I'll have a tall glass of fresh-squeezed fructose

Orange juice delivers a potent dose of what is roughly half glucose and half fructose [1].

Glucose, we know, is the simple sugar that serves as the primary source of fuel to the blood, brain and muscle [2p735]. Its intake stimulates the release of insulin, goes through glycolysis to create energy, and is used to synthesize of glycogen for storage [2p735].

Fructose does not stimulate the release of insulin, nor does it enter glycolysis in the same way as glucose [3]. In fact it enters glycolysis a few steps later after going through its own metabolism. After being transported to the liver, fructose is phosphorylated by fructokinase to form fructose 1-phosphate, then by aldolase B to dihydroxyacetone phosphate and glyceraldehyde [3p58]. Glyceraldehyde is phosphorylated to glyceraldehydde 3-phosphate, and this molecule along with dihydroxyacetone enter glycolysis [3p58]. In the muscle, fructose is phosphorylated by hexokinase to fructose 6-phosphate, which is then used for glycogenesis or glycolysis [3p358].

Apart from being famous for being sweeter than glucose and the disaccharide sucrose (of which fructose is half part of), would the low-glycemic "fruit sugar" be better for the body since it create less of an insulin response? Science says "probably not."

In fact, high consumption of fructose is now being blamed for type 2 diabetes. The influx of fructose to the liver from soda with high-fructose corn syrup is found to interfere with glucose metabolism through metabolic dyslipidemia, a disturbance that may induce insulin resistance [4]. You get extra lipogenesis from fructose. Fructose by-passes the conversion of glucose 6-phosphate to fructose 1,6-phosphate. This is glycolysis's main regulatory step. Fructose, then, is "unregulated" and able to "uncontrollably" over-produce triglycerides. Evidence is now showing that the diabetes and obesity, which have become modern-day epidemics, could be prevented through significant reduction of fructose in the diet [4].

Research is also showing fructose may be more detrimental than glucose in high amounts. A study at the University of California on overweight or obese adults who were given beverages sweetened with fructose or glucose showed that those drinking the beverage with fructose gained pounds and had higher triglycerides and higher serum LDL cholesterol levels [5].

References

1. Ghanim H, Mohanty P, Pathak R, Chaudhuri A, Sia CL, Dandona P. Orange juice or fructose intake does not induce oxidative and inflammatory response. Available at:
http://care.diabetesjournals.org/cgi/content/abstract/30/6/1406. Accessed on November 20, 2008.
2. Denniston KJ, Topping JJ, Caret RL. General, Organic, And Biochemistry, 5th ed. New York: McGraw Hill; 2007.
3. Salway JG. Medical biochemistry at a glance, 2nd ed. 2006; Malden, Mass: Blackwell Publishing. (excellent book!!)
4. Basciano H, Federico L, Khosrow A. Fructose, insulin resistance and metabolic dyslipidemia. Nutrition & Metabolism. Available at: http://www.nutritionandmetabolism.com/content/2/1/5. Accessed on November 22, 2008.
5. DeNoon DJ. Study: Fructose increases heart risk factors and weight. WebMD Health News. Available at: http://www.medicinenet.com/script/main/art.asp?articlekey=82117. Accessed on November 20, 2008.

When you can't degrade glycogen

Your brain, blood and muscles depend almost entirely on dietary glucose as a fuel source so your body must store the sugar for continual supply [1p733]. If you go without eating for a while or jog a mile or two you’ll find yourself relying on glycogen for energy [1p733]. The long-branched glucose polymer acts as a store of glucose molecules, ready for the moment’s need [1p733]. But imagine having inherited a defective gene that resulted in not allowing your body to degrade glycogen stores.

If it wasn’t for Mendelian genetics, von Gierke’s disease may never have been completely understood [2]. Also called type 1 glycogen storage disease, the inherited disorder was found in 1952 using Mendel’s principles to result from a defective gene that causes the lack of glucose-6-phosphate [2 & 1p740]. The enzyme is necessary for catalyzing the final step in gluconeogenesis and glycogenolysis, which is needed for synthesis of glucose from noncarbohydrates precursors and removal of glucose from glycogen when blood glucose levels are low [1p740].

Without an ability to degrade glycogen, those with the disease suffer from low blood sugar between meals that can reach dangerous levels, and excessive accumulation of glycogen in the liver, muscle and in the tubules of the kidneys that can create further health complications [1p740 & 3]. Symptoms include an enlarged liver; puffy cheeks and limbs; a swollen belly; constant hunger; stunted growth; delayed or underdeveloped puberty, gout, easy bruising and nosebleeds, fatigue, and irritability [3].

Living with von Gierke’s disease requires avoiding low blood sugar through frequent meals that include carbohydrates and feeding tubes used at night [3]. Because lactose and fructose can’t be broken down properly, milk and fruits are usually avoided [3].

References

1. Denniston KJ, Topping JJ, Caret RL. General, Organic, And Biochemistry, 5th ed. New York: McGraw Hill; 2007.
2. Lorentz CP, Wieben ED, Tefferi A, Whiteman D, Dewald G. Primer on medical genomics part I: History of genetics and sequencing of the human genome. Mayo Clin Proc. 2002;77:773-782. Available at: http://www.mayoclinicproceedings.com/inside.asp?AID=165&UID=. Accessed on November 19, 2008.
2. MedlinePlus. Von Gierke disease. Medical Encyclopedia. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/000338.htm. November 19, 2008.

A little history on breast cancer

It was good to learn a bit about breast cancer, especially considering that I walked for breast cancer just recently and was among many breast cancer survivors. Now I know a little more about what their lives are like.

A little history lesson summarized (see source below):

Breast cancer dates back to 1600 BC (as far as we know) in ancient Egypt. The Egyptians used to cauterize the tumors. The first surgeries removing lymph nodes didn't occur until the early 1800s. In 1882 the first mastectomies occurred, particularly the radical mastectomy. The procedure was popular up until the 1970s and is still common. One in 12-13 women will suffer from breast cancer. Research continues to find a cure.

Source: http://www.syl.com/articles/thehistoryofbreastcancerfightingthemostcommoncancerinwomen.html

David

Preventing spread of breast cancer

We may soon see drugs that can help prevent the spread of breast cancer. Last year in April it was found that breast cancers produce an overabundance of the protein Akt, which plays a key role in metastasis.(1)

Akt's role was tested by researchers who bred mice with a missing gene for Akt.(1) Mice with no copies of the gene for Akt rarely developed tumors, those with only one copy of the gene for Akt developed some tumors, while mice with two copies of the gene developed cancer rapidly.1

The research could potentially lead to drugs that target this protein in humans.(1)

Reference

1. Thomas Jefferson University (2007, April 11). Scientists Identify Protein Key To Breast Cancer Spread, Potential New Drug Target. ScienceDaily. Retrieved November 16, 2008, from http://www.sciencedaily.com­ /releases/2007/04/070409181641.htm

Radical Mastectomy and Arm Swelling

Due to the presence of breast cancer, Mrs. Franco had a right radical mastectomy in which her right breast and underlying muscle, right axillary lymph nodes and vessels were removed. Now she is experiencing swelling in her right arm Why did the surgeon remove lymph tissue as well as the breast? Why is Mrs. Franco's right arm swollen?

Radical mastectomy is now rarely performed and only used in cases of extensive tumors or cancer cells that have invaded the chest wall (1). In this case, the cancer may have moved into lymph nodes under the arm and in the chest muscle.(2) The spread of the cancer would have occurred via metastasis, cells traveling through the lymph or blood and establishing new tumors wherever they lodge (3p811).

The right arm is swollen due to lymphedema, which is an accumulation of lymph in lymphatic vessels (3p841). If the swelling comes with tenderness and redness and she is feeling a fever come on, it is possible that infection may have occurred.(4) She should seek treatment immediately to not see symptoms worsen.

References

1. http://www.oncologychannel.com/mastectomy/index.shtml
2. Tortora, GJ, Derrickson, B. Principles of Anatomy and Physiology, 11th ed; 2006. New York: John Wiley & Sons.
3. http://som.medselfed.com/asp/prodDisplay.asp?prodId=407&partnerId=som&id=&cachedate=
4. http://www.breastcancer.org/tips/lymphedema/avoid.jsp

Scuba Diving Hypoxia

Just reading and writing about blood loss has made me feel a little lightheaded, and then I realized where I'd seen the term hypoxia.

Hypoxia can occur at high altitudes, especially if scuba diving at high altitudes, because the air has less pressure than at sea level and you inhale less oxygen.(1)

To prevent hypoxia while scuba diving at high altitudes (which could kill you), you should take a few days to acclimatize yourself to thinner air, make sure you don't over-exert yourself underwater, catch your breath regularly, and rise to the survace slowly.(1)

Reference

1. http://www.ehow.com/how_2238064_prevent-hypoxia-scuba-diving.html

Gunshot hypovolemic shock

A gunshot wound and bleeding is sure to cause hypovolemic shock due to blood loss, external and internal (1p756). The body is generating the response as part of a negative feedback system that is attempting to correct the problem (1p756):

- Low systolic blood pressure is due to reduced amount of blood.

- Rapid heart rate is caused by sympathetic increase of blood levels of epinephrine and norepinephrine.

- Weak, rapid pulse is due to reduced amount of blood and cardiac output.

- Reduced blood flow to kidneys causes secretion of antidiuretic hormone that increases water reabsorption and causes blood vessel constriction by secreting renin.

- The thirst is due to loss of extracellular liquid.

- Cool, pale, and clammy skin is due to the sympathetic constriction of blood vessels and stimulation of sweating.

- The confused and disoriented mental state is because of reduced oxygen supply to the brian.

An emergency room will need to stop the bleeding right away and replace loss of blood and fluids.(2) This is in addition to helping whatever other situation the bullet might have caused.

Reference

1. Tortora GJ, Derrickson B. Principles of Anatomy and Physiology, 11th ed; 2006. New York: John Wiley & Sons, p756-758.
2. MedlinePlus. Hypovolemic shock. Medical Encyclopedia. Available at: http://www.nlm.nih.gov/medlineplus/ency/article/000167.htm.