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1.
Crit Rev Food Sci Nutr ; 61(22): 3783-3803, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-32838552

RESUMEN

Evidence shows that polyphenols can attenuate postprandial blood glucose responses to meals containing digestible carbohydrate. Polyphenol-rich plant extracts are emerging as potential ingredients in functional foods and/or beverages despite limited understanding of their physiological effects. Many studies have investigated the mechanisms of polyphenol-rich fruit extracts on inhibition of digestive enzymes. However, the evidence available has yet to be critically evaluated systematically. This report reviews the in vitro literature to quantify the effect of fruit polyphenol extracts on the activities of digestive carbohydrases. A systematic literature search was conducted using six science databases. Included studies, totaling 34 in number, were in vitro digestion models which quantified gut digestive enzyme(s) activity on starch digestion in the presence of fruit polyphenol extracts. Most studies assessed the effects of fruit extracts on either α-amylase (n = 30) or α-glucosidase (n = 30) activity. Studies were consistent overall in showing stronger inhibition of α-amylase compared to α-glucosidase by proanthocyanidin- and/or ellagitannin-rich fruit extracts. Recommendations are proposed for future reporting of this type of research to enable meaningful synthesis of the literature as a whole. Such knowledge could allow effective choices to be made for development of novel functional foods and beverages.


Asunto(s)
Frutas , Polifenoles , Frutas/química , Inhibidores de Glicósido Hidrolasas , Extractos Vegetales/farmacología , Polifenoles/análisis , Almidón , alfa-Amilasas , alfa-Glucosidasas
2.
BMC Med Res Methodol ; 20(1): 55, 2020 03 05.
Artículo en Inglés | MEDLINE | ID: mdl-32138694

RESUMEN

BACKGROUND: Single time-point assessments of psychological distress are often used to indicate chronic mental health problems, but the validity of this approach is unclear. The aims of this study were to investigate how a single assessment of distress relates to longer-term assessment and quantify misclassification from using single measures to indicate chronic distress. METHODS: Data came from the Household, Income and Labour Dynamics in Australia Survey, a nationally representative study of Australian adults. Psychological distress, measured with the Kessler10 and categorised into low (scores:10- < 12), mild (12- < 16), moderate (16- < 22) and high (22-50), has been assessed in the Survey biennially since wave 7. Among respondents who were aged ≥25 years and participated in all waves in which distress was measured, we describe agreement in distress categories, and using a mixed linear model adjusting for age and sex we estimate change in scores, over a two-, four-, six- and eight-year follow-up period. We applied weights, benchmarked to the Australian population, to all analyses. RESULTS: Two-years following initial assessment, proportions within identical categories of distress were 66.0% for low, 54.5% for mild, 44.0% for moderate and 50.3% for high, while 94.1% of those with low distress initially had low/mild distress and 81.4% with high distress initially had moderate/high distress. These patterns did not change materially as follow-up time increased. Over the full eight-year period, 77.3% of individuals with high distress initially reported high distress on ≥1 follow-up occasion. Age-and sex- adjusted change in K10 scores over a two-year period was 1.1, 0.5, - 0.7 and - 4.9 for low, mild, moderate and high distress, respectively, and also did not change materially as follow-up time increased. CONCLUSION: In the absence of repeated measures, single assessments are useful proxies for chronic distress. Our estimates could be used in bias analyses to quantify the magnitude of the bias resulting from use of single assessments to indicate chronic distress.


Asunto(s)
Encuestas Epidemiológicas/métodos , Encuestas Epidemiológicas/estadística & datos numéricos , Salud Mental/estadística & datos numéricos , Distrés Psicológico , Estrés Psicológico/diagnóstico , Adulto , Anciano , Ansiedad/diagnóstico , Ansiedad/psicología , Australia , Depresión/diagnóstico , Depresión/psicología , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Clase Social , Estrés Psicológico/psicología
3.
Int Arch Occup Environ Health ; 93(5): 611-622, 2020 07.
Artículo en Inglés | MEDLINE | ID: mdl-31932956

RESUMEN

PURPOSE: There is no review on the effect of work-related stressors on mental health of young workers. We systematically reviewed epidemiological evidence on this relationship. METHODS: The review searched eight databases: Embase, PubMed, Web of Science, Cinahl, Cochrane Library, Informit, PsycINFO, and Scopus from their respective start dates until May 2017. Studies that have examined a mental health outcome in relation to a work-related stressor as exposure in young workers were included. The review was reported based on the PRISMA statement. RESULTS: Three cross-sectional studies and six longitudinal cohort studies were included. Cross-sectional evidence showed that adverse work conditions including working overtime, job boredom, low skill variety, low autonomy, high job insecurity, and lack of reward were associated with poor mental health of young workers. Longitudinal evidence showed that high job demands, low job control, effort-reward imbalance, and low work support (men only) were associated with poor mental health. There was evidence on the contemporaneous relationship between two or more adverse work conditions and poor mental health. CONCLUSIONS: Although more research (particularly high-quality longitudinal studies) is warranted in this area, our review indicates that work-related stressors have a negative impact on the mental health of young workers. The current review suggests that workplace interventions and policy are required to improve the quality of work for young workers.


Asunto(s)
Trastornos Mentales/epidemiología , Salud Mental/estadística & datos numéricos , Estrés Laboral/psicología , Adolescente , Femenino , Humanos , Masculino , Estrés Psicológico , Carga de Trabajo/estadística & datos numéricos , Adulto Joven
4.
Crit Rev Food Sci Nutr ; 57(2): 237-253, 2017 Jan 22.
Artículo en Inglés | MEDLINE | ID: mdl-25921546

RESUMEN

Polysaccharides derived from plant foods are major components of the human diet, with limited contributions of related components from fungal and algal sources. In particular, starch and other storage carbohydrates are the major sources of energy in all diets, while cell wall polysaccharides are the major components of dietary fiber. We review the role of these components in the human diet, including their structure and distribution, their modification during food processing and effects on functional properties, their behavior in the gastrointestinal tract, and their contribution to healthy diets.


Asunto(s)
Pared Celular/metabolismo , Carbohidratos de la Dieta/metabolismo , Fibras de la Dieta/metabolismo , Digestión , Ingestión de Energía , Modelos Biológicos , Plantas Comestibles/química , Carbohidratos/biosíntesis , Carbohidratos/química , Enfermedad Crónica/epidemiología , Enfermedad Crónica/prevención & control , Frío/efectos adversos , Carbohidratos de la Dieta/efectos adversos , Carbohidratos de la Dieta/uso terapéutico , Fibras de la Dieta/efectos adversos , Fibras de la Dieta/análisis , Fibras de la Dieta/uso terapéutico , Manipulación de Alimentos , Índice Glucémico , Calor/efectos adversos , Humanos , Desnutrición/epidemiología , Desnutrición/metabolismo , Desnutrición/prevención & control , Estructura Molecular , Plantas Comestibles/efectos adversos , Plantas Comestibles/metabolismo , Factores de Riesgo , Respuesta de Saciedad , Almidón/efectos adversos , Almidón/química , Almidón/metabolismo , Almidón/uso terapéutico
5.
J Public Health (Oxf) ; 39(4): e134-e141, 2017 12 01.
Artículo en Inglés | MEDLINE | ID: mdl-27899480

RESUMEN

Background: While international research shows that receipt of welfare benefits is associated with poor mental health, less is known about the relationship between welfare receipt and mental health service use. We investigate whether within-person change in welfare recipient status is associated with change in mental health service use. Methods: Analysis of two waves of data from an Australian national household survey. Random- and fixed-effect models considered the effect of change in welfare receipt status, and assessed whether change in mental health service use differed by type of welfare benefit or the direction of welfare transition. Results: Individuals were more likely to report greater mental health service use at times of welfare receipt. These associations were attenuated, but remained significant, after adjusting for mental health. Increased health service use was not tied to specific types of welfare benefits. The increase in mental health service use associated with a transition onto welfare benefits was much greater than the decline in service use associated with the transition off benefits. Conclusions: Within individuals, welfare receipt is associated with greater mental health service use. While this does reflect poorer mental health at the time of welfare receipt, other factors seem to facilitate health service use.


Asunto(s)
Servicios de Salud Mental/estadística & datos numéricos , Bienestar Social/estadística & datos numéricos , Adolescente , Adulto , Anciano , Australia/epidemiología , Femenino , Humanos , Renta/estadística & datos numéricos , Estudios Longitudinales , Masculino , Salud Mental/estadística & datos numéricos , Persona de Mediana Edad , Aceptación de la Atención de Salud/estadística & datos numéricos , Encuestas y Cuestionarios , Adulto Joven
6.
Psychol Med ; 43(8): 1763-72, 2013 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-23190443

RESUMEN

BACKGROUND: Employment is associated with health benefits over unemployment, but the psychosocial characteristics of work also influence health. There has, however, been little research contrasting the prevalence of psychiatric disorders among people who are unemployed with those in jobs of differing psychosocial quality. METHOD: Analysis of data from the English Adult Psychiatric Morbidity Survey (APMS) considered the prevalence of common mental disorders (CMDs) among 2603 respondents aged between 21 and 54 years who were either (i) employed or (ii) unemployed and looking for work at the time of interview in 2007. Quality of work was assessed by the number of adverse psychosocial job conditions reported (low control, high demands, insecurity and low job esteem). RESULTS: The prevalence of CMDs was similar for those respondents who were unemployed and those in the poorest quality jobs. This pattern remained after controlling for relevant demographic and socio-economic covariates. CONCLUSIONS: Although employment is thought to promote mental health and well-being, work of poor psychosocial quality is not associated with any better mental health than unemployment. Policy efforts to improve community mental health should consider psychosocial job quality in conjunction with efforts to increase employment rates.


Asunto(s)
Empleo/psicología , Trastornos Mentales/psicología , Desempleo/psicología , Adulto , Empleo/normas , Empleo/estadística & datos numéricos , Inglaterra/epidemiología , Femenino , Encuestas Epidemiológicas , Humanos , Masculino , Trastornos Mentales/epidemiología , Trastornos Mentales/etiología , Persona de Mediana Edad , Desempleo/estadística & datos numéricos , Adulto Joven
7.
Int Psychogeriatr ; 25(11): 1765-73, 2013 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-23835052

RESUMEN

BACKGROUND: Gender differences in depression are well established. Whether these differences persist into late life and in the years preceding death is less clear. There is a suggestion that there is no increased likelihood of depression in late life, but that there is an increase in depressive symptomology, particularly with proximity to death. We compared trajectories of probable depression and depressive symptomology between men and women over age and distance-to-death metrics to determine whether reports of depressive symptoms are more strongly related to age or mortality. METHODS: Participants (N = 2,852) from the Dynamic Analyses to Optimise Ageing (DYNOPTA) project had a mean age of 75 years (SD = 5.68 years) at baseline and were observed for up to 16 years prior to death. Multi-level regression models estimated change in depressive symptomology and probable depression over two time metrics, increasing age, and distance-to-death. RESULTS: Increases in depressive symptomology were reported over increasing age and in the years approaching death. Only male participants reported increased probable depression in the years preceding death. Models that utilized distance-to-death metrics better represented changes in late-life depression, although any changes in depression appear to be accounted for by co-varying physical health status. CONCLUSIONS: As death approaches, there are increases in the levels of depressive symptomology even after controlling for socio-demographic and health covariates. In line with increases in suicide rates in late life, male participants were at greater risk of reporting increases in depressive symptomology.


Asunto(s)
Depresión/psicología , Factores de Edad , Anciano , Anciano de 80 o más Años , Muerte , Femenino , Humanos , Estudios Longitudinales , Masculino , Persona de Mediana Edad , Escalas de Valoración Psiquiátrica , Factores de Riesgo , Factores Sexuales
8.
Occup Environ Med ; 68(11): 806-12, 2011 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-21406384

RESUMEN

OBJECTIVES: Although employment is associated with health benefits over unemployment, the psychosocial characteristics of work also influence health. We used longitudinal data to investigate whether the benefits of having a job depend on its psychosocial quality (levels of control, demands and complexity, job insecurity, and unfair pay), and whether poor quality jobs are associated with better mental health than unemployment. METHOD: Analysis of seven waves of data from 7,155 respondents of working age (44,019 observations) from a national household panel survey. Longitudinal regression models evaluated the concurrent and prospective association between employment circumstances (unemployment and employment in jobs varying in psychosocial job quality) and mental health, assessed by the MHI-5. RESULTS: Overall, unemployed respondents had poorer mental health than those who were employed. However the mental health of those who were unemployed was comparable or superior to those in jobs of the poorest psychosocial quality. This pattern was evident in prospective models: those in the poorest quality jobs showed greater decline in mental health than those who were unemployed (B = 3.03, p<0.05). The health benefits of becoming employed were dependent on the quality of the job. Moving from unemployment into a high quality job led to improved mental health (mean change score of +3.3), however the transition from unemployment to a poor quality job was more detrimental to mental health than remaining unemployed (-5.6 vs -1.0). CONCLUSIONS: Work of poor psychosocial quality does not bestow the same mental health benefits as employment in jobs with high psychosocial quality.


Asunto(s)
Empleo/psicología , Trastornos Mentales/psicología , Tolerancia al Trabajo Programado/psicología , Adulto , Australia , Femenino , Humanos , Estudios Longitudinales , Masculino , Desempleo/psicología
9.
Epidemiol Psychiatr Sci ; 29: e141, 2020 Jul 15.
Artículo en Inglés | MEDLINE | ID: mdl-32665045

RESUMEN

AIMS: Mental health problems in early adulthood may disrupt partner relationship formation and quality. This prospective study used four waves of Australian data to investigate the effects of depression and anxiety in early adulthood on the quality of future partner (i.e. marriage or cohabiting) relationships. METHODS: A representative community sample of Australian adults aged 20-24 years was assessed in 1999, 2003, 2007 and 2011. Analyses were restricted to those who at baseline had never entered a marriage or cohabiting relationship with no children (n = 1592). Associations were examined between baseline depression and anxiety levels (using the Goldberg Depression and Anxiety scales) and (a) future relationship status and (b) the quality of marriage or cohabiting relationships recorded at follow-up (up to 12 years later) (partner social support and conflict scales). RESULTS: Depression in early adulthood was associated with never entering a partner relationship over the study period. For those who did enter a relationship, both depression and anxiety were significantly associated with subsequently lower relationship support and higher conflict. Supplementary analyses restricting the analyses to the first relationship entered at follow-up, and considering comorbid anxiety and depression, strongly supported these findings. CONCLUSIONS: Depression and anxiety in early adulthood is associated with poorer partner relationship quality in the future. This study adds to evidence showing that mental health problems have substantial personal and inter-personal costs. The findings support the need to invest in prevention and early intervention.


Asunto(s)
Ansiedad/epidemiología , Depresión/epidemiología , Relaciones Interpersonales , Estado Civil , Matrimonio/estadística & datos numéricos , Ansiedad/psicología , Australia/epidemiología , Depresión/psicología , Femenino , Encuestas Epidemiológicas , Humanos , Masculino , Matrimonio/psicología , Estudios Prospectivos , Calidad de Vida , Apoyo Social , Factores Socioeconómicos , Adulto Joven
10.
J Affect Disord ; 258: 83-88, 2019 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-31398595

RESUMEN

BACKGROUND: Australia has the second highest per capita users of antidepressants globally, and their use is pronounced in older Australians. A better understanding of antidepressant use in older adults is important because the elderly are often prescribed multiple drugs, without review, for long periods. METHODS: This study analysed questionnaire data obtained from the Personality and Total Health through life project. Individual respondent data was linked to Pharmaceutical Benefits Scheme (PBS) records. Associations between self-reported medicine use and current symptoms with antidepressant dispensing were examined. RESULTS: 1275 participants aged over 65 were included in the final analysis. One hundred and forty-six (11.5%) participants were dispensed an antidepressant within the specified timeframe. Of those, 38.4% self-reported that they use medicine for depression, 12.3% for anxiety, 17.8% for both depression and anxiety, 6.2% for sleep problems and 3.4% for pain. One fifth of those dispensed an antidepressant did not self-report use of the medicine. Being female or reporting symptoms of depression, anxiety or suicidality were significant predictors of being on an antidepressant. Increasing pain severity was also associated with increased likelihood of being on an antidepressant. LIMITATIONS: We have presented a cross-sectional analysis, which can only provide associations between current symptoms and medicine use. We have only assessed respondents who received their scripts with PBS concession, which limits generalizability. CONCLUSION: Our analysis highlights the high use of antidepressants in the elderly for various reasons. Our findings also uncovered a high amount of under-reporting of antidepressant use by respondents.


Asunto(s)
Antidepresivos/uso terapéutico , Ansiedad/tratamiento farmacológico , Depresión/tratamiento farmacológico , Anciano , Australia , Estudios Transversales , Femenino , Humanos , Masculino , Autoinforme , Encuestas y Cuestionarios
11.
Epidemiol Psychiatr Sci ; 27(1): 74-83, 2018 02.
Artículo en Inglés | MEDLINE | ID: mdl-27927267

RESUMEN

AIMS: Findings that describe the mental health risk associated with non-heterosexual orientation in young and middle-aged adults are from cross-sectional designs or fail to discriminate homosexual and bisexual orientations. This study examines the mental health risk of homosexual and bisexual orientation over an 8-year period. METHODS: Participants were from the age-cohort study, the Personality and Total Health Through Life Project, were observed twice every 4 years, and aged 20-24 (n = 2353) and 40-44 (n = 2499) at baseline. RESULTS: Homosexual orientation was unrelated to long-term depression risk. Risk for anxiety and depression associated with homosexual and bisexual orientations, respectively, were attenuated in fully-adjusted models. Bisexual orientation risk associated with anxiety was partially attenuated in fully-adjusted models. CONCLUSIONS: Non-heterosexual orientation was not a major risk factor for long-term mental health outcomes. Instead, those with a non-heterosexual orientation were more likely to experience other mental health risk factors, which explain most of the risk observed amongst those with a non-heterosexual orientation.


Asunto(s)
Bisexualidad/psicología , Homosexualidad/psicología , Salud Mental , Minorías Sexuales y de Género/psicología , Adulto , Ansiedad/epidemiología , Australia/epidemiología , Estudios de Cohortes , Estudios Transversales , Depresión/epidemiología , Femenino , Encuestas Epidemiológicas , Humanos , Persona de Mediana Edad , Factores de Riesgo , Apoyo Social , Adulto Joven
12.
Epidemiol Psychiatr Sci ; 27(5): 500-509, 2018 10.
Artículo en Inglés | MEDLINE | ID: mdl-28367772

RESUMEN

AIMS: Rural and remote regions tend to be characterised by poorer socioeconomic conditions than urban areas, yet findings regarding differences in mental health between rural and urban areas have been inconsistent. This suggests that other features of these areas may reduce the impact of hardship on mental health. Little research has explored the relationship of financial hardship or deprivation with mental health across geographical areas. METHODS: Data were analysed from a large longitudinal Australian study of the mental health of individuals living in regional and remote communities. Financial hardship was measured using items from previous Australian national population research, along with measures of psychological distress (Kessler-10), social networks/support and community characteristics/locality, including rurality/remoteness (inner regional; outer regional; remote/very remote). Multilevel logistic regression modelling was used to examine the relationship between hardship, locality and distress. Supplementary analysis was undertaken using Australian Household, Income and Labour Dynamics in Australia (HILDA) Survey data. RESULTS: 2161 respondents from the Australian Rural Mental Health Study (1879 households) completed a baseline survey with 26% from remote or very remote regions. A significant association was detected between the number of hardship items and psychological distress in regional areas. Living in a remote location was associated with a lower number of hardships, lower risk of any hardship and lower risk of reporting three of the seven individual hardship items. Increasing hardship was associated with no change in distress for those living in remote areas. Respondents from remote areas were more likely to report seeking help from welfare organisations than regional residents. Findings were confirmed with sensitivity tests, including replication with HILDA data, the use of alternative measures of socioeconomic circumstances and the application of different analytic methods. CONCLUSIONS: Using a conventional and nationally used measure of financial hardship, people residing in the most remote regions reported fewer hardships than other rural residents. In contrast to other rural residents, and national population data, there was no association between such hardship and mental health among residents in remote areas. The findings suggest the need to reconsider the experience of financial hardship across localities and possible protective factors within remote regions that may mitigate the psychological impact of such hardship.


Asunto(s)
Salud Mental , Pobreza/psicología , Población Rural/estadística & datos numéricos , Apoyo Social , Estrés Psicológico , Adulto , Anciano , Australia , Femenino , Humanos , Estudios Longitudinales , Persona de Mediana Edad , Características de la Residencia , Salud Rural
13.
J Affect Disord ; 203: 14-21, 2016 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-27285722

RESUMEN

OBJECTIVE: The subjective burden of suicidality on mental and physical health-related quality of life (HRQoL) remains to be examined. Eight-year trajectories of mental and physical components of HRQoL were compared for suicidal and non-suicidal participants at baseline. The effect of poor mental and/or physical HRQoL on subsequent suicidality was also investigated. METHOD: Randomly-selected community data (W1=7485; W2=6715; W3=6133) were analysed with multivariate latent growth curve (LGC) and logistic regression models. RESULTS: Adjusted LGC modelling identified that baseline ideation was associated with poorer mental, but better physical HRQoL at baseline (b=-3.93, 95% CI=-4.75 to -3.12; b=1.38, 95% CI=0.53-2.23, respectively). However, ideation was associated with a declining physical HRQoL trajectory over 8 subsequent years (b=-0.88, 95% CI=-1.42 to -0.35). Poorer mental HRQoL was associated with higher odds of ideation onset (OR=0.98, 95% CI=0.96-0.99). LIMITATIONS: Frequency of data collection was four-yearly, while suicidality was reported for the previous 12-months; analyses did not control for physical health problems at baseline, baseline depression may have influenced physical QoL; suicidality was assessed with binary measures; and, prior analyses of attrition over time showed those with poorer health were less likely to continue participating in the study. CONCLUSIONS: Suicidality has differential longitudinal effects on mental and physical HRQoL. Findings emphasise the considerable subjective HRQoL burden upon suicidal individuals. HRQoL may be useful to compare relative social and economical impacts.


Asunto(s)
Calidad de Vida/psicología , Ideación Suicida , Intento de Suicidio/psicología , Adulto , Anciano , Femenino , Estado de Salud , Indicadores de Salud , Humanos , Modelos Logísticos , Estudios Longitudinales , Masculino , Salud Mental , Persona de Mediana Edad , Factores de Riesgo
14.
SSM Popul Health ; 2: 175-181, 2016 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-29349138

RESUMEN

OBJECTIVES: There is growing international policy interest in disability employment, yet there has been little investigation of job quality among people working with disability. This study uses Australian national data to compare the psychosocial job quality of people working with versus without disability. METHODS: We used 10 annual waves of data from a large representative Australian panel survey to estimate the proportion of the population experiencing poorer psychosocial job quality (overall and by individual 'adversities' of low job control, high demands, high insecurity, and low fairness of pay) by disability status and impairment type. We used logistic regression to examine the pooled cross-sectional associations between disability and job quality, adjusting for age, sex, education and job type. RESULTS: Those working with any disability showed approximately 25% higher odds of reporting one or more adversity at work (OR: 1.23, 95% CI: 1.15, 1.31), and this finding was consistent across impairment types with the exception of intellectual/developmental disability. Estimates were largely unchanged after adjustments. Similar results were found for reporting two or more adversities compared one or more. CONCLUSIONS: We observed that working people with a disability in Australia reported systematically poorer psychosocial job quality than those working without disability. These results suggest the need for further research to understand the reasons for these patterns, as well as policy and practice efforts to address this inequity.

15.
Biochim Biophys Acta ; 1148(1): 117-22, 1993 May 14.
Artículo en Inglés | MEDLINE | ID: mdl-8499458

RESUMEN

Primary cultures of rat hepatocytes take up phosphate by a saturable Na(+)-dependent process. Thus the plasma membrane possesses an N(+)-Pi cotransporter of the type described for many cell types, e.g., kidney proximal tubular cells and enterocytes. Coupling to Na+ overcomes the barrier to anion entry represented by the membrane potential. At 0.12 mM Pi, the effect of Na+ is cooperative with a Hill coefficient of 1.7 suggesting two sodium sites per molecule of carrier. At 37 degrees C, the Km (for Pi) and Vmax for the sodium-dependent fraction of Pi uptake are approx. 1 mM and 0.35 nmol Pi/min per mg cell protein, respectively. Insulin stimulates Vmax four-fold with no significant effect on Km. Pi uptake in the absence of sodium is not affected by insulin. The stimulation by insulin could be of metabolic significance. Glucose phosphorylation at the expense of ATP is raised in liver following insulin stimulation, and thus, initially there may be an increased demand for Pi for oxidative phosphorylation until new steady-state conditions of hexose phosphate concentrations and of ATP turnover become established.


Asunto(s)
Insulina/farmacología , Hígado/metabolismo , Fosfatos/metabolismo , Animales , Transporte Biológico/efectos de los fármacos , Células Cultivadas/efectos de los fármacos , Hígado/efectos de los fármacos , Ratas , Sodio/farmacología
16.
Biochim Biophys Acta ; 1143(2): 158-62, 1993 Jul 05.
Artículo en Inglés | MEDLINE | ID: mdl-8318517

RESUMEN

Plasma membrane fractions were prepared from homogenates of rat liver by density gradient centrifugation and then used for the formation of right-side-out vesicles. Uptake of Pi into the vesicles is rapid when an inwardly directed sodium gradient is present and an overshoot of uptake occurs indicative of accumulation against a Pi concentration gradient. Initial Pi uptake rate in the presence of a K+ gradient is approx half that seen with Na+, but uptake in the presence of a choline chloride gradient is very slow. An overshoot does not occur with either K+ or choline gradients. The Km(Pi) for the Na-dependent component of Pi uptake is approx. 1 mM and Vmax at 20 degrees C is 0.8 nmol/min per mg protein. The relationship between initial uptake rate and Na+ concentration is sigmoid, with a Hill coefficient of 2.6. It is concluded that the cotransporter resembles that of kidney and intestine in possessing at least two interacting sites for Na+ and that in intact cells the Na+ gradient maintained by the sodium pump ATPase provides the energy for accumulation of Pi against the unfavourable membrane potential.


Asunto(s)
Hígado/metabolismo , Fosfatos/metabolismo , Sodio/farmacología , Animales , Transporte Biológico/efectos de los fármacos , Membrana Celular/efectos de los fármacos , Membrana Celular/metabolismo , Hígado/efectos de los fármacos , Masculino , Matemática , Potasio/farmacología , Ratas , Ratas Sprague-Dawley
17.
Biochim Biophys Acta ; 384(1): 146-58, 1975 Mar 28.
Artículo en Inglés | MEDLINE | ID: mdl-236767

RESUMEN

1. The interaction of NAD+, NADH and various nucleotide analogues with pig kidney alkaline phosphatase (orthophosphoric-monoester phosphohydrolase (alkaline optimum) EC 3.1.3.1) has been investigated by kinetic means. Some inhibitors act uncompetitively whereas others markedly increase the slopes of double reciprocal plots suggesting they have some affinity for the free enzyme. 2. The compounds seem to bind to alkaline phosphatase through interactions of their bases with a relatively non-specific region of the enzyme, although it is likely that for those nucleotides having some affinity for the free enzyme there is some attraction between the pyrophosphate backbone and the active site. 3. From studies of the effect of NAD+ and NADH on ATPase activity it was concluded that the substrate inhibition that is characteristic of the ATPase activity of alkaline phosphatase originates from binding of ATP to the site assumed to exist for NAD+ and NADH. The potentiation of NAD+-inhibition of ATPase activity by Mg-2+ is probably a result of the depletion of [ATP-4-] the true substrate. The depletion allows NAD+ to complete more effectively for the active site. 4. Binding of NADH is favoured by protonation of an enzymic group with a pK of approx. 9.0 belonging possibly to a tyrosine residue or a zinc hydrate. 5. A large entropy decrease was found to accompany the binding of NAD+ and NADH to alkaline phosphatase. This may be further evidence of an "induced-fit" mechanism previously suspected because of the synergistic inhibitory effects of adenosine and nicotinamide.


Asunto(s)
Fosfatasa Alcalina/antagonistas & inhibidores , Riñón/enzimología , NAD/farmacología , Adenosina Trifosfatasas/análisis , Adenosina Trifosfato/farmacología , Animales , Sitios de Unión , Concentración de Iones de Hidrógeno , Cinética , Magnesio/farmacología , Niacinamida/farmacología , Unión Proteica , Porcinos , Temperatura , Tetranitrometano/farmacología , Termodinámica
18.
Biochim Biophys Acta ; 446(1): 105-14, 1976 Sep 28.
Artículo en Inglés | MEDLINE | ID: mdl-974105

RESUMEN

Rat intestinal alkaline phosphatase is an heterogeneous glycoprotein that contains three protein sub-forms separable by electrophoresis. The molecular weight for the glycoprotein (i.e. the average for the three sub-forms) is 157 000-160 000. Three protein sub-forms are detectable on sodium dodecyl sulphate-polyacrylamide gel electrophoresis that migrate at rates corresponding with molecular weights of 64 000, 79 000 and 92 000. Treatment of native alkaline phosphatase with 6 M guanidine - HC1 or buffer at pH 3.0 results in a product with a molecular weight of 78 000 and 70 000, respectively. Thus it is concluded that each of the three sub-forms is a dimer of identical or closely similar subunits. Limited proteolysis results in the production of new enzymically active sub-forms separable by electrophoresis. Using a bacterial protease it is possible to convert intestinal alkaline phosphatase into a form with a molecular weight of 132 000 without causing any significant change in kinetic properties. Electrophoresis of this new form on sodium dodecyl sulphate polyacrylamide gel suggests that it is composed of 66 000-dalton subunits. The native enzyme contains at least 20% by weight of carbohydrate that probably contributes to microheterogeneity of a second degree superimposed on that stemming from the presence of three protein sub-forms. Treatment with various glycosidases has no effect on electrophoretic behaviour, however. It is suggested that the three sub-forms possibly represent different stages of a maturation process that operates by limited proteolysis of a single parent protein.


Asunto(s)
Fosfatasa Alcalina , Intestino Delgado/enzimología , Fosfatasa Alcalina/metabolismo , Animales , Carbohidratos/análisis , Glicósido Hidrolasas , Sustancias Macromoleculares , Peso Molecular , Péptido Hidrolasas , Ratas
19.
Biochim Biophys Acta ; 856(3): 624-8, 1986 Apr 25.
Artículo en Inglés | MEDLINE | ID: mdl-3964699

RESUMEN

Previous work from this laboratory has shown that isolated chick renal proximal tubule cells possess an Na+-dependent Pi transport system and that Pi uptake is stimulated under gluconeogenic conditions. It is shown in the present paper that gluconeogenesis is associated with a rapid incorporation of Pi into membrane phospholipids, particularly phosphatidylinositol, and some evidence has been obtained for a change in the relative amounts of phosphatidylinositol polyphosphates under gluconeogenic conditions. There is no increase in the total phospholipid phosphate content however, suggesting that pyruvate-induced incorporation of Pi into phospholipids represents accelerated turnover rather than a net increase in synthesis. It is suggested that the stimulation of Na+-dependent Pi uptake by pyruvate is related to the increased rate of phospholipid turnover. Thus Pi transport may be a further example of a physiological system that is influenced by phosphatidylinositol metabolism. The role of phosphatidylinositol phosphates could be to stimulate transfer of transporter molecules from internal stores to the brush-border membrane of the cell.


Asunto(s)
Gluconeogénesis , Túbulos Renales Proximales/metabolismo , Fosfolípidos/metabolismo , Adenosina Trifosfato/biosíntesis , Animales , Pollos , Técnicas In Vitro , Fosfatos/metabolismo , Radioisótopos de Fósforo , Piruvatos/farmacología , Ácido Pirúvico
20.
Biochim Biophys Acta ; 1190(2): 444-8, 1994 Mar 23.
Artículo en Inglés | MEDLINE | ID: mdl-8142448

RESUMEN

Na(+)-dependent phosphate uptake by rat hepatocytes in primary culture is inhibited in a time-dependent fashion by cyclic AMP and by the myristate, acetate ester of phorbol. After incubation for 15 min at 37 degrees C with 10(-7) M dibutyryl cAMP, the Vmax of transport is decreased from 0.52 to 0.23 nmol Pi/min per mg protein but the Km value of approximately 1 mM is hardly affected by the treatment. Thus, physiological control of Pi uptake by liver cells probably involves protein phosphorylation(s) catalysed by protein kinases. Protein kinase C may be important but the relatively high concentration of phorbol ester needed to cause inhibition of transport is not convincing evidence for protein kinase C involvent. In the presence of fructose, the rate of Pi uptake is decreased by 50%. This effect is probably secondary to a depletion of cellular ATP.


Asunto(s)
AMP Cíclico/farmacología , Hígado/metabolismo , Ésteres del Forbol/farmacología , Fosfatos/metabolismo , Sodio/farmacología , Animales , Transporte Biológico/efectos de los fármacos , Células Cultivadas , Cinética , Ratas
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