Transgenic mouse models for studying the functions of insulin-like growth factor-binding proteins.
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The insulin-like growth factor-binding proteins (IGFBPs) comprise a family of six related peptides that interact with high affinity with IGFs. IGFBPs compete with IGF receptors for IGF binding, and as a consequence of this competition they can affect cell growth. In addition, IGF-independent regulatory mechanisms of IGFBPs have been described. Despite their common property to interact with IGFs every IGFBP is expressed in a tightly regulated time- and tissue-specific manner suggesting that each protein may have its own distinct functions. Several transgenic mouse models overexpressing IGFBP-1, -2, -3, or -4 were developed in the past few years. Brain abnormalities were a common feature of IGFBP-1 transgenic models. Individual strains showed alterations in glucose homeostasis, reproductive performance, and a reduction of somatic growth as the most prominent phenotypes. The latter was also the main effect observed in IGFBP-2 transgenic mice. The overexpression of IGFBP-3 under the control of an ubiquitous promoter resulted in selective organomegaly, whereas mammary gland-targeted expression of this protein caused an altered involution after pregnancy in this organ. Tissue-specific overexpression of IGFBP-4 resulted in hypoplasia and reduced weight of smooth muscle-rich tissues such as bladder, aorta, and stomach. This review summarizes the current knowledge about the actions of IGFBPs in vivo based on the presently established transgenic mice. (+info)
Mutation analysis and embryonic expression of the HLXB9 Currarino syndrome gene.
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The HLXB9 homeobox gene was recently identified as a locus for autosomal dominant Currarino syndrome, also known as hereditary sacral agenesis (HSA). This gene specifies a 403-amino acid protein containing a homeodomain preceded by a very highly conserved 82-amino acid domain of unknown function; the remainder of the protein is not well conserved. Here we report an extensive mutation survey that has identified mutations in the HLXB9 gene in 20 of 21 patients tested with familial Currarino syndrome. Mutations were also detected in two of seven sporadic Currarino syndrome patients; the remainder could be explained by undetected mosaicism for an HLXB9 mutation or by genetic heterogeneity in the sporadic patients. Of the mutations identified in the 22 index patients, 19 were intragenic and included 11 mutations that could lead to the introduction of a premature termination codon. The other eight mutations were missense mutations that were significantly clustered in the homeodomain, resulting, in each patient, in nonconservative substitution of a highly conserved amino acid. All of the intragenic mutations were associated with comparable phenotypes. The only genotype-phenotype correlation appeared to be the occurrence of developmental delay in the case of three patients with microdeletions. HLXB9 expression was analyzed during early human development in a period spanning Carnegie stages 12-21. Signal was detected in the basal plate of the spinal cord and hindbrain and in the pharynx, esophagus, stomach, and pancreas. Significant spatial and temporal expression differences were evident when compared with expression of the mouse Hlxb9 gene, which may partly explain the significant human-mouse differences in mutant phenotype. (+info)
Growth failure occurs through a decrease in insulin-like growth factor 1 which is independent of undernutrition in a rat model of colitis.
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BACKGROUND: Linear growth retardation is a frequent complication of inflammatory bowel disease in children. The precise mechanisms causing growth failure are not known. AIMS: To determine the relative contribution of reduced calorie intake and inflammation to linear growth delay and to determine the effect of inflammation on the hypothalamic-pituitary-growth axis. METHODS: Linear growth was assessed in prepubertal rats with trinitrobenzenesulphonic acid (TNBS) induced colitis, in healthy free feeding controls, and in a pair-fed group (i.e. healthy animals whose daily food intake was matched to the colitic group thereby distinguishing between the effects of undernutrition and inflammation). RESULTS: Changes in length over five days in the TNBS colitis and pair-fed groups were 30% and 56%, respectively, of healthy free feeding controls. Linear growth was significantly reduced in the colitic group compared with the pair-fed group. Nutritional supplementation in the colitic group increased weight gain to control values but did not completely reverse the growth deficit. Plasma interleukin 6 (IL-6) concentrations were sixfold higher in the colitic group compared with controls. Plasma concentrations of insulin-like growth factor 1 (IGF-1) but not growth hormone (GH) were significantly lower in the colitic compared with the pair-fed group. Administration of IGF-1 to the colitic group increased plasma IGF-1 concentrations and linear growth by approximately 44-60%. CONCLUSIONS: It seems likely that approximately 30-40% of linear growth impairment in experimental colitis occurs as a direct result of the inflammatory process which is independent of undernutrition. Inflammation acts principally at the hepatocyte/IGF-1 level to impair linear growth. Optimal growth in intestinal inflammation may only be achieved by a combination of nutritional intervention and anticytokine treatment. (+info)
Clinical and biochemical characteristics associated with anthropometric nutritional categories.
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Clinical nutrition status as well as selected biochemical characteristics, levels of parasitic infection and aspects of family and health history were assessed in rural EI Salvadoran children categorized as severely malnourished by anthropometric measurements. The anthropometric categories used were based on weight-for-age, weight-for-height, height-for-age, and simple mid-upper-arm circumference. Results indicated that 16 of 17 children with less than 80% of expected weight-for-height ("wasted") and all 17 children with arm circumference below 12.5 cm had clinically evident malnutrition. Children with less than 82.5% of expected height-for-age ("stunted") were more frequently anemic than controls and had a higher intestinal parasite burden, but only 3 of 23 were malnourished clinically. Sixteen of 22 children with severe weight-for-age deficit (Gomez grade III) were judged clinically malnourished, but the remaining six were underweight primarily because of short stature and did not appear malnourished clinically. The results illustrated the inability of weight-for-age classification to distinguish between acute and chronic malnutrition. The interrelationships between weight-for-height, height-for-age, and weight-for-age classification are illustrated graphically as a guide to the interpretation of these results. (+info)
The relationship of growth failure (chronic undernutrition) to the prevalence of clinically severe protein-energy malnutrition and to growth retardation in protein-energy malnutrition.
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A total of 72 of 276 children from a rural Mexican village were chronically undernourished as judged by their growth failure between 6 and 36 months of age. Fourteen of the 72 and five of the remaining 204 children developed clinically severe protein-energy malnutrition (PEM) as judged by clinical signs other than weight or length. This amounted to an 8-fold higher prevalence of PEM in the group of children with growth failure. When children were grouped into quartiles of length at 6 months by sex, quartile was not related to the subsequent occurrence of PEM or to the age when PEM developed. However, analysis indicated that the growth of children with PEM and growth failure had slowed relative to their quartiles before PEM developed; they were also retarded according to the Harvard standards. The children with PEM were then compared to others with a similar growth history (growth failure, no growth failure) who never developed PEM. PEM children did not differ significantly in over weight or length and displayed a significant difference in upper arm muscle circumference at only one age. The 14 with growth failure and PEM had poorer overall growth, including arm muscle circumference, than the five with PEM and no growth failure. (+info)
Birth weight influences long-term catch-up growth and height prognosis of GH-deficient children treated before the age of 2 years.
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OBJECTIVE: To investigate which pretreatment variables most significantly affect long-term growth response to GH therapy in children with apparently idiopathic GH deficiency (GHD) treated from a similar and very young age (less than 2 years), for the same period (7 years) and with the same therapeutic protocol. DESIGN AND METHODS: Twelve children with either isolated GHD or multiple pituitary hormone deficiency were treated with biosynthetic human GH (0.7IU/kg per week) and were examined every 6 months. Height measurements were performed by Harpenden stadiometers. Bone age was evaluated every 12 months. RESULTS: The onset of therapy was followed in all patients by an important height gain, which attained its zenith during the first year of treatment and became progressively less evident during the next 4 years. Cumulative height gain was 3.0+/-1.7SDS. Thanks to the therapy, at the end of the 7-year treatment period, average height in the entire series was not significantly far from mean target height (TH) (-0.7+/-1.3 vs -0. 3+/-0.4SDS) and average predicted height (PH) (-0.2+/-1.4SDS) was very close to TH. A stepwise regression analysis showed that both catch-up growth under therapy and PH at the end of the 7-year treatment period were positively influenced by birth weight (BW). CONCLUSIONS: a) Our 7-year prospective study on GHD infants treated with GH from less than 2 years of age confirmed the importance of early diagnosis and treatment of GHD in childhood. b) The influence of BW on growth response to GH therapy in GHD children persists over time, at least when treatment is begun from less than 2 years of age. (+info)
Delayed growth and puberty in patients with Gaucher disease type 1: natural history and effect of splenectomy and/or enzyme replacement therapy.
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BACKGROUND: Growth retardation in childhood was only recently recognized as a prominent feature of Gaucher disease type 1, but there are few data on both the pubertal development and the final outcome of growth and sexual maturation. OBJECTIVE: To investigate the natural pattern of growth and puberty in patients with Gaucher disease type 1 and the effect of splenectomy and enzyme replacement therapy. METHODS: We retrospectively analyzed growth and puberty in 57 patients with Gaucher disease type 1; 52 were followed since childhood and/or prepuberty and 42 have reached sexual maturity and final height. In the analysis we considered severity of disease, time of splenectomy, and start of enzyme replacement therapy. RESULTS: Deceleration of growth at age 3-5 years was observed in 30 of 57 patients followed since early childhood while untreated: height-SDS decreased from -0.34 +/- 0.42 at age 0-3 years to -1.93 +/- 0.95 (P < 0.01) at age 7-10 years and was more pronounced with severe disease. A high prevalence (59.6%) of delayed puberty, which was more frequent with severe disease, was observed in 47 patients followed before and throughout puberty. No primary endocrine pathology was found. All patients, untreated as well as treated, with growth and pubertal delay had a spontaneous catch-up, achieved full sexual maturation, and most (83.3%) reached a final height within the range of parental height-standard deviation score. Splenectomy (partial and/or total) performed in 20 patients while still growing had a beneficial effect on growth, which was temporary in some and did not affect puberty. ERT improved growth in 11 patients who started therapy before puberty, as evidenced by a progressive increase in the height-SDS, and seemed to normalize the onset of puberty. CONCLUSIONS: Growth retardation in childhood and delay of puberty are characteristic of Gaucher disease type 1 and are more frequent with severe disease. There is a spontaneous catch-up later in life and most patients reach a final height within their genetic growth potential. Enzyme replacement therapy apparently normalizes growth and possibly also the onset of puberty. (+info)
Inactivation of the acid labile subunit gene in mice results in mild retardation of postnatal growth despite profound disruptions in the circulating insulin-like growth factor system.
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Insulin-like growth factors (IGFs) I and II are important regulators of cell proliferation and differentiation. After birth, plasma IGFs, representing mostly liver-derived IGFs, circulate in ternary complexes of 150 kDa consisting of one molecule each of IGF, IGF-binding protein (IGFBP) 3, and an acid labile subunit (ALS). Onset of ALS synthesis after birth is the primary factor driving the formation of ternary complexes. Capture of IGFs by ALS is thought to allow the development of a plasma reservoir without negative effects such as hypoglycemia and cell proliferation. To evaluate the importance of ALS and ternary complexes, we have created mice in which the ALS gene has been inactivated. The mutation was inherited in a Mendelian manner, without any effects on survival rates and birth weights. A growth deficit was observed in null mice after 3 weeks of life and reached 13% by 10 weeks. This modest phenotype was observed despite reductions of 62 and 88% in the concentrations of plasma IGF-I and IGFBP-3, respectively. Increased turnover accounted for these reductions because indices of synthesis in liver and kidney were not decreased. Surprisingly, absence of ALS did not affect glucose and insulin homeostasis. Therefore, ALS is required for postnatal accumulation of IGF-I and IGFBP-3 but, consistent with findings supporting a predominant role for locally produced IGF-I, is not critical for growth. This model should be useful to determine whether presence of ALS is needed for other actions of liver-derived IGF-I and for maintenance of homeostasis in presence of high circulating levels of IGF-II. (+info)