Alterations of growth plate and abnormal insulin-like growth factor I metabolism in growth-retarded hypokalemic rats: effect of growth hormone treatment

TNF overexpression and dexamethasone treatment impair chondrogenesis and bone growth in an additive manner

Children with chronic inflammation are often treated with glucocorticoids (GCs) and many of them experience growth retardation. It is poorly understood how GCs interact with inflammatory cytokines causing growth failure as earlier experimental studies have been performed in healthy animals. To address this gap of knowledge, we used a transgenic mouse model where human TNF is overexpressed (huTNFTg) leading to chronic polyarthritis starting from the first week of age. Our results showed that femur bone length and growth plate height were significantly decreased in huTNFTg mice compared to wild type animals. In the growth plates of huTNFTg mice, increased apoptosis, suppressed Indian hedgehog, decreased hypertrophy, and disorganized chondrocyte columns were observed. Interestingly, the GC dexamethasone further impaired bone growth, accelerated chondrocyte apoptosis and reduced the number of chondrocyte columns in huTNFTg mice. We conclude that TNF and dexamethasone separately suppress chondrogenesis and bone growth when studied in an animal model of chronic inflammation. Our data give a possible mechanistic explanation to the commonly observed growth retardation in children with chronic inflammatory diseases treated with GCs.

Co-Existence of Congenital Adrenal Hyperplasia and Bartter Syndrome due to Maternal Uniparental Isodisomy of HSD3B2 and CLCNKB Mutations

INTRODUCTION

We present a patient with co-existence of 3β-hydroxysteroid dehydrogenase type 2 (HSD3B2) deficiency and Bartter syndrome, a unique dual combination of opposing pathologies that has not been reported previously in the literature.

CASE

A female infant (46,XX) born at 34/40 weeks' gestation, weighing 2.67 kg (-1.54 standard deviation score) to non-consanguineous parents presented on day 4 of life with significant weight loss. Subsequent investigations revealed hyponatraemia, hypochloraemia, metabolic alkalosis, elevated 17-hydroxyprogesterone, ACTH, and renin. Urine steroid profile suggested HSD3B2 deficiency, which was confirmed by the identification of a homozygous HSD3B2 mutation. Due to the persistence of the hypochlo-raemic and hypokalemic alkalosis, an underlying renal tubulopathy was suspected. Sequence analysis of a targeted tubulopathy gene panel revealed a homozygous deletion in CLCNKB, consistent with Bartter syndrome type 3. The mother was found to be heterozygous for both mutations in -HSD3B2 and CLCNKB, and the father was negative for both. Single-nucleotide polymorphism microarray analysis confirmed 2 segments of homozygosity on chromosome 1 of maternal ancestry, encompassing both HSD3B2 and CLCKNB.

DISCUSSION

Identification of a homozygous rare mutation in an offspring of non-consanguineous parents should raise suspicion of uniparental disomy, especially if the phenotype is unusual, potentially encompassing more than one disorder. The persistence of hypokalemic alkalosis, the biochemical fingerprint of hyperaldosteronism in a child with a form of CAH in which aldosterone production is severely impaired, challenges our current understanding of mineralocorticoid-mediated effects in the collecting duct.

Gitelman syndrome combined with growth hormone deficiency: Three cases report

RATIONALE

Gitelman syndrome (GS) is a rare autosomal recessive hereditary salt-losing tubulopathy caused by loss-of-function mutations in the SLC12A3 gene. It is usually characterized by hypokalemia, metabolic alkalosis, hypomagnesemia, and hypocalciuria. There are only a few reports on GS combined with growth hormone deficiency (GHD).

PATIENT CONCERNS

Three patients presented with weakness, spasm, and growth retardation, respectively.

DIAGNOSES

GS was diagnosed based on the clinical symptoms, laboratory test results, and genetic analysis. GH stimulation tests were performed when the magnesium level returned to normal under magnesium oxide (MgO) therapy.

INTERVENTIONS

Initially, all patients received oral replacement of MgO and potassium chloride, and 2 of them received simultaneous spironolactone therapy. Recombinant human growth hormone (rhGH) therapy was initiated after they were diagnosed with GHD.

OUTCOMES

All 3 patients exhibited satisfactory growth velocity and normal serum magnesium level, although the potassium level was still slightly lower than normal.

LESSONS

We suggest that all GS patients should undergo genetic evaluation, especially regarding SLC12A3 gene mutation. GHD should be considered if these patients have short stature. rhGH therapy is useful for stimulating the patients' growth, and it may increase the serum magnesium level.

A novel CLCNKB mutation in a Chinese girl with classic Bartter syndrome: a case report

Background

Bartter syndrome (BS) is a rare autosomal recessive disorder of salt reabsorption at the thick ascending limb of the Henle loop, characterized by hypokalemia, salt loss, metabolic alkalosis, hyperreninemic hyperaldosteronism with normal blood pressure. BS type III, often known as classic BS (CBS), is caused by loss-of-function mutations in CLCNKB (chloride voltage-gated channel Kb) encoding basolateral ClC-Kb.

Case presentation

We reported a 15-year-old CBS patient with a compound heterozygous mutation of CLCNKB gene. She first presented with vomiting, hypokalemic metabolic alkalosis at the age of 4 months, and was clinically diagnosed as CBS. Indomethacin, spironolactone and oral potassium were started from then. During follow-up, the serum electrolyte levels were generally normal, but the patient showed failure to thrive and growth hormone (GH) deficiency was diagnosed. The recombinant human GH therapy was performed, and the growth velocity was improved. When she was 14, severe proteinuria and chronic kidney disease (CKD) were developed. Renal biopsy showed focal segmental glomerulosclerosis (FSGS) with juxtaglomerular apparatus cell hyperplasia, and genetic testing revealed a point deletion of c.1696delG (p. Glu566fs) and a fragment deletion of exon 2–3 deletions in CLCNKB gene. Apart from the CBS, ostium secundum atrial septal defect (ASD) was diagnosed by echocardiography.

Conclusions

This is the first report of this compound heterozygous of CLCNKB gene in BS Children. Our findings contribute to a growing list of CLCNKB mutations associated with CBS. Some recessive mutations can induce CBS in combination with other mutations.

Bartter Syndrome and Gitelman Syndrome

Bartter and Gitelman syndromes are conditions characterized by renal salt-wasting. Clinical presentations range from severe antenatal disease to asymptomatic with incidental diagnosis. Hypokalemic hypochloremic metabolic alkalosis is the common feature. Bartter variants may be associated with polyuria and weakness. Gitelman syndrome is often subtle, and typically diagnosed later life with incidental hypokalemia and hypomagnesemia. Treatment may involve fluid and electrolyte replenishment, prostaglandin inhibition, and renin-angiotensin-aldosterone system axis disruption. Investigators have identified causative mutations but genotypic-phenotypic correlations are still being characterized. Collaborative registries will allow improved classification schema and development of effective treatments.

Endurance exercise and growth hormone improve bone formation in young and growth-retarded chronic kidney disease rats

BACKGROUND

Childhood chronic kidney disease (CKD) is associated with both short stature and abnormal bone mineralization. Normal longitudinal growth depends on proper maturation of epiphyseal growth plate (EGP) chondrocytes, leading to the formation of trabecular bone in the primary ossification centre. We have recently shown that linear growth impairment in CKD is associated with impaired EGP growth hormone (GH) receptor signalling and that exercise improved insulin-like growth factor I (IGF-I) signalling in CKD-related muscle atrophy.

METHODS

In this study, 20-day-old rats underwent 5/6 nephrectomy (CKD) or sham surgery (C) and were exercised with treadmill, with or without GH supplementation.

RESULTS

CKD-related growth retardation was associated with a widened EGP hypertrophic zone. This was not fully corrected by exercise (except for tibial length). Exercise in CKD improved the expression of EGP key factors of endochondral ossification such as IGF-I, vascular endothelial growth factor (VEGF), receptor activator of nuclear factor kappa-B ligand (RANKL) and osteocalcin. Combining GH treatment with treadmill exercise for 2 weeks improved the decreased trabecular bone volume in CKD, as well as the expression of growth plate runt-related transcription factor 2, RANKL, metalloproteinase 13 and VEGF, while GH treatment alone could not do that.

CONCLUSIONS

Treadmill exercise improves tibial bone linear growth, as well as growth plate local IGF-I. When combined with GH treatment, running exercise shows beneficial effects on trabecular bone formation, suggesting the potential benefit of this combination for CKD-related short stature and bone disease.

Hypophosphatemia and growth

Over the last decade the discovery of fibroblast growth factor 23 (FGF23) and the progressive and ongoing clarification of its role in phosphate and mineral metabolism have led to expansion of the diagnostic spectrum of primary hypophosphatemic syndromes. This article focuses on the impairment of growth in these syndromes. Growth retardation is a common, but not constant, feature and it presents with large variability. As a result of the very low prevalence of other forms of primary hypophosphatemic syndromes, the description of longitudinal growth and the pathogenesis of its impairment have been mostly studied in X-linked hypophosphatemia (XLH) patients and in Hyp mice, the animal model of this disease. In general, children with XLH have short stature with greater shortness of lower limbs than trunk. Treatment with phosphate supplements and 1α vitamin D derivatives heals active lesions of rickets, but does not normalize growth of XLH patients. Patients might benefit from recombinant human growth hormone (rhGH) therapy, which may accelerate the growth rate without increasing body disproportion or correcting hypophosphatemia. These clinical data as well as research findings obtained in Hyp mice suggest that the pathogenesis of defective growth in XLH and other hypophosphatemic syndromes is not entirely dependent on the mineralization disorder and point to other effects of hypophosphatemia itself or FGF23 on the metabolism of bone and growth plate.

Gitelman syndrome combined with complete growth hormone deficiency

Gitelman syndrome is a rare autosomal recessive hereditary salt-losing tubulopathy, that manifests as hypokalemic metabolic alkalosis, hypomagnesemia, and hypocalciuria. It is caused by mutations in the solute carrier family 12(sodium/chloride transporters), member 3 (SLC12A3) gene encoding the thiazide-sensitive sodium chloride cotransporter channel (NCCT) in the distal convoluted tubule of the kidney. It is associated with muscle weakness, cramps, tetany, vomiting, diarrhea, abdominal pain, and growth retardation. The incidence of growth retardation, the exact cause of which is unknown, is lower than that of Bartter syndrome. Herein, we discuss the case of an overweight 12.9-year-old girl of short stature presenting with hypokalemic metabolic alkalosis. The patient, on the basis of detection of a heterozygous mutation in the SLC12A3 gene and poor growth hormone (GH) responses in two provocative tests, was diagnosed with Gitelman syndrome combined with complete GH deficiency. GH treatment accompanied by magnesium oxide and potassium replacement was associated with a good clinical response.

Bartter syndrome and growth hormone deficiency: three cases

BACKGROUND

Bartter syndrome is a rare autosomal recessive disorder characterized by hypokalemia, salt loss, and metabolic alkalosis. Short stature is one of the clinical manifestations in these children. Although polyuria, polydipsia, hypokalemia, and salt loss may be responsible for growth retardation, the exact pathogenesis of short stature in Bartter syndrome is not known.

CASE DIAGNOSIS AND TREATMENT

In this study, we present three children diagnosed as having Bartter syndrome with short stature and growth hormone (GH) deficiency. After recombinant human growth hormone therapy (rhGH), their growth velocities were improved.

CONCLUSIONS

These results indicate that GH deficiency may contribute to short stature in children with Bartter syndrome, and rhGH therapy would be an excellent adjunctive treatment for short children with this syndrome whose condition is resistant to conventional therapies in terms of growth.

Growth cartilage expression of growth hormone/insulin-like growth factor I axis in spontaneous and growth hormone induced catch-up growth

INTRODUCTION

Catch-up growth following the cessation of a growth inhibiting cause occurs in humans and animals. Although its underlying regulatory mechanisms are not well understood, current hypothesis confer an increasing importance to local factors intrinsic to the long bones' growth plate (GP).

AIM

The present study was designed to analyze the growth-hormone (GH)-insulin-like growth factor I (IGF-I) axis in the epiphyseal cartilage of young rats exhibiting catch-up growth as well as to evaluate the effect of GH treatment on this process.

MATERIAL AND METHODS

Female Sprague-Dawley rats were randomly grouped: controls (group C), 50% diet restriction for 3 days+refeeding (group CR); 50% diet restriction for 3 days+refeeding & GH treatment (group CRGH). Analysis of GH receptor (GHR), IGF-I, IGF-I receptor (IGF-IR) and IGF binding protein 5 (IGFBP5) expressions by real-time PCR was performed in tibial growth plates extracted at the time of catch-up growth, identified by osseous front advance greater than that of C animals.

RESULTS

In the absence of GH treatment, catch-up growth was associated with increased IGF-I and IGFBP5 mRNA levels, without changes in GHR or IGF-IR. GH treatment maintained the overexpression of IGF-I mRNA and induced an important increase in IGF-IR expression.

CONCLUSIONS

Catch-up growth that happens after diet restriction might be related with a dual stimulating local effect of IGF-I in growth plate resulting from overexpression and increased bioavailability of IGF-I. GH treatment further enhanced expression of IGF-IR which likely resulted in a potentiation of local IGF-I actions. These findings point out to an important role of growth cartilage GH/IGF-I axis regulation in a rat model of catch-up growth.

Mex3c regulates insulin-like growth factor 1 (IGF1) expression and promotes postnatal growth

Mex3c is highly expressed in the testis, brain, and developing bone. Mex3c mutation causes postnatal growth retardation and background-dependent perinatal lethality, possibly through impairing the translation of insulin-like growth factor 1 mRNA in bone-forming cells.

Insulin-like growth factor 1 (IGF1) mediates the growth-promoting activities of growth hormone. How Igf1 expression is regulated posttranscriptionally is unclear. Caenorhabditis elegans muscle excess 3 (MEX-3) is involved in cell fate specification during early embryonic development through regulating mRNAs involved in specifying cell fate. The function of its mammalian homologue, MEX3C, is unknown. Here we show that MEX3C deficiency in Mex3c homozygous mutant mice causes postnatal growth retardation and background-dependent perinatal lethality. Hypertrophy of chondrocytes in growth plates is significantly impaired. Circulating and bone local production of IGF1 are both decreased in mutant mice. Mex3c mRNA is strongly expressed in the testis and the brain, and highly expressed in resting and proliferating chondrocytes of the growth plates. MEX3C is able to enrich multiple mRNA species from tissue lysates, including Igf1. Igf1 expression in bone is decreased at the protein level but not at the mRNA level, indicating translational/posttranslational regulation. We propose that MEX3C protein plays an important role in enhancing the translation of Igf1 mRNA, which explains the perinatal lethality and growth retardation observed in MEX3C-deficient mice.

Longitudinal growth in chronic hypokalemic disorders

Growth retardation remains a major complication in children with primary tubular disorders, despite adequate supplemental treatment with electrolytes, water and bicarbonate. Chronic hypokalemia, characteristic of some tubulopathies, impairs growth by mechanisms that are not well known. Association with growth hormone deficiency has been reported in patients with Bartter's or Gitelman's syndrome. Tissue-specific alterations of growth hormone and insulin-like growth factor I axis have been described in experimental models of potassium depletion. Hypokalemic rats gain less body length and weight than pair-fed normokalemic animals and, by contrast, develop renal hypertrophy. These rats have low circulating concentrations of insulin-like growth factor I, depressed messenger ribonucleic acid (mRNA) levels of this peptide in the tibial growth plate, and they are resistant to the longitudinal growth-promoting effects of exogenous growth hormone. The reason for this resistance remains to be defined. No alterations in the intracellular signaling for growth hormone have been found in the liver of hypokalemic rats. However, treatment with high doses of growth hormone is unable to normalize hypertrophy of the epiphyseal cartilage chondrocytes, which are severely disturbed in potassium depletion and likely play an important role in the pathogenia of growth impairment in this condition.

Recent advances in the regulation of cholangiocyte proliferation and function during extrahepatic cholestasis

Bile duct epithelial cells (i.e., cholangiocytes), which line the intrahepatic biliary epithelium, are the target cells in a number of human cholestatic liver diseases (termed cholangiopathies). Cholangiocyte proliferation and death is present in virtually all human cholangiopathies. A number of recent studies have provided insights into the key mechanisms that regulate the proliferation and function of cholangiocytes during the pathogenesis of cholestatic liver diseases. In our review, we have summarised the most important of these recent studies over the past 3 years with a focus on those performed in the animal model of extrahepatic bile duct ligation. In the first part of the review, we provide relevant background on the biliary ductal system. We then proceed with a general discussion of the factors regulating biliary proliferation performed in the cholestatic animal model of bile duct ligation. Further characterisation of the factors that regulate cholangiocyte proliferation and function will help in elucidating the mechanisms regulating the pathogenesis of biliary tract diseases in humans and in devising new treatment approaches for these devastating diseases.