorticoids released slowly Also the clearance is similar – CRH fast, Cortisol slow
Prolonged stressor will cause appetite to ↑ Appetite for calorie dense food is preferentially simulated –
ice cream!
Apples and Pears
Apple shaped people prefer to store fat in abdominal area
Pear shaped people prefer to store fat in gluts Abdominal adipocytes are more sensitive to
cortisol in presence of insulin to store fat Waist-hip ration is a more accurate predictor for CVD
and metabolic syndrome than obesity alone FFA’s more easily transported to liver
Vs.
Coping Strategies Exercise
Gets rid of the energy, must be voluntary and regular, aerobic is better for stress reduction
Meditation Any kind of parasympathetic activation activity
done regularly Gain control/predictability
Can be a double edge sword Social support
Both utilizing others when needed and feeling need for others
Religion/spirituality Allows for social support in fairly healthy decision
group Cognitive flexibility
Chose the right coping strategies Study for the test before hand, and talk about how
it doesn’t matter afterwards Conditioning
Sharpen the on and off times Stress yourself and learn to deal with it – make it a
choice 80/20 Rule
80% of stress reduction occurs within first 20% effort You have to decide to make a change
Exercise effects Cardiovascular and
Respiratory Redistribute blood flow,
regular BP Blood clotting in anticipation
of injury Modulate Pain Mediate tissue repair post-
event Engage Immune defenses
post-event Not a ‘true’ homeostatic
mechanism Spontaneous activity in
positive energy balance?
Endocrine support
Sympathoadrenal Catecholamines NE, Epi
Hypothalamo-pituitary-adrenal axis (HPA) CRH, ACTH, Glucocorticoids
Endogenous Opiates Endorphins (POMC cells)
Hydromineral hormones ADH, Aldosterone, Ang II
Acute Physical Stress
Low intensity Exercise (under 50% VO2) Below 50% VO2 max
Oxidative metabolism Type 1 fibers – red (mitochondria)
40 - 85% energy from FFA’s Carb sparing mechanism
100mg/dl glucose in plasma + 100g liver glycogen 85% utilized during normal daily activity 50% used during overnight fast
10 – 20kg of TG’s storage ↓ Insulin slightly
Hexokinase has a high affinity for Glucose even in absence of Insulin Glut -4 transporter tranlocates to membrane with muscle contraction
↑ NE slightly ↓ Glucose
Moderate Intensity Exercise
50-75% VO2 max Mixed metabolic demands
Endogenous and peripheral storage Mixed fiber types IC- IIA
Endogenous lipids and glycogen primarily used (80%) FFA’s used are from abdominal area/upper body ↓ Insulin with a spike after activity ↑ GH after mild duration of activity ↑ Glucocorticoid during and after activity ↑ Lactate ↑ Glucose with a drop after duration ↑ NE during and after activity
High Intensity Exercise >80% VO2 max 25% lipids and 75% Glucose energy
Mostly intracellular glycogen Stimulate PFK and PDH Increases lactate – inhibits lipolysis Excess acetyl Co-A produces acetyl-Carnitine, Coenzyme A Activates Malonyl Co-A – inhibits fat oxidation
ALL are non-insulin mechanisms to utilize carb catabolism Equal amts TG and peripheral adipose tissue
FFA blocked from entering circulation by NE/E White type IIX fibers
Creatine phosphate systems – early fatigue ↑ NE/E ↑ GH ↑ Glucagon ↓ Insulin with rebound spike after activity ↑ IL-6
Stim GH, PRL, CRH, and ADH secretion
Physical Stress
Nutrition during exercise
Carb supplementation ↑ Carb metabolism, ↓ lipolysis
Insulin mediated Stimulates PDH and ACC (makes malonyl CoA)
Inhibits Carnitine Glucose will cause a mild hypoglycemia for 20mins Fructose will not - ↓ insulin response
↓ Fatigue when eaten after 2 hours moderate intensity
Lipid Suppementation ↑ Lipid Oxidation
After several days of adaptation to high fat diet ↑ FFA uptake in muscle
↑ Lipoprotein Lipase Improves endurance in low and moderate intensity exercise
Spares muscle gylcogen and PCr systems Creatine
Good stuff for power movements
Big Picture
Is stress bad? Yes And no
Stress can do our physiology very well when applied under ‘normal’ circumstances When we get endocrine adaptation things can go
well and we can make gains Stress can also be bad in excess and when
we don’t have any way to channel it Like anything else in life
Coping Strategies Exercise
Gets rid of the energy, must be voluntary and regular, aerobic is better for stress reduction
Meditation Any kind of parasympathetic activation activity
done regularly Gain control/predictability
Can be a douple edge sword Social support
Both utilizing others when needed and feeling need for others
Religion/spirituality Allows for social support in fairly healthy decision
group Cognitive flexibility
Chose the right coping stradegie Study for the test before hand, and talk about how
it doesn’t matter afterwards Conditioning
Sharpen the on and off times Stress yourself and learn to deal with it – make it a
choice 80/20 Rule
80% of stress reduction occurs within first 20% effort You have to decide to make a change