Lecture 12

Question 1

What is the recommended sodium intake for adults (dietary guidelines and AHA)?

Answer 1

• Dietary guidelines: 2300 mg

- AHA: 1500 mg

Question 2

What is the Na amount a typical American consumes per day?

Answer 2

3.3 g/day, too much!

Question 3

What tissues are directly affected by elevated sodium?

Answer 3

High intake of sodium affects the blood vessels, heart, and kidneys. Increases blood pressure and stress on these organs.

Question 4

What is the fraction of people who have HBP in the USA?

Answer 4

1/3 U.S. adults have HBP

Question 5

What is the number of mg of sodium in a teaspoon of salt?

Question 6

What is the important of processing in sodium levels of food?

Answer 6

As you process foods, sodium becomes more and more concentrated

Question 7

What is heme?

Answer 7

• a metabolite we make

- Heme iron: bound in organic form, found in meat; most readily absorbed form about 30%

Question 8

What is mineral iron?

Answer 8

• not bound by heme (aka non-heme)

- Fe3+ (ferric) or Fe2+ (ferrous)

Question 9

How is heme absorbed?

Answer 9

Heme iron is transported across brush border and enters the same pool as nonheme iron. Ferroportin aids in export of iron out of the intestinal cell for incorporation into serum transferrin to bind transferrin (Fe- transport protein in blood). Transferrin travels in blood to live and other organs

Question 10

How is mineral iron (non-heme) absorbed?

Answer 10

Fe2+ transported across brush border. Fe3+ must be reduced for transport across the brush border (Fe3+ -> Fe2+). Transported out of absorptive cells by ferroportin to transferrin. Transferrin travels in blood to live and other organs

Question 11

What promotes Fe absorption?

Answer 11

Mineral iron- Gastric acid from parietal cells and Vitamin C (reduces Fe3+ to Fe2+ and forms chelate)

Question 12

What inhibits Fe absorption?

Answer 12

Mineral iron- physic acid, oxalic acid, tannins in tea and coffee, low gastric acid, some antacids

Question 13

What is the route of uptake, storage, and transport of Fe?

Answer 13

• Iron taken up by absorptive cells in duodenum-> binds Ferratin (Fe storage protein)
• Transported out of absorptive cells by Ferroportin (protein) to Transferrin (Fe transport protein in blood)
• Transferrin travels in blood to liver and other organs where it is taken up by a transferrin receptor then released inside the cell as Fe then incorporated into other proteins
• In liver Fe can also be stored as an iron ferritin complex

Question 14

What are the functions of iron?

Answer 14

• Oxygen/CO2 transport: hemoglobin in blood, myoglobin in muscle
• Metabolism: cytochromes in mitochondria for e-transfer
• Detoxification: cytochrome P450

Question 15

What is the highest dietary source of iron?

Answer 15

Clams-> Fe-form: Heme

Question 16

What is the Fenton reaction and why is it so toxic?

Answer 16

• involves the generation of free radicals directly through iron chemistry and happens when iron toxicity is occurring: hydroxyl radical-> inflammation, CVD, diabetes, stroke, glaucoma

Question 17

What are the basic components of iron homeostasis?

Answer 17

If irons levels too high, uptake and transport are reduced:

1) increase ferritin in intestinal absorptive cells. Fe trapped by ferritin gets sloughed off as cells die (If body iron is low, ferritin levels reduced so Fe gets through)
2) Release of Hepcidin (peptide hormone from liver into blood). Hepcidin-> internalization and degradation of ferroportin-> blocks iron release from absorptive cells

Question 18

What are the key functions of Zinc?

Answer 18

• Many enzymes- ADH, Carbonic anhydrase, superoxide disputase
• Normal growth and sexual maturation
• Taste

Question 19

What is the importance of Iodine in thyroid function?

Answer 19

• Part of the thyroid hormone

Question 20

What is the connection between goiters and Iodine availability?

Answer 20

• if not producing enough thyroid (often bc of I deficiency) the TSH and TRH will amp up and sends signal to the thyroid gland to send more-> hypertrophy (swells) of this gland (goiter)

Question 21

What is the role of TRH, TSH, and T3/T4 in thyroid homeostasis?

Answer 21

• TRH and TSH send thyroid (double-check this)

- T3/T4: sends signal to hypothalamus if more thyroid is needed or not

Question 22

What is the highest dietary source of iodine?

Answer 22

Seaweed

Question 23

What are some of the possible strengths and weaknesses of epidemiological studies?

Answer 23

Strengths: can lead to hypotheses and allow the development of specific questions for testing and further examination; doesn’t make any assumptions about mechanism
Weaknesses: rarely does it give a mechanism; important to separate correlation and causation

Question 24

What is a confounding variable?

Answer 24

A hidden or unknown variable that affects the interaction between a proposed cause and a medical effect (disease)

Question 25

What example is presented in class about a confounding variable?

Answer 25

Alcohol was found to be correlated with increased lung cancer. However, many people who drink are around smokers or smoke, and smoking turned out to be the confounding variable. Smoking is correlated with alcohol consumption and a risk factor even for those who do not drink alcohol.