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Addressing key issues in HIV self-test program implementation for Black and Latino sexual minority men in the Southern United States: a multiphase study protocol. Implement Sci Commun 2023; 4:14. [PMID: 36782303 PMCID: PMC9926573 DOI: 10.1186/s43058-023-00395-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Accepted: 01/30/2023] [Indexed: 02/15/2023] Open
Abstract
BACKGROUND Black and Latino sexual minority men in the Southern United States have the highest HIV infection rates in the country. Increased HIV testing can help decrease onward HIV transmission through detecting previously undiagnosed infections. HIV self-testing is an evidence-based strategy to increase HIV testing among sexual minority men, but the implementation of this intervention in the Southern United States is limited. One implementation barrier is the lack of knowledge of Black and Latino sexual minority men's preferences for various HIV self-testing program characteristics and their willingness to pay for these preferences. In addition, little is known about facilitators and barriers to initiating HIV self-testing programs from the perspectives of HIV prevention implementation decision-makers in this region. METHODS We will conduct an online discrete choice experiment among Black and Latino sexual minority men in the Southern United States (n = 300) to estimate this population's preferences for the following HIV self-testing program characteristics: delivery strategy (home delivery, peer delivery, clinic pickup); delivery speed (same day, next day, 3 days, and 5 days); support (instructions only, during test, and 1 week after delivery); and price ($0, $20, $40, $50, $60). We will also use this choice data to generate willingness-to-pay estimates for each program characteristic. Guided by the Consolidated Framework for Implementation Research, we will then conduct semi-structured interviews (n = 30) with HIV prevention program decision-makers at various health organizations serving Black and Latino sexual minority men in the region to further understand facilitators and barriers to implementation of the most preferred HIV self-testing program design. DISCUSSION By gaining perspectives on HIV self-testing implementation from patients and providers, this project will build a roadmap for the initiation of HIV self-testing programs to decrease HIV incidence among one of the most disproportionately impacted populations in the USA.
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Demographics and Health Beliefs of Black Gay, Bisexual, and Other Sexual Minority Men Receiving a Mpox Vaccination in the United States. J Urban Health 2023; 100:204-211. [PMID: 36662397 PMCID: PMC9854406 DOI: 10.1007/s11524-022-00712-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 12/22/2022] [Indexed: 01/21/2023]
Abstract
An outbreak of mpox virus (MPV) among humans in the United States (U.S.) was described in May 2022. This outbreak disproportionately affects Black and Hispanic sexual minority men (SMM) and these groups have lower rates of vaccination compared to Whites. Between July and August 2022, a partnership between a nonprofit and two local health departments successfully designed and implemented a community intervention to administer MPV vaccines to Black SMM in the Washington D.C. metropolitan area. We administered a quantitative survey to 178 respondents across four vaccinations clinics. We found that study participants had high socioeconomic status, high levels of anticipated MPV stigma, and were relatively skeptic about MPV. We demonstrated how a partnership between an urban nonprofit and government agency can facilitate quick and effective dissemination of a community intervention in a relatively low cost manner.
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"To Me, Everybody Is infected": Understanding Narratives about HIV Risk among HIV-negative Black Men Who Have Sex with Men in the Deep South. JOURNAL OF HOMOSEXUALITY 2021; 68:973-992. [PMID: 31794351 PMCID: PMC7266721 DOI: 10.1080/00918369.2019.1694338] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
For black MSM living in the Deep South, the intersection of sexuality, race, and geography impacts HIV risk substantially. Between July and September 2016, we conducted a qualitative study among HIV-negative black MSM in five southern cities in the US with elevated HIV prevalence. Analysis included assessment of interrater reliability, cluster analysis, and descriptive statistics. We enrolled 99 black MSM (mean age: 33.6; SD = 12.8; range: 17-68 years). Four overarching themes emerged: harboring fear of HIV and the internalization of HIV stigma; scrutinizing potential partners to assess riskiness and HIV status; embracing distance and isolation from those perceived as a threat to HIV status; and exhibiting self-efficacy toward HIV prevention and utilizing risk reduction strategies. Future HIV prevention efforts may benefit by balancing risk and deficit based strategies with those that emphasize resilience, address disenfranchisement via structural interventions, and assess and treat inherent trauma(s).
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Remote science activities during the AMADEE-18 Mars analog mission: Preparation and execution during a simulated planetary surface mission. ACTA ACUST UNITED AC 2021. [DOI: 10.1016/j.jsse.2020.12.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Stigma, medical mistrust, and perceived racism may affect PrEP awareness and uptake in black compared to white gay and bisexual men in Jackson, Mississippi and Boston, Massachusetts. AIDS Care 2017; 29:1351-1358. [PMID: 28286983 DOI: 10.1080/09540121.2017.1300633] [Citation(s) in RCA: 269] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Gay and bisexual men and other men who have sex with men (MSM) account for more than two thirds of new HIV infections in the U.S., with Black MSM experiencing the greatest burden. Antiretroviral pre-exposure prophylaxis (PrEP) can reduce MSM's vulnerability to HIV infection. Uptake of PrEP has been limited, particularly among racial and ethnic minority MSM. Four semi-structured focus groups with gay and bisexual men and other MSM at risk for HIV infection were convened in Boston and Jackson in late 2013. The analysis plan utilized a within-case, across-case approach to code and analyze emerging themes, and to compare results across the two cities. Participants recruited in Jackson were primarily Black gay men, while Boston participants were mostly non-Hispanic White gay men. Participants in both sites shared concerns about medication side effects and culturally insensitive health care for gay men. Jackson participants described stronger medical mistrust, and more frequently described experiences of anti-gay and HIV related stigma. Multiple addressable barriers to PrEP uptake were described. Information about side effects should be explicitly addressed in PrEP education campaigns. Providers and health departments should address medical mistrust, especially among Black gay and bisexual men and other MSM, in part by training providers in how to provide affirming, culturally competent care. Medicaid should be expanded in Mississippi to cover low-income young Black gay and bisexual men and other MSM.
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Post-exposure prophylaxis awareness and use among men who have sex with men in London who use geosocial-networking smartphone applications. AIDS Care 2016; 29:579-586. [PMID: 27910722 DOI: 10.1080/09540121.2016.1259455] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The number of new HIV infections continues to be on the rise in many high-income countries, most notably among men who have sex with men (MSM). Despite recent attention to the use of antiretroviral medications as pre-exposure prophylaxis (PrEP) among MSM, considerably less research has been devoted to examining the awareness and use of post-exposure prophylaxis (PEP). Based on a convenience sample of 179 self-reported HIV-uninfected MSM using a geosocial-networking smartphone application, this study is among the first to examine the awareness and use of PEP and their demographic and behavioral correlates among MSM in London. Most respondents (88.3%) had heard of PEP, where 27.4% reported having used it. In multivariable models, the disclosure of one's sexual orientation to their general practitioner (Prevalence ratio [PR]: 3.49; 95% confidence interval (CI): 1.14, 10.70; p = .029) and reporting one's HIV status as negative (rather than unknown) (PR: 11.49; 95% CI: 1.68, 76.92; p = .013) were associated with having heard of PEP; while the recent use of club drugs (PR: 3.02; 95% CI: 1.42, 6.43; p = .004) was associated with having ever used PEP. High awareness and use in this sample suggest that PEP is a valuable risk-reduction strategy that should be capitalized on, be it in addition to or in the absence of PrEP.
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Psychometric properties of the Gay-Friendliness of Neighbourhood Scale in New York City. Eur J Public Health 2016. [DOI: 10.1093/eurpub/ckw174.086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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The Social Patterning of Sleep in African Americans: Associations of Socioeconomic Position and Neighborhood Characteristics with Sleep in the Jackson Heart Study. Sleep 2016; 39:1749-59. [PMID: 27253767 DOI: 10.5665/sleep.6106] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Accepted: 04/18/2016] [Indexed: 11/03/2022] Open
Abstract
STUDY OBJECTIVES We investigated cross-sectional associations of individual-level socioeconomic position (SEP) and neighborhood characteristics (social cohesion, violence, problems, disadvantage) with sleep duration and sleep quality in 5,301 African Americans in the Jackson Heart Study. METHODS All measures were self-reported. Sleep duration was assessed as hours of sleep; sleep quality was reported as poor (1) to excellent (5). SEP was measured by categorized years of education and income. Multinomial logistic and linear regression models were fit to examine the associations of SEP and neighborhood characteristics (modeled dichotomously and tertiles) with sleep duration (short vs. normal, long vs. normal) and continuous sleep duration and quality after adjustment for demographics and risk factors. RESULTS The mean sleep duration was 6.4 ± 1.5 hours, 54% had a short (≤ 6 h) sleep duration, 5% reported long (≥ 9 h) sleep duration, and 24% reported fair to poor sleep quality. Lower education was associated with greater odds of long sleep (odds ratio [OR] = 2.19, 95% confidence interval [CI] = 1.42, 3.38) and poorer sleep quality (β = -0.17, 95% CI = -0.27, -0.07) compared to higher education after adjustment for demographics and risk factors. Findings were similar for income. High neighborhood violence was associated with shorter sleep duration (-9.82 minutes, 95% CI = -16.98, -2.66) and poorer sleep quality (β = -0.11, 95% CI = -0.20, 0.00) after adjustment for demographics and risk factors. Results were similar for neighborhood problems. In secondary analyses adjusted for depressive symptoms in a subset of participants, most associations were attenuated and only associations of low SEP with higher odds of long sleep and higher neighborhood violence with poorer sleep quality remained statistically significant. CONCLUSIONS Social and environmental characteristics are associated with sleep duration and quality in African Americans. Depressive symptoms may explain at least part of this association.
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Similarities and Differences in Sexual Risk Behaviors Between Young Black MSM Who Do and Do Not Have Sex with Females. AIDS Behav 2016; 20:717-21. [PMID: 26547716 DOI: 10.1007/s10461-015-1227-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The objective of this study is to determine whether young Black MSM who also have sex with females report similar levels of sexual risk behaviors as those not having sex with females. YBMSM (N = 400) were recruited from an STI clinic, located in the Southern U.S. Men completed an audio-computer assisted self-interview and donated specimens for STI/HIV testing. Forty-three percent recently engaged in penile-vaginal sex. They were less likely to report having concurrent partners (P = .01), unprotected fellatio (P = .04), multiple partners as a bottom (P < .02), any unprotected anal sex as a bottom (P < .013), and any anal sex (P = .007). They were equally likely to report favorable attitudes toward serosorting (P = .80), multiple male partners as a top (P = .20), unprotected anal insertive sex with males (P = .15). Frequency of sex with males as a top (P = .61) or bottom (P = .61) did not differ. Compared to YBMSM not having sex with females, those having sex with females may be exercising greater caution.
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What is in a label? Multiple meanings of 'MSM' among same-gender-loving Black men in Mississippi. Glob Public Health 2016; 11:937-52. [PMID: 26950431 DOI: 10.1080/17441692.2016.1142593] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Men who have sex with men (MSM) and other same-gender-loving (SGL) men continue to be disproportionately affected by HIV and AIDS, particularly among the Black population. Innovative strategies are needed to support the health of this community; however, public health efforts primarily approach MSM as a monolithic population erasing the diverse identities, practices, and sexualities within and beyond this category. To better understand diversity within MSM in a geographic region with the largest proportion of Black Americans in the U.S.A. and among the most heavily affected by the epidemic, the Deep South, we conducted four focus groups (n = 29) with Black men who reported having sex with other men residing in Jackson, Mississippi. Results suggest multiple overlapping usages of MSM as identity and behaviour, reflecting internalisation of behavioural categories and co-creation of identities unique to the Black community. These narratives contribute to the literature by documenting the evolving understandings of the category 'MSM' among Black men to reflect intersections between race, socioeconomic status, sexual behaviour, sexuality, subjectivities, and social context. Findings suggest the current monolithic approach to treating MSM may limit public health efforts in developing effective HIV prevention and promotion programmes targeting SGL Black men in the Deep South.
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Perceived discrimination is associated with health behaviours among African-Americans in the Jackson Heart Study. J Epidemiol Community Health 2015; 70:187-94. [PMID: 26417003 DOI: 10.1136/jech-2015-206390] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2015] [Accepted: 09/11/2015] [Indexed: 11/04/2022]
Abstract
BACKGROUND Using Jackson Heart Study data, we examined associations of multiple measures of perceived discrimination with health behaviours among African-Americans (AA). METHODS The cross-sectional associations of everyday, lifetime and burden of discrimination with odds of smoking and mean differences in physical activity, dietary fat and sleep were examined among 4925 participants aged 35-84 years after adjustment for age and socioeconomic status (SES). RESULTS Men reported slightly higher levels of everyday and lifetime discrimination than women and similar levels of burden of discrimination as women. After adjustment for age and SES, everyday discrimination was associated with more smoking and a greater percentage of dietary fat in men and women (OR for smoking: 1.13, 95% CI 1.00 to 1.28 and 1.19, 95% CI 1.05 to 1.34; mean difference in dietary fat: 0.37, p<0.05 and 0.43, p<0.01, in men and women, respectively). Everyday and lifetime discrimination were associated with fewer hours of sleep in men and women (mean difference for everyday discrimination: -0.08, p<0.05 and -0.18, p<0.001, respectively; and mean difference for lifetime discrimination: -0.08, p<0.05 and -0.24, p<0.001, respectively). Burden of discrimination was associated with more smoking and fewer hours of sleep in women only. CONCLUSIONS Higher levels of perceived discrimination were associated with select health behaviours among men and women. Health behaviours offer a potential mechanism through which perceived discrimination affects health in AA.
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The effects of neighborhood and individual level covariates on individual dietary patterns: the Jackson Heart Study. FASEB J 2013. [DOI: 10.1096/fasebj.27.1_supplement.847.11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Fatty liver, abdominal visceral fat, and cardiometabolic risk factors: the Jackson Heart Study. Arterioscler Thromb Vasc Biol 2012; 31:2715-22. [PMID: 21885852 DOI: 10.1161/atvbaha.111.234062] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
OBJECTIVE The goal of this study was to examine whether fatty liver and abdominal visceral adipose tissue (VAT) are jointly associated with cardiometabolic abnormalities. METHODS AND RESULTS Black participants were from the Jackson Heart Study (n=2882, 65% women) who underwent computed tomography. Fatty liver was measured by liver attenuation in Hounsfield units (LA), and VAT was quantified volumetrically. Cross-sectional associations between LA, VAT, and cardiometabolic risk factors were assessed using linear and logistic regression, and their joint associations were further examined in 4 subgroups: high-LA/low-VAT (n=1704), low-LA/low-VAT (n=422), high-LA/high-VAT (n=436), and low-LA/high-VAT (n=320). Both LA and VAT were associated with most cardiometabolic traits (all P<0.0001), which persisted after additional adjustment for each other (LA, P<0.01-0.0001; VAT, P<0.0001). In bootstrap analyses, the regression coefficient of VAT was significantly greater than LA for triglycerides, high-density lipoprotein cholesterol, impaired glucose, and metabolic syndrome (P=0.009-0.0001). The interaction between LA and VAT was significant for high-density lipoprotein cholesterol (P=0.002), impaired glucose (P=0.003), and metabolic syndrome (P=0.04). Among 4 subgroups, participants with higher VAT and lower LA had higher prevalence of cardiometabolic traits than those with each condition alone. CONCLUSION Both fatty liver and VAT are independent correlates of cardiometabolic risk, but the associations are stronger for VAT than for fatty liver.
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Large-scale international validation of the ADO index in subjects with COPD: an individual subject data analysis of 10 cohorts. BMJ Open 2012; 2:bmjopen-2012-002152. [PMID: 23242246 PMCID: PMC3533065 DOI: 10.1136/bmjopen-2012-002152] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Little evidence on the validity of simple and widely applicable tools to predict mortality in patients with chronic obstructive pulmonary disease (COPD) exists. OBJECTIVE To conduct a large international study to validate the ADO index that uses age, dyspnoea and FEV(1) to predict 3-year mortality and to update it in order to make prediction of mortality in COPD patients as generalisable as possible. DESIGN Individual subject data analysis of 10 European and American cohorts (n=13 914). SETTING Population-based, primary, secondary and tertiary care. PATIENTS COPD GOLD stages I-IV. MEASUREMENTS We validated the original ADO index. We then obtained an updated ADO index in half of our cohorts to improve its predictive accuracy, which in turn was validated comprehensively in the remaining cohorts using discrimination, calibration and decision curve analysis and a number of sensitivity analyses. RESULTS 1350 (9.7%) of all subjects with COPD (60% male, mean age 61 years, mean FEV(1) 66% predicted) had died at 3 years. The original ADO index showed high discrimination but poor calibration (p<0.001 for difference between predicted and observed risk). The updated ADO index (scores from 0 to 14) preserved excellent discrimination (area under curve 0.81, 95% CI 0.80 to 0.82) but showed much improved calibration with predicted 3-year risks from 0.7% (95% CI 0.6% to 0.9%, score of 0) to 64.5% (61.2% to 67.7%, score of 14). The ADO index showed higher net benefit in subjects at low-to-moderate risk of 3-year mortality than FEV(1) alone. INTERPRETATION The updated 15-point ADO index accurately predicts 3-year mortality across the COPD severity spectrum and can be used to inform patients about their prognosis, clinical trial study design or benefit harm assessment of medical interventions.
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Is Pericardial Fat a Regional Risk Factor for Pulmonary Vascular Health? The Association Between Pericardial Fat and Pulmonary Artery Systolic Pressure (The Jackson Heart Study). Chest 2011. [DOI: 10.1378/chest.1120174] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
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The socioeconomic gradient of diabetes prevalence, awareness, treatment, and control among African Americans in the Jackson Heart Study. Ann Epidemiol 2011; 21:892-8. [PMID: 21737303 DOI: 10.1016/j.annepidem.2011.05.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 04/22/2011] [Accepted: 05/01/2011] [Indexed: 10/18/2022]
Abstract
PURPOSE Little research has focused on the social patterning of diabetes among African Americans. We examined the relationship between socioeconomic status (SES) and the prevalence, awareness, treatment, and control of diabetes among African Americans. METHODS Education, income and occupation were examined among 4,303 participants (2,726 women and 1,577 men). Poisson regression estimated relative probabilities (RP) of diabetes outcomes by SES. RESULTS The prevalence of diabetes was 19.6% in women and 15.9% in men. Diabetes awareness, treatment, and control were 90.0%, 86.8%, and 39.2% in women, respectively, and 88.2%, 84.4%, and 35.9% in men, respectively. In adjusted models, low-income men and women had greater probabilities of diabetes than high-income men and women (RP, 1.94; 95% confidence interval [CI], 1.28-2.92; and RP, 1.35; 95% CI, 1.04-1.74, respectively). Lack of awareness was associated with low education and low occupation in women (RP, 2.28; 95%CI 1.01-5.18; and RP, 2.62; 95% CI, 1.08-6.33, respectively) but not in men. Lack of treatment was associated with low education in women. Diabetes control was not patterned by SES. CONCLUSIONS Diabetes prevalence is patterned by SES, and awareness and treatment are patterned by SES in women but not men. Efforts to prevent diabetes in African Americans need to address the factors that place those of low SES at higher risk.
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Ian Michael Elliott. West J Med 2001. [DOI: 10.1136/bmj.323.7323.1255e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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Measurement and prediction of the rates of spontaneous transfer of phospholipids between plasma lipoproteins. BIOCHIMICA ET BIOPHYSICA ACTA 1984; 794:274-80. [PMID: 6733137 DOI: 10.1016/0005-2760(84)90156-5] [Citation(s) in RCA: 85] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The purpose of this report is to develop a correlation between the hydrophobicity of a phospholipid as measured by reversed-phase high-performance liquid chromatography and its rate of spontaneous transfer and to use this correlation to predict the rate of transfer of any homologous lipid from any lipoprotein. We have studied the mechanism of transfer of a series of fluorescent or radiolabeled phospholipids among natural and reassembled serum lipoproteins. Fluorescent phosphatidylcholines included those with 9-(1-pyrenyl)nonanoic acid in the sn-2 position and lauric, myristic, palmitic, stearic, oleic or linoleic acid at sn-1. The radioactive phosphatidylcholines contained [3H]oleic acid in the sn-2 position and lauric, myristic, or palmitic acid at sn-1. The kinetics of transfer of the pyrene-labeled lipid were followed by changes in the excimer fluorescence, and that of the radioactive lipids by separation of the donor (lipid-apolipoprotein recombinant) from the acceptor (single bilayer vesicles) on a column of Sephacryl S-200. The retention time of each lipid was measured by high-performance hydrophobic chromatography through a Waters radially compressed C18 column eluted with 75% isopropanol and 25% triethylammonium phosphate (0.15 M). A linear relationship was observed between the rate-constant of transfer and the retention time which suggest that the rate of desorption of phosphatidylcholines from lipoproteins and vesicles is controlled predominately by the hydrophobic effect. For a homologous series of lipids, the rate of transfer can be predicted from retention times obtained from hydrophobic chromatography. The kinetics of transfer of 1-lauroyl-2-[9-(1-pyrenyl)nonanoyl] phosphatidylcholine between isolated human serum lipoproteins exhibits a linear correlation between the transfer half-time and the size of the donor lipoproteins. As a consequence, transfer from very-low-density lipoprotein is 10-times slower than that observed from high-density lipoproteins. The observed correlations between phospholipid transfer rates and both the Stokes radius of the donor and the retention time of the phospholipid on a hydrophobic column permit one to calculate the rate of transfer of homologous molecules between lipid-protein complexes. The results predict that the spontaneous transfer of phospholipids between plasma lipoproteins would be too slow to be a physiologically important phenomena.
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Kinetics of spontaneous and plasma-stimulated sphingomyelin transfer. BIOCHIMICA ET BIOPHYSICA ACTA 1982; 712:169-76. [PMID: 6810944 DOI: 10.1016/0005-2760(82)90099-6] [Citation(s) in RCA: 38] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The mechanism of transfer of a pyrene-labeled sphingomyelin (PySM) between different lipid compartments was studied by a fluorescence technique. The first-order kinetics are independent of donor and acceptor concentration and the identity of the acceptor; the rates are accelerated by 'structure-breaking' solutes and inhibited by 'structure-making' solutes. These observations are consistent with the transfer of PySM occurring via the aqueous phase that separates the donor and acceptor compartments. We have partially purified a plasma factor that stimulates the transfer rate. Our in vitro results suggest that both spontaneous and stimulated transfer might contribute to the redistribution of sphingomyelin in vivo,
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Kinetics and mechanism of association of human plasma apolipoproteins with dimyristoylphosphatidylcholine: effect of protein structure and lipid clusters on reaction rates. Biochemistry 1981; 20:6630-5. [PMID: 7306528 DOI: 10.1021/bi00526a017] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We have used a series of lipid-associating proteins with similar pI's and with molecular weights between 2280 and 28000 to study the mechanism of lipid-protein association. All of these polypeptides spontaneously associate with dimyristoylphosphatidylcholine (DMPC) to give quasi-discrete products. The reaction of the apoproteins with unsaturated lecithins is slow, if it occurs at all. Our data support the Kanehisa-Tsong cluster model [Kanehisa & Tsong (1978) J. Am. Chem. Soc. 100, 424] of lipid permeability in many of its qualitative aspects. These are (a) that the rate of lipid- protein association increases with decreasing polypeptide molecular weight, (b) that there is a small temperature dependence for the rate of association of small peptides with DMPC but with large polypeptides the temperature at which association with lipid is rapid is confined to the solid leads to fluid transition temperature (Tc) of DMPC, and (c) that the rate is asymmetric about Tc, with the change in the rate with respect to temperature below Tc being greater than at T greater than Tc. In addition, we have shown that unfolded monomeric proteins with a large number of exposed hydrophobic residues associate with DMPC faster than self-associated and/or folded proteins. Our data suggest that the association of some of the apoproteins with phospholipids is subject to kinetic control.
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Thermodynamics of lipid-protein association. The free energy of association of lecithin with reduced and carboxymethylated apolipoprotein A-II from human plasma high density lipoprotein. J Biol Chem 1981; 256:9849-54. [PMID: 6792197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
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Thermodynamics of lipid-protein association. The free energy of association of lecithin with reduced and carboxymethylated apolipoprotein A-II from human plasma high density lipoprotein. J Biol Chem 1981. [DOI: 10.1016/s0021-9258(19)68707-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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