Expression of acid-labile subunit (ALS) in developing and adult zebrafish and its role in dorso-ventral patterning during development.

Mammalian acid-labile subunit (ALS) is a serum protein that binds binary complexes between Insulin-like growth factors (IGFs) and Insulin-like growth factor-binding proteins (IGFBPs) extending their half-life and keeping them in the vasculature. Human ALS deficiency (ACLSD), due to homozygous or compound heterozygous mutations in IGFALS, leads to moderate short stature with reduced levels of IGF-I and IGFBP-3. There is only one corresponding zebrafish ortholog gene and it has not yet been studied. In this study we elucidate the role of igfals during zebrafish development. In zebrafish embryos igfals mRNA is expressed throughout development, mainly in the brain and subsequently also in the gut and swimbladder. To determine its role during development, we knocked down igfals gene product using morpholinos (MOs). Igfals morphant embryos displayed dorsalization in different degrees of severity, including a shortened trunk and loss of tail. Furthermore, co-injection of human IGFALS (hIGFALS) mRNA was able to rescue the MO-induced phenotype. Finally, overexpression of either hIGFALS or zebrafish igfals (zigfals) mRNA leads to ventralization of embryos including a reduced head and enlarged tail. These findings suggest that als plays an important role in dorso-ventral patterning during zebrafish development.

Circulating IGF-I, IGFBP-3 and the IGF-I/IGFBP-3 Molar Ratio Concentration and Height Outcome in Prepubertal Short Children on rhGH Treatment over Two Years of Therapy.

OBJECTIVE: To investigate the occurrence of abnormally elevated values of biomarkers of growth hormone (GH) action in short children on recombinant human GH (rhGH) therapy. METHODS: Sixty-three prepubertal short children were examined: 31 with GH deficiency (GHD), 25 small for gestational age (SGA), and 9 with Turner syndrome (TS). The main outcomes were the following: standard deviation score (SDS) values of IGF-I, IGFBP-3, and IGF-I/IGFBP-3 molar ratio before, at the 1st and at the 2nd year on rhGH and Δheight (Ht)-SDS to evaluate GH treatment efficacy (adequate 1st-year ΔHt SDS: >0.4 SDS for GHD and >0.3 SDS for non-GHD). RESULTS: Seventy-eight percent of GHD, 78% of SGA and 55% of TS children had adequate 1st-year ΔHt SDS. In GHD, 88% of IGF-I SDS and IGFBP-3 SDS that were ≤-2.0 SDS at baseline normalized on treatment. Abnormal IGF-I values >+2.0 SDS were observed in 52% of SGA and in 55% of TS patients on rhGH. Within each group, the IGF-I/IGFBP-3 molar ratio increased significantly from pretreatment and throughout therapy, remaining within normal range for most patients. ΔIGF-I/IGFBP-3 molar ratio SDS were significantly higher in children with an adequate response (p < 0.01). CONCLUSION: Non-GHD groups presented markedly elevated concentrations of GH biomarkers on rhGH and normal IGF-I/IGFBP-3 molar ratio in most patients. Since there is a lack of consensus regarding the molar ratio usefulness, we think that interventions towards a more physiological IGF-I serum profile should be implemented.

Differential impact of simple childhood obesity on the components of the growth hormone-insulin-like growth factor (IGF)-IGF binding proteins axis.

Simple childhood obesity is characterized by normal or even accelerated growth in spite of reduced growth hormone (GH) secretion. There are conflicting reports on the effects of obesity upon components of the GH-insulin-like growth factor-I (IGF-I)-IGF binding proteins (IGFBPs) system. In the present study we aimed to determine GH, IGF-I, IGFBP-3 and IGFBP-2 as well as some of the less explored components of this axis (IGFBP-3 proteolytic activity, IGFBP-3 plasma fragments, and total acid labile subunit [ALS]) in 22 obese and 17 age-matched control children. We also evaluated not only total GH binding protein (GHBP) serum levels but also GHBP bound to GH (complexed) in both groups. Obese and control groups strongly differed in BMI (obese: 4.7 +/- 0.36 vs control: 0.37 +/- 0.25 SDS, p <0.0001). In the obese group, we found lower GH serum levels, but normal serum levels of GH-GHBP complex, IGF-I, IGFBP-3, IGF-I/IGFBP-3 molar ratio, IGFBP-3 proteolytic activity, IGFBP-3 plasma fragments and total ALS. Obese children presented higher total circulating GHBP (6.0 +/- 0.44 vs 2.9 +/- 0.29 nmol/l, p <0.001) and insulin levels (10.5 +/- 1.5 vs 5.1 +/- 0.8 mU/l, p <0.001), while IGFBP-2 (4.6 +/- 0.5 vs 6.6 +/- 0.7%, p <0.05) and the ratio IGFBP-2/IGF-I (0.032 +/- 0.019 vs 0.095 +/- 0.01, p = 0.013) were lower than in controls. BMI and insulin were directly, and IGFBP-2 serum levels inversely, correlated to total GHBP serum levels when multiple regression analysis was performed (r = 0.74, p <0.001). By stepwise regression analysis, insulin (r = -0.37, p <0.05) and BMI (r = -0.52, p <0.01) inversely determined IGFBP-2. In summary, obese children present normal growth in spite of reduced GH secretion, probably because the combination of increased total GHBP and normal GH-GHBP complex serum levels (suggesting increased GH receptor [GHR] number and a normal serum GH reservoir, respectively) allow for the achievement of normal levels of IGF-I, IGFBP-3, IGFBP-3 proteolytic activity, IGFBP-3 plasma fragments and total ALS. Reduced IGFBP-2 serum levels and a lower ratio of IGFBP-2/IGF-I in obese children may suggest an increase of tissue IGF-I bioavailability, thus promoting its action. Normal IGF-I and GH availability may be contributing to maintain normal growth in obese children.

Association of serum components of the GH-IGFs-IGFBPs system with GHR-exon 3 polymorphism in normal and idiopathic short stature children.

OBJECTIVE: To investigate the possible association of circulating components of GH-IGFs-IGFBPs system with the GHR-exon 3 genotype in normal and idiopathic short stature (ISS) children. DESIGN: Descriptive, cross-sectional study in normal and ISS children. SUBJECTS AND METHODS: 192 normal and 81 ISS children (age: 5-17 years) were included. Serum IGF-I, IGFBP3, ALS and GHBP levels were measured. GHR-exon 3 polymorphism (GHRd3) was analyzed by multiplex PCR assay. Normal and ISS children were divided according to GHR-exon 3 genotype: homozygous for the full-length GHR isoform (GHRfl) and carriers of one or two copies of the GHRd3 allele. RESULTS: GHRd3 genotype distribution (fl:fl/fl:d3/d3:d3,%) in normal (60:34:6) and ISS (64:32:4) was similar and reached Hardy-Weinberg equilibrium. ISS children had significantly reduced levels of GHBP and GH-dependent factors as compared to controls (p<0.0001). Within the normal group, homozygous carriers of the GHRfl allele had significantly higher GHBP serum levels than those with one or two copies of the GHRd3 allele (Mean ± SEM; GHRfl: 3.2 ± 0.2 vs GHRd3: 2.7 ± 0.2 nmol/L, p = 0.04). No other significant association with GHR exon 3 polymorphism was found in either the normal or the ISS groups. CONCLUSIONS: GHR exon 3 polymorphism is distributed similarly in normal and ISS children, however only normal homozygous children for GHRfl allele showed higher GHBP levels. The lack of association between GHBP and GHR polymorphism in ISS children might be related to the heterogeneity of this group, where potential defects in GH receptor action may result in partial GH insensitivity.