Os hidrocarbonetos cuticulares têm importante papel no processo de reconhecimento dos membros da colônia de insetos sociais. Muitos estudos têm mostrado variações qualitativas e quantitativas nestes compostos entre os insetos adultos. Contudo, abordagens referentes à modulação do perfil destes compostos durante a formação da cutícula são escassas, e se restringem aos estágios larval de holometábolos e de ninfas de hemimetábolos. O principal objetivo dessa pesquisa foi caracterizar o perfil de hidrocarbonetos cuticulares e a expressão de genes potencialmente relacionados à sua biossíntese durante o processo de formação e maturação da cutícula adulta. Os perfis de hidrocarbonetos foram caracterizados por meio de GC/MS e mostraram diferenças quantitativas marcantes que significativamente discriminaram as cutículas pupal, adulta-farata e adulta. Em paralelo, sequências de enzimas que catalisam a desaturação (desaturases) ou elongação (elongases) de lipídeos, disponíveis no banco de dados do NCBI, foram utilizadas para o desenho de primers e estudo da expressão gênica por meio de RT-qPCR. Cinco genes de desaturases, e oito genes de elongases mostraram variação de expressão estatisticamente significante no tegumento de abelhas adultas em comparação com pupas e adultas-faratas. Testes de correlação entre os perfis de expressão gênica e de hidrocarbonetos cuticulares evidenciaram os genes potencialmente envolvidos com a biossíntese destes compostos para a formação e maturação da cutícula. Estes resultados corroboram a hipótese de que nos insetos sociais, a cutícula só amadurece completamente por ocasião do início da atividade de forrageamento. Associando estes dados a análises de evolução molecular das desaturases e elongases, pudemos sugerir as etapas da via de síntese de hidrocarbonetos catalisadas por estas enzimas, e assim eleger genes candidatos a futuro silenciamento mediado por RNA de interferência para pesquisa de função. / Cuticular hydrocarbons are important for recognition of nestmates in social insect colonies. Many studies have shown qualitative and quantitative variations in the cuticular hydrocarbons between adult insects. However, approaches on developmental profiles of these compounds during cuticle formation and differentiation are scarce, and restricted to larval stages of holometabolous and nymphs of hemimetabolous. The main objective of this work was to characterize the cuticular hydrocarbons profiles and the expression of genes potentially involved in the biosynthesis of these compounds during the synthesis and differentiation of the adult cuticle in the honeybee. The hydrocarbons profiles were characterized using GC/MS and showed remarkable quantitative differences, thus discriminating the pupal, pharate-adult and adult cuticles from each other. In parallel, we used annotated sequences of enzymes catalyzing lipid desaturation (desaturases) or elongation (elongases), available in NCBI data bank, for primers design and gene expression analysis using RT-qPCR. Five desaturase genes and eight elongase genes showed statistically significant expression changes in the integument of adult bees in comparison to pupae and pharate-adults. Correlation tests supported roles of some of the desaturase and elongase genes in hydrocarbons biosynthesis for incorporation into adult cuticle. In addition, these results go along with the hypothesis that in social insects the cuticle is just completed when the insect starts forager activity. Taken together, these data and an analysis on the molecular evolution of desaturases and elongases allowed suggesting the steps in the pathway of cuticular hydrocarbons biosynthesis that are catalyzed by these enzymes, and also allowed to elect candidate genes for further functional studies using gene silencing mediated by RNAi.

Os hidrocarbonetos cuticulares têm importante papel no processo de reconhecimento dos membros da colônia de insetos sociais. Muitos estudos têm mostrado variações qualitativas e quantitativas nestes compostos entre os insetos adultos. Contudo, abordagens referentes à modulação do perfil destes compostos durante a formação da cutícula são escassas, e se restringem aos estágios larval de holometábolos e de ninfas de hemimetábolos. O principal objetivo dessa pesquisa foi caracterizar o perfil de hidrocarbonetos cuticulares e a expressão de genes potencialmente relacionados à sua biossíntese durante o processo de formação e maturação da cutícula adulta. Os perfis de hidrocarbonetos foram caracterizados por meio de GC/MS e mostraram diferenças quantitativas marcantes que significativamente discriminaram as cutículas pupal, adulta-farata e adulta. Em paralelo, sequências de enzimas que catalisam a desaturação (desaturases) ou elongação (elongases) de lipídeos, disponíveis no banco de dados do NCBI, foram utilizadas para o desenho de primers e estudo da expressão gênica por meio de RT-qPCR. Cinco genes de desaturases, e oito genes de elongases mostraram variação de expressão estatisticamente significante no tegumento de abelhas adultas em comparação com pupas e adultas-faratas. Testes de correlação entre os perfis de expressão gênica e de hidrocarbonetos cuticulares evidenciaram os genes potencialmente envolvidos com a biossíntese destes compostos para a formação e maturação da cutícula. Estes resultados corroboram a hipótese de que nos insetos sociais, a cutícula só amadurece completamente por ocasião do início da atividade de forrageamento. Associando estes dados a análises de evolução molecular das desaturases e elongases, pudemos sugerir as etapas da via de síntese de hidrocarbonetos catalisadas por estas enzimas, e assim eleger genes candidatos a futuro silenciamento mediado por RNA de interferência para pesquisa de função. / Cuticular hydrocarbons are important for recognition of nestmates in social insect colonies. Many studies have shown qualitative and quantitative variations in the cuticular hydrocarbons between adult insects. However, approaches on developmental profiles of these compounds during cuticle formation and differentiation are scarce, and restricted to larval stages of holometabolous and nymphs of hemimetabolous. The main objective of this work was to characterize the cuticular hydrocarbons profiles and the expression of genes potentially involved in the biosynthesis of these compounds during the synthesis and differentiation of the adult cuticle in the honeybee. The hydrocarbons profiles were characterized using GC/MS and showed remarkable quantitative differences, thus discriminating the pupal, pharate-adult and adult cuticles from each other. In parallel, we used annotated sequences of enzymes catalyzing lipid desaturation (desaturases) or elongation (elongases), available in NCBI data bank, for primers design and gene expression analysis using RT-qPCR. Five desaturase genes and eight elongase genes showed statistically significant expression changes in the integument of adult bees in comparison to pupae and pharate-adults. Correlation tests supported roles of some of the desaturase and elongase genes in hydrocarbons biosynthesis for incorporation into adult cuticle. In addition, these results go along with the hypothesis that in social insects the cuticle is just completed when the insect starts forager activity. Taken together, these data and an analysis on the molecular evolution of desaturases and elongases allowed suggesting the steps in the pathway of cuticular hydrocarbons biosynthesis that are catalyzed by these enzymes, and also allowed to elect candidate genes for further functional studies using gene silencing mediated by RNAi.

The increasing demand for healthy edible oil has generated the need to identify promising oil crops. Tree peony (Paeonia section Moutan DC.) is a woody oil crop with α-linolenic acid contributing for 45% of the total fatty acid (FA) content in seeds. Molecular and genetic differences that contribute to varied FA content and composition among the wild peony species are however, poorly understood. Analyses of FA content and composition during seed development in three tree peony species (P. rockii, P. potaninii, and P. lutea) showed varied FA content in the three species with highest in P. rockii, followed by P. potaninii, and P. lutea. Total FA content increased with seed development and reached its maximum in its final stage. Seed FA composition analysis of the three species also revealed that α-linolenic acid (C18:3) was the most abundant, followed by oleic (C18:1) and linoleic (C18:2) acids. Additionally, quantitative real-time RT-PCR analyses of 10 key seed oil synthesis genes in the three tree peony species revealed that FAD3, FAD2, β-PDHC, LPAAT and Oleosin gene expression levels positively correlate with total FA content and rate of accumulation. Specifically, the abundance of FAD3 transcripts in P. rockii compared with P. potaninii, and P. lutea suggests that FAD3 might play in an important role in synthesis of α-linolenic acid via phosphatidylcholine-derived pathway. Overall, comparative analyses of FA content and composition in three different peony species revealed correlation between efficient lipid accumulation and lipid gene expression during seed development. Further characterization and manipulation of these key genes from peonies will allow for subsequent improvement of tree peony oil quality and production.

lsoflurane interacts with cytochrome P-450 in rat and human hepatic microsomes and the Δ6- and Δ5-desaturases in rat hepatic microsomes. The interaction of isoflurane with cytochrome P-450 results in its metabolism to fluoride ion and organofluorine metabolites. The cytochrome P-450 isozymes catalysing the defluorination of isoflurane were assessed in hepatic microsomes from phenobarbital-, β-naphthoflavone- and pregnenolone-16α-carbonitrilepretreated and untreated rats. One or more of the cytochrome P-450 isozymes induced by phenobarbital and pregnenolone-16α-carbonitrile appear to defluorinate isoflurane, but those induced by β-naphthoflavone do not. From a comparison of the extent of defluorination of isoflurane in hepatic microsomes from phenobarbital- and pregnenolone-16α-carbonitrile-pretreated rats, and their Kₘ and Vₘₐₓ values, it appears that isoflurane is defluorinated by one or more isozymes induced by both phenobarbital and pregnenolone-16α-carbonitrile. The major isozyme is probably cytochrome P-450PCN1. The metabolites of isoflurane were identified in human and phenobarbital-induced rat hepatic microsomes. In microsomes from phenobarbital-pretreated rats, isoflurane is metabolised to fluoride ion and trifluoroacetaldehyde; trifluoroacetic acid is not produced in measureable amounts. The trifluoroacetaldehyde produced binds to microsomal constituents. In human hepatic microsomes, the organofluorine metabolite is identified as trifluoroacetic acid. It is proposed that isoflurane is metabolised by different pathways in human and phenobarbital-induced rat hepatic microsomes. The interaction of isoflurane with the cyanide-sensitive factors was assessed by several criteria. Firstly, using the reoxidation of cytochrome b₅ as an index of fatty acid desaturase activity, isoflurane appears to interact with the Δ6- and/or Δ5-desaturases, but not the Δ9-desaturase. Secondly, these results were confirmed and clarified by the use of direct assays to measure the fatty acid desaturase activity. Using the direct assay, we confirmed that isoflurane did not inhibit the Δ9-desaturase and inhibited Δ6-desaturation of linoleic acid, but not the Δ6-desaturation of α-linolenic acid. The inhibition of the Δ6-desaturation of linoleic acid occurred at low millimolar concentrations of isoflurane. lsoflurane inhibits the Δ5-desaturation of eicosa-8, 11, 14-trienoic acid to a small extent which is only apparent at much higher concentrations of isoflurane than that which inhibits the Δ6-desaturase. Further studies focussed on measurement of the activity of Δ6-desaturase in order to attempt to study the kinetics of the inhibition of the Δ6-desaturase by isoflurane: Δ6-desaturase activity was assessed using hepatic microsomes as the source of the enzyme and linoleic acid as substrate precursor. In the course of these studies, we identified a number of factors that affected the apparent activity of the Δ6-desaturase in hepatic microsomes. These included significant levels of endogenous substrate and competing reactions in the hepatic microsomes. Endogenous substrate levels were quantified and corrected for. We then resorted to computer modelling to extract the kinetics of the Δ6-desaturase free of contributions from acyl-CoA synthetase and lysophospholipid acyltransferase, as well as enzyme decay. The kinetics of isoflurane inhibition of the Δ6-desaturase were then superimposed and studied by computer modelling.

Made available in DSpace on 2015-03-26T13:42:08Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1395291 bytes, checksum: c18b5a982983cd4231258a4941494a76 (MD5) Previous issue date: 2008-07-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The fatty acid composition of soybean seeds has a direct impact on its oxidative stability. High levels of polyunsaturated fatty acids such as linoleic and linolenic acids make the oil more susceptible to hydrolytic and oxidative degradation leading to the formation of volatile compounds which alter the quality and flavor of foods. For this reason, there is a world demand for oils with high content of monounsaturated fatty acids and reduced levels of linolenic acid. The regulation of the fatty acid biosynthetic pathway in soybean seeds possibly involves transcriptional and post- transcriptional control of the w-6 and w-3 desaturases. However, the precise control mechanism is not known. The present work is part of the Breeding Program for Soybean Quality developed at BIOAGRO/UFV and its main goal is to determine the mRNA levels of the main desaturases during the development of soybean seeds, and to correlate them with the fatty acid levels and the enzymatic activities in different genotypes during seed filling. The following genotypes were used: A29, low linolenic acid content (~1%); FA22, high oleic content (~50%); N85-2176, low linolenic acid content (~3%) and medium oleic acid content (~30%); and Tucunaré, commercial cultivar with normal contents of oleic (~19%) and linolenic acids (~8%). The seeds were divided into five stages according to their fresh weight: 1st (0-125 mg); 2nd (126- 250 mg); 3rd (251-375 mg), 4th (376-450 mg) and 5th (dry seed). The following parameters were determined: fatty acid content; total oil content; relative enzymatic activities of w- 6 and w-3-desaturases; mRNA levels of FAD2-1 and FAD2-2 genes which encode the w-6-desaturases, and of genes GmFAD3A, GmFAD3B and GmFAD3C, which encode the w-3- desaturases. The results show that the oleic acid content increased between the 1st and 4th stages and reduced after that. The genotype FA22, followed by N85-2176, presented the highest oleic acid content during the development of the seed. As for the linolenic acid a drastic reduction was observed between the 1st and the 3rd stages in all genotypes. The genotype A29, followed by N85-2176 presented the lowest linolenic acid content during the development of the seed. The total oil content in mature seeds (5th stage) was 22% for Tucunaré, 24% for A29, 21% for N85-2176 and 19% for FA22. The values obtained for the desaturases relative activities were proportional to the average concentrations of the fatty acids in the genotypes. The relative enzymatic activities estimated as a function of the average contents of the fattey acids did not allow much conclusion and further determinations in vitro are necessary. The amount of transcripts for FAD2-1 was higher than that of FAD2-2. FAD2-1 levels were low in the first stages of development and increased with time, whereas FAD2-2 levels reduced with the development of the seed. These results are in accordance with the idea that FAD2-1 is related with the biosynthesis of storage fatty acids in the seeds and FAD2-2, with the biosynthesis of membrane fatty acid. Although genotypes FA22 and N85-2176 present high oleic acid contents, this fact cannot be explained by the reduction on transcript levels for the genes FAD2-2 and FAD2-1. This indicates that post-transcriptional events or even other genes control the expression of this trait. Transcript levels for the GmFAD3A gene were higher than those of the GmFAD3B and GmFAD3C genes in all genotypes tested. The transcripts for the GmFAD3A gene were barely detected in genotypes A29 and N85-2176, wheres GmFAD3B transcript levels were extremely low in A29. This fact explains the low level of linolenic acid in this genotype. It is conceivable that post- transcriptional control events regulate the expression of the GmFAD3C gene which encodes for the w-3-desaturase in A29 as this genotype harbors a mutation in this gene and no alteration has been detected in the corresponding transcript profile in relation to the normal cultivar Tucunaré. / A composição de ácidos graxos na fração óleo da soja influencia diretamente na sua estabilidade oxidativa. Conteúdos elevados de ácidos graxos polinsaturados, tais como o linoléico e linolênico, resultam em óleos mais susceptíveis a degradações hidrolíticas e oxidativas, levando à formação de compostos voláteis que alteram a qualidade e sabor dos alimentos. Assim, a tendência atual do mercado alimentício é buscar óleos com conteúdos mais elevados de ácidos graxos monoinsaturados e reduzido conteúdo de ácido linolênico. A regulação da via de biossíntese de ácidos graxos polinsaturados em sementes de soja possivelmente envolve controle transcricional e pós-transcricional das w-6 e w-3 dessaturases. No entanto, os mecanismos precisos de controle ainda não são muito claros. O presente trabalho está inserido no Programa de Melhoramento da Qualidade da Soja (PMQS) do BIOAGRO/UFV e tem como principal objetivo determinar os níveis de mRNAs das principais dessaturases de soja durante o desenvolvimento da semente, correlacionando- os com as concentrações relativas de ácidos graxos e atividade enzimática em diferentes cultivares durante o enchimento do grão. Para isso, foram utilizados os genótipos: A29, com baixa concentração de ácido linolênico (~1%); FA22, com elevada concentração de ácido oléico (~50%); N85-2176, com baixa concentração de ácido linolênico (~3%) e concentração média de ácido oléico (~30%); e Tucunaré, variedade comercial com concentrações normais de ácido oléico (~19%) e ácido linolênico (~8%). As sementes de soja foram subdivididas em cinco estádios de desenvolvimento de acordo com o seu peso úmido: 1° (0-125 mg); 2° (126-250 mg); 3° (251-375 mg), 4° (376-450 mg) e 5° (semente madura). Foram determinados: as concentrações de ácidos graxos; a concentração de óleo total; as atividades enzimáticas relativas das w-6 e w-3-dessaturases; e a expressão dos genes de FAD2-1 e FAD2-2, que codificam as w-6-dessaturases, e GmFAD3A, GmFAD3B e GmFAD3C, que codificam as w-3-dessaturases. De modo geral, a concentração de ácido oléico aumentou do 1° ao 4° estádio tendo uma redução entre o 4° e 5° estádios. O genótipo FA22, seguido de N85-2176, apresentou a maior concentração de ácido oléico durante todo o desenvolvimento da semente. Para o conteúdo de ácido linolênico, observou-se uma redução drástica do 1° ao 3° estádio em todos os genótipos. O genótipo A29, seguido de N85-2176, apresentou a menor concentração de ácido linolênico durante todo o desenvolvimento da semente. A concentração de óleo total nas sementes maduras fisiologicamente (5° estádio) foi de 22% para Tucunaré, 24% para A29, 21% para N85-2176 e 19% para FA22. A atividade enzimática relativa foi estimada com base nas concentrações médias dos ácidos graxos e não foi conclusiva, sendo necessárias determinações posteriores de atividade in vitro. Os níveis de transcritos do gene FAD2-1 foram superiores aos do gene FAD2-2, sendo que o acúmulo de transcritos de FAD2-1 foi menor nos estádios iniciais e aumentou com o desenvolvimento da semente, enquanto que para o gene FAD2-2 os níveis de transcritos reduziram com o desenvolvimento da semente. Esses resultados estão coerentes com a idéia de que FAD2-1 está relacionado com a biossíntese de ácido graxos de reserva em sementes e FAD2- 2, com a biossíntese de ácido graxos de membrana. Embora os genótipos FA22 e N85-2176 apresentem elevadas concentrações de ácido oléico, o mesmo não pode ser explicado pela redução na expressão dos genes FAD2-1 e FAD2-2, evidenciando a existência de mecanismos de regulação pós-transcricionais, ou até mesmo a presença de outros genes que controlem esta característica. Os níveis de transcritos do gene GmFAD3A foram superiores aos demais genes GmFAD3B e GmFAD3C no genótipo Tucunaré. Os acúmulos de transcritos do gene GmFAD3A foram praticamente nulos em A29 e N85-2176, enquanto GmFAD3B apresentou baixo acúmulo de transcritos em A29. Tal fato explica as baixas concentrações de ácido linolênico observados nesses genótipos. Mecanismos de regulação pós- transcricionais devem alterar a expressão final do gene GmFAD3C, que codifica a w-3-dessaturase neste genótipo, uma vez que A29 possui mutação nesse gene e nenhuma alteração no seu perfil de acúmulo de mRNA foi observado.

La picoalgue verte marine Ostreococcus tauri est un eucaryote minimal développé en système modèle et qui a servi de ressource de gènes en biologie des lipides. Des informations détaillées sur ces caractéristiques lipidiques étaient cependant manquantes. Lors de ma thèse j’ai caractérisé le glycérolipidome d’O. tauri et ai cherché à déterminer quelles sont les cibles enzymatiques responsables de la dynamique des acides gras (FA) et de la régulation du métabolisme lipidique en réponse à des modifications de l’environnement (carences nutritives et refroidissement). O. tauri présente des caractéristiques uniques de composition en lipides et en FA mixtes entre les algues vertes et les Chromalveolates, et a été validé comme espèce modèle pour la classe des Mamiellophyceae. L’acide docosahexaénoïque (DHA) est confiné dans les lipides présumés extraplastidiaux : le phosphatidyldimethylpropanethiol (PDPT) et le bétaïne-lipide diacylglyceryl-hydroxymethyl-trimethyl-β-alanine (DGTA), tous deux marqueurs lipidiques des Chromalveolates. Les lipides plastidiaux de type procaryotique sont caractérisés par une prépondérance de FA polyinsaturés (PUFA) en C18 n-3, le 18:5 n-3 étant restreint aux galactolipides. Le 16:4 n-3, PUFA typique des galactolipides des microalgues vertes, est également un composant majoritaire des lipides extraplastidiaux chez O. tauri. Les triacylglycérols (TAG) présentent tout le panel d’acides gras d’O. tauri et leurs combinaisons moléculaires indiquent une origine plastidiale majoritaire. La carence azote provoque une forte accumulation de TAG, notamment des espèces présentant des combinaisons sn-1/sn-2 en 18:X/16:X et s'accompagne d'un transfert de carbone du phosphatidylglycérol (PG) et du monogalactosyldiacylglycérol (MGDG) aux TAG ce qui indique une contribution croissante de la voie plastidiale à la synthèse des TAG. Des expériences préliminaires de RT-qPCR sur des gènes du métabolisme des TAG révèlent une forte activation transcriptionnelle de certaines diacylglycérol acyltransférases (DAGT). Les carences nutritives répriment sévèrement l’activité Δ6 désaturase, générant une inversion du ratio 18:3/18:4 dans les lipides plastidiaux qui se répercute dans les TAG. La régulation fine et dynamique de ce ratio suggère un rôle important du 18:3 et du 18:4 dans les membranes plastidiales. Le refroidissement engendre une augmentation spécifique du 18:5 des galactolipides. La recherche active de la désaturase responsable de ce phénotype par une approche d'expression de gènes candidats en systèmes homologue et hétérologues (S. cerevisiae, N. Benthamiana) a conduit à l’indentification de deux Δ6 désaturases plastidiales jamais caractérisées dans d'autres systèmes. Celles-ci possèdent des spécificités non redondantes et originales entre elles et par rapport à l'acyl-CoA-Δ6 d'O. tauri. / The marine green picoalga Ostreococcus tauri is a minimal eukaryote implemented as model system that has been used as gene resource for lipid biology. Detailed information about its lipidic features was however missing. During my PhD, I characterized O. tauri glycerolipidome and associated dynamics under environmental stresses such as nutrient starvations and chilling and investigated transcriptional variations of putative target enzymes responsible for these changes. O. tauri which could be validated as model for related species of the class Mamiellophyceae, was found to display unique lipidic features related to both green and Chromalveolates microalgae. Docosahexaenoic acid (DHA) is confined to presumed extraplastidial lipids i.e. phosphatidyldimethylpropanethiol (PDPT) and the betaine lipid diacylglyceryl-hydroxymethyl-trimethyl-β-alanine (DGTA); all of these compounds are hallmarks of Chromalveolates. Plastidial lipids found to be of prokaryotic type are characterized by the overwhelming presence of C18 n-3 polyunsaturated FA (PUFA), 18:5 n-3 being restricted to galactolipids. C16:4 n-3, an FA typical of green microalgae galactolipids, also was a major component of O. tauri extraplastidial lipids. Triacylglycerols (TAGs) display the complete panel of FAs, and their molecular combinations designate a major plastidial origin of DAG precursors. Nitrate starvation greatly increases TAG content, in particular 18:X/16:X (sn-1/sn-2) combinations, and was associated with the transfer of carbon from phosphatidylglycerol (PG) and monogalactosyldiacylglycerol (MGDG) to TAG indicating an increased contribution of the plastidial pathway to the TAG synthesis. Preliminary RT-qPCR experiments on TAG metabolism genes revealed an important transcriptional activation of some diacylglycerol acyltransferases (DGAT). Nutrient starvations severely repress Δ6 desaturase activity and result in the inversion of the 18:3/18:4 ratio in plastidial lipids that was feedback into TAG. The fine-tuning and dynamic regulation of the 18:3/18:4 ratio suggests an important physiological role of these FAs in photosynthetic membranes. Chilling generates an increase of 18:5 in galactolipids. The active quest for the desaturases responsible for this phenotype was achieved by expressing candidate genes in homologuous and heterologous (S. cerevisiae, N. Benthamiana) systems and led to the identification of two yet uncharacterized plastidial Δ6 desaturases. These desaturases display original and non-redundant specificity between each other and with the previously characterized in O. tauri Δ6 acyl-CoA desaturase.

Cardiovascular diseases are the leading cause of death in most industrialised countries and in developing countries the trend in cardiovascular-related deaths is increasing. World-wide, type 2 diabetes mellitus (T2DM) is an emerging cause of disability and premature death. Both these conditions are closely associated with the consumption of energy-dense foods and food products that are poor in nutrients, as well as with a sedentary lifestyle. Pharmacological and surgical interventions can improve the outcome and delay the progression of the disease, but in terms of population-level prevention there is no substitute for the adoption of a healthy lifestyle. SETTING The underlying studies were conducted in Västerbotten (the VIP study), and in Norrbotten and Västerbotten combined (the MONICA Project). Norrbotten andVästerbotten are the two northernmost counties in Sweden. Since the mid-1980sthe prevalence of cardiovascular disease has decreased and diabetes rates haveremained stable in this region, despite of an unbroken trend of increasing body weight. OBJECTIVE The aim of this thesis is to describe changes in reported dietary habits, estimatetheir relative importance as risk factors for diabetes and cardiovascular disease, and finally to identify lifestyle components as potential targets for intervention. RESULTS The first paper describes changes in self-reported food consumption between 1986 and 1999. During this period, the population in question switched from products with high saturated fatty acid content (e.g. milk containing 3% fat, butter) to foods containing less saturated fat (e.g. milk containing 1.5% fat, vegetable oil, low-fat margarine); pasta and rice were consumed more often, and potatoes were consumed less. Convenience foods (e.g. hamburgers, snacks, sweets) became more popular, whilst traditional dishes (e.g. potato dumplings, black pudding, blöta) decreased in popularity. Fruit and vegetable intake remained low. In paper two we study the effects of these changes in food intake on the risk of developing T2DM using body fat distribution as an early indicator. Increased consumption of convenience foods was associated with unfavourable changes (smaller hip circumference and larger waist circumference), whereas the increased consumption of vegetable oil and pasta was associated with low-risk fat distribution. In the third paper we report studies on the association between fat consumption and T2DM. We used the pattern of fatty acids in the membranes of red blood cells as a marker of fat intake. In addition to confirming earlier findings (markers of the intake of saturated fat are associated with increased risk of T2DM and markers of unsaturated fat are associated with reduced T2DM risk), we also identified associations between two markers of milk-derived saturated fat intake and enterolactone, a biomarker of dietary fibre intake, and the risk of developing myocardial infarction. Our results indicate that moderately high levels of enterolactone intake in men are associated with lower risk of experiencing myocardial infarction. Manuscript 5 ranks education level, physical activity, smoking status, and self-reported intake of dietary fibre and fatty acids according to their effects on body fat distribution. Increased levels of physical activity, a higher education level and a reduced intake of saturated fat from meat were ranked as the most strongly associated factors in both men and women. Increased intake of dietary fibre from grains in women, and increased intake of dietary fibre from fruits and vegetables in men, was also inversely associated with average waist circumference. CONCLUSION Both questionnaire-based and biological markers of the risk of developing diabetes or cardiovascular disease have been identified. Based on available population level measurements, reduced consumption of convenience foods, increased consumption of whole-grain products, fruits and vegetables, vegetable oil and pasta as well as increased physical activity are potential goals for interventions in northern Sweden.