Biomedical subjects

L M Carlsson

Publications and source records attributed to L M Carlsson.

At least 37 records · Page 2Linked to original sources

PubMed1998

Cloning of two novel growth hormone transcripts expressed in human placenta.

Several isoforms of human GH (hGH) are produced by two related genes expressed in the pituitary (hGH-N) and in the placenta (hGH-V). These genes consist of five exons (denoted 1-5) separated by four introns (denoted A-D). In the present report, two new transcripts of the hGH-V gene are described. The coding region of the hGH-V gene was amplified by RT-PCR using placental complementary DNA as template. DNA sequencing of several clones revealed two novel transcripts. One had a 45-bp deletion caused by the use of an alternative splice acceptor site within exon 3, similar to that in the hGH-N gene, predicting a 20-kDa isoform of hGH-V. The other transcript was generated by the use of an alternative splice donor site causing a 4-bp deletion in the end of exon 4, predicting a 24-kDa protein with 219 amino acids, which we refer to as hGH-V3. The carboxy-terminal sequence of hGH-V3 differs from 22-kDa hGH-V and hGH-V2, the two previously reported transcripts of the hGH-V gene, and does not contain a predicted transmembrane domain as described for hGH-V2. Ligase chain reaction was then used to analyze the possible use of the same splicing pattern in transcripts derived from the other genes of the hGH-gene cluster. Alternatively spliced transcripts encoding the 20-kDa hGH isoform were detected from the hGH-N and hGH-V genes, but not from the human chorionic somatomammotropin-A/B genes. The alternative splicing generating hGH-V3 was only demonstrated in transcripts derived from the hGH-V gene. Using competitive RT-PCR, the expression of hGH-V3 was estimated to be 10% of the hGH-V messenger RNA in full-term normal placentas and in placentas from pathological pregnancies. The 20-kDa hGH-V was detected in two of four full-term normal placentas, whereas a weak signal was observed in one of the pathological placentas. We conclude that the hGH-V primary transcript undergoes alternative splicing pathways generating at least four different messenger RNAs, predicting the expression of different hGH isoforms, including two with a complete sequence divergence in the carboxy-terminus.

Alternative Splicing↗

PubMed1998

Short-term changes in serum leptin levels provide a strong metabolic marker for the growth response to growth hormone treatment in children. Swedish Study Group for Growth Hormone Treatment.

The growth response to GH treatment varies between children. Besides regulating longitudinal growth, GH exerts important metabolic effects, including lipolysis. In this study we examined whether GH-induced changes in serum levels of the adipose tissue-derived hormone leptin can be used as a marker for the long term growth response to GH treatment in short prepubertal children. The study group consisted of 150 children (21 girls and 129 boys), who were 3-15 yr of age at the start of GH treatment and had a maximum GH secretory capacity ranging from very low to high. They were treated with GH (0.1 IU/kg x day) and followed for at least 1 yr. The first year mean increase in height SD score was 0.79 (SD, 0.34), with a broad range (0.08-2.27). Serum leptin concentrations were significantly reduced after 1, 3, and 12 months of GH treatment compared with levels at the start of treatment. The growth response correlated with the serum leptin concentration at the start of treatment (r = 0.49; P < 0.0001) and with the change in serum leptin concentration after both 1 month (r = -0.41; P < 0.01) and 3 months (r = -0.60; P < 0.0001) of treatment. When multiple stepwise regression analysis was applied to the auxological and biochemical variables that correlated (P < 0.10) with the first year growth response to GH treatment, the 3-month change in serum leptin concentration was the single most important variable for explaining the variance in individual growth responses. We conclude that leptin levels at the start of GH treatment as well as short term changes in leptin levels in response to GH treatment are valuable markers of the long term growth response.

Adolescent↗

PubMed1998

Effects of growth hormone treatment on the leptin system and on energy expenditure in abdominally obese men.

The present study has examined the short- and long-term effects of growth hormone (GH) treatment on the leptin system and energy expenditure. Thirty male individuals with abdominal obesity were randomised to GH or placebo treatment in a 9-month, double-blind study. The dose of GH was 9.5 microg/kg, administered subcutaneously every evening. Serum leptin concentrations were measured by a human leptin RIA. Total RNA was isolated from adipose tissue biopsies and leptin mRNA levels were determined by a semi-quantitative reverse transcriptase-PCR assay. Body composition was determined by potassium-40 and the basal metabolic rate (BMR) was measured by a computerised, ventilated, open-hood system. As compared with placebo, an overall decrease in serum leptin concentrations as assessed by the area under the curve (AUC) (P < 0.05) and an increase in BMR (AUC, P < 0.05) were observed during GH treatment. The overall GH-induced changes were due to marked changes in serum leptin concentrations and BMR after 6 weeks of treatment. After 9 months of GH treatment there was a significant reduction in body fat (BF) while serum leptin concentrations and BMR did not differ from baseline values. Leptin mRNA levels did not change over the study period. We speculate that long-term GH treatment induces a new energy balance steady state with decreased BF stores. The effects of GH on the leptin system is suggested to be of importance for the maintenance of a lower BF mass.

Abdomen↗

PubMed1997

Obese (ob) gene defects are rare in human obesity.

Our knowledge of the role of the recently cloned ob-protein (leptin) in the regulation of body fat stores is largely derived from experiments performed in mice. Different mouse models exhibit abnormalities in ob-gene expression, with extreme overexpression in mice which lack bioactive ob-protein, have nonfunctional ob-receptors or hypothalamic lesions, and undetectable expression in mice with suggested defects in regulatory elements. The aim of this study is to examine if defects, corresponding to those in mice, exist in human obesity. Adipose tissue was obtained from 94 adult obese subjects and from six children who had developed obesity after surgery in the hypothalamic region. Total RNA was isolated and ob-gene expression was examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and Northern blot. The coding region of the ob-gene was sequenced in both directions in the 94 obese adults. No mutations were detected in the coding region of the ob-gene and ob-gene expression was detectable in all subjects and none of the subjects had an extreme overexpression. There was no systematic increase in ob-expression in obese children with hypothalamic disease compared to their healthy brothers and sisters. These results show that severe abnormalities involving the ob-gene, analogous to those described in mouse models, are rare in human obesity. We therefore conclude that the cloning and subsequent analysis of the ob-gene has not provided information that can, by itself, explain the genetic component in the development of human obesity.

Adipose Tissue↗

PubMed1997

No evidence for involvement of the growth hormone/insulin-like growth factor-1 axis in psoriasis.

We have examined whether alterations in the growth hormone/insulin-like growth factor-1 axis play a role in the pathogenesis of psoriasis. Serum, urine, full skin biopsies, and suction blister roofs were obtained from patients with psoriasis and from healthy controls. Serum concentrations of insulin-like growth factor-1 and insulin-like growth factor binding protein-3 were measured by radioimmunoassay. Growth hormone-binding protein was measured by ligand-mediated immunofunctional assay. Growth hormone concentration in urine was measured by an immunometric assay, and growth hormone receptor-gene expression was measured by RNase protection assay or by quantitative reverse transcriptase polymerase chain reaction in total RNA isolated from epidermal suction blister roofs. Serum concentrations of insulin-like growth factor-1 (249 +/- 12 micrograms per liter, mean +/- SEM, n = 42, and 277 +/- 21 micrograms per liter, n = 9, for psoriatic patients and controls, respectively), insulin-like growth factor binding protein-3 (3.1 +/- 0.08 mg per liter, n = 42, and 3.3 +/- 0.22 mg per liter, n = 9), growth hormone-binding protein (344 +/- 65 pmol per liter, n = 10, and 311 +/- 83 pmol per liter, n = 9), urinary growth hormone excretion during 24 h (12.8 +/- 2.7 microIU per 24 h, n = 12, and 12.3 +/- 1.6 microIU per 24 h, n = 9), and epidermal growth hormone receptor gene expression [32 +/- 12 x 10(3) mRNA transcripts per microgram total RNA (involved skin), n = 11, and 47 +/- 14 x 10(3) mRNA transcripts per microgram total RNA, n = 9] were similar in patients and controls. For insulin-like growth factor-1 and insulin-like growth factor binding protein-3 the values in psoriatic patients were also similar to those in larger control groups, n = 195 and n = 400, respectively. In addition, we found no evidence of local expression of growth hormone or prolactin in full skin punch biopsies from psoriatic involved skin by reverse transcriptase polymerase chain reaction. In conclusion, our results suggest that alterations in the growth hormone/ insulin-like growth factor-1 axis do not play a major role in the pathogenesis of psoriasis.

Adult↗

PubMed1997

Serum leptin concentrations in relation to pubertal development.

OBJECTIVES: The amount of adipose tissue influences pubertal development and fertility in girls. A candidate for mediating this is the hormone leptin, derived from adipocytes. This work was carried out to determine whether the leptin concentration in serum is regulated during pubertal development. SUBJECTS AND METHODS: Serum concentrations of leptin were determined by radioimmunoassay in a sample of 252 healthy children representing all pubertal stages. RESULTS: Serum leptin concentrations correlated directly with age (r = 0.53), body mass index (BMI) (r = 0.71), and weight for height SD score (r = 0.44) in girls and with BMI (r = 0.33) and weight for height SD score in boys (r = 0.36). Leptin concentrations increased with pubertal development in girls, resulting in significantly higher concentrations at pubertal stages 4 and 5 than at the prepubertal stage, whereas there was no change in the boys. CONCLUSIONS: Serum leptin concentrations increased during pubertal development in the girls, but remained constant in the boys. Whether the increase in serum leptin concentrations in girls is of importance for, or a consequence of, pubertal development is still to be determined.

Adolescent↗

PubMed1997

Mechanisms of growth failure in non-growth-hormone deficient children of short stature.

So far, the clinical evaluation of short children has focused on the measurement of immunoreactive growth hormone (GH) in the blood to determine if the growth retardation is due to GH deficiency. However, GH-dependent short stature may be caused by defects in either the secretion of bioactive GH or by the inability to respond to GH. Both GH secretion and GH responsiveness should, therefore, be evaluated when investigating the cause of short stature. Recent advances in molecular biology have generated new ways of studying different molecules involved in growth regulation, and new genetic defects have been identified in short children.

Child↗

PubMed1997

Expression of functional leptin receptors in the human ovary.

The size of body fat stores is known to influence fertility, indicating a link between adipose tissue and the reproductive system. Studies in mice have identified the adipocyte-derived hormone, leptin (Ob protein), as a possible mediator of this effect. The aim of this study was to investigate the possibility that leptin may have direct effects on the human ovary. To probe this hypothesis we first analyzed the expression of leptin receptors in the human ovary. Transcripts encoding both the long and short isoforms of the leptin receptor were present in human granulosa cells and thecal cells; however, the short isoforms were expressed at much higher levels. Immunoreactive leptin was present in follicular fluid at levels similar to those found in serum. ob gene expression, however, was undetectable in the ovary, as determined by reverse transcription-PCR, whereas it was easily detected in adipose tissue. To determine whether leptin could induce a biological response in ovarian cells, we examined the effect of leptin on estradiol production in cultured granulosa cells. Leptin (100 ng/mL) inhibited LH (0.1 ng/mL)-stimulated estradiol production. In contrast, leptin had no effect on estradiol production in the absence of LH. In conclusion, this study has demonstrated that the leptin receptor is expressed in the human ovary, that leptin is present in follicular fluid, and that leptin can induce a biological response in ovarian cells. These results suggest that leptin may have a direct effect on the human ovary.

Adult↗

PubMed1997

Measurement of human growth hormone receptor messenger ribonucleic acid by a quantitative polymerase chain reaction-based assay: demonstration of reduced expression after elective surgery.

Studies of GH receptor (GHR) gene expression in human tissues have been hampered by the limited amount of tissue available for analysis and the low sensitivity of conventional methods. We have developed a quantitative reverse transcriptase-PCR assay for measurement of GHR messenger ribonucleic acid levels in small human tissue biopsies. To compensate for sample to sample variation, an internal RNA standard, which differs from the wild-type GHR transcript by only a few nucleotides, was reverse transcribed and amplified together with the GHR transcripts. PCR was carried out using one biotinylated primer to permit the purification of single stranded PCR products on streptavidin-coated microtiter plates. The ratio between the wild-type and mutated transcripts was determined by two separate minisequence reactions in which a primer, annealed immediately 3' of a variable nucleotide, was extended by a single 3H-labeled nucleotide, complementary to either the wild-type or mutated sequence. The assay range was 0.125-8 x 10(5) transcripts/sample, the mean intraassay coefficient of variation was 8.7%, and the lower limit of detection was 0.125 x 10(5) transcripts/sample. GHR messenger ribonucleic acid levels were detectable in small amounts (10-100 ng) of total RNA extracted from adipose tissue, skeletal muscle, and liver. The GHR gene expression in liver was approximately 10-fold higher than that in skeletal muscle, whereas intermediate levels were found in adipose tissue. In nine patients undergoing elective abdominal surgery, GHR gene expression in skeletal muscle was reduced on day 3 after surgery compared to the baseline level. The decrease in GHR gene expression was accompanied by a decrease in skeletal muscle glutamine. This suggests that the postoperative protein catabolism may be caused at least partly by acquired GH insensitivity due to reduced expression of the GHR gene.

Abdomen↗

PubMed1997

Growth hormone (GH)-binding protein in prepubertal short children born small for gestational age: effects of growth hormone treatment. Swedish Study Group for Growth Hormone Treatment.

This study was undertaken to characterize the serum levels of GH-binding protein (GHBP) before and during GH treatment in prepubertal short children born small for gestational age (SGA) and their relationship with growth parameters. Sixty-seven prepubertal short children (49 boys and 18 girls; height SD score, -5.4 to -2.0; age, 2.0-12.8 yr) born SGA, 8 of whom (6 boys and 2 girls) had signs of Silver-Russell syndrome, participated in the study. Total GHBP was measured by a ligand-mediated immunofunctional assay. The mean (SD) change in height SD score during the year before the start of GH treatment (0.1 IU/kg.day) was 0.11 (0.20) SD score, and this value increased to a 0.84 (0.43) SD score during the first year (P < 0.001) and to a 1.27 (0.63) SD score during the 2-yr period of therapy (P < 0.001). The baseline GHBP values ranged from 49-392 pmol/L, and no relationships were found among sex, chronological age, and maximal GH response to an arginine-insulin tolerance test. A positive correlation between GHBP and body composition, expressed as weight for height SD score, was found in the whole group (r = 0.28; P < 0.05) and in boys (r = 0.44; P < 0.01). No relationship was found between GHBP and spontaneous 24-h GH secretion, in terms of either GH secretion rate or pulsatile pattern, whereas GHBP was positively correlated with insulin-like growth factor I (IGF-I) SD score (r = 0.28; P < 0.05) and IGF-binding protein-3 SD score (r = 0.39; P < 0.01). Using a multiple stepwise linear regression analysis, the model using the IGF-binding protein-3 SD score and the weight for height SD score at the start of GH therapy accounted for 33% of the variance in the baseline GHBP values. A mean increase of 27 (51)% in GHBP levels was found after 1 yr of therapy. However, a high degree of variability in the response of individuals to GH treatment in terms of GHBP levels was observed: in some children GHBP levels increased, whereas in others they decreased. In conclusion, GHBP levels in short prepubertal children born SGA were mostly within the normal range previously reported and correlated directly with body composition. An increase in GHBP levels was observed during GH treatment in some SGA children. No correlation was found between pretreatment GHBP levels and growth response to GH treatment.

Body Composition↗

PubMed1997

Circulating non-22-kilodalton growth hormone isoforms in acromegalic men before and after transsphenoidal surgery.

GH represents several molecular isoforms in addition to the main 22-kDa (22K) GH. There have been reports suggesting that circulating non-22K GH isoforms are increased in acromegaly, but the possible implications of such observations in the management of the disease have not been addressed. The aim of this study was to evaluate the proportion of circulating non-22K GH isoforms in acromegaly. In addition, the relationships between the amount of non-22K GH and tumor size, biochemical measurements, and body composition also were investigated. Samples with different GH levels were selected from 24-h GH profiles from 15 acromegalic men evaluated before and 1 yr after transsphenoidal surgery and from 13 healthy men. The serum non-22K GH levels, expressed as percentage of total GH concentration, were determined by the 22K GH exclusion assay, which is based on immunomagnetic extraction of 22K GH from serum and quantitation of non-22K GH using a polyclonal GH assay. The proportion of non-22K GH isoforms was fairly constant in different samples from the same patient, regardless of the GH level. However, a wide variation of values was observed among acromegalics, both before (14-51%) and after surgery (8-62%). The proportion of non-22K GH isoforms was increased in untreated patients, compared with controls (26.6 vs. 17.4%; P < 0.01), and the values correlated significantly to tumor size, mean 24-h GH concentration, serum PRL, and extracellular water. After surgery, patients not truly cured, with mean 24-h GH concentration of 1 microg/L or more, had an increased proportion of non-22K GH, compared with those with levels less than 1 microg/L (P < 0.01). In the former group, the median values were similar than those in untreated acromegalics (34 vs. 26.6%, respectively), whereas in the latter, they were comparable with those in the controls (15.2 vs. 17.4%, respectively). We conclude that acromegalics have an increased proportion of circulating non-22K GH isoforms. The values are fairly constant in different samples from an individual, regardless of GH level, but a large spectrum can be observed among patients. This variability suggests that different pituitary adenomas secrete GH isoforms in variable amounts. Our observation that a higher proportion of non-22K GH isoforms is present in patients not truly cured after surgery suggests that the evaluation of non-22K GH isoforms can be useful in the follow-up of acromegalic patients.

Acromegaly↗

PubMed1997

Increased proportion of circulating non-22-kilodalton growth hormone isoforms in short children: a possible mechanism for growth failure.

Current knowledge about the interaction between GH and its receptor suggests that the molecular heterogeneity of circulating GH may have important implications for growth. The aim of this study was to investigate the proportion of circulating non-22-kDa GH isoforms in prepubertal children with short stature (height less than -2 SD score) of different etiologies. We have also evaluated the relationships among the ratio of non-22-kDa GH isoforms, auxology, and spontaneous GH secretion. The study groups consisted of 17 girls with Turner's syndrome (TS), aged 3-13 yr, 25 children born small for gestational age (SGA) without postnatal catch-up growth, aged 3-13 yr; and 24 children with idiopathic short stature (ISS), aged 4-15 yr. The results were compared with those from 23 prepubertal healthy children of normal stature (height +/- 2 SD score), aged 4-13 yr. Serum non-22-kDa GH levels, expressed as a percentage of the total GH concentration, were determined by the 22-kDa GH exclusion assay, which is based on immunomagnetic extraction of monomeric and dimeric 22-kDa GH from serum and quantitation of non-22-kDa GH using a polyclonal antibody-based GH assay. All samples were selected from spontaneous GH peaks in 24-h GH profiles. The median proportion of non-22-kDa GH isoforms was increased in children born SGA (9.8%; P = 0.05) and girls with TS (9.9%; P = 0.01), but not in the group of children with ISS (8.9%), compared with that in normal children (8.1%). Individually, increased proportions of non-22-kDa GH isoforms, with values more than 2 SD above the mean for the normal group, were observed in 5 girls with TS, 5 children born SGA, and 4 children with ISS. In children born SGA, the proportion of non-22-kDa GH isoforms was directly correlated with different estimates of spontaneous GH secretion [mean 24-h GH concentration (r = 0.41; P = 0.04), area under the curve over baseline (r = 0.41; P = 0.04), and GH peak area (r = 0.61; P = 0.003)], whereas it was inversely correlated with height SD score (r = -0.42; P = 0.04). In conclusion, an increased proportion of circulating non-22-kDa GH isoforms was observed at spontaneous GH peaks in some non-GH-deficient short children. Our results suggest that the ratio of non-22-kDa GH isoforms in the circulation may have important implications for normal and abnormal growth.

Adolescent↗

PubMed1997

Leptin levels are strongly correlated with those of GH-binding protein in prepubertal children.

OBJECTIVE: Nutritional status is an important determinant of growth, and previous studies have indicated that this is due, at least in part, to an increased target-tissue sensitivity to GH. An attractive candidate for mediating this effect is leptin, a hormone secreted by the adipose tissue. The aim of this study was to investigate if there was a connection between GH-binding protein (GHBP) and leptin. DESIGN AND METHODS: We investigated the relationship between serum levels of leptin and those of GHBP in 229 prepubertal children. These included 107 healthy children with normal GH secretion, 55 GH-deficient (GHD) children and 55 children born small for gestational age (SGA) sampled on one occasion for GHBP and leptin, and 12 healthy children followed longitudinally at monthly interval for 1 year. RESULTS: In the healthy children and in those born SGA, the serum concentration of GHBP was positively correlated with that of leptin (r = 0.65, P < 0.001; r = 0.74, P < 0.001 respectively). There was no correlation between GHBP and leptin in the group of children with GHD (r = 0.27, not significant). This means that leptin alone explained 42% of the variation of GHBP in the healthy group and 55% in the SGA group. The correlation remained after adjustment for body mass index and age in the healthy children (r = 0.57, P < 0.0001, r2 = 0.33) and for children born SGA (r = 0.74, P < 0.0001, r2 = 0.55). There was a positive correlation between the intra-individual monthly changes in GHBP and changes in leptin respectively, in the 12 healthy children followed longitudinally, the mean of the correlation coefficients was 0.38 (median = 0.29; range 0.03 to 0.86; P < 0.05). CONCLUSIONS: There was a highly significant correlation between serum levels of leptin and those of GHBP, except in children with GHD. The possibility that leptin could mediate the effects of body fat mass on GH sensitivity, therefore, merits further investigation.

Adolescent↗

PubMed1997

Circulating non-22 kDa growth hormone isoforms in healthy children of normal stature: relation to height, body mass and pubertal development.

The proportion of non-22 kDa GH isoforms was evaluated in 93 healthy children (48 boys aged 6.8-18.4 years and 45 girls aged 3.9-18.4 years) of normal stature (height +/- 2 s.d. score) at different stages of puberty. In addition, correlations among the proportion of non-22 kDa GH isoforms, auxology, spontaneous GH secretion and biochemical measurements were investigated. Serum non-22 kDa GH levels, expressed as percentage of total GH concentration in the samples, were determined by the 22 kDa GH exclusion assay, in which monomeric and dimeric 22 kDa GH are removed from serum and the non-22 kDa GH isoforms are quantitated using a polyclonal antibody GH assay. Samples were selected from spontaneous GH peaks in 24-h GH profiles. For boys, the median proportion of non-22 kDa GH isoforms was 8.5% (range 3.2-26.6%) and for girls it was 9.6% (1.8-17.4%), with no influence of age and no sex-related difference in prepubertal (boys, 7.2%; girls, 8.8%) or pubertal children (boys, 9.1%; girls, 9.9%). However, the median proportion of non-22 kDa GH isoforms was significantly higher in pubertal boys (9.1%) than in prepubertal boys (7.2%; P = 0.03). In pubertal boys, height S.D. scores (SDS) were inversely correlated to the proportion of non-22 kDa GH isoforms (r = -0.38; P = 0.02), especially at mid-puberty (r = -0.7; P = 0.01), indicating that the presence of increased amounts of circulating non-22 kDa GH isoforms was associated with less growth. In prepubertal children, positive correlations between non-22 kDa GH and weight SDS (r = 0.46; P = 0.03), weight-for-height SDS (r = 0.51; P = 0.01) and body mass index (r = 0.42; P = 0.04) were observed. No significant correlations were seen with spontaneous GH secretion or measurements of IGF-1, IGF-binding protein-3, insulin and leptin. These findings in normal children indicate that the proportion of circulating non-22 kDa GH isoforms may have physiologic significance for growth and metabolism in different stages of development, and emphasize the importance of evaluating the circulating ratio of 22 kDa and non-22 kDa GH in children with growth disorders.

Adolescent↗

PubMed1997

Serum leptin in short children born small for gestational age: relationship with the growth response to growth hormone treatment. The Swedish Study Group for Growth Hormone Treatment.

The product of the obese (ob) gene, leptin, is an adipocyte-derived hormone that is involved in the regulation of appetite and body weight. This study was undertaken in order to describe the basal serum levels of leptin in prepubertal short children born small for gestational age (SGA) and their relationship with growth parameters, before and during growth hormone (GH) treatment. Eighty-nine prepubertal short children (66 boys, 23 girls; height standard deviation score (SDS), -5.4 to -2.0; age, 2.0 to 12.8 years) born SGA, 12 of whom (9 boys, 3 girls) had signs of Silver-Russell syndrome, were included in the study. Serum leptin concentrations were measured by radioimmunoassay. Leptin levels in the children born SGA were compared with those in a reference group of 109 prepubertal healthy children born at an appropriate size for gestational age (AGA). The mean (S.D.) change in height SDS was 0.11 (0.22) during the year before the start of GH therapy (0.1 IU/kg/day) and increased to 0.82 (0.44) during the first year (P < 0.001) and to 1.28 (0.59) during the 2-year period of GH therapy (P < 0.001). The children born SGA were significantly leaner than the reference group. An inverse correlation was found between leptin and chronological age in the SGA group (r = -0.31, P < 0.01). The mean serum level of leptin in the children born SGA who were older than 5.5 years of age was 2.8 micrograms/l which was significantly lower than the mean value of 3.7 micrograms/l found in the children born AGA of the same age range. The difference remained after adjustment of leptin levels for sex, age, body mass index (BMI) and weight-for-height SDS (WHSDSSDS). Leptin correlated with WHSDSSDS (r = 0.32, P < 0.001) and BMI (r = 0.36, P < 0.01) in the reference population, but not in the SGA group. No correlation was found between leptin and spontaneous 24-h GH secretion, insulin-like growth factor (IGF)-I or IGF-binding protein-3 levels, or with fasting insulin or cortisol levels. Leptin levels at the start of GH treatment were correlated with the growth response over both 1 year (r = 0.46, P < 0.001) and 2 years (r = 0.51, P < 0.001) of GH therapy. Using multiple regression analysis, models including leptin levels at the start of GH therapy could explain 51% of the variance in the growth response after 1 year and 44% after 2 years of GH treatment. In conclusion, serum leptin levels are reduced in short children born SGA and are inversely correlated with chronological age. Leptin concentrations correlate with the growth response to GH treatment and might be used as a marker for predicting the growth response to GH treatment.

Aging↗

PubMed1996

The rat extracellular superoxide dismutase dimer is converted to a tetramer by the exchange of a single amino acid.

Extracellular superoxide dismutase (EC-SOD) is a secreted Cu and Zn-containing glycoprotein. While EC-SOD from most mammals is tetrameric and has a high affinity for heparin and heparan sulfate, rat EC-SOD has a low affinity for heparin, does not bind to heparan sulfate in vivo, and is apparently dimeric. To examine the molecular basis of the deviant physical properties of rat EC-SOD, the cDNAs of the rat and mouse EC-SODs were isolated and the deduced amino acid sequences were compared with that of human EC-SOD. Comparison of the sequences offered no obvious explanation of the differences. Analysis of a series of chimeric and point mutated EC-SODs showed that the N-terminal region contributes to the oligomeric state of the EC-SODs, and that a single amino acid, a valine (human amino acid position 24), is essential for the tetramerization. This residue is replaced by an aspartate in the rat. Rat EC-SOD carrying an Asp --> Val mutation is tetrameric and has a high heparin affinity, while mouse EC-SOD with a Val --> Asp mutation is dimeric and has lost its high heparin affinity. Thus, the rat EC-SOD dimer is converted to a tetramer by the exchange of a single amino acid. Furthermore, the cooperative action of four heparin-binding domains is necessary for high heparin affinity. These results also suggest that tetrameric EC-SODs are not symmetrical tetrahedrons, but composed of two interacting dimers, further supporting an evolutionary relationship with the dimeric cytosolic Cu and Zn-containing SODs.

Amino Acid Sequence↗

PubMed1996

Partial growth hormone insensitivity in childhood.

There appears to be a continuum of GH-responsiveness, ranging from complete GH-resistance in Laron syndrome to normal GH-sensitivity. Partial GHI is suggested by findings at both ends of this spectrum; some patients with Laron-type dwarfism are less severely affected by their GHI than others (Savage et al, 1993; for a review, see Savage et al, 1995) and some short, non-GH-deficient, children have reduced responsiveness to GH. Among children with ISS, we have identified a subgroup where defects at the level of the GH receptor lead to a partial-GHI syndrome (Carlsson et al, 1994; Attie et al, 1995; Goddard et al, 1995). Partial-GHI may explain the growth failure in some children who do not meet the criteria for GHD. So far, the clinical evaluation of short children has been focused on the exclusion or demonstration of GHD. The diagnosis of GHD at present requires that stimulated or spontaneous GH concentrations should fail to reach a certain, arbitrarily determined level. This assumes that GH-sensitivity is equal in all subjects, with the exception of rare cases with Laron syndrome. The diagnosis of GHD is in itself controversial, and it has been suggested that GH testing should be supplemented by other measures such as auxological evaluation and measurement of other components of the GH/IGF-I axis (Rosenfeld et al, 1995). However, the fact that some short children have partial-GHI suggests that both GH secretion and GH responsiveness should be taken into consideration when investigating the cause of short stature (Figure 5). Many short children do not have GHD per se, but may be short due to inadequate GH stimulation because of reduced GH-sensitivity.

Age Factors↗

PubMed1996

Recombinant human growth hormone (GH)-binding protein enhances the growth-promoting activity of human GH in the rat.

To address the role of the GH-binding protein (GHBP) in GH physiology, two forms of recombinant human GHBP (rhGHBP) were given alone or in combination with rhGH to hypophysectomized rats or GH-deficient dwarf rats. Hypophysectomized rats were given daily sc injections of excipient, hGH, rhGHBP, or rhGH plus rhGHBP (produced in Escherichia coli) for 7 days. Injections of rhGH induced dose-related body weight gain and bone growth that were increased by the coadministration of rhGHBP with rhGH; rhGHBP alone had no effect. Serum insulin-like growth factor increased 24 h later when rhGH was given together with rhGHBP (P < 0.01), but not when rhGH was given alone. E. coli-derived rhGHBP also enhanced the bioactivity of coadministered rhGH in the GH-deficient dwarf rat. In contrast, the glycosylated rhGHBP, made in human A293 cells, inhibited the growth-promoting activity of coadministered rhGH. The opposite effects of these two forms of rhGHBP could be explained by clearance studies that showed radiolabeled rhGH bound to A293 cell-derived rhGHBP to be cleared more rapidly from the blood than free rhGH. Natural rabbit GHBP and E. coli-derived rhGHBP both prolonged the presence of rhGH in blood. It is proposed that by slowing the clearance of GH, GHBP increased the bioactivity of GH. In summary, codelivery of rhGHBP and rhGH caused a dose-dependent enhancement of the activity of rhGH in two rat models of GH deficiency. This suggests that endogenous circulating GHBP may increase the activity of blood-borne GH in a similar manner.

Animals↗