Genetic variation at the growth hormone (GH1) and growth hormone receptor (GHR) loci as a risk factor for hypertension and stroke

Association of growth hormone receptor gene variant with longevity in men is due to amelioration of increased mortality risk from hypertension

The single nucleotide polymorphism (SNP) rs4130113 of the growth hormone receptor gene (GHR) is associated with longevity. Here we explored whether longevity-associated genotypes protect against mortality in all individuals, or only in individuals with aging-related diseases. Rs4130113 genotypes were tested for association with mortality in 3,557 elderly American men of Japanese ancestry. At baseline (1991–1993), 1,000 had diabetes, 730 had coronary heart disease (CHD), 1,901 had hypertension, 485 had cancer, and 919 lacked these diseases. The men were followed from baseline until Dec 31, 2019 or death (mean 10.8 ± 6.5 SD years, range 0.01–28.8 years; 99.0% deceased by that date). In a heterozygote disadvantage model, longevity-associated genotypes were associated with significantly lower mortality risk in individuals having hypertension (covariate-adjusted hazard ratio [HR] 0.83 [95% CI: 0.76–0.93, p = 4.3 x10^–4]. But in individuals with diabetes, CHD, and cancer there was no genotypic difference in lifespan. As expected, normotensive men outlived men with hypertension (p = 0.036). There was no effect, however, of genotypic difference on lifespan in normotensive men (p = 0.11). We found that SNP rs4130113 potentially influenced the binding of transcription factors E2A, MYF, NRSF, TAL1, and TCF12 so as to alter GHR expression. We propose that in individuals with hypertension, longevity-associated genetic variation in GHR enhances cell resilience mechanisms to help protect against cellular stress caused by hypertension. As a result, hypertension-affected men who possess the longevity-associated genetic variant of GHR live as long as normotensive men.

Adult Body Height and Cardiometabolic Disease Risk: The China National Health Survey in Shaanxi

OBJECTIVES

Based on data from the China National Health Survey, we aimed to examine the association between body height and cardiometabolic disease (CMD) in a large adult population from Shaanxi province, and further to test whether this association was hinged upon other population characteristics.

METHODS

This population-based study was conducted in 2014 in Shaanxi Province, China. Utilizing a multi-stage stratified cluster sampling method, total 5,905 adults with complete data were eligible for analysis, and 1,151 (19.5%) of them had CMD. Of 1,151 CMD patients, 895 (15.1%) had one disorder and 256 (4.4%) had ≥2 disorders.

RESULTS

Using the bi-directional stepwise method and all-subsets regression, five factors-age, body mass index, family histories of CMD, exercise, and height-constituted the optimal model when predicting CMD risk. Restricted cubic spline regression showed a reduced tendency towards CMD with the increase of body height, with per 10 cm increment in body height corresponding to 14% reduced risk. Ordinal Logistic regression supported the contribution of body height on both continuous and categorical scales to CMD risk before and after adjustment, yet this contribution was significantly confounded by exercise and education, especially by exercise, which can explain 65.4% of total impact. For example, short stature was associated with an increased risk of CMD after multivariable adjustment not including exercise and education (odds ratio, 95% confidence interval, P: 1.42, 1.21 to 1.66, <0.001), and tall stature was associated with a reduced risk (0.77, 0.64 to 0.92, 0.003).

CONCLUSIONS

Our findings indicate short stature was a risk factor, yet tall stature was a protective factor for CMD in Chinese. Notably, the prediction of short and tall stature for CMD may be mediate in part by exercise.

The clinical and cardiometabolic effects of d3-growth hormone receptor polymorphism in acromegaly

PURPOSE

Exon 3-deleted GH receptor variant (d3-GHR) is associated with increased responsiveness to exogenous GH. The aim of this study was to determine the effect of d3-GHR polymorphism on the GH/IGF-1 relationship, clinical parameters, and comorbidity in acromegalic patients.

METHODS

The study included 118 acromegalic patients (61 female and 57 male; mean age: 50.3 ± 12.2 years) and 108 healthy controls (94 female and 14 male: mean age: 41.1 ± 11.1 years). The prevalence of GHR genotypes was evaluated via PCR.

RESULTS

In all, 71 (60.2%) patients had the fl/fl-GHR genotype, 40 (33.9%) were heterozygous for the fl/d3-GHR genotype, and 7 (5.9%) were homozygous for the d3/d3-GHR genotype. The prevalence of fl/fl-GHR, fl/d3-GHR, and d3/d3-GHR genotypes in the control group was 57.4, 29.6, and 13.0%, respectively-similar prevalences as in the patient group. Patients that were heterozygous and homozygous for the d3 allele were subgrouped (d3-GHR subgroup), and were compared to those with the fl/fl-GHR genotype (fl/fl-GHR subgroup). Anthropometric measures, features of pituitary adenoma, and baseline GH and IGF-1 levels were similar in both subgroups. The prevalence of coronary artery disease, hypertension, hyperlipidemia, type 2 diabetes mellitus, and multinodular goiter did not differ between patient subgroups. In total, 24 (20.3%) of the patients had cancer and the prevalence of cancer was similar in the d3-GHR (14.9%) and fl/fl-GHR (23.9%) subgroups (P = 0.23). More of the acromegalic patients that were d3 carriers had discordant GH and IGF-1 levels at baseline and post surgery, but the difference was not significant. A significant correlation between basal GH and IGF-1 levels was observed only in the patients with the fl/fl-GHR genotype (R(2) = 0.227, P < 0.001).

CONCLUSION

The d3-GHR variant genotype did not have an effect on clinical features or comorbidity in acromegalic patients, but it might play a role in GH/IGF-1 level discordance in acromegaly.

The growth hormone receptor exon 3 polymorphism is not associated with height or metabolic traits in healthy young adults

CONTEXT

The GHR polymorphisms contribution to the interindividual variability in prenatal and postnatal growth as well as to metabolic traits is controversial.

OBJECTIVE

The aim of this study is to analyze the association of the GHRfl/d3 polymorphism with prenatal and postnatal growth and metabolic outcomes in adult life and to compare the genotype distribution in different populations.

DESIGN

385 community healthy subjects followed from birth to adult life (23-25years old) were grouped according to birth size: small-SGA (n=130, 62 males), appropriate-AGA (n=162, 75 males) and large for gestational age-LGA (n=93, 48 males). GHRfl/d3 genotype distribution and its potential association with anthropometric (at birth, childhood and adult life) and metabolic features (in adult life) were analyzed and compared with data obtained from a systematic review of GHRfl/d3 association studies (31 articles).

RESULTS

The frequency of the GHR d3/d3 genotype was lower in the LGA (χ2 p=0.01); SGA and AGA subjects exhibited an increased chance of the d3/d3 genotype (OR=3.58; 95%CI: 1.55; 8.24) and (OR=2.39; 95%CI: 1.02; 5.62), respectively. Despite the different prevalence among different birth size groups, in adults, GHRfl/d3 genotype was not associated with height, plasma IGF1 levels or metabolic phenotype and cardiovascular risk. GHRfl/d3 genotype distributions in AGA, SGA and LGA groups were comparable with those found in subjects of European origin but not with those of Asian ancestry.

CONCLUSIONS

The GHRd3 genotype was negatively associated with birth size but it was not associated with adult height or weight, plasma IGF1, metabolic phenotype or any marker of increased cardiovascular risk in young adults.

Effects of growth hormone (GH) therapy withdrawal on glucose metabolism in not confirmed GH deficient adolescents at final height

CONTEXT OBJECTIVE

Growth hormone deficiency (GHD) is associated with insulin resistance and diabetes, in particular after treatment in children and adults with pre-existing metabolic risk factors. Our aims were. i) to evaluate the effect on glucose metabolism of rhGH treatment and withdrawal in not confirmed GHD adolescents at the achievement of adult height; ii) to investigate the impact of GH receptor gene genomic deletion of exon 3 (d3GHR).

DESIGN SETTING

We performed a longitudinal study (1 year) in a tertiary care center.

METHODS

23 GHD adolescent were followed in the last year of rhGH treatment (T0), 6 (T6) and 12 (T12) months after rhGH withdrawal with fasting and post-OGTT evaluations. 40 healthy adolescents were used as controls. HOMA-IR, HOMA%β, insulinogenic (INS) and disposition (DI) indexes were calculated. GHR genotypes were determined by multiplex PCR.

RESULTS

In the group as a whole, fasting insulin (p<0.05), HOMA-IR (p<0.05), insulin and glucose levels during OGTT (p<0.01) progressively decreased from T0 to T12 becoming similar to controls. During rhGH, a compensatory insulin secretion with a stable DI was recorded, and, then, HOMAβ and INS decreased at T6 and T12 (p<0.05). By evaluating the GHR genotype, nDel GHD showed a decrease from T0 to T12 in HOMA-IR, HOMAβ, INS (p<0.05) and DI. Del GHD showed a gradual increase in DI (p<0.05) and INS with a stable HOMA-IR and higher HDL-cholesterol (p<0.01).

CONCLUSIONS

In not confirmed GHD adolescents the fasting deterioration in glucose homeostasis during rhGH is efficaciously coupled with a compensatory insulin secretion and activity at OGTT. The presence of at least one d3GHR allele is associated with lower glucose levels and higher HOMA-β and DI after rhGH withdrawal. Screening for the d3GHR in the pediatric age may help physicians to follow and phenotype GHD patients also by a metabolic point of view.

Shared genetic architecture in the relationship between adult stature and subclinical coronary artery atherosclerosis

BACKGROUND

Short stature is associated with increased risk of coronary heart disease (CHD); although the mechanisms for this relationship are unknown, shared genetic factors have been proposed. Subclinical atherosclerosis, measured by coronary artery calcification (CAC), is associated with CHD events and represents part of the biological continuum to overt CHD. Many molecular mechanisms of CAC development are shared with bone growth. Thus, we examined whether there was evidence of shared genes (pleiotropy) between adult stature and CAC.

METHODS

877 Asymptomatic white adults (46% men) from 625 families in a community-based sample had computed tomography measures of CAC. Pleiotropy between height and CAC was determined using maximum-likelihood estimation implemented in SOLAR.

RESULTS

Adult height was significantly and inversely associated with CAC score (P = 0.01). After adjusting for age, sex and CHD risk factors, the estimated genetic correlation between height and CAC score was -0.37 and was significantly different than 0 (P = 0.001) and -1 (P < 0.001). The environmental correlation between height and CAC score was 0.60 and was significantly different than 0 (P = 0.024).

CONCLUSIONS

Further studies of shared genetic factors between height and CAC may provide important insight into the complex genetic architecture of CHD, in part through increased understanding of the molecular pathways underlying the process of both normal growth and disease development. Bivariate genetic linkage analysis may provide a powerful mechanism for identifying specific genomic regions associated with both height and CAC.

Characterisation of a functional intronic polymorphism in the human growth hormone (GH1) gene

The +1169A allele of the A/T single nucleotide polymorphism (SNP; rs2665802), located within intron 4 of the human growth hormone I (GHI) gene, has been associated with reduced levels of circulating GH and insulin-like growth factor I, a reduced risk of colorectal cancer and a predisposition to osteoporosis. Whether this intronic SNP is itself the functional polymorphism responsible for exerting a direct effect on GHI gene expression, however, or whether it is instead in linkage disequilibrium with the functional SNP, has been an open question. The evolutionary conservation of the +1169T allele (and the surrounding intronic sequence) in the bovine genome, as well as in primate genomes, is, however, suggestive of its functionality. Although a potential alternative splice site spans the location of the +1169 SNP, polymerase chain reaction-based assays failed to yield any evidence for alternative splicing associated with either allele. To determine whether the +1169 SNP, in different allelic combinations with SNPs at -278 (G/T), -57 (T/G) and +2103 (C/T), exerts a direct effect on gene expression and/or GH secretion, we performed a series of transfections of various GHI haplotype-expressing constructs into rat GC (somatotroph) cells. The results obtained provided evidence to support the contention that the +1169A allele contributes directly to the observed reduction in both GHI gene expression and GH secretion. Part of the apparent influence of the +1169A-bearing allele on GHI gene expression and GH secretion may still, however, be attributable to alleles of additional SNPs in cis to +1169A and located within either the promoter or the 3^'-flanking region.

d3-Growth hormone receptor polymorphism in acromegaly: effects on metabolic phenotype

OBJECTIVE

A common polymorphic variant of the growth hormone receptor (GHR) is because of genomic deletion of exon 3 and has been linked with increased responsiveness to exogenous GH. The impact of this polymorphism in acromegaly, a disease characterized by endogenous excess of GH and partial loss of IGF-I feedback on tumoural GH secretion, is not clear. The aim of this study was to investigate possible influences of d3GHR on the GH/IGF-I relationship and metabolic parameters in acromegaly.

DESIGN AND METHODS

Retrospective study on 76 acromegalic patients. Genotype analysis was carried out on leucocyte DNA by multiplex PCR assay. Clinical, hormonal and biochemical parameters at diagnosis were collected from patients' medical records.

RESULTS

Forty-two patients (55.3%) were homozygotes for the allele encoding the full-length GHR (fl/flGHR), 27 patients were heterozygotes (fl/d3) and seven homozygotes (d3/d3) for the genomic deletion of exon 3. Heterozygotes and homozygotes for the d3 allele were considered together (d3GHR) and compared with fl/flGHR patients. d3GHR and fl/flGHR patients showed no difference in GH and IGF-I levels or in the relationship between these two parameters. Patients bearing d3GHR had a lower body mass index (BMI) than patients bearing fl/flGHR (25.8 +/- 2.1 vs. 28.1 +/- 4.8 kg/m(2), P < 0.05). Diabetes mellitus and hypertension were equally distributed, but more d3GHR patients had a normal glucose tolerance (66.7%vs. 56.3%, P < 0.05). The presence of d3GHR allele, and not BMI or age, was a significant negative predictor of insulin levels 120 min after oral glucose load (beta = -80.8, P < 0.05).

CONCLUSIONS

This study supports the hypothesis that the d3GHR is functionally different from the fl/fl variant mostly for the effects on body weight regulation and on glucose metabolism.

Application of serial analysis of gene expression to the study of human genetic disease

Sequence tag analysis using serial analysis of gene expression (SAGE) is a powerful strategy for the quantitative analysis of gene expression in human genetic disorders. SAGE facilitates the measurement of mRNA transcripts and generates a non-biased gene expression profile of normal and pathological disease tissue. In addition, the SAGE technique has the capacity of detecting the expression of novel transcripts allowing for the identification of previously uncharacterised genes, thus providing a unique advantage over the traditional microarray-based approach for expression profiling. The technique has been successful in providing pathological gene expression profiles in a number of common genetic disorders including diabetes, cardiovascular disease, Parkinson disease and Down syndrome. When combined with next generation sequencing platforms, SAGE has the potential to become a more powerful and sensitive technique making it more amenable for diagnostic use. This review will therefore discuss the application of SAGE to several common genetic disorders and will further evaluate its potential use in diagnosing human genetic disease.

Growth hormone (GH1) gene variation and the growth hormone receptor (GHR) exon 3 deletion polymorphism in a West-African population

Among Europeans, functionally significant GH1 gene variants occur not only in individuals with idiopathic growth hormone (GH) deficiency and/or short stature but also fairly frequently in the general population. To assess the generality of these findings, 163 individuals from Benin, West Africa were screened for mutations and polymorphisms in their GH1 genes. A total of 37 different sequence variants were identified in the GH1 gene region, 24 of which occurred with a frequency of >1%. Although four of these variants were novel missense substitutions (Ala13Val, Arg19His, Phe25Tyr and Ser95Arg), none of these had any measurable effect on either GH function or secretion in vitro. Some 37 different GH1 promoter haplotypes were identified, 23 of which are as yet unreported in Europeans. The mean in vitro expression level of the GH1 promoter haplotypes observed in the African population was significantly higher than that previously measured in Britons (p<0.001). A gene conversion in the GH1 promoter, previously reported in a single individual of British origin, was found to occur at polymorphic frequency (5%) in the West-African population and was associated with a 1.7-fold increase in promoter activity relative to the wild-type. The d3 allele of the GHR exon 3 deletion polymorphism, known to be associated with increased GH responsiveness, was also found to occur at an elevated frequency in these individuals from Benin. We speculate that both elevated GH1 gene expression and increased GHR-mediated GH responsiveness may constitute adaptive responses to the effects of scarce food supply in this West-African population since increased circulating GH appears to form part of a physiological response to nutritional deprivation.

Clinical and biochemical impact of the d3 growth hormone receptor genotype in acromegaly

CONTEXT

Lack of exon 3 of the GH receptor (d3-GHR) has been associated with increased responsiveness to GH therapy. By analogy, we hypothesized that patients with acromegaly bearing the d3-GHR genotype may have a more morbid clinical and biochemical picture.

OBJECTIVE

Our objective was to determine whether the GHR genotype, by modifying tissue sensitivity to GH, influences the clinical/biochemical expression of acromegaly and its outcome after treatment.

SETTING

The study was conducted at a specialized clinic at a tertiary care hospital.

DESIGN, PATIENTS, AND METHODS

We conducted a prospective genotype investigation and retrospective analysis and correlation with clinical, biochemical, and outcome data from a group of 148 patients. Samples from 175 healthy blood donors were used as controls. GHR genotyping was performed by real-time PCR.

MAIN OUTCOME MEASURES

We assessed prevalence of the three GHR genotypes (fl/fl, d3/d3, and d3/fl), associations between the genotypes, and baseline as well as post-therapeutic characteristics.

RESULTS

Prevalence of the fl/fl, d3/d3, and d3/fl genotypes was 45, 22, and 32%, respectively, similar to what was found in the controls. Baseline characteristics were similar in carriers of the three genotypes. A positive correlation between IGF-I and log GH concentrations was significant only in homo- or heterozygous d3 carriers. Among d3-GHR carriers, diabetes, but no other comorbidities, was more prevalent (odds ratio = 2.02; 95% confidence interval = 0.96-4.2). d3-GHR carriers had significantly higher IGF-I concentrations after treatment. Multiple regression analysis revealed that the homo- or heterozygous lack of exon 3 was the strongest predictor of persistent biochemical activity (odds ratio = 1.29; 95% confidence interval = 0.65-2.58).

CONCLUSIONS

The absence of exon 3 of the GHR may be associated with a more morbid acromegalic clinical and biochemical picture and a lower chance of achieving IGF-I normalization after therapy.

O hormônio de crescimento na síndrome de Turner: dados e reflexões

A baixa estatura é a principal característica na síndrome de Turner (ST). O agravo estatural na ST é precoce e torna-se mais evidente na puberdade. A haploinsuficiência do gene SHOX tem sido implicada como principal fator na definição da estatura de mulheres, no entanto, ainda que a maioria das pacientes não tenha deficiência do hormônio de crescimento, a terapia com GHr melhora a altura final. Recentemente, tem-se chamado a atenção para a associação entre GH e câncer. O risco de câncer nessas pacientes está associado à presença de fragmentos do cromossomo Y que pode levar ao desenvolvimento de gonadoblastoma. Dessa forma, a administração de GHr na ST deve ser feita com cautela. A investigação de seqüências do cromossomo Y deve ser realizada, bem como a gonadectomia profilática nos casos positivos, conferindo maior segurança ao tratamento.

A functional common polymorphism in the vitamin D-responsive element of the GH1 promoter contributes to isolated growth hormone deficiency

CONTEXT

Causal mutations have been detected only in a minority of isolated GH deficiency (IGHD) patients. Idiopathic IGHD might be the result of the interaction between several low-penetrance genetic factors and the environment.

OBJECTIVE

The aim of this study was to test the contribution to IGHD of genetic variations in the GH1 gene regulatory regions.

DESIGN AND PATIENTS

A case-control association study was performed including 118 sporadic IGHD patients with a nonsevere phenotype (height -4/-1 sd score and partial GH deficiency) and two control groups, normal stature (n=200) and short-stature individuals with normal GH secretion (n=113). Seven single-nucleotide polymorphisms in the GH1 promoter, one in the IVS4 region, and two in the locus control region were analyzed.

RESULTS

The -57T allele within the vitamin D-responsive element showed a positive significant association when comparing patients with normal (P=0.006) or short stature (P=0.0011) controls. The genotype -57TT showed an odds ratio of 2.93 (1.44-5.99) and 2.99 (1.42-6.31), respectively. The functional relevance of the -57 variation was demonstrated by the luciferase assay in the presence of vitamin D. The vitamin D-induced inhibition of luciferase activity was significantly (P=0.012) stronger for the promoter haplotype carrying the associated variation -57T [haplotype #1 (hp#1)] with respect to hp#2, bearing -57G. Replacement of the T with a G at -57 on hp#1 abolished the repression, demonstrating that the T at position -57 is necessary to determine the greater vitamin D-induced inhibitory effect of hp#1. EMSA experiments showed a different band-shift pattern of the T and G sequences.

CONCLUSION

The common -57G-->T polymorphism contributes to IGHD susceptibility, indicating that it may have a multifactorial etiology.

Growth hormone (GH) dose, but not exon 3-deleted/full-length GH receptor polymorphism genotypes, influences growth response to two-year GH Therapy in Short Small-for-Gestational-Age Children

CONTEXT

In short small-for-gestational-age (SGA) patients, the exon 3-deleted(d3)/full-length (fl)-GHR polymorphism was associated with responsiveness to GH therapy (30-48 microg/kg.d); however, these results were not confirmed for higher GH doses (56-66 microg/kg.d). We hypothesized that higher doses would mask the lower dose differences.

OBJECTIVE

Our objective was to evaluate, in short SGA patients, 2-yr growth response to GH therapy (32.1 +/- 3.8 microg/kg.d) according to exon d3/fl-GHR genotypes.

SETTING

This was a 2-yr follow-up study.

PATIENTS

There was a total of 60 short SGA children (d3/d3 n = 8, d3/fl n = 23, and fl/fl n = 29). There were 11 children that entered puberty during the second follow-up year. Results were evaluated for all patients (group A1, n = 60, 7.7 +/- 2.7 yr) and for patients who remained prepubertal (group A2, n = 49, 6.9 +/- 2.2 yr).

MAIN OUTCOME MEASURES

Patients were followed by a single clinical team, and exon d3/fl-GHR genotypes were determined and analyzed in the same hospital.

RESULTS

In groups A1 and A2, growth velocity significantly (P < 0.0001) increased during the first and second years of therapy, as did height sd score (SDS). These increases were similar in each exon d3/fl-GHR genotype. Total 2-yr height gain (cm, SDS) did not differ statistically among genotypes: group A1, 15.0 +/- 2.0 cm and 1.15 +/- 0.45 SDS in d3/d3, 16.0 +/- 2.4 cm and 1.17 +/- 0.51 SDS in d3/fl, 16.1 +/- 2.4 cm and 1.15 +/- 0.53 SDS in fl/fl; and group A2, 15.4 +/- 2.0 cm and 1.03 +/- 0.42 SDS in d3/d3, 15.6 +/- 2.1 cm and 1.22 +/- 0.51 in d3/fl, and 16.2 +/- 2.6 cm and 1.21 +/- 0.56 SDS in fl/fl.

CONCLUSIONS

These results did not confirm our hypothesis and show that, in short SGA children, 2-yr growth response to GH therapy 32.1 +/- 3.8 microg/kg.d was similar for each exon d3/fl-GHR genotype carried, as occurred in our previous study using 66 microkg.d.

Growth Hormone (GH) receptor C.1319 G>T polymorphism, but not exon 3 retention or deletion is associated with better first-year growth response to GH therapy in patients with GH deficiency

We investigated possible influences of single nucleotide polymorphisms (SNPs) on first-year growth velocity in response to growth hormone (GH) therapy in GH-deficient (GHD) children. We recruited a total of 154 GHD prepubertal children who had undergone GH therapy for 1 y. To exclude the possibility that the genotype/allele variants influenced the height of GHD patients, we studied the same gene polymorphisms in 208 familial short stature (FSS) patients and 100 normal control individuals. In the present study, the first-year growth velocities of GHD patients treated with GH were measured and then compared with the allelic frequencies of various SNP of genes involved in the GH-insulin-like growth factor-I (IGF-I) axis. Only c.1319 G>T of the GH receptor (GHR) gene showed significant correlation with first-year growth velocity (p = 0.02). However, the genetic frequency of the c.1319 G>T polymorphism of GHD did not correlate with FSS and normal controls. Therefore, the c.1319 G>T polymorphism does not influence the height of individuals but can affect the therapeutic efficacy of GH in GHD patients. Moreover, the GHR c.1319 T allele showed higher transcriptional activity and stronger signal transducers and activators of transcription (STAT)-5 Tyr694 phosphorylation. Based on these findings, we conclude that the GHRc.1319 T allele is associated with the therapeutic efficacy of GH replacement therapy.

GHR exon 3 polymorphism: association with type 2 diabetes mellitus and metabolic disorder

Growth hormone (GH) signaling via the growth hormone receptor (GHR) forms a major part of the GH-IGF-I axis, which is crucial for controlling metabolism and anabolism. Two common variants of the GHR differ by the presence (full length or GHR(fl)) or absence of exon 3 (exon 3 deleted or GHR(d3)), the function of which is unknown. However, differential response to GH treatment has been observed with carriers of the GHR(d3) variant conferring a greater growth rate. This study investigates these GHR variants in subjects with normal glucose tolerance (NGT) and impaired glucose tolerance (IGT), including Type 2 diabetes mellitus (T2DM). DNA was extracted from blood samples from subjects with NGT (n=158), IGT (n=116) and T2DM (n=194). The T2DM subjects in set 1 (n= 39) were newly diagnosed, whilst those in set 2 (n=155) had a mean duration of 7 years. Set 1 also included NGT and IGT subjects. Genotyping by standard PCR and gel electrophoresis were carried out. A significant difference was observed between T2DM and NGT (p<0.0001) with a significantly lower frequency of GHR(d3) in T2DM (3.6% compared to 17% in NGT). Both sets of T2DM subjects with at least one GHR(d3) allele had significantly higher BMI. In the larger subset of T2DM, GHR(d3) was associated with higher CRP levels as well as age adjusted IGF-I, with a trend of higher C-peptide secretion and impaired lipid levels, indicating a phenotype with metabolic disorder when compared to the GHR(fl/fl) T2DM subjects. In conclusion, homozygosity for the GHR(d3) allele appears to be preventive of T2DM. However, when other factors cause overt T2DM, the GHR(d3) allele confers a phenotype indicative of metabolic disorder. This study supports the hypothesis that the two GHR alleles by their inclusion or exclusion of exon 3 are functionally different.

The presence of the d3-growth hormone receptor polymorphism is negatively associated with fetal growth but positively associated with postnatal growth in healthy subjects

CONTEXT

A common polymorphism in the GH receptor (GHR) gene has been linked to increased growth response in GH-treated patients. No former study has focused on the association to prenatal growth.

OBJECTIVE

The aim of the study was to evaluate the association between the d3-GHR isoforms and spontaneous pre- and postnatal growth.

DESIGN

A prospective study was conducted on third-trimester fetal growth velocity (FGV), birth weight, birth length, and postnatal growth.

SETTING

The study was conducted at Copenhagen University Hospital.

PARTICIPANTS

A total of 115 healthy adolescents were divided into those born small for gestational age (SGA) and appropriate for gestational age with or without intrauterine growth restriction.

MAIN OUTCOME MEASURES

FGV was measured by serial ultrasonography, birth weight, birth length, and adolescent height. Isoforms of the d3-GHR gene (fl/fl, d3/fl, and d3/d3) were determined.

RESULTS

The prevalence of the d3-GHR isoforms was 50% but differed among the groups (P = 0.006), with a high prevalence (88%) in the group born SGA with verified intrauterine growth restriction. The d3-GRH allele were associated with decreased third-trimester FGV (P = 0.05) in SGA subjects. In the entire cohort, carriers of the d3-GHR allele had a significantly increased height (-0.10 vs. 0.34 SD score; P = 0.017) and change in height from birth to adolescence compared with carriers of the full-length GHR allele (0.57 vs. -0.02 SD score; P = 0.005).

CONCLUSIONS

This study showed an increased spontaneous postnatal growth velocity in the carriers of the d3-GHR allele. Interestingly, we found the opposite effect on prenatal growth in the SGA group, with a decreased FGV in carriers of the d3-GHR allele.

Molecular genetics of human growth hormone, insulin-like growth factors and their pathways in common disease

The human growth hormone gene (GH1) and the insulin-like growth factor 1 and 2 genes (IGF1 and IGF2) encode the central elements of a key pathway influencing growth in humans. This "growth pathway" also includes transcription factors, agonists, antagonists, receptors, binding proteins, and endocrine factors that constitute an intrincate network of feedback loops. GH1 is evolutionarily coupled with other genes in linkage disequilibrium in 17q24.2, and the same applies to IGF2 in 11p15.5. In contrast, IGF1 in 12q22-24.1 is not in strong linkage disequilibrium with neighbouring genes. Knowledge of the functional architecture of these regions is important for the understanding of the combined evolution and function of GH1, IGF2 and IGF1 in relation to complex diseases. A number of mutations accounting for rare Mendelian disorders have been described in GH-IGF elements. The constellation of genes in this key pathway contains potential candidates in a number of complex diseases, including growth disorders, metabolic syndrome, diabetes (notably IGF2BP2) cardiovascular disease, and central nervous system diseases, and in longevity, aging and cancer. We review these genes and their associations with disease phenotypes, with special attention to metabolic risk traits.