Nutrition Modules 5 & 6: Diabetes Flashcards
Where is amylase found? What is its function?
Saliva and small intestine (pancreas secretion)
Breaks down 1,4-glycosidic bonds to give glucose and maltose
What are the 3 brush-border enzymes?
- Maltase
- Sucrase
- Lactase
What are the 3 monosaccharides absorbed by the small intestine? Through which transport mechanism?
- Glucose: active transport
- Galactose: active transport
- Fructose: facilitated diffusion
Where are monosaccharides transported once absorbed by the small intestine? How? Why?
The liver via the portal vein to 3 pathways: 1. Glycolysis 2. PPP 3. Glycogen synthesis
What quantity of carbs can be absorbed by the small intestine in an hour?
1g/kg
Which cells in the small intestine absorb monosaccharides?
Enterocytes
What are dietary fibers?
Plant polysaccharides that cannot be absorbed by small intestine
What are the 2 types of glucose protein carriers for entry into cells?
- Energy dependent Na+/Glc co-transporters
3. GLUTs
Which GLUT is most widely expressed?
GLUT 1
GLUT 1
- Location?
- Function?
- Characteristics?
- Erythrocytes and barrier tissues
- Basal glucose transport: absorption
- High affinity
GLUT 2
- Location?
- Function?
- Characteristics?
- Liver, pancreatic B-cells, small intestine, kidney
- Transports all 3 monosaccharides and serves as the “glucose sensor”
- Low affinity, high capacity
GLUT 3
- Location?
- Function?
- Characteristics?
- Testes and brain
- Primary Glc transporter in neurons
- High affinity for Glc and Gal
GLUT 4
- Location?
- Function?
- Characteristics?
- Adipose tissue, skeletal muscle, heart
- Glucose uptake
- High affinity when insulin present
GLUT 5
- Location?
- Function?
- Characteristics?
- Small intestine
- Fructose transporter
- High affinity for fructose
What are the 4 monosaccharide transporters of the small intestine?
- Energy dependent Na+/Glc co-transporters
- GLUT 1
- GLUT 2
- GLUT 5
When is the PPP stimulated?
When glucose is high
In which 4 organs/cells does the PPP happen?
- RBCs
- Liver
- Adipose tissue
- Adrenal glands
What are the 3 types of precursors for gluconeogenesis?
- Glycerol
- Lactate
- Some AAs
In which 2 organs does gluconeogenesis occur?
- Liver
2. Kidneys
What is the Cori cycle?
Gluconeogenesis in liver using the lactate produced in muscle because of anaerobic glycolysis
What % of glucose is recycled through the Cori cycle?
20%
Describe glycogen synthesis.
- G6P converted to G1P
2. G1P activated by UTP and added to existing glycogen by glycogen synthase
How is glycogen synthase activated?
High G6P
How does glucagon stimulate glycogen breakdown? In which tissues?
- Activates glycogen phosphorylase in muscles, liver, and kidney by phosphorylating it
- Inhibits glycogen synthase by phosphorylating it
What are the 3 short-term complications of DM?
- Ketoacidosis
- Hyperosmolarity
- Lactacidosis
What are the 3 long-term complications of DM?
- Microvascular: diabetic retinopathy, nephropathy
- Macrovascular: peripheral, cerebrovascular, CVD
- Neuropathological
How is DM diagnosed?
1 of the following:
- Random plasma glucose > 200 mg/dL + DM symptoms
- FPG > 126 mg/dL*
- PG > 200 mg/dL 2 hrs after 75g glucose load*
- Hb A1C > 6.5%
- need to be repeated the next day
What % of DM cases are T1?
5-10%
What % of DM cases are T2?
90-95%
T1D peak onset?
11-12 yo
T2D peak onset?
50-60 yo
State of beta cells in T2D patients at diagnosis?
Intact
What 5 metabolic processes does insulin stimulate?
- Glucose uptake
- FA/TAG synthesis
- Glycogen synthesis
- AA uptake/protein synthesis
- Glycolysis
What 4 metabolic processes does insulin inhibit?
- Glycogen breakdown
- Lipolysis
- Proteolysis
- Gluconeogenesis
Describe the glucose uptake mechanism by GLUT 4 (3 steps)
- Insulin/GLUT 4 dimerization
- Autophosphorylation of receptor tyrosine kinase
- Signaling cascase promoting glucose entry via GLUT 4 fusion with plasma membrane
Describe how chromium contributes to glucose uptake.
Chromium enhances the activity of tyrosine kinase by binding chromodulin, which then binds to the receptor => it enhances glucose uptake
What is the result of chromium deficiency?
Insulin resistance
Can increase chromium intake help T2D patients?
NOPE
What 4 metabolic processes does glucagon stimulate?
- Glycogen breakdown
- Gluconeogenesis
- Ketogenesis
- Lipolysis
What 2 metabolic processes does glucagon inhibit?
- Glycolysis
2. Glycogen synthesis