Insulin and Glucagon Flashcards
Energy balance/homeostasis
- Optimal metabolic status: Energy intake and energy expenditure is equal
- Obesity and Metabolic disorders: Energy intake is much higher than energy expenditure. Often results in negative impacts on endocrine hormones resulting in further conditions
What results in differences in hormone actions?
- Age
- Sex
- Species
- Tissue-specific differences
Anabolic hormones
- Insulin
- Ghrelin
- Glucagon like peptide-1 (GLP-1)
Catabolic hormones
- Glucagon
- Cortisol/corticosterone
- Thyroid hormone
- Catecholamines (epinephrine and norepinephrine)
- GLP-1 (some catabolic effects)
- Leptin
Meal responsive and counter-regulatory hormones
Insulin and glucagon
- These are the primary hormones that regulate glucose homeostasis. They oppose each other and their levels in circulation are mostly decided by glucose
Insulin high, glucagon low
As insulin drops and glucagon increases, FFAs will begin to be used, followed by ketone bodies
Counter regulation hormone example
Insulin and glucagon
Cells of the pancreas and their function
- Beta cells- produce insulin
- Alpha cells- produce glucagon
Glucagon
Stimulates lipolysis in white adipose tissue and gluconeogenesis in liver
Insulin
- Stimulates glucose uptake in skeletal muscle
- Inhibits gluconeogenesis in liver and lipolysis in white adipose tissue
Liver during fed state
- hyperglycemia
- Receives insulin from B cells from pancreas that stimulates glucose uptake of cells and liver (glycogenesis in liver). Glucose stored as glycogen.
- Plasma glucose returns to normal
Liver during fasting state
- Hypoglycemia
- Pancreas released glucagon from alpha cells
- Glucagon stimulates gluconeogenesis and glycogenolysis in liver and release of glucose into plasma
- Plasma glucose returns to normal levels
Glucose and insulin levels in normal/diabetic animal
- After meal, glucose levels should immediately increase and insulin levels should rise.
- If you don’t see this increase in insulin, then can assume diabetes
Cells in which insulin increases glucose uptake
- Muscle cells
- Skeletal cells
- Smooth cells
- Cardiac cells
- Adipose cells
Cells in which insulin does not affect glucose uptake
- Neurons
- Intestinal epithelium
- Red blood cells
- Kidney tubular epithelium
- Liver
- Leukocytes
Insulin effects on liver
- Increase glycogenesis
- Decrease gluconeogenesis
- Increase glycolysis
- Increase lipogenesis
- Decrease ketoacids
- Increases proteogenesis