Obesity and Diabetes Flashcards
Blood glucose levels are determined by… (4)
Dietary intake
Tissue uptake
Mobilization
Excretion
What molecules does
1. Liver
2. Adipose
store caloric excess as?
- Glycogen
2. Triglycerides
What are the blood glucose values for
- Post-prandial
- Mean
- Fasting
- ~6.0-8.0 mmol/L
- ~5.5 mmol/L
- ~4.5-6.0 mmol/L
Glucagon
- Target
- Result on target
- Overall effect
- Stimuli
- Hepatocytes (liver)
- Increase glucose release, increase glucose synthesis, increase glycogen breakdown, decrease glucose storage
- Raises blood glucose level (promotes glucose mobilization)
- Low blood glucose (hypoglycemia) - alpha cells secrete it
Insulin
- Targets
- Results on targets
- Overall effect
- Stimuli
- Liver, fat, skeletal muscle
- Increase glucose uptake (all), increase glucose storage (l, f), increase glucose utilization (sm), decrease glycogen breakdown (l), decrease glucose synthesis (l)
- Lowers blood glucose levels (promotes glucose storage and utilization)
- High blood glucose (hyperglycemia) - beta cells secrete it
Insulin protein stucture
Anabolic polypeptide hormone
Secreted exclusively by beta cells of pancreatic islets of Langerhans
Synthesized as a 51 amino acid (proinsulin)
Cleaved by intracellular proteases to generate A and B chain
Linked by 2 disulphide bridges
How does Glucose-Stimulated Insulin Secretion work?
- Glucose enters the pancreatic beta cell via GLUT2 (low affinity transporter, only works when glucose levels are high)
- Glucose is metabolized, elevating intracellular [ATP]
- Elevated [ATP] inhibits ATP-sensitive K+ channel
- Accumulation of K+ inside the cell results in depolarization
- Voltage gated Ca2+ channel is opened, and Ca2+ flows in
- increased intracellular Ca2+ results in exocytic secretion of insulin from storage vesicles into the blood
Diabetes Mellitus
First noticed as causing rapid weight loss and excessive urination
All characterized by high blood glucose
2 primary causes: inadequate insulin secretion, or impairment of insulin action
Type 1 Diabetes
5-10% of all cases Most commonly arises under 20 years old Autoimmune destruction of pancreatic beta cells Reduced or absent insulin secretion Chronic disease
Type 2 Diabetes
90-95% of all cases
Most commonly arises >40 yrs old, but getting younger
Tissue resistance to the biological actions of insulin
Advanced stages associated with insufficient insulin secretion
Chronic disease
Gestational diabetes
5-10% of all pregnancies
Tissue resistance to the biological actions of insulin (mother)
Acute disorder that generally resolves shortly after birth
Pathophysiology of Type 1 Diabetes
Autoimmune destruction of pancreatic beta cells
Cause not well characterized (multifactorial - genetics, environment, pathogen exposure)
Progressive loss of insulin production and GSIS
Loss of tissue glucose uptake and energy storage
Failure to inhibit glucose production and release from the liver
Chronically elevated blood glucose
Acute effects of type 1 diabetes
Excessive urine production Extreme thirst and hunger Rapid heartbeat Nausea, dizziness, confusion Weakness, shaking, fainting
Chronic complications of type 1 diabetes
Extreme weight loss, wasting Damage to blood vessels of eyes and in extremities Kidney damage Peripheral nerve damage Hyperlipidemia Hypertension CV disease
Treatment of Type 1 diabetes
Careful control of diet
Insulin replacement
Even with good management of hyperglycemia, there is an elevated risk of chronic complications
Pathophysiology of type 2 diabetes
Development of insulin resistance in tissues
At early stages, increases insulin secretion can compensate for moderate insulin resistance
But later on elevated insulin secretion cannot compensate for worsening insulin resistance
Reduced glucose uptake and energy storage
Increased liver glucose synthesis and release
Chronic hyperglycemia
Chronic insulin resistance and hyperglycemia is toxic for pancreatic beta cells
What is insulin resistance and what does it result in (5)?
Reduced response of tissues to insulin Results in: Decreased activation of membrane glucose transporters by insulin receptor Decreased glucose uptake Decreased glucose storage Increased glucose synthesis Elevated blood glucose levels
Adipokines
Signalling molecules with hormone-like actions
Synthesized and secreted by adipose tissue
Regulate energy metabolism in adipose as well as other tissues
Ex: leptin, adiponectin, TNFalpha, etc
Acute effects of type 2 diabetes
Same as type 1 Excessive urine production Extreme thirst and hunger Rapid heartbeat Nausea, dizziness, confusion Weakness, shaking, fainting