Role of FbpA and FbpB in the pathogenesis and mycolyltransferase activity of Mycobacterium tuberculosis

Mycobacterium tuberculosis infects more people worldwide each year than any other single organism. The Antigen 85 Complex, a family of fibronectin-binding proteins (Fbps) found in several species of mycobacteria and possibly involved in host interaction, is considered among the putative virulence factors of M. tuberculosis. These proteins are implicated in the production of trehalose dimycolate (TDM) and arabinogalactan-mycolate (AG-M), two prominent components of the mycobacterium cell wall and potent modulators of the immune system during infection. For these reasons, the principal members of the complex, FbpA and FbpB, were the focus of these studies. The genes encoding these proteins, fbpA and fbpB, were each disrupted by insertion of a kanamycin resistance cassette in a pathogenic strain of M. tuberculosis, H37Rv. Neither mutation affected growth in routine broth culture. Thin layer chromatography analysis of TDM and AG-M showed no difference in content between the parent strain H37Rv and the FbpA- and FbpB-deficient mutants grown under two different culture conditions. However, metabolic radiolabeling of the strains showed that the production of TDM (but not its precursor TMM) was delayed in the FbpA- and FbpB-deficient mutants compared to the parent H37Rv. During this same labeling period, FbpA-deficient mutant LAa1 failed to produce AG-M and in the FpbB-deficient mutant LAb1 production was decreased. In macrophage tissue culture assay, LAa1 failed to multiply when bacteria in early log phase were used to infect monolayers while LAb1 grew like the parent strain. The growth deficiency of LAa1 as well as the deficiencies in TDM and AG-M production were restored by complementing LAa1 with a functional fbpA gene. These results suggest that the FbpA and FbpB proteins are involved in synthesis of TDM (but not its precursor TMM) as well as AG-M. Other members of the complex appear to compensate for defects in synthesis caused by mutation of single genes in the complex over time. Mutation of the FbpA gene causes greater in vivo effect than mutation of the FbpB gene despite very similar deficiencies in the rate of production of mycolate containing molecules on the cell surface. ^

Community referral for promoting physical activity among primary care patients

Introduction. There is a need for physical activity interventions based in primary care clinics that take advantage of community resources. The purpose of this randomized controlled trial was to compare the effects of two physical activity interventions: (1) physical activity prescription by a primary care provider plus referral to community physical activity resources and (2) physical activity prescription only. ^ Methods. Sedentary adult patients recruited from a general medicine clinic were randomized to receive a physical activity prescription, delivered by the primary care provider, plus referral to community physical activity resources (n=38) or physical activity prescription only (n=32). Outcomes were use of community resources (exercise facility and personal trainers), physical activity levels (self-report questionnaire and pedometer), and attitudes regarding physical activity assessed at 8 weeks. ^ Results. Three of 38 (7.9%) subjects referred to the community resources and none of the 32 subjects in the prescription only group used the community resources during the 8 week trial. Sixteen of 32 subjects in the prescription plus referral group and 19 of 38 in the prescription group completed the self-report follow-up forms at 8 weeks. For minutes of moderate- or vigorous-intensity physical activity per week, there were no between-group differences at baseline, follow-up, or change from baseline to follow-up. However, for moderate- and vigorous-intensity physical activity, there were significant improvements from baseline to follow-up within each group. For attitudes related to physical activity, there were no between-group differences at baseline, follow-up, or change from baseline to follow-up; neither were there any within-group changes. ^ Discussion. Physical activity prescription delivered by a healthcare provider in the context of a routine primary care visit can improve physical activity levels, with no additional improvement gained by referring to community resources. The intervention was feasible for primary care providers to deliver, but only 50% of subjects returned the self-report physical activity questionnaire at the 8 week assessment. ^

Physical activity, body composition, exogenous estrogen use and their association with insulin-like growth factors

Obesity and physical inactivity are modifiable risk factors that are associated with several health issues; they are major factors in up to 30% of major cancers. Elevated levels of circulating insulin-like growth factor-I (IGF-I) have been associated with high body composition measurements and high cancer risk; exogenous estrogen use is associated with low circulating IGF-I levels and high cancer risk. The relationship between physical activity and circulating IGF levels is complex and findings of previous studies of their relationship remain inconsistent; however, these studies included vague definitions of physical activity. In this study, we used cross-sectional data from the Women's Health Initiative to determine the relationship between specific measures of physical activity (e.g., intensity, duration, and frequency) and circulating IGF-I levels, accounting for exogenous estrogen use and body composition. These data were collected from women enrolled at Women's Health Initiative clinical centers at Baylor College of Medicine and Wake Forest University School of Medicine. Multivariate linear regression analysis showed that circulating IGF-I and IGF-binding protein (BP) 3 levels were positively associated with frequency, duration, and intensity of physical activity. Circulating IGF-I levels and the molar IGF-I:IGF-BP3 ratio were significantly associated with frequency of walking, whereas circulating IGF-BP3 levels were significantly associated with strenuous physical activity, suggesting that different aspects of physical activity and their effects on fitness affect members of the IGF family differently. The results from our study support the recommendation of a regular exercise routine, particularly that of strenuous intensity, for postmenopausal women as a means to prevention of cancer.^