Diabetes Flashcards
What are the risk factors for diabetes?
- Hypertension
- Impaired glucose tolerance
- Insulin resistance
- Metabolic syndrome
- Dyslipidemia
- Obesity
- Hypertension
- Smoking, alcoholism
- Genetic predisposition
- Environmental factors
Type 1 Diabetes Pathophysiology
- (Genetic Predisposition + Environmental Factors) -> influence formation of auto antigens on insulin-producing B cells & they circulate in the blood stream & lymphatics
- Processing and presentation of autoantigen by antigen presenting cells leads to activation of T helper 1 lymphocytes and/or T helper 2 lymphocytes
- T helper 1 lymphocytes:
o Activation of macrophages with release of IL-1 and TNF-alpha - resulting in destruction of B cells & decreased insulin secretion
o AND/OR activation of auto antigen-specific T cytotoxic (CD8) cells - resulting in destruction of B cells with decreased insulin secretion - T helper 2 lymphocytes:
o activation of B lymphocytes to produce islet cell autoantibodies and antiGAD antibodies - resulting in destruction of B cells with decreased insulin secretion
What are the steps in Insulin-dependant Carb Metabolism in a normal fed state?
- Consume carbs in meal
- Increase [Blood glucose (BG)] stims pancreases secrete insulin
- Insulin binds to receptors in adipose tissue & liver:
a. Stims translocation of GLUT-4 receptors to cell surfaces in muscles and adipose tissue
b. GLUT-4 then allows glucose into the cells out of blood
c. Inhibits hormone sensitive lipase in adipose - which decreases lipolysis -> TG not broken down -> No FFA & Glycerol formed - In muscles: Glucose can be used for energy (glycolysis) OR stored as glycogen for later
- In liver:
a. Takes up blood glucose & converts glucose to glycogen
b. Decreased glycogenolysis & gluconeogenesis -> decreased hepatic glucose production - This decreases [BG]
What are the major effects of insulin?
- Promotes anabolism [uptake, rebuilding & storage]
a. Increased Glucose uptake
b. Increased Glycolysis in all tissues
c. Increased Glycogen synthesis in liver & muscle
d. Increased Protein synthesis in muscle
e. Increased Uptake of ions - Inhibits catabolism [breakdown & release]
a. Decreased Gluconeogenesis in liver
i. Blood glucose (BG) can’t be increased by release of glucose from the liver
b. Decreased Glycogenolysis in muscle & liver
c. Decreased Lipolysis in adipose tissue
d. Decreased Ketogenesis in liver
e. Decreased Proteolysis in muscle - In the liver:
a. Increased FFA uptake
b. Increased De novo lipogenesis
What are the steps of insulin-dependant Carb metabolism in an insulin resistant state?
- Insulin doesn’t bind to receptors
- Decreased ability to inhibit lipolysis at adipose tissue -> FFA & glycerol form -> increased plasma FFA and glycerol
- Excess FFA in plasma -> decreased Insulin-inhibition of hepatic glucose output
- Increased Gluconeogenesis and glycogenolysis -> increased hepatic glucose output
- Reduced ability of insulin to stimulate glucose uptake (decreased insulin signaling of GLUT4 translocation)
- Results in hyperglycemia maintained -> compensation of even more insulin secretion -> hyper insulinemia
- Increased Plasma FFA -> hyperlipidemia: risk for ectopic [abnormal positioning] fat deposition
What are the negative effects of excess FFA?
- Excess FFA have a direct toxic effect on pancreatic β-cells
- Increased FFA cause:
o Formation of DAG (glycerol with 2 FA):
• DAG promotes muscle insulin resistance & impairs fat oxidation via negative feedback mechanism
o Excess ceramide & sphingolipid accumulation in skeletal muscle -> decreased insulin signaling -> insulin resistance
o Taken up by various tissues and esterified into triglycerides -> triglyceride accumulation in tissues is associated with tissue & systemic insulin resistance
o ER stress (endoplasmic reticulum)
o Inflammation, ROS Generation, Mitochondrial Dysfunction
o Increased TG in liver -> Increased VLDL -> Increased LDL -> Increased HL -> Decreased HDL
What is the relationship between Obesity, Insulin Resistance & Dyslipidemia?
Central obesity -> Inc. FFA ( Insulin Resistance) -> Inc. ApoB & Inc. Hepatic Lipase (HL) -> Inc. TG ;
Inc. Small, dense LDL -> Dec. HDL
What is the effect of FFA on B-cells of the pancreas?
- FFA is essential for glucose-mediated insulin secretion in pancreatic islet B-cells
- Persistent excess FFA augments glucose-mediated insulin secretion
- This plus hyperglycemia – B-cells want to secrete even more insulin
- Results in impairment of insulin synthesis and B-cell apoptosis
What is mitophagy?
Control process that removes damaged mitochondrion
What is the Mitochondrial Dysfunction association with Insulin Resistance?
- Direct consequence of oxidative stress & Inc. pro-inflammation cytokines
- Occurs late – i.e. not primary cause of IR in obese persons
- Promotes further ROS production
- Results in impaired mitochondrial FA oxidation
- Worsened by FA accumulation & lipotoxicity
- Impaired mitophagy
o Damaged mitochondria aren’t removed and replaced - All of these lead to accumulation of dysfunctional mitochondria
What are the symptoms of T1 DM?
3 P’s:
o Polydipsia: Excessive thirst
o Polyphagia: Excessive hunger/increased appetite
o Polyuria: Frequent urination
What are the symptoms of T2 DM?
- Any Type 1 symptom
- Frequent infections
- Blurred vision
- Cuts/bruises that are slow to heal
- Tingling/numbness in the hands/feet
- Recurring skin, gum, or bladder infections
What is FPG?
Fasting Plasma Glucose
What is IFG?
Impaired Fasting Glucose
What is IGT?
Impaired Glucose Tolerance
What is OGTT?
Oral glucose tolerance test
What is RPG?
Random plasma glucose
What is HbA1c?
Glycated hemoglobin
Is 1 single abnormal test enough to diagnose diabetes in an asymptomatic individual?
No.
1 single abnormal test must be repeated to confirm diagnosis of diabetes, IFG or IGT, using the same testing method