Expression of matrix metalloproteinases in human growth plate chondrocytes is enhanced at high levels of mechanical loading

Matrix metalloproteinases (MMPs), responsible for extracellular matrix remodelling and angiogenesis, might play a major role in the response of the growth plate to detrimental loads that lead to overuse injuries in young athletes. In order to test this hypothesis, human growth plate chondrocytes were subjected to mechanical forces equal to either physiological loads, near detrimental or detrimental loads for two hours. In addition, these cells were exposed to physiological loads for up to 24 hours. Changes in the expression of MMPs -2, -3 and -13 were investigated.

We found that expression of MMPs in cultured human growth plate chondrocytes increases in a linear manner with increased duration and intensity of loading. We also showed for the first time that physiological loads have the same effect on growth plate chondrocytes over a long period of time as detrimental loads applied for a short period.

These findings confirm the involvement of MMPs in overuse injuries in children. We suggest that training programmes for immature athletes should be reconsidered in order to avoid detrimental stresses and over-expression of MMPs in the growth plate, and especially to avoid physiological loads becoming detrimental.

Cite this article: Bone Joint J 2013;95-B:568–73.

Procalcitonin and C-reactive protein levels in HIV-positive subjects with tuberculosis and pneumonia

Pulmonary tuberculosis (PTB) and pneumococcal community-acquired pneumonia (PCAP) are common causes of lower respiratory tract infections in HIV-seropositive patients and may have similar clinical and radiological features. This study aimed to assess the value of serum procalcitonin (PCT) and C-reactive protein (CRP) levels in HIV-seropositive patients with pneumonia, and to investigate their potential role in differentiating pneumococcal from mycobacterial infections. HIV-seropositive patients admitted with pneumonia were evaluated prospectively, 34 with PTB and 33 with PCAP. All 33 patients in the PCAP group and 20 of 34 patients in the PTB group had elevated PCT levels (>0.1 ng x mL(-1)). All patients in both groups had elevated CRP levels (>10 mg x L(-1)). The PTB group had significantly lower CD4 T-lymphocyte counts, lower CRP levels, lower white cell counts, and lower PCT levels than the PCAP group. Receiver operating characteristic analysis showed that optimal discrimination between PTB and PCAP could be performed at a cut-off point of 3 ng x mL(-1) for PCT (sensitivity 81.8%; specificity 82.35%) and 246 mg x L(-1) for CRP (sensitivity 78.8%; specificity 82.3%). In conclusion, HIV-seropositive patients with pneumococcal community-acquired pneumonia had significantly higher procalcitonin and C-reactive protein levels than those with pulmonary tuberculosis. A procalcitonin level >3 ng x mL(-1) and a C-reactive protein level >246 mg x L(-1) were both highly predictive of pneumococcal infection.

Levels of plasma homocysteine in persons with spinal cord injury

BACKGROUND

Premature coronary vascular disease is a leading cause of morbidity and mortality in persons with chronic spinal cord injury (SCI). Evidence indicates that an elevated plasma homocysteine level is an independent risk factor for vascular disease.

METHODS

Plasma homocysteine levels were collected in 845 subjects with SCI and compared to those in a reference population. Differences in plasma homocysteine were determined for sex, race/ethnicity, neurological deficit, and age, as well as for serum creatinine concentration.

RESULTS

Plasma homocysteine was significantly higher in men than in women. Men were more likely to have moderately or severely elevated plasma homocysteine levels. Stratifying by male sex, greater percentages of whites and African Americans had severely elevated plasma homocysteine levels (>20 micromol/L) compared with Latinos (12% and 14% versus 8%; P > .01). For the total group with SCI, plasma homocysteine levels were not significantly different by race/ethnicity or neurological deficit subgroup. For the total group (P < .05) and within each sex (men, P < .05; women, P < .01), the older age group with SCI (>50 years) had significantly higher mean plasma homocysteine levels than the younger age group. Age was positively related to plasma homocysteine levels in men (P < .05) and women (P < .01). Plasma homocysteine levels were higher among men for any given age than among women (P < .0001) by an average of 3.19 +/- 0.51 micromol/L. Regardless of age or sex, persons with SCI tended to have higher levels of plasma homocysteine than able-bodied persons matched for age and sex.

CONCLUSION

Because the risk of a vascular event increases with age, elevated levels of plasma homocysteine place older persons with SCI at further increased risk for a vaso-occlusive event. Of note, there was a stepwise increase in plasma homocysteine concentration for each quartile of higher serum creatinine concentration. Patients who have elevated levels of plasma homocysteine should receive a trial course of daily supplementation with oral folic acid and vitamin B12. If that is ineffective, they should receive vitamin B6 supplementation to lower their plasma homocysteine levels.

Increased intake of calcium reverses vitamin B12 malabsorption induced by metformin

OBJECTIVE

Of patients who are prescribed metformin, 10-30% have evidence of reduced vitamin B12 absorption. B12-intrinsic factor complex uptake by ileal cell surface receptors is known to be a process dependent on calcium availability Metformin affects calcium-dependent membrane action. The objective of this study was to determine the magnitude and mechanism of the reduction in serum vitamin B12 after metformin administration.

RESEARCH DESIGN AND METHODS

A comparative study design was employed using 2 groups (metformin and control). A total of 21 patients with type 2 diabetes received sulfonylurea therapy; 14 of these 21 patients were switched to metformin. Monthly serum total vitamin B12 measurements and holotranscobalamin (holoTCII) (B12-TCII) were performed. After 3 months of metformin therapy, oral calcium supplementation was administered.

RESULTS

Serial serum vitamin B12 determinations revealed a similar decline in vitamin B12 and holoTCII. Oral calcium supplementation reversed the metformin-induced serum holoTCII depression.

CONCLUSIONS

Patients receiving metformin have diminished B12 absorption and low serum total vitamin B12 and TCII-B12 levels because of a calcium-dependent ileal membrane antagonism, an effect reversed with supplemental calcium.

Nutrition as a component of alternative therapy

OBJECTIVES

To discuss common "alternative" nutritional strategies that may be used by patients as a primary or adjunctive means of cancer treatment.

DATA SOURCES

Government reports, textbook chapters, published articles, and research reports.

CONCLUSIONS

The use of diet and nutrition to prevent and treat disease is one of six fields of alternative medicine. A number of dietary regimens have been purported to be effective in the treatment of cancer. Most have been inadequately tested with regard to safety and efficacy.

IMPLICATIONS FOR NURSING PRACTICE

Oncology nurses need to be knowledgeable of the use of alternative methods so that they may provide accurate information to patients considering these approaches.

Nutritional anemias

Folate, vitamin B12, and iron are the subjects of active biochemical and molecular research so that further understanding of their metabolism in health and in a wide variety of Inherited and acquired diseases can be achieved. The roles of folate and vitamin B12 in cardiovascular and neurologic diseases and in neural tube defects (NTDs) will be further explored in the next decade. The effects of prophylactic therapy and of food fortification with the vitamins on these diseases remain to be established. Iron deficiency is a public health problem in all countries and prevention or treatment, particularly in children in developing countries, are major goals. The increased recent understanding of iron metabolism and absorption may clarify the etiology of diseases of iron metabolism and of dietary iron overload. Improved iron chelation therapy for transfusion-dependent patients with refractory anemias will continue to be actively researched over the next decades.

Atherogenesis and the homocysteine-folate-cobalamin triad: do we need standardized analyses?

BACKGROUND

Bioscientists, physicians and nutritionists are newly interested in the homocysteine-folate-cobalamin triad, in part because homocysteine may be important both in atherogenesis and thrombogenesis. Homocysteine imbalance may be an early marker for cobalamin disorders because cobalamin is a cofactor in remethylation of homocysteine to methionine.

METHODS

In 139 men and 32 women of similar mean age of 65 years, we measured markers which have been cited as risk for atherosclerosis: serum homocysteine, folate, total cobalamin, holotranscobalamin I and II, (TCI and TCII), total serum cholesterol (SCHOL), high density lipoprotein cholesterol (HDLC), triglycerides (STG) as well as red blood cell (RBC) folate, food records and body composition by whole body counting of potassium-forty (40K).

RESULTS

Statistical relationships among the data showed healthy women had lower mean serum homocysteine and their mean RBC folate and TCI and TCII were higher than men. Eighty-three subjects had TCII much lower than 60 pg/ml (subnormal), yet only 11 of these men and two women had total cobalamin < 200 pg/ml (abnormal). Fifty-two subjects with serum homocysteine greater than 17.5 nmol/ml had TCII less than 60 pg/ml, suggesting serum homocysteine may be a marker for early cobalamin negative balance. None of the subjects in the study had serum folate below abnormal values, i.e., less than 1.6 mg/ml. All subjects had RBC folate within normal range. Serum homocysteine showed inverse relationship with RBC folate and serum total cobalamin, TCI and TCII.

CONCLUSIONS

1) importance of using serum holotranscobalamin TCI and TCII as markers of cobalamin deficiency, 2) necessity to use documented quantitative components of dietary intake if strong comparisons are to be made among quantitative values of serum or plasma homocysteine, folate, cobalamin, and nutrients in food intake.

Serum ferritin iron, a new test, measures human body iron stores unconfounded by inflammation

Serum ferritin protein is an acute phase reactant. We hypothesized that serum ferritin protein generated in response to an inflammatory process would have much less iron (Fe) in it than would "normal" ferritin protein, and therefore measuring serum ferritin iron would assess human body iron status unconfounded by inflammation.

BASIC METHODS

We measured serum ferritin iron in 140 clinical samples obtained from the serum banks of Bronx VA Medical Center Hematology and Nutrition Laboratory (Bronx, NY), the CDC Nutritional Biochemistry serum sample bank (Atlanta, GA), and the sample bank from patients with thalassemia and iron overload treated at New York Hospital (New York, NY). Each was analyzed for three conventional criteria of iron status: serum iron, percentage of transferrin saturation and ferritin protein. In addition, tests for inflammation were also performed: C-reactive protein, WBC and transaminases. Seventy-seven patients' sera from 140 screened met each of three consistent criteria for stages of iron status. Serum ferritin was immobilized by immunoprecipitation with rabbit antihuman polyclonal antibody bound to agarose and separated from other iron-containing proteins, digested with 0.2 ml of 3N nitric acid and analyzed for iron content by atomic absorption spectroscopy.

RESULTS

Serum ferritin iron ranged in normal controls from 10 ng to 35 ng Fe/ml. The patients with iron deficiency (4/4) and those in negative iron balance (5/6) had values < or = 10 ng. Positive iron balance (8/9) and iron overload (22/22) values were > 35 ng/ml, in contrast to 11/19 with inflammation. Seventeen of twenty-two with overload had values > 100 ng/ml while only 1/19 with inflammation had such a value. Ferritin iron in ferritin protein was > 15% by weight in 14/22 with iron overload but in 0/19 with inflammation.

IMPLICATIONS OF THE WORK

Serum ferritin iron is a simple, direct measure of iron stores that we propose, in conjunction with measuring serum ferritin protein, as a minimally invasive screening procedure for accurately assessing the whole range of human body iron status, unconfounded by inflammation.

Vitamin C-driven free radical generation from iron

Circulating free iron is lethal. Humans have two circulating iron binding proteins to soak up free iron to prevent it from generating toxic quantities of free radicals. These proteins are transferrin, a high-affinity, low-capacity protein (2 atoms of iron per molecule of transferrin) for which there are receptors on the surface of every iron-requiring cell; and ferritin, a lower-affinity, high-capacity protein (maximum of 4500 atoms of iron per molecule of ferritin) for which there are receptors only on the surface of iron-storage cells such as RE (reticulo-endothelial) cells. Iron is trapped inside the ferritin protein shell as harmless Fe3. When there is a high serum level of reduced ascorbic acid, it drives through the pores of the ferritin protein shell to the inside surface, where it converts the Fe3 to catalytic Fe2, which then leaks out of the pores of the ferritin protein shell and generates billions of free radicals. In normal individuals, per milliliter of serum, there are approximately 300,000 molecules of transferrin per molecule of ferritin. Ferritin protein is an acute phase reactant that sharply rises in the presence of inflammation of any kind, whereas transferrin is a reverse acute phase reactant that falls in the presence of inflammation of any kind.

Most free-radical injury is iron-related: it is promoted by iron, hemin, holoferritin and vitamin C, and inhibited by desferoxamine and apoferritin

Iron is a double-edged sword. In moderate quantities and leashed to protein, it is an essential element in all cell metabolism and growth, but it is toxic when unleashed. Because of its ability to switch back and forth between ferrous and ferric oxidation states, iron is both a strong biological oxidant and reductant. The human diet contains a multitude of natural chemicals which are carcinogens and anticarcinogens, many of which act by generating oxygen radicals, which initiate degenerative processes related to cancer, heart disease and aging (the "oxygen radical hypothesis of aging"). Among these many dietary chemicals are many redox agents, including vitamin C and beta carotene. Free radical damage is produced primarily by the hydroxyl radical (.OH). Most of the .OH generated in vivo comes from iron-dependent reduction of H2O2. Supporting too much iron as a free radical-generating culprit in the risk of cancer, NHANES I data indicated that high body iron stores, manifested by increased transferrin saturation, are associated with an increased cancer risk. Other data shows an increased heart attack risk.

Staging vitamin B-12 (cobalamin) status in vegetarians

When one stops eating vitamin B-12 (cobalamins), one passes through four stages of negative cobalamin balance: serum depletion [low holotranscobalamin II, ie, low vitamin B-12 on transcobalamin II (TCII)], cell depletion (decreasing holohaptocorrin and low red cell vitamin B-12 concentrations), biochemical deficiency (slowed DNA synthesis, elevated serum homocysteine and methylmalonate concentrations), and, finally, clinical deficiency (anemia). Serum vitamin B-12 is on two proteins: the circulating vitamin B-12 delivery protein, TCII, and the circulating vitamin B-12 storage protein, haptocorrin. Because TCII is depleted of vitamin B-12 within days after absorption stops, the best screening test for early negative vitamin B-12 balance is a measurement of vitamin B-12 on TCII (holoTCII). HoloTCII falls below the bottom of its normal range long before total serum vitamin B-12 (which is mainly vitamin B-12 on haptocorrin) falls below the bottom of its normal range.

Everyone should be tested for iron disorders

Routinely measuring iron status is necessary because about 6% of Americans have negative iron balance, about 10% have a gene for positive balance, and about 1% have iron overload. Deviations from normal iron status are as follows. (a) Stage I and II negative iron balance, ie, iron depletion: In these stages iron stores are low and there is no dysfunction. In stage I negative iron balance, reduced iron absorption produces moderately depleted iron stores. Stage II negative iron balance is characterized by severely depleted iron stores. More than half of all cases of negative iron balance fall into these two stages. When persons in these stages are treated with iron, they never develop dysfunction or disease. (b) Stage III and IV negative iron balance, ie, iron deficiency: Iron deficiency is characterized by inadequate body iron for normal function, producing dysfunction and disease. In stage III negative iron balance, dysfunction is not accompanied by anemia; anemia develops in stage IV negative iron balance. (c) Stage I and II positive iron balance: Stage I positive balance usually lasts for several years with no dysfunction. Supplements of iron and/or vitamin C promote progression to dysfunction or disease. Iron removal prevents progression to disease. Iron overload disease develops in stage II positive iron balance after years of iron overload has caused progressive damage to tissues and organs. Again, iron removal stops disease progression. There are a variety of indicators of iron status. Serum ferritin is in equilibrium with body iron stores.(ABSTRACT TRUNCATED AT 250 WORDS)

Iron disorders can mimic anything, so always test for them

Routinely measuring iron status is necessary because not only are about 6% of Americans in significant negative iron balance, but about 1% have iron overload. Serum ferritin is in equilibrium with body iron stores, and is the only blood test that measures them. Barring inflammation, each one ng (0.0179 pmol) ferritin/ml of serum indicates approximately 10 mg (0.179 mmol) of body iron stores. Very early Stage I positive balance is best recognized by measuring saturation of iron binding capacity. Conversely, serum ferritin best recognizes early (Stage I and II) negative balance. Deviations from normal are: 1. Both stages of iron depletion (i.e. low stores, no dysfunction). Negative iron balance Stage I is reduced iron absorption producing moderately depleted iron stores. Stage II is severely depleted stores, without dysfunction. These stages include over half of all cases of negative iron balance. Treated with iron, they never progress to dysfunction, i.e. to disease. 2. Both stages of iron deficiency. Deficiency is inadequate iron for normal function, i.e. dysfunction, disease. Negative balance Stage III is dysfunction without anemia; Stage IV is with anemia. 3. Positive iron balance: Stage I is a multi-year period without dysfunction. Supplements of iron and/or vitamin C promote progression to dysfunction (disease). Iron removal prevents progression. Stage II is iron overload disease, encompassing years of insidiously progressive damage to tissues and organs from iron overload. Iron removal arrests progression.

Low holotranscobalamin II is the earliest serum marker for subnormal vitamin B12 (cobalamin) absorption in patients with AIDS

In AIDS, as previously found in pernicious anemia (PA), the earliest serum marker of subnormal vitamin B12 (cobalamin) absorption, and therefore of negative B12 balance, is low serum holotranscobalamin II (holo-TC II; B12-TC II) despite normal total serum B12 level, normal serum homocysteine, and normal classic (oral free radio-B12) Schilling test. This may be accompanied by subtle and insidious damage to hematopoietic, immunologic, neuropsychiatric, nutritional and alimentary systems, confirmed by correction on therapeutic trial with B12 therapy. Our studies suggest such selective B12 deficiency occurs in about half of the HIV-1 infected, in part due to frequent depression of B12 absorption by HIV-1 attack on the gastric mucosa and/or opportunistic infection attack on the small bowel, and in part due to a telescoping of the continuum of the stages of negative B12 balance in relation to damage to B12 delivery by the infective and/or systemic disease process. In AIDS, when total serum B12 is normal despite tissue depletion of B12, if the classic Schilling test does not reveal subnormal food B12 absorption, the food Schilling test does. We hypothesize that DNA-synthesizing cells of the hematopoietic, immunologic, neurologic and other systems which have surface receptors solely for holo-TC II, and which have low B12 stores, rapidly become dysfunctional due to B12 deficiency when holo-TC II is low, while cells (such as liver cells) which also have surface receptors for holohaptocorrin (B12-haptocorrin) remain B12-replete. We believe this to be another example of the concept of selective nutrient deficiency in one cell line but not another.

Synergy of inhibition of DNA synthesis in human bone marrow by azidothymidine plus deficiency of folate and/or vitamin B12?

The effect of azidothymidine (Zidovudine, AZT) on pyrimidine (thymidine, deoxyuridine, and thymidine triphosphate) incorporation into DNA in folate- and/or vitamin B12-deficient and normal human bone marrow cells was studied to investigate whether such vitamin deficiency affects susceptibility to AZT-induced hematologic toxicity. Bone marrow cells from 12 patients were studied: 5 had folate and/or vitamin B12 deficiency; 7 controls included 5 with anemia related to chronic disease and 2 with iron deficiency. At 0.2 microM AZT (3 hr, 37 degrees C), the approximate pharmacologic serum trough level, pyrimidine incorporation into DNA was suppressed by 12 to 19% in folate- and/or vitamin B12-deficient cells and by 16 to 23% in normal cells. At 2.0 microM AZT (3 hr, 37 degrees C), the approximate pharmacologic serum peak level, this was suppressed by 15 to 40% in folate- and/or vitamin B12-deficient cells and by 32 to 47% in controls. Deoxyuridine incorporation into DNA was inhibited significantly greater than thymidine at 2.0 microM AZT (3 hr, 37 degrees C) in both groups. Inhibition of deoxyuridine incorporation was not reversed with methyltetrahydrofolate or vitamin B12. There tended to be less striking suppression by AZT of deoxyuridine incorporation into DNA in bone marrow cells from vitamin B12-deficient patients, which was made more striking by adding vitamin B12. This suggests that some of what passes for "AZT damage" to bone marrow cells may in fact be coincident deficiency of vitamin B12. AZT inhibition of DNA synthesis in 3 hr bone marrow cultures is relatively consistent in a variety of hematologic disorders. As approximately two-thirds of AIDS patients appear to be in negative balance with respect to folate and/or vitamin B12, the fact that AZT-induced inhibition of pyrimidine incorporation into DNA is occurring in cells which may be megaloblastic, i.e., in a state of impaired DNA synthesis, suggests that these cells may be more susceptible to AZT toxicity. The data also support the notion that AZT inhibition results predominantly from termination of DNA chain elongation. Whether folate or vitamin B12 supplementation may partially overcome apparent "AZT inhibition" of DNA synthesis (hematologic toxicity) and whether the benefit of such therapy exceeds the risk will require further study.

Effect of ethanol-generated free radicals on gastric intrinsic factor and glutathione

The oxidation of acetaldehyde (generated from the metabolism of ethanol) by oxidases such as xanthine oxidase generates free radicals which can mobilize ferritin iron, alter hepatic glutathione and produce lipid peroxidation. The stomach, a site of ethanol metabolism and rich in xanthine oxidase, was studied with respect to the effects of ethanol on intrinsic factor (IF) binding of vitamin B-12 as well as gastric glutathione (GSH). Incubations of gastric homogenates with acetaldehyde-xanthine oxidase inhibited the B-12 binding ability by IF. A large acute dose of ethanol in vivo (5 g/kg, conc. greater than 40% w/v) decreased gastric IF binding of B-12 and depressed gastric GSH; these effects were markedly attenuated by the feeding of sodium tungstate which inhibited xanthine oxidase. Changes in B-12 binding paralleled changes in gastric GSH. Scatchard plots of IF binding of B-12 for homogenates suggested decreased number of binding sites rather than altered affinity. In conclusion, the gastric metabolism of ethanol generates free radicals which alter IF binding of B-12, depress gastric GSH and may play a role in alcohol-induced gastric injury.

In vitro DNA synthesis by megaloblastic bone marrow: effect of folates and cobalamins on thymidine incorporation and de novo thymidylate synthesis

The de novo pathway of thymidylate synthesis (i.e., methylation of dUMP to dTMP) is directly folate dependent and indirectly vitamin B12 (cobalamins) dependent. In deficiency of these vitamins, this pathway is impaired, and exogenous deoxyuridine (dU) fails to suppress adequately in vitro incorporation of [3H]thymidine (3H-TdR) into DNA via the salvage pathway (i.e., abnormal dU suppression). This abnormality is corrected by the addition of folate compounds (analogues) and/or vitamin B12 depending on the nature of the underlying deficiency. We studied the effects of addition of PteGlu, 5-methyl THF (5-CH3-FH4), 5-formyl-THF (5-CHO-FH4), and hydroxy-cobalamin (OH-cbl) on 3H-TdR incorporation into DNA and thymidine kinase activity (salvage pathway), and on [3H]deoxyuridine (3H-dU) incorporation and dU suppression values (de novo pathway) in cultures of normal and megaloblastic bone marrows. The results showed that 3H-TdR incorporation into DNA and the salvage enzyme, thymidine kinase, activity were greater and 3H-dU incorporation into DNA less in megaloblastic cells as compared with normal cells. The addition of folates significantly reduced 3H-TdR incorporation and thymidine kinase activity and enhanced 3H-dU incorporation in folate and vitamin B12-deficient cells except that 5-CH3-FH4 had no effect on vitamin B12-deficient cells. None of these additives had any significant effect on normal cells. This study also showed that the addition of the deficient vitamin(s) to the "control tubes" in the dU suppression test is inappropriate, as these vitamins may at least partially correct the defect in cellular DNA synthesis caused by the deficiencies of these vitamins and may mask these deficiencies in the results of the in vitro correction of the dU suppression abnormalities in mild cases of megaloblastic anemia.