Linking Cardiac Psychology and Cardiovascular Medicine via Self-Determination Theory and Shared Decision-Making

Despite considerable progress in recent years, research in cardiac psychology is not widely translated into routine practice by clinical cardiologists or clinical health psychologists. Self-determination theory (SDT), which addresses how basic psychological needs of autonomy, competence, and relatedness contribute to the internalization of motivation, may help bridge this research-practice gap through its application to shared decision-making (SDM). This narrative review discusses the following: (a) brief background information on SDT and SDM, (b) the application of SDT to health behavior change and cardiology interventions, and (c) how SDT and SDM may be merged using a dissemination and implementation (D&I) framework. We address barriers to implementing SDM in cardiology, how SDM and SDT address the need for respect of patient autonomy, and how SDT can enhance D&I of SDM interventions through its focus on autonomy, competence, and relatedness and its consideration of other constructs that facilitate the internalization of motivation.

Do Purpose in Life and Social Support Mediate the Association between Religiousness/Spirituality and Mortality? Evidence from the MIDUS National Sample

We examined prospective associations between religiousness/spirituality (R/S; i.e., service attendance, R/S identity, R/S coping, spirituality) and all-cause mortality in the Midlife in the United States (MIDUS) sample, including whether having a purpose in life and positive social support are indirect pathways through which R/S predicts mortality. We examined service attendance and a composite of R/S identity, R/S coping, and spirituality from the baseline wave (1995-1996; n = 6120 with complete data), purpose in life and positive social support from the second wave (2004-2006), and vital status through 2020 (n = 1711 decedents). Cox regression models showed that attending religious services more than weekly and approximately weekly was associated with a lower mortality risk compared to never attending in the adjusted models (>weekly vs. never, HR (95% CI) = 0.72 (0.61, 0.85); weekly vs. never, HR (95% CI) = 0.76 (0.66, 0.88)). The R/S composite was also associated with lower mortality risk in the adjusted models (HR (95% CI) = 0.92 (0.87, 0.97)). Indirect effects from R/S to mortality via purpose in life and positive social support were significantly different from zero. These findings highlight the importance of multidimensional aspects of R/S for population health and point to purpose in life and positive social support as underlying pathways between R/S and mortality.

Meaning Salience and Meaning in Life Prospectively Predict Lower Distress During the COVID-19 Pandemic

BACKGROUND

The COVID-19 pandemic is a widespread source of stress with adverse mental health impacts. Meaning in life, both as a trait and as momentary awareness of what is personally meaningful (meaning salience), is associated with positive health outcomes and may buffer against the deleterious effects of stress.

PURPOSE

This project examines prospective associations between baseline meaning salience (daily, post-laboratory stressor) and meaning in life with perceived stress during COVID-19.

METHODS

A community sample of healthy adults (n = 147) completed a laboratory stress protocol in 2018-2019, where perceived stress, meaning in life, and meaning salience (daily, post-stressor) were assessed. During April and July 2020 (n = 95, and 97, respectively), participants were re-contacted and reported perceived stress. General linear mixed-effects models accounting for repeated measures of stress during COVID-19 were conducted.

RESULTS

Partial correlations holding constant baseline perceived stress showed that COVID-19 perceived stress was correlated with daily meaning salience (r = -.28), post-stressor meaning salience (r = -.20), and meaning in life (r = -.22). In mixed-effects models, daily and post-stressor meaning salience and higher meaning in life, respectively, predicted lower perceived stress during COVID-19, controlling for age, gender, and baseline perceived stress.

CONCLUSIONS

Individuals more capable of accessing meaning when exposed to laboratory stress reported lower perceived stress during a global health crisis. Despite study limitations concerning generalizability, results support meaning in life and meaning salience as important aspects of psychological functioning that may promote well-being by affecting stress appraisals and available resources for coping.

Psychological well-being, education, and mortality

OBJECTIVES

Research on older adults often focuses on mitigating health risks, and less is known about protective factors that contribute to longer, healthier lives. We examine longitudinal associations between psychological well-being and mortality among a national sample of older adults and test competing hypotheses about whether the education/mortality association depends on the level of psychological well-being.

METHOD

We use six waves (2006-2016) of the Health and Retirement Study, a national sample of adults over age 50 (n = 21,172), with 14 years of mortality follow-up. Psychological well-being is measured up to three times and includes positive affect, life satisfaction, purpose in life, social support, and optimism. Discrete-time survival models examine (a) the association between time-varying psychological well-being and mortality, and (b) interactions between psychological well-being and education on mortality.

RESULTS

Higher purpose in life, positive affect, optimism, social support, and life satisfaction predicted lower mortality. A 1 SD increase in most measures of psychological well-being was associated with a 2-4 year increase in life expectancy at age 50. Positive affect and purpose in life moderated the education/mortality association-the inverse association between education and mortality was stronger for those with high psychological well-being.

CONCLUSIONS

We find strong evidence that psychological well-being predicts lower mortality risk and modifies the association between education and mortality. The inverse association between education and mortality becomes stronger at higher levels of purpose in life and positive affect. Therefore, efforts to promote life satisfaction, social support, and optimism may support longer lives without widening education disparities. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Effects of the Great Recession on Educational Disparities in Cardiometabolic Health

BACKGROUND

Macroeconomic crises can exaggerate existing educational disparities in health. Few studies, however, have examined whether macroeconomic crises get under the skin to affect educational disparities in health-related biological processes.

PURPOSE

This study aimed to examine the effect of the economic recession of 2008 (i.e., Great Recession) on educational disparities in cardiometabolic risk and self-reported psychological distress.

METHODS

Data were drawn from two subsamples of the Midlife in the United States (MIDUS) study: the second wave of the MIDUS sample (pre-recession cohort, N = 985) and the refresher sample (post-recession cohort, N = 863). Educational attainment was categorized into high school education or less, some college, and bachelor's degree or higher. Outcomes included metabolic syndrome, C-reactive protein, and interleukin-6, as well as self-reported perceived stress, depressive symptoms, and financial distress.

RESULTS

Results showed that having a bachelor's degree or higher (compared to having a high school education or less) was more strongly associated with decreased metabolic syndrome symptoms in the post-recession cohort than the pre-recession cohort, above and beyond demographic, health, and behavioral covariates. These findings did not extend to systemic inflammation or psychological distress.

CONCLUSIONS

Our findings suggest that chronic macroeconomic stressors may widen the educational gap in physical health, particularly cardiometabolic health, by modifying biological and anthropometric risk factors implicated in metabolic syndrome.

Childhood socioeconomic status and inflammation: Psychological moderators among Black and White Americans

OBJECTIVE

The current study examined race differences in how childhood socioeconomic status (SES) predicted midlife inflammation. It also tested psychological resources (purpose in life, optimism, and conscientiousness) as moderators of the association between childhood SES and inflammation among Black and White adults.

METHOD

Data came from the biomarker subsamples of the Midlife in the United States Core and Refresher studies (n = 1,578 White and n = 395 Black participants). Childhood SES was operationalized as a composite of parental education, perceived financial status, and welfare status. Outcomes included circulating IL-6 and CRP.

RESULTS

Childhood SES did not predict IL-6 or CRP among Black or White adults in fully adjusted models. Among Black adults with low optimism, lower childhood SES predicted higher IL-6 and CRP. Among Black adults with low purpose in life, lower childhood SES predicted higher CRP (but not IL-6). Conscientiousness did not moderate childhood SES-inflammation associations among Black adults. Among White adults with low conscientiousness or low optimism, lower childhood SES predicted higher IL-6 (but not CRP). Purpose in life did not moderate associations among White adults. Effect sizes were small (≤1% variance explained) and comparable to effects of clinical risk factors in this sample (e.g., age, chronic conditions).

CONCLUSIONS

Race differences in the childhood SES and inflammation association were not apparent. Childhood SES was linked to inflammation more strongly among those with fewer psychological resources across both racial groups. Psychological resources may be important moderators of inflammation in the context of early life SES disadvantage. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

The Pathway From Social Status to Physical Health: Taking a Closer Look at Stress as a Mediator

Stress is often invoked as a potential contributor to disparities in physical health as a function of social status. Although there is good reason to believe that stress exposure and stress responses may be an important pathway linking lower social status to poor health, direct evidence is lacking. We summarize the evidence for this pathway and limitations of that evidence, focusing particularly on how stress is conceptualized and measured. We argue that in addition to more direct tests of mediation, the measurement of the mediator—stress—could also be improved. We also propose that measuring theory-specific stress exposures may be more fruitful than assessing general stress exposures (e.g., life events, global perceived stress) by increasing theoretical clarity and predictive utility of stress in this context.

Pathways Linking Childhood SES and Adult Health Behaviors and Psychological Resources in Black and White Men

Background

Exposure to low socioeconomic status (SES) in childhood predicts increased morbidity and mortality. However, little prospective evidence is available to test pathways linking low childhood SES to adult health.

Purpose

In the current study, indirect effects through positive parenting in adolescence and adult SES were tested in the association between childhood SES and adult health behaviors and psychological resources.

Methods

Men (n = 305; 53% Black) were followed longitudinally from ages 7 to 32. SES was measured annually in childhood (ages 7-9) and again in adulthood (age 32) using the Hollingshead index. Parenting was assessed annually (ages 13-16) using caregivers' and boys' self-report of supervision, communication, and expectations for their son's future. Health behaviors (cigarette and alcohol use, fruit and vegetable consumption, and physical activity) and psychological resources (optimism, purpose in life, self-mastery, and self-esteem) were assessed in adulthood (age 32).

Results

Structural equation modeling showed that higher childhood SES was associated with more positive parenting in adolescence and higher adult SES. Higher childhood SES was indirectly associated with healthier behaviors and higher psychological resources in adulthood through pathways involving positive parenting during adolescence and SES in adulthood. Findings were consistent in both racial groups.

Conclusions

Positive parenting in adolescence was an important pathway in understanding associations among childhood SES and health behaviors and psychological resources in adulthood. Low childhood SES was prospectively associated with healthier behaviors and greater psychological resources in part through more positive parenting in adolescence.

Behavioral Adjustment Moderates the Link Between Neuroticism and Biological Health Risk: A U.S.-Japan Comparison Study

Neuroticism, a broad personality trait linked to negative emotions, is consistently linked to ill health when self-report is used to assess health. However, when health risk is assessed with biomarkers, the evidence is inconsistent. Here, we tested the hypothesis that the association between neuroticism and biological health risk is moderated by behavioral adjustment, a propensity to flexibly adjust behaviors to environmental contingencies. Using a U.S.-Japan cross-cultural survey, we found that neuroticism was linked to lower biological health risk for those who are high, but not low, in behavioral adjustment. Importantly, Japanese were higher in behavioral adjustment than European Americans, and as predicted by this cultural difference, neuroticism was linked to lower biological health risk for Japanese but not for European Americans. Finally, consistent with prior evidence, neuroticism was associated with worse self-reported health regardless of behavioral adjustment or culture. Discussion focused on the significance of identifying sociocultural correlates of biological health.

Culture and social hierarchy: Self- and other-oriented correlates of socioeconomic status across cultures

Current theorizing on socioeconomic status (SES) focuses on the availability of resources and the freedom they afford as a key determinant of the association between high SES and stronger orientation toward the self and, by implication, weaker orientation toward others. However, this work relies nearly exclusively on data from Western countries where self-orientation is strongly sanctioned. In the present work, we predicted and found that especially in East Asian countries, where other-orientation is strongly sanctioned, high SES is associated with stronger other-orientation as well as with self-orientation. We first examined both psychological attributes (Study 1, N = 2,832) and socialization values (Study 2a, N = 4,675) in Japan and the United States. In line with the existent evidence, SES was associated with greater self-oriented psychological attributes and socialization values in both the U.S. and Japan. Importantly, however, higher SES was associated with greater other orientation in Japan, whereas this association was weaker or even reversed in the United States. Study 2b (N = 85,296) indicated that the positive association between SES and self-orientation is found, overall, across 60 nations. Further, Study 2b showed that the positive association between SES and other-orientation in Japan can be generalized to other Confucian cultures, whereas the negative association between SES and other-orientation in the U.S. can be generalized to other Frontier cultures. Implications of the current findings for modernization and globalization are discussed. (PsycINFO Database Record

Socioeconomic Status and Cardiovascular Responses to Standardized Stressors: A Systematic Review and Meta-Analysis

OBJECTIVE

Disparities in cardiovascular health by socioeconomic status (SES) are a pressing public health concern. Hypothesized mechanisms linking low SES to poor health are large cardiovascular responses to and delayed recovery from psychological stress. The current study presents a meta-analysis of the literature on the association of SES with blood pressure and heart rate reactivity to and recovery from acute stress tasks.

METHODS

The PubMed database was searched, and 26 unique studies with relevant data were identified (k = 25 reactivity [n = 14,617], k = 6 recovery [n = 1,324]).

RESULTS

Using random-effects models, no significant association between SES and cardiovascular reactivity to stress emerged (r = .008, 95% confidence interval = -.02 to .04), although higher SES was associated with better recovery from stress (r = -.14, 95% confidence interval -.23 to -.05). Stressor type moderated the reactivity effect, wherein higher SES was associated with greater reactivity to cognitive stressors (r = .036, p = .024), not with reactivity to interpersonal stressors (r = -.02, p = .62), but was associated with lower reactivity to tasks with combinations of cognitive, interpersonal, and physical challenges (r = -.12, p = .029). Accounting for publication bias revealed a significant association between SES and reactivity in the opposite direction of hypotheses.

CONCLUSIONS

Cardiovascular recovery from acute stress, but not reactivity to stress, may be a key pathway between low SES and risk for cardiovascular diseases. Heterogeneity in effect size and direction, challenges related to working across temporal dynamics, and recommendations for future research are discussed.

Psychological resources and glucoregulation in Japanese adults: Findings from MIDJA

OBJECTIVE

To examine associations between glucoregulation and 3 categories of psychological resources: hedonic well-being (i.e., life satisfaction, positive affect), eudaimonic well-being (i.e., personal growth, purpose in life, ikigai), and interdependent well-being (i.e., gratitude, peaceful disengagement, adjustment) among Japanese adults. The question is important given increases in rates of type 2 diabetes in Japan in recent years, combined with the fact that most prior studies linking psychological resources to better physical health have utilized Western samples.

METHOD

Data came from the Midlife in Japan Study involving randomly selected participants from the Tokyo metropolitan area, a subsample of whom completed biological data collection (N = 382; 56.0% female; M(SD)age = 55.5(14.0) years). Glycosylated hemoglobin (HbA1c) was the outcome. Models adjusted for age, gender, educational attainment, smoking, alcohol, chronic conditions, body mass index (BMI), use of antidiabetic medication, and negative affect.

RESULTS

Purpose in life (β = -.104, p = .021) was associated with lower HbA1c, and peaceful disengagement (β = .129, p = .003) was associated with higher HbA1c in fully adjusted models. Comparable to the effects of BMI, a 1 standard deviation change in well-being was associated with a .1% change in HbA1c.

CONCLUSIONS

Associations among psychological resources and glucoregulation were mixed. Healthy glucoregulation was evident among Japanese adults with higher levels of purpose in life and lower levels of peaceful disengagement, thereby extending prior research from the United States. The results emphasize the need for considering sociocultural contexts in which psychological resources are experienced in order to understand linkages to physical health. (PsycINFO Database Record

Moving up matters: Socioeconomic mobility prospectively predicts better physical health

OBJECTIVE

Low socioeconomic status (SES) in childhood confers risk for poor physical health later in life. This study prospectively examines whether improvements in family SES protect youth from developing physical health problems by adulthood and whether such effects differ by race or age.

METHOD

Participants are a school-based sample of urban Black (53%) and White (47%) men (N = 311). Using latent growth curve modeling, we prospectively examined whether changes in family SES measured annually between Ages 7 and 16 predicted physical health diagnoses in adulthood (Age 32). Family SES was assessed as a weighted composite of parental education and occupational status. Physical health diagnoses were assessed as a count of self-reported medical conditions from a health history interview.

RESULTS

Consistent with macroeconomic trends, on average, family SES increased until the early 1990s, then remained flat until rising again in the mid-1990s. During each of 3 independent developmental periods, boys raised in families who experienced more positive changes in SES reported fewer physical health diagnoses in adulthood. These effects did not vary significantly by race and remained after controlling for initial childhood SES, childhood health problems, concurrent adult SES, and weight (Body Mass Index or reported overweight).

CONCLUSIONS

Initial childhood SES did not predict physical health, whereas relative improvements in SES over a 10-year period did. If the families of Black and White boys were upwardly mobile, it appeared to protect them from developing physical disease, and upward mobility was additively protective across developmental periods examined here. (PsycINFO Database Record

Racial disparities in sleep: the role of neighborhood disadvantage

OBJECTIVE

Disparities in sleep duration and efficiency between Black/African American (AA) and White/European American (EA) adults are well-documented. The objective of this study was to examine neighborhood disadvantage as an explanation for race differences in objectively measured sleep.

METHODS

Data were from 133 AA and 293 EA adults who participated in the sleep assessment protocol of the Midlife in the United States (MIDUS) study (57% female; Mean Age = 56.8 years, SD = 11.4). Sleep minutes, onset latency, and waking after sleep onset (WASO) were assessed over seven nights using wrist actigraphy. Neighborhood characteristics were assessed by linking home addresses to tract-level socioeconomic data from the 2000 US Census. Multilevel models estimated associations between neighborhood disadvantage and sleep, and the degree to which neighborhood disadvantage mediated race differences in sleep controlling for family socioeconomic position and demographic variables.

RESULTS

AAs had shorter sleep duration, greater onset latency, and higher WASO than EAs (ps < 0.001). Neighborhood disadvantage was significantly associated with WASO (B = 3.54, p = 0.028), but not sleep minutes (B = -2.21, p = 0.60) or latency (B = 1.55, p = 0.38). Furthermore, race was indirectly associated with WASO via neighborhood disadvantage (B = 4.63, p = 0.035), which explained 24% of the race difference. When measures of depression, health behaviors, and obesity were added to the model, the association between neighborhood disadvantage and WASO was attenuated by 11% but remained significant.

CONCLUSION

Findings suggest that neighborhood disadvantage mediates a portion of race differences in WASO, an important indicator of sleep efficiency.

Culture and Healthy Eating: The Role of Independence and Interdependence in the United States and Japan

Healthy eating is important for physical health. Using large probability samples of middle-aged adults in the United States and Japan, we show that fitting with the culturally normative way of being predicts healthy eating. In the United States, a culture that prioritizes and emphasizes independence, being independent predicts eating a healthy diet (an index of fish, protein, fruit, vegetables, reverse-coded sugared beverages, and reverse-coded high fat meat consumption; Study 1) and not using nonmeat food as a way to cope with stress (Study 2a). In Japan, a culture that prioritizes and emphasizes interdependence, being interdependent predicts eating a healthy diet (Studies 1 and 2b). Furthermore, reflecting the types of agency that are prevalent in each context, these relationships are mediated by autonomy in the United States and positive relations with others in Japan. These findings highlight the importance of understanding cultural differences in shaping healthy behavior and have implications for designing health-promoting interventions.

Educational Status, Anger, and Inflammation in the MIDUS National Sample: Does Race Matter?

BACKGROUND

Racial differences in anger frequency and expression styles have been found. Further, African Americans receive fewer health benefits from higher education than Whites.

PURPOSE

This study seeks to investigate racial differences in how anger moderates the association between education and inflammation.

METHODS

Midlife in the US participants (n = 1,200; 43.0 % male; 18.5 % African American) provided education and anger data via survey assessments. Interleukin-6 (IL-6) and fibrinogen were determined from a fasting blood sample following an overnight clinic visit.

RESULTS

African Americans reported higher anger-out, IL-6, and fibrinogen and lower anger-control than Whites. Anger-out predicted higher IL-6 and fibrinogen among African Americans with higher education; whereas, trait anger and anger-out predicted lower fibrinogen among Whites with higher education. Anger-out marginally predicted higher IL-6 in less educated Whites.

CONCLUSIONS

Findings underscore racial differences in the benefits and consequences of educational attainment, and how social inequities and anger are manifested in inflammatory physiology.

Childhood socioeconomic status and cardiovascular reactivity and recovery among Black and White men: Mitigating effects of psychological resources

OBJECTIVE

To evaluate a possible physiological mechanism underlying links between low childhood socioeconomic status (SES) and poor adult health by (a) testing whether childhood SES is prospectively related to cardiovascular responses to laboratory stress in adulthood, and (b) by determining whether psychological resources buffer cardiovascular reactivity and promote better recovery from stress.

METHOD

Participants (n = 246; 55% Black; mean age = 32 years) were from a population-based sample of men in Pittsburgh, PA. Childhood SES was measured through the Hollingshead index (parental education and occupation) across 10 waves between the ages of 6 and 16. In adulthood, cardiovascular measures, including systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), and high-frequency heart rate variability (HF-HRV), were taken during and following standardized laboratory psychological stressors. Participants completed measures of optimism, purpose in life, self-esteem, positive affect, and self-mastery, which were combined into a psychological resource factor.

RESULTS

Lower childhood SES predicted higher HR and SBP at recovery, independent of age, race, body mass index, current smoking, task demand, and current SES. Psychological resources moderated the association between childhood SES and SBP. Lower childhood SES predicted SBP recovery only among men with fewer psychological resources.

CONCLUSIONS

Psychological resources may buffer the relation between low childhood SES and cardiovascular recovery from stress. This buffering may improve adult health to the extent that cardiovascular recovery contributes to the risk of low childhood SES for subsequent disease. (PsycINFO Database Record

Expression of anger and ill health in two cultures: an examination of inflammation and cardiovascular risk

Expression of anger is associated with biological health risk (BHR) in Western cultures. However, recent evidence documenting culturally divergent functions of the expression of anger suggests that its link with BHR may be moderated by culture. To test this prediction, we examined large probability samples of both Japanese and Americans using multiple measures of BHR, including pro-inflammatory markers (interleukin-6 and C-reactive protein) and indices of cardiovascular malfunction (systolic blood pressure and ratio of total to HDL cholesterol). We found that the link between greater expression of anger and increased BHR was robust for Americans. As predicted, however, this association was diametrically reversed for Japanese, among whom greater expression of anger predicted reduced BHR. These patterns were unique to the expressive facet of anger and remained after we controlled for age, gender, health status, health behaviors, social status, and reported experience of negative emotions. Implications for sociocultural modulation of bio-physiological responses are discussed.

Social status and anger expression: the cultural moderation hypothesis

Individuals with lower social status have been reported to express more anger, but this evidence comes mostly from Western cultures. Here, we used representative samples of American and Japanese adults and tested the hypothesis that the association between social status and anger expression depends on whether anger serves primarily to vent frustration, as in the United States, or to display authority, as in Japan. Consistent with the assumption that lower social standing is associated with greater frustration stemming from life adversities and blocked goals, Americans with lower social status expressed more anger, with the relationship mediated by the extent of frustration. In contrast, consistent with the assumption that higher social standing affords a privilege to display anger, Japanese with higher social status expressed more anger, with the relationship mediated by decision-making authority. As expected, anger expression was predicted by subjective social status among Americans and by objective social status among Japanese. Implications for the dynamic construction of anger and anger expression are discussed.

Purpose in life predicts better emotional recovery from negative stimuli

Purpose in life predicts both health and longevity suggesting that the ability to find meaning from life’s experiences, especially when confronting life’s challenges, may be a mechanism underlying resilience. Having purpose in life may motivate reframing stressful situations to deal with them more productively, thereby facilitating recovery from stress and trauma. In turn, enhanced ability to recover from negative events may allow a person to achieve or maintain a feeling of greater purpose in life over time. In a large sample of adults (aged 36-84 years) from the MIDUS study (Midlife in the U.S., http://www.midus.wisc.edu/), we tested whether purpose in life was associated with better emotional recovery following exposure to negative picture stimuli indexed by the magnitude of the eyeblink startle reflex (EBR), a measure sensitive to emotional state. We differentiated between initial emotional reactivity (during stimulus presentation) and emotional recovery (occurring after stimulus offset). Greater purpose in life, assessed over two years prior, predicted better recovery from negative stimuli indexed by a smaller eyeblink after negative pictures offset, even after controlling for initial reactivity to the stimuli during the picture presentation, gender, age, trait affect, and other well-being dimensions. These data suggest a proximal mechanism by which purpose in life may afford protection from negative events and confer resilience is through enhanced automatic emotion regulation after negative emotional provocation.

Negative emotions predict elevated interleukin-6 in the United States but not in Japan

Previous studies conducted in Western cultures have shown that negative emotions predict higher levels of pro-inflammatory biomarkers, specifically interleukin-6 (IL-6). This link between negative emotions and IL-6 may be specific to Western cultures where negative emotions are perceived to be problematic and thus may not extend to Eastern cultures where negative emotions are seen as acceptable and normal. Using samples of 1044 American and 382 Japanese middle-aged and older adults, we investigated whether the relationship between negative emotions and IL-6 varies by cultural context. Negative emotions predicted higher IL-6 among American adults, whereas no association was evident among Japanese adults. Furthermore, the interaction between culture and negative emotions remained even after controlling for demographic variables, psychological factors (positive emotions, neuroticism, extraversion), health behaviors (smoking status, alcohol consumption), and health status (chronic conditions, BMI). These findings highlight the role of cultural context in shaping how negative emotions affect inflammatory physiology and underscore the importance of cultural ideas and practices relevant to negative emotions for understanding of the interplay between psychology, physiology, and health.

High anger expression exacerbates the relationship between age and metabolic syndrome

OBJECTIVE

Building on prior work linking high anger expression to poor health, this cross-sectional study addressed whether anger expression exacerbated age-related risk for metabolic syndrome in a national sample of adults, known as MIDUS (Midlife in the United States).

METHOD

Respondents reported anger expression via survey assessments and completed an overnight clinic visit.

RESULTS

Unadjusted metabolic syndrome prevalence was 40.6%. Men, less educated individuals, and those who reported not getting regular physical activity were at significantly higher risk for metabolic syndrome. Anger expression did not predict higher risk for metabolic syndrome in main effects models, but it moderated the relationship between age and metabolic syndrome. Age-associated risk for metabolic syndrome was significant only for adults with high anger expression.

DISCUSSION

Among older adults, anger expression predicted higher prevalence of metabolic syndrome. Older adults reporting low anger expression had metabolic syndrome rates comparable to younger adults. Results highlight that failing to show the frequently observed decline in anger expression with age may have pernicious health concomitants.

Ribosomal protein S6 phosphorylation and function during late gestation liver development in the rat

The phosphorylation of ribosomal protein S6 is thought to be required for biosynthesis of the cell's translational apparatus, a critical component of cell growth and proliferation. We have studied the signal transduction pathways involved in hepatic S6 phosphorylation during late gestation in the rat. This is a period during which hepatocytes show a high rate of proliferation that is, at least in part, independent of mitogenic signaling pathways that are operative in mature hepatocytes. Our initial studies demonstrated that there was low basal activity of two S6 kinases in liver, S6K1 and S6K2, on embryonic day 19 (2 days preterm). In addition, insulin- and growth factor-mediated S6K1 and S6K2 activation was markedly attenuated compared with that in adult liver. Nonetheless, two-dimensional gel electrophoresis demonstrated that fetal liver S6 itself was highly phosphorylated. To characterize the fetal hepatocyte pathway for S6 phosphorylation, we went on to study the sensitivity of hepatocyte proliferation to the S6 kinase inhibitor rapamycin. Unexpectedly, administration of rapamycin to embryonic day 19 fetuses in situ did not affect hepatocyte DNA synthesis. This resistance to the growth inhibitory effect of rapamycin occurred even though S6K1 and S6K2 were inhibited. Furthermore, fetal hepatocyte proliferation was sustained even though rapamycin administration resulted in the dephosphorylation of ribosomal protein S6. In contrast, rapamycin blocked hepatic DNA synthesis in adult rats following partial hepatectomy coincident with S6 dephosphorylation. We conclude that hepatocyte proliferation in the late gestation fetus is supported by a rapamycin-resistant mechanism that can function independently of ribosomal protein S6 phosphorylation.

Growth regulation via p38 mitogen-activated protein kinase in developing liver

During normal development in the rat, hepatocytes undergo marked changes in the rate of proliferation. We have previously observed transient G(1) growth arrest at term, re-activation of proliferation immediately after birth, and a gradual transition to the quiescent adult hepatocyte phenotype after postnatal day 4. We hypothesized that these changes in proliferation are due in part to growth inhibitory effects mediated by the p38 mitogen-activated protein kinase pathway. p38 kinase activity measurements showed an inverse relationship with hepatocyte proliferation during the perinatal and postnatal transitions, whereas p38 content remained constant. Anisomycin activated the p38 pathway in fetal hepatocyte cultures while inducing growth inhibition that was sensitive to the p38 inhibitor, SB203580. Activation of p38 in these cultures, via transient transfection with a constitutively active form of its upstream kinase MKK6, also inhibited DNA synthesis as well as reducing cyclin D1 content. Transfection with inactive MKK6 did neither. Furthermore, MKK6-induced growth arrest was sensitive to SB203580. Finally, administration of SB203580 to near-term fetal rats in utero abrogated the transient hepatocyte growth arrest that occurs at term. These findings indicate a role for the p38 mitogen-activated protein kinase pathway in the physiological regulation of hepatocyte proliferation during normal development in the rat.

Identification of candidate growth-regulating genes that are overexpressed in late gestation fetal liver in the rat

We have shown previously that hepatocyte proliferation in the late gestation fetal rat is mediated by growth factor-independent mechanisms that are distinct from the signaling pathways that promote proliferation of adult rat hepatocytes. In the present studies, we identified six candidate growth-regulating genes that are overexpressed in fetal rat liver (embryonic day 19, 2 days pre-term) relative to adult rat liver using suppressive subtractive hybridization. These included the following: Grb10, a growth factor receptor binding protein; eps15, a growth factor receptor substrate; nuc2+, a retinoblastoma protein binding protein; cdc25B, a cell cycle tyrosine phosphatase; the peroxisome proliferator-activated receptor PPAR alpha; and a deoxyuridine triphosphatase that functions as a PPAR alpha binding partner. In every case, the ontogeny of the expression of these genes declined postnatally in a manner consistent with the transition from a fetal to an adult hepatocyte phenotype. None were found to be cell cycle-dependent, in that they did not show expression that followed perinatal changes in hepatocyte cell cycle activity. Based on our identification of these genes and previous work characterizing their role in growth regulation, we conclude that they may contribute to the mitogenic signaling phenotype of fetal rat hepatocytes.

Hepatic epidermal growth factor-regulated mitogen-activated protein kinase kinase kinase activity in the rat: lack of identity with known forms of raf and MEKK

Mitogenic signaling involves protein kinases that phosphorylate the mitogen-activated protein kinase (MAPK) activator, MEK. In rats, basal hepatic MEK kinase activity is low in vivo in both adult rats and late gestation fetal rats, and is markedly stimulated by intraperitoneal administration of epidermal growth factor (EGF). The level of stimulated MEK phosphorylating activity is approximately 15 times higher in fetal liver than in adult liver. To identify regulated forms of the two categories of MEK kinase, Raf and MEKK, Western immunoblotting, immunoprecipitation kinase assays and immunodepletion studies were performed. Western immunoblotting confirmed that Raf-1, A-Raf, B-Raf, MEKK1 and MEKK2 were present at similar levels in E19 and adult liver. However, specific immunoprecipitation kinase assays did not detect any kinases that could account for marked EGF sensitivity or the higher level of activity in E19 fetuses. Immunodepletion studies produced a marked reduction in immunoreactive Raf/MEKK content and activity, but a minimal decrease in the ability of chromatography fractions to phosphorylate and activate recombinant MEK-1. Our results indicate that hepatic, EGF-sensitive MEK kinase activity may reside with a previously unidentified and physiologically relevant form of Raf and/or MEKK.

Uncoupling of hepatic, epidermal growth factor-mediated mitogen-activated protein kinase activation in the fetal rat

Stimulation of cell proliferation by mitogens involves tyrosine phosphorylation of proteins at the cell membrane by receptor tyrosine kinases. This promotes formation of multi-protein complexes that can activate the small G-protein, Ras. Activation of Ras, in turn, leads to sequential activation of the following three serine-threonine kinases: Raf, extracellular signal-regulated kinase kinase (MEK), and members of the family of mitogen-activated protein (MAP) kinases. Prior studies have shown that intraperitoneal injection of epidermal growth factor (EGF) leads to rapid activation of hepatic MAP kinases in adult rats but not in late gestation (E19) fetal rats (Boylan, J. M., and Gruppuso, P. A. (1996) Cell Growth & Differ. 7, 1261-1269). The present studies were undertaken to determine the mechanism for this "uncoupling" of the MAP kinase pathway. E19 fetal rats and adult male rats were injected with EGF (0.5 microg/g body weight, intraperitoneally) or with saline. After 15 min, livers were removed and prepared for kinase analyses. EGF injection led to a rapid and marked activation of hepatic Raf and MEK in both fetal and adult rats, whereas MAP kinase activation was minimal in fetal as opposed to adult rats. Examination of the ontogeny of this dissociation of MAP kinase activation from MEK activation showed gradual acquisition of intact signaling as an adult hepatocyte phenotype was attained during the first 4 postnatal weeks. Over this period, MAP kinase content as determined by Western immunoblotting was constant. Recombination experiments using partially purified fetal and adult rat liver MEK and MAP kinase showed intact MAP kinase activation in vitro, indicating that neither enzyme was irreversibly altered in the fetus. In studies using primary cultures of E19 fetal rat hepatocytes, uncoupling of MAP kinase activation from MEK activation could be induced by incubation of fetal hepatocytes for 24 h with a potent fetal hepatocyte mitogen, transforming growth factor-alpha. These findings indicate that a novel negative feedback mechanism for MAP kinase regulation may be active in developing rat hepatocytes.

Modulation of mitogen-independent hepatocyte proliferation during the perinatal period in the rat

Late gestation fetal rat hepatocytes can proliferate under defined in vitro conditions in the absence of added mitogens. However, this capacity declines with advancing gestational age of the fetus from which the hepatocytes are derived. The present studies were undertaken to investigate this change in fetal hepatocyte growth regulation. Examination of E19 fetal hepatocyte primary cultures using immunocytochemistry for 5-bromo-2'-deoxyuridine (BrdU) incorporation showed that approximately 80% of these cells traverse S-phase of the cell cycle over the first 48 h in culture. Similarly, 65% of E19 hepatocytes maintained in culture under defined mitogen-free conditions for 24 h showed nuclear expression of proliferating cell nuclear antigen (PCNA). These in vitro findings correlated with a high level of immunoreactive PCNA in immunofluorescent analyses of E19 liver. In contrast, E21 (term) liver showed little immunoreactive PCNA. The in vivo finding was recapitulated by in vitro studies showing that E21 hepatocytes had low levels of BrdU incorporation during the first day in culture and were PCNA negative shortly after isolation. However, within 12 h of plating, E21 hepatocytes showed cytoplasmic staining for PCNA. Although maintained under mitogen-free conditions, PCNA expression progressed synchronously to a nucleolar staining pattern at 24 to 48 h in culture followed by intense, diffuse nuclear staining at 60 h which disappeared by 72 h. This apparently synchronous cell cycle progression was confirmed by studies showing peak BrdU incorporation on the third day in culture. Whereas DNA synthesis by both E19 and E21 hepatocytes was potentiated by transforming growth factor alpha (TGF alpha), considerable mitogen-independent DNA synthesis was seen in hepatocytes from both gestational ages. These results may indicate that fetal hepatocytes come under the influence of an exogenous, in vivo growth inhibitory factor as term approaches and that this effect is relieved when term fetal hepatocytes are cultured.

Developmental regulation of CRD-BP, an RNA-binding protein that stabilizes c-myc mRNA in vitro

We previously isolated and characterized a coding region determinant-binding protein (CRD-BP) that might regulate c-myc mRNA post-transcriptionally. CRD-BP binds specifically to the coding region of c-myc mRNA and might stabilize c-myc mRNA in vitro by protecting it from endonucleolytic cleavage. Since c-myc abundance is regulated during embryonic development and cell replication, we investigated whether CRD-BP is also regulated in animal tissues. We focused on CRD-BP expression during rat liver development and liver regeneration, because c-myc mRNA is regulated post-transcriptionally in both cases. CRD-BP expression parallels c-myc expression during liver development; the protein is present in fetal and neonatal liver but is absent or in low abundance in adult liver. In contrast, the up-regulation of c-myc mRNA following partial hepatectomy is not accompanied by up-regulation of CRD-BP. To our knowledge, CRD-BP is the first example of a putative mammalian mRNA-binding protein that is abundant in a fetal tissue but either absent from or scarce in adult tissues. Its expression in fetal liver and in transformed cell lines suggests CRD-BP is an oncofetal protein.

A comparative study of the hepatic mitogen-activated protein kinase and Jun-NH2-terminal kinase pathways in the late-gestation fetal rat

Mitogen-activated protein kinases (MAPKs) and Jun-NH2-terminal kinases (JNKs) are considered members of parallel but separate signal transduction cascades. We have compared the regulation and, indirectly, the role of these two pathways in hepatic development during late gestation in the rat. Our initial experiments showed that the two pathways crossed over to a significant degree. Both could be activated in primary cultures of fetal rat hepatocytes by exposure to transforming growth factor alpha (TGF-alpha), a potent MAPK activator, or tumor necrosis factor alpha (TNF-alpha), a potent JNK activator. Fractionation of fetal hepatocyte lysates showed that the same MAPKs were stimulated by TGF-alpha as by TNF-alpha. In contrast, TGF-alpha activated only one JNK, whereas TNF-alpha stimulated multiple kinases with activity toward Jun. JNKs were found to be active under normal conditions in 19-day fetal liver compared with adult liver, whereas MAPK was not. Moreover, although JNKs could be activated further by intraperitoneal injection of TNF-alpha to the intact 19-day fetus, MAPKs could not be activated in vivo by i.p. injection of epidermal growth factor (EGF), which, like TGF-alpha, acts via the EGF receptor. EGF could not activate fetal hepatic MAPKs even though signal initiation was intact, as indicated by tyrosine phosphorylation of the adaptor protein Shc and Shc/Grb2 complex formation. These results indicate that the JNK-signaling pathway may support fetal hepatocyte proliferation in vivo. In contrast, MAPK signaling is uncoupled, possibly indicating that it is not involved in maintaining hepatocyte proliferation in the late-gestation rat.

A comparison of epidermal growth factor receptor-mediated mitogenic signaling in response to transforming growth factor alpha and epidermal growth factor in cultured fetal rat hepatocytes

We compared the ability of Epidermal Growth Factor (EGF) and Transforming Growth Factor alpha (TGF alpha) to transduce a mitogenic signal via their common receptor, the EGF receptor, in primary cultures of fetal rat hepatocytes. Mitogenic potency, measured as DNA synthesis, was similar in response to EGF and TGF alpha although signal initiation, measured as EGF receptor tyrosine phosphorylation, was more than 3-fold higher in response to EGF compared to TGF alpha. Downstream signal transduction events including Shc tyrosine phosphorylation, Shc/Grb2 complex formation and MAP kinase activation were similar in response to EGF and TGF alpha, thus indicating a dissociation between potency for receptor activation versus signal propagation. These data suggest that TGF alpha may preferentially activate an EGF receptor population linked to the Ras/MAP kinase pathway. In contrast, EGF shows no such selectivity, thereby reducing the mitogenic potency of EGF relative to its ability to activate the EGF receptor.

Developmental changes in the activity and cellular localization of hepatic casein kinase II in the rat

The activity and cellular localization of hepatic casein kinase II (CKII) was examined during late fetal development in the rat. Cultured fetal hepatocytes displayed constitutive CKII activity which was not further activated by growth factor exposure. Similarly, fetal liver CKII showed approximately fivefold greater activity than adult liver. The fetal hepatic activity was, to a large degree, localized to a nuclear fraction. Postnuclear cytosol preparations from fetal and adult liver showed similar CKII activity. In all cases, FPLC ion exchange chromatography followed by Western immunoblotting showed that immunoreactive CKII coincided with kinase activity. However, parallel determinations of CKII activity and immunoreactive CKII levels showed a higher (five- to sixfold) CKII specific activity in nuclear extracts compared to cytosol. In summary, fetal hepatic CKII demonstrates coincident nuclear localization and activation. We hypothesize that the regulation of hepatic CKII is relevant to the mitogen-independent proliferation displayed by fetal rat hepatocytes.

In vitro and in vivo regulation of hepatic mitogen-activated protein kinases in fetal rats

We have studied the role of mitogen-activated protein (MAP) kinases in fetal hepatocyte growth in vitro and in vivo. With myelin basic protein (MBP) as the phosphate acceptor, kinase activity in cultured fetal hepatocyte lysates increased fourfold after exposure to transforming growth factor-alpha (TGF-alpha) for 10 min. This TGF-alpha-responsive MBP kinase activity was accounted for by five distinct MAP kinase isoforms detected by Western immunoblotting. All had negligible activity in cultured fetal hepatocytes under basal conditions. Treatment of fetal hepatocytes with hepatocyte growth factor led to activation of the predominant isoforms, relative molecular weight (M(r)) = 42,000 and 44,000 in a manner indistinguishable from TGF-alpha, whereas insulin had no effect. All five of the immunoreactive MAP kinases were present in both fetal and adult liver homogenates. The M(r) = 42,000 and 44,000 isoforms were only minimally activated in vivo. We conclude that the mitogen-independent growth exhibited by fetal hepatocytes in primary culture is not associated with tonic activation of the MAP kinase system. Our data support the possibility that fetal hepatic growth may be, in part, independent of the action of growth factors as mediated via the MAP kinase system.

Evidence for a direct hepatotrophic role for insulin in the fetal rat: implications for the impaired hepatic growth seen in fetal growth retardation

Perturbations of fetal growth produce parallel but disproportionate changes in fetal liver growth that correlate with circulating fetal insulin concentration. We have studied the effects of insulin and two hepatotrophic factors, transforming growth factor-alpha (TGF alpha) and hepatocyte growth factor (HGF), on DNA synthesis by fetal and adult rat hepatocytes in primary culture. Using serum-free Minimum Essential Medium, fetal hepatocytes synthesized DNA without growth factors, unlike adult hepatocytes. Insulin augmented fetal hepatocyte DNA synthesis after 16-24 h in culture. In contrast, TGF alpha or HGF maximally stimulated fetal hepatocyte DNA synthesis after 40 h in culture. Insulin and TGF alpha were not synergistic in stimulating fetal hepatocyte DNA synthesis, but were synergistic in their action on adult hepatocytes. Brief (10-min) exposure of fetal hepatocytes to TGF alpha or HGF, but not insulin, activated mitogen-activated protein kinases 4-fold. Prolonged (24-h) exposure to TGF alpha or HGF abolished the ability of either to activate mitogen-activated protein kinases, whereas insulin had no effect. Maternal fasting for 48 h before isolation and culturing of fetal hepatocytes abolished the in vitro stimulation of DNA synthesis by insulin without affecting TGF alpha action. We conclude that insulin has growth-promoting actions on fetal hepatocytes that are distinct and independent from those of TGF alpha of HGF.

Insulin receptor tyrosine kinase domain auto-dephosphorylation

We have observed dephosphorylation of the soluble, 48 kDa insulin receptor tyrosine kinase domain following its tyrosine autophosphorylation. Dephosphorylation was associated with generation of inorganic phosphate, thereby making catalysis by reversal of the kinase reaction unlikely. The kinase domain preparations could not be shown to contain detectable, contaminating protein tyrosine phosphatase activity. In addition, dephosphorylation was insensitive to protein phosphatase inhibitors. However, it was blocked by the kinase inhibitor staurosporine. These results are consistent with insulin receptor kinase domain auto-dephosphorylation via catalysis involving the kinase itself. These findings raise the possibility of a novel mechanism for termination of the insulin receptor signal.

Persistence of impaired insulin secretion in infant rhesus monkeys that had been hyperinsulinemic in utero

Chronic in utero hyperinsulinemia in the fetal rhesus monkey produces a number of changes in the fetus that are similar to those found in the human infant of the diabetic mother, including macrosomia, selective organomegaly, and altered insulin secretion during the neonatal period. The chronically hyperinsulinemic fetal rhesus model has been used to test the hypothesis that the effects of chronic hyperinsulinemia persist beyond the neonatal period into later life and may, in part, be responsible for the increased prevalence of impaired glucose tolerance or diabetes found in the human infant of the diabetic mother. We report that infant rhesus monkeys that had plasma insulin concentrations of approximately 10 times basal levels (2176 +/- 808 pmol compared to 172 +/- 101 pmol) exhibited reduced insulin secretion during the first 5 months of life. The integrated incremental change in plasma insulin and immunoreactive C-peptide (IRCP) concentration was significantly reduced by approximately 50% in response to i.v. glucose, arginine, and tolbutamide when given at 3, 4, and 5 months of age. The response to glucagon at 2 months of age was equivocal with a significantly reduced insulin response but without the corresponding IRCP reduction. There was no difference between groups in insulin sensitivity as measured at 6 months of age by an i.v. insulin tolerance test. The glucagon and glucose tolerance tests were repeated annually in both groups until the animals were 3 yr of age with no differences in insulin or IRCP secretion being observed. We conclude that chronic in utero euglycemic hyperinsulinemia results in impaired insulin secretion that persists beyond the neonatal period.

Differential regulation of multiple hepatic protein tyrosine phosphatases in alloxan diabetic rats

The involvement of tyrosine phosphorylation in insulin action led us to hypothesize that increased activity of protein tyrosine phosphatases (PTPases) might contribute to insulin resistance in alloxan diabetes in the rat. Hepatic PTPase activity was measured using two artificial substrates phosphorylated on tyrosine: reduced, carboxyamidomethylated, and maleylated lysozyme (P-Tyr-RCML) and myelin basic protein (P-Tyr-MBP), as well as an autophosphorylated 48-kD insulin receptor tyrosine kinase domain (P-Tyr-IRKD). Rats that were made alloxan diabetic exhibited a significant increase in hepatic membrane (detergent-soluble) PTPase activity measured with P-Tyr-MBP, without a change in activity measured with P-Tyr-RCML or the P-Tyr-IRKD. The PTPase active with P-Tyr-MBP behaved as a high molecular weight peak during gel filtration chromatography. Characterization of this enzyme indicated it shared properties with CD45, the prototype for a class of transmembrane, receptor-like PTPases. Our results indicate that alloxan diabetes in the rat is associated with an increase in the activity of a large, membrane-associated PTPase which accounts for only a small proportion of insulin receptor tyrosine dephosphorylation. Nonetheless, increased activity of this PTPase may oppose tyrosine kinase-mediated insulin signal transmission, thus contributing to insulin resistance.

Impaired insulin secretion after intravenous glucose in neonatal rhesus monkeys that had been chronically hyperinsulinemic in utero

Chronic hyperinsulinemia in the fetal rhesus monkey results in fetal macrosomia without change in fetal plasma glucose concentration. After 18 days of hyperinsulinemia, fetuses were delivered by cesarean section, at which time experimental animals had significantly (P less than 0.05) elevated umbilical artery plasma insulin concentrations of 2039 +/- 854 pM compared with 129 +/- 72 pM. Plasma immunoreactive C peptide (IRCP) was significantly reduced to 39 +/- 17 pM compared with 286 +/- 134 pM. Eight hours after the insulin-delivering pumps were removed, plasma glucose, insulin, and IRCP were the same in both the experimental and control groups. At this time, 0.5 g glucose/kg was given intravenously and insulin and IRCP secretion was measured over a 1-hr period. The secretion, as assessed by integrating the incremental response of both insulin and IRCP, was significantly (P less than 0.05) lower by 80% in the experimental animals compared with the controls. Our data show that experimentally produced in utero euglycemic hyperinsulinemia in the fetal rhesus monkey produces a defect in the glucose-mediated insulin secretory mechanism that is detectable in the neonatal period even when hyperinsulinemia is no longer present. This study provides more support for the concept that fuel/hormone-mediated fetal teratogenesis may explain some of the fetopathy of the infant of the diabetic mother.

Hepatic insulin and EGF receptor phosphorylation and dephosphorylation in fetal rats

Hepatic insulin receptor and epidermal growth factor (EGF) receptor phosphorylation and dephosphorylation were studied in normal and growth-retarded fetal rats. Insulin receptor autophosphorylation at a subsaturating ATP concentration (0.5 microM) increased by 10-fold from day 17 to 21 of gestation and decreased by 50% in term growth-retarded fetuses of fasted mothers. In vitro kinase activation at 0.5 mM ATP did not change with gestation or maternal fasting. EGF receptor autophosphorylation increased in parallel with receptor number with advancing gestation and did not change with maternal fasting. Protein tyrosine phosphatases (PTPases), which might attenuate receptor signaling in livers from growth-retarded fetuses, were measured using polybasic and polyacidic artificial substrates as well as the insulin receptor kinase domain. Fetal membrane PTPase activities were twofold higher than in the adult and declined with advancing gestation. However, activities were similar in normal and growth-retarded fetuses. We conclude that decreased hepatic growth in growth-retarded fetuses may involve decreased insulin receptor tyrosine kinase activation in vivo, as indicated by diminished receptor autophosphorylation at subsaturating ATP concentrations. Changes in EGF receptor kinase activity and PTPases could not be implicated based on our in vitro findings.

Heterogeneity of hepatic protein tyrosine phosphatases

We have identified multiple members of the protein tyrosine phosphatase family in three subcellular compartments from rat liver; membrane, cytoskeleton and cytosol. Characterization based on substrate specificity, size, and reactivity with an anti-peptide antiserum against human placental PTP1B indicate the presence of at least three PTPases in Triton X-100 extracts of particulate membranes. Of these, one of 600 kDa possesses characteristics of a transmembrane, receptor-like enzyme. A fourth particulate PTPase (70 kDa) represents a distinct cytoskeletal PTPase. Cytosol contains one main PTPase species which was detected as a 41 kDa protein in Western immunoblots. These data indicate the existence of multiple hepatic PTPases whose differences in structure and subcellular localization may reflect functional heterogeneity.

Hepatic protein tyrosine phosphatases in the rat

Regulation of cell growth and metabolism by protein tyrosine phosphorylation involves dephosphorylation via the action of protein tyrosine phosphatases (PTPases). We have characterized the membrane PTPases in rat liver, monitoring their activity by measuring the dephosphorylation of P-Tyr-reduced, carboxyamidomethylated and maleylated lysozyme (P-Tyr-RCML) and P-Tyr-myelin basic protein (P-Tyr-MBP). Separation of membrane PTPases by poly (L-lysine) chromatography yielded three peaks of PTPase, termed I, II and III. PTPases I and II were most active with P-Tyr-RCML, whereas PTPase III showed greater activity with P-Tyr-MBP than with P-Tyr-RCML (ratio of activities 4:1). Separation of membrane proteins by gel-filtration chromatography yielded two peaks of activity. Based on substrate specificity, sensitivity to inhibitors and requirement for thiol-containing compounds, the activity peak with an Mr of approximately 400,000 corresponded to PTPase III, whereas that with an Mr of approx. 40,000 contained PTPases I and II. All three PTPases dephosphorylated epidermal growth factor receptors and insulin receptors, but only PTPases I and II were active with P-Tyr-asialoglycoprotein receptors. Although none of the above characteristics distinguished between PTPases I and II, only PTPase I reacted in a Western immunoblotting procedure with anti-peptide antibodies directed towards human placental PTPase. We conclude that the membrane fraction from rat liver contains at least three distinct PTPases.

Impaired insulin secretion in the neonatal rhesus monkey after chronic hyperinsulinemia in utero

The secretion of insulin by the pancreas of the newborn rhesus monkey that had been made experimentally hyperinsulinemic in utero was studied in 18 animals. Chronic in utero hyperinsulinemia was produced by the continuous subcutaneous delivery of 4.75 units of insulin per day for 18 +/- 1 days. After delivery, the insulin-containing pump was removed to allow neonatal insulin levels to drop to normal levels. By 6.5 +/- 1.0 hr after pump removal, plasma glucose, insulin, and C-peptide immunoreactivity (CPIR) were comparable in the control and experimental animals. At that point 300 micrograms of glucagon/kg body weight was given iv to stimulate insulin secretion. After 30 min a significant elevation (expressed as the percentage of basal levels) in plasma glucose by 250%, insulin by 200%, and CPIR by 200% was observed in the control animals. In contrast, no changes in plasma insulin or CPIR concentrations occurred, with an attenuated glucose response that was only one-fifth of the control response, in the experimental animals. These results along with the observed lowered concentrations of CPIR in the plasma and insulin in the pancreas at birth can be interpreted as evidence that insulin is an inhibitor of its synthesis and secretion in utero and that this abnormal intrauterine environment causes changes that persist into extrauterine life.

Hepatic protein phosphotyrosine phosphatase. Dephosphorylation of insulin and epidermal growth factor receptors in normal and alloxan diabetic rats

Polypeptide hormone signal transmission by receptor tyrosine kinases requires the rapid reversal of tyrosine phosphorylation by protein phosphotyrosine phosphatases (PPTPases). We studied hepatic PPTPases in the rat with emphasis on acute and chronic regulation by insulin. PPTPase activity with artificial substrates ([32P]Tyr-reduced, carboxyamidomethylated, and maleylated lysozyme and [32P]Tyr-poly[glutamic acid:tyrosine] 4:1) was present in distinct membrane, cytoskeletal, and cytosolic fractions. These PPTPase activities were unaffected by alloxan diabetes. Acute administration of insulin to normal animals also did not change PPTPase activity in liver plasma membranes or endosomal membranes. Although alloxan diabetes did not affect PPTPase activity measured with artificial substrates or with epidermal growth factor receptors, a decrease in insulin receptor dephosphorylation was noted. Dephosphorylation of hepatic receptors from normal and diabetic rats by membrane PPTPase from control rats was similar. These results indicate that alloxan diabetes does not lead to a generalized effect on hepatic PPTPase activity, although a substrate-specific decrease in activity with the insulin receptor may occur.

Relationships among maternal and fetal amino acid blood concentrations and amniotic fluid amino acid levels in pregnant rhesus monkeys

This study was designed to explore relationships among maternal and fetal amino acid blood concentrations and amniotic fluid amino acid levels in pregnant rhesus monkeys. Although there was no constant pattern for all amino acids in the three body fluids, we observed specific patterns for most neutral amino acids, imino acids, and acidic amino acids relative to their concentrations in maternal blood, fetal blood, and amniotic fluid. Moreover, there was no correlation between fetal phenylalanine blood levels and phenylalanine concentrations in amniotic fluid indicating that amniotic fluid phenylalanine levels would not be useful to monitor fetal phenylalanine blood concentrations during pregnancy.

Fetomaternal placental transfer mechanisms of aromatic amino acids in Macaca mulatta

We investigated aromatic amino acid transfer mechanisms from fetus to mother in third-trimester pregnancies in rhesus monkeys after the administration of radioactive phenylalanine to the fetal circulation. The results indicated that fetomaternal transfer takes place mainly by facilitated diffusion via specific membrane carriers. This mechanism might participate in regulating amino acid concentrations in the fetus.

Adolescent development in males with Down syndrome

We investigated growth features, development of primary and secondary sex characteristics, and specified pituitary and testicular hormone levels in 46 male adolescents and young adults with Down syndrome. Their mean height age was significantly less than and their mean bone age was slightly more than their chronological age. The subjects' secondary sex characteristics followed the same developmental pattern noted in youngsters without Down syndrome. Penile length and circumference and testicular volume of our patients with Down syndrome were not statistically different from those of normal adolescents. Follicle-stimulating hormone, luteinizing hormone, and testosterone levels in our study population were similar to those reported for normal adolescents during sexual maturation.

Placental transfer of aromatic amino acids in non-human primates

Macaca fascicularis (crab-eating monkeys) underwent an operative procedure at 120 to 130 days of pregnancy that allowed fetal blood sampling. During subsequent experiments L-phenylalanine and p-chlorophenylalanine were injected into the maternal circulation. Blood obtained from mother and fetus revealed that phenylalanine is actively transported across the placenta and hence is markedly increased in the fetus if the maternal blood phenylalanine concentration is below the "saturation" level of 1.82 mM to 2.12 mM. The results of these studies which provide a better understanding of placental transport mechanisms of aromatic amino acids will be of assistance in future management of pregnant phenylketonuric females.

A study of placental transfer mechanisms in nonhuman primates using [14C]phenylalanine

Placental transfer mechanisms were investigated in pregnant Macaca Fascicularis and Macaca mulatta during the gestational age of 120 to 130 days. These primates underwent an operative procedure that allowed continuous fetal blood sampling. The administration of [14C]phenylalanine into the maternal circulation revealed a significant increase of radioactive material in the fetal circulation, indicating an active placental transport mechanism unidirectional to the fetus. When [14C]phenylalanine was injected into the fetus, radioactive aromatic amino acids in the maternal circulation increased only slightly over time, resembling a simple diffusion process.