Beyond the classic endocrine glands Flashcards
How do adipocytes store energy?
As triglycerides and release energy as free fatty acids
What does LPL do?
Lipoprotein lipase hydrolyses triglycerides (packaged in chylomicrons or LDL) in the bloodstream into FFA so they can enter adipocyte cells where they can be re-esterified to be stored as TG (triglycerides).
It is involved in receptor-mediated lipoprotein uptake)
What regulates LPL?
Insulin (fat storage)
What does HSL do?
When the energy balance is negative, hormone-sensitive lipase breaks down TG into FFA and glycerol.
What regulates HSL?
Counter-regulatory hormones like epinephrine, adrenaline (short-term), GH and cortisol (long-term)
How does fat act as an endocrine gland?
Leptin - Signals satiety to the brain Adiponectin - Increases insulin sensitivity Resistin - possibly insulin resistance Cytokines Oestrogens Androgens
All adipocytokines
What is the connection between leptin and obesity?
Mutations in the leptin (LEP) gene in adipose tissue or the leptin receptor (LEPR) gene expressed in the hypothalamus lead to abnormal eating behaviour.
Obesity is associated with leptin resistance.
How does leptin work in healthy adipose tissue?
Leptin signals satiety to the brain
Adiponectin increases insulin sensitivity
Resistin levels low
How does doe leptin work in obesity?
Leptin secretion high but resistance to leptin
Adiponectin secretion low
Insulin resistance, diabetes and metabolic syndrome
Cytokines (e.g., IL-6, TNF-α)
-Normal balance disturbed
Chemokines (chemotactic cytokines)
-Attract macrophages
What does metabolic syndrome include?
Obesity (especially visceral)
Hypertension
Hyperglycaemia (prediabetes)
High serum triglycerides (but low HDL)
Insulin resistance
Visceral (VS) or intra-abdominal fat versus subcutaneous (SC) fat
VS and SC fat express different developmental genes
Different signalling profiles
Free fatty acids and adipocytokines released from VS fat drain directly to liver to alter metabolism
What is Cholecystokinin?
Hormone that stimulates secretion of pancreatic enzymes, and contraction and emptying of the gallbladder
What are the stimuli for cholecystokinin?
Presence of fatty acids and amino acids in the small intestine
What does ghrelin do?
Stimulates secretion of water and bicarbonate from the pancreas and bile ducts
What are the stimuli for release for ghrelin?
Acidic pH in the lumen of the small intestine
What does GLP-1 do?
Potentiates insulin secretion in response to rising plasma glucose; reduces appetite
