Relationship of body fat and cardiorespiratory fitness with cardiovascular risk in Chinese children

Backgrounds/Objectives

Cardiorespiratory fitness (CRF) and body fat play an important role in elevated risk for cardiovascular disease (CVD). However, the combined effects of CRF and obesity on metabolic health in Chinese children are unclear. The purpose of this study was to investigate the independent and combined associations between body fat, CRF, and CVD risk in Chinese schoolchildren.

Methods

The study subjects comprised 676 schoolchildren (392 boys and 284 girls, aged 9.6±0.7 yrs old) in Wuhan, China. Their body mass index (BMI), waist circumference (WC), CRF, blood pressure (BP), lipids, glucose, and pubertal status were assessed. Children were categorized into different groups based on their BMI, WC, and CRF using Chinese obesity cut-off points and CRF sex-specific median points. Metabolic Risk Score (MRS) was computed based on the standardized scores of BP, lipids, and glucose.

Results

Multiple linear regression models showed that, in the separate models, body fat was positively associated with MRS while CRF was inversely associated with MRS (p<0.001). However, when assessed simultaneously, only body fat had a significant association with MRS (p<0.001). In general, low-fit children had a lower MRS compared to their counterparts, and a significant difference between the two extreme groups was observed (low CRF and high fat vs. high CRF and low fat, p<0.001).

Conclusions

These findings suggest that both body fat and CRF should be considered when interpreting CVD risk in Chinese children, while body fat may be correlated with CVD risk more than CRF.     

Group X secretory phospholipase A2 enhances TLR4 signaling in macrophages

Secretory phospholipase A(2)s (sPLA(2)) hydrolyze glycerophospholipids to liberate lysophospholipids and free fatty acids. Although group X (GX) sPLA(2) is recognized as the most potent mammalian sPLA(2) in vitro, its precise physiological function(s) remains unclear. We recently reported that GX sPLA(2) suppresses activation of the liver X receptor in macrophages, resulting in reduced expression of liver X receptor-responsive genes including ATP-binding cassette transporters A1 (ABCA1) and G1 (ABCG1), and a consequent decrease in cellular cholesterol efflux and increase in cellular cholesterol content (Shridas et al. 2010. Arterioscler. Thromb. Vasc. Biol. 30: 2014-2021). In this study, we provide evidence that GX sPLA(2) modulates macrophage inflammatory responses by altering cellular cholesterol homeostasis. Transgenic expression or exogenous addition of GX sPLA(2) resulted in a significantly higher induction of TNF-α, IL-6, and cyclooxygenase-2 in J774 macrophage-like cells in response to LPS. This effect required GX sPLA(2) catalytic activity, and was abolished in macrophages that lack either TLR4 or MyD88. The hypersensitivity to LPS in cells overexpressing GX sPLA(2) was reversed when cellular free cholesterol was normalized using cyclodextrin. Consistent with results from gain-of-function studies, peritoneal macrophages from GX sPLA(2)-deficient mice exhibited a significantly dampened response to LPS. Plasma concentrations of inflammatory cytokines were significantly lower in GX sPLA(2)-deficient mice compared with wild-type mice after LPS administration. Thus, GX sPLA(2) amplifies signaling through TLR4 by a mechanism that is dependent on its catalytic activity. Our data indicate this effect is mediated through alterations in plasma membrane free cholesterol and lipid raft content.     

Reversal by green light of blue light-stimulated stomatal opening in intact, attached leaves of Arabidopsis operates only in the potassium-dependent, morning phase of movement

Green light reversal of blue light-stimulated stomatal opening was discovered in isolated stomata. The present study shows that the response also occurs in stomata from intact leaves. Arabidopsis thaliana plants were grown in a growth chamber under blue, red and green light. Removal of the green light opened the stomata and restoration of green light closed them to baseline values under experimental conditions that rule out a mesophyll-mediated effect. Assessment of the response to green light over a daily time course showed that the stomatal sensitivity to green light was observed only in the morning, which coincided with the use of potassium as a guard cell osmoticum. Sensitivity to green light was absent during the afternoon phase of stomatal movement, which was previously shown to be dominated by sucrose osmoregulation in Vicia faba. Hence, the shift away from potassium-based osmoregulation in guard cells is further postulated to entail a shift from blue light to photosynthesis as the primary component of the stomatal response to light. Stomata from intact leaves of the zeaxanthin-less, npq1 mutant of Arabidopsis failed to respond to the removal or restoration of green light in the growth chamber, or to short, high fluence pulses of blue or green light. These data confirm previous studies showing that npq1 stomata are devoid of a specific blue light response. In contrast, stomata from intact leaves of phot1 phot2 double mutant plants had a reduced but readily detectable response to the removal of green light and to blue and green pulses.     

The blue light-specific response of Vicia faba stomata acclimates to growth environment

Stomata in epidermal strips from growth chamber-grown Vicia faba leaves opened less in response to white light than did stomata from greenhouse-grown leaves. Chlorophyll-mediated, red light-stimulated opening was similar in stomata from the two growth conditions, but stomata from the growth chamber environment had a severely reduced response to blue light. Transfer of plants between the two growth conditions resulted in an acclimation of the stomatal blue light response. Stomata lost blue light sensitivity within 1 d of transfer to growth chamber conditions and gained sensitivity to blue light over an 8 d period after transfer to a greenhouse. Short-term transfer experiments confirmed that the rapid loss of blue light sensitivity was an acclimation response, requiring between 12 and 20 h exposure to growth chamber conditions. The acclimation of the stomatal response to blue light was inversely related to a previously reported acclimation response in which stomata change between high CO2 sensitivity under growth chamber conditions and low CO2 sensitivity under greenhouse conditions. The time courses of the blue light and CO2 acclimation responses were virtually identical, suggesting the possibility of a common acclimation mechanism.     

Blue light and phytochrome-mediated stomatal opening in the npq1 and phot1 phot2 mutants of Arabidopsis

Recent studies have shown that blue light-specific stomatal opening is reversed by green light and that far-red light can be used to probe phytochrome-dependent stomatal movements. Here, blue-green reversibility and far-red light were used to probe the stomatal responses of the npq1 mutant and the phot1 phot2 double mutant of Arabidopsis. In plants grown at 50 micromol m-2 s-1, red light (photosynthetic)-mediated opening in isolated stomata from wild type (WT) and both mutants saturated at 100 micromol m-2 s-1. Higher fluence rates caused stomatal closing, most likely due to photo-inhibition. Blue light-specific opening, probed by adding blue light (10 micromol m-2 s-1) to a 100 micromol m-2 s-1 red background, was found in WT, but not in npq1 or phot1 phot2 double mutant stomata. Under 50 micromol m-2 s-1 red light, 10 micromol m-2 s-1 blue light opened stomata in both WT and npq1 mutant stomata but not in the phot1 phot2 double mutant. In npq1, blue light-stimulated opening was reversed by far-red but not green light, indicating that npq1 has a phytochrome-mediated response and lacks a blue light-specific response. Stomata of the phot1 phot2 double mutant opened in response to 20 to 50 micromol m-2 s-1 blue light. This opening was green light reversible and far-red light insensitive, indicating that stomata of the phot1 phot2 double mutant have a detectable blue light-specific response.     

Eustenopus villosus (Coleoptera: Curculionidae) Feeding of Herbicide-Resistant Yellow Starthistle (Centaurea solstitialis L.)

A population of yellow starthistle (Centaurea solstitialis L.) near Dayton, Washington developed herbicide resistance in response to repeated applications of picloram and other auxin-type herbicides. Laboratory and field experiments were conducted in 1998 to determine host acceptability and suitability of this herbicide-resistant yellow starthistle population to the biological control weevil Eustenopus villosus (Boheman) (Coleoptera: Curculionidae). In choice and no-choice feeding and oviposition experiments using excised buds, the weevil did not demonstrate a consistent preference for either herbicide-resistant (R) or -susceptible (S) yellow starthistle. When caged on buds of intact plants, the E. villosus feeding rate of 97% did not differ between R and S types. Host plant suitability, measured as larval damage and development to adult weevils, was equivalent in R and S types, with weevils maturing in 46% of the R and in 32% of the S capitula bearing oviposition scars. The number of viable achenes per capitulum was reduced by 87% due to larval feeding, with no difference between R and S types. Observations at the field site where resistance was found revealed oviposition scars on 78% of the late-bud-stage capitula on 23 June 1998 and 73% of the flowering and postflowering capitula on 15 August 1998. Selection for herbicide resistance has not created host incompatibility for E. villosus nor reduced the effectiveness of E. villosus as a biological control agent.     

Effect of Indoleacetic Acid- and Fusicoccin-Stimulated Proton Extrusion on Internal pH of Pea Internode Cells

Using ³¹P nuclear magnetic resonance spectroscopy, we followed cytoplasmic and vacuolar pH in pea (Pisum sativum cv Alaska) internode segments during treatment with indoleacetic acid (IAA) or fusicoccin (FC) in continuously perfused, oxygenated buffer. Although IAA and FC induced normal H⁺ extrusion, elongation, and glucan synthase activity responses during the measurements, neither the cytoplasmic nor the vacuolar pH showed significant change at any time between 5 minutes and 1 to 3 hours of treatment. Changes in cytoplasmic pH as small as about 0.04 pH unit were detected after treatment with 1-naphthyl acetate. Therefore, cytoplasmic pH changes do not appear to mediate IAA or FC stimulation of H⁺ extrusion or other metabolic responses to these effectors.     

Electrophoretic Variants of Phosphoglucomutase in Saccharomyces Species

Strains of Saccharomyces cerevisiae and species with which S. cerevisiae is interfertile display a characteristic pattern of electrophoretic variants of phosphoglucomutase (PGM) consisting of a major component and one or two minor components, all of which migrate toward the cathode. The patterns are consistent with an earlier finding that two unlinked genes, one of which has two known alleles, determine the synthesis of PGM in S. cerevisiae. The PGM patterns of strains of S. fragilis, S. lactis, and S. marxianus, species thought to be closely related to each other and only distantly related to S. cerevisiae, also displayed a characteristic pattern of PGM variants, but it was quite different from that of S. cerevisiae. In these species five or six electrophoretic variants could be detected, all of which migrated toward the anode. We interpret the differences in the PGM variants of the two groups of species as a reflection of differences in genetic composition which have arisen in two phylogenetically distinct groups that have become sexually isolated from each other.