Assessment of SNRPN expression as a molecular tool in the diagnosis of Prader-Willi syndrome

Associations Between Fetal Imprinted Genes and Maternal Blood Pressure in Pregnancy

In addition to maternal genes and environmental exposures, variation in fetal imprinted genes could also affect maternal blood pressure during pregnancy. Our objective was to test the associations between polymorphic variants in 16 imprinted genes and maternal mean arterial blood pressures in 1160 DNA trios from 2 established birth cohorts (the Cambridge Baby Growth and Wellbeing Studies) and seek replication in 1367 Hyperglycemia and Adverse Pregnancy Outcome Study participants. Significant univariate associations, all independent of fetal sex, were observed in the Cambridge cohorts, including FAM99A rs1489945 transmitted from the mother (P=2×10^-4), DLK1 rs10139403 (mother; P=9×10^-4), DLK1 rs12147008 (mother; P=1×10^-3), H19 rs217222 (father; P=1×10^-3), SNRPN rs1453556 (father; P=1×10^-3), IGF2 rs6356 (father; P=1×10^-3), and NNAT rs6066671 (father; P=1×10^-3). In meta-analysis including additional independent Hyperglycemia and Adverse Pregnancy Outcome Study data, the association with maternally transmitted fetal DLK1 rs10139403 reached genome-wide significance (P=6.3×10^-10). With the exception of fetal rs1489945 and rs217222, all of other associations were unidirectional and most were statistically significant. To further explore the significance of these relationships, we developed an allele score based on the univariate findings. The score was strongly associated with maternal blood pressure at 31 weeks (P=4.1×10^-8; adjusted r²=5.6%) and 37 weeks of pregnancy (P=1.1×10^-4; r²=3.6%), and during the last 2 weeks before parturition (P=1.1×10^-10; r²=8.7%). It was also associated with gestational hypertension (odds ratio, 1.54 [range, 1.14-2.09] per allele; P=0.005; 45 cases and 549 controls). These data support the concept that fetal imprinted genes are related to the development of gestational hypertension.

Sustained benefit after 2 years of growth hormone on body composition, fat utilization, physical strength and agility, and growth in Prader-Willi syndrome

BACKGROUND

Obesity and hypotonia in children with Prader-Willi syndrome (PWS) are accompanied by abnormal body composition resembling a growth hormone (GH)-deficient state. Hypothalamic dysfunction in PWS includes decreased GH secretion, suggesting a possible therapeutic role for GH treatment. Although recent studies have demonstrated short-term benefits of treatment with GH, a critical question is whether beneficial changes persist or wane with prolonged therapy.

OBJECTIVES AND METHODS

Effects of 24 months of GH treatment (1 mg/m(2)/d) on growth, body composition, strength and agility, pulmonary function, resting energy expenditure, and fat utilization were assessed in 35 children with PWS. Percent body fat, lean muscle mass, and bone mineral density were measured by dual-energy x-ray absorptiometry. Indirect calorimetry was used to determine resting energy expenditure and to calculate the respiratory quotient.

RESULTS

Compared with baseline evaluations, increased height velocity (SD score -1.1 +/- 2.5 to 2.2 +/- 2.3; P <. 001), reduced percent body fat (46.4% +/- 8.4% to 40.3% +/- 10.0%, P <.001), and improved respiratory muscle function and physical strength and agility (sit-ups, weight-lifts, running speed, and broad jump; P <.01) were observed after 24 months of GH treatment. A decline in respiratory quotient (0.81 +/- 0.07 to 0.75 +/- 0.06; P <. 01) and a trend toward increased resting energy expenditure were also observed. Changes in response to GH occurred predominantly during the initial 12 months of GH therapy.

CONCLUSIONS

Children with PWS had sustained increases in lean body mass, decreases in percent body fat, improvements in physical strength and agility, and increased fat oxidation after 24 months of GH therapy. However, between 12 and 24 months, the growth rate slowed. Consequently, encouraging initial results require even more prolonged study to draw conclusions regarding the long-term value of GH therapy in changing body composition in children with PWS.