Angiotensin-Converting Enzyme Gene Polymorphism and Respiratory Muscle Function in Infants

Objective Angiotensin-converting enzyme (ACE) gene contains a polymorphism consisting of either the presence (I) or absence (D) of a 287-bp fragment. Recent studies have suggested that the I-allele may be associated with superior exercise endurance; respiratory muscle function may be similarly influenced. The pressure–time index of inspiratory muscles (PTImus) is a measure of the load–capacity ratio of the inspiratory muscles. The objective of this study was to determine whether infants homozygous for the I-allele have lower PTImus compared to infants homozygous for the D-allele or heterozygous I/D. Patients and Methods One hundred thirty-two infants were studied. ACE genotyping was performed by polymerase chain reaction amplification, using DNA from peripheral blood. PTImus was calculated as (Pimean/Pimax) × (Ti/Ttot), where Pimean was the mean inspiratory pressure estimated from airway pressure, generated 100 ms after an occlusion (P0.1), Pimax was the maximum inspiratory pressure and Ti/Ttot was the ratio of the inspiratory time to the total respiratory cycle time. Pimax was the largest pressure generated during brief airway occlusions performed at the end of a spontaneous crying effort. Results Infants with I/I genotype had significantly lower PTImus than infants with either D/D or I/D genotypes (P = 0.000007). ACE genotype was significantly related (P = 0.005) to PTImus measurements, independent of other factors that may affect respiratory muscle function. Conclusion These results suggest that an association of ACE genotypes with PTImus measurements may exist in infants. Pediatr Pulmonol. 2010;45:1233–1239. © 2010 Wiley-Liss, Inc.