Downregulation of Insulin-Like Growth Factor-1 via Nitric Oxide Production in a Hypergalactosemic Model of Neonate Skin Fibroblast Cultures

Abstract

Background: Galactosemia is a severe metabolic disorder known to cause hepatosplenomegaly, jaundice and cataracts in neonates, and many patients develop later complications such as mental retardation, disorders of motor function or speech, and hypergonadotrophic hypogonadism. The pathogenetic mechanisms of classical galactosemia are unclear; however, nitric oxide (NO) has been suggested to play a role. Objectives: Insulin-like growth factor-1 (IGF-1) is important for the growth and development of children, and the aim of this study was to examine the association of NO production with IGF-1 gene expression under galactosemic conditions. Methods: Serum levels of IGF-1 and nitrite were measured in 15 galactosemia patients and 15 age- and gender-matched healthy controls. Fibroblast cultures established from postcircumcision foreskin of 3- to 8-day-old healthy neonates were treated for 72 h with 0-10 m<smlcap>M</smlcap> of galactose or 0-5 m<smlcap>M</smlcap> of galactose-1-phosphate (Gal-1-P) in the presence or absence of NO synthase inhibitor (<smlcap>L</smlcap>-NAME), and inducible NO synthase (iNOS) protein was measured using Western blot analysis. RT-PCR was performed to assess the IGF-1 gene expression. Results: Galactosemia patients were observed to have significantly (p < 0.01) elevated serum nitrites and markedly decreased levels (p < 0.01) of serum IGF-1 as compared to healthy controls. The cotreatment of neonate skin fibroblast cultures with galactose and Gal-1-P significantly (p < 0.01) increased cellular levels of NO and iNOS protein expression, and decreased (p < 0.01) IGF-1 mRNA levels. Treatment with <smlcap>L</smlcap>-NAME, a NOS inhibitor, significantly (p < 0.05) alleviated a galactose/Gal-1-P-induced decrease in IGF-1 mRNA levels. Conclusion: These results suggest that NO mediates the downregulation of IGF-1 by Gal-1-P/galactose, thereby providing a new molecular mechanism and possible therapeutic insight for galactosemia-related complications.

Galactose-Induced Skin Aging: The Role of Oxidative Stress

“…It can be assumed that D-gal induces skin aging in two ways: the direct impact of D-gal on skin cells and/or the indirect effect associated with the accumulation of toxic metabolites in the skin. Our understanding at this age leads us to suggest that cytotoxicity of D-gal is based on activated oxidative stress, as confirmed by the in vitro [65,[111][112][113][114][115][116][117][118]144] and in vivo experiments [70, 72-74, 76, 78, 82-85].…”

“…In case of metabolic dysfunction or a very high level of galactose, it was established that Gal-1-P accumulates in different tissues [142], including skin fibroblasts [143] of galactosemic patients exposed to galactose. Recent studies have shown that the treatment of neonate skin fibroblast cultures with Gal-1-P significantly enhanced cellular levels of NO and inducible nitric oxide (iNOS) more than galactose treatment [144]. In addition, Gal-1-P downregulates expression of insulin-like growth factor 1 (IGF-1) [144].…”

“…Recent studies have shown that the treatment of neonate skin fibroblast cultures with Gal-1-P significantly enhanced cellular levels of NO and inducible nitric oxide (iNOS) more than galactose treatment [144]. In addition, Gal-1-P downregulates expression of insulin-like growth factor 1 (IGF-1) [144]. Another study showed that elevated levels of Gal-1-P disrupt the phosphatidylinositol bisphosphate-(PI(P)2-) dependent signaling pathway in GALT-deficient tissues by restriction of the inositol phosphate turnover and reduction of the inositol level in tissues [145,146].…”

AAV‐mediated expression of galactose‐1‐phosphate uridyltransferase corrects defects of galactose metabolism in classic galactosemia patient fibroblasts

“…1,2 This imbalance of metabolite levels may lead to glycosylation defects, endoplasmic reticulum (ER) stress, and oxidative stress. [3][4][5] Ultimately, this disease results in inflammation, tissue damage, and other phenotypes as seen in untreated infants including liver and kidney failure, cataracts, and death. 1,2 Standard newborn screening and a diet low in galactose content has largely eliminated such dire Click here to access the podcast for this paper.…”

“…A reduction in GALT activity results in the buildup of galactose, galactose‐1‐phosphate, and galactitol as well as an imbalance in UDP‐glucose and UDP‐galactose 1,2 . This imbalance of metabolite levels may lead to glycosylation defects, endoplasmic reticulum (ER) stress, and oxidative stress 3‐5 . Ultimately, this disease results in inflammation, tissue damage, and other phenotypes as seen in untreated infants including liver and kidney failure, cataracts, and death 1,2 .…”