Increased mRNA levels of Mn-SOD and catalase in embryos of diabetic rats from a malformation-resistant strain.

Abstract

Previous studies have suggested that reactive oxygen species (ROS) are mediators in the teratogenic process of diabetic pregnancy. In an animal model for diabetic p r e g n a n c y, offspring of the H rat strain show minor dysmorphogenesis when the mother is diabetic, whereas the offspring of diabetic rats of a sister strain, U, display major morphologic malformations. Earlier studies have shown that embryonic catalase activity is higher in the H than in the U strain, and maternal diabetes increases this difference in activity. The aim of this study was to characterize the influence of genetic predisposition on diabetic embryopathy by comparing the mRNA levels of ROS-metabolizing enzymes in the two strains. We determined the mRNA levels of catalase, glutathione peroxidase, -g l u t a m y l c y s t e i n -s y n t h e t a s e , glutathione reductase, and superoxide dismutase (CuZn-SOD and Mn-SOD) in day 11 embryos of normal and diabetic H and U rats using semiquantitative reverse transcription-polymerase chain reaction. The mRNA levels of catalase and Mn-SOD were increased in H embryos as a response to maternal diabetes, and no d i fferences were found for the other genes. Sequence analysis of the catalase promoter indicated that the d i fference in mRNA levels may result from diff e r e n t regulation of transcription. Sequence analysis of the catalase cDNA revealed no differences between the two strains in the translated region, suggesting that the previously observed difference in the electrophoretic mobility in zymograms is due to posttranslational modifications. An impaired expression of scavenging enzymes in response to ROS excess can thus be an integral part of a genetic predisposition to embryonic dysmorphogenesis. D i a b e t e s 4 9 :1 0 1-107, 2000 M aternal type 1 diabetes during pregnancy has been known for many years to be associated with an increased risk for congenital malformations in the offspring (1-4). Clinical studies have estimated the risk for a malformed fetus in a t y p e 1 diabetic pregnancy to be in the range of 5-10% (5-9). The malformations are induced before the 7th postconceptional week in human diabetic pregnancy (10). In rats, the teratogenic process is believed to occur during organogenesis (11). Recent reports, however, indicate that a diabetic environment may decrease the inner cell mass (12) and that a high glucose concentration can lead to increased apoptosis already in the preimplantation embryo (13). The teratogenic process and its predisposing factors are not known in detail. In pregnancies with poorly controlled diabetes, however, there is a correlation between the level of H b A 1 c in maternal blood and the risk for having a malformed child (5,14,15).The hypothesis has been put forward that an excess of reactive oxygen species (ROS) mediates the teratogenicity of diabetic pregnancy (16)(17)(18)(19). The oxygen radicals may be harmful to the cell and its functions by reacting with unsaturated fatty acids in membranes, yielding lipid peroxides and causing decreased membran...

Maternal diabetes in the rat impairs the formation of neural-crest derived cranial nerve ganglia in the offspring

“…Provided that there is an increased cell death also in the cells migrating from the crest, it can be assumed that the delay in cranial nerve ganglion development is due to enhanced cell death rather than merely a delayed neural crest-cell migration. Moreover, the malformations induced by diabetic pregnancy are often attributed to free oxygen radicals [28,29,30,31] and the neural crest cells are reported to have low activity of the radical scavenging enzyme superoxide dismutase [32]. The combination of increased oxidative stress and a cell type with low antioxidant capacity could therefore cause the malformations present in neural crest-derived organs in diabetic pregnancy.…”

Similar rhythms of seasonal conceptions in neural tube defects and schizophrenia: A hypothesis of oxidant stress and the photoperiod

“…Cederberg et al (2000) found that rat embryos of a strain resistant to maternal diabetesinduced malformations had higher constitutive and inducible levels of mRNAs for catalase and superoxide dismutase. Studies of homocysteine also found stronger associations between maternal hyperhomocysteinemia and NTDs among fetal groups carrying the C3 T MTHFR enzyme mutation (Wenstrom et al, 2000).…”

The Role of Reactive Oxygen Species in Diabetes‐Induced Anomalies in Embryos of Cohen Diabetic Rats

“…Eriksson et al also described a high rate of congenital malformations in a substrain of Sprague-Dawley rat, denoted U strain, that was developed spontaneously out of the H strain and did not develop congenital anomalies [7]. The catalase activity and levels of catalase and Mn-SOD mRNA were decreased in the U embryos when compared with that of the H embryos, reducing further when the mother was diabetic [5,11,22]. The authors suggested that the impaired expression of scavenging enzymes in response to reactive oxygen species excess might be genetically determined.…”

“…It has, however, been suggested that both intrauterine (maternal) environment as well as genetic background may be important [1][2][3][4][5][6][7] in the teratogenic process. As of today, the literature describes 3 main pathways by which diabetes may affect the normal development of the embryos: disturbed inositol uptake, yielding lowered intracellular inositol concentration [8]; diminished flow in the arachidonic acid-prostaglandin pathway, yielding decreased PGE2 concentration [9]; and excess amount of reactive oxygen species, resulting in decreased amount of low-molecular-weight antioxidants, such as vitamin C, uric acid, glutathione, and vitamin E [5,6,10,11]. The reactive oxygen species pathway seems to be the most important pathway because antioxidants may protect against the disturbances of both the inositol and the arachidonic pathways.…”