| 1. |
- Alsehli, Ahmed
(författare)
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The role of HMG-coenzyme A reductase (HMGCR) and statin medication in the Central Nervous System : Cognitive Functions, Metabolism, Feeding and Sleep Behaviour
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Millions of people are currently on statin medications (HMGCR inhibitors) to prevent cardiovascular diseases. Despite considerable central nervous system expression, little is known about HMGCR function in the brain. In Paper I, we used Drosophila and rodent models and found that inhibiting Hmgcr expression in the insulin-producing cells of the Drosophila hypothalamus equivalent, known as the pars intercerebralis (PI), throughout development, significantly reduces the expression of Insulin–like peptides 2 and 3 (ILP2 and ILP3), severely decreasing insulin signalling. This reduction causes decreased body size, hyperglycemia, increased lipid storage, and hyperphagia. We also discovered that Farnesyl pyrophosphate synthase (Fpps), an enzyme downstream of Hmgcr in the mevalonate pathway, is required for ILP2 expression in the PI. In rodents, acute inhibition of hypothalamic Hmgcr stimulates food intake as well. Furthermore, in rats, we found two regions within the hypothalamus that had significantly increased neural activity, the paraventricular nucleus and arcuate nucleus, which are known to regulate food intake. In Paper II, we explored the effects of statins on cognition and performed an observational study on a population-based sample from the UK Biobank. Cognitive performance in terms of reaction time, working memory and fluid intelligence was analysed at baseline and two follow-ups. Subjects were classified depending on age (up to 65 and over 65 years). The effect of statin use differed between the two age groups, with a beneficial effect on reaction time in older persons and fluid intelligence in both age groups, and a negative effect on working memory in younger subjects. In Paper III, we examined association of single nucleotide polymorphisms within the HMGCR gene, rs17238484 and rs12916, with self-reported insomnia symptoms. We found that statin users are associated with a higher risk for self-reported insomnia. The HMGCR genetic variants were also associated with self-reported insomnia, but in different manner. Carriers the rs12916-T risk allele had a protective effect from insomnia symptoms. No associations were found for either statin takers or carriers of these HGCMR risk alleles and late evening chronotype. The increased risk of insomnia noted with statins is partially explained by a mechanism that might be independent of HMGCR inhibition. In Paper IV, we discovered a novel role for Hmgcr in sleep regulation in Drosophila, where lacking of pan-neuronal Hmgcr expression causes sleep-promoting effects. We also found that loss of Hmgcr expression specifically in the PI insulin-producing cells, recapitulates the effect of pan-neuronal Hmgcr inhibition. Conversely, inhibiting Hmgcr in only six PI DH44 expressing neurons has the opposite effect on sleep, increasing sleep latency and decreasing sleep duration. This bi-functional property of Hmgcr in the fly brain underlies its importance in sleep regulation. Furthermore, loss of Hmgcr showed no effect on circadian rhythm, suggesting that Hmgcr regulates sleep by pathways distinct from the circadian clock.
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| 2. |
- Alsiö, Johan
(författare)
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From Food Preference to Craving : Behavioural Traits and Molecular Mechanisms
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Preference for palatable and energy-dense foods may be a risk factor for body weight gain and has both genetic and environmental components. Once obesity develops in an individual, weight loss is difficult to achieve. Indeed, obesity is often characterized by repeated attempts to reduce the overconsumption of energy-dense foods, followed by food craving and relapse to overconsumption. Relapse and loss of control over intake are observed also in drug addicts, and it has been shown that obesity and drug addiction not only share behavioural features but also neural circuitry, e.g. the mesolimbic dopamine pathway. In this thesis, we sought to investigate the mechanisms related to food preferences and craving using animal models previously used in addiction research. The risk of gaining weight may implicate behavioural traits and emotional states. We showed in rats that a risk-taking behavioural profile was associated both with increased preference for a high-fat (HF) diet and with increased motivational response to a palatable high-sucrose (HS) diet. Hypothalamic urocortin 2 expression was associated with the preference for the HF diet. We also tested the hypothesis that consumption of HS and HF diets separately or provided simultaneously (HFHS) affect anxiety-like behaviour and locomotion. Furthermore, we showed that withdrawal from HFHS food affects diet-induced obesity-prone (OP) and obesity-resistant (OR) animals differently. OP animals had increased motivation (craving) for HS food pellets as measured by the operant self-administration technique during withdrawal. Dopamine receptor expression in the striatum differed between OP and OR animals both at access to HFHS and during withdrawal. This strongly implicates dopaminergic signaling in the OP phenotype. In humans, food preferences may be monitored using questionnaires. We analyzed food preference data from parents of preschool children, and identified an inverse association of parental preference for high-fat high-protein food and overweight in children. In conclusion, we have employed animal models previously used in the addiction field to identify molecular mechanisms related both to food preference and vulnerability to obesity, and to food craving associated with withdrawal from palatable food. These findings add to our current understanding of obesity.
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| 3. |
- Attwood, Misty M.
(författare)
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Membrane-bound proteins : Characterization, evolution, and functional analysis
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Alpha-helical transmembrane proteins are important components of many essential cell processes including signal transduction, transport of molecules across membranes, protein and membrane trafficking, and structural and adhesion activities, amongst others. Their involvement in critical networks makes them the focus of interest in investigating disease pathways, as candidate drug targets, and in evolutionary analyses to identify homologous protein families and possible functional activities. Transmembrane (TM) proteins can be categorized into major groups based the same gross structure, i.e., the number of transmembrane helices, which are often correlated with specific functional activities, for example as receptors or transporters. The focus of this thesis was to analyze the evolution of the membrane proteome from the last holozoan common ancestor (LHCA) through metazoans to garner insight into the fundamental functional clusters that underlie metazoan diversity and innovation. Twenty-four eukaryotic proteomes were analyzed, with results showing more than 70% of metazoan transmembrane protein families have a pre-metazoan origin. In concert with that, we characterized the previously unstudied groups of human proteins with three, four, and five membrane-spanning regions (3TM, 4TM, and 5TM) and analyzed their functional activities, involvement in disease pathways, and unique characteristics. Combined, we manually curated and classified nearly 11% of the human transmembrane proteome with these three studies. The 3TM data set included 152 proteins, with nearly 45% that localize specifically to the endoplasmic reticulum (ER), and are involved in membrane biosynthesis and lipid biogenesis, proteins trafficking, catabolic processes, and signal transduction due to the large ionotropic glutamate receptor family. The 373 proteins identified in the 4TM data set are predominantly involved in transport activities, as well as cell communication and adhesion, and function as structural elements. The compact 5TM data set includes 58 proteins that engage in localization and transport activities, such as protein targeting, membrane trafficking, and vesicle transport. Notably, ~60% are identified as cancer prognostic markers that are associated with clinical outcomes of different tumour types. This thesis investigates the evolutionary origins of the human transmembrane proteome, characterizes formerly dark areas of the membrane proteome, and extends the fundamental knowledge of transmembrane proteins.
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| 4. |
- Cedernaes, Jonathan
(författare)
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Intestinal Gene Expression Profiling and Fatty Acid Responses to a High-fat Diet
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The gastrointestinal tract (GIT) regulates nutrient uptake, secretes hormones and has a crucial gut flora and enteric nervous system. Of relevance for these functions are the G protein-coupled receptors (GPCRs) and the solute carriers (SLCs). The Adhesion GPCR subfamily is known to mediate neural development and immune system functioning, whereas SLCs transport e.g. amino acids, fatty acids (FAs) and drugs over membranes. We aimed to comprehensively characterize Adhesion GPCR and SLC gene expression along the rat GIT. Using qPCR we measured expression of 78 SLCs as well as all 30 Adhesion GPCRs in a twelve-segment GIT model. 21 of the Adhesion GPCRs had a widespread (≥5 segments) or ubiquitous (≥11 segments) expression. Restricted expression patterns were characteristic for most group VII members. Of the SLCs, we found the majority (56 %) of these transcripts to be expressed in all GIT segments. SLCs were predominantly found in the absorption-responsible gut regions. Both Adhesion GPCRs and SLCs were widely expressed in the rat GIT, suggesting important roles. The distribution of Adhesion GPCRs defines them as a potential pharmacological target.FAs constitute an important energy source and have been implicated in the worldwide obesity increase. FAs and their ratios – indices for activities of e.g. the desaturase enzymes SCD-1 (SCD-16, 16:1n-7/16:0), D6D (18:3n-6/18:2n-6) and D5D (20:4n-6/20:3n-6) – have been associated with e.g. overall mortality and BMI. We examined whether differences in FAs and their indices in five lipid fractions contributed to obesity susceptibility in rats fed a high fat diet (HFD), and the associations of desaturase indices between lipid fractions in animals on different diets. We found that on a HFD, obesity-prone (OP) rats had a higher SCD-16 index and a lower linoleic acid (LA) proportions in subcutaneous adipose tissue (SAT) than obesity-resistant rats. Desaturase indices were significantly correlated between many of the lipid fractions. The higher SCD-16 may indicate higher SCD-1 activity in SAT in OP rats, and combined with lower LA proportions may provide novel insights into HFD-induced obesity. The associations between desaturase indices show that plasma measurements can serve as proxies for some lipid fractions, but the correlations seem to be affected by diet and weight gain.
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| 5. |
- Desai Boström, Adrian, 1990-
(författare)
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Epigenetic dysregulation in relation to psychiatric traits in adolescence and adulthood
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Epigenetics has evolved into a key research focus in the field of psychiatry. DNA methylation is the most researched epigenetic mechanism. In paper I-III, 130 and 93 adolescents were randomly recruited at two separate intervals. Subjects were evaluated by web-based diagnostic interviews using the Development and Well-Being Assessment (DAWBA), providing computer generated diagnostic predictions of probability of diagnosis, covering several psychiatric disorders. For Paper I-II, the genome-wide DNA methylation pattern was measured from whole blood using the Illumina 450K array, and for paper IV by the Illumina EPIC BeadChip. In paper I, a methylome-wide association study (MWAS) was conducted (n=93) followed by a validation analysis (n=78), contrasting methylation levels in groups stratified by DAWBA depression risk scores. A microRNA4646 (MIR4646) associated methylation locus was differentially methylated in the MWAS (pbonf<0.05) and results were replicated in the validation cohort (p<0.05). Methylation levels at the identified locus correlated inversely with gene expression levels of MIR4456 (p<0.05). In silico analysis suggests MIR4646 may influence synthesis of omega-3 fatty acids, previously implicated in major depressive disorder. In paper II, 37 single nucleotide polymorphisms (SNP:s) previously associated with psychiatric disease were evaluated in relation to genome-wide DNA methylation levels in 130 adolescents in a methylome-wide (mQTL) analysis. Five SNP-CpG pairs were identified (pbonf<0.05) and replicated (p<0.05). Methylation of three of these were shown to be significantly correlated with gene expression levels of the associated genes (p<0.05). One identified GAD1-coupled methylation site was differentially methylated to a general psychiatric risk score in adolescents (p<0.05). In Paper III, hypothalamic-pituitary-adrenal (HPA)-axis coupled DNA methylation loci were investigated in 88 suicide attempters to identify associations to severity of suicide attempt. One corticotropin releasing hormone (CRH)-associated CpG-site was significantly hypomethylated in the high-risk group of suicide-attempters (n=31)(cg19035496, p<0.001) and exhibited hypermethylation in an external study group of adolescents in dependency of a general psychiatric risk score (p<0.05). In paper IV, 8,852 microRNA (miRNA) associated CpG-sites were investigated for an association with hypersexual disorder (HD). A microRNA-4456 (MIR4456) associated CpG-site (cg01299774) was borderline significant in HD (pFDR=5.81E-02) and differentially methylated in alcohol dependence (p<0.05) in an independent study group. Methylation levels at cg01299774 correlated inversely with expression levels of MIR4456 (p<0.01) and MIR4456 was lower expressed in HD (p<0.05). In-silico analyses suggests MIR4456 putatively targets genes preferentially expressed in brain and that are involved in major neuronal molecular mechanisms thought to be relevant for HD, e.g., the oxytocin signaling pathway.
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| 6. |
- Höglund, Pär J., 1980-
(författare)
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Identification, Characterization and Evolution of Membrane-bound Proteins
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Membrane proteins constitute approximately 30% of all genes in the human genome and two large families of membrane proteins are G protein-coupled receptors (GPCRs) and Solute Carriers (SLCs) with about 800 and 380 human genes, respectively.In Papers I, II and IV, we report 16 novel human Adhesion GPCRs found by searches in NCBI and Celera databases. In Paper I, we report eight novel human GPCRs, and six in Paper II. We identified two new human Adhesion GPCRs and 17 mouse orthologs in Paper IV. Phylogenetic analysis demonstrates that the 16 novel human genes are additional members of the Adhesion GPCR family and can be divided into eight phylogenetic groups. EST expression charts for the entire repertoire of Adhesions in human and mouse were established, showing widespread distribution in both central and peripheral tissues. Different domains were found in their N-terminus, some, such as pentraxin in GPR112, indicates that they take part in immunological processes.In Paper III, we discovered seven new human Rhodopsin GPCRs.In Paper V, we present the identification of two new human genes, termed SLC6A17 and SLC6A18 from the Solute Carriers family 6 (SLC6). We also identified the corresponding orthologs and additional genes from the mouse and rat genomes. We analysed, in total, 430 unique SLC6 proteins from 10 animal, one plant, two fungi and 196 bacterial genomes.In Paper VI, we provide the first systematic analysis of the evolutionary history of the different SLC families in Eukaryotes. In all, we analysed 2403 sequences in eight species and we delineate the evolutionary history of each of the 46 SLC families.
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| 7. |
- Nordström, Karl J. V., 1980-
(författare)
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Characterization and Evolution of Transmembrane Proteins with Focus on G-protein coupled receptors in Pre-vertebrate Species
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- G protein-coupled receptors (GPCRs) are one of the largest protein families in mammals. GPCRs are instrumental for hormonal and neurotransmitter signalling and are important in all major physiological systems of the body. Paper I describes the repertoire of GPCRs in Branchiostoma floridae, which is one of the species most closely related species to vertebrates. Mining and phylogenetic analysis of the amphioxus genome showed the presence of at least 664 distinct GPCRs distributed among all the main families of GPCRs; Glutamate (18), Rhodopsin (570), Adhesion (37), Frizzled (6) and Secretin (16). Paper II contains studies of the Adhesion, Methuselah and Secretin GPCR families in nine genomes. The Adhesion GPCRs are the most complex gene family among GPCRs with large genomic size, multiple introns and a fascinating flora of functional domains. Phylogenetic analysis showed Adhesion group V (that contains GPR133 and GPR144) to be the closest relative to the Secretin family among the groups in the Adhesion family, which was also supported by splice site setup and conserved motifs. Paper III examines the repertoire of human transmembrane proteins. These form key nodes in mediating the cell’s interaction with the surroundings, which is one of the main reasons why the majority of drug targets are membrane proteins. We identified 6,718 human membrane proteins and classified the majority of them into 234 families of which 151 belong to the three major functional groups; Receptors (63 groups, 1,352 members), Transporters (89 groups, 817 members) or Enzymes (7 groups, 533 members). In addition, 74 Miscellaneous groups were shown to include 697 members. Paper IV clarifies the hierarchy of the main families and evolutionary origin of majority of the metazoan GPCR families. Overall, it suggests common decent of at least 97% of the GPCRs sequences found in humans, including all the main families.
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