Combined GWAS and 'guilt by association'-based prioritization analysis identifies functional candidate genes for body size in sheep.

BACKGROUND: Body size in sheep is an important indicator of productivity, growth and health as well as of environmental adaptation. It is a composite quantitative trait that has been studied with high-throughput genomic methods, i.e. genome-wide association studies (GWAS) in various mammalian species. Several genomic markers have been associated with body size traits and genes have been identified as causative candidates in humans, dog and cattle. A limited number of related GWAS have been performed in various sheep breeds and have identified genomic regions and candidate genes that partly account for body size variability. Here, we conducted a GWAS in Frizarta dairy sheep with phenotypic data from 10 body size measurements and genotypic data (from Illumina ovineSNP50 BeadChip) for 459 ewes. RESULTS: The 10 body size measurements were subjected to principal component analysis and three independent principal components (PC) were constructed, interpretable as width, height and length dimensions, respectively. The GWAS performed for each PC identified 11 significant SNPs, at the chromosome level, one on each of the chromosomes 3, 8, 9, 10, 11, 12, 19, 20, 23 and two on chromosome 25. Nine out of the 11 SNPs were located on previously identified quantitative trait loci for sheep meat, production or reproduction. One hundred and ninety-seven positional candidate genes within a 1-Mb distance from each significant SNP were found. A guilt-by-association-based (GBA) prioritization analysis (PA) was performed to identify the most plausible functional candidate genes. GBA-based PA identified 39 genes that were significantly associated with gene networks relevant to body size traits. Prioritized genes were identified in the vicinity of all significant SNPs except for those on chromosomes 10 and 12. The top five ranking genes were TP53, BMPR1A, PIK3R5, RPL26 and PRKDC. CONCLUSIONS: The results of this GWAS provide evidence for 39 causative candidate genes across nine chromosomal regions for body size traits, some of which are novel and some are previously identified candidates from other studies (e.g. TP53, NTN1 and ZNF521). GBA-based PA has proved to be a useful tool to identify genes with increased biological relevance but it is subjected to certain limitations.

Correlates of serum resistin in elderly, non-diabetic patients with chronic kidney disease.

BACKGROUND: Renal function may be a major determinant of resistin levels, since most studies revealed association between elevated resistin levels and decreased glomerular filtration rate (GFR) in patients with chronic kidney disease (CKD). The aim of the present study was to test the hypothesis whether serum resistin is associated with markers of malnutrition and inflammation in elderly non-diabetic adults in different stages of CKD including hemodialysis. METHODS: This was a cross-sectional study of 80 elderly patients divided in four groups of 20 patients each according to eGFR and matched for age (+/- 5 years) and gender. Patients with eGFR more than 1.5 mL/second served as controls. Multivariate regression was used to evaluate the association of resistin with eGFR, demographic, metabolic and inflammatory markers, and insulin resistance. Hematological, biochemical, and immunochemical analyses were performed using commercially available enzyme immunoassays. RESULTS: Our results showed that: 1) serum resistin levels were two times higher in patients with advanced CKD especially those undergoing hemodialysis compared to controls, 2) in univariate analysis, resistin levels correlated directly with Tumor Necrosis Factor-alpha (TNF-alpha), high sensitive C-Reactive Protein (hsCRP), and serum phosphate and inversely correlated with albumin, eGFR, and hematocrit levels. We failed to reveal any relationship between resistin levels and Homeostasis Model Assessment Score of Insulin Resistance (HOMA-IR), body mass index (BMI), cholesterol and leptin levels, 3) in multivariate analysis, only TNF-alpha (p < 0.001) and hsCRP (p = 0.032) were the most important independent determinants of serum resistin levels. CONCLUSIONS: These results indicate that resistin increases as GFR declines and may be involved in the malnutrition-inflammation state and the reverse epidemiology phenomenon present in elderly, non-diabetic patients with CKD.

Hypovitaminosis D in Healthy Pregnant Women and their Newborns in Greece.

BACKGROUND/OBJECTIVES: The aim of this work was to evaluate the current vitamin D status in healthy pregnant women and their newborns living in Greece and assess possible associations between 25(OH)D and anthropometric features of their fetuses and newborns. MATERIALS & METHODS: 81 healthy women were monitored during pregnancy. Biochemical markers related to bone metabolism, 25(OH)D and PTH levels were measured in serum samples of mothernewborn pairs at 1st trimester of pregnancy and at delivery in mothers, in cord blood and at the 3rd day of life of newborns. RESULTS: Maternal 25(OH)D levels at the 1st trimester of pregnancy (22.6±9.2ng/ml) were significantly higher than those at delivery (19.2±9.2ng/ml) (p<0.001). Furthermore, umbilical 25(OH)D levels (21.3±9.3ng/ml) were higher than maternal at delivery (p=0.005) and neonatal levels (19.4±10.4 ng/ml) (p=0.021). Only 57.3% of the mothers at the first trimester and 46.7% at delivery as well as 55.8% of the fetuses and 38.5% of the neonates had adequate vitamin D levels (25(OH)D≥30ng/ml). A significant positive correlation was found between fetal femur length at the 22nd week of gestation and maternal 25(ΟΗ)D at the 1st trimester of pregnancy (r=0.36, p=0.048) while body length was significantly higher in newborns whose mothers had sufficient 25(OH)D levels (51.5±2.1cm) compared with those whose mothers had insufficient or deficient 25(OH)D levels at delivery (50.6±2.0cm) (p=0.047). CONCLUSION: The study confirms inadequate levels of vitamin D in pregnant women in Greece associated with inadequate vitamin D levels of their fetuses and newborns.

Copeptin levels in patients with vasovagal syncope.

BACKGROUND AND PURPOSE: Vasovagal syncope (VVS) is linked to more than one pathophysiologic mechanisms. Copeptin, an emerging cardiovascular marker, is a surrogate for arginine-vasopressin, which increases following VVS. We aimed to assess the dynamic pattern of copeptin levels in typical VVS, categorized by the degree of vasoconstriction during orthostasis, and healthy controls. METHODS: The following groups were studied: Group A (n=21), with adequate limb vasoconstriction during the first min. of tilt, assessed by limb plethysmography (at least 30% flow reduction); Group B (n=15), showing impaired vasoconstriction during orthostasis (<10% reduction); Group C (n=18), history of VVS and negative tilt test result; Group D (n=18), healthy controls. Copeptin plasma levels were assessed before and 5min following tilt test positivity or termination. RESULTS: Baseline copeptin values were similar in all groups (8.3±6.4 in Group A, 5.7±2.3pmol/l in B, 6.0±1.9 in C, and 6.9±2.6 in D, p: 0.41). Significant increases in copeptin during tilt were observed in all Groups of VVS patients (A, B, C), including those with negative tilt (Group C: from 6.0±1.9 to 27.7±12.6pmol/l, p: 0.001), but not in controls. Following tilt termination, a greater increase was observed in copeptin values in Group B vs all other Groups A, C, and D (111.6±63.5 vs 29.5±51.3, 27.7±12.6, and 8.3±2.9, respectively). CONCLUSIONS: Copeptin increases following tilt not only in VVS with a positive response, but also in typical history patients with a negative test. Increased copeptin levels following orthostasis may be useful for diagnosing VVS.

Angiopoietin-2 Levels as Predictors of Outcome in Mechanically Ventilated Patients with Acute Respiratory Distress Syndrome.

Pulmonary endothelium dysfunction is a key characteristic of ARDS. The aim of this study was to investigate endothelium-derived markers, such as angiopoietin-2 (Ang-2) and endothelial cell-specific molecule-1 (endocan), at the vascular and alveolar compartments as outcome predictors in ARDS. Fifty-three consecutive ARDS patients were studied. The primary outcome was 28-day mortality. Secondary endpoints were days of unassisted ventilation and days with organ failure other than ARDS, during the 28-day study period. Nonsurvivors presented higher lung injury scores and epithelial lining fluid (ELF) Ang-2 levels compared to survivors, with no significant differences in plasma Ang-2, endocan, and protein C concentrations between the two groups. In logistic regression analysis, ELF Ang-2 levels > 705 pg/ml were the only independent variable for 28-day mortality among the previous four. Plasma endocan values > 13 ng/pg were the only parameter predictive against days of unassisted ventilation during the 28-day study period. Finally, lung injury score > 2.25 and ELF Ang-2 levels > 705 pg/ml were associated with increased number of days with organ failure, other than ARDS. Our findings suggest that Ang-2 levels are increased in the alveolar compartment of ARDS patients, and this may be associated both with increased mortality and organ failure besides lung.

Platelet markers correlate with glycemic indices in diabetic, but not diabetic-myelodysplastic patients with normal platelet count.

BACKGROUND: Altered thrombocyte morphology and function have been reported in patients with diabetes mellitus (DM) type 2. The aim of the present study was to determine the associations between platelet morphology markers and hemoglobin A1C (HbA(1c)), fasting glucose (FG), hypertension and coronary heart disease (CHD) in patients with myelodysplastic syndromes (MDS) and DM, in patients with DM and in controls. METHODS: This cross-sectional study included 30 cases with primary MDS with normal platelet count and non-insulin dependent diabetes, 30 non-insulin dependent diabetic patients and 30 non-diabetic, non-MDS controls matched on age and gender. RESULTS: After adjusting for body mass index, platelet number, CHD and hypertension, HbA(1c) and FG were significant predictors of mean platelet volume (MPV) and platelet distribution width (PDW) in diabetic patients. There was no correlation between platelet parameters and HbA(1c) or FG in diabetic MDS patients. In controls, FG and hypertension predicted significant differences in platelet morphology. Platelet count correlated with platelet morphology in diabetic MDS and control groups, but not in diabetics. CONCLUSIONS: MPV and PDW are associated with glycemic indices in diabetic patients but not in diabetic MDS patients with normal platelet counts. Non-diabetic controls also exhibit FG related changes in platelet morphology. This suggests other factors inherent to bone marrow dysplasia, platelet turnover and biochemistry, or vascular environment affect platelet morphology in diabetic MDS patients even with normal platelet count. Platelet morphology in this population may be an early marker for myelodysplasia. These findings also support platelet morphology change as a marker for elevated macrovascular disease risk.