Gene expression and proliferation biomarkers for antidepressant treatment resistance.

The neurotrophic hypothesis of depression suggests an association between effects on neuroplasticity and clinical response to antidepressant drug therapy. We studied individual variability in antidepressant drug effects on cell proliferation in lymphoblastoid cell lines (LCLs) from n=25 therapy-resistant patients versus n=25 first-line therapy responders from the Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study. Furthermore, the variability in gene expression of genes associated with cell proliferation was analyzed for tentative candidate genes for prediction of individual LCL donor's treatment response. Cell proliferation was quantified by EdU (5-ethynyl-2'-deoxyuridine) assays after 21-day incubation of LCLs with fluoxetine (0.5 ng µl-1) and citalopram (0.3 ng µl-1) as developed and described earlier. Gene expression of a panel of candidate genes derived from genome-wide expression analyses of antidepressant effects on cell proliferation of LCLs from the Munich Antidepressant Response Signature (MARS) study was analyzed by real-time PCR. Significant differences in in vitro cell proliferation effects were detected between the group of LCLs from first-line therapy responders and LCLs from treatment-resistant patients. Gene expression analysis of the candidate gene panel revealed and confirmed influence of the candidate genes ABCB1, FZD7 and WNT2B on antidepressant drug resistance. The potential of these genes as tentative biomarkers for antidepressant drug resistance was confirmed. In vitro cell proliferation testing may serve as functional biomarker for individual neuroplasticity effects of antidepressants.

Proliferation rates and gene expression profiles in human lymphoblastoid cell lines from patients with depression characterized in response to antidepressant drug therapy.

The current therapy success of depressive disorders remains in need of improvement due to low response rates and a delay in symptomatic improvement. Reliable functional biomarkers would be necessary to predict the individual treatment outcome. On the basis of the neurotrophic hypothesis of antidepressant's action, effects of antidepressant drugs on proliferation may serve as tentative individual markers for treatment efficacy. We studied individual differences in antidepressant drug effects on cell proliferation and gene expression in lymphoblastoid cell lines (LCLs) derived from patients treated for depression with documented clinical treatment outcome. Cell proliferation was characterized by EdU (5-ethynyl-2'-deoxyuridine) incorporation assays following a 3-week incubation with therapeutic concentrations of fluoxetine. Genome-wide expression profiling was conducted by microarrays, and candidate genes such as betacellulin-a gene involved in neuronal stem cell regeneration-were validated by quantitative real-time PCR. Ex vivo assessment of proliferation revealed large differences in fluoxetine-induced proliferation inhibition between donor LCLs, but no association with clinical response was observed. Genome-wide expression analyses followed by pathway and gene ontology analyses identified genes with different expression before vs after 21-day incubation with fluoxetine. Significant correlations between proliferation and gene expression of WNT2B, FZD7, TCF7L2, SULT4A1 and ABCB1 (all involved in neurogenesis or brain protection) were also found. Basal gene expression of SULT4A1 (P=0.029), and gene expression fold changes of WNT2B by ex vivo fluoxetine (P=0.025) correlated with clinical response and clinical remission, respectively. Thus, we identified potential gene expression biomarkers eventually being useful as baseline predictors or as longitudinal targets in antidepressant therapy.

Serum adiponectin and progranulin levels are associated with gallstone disease.

BACKGROUND/AIM: Aberrant adipokine serum concentrations are associated with a variety of obesity-related diseases. This study was designed to investigate the putative role of the adipokines adiponectin, chemerin, progranulin, vaspin, fibroblast growth factor 21 (FGF21) and adipocyte fatty acid binding protein (AFABP) in gallstone disease. METHODS: Serum levels of adiponectin, chemerin, progranulin, vaspin, FGF21 and AFABP of 189 gallstone patients and 833 healthy controls were measured by enzyme-linked immunosorbent assays. RESULTS: Increased adiponectin levels were nominally associated with lower gallstone risk in women (p=0.036, odds ratio (OR) 0.47, 95% confidence interval (CI) [0.23; 0.95]). Furthermore progranulin serum concentrations in men were significantly elevated in gallstone carriers in comparison to controls (p=0.012, OR 6.1, 95% CI [1.5; 24.9]). Serum levels of chemerin, vaspin, FGF21 and AFABP did not differ between controls and subjects with gallstones. CONCLUSION: Our data further support a protective effect of adiponectin on gallstone risk and suggest a role of progranulin in the pathophysiology of cholelithiasis. Nevertheless, longitudinal data and functional analyses would be required to assess the pathogenetic link between gallstone formation and adipokine serum levels.

Fat depot-specific mRNA expression of novel loci associated with waist-hip ratio.

OBJECTIVE: We hypothesized that genes within recently identified loci associated with waist-hip ratio (WHR) exhibit fat depot-specific mRNA expression, which correlates with obesity-related traits. METHODS: Adipose tissue (AT) mRNA expression of 6 genes (TBX15/WARS2, STAB1, PIGC, ZNRF3 and GRB14) within these loci showing coincident cis-expression quantitative trait loci was measured in 222 paired samples of human visceral (vis) and subcutaneous (sc) AT. The relationship of mRNA expression levels with obesity-related quantitative traits was assessed by Pearson's correlation analyses. Multivariate linear relationships were assessed by generalized linear regression models. RESULTS: Whereas only PIGC, ZNFR3 and STAB1 mRNA expression in sc AT correlated nominally with WHR (P<0.05, adjusted for age and sex), mRNA expression of all studied genes in at least one of the fat depots correlated significantly with vis and/or sc fat area (P ranging from 0.05 to 4.0 × 10(6), adjusted for age and sex). Consistently, the transcript levels of WARS, PIGC and GRB14 were nominally associated with body mass index (BMI) (P ranging from 0.02 to 9.2 × 10(5), adjusted for age and sex). Moreover, independent of sex, obesity and diabetes status, differential expression between vis and sc AT was observed for all tested genes (P<0.01). Finally, the rs10195252 T-allele was nominally associated with increased GRB14 sc mRNA expression (P=0.025 after adjusting for age, sex and BMI). CONCLUSIONS: Our data including the inter-depot variability of mRNA expression suggests that genes within the WHR-associated loci might be involved in the regulation of fat distribution.

Genetic variation in the vaspin gene affects circulating serum vaspin concentrations.

OBJECTIVE: Visceral adipose tissue-derived serine protease inhibitor (vaspin) is an adipokine potentially linking obesity, insulin resistance and type 2 diabetes. Here, we searched for genetic determinants that could explain the variability in serum vaspin concentrations. RESEARCH DESIGN AND METHODS: First, we conducted a genome-wide association study (GWAS) for serum vaspin in the Sorbs cohort (N=826). Subsequently, 26 single-nucleotide polymorphisms (SNPs) covering genetic variation in the vaspin locus were genotyped in the Sorbs. In addition, we measured serum vaspin concentrations in 1806 samples from Augsburg/the Cooperative Health Research in the Region of Augsburg (KORA) for replication of the association signals. Finally, we conducted association analyses of vaspin SNPs with metabolic traits in the Sorbs (N=1013), KORA (N=1813) and a further cohort from Germany (Leipzig: N=1857). RESULTS: Six SNPs mapping between serpinA1 and serpinA4, including the vaspin locus, on chromosome 14 reached P-values < or = 10(-8) in the GWAS in the Sorbs. The fine mapping of variants within the vaspin locus in the Sorbs and subsequent replication in the KORA sample revealed several SNPs significantly associated with serum vaspin concentrations reaching P-values of up to 10(-35). However, no significant association with type 2 diabetes or related traits was found in either cohort after the Bonferroni correction for multiple comparisons. CONCLUSION: Our data show that the variability in serum vaspin concentrations might be explained by its genetic variants.

Association and evolutionary studies of the melatonin receptor 1B gene (MTNR1B) in the self-contained population of Sorbs from Germany.

AIMS: Several polymorphisms of the melatonin receptor 1B gene (MTNR1B) have been shown to be associated with elevated fasting plasma glucose and impaired early insulin release. The aim of this study was to assess the effects of MTNR1B variants on traits related to the metabolic syndrome in the self-contained population of Sorbs from Germany. As comprehensive studies concerning the conservation of MTNR1B are lacking, we also evaluated natural selection in vertebrates and human populations at this locus. METHODS: Five single nucleotide polymorphisms representing all blocks of linkage disequilibrium within and surrounding the MTNR1B locus were genotyped in 937 Sorbs for association analyses on metabolic traits related to Type 2 diabetes. The associations were assessed by regression analyses, the conservation between species was investigated with phylogenetic analysis by maximum likelihood (PAML). In addition, various tests of population genetic measures (e.g. fixation index, Tajima's D) were performed. RESULTS: Previously reported association between MTNR1B variants (rs10830963, rs4753426) and oral glucose tolerance test-derived indices of ß-cell function (homeostasis model assessment-B, P = 3.7 × 10⁻6 and P = 0.004, respectively), as well as insulin (fasting insulin: P=2×10⁻³ and P=0.02; 30-min insulin: P = 2.1 × 10⁻4 and P=0.03, respectively) and fasting glucose (rs10830963, P=1.2×10⁻6) parameters could be replicated in the present study. Phylogenetic analysis by maximum likelihood analyses showed that the gene was strongly conserved between species (ω=0.2583). Structures important for the receptor function are also conserved. On the lineage leading to human adaptive selection was present (ω=1.1030). Population genetic measures further indicated natural selection. CONCLUSIONS: Our data support the physiologic importance of MTNR1B in the context of glucose homeostasis and suggest evidence of selection at this locus.