Implementation of stable isotopes lipoprotein kinetic studies: effects on HDL metabolism of a Mediterranean type diet rich in MUFAs from virgin olive oil.

• Autores: Katia Uliaque Cugat
• Directores de la Tesis: Joan Carles Vallvé Torrente (dir. tes.), Rosa Solà i Alberich (dir. tes.)
• Lectura: En la Universitat Rovira i Virgili ( España ) en 2007
• Idioma: inglés
• Tribunal Calificador de la Tesis: Lluís Masana Marín (presid.), Josep Ribalta Vives (secret.), Muriel Caslake (voc.), Montserrat Giralt Batista (voc.), María Isabel Covas Planells (voc.)
• Materias:
  • Química
    • Química analítica
      • Espectroscopia de masas
    • Bioquímica
      • Lípidos
  • Ciencias médicas
    • Ciencias de la nutrición
      • Nutrientes
    • Patología
      • Arterioesclerosis
• Enlaces
  • Tesis en acceso abierto en: TDX
• Resumen

  • The anti-atherogenic effects ascribed to a Mediterranean-type diet rich in monounsaturatedfatty acids (MUFAs) from virgin olive oil are due, partly, to an increase in, or maintenance of,plasma concentrations of high density lipoprotein (HDL) cholesterol. However, the underlyingmechanisms that may explain these concentrations are not well characterised, to-date.Apolipoprotein (apo) A-I (apoA-I) is the major HDL apo and its kinetic parameters, such asproduction rate and catabolic rate, reflect the kinetics of the HDL particle. Our workinghypothesis is as follows: a Mediterranean-type diet rich in MUFAs from virgin olive oil,compared to a STEP II diet, increases or preserves HDL cholesterol concentrations due to anincrease in apoA-I production and not to a decrease in apoA-I catabolism. Kinetic studiesusing stable isotopes are, perhaps, the best approach in physiologically evaluating apoproduction and catabolism in humans. This methodology has not as yet been implemented inSpain. Objectives: to implement the necessary methodology to perform kinetic studies of apoB-100 and, especially, of apoA-I and apoA-II in volunteers in vivo using stable isotopes tolabel proteins in vivo. Further, we used this methodology to analyse the overall effects of aMediterranean-type diet rich in monounsaturated fatty acids from virgin olive oil comparedwith a low-fat, STEP II diet, on HDL and low density lipoprotein (LDL) metabolism. Design:we conducted a crossover, randomised study with dietary intervention periods of 4 weeks,interspersed with a washout period between diets. A total of 10 healthy, moderatelyhypercholesterolaemic, male volunteers consumed the two diets. The project was approvedby the Clinical Research Ethical Committee of the Hospital Universitari de Sant Joan, Reus.Instrumentation: kinetic studies were performed at the end of each diet using a 16h primedconstant infusion of stable isotope2H3-L-leucine. Lipoprotein fractions were separated usingultracentrifugation technique. Stable isotope incorporated into proteins was measured usingGC-MS. The data obtained were analysed applying multi-compartmental modelling techniquewith the SAAM II program. ApoA-I and A-II kinetic studies were conducted in our ResearchUnit in Reus. Apo B-100 kinetic studies and kinetic parameter modelling were performed incollaboration with Dr. Caslake and Professor Packard of the Vascular Biochemistry Section,Division of Cardiovascular & Medical Sciences, Royal Infirmary, University of Glasgow,Glasgow, Scotland. Results: the Mediterranean diet, compared to the STEP II diet,significantly increases apoA-I plasma concentrations. A total of 17 kinetic studies have beenperformed but, due to methodological complexity, only the results of 7 kinetic studies (4following a Mediterranean diet and 3 following a STEP II diet) that have been analysed in aGC-MS to-date, are presented in this thesis. Despite the limitation of the low number ofkinetic studies analysed, we are able to document that the Mediterranean diet induces a highapoA-I HDL production rate compared to the STEP II diet. Also, the Mediterranean dietinduces a high apo B-100 LDL production rate and fractional catabolic rate compared to theSTEP II diet. Conclusions: we have, for the first time in Spain, implemented the necessarymethodology to perform apo B-100, apoA-I and A-II kinetic studies in vivo using stableisotopes in human subjects. A high apoA-I production rate is the main determinant of highplasma concentrations of apoA-I, and not variations in its catabolism. Lipoprotein kineticstudies enable the monitoring of lipoprotein metabolic parameters and the investigation ofnutritional and pharmacologic interventions in the primary and secondary prevention ofcardiovascular disease targets.