Body composition in children with celiac disease and the effects of a gluten-free diet: a prospective case-control study

BACKGROUND

Celiac disease is the most common cause of malnutrition in children of Western countries.

OBJECTIVE

The objective was to measure body composition in children at the time celiac disease was diagnosed and after consumption of a gluten-free diet (GFD).

DESIGN

We assessed body composition by dual-energy X-ray absorptiometry in 29 children and adolescents with a mean (+/-SD) age of 9.5 +/- 3.4 y at the time celiac disease was diagnosed and in a subset of 20 patients after 1.2 +/- 0.2 y of a GFD. We also studied 23 patients aged 21.2 +/- 4.6 y who consumed a GFD for 10.6 +/- 4.5 y. Each patient was matched with a healthy control subject of the same age and sex.

RESULTS

Untreated patients weighed less than control subjects (P = 0.04). Fat mass and bone mineral content were lower in the patients than in the control subjects (P < 0.01), as was lean mass of the limbs (P = 0.0013). After approximately 1 y of the GFD, there were no significant differences in body-composition values between patients and control subjects. Similarly, body-composition values of celiac disease patients who consumed the GFD long term were comparable with those of healthy subjects.

CONCLUSIONS

Remarkable abnormalities in body composition were found in children at the time of diagnosis of celiac disease. Appropriate dietary treatment reverses body-composition abnormalities quickly and the beneficial effects of gluten withdrawal are persistent. Because these results are harder to achieve if celiac disease is first diagnosed in adulthood, efforts to encourage early diagnosis of celiac disease should be made.

The MEF2A isoform is required for striated muscle-specific expression of the insulin-responsive GLUT4 glucose transporter

Previously, we have demonstrated that an MEF2 consensus sequence located between -473/-464 in the human GLUT4 gene was essential for both tissue-specific and hormonal/metabolic regulation of GLUT4 expression (Thai, M. V., Guruswamy, S., Cao, K. T., Pessin, J. E., and Olson, A. L. (1998) J. Biol. Chem. 273, 14285-14292). To identify the specific MEF2 isoform(s) responsible for GLUT4 expression, we studied the pattern of expression of the MEF2 isoforms in insulin-sensitive tissues. Both heart and skeletal muscle were found to express the MEF2A, MEF2C, and MEF2D isoforms but not MEF2B. However, only the MEF2A protein was selectively down-regulated in insulin-deficient diabetes. Co-immunoprecipitation with isoform-specific antibodies revealed that, in the basal state, essentially all of the MEF2A protein was presented as a MEF2A-MEF2D heterodimer without any detectable MEF2A-MEF2A homodimers or MEF2A-MEF2C and MEF2C-MEF2D heterodimers. Electrophoretic mobility shift assays revealed that nuclear extracts from diabetic animals had reduced binding to the MEF2 binding site compared with extracts from control or insulin-treated animals. Furthermore, immunodepletion of the MEF2A-MEF2D complex from control extracts abolished binding to the MEF2 element. However, addition of MEF2A to diabetic nuclear extracts fully restored binding activity to the MEF2 element. These data strongly suggest that the MEF2A-MEF2D heterodimer is selectively decreased in insulin-deficient diabetes and is responsible for hormonally regulated expression of the GLUT4 gene.

Longitudinal changes of bone density and bone resorption in hyperthyroid girls during treatment

Low bone mineral density (BMD) and increased bone turnover are common features of untreated hyperthyroidism in adult patients. The effect of treatment on BMD is still controversial. BMD and bone metabolism in hyperthyroid children have not been thoroughly investigated. In the present study, we measured spinal and whole body BMD by dual-energy X-ray absorptiometry in a group of 13 girls (aged 5.0-14.9 years) at diagnosis of hyperthyroidism. The bone resorption rate was assessed by urine measurement of N-terminal telopeptide of type I collagen (NTX). Hyperthyroid patients have been studied longitudinally during treatment. BMD values and NTX urine concentrations have been also determined in 155 healthy Caucasian girls (aged 2.4-24.2 years). Spinal and whole body bone density measurements were significantly lower compared with healthy controls in untreated hyperthyroid girls, after correction for differences in age and anthropometric measurements (p </= 0.033). Bone density measurements obtained after 12 and 24 months of treatment were no longer different from those of healthy girls. NTX urine levels at diagnosis of thyrotoxicosis were significantly higher than those found in healthy controls (p < 0.0001); 6 months after treatment, the urine levels did not show significant differences, and they remained stable after 12 and 24 months of therapy. Inverse correlations at diagnosis were found between serum-free thyroxine (FT4) serum levels and spinal (r = -0.42) and whole body bone density (r = -0.41); FT4 and free triiodothyronine serum levels directly correlated with the NTX concentration (r = 0. 77, and r = 0.71, respectively). In conclusion, the results of the present study demonstrate that low bone density values and high bone resorption rates are found in hyperthyroid children and adolescents at diagnosis of the disease. Our data also demonstrate that antithyroid treatment is able to reduce dramatically the bone resorption and to increase significantly both spinal and total body BMD, granting physiologic conditions for the achievement of the best obtainable peak bone mass.

Biochemical markers of bone turnover and the volume and the density of bone in children at different stages of sexual development

Bone mass and biochemical markers of bone turnover increase significantly during puberty. We studied the possible relationships between markers of bone formation and bone resorption and increases in skeletal size, bone volume, and bone density in healthy children at different stages of sexual development. Serum concentrations of bone specific alkaline phosphatase (BALP) and osteocalcin (bone Gla protein, BGP), urinary levels of pyridinoline (Pyr) and deoxypyridinoline (Dpyr) and computed tomography (CT) measurements of the cross-sectional areas of the vertebrae and the femurs, the apparent density of cancellous bone in the vertebrae, and the volume and the material density of cortical bone in the femurs were determined in 126 boys and 143 girls, ages 7-18 years. Serum levels of BALP and BGP and urinary concentrations of Pyr and Dpyr peaked in early puberty and were lowest in the later stages of puberty. CT measurements for the cross-sectional areas of the vertebrae and the femurs, the femoral cortical bone areas, and the apparent density of cancellous bone increased in all children during puberty, while values for material bone density did not change significantly with the stage of sexual development. BALP and BGP showed significant inverse correlations with the material density of bone (r = -0.23 and -0.24, respectively), but no association with bone volume in the appendicular or axial skeleton. In contrast, Pyr and Dpyr correlated with femoral cross-sectional area (r = -0.24 and -0.33, respectively) and cortical bone area (r = -0.29 and -0.33, respectively), and with the apparent density of vertebral cancellous bone (r = -0.26 and -0.19, respectively), but not with the material density of bone. We conclude that, during puberty, there is a differential association between the two components of bone mass and the markers of bone formation and bone resorption; while markers of bone formation are related to the material density of bone, markers of bone resorption are related to the volume of bone.

Prolactin is an autocrine or paracrine growth factor for human myometrial and leiomyoma cells

OBJECTIVE

To test the hypothesis that prolactin (PRL) acts as a mitogenic growth factor for human leiomyoma and myometrial cells.

METHODS

To test this hypothesis, we performed three different types of experiments. First, we assessed whether exogenous PRL acted as a mitogen for cultured uterine smooth muscle cells. Second, we examined the role of endogenous PRL by assessing the cell number after exposure of the cultures to a neutralizing antibody to PRL. Finally, we examined both fresh tissues and cultured cells for expression of the PRL receptor messenger ribonucleic acid using the techniques of reverse-transcriptase polymerase chain reaction and Southern blotting.

RESULTS

A significant suppression in cell number was seen after 5 days of culture for leiomyoma cells but not for myometrial cells after treatment with exogenous PRL. Both cell types showed a significant decrease in cell number after treatment with anti-PRL antibody. A 893-bp segment consistent with the cytoplasmic domain of the long form of the PRL receptor was amplified from both fresh and cultured tissues and confirmed by Southern blotting and sequencing.

CONCLUSIONS

PRL appears to be an autocrine or paracrine growth factor for both leiomyoma and myometrial cells. However, there are some differences between tissues in their sensitivity to this growth factor.

Serum levels of insulin-like growth factor I and the density, volume, and cross-sectional area of cortical bone in children

Insulin-like growth factor I (IGF-I) is a major regulator of bone growth during childhood. However, beyond knowledge that IGF-I influences longitudinal growth, its associations to changes in the cross-sectional dimensions, the volume, or the material density of bone during growth are unknown. We assessed the relationships between serum IGF-I and measurements of cross-sectional area, cortical bone area, and cortical bone density at the midshaft of the femur in 197 normal healthy white children and adolescents (103 boys and 94 girls; aged 7.8-18.2 yr). Bone determinations were obtained using computed tomography, and levels of IGF-I were measured by RIA after an extraction procedure. IGF-I correlated significantly with both cross-sectional area (r = 0.49; P < 0.0001) and cortical bone area (r = 0.50; P < 0.0001), but did not correlate with the material density of cortical bone (r = -0.08). Multiple regression analyses showed that circulating levels of IGF-I were associated with cross-sectional area (P = 0.03) and cortical bone area (P = 0.04) values, even after correcting for the confounding effects of age, gender, weight, and femoral length. We conclude that IGF-I is a major determinant of the cross-sectional properties of bone, but does not influence the material density of bone, in the appendicular skeleton.

Bone density and bone metabolism are normal after long-term gluten-free diet in young celiac patients

OBJECTIVES

Osteoporosis and alterations of bone metabolism are frequent complications of celiac disease. We evaluated the impact of long-term gluten-free diet (GFD) initiated during childhood and adolescence on bone mineralization and bone metabolism.

METHODS

We studied 30 celiac patients on GFD for > or = 5 yr. The mean age at diagnosis was 11.4+/-5.0 yr, and the mean duration of GFD was 10.7+/-4.3 yr. Results were compared with those obtained in 240 healthy controls. Bone mineral density (BMD) was measured in the lumbar spine and in the whole skeleton by dual-energy x-ray absorptiometry. Serum levels of bone-specific alkaline phosphatase (BALP) and N-terminal propeptide of type I procollagen (PINP) were measured as bone formation indices, and urine levels of N-telopeptide of type I collagen (NTx) as bone resorption index.

RESULTS

BMD measurements of celiac patients (lumbar spine: 1.131+/-0.121 g/cm2; total body: 1.145+/-0.184 g/cm2) did not differ from those of control subjects (lumbar spine: 1.131+/-0.184 g/cm2; total body: 1.159+/-0.118 g/cm2). The levels of BALP, PINP, and NTx of celiac patients did not differ from those of controls. Patients who started GFD before puberty had BMD and bone metabolism measurements comparable to those of patients who started GFD during puberty.

CONCLUSIONS

Our data show that long-term dietary treatment ensures normal mineralization and bone turnover.

Behavioral effects of dopamine agonists and antagonists: influence of estrous cycle, ovariectomy, and estrogen replacement in rats

The influence of the hormonal condition on the reactivity of central dopamine (DA) receptors was studied in male and in intact and ovariectomized (OVX) female rats. They were injected with selective DA agonists, acting either on D1 (SKF 38393, 2.5 or 10 mg/kg) or D2 receptors (PPHT, 31.3 or 125 microg/kg), or with selective DA antagonists, acting either on D1 (SCH 23390, 6.25 or 25 microg/kg), or D2 receptors (sulpiride, 10 or 40 mg/kg). The acquisition of an avoidance conditioning response (CAR) and the performance of some spontaneous motor behaviors were tested. Both D1 and D2 agonists and antagonists impaired the acquisition of CARs in diestrous, OVX, and male rats. Nevertheless, the effects of these drugs during estrus and in estradiol-primed OVX rats were different according to the drug and the dose injected. Whereas SKF 38393 failed to induce significative changes, PPHT and low doses of SCH 23390 and sulpiride improved the acquisition of CARS in those groups. The effects on conditioning were not accompanied with equivalent changes in spontaneous motor activity. Estradiol level fluctuations that occur in female rats within the estrous cycle or in OVX rats primed with estradiol would be responsive of changes in the response to DA agents. Although the reactivity of central DA systems is differentially affected by the hormonal condition of the rat, the precise mechanism of this modulatory action remains unknown.

Effects of LHRH on avoidance conditioning in normally cycling and ovariectomized female rats

Several studies have demonstrated that the peptide LHRH can modify behavior in the male rat. Peripheral and intracerebral infusions of LHRH impair the acquisition of conditioned avoidance responses (CARs) and increase some spontaneous motor behaviors, such as head shaking and grooming. The present study was undertaken to detect the effects of LHRH on the acquisition of CARs and spontaneous motility in normally cycling and ovariectomized (OVX) Sprague-Dawley female rats. Normally cycling females were separated in four groups, according to the stage of the estrous cycle. Ovariectomized female rats were pretreated, 48 h before the experiment, with estradiol benzoate (10 microg/kg) or corn oil. LHRH (6.25, 25, or 50 microg/kg) was subcutaneously injected and the behavioral tests began 1 h after. Low doses of LHRH stimulated the acquisition of CARs during proestrus, estrus, and metestrus, whereas higher doses impaired conditioning in all the four stages of the cycle. High doses of LHRH impaired acquisition in OVX rats treated with oil and potentiated the depressant effects of EB on this behavior. The effects of LHRH on spontaneous motor activity were either stimulatory or inhibitory, according to the hormonal status and the dose administered. High doses of LHRH decreased motor responses in the diestrous rat. All the doses of LHRH increased the number of headshakes during proestrus, estrus, and metestrus, while the other motor responses were scarcely or not affected by LHRH in these stages. In OVX rats LHRH increased rearing, head shaking, and grooming behavior. These results support a role of LHRH in the modulation of conditioned and spontaneous behavior. They could provide an explanation to the behavioral changes observed across the estrous cycle and those observed after EB priming in OVX rats.

Urinary markers of bone turnover in healthy children and adolescents: age-related changes and effect of puberty

During growth, bones change their dimensions rapidly with the changes involving both formation and resorption processes. Small cross-linked peptides coming from type I collagen molecules are excreted in urine when bone is resorbed. To date, conflicting results have been presented concerning the age- and puberty-related changes of urinary markers. The purpose of the present study was to verify the effect of age, gender, and puberty on the urinary excretion of type I collagen degradation products in healthy children and adolescents. Timed spot urines from 176 children (4-20 years old) and 50 young adults were analyzed. The concentrations of N-telopeptides of type I collagen (NTx), pyridinolines (Pyr), and deoxypyridinolines (Dpyr) were measured, and the results were normalized to creatinine. Age-related changes in cross-links excretion were observed. The levels decreased with age, and a peak of excretion was shown at the beginning of adolescence. Prepubertal levels of all the markers were four- to five-fold higher than in adults, and they decreased towards adult levels in late puberty. Girls had significantly higher levels of all biochemical markers than boys at pubertal stage 2. We also observed a remarkable effect of puberty on the levels of bone degradation products that was independent of age and gender. Our results indicate that bone resorption is high in children relative to that in adults, and that urinary levels of NTx, Pyr, and Dpyr change as a function of age, gender, and puberty.

Assessment of skeletal maturation in infants: comparison between two methods in hypothyroid patients

BACKGROUND

Conventional skeletal radiography is the standard technique for assessing skeletal age. However, radiography cannot demonstrate cartilage and is therefore of lesser value in infancy when the ossification centres are composed mainly of cartilage. By comparison, US clearly demonstrates cartilage and bone.

OBJECTIVE

In the present study, we compared radiography and sonography for the assessment of skeletal age in neonates and infants.

MATERIALS AND METHODS

Because delayed skeletal maturation is a feature of congenital hypothyroidism and assessment of skeletal age is routinely performed in our centre, we studied 55 hypothyroid infants (aged 7-66 days). AP radiographs and sonograms, acquired using high-frequency scanners, were obtained and dimensions of the distal femoral epiphyseal ossification centre (DFE) were compared.

RESULTS

Measurements of DFE by the two methods showed excellent correlation (R = 0.94, P = 0.0001). Radiographs did not demonstrate a DFE in 11 infants, and US did not show it in 6. In no infant did radiography demonstrate DFE not seen by US. Moreover, DFE dimensions on US were larger than those measured on radiographs. Infants with absent thyroid gland had a DFE significantly smaller than those infants with ectopic or normally placed glands (P < 0.001), on both radiographs and sonograms.

CONCLUSION

Our data suggest that sonography is a valid alternative to standard radiography for the assessment of skeletal age in infants.

Reversal of low bone density with a gluten-free diet in children and adolescents with celiac disease

Osteoporosis is a common finding in adult celiac disease patients; however, there are still few data regarding children and adolescents. In the present study we measured the bone mineral density (BMD) in children and adolescents at diagnosis of celiac disease and after approximately 1 y of a gluten-free diet. BMD was measured at the lumbar spine and in the whole skeleton by dual-energy X-ray absorptiometry in 44 celiac disease patients aged 2.58-20.42 y at diagnosis. BMD was also measured in a subset of 25 patients after 1.4 +/- 0.04 y of a gluten-free diet. BMD was compared with that of 177 healthy control subjects aged 1.52-20.99 y. Lumbar spine and whole-body BMD values at diagnosis of celiac disease were significantly lower than in control subjects (P = 0.015 and P = 0.0001, respectively) after differences in age and anthropomorphic variables were controlled for. The subjects studied after the gluten-free diet had BMD values not significantly different from those of control subjects. In conclusion, children and adolescents with celiac disease have remarkably reduced lumbar spine and whole-body bone density. A gluten-free diet promotes a rapid increase of BMD that leads to a complete recovery of bone mineralization. These results emphasize the need for an early diagnosis and treatment in patients with celiac disease to obtain an adequate peak bone mass at the end of puberty.

Dexamethasone in the diagnostic work-up of growth hormone deficiency

OBJECTIVE

Acute administration of dexamethasone (dexa) has recently been shown to induce growth hormone (GH) release. To ascertain the efficacy of this stimulus in assessing GH secretory status in children, we tested it in a large group of patients with short stature.

METHODS

We administered dexamethasone at the dose of 2 mg/m2 to 44 short normal children and 19 GH deficient (GHD) children, either orally or intravenously and compared the results of the dexa-test to the more classical clonidine test.

RESULTS

The oral dexa-test induced a GH peak similar to the clonidine test (clo) (controls clo: 23.8 +/- 7.8 mU/l, median 22.8, range 15.2-45.4 vs. control dexa: 20.6 +/- 10.8, median 16.8, range 8-47, P = 0.2. GHD clo: 9.8 +/- 2.6, median 9.2, range 6.4-13.4 vs. GHD dexa: 9.4 +/- 3.4, median 10.2, range 4.6-14, P = 0.8). Its sensitivity and specificity with respect to the clonidine test were 91% (10/11 GHD) and 65% (15/23 controls), respectively. The GH peak after i.v. dexa was smaller than that after clonidine (control clo: 30.6 +/- 14 micrograms/l, median 24.8, range 14.2-62.4 vs. control dexa: 21.6 +/- 5.4, median 21.6, range 11.2-33, P = 0.01. GHD clo: 7.4 +/- 4.2, median 8.8, range 0.4-11.8 vs. GHD dexa: 6.4 +/- 5.6, median 5.8, range 0.4-16.2, P = 0.17) with sensitivity and specificity of 87% (7/8 GHD) and 90% (19/21 controls), respectively. The lower potency of dexamethasone could account for these figures, since when a different cut-off was used (12 mU/l and 11 mU/l for the oral and i.v. route) both sensitivity and specificity were improved. More data are needed to support these findings and establish a clear cut-off. In the control group, no difference was found between GH peak after oral or i.v. dexa but GH-area under the curve (AUC) was larger for i.v. than for oral dexa. No side effects were noted.

CONCLUSIONS

Intravenous dexamethasone appears to be a promising stimulus for the detection of GH deficiency in children, particularly for use in outpatients.

Comparison of clinical-radiological and molecular findings in hypochondroplasia

Hypochondroplasia is an autosomal dominant skeletal dysplasia characterized by disproportionate short stature. A mutation (N540K) in the fibroblast growth factor receptor 3 (FGFR3) gene was described in some patients with this condition. The aims of the study were to identify the frequency of the FGFR3 gene mutation, to define the salient clinical and radiological abnormalities of the affected subjects, and to verify the contribution of molecular findings to the clinical and radiological definition of hypochondroplasia. Based on the most common radiological criteria, we selected 18 patients with a phenotype compatible with hypochondroplasia. Height, sitting height, and cranial circumference were measured in all patients. Radiographs of the lumbar spine, left leg, pelvis, and left hand were also obtained. The presence of the N540K mutation was verified by restriction enzyme digestions. Half of our patients carried the N540K mutation. Although similar in phenotype to the patients without the mutation, they showed in addition relative macrocephaly. The association of the unchanged/narrow interpedicular distance with the fibula longer than the tibia was more common in patients with gene mutation. Although we did not find a firm correlation between genotype and phenotype, in our study the N540K mutation was most often associated with disproportionate short stature, macrocephaly, and with radiological findings of unchanged/narrow interpedicular distance and fibula longer than tibia.

Ketanserin and anxiety levels: influence of gender, estrous cycle, ovariectomy and ovarian hormones in female rats

The influence of gender, estrous cycle, ovariectomy and ovarian hormones on the behavioral effects of the 5-HT2 receptor antagonist, ketanserin (KET), was studied. Intact males, female rats in the four stages of the estrous cycle and ovariectomized (OVX) female rats 14 days after surgery were used. The OVX rats received progesterone [PROG, 25 mg/kg, subcutaneously (SC)] and/or estradiol benzoate (EB, 10 micrograms/kg, SC). KET (3 mg/kg, SC) was injected 30 min before testing. All the animals were subjected to the following behavioral tests: exploration of an elevated plus-maze and retention of a passive-avoidance response. KET enhanced the exploration of the open arms in diestrous female rats but inhibited this behavior during the other stages of the cycle and in OVX rats injected either with oil or EB. This dose of KET was ineffective in males and in OVX rats injected with PROG. Furthermore, KET inhibited the retention of the passive avoidance response in males, in diestrous and metestrous female rats and in OVX rats injected with oil. In estrous females and in OVX rats injected with EB, KET enhanced the passive-avoidance response. These results demonstrate that the sensitivity to KET differs with the gender, estrous cycle and hormonal treatment and suggest that central serotonergic activity is influenced by the hormonal status of the animal.

Ketanserin effects on rat behavioral responses: modifications by the estrous cycle, ovariectomy and estradiol replacement

The present investigation was designed to explore the influence of estrous cycle phase, ovariectomy, and estradiol replacement on the behavioral effects of the 5-HT2 receptor antagonist, ketanserin. The parameters under investigation were ketanserin-influenced acquisition of conditioning avoidance responses (CARs), and the performance of some spontaneous motor behaviors. Ketanserin (KET 3 mg/kg) injected subcutaneously 30 min before testing improved active conditioned avoidance in intact female rats at estrus, and in ovariectomized (OVX) rats with estradiol replacement. Furthermore, KET impaired performance in female rats at diestrus and after ovariectomy. In male rats, which were included in this study in order to compare their behavioral responses with those exhibited by female rats, KET administration enhanced acquisition of CARs. These results provide behavioral evidence for the hypothesis that central serotonergic activity is a function of the hormonal status of the animal. An additional segment of the present study focussed on motoric behaviors. Spontaneous motor activity, number of rears, and time spent in grooming behavior were significantly increased by KET in all groups studied. In contrast, blockade of 5-HT2 receptors failed to induce significant changes in the number of head shakes. Relationships between ovarian hormones and the central serotonergic system are discussed.

Chronic high-fat feeding and middle-aging reduce in an additive fashion Glut4 expression in skeletal muscle and adipose tissue

The interaction of middle-aging and chronic high-fat feeding on glucose transport in skeletal muscle and adipose tissue was examined. To this end, we studied the effects of 6 month treatment with a high-fat diet in 12-month old rats. Chronic high-fat feeding led to a substantial reduction in GLUT4 glucose transporter expression both in adipose tissue and in skeletal muscle, which was additive to the reduction in GLUT4 protein content detected in aged rats. In parallel, the high-fat diet led to a reduced insulin-stimulated glucose transport in the incubated soleus muscle and isolated adipocytes; insulin resistance induced by high-fat feeding was superimposed to the decreased insulin response detected in aged rats. Different mechanisms were responsible for GLUT4 repression in response to high-fat feeding or aging in skeletal muscles and adipose tissue.

Heterologous expression of rab4 reduces glucose transport and GLUT4 abundance at the cell surface in oocytes

To evaluate the role of the small rab GTP-binding proteins in glucose transporter trafficking, we have heterologously co-expressed rab4 or rab5 and GLUT4 or GLUT1 glucose transporters in Xenopus oocytes. Co-injection of rab4 and GLUT4 cRNAs resulted in a dose-dependent decrease in glucose transport; this effect was specific for rab4, since co-injection of an inactive rab4 mutant or rab5 cRNA did not have any effect on glucose transport. The effect of rab4 was selective for GLUT4, since no effect was detected in GLUT1-expressing oocytes. The inhibitory effect of rab4 on GLUT4-induced glucose transport was not the result of a change in overall cellular levels of GLUT4 glucose transporters. However, rab4 expression caused a marked decrease in the abundance of GLUT4 transporters present at the cell surface. Finally, rab4 and inhibitors of PtdIns 3-kinase showed additive effects in decreasing glucose transport in GLUT4-expressing oocytes. We conclude that rab4 plays an important role in the regulation of the intracellular GLUT4 trafficking pathway, by contributing to the intracellular retention of GLUT4 through a PtdIns 3-kinase-independent mechanism.

Bone turnover in neonates: changes of urinary excretion rate of collagen type I cross-linked peptides during the first days of life and influence of gestational age

New markers have been used to monitor the changes of bone turnover occurring during growth. Data on bone turnover rate during the perinatal period are, however, very scarce. In the present study we evaluated bone turnover rate, assessed by the measurement of urinary N-terminal telopeptide of type I collagen (NTx) concentrations, at different gestational ages, and we documented the trend of bone turnover rate occurring in the first days after birth. Urine samples were obtained from 83 healthy full term newborn infants, 16 preterm, and 17 infants of diabetic mothers (IDMs). The first miction after birth was collected. Urine samples were also collected 24 and 48 h after birth. NTx was measured by an enzyme-linked immunosorbent assay (Osteomark, Ostex International, Inc. Seattle, WA). The relationship between NTx at birth and all the other variables has been evaluated using multiple regression analysis. The changes of NTx excretion over time and the effect of the groups were studied by multivariate analysis of variance (MANOVA) for repeated measures. We found a remarkable association between gestational age and NTx concentrations at birth (R = 0.56; p < 0.00001). NTx concentrations showed a progressive decrement, reaching a nadir between the 38th and the 42nd week of gestation. The NTx concentrations changed significantly during the first 48 h of life in the three groups. Moreover, preterm infants had NTx excretion values at birth significantly higher than full term infants (p < 0.001), whereas NTx excretion rates of IDMs were not different from those of the other two groups of subjects. In conclusion, gestational age seems to be the major determinant of bone turnover in neonates; NTx excretion rate is higher before term, it slows in proximity of delivery, and it increases significantly during the first 48 h of life. Preterm infants have higher bone turnover rate than full term infants. NTx excretion rate of IDMs was comparable with those of the control subjects.

Bone modeling indexes at onset and during the first year of follow-Up in insulin-dependent diabetic children

Osteopenia has been described as a complication of insulin-dependent diabetes mellitus (IDDM). We measured bone modeling indexes during the first year of IDDM. At each time point the values obtained from diabetic children have been compared with those of control subjects. We selected 27 prepubertal children with IDDM (6.35 +/- 2.16 years). We also enrolled 30 healthy prepubertal children of comparable age (5.85 +/- 3.05 years). Height, height standard deviation scores, glycated haemoglobin (HbA1C), basal c-peptide concentrations, insulin dose, serum concentrations of procollagen type I C-terminal propeptide (PICP), and collagen type I C-terminal telopeptide (ICTP) were measured at onset of IDDM and at 3, 6 and 12 months. ICTP was in the normal range at onset of IDDM and decreased during the follow-up to reach a significant difference compared to controls after 3, 6 and 12 months of insulin treatment (P < 0.04). PICP concentrations increased significantly at 3 months (P = 0.05) compared to onset. At 3 and 12 months PICP values were significantly higher than those of control children (P = 0.04). Correlations were found between PICP concentrations and HbA1C and c-peptide at onset of diabetes (r = -0.45 and r = 0.47, respectively). Bone formation at onset of IDDM is not impaired; the introduction of insulin therapy, together with the achievement of a good metabolic control, determines an increase of bone matrix formation coupled with a decrease of bone resorption, that determines a positive balance of bone modeling.

Nonacidotic proximal tubulopathy transmitted as autosomal dominant trait

The family of a patient with a nonacidotic and hypercalciuric proximal tubulopathy was studied. The proband showed glycosuria, aminoaciduria, tubular proteinuria, renal hypophosphatemia, and urate tubular hyporeabsorption without bicarbonate loss. He also presented increased urine calcium excretion, plasma 1,25-dihydroxyvitamin D, and enteral calcium absorption. Clinical consequences of the tubulopathy were osteopenia and calcium kidney stones. Fifteen of the proband's relatives were studied; six of them had renal hypophosphatemia, 10 presented hypercalciuria, and three showed both hypercalciuria and hypophosphatemia. No other reabsorption defects were observed. High plasma levels of 1,25-dihydroxyvitamin D were found in 13 family members; their values correlated positively with calcium excretion and negatively with tubular phosphate reabsorption. None produced stones or had reduced mineral bone density. Hypophosphatemia and hypercalciuria occurred in the two generations studied; their transmission was independent of gender, and male-to-male transmission occurred for both defects. Our findings suggest that a genetic alteration of proximal tubular function could cause multiple reabsorption defects in the proband or renal phosphate leakage in the proband's relatives. The genotypic alteration causing the proximal dysfunctions may be monogenic, with an autosomal dominant pattern of inheritance and variable expressivity. Increased calcium excretion may be due to the proximal tubular alteration; alternatively, it may be the result of a genetic background predisposing to idiopathic hypercalciuria. Phosphate and calcium loss could stimulate 1,25-dihydroxyvitamin D synthesis in proximal tubular cells.

Chondrosarcoma of the hand arising in a young patient with multiple hereditary exostoses

An unusually large chondrosarcoma arising in the hand of a young patient with multiple hereditary exostoses is presented.