Factors associated with diabetes in tuberculosis patients in Harris County, Texas 1995--2004

Objective. To determine the prevalence and factors associated with diabetes in tuberculosis patients in Harris County, Texas. ^ Background. Tuberculosis and diabetes mellitus are two diseases of immense public health significance. Various epidemiologic studies have established an association between the two conditions. While many studies have identified factors associated with the conditions individually, few have looked at factors associated with their co-occurrence particularly in the United States. Furthermore, most of those studies are hospital-based and may not be representative of the population. The aim of this study was to determine the prevalence and distribution of diabetes among tuberculosis patients in Harris County, Texas and to identify the factors associated with diabetes in tuberculosis. ^ Methods. A population-based case control study was performed using secondary data from the Houston Tuberculosis Initiative (HTI) collected from October 1995 to September 2004. Socio-demographic characteristics and clinical variables were compared between tuberculosis patients with diabetes and non-diabetic tuberculosis patients. Logistic regression analysis was performed to identify associations. Survival at 180 days post tuberculosis diagnosis was assessed by Cox regression. ^ Results. The prevalence of diabetes among the tuberculosis (TB) population was 14.4%. The diabetics (cases) with a mean age 53 �� 13.3 years were older than the non-diabetics (controls) with a mean age of 39 �� 18.5 years (p<0.001). Socio-demographic variables that were independently associated with the risk of diabetes were age (OR 1.04, p<0.001) and Hispanic ethnicity (OR 2.04, p<0.001). Diabetes was associated with an increased risk of pulmonary tuberculosis disease (OR 1.33, p<0.028). Among individuals with pulmonary TB, diabetes was associated with positive sputum acid-fast bacilli (AFB) smear (OR 1.47, p<0.005) and culture (OR 1.83, p<0.018). Diabetics were more likely to have cavitary lung disease than non-diabetics (OR 1.50, p<0.002). After adjustment for age and HIV status, the risk of dying within 180 days of TB diagnosis was significantly increased in the diabetics (HR 1.51, p<0.002). ^ Conclusion. Diabetes mellitus was more prevalent in our tuberculosis patients than in the general population. The tuberculous diabetic may be more infectious and has a higher risk of death. It is therefore imperative to screen diabetics for TB and TB patients for diabetes. ^

Role of T cell response during vaccine immunity to tuberculosis

Tuberculosis remains one of the leading causes of death in man due to a single infectious agent. An estimated one-third of the world's population is infected with the causative agent, Mycobacterium tuberculosis (Mtb), despite the availability of the widely used vaccine, BCG. BCG has significantly varying protection rates with the lowest level of protection seen with the most common form of TB, adult pulmonary TB. Thus, numerous studies are being conducted to develop a more efficient vaccine. The ideal candidate vaccine would possess the ability to induce a solid and strong Th1 response, as this is the subset of T cells primarily involved in clearance of the infection. A novel vaccine should also induce such a response that may be recalled and expanded upon subsequent infection. Our group has introduced a mutant of a virulent strain of Mtb which lacks a component of the immunogenic antigen 85 complex (Ag85). Our vaccine, ��fbpA, does not secrete the fibronectin binding protein Ag85A, and this has shown to lead to its attenuation in both murine macrophages and mice. Previous studies have also proven that ��fbpA is more protective in mice than BCG against virulent aerosol challenge with Mtb. This study addresses the mechanisms of protection observed with ��fbpA by phenotyping responding T cells. We first evaluated the ability of dendritic cells to present the mycobacteria to na��ve T cells, an in vitro mock of primary immunization. We also measured the response of primed T cells to macrophage-presented mycobacteria to interpret the possible response of a vaccinated host to a boost. We concluded that ��fbpA can elicit a stronger Th1 response compared to BCG in vitro, and further observed that this enhanced response is at least partly due to the presence of proteins encoded by a region of the genome absent in all strains of BCG. Finally, we observed this heightened Th1 response in the mouse model after primary vaccination and a virulent aerosol challenge. The cytolytic T cell response was also measured after virulent challenge and was found to be superior in the ��fbpA-treated group when compared to the BCG group. ^

Association of pellicle growth morphological characteristics and clinical presentation of Mycobacterium tuberculosis isolates

Trehalose dimycolate (TDM) is a mycobacterial glycolipid that is released from the surface of virulent M. tuberculosis. We evaluated the rate of growth, colony characteristics and production of TDM by Mycobacterium tuberculosis strains isolated from different clinical sites. Since detergent removes TDM from organisms, we analyzed growth rate and colony morphology of 79 primary clinical isolates grown as pellicles on the surface of detergent free Middlebrook 7H9 media. The genotype of each had been previously characterized. TDM production was measured by thin layer chromatography on 32 of these isolates. We found that strains isolated from pulmonary sites produced large amounts of TDM, grew rapidly as thin spreading pellicles, showed early cording (<1 week) and climbed the sides of the dish. In contrast, the extrapulmonary isolates (lymph node and bone marrow) produced less TDM (p<0.01), grew as discrete patches with little tendency to spread or climb the walls (p<0.02). The Beijing pulmonary (BP) isolates produced more TDM than non Beijing pulmonary isolates. The largest differences were observed in Beijing strains. The Beijing pulmonary isolates produced more TDM and grew faster than the Beijing extrapulmonary isolates (p<0.01). This was true even when the pulmonary and extrapulmonary isolates were derived from the same clade. These growth characteristics were consistently observed only on the first passage after primary isolation. This suggests that the differences in growth rate and TDM production observed reflect differences in gene expression patterns of pulmonary and extrapulmonary infections, that Mycobacterium tuberculosis in the lung grows more rapidly and produces more TDM than it does in extrapulmonary sites. This provides new opportunities to investigate gene expression of Mycobacterium tuberculosis in human.^

11beta-hydroxysteroid dehydrogenases as regulators of pulmonary corticosterone during the granulomatous response to trehalose 6,6'-dimycolate

Protection against Mycobacterium tuberculosis requires development and maintenance of granulomatous lesions, a feature considered to be the pathological hallmark of Tuberculosis (TB) disease. Upon encountering Mtb or mycobacterial antigens, specifically trehalose 6,6'-dimycolate (TDM), a strong local pro-inflammatory response is initiated. Systemic production of anti-inflammatory glucocorticoids (GCs) is also induced. Emergence of these antagonists at the inflammatory foci is counterproductive to development of the granulomatous structure and detrimental to host protection against TB. Therefore, it was hypothesized that local enzymatic regulation of GCs occurs locally at the site of granulomatous inflammation. The experiments described here strongly suggest that 11��-hydroxysteroid dehydrogenases (11��HSDs) shuttle GCs between active and inert forms during the acute granulomatous response, supporting the net reduction of corticosterone. The patterns of GC and 11��HSD regulation were specific to the lung (the site of inflammation) and were not observed in other tissues. Furthermore, 11��HSD2, which decreases corticosterone concentrations, was not expressed in models of dysregulated granulomatous inflammation. These findings suggest that cellular exposure to local active GC concentrations is restricted via 11��HSDs as a mechanism to initiate and maintain granuloma formation. The information derived from the experiments outlined in this dissertation provides a better understanding of the events required for establishment and maintenance of the protective granulomatous response. As a practical consequence, exploiting 11��HSD2 modulation of GCs at the site of Mtb infection may lead to improvement of Tuberculosis treatment strategies.^

Predictors of diagnostic delay among tuberculosis patients in a U.S.-Mexico border community

Delays in diagnosis of pulmonary tuberculosis have detrimental effects on the health of the ailing patient as well as the people around him or her. These effects are magnified in highly-travelled parts of the world. Identifying factors predictive of diagnostic delay is challenging, as these vary widely by culture and geography. Predictors of delay for tuberculosis patients living in the Northeastern Mexican city of Matamoros, a binationally-transited area, have yet to be described. Using secondary analysis of a retrospective survey, this study sought to identify predictors of diagnostic delay in a sample of culture-positive tuberculosis patients in Matamoros. Sociodemographic, behavioral, and health-related factors were measured and compared. Using bivariate and step-wise regression analyses at an alpha level of 0.05, the author found the following to be statically significant predictors for this sample (R 2=0.171): prior treatment of diabetes, recurrence of tuberculosis, and having ever used cocaine. A question assessing knowledge of immunocompromised subgroups was also identified as a predictor, although its implications are unclear. Notably, the instrument did not distinguish between patient and health system delay. In summary, more research should be conducted in the Matamoros area in order to fully understand the dynamics of delayed diagnosis and its application to public health practice.^

Epidemiology of tuberculosis and nontuberculous mycobacterial infections in Houston children

Background. Nontuberculous mycobacteria (NTM) are environmentally ubiquitous organisms whose epidemiology is poorly understood. Species differ with respect to disease presentation, prognosis, and antimicrobial susceptibility. We reviewed one Texas pediatric hospital's experience with NTM and tuberculosis (TB) disease.^ Methods. This was a retrospective case series of children with culture-confirmed mycobacterial infections seen at a children's hospital from 2003-2008.^ Results. One hundred sixty-two isolates were identified from 150 children; 132 (81.5%) had NTM species isolated, and 30 (18.5%) had M. tuberculosis isolated; 2 children had both NTM and M. tuberculosis isolated. The most common species were Mycobacterium avium complex (MAC) (29%), M. tuberculosis (18.5%), M. abscessus (13%), M. fortuitum (11.7%), and M. chelonae-abscessus (9.9%). TB was the most common organism isolated from respiratory specimens. MAC and M. simiae were significantly more likely to be associated with lymphadenopathy than other NTM species (p < 0.001). Mycobacterium fortuitum was significantly more likely to be associated with soft tissue infections than other NTM species (p < 0.001). Seventy-five children met criteria for NTM disease (30 lymphadenopathy, 17 pulmonary, 17 soft tissue infections, 11 bacteremia). Children with NTM lymphadenopathy were more likely to be Hispanic (OR 24, CI 2.8-1063), younger (3.3 years vs. 10.6 years, p < 0.001), and previously healthy (OR 0.004, CI 0-0.06) than children with NTM pulmonary disease. Children with NTM disease were less likely to be previously healthy (OR 0.30, 95% CI 0.09-0.88) and foreign-born (OR 0.09, CI 0.03-0.29) than children with TB.^ Conclusions. Children with NTM lymphadenopathy were younger and more likely to be healthy than children with NTM pulmonary disease. Tuberculosis comprised a large proportion of mycobacterial disease in this series. Children with NTM pulmonary disease were less likely to be previously healthy and born abroad when compared to children with TB. There was wide variation in antimicrobial susceptibility patterns among NTM species. This, together with the large percentage of disease caused by TB, emphasizes the importance of securing a specific microbiologic diagnosis in children with pulmonary or lymph node disease caused by mycobacteria.^

Tuberculosis in persons with concomittant diseases in Houston, Texas, 2004 to 2008

The purpose of this study is to evaluate characteristics of tuberculosis (TB) in diabetics and persons infected with HIV from 2004 to 2008 in Houston, Texas. This analysis will allow us to identify demographic trends. Previous studies have shown that in general, there is a higher risk for HIV+ persons to develop active TB, or to re-activate latent TB, as they progress in their HIV infection. In addition, similar to HIV, diabetes mellitus (DM) weakens the immune system so that persons with DM have also been shown to have a tendency to develop TB. This analysis will examine three areas of research: (a) to explore existing TB trends in Houston/Harris County and associated characteristics, (b) to ascertain the common risk factors of DM and HIV that are correlate with TB infections, and (c) from the analysis of the data, to determine if subsequent TB prevention programs are needed for specific subgroups.^

Tuberculosis in HIV-infected individuals in Ho Chi Minh City, Vietnam

Early and accurate detection of TB disease in HIV-infected individuals is a critical step for a successful TB program. In Vietnam, the diagnosis of TB disease, which is based predominantly on the clinical examination, chest radiography (CXR) and acid fast bacilli (AFB) sputum smear, has shown to be of low sensitivity in immunocompromised patients. The sputum culture is not routinely performed for patients with AFB negative smears, even in HIV-infected individuals.^ In that background, we conducted this cross-sectional study to estimate the prevalence of sputum culture-confirmed pulmonary tuberculosis (PTB), smear-negative PTB, and multidrug-resistant TB (MDR-TB) in the HIV-infected population in Ho Chi Minh City (HCMC), the largest city in Vietnam where both TB and HIV are highly prevalent. We also evaluated the diagnostic performance of various algorithms based on routine available tools in Vietnam such as symptoms screening, CXR, and AFB smear. Nearly 400 subjects were consecutively recruited from HIV-infected patients seeking care at the An Hoa Clinic in District 6 of Ho Chi Minh City from August 2009 through June 2010. Participants��� demographic data, clinical status, CXR, and laboratory results were collected. A multiple logistic regression model was developed to assess the association of covariates and PTB. ^ The prevalence of smear-positive TB, smear-negative TB, resistant TB, and MDR-TB were 7%, 2%, 5%, 2.5%, and 0.3%, respectively. Adjusted odds ratios for low CD4+ cell count, positive sputum smear, and CXR to positive sputum culture were 3.17, 32.04, and 4.28, respectively. Clinical findings alone had poor sensitivity, but the combination of CD4+ cell count, sputum smear, and CXR proved to perform a more accurate diagnosis.^ This study results support the routine use of sputum culture to improve the detection of TB disease in HIV-infected individuals in Vietnam. When routine sputum culture is not available, an algorithm combining CD4+ cell count, sputum smear, and CXR is recommended for diagnosing PTB. Future studies on more affordable, rapid, and accurate tests for TB infection would also be necessary to timely provide specific treatments for patients in need, reduce mortality, and minimize TB transmission to the general population.^

Endemic tuberculosis, the homeless, and public transportation: A merging of geographical information systems surveillance and the Houston Tuberculosis Initiative Surveillance project

To reach the goals established by the Institute of Medicine (IOM) and the Centers for Disease Control's (CDC) STOP TB USA, measures must be taken to curtail a future peak in Tuberculosis (TB) incidence and speed the currently stagnant rate of TB elimination. Both efforts will require, at minimum, the consideration and understanding of the third dimension of TB transmission: the location-based spread of an airborne pathogen among persons known and unknown to each other. This consideration will require an elucidation of the areas within the U.S. that have endemic TB. The Houston Tuberculosis Initiative (HTI) was a population-based active surveillance of confirmed Houston/Harris County TB cases from 1995���2004. Strengths in this dataset include the molecular characterization of laboratory confirmed cases, the collection of geographic locations (including home addresses) frequented by cases, and the HTI time period that parallels a decline in TB incidence in the United States (U.S.). The HTI dataset was used in this secondary data analysis to implement a GIS analysis of TB cases, the locations frequented by cases, and their association with risk factors associated with TB transmission. ^ This study reports, for the first time, the incidence of TB among the homeless in Houston, Texas. The homeless are an at-risk population for TB disease, yet they are also a population whose TB incidence has been unknown and unreported due to their non-enumeration. The first section of this dissertation identifies local areas in Houston with endemic TB disease. Many Houston TB cases who reported living in these endemic areas also share the TB risk factor of current or recent homelessness. Merging the 2004���2005 Houston enumeration of the homeless with historical HTI surveillance data of TB cases in Houston enabled this first-time report of TB risk among the homeless in Houston. The homeless were more likely to be US-born, belong to a genotypic cluster, and belong to a cluster of a larger size. The calculated average incidence among homeless persons was 411/100,000, compared to 9.5/100,000 among housed. These alarming rates are not driven by a co-infection but by social determinants. The unsheltered persons were hospitalized more days and required more follow-up time by staff than those who reported a steady housing situation. The homeless are a specific example of the increased targeting of prevention dollars that could occur if TB rates were reported for specific areas with known health disparities rather than as a generalized rate normalized over a diverse population. ^ It has been estimated that 27% of Houstonians use public transportation. The city layout allows bus routes to run like veins connecting even the most diverse of populations within the metropolitan area. Secondary data analysis of frequent bus use (defined as riding a route weekly) among TB cases was assessed for its relationship with known TB risk factors. The spatial distribution of genotypic clusters associated with bus use was assessed, along with the reported routes and epidemiologic-links among cases belonging to the identified clusters. ^ TB cases who reported frequent bus use were more likely to have demographic and social risk factors associated with poverty, immune suppression and health disparities. An equal proportion of bus riders and non-bus riders were cultured for Mycobacterium tuberculosis, yet 75% of bus riders were genotypically clustered, indicating recent transmission, compared to 56% of non-bus riders (OR=2.4, 95%CI(2.0, 2.8), p<0.001). Bus riders had a mean cluster size of 50.14 vs. 28.9 (p<0.001). Second order spatial analysis of clustered fingerprint 2 (n=122), a Beijing family cluster, revealed geographic clustering among cases based on their report of bus use. Univariate and multivariate analysis of routes reported by cases belonging to these clusters found that 10 of the 14 clusters were associated with use. Individual Metro routes, including one route servicing the local hospitals, were found to be risk factors for belonging to a cluster shown to be endemic in Houston. The routes themselves geographically connect the census tracts previously identified as having endemic TB. 78% (15/23) of Houston Metro routes investigated had one or more print groups reporting frequent use for every HTI study year. We present data on three specific but clonally related print groups and show that bus-use is clustered in time by route and is the only known link between cases in one of the three prints: print 22. (Abstract shortened by UMI.)^

Tuberculosis in Texas correctional facilities between 2005--2009

It has been well documented that inmates incarcerated in prisons and correctional facilities exhibit higher incidence and prevalence of mycobacterium tuberculosis (TB) disease than the general population. This has public health implications because correctional systems may serve as reservoirs for TB disease that can lead to TB outbreaks in the facilities or can be spread to the general public once inmates are released. Although Texas has one of the largest correctional systems in both the US and the world, little is known about TB prevalence and incidence among Texas inmates. The purpose of this study was to elucidate the relationship between TB incidence and incarceration in Texas correctional facilities and investigate differences in various demographic factors. ^ The study used the national TB database from the US Centers for Disease Control and Prevention (CDC) to calculate and compare the overall incidences of TB disease among correctional facility inmates and similar non-inmates in Texas during 2005���2009. Data were also stratified by age, gender, race/ethnicity, birth status, and HIV status and compared between inmates and non-inmates using chi-squared analysis and relative risks with 95% confidence intervals to assess any significant differences. ^ Results suggest that the overall TB incidence among Texas correctional facility inmates per year (88.6 per 100,000) was significantly higher than that of Texas non-inmates (6.3 per 100,000); a 14 fold difference. Relative risk analyses by gender, race/ethnicity, and those with HIV infection found that the TB incidences for all these demographics were significantly and consistently higher in inmates compared to non-inmates. In particular, Hispanic inmates were more likely to develop TB than their non-inmate counterparts by a relative risk of 23.9 (95% CI 19.4���29.4). Likewise, both male and female inmates were more likely to develop TB than non-inmates (RR = 10.2, 95% CI 8.5���12.2; RR = 20.8, 95% CI 12.2���25.3, respectively), although female inmates unconventionally exhibited a higher TB incidence and relative risk than males inmates, which has not been shown. Among those with HIV infections, correctional facility inmates were 2.6 times were likely to develop TB disease than non-inmates (95% CI 1.5���4.4). ^ Inmates in Texas correctional facilities have a higher incidence of TB than non-inmates. Part of this higher risk may be because a large proportion of inmates come from populations already at high risks for TB, such as foreign born immigrants, those infected with HIV, and low SES groups such as many racial/ethnic minorities. Thus, these results may be used as a basis for more controlled and detailed research in the area, and to further characterize incarceration as a risk factor for TB incidence. They may also bring much needed attention about this health disparity to public health officials, legislators, and health administrators to expand and improve TB control in Texas correctional facilities, particularly among inmates released to the community, and reduce the risk of TB transmission to the general population.^

Correlation of tuberculosis and human immunodeficiency virus in Harris County, Texas from 2009 through 2010 using Geographic Information Systems

A population based ecological study was conducted to identify areas with a high number of TB and HIV new diagnoses in Harris County, Texas from 2009 through 2010 by applying Geographic Information Systems to determine whether distinguished spatial patterns exist at the census tract level through the use of exploratory mapping. As of 2010, Texas has the fourth highest occurrence of new diagnoses of HIV/AIDS and TB.[31] The Texas Department of State Health Services (DSHS) has identified HIV infected persons as a high risk population for TB in Harris County.[29] In order to explore this relationship further, GIS was utilized to identify spatial trends. ^ The specific aims were to map TB and HIV new diagnoses rates and spatially identify hotspots and high value clusters at the census tract level. The potential association between HIV and TB was analyzed using spatial autocorrelation and linear regression analysis. The spatial statistics used were ArcGIS 9.3 Hotspot Analysis and Cluster and Outlier Analysis. Spatial autocorrelation was determined through Global Moran's I and linear regression analysis. ^ Hotspots and clusters of TB and HIV are located within the same spatial areas of Harris County. The areas with high value clusters and hotspots for each infection are located within the central downtown area of the city of Houston. There is an additional hotspot area of TB located directly north of I-10 and a hotspot area of HIV northeast of Interstate 610. ^ The Moran's I Index of 0.17 (Z score = 3.6 standard deviations, p-value = 0.01) suggests that TB is statistically clustered with a less than 1% chance that this pattern is due to random chance. However, there were a high number of features with no neighbors which may invalidate the statistical properties of the test. Linear regression analysis indicated that HIV new diagnoses rates (��=���0.006, SE=0.147, p=0.970) and census tracts (��=0.000, SE=0.000, p=0.866) were not significant predictors of TB new diagnoses rates. ^ Mapping products indicate that census tracts with overlapping hotspots and high value clusters of TB and HIV should be a targeted focus for prevention efforts, most particularly within central Harris County. While the statistical association was not confirmed, evidence suggests that there is a relationship between HIV and TB within this two year period.^

Biochemical mechanisms involved in pulmonary hypo-alveolarization induced by peroxides contaminating parenteral nutrition in newborn guinea pig

La dysplasie broncho-pulmonaire (DBP), caract��ris��e par un d��faut de l���alv��olarisation, est une complication pathologique associ��e �� un stress oxydant chez le nouveau-n�� pr��matur��. La DBP est pr��sente chez pr��s de 50 % des nouveau-n��s de moins de 29 semaines de gestation. La nutrition parent��rale (NP) que ces nouveau-n��s re��oivent pour cause d���immaturit�� gastro-intestinale est une source importante de stress oxydant. En effet, leur NP est contamin��e par des peroxydes, dont l���ascorbylperoxyde qui est une forme peroxyd��e du d��shydroascorbate. La g��n��ration des peroxydes est catalys��e par la lumi��re ambiante. La photoprotection de la NP, quoique difficile d���application en clinique, est associ��e �� une diminution de l���incidence de la DBP chez les enfants pr��matur��s. Chez l���animal nouveau-n��, la photoprotection de la NP est associ��e �� un meilleur d��veloppement alv��olaire. Ainsi, nous ��mettons l���hypoth��se que l���ascorbylperoxide infus�� avec la NP cause la perte d���alv��oles suite �� une apoptose exag��r��e induite par l���oxydation du potentiel redox du glutathion. Cette oxydation du potentiel redox serait occasionn��e par l���inhibition de la transformation h��patique de la m��thionine en cyst��ine, menant �� une diminution de la synth��se de glutathion au foie et dans les tissus tels que les poumons. La confirmation de cette hypoth��se sugg��rera qu���un ajout de glutathion dans la NP permettra une meilleure d��toxification de l���ascorbylperoxide par l���action de la glutathion peroxydase, et pr��viendra l���oxydation du potentiel redox et ainsi, la perte d'alv��oles par apoptose. Objectifs : Le but de mon projet de recherche est de comprendre les m��canismes biochimiques liant la NP et le d��veloppement de la DBP chez le nouveau-n�� pr��matur�� et de proposer une alternative nutritionnelle pr��venant le d��veloppement de cette complication fr��quemment observ��e dans cette population. Les objectifs sp��cifiques sont : 1) d�����valuer l���impact, au poumon, de l���infusion de l���ascorbylperoxyde sur l���axe m��tabolique potentiel redox du glutathion - apoptose - le d��veloppement alv��olaire; 2) d�����tudier l���impact de l���ascorbylperoxyde et du potentiel redox sur l���activit�� h��patique de la m��thionine ad��nosyltransf��rase (MAT), premi��re enzyme de la cascade m��tabolique transformant la m��thionine en cyst��ine; et 3) de tenter de pr��venir l���impact n��gatif de la NP ou de l���infusion d���ascorbylperoxyde sur le poumon en am��liorant le statut en glutathion. M��thodes: Par un cath��ter fix�� dans la jugulaire, des cochons d���Inde de trois jours de vie (n = 8 par groupe) ont re��u en continu durant 4 jours une NP ou une solution de base (dextrose + NaCl) enrichie des diff��rentes mol��cules �� l���essai. Le premier objectif a ��t�� atteint en enrichissant la solution de base en ascorbylperoxyde �� 0, 20, 60 et 180 ��M. Ces solutions contenaient ou non 350 ��M H2O2 pour se rapprocher des conditions cliniques. Le second objectif a ��t�� atteint en investiguant les m��canismes d���inhibition de la MAT dans des animaux infus��s ou non avec des solutions contenant la solution de base, des peroxydes, du glutathion et la NP (dextrose + acides amin��s + multivitamines + lipides). Le troisi��me objectif a ��t�� atteint en ajoutant ou non �� une solution d���ascorbylperoxide ou �� la NP 10 ��M de glutathion (GSSG), afin d���obtenir une concentration plasmatique normale de glutathion. Apr��s 4 jours, les poumons ��taient pr��lev��s et trait��s pour la d��termination de GSH et GSSG par ��lectrophor��se capillaire, le potentiel redox ��tait calcul�� selon l'��quation de Nernst et le niveau de caspase-3 actif (marqueur d���apoptose) par Western blot et l���index d���alv��olarisation quantifi�� par le nombre d���interceptes entre des structures histologiques et une droite calibr��e. Les donn��es ��taient compar��es par ANOVA, les effets ��taient consid��r��s comme significatifs si le p ��tait inf��rieur �� 0,05. R��sultats: L���infusion de l���ascorbylperoxyde, ind��pendamment du H2O2, a induit une hypoalv��olarisation, une activation de la caspase-3 et une oxydation du potentiel redox de mani��re dose-d��pendante. Ces effets ont ��t�� emp��ch��s par l���ajout de GSSG �� la NP ou �� la solution d���ascorbylperoxyde (180 ���M). L���ascorbylperoxyde et le H2O2 ont inhib�� l���activit�� de MAT tandis qu���elle ��tait lin��airement modul��e par la valeur du potentiel redox h��patique. Conclusion : Nos r��sultats sugg��rent que l���ascorbylperoxyde est l���agent actif de la NP conduisant au d��veloppement de la DBP. Ainsi la correction des bas niveaux de glutathion induits par les peroxydes de la NP favorise la d��toxification des peroxydes et la correction du potentiel redox pulmonaire ; ce qui a prot��g�� les poumons des effets d��l��t��res de la NP en outrepassant l���inhibition de la MAT h��patique. Nos r��sultats sont d'une grande importance car ils donnent de l'espoir pour une pr��vention possible de la DBP.

Biochemical mechanisms involved in pulmonary hypo-alveolarization induced by peroxides contaminating parenteral nutrition in newborn guinea pig

La dysplasie broncho-pulmonaire (DBP), caract��ris��e par un d��faut de l���alv��olarisation, est une complication pathologique associ��e �� un stress oxydant chez le nouveau-n�� pr��matur��. La DBP est pr��sente chez pr��s de 50 % des nouveau-n��s de moins de 29 semaines de gestation. La nutrition parent��rale (NP) que ces nouveau-n��s re��oivent pour cause d���immaturit�� gastro-intestinale est une source importante de stress oxydant. En effet, leur NP est contamin��e par des peroxydes, dont l���ascorbylperoxyde qui est une forme peroxyd��e du d��shydroascorbate. La g��n��ration des peroxydes est catalys��e par la lumi��re ambiante. La photoprotection de la NP, quoique difficile d���application en clinique, est associ��e �� une diminution de l���incidence de la DBP chez les enfants pr��matur��s. Chez l���animal nouveau-n��, la photoprotection de la NP est associ��e �� un meilleur d��veloppement alv��olaire. Ainsi, nous ��mettons l���hypoth��se que l���ascorbylperoxide infus�� avec la NP cause la perte d���alv��oles suite �� une apoptose exag��r��e induite par l���oxydation du potentiel redox du glutathion. Cette oxydation du potentiel redox serait occasionn��e par l���inhibition de la transformation h��patique de la m��thionine en cyst��ine, menant �� une diminution de la synth��se de glutathion au foie et dans les tissus tels que les poumons. La confirmation de cette hypoth��se sugg��rera qu���un ajout de glutathion dans la NP permettra une meilleure d��toxification de l���ascorbylperoxide par l���action de la glutathion peroxydase, et pr��viendra l���oxydation du potentiel redox et ainsi, la perte d'alv��oles par apoptose. Objectifs : Le but de mon projet de recherche est de comprendre les m��canismes biochimiques liant la NP et le d��veloppement de la DBP chez le nouveau-n�� pr��matur�� et de proposer une alternative nutritionnelle pr��venant le d��veloppement de cette complication fr��quemment observ��e dans cette population. Les objectifs sp��cifiques sont : 1) d�����valuer l���impact, au poumon, de l���infusion de l���ascorbylperoxyde sur l���axe m��tabolique potentiel redox du glutathion - apoptose - le d��veloppement alv��olaire; 2) d�����tudier l���impact de l���ascorbylperoxyde et du potentiel redox sur l���activit�� h��patique de la m��thionine ad��nosyltransf��rase (MAT), premi��re enzyme de la cascade m��tabolique transformant la m��thionine en cyst��ine; et 3) de tenter de pr��venir l���impact n��gatif de la NP ou de l���infusion d���ascorbylperoxyde sur le poumon en am��liorant le statut en glutathion. M��thodes: Par un cath��ter fix�� dans la jugulaire, des cochons d���Inde de trois jours de vie (n = 8 par groupe) ont re��u en continu durant 4 jours une NP ou une solution de base (dextrose + NaCl) enrichie des diff��rentes mol��cules �� l���essai. Le premier objectif a ��t�� atteint en enrichissant la solution de base en ascorbylperoxyde �� 0, 20, 60 et 180 ��M. Ces solutions contenaient ou non 350 ��M H2O2 pour se rapprocher des conditions cliniques. Le second objectif a ��t�� atteint en investiguant les m��canismes d���inhibition de la MAT dans des animaux infus��s ou non avec des solutions contenant la solution de base, des peroxydes, du glutathion et la NP (dextrose + acides amin��s + multivitamines + lipides). Le troisi��me objectif a ��t�� atteint en ajoutant ou non �� une solution d���ascorbylperoxide ou �� la NP 10 ��M de glutathion (GSSG), afin d���obtenir une concentration plasmatique normale de glutathion. Apr��s 4 jours, les poumons ��taient pr��lev��s et trait��s pour la d��termination de GSH et GSSG par ��lectrophor��se capillaire, le potentiel redox ��tait calcul�� selon l'��quation de Nernst et le niveau de caspase-3 actif (marqueur d���apoptose) par Western blot et l���index d���alv��olarisation quantifi�� par le nombre d���interceptes entre des structures histologiques et une droite calibr��e. Les donn��es ��taient compar��es par ANOVA, les effets ��taient consid��r��s comme significatifs si le p ��tait inf��rieur �� 0,05. R��sultats: L���infusion de l���ascorbylperoxyde, ind��pendamment du H2O2, a induit une hypoalv��olarisation, une activation de la caspase-3 et une oxydation du potentiel redox de mani��re dose-d��pendante. Ces effets ont ��t�� emp��ch��s par l���ajout de GSSG �� la NP ou �� la solution d���ascorbylperoxyde (180 ���M). L���ascorbylperoxyde et le H2O2 ont inhib�� l���activit�� de MAT tandis qu���elle ��tait lin��airement modul��e par la valeur du potentiel redox h��patique. Conclusion : Nos r��sultats sugg��rent que l���ascorbylperoxyde est l���agent actif de la NP conduisant au d��veloppement de la DBP. Ainsi la correction des bas niveaux de glutathion induits par les peroxydes de la NP favorise la d��toxification des peroxydes et la correction du potentiel redox pulmonaire ; ce qui a prot��g�� les poumons des effets d��l��t��res de la NP en outrepassant l���inhibition de la MAT h��patique. Nos r��sultats sont d'une grande importance car ils donnent de l'espoir pour une pr��vention possible de la DBP.

Prevention of consumption ...

Reprint fr. Annual report of the Mich. State Board of Health, 1893.

Core curriculum on tuberculosis.

"00-5763."