Enhancer deletions of the SHOX gene as a frequent cause of short stature: the essential role of a 250 kb downstream regulatory domain.

BACKGROUND: Mutations and deletions of the homeobox transcription factor gene SHOX are known to cause short stature. The authors have analysed SHOX enhancer regions in a large cohort of short stature patients to study the importance of regulatory regions in developmentally relevant genes like SHOX. METHODS: The authors tested for the presence of copy number variations in the pseudoautosomal region of the sex chromosomes in 735 individuals with idiopathic short stature and compared the results to 58 cases with Leri-Weill syndrome and 100 normal height controls, using fluorescence in situ hybridisation (FISH), single nucleotide polymorphism (SNP), microsatellites, and multiplex ligand dependent probe amplification (MLPA) analysis. RESULTS: A total of 31/735 (4.2%) microdeletions were identified in the pseudoautosomal region in patients with idiopathic short stature; eight of these microdeletions (8/31; 26%) involved only enhancer sequences residing a considerable distance away from the gene. In 58 Leri-Weill syndrome patients, a total of 29 microdeletions were identified; almost half of these (13/29; 45%) involve enhancer sequences and leave the SHOX gene intact. These deletions were absent in 100 control persons. CONCLUSION: The authors conclude that enhancer deletions in the SHOX gene region are a relatively frequent cause of growth failure in patients with idiopathic short stature and Leri-Weill syndrome. The data highlights the growing recognition that regulatory sequences are of crucial importance in the genome when diagnosing and understanding the aetiology of disease.

Increase in salicylic Acid at the onset of systemic acquired resistance in cucumber.

In an effort to identify the signal compound that mediates systemic acquired resistance (SAR), changes in the content of phloem sap were monitored in cucumber plants inoculated with either tobacco necrosis virus or the fungal pathogen Colletotrichum lagenarium. The concentration of a fluorescent metabolite was observed to increase transiently after inoculation, with a peak reached before SAR was detected. The compound was purified and identified by gas chromatography-mass spectrometry as salicylic acid, a known exogenous inducer of resistance. The data suggest that salicylic acid could function as the endogenous signal in the transmission of SAR in cucumber.

Arsenic contamination of soils and agricultural plants through irrigation water in Nepal.

This study monitored the influence of arsenic-contaminated irrigation water on alkaline soils and arsenic uptake in agricultural plants at field level. The arsenic concentrations in irrigation water ranges from <0.005 to 1.014 mg L(-1) where the arsenic concentrations in the soils were measured from 6.1 to 16.7 mg As kg(-1). The arsenic content in different parts of plants are found in the order of roots>shoots>leaves>edible parts. The mean arsenic content of edible plant material (dry weight) were found in the order of onion leaves (0.55 mg As kg(-1))>onion bulb (0.45 mg As kg(-1))>cauliflower (0.33 mg As kg(-1))>rice (0.18 mg As kg(-1))>brinjal (0.09 mg As kg(-1))>potato (<0.01 mg As kg(-1)).

Contribution of androgens to the gender difference in leptin production in obese children and adolescents.

Recent studies demonstrated significantly higher serum leptin concentrations in females as compared with males, even after correction for differences in body fat mass. The aim of our study was to measure serum leptin concentrations in a large group of obese children and adolescents to determine the possible role of sex steroid hormones on both leptin serum concentrations and production in human adipocytes. Obese girls were found to have significantly higher leptin concentrations than boys at the same degree of adiposity (25.2+/-14.1 vs. 17.2+/-12.6 ng/ml, P < 0.001). In a multiple regression analysis with age and body mass index (percent body fat) as fixed variables, it turned out that testosterone had a potent negative effect on serum leptin in boys, but not in girls. In vitro experiments using newly developed human adipocytes in primary culture showed that both testosterone and its biologically active metabolite dihydrotestosterone are able to reduce leptin secretion into the culture medium by up to 62%. Using a semiquantitative reverse transcriptase-PCR method, testosterone was found to suppress leptin mRNA to a similar extent. These results suggest that, apart from differences in body fat mass, the higher androgen concentrations in obese boys are responsible for the lower leptin serum concentrations compared with obese girls.

Parathyroid hormone increases the concentration of insulin-like growth factor-I and transforming growth factor beta 1 in rat bone.

Intermittent treatment with parathyroid hormone (PTH) increases bone mass in experimental animals and humans. In vitro studies have suggested that the anabolic effect of PTH may be mediated by local growth factors. However, the relevance of these findings to in vivo situations remains unclear. In this study, we examined a time course of daily s.c. injections of hPTH (1-34) on the skeletal concentration of insulin-like growth factor (IGF)-I, IGF-II, and transforming growth factor beta (TGF-beta) in the proximal tail vertebrae of male rats. PTH caused a time and dose-dependent increase in the bone mineral density of the lumbar spine. This anabolic effect on bone mass was accompanied by progressive increases in bone matrix-associated IGF-I and TGF-beta 1. Increases in IGF-I and TGF-beta 1 became apparent after four and eight weeks of PTH treatment respectively and persisted through week 12. PTH had no effect on circulating IGF-I, suggesting that the increase of bone matrix IGF-I was due to the local effect of PTH on bone tissue directly rather than to an increase of circulating IGF-I. These data are consistent with the hypothesis that IGF-I and TGF-beta 1 may play a role as local mediators of the anabolic effects of PTH on bone metabolism.

Vitreous levels of the insulin-like growth factors I and II, and the insulin-like growth factor binding proteins 2 and 3, increase in neovascular eye disease. Studies in nondiabetic and diabetic subjects.

Retinal capillary nonperfusion results in neovascularization of the eye, which is restricted to the retina in less severe cases and progresses to the anterior chamber and the iris angle in the most advanced case, called rubeosis. This angioneogenesis may be induced by the release of retinal growth factors into the vitreous. This study compared levels of the IGF-I and IGF-II, and of the IGF binding protein-2 (IGFBP-2) and IGFBP-3 in vitreous from three groups with different degrees of retinal ischemia, as judged by the extent of neovascularization: a control group without new vessel formation, retinal neovascularization in patients with proliferative diabetic retinopathy, and massive ischemia of various causes resulting in rubeosis. IGF-I and IGFBP-3 were increased 10- and 13-fold in rubeosis (P << 0.01) compared with no ischemia (n = 10), while IGF-II and IGFBP-2 were elevated 2.7- and 4.3-fold (P < 0.01). Within the rubeosis group similar changes were observed independently of the cause of ischemia, which was central vein occlusion, ischemic ophthalmopathy, or intraocular tumor in seven cases and diabetic retinopathy in three samples from two patients. Vitreous from patients with proliferative diabetic retinopathy but without rubeosis (n = 16) contained 2.5- and 2.2-fold elevated levels of IGF-I and of IGFBP-2 (P < 0.05), while IGF-II and IGFBP-3 were increased 1.4- and 1.6-fold, which was not significant. We conclude that: (a) ischemia appears to be a strong stimulus for the local production of IGF-I and -II and of IGFBP-2 and -3 in the eye. (b) Changes in IGF-I and IGFBP-2 in proliferative diabetic retinopathy may be secondary to local ischemia rather than being specific for diabetic retinopathy. (c) IGF-I and IGFBP-3 may play a role in mediating angioneogenesis in the eye.

Breakthrough zygomycosis after voriconazole administration among patients with hematologic malignancies who receive hematopoietic stem-cell transplants or intensive chemotherapy.

Zygomycosis is increasingly reported as a cause of life-threatening fungal infections. A higher proportion of cases reported over the last decades have been in cancer patients, with or without hematopoietic stem cell transplantation (HSCT). The new anti-fungal agent voriconazole is a recently identified risk factor for developing zygomycosis. We reviewed the clinical characteristics and outcomes of a large cohort of cancer patients who developed zygomycosis after exposure to voriconazole. Health care professionals at 13 large cancer centers provided clinical information on cancer patients with zygomycosis and prior exposure to voriconazole. Criteria for inclusion were 5 days or more of voriconazole use and diagnostic confirmation with tissue or histology. Fifty-eight cases were identified among patients with hematologic malignancies, 62% including patients who underwent a HSCT procedure. Fifty-six patients received voriconazole for primary or secondary prophylaxis against fungal infection. In addition to prior exposure to voriconazole, patients also had several of the previously established risk factors for zygomycosis. Amphotericin B was the most commonly prescribed anti-fungal therapy. Overall mortality was 73%. We conclude that zygomycosis after exposure to voriconazole is a recently described entity that is frequently fatal, despite treatment with currently available anti-fungal agents and surgery.

Maintenance therapy with decitabine in younger adults with acute myeloid leukemia in first remission: a phase 2 Cancer and Leukemia Group B Study (CALGB 10503).

In this prospective phase 2 clinical trial conducted by Cancer and Leukemia Group B (CALGB, now the Alliance), we studied decitabine as maintenance therapy for younger adults with acute myeloid leukemia (AML) who remained in first complete remission (CR1) following intensive induction and consolidation. Given that decitabine is clinically active in AML and with hypomethylating activity distinct from cytotoxic chemotherapy, we hypothesized that 1 year of maintenance therapy would improve disease-free survival (DFS) for AML patients <60 years, who did not receive allogeneic stem cell transplantation in CR1. After blood count recovery from final consolidation, patients received decitabine at 20 mg/m2 intravenously daily for 4-5 days, every 6 weeks for eight cycles. One hundred and thirty-four patients received decitabine and 85 (63%) had favorable risk AML. The median number of cycles received was 7 (range: 1-8) and the primary reason for discontinuation was relapse. DFS at 1 year and 3 years was 79% and 54%, respectively. These results are similar to the outcomes in the historical control comprising similar patients treated on recent CALGB trials. Thus, maintenance with decitabine provided no benefit overall. Standard use of decitabine maintenance in younger AML patients in CR1 is not warranted. This trial was registered at www.clinicaltrials.gov as NCT00416598.

Treatment of landfill leachate by irrigation and interaction with landfill gas.

The treatment efficiency of landfill leachate irrigation and the effect of landfill gas addition were investigated in a vegetated compost/gravel substrate by monitoring soil moisture content, drainage water volume and quality in a two years lysimeter experiment. Landfill leachate irrigation exceeding 350 mm increased soil moisture and drainage volumes owing to the deterioration of the vegetation resulting from high sodium chloride inputs. Even so sodium chloride was lost in between the irrigation periods, the total reduction of the landfill leachate volume by irrigation decreased from 71% in the first year to 38% in the second year. Landfill gas addition also increased drainage volumes, but was less pronounced. Twenty-two percent of magnesium was retained under landfill leachate irrigation, while decreasing pH values, redox potential and high initial concentrations in the substrate released calcium, iron and potassium. Ninety-eight percent of ammonium was removed by irrigation, but 44% of the applied ammonium was leached as nitrate after oxidation took place due to a decreased uptake after the vegetation deteriorated. Landfill gas fumigation influenced landfill leachate treatment by decreasing the redox potential and the pH and increasing the drainage water content, which improved the retention of total nitrogen and sulfate, but increased the release of iron, calcium and magnesium. To conclude, landfill leachate irrigation is a valuable treatment option to minimize leachate quantities and remove ammonium independent from the presence of landfill gas if salt accumulation is avoided.

Overexpression of insulin-like growth factor-binding protein-2 results in increased tumorigenic potential in Y-1 adrenocortical tumor cells.

Increased concentrations of insulin-like growth factor-binding protein-2 (IGFBP-2) have been observed in human malignancies including adrenocortical carcinomas. To elucidate the functional consequences of IGFBP-2 overexpression, we have stably transfected the cDNA of murine IGFBP-2 in mouse adrenocortical tumor cells (Y-1). Long-term overexpression of IGFBP-2 was associated with significant morphological alterations, enhanced cell proliferation, and increased cloning efficiency as compared with mock transfected control cells. The enhanced proliferation of IGFBP-2 secreting clones was independent of exogenous insulin-like growth factors (IGFs). These data suggest that elevated levels of IGFBP-2 may contribute to the highly malignant phenotype of adrenocortical cancer by a thus far unknown, presumably IGF-independent, mechanism.

Insulin and cortisol promote leptin production in cultured human fat cells.

The aim of this study was to investigate the regulation of leptin expression and production in cultured human adipocytes using the model of in vitro differentiated human adipocytes. Freshly isolated human preadipocytes did not exhibit significant leptin mRNA and protein levels as assessed by reverse transcriptase (RT)-polymerase chain reaction (PCR) and radioimmunoassay (RIA). However, during differentiation induced by a defined adipogenic serum-free medium, cellular leptin mRNA and leptin protein released into the medium increased considerably in accordance with the cellular lipid accumulation. In fully differentiated human fat cells, insulin provoked a dose-dependent rise in leptin protein. Cortisol at a near physiological concentration of 10(-8) mol/l was found to potentiate this insulin effect by almost threefold. Removal of insulin and cortisol, respectively, was followed by a rapid decrease in leptin expression, which was reversible after readdition of the hormones. These results clearly indicate that both insulin and cortisol are potent and possibly physiological regulators of leptin expression in human adipose tissue.

Seasonality of growth response to GH therapy in prepubertal children with idiopathic growth hormone deficiency.

OBJECTIVE: Longitudinal growth of children exhibits seasonal variation. In both healthy children and in children with growth hormone (GH) deficiency (GHD) receiving GH therapy, growth rate is maximal during spring and summer. In the present study, we analyzed the growth response to GH therapy in children with GHD as a function of the season when therapy was started. SUBJECTS AND METHODS: Anthropometric measurements and biochemical analyses of GH secretion status and bone formation were longitudinally assessed in a cohort of 52 prepubertal children with GHD (14 girls, mean age 7.6 years) who were treated with a fixed dose of GH (0.025 mg/kg/day). RESULTS: Auxological assessments over the 2-year observation period revealed a significantly better growth response to GH therapy in children who started therapy between the spring and summer (group 1) compared with children who started in the autumn or winter (group 2). The difference was largest in the initial 3-month treatment period (35%; P<0.01). The initial better gain in height of group 1 was sustained during the study period. Baseline peak GH levels during stimulation tests and insuin-like growth factor-I levels did not differ between the two groups. However, group 1 had significantly higher bone resorption and formation markers, either at the start or shortly after initiation of GH treatment. This suggests that children with GHD have higher bone turnover during spring and early summer, irrespective of GH therapy. CONCLUSIONS: In summary, this study suggests that the season of GH initiation is a determinant of the initial growth response to GH replacement in prepubertal children with GHD.

High-dose busulfan, cyclophosphamide, and etoposide does not improve outcome of allogeneic stem cell transplantation compared to BuCy2 in patients with acute myeloid leukemia.

SUMMARY: To reduce relapse following allogeneic transplantation for AML, intensification of high-dose busulfan/cyclophosphamide using additional agents has been investigated but with few reported comparisons. We compared an intensified regimen of etoposide (60 mg/kg), busulphan (14 mg/kg), and cyclophosphamide (120 mg/kg) (BuCyVP) with BuCy2 in 237 AML patients. No significant difference in overall outcome was observed following BuCyVP (n=127) or BuCy2 (n=110). The 5-year survival was 27.3 and 30.1% following BuCyVP and BuCy2, respectively (P=0.48). Similarly, the 5-year cumulative incidence of relapse (CIR) was 28.3 and 34.8% with BuCyVP and BuCy2 (P=0.45), respectively. On multivariable analysis, patients transplanted in CR1 (P=0.002) and from related donors (P=0.013) had longer survival, while disease status at transplant was the only factor predicting CIR (P=0.002). In a separate analysis of CR1 patients (n=56), there was no significant difference in survival (P=0.37) or CIR (P=0.87) between the two regimens. However, for more advanced disease, there was a trend towards less relapse with BuCyVP (P=0.08), which was balanced by a higher cumulative incidence of transplant-related deaths (P=0.03) compared to BuCy2, resulting in similar survival. Overall, our results do not support the use of the more intensive BuCyVP regimen over BuCy2 in either early or more advanced disease AML patients.

The natural course of multiple endocrine neoplasia type IIb. A study of 18 cases.

BACKGROUND: Multiple endocrine neoplasia (MEN) type IIb is an autosomal dominantly inherited disorder associated with medullary thyroid cancer, pheochromocytoma, and a characteristic phenotype. The present study was performed to investigate the natural course of the syndrome and to describe its expression. METHODS: The medical records of 18 patients with MEN IIb, seven male and 11 female, were reviewed. RESULTS: The mean age at diagnosis of MEN IIb was 18 years (range, 8 to 41 years). All 18 patients had medullary thyroid cancer. In three patients, medullary thyroid cancer was diagnosed via screening. In two of these patients, the calcitonin value normalized after thyroidectomy. One patient died of metastases from medullary thyroid cancer at the age of 20 years (median duration of follow-up, 10 years). Eight of the 18 patients had pheochromocytomas. All of our patients had neuromas and bumpy lips, and all but one had a marfanoid habitus. A large proportion of the patients had intestinal abnormalities (75%), thickened corneal nerves (69%), skeletal abnormalities (87%), and delayed puberty (43%). CONCLUSIONS: The course of medullary thyroid cancer in MEN IIb is not always as aggressive as is generally thought. Periodic examination of relatives who are at risk may lead to early diagnosis and curative treatment. Intestinal abnormalities, skeletal abnormalities, and delayed puberty are commonly found in association with MEN IIb.

Leptin and variables of body adiposity, energy balance, and insulin resistance in a population-based study. The Hoorn Study.

OBJECTIVE: Leptin is thought to play a key role in the control of body weight. There is a complex interrelationship between leptin and insulin or insulin resistance, but it is unknown how leptin is regulated. We therefore explored, in a large population-based study of 2,484 Caucasian subjects aged 50-74 years, the relationship between leptin and variables of body adiposity, energy balance, and insulin resistance. RESEARCH DESIGN AND METHODS: Leptin was measured by means of a radioimmunoassay. Multiple linear regression analyses were performed with leptin as dependent variable and age, sex, BMI, waist circumference, daily energy intake, physical activity, smoking, hypertension, fasting triglyceride concentrations, HDL cholesterol, fasting plasma glucose, and fasting plasma insulin concentrations as independent variables (determinants) RESULTS: Leptin concentrations were found to be four times higher in women than in men. Effect modification between sex and potential determinants was expected, and the analyses were performed separately for women and men. BMI was the strongest determinant of leptin in women and waist circumference the strongest determinant in men. BMI, waist circumference, insulin, and triglyceride concentrations were independently and significantly (P < 0.05) associated with leptin, while inverse associations were shown for smoking and daily energy intake (borderline significance). CONCLUSIONS: This study confirms the relationship between insulin and leptin and, in addition, suggests a relationship between triglyceride concentrations and leptin independent of sex, BMI, waist circumference, and insulin.

Serum leptin in neonatal lambs is associated with temperature, plasma lipids and metabolites.

In this study we investigated changes of serum leptin in 74 newborn lambs and associations with environmental temperature (from - 8°C to + 25°C), body temperature, and concentrations of plasma lipids, 3-beta-hydroxybutyric acid and blood glucose. A leptin radioimmunoassay was established, using an antiserum (rabbit) produced against a partial sequence of ovine leptin (31-44). Before measurement, serum samples were denatured. The sensitivity of the assay was 0.4 µg l(-1) and intra- and interassay coefficients of variation were 5.1% and 2.5%, respectively. Blood samples were collected immediately after birth up to 24 h postnatally (pn). Median leptin concentrations at birth and 24 h pn were 20.9 and 52.7 µg l(-1), respectively. Because of non-normal distribution, leptin concentrations were converted to log(leptin) before further statistical processing. The change in log(leptin) during the first 24 h was highly significant (p<0.0001). Correlation analysis showed significant associations between serum leptin and the following variables: environmental temperature 24 h pn (r=0.34, p<0.005), log(plasma triglycerides) 24 h pn (r=0.50, p<0.001), log(plasma 3-beta-hydroxybutyric acid) 24 h pn (r=-0.50, p<0.001), blood glucose 6 h pn (r=0.43, p<0.001) and plasma cholesterol 12 h pn (r=0.38, p=0.001). We conclude that this radioimmunoassay is suited to measure total serum ovine leptin and that total leptin is already regulated in the very early postnatal phase. Leptin is increased at higher environmental temperatures, consistent with leptin's suppressive effect on energy expenditure and appetite. Furthermore, leptin levels are associated with plasma concentrations of lipids and lipid metabolites.

Receptor tyrosine kinase Axl is required for resistance of leukemic cells to FLT3-targeted therapy in acute myeloid leukemia.

In acute myeloid leukemia (AML), about 25-30% of patients harbor a constitutively active receptor tyrosine kinase (RTK) FLT3 encoded by a FLT3 allele harboring internal tandem duplication (FLT3-ITD) mutation. The presence of FLT3-ITD correlates with poor prognosis in AML and it makes FLT3 an attractive therapeutic target in AML. Unfortunately, to date small-molecule inhibitors of FLT3 have resulted in only partial and transient clinical responses with residual leukemic blasts resistant to FLT3 inhibitors detected in blood or bone marrow. In this study, we investigated whether the RTK Axl is responsible for resistance of FLT3-ITD(+) AML cells to PKC412 and AC220, FLT3 inhibitors currently under clinical trials for FLT3-ITD(+) AML patients. Upon treatment with PKC412 or AC220, phosphorylation of Axl was significantly enhanced in the FLT3-ITD(+) MV4-11 AML cell line and in primary blasts from a FLT3-ITD(+) AML patient. Consistently, a PKC412-resistant AML cell line and PKC412-resistant primary blasts from FLT3-ITD(+) AML patients had significantly higher levels of constitutively phosphorylated Axl and total Axl when compared with a PKC412-sensitive AML cell line and PKC412-sensitive primary blasts from FLT3-ITD(+) AML patients. We also found that resistance of AML cells against the FLT3 inhibitor PKC412 and AC220 was substantially diminished by the inhibition of Axl via a small-molecule inhibitor TP-0903, a soluble receptor Axl fusion protein Axl-Fc or knockdown of Axl gene expression by shRNA. Collectively, our study suggests that Axl is required for resistance of FLT3-ITD(+) AML cells against the FLT3 inhibitor PKC412 and AC220, and that inhibition of Axl activation may overcome resistance to FLT3-targeted therapy in FLT3-ITD(+) AML.

Normal osteoclastic and osteoblastic responses to exogenous growth hormone in patients with postmenopausal spinal osteoporosis.

The cause of bone loss in patients with osteoporosis is not known, but both increased bone resorption and decreased bone formation have been reported. Theoretically, these effects may result from either increased activity of osteoclasts or decreased activity of osteoblasts, or both. In vivo, growth hormone (GH) administration leads to activation of osteoclasts and osteoblasts as evidenced by increased biochemical markers of bone resorption and bone formation. To test for disturbances in responsiveness of bone cells to exogenous hormonal stimuli in osteoporosis, we compared 15 patients with postmenopausal osteoporosis with 15 healthy age-matched postmenopausal women before and during a 3 day stimulation test with GH (0.2 IU/kg/day). Serum insulin-like growth factor I increased in both groups (p < 0.001). GH treatment increased biochemical markers of bone resorption (serum carboxyl-terminal telopeptide of type I collagen [ICTP] [p < 0.001] and, to a lesser extent, 24 h urinary hydroxyproline/creatinine) in the two groups. Similarly, biochemical markers for bone formation increased in both groups [osteocalcin (p < 0.01) and procollagen type I C-terminal propeptide, PICP (p < 0.001)]. GH treatment reduced alkaline phosphatase (ALP, p < 0.05) and its bone-specific isoenzyme (bone ALP, p < 0.01) in both groups. The maximal response, the area under the curve (AUC) of response curves for IGF-I, bone resorption markers, and bone formation markers were not different between groups. Our data do not support the hypothesis that osteoporotic patients display major disturbances in responsiveness to GH.

Growth hormone-dependent insulin-like growth factor binding protein is a major determinant of bone mineral density in healthy men.

To establish the major determinants of bone mass, we assessed relationships between bone mineral density (BMD) and height, weight, body mass index (BMI), muscle strength, physical capacity (VO2max), body composition, serum concentrations of insulin-like growth factor I (IGF-I), growth hormone (GH), the GH-dependent IGF binding protein (IGFBP-3), testosterone, sex hormone binding globulin (SHBG), osteocalcin, and parathyroid hormone (PTH) in 38 healthy men between 25 and 59 years of age. Values of BMD at all sites (total body, lumbar spine, and hip) were strongly correlated with IGFBP-3 (r = 0.51-0.64, p < 0.001 at all sites), and total-body BMD was also significantly correlated with IGF-I (r = 0.43, p = 0.01). BMD measurements of the total body and of the different sites of the hip were negatively correlated with age and positively with weight, BMI, muscle strength, VO2max, and fat-free weight. IGF-I and IGFBP-3 were both positively related to muscle strength and VO2max. In a stepwise forward multiple-regression analysis, the best model was obtained for the femoral neck, where IGFBP-3, GH, PTH, age, IGF-I, and BMI explained 77% of the variation in BMD. The partial regression coefficients of IGFBP-3, PTH, and BMI were all positive, whereas age, GH, and IGF-I were negatively correlated with BMD. In summary, IGFBP-3 correlated better with BMD than any other study parameter. The findings indicate that GH is of importance for bone mass and suggest that IGFBP-3 not only reflects the integrated GH secretion but also has a direct role in the endocrine regulation of bone metabolism.

Consequences of postnatally elevated insulin-like growth factor-II in transgenic mice: endocrine changes and effects on body and organ growth.

Insulin-like growth factor-II (IGF-II) is an important regulator of embryonic growth and differentiation, but its function in postnatal life is unclear. To address this point, we generated transgenic mice harboring fusion genes in which a human IGF-II complementary DNA is placed under the transcriptional control of the rat phosphoenolpyruvate carboxykinase promoter. Transgene-specific messenger RNA was detected in liver, kidney, and several parts of the gut. Serum IGF-II levels in transgenic mice were 2-3 times higher than those in controls and increased after starvation. Circulating IGF-I correlated negatively and IGF-binding protein-2 (IGFBP-2) positively with IGF-II levels, suggesting that IGF-I is displaced from IGFBPs by IGF-II and that IGF-II is a major regulator of IGFBP-2. Serum levels of IGFBP-3 and IGFBP-4 tended to be higher in phosphoenolpyruvate carboxykinase-IGF-II transgenic mice than in controls, as evaluated by ligand blot analysis. Starvation reduced serum IGF-I, but increased IGFBP-2 in transgenic mice more markedly than in controls. Fasting insulin levels were significantly reduced in transgenic mice, whereas glucose levels were not influenced by elevated IGF-II. The body growth of 4- and 12-week-old mice was not significantly influenced by elevated IGF-II, but transgenic mice displayed increased kidney and testis weight at the age of 4 weeks, and increased adrenal weight at the age of 12 weeks. Our results demonstrate that elevated IGF-II in postnatal life has multiple endocrine consequences and subtle time-specific effects on organ growth.