Beyond the Classic Endocrine Glands Flashcards
What is the main function of adipocytes?
→ Store energy as triglycerides
→ Release them as free fatty acids
How do triglycerides get inside cells?
→ As free fatty acids
→ hydrolyzed by lipoprotein lipase
What are free fatty acids bound to?
→ Albumin
What is the main source of triglycerides?
→ Chylomicrons from digestion
→ VLDL
What happens when free fatty acids are in the cell?
→ Become triglycerides again
What happens when the body needs fat for energy?
→ HSL (hormone sensitive lipase) breaks down fat stored as triglycerides
→ Adrenaline, glucagon,cortisol and GH stimulate this
What happens when the body has excess fat and needs to store it?
→ Insulin stimulates LPL to break down TG into FFA
→ FFA enter the cell
What is glucose usually converted to for storage?
→ Glycogen
What is glucose converted to when it can no longer be stored as glycogen?
→ converted into fat
→ Stored in larger quantities
Why is adipose tissue needed?
If fat was allowed to accumulate it would be toxic
→ Lipotoxicity
What does leptin do?
→ Signals satiety to the brain
What does adiponectin do?
→ Increases insulin sensitivity
What is leptin released from?
→ Adipose tissue
What do mutations of leptin cause?
→ LEP gene or LEPR (leptin receptor)
→ lead to abnormal eating behavior and morbid obesity
What is obesity associated with?
→ Leptin resistance
What is obesity a state of?
→ Chronic low level inflammation
Attract macrophages
What are the signals like in healthy adipose tissue?
→ Leptin signals satiety to the brain
→ Adiponectin increases insulin sensitivity
→ Resistin levels low
What are the signals like in obesity?
→ Leptin is high but resistance to leptin
→ Adiponectin is low
→ Insulin resistance
What happens as adipose tissue expands?
→ as adipose tissue expands
→ cytokines are secreted eg IL6 and TNF alpha
→ They attract more macrophages
What are general disorders of energy metabolism?
→ Obesity → Hypertension → Hyperglycaemia → High triglycerides → Insulin resistance
What is visceral fat exposed to?
→ Portal circulation
→Free fatty acids and adipocytokines released
→Alter metabolism
Why is losing weight when obese difficult?
→ The body remembers its highest body weight and defends this as the new normal
→ During weight loss there are appetite regulating hormones increase hunger
What does gastrin do?
→ Stimulates gastric acid secretion
What is gastrin stimulated by?
→ Peptides and amino acids in gastric lumen
What does CCK do?
→ Stimulates secretion of pancreatic enzymes
→ Contraction of the gall bladder and emptying
What is CCK stimulated by?
→ Presence of fatty acids and amino acids in small intestine
What does secretin do?
→ Stimulates secretion of water and bicarbonate from the pancreas and bile ducts
What is secretin stimulated by?
→ Acidic pH in the lumen of the small intestine
What does ghrelin do?
→ strong stimulant for feeding and appetite
→ Stimulates growth hormone
What does GIP(gastric inhibitory peptide) do?
→ Inhibits gastric secretion and motility
→ potentiates release of insulin from beta cells in response to high blood glucose levels
What is GIP stimulated by?
→ Presence of fat and glucose in the small intestine
What are the three factors for regulation of food intake?
→ Hormones from stomach
→ Vagal afferents to NTS
→ Leptin from adipocytes
What does GLP do?
→ Potentiates insulin secretion in response to rising plasma glucose
→ Reduces appetite
What happens if you stimulate the lateral hypothalamus?
→ Increased feeding
What happens if you stimulate the ventro medial hypothalamus?
→ Stops feeding
What are other non classical endocrine organs?
→ Heart → Kidney → Bone → Tumors → Pineal gland
What is the pathway for inhibiting food intake?
→Leptin, Insulin, PPY, CCK, GLP1 increase
→ POMC/CART neurons in the ventromedial hypothalamus are stimulated
→ Decreases food intake
What is the pathway for stimulating food intake?
→ Ghrelin increases and leptin decreases
→ AGRP and NPY neurons are stimulates in the lateral hypothalamus
→ Stimulates food
What do the kidneys secrete and in response to what?
→ EPO
→ low partial pressures of oxygen
What does EPO do?
→ Stimulates the production of erythrocytes
What is recombinant EPO used for?
→ Treat anaemia due to renal failure
→ Blood doping agent
What are circadian rhythms driven by?
→ The biological clock in the suprachiasmatic nucleus
Where is the suprachiasmatic nucleus?
→ Above the optic chiasm
In the absence of sensory cues what does the circadian cycle do?
→ Generates its own rhythm of 25 hours
What hormones does the suprachiasmatic nucleus control?
→ Melatonin
→ Cortisol
What is the pathway from retina to pineal gland?
→ Retina → SCN → Paraventricular nucleus → sympathetic chain → Pineal gland
What are the steps in the synthesis of melatonin?
→L- tryptophan
→ Serotonin
→ Melatonin
What stimulates and inhibits melatonin?
→ Darkness stimulates production and secretion of melatonin
→ Light inhibits it
