👤 Donald Gullberg

The unclear link between intake of polyunsaturated fatty acids (PUFAs) and risk of cardiovascular disease (CVD) could depend on genetic differences between individuals. Minor alleles of single-nucleotide polymorphisms (SNPs) in the ∆5 fatty acid desaturase (FADS) 1 gene were associated with lower blood concentrations of long-chain ω-3 (n-3) and ω-6 (n-6) PUFAs, indicating an associated loss of function effect. We examined whether the SNP rs174546 in FADS1 modifies the association between PUFA intakes and CVD risk. We included 24,032 participants (62% women, aged 44-74 y) from the Malmö Diet and Cancer cohort without prevalent CVD and diabetes. During a mean follow-up of 14 y, 2648 CVD cases were identified. Diet was assessed by a modified diet history method. A borderline interaction was observed between the α-linolenic acid (ALA) (18:3n-3)-to-linoleic acid (LA) (18:2n-6) intake ratio and FADS1 genotype on CVD incidence (P = 0.06). The ALA-to-LA intake ratio was inversely associated with CVD risk only among participants homozygous for the minor T-allele (HR for quintile 5 vs. quintile 1 = 0.72; 95% CI: 0.50, 1.04; P-trend = 0.049). When excluding participants reporting unstable food habits in the past (35%), the interaction between the ALA-to-LA intake ratio and FADS1 genotype on CVD incidence was strengthened and statistically significant (P = 0.04). Additionally, we observed a significant interaction between ALA and FADS1 genotype on ischemic stroke incidence (P = 0.03). ALA was inversely associated with ischemic stroke only among TT genotype carriers (HR for quintile 5 vs. quintile 1 = 0.50; 95% CI: 0.27, 0.94; P-trend = 0.02). In this large cohort, we found some weak, but not convincing, evidence of effect modification by genetic variation in FADS1 on the associations between PUFA intakes and CVD risk. For the 11% of the population homozygous for the minor T-allele of rs174546 that associates with lower ∆5 FADS activity, high ALA intake and ALA-to-LA intake ratio may be preferable in the prevention of CVD and ischemic stroke. Show less

A common genetic variant (rs10423928, A-allele) in the glucose-dependent insulinotropic polypeptide receptor gene (GIPR) is associated with decreased insulin secretion. Glucose-dependent insulinotropic polypeptide is secreted after food consumption and gipr knockout mice fed a high-fat diet are protected against obesity and disturbances in glucose homeostasis. Our objective was to examine the interactions between rs10423928 and macronutrients and fiber intakes on body mass index and type 2 diabetes risk. Among nondiabetic subjects in the Swedish population-based Malmö Diet and Cancer cohort (n = 24,840; 45-74 yr), 1541 diabetes cases were identified during 12 yr of follow-up. Dietary intakes were assessed using a diet history method. Incident type 2 diabetes was identified through registers. There was no indication that dietary intakes significantly modify the association between GIPR genotype and body mass index (P interaction >0.08). We observed significant interactions between GIPR genotype and quintiles of carbohydrate (P = 0.0005) and fat intake (P = 0.0006) on incident type 2 diabetes. The TT-genotype carriers within the highest compared with the lowest carbohydrate quintile were at 23% (95% confidence interval = 5-39%) decreased type 2 diabetes risk. In contrast, AA-genotype carriers in the highest compared with the lowest fat quintile were at 69% (95% confidence interval = 29-86%) decreased risk. Our prospective, observational study indicates that the type 2 diabetes risk by dietary intake of carbohydrate and fat may be dependent on GIPR genotype. In line with results in gipr knockout mice, AA-genotype carriers consuming high-fat low-carbohydrate diets had reduced type 2 diabetes risk, whereas high-carbohydrate low-fat diets benefitted the two thirds of population homozygous for the T-allele. Show less

Stromal fibroblasts are important determinants of tumor cell behavior. They act to condition the tumor microenvironment, influence tumor growth, support tumor angiogenesis and affect tumor metastasis. Heparan sulfate proteoglycans, present both on tumor and stromal cells, interact with a large number of ligands including growth factors, their receptors, and structural components of the extracellular matrix. Being ubiquitously expressed in the tumor microenvironment heparan sulfate proteoglycans are candidates for playing central roles in tumor-stroma interactions. The objective of this work was to investigate the role of heparan sulfate expressed by stromal fibroblasts in modulating the growth of tumor cells and in controlling the interstitial fluid pressure in a 3-D model. We generated spheroids composed of fibroblasts alone, or composite spheroids, composed of fibroblasts and tumor cells. Here we show that stromal fibroblasts with a mutation in the heparan sulfate elongating enzyme Ext1 and thus a low heparan sulfate content, formed composite fibroblast/tumor cell spheroids with a significant lower interstitial fluid pressure than corresponding wild-type fibroblast/tumor cell composite spheroids. Furthermore, immunohistochemistry of composite spheroids revealed that the cells segregated, so that after 6 days in culture, the wild-type fibroblasts formed an inner core and the tumor cells an outer layer of cells. For composite spheroids containing Ext1-mutated fibroblasts this segregation was less obvious, indicating impaired cell migration. Analysis of tumor cells expressing the firefly luciferase gene revealed that the changes in tumor cell migration in mutant fibroblast/tumor cell composite spheroids coincided with a lower proliferation rate. This is the first demonstration that stromal Ext1-levels modulate tumor cell proliferation and affect the interstitial fluid pressure in a 3-D spheroid model. Learning how structural changes in stromal heparan sulfate influence tumor cells is essential for our understanding how non-malignant cells of the tumor microenvironment influence tumor cell progression. Show less

MTG16, MTGR1 and ETO are nuclear transcriptional corepressors of the human ETO protein family. MTG16 is implicated in hematopoietic development and in controlling erythropoiesis/megakaryopoiesis. Furthermore, ETO homologue genes are 3'participants in leukemia fusions generated by chromosomal translocations responsible of hematopoietic dysregulation. We tried to identify structural and functional promoter elements of MTG16 and MTGR1 genes in order to find associations between their regulation and hematopoiesis. 5' deletion examinations and luciferase reporter gene studies indicated that a 492 bp sequence upstream of the transcription start site is essential for transcriptional activity by the MTG16 promoter. The TATA- and CCAAT-less promoter with a GC box close to the start site showed strong reporter activity when examined in erythroid/megakaryocytic cells. Mutation of an evolutionary conserved GATA -301 consensus binding site repressed promoter function. Furthermore, results from in vitro antibody-enhanced electrophoretic mobility shift assay and in vivo chromatin immunoprecipitation indicated binding of GATA-1 to the GATA -301 site. A role of GATA-1 was also supported by transfection of small interfering RNA, which diminished MTG16 expression. Furthermore, expression of the transcription factor HERP2, which represses GATA-1, produced strong inhibition of the MTG16 promoter reporter consistent with a role of GATA-1 in transcriptional activation. The TATA-less and CCAAT-less MTGR1 promoter retained most of the transcriptional activity within a -308 to -207 bp region with a GC-box-rich sequence containing multiple SP1 binding sites reminiscent of a housekeeping gene with constitutive expression. However, mutations of individual SP1 binding sites did not repress promoter function; multiple active SP1 binding sites may be required to safeguard constitutive MTGR1 transcriptional activity. The observed repression of MTG16/MTGR1 promoters by the leukemia associated AML1-ETO fusion gene may have a role in hematopoietic dysfunction of leukemia. An evolutionary conserved GATA binding site is critical in transcriptional regulation of the MTG16 promoter. In contrast, the MTGR1 gene depends on a GC-box-rich sequence for transcriptional regulation and possible ubiquitous expression. Our results demonstrate that the ETO homologue promoters are regulated differently consistent with hematopoietic cell-type- specific expression and function. Show less

Philadelphia (Ph) chromosome-positive leukemia is characterized by the BCR/ABL1 fusion protein that affects a wide range of signal transduction pathways. The knowledge about its downstream target genes is, however, still quite limited. To identify novel BCR/ABL1-regulated genes we used global gene expression profiling of several Ph-positive and Ph-negative cell lines treated with imatinib. Following imatinib treatment, the Ph-positive cells showed decreased growth, viability, and reduced phosphorylation of BCR/ABL1 and STAT5. In total, 142 genes were identified as being dependent on BCR/ABL1-mediated signaling, mainly including genes involved in signal transduction, e.g. the JAK/STAT, MAPK, TGFB, and insulin signaling pathways, and in regulation of metabolism. Interestingly, BCR/ABL1 was found to activate several genes involved in negative feedback regulation (CISH, SOCS2, SOCS3, PIM1, DUSP6, and TNFAIP3), which may act to indirectly suppress the tumor promoting effects exerted by BCR/ABL1. In addition, several genes identified as deregulated upon BCR/ABL1 expression could be assigned to the TGFB and NFkB signaling pathways, as well as to reflect the metabolic adjustments needed for rapidly growing cells. Apart from providing important pathogenetic insights into BCR/ABL1-mediated leukemogenesis, the present study also provides a number of pathways/individual genes that may provide attractive targets for future development of targeted therapies. This article contains Supplementary Material available at http://www.interscience.wiley.com/jpages/1045-2257/suppmat. Show less