Biomedical subjects

Chengcheng Hu

Publications and source records attributed to Chengcheng Hu.

9 recordsLinked to original sources

PubMed2026

Plasma Proteomic Signatures of Physical Activity Provide Insights into Biological Impacts and its Protective Role against Dementia.

PURPOSE: Physical activity (PA) and sedentary behavior (SB) are associated with many diseases, including Alzheimer disease and all-cause dementia. However, the specific biological mechanisms through which PA protects against disease are not entirely understood. This study aims to address this gap, with a specific focus on all-cause dementia. METHODS: We first assessed the conventional observational associations of three self-reported and three device-based PA/SB measures with circulating levels of 2911 plasma proteins measured in the UK Biobank ( nmax = 39,160) and assessed functional enrichment of identified proteins. We then used bidirectional Mendelian randomization to further evaluate the evidence for causal relationships of PA/SB with protein levels. Finally, we performed mediation analyses to identify proteins that may mediate the relationship of PA with incident all-cause dementia. RESULTS: Our findings revealed 41 proteins consistently associated with all PA measures and 1027 proteins associated with at least one PA measure. Both conventional observational and Mendelian randomization study designs converged on proteins that appear to increase as a result of PA, including integrins such as ITGAV and ITGAM, as well as MXRA8, CLEC4A, CLEC4M, LPL, and ADGRG2; and on proteins that appear to decrease as a result of PA such as LEP, INHBC, CLMP, PTGDS, ADM, OGN, and PI3; and on proteins that are more responsive to high-intensity PA, such as CA14, CA6, CA4, KIT, and ANGPT2. Functional enrichment analyses revealed processes such as cell-matrix adhesion, integrin-mediated signaling, and collagen binding. Finally, GDF15, ITGAV, ITGAM, ITGA11, HPGDS, GFAP, ADM, AHNAK, and DPP4 were among 21 unique proteins found to mediate the relationship of PA with all-cause dementia, implicating processes such as synaptic plasticity, neurogenesis, and inflammation. CONCLUSIONS: Our results provide insights into how PA affects biological processes and protects against dementia, and provide avenues for future research into the health-promoting effects of PA.

Humans↗

PubMed2007

Autophagy regulates ageing in C. elegans.

The role of autophagy in ageing regulation has been suggested based on studies in C. elegans, in which knockdown of the expression of bec-1 (ortholog of the yeast and mammalian autophagy genes ATG6/VPS30 and beclin 1, respectively) shortens lifespan of the daf-2(e1370) mutant C. elegans. However, Beclin1/ATG6 is also known to be involved in other cellular functions in addition to autophagy. In the current study, we knocked down two other autophagy genes, atg-7 and atg-12, in C. elegans using RNAi. We showed that RNAi shortened the lifespan of both wild type and daf-2 mutant C. elegans, providing strong support for a role of autophagy in ageing regulation.

Aging↗

PubMed2006

Reduced lopinavir exposure during pregnancy.

BACKGROUND: Optimal antiretroviral exposure during pregnancy is critical for prevention of mother-to-child HIV transmission and for maternal health. Pregnancy can alter antiretroviral pharmacokinetics. Our objective was to describe lopinavir/ritonavir (LPV/r) pharmacokinetics during pregnancy. METHODS: We performed intensive steady-state 12-h pharmacokinetic profiles of lopinavir and ritonavir (three capsules: LPV 400 mg/r 100 mg) at 30-36 weeks gestation and 6-12 weeks postpartum. Maternal and umbilical cord blood samples were obtained at delivery. We measured LPV and ritonavir by reverse-phase high-performance liquid chromatography. Target LPV area under concentration versus time curve (AUC) was > or = 52 microg h/ml, the estimated 10th percentile LPV AUC in non-pregnant historical controls (mean AUC = 83 microg h/ml). RESULTS: Seventeen women completed antepartum evaluations; average gestational age was 35 weeks. Geometric mean antepartum LPV AUC was 44.4 microg h/ml [90% confidence interval (CI), 38.7-50.9] and 12-h post-dose concentration (C12h) was 1.6 microg/ml (90% CI, 1.1-2.5). Twelve women completed postpartum evaluations; geometric mean LPV AUC was 65.2 microg h/ml (90% CI, 49.7-85.4) and C12h was 4.6 microg/ml (90% CI, 3.7-5.7). The geometric mean ratio of antepartum/postpartum LPV AUC was 0.72 (90% CI, 0.54-0.96). Fourteen of 17 (82%) pregnant and three of 12 (25%) postpartum women did not meet our target LPV AUC. The ratio of cord blood/maternal LPV concentration in ten paired detectable samples was 0.2 +/- 0.13. CONCLUSIONS: LPV/r exposure during late pregnancy was lower compared to postpartum and compared to non-pregnant historical controls. Small amounts of lopinavir cross the placenta. The pharmacokinetics, safety, and effectiveness of increased LPV/r dosing during the third trimester of pregnancy should be investigated.

Adolescent↗

PubMed2006

In vivo two-photon imaging reveals a role of arc in enhancing orientation specificity in visual cortex.

Cortical representations of visual information are modified by an animal's visual experience. To investigate the mechanisms in mice, we replaced the coding part of the neural activity-regulated immediate early gene Arc with a GFP gene and repeatedly monitored visual experience-induced GFP expression in adult primary visual cortex by in vivo two-photon microscopy. In Arc-positive GFP heterozygous mice, the pattern of GFP-positive cells exhibited orientation specificity. Daily presentations of the same stimulus led to the reactivation of a progressively smaller population with greater reactivation reliability. This adaptation process was not affected by the lack of Arc in GFP homozygous mice. However, the number of GFP-positive cells with low orientation specificity was greater, and the average spike tuning curve was broader in the adult homozygous compared to heterozygous or wild-type mice. These results suggest a physiological function of Arc in enhancing the overall orientation specificity of visual cortical neurons during the post-eye-opening life of an animal.

Animals↗

PubMed2006

Impact of pregnancy on abacavir pharmacokinetics.

OBJECTIVE: To describe abacavir pharmacokinetics during pregnancy and postpartum; physiological changes during pregnancy are known to affect antiretroviral drug disposition. DESIGN: The Pediatric AIDS Clinical Trials Group P1026s study is an on-going, prospective, non-blinded pharmacokinetic study of pregnant women receiving one or more antiretroviral drugs for routine clinical care, including a cohort receiving abacavir 300 mg twice daily. METHODS: Serial plasma samples (predose, 1, 2, 4, and 6 h postdose) obtained antepartum (30-36 weeks of gestation) and again postpartum (6-12 weeks after delivery) were assayed for abacavir concentration by reversed-phase high-performance liquid chromatography. RESULTS: Antepartum evaluations were available for 25 women [mean age, 28.6 years (SD, 6); mean third-trimester weight 92 kg (SD, 35.4); and race/ethnicity 52% black, 28% Hispanic, 16% white, 4% Asian], with geometric mean abacavir area under the concentration-time curve (AUC) of 5.9 mg.h/l [90% confidence interval (CI), 5.2-6.8] and maximum plasma concentration (Cmax) of 1.9 mg/l (90% CI, 1.6-2.2). Seventeen women completed postpartum sampling, and the ratios of antepartum to postpartum AUC and Cmax were 1.04 (90% CI, 0.91-1.18) and 0.79 (90% CI, 0.65-0.98), respectively. CONCLUSIONS: Abacavir AUC during pregnancy was similar to that at 6-12 weeks postpartum and to that for non-pregnant historical controls (5.8 mg.h/l). Consequently, pregnancy does not appear to affect overall abacavir exposure significantly or to necessitate dose adjustments.

Adult↗

PubMed2006

Attributable risk function in the proportional hazards model for censored time-to-event.

Time-to-event endpoints are often used in clinical and epidemiological studies to evaluate disease association with hazardous exposures. In the statistical literature of time-to-event analysis, such association is usually measured by the hazard ratio in the proportional hazards model. In public health, it is also of important interest to assess the excess risk attributable to an exposure in a given population. In this article, we extend the notion of 'population attributable fraction' for the binary outcomes to the attributable risk function for the event times in prospective studies. A simple estimator of the time-varying attributable risk function is proposed under the proportional hazards model. Its inference procedures are established. Monte-Carlo simulation studies are conducted to evaluate its validity and performance. The proposed methodology is motivated and demonstrated by the data collected in a multicenter acquired immunodeficiency syndrome (AIDS) cohort study to estimate the attributable risk of human immunodeficiency virus type 1 (HIV-1) infections due to several potential risk factors.

Biometry↗

PubMed2005

Increased serum cathepsin S in patients with atherosclerosis and diabetes.

Atherosclerosis and diabetes are closely associated and both involve extensive degradation of the aortic elastin. Increased elastase activity has been detected in diabetic animal aortae. We have demonstrated enhanced elastolytic cathepsin S in human atherosclerotic lesions but insufficient amounts of its endogenous inhibitor cystatin C, suggesting alterations of serum cathepsin S and/or cystatin C in patients with atherosclerosis or diabetes. In this study, we measured levels of both cathepsin S and cystatin C in sera from 240 patients by ELISA. Among these patients, 107 had a diagnosis of atherosclerotic stenosis, 103 were diabetic, and 30 had neither condition. Multiple linear regression analysis demonstrated that significantly higher serum levels of cathepsin S in patients with either atherosclerotic stenosis (p<0.04) or diabetes (p=0.0005) persisted after adjustment for cystatin C level, renal function, smoking, and serum glucose levels (p=0.008, p=0.0005). Furthermore, patients with acute (p=0.009) or previous myocardial infarction (p<0.02) or unstable angina pectoris (p<0.05) had elevated levels of cathepsin S after adjustment for smoking, creatinine, cystatin C, and serum glucose. In contrast, serum cystatin C levels were higher in diabetic patients (p=0.00001), but not in atherosclerotic subjects (p=0.14), than in the non-involved population after adjustment for age, smoking, and renal function. Although the pathophysiology of cathepsin S or cystatin C in atherosclerosis and diabetes requires further investigation, increased serum cathepsin S may serve as a biomarker for both diseases.

Aged↗

PubMed2005

Cathepsin L expression and regulation in human abdominal aortic aneurysm, atherosclerosis, and vascular cells.

The cysteine protease cathepsin L is one of the most potent mammalian elastases and collagenases, widely expressed at basal levels in most tested tissues and cell types, and regulated by pro-inflammatory stimuli. The inflammatory arterial diseases abdominal aortic aneurysm (AAA) and atherosclerosis involve extensive vascular remodeling that requires elastolysis and collagenolysis. This study examined the hypothesis that cathepsin L is over-expressed in human AAA and atherosclerotic lesions and its expression in vascular cell types found in these lesions is regulated by pro-inflammatory cytokines. Immunohistochemical and tissue extract immunoblot analysis demonstrated increased expression of cathepsin L in human AAA and atheromata and localized its expression to lesional smooth muscle cells (SMC), endothelial cells (EC), and macrophages. In primary cultured human SMC, EC, and monocyte-derived macrophages, pro-inflammatory cytokines or growth factors induced the expression of cathepsin L and its activity against extracellular collagen and elastin. Patients with coronary artery stenosis (n=65) had higher serum cathepsin L levels than those without lesions detectable by quantitative coronary angiography (n=30) (1.47+/-0.33 ng/ml versus 0.60+/-0.06 ng/ml, p<0.02). A strong correlation between the percent of stenosis of left anterior descending coronary artery and serum cathepsin L levels in patients with stenosis (R=0.542, p<0.0001), also suggests involvement of cathepsin L in these vascular diseases.

Animals↗

PubMed2004

A test for informative censoring in clustered survival data.

Frailty models are frequently used to analyse clustered survival data. The assumption of non-informative censoring is commonly used by these models, even though it may not be true in many situations. This article proposes a test for this assumption. It uses the estimated correlation between two types of martingale residuals, one from a model for failure and the other from a model for censoring. It distinguishes two types of censoring, namely withdrawal and the end of the study. Simulation studies show that the proposed test works well under various scenarios. For illustration, the test is applied to a data set for kidney disease patients from multiple dialysis centres.

Cluster Analysis↗