[CBS gene variations and serum homocysteine level associated with congenital heart defects]

OBJECTIVE

To study the relationship between two common CBS gene variations, tHcy level and CHDs in a nuclear family-based study.

METHODS

234 Chinese CHDs patients and their biological parents were recruited as case groups. And another 136 normal individuals and their parents were recruited as controls. The CBS gene 844ins68 and G919A variants were analyzed by PCR and PCR-ARMS methods. The serum fasting total homocysteine (tHcy) level was detected by Fluorescence Polarization Immunoassay.

RESULTS

CBS 844ins68 variant was associated with high risk of CHDs, the odds ratios (ORs) between heterozygotes (DI) versus wild homozygotes (DD) were 14.19 (95% CI: 2.21-591.52), 4.37 (95% CI: 1.24-23.47) and 4.77 (95% CI: 1.38-25.37) in mothers, fathers and offspring respectively (P < 0.05). CBS G919A was significantly associated with low risk of CHDs. The ORs of offspring between heterozygotes (GA) and mutant homozygotes (AA) versus wild homozygotes (GG) were 0.45 (95% CI: 0.23-0.87) and 0.34 (95% CI: 0.11-1.01), P < 0.05. And the parents carrying GA and AA genotypes also was lower risk of CHDs. For both of above two variants, the significant relations occurred especially in ventricular septal defect subgroup. Genotype combination analysis showed the more risk alleles (I and G) the family members carried, the higher the offspring risk of CHDs. And the serum fasting tHcy level was not significantly different among various groups and genotypes.

CONCLUSION

CBS gene 844ins68 and G919A variations in nuclear families could be associated with CHDs risk of offspring, but not with serum fasting tHcy level.

Maternal and offspring MTHFR gene C677T polymorphism as predictors of congenital atrial septal defect and patent ductus arteriosus

To observe the association of MTHFR gene C677T locus polymorphism with occurrence of congenital heart defects (CHDs), 21 patients with atrial septal defect (ASD), 35 patients with patent ductus arteriosus (PDA), one patient with both conditions combined, and their biological parents were collected as the case group. Another 104 normal individuals and their biological parents without a family history of birth defects were selected as the control group. MTHFR C677T genotypes of each sample were determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The results showed for the occurrence of ASD, the odds ratio (OR) of TT genotype was 4.08 [95% confidence interval (95% CI) = 1.28-13.24] compared with CT genotype. For the occurrence of PDA, the ORs of TT were 3.44 (95% CI = 0.89-16.13) and 2.38 (95% CI = 0.92-6.14) compared with CC and CT genotypes, respectively. Author as meant? Compared with CC + CT genotype combination, the ORs of TT were 3.95 (95% CI = 1.38-11.44) and 2.60 (95% CI = 1.02-6.36) for ASD and PSD respectively. The results also had sex differences and the statistical significance was only observed in male ASD and female PDA. The ORs of T allele carriers were 2.29 (95% CI = 1.08-4.92) and 1.88 (95% CI = 1.02-3.47) compared with C allele for the occurrences of ASD and PDA respectively. The analysis of parents genotype showed that the OR of TT mothers was 2.31 (95% CI = 0.96-5.59, P < 0.05) compared with (CC + CT) for the occurrence of PDA in offspring. So this study could give a clue that MTHFR C677T locus variation was related with occurrence of ASD and PDA, and the carriers of TT genotype and T allele had higher risk of diseases. The mother carrying TT genotype was associated with occurrence of PDA in offspring.

The effect of sterol regulatory element-binding protein 2 polymorphism on the serum lipid in northern Chinese subjects

Sterol regulatory element-binding protein 2 (SREBP-2) is an important nuclear transcription factor in the regulation of cellular cholesterol metabolism. To determine allele frequency of the 1784G>C polymorphism at the SREBP-2 locus and investigate the relationship between this polymorphism and serum lipid levels in Chinese people, we selected 486 individuals (118 men and 368 women) from the Xicheng District of Beijing. The subjects were divided into four groups: hypercholesterolemic subjects, hypertriglyceridemic subjects, combined hyperlipidemic subjects, and normal subjects. Serum lipid profiles were measured in all subjects, and 1784G>C was analyzed using polymerase chain reaction-restriction fragment length polymorphism analysis. There was no significant difference in genotype frequencies or allele frequencies of this polymorphism between the hyperlipidemic and control groups. The serum total cholesterol (TC) and LDL cholesterol (LDL-C) levels of the individuals carrying the C allele were higher than the noncarriers in both males and females in the hypercholesterolemic group, but statistical significance was only observed in females. The results of this study indicate that the SREBP-2 polymorphism is related to elevated concentrations of serum TC and LDL-C in hypercholesterolemic subjects. Further work is necessary to confirm the role of 1784G>C in the development of hyperlipidemia.

[Relations between polymorphism of sterol regulatory element binding protein-2 gene and hyperlipidemia in the Han ethics of China]

OBJECTIVE

To determine allele frequencies of 1784G > C polymorphism in Sterol Regulatory Element Binding Protein-2 (SREBP-2) gene and investigate the relationship between this polymorphism and serum lipid levels in hyperlipidemic and normolipidemic individuals residing in Beijing City, China.

METHODS

A total of 322 unrelated hyperlipidemic individuals and 164 unrelated normolipidemic individuals were selected from Xicheng District of Beijing. For all subjects the serum lipids profiles were measured and the 1784G > C polymorphism was analyzed (PCR-RFLP).

RESULTS

The frequencies of C allele in hyperlipidemic and control groups were 0.196 and 0.201, respectively. There was no significant difference in genotype frequencies or allele frequencies of this polymorphism between hyperlipidemic and control groups. When the hyperlipidemic subjects were divided into three subgroups according to lipid levels, it was shown that the serum TC and LDL-C levels of the individuals carrying C allele were significantly higher than the non-carriers in the hypercholesterolemic subgroup. There were no statistically significant differences for any of these parameters across genotypes in hypertriglyceridemic, combined hyperlipidemic and normolipidemic groups.

CONCLUSION

The study indicated that 1784GC/CC genotypes of SREBP-2 were significantly related with the elevated concentrations of serum TC and LDL-C in hypercholesterolemic subjects, and further work is necessary to confirm the role of 1784G > C polymorphism of SREBP-2 gene in the development of hyperlipidemia.

[Relations of methionine synthase gene variation with congenital heart disease]

OBJECTIVE

Methionine synthase (MS) is the key enzyme in the homocysteine metabolism. To investigate the relations of MS gene variation with occurrence of congenital heart disease (CHD).

METHODS

186 CHD patients (0-31 years old) were selected as case group and 103 normal population as control. For all subjects the gene polymorphism at MS A2756G locus was analysed by PCR-RFLP method, and the serum folic acid/vitamin B12 levels were detected by radio-immunity assay.

RESULTS

The heterozygotes (+/-) were detected in the subjects but without homozygotes (+/+). In control group the frequencies of (+/-) genotype and (+) allele were 10.7% and 5.3%, lower than Caucasian and Japanese population. In case group the frequencies of (+/-) genotype and (+) allele were 9.1% and 4.6%, without significantly different from control. The odds ratio of (+/-) genotype was 0.84 (0.35, 2.01). The genotype distributions in different types of CHD were also not apparently different with control. The serum vitamin B12 level was decreased in case group compared with control (336.66 pmol/L vs 465.72 pmol/L, P > 0.05), but the serum folic acid level no different. Also there were not significant difference for folic acid/vitamin B12 levels between different genotypes in case group.

CONCLUSION

The results indicated that there was not apparent association between MS gene A2756G locus variation with CHD and serum folic acid/vitamin B12 levels. It need further investigations.

How does the European common lizard, Lacerta vivipara, survive the cold of winter?

Although the European common lizard, Lacerta vivipara, is among the most common Eurasian reptile species, we know little about how these lizards cope with very low temperatures. In this study we examined microenvironmental conditions, body temperature, behavior, and cold strategies to see whether strategies of freezing and supercooling, while normally considered to be mutually exclusive, may in fact be adopted simultaneously by the common lizard. Following up on an earlier study of a lowland population, this time we used a mountain population (850 m) to discover differences in overwintering strategies between the two populations. Differential scanning calorimetry conducted during the hibernation period (vs. the activity period) showed that the blood of highland lizards had an increased ability to resist ice formation, confirming an ecophysiological effect most likely mediated by physical properties of the blood. Mean blood glucose level of unfrozen L. vivipara in the field increased significantly (about fourfold) from 8.5+/-0.7 mmol l(-1) in September to 33.2+/-5.6 mmol l(-1) in March. The blood glucose level then experienced a significant decline as it fell to 6. 2+/-0.8 mmol l(-1) after hibernation in April. Glucose, in conclusion, seems to play a role of cryoprotectant rather than antifreeze.

[Study on genotypes of cystathionine beta-synthase in neural tube defects]

Mildly elevated maternal plasma homocysteine (Hcy) levels (hyperhomocysteinemia) have recently been observed in some neural tube defects(NTDs) pregnancies. The aetiology of NTDs is also known to have both genetic and nutritional components. The frequency of two relatively common mutations in the enzyme of cystathionine beta-synthase (CBS), which is one of the main enzymes that controls Hcy level, was examined. Among 76 nonpregnant women in the study, 40 of whom had given birth to infants with NTDs and 36 control women previously had normal offspring. The results showed that no significant difference was found between NTDs mothers and non-NTDs mothers for the frequency of T833-C and the G919-A mutations in the CBS gene. The data suggests that the mother's genotype is not the direct factor involved in the pathogenesis of NTDs.

Osmotic activation of the hypothalamo-neurohypophysial system reversibly downregulates the NMDA receptor subunit, NR2B, in the supraoptic nucleus of the hypothalamus

NMDA receptor activation produces a characteristic pattern of neuronal firing in magnocellular neuroendocrine cells (MNCs) of the supraoptic nucleus of the hypothalamus (SON) which has been associated with greater hormone release in vivo and in vitro. In addition, i.c.v. administered NMDA receptor blockers suppress the dehydration-induced rise in plasma vasopressin and drinking. To investigate the role of NMDA receptor subunits in the neuroendocrine functions of the magnocellular neuroendocrine cells of the hypothalamus, we examined the effects of osmotic stimulation on the protein expression of the NMDA receptor subunits, NR1 and NR2B, important in binding glycine and glutamate, respectively. Homogenates of SON, paraventricular nucleus of the hypothalamus (PVN), cortex and lateral hypothalamus from control rats and rats given 2% saline water to drink for 4-10 days were subjected to SDS-PAGE and Western blot analysis. This saline water drinking regimen produced a significant rise in plasma osmolality levels. NR1 and NR2B immunoreactivity was detected in SON, PVN, lateral hypothalamus and cortex but not in liver homogenates using subunit-specific polyclonal antibodies and quantified using computer-assisted densitometry. Mean NR2B immunoreactivity was significantly lower in SON (29%) and PVN homogenates (23%) from saline-treated rats than in those from control rats. In addition, the effect of dehydration on NR2B was regionally specific since no significant changes in NR2B expression were observed in homogenates of cortex and lateral hypothalamus. Rehydration allowed recovery of plasma osmolality as well as NR2B protein levels in the SON. These results suggest that changes in NMDA receptor subunit expression contribute to the plasticity manifested by in magnocellular neuroendocrine cells in response to osmotic activation of the hypothalamo-neurohypophysial system. In addition, our results indicate that NMDA receptors on SON and PVN MNCs may contribute to neuroendocrinological functions associated with body fluid homeostasis.

Lateral hypothalamic NMDA receptor subunits NR2A and/or NR2B mediate eating: immunochemical/behavioral evidence

Cells within the lateral hypothalamic area (LHA) are important in eating control. Glutamate or its analogs, kainic acid (KA) and N-methyl-D-aspartate (NMDA), elicit intense eating when microinjected there, and, conversely, LHA-administered NMDA receptor antagonists suppress deprivation- and NMDA-elicited eating. The subunit composition of LHA NMDA receptors (NMDA-Rs) mediating feeding, however, has not yet been determined. Identifying this is important, because distinct second messengers/modulators may be activated by NMDA-Rs with differing compositions. To begin to address this, we detected LHA NR2A and NR2B subunits by immunoblotting and NR2B subunits by immunohistochemistry using subunit-specific antibodies. To help determine whether NMDA-Rs mediating feeding might contain these subunits, we conducted behavioral studies using LHA-administered ifenprodil, an antagonist selective for NR2A- and/or NR2B-containing NMDA-Rs at the doses we used (0.001-100 nmol). Ifenprodil maximally suppressed NMDA- and deprivation-elicited feeding by 63 and 39%, respectively, but failed to suppress KA-elicited eating, suggesting its actions were behaviorally specific. Collectively, these results suggest that LHA NMDA-Rs, some of which contribute to feeding control, are composed of NR2A and/or NR2B subunits, and implicate NR2A- and/or NR2B-linked signal transduction in feeding behavior.

Developmental plasticity of NR1 and NR2B subunit expression in the supraoptic nucleus of the rat hypothalamus

Vasopressin and oxytocin neuroendocrine cells within the supraoptic nucleus of the adult hypothalamus (SON) display mRNA expression for the NMDA receptor subunits, NR1 and NR2B, NR2C and NR2D. The NR2B subunit confers slow decay kinetics (relative to NR1/NR2A receptors) and high magnesium sensitivity to NMDA receptor responses--properties which may contribute to the NMDA receptor-mediated bursting manifested by these cells. Therefore, we examined NR2B protein expression and its developmental profile in the SON and compared it to that in the cortex and cerebellum--areas which have been studied previously. We performed Western blot analysis on SON homogenates from embryonic, postnatal (PN7, 14, 21), and adult rats using an NR2B-specific antibody. Adult NR2B levels in the SON and PVN were similar but low relative to those of cortex. SON NR2B protein levels rose in the first postnatal week, remained high through PN21, and later declined to significantly lower levels in the adult. A similar profile was observed in cerebellum, where NR2B expression displayed a sharp peak at PN14 and later declined to minimal or undetectable levels in the adult. In contrast, NR2B continued to be overexpressed through adulthood in the cortex. The ontogenic pattern for NR1 expression, which included unregulation during early postnatal life and adulthood, was similar in the SON and cortex. A different pattern was observed for the cerebellum, where NR1 levels increased gradually after ED17 to reach significantly greater adult levels. Of all three areas studied, the SON displayed the earliest developmental rise in NR1 levels. SON explant cultures proved to be a useful preparation, since they contained neurons which synthesized NR1 and NR2B subunits in quantities similar to those of ED17 SON. Our findings suggest that NMDA receptors on SON neuroendocrine cells are assembled using NR1 and NR2B subunits, and that their plastic expression in early postnatal life may play a role during development.