Metabolism and Disease Flashcards
1
Q
metabolism at organism level
A
- role and structure of specific tissues and organs
- flux of metabolites from organ to organ
- hormonal regulation of metabolism
- control of body mass
2
Q
major endocrine glands
A
- Brain: hypothalmus, pituitary
- Thyroid, parathyroid
- Adipose (fat) tissue
- Adrenals (on top of the kidneys)
- Pancreas
- Ovaries/Testes
3
Q
hormones and target tissues
A
Signals originating in the central nervous system (top) pass via a series of relays to the ultimate target tissues (bottom). In addition to the systems shown, the thymus, pineal gland, and groups of cells in the gastrointestinal tract secrete hormones. Dashed lines represent neuronal connections.
4
Q
top down vs bottom up signalling
A
Top down: Some signals originate in the brain, and the signal is sent out to the body.
o examples: oxytocin, vasopressin, cortisol (eg above diagram)
Bottom up: Some signals originate from elsewhere in the body and send messages to the brain.
o examples: epinepherine (adrenaline), insulin, leptin
5
Q
bottom up signalling
A
- requires tissue-specific responses to fuel
- Regulation of feeding behavior by two-way information flow between tissues and the hypothalamus. When food intake and energy production are adequate, peptide hormones released by the stomach, intestine, and adipose tissue feed back on the hypothalamus to signal satiety and reduce feeding behaviour
6
Q
example of bottom up: liver
A
- The portal vein carries nutrients to the liver.
- Hepatocytes turn nutrients into fuel.
- Hepatocyte enzymes turn over quickly.
- Enzymes increase or decrease with changes in diet and the needs of other tissues
7
Q
summary of fuel movement during starvation
A
- Initially liver glycogen –> glucose
- Then gluconeogenesis is required. The liver needs substrates from other tissues.
- Ie glycogenic amino acids mostly from the muscle
- After a few days of fasting most of the energy requirements of the the body are met by fat catabolism = glucose sparing mechanism
- Remainder is supplied by glycogenic amino acids
- The brain adapts to using ketones
draw diagram
8
Q
ketosis in starvation
A
- Liver makes inc Acteyl CoA when fat is mobilised & glucose is dec.
- inc Acteyl CoA normally -> TAG synthesis but if glucose is dec –> dec TAG
- Therefore excess Acteyl CoA –> ketones –> acidosis in starvation
- The liver maintains glucose output the amino acids for gluconeogenesis come from muscle
9
Q
forms of diabetes mellitus
A
Type 1: insufficient production of insulin
- usually due to autoimmune destruction of B cells
- usually develops early in life
- used to be called insulin-dependent or juvenile diabetes
Type 2: insulin resistance
- usually develops in late adulthood
- usually associated with obesity
- cells don’t respond appropriately to insulin
10
Q
diabetes symptoms
A
- In both forms of diabetes, blood sugar becomes elevated.
o The body tries to dilute the glucose, leading to excessive urination and thirst. - In Type 1, fat breakdown is accelerated, which leads to high production of ketone bodies.
o Some of the ketones are ketoacids, which raise blood [H+], leading to ketoacidosis.
o The bicarbonate buffering system is activated, leading to altered breathing
o The breakdown of ketone body acetoacetate produces acetone, which is expelled via the breath
o Untreated diabetes leads to dramatic weight loss.
11
Q
physiological effects of BGL
A
- Random blood glucose >11.1mmol/L - abnormal
- Blood glucose is normally determined after several hours of fasting. (<5.6mmol/L normal)
- A high fasting blood glucose level (5.6 to 6.9 mmol/L) is a warning sign for diabetes (pre-diabetic).
- > 7mmol/L indicates Diabetes – requires glucose tolerance test for definitive diagnosis
- A low blood glucose level below 4mmol/L considered hypoglycemic in diabetics.
- Blood glucose levels after a meal (postprandial) are typically higher (up to 145 mg/100 mL is normal).
12
Q
long-term effects of elevated BGL
A
- Proteins can be glycosylated, especially at free amino groups.
- Hemoglobin is abundant, has many exposed amino groups during formation, and entry of glucose into erythrocytes is not regulated.
o hence, Hb easily glycosylated
o compromises O2 delivery, especially in extremities - Blood test A1C between 5.7 and 6.4 percent indicates pre-diabetes
- It increases the risk of cardiovascular disease, renal failure, and damage to small blood vessels and nerves.
13
Q
metabolic syndrome
A
Metabolic Syndrome is not a disease, but is a cluster of disorders of metabolism, including: o High blood pressure o elevated insulin levels o Obesity (waist circumference) o Abnormal cholesterol levels
- Each of these disorders is by itself a risk factor for other diseases.
- In combination, these disorders dramatically boost the chances of developing potentially life-threatening illnesses, such as diabetes, heart disease or stroke.
14
Q
obesity
A
- Metabolic Syndrome largely linked to obesity
- Obesity is largely an energy storage issue
- Regulated by hormones
- Complex regulation influenced by:
o appetite and eating behaviour
o Exercise
o Metabolic processing of fuel - Fat stored in the adipose tissue.
15
Q
adipose tissue releases adipokines
A
- Adipose tissue is also an endocrine organ.
- It releases peptide hormones called adipokines.
- Adipokines carry information about fuel stores to brain
- 2 key adipokines include leptin & adiponectin
