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Articles by K Liu
Total Records ( 7 ) for K Liu
  K Liu , S Zhou , J. Y Kim , K Tillison , D Majors , D Rearick , J. H Lee , R. F Fernandez Boyanapalli , K Barricklow , M. S Houston and C. M. Smas
 

The adipocyte-specific protein FSP27, also known as CIDEC, is one of three cell death-inducing DFF45-like effector (CIDE) proteins. The first known function for CIDEs was promotion of apoptosis upon ectopic expression in mammalian cells. Recent studies in endogenous settings demonstrated key roles for CIDEs in energy metabolism. FSP27 is a lipid droplet-associated protein whose heterologous expression enhances formation of enlarged lipid droplets and is required for unilocular lipid droplets typical of white adipocytes in vivo. Here, we delineate relationships between apoptotic function and lipid droplet localization of FSP27. We demonstrate that ectopic expression of FSP27 induces enlarged lipid droplets in multiple human cell lines, which is indicative that its mechanism involves ubiquitously present, rather than adipocyte-specific, cellular machinery. Furthermore, promotion of lipid droplet formation in HeLa cells via culture in exogenous oleic acid offsets FSP27-mediated apoptosis. Using transient cotransfections and analysis of lipid droplets in HeLa cells stably expressing FSP27, we show that FSP27 does not protect lipid droplets from action of ATGL lipase. Domain mapping with eGFP-FSP27 deletion constructs indicates that lipid droplet localization of FSP27 requires amino acids 174–192 of its CIDE C domain. The apoptotic mechanism of FSP27, which we show involves caspase-9 and mitochondrial cytochrome c, also requires this 19-amino acid region. Interaction assays determine the FSP27 CIDE C domain complexes with CIDEA, and Western blot reveals that FSP27 protein levels are reduced by coexpression of CIDEA. Overall, our findings demonstrate the function of the FSP27 CIDE C domain and/or regions thereof for apoptosis, lipid droplet localization, and CIDEA interaction.

  K. L Knutson , E Van Cauter , P. J Rathouz , L. L Yan , S. B Hulley , K Liu and D. S. Lauderdale
 

Background  Epidemiological studies have reported an association between self-reported short sleep duration and high blood pressure (BP). Our objective was to examine both cross-sectional and longitudinal associations between objectively measured sleep and BP.

Methods  This study is ancillary to the Coronary Artery Risk Development in Young Adults (CARDIA) cohort study. Blood pressure was measured in 2000 and 2001 and in 2005 and 2006. Sleep was measured twice using wrist actigraphy for 3 consecutive days between 2003 and 2005. Sleep duration and sleep maintenance (a component of sleep quality) were calculated. Analyses included 578 African Americans and whites aged 33 to 45 years at baseline. Outcome measures were systolic BP (SBP) and diastolic BP (DBP) levels, 5-year change in BP, and incident hypertension.

Results  After we excluded the patients who were taking antihypertensive medications and adjusted for age, race, and sex, shorter sleep duration and lower sleep maintenance predicted significantly higher SBP and DBP levels cross-sectionally as well as more adverse changes in SBP and DBP levels over 5 years (all P < .05). Short sleep duration also predicted significantly increased odds of incident hypertension (odds ratio, 1.37; 95% confidence interval, 1.05-1.78). Adjustment for 16 additional covariates, including snoring and daytime sleepiness, slightly attenuated the associations between sleep and BP. Sleep duration appeared to mediate the difference between African Americans and whites in DBP change over time (P = .02).

Conclusion  Reduced sleep duration and consolidation predicted higher BP levels and adverse changes in BP, suggesting the need for studies to investigate whether interventions to optimize sleep may reduce BP.

  M. M McDermott , L Ferrucci , J Guralnik , L Tian , K Liu , F Hoff , Y Liao and M. H. Criqui
 

Background— Associations of pathophysiological calf muscle characteristics with functional decline in people with lower extremity peripheral arterial disease are unknown.

Methods and Results— Three hundred seventy participants with peripheral arterial disease underwent baseline measurement of calf muscle area, density, and percent fat with the use of computed tomography. Participants were followed up annually for 2 years. The outcome of mobility loss was defined as becoming unable to walk 1/4 mile or walk up and down 1 flight of stairs without assistance among those without baseline mobility limitations. Additional outcomes were ≥20% decline in 6-minute walk distance and becoming unable to walk for 6 minutes continuously among participants who walked continuously for 6 minutes at baseline. With adjustment for age, sex, race, body mass index, the ankle-brachial index, smoking, physical activity, relevant medications, and comorbidities, lower calf muscle density (P for trend <0.001) and lower calf muscle area (P for trend=0.039) were each associated with increased mobility loss rates. Compared with participants in the highest baseline tertiles, participants in the lowest tertile of calf muscle percent fat had a hazard ratio of 0.18 for incident mobility loss (95% confidence interval, 0.06 to 0.55; P=0.003), and participants in the lowest tertile of muscle density had a 3.50 hazard ratio for incident mobility loss (95% confidence interval, 1.28 to 9.57; P=0.015). No significant associations of calf muscle characteristics with 6-minute walk outcomes were observed.

Conclusions— Our findings suggest that interventions to prevent mobility loss in peripheral arterial disease should focus on reversing pathophysiological findings in calf muscle.

  L. A Colangelo , P Ouyang , K Liu , P Kopp , S. H Golden , A. S Dobs , M Szklo , D Vaidya , M Cushman and S. M. Gapstur
  OBJECTIVE

To assess associations of sex hormones with impaired fasting glucose (IFG) and type 2 diabetes in men.

RESEARCH DESIGN AND METHODS

A total of 3,156 African American, Non-Hispanic white, Hispanic, and Chinese-American men aged 45–84 years who participated in the baseline visit of the Multi-Ethnic Study of Atherosclerosis (MESA) were included. Oddsratios and95% CIs for type 2 diabetes and IFG compared with normal fasting glucose for quartiles of hormones were estimated.

RESULTS

After adjusting for age, ethnicity, BMI, and waist circumference, IFG and diabetes were associated inversely with total testosterone and sex hormone–binding globulin (SHBG) and positively with estradiol (E2). Dehydroepiandrosterone was positively associated with IFG but not with diabetes. Associations did not differ across ethnic groups.

CONCLUSIONS

Regardless of obesity, total testosterone and SHBG were associated inversely and E2 was associated positively with IFG and diabetes in men. Further research is warranted to better understand the underlying biological mechanisms.

  P Gao , K Liu , L Liu , Z Wang , Z Liao , Z Xu , W Wang , X Bai , E Wang and Y. Li
 

The higher-order harmonic resonances, including second and third harmonic modes, were induced by applying alternative current signals inside a high-resolution transmission electron microscope (HRTEM), which have been used to study the mechanical properties of individual cadmium sulphide (CdS) nanowires. Young's moduli (E) and mechanical quality factors (Q) of individual CdS nanowires with diameters in the range of 50–350 nm were measured with the assistance of the mechanical resonances. The results indicate that the smooth nanowires have larger E and Q in comparison with the rough nanowires, and for the rough nanowires, E and Q increase with increasing diameters. The morphology- and size-dependent mechanical properties of CdS nanowires are directly correlated with their structure, as imaged by in situ TEM.

  G Darrasse Jeze , S Deroubaix , H Mouquet , G. D Victora , T Eisenreich , K. h Yao , R. F Masilamani , M. L Dustin , A Rudensky , K Liu and M. C. Nussenzweig
 

CD4+CD25+Foxp3+ natural regulatory T cells (T reg cells) maintain self-tolerance and suppress autoimmune diseases such as type 1 diabetes and inflammatory bowel disease (IBD). In addition to their effects on T cells, T reg cells are essential for maintaining normal numbers of dendritic cells (DCs): when T reg cells are depleted, there is a compensatory Flt3-dependent increase in DCs. However, little is known about how T reg cell homeostasis is maintained in vivo. We demonstrate the existence of a feedback regulatory loop between DCs and T reg cells. We find that loss of DCs leads to a loss of T reg cells, and that the remaining T reg cells exhibit decreased Foxp3 expression. The DC-dependent loss in T reg cells leads to an increase in the number of T cells producing inflammatory cytokines, such as interferon and interleukin 17. Conversely, increasing the number of DCs leads to increased T reg cell division and accumulation by a mechanism that requires major histocompatibility complex II expression on DCs. The increase in T reg cells induced by DC expansion is sufficient to prevent type 1 autoimmune diabetes and IBD, which suggests that interference with this feedback loop will create new opportunities for immune-based therapies.

  F Ginhoux , K Liu , J Helft , M Bogunovic , M Greter , D Hashimoto , J Price , N Yin , J Bromberg , S. A Lira , E. R Stanley , M Nussenzweig and M. Merad
 

CD103+ dendritic cells (DCs) in nonlymphoid tissues are specialized in the cross-presentation of cell-associated antigens. However, little is known about the mechanisms that regulate the development of these cells. We show that two populations of CD11c+MHCII+ cells separated on the basis of CD103 and CD11b expression coexist in most nonlymphoid tissues with the exception of the lamina propria. CD103+ DCs are related to lymphoid organ CD8+ DCs in that they are derived exclusively from pre-DCs under the control of fms-like tyrosine kinase 3 (Flt3) ligand, inhibitor of DNA protein 2 (Id2), and IFN regulatory protein 8 (IRF8). In contrast, lamina propria CD103+ DCs express CD11b and develop independently of Id2 and IRF8. The other population of CD11c+MHCII+ cells in tissues, which is CD103CD11b+, is heterogenous and depends on both Flt3 and MCSF-R. Our results reveal that nonlymphoid tissue CD103+ DCs and lymphoid organ CD8+ DCs derive from the same precursor and follow a related differentiation program.

 
 
 
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