Biomedical subjects

Jan W Koper

Publications and source records attributed to Jan W Koper.

26 records · Page 2Linked to original sources

PubMed2004

Characterization of a promoter polymorphism in the glucocorticoid receptor gene and its relationship to three other polymorphisms.

OBJECTIVE: Sensitivity to glucocorticoids within the normal population is highly variable and partly determined by polymorphisms in the glucocorticoid receptor (GR) gene (NR3C1). We investigated the exact sequence alteration of a TthIIII polymorphism in the GR gene, whether it is associated with glucocorticoid sensitivity, and its relationship to 3 polymorphisms of the GR gene (N363S, BclI, ER22/23EK). DESIGN: Two dexamethasone (DEX) suppression tests were performed with 1 and 0.25 mg DEX, respectively. PATIENTS: We genotyped a random subgroup of 209 participants of the Rotterdam Study, a population-based study in the elderly. MEASUREMENTS: Anthropometric parameters, cortisol, insulin and glucose levels, and lipid concentrations were measured. RESULTS: We identified the TthIIII polymorphism as a C to T mutation, 3807 bp upstream from the mRNA start site. We found 39.7% CC-carriers, 44.5% CT-carriers, and 15.8 % TT-carriers. No differences were found between TthIIII genotypes in sensitivity to DEX, baseline cortisol, insulin, glucose or cholesterol levels, or in anthropometric variables. However, all ER22/23EK-carriers also carried the TthIIII T-allele, and carriers of both these polymorphisms had a significantly smaller cortisol suppression after 1 mg DEX, lower fasting insulin levels, and lower total and low-density lipoprotein (LDL) cholesterol levels than TthIIII T carriers without the ER22/23EK variant and noncarriers. No interaction was found between the TthIIII variant and N363S or BclI polymorphisms. CONCLUSIONS: The TthIIII polymorphism is not functional by itself. However, the ER22/23EK polymorphism is without exception linked to the TthIIII T polymorphism and this haplotype is associated with a relative resistance to glucocorticoids, and a healthy metabolic profile.

Aged↗

PubMed2004

A psychobiological perspective on genetic determinants of hypothalamus-pituitary-adrenal axis activity.

From the perspective of psychobiological stress research we present a brief overview of findings documenting a significant impact of genetic factors on the activity of the hypothalamus-pituitary-adrenal (HPA) axis. Quantitative genetic studies in twins as well as association studies, primarily on polymorphisms in the glucocorticoid receptor gene, are depicted. Recent findings suggest that the collaboration of psychobiology and molecular genetics is a promising interdisciplinary approach that will significantly contribute to the understanding of the mechanisms underlying the link between stress, the HPA axis, and HPA-related clinical states.

Animals↗

PubMed2004

Common polymorphisms in the glucocorticoid receptor gene are associated with adrenocortical responses to psychosocial stress.

Chronic dysregulation of hypothalamus-pituitary-adrenal axis activity is related to several stress-related disorders. Evidence suggests that polymorphisms in the glucocorticoid receptor (GR) gene may have an impact on this neuroendocrine system. In the present investigation, 112 healthy males were studied to estimate the impact of three GR gene polymorphisms (BclI RFLP, N363S, ER22/23EK) on cortisol and ACTH responses to psychosocial stress (Trier Social Stress Test) and pharmacological stimulation (1 microg ACTH(1-24), 0.5 mg dexamethasone). Because only four ER22/23EK heterozygotes were identified, these subjects were not statistically analyzed. Compared with subjects with the wild-type GR genotype (n = 36), 363S allele carriers (n = 10) showed significantly increased salivary cortisol responses to stress, whereas the BclI genotype GG (n = 18) was associated with a diminished cortisol response. BclI heterozygotes and homozygotes (GG) exhibited a trend toward lower ACTH responses, compared with wild-type subjects and 363S carriers. The cortisol response to ACTH(1-24) administration was not significantly different between genotypes. After dexamethasone ingestion, 363S carriers showed a trend toward an enhanced cortisol suppression. This is the first report documenting an impact of GR gene polymorphisms on cortisol (and perhaps ACTH) responses to psychosocial stress. These variants may contribute to the individual vulnerability for hypothalamus-pituitary-adrenal-related disorders.

Adrenal Cortex↗

PubMed2004

The ER22/23EK polymorphism in the glucocorticoid receptor gene is associated with a beneficial body composition and muscle strength in young adults.

Glucocorticoids play an important role in determining body composition. A polymorphism of the glucocorticoid receptor gene (in codons 22 and 23) has previously been found to be associated with relative glucocorticoid resistance, low cholesterol levels, and increased insulin sensitivity. In this study, we investigated whether this ER22/23EK polymorphism is associated with differences in body composition and muscle strength. We studied a cohort of 350 subjects who were followed from age 13 until 36 yr. We compared noncarriers and carriers of the ER22/23EK variant in anthropometric parameters, body composition, and muscle strength, as measured by arm pull tests and high jump from standing. We identified 27 (8.0%) heterozygous ER22/23EK carriers. In males at 36 yr of age, we found that ER22/23EK carriers were taller, had more lean body mass, greater thigh circumference, and more muscle strength in arms and legs. We observed no differences in body mass index or fat mass. In females, waist and hip circumferences tended to be smaller in ER22/23EK carriers at the age of 36 yr, but no differences in body mass index were found. Thus, the ER22/23EK polymorphism is associated with a sex-specific, beneficial body composition at young-adult age, as well as greater muscle strength in males.

Adolescent↗

PubMed2003

The relation between two polymorphisms in the glucocorticoid receptor gene and body mass index, blood pressure and cholesterol in obese patients.

OBJECTIVE: We have recently reported that, in healthy elderly Dutch individuals, a N363S polymorphism in the glucocorticoid receptor (GR) gene is associated with higher sensitivity to low-dose dexamethasone (0.25 mg), evaluated as both cortisol suppression and insulin response, and with an increased body mass index (BMI). In the present study we investigated the role of the N363S polymorphism, and a BclI restriction site polymorphism in a group of Italian patients with severe obesity. DESIGN: Two hundred and seventy-nine patients (mean BMI 45.9 +/- 0.9 kg/m2) were genotyped using both PCR-restriction fragment length polymorphism analysis and Taqman Sequence Detection System. Determination of several metabolic and antropometric parameters was also performed in order to correlate them to the genotype. RESULTS: In this group of obese patients, 13 subjects (eight female, five males) were heterozygous for the N363S variant (allelic frequency 2.3%) and had significantly higher BMI (P < 0.04), resting energy expenditure (P < 0.03) and food intake (P < 0.01) when compared to wild-type homozygotes. When the data were analysed according to sex, female heterozygotes for the N363S allele had significantly higher BMI (P = 0.04), resting energy expenditure (P = 0.03) and food intake (P = 0.008) than obese women with the wild-type 363 GR gene. Male carriers of this variant also had higher values for these variables although the differences did not reach statistical significance. A case-control study with homozygous wild-type obese subjects which were age-, sex- and BMI-matched, revealed no difference in resting energy expenditure and food intake. The allele frequency of the BclI variant was 27% (89 females and 41 males out of 269 subjects). No differences in anthropometric and metabolic parameters were found between subjects heterozygous or homozygous for this variant GR in this obese population. However, when we studied the effect of the presence of the BclI polymorphism and the N363S variant in the same individual, we found that the subjects who carried both polymorphisms had a tendency towards higher systolic and diastolic blood pressure and significantly higher total and LDL-cholesterol levels (P = 0.005 and P = 0.05, respectively). DISCUSSION: Taking the results of this study and those obtained in the Dutch population, we speculate that heterozygous carriers of the N363S variant who develop obesity, may become even more obese, possibly because they have a hypersensitive insulin response and thus, via activation of lipogenesis, store fat more efficiently. Furthermore, these data suggest that N363S carriers who carry the BclI polymorphism as well, tend to have a slightly unfavourable cardiovascular profile.

Adult↗

PubMed2003

Identification of the BclI polymorphism in the glucocorticoid receptor gene: association with sensitivity to glucocorticoids in vivo and body mass index.

OBJECTIVE: Sensitivity to glucocorticoids differs between individuals, partially due to genetic variation in the glucocorticoid receptor (GR) gene. We studied the sequence alteration of a previously described intronic BclI polymorphism of the GR gene, and investigated whether there was an association with sensitivity to glucocorticoids and anthropometric parameters in a group of healthy elderly individuals. DESIGN AND MEASUREMENTS: In study group 1, two overnight dexamethasone suppression tests (DSTs) were performed: with 1 mg dexamethasone, and 2.5 years later with 0.25 mg dexamethasone. Anthropometric parameters were measured in a larger population (study group 2), as well as in a third study group, in which we also measured body composition by dual-energy X-ray absorbtiometry (DEXA) scans. SUBJECTS: Groups 1 and 2, respectively, 191 and 1963 male and female participants of the Rotterdam study, a population-based study in Dutch elderly. Study group 3: 370 elderly males (mean age 77.8 +/- 0.2 years) from Zoetermeer, the Netherlands. RESULTS: We identified the BclI restriction site polymorphism as a C/G substitution in intron 2, 646 nucleotides downstream from exon 2. After both 1 mg and 0.25 mg DST, heterozygous (CG) and homozygous G-allele carriers (GG) had lower cortisol levels than CC-carriers (P = 0.01 and P = 0.02, respectively). In study group 2, we found a lower body mass index (BMI; P = 0.006) and waist-hip ratio (WHR; P = 0.02) in G-allele carriers. In study group 3, again we found a lower BMI (P = 0.05) in G-allele carriers. No differences were found in fat mass. However, lean mass tended to be lower in G-allele carriers (P = 0.07). CONCLUSIONS: We characterized a BclI-RFLP (restriction fragment length polymorphism) of the GR gene as a C/G polymorphism in intron 2 of which the G-allele was associated with hypersensitivity to glucocorticoids. This resulted in a lower BMI in older individuals in general, while our study in elderly males suggests that the lower BMI is probably due to a greater loss of lean mass during the ageing process.

Aged↗

PubMed2002

Differential inhibition of 17alpha-hydroxylase and 17,20-lyase activities by three novel missense CYP17 mutations identified in patients with P450c17 deficiency.

The microsomal enzyme cytochrome P450c17 is an important regulator of steroidogenesis. The enzyme has two functions: 17alpha-hydroxylase and 17,20-lyase activities. These functions determine the ability of adrenal glands and gonads to synthesize 17alpha-hydroxylated glucocorticoids (17alpha-hydroxylase activity) and/or sex steroids (17,20-lyase activity). Both enzyme functions depend on correct steroid binding, but it was recently shown that isolated lyase deficiency can also be caused by mutations located in the redox partner interaction domain. In this article we present the clinical history and molecular analysis of two patients with combined 17alpha-hydroxylase/17,20-lyase deficiency and four patients with isolated 17,20-lyase deficiency. In these six patients, four missense CYP17 mutations were identified. Two mutations were located in the steroid-binding domain (F114V and D116V), and the other two mutations were found in the redox partner interaction domain (R347C and R347H). We investigated the activity of these mutated proteins by transfection experiments in COS-1 cells using pregnenolone, progesterone, or their hydroxylated products as a substrate and measuring 17alpha-hydroxylase- and 17,20-lyase-dependent metabolites in the medium. The mutations in the steroid-binding domain (F114V and D116V) of P450c17 caused combined, complete (F114V), or partial (D116V) 17alpha-hydroxylase and 17,20-lyase deficiencies, whereas mutations in the redox partner interaction domain (R347C and R347H) displayed less severe 17alpha-hydroxylase deficiency, but complete 17,20-lyase deficiency. These findings are consistent with the clinical data and support the observation that the redox partner interaction domain is essential for normal 17,20-lyase function of P450c17.

Adolescent↗

PubMed2002

A polymorphism in the glucocorticoid receptor gene, which decreases sensitivity to glucocorticoids in vivo, is associated with low insulin and cholesterol levels.

We investigated whether a polymorphism in codons 22 and 23 of the glucocorticoid (GC) receptor gene [GAGAGG(GluArg) --> GAAAAG(GluLys)] is associated with altered GC sensitivity, anthropometric parameters, cardiovascular risk factors, and sex steroid hormones. In a subgroup of 202 healthy elderly subjects of the Rotterdam Study, we identified 18 heterozygotes (8.9%) for the 22/23EK allele (ER22/23EK carriers). In the highest age group, the number of ER22/23EK carriers was higher (67-82 years, 12.9%) than in the youngest age group (53-67 years, 4.9%; P < 0.05). Two dexamethasone (DEX) suppression tests with 1 and 0.25 mg DEX were performed, and serum cortisol and insulin concentrations were compared between ER22/23EK carriers and noncarriers. After administration of 1 mg DEX, the ER22/23EK group had higher serum cortisol concentrations (54.8 +/- 18.3 vs. 26.4 +/- 1.4 nmol/l, P < 0.0001), as well as a smaller decrease in cortisol (467.0 +/- 31.7 vs. 484.5 +/- 10.3 nmol/l, P < 0.0001). ER22/23EK carriers had lower fasting insulin concentrations (P < 0.001), homeostasis model assessment- insulin resistance (IR) (index of IR, P < 0.05), and total (P < 0.02) and LDL cholesterol concentrations (P < 0.01). Our data suggest that carriers of the 22/23EK allele are relatively more resistant to the effects of GCs with respect to the sensitivity of the adrenal feedback mechanism than noncarriers, resulting in a better metabolic health profile.

Aged↗