Natascha Schweighofer

Medical University of Graz, Gratz, Styria, Austria

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Publications (19)53.42 Total impact

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    ABSTRACT: Insulin-sensitizer treatment with metformin is common in polycystic ovary syndrome (PCOS). OCT alleles were investigated in PCOS patients to identify genetic 'bad responders' and 'nonresponders' to metformin including their possible effects on glucose metabolism without treatment. We genotyped eight SNPs in OCT1, OCT2 and ATM genes in 676 women with PCOS and 90 control women, we also measured oral glucose tolerance tests prior to treatment. Nonfunctional alleles were present in 29.8% and low-functional alleles in 57.9% of our PCOS cohort. OCT variants were significantly associated with elevated baseline and glucose-induced C-peptide levels in PCOS. Metformin bad responders or nonresponders based on OCT genotypes might be relevant in clinical practice - their modulation of metformin pharmacokinetics and pharmacodynamics and metformin-independent glucose effects remain to be elucidated. Original submitted 7 June 2013; Revision submitted 28 October 2013.
    Pharmacogenomics 02/2014; 15(3):305-17. · 3.86 Impact Factor
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    ABSTRACT: Polycystic ovary syndrome (PCOS) shows not only hyperandrogenemia, hirsutism and fertility problems, but also metabolic disturbances including obesity, cardiovascular events and type-2 diabetes. Accumulating evidence suggests some degree of inflammation associated with prominent aspects of PCOS. We aimed to investigate the association of genetic variants 3'UTR rs17468190 (G/T) of the inflammation-associated gene MEP1A (GeneBank ID: NM_005588.2) with metabolic disturbances in PCOS and healthy control women. Genetic variants rs17468190 (G/T) of MEP1A gene were analyzed in 576 PCOS women and 206 controls by using the Taqman fluorogenic 5'-exonuclease assay. This polymorphism was tested for association with anthropometric, metabolic, hormonal, and functional parameters of PCOS. There was a borderline significant difference in genotype distribution between PCOS and control women (p=0.046). In overweight/obese PCOS patients, the variants rs17468190 (G/T) in the MEP1A gene are associated with glucose and insulin metabolism. In a dominant model, the GG genotype of the MEP1A gene was more strongly associated with insulin metabolism in overweight/obese PCOS women (body mass index, BMI>25kg/m(2)), than in GT+TT genotypes. The MEP1A GG-carriers showed a significantly increased homeostatic model assessment-insulin resistance (HOMA-IR) (p=0.003), elevation of fasting insulin (p=0.004) and stimulated insulin (30min, p<0.001; 60min, p=0.009; 120min, p=0.009) as well as triglyceride (p=0.032) levels. MEP1A is a possible target gene for disease modification in PCOS. It might contribute to the abnormalities of glucose metabolism and insulin sensitivity and serve as a diagnostic or therapeutic target gene for PCOS.
    Gene 01/2014; · 2.20 Impact Factor
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    ABSTRACT: The serum amyloid A (SAA) family of proteins is encoded by multiple genes, which display allelic variation and a high degree of homology in mammals. The SAA1/2 genes code for non-glycosylated acute-phase SAA1/2 proteins, that may increase up to 1000-fold during inflammation. The SAA4 gene, well characterized in humans (hSAA4) and mice (mSaa4) codes for a SAA4 protein that is glycosylated only in humans. We here report on a previously uncharacterized SAA4 gene (rSAA4) and its product in Rattus norvegicus, the only mammalian species known not to express acute-phase SAA. The exon/intron organization of rSAA4 is similar to that reported for hSAA4 and mSaa4. By performing 5′- and 3′RACE, we identified a 1830-bases containing rSAA4 mRNA (including a GA-dinucleotide tandem repeat). Highest rSAA4 mRNA expression was detected in rat liver. In McA-RH7777 rat hepatoma cells, rSAA4 transcription was significantly upregulated in response to LPS and IL-6 while IL-1α/β and TNFα were without effect. Luciferase assays with promoter-truncation constructs identified three proximal C/EBP-elements that mediate expression of rSAA4 in McA-RH7777 cells. In line with sequence prediction a 14-kDa non-glycosylated SAA4 protein is abundantly expressed in rat liver. Fluorescence microscopy revealed predominant localization of rSAA4-GFP-tagged fusion protein in the ER.
    Biochemical and Biophysical Research Communications 01/2014; · 2.28 Impact Factor
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    ABSTRACT: Objective: Osteocalcin (OC) might play a hormone-like role in energy metabolism and the regulatory circuit between pancreas and osteoblasts. Effects of a 75g oral glucose tolerance test (OGTT) on total OC, undercarboxylated (ucOC), and carboxylated osteocalcin (cOC) in insulin-resistant (IR) and non-insulin-resistant (nIR) premenopausal women is evaluated and the relationship of changes in OC, ucOC, and cOC with AUCinsulin and Matsuda index examined.Methods: In this cross-sectional study, 105 premenopausal women underwent OGTT. 18 were IR (HOMA-IR > 2.6) (2 with type 2 diabetes, 2 with impaired glucose tolerance) and 87 nIR (3 with impaired glucose tolerance). After glucose load, changes in total OC, ucOC, and cOC were evaluated after 60 and 120 minutes.Results: At baseline, IR women had significantly lower levels of total OC, cOC, and ucOC. In nIR women, total OC decreased by 19% from 18.0ng/ml (14.5-24.7) at baseline to 14.6ng/ml (10.9-17.8) after 120 minutes; ucOC decreased by 22% from 3.2ng/ml (2.1-4.5) to 2.5ng/ml (1.7-3.5); cOC decreased by 26% from 14.9ng/ml (12.1-20.4) to 11.1ng/ml (9.0-14.5) (p<0.001, respectively). In IR women, neither decreased significantly. The declines in OC and cOC predicted AUCinsulin (ΔOC: beta=0.301, p=0.001; ΔcOC: beta=0.315, p<0.001) and Matsuda (ΔOC: beta=-0.235, p=0.003; ΔcOC: beta=-0.245, p=0.002).Conclusions: Glucose intake lowers levels of OC, ucOC, and cOC in nIR women, the extent of which predicts insulin resistance and sensitivity in premenopausal women. In IR women OC parameters seem suppressed. There might be a differing osteoblast response to oral glucose in IR and nIR women - OC reflects this finding.
    Endocrine Practice 09/2013; · 2.49 Impact Factor
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    ABSTRACT: Osteocalcin (OC) - released by osteoblasts and known as a marker of bone turnover - has been suggested to influence male fertility in murine models by enhancing testosterone production and sperm count. Results from clinical studies are scarce, however. The aim of this cross-sectional study was to investigate the proposed association of OC, undercarboxylated osteocalcin (ucOC) or carboxylated osteocalcin (cOC) with testosterone and sperm count in a cohort of 159 young male adults from infertile couples. Semen analysis was performed. Testosterone, free testosterone, LH, OC and ucOC were measured in serum samples after an overnight fast. cOC and OC correlated weakly but significantly with testosterone (OC: r = 0.165, p = 0.040, cOC: r = 0.193, p = 0.017), but not after adjusting for age and body mass index (BMI) or waist-hip ratio (WHR). %ucOC (ucOC levels expressed as percentage of total OC) correlated inversely with LH (r = -0.184, p = 0.023) and remained significant after the same adjustment. No significant correlations were observed between OC, cOC, ucOC, %ucOC and sperm count, semen volume and number of vital spermatozoa. In binary logistic regression analyses, none of the parameters of OC were predictors of oligozoospermia after adjusting for age and BMI or WHR. The weak association between %ucOC and LH has marginal clinical importance because of the lack of associations of parameters of OC with testosterone and sperm count. The current data thus cannot support the notion that OC is associated with male fertility in young men from infertile couples.
    Andrology 05/2013; · 3.37 Impact Factor
  • Bone 12/2012; 51(6):S10. · 4.46 Impact Factor
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    ABSTRACT: The polycystic ovary syndrome (PCOS), characterized by hyperandrogenism, is one of the most common hormonal disorders among premenopausal women and is associated with infertility, obesity, and insulin resistance. Accumulating evidence suggests a role of the blood coagulation factor gene F13A1 in obesity (GeneBank ID: NM_000129.3). The aim of this study was to investigate the association of intronic allelic variants of the F13A1 gene with PCOS susceptibility and metabolic parameters in lean and obese PCOS women. In a case-control study, we determined an intronic F13A1 single nucleotide polymorphism (SNP) (dbSNP ID: rs7766109) in 585 PCOS and 171 control women and tested for PCOS susceptibility and associations with anthropometric, metabolic and hormonal parameters. Genotype frequencies of the F13A1 SNP rs7766109 were equivalent in PCOS and control women. In PCOS women, F13A1 gene variants were significantly associated with body mass index (BMI) (p=0.013), systolic blood pressure (p=0.042), insulin response (AUCins) (p=0.015), triglycerides (TG) (p=0.001), and high density lipoprotein cholesterol (HDL) (p=0.012). In the subgroup of obese PCOS women free androgen index (FAI), free testosterone and sex hormone binding globulin (SHBG) as well as glucose measurements showed a significantly different pattern across F13A1 gene variants (p=0.043; p=0.039 and p=0.013, respectively). We report for the first time an association of the F13A1 SNP rs7766109 with BMI, androgens, and insulin resistance in PCOS women. Further studies are needed to confirm our findings and to evaluate whether F13A1 is causally involved in the pathogenesis of PCOS related metabolic and hormonal disturbances.
    Gene 04/2012; 504(1):133-9. · 2.20 Impact Factor
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    ABSTRACT: Given its role in converting testosterone to dihydrotestosterone and cortisol to dihydrocortisol, 5α-reductase may be important in the pathophysiology of the polycystic ovary syndrome (PCOS). Increased activity of this enzyme has already been demonstrated in ovaries of affected women, and might be caused by genetic alterations. The aim of this study was to analyze representative genetic variants of both isoforms of 5α-reductase with regard to PCOS parameters in lean and obese women. We analyzed one single nucleotide polymorphism (SNP) (rs523349) of the isoform 2 (SRD5A2) and one haplotype of the isoform 1 (SRD5A1), consisting of the two SNPs rs39848 and rs3797179, in 249 women with PCOS and 226 healthy women using a 5'-exonuclease-assay. The genotypes were associated with anthropometric, metabolic and hormonal as well as functional tests in these women. In the investigated haplotype of SRD5A1, the TA variant was associated with an increased frequency of PCOS (P=0.022) and an increased Ferriman-Gallwey Score (hirsutism) (P=0.016) in women with normal weight. The G allele at the examined position of the SRD5A2 showed a decreased frequency of PCOS (P=0.03) in women with normal weight. One of the keys in the development of the PCOS is hyperandrogenism, which might be caused by an increased 5α-reductase activity, as it is often seen in obesity. This mechanism might therefore be of importance in lean PCOS patients and contribute to the clinical findings.
    European journal of obstetrics, gynecology, and reproductive biology 04/2011; 157(2):175-9. · 1.97 Impact Factor
  • Bone 01/2011; 48. · 4.46 Impact Factor
  • Bone 01/2011; 48. · 4.46 Impact Factor
  • Bone 01/2010; 47. · 4.46 Impact Factor
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    ABSTRACT: Variants in the fat mass and obesity-associated gene (FTO) are associated with obesity and type 2 diabetes mellitus. Women with polycystic ovary syndrome (PCOS) are frequently affected by obesity and impaired glucose tolerance. The aim of this study was to investigate the impact of FTO variants (rs9939609) on metabolic and endocrine parameters in PCOS women. We genotyped the single nucleotide polymorphism rs9939609 (T/A) in 288 PCOS women and performed metabolic and hormonal measurements, oral glucose tolerance test, hirsutism score, and lipometry. The A/T + A/A genotype showed an increased prevalence in overweight/obese PCOS patients (odds ratio [OR] = 1.91, P = .028) and in PCOS women with impaired glucose tolerance (OR = 3.23, P = .009). The A allele was associated with a significant increase in free testosterone (P = .042), weight (P = .024), body mass index (P = .011), 2-hour glucose (P = .047), 1-hour insulin (P = .032), and AUCins (area under the curve insulin) (P = .038). In a logistic regression analysis, the A allele was associated with free testosterone (P = .025; OR = 1.54; 95% confidence interval, 1.06-2.25; B = 0.86). Total body fat (percentage) (P = .016), total fat mass (P = .013), visceral adipose tissue mass (P = .044), and subcutaneous fat mass (P = .011) were significantly increased in PCOS women carrying the A allele. We demonstrated that variants within the FTO gene influence hyperandrogenemia and anthropometric parameters in women with PCOS, indicating an important role of FTO variants not only in obesity and diabetes but also in hyperandrogenism in women with PCOS.
    Metabolism: clinical and experimental 11/2009; 59(4):575-80. · 3.10 Impact Factor
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    ABSTRACT: Women with polycystic ovary syndrome (PCOS) frequently suffer from metabolic disturbances, in particular from insulin resistance. Accumulating evidence suggests that vitamin D deficiency may contribute to the development of the metabolic syndrome (MS). Hence, the aim of our study was to investigate the association of 25(OH)D levels and the components of the MS in PCOS women. 25(OH)D levels were measured by means of ELISA in 206 women affected by PCOS. Metabolic, endocrine, and anthropometric measurements and oral glucose tolerance tests were performed. The prevalence of insufficient 25(OH)D levels (<30 ng/ml) was 72.8% in women with PCOS. PCOS women with the MS had lower 25(OH)D levels than PCOS women without these features (17.3 vs 25.8 ng/ml respectively; P<0.05). In multivariate regression analysis including 25(OH)D, season, body mass index (BMI), and age, 25(OH)D and BMI were independent predictors of homeostatic model assessment-insulin resistance (HOMA-IR) and quantitative insulin sensitivity check index (QUICKI; P<0.05 for all). In binary logistic regression analyses, 25(OH)D (OR 0.86, P=0.019) and BMI (OR 1.28, P<0.001) were independent predictors of the MS in PCOS women. We found significantly negative correlations of 25(OH)D levels with BMI, waist circumference, waist-to-hip ratio, systolic and diastolic blood pressure, fasting and stimulated glucose, area under the glucose response curve, fasting insulin, HOMA-IR, HOMA-beta, triglycerides, and quotient total cholesterol/high-density lipoprotein (HDL) and positive correlations of 25(OH)D levels with QUICKI and HDL (P<0.05 for all). We demonstrate that low 25(OH)D levels are associated with features of the MS in PCOS women. Large intervention trials are warranted to evaluate the effect of vitamin D supplementation on metabolic disturbances in PCOS women.
    European Journal of Endocrinology 08/2009; 161(4):575-82. · 3.14 Impact Factor
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    ABSTRACT: Polycystic ovary syndrome (PCOS) is the most common endocrine disorder affecting women of reproductive age. Central obesity plays a major role in the pathophysiology of PCOS. However, there is little information on the impact of subcutaneous adipose tissue (SAT) on metabolic disturbances in PCOS. The aim of this study was to investigate whether SAT topography influences insulin resistance, impaired glucose tolerance and metabolic parameters in women with PCOS. 36 women aged 16-41 years with PCOS and 87 healthy women aged 20-34 years were examined using lipometry, metabolic and hormonal measurements, oral glucose tolerance tests, hirsutism scores, and questionnaires. The homeostasis model assessment (HOMA) index was used for determination of insulin resistance. SAT measurement points on the trunk showed significant positive correlation with the HOMA index. A negative correlation between calf SAT and the HOMA index was seen. Multiple regression analysis detected a positive association between the HOMA index and lower-abdomen SAT and upper-back SAT, whereas hip SAT showed a negative association with the HOMA index. In overweight/obese patients with PCOS, lower-abdomen and upper-back SAT showed significant positive correlations with insulin resistance. There was no correlation of SAT topography with insulin resistance in lean women with PCOS. Compared with PCOS women with normal glucose tolerance, patients with glucose intolerance had significantly increased trunk obesity and decreased leg fat. Increased SAT layers on the trunk were related to an unfavorable serum lipid profile, whereas increased leg fat correlated positively with HDL cholesterol. Increased SAT layers on the trunk are associated with insulin resistance, impaired glucose tolerance and an unfavorable lipid profile in women suffering from PCOS. Increased thickness of leg SAT emerges as being protective against metabolic disturbances in PCOS.
    Wiener klinische Wochenschrift 06/2009; 121(7-8):262-9. · 0.81 Impact Factor
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    ABSTRACT: Primary aldosteronism (PA) affects approximately 5 to 10% of all patients with arterial hypertension and is associated with an excess rate of cardiovascular complications that can be significantly reduced by a targeted treatment. There exists a general consensus that the aldosterone to renin ratio should be used as a screening tool but valid data about the accuracy of the aldosterone to renin ratio in screening for PA are sparse. In the Graz endocrine causes of hypertension (GECOH) study we aim to prospectively evaluate diagnostic procedures for PA. In this single center, diagnostic accuracy study we will enrol 400 patients that are routinely referred to our tertiary care center for screening for endocrine hypertension. We will determine the aldosterone to active renin ratio (AARR) as a screening test. In addition, all study participants will have a second determination of the AARR and will undergo a saline infusion test (SIT) as a confirmatory test. PA will be diagnosed in patients with at least one AARR of >or= 5.7 ng/dL/ng/L (including an aldosterone concentration of >or= 9 ng/dL) who have an aldosterone level of >or= 10 ng/dL after the saline infusion test. As a primary outcome we will calculate the receiver operating characteristic curve of the AARR in diagnosing PA. Secondary outcomes include the test characteristics of the saline infusion test involving a comparison with 24 hours urine aldosterone levels and the accuracy of the aldosterone to renin activity ratio in diagnosing PA. In addition we will evaluate whether the use of beta-blockers significantly alters the accuracy of the AARR and we will validate our laboratory methods for aldosterone and renin. Screening for PA with subsequent targeted treatment is of great potential benefit for hypertensive patients. In the GECOH study we will evaluate a standardised procedure for screening and diagnosing of this disease.
    BMC Endocrine Disorders 05/2009; 9:11. · 2.65 Impact Factor
  • Bone 01/2009; 44. · 4.46 Impact Factor
  • Wiener Klinische Wochenschrift - WIEN KLIN WOCHENSCHR. 01/2009; 121:262-269.
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    ABSTRACT: Although the liver is the primary site of cytokine-mediated expression of acute-phase serum amyloid A (SAA) protein, extrahepatic production has also been reported. Besides its role in amyloidosis and lipid homeostasis during the acute-phase, SAA has recently been assumed to contribute to bone and cartilage destruction. However, expression of SAA in human osteogenic tissue has not been studied. Therefore, we first show that SAA1 (coding for the major SAA isoform) but not SAA2 transcripts are expressed in human trabecular and cortical bone fractions and bone marrow. Next, we show expression of (i) IL-1, IL-6, and TNF receptor transcripts; (ii) the human homolog of SAA-activating factor-1 (SAF-1, a transcription factor involved in cytokine-mediated induction of SAA genes); and (iii) SAA1/2 transcripts in non-differentiated and, to a higher extent, in osteoblast-like differentiated human mesenchymal stem cells. Third, we provide evidence that human osteoblast-like cells of tumor origin (MG-63 and SAOS-2) express SAF-1 under basal conditions. SAA1/2 transcripts are expressed under basal conditions (SAOS-2) and cytokine-mediated conditions (MG-63 and SAOS-2). RT-PCR, Western blot analysis, and immunofluorescence technique confirmed cytokine-mediated expression of SAA on RNA and protein level in osteosarcoma cell lines while SAA4, a protein of unknown function, is constitutively expressed in all osteogenic tissues investigated.
    Journal of Cellular Biochemistry 03/2008; 103(3):994-1004. · 3.06 Impact Factor
  • Experimental and Clinical Endocrinology & Diabetes - EXP CLIN ENDOCRINOL DIABETES. 01/2007; 115.