Bone Turnover Biochemical Markers

With estimates that one out of two white women in North America will suffer from an osteoporotic fracture sometime in their life, prevention of osteoporosis should be a major health objective for all women (and men). In addition, especially in post-menopausal women it is useful to predict the rate of bone loss and to further monitor how bone therapies are assisting over time.

Biochemical markers for bone turnover have improved over the last few years (1) and may help with prediction of rate of bone loss. Serum bone alkaline phosphatase, total osteocalcin and procollagen type 1 N-terminal propetide assays are best markers for bone formation (1). N- and C-terminal crosslinked telopeptides in urine and C-terminal telopeptides in serum are sensitive for bone resorption (1). Deoxypiridinoline in urine is another measurement of bone resorption, primarily useful during treatment (2).

Monitoring these biochemical markers can be useful for predicting rate of bone loss thereby can be supportive of recognizing osteoporosis or how effective antiresorptive or hormone-replacement therapies are on a patient. Depending on the rate status, a clinician can decide what therapies are most useful and make adjustments as seen fit.

A disadvantage is that biomarkers may not be as specific as needed to adequately detect rates of bone turnover, because any significant increase in resorption or formation results in increases in all biochemical markers (3). The markers are also not indicative of any certain disease, only reflecting on bone metabolism despite reason for changes (3).

Reference List

1. Eastell R, Hannon RA. Biomarkers of bone health and osteoporosis risk. Proc Nutr Soc 2008;67:157-62.
2. Kitatani K, Nakatsuka K, Naka H, Miki T, Morii H, Nishizawa Y. Clinical usefulness of measurements of urinary deoxypyridinoline (DPD) in patients with postmenopausal osteoporosis receiving intermittent cyclical etidronate: advantage of free form of DPD over total DPD in predicting treatment efficacy. J Bone Miner Metab 2003;21:217-24.
3. Srivastava AK, Vliet EL, Lewiecki ML, Abdelmalek A, Gluck O, Baylink DJ. Clinical Use of Serum and Urine Bone Markers in the Management of Osteoporosis [Abstract and Introduction]. Curr Med Res Opin 2005;21(7):1015-1026. Available at: http://www.medscape.com/viewarticle/508542_print. Accessed on 22 Jan 2010.

Detecting Levels of Iron Storage

Ferritin is the body's major iron-storage protein and its levels in serum are parallel to iron stores. Normally, 1 ng/mL of serum ferritin is related to about 8 mg  of iron in storage. It rises somewhat in males and post-menopausal females. Any rise or decrease in levels of serum ferritin indicates available iron stores in the body. 

As a diagnostic tool, serum ferritin is the most sensitive test of iron-deficiency anemia in a patient. In presence of iron deficiency, ferritin is generally the first sign followed by decreased iron levels and changes noted in red blood cells such as size, color and number. Low levels of ferritin indicate reduced iron stores or, rarely, malnutrition due to protein depletion. A decrease can also result from hemodialysis. Levels below 10 mg/100 mL is a diagnosis of iron-deficiency anemia. 

Higher levels, in contrast, indicate hemochromatosis, hemosiderosis, iron poisoning, or a recent blood transfusion. A higher level of ferritin can also be found in patients with megaloblastic anemia, hemolytic anemia and chronic hepatitis. It is also elevated in those with chronic disease states such as chronic liver disease, uremia, alcoholism, collagen diseases or neoplasm. 

The serum ferritin study is limited because ferritin may act as an acute-phase reactant protein such as in states of inflammatory diseases, infections, metastatic cancer and lymphomas. In these cases, ferritin levels may increase one or two days after onset and peak at three to five days. To classify anemias, tests of serum ferritin should be accompanied with serum iron levels and total iron-binding capacity. 

There are also interfering factors with serum ferritin, mainly blood transfusions, recent dietary intake of red meat, hemolytic diseases, iron storage disorders like hemochromatosis, menstruation (women will have decreased ferritin levels after menstruation), and drugs that increase ferritin levels.

Summarized from

Pagana, K.D., Pagana, T.J. Mosby's Manual of Diagnostic and Laboratory Tests, 3rd ed. Mosby Elsvier, 2006, pp 249-50.

Heavy Metal Biochemical Assessments

Mercury

Mercury’s recent presence in the body can be assessed with blood and urine samples because the initial half-life of blood mercury elimination is 3 days. The half-life of elimination for whole body mercury is between 60 and 90 days. Generally, the levels of mercury are below 10 mcg per liter in urine and below 40 mcg per liter in blood. Hair analysis can be useful as an estimate of long-term exposure to mercury.

To diagnose acute mercury toxicity, symptoms of respiratory distress are evaluated along with lab evaluation with a complete blood count and differential, serum electrolytes, glucose, liver and renal function tests, and urinalysis. Chest readiography and serial ABG measurements should be used for patients with severe inhalation exposure.

Reference: http://www.atsdr.cdc.gov/MHMI/mmg46.html

Lead

Blood lead levels can assess recent exposure to lead. It’s the primary screening method for lead exposure. It can also be measured with erythrocyte protoporphoryn, but this test is not sensitive enough to determine if children have levels below 25 mcg per deciliter. Because lead later travels to soft tissues and eventually to bones and teeth after several weeks, long-term exposure can be measured in bones and teeth with x-ray techniques.

Reference: http://www.atsdr.cdc.gov/toxprofiles/phs13.html

Cadmium

Cadmium in urine is best for determining level of recent and past exposure in the body. Analysis of hair and nails is not as useful because of factors of contamination from environment. Blood calcium can be useful to determine recent exposure in the body.

Reference: http://www.atsdr.cdc.gov/tfacts5.html

What's wrong with hair zinc analysis?

Hair used for nutritional status of a mineral can be flawed because of exogenous contamination--from water, dust, cosmetics, shampoos, etc--and because of endogenous, nonnutritional factors such as hair growth rate, color, sex, pregnancy and age.

However, I do find it quite interesting that hair analysis could indicate a history of nutrition. Historical measurements would be otherwise difficult to get, but hair grows lsowly and so hair can reflect levels of zinc and other elements over time. Plus, it's an easy test since hair is easy to get.

Better non-invasive indicators of zinc deficiency are Bryce-Smith taste and sweat analysis. Loss of taste is one of the first symptoms of a deficiency because zinc is needed for an enzyme, gustin, present in saliva that modulates sense of taste. And sweat analysis may be even more sensitive as an index than blood biomarkers.

Use of Organic Acids as Detoxification Markers

Environmental toxins, or xenobiotics, are foreign chemicals that enter our bodies and can potentially cause harm to our organs, tissues and cells. There are more than 60,000 known everyday chemicals that we are exposed to of which at least 200 are found in newborns at moment of birth. The most prevalent pollutants nowadays are phthalates and plasticizers, of which have been determined to be endocrine disruptors, and have been linked to thyroid diseases and various health conditions such as insulin resistance, metabolic syndrome, obesity, osteoporosis and arteriosclerosis. Other toxins are implicated in depleting folic acid leading to digestive disorders such as colitis or are known carcinogens.

Organic acids, of which are compounds used in metabolism, can be measured to assess how the body responds to toxins in the body or to evaluate nutrients related to processes of detoxification. For example, methylation is a vital step in the facilitation of converting homocysteine to methionine and in detoxifying chemicals. Without B12, methylation would be suppressed; thus, a resulting methylmalonic acid could be measured in urine at this point. If folic acid deficiency results, then the organic acid formiminoglutamate will accumulate and can be measured. A second example of an organic acid that can be used to evaluate nutrient deficiency resulting from toxins is xanthurenic acid. This acid appears in urine when chemicals deplete B6 (pyridoxine). A third example is measurement of fatty acids. When pthalates interfere with carnitine synthesis, then beta-oxidation in the mitochondria is impaired. THis, in turn, can result in elevated adipate, suberate, and ethylmalonate.

As markers of impaired detoxification or nutrient deficiency resulting from toxins, organic acids can help the clinical practitioner determine nutritional needs as well as possible nutrient or bioactive therapies. These therapies may include supplementation with B12, folic acid, n-acetyl cysteine, glutathione, CoQ10 and glycine. By correcting deficiency or otherwise, these nutrients potentially restore or boost detoxification in efforts to improve health of patients.

Summarized from

Rogers SA. Using Organic Acids to Diagnose and Manage Recalcitrant Patients. Alternative Therapies; July/Aug;12,4, 2006. Available at: http://blackboard.bridgeport.edu/@@437EB59FF6DF953742043192DBAC3894/courses/1/NUTR-560E-DLB-2009NF/content/_22128_1/OrganicsAcidCME.pdf

How to differentiate between a B12 and a folate deficiency

Despite whether or not megaloblastic anemia is caused by a deficiency of folate or vitamin B12 (cobalamin), large doses of folate will correct the anemia (1). Because this is the case, the extra folate can potentially "mask" symptoms of vitamin B12 deficiency such as from pernicious anemia.

Unfortunately, an undiagnosed chronic vitamin B12 deficiency can lead to irreversible neuropathy. The cobalamin in methyl derivative form is necessary to methylate homocysteine to methionine (2). It's also necessary to convert methylmalonyl CoA to succinyl coA. In the absence of B12, then, leads to accumulation of both methylmalonic acid and homocysteine levels (2). As they accumulate, they lead to possible neuropathy via irreversible demyelination of nerves (3).

The mechanism by which this occurs is thought to be related to methylmalonyl CoA acting as an inhibitor of malonyl CoA's role in biosynthesis of fatty acids, which leads to myelin sheath degeneration (3). However, because this does not explain why both homocysteine and methylmalonic acid must be elevated for demyelination, more research is needed.

Correct treatment can depend on telling the difference between a deficiency of B12 from folate. It can be achieved through an assessment of both methylmalonic acid and homocysteine blood levels (2 & 4). A clinician can determine that an elevated level of both will indicate a B12 deficiency in tissues (4). Further, if both are normal, no B12 deficiency exists; and if only homocysteine levels are elevated, then a possible folate deficiency may exist (4).

References

1. Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. Belmont, CA: Thomson Wadsworth, 2009.
2. Devlin TM. Textbook of Biochemistry with Clinical Correlations. Philadelphia: Wiley-Liss, 2002
3. Pagana, K.D., Pagana, T.J. Mostby's Manual of Diagnostic and Laboratory Tests, 3rd ed. Mosby Elsvier, 2006
4. Lab tests online. Methylmalonic acid. Available at: http://www.labtestsonline.org/understanding/analytes/mma/test.html

What's an ALT test?

Alanine aminotransferase (ALT) is an enzyme that is concentrated in the hepatocytes. When the liver is injured or affected by disease, the enzyme is released into the bloodstream. When jaundice occurs, for example, elevated ALT levels can distinguish a liver injury or disease instead of red blood cell hemolysis.

The test is performed on a patient by collecting 7-10 mL of blood in a red-top tube, then sending it to a lab for analysis. If a patient does have liver dysfunction, then the clinician should note that bleeding times may be longer.

Significantly elevated ALT levels may indicate hepatits, hepatitis necrosis or hepatits ischemia. Moderately increased levels may indicate cirrhosis, cholestatis, a hepatic tumor, a hepatotoxic drug, obstructive jaundice, severe burns or trauma to striated muscle. Drugs that may elevate ALT levels include acetaminophens, clofibrate, codeine, salicylates, tetracyclines among many others.

ALT levels may also increase to a lesser extent due to myositis, acute pancreatitis, myocardial infarction, mononucleosis or shock.

Summarized from the following:

Pagana, K.D., Pagana, T.J. Mostby's Manual of Diagnostic and Laboratory Tests, 3rd ed. Mosby Elsvier, 2006, pp. 40-42.

Lee RD, Nieman DC. Nutritional Assessment. New York: McGraw-Hill, 2007.

When You Have an Abnormal Lipid Profile

An abnormal lipid profile is a consistent indicator of atherosclerosis and cardiovascular disease (CHD). Blood lipids include total cholesterol, LDL-C, HDL-C and triglycerides. Because each of these factors are ultimately affected by diet, it serves to reason to recommend dietary strategies to help lower total cholesterol and LDL-C, increase HDL-C and reduce triglyceride levels.

ATP III uses the term therapeutic lifestyle changes (TLC) for recommendations that can help to improve abnormal lipid profiles and reduce risk of CHD. TLC makes recommendations for saturated fat (less than 7% of total calories), polyunsaturated fat (up to 10% of total calories), monounsaturated fat (up to 20% of total calories), total fat (25-35% of total calories, fiber (20-30g/d), protein (approx. 15% of total calories), and cholesterol (less than 200 mg/d). The total calories recommendation, in addition, is based on a balance of energy intake and expenditure to maintain a healthy weight (1).

Because it is often difficult for patients to adhere to specific percentages, a nutritionist can help patients by summarizing recommendations as eating less to lose weight as appropriate, exercising regularly as appropriate, avoiding animal fats in keeping to a low-cholesterol diet, replacing saturated fats with polyunsaturated fats whenever possible, and eating more fruits and vegetables.

A nutritionist could also approach patients with a Mediterranean-style diet. Recent research is showing that this diet is appropriate because it represents many of the same diet recommendations included in TLC. This diet may also have lipid-lowering effects and cardio-protective benefits from the regular intake of red wine, olive oil and fish (2).

Reference List

1. Lee RD, Nieman DC. Nutritional Assessment. New York: McGraw-Hill, 2007.
2. Cheskin LJ, Kahan S. Low-carbohydrate and Mediterranean diets led to greater weight loss than a low-fat diet in moderately obese adults. Evid Based Med 2008;13:176.

When should prevention of atherosclerosis start?

I have three children, one boy, 13 and two girls, 10 and 11. As far as I’m concerned prevention of atherosclerosis should begin as early as possible. That means yesterday. However, I understand that there exists some uncertainty of exactly what age to begin prevention. It has to do partly with juvenile fatty streaks. What may appear unimaginable is that the occurrence of juvenile fatty streaks somehow may have an importance in child development.

Most North American children develop fatty streaks in their aortas by age 3 and in coronary arteries along with macrophage foam cells by age 10 (1); by the time children are reaching puberty, they may already have developed fatty streak lesions. Fatty streaks are nothing new. As offered by McGill et al, our hominin forebears likely developed them as do current non-human Old and New World primates even when living in natural habitats. Studies of other mammals reveal that many of them also develop fatty streaks.

From an evolutionary perspective, then, fatty streaks may have provided a selective advantage to pre-human or human ancestors. Or, as in most cases, there are “trade-offs” in evolution. What may have been a cause of poor health in the long run for human ancestors may have been important part of early development. Fats and calories, for example, may have helped a child's brain or muscle development (3). It also stands to reason that while fatty streaks are normal, they may not necessarily lead to atherosclerosis. Wild mice develop fatty streaks, for example, but won’t develop lesions. Caged mice on a high-fat/cholesterol diet, however, will develop lesions and atherosclerosis as they age (2). When comparisons are given of mice and men (or women), our modern “caged” sedentary lifestyles and high-fat/cholesterol diets suggest humans are a burden to their own health.

Long-range prevention, then, should be focused on encouraging an improved diet early. How early? The American Heart Association’s guidelines suggest starting children on a widely varied diet low in fat and calories by age 2 (4). The amounts of fats and calories, however, must take child development into consideration. Even once children reach puberty this should be the case. As with my own children, who I have on a Mediterranean-style DASH diet rich in fats from olive oil and fish, it is important to give the body a holistic approach.

Reference List

1. McGill HC, Jr., McMahan CA, Herderick EE, Malcom GT, Tracy RE, Strong JP. Origin of atherosclerosis in childhood and adolescence. Am J Clin Nutr 2000;72:1307S-15S.
2. Li Y, Gilbert TR, Matsumoto AH, Shi W. Effect of aging on fatty streak formation in a diet-induced mouse model of atherosclerosis. J Vasc Res 2008;45:205-10.
3. Mitchell MK. Nutrition Across the Life Span. "Chapter 9: Nutrition During Growth: Preschool through Preadolescence". Second Edition. Waveland Press: Long Grove, Illinois, 2003, pp. 271-300.
4. Lee RD, Nieman DC. Nutritional Assessment. New York: McGraw-Hill, 2007.

When to use a C-peptide test

Normally, measuring insulin directly is more accurate with diabetics. But C-peptide levels more accurately reflect islet cell function in situations of insulinomas as well as cases of diabetics taking exogenous insulin (for treatment or secretly).

C-peptide, short for "connecting peptide" is the protein connecting beta/alpha chains of proinsulin. The chains are separated when proinsulin becomes insulin and C-peptide. C-peptide ends up in equal amounts to insulin in the portal vein, lasts longer than insulin so can be found more readily in peripheral circulation, and correlates with insulin levels.

Summarized from

Pagana, K.D., Pagana, T.J. Mostby's Manual of Diagnostic and Laboratory Tests, 3rd ed. Mosby Elsvier, 2006, p. 197.

Why get a glycosylated hemoglobin test?

Measuring blood glucose periodically is critical for staying off the blood sugar rollercoaster. But how can a clinician be sure a patient hasn't gotten on board the rollercoaster? This is when glyosylated hemoglobin comes into the picture.

What happens is that when a person is diabetic and doesn't adequately control blood glucose, her or his blood glucose becomes elevated. The hyperglycemia that results begins to affect certain proteins in the blood as well as hemoglobin. Blood glucose bonds to the hemoglobin and it becomes "glycosylated". The glycosylation mainly happens to hemoglobin A (HbA, the major form of hemoglobin, and it's pretty much irreversible.

After a few weeks, the amount of glycosylated hemoglobin will decline, but only if blood sugar is controlled. If it's not controlled, then a physician can order a glycosylated HbAIC test, or AIC test. A person without diabetes should have about 4-8% HbAIC and the American Diabetes recommends diabetics to stay below at least 7%. The glycosylated hemoglobin test is meant to evaluate how well treatment is going and how well a patient is following recommendations. It also serves as a method to individualize programs, compare therapys, differentiate short-term hyperglycemia in nondiabetics and diabetics, and also to offer as a reward for patients who do well in their control.

Summarized from

Lee, R.D. & Nieman, D.C. Nutritional Assessment, 4th ed. McGraw Hill Higher Education. Boston, 2007, p. 307.

Pagana, K.D., Pagana, T.J. Mostby's Manual of Diagnostic and Laboratory Tests, 3rd ed. Mosby Elsvier, 2006, p. 282.

Gut inflammation and stool tests overview

The gut’s immune system is ultimately responsible for maintaining a healthy gut free of infection or infestation. It must accomplish this task while at the same time being unresponsive to food and helpful bacteria (1).

Gastrointestinal inflammation etiology is largely infection such as via parasite. However, modern lifestyles have increasingly been harassed by new chronic inflammatory diseases such as Crohn’s or ulcerative colitis (1). These are associated mainly with genetic mutations or adaptive immunity affecting immune system recognition as well as by epithelial permeability (1).

Stool tests indicating gastrointestinal inflammation include those for fecal proteins such as eosinophil protein-X (EPX), fecal calprotectin (FC) and fecal myeloperoxidase (MPO):

• FC is a calcium-binding protein found in large amounts in neutrophils and macrophages, which rush into the lumen at onset of inflammation (2-4). FC is considered more sensitive than endoscopy, for example, for evaluating inflammatory bowel disease such as ulcerative colitis and Crohn’s disease. Calprotectin can also be used to determine post-infectious irritable bowel syndrome, NSAID enteropathy or cancer.
  
• MPO is a derivative of neutrophil granulocytes (2). It’s useful diagnostically because it’s found in intestinal mucosa and in feces. Levels of MPO are elevated in active inflammatory bowel disease and mark mucosal inflammation. MPO and FC appear to be better markers in comparison to EPX during the treatment of inflammatory diseases ulcerative colitis or Crohn’s disease (2).
  
• EPX is a glycoprotein that is released when eosinophil granulocytes (white blood cells responsible for battling infectious parasites and bacteria) (2). Its increased levels in feces reflect infection, inflammation and tissue damage relating to food allergies, celiac disease, helminthic infection, inflammatory bowel disease, and cancer (5).

Reference List

1. MacDonald TT, Monteleone G. Immunity, inflammation, and allergy in the gut. Science 2005;307:1920-5.
2. Wagner M, Peterson CG, Ridefelt P, Sangfelt P, Carlson M. Fecal markers of inflammation used as surrogate markers for treatment outcome in relapsing inflammatory bowel disease. World J Gastroenterol 2008;14:5584-9.
3. Savino F, Castagno E, Calabrese R, Viola S, Oggero R, Miniero R. High Faecal Calprotectin Levels in Healthy, Exclusively Breast-Fed Infants. Neonatology 2009;97:299-304.
4. Gaya DR, Mackenzie JF. Faecal calprotectin: a bright future for assessing disease activity in Crohn's disease. QJM 2002;95:557-8.
5. Genova Diagnostics. 2009. "Comprehensive Digestive Stool Analysis 2.0" Gastrointestinal Assessments. Available at: http://blackboard.bridgeport.edu/@@651E45893EFF586CEA74E9CF68D701AA/courses/1/NUTR-560E-DLB-2009NF/content/_22116_1/Comprehensive%20Digestive%20Stool%20Analysis-%20Genova.pdf. Accessed 28 Nov 2009.

Somatic Protein Status

Protein status is assessed by evaluating both somatic and visceral protein status. Somatic protein status is a measure of the protein in skeletal muscle while visceral protein status is a measure of all other proteins (organs, viscera, serum, blood cells, white blood cells).

Evaluation of somatic protein status can generally be performed using muscle circumference or mid-arm muscle area. However, because no single indicator is completely accurate biochemical measures can help better provide perspective for somatic protein status.

Creatinine serves as a useful measure because creatinine is produced in the skeletal muscle. The more skeletal muscle a person has, the more creatinine will be excreted. A 24-hour urinary creatinine excretion test is easily tested in the laboratory. The measure can then be compared to standards based on stature and body weight. The 24-hour urinary creatinine excretion can also be compared to reference values from the creatinine-height index (CHI). The CHI is a ratio of 24-hour urinary creatinine excretion and an expected amount depending on sex and stature. Creatinine measures have their limits samples have to be collected in exactly 24 hours and diet can compromise creatinine measurements and, thus, measures of excretion and CHI.

The amino acid, 3-methylhistidine, is another useful measure of muscle mass because it is found in the contractile proteins of muscle, actin and myosin. It is releasaed when the contractile proteins are catabolized and excreted in the urine. As long as protein synthesis and degradation is steady, the amount of 3-methylhistidine should paint a picture of muscle mass. However, just as 24-hour urinary creatinine excretion, the measure of 3-methylhistine is limited. The value can be affected by diet, age, sex, maturity, hormonal status, physical shape, any recent intense exercise, injury or disease. A significant pool of 3-mehtylhistidine also lies outside of skeletal muscle that also creates complication as an index of skeletal protein breakdown.