👤 Jussi Pihlajamäki

Fatty acid desaturase (FADS1) variant-rs174550 strongly regulates polyunsaturated fatty acid (PUFA) biosynthesis. Additionally, the FADS1 is related to mitochondrial function. Thus, we investigated whether changes in mitochondrial function are associated with the genetic variation in FADS1 (rs174550) in human adipocytes isolated from individuals consuming diets enriched with either dietary alpha-linolenic (ALA) or linoleic acid (LA). Two cohorts of men homozygous for the genotype of FADS1 (rs174550) were studied: FADSDIET2 dietary intervention study with ALA- and LA-enriched diets and Kuopio Obesity Surgery study (KOBS), respectively. We could demonstrate that differentiated human adipose-derived stromal cells from subjects with the TT genotype had higher mitochondrial metabolism compared with subjects with the CC genotype of FADS1-rs174550 in the FADSDIET2. Responses to PUFA-enriched diets differed between the genotypes of FADS1-rs174550, showing that ALA, but not LA, -enriched diet stimulated mitochondrial metabolism more in subjects with the CC genotype when compared with subjects with the TT genotype. ALA, but not LA, proportion in plasma phospholipid fraction correlated positively with adipose tissue mitochondrial-DNA amount in subjects with the CC genotype of FADS1-rs174550 in the KOBS. These findings demonstrate that the FADS1-rs174550 is associated with modification in mitochondrial function in human adipocytes. Additionally, subjects with the CC genotype, when compared with the TT genotype, benefit more from the ALA-enriched diet, leading to enhanced energy metabolism in human adipocytes. Altogether, the FADS1-rs174550 could be a genetic marker to identify subjects who are most suitable to receive dietary PUFA supplementation, establishing also a personalized therapeutic strategy to improve mitochondrial function in metabolic diseases. Show less

Lipoprotein(a) [Lp(a)] is a causal, genetically determined cardiovascular risk factor. Limited evidence suggests that dietary unsaturated fat may increase serum Lp(a) concentration by 10-15 %. Linoleic acid may increase Lp(a) concentration through its endogenous conversion to arachidonic acid, a process regulated by the fatty acid desaturase (FADS) gene cluster. We aimed to compare the Lp(a) and other lipoprotein trait-modulating effects of dietary alpha-linolenic (ALA) and linoleic acids (LA). Additionally, we examined whether FADS1 rs174550 genotype modifies Lp(a) responses. A genotype-based randomized trial was performed in 118 men homozygous for FADS1 rs174550 SNP (TT or CC). After a 4-week run-in period, the participants were randomized to 8-week intervention diets enriched with either Camelina sativa oil (ALA diet) or sunflower oil (LA diet) 30-50 mL/day based on their BMI. Serum lipid profile was measured at baseline and at the end of the intervention. ALA diet lowered serum Lp(a) concentration by 7.3 % (p = 0.003) and LA diet by 9.5 % (p < 0.001) (p = 0.089 for between-diet difference). Both diets led to greater absolute decreases in individuals with higher baseline Lp(a) concentration (p < 0.001). Concentrations of LDL cholesterol (LDL-C), non-HDL-C, remnant-C, and apolipoprotein B were lowered more by the ALA diet (p < 0.01). Lipid or lipoprotein responses were not modified by the FADS1 rs174550 genotype. A considerable increase in either dietary ALA or LA from vegetable oils has a similar Lp(a)-lowering effect, whereas ALA may lower other major atherogenic lipids and lipoproteins to a greater extent than LA. Genetic differences in endogenous PUFA conversion may not influence serum Lp(a) concentration. Show less

Abdominal obesity increases the risk for non-alcoholic fatty liver disease (NAFLD), now known as metabolic dysfunction-associated steatotic liver disease (MASLD). To elucidate the directional cell-type level biological mechanisms underlying the association between abdominal obesity and MASLD, we integrated adipose and liver single nucleus RNA-sequencing and bulk cis-expression quantitative trait locus (eQTL) data with the UK Biobank genome-wide association study (GWAS) data using colocalization. Then we used colocalized cis-eQTL variants as instrumental variables in Mendelian randomization (MR) analyses, followed by functional validation experiments on the target genes of the cis-eQTL variants. We identified 17 colocalized abdominal obesity GWAS variants, regulating 17 adipose cell-type marker genes. Incorporating these 17 variants into MR discovers a putative tissue-of-origin, cell-type-aware causal effect of abdominal obesity on MASLD consistently with multiple MR methods without significant evidence for pleiotropy or heterogeneity. Single cell data confirm the adipocyte-enriched mean expression of the 17 genes. Our cellular experiments across human adipogenesis identify risk variant -specific epigenetic and transcriptional mechanisms. Knocking down two of the 17 genes, PPP2R5A and SH3PXD2B, shows a marked decrease in adipocyte lipidation and significantly alters adipocyte function and adipogenesis regulator genes, including DGAT2, LPL, ADIPOQ, PPARG, and SREBF1. Furthermore, the 17 genes capture a characteristic MASLD expression signature in subcutaneous adipose tissue. Overall, we discover a significant cell-type level effect of abdominal obesity on MASLD and trace its biological effect to adipogenesis. NIH grants R01HG010505, R01DK132775, and R01HL170604; the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (Grant No. 802825), Academy of Finland (Grants Nos. 333021), the Finnish Foundation for Cardiovascular Research the Sigrid Jusélius Foundation and the Jane and Aatos Erkko Foundation; American Association for the Study of Liver Diseases (AASLD) Advanced Transplant Hepatology award and NIH/NIDDK (P30DK41301) Pilot and Feasibility award; NIH/NIEHS F32 award (F32ES034668); Finnish Diabetes Research Foundation, Kuopio University Hospital Project grant (EVO/VTR grants 2005-2021), the Academy of Finland grant (Contract no. 138006); Academy of Finland (Grant Nos 335443, 314383, 272376 and 266286), Sigrid Jusélius Foundation, Finnish Medical Foundation, Finnish Diabetes Research Foundation, Novo Nordisk Foundation (#NNF20OC0060547, NNF17OC0027232, NNF10OC1013354) and Government Research Funds to Helsinki University Hospital; Orion Research Foundation, Maud Kuistila Foundation, Finish Medical Foundation, and University of Helsinki. Show less

The fatty acid composition of plasma lipids, which is associated with biomarkers and risk of non-communicable diseases, is regulated by dietary polyunsaturated fatty acids (PUFAs) and variants of fatty acid desaturase (FADS). We investigated the interactions between dietary PUFAs and FADS1 rs174550 variant. Participants (n = 118), homozygous for FADS1 rs174550 variant (TT and CC) followed a high alpha-linolenic acid (ALA, 5 percent of energy (E-%)) or a high linoleic acid (LA, 10 E-%) diet during an 8-week randomized controlled intervention. Fatty acid composition of plasma lipids and PUFA-derived lipid mediators were quantified by gas and liquid chromatography mass spectrometry, respectively. The high-LA diet increased the concentration of plasma LA, but not its lipid mediators. The concentration of plasma arachidonic acid decreased in carriers of CC and remained unchanged in the TT genotype. The high-ALA diet increased the concentration of plasma ALA and its cytochrome P450-derived epoxides and dihydroxys, and cyclooxygenase-derived monohydroxys. Concentrations of plasma eicosapentaenoic acid and its mono- and dihydroxys increased only in TT genotype carriers. These findings suggest the potential for genotype-based recommendations for PUFA consumption, resulting in modulation of bioactive lipid mediators which can exert beneficial effects in maintaining health. Show less

Fatty acid desaturase (FADS) variants associate with fatty acid (FA) and adipose tissue (AT) metabolism and inflammation. Thus, the role of FADS1 variants in the regulation of dietary linoleic acid (LA)-induced effects on AT inflammation was investigated. Subjects homozygotes for the TT and CC genotypes of the FADS1-rs174550 (TT, n = 25 and CC, n = 28) or -rs174547 (TT, n = 42 and CC, n = 28), were either recruited from the METabolic Syndrome In Men cohort to participate in an intervention with LA-enriched diet (FADSDIET) or from the Kuopio Obesity Surgery (KOBS) study. GC and LC-MS for plasma FA proportions and eicosanoid concentrations and AT gene expression for AT inflammatory score (AT-InSc) was determined. We observed a diet-genotype interaction between LA-enriched diet and AT-InSc in the FADSDIET. In the KOBS study, interleukin (IL)1 beta mRNA expression in AT was increased in subjects with the TT genotype and highest LA proportion. In the FADSDIET, n-6/LA proportions correlated positively with AT-InSc in those with the TT genotype but not with the CC genotype after LA-enriched diet. Specifically, LA- and AA-derived pro-inflammatory eicosanoids related to CYP450/sEH-pathways correlated positively with AT-InSc in those with the TT genotype, whereas in those with the CC genotype, the negative correlations between pro-inflammatory eicosanoids and AT-InSc related to COX/LOX-pathways. LA-enriched diet increases inflammatory AT gene expression in subjects with the TT genotype, while CC genotype could play a protective role against LA-induced AT inflammation. Overall, the FADS1 variant could modify the dietary LA-induced effects on AT inflammation through the differential biosynthesis of AA-derived eicosanoids. Show less

Fatty acid desaturase 1 (FADS1) gene encodes for delta-5 desaturase enzyme which is needed in conversion of linoleic acid (LA) to arachidonic acid (AA). Recent studies have shown that response to dietary PUFAs differs between the genotypes in circulating fatty acids. However, interactions between the FADS1 genotype and dietary LA on overall metabolism have not been studied. We aimed to examine the interactions of FADS1 rs174550 genotypes (TT and CC) and high-LA diet to identify plasma metabolites that respond differentially to dietary LA according to the FADS1 genotype. A total of 59 men (TT n = 26, CC n = 33) consumed a sunflower oil supplemented diet for 4 weeks. Daily dose of 30, 40, or 50 ml was calculated based on body mass index. It resulted in 17-28 g of LA on top of the usual daily intake. Fasting plasma samples at the beginning and at the end of the intervention were analyzed with LC-MS/MS non-targeted metabolomics method. At the baseline, the carriers of FADS1 rs174550-TT genotype had higher abundance of long-chain PUFA phospholipids compared to the FADS1 rs174550-CC one. In response to the high-LA diet, LA phospholipids and long-chain acylcarnitines increased and lysophospholipids decreased in fasting plasma similarly in both genotypes. LysoPE (20:4), LysoPC (20:4), and PC (16:0₂₀:4) decreased and cortisol increased in the carriers of rs174550-CC genotype; however, these genotype-diet interactions were not significant after correction for multiple testing. Our findings show that both FADS1 rs174550 genotype and high-LA diet modify plasma phospholipid composition. The study was registered to ClinicalTrials: NCT02543216, September 7, 2015 (retrospectively registered). Show less

The article investigates the FADS1 rs174550 genotype interaction with dietary intakes of high linoleic acid (LA) and high alpha-linolenic acid (ALA) on the response of fatty acid composition of plasma phospholipids (PLs), and of markers of low-grade inflammation and glucose-insulin homeostasis. One-hundred thirty homozygotes men for FADS1 rs174550 SNP (TT and CC genotypes) were randomized to an 8-week intervention with either LA- or ALA-enriched diet (13 E% PUFA). The source of LA and ALA are 30-50 mL of sunflower oil (SFO, 62-63% LA) and Camelina sativa oil (CSO, 30- are randomized to an 35% ALA), respectively. In the SFO arm, there is a significant genotype x diet interaction for the proportion of arachidonic acid in plasma phospholipids (p < 0.001), disposition index (DI The FADS1 genotype modifies the response to high PUFA diets, especially to high-LA diet. These findings suggest that approaches considering FADS variation may be useful in personalized dietary counseling. Show less

Non-alcoholic fatty liver disease has been associated with increased mRNA expression of FADS2 in the liver and estimated activity of delta-6 desaturase in serum, encoded by the FADS2 gene. Since DNA methylation in the FADS1/2/3 gene cluster has been previously linked with genetic variants and desaturase activities, we now aimed to discover factors regulating DNA methylation of the CpG sites annotated to FADS1/2 genes. DNA methylation levels in the CpG sites annotated to FADS2 and FADS1 were analyzed from liver samples of 95 obese participants of the Kuopio Obesity Surgery Study (34 men and 61 women, age 49.5 ± 7.7 years, BMI 43.0 ± 5.7 kg/m We found a negative correlation between DNA methylation levels of cg06781209 and cg07999042 and hepatic FADS2 mRNA expression (both p < 0.05), and with estimated delta-6 desaturase activity based on both liver and serum fatty acids (all p < 0.05). Interestingly, the methylation level of cg07999042 (p = 0.001) but not of cg06781209 (p = 0.874) was associated with FADS2 variant rs174616. Genetic variants of FADS2 may contribute to the pathogenesis of non-alcoholic fatty liver disease by modifying DNA methylation. Show less

The health benefits of substituting dietary polyunsaturated fatty acids (PUFAs) for saturated fatty acids are well known. However, limited information exists on how the response to dietary intake of linoleic acid (LA; 18:2n-6) is modified by polymorphisms in the fatty acid desaturase (FADS) gene cluster. The aim of the current study was to test the hypothesis that the FADS1 rs174550 genotype modifies the effect of dietary LA intake on the fatty acid composition of plasma lipids, fasting glucose, and high-sensitivity C-reactive protein (hsCRP). Associations were investigated between genotype, plasma PUFAs, fasting glucose, and hsCRP concentrations in the cross-sectional, population-based Metabolic Syndrome in Men cohort (n = 1337). In addition, 62 healthy men from the cohort who were homozygotes for the TT or CC genotype of the FADS1 rs174550 were recruited to a 4-wk intervention (FADSDIET) with an LA-enriched diet. The fatty acid composition of plasma PUFAs and concentrations of plasma fasting glucose, serum hsCRP, and plasma lipid mediators (eicosanoids and related analogs) were measured at the beginning and end of the 4-wk intervention period. In the FADSDIET trial, the plasma LA proportion increased in both genotype groups in response to an LA-enriched diet. Responses in concentrations of serum hsCRP and plasma fasting glucose and the proportion of arachidonic acid (20:4n-6) in plasma phospholipids and cholesteryl esters differed between genotype groups (interaction of diet × genotype, P < 0.05). In TT homozygous subjects, plasma eicosanoid concentrations correlated with the arachidonic acid proportion in plasma and with hsCRP (r = 0.4-0.7, P < 0.05), whereas in the CC genotype there were no correlations. Our findings show that the FADS1 genotype modifies metabolic responses to dietary LA. The emerging concept that personalized dietary counseling should be modified by the FADS1 genotype needs to be tested in larger randomized trials. The study was registered at clinicaltrials.gov as NCT02543216. Show less

Non-alcoholic steatohepatitis (NASH) is associated with changes in fatty acid (FA) metabolism. However, specific changes in metabolism and hepatic mRNA expression related to NASH independent of simple steatosis, obesity and diet are unknown. Liver histology, serum and liver FA composition and estimated enzyme activities based on the FA ratios in cholesteryl esters and triglycerides were assessed in 92 obese participants of the Kuopio Obesity Surgery Study (KOBS) divided to those with normal liver, steatosis or NASH (30 men and 62 women, age 46.8±9.5years (mean±SD), BMI 44.2±6.2kg/m(2)). Plasma FA composition was also investigated in the Metabolic Syndrome in Men (METSIM) Study (n=769), in which serum alanine aminotransferase (ALT) was used as a marker of liver disease. Obese individuals with NASH had higher activity of estimated activities of delta-6 desaturase (D6D, p<0.002) and stearoyl-CoA desaturase 1 (SCD1, p<0.002) and lower activity of delta-5 desaturase (D5D, p<0.002) when compared to individuals with normal liver. Estimated activities of D5D, D6D and SCD1 correlated positively between liver and serum indicating that serum estimates reflected liver metabolism. Accordingly, NASH was associated with higher hepatic mRNA expression of corresponding genes FADS1, FADS2 and SCD. Finally, differences in FA metabolism that associated with NASH in obese individuals were also associated with high ALT in the METSIM Study. We demonstrated alterations in FA metabolism and endogenous desaturase activities that associate with NASH, independent of obesity and diet. This suggests that changes in endogenous FA metabolism are related to NASH and that they may contribute to the progression of the disease. Show less

Obesity is associated with disturbed lipid metabolism and low-grade inflammation in tissues. The aim of this study was to investigate the association between FA metabolism and adipose tissue (AT) inflammation in the Kuopio Obesity Surgery study. We investigated the association of surgery-induced weight loss and FA desaturase (FADS)1/2 genotypes with serum and AT FA profile and with AT inflammation, measured as interleukin (IL)-1β and NFκB pathway gene expression, in order to find potential gene-environment interactions. We demonstrated an association between serum levels of saturated and polyunsaturated n-6 FAs, and estimated enzyme activities of FADS1/2 genes with IL-1β expression in AT both at baseline and at follow-up. Variation in the FADS1/2 genes associated with IL-1β and NFκB pathway gene expression in SAT after weight reduction, but not at baseline. In addition, the FA composition in subcutaneous and visceral fat correlated with serum FAs, and the associations between serum PUFAs and estimated D6D enzyme activity with AT inflammation were also replicated with corresponding AT FAs and AT inflammation. We conclude that the polymorphism in FADS1/2 genes associates with FA metabolism and AT inflammation, leading to an interaction between weight loss and FADS1/2 genes in the regulation of AT inflammation. Show less

Limited information exists on how the relationship between dietary intake of fat and fatty acids in erythrocytes and plasma is modulated by polymorphisms in the FADS gene cluster. We examined gene-diet interaction of total marine PUFA intake with a known gene encoding Δ-5 desaturase enzyme (FADS1) variant (rs174550) for fatty acids in erythrocyte membranes and plasma phospholipids (PL), cholesteryl esters (CE), and triglycerides (TG). In this cross-sectional study, fatty acid compositions were measured using GC, and total intake of polyunsaturated fat from fish and fish oil was estimated using a food frequency questionnaire in a subsample (n = 962) of the Metabolic Syndrome in Men Study. We found nominally significant gene-diet interactions for eicosapentaenoic acid (EPA, 20:5n-3) in erythrocytes (pinteraction = 0.032) and for EPA in plasma PL (pinteraction = 0.062), CE (pinteraction = 0.035), and TG (pinteraction = 0.035), as well as for docosapentaenoic acid (22:5n-3) in PL (pinteraction = 0.007). After excluding omega-3 supplement users, we found a significant gene-diet interaction for EPA in erythrocytes (pinteraction < 0.003). In a separate cohort of the Kuopio Obesity Surgery Study, the same locus was strongly associated with hepatic mRNA expression of FADS1 (p = 1.5 × 10(-10) ). FADS1 variants may modulate the relationship between marine fatty acid intake and circulating levels of long-chain omega-3 fatty acids. Show less

Low-grade inflammation in obesity is associated with accumulation of the macrophage-derived cytokine osteopontin (OPN) in adipose tissue and induction of local as well as systemic insulin resistance. Since glucose-dependent insulinotropic polypeptide (GIP) is a strong stimulator of adipogenesis and may play a role in the development of obesity, we explored whether GIP directly would stimulate OPN expression in adipose tissue and thereby induce insulin resistance. GIP stimulated OPN protein expression in a dose-dependent fashion in rat primary adipocytes. The level of OPN mRNA was higher in adipose tissue of obese individuals (0.13 ± 0.04 vs. 0.04 ± 0.01, P < 0.05) and correlated inversely with measures of insulin sensitivity (r = -0.24, P = 0.001). A common variant of the GIP receptor (GIPR) (rs10423928) gene was associated with a lower amount of the exon 9-containing isoform required for transmembrane activity. Carriers of the A allele with a reduced receptor function showed lower adipose tissue OPN mRNA levels and better insulin sensitivity. Together, these data suggest a role for GIP not only as an incretin hormone but also as a trigger of inflammation and insulin resistance in adipose tissue. Carriers of the GIPR rs10423928 A allele showed protective properties via reduced GIP effects. Identification of this unprecedented link between GIP and OPN in adipose tissue might open new avenues for therapeutic interventions. Show less

Hypertrophic cardiomyopathy (HCM) is a genetic disorder characterized by cardiac hypertrophy caused by mutations in genes encoding sarcomere proteins. This study screened all patients with HCM from the Kuopio University Hospital region in eastern Finland for variants in the cardiac myosin-binding protein C gene ( MYBPC3). All 35 exons of MYBPC3 were screened by the single-strand conformation polymorphism method in 37 unrelated patients with HCM. In MYBPC3 we identified seven novel (Gln1061X, IVS5-2A-->C, IVS14-13G-->A, Ex25DeltaLys, Pro147Leu, Ser236Gly, and Arg1138His) and two previously reported (Arg326Gln, Val896Met) variants, all of which are predicted to affect the structure of the encoded protein. Four of the nine variants, a nonsense mutation Gln1061X, a splice acceptor mutation (IVS5-2A-->C), a novel substitution in intron 14 (IVS14-13G-->A), and a novel 3-bp deletion in exon 25 (Ex25DeltaLys) were concluded to be disease-causing mutations because they cosegregated with the HCM phenotype or were absent in more than 200 normal chromosomes, or both. The mutation Gln1061X was found most frequently, being present in 6 families (23 subjects) while the other three mutations were found in single families each. Haplotype analysis indicated a likely founder effect among the families carrying the Gln1061X mutation. We found four novel mutations in MYBPC3, accounting for approx. 38% of familial and 24% of all cases of HCM. In our previous and unpublished studies no more frequent cause of HCM has been found in genetic analyses of other eight sarcomeric proteins. Consequently MYBPC3 is the predominant gene for HCM in eastern Finland. In addition, several amino acid substitutions in MYBPC3 suspected to be not associated with HCM were identified, indicating that some of the missense variants found in MYBPC3 are possibly not disease-causing mutations. Show less