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Showing posts from April, 2009

Biochem of starvation

Humans didn’t always have restaurants and grocery stores to visit on every corner. As part of human evolution, in fact, most of the time it’s likely our ancestors were starving quite often and got pretty good at it while foraging and hunting. It took the agricultural revolution to really make a shift to food aplenty. But starvation hasn’t gone away by any stretch. It’s a daily reality for much of the underdeveloped world. And, a bit closer to my reality, my own great grandmother often shared stories with me about how she’d go for weeks without meals as a little girl. To be able to survive from meal to meal, we depend on a starve-feed cycle. It refers to the changes in metabolism that allows variable fuel and nitrogen consumption to meet variable metabolic and anabolic demand (1). In plain English, it is what gives humans capacity to eat food well beyond caloric requirements and store it as glycogen and triacylglycerol to utilize when needed (1). This is what happens to someone biochemi

How does fat get absorbed and stored as fat?

Fat is absorbed in the intestine contained in chylomicrons and then secreted into lymphatics (1). The lymphatics drain the intestine, then lead to the thoracic duct and deliver the chylomicrons into the blood at a site of rapid blood flow (1). The rapidity is necessary to distribute the chylomicrons well preventing them from coalescing (1). Then lipoprotein lipase, which is attached to endothelial cell survaces in the lumen of capillaries, acts on the chylomicrones to liberate fatty acids via hydrolysis (1). The fatty acids are taken up by adipocytes and reesterified with glycerol 3-phosphate to form triacylglycerols and be stored as fat droplets (1). Reference 1. Devlin TM. Textbook of Biochemistry with Clinical Correlations. Philadelphia: Wiley-Liss, 2002.

Levels of consciousness (and no, I'm not Deepak Chopra)

Odd as it is to measure something like consciousness, it is a must to determine a possible medical condition, and the levels must be precise to give an accurate status before and after treatment (1). A state of consciousness can indicate a person’s wakefulness, awareness and alertness (2). Consciousness may “lower” a level or more depending on a range of factors that include alcohol or barbiturate overdose, stroke, epilepsy, bacterial meningitis, diabetes, kidney failure or heart disease (1). Example of consciousness terminology (1): Normal consciousness is characterized by a fully responsive, self-awareness and awareness of surroundings Inattention is when a patient finds it difficult to identify and attend revelant stimuli Confusion happens when thinking is slower or less clear; or when a patient is distracted Clouding (obtundation) is when inattention and confusion are more profound; rousing is more difficult Stupor is physical and mental activity at its minimum (kind of like me in

Don't depend on Glasgow Coma Scale

The Glasgow Coma Scale is easy to use for almost anyone to determine the state of a head injury. It includes eye, verbal and motor responses (see http://en.wikipedia.org/wiki/Glasgow_Coma_Scale ). But it should be clear that it should not be the only test used. This was a hard lesson for the medics that treated Natasha Richardson after her skiing head injury (2). For this reason when my daughter fell off a scooter and hurt her head, her doctor suggested I take her to the hospital for a scan. Reference 1. Nowak TJ, Handford AG. Pathophysiology: Concepts and Applications for Health Professionals. New York: McGraw-Hill, 2004. 2. Tremblant M. 2009. 911 Calls Show Urgency of Richardson Fall. CBS News. Available at: http://www.cbsnews.com/stories/2009/03/31/entertainment/main4906004.shtml

Neural tube defects may not be related to high sugar intake

High glycemic load was previously thought to increase risk of neural tube defects after California researchers found that there appeared to be an association with maternal diets high in sugar in their state (1). However, the more recent National Birth Defects Prevention Study has found that the association does not exist among national population and other regions in the country (1). It is unclear why this is the case (1). Reference List 1. Shaw GM, Carmichael SL, Laurent C, Siega-Riz AM. Periconceptional glycaemic load and intake of sugars and their association with neural tube defects in offspring. Paediatr Perinat Epidemiol 2008;22:514-9.

Going senile

My grandfather has, more than once, left my stove on for hours until a pan burns and a cloud sets off the smoke alarm. The other day he forgot to turn off the faucet and flooded my bathroom. I fear I can’t leave him alone. He could hurt himself or he could burn down my house. Dementia is a symptom used in a broad way to describe any loss of ordered neural function. It affects my grandfather as senility—its cause being his age of 82. It is a relief that my grandmother, just as old, does not show similar signs. And I just hope my parents don’t get it. I hope I don’t get it. Worst case scenario would be Alzheimer’s disease—the slow progression of dementia to the point that mental function is surrendered. If you happen to live with a parent or grandparent who is one of the 6 percent of the population that has Alzheimer’s, then, yes, I feel for you. My situation doesn’t come close. Depending on the pathological cause, dementia can be reversible. If altered mental function is due to depress

MS patients can look forward to stem cell therapy

Stem cell therapy may be the treatment of the future for severe multiple sclerosis patients. Swedish researchers reported last February that bone marrow stem cell transplantation was successful for treating severe multiple sclerosis (1). The researchers found improvement in symptoms after testing the therapy for five years on nine patients with severe MS, ages between 9 and 34 (1). The therapy has been studied for a total of 15 years (1). Reference List 1. Fagius J, Lundgren J, Oberg G. Early highly aggressive MS successfully treated by hematopoietic stem cell transplantation. Mult Scler 2009;15:229-37.

Feel down in the dumps? Could be Alzheimer’s disease

Lack of motivation may serve as a diagnostic criteria for Alzheimer’s disease. According to a discussion during the European Alzheimer’s Disease Consortium earlier this month, the apathy may be caused by functional impairment (1). The researchers noted that reduced “goal-oriented behavior, goal-directed cognitive activity and emotions” must persist over time, thought to be “at least four weeks”. Reference List 1. Robert P, Onyike CU, Leentjens AF et al. Proposed diagnostic criteria for apathy in Alzheimer's disease and other neuropsychiatric disorders. Eur Psychiatry 2009;24:98-104.

Why insulin is key for intracellular protein synthesis

When you’ve just eaten some protein, insulin, glucagon, growth hormone and glucocorticoids increase because of the presence of elevated amino acid concentration (1p232). The insulin promotes the protein synthesis and the other hormones have an opposite effect (1p232). Growth hormone is anabolic like insulin, although counterregulatory (1p232). Insulin to glucagon ratio favoring insulin stimulates protein synthesis enzymes and vice versa (1p232). The insulin is needed for uptake of amino acids across the cell membrane and antagonizing activation of amino acid oxidation by some enzymes (1p206-207). Protein synthesis is also sensitive to multiple influences including stability of mRNA, amount of rRNA, activity of ribosomes, and (most important from diet), the presence of essential and nonessential amino acids in appropriate concentration to charge the tRNA and hormone environment (1p232). When amino acids are not present or not present in sufficient quantity, amino acid oxidation increase

After my high-protein shake

I just got done working out, sort of; I did manage to break a sweat. Then I made myself a high-protein shake and was sure to include a banana for carbs. Why do I do this again? Aren’t carbs a bad thing? Well, it turns out that I need those carbs to stimulate insulin secretion to promote tissue cell uptake and use of the amino acids (1p206)(1). For this reason, it doesn’t make too much sense to take protein with some other kind of sweetener. The insulin affects movement of amino cid transporters to the membrane and their activity while also antagonizing activation of some enzymes that oxidize amino acids—very important if you’re trying to put on muscle (1p206-207)! You don’t want glucagon to dominate, leaving you with protein degradation (1p207). At least I don’t. Insulin stimulates protein synthesis and inhibits its degradation (1p207). My shake’s protein content happens to be made up of contain whey and casein. That’s a good thing for me because whey is considered a “fast” protein tha

Should I starve or should I receive bodily injury?

Last week while attempting to meet a deadline at work I skipped lunch and soon enough began hearing my stomach growl. The “hunger hormone” ghrelin, I knew, had kicked in; it would react with the receptors of my hypothalamus to release certain neurotransmitters and my brain would tell me I wanted macronutrients (1p299). Carbs, fats, protein, anything would do. But I didn’t have anything to eat so I thought, “What happens if I starve?” The answer is pretty straightforward. My body’s insulin would drop while glucagon would rise (1p246). Muscle and fat tissue would also become a bit resistant to insulin (1p246). Protein synthesis would drop (1p246). Glycogen from my liver would start becoming used up and muscles would release a mix of amino acids for gluconeogenesis (stimulating the glucagon) (1p246). The liver would keep my blood sugar level stable (1p246). If I didn’t eat for awhile, then my tissues would keep using fatty acids and glucose, but also start using ketones (from the fatty a

Raw or pasteurized

Raw milk and undenatured whey has been claimed to be better for you than their pasteurized and ultra-high-heat treated alternatives. Considering, however, that protein simply becomes denatured anyway in your gut (1), it would hardly make sense to care whether or not it was denatured. But a French study in the latest J Nutr and other studies explain that when milk protein is exposed to ultra-high heat (but not pasteurization), digestibility and nutritional content due can be affected (2-4). The change occurs not specifically due to denaturation, but due to Maillard reactions (reaction between amino acids and sugars) from heat, production of unusual amino acids such as furosine, and reduced availability of essential amino acids (2-4). Pasteurization resulting in partial denaturation of milk and whey has also been shown to create a biological significance on the bioavailability of nutrients such as folic acid (5). Still, I fear microbes, so suggest avoiding raw milk. Instead, try low-temp

Deamination and transamination

Deamination examples The amino acid threonine has its amino group removed by threonine dehydratase (1p209). This particular amino acid is commonly deaminated along with glutamate, histidine, serine and glycine (1p209). In the case of thronine, the reaction proceeds with loss of water, which is why the enzyme catalyzing the reaction is called a dehydratase instead of a deaminase (1p209). Vitamin B6 is important for this reaction to occur (1p209). The amino group is used by periportal hepatocytes to synthesize urea (1p209). Transamination examples The transfer of an amino groupf from one amino acid to an amino acid carbon skeleton or alpha-keto acid occurs to feed protein synthesis (1p209). The enzymes include tyrosine aminotransferase, branched-chain aminotransferases, alanine aminotransferase, and aspartate aminotransferase (1p209). The enzymes can often require vitamin B6 in a coenzyme form (1p209). The reactions are reversible and are often used to create non-essential amino acids f

Emergency contraception and ectopic pregnancy

One of the worst risks of emergency contraception is possible failure leading to ectopic pregnancy. Yes, it can occur, according to Indian researchers from All India Institute of Medical Sciences (1). A case report in 2001 occurred as a result of the use of levonorgestrel (1). For the most part, however, levonorgestrel is considered safe and effective (1). Reference List 1. Ghosh B, Dadhwal V, Deka D, Ramesan CK, Mittal S. Ectopic pregnancy following levonorgestrel emergency contraception: a case report. Contraception 2009;79:155-7.

Dysmenorrhea news

Endometriosis can ultimately result in causing dysmenorrhea (1). According to Chinese researchers, there has been conflicting reports leading to debate about the actual relationship, but statistical models suggest a stage and site of the endometriotic lesions (1). According to the researchers, there is still variation recognized and further research is needed (1). Reference List 1. Liu X, Guo SW. Dysmenorrhea: risk factors in women with endometriosis. Womens Health (Lond Engl ) 2008;4:399-411.

Increased Intracranial Pressure

Although its name sounds as though it may occur from studying for a pathophysiology exam, increased Intracranial Pressure (ICP) actually is associated with impaired cerebral venous drainage and reabsorption of cerebrospinal fluid (CSF) (1). The potential complication can come from a variety of pathologies including central nervous system edema, tumor masses, hematoma, hydrocephalus, venous obstruction and increased CSF volume (1p557-8). Increased ICP can occur in four stages: Stage 1 is a phase of potential danger from one of the complications listed previously. Stage 2 is a gradual rise in ICP effectively causing cerebral perfusion to drop and a decrease in oxygenation that stimulates vasoconstriction to increase cardiac output, resulting in lowered consciousness of the patient. Stage 3 is the established condition of rapid rise of ICP at a point where it is called the stage of decompensation and autoregulation is lost, resulting in increased blood volume in the brain, hypoxia and cy

Post-32-HyperPsychoProteinuria Stages 1 and 2

When a woman reaches 32 weeks into a first pregnancy, it’s possible that a peculiar syndrome may occur—possibly due to loss of a genetic imprinting in placental tissues (1)—that appears to originate from an implantation abnormality (1). The abnormality causes ischemia in placental blood vessels and could potentially cause a placental infarct, but usually triggers vasoconstrictors to activate fluid retention that causes hypertension (1). The ischemic placenta also disrupts endothelia causing a predisposition to disseminated intravascular coagulation (1). This blocks microcirculation causing tissue hypoxia and reduced blood flow in the kidney causes albuminuria, which leads to systemic edema (1). The symptoms may be accompanied by headache and vision disruption (2). In addition, the woman may have memory and concentration problems, according to a study published in March (3). Also, a March-published “revised view” in Placenta also reviews placental stress as leading to the syndrome (4).

When insulin becomes denatured

Protein denaturation is the unfolding of the secondary or tertiary structures (1). For example, heat can denature proteins in eggs by disrupting hydrogen bonds and non-polar hydrophobic interactions and as a result the egg proteins coagulate during cooking (1). Alcohol, like heat, can also disrupt hydrogen bonds, and acids, bases and heavy metal salts denature proteins by disrupting salt bridges (1). What are biochemical consequences of denaturation of insulin? In the body, protein denaturation can affect processes biochemically. Native insulin, for example, in the presence of increased, urea may be denatured because of changes in pH or, in the presence of a thiol catalyst, may be denatured due to isomerization (2). The insulin, thus, is unable to properly cause cells to take up glucose as it should (2). Reference List 1. Ophardt CE. 2003. “Denaturation of Proteins.” Virtual Chembook. Available at: http://www.elmhurst.edu/~chm/vchembook/568denaturation.html 2. Jiang C, Jui-Yoa Chang.

What happens in untreated type 1 diabetes?

Type 1 diabetes is characterized by autoimmune destruction of beta cells in the islets of Langerhans, which results in lack of insulin secretion (1). Glucose, then cannot be taken up by cells leading to hyperglycemia and osmotic diuresis (1). The low insulin will also stimulate hepatic glycogenolysis and gluconeogenesis to produce glucose released into blood leading into accentuated hyperglycemia (1). What’s more is that gluconeogenesis becomes chronic depleting body proteins to break down into amino acids (1). Muscle,in effect, atrophes converting to glucose and lost through the diuresis (1). Weakness, fatigue and weight loss all occur (1). Insulin inhibits degradation of protein and increases protein synthesis (2). Opposite to this, lack of insulin creates an environment favoring glucagon leaving degradation of protein unchecked and protein synthesis diminished (2). The degradation occurs by action of proteases—lysosomal or proteosomal—or via the calcium-activated proteolytic degrada

When do you need arginine?

Arginine is used for synthesis of protein, agmatine, polyamines and creatine [1]. Because kidneys synthesize arginine usually in sufficient amounts in the urea cycle(releasing 2-4g daily), it's normally not necessary to attain it from the diet [1p196;229]. At times, however, arginine can become conditionally essential [1p229]. Such times would include protein malnutrition, excessive ammonia production, excessive lysine intake, burns, infections, peritoneal dialysis, rapid growth, urea synthesis disorders, or in the inflammatory state of sepsis [2]. A deficiency could result in fatty liver, poor wound healing, hair loss, skin rash and constipation [2]. Arginine is changed into nitric oxide causing blood vessel relaxation [2], which can lower blood pressure. Thus, should not be used by a patient with low blood pressure [3]. If suffering of sickle cell disease, arginine can worsen symptoms [3]. One should exercise caution if supplementing with arginine because the amino acid is known

Hypoparathyroidism

Hypoparathyroidism is not as common as hyperparathyroidism and is characterized by secretion of low levels of parathyroid hormone (1). The disorder can be result of removal of parathyroid glands, the glands’ possible autoimmune destruction, or, in some genetic cases, when the kidney is insensitive to parathyroid output (1). When low parathyroid hormone occurs, hypocalcemia and hyperphosphatemia can become end results. Symptoms include weakness, mental process alterations and faulty muscular function (1). Patients with hypoparathyroidism are advised to make dietary changes to increase calcium and avoid phosphorus such as found in many soft drinks (2). Treatment for hypoparathyroidism include dietary supplementation with calcium and vitamin D, which helps the body absorb calcium and get rid of phosphorus (2). Reference List 1. Nowak TJ, Handford AG. Pathophysiology: Concepts and Applications for Health Professionals. New York: McGraw-Hill, 2004. 2. Mayo Clinic. Hypoparathyroidism. Avai

How is urea regulated?

Urea cycle regulation is dependent on dietary factors and hormone concentrations (1). A feed-forward regulation exists in that available ammonia causes more urea to be created (1). This can also mean that higher protein can also act as a feed-forward regulation since it increases urea enzyme levels (1-2). Ammonia can come from diet, from deamination, or bacteria in the GI tract inducing formation of carbamoyl phosphate by mitochondrial carbamoyl phosphate synthetase (1). Other regulation also exists. First, synthesis of n-acetyl glutamate, which is the allosteric activator of the carbamoyl phosphate synthetase (2). The activator is made in the liver and intestine when stimulated by available arginine (1-2). Second, arginase is inhibited by ornithine and lysine making it able to become rate limiting (1). Reference List 1. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Belmont, CA: Thomson Wadsworth, 2009. 2. Lieberman M, Marks A, Smith CM, Marks DB. Marks’ basi

“Goods” and “bads” of extra protein in sports

While Dietary Reference Intakes for protein are 0.8g protein per kg for adults, data suggest athletes may need more depending on their sport, particularly strength-training athletes (1). Research also indicates that even non-athletes who weight train may benefit from the added protein (2). Endurance exercise sports such as cycling and running increase protein turnover, including a lot more oxidation amino acids, so it is suggested that extra protein would also be wise (3;4). However, many athletes often exceed intake required (5). While the positive balance may not affect competitiveness, excessiveness does not encourage further muscle growth or strength gain (5). It should also be noted that strength-training itself also encourages improved utilization of dietary protein possibly reducing need of added protein (5). When consumed with carbohydrate, net protein balance during and after endurance exercise is improved, but there is little evidence of actual improved performance due to the

Spoonful of any kind of sugar makes the protein go down after exercise

It's clear that carbohydrates with protein affects insulin, thereby inducing glycogen synthesis. However, I was left thinking, “But what kind of carbohydrate is best?” And I found a study that suited my curiosity. One published in 2007 in J Int Soc Sports Nutr showed that 40 subjects who weight trained taking 40g of whey protein were also given 120g of sucrose, honey or maltodextrin (1). After 30 minutes, the honey group showed greatest glucose concentration and best degree of blood glucose maintenance; however, there was really no significant difference and either can be used (1). Reference List 1. Tipton KD, Elliott TA, Cree MG, Aarsland AA, Sanford AP, Wolfe RR. Stimulation of net muscle protein synthesis by whey protein ingestion before and after exercise. Am J Physiol Endocrinol Metab 2007;292:E71-E76.

Can arginine make you look like Arnold?

Arginine is a precursor for nitric oxide, which relaxes vascular smooth muscle leading to improved blood flow and, thus, the flow of nutrients to muscles (1;2). Oral arginine appears to also stimulate growth hormone release, especially when taken with exercise (3). Supplementation with arginine didn’t increase body mass significantly in a study in 2008; although, when taken with creatine, arginine did improve endurance and power of muscle (2). Reference List 1. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Belmont, CA: Thomson Wadsworth, 2009. 2. Little JP, Forbes SC, Candow DG, Cornish SM, Chilibeck PD. Creatine, arginine alpha-ketoglutarate, amino acids, and medium-chain triglycerides and endurance and performance. Int J Sport Nutr Exerc Metab 2008;18:493-508. 3. Kanaley JA. Growth hormone, arginine and exercise. Curr Opin Clin Nutr Metab Care 2008;11:50-4.

Will glutamine give you big guns?

You might think so. In theory, glutamine supplementation appears to make sense. Supplementation increases plasma glutamine in the plasma (1), which is thought to support the immune system (2;3) because the immune system uses glutamine for energy production (4). Plus, because exercise causes muscles to increase use of glutamine, stores are depleted (4). However, according to a 2001 study showed glutamine does not have any “significant effect on muscle performance, body composition or muscle protein degradation” (5). Reference List 1. Maughan RJ. Nutritional ergogenic aids and exercise performance. Nutr Res Rev 1999;12:255-80. 2. Williams MH. Facts and fallacies of purported ergogenic amino acid supplements. Clin Sports Med 1999;18:633-49. 3. Nieman DC. Exercise and resistance to infection. Can J Physiol Pharmacol 1998;76:573-80. 4. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Belmont, CA: Thomson Wadsworth, 2009. 5. Candow DG, Chilibeck PD, Burke DG, Davison