Influence of genetic polymorphisms on bone disease of preterm infants

Prenatal and Neonatal Bone Health: Updated Review on Early Identification of Newborns at High Risk for Osteopenia

Bone health starts with maternal health and nutrition, which influences bone mass and density already in utero. The mechanisms underlying the effect of the intrauterine environment on bone health are partly unknown but certainly include the 'foetal programming' of oxidative stress and endocrine systems, which influence later skeletal growth and development. With this narrative review, we describe the current evidence for identifying patients with risk factors for developing osteopenia, today's management of these populations, and screening and prevention programs based on gestational age, weight, and morbidity. Challenges for bone health prevention include the need for new technologies that are specific and applicable to pregnant women, the foetus, and, later, the newborn. Radiofrequency ultrasound spectrometry (REMS) has proven to be a useful tool in the assessment of bone mineral density (BMD) in pregnant women. Few studies have reported that transmission ultrasound can also be used to assess BMD in newborns. The advantages of this technology in the foetus and newborn are the absence of ionising radiation, ease of use, and, above all, the possibility of performing longitudinal studies from intrauterine to extrauterine life. The use of these technologies already in the intrauterine period could help prevent associated diseases, such as osteoporosis and osteopenia, which are characterised by a reduction in bone mass and degeneration of bone structure and lead to an increased risk of fractures in adulthood with considerable social repercussions for the related direct and indirect costs.

Screening of Serum Alkaline Phosphatase and Phosphate Helps Early Detection of Metabolic Bone Disease in Extremely Low Birth Weight Infants

Background: Extremely low birth weight (ELBW, <1,000 g) infants have a high risk of metabolic bone disease (MBD). Because of the late appearance of radiological signs, diagnosis of MBD in ELBW infants might be delayed, and its prevalence underestimated in this group of patients. This study adopted serial screening of serum alkaline phosphatase (ALP) and phosphate (P) of ELBW infants to determine whether such screening is helpful for the early detection of MBD. Materials and Methods: We performed a retrospective study of preterm infants with a gestational age ≤ 31 weeks and birth weight <1,000 g. MBD was absent (ALP ≤500 IU/L), mild (ALP >500 IU/L, P ≥4.5 mg/dL), and severe (ALP >500 IU/L, P <4.5 mg/dL); MBD was divided into early MBD (≤4 weeks after birth) and late MBD (>4 weeks after birth) according to the time of onset. Results: A total of 142 ELBW infants were included, with a median gestational age of 28.1 (26.5-29.7) weeks and a median birth weight of 875 (818-950) g. Seventy-three cases of MBD were diagnosed, and the total prevalence was 51.4% (mild MBD, 10.6%; and severe MBD, 40.8%). Male sex, breastfeeding, and sepsis would increase the risk of severe MBD. Most MBD in ELBW infants occurred at 3-4 weeks after birth. Sixty-two percent (45/73) of infants were diagnosed as having early MBD, which are diagnosed earlier than late MBD [24 (21-26) vs. 39 (36-41), t = -7.161; P < 0.001]. Male sex [odds ratio (OR), 2.86; 95% confidence interval (CI), 1.07-7.64; P = 0.036], initial high ALP levels (OR, 1.02; 95% CI, 1.01-1.03; P < 0.001), and breastfeeding (OR, 5.97; 95% CI, 1.01-25.12; P = 0.049) are independent risk factors for the development of early MBD. Conclusion: The risk of MBD among ELBW infants is very high. Most cases occurred early and were severe. Male sex, initial high ALP levels, and breastfeeding are closely related to the increased risk of early MBD. Serial screening of serum ALP and P helps early detection of MBD; it is recommended to start biochemical screening for ELBW infants 2 weeks after birth and monitor their biochemical markers weekly.

Association of vitamin D receptor gene FokI and TaqI polymorphisms and risk of RDS

Background: Vitamin D and its receptor (VDR) have important roles in perinatal lung development. The objective of this study was to investigate the possible association between VDR FokI and TaqI polymorphism and development of respiratory distress syndrome (RDS) in preterm infants.Method: A total of 173 premature infants <34 weeks: 82 with RDS and 91 without RDS were enrolled. Genotyping of VDR polymorphisms was assayed by real-time PCR. Serum 25-hydroxyvitamin D (25-OHD) levels were measured by ELISA in blood samples that were obtained at the time of admission to the neonatal intensive care unit.Results: Gestational age (GA) was significantly lower in the RDS group compared with the controls. In univariate analysis, VDR TaqI CT and CC genotypes were associated with the increased risk of RDS (OR = 3.264, p = .001, 95% CI = 1.597-6.672 and OR = 5.222, p < .001, 95% CI = 2.165-12.597, respectively); while VDR FokI showed no association with RDS. In multivariate logistic regression analysis, variant TaqI genotype increased risk of RDS (p = 0.001, OR = 3.464, 95% CI = 1.655-7.251) independent of gestational age, birth weight and gender. 25-OHD levels in the RDS group were significantly lower compared with those in without the RDS group (p = .002). Serum 25-OHD levels were not significantly different among the different FokI and TaqI genotypes in RDS group.Conclusions: This is the first report of association of VDR polymorphism with RDS development in preterm neonates. Current study suggests that VDR TaqI polymorphism may be involved in predisposition to RDS in premature neonates. Further studies are needed to assess the contribution of vitamin D and VDR signaling to the pathogenesis RDS.

Metabolic Bone Disease of Prematurity: Diagnosis and Management

Metabolic Bone Disease (MBD) of prematurity is a multifactorial disorder commonly observed in very low birth weight (VLBW, <1,500 g) newborns, with a greater incidence in those extremely low birth weight (ELBW, <1,000 g). MBD is characterized by biochemical and radiological findings related to bone demineralization. Several antenatal and postnatal risk factors have been associated to MBD of prematurity, although the main pathogenetic mechanism is represented by the reduced placental transfer of calcium and phosphate related to preterm birth. The diagnosis of MBD of prematurity requires the assessment of several biochemical markers, radiological, and ultrasonographic findings. However, the best approach is the prevention of the symptomatic disease, based on the screening of subjects exposed to the risks of developing MBD. Regarding the subjects who need to be screened, there is a substantial agreement on the potential risk factors for MBD. On the contrary, different recommendations exist on the diagnosis, management and treatment of this disorder of bone metabolism. This review was aimed at: (1) identifying the subjects at risk for MBD of prematurity; (2) indicating the biochemical findings to take in consideration for the prevention of MBD of prematurity; (3) suggesting practical recommendations on nutritional intake and supplementation in these subjects. We searched for papers which report the current recommendations for biochemical assessment of MBD of prematurity and for its prevention and treatment. The majority of the authors suggest that MBD of prematurity is a disease which tends to normalize overtime, thus it is not mandatory to mimic the rate of mineral fetal accretion through parenteral or enteral supplementation. The optimization of total parenteral nutrition (TPN) and the early achievement of a full enteral feeding are important goals for the prevention and management of MBD of prematurity.

Association of vitamin D receptor gene polymorphisms and bronchopulmonary dysplasia

BACKGROUND

Vitamin D and its receptor (VDR) have important roles in perinatal lung development. The aim of this study was to investigate the relationship between VDR gene polymorphism and bronchopulmonary dysplasia (BPD) in preterm infants.

METHODS

VDR Fok I, Bsm I, Apa I, and Taq I polymorphisms were genotyped using restriction fragment length polymorphism in 109 preterm infants (47 with BPD, 62 without BPD).

RESULTS

In univariate analysis, Ff (odds ratio (OR) = 3.937, P = 0.022, 95% confidence interval (CI) = 1.22-12.69) and ff (OR = 5.23, P = 0.004, 95% CI = 1.69-16.23) genotypes of Fok I were associated with the increased risk of BPD; whereas tt genotype of Taq 1 was associated with a protective effect against BPD (OR = 0.30, P = 0.04, 95% CI = 0.09-0.94). In multivariate logistic regression analysis, variant Fok 1 genotype increased risk of BPD (OR = 4.11, 95% CI = 1.08-15.68, P = 0.038) independent of patent ductus arteriosus, sepsis, mechanical ventilation, and surfactant treatment. Taq 1, Bsm 1, and Apa 1 polymorphisms did not have any effect.

CONCLUSION

After adjusting for multiple confounders, VDR Fok 1 polymorphism was associated with the increased frequency of BPD. Further studies are needed to assess the contribution of VDR signaling to the pathogenesis of BPD and to determine if VDR polymorphisms may be suitable for identifying infants at high risk for BPD.

Metabolic bone disease in premature infants and genetic polymorphisms

Koraszülöttekben a csontmineralizációt érintő betegség gyakori jelenség az igen alacsony születési súllyal (születési súly < 1500 g) született újszülöttek körében. Felnőttekben kimutatták, hogy az osteoporosis összefüggésbe hozható a D-vitamin-receptor, az ösztrogénreceptor, valamint a kollagén Iα1-receptor-gének polimorfizmusaival. Célkitűzés: A vizsgálat elsődleges célja annak a tisztázása volt, hogy található-e ilyen jellegű összefüggés a koraszülöttek csontanyagcsere-betegsége és a genetikai polimorfizmusok között. Módszer: 104, igen alacsony születési súllyal született újszülöttet vizsgáltak. Meghatározták a csontképzés (szérum alkalikus foszfatáz, osteocalcin) és a csontreszorpció (vizeletkalcium- és pyridinolinürítés) markereit, mellkasi, valamint hosszú csöves csontröntgenfelvételt készítettek. Eredmények: Harminc koraszülöttben (28,8%) diagnosztizáltak csontmineralizációt érintő betegséget aktív csontképzés és csontreszorpciós paraméterek, valamint pozitív radiológiai jelek alapján. Statisztikailag szignifikáns összefüggést találtak az ösztrogénreceptor-gén thymin-adenin repeat [(TA) n ] allél variánsa és a csontmetabolizmust érintő betegségek között. Csontanyagcsere-betegségben szenvedő koraszülötteknél az alacsonyabb repeatszámok [(TA) n < 19] szignifikánsan gyakrabban fordultak elő [esélyhányados (EH): 5,82; 95%-os megbízhatósági tartomány (MT): 2,26–14,98]. Magasabb számú repeateket [(TA) n > 18] azonban a kontrollcsoportban észleltek (EH: 0,20; 95% MT: 0,05–0,82). A D-vitamin-receptor és kollagén Iα1-receptor ( p = 0,023) egyes genotípusai között találtak szintén szignifikáns interakciót. Lépésenként bővített logisztikus regressziós modellben, mely magában foglalta a klinikai és genetikai jellemzőket, a csontmetabolizmust érintő csontbetegségek szignifikánsan korreláltak a férfinemmel ( p = 0,001), az ápolási napok számával ( p = 0,007), az ösztrogénreceptor- [(TA) n ] variáns magasabb repeatek száma homozigóta formájával ( p = 0,025), ezenkívül a D-vitamin-receptor (Tt) és kollagén Iα1 (CC) genotípusainak ( p = 0,014) és a D-vitamin-receptor (Tt) és ösztrogénreceptor (alacsony repeatszám mindkét allélban) genotípusainak ( p = 0,037) interakcióival. Következtetés: A szerzők eredményei arra mutatnak, hogy genetikai polimorfizmusok összefüggésben állhatnak a koraszülöttek csontanyagcsere-betegségének kialakulásával.