Radiol med (2015) 120:277–282 DOI 10.1007/s11547-014-0440-x
MUSCULOSKELETAL RADIOLOGY
Quantitative ultrasound at the phalanges in a cohort of monozygotic twins of different ages Giuseppe Guglielmi · Francesca De Terlizzi · Michelangelo Nasuto · Lorenzo Sinibaldi · Francesco Brancati
Received: 10 December 2013 / Accepted: 1 April 2014 / Published online: 5 August 2014 © Italian Society of Medical Radiology 2014
Abstract Purpose The aim of our study was to evaluate bone quality by quantitative ultrasound (QUS) at the phalanges in 129 monozygotic twin couples, outlining the differences between growing subjects and adults. Materials and methods A total of 129 healthy monozygotic twin couples (42 of children under 18 years of age and 87 of adults) were studied by phalangeal QUS, measuring amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT). Anthropometric data were also recorded. Results In children AD-SoS and BTT were positively correlated with age (r = 0.91, r = 0.91), height (r = 0.88, r = 0.90) and weight (r = 0.81, r = 0.87); in adults ADSoS was negatively related to age (r = −0.36), AD-SoS G. Guglielmi (*) · M. Nasuto Department of Radiology, University of Foggia, Viale Luigi Pinto 1, 71100 Foggia, Italy e-mail:
[email protected] G. Guglielmi Department of Radiology, Scientific Institute Hospital “Casa Sollievo della Sofferenza”, Viale Cappuccini 1, 71013 San Giovanni Rotondo, FG, Italy F. De Terlizzi Clinical Biophysics Laboratory, IGEA SpA, Modena, Italy L. Sinibaldi Mendel Laboratory, IRCCS “Casa Sollievo della Sofferenza”, San Giovanni Rotondo, Foggia, Italy F. Brancati Policlinico Tor Vergata University Hospital, Rome, Italy F. Brancati Department of Medical, Oral and Technological Sciences, D’Annunzio University, Chieti, Italy
and BTT were positively related to height (r = 0.37, r = 0.58). Absolute value differences between twins for AD-SoS and BTT were significantly higher in adult twins (25.9 ± 21.9 for AD-SoS and 0.08 ± 0.08 for BTT) than in children (14.5 ± 12.4 for AD-SoS and 0.05 ± 0.04 for BTT). Conclusion Differentiation in bone tissue quality in twins increases with age, probably reflecting lifestyle, personal habits, likely acting through epigenetic mechanisms. Keywords Bone mass regulation · Bone tissue · Hand phalanges · Quantitative ultrasound · Twins
Introduction Prospective studies have shown that the incidence of osteoporotic fractures is inversely related to bone mass [1] (National Osteoporosis Foundation 1998). Peak bone mass is considered a main determinant of bone mineral density (BMD) in adulthood, so that maximising peak bone mass is important for preventing osteoporosis. Failure to gain sufficient bone mass during skeletal growth and the period of bone consolidation may predispose to the development of senile osteoporosis [2]. In fact Dent [3] and Kreipe [4] suggested that “senile osteoporosis is a paediatric disease”. The mechanisms of bone homeostasis are influenced by both environmental and genetic factors, and it is known from the literature that specific genes have a strong influence on bone formation and resorption, as demonstrated by the higher correlation level of osteocalcin found in monozygotic twins compared with dizygotic ones [5–11]. Although several studies have explored the genetic contribution to BMD and osteoporosis in general [6, 7], most of them have been based on a quantitative assessment of
13
278
bone mass per surface unit (g/cm2) by dual-energy X-ray absorptiometry (DXA) [11, 12], and of volumetric unit (g/ cm3) by quantitative computed tomography (QCT) [13, 14]. However, the associated structural bone impairment observed in osteoporosis encouraged the search of genetic factors influencing bone architecture and, therefore, the identification of alternative techniques, capable of assessing not only BMD, but also bone quality. Quantitative ultrasound (QUS) has been recently proposed as a noninvasive method of estimating bone tissue properties such as structure and elasticity [15–18]. This technique is safe, easy to use, and radiation-free; the equipment can be transported, and it is relatively cheap in comparison with more expensive densitometric techniques such as DXA and QCT. Clinical studies showed QUS capability to discriminate between osteoporotic and healthy women [19–24], and it may predict fracture independently of BMD [19, 24]. Up to now two peripheral sites have been mostly investigated by QUS: calcaneus and hand phalanges. In this cross-sectional observational study we investigated the QUS parameters of the hand phalanges in two groups of monozygotic twins divided by age into growing individuals (up to the age of 18 years) and adults (more than 18 years of age). We used the QUS technique to examine the phalanges due to its capability to provide different information on ultrasound propagation: besides measurement of the velocity of transmission (amplitude-dependent speed of sound—Ad-SoS), it enables quantification of the morphological changes in the characteristics of the ultrasound wave propagated through the bone tissue. Furthermore this technique is able to provide precise and accurate measurement on adults as well as growing children by the age of 2 years [25]. Thus, the purpose of this study was to evaluate the similarities and differences in bone mass and structure between couples of monozygotic twins as measured by means of the QUS technique at the hand phalanges, outlining the differences between growing subjects and adults.
Materials and methods Subjects One hundred and twenty-nine pairs of monozygotic twins were measured by QUS at the phalanges at a twins’ community convention in Italy; of these, 42 pairs of paediatric age (range 1–18 years, 30 girls and 12 boys) and 87 pairs aged 18–71 years (51 males and 36 females). For each subject additional information on age, height and weight was collected. All subjects were healthy as regards diseases influencing bone metabolism. No information on previous
13
Radiol med (2015) 120:277–282
fractures was collected. Zygosity was self-reported by the examined subjects and evaluated by clinical observation. The study was approved by local institutional review board and informed consent for the study was obtained from all human subjects according to the Declaration of Helsinki. QUS measurement QUS measurements were performed using a DBM Sonic Bone Profiler (IGEA, Carpi (MO) Italy), an ultrasound device emitting 1.25 MHz ultrasound frequency pulses by piezoelectricity [15, 16, 18]. The device consists of a transmitting and a receiving probe attached to a calliper that measures the thickness of the phalanx. The QUS measurement was performed at the distal meta-diaphyseal region of the proximal phalanges of fingers 2–5 of the non-dominant hand; however, studies have demonstrated that no differences could be observed in QUS measurements between the dominant and nondominant hand [23]. The device automatically calculates the average AD-SoS (Amplitude-Dependent Speed of Sound— unit: m/s) through the finger phalanges of the four acquisitions. Amplitude-dependent speed of sound means that the speed of sound is calculated when the signal reaches a fixed amplitude threshold of the ultrasound-received signal by dividing the measured thickness of the phalanx by the time elapsed between emission and reception of the ultrasound pulse at the probes. The device also stores and analyses the digitised waveform of the received ultrasound signal after it has crossed the phalanx; this analysis involves the calculation of a set of parameters for each ultrasound signal. We considered in this study the analysis of bone transmission time (BTT), expressed in μs, which is the interval between the first received signal and the received signal that is propagated through soft tissue only (speed of sound in soft tissue is 1,570 m/s). All values are automatically and immediately calculated by the device and displayed on the screen. BTT seems to reflect bone tissue properties that are different from BMD, linked to bone structure and mechanical competence [22, 24]. Measurements were performed using two cross-calibrated devices; calibration was done with a Plexiglas phantom. In vitro precision in a single device using the Plexiglas phantom was 0.4 %; the two devices were cross-calibrated and a difference in Plexiglas velocity between the two devices was lower than 10 m/s. Measurements were made by two technicians with 5 years’ experience of phalangeal QUS measurements. The short-term in vivo precision was calculated by measuring five times, once a week for a period of about 1 month in ten healthy young adult women. The short-term
Radiol med (2015) 120:277–282
279
in vivo precision was 0.5 % for AD-SoS and 1.8 % for BTT in our centre [22, 26, 27]. Statistical analysis The analyses were performed for the whole population and separately for children and adults. Mean and standard deviation values were calculated for all collected variables in the analysed groups. Student’s t test was used to compare the groups. Spearman linear correlation analysis was used to assess the intrapair association between QUS parameters, height and weight. The minimum level of significance was settled at p = 0.05. All analyses were carried out using SPSS 21.0 software (IBM, Armonk, NY, USA).
In adults, the AD-SoS and BTT were not significantly related to age (r = −0.360, p = 0.122 and r = 0.020, p = 0.411 for AD-SoS and BTT respectively), whilst both parameters were positively related to height (r = 0.37, r = 0.58, p < 0.0001). The correlation coefficients for AD-SoS and UBPI between pairs of twins were significantly higher for children (r = 0.985 for AD-SoS and r = 0.987 for BTT) than for adults (r = 0.882 for AD-SoS and r = 0.920 for BTT) (Fig. 1). The absolute value of the differences between twins for AD-SoS and BTT was significantly higher in adult twins than in children, as reported in Table 3. The absolute difference between twins increases significantly with age (r = 0.374, p < 0.0001 for AD-SoS and r = 0.400, p < 0.0001 for BTT).
Results Discussion Characteristics of the child population are reported in Table 1. Characteristics of the adult population are reported in Table 2. In children, the AD-SoS and BTT were positively correlated with age (r = 0.91, r = 0.91 p < 0.0001), height (r = 0.88, r = 0.90 p < 0.0001) and weight (r = 0.81, r = 0.87 p < 0.0001). Table 1 Characteristics of the child population Mean
SD
Min
Max
Age (years) Height (cm) Weight (kg) BMI AD-SoS (m/s) Z-score
11.6 143.2 40.7 18.5 1985 0.19
5.2 28.6 18.6 2.7 109 1.40
17.9 188.0 80.0 24.7 2164 2.27
BTT (μs)
1.10
0.42
0.7 74.0 10.4 13.2 1614 −6.44
0.00
1.94
SD standard deviation, BMI body mass index, AD-SoS amplitudedependent speed of sound, BTT bone transmission time
Table 2 Characteristics of the adult population Mean
SD
Min
Max
Age (years) Height (cm) Weight (kg) BMI AD-SoS (m/s) Z-score
31.2 169.5 62.4 21.6 2123 0.16
12.2 8.7 11.5 3.1 65 0.84
71.0 192.0 92.0 30.8 2242 1.87
BTT (μs)
1.74
0.27
18.0 150.0 44.0 15.6 1908 −1.88
0.98
2.32
SD standard deviation, BMI body mass index, AD-SoS amplitudedependent speed of sound, BTT bone transmission time
In this study we investigated a cohort of Italian monozygotic twins of both genders, divided into two groups by age. We aimed to describe the bone tissue quality similarities and differences between growing twin subjects and twin adults to estimate the capability of QUS to disclose the relevance of epigenetic changes in the modulation of such a hereditary character between twin subjects. In fact, recent evidence shows that although monozygotic twins share the same or a very similar DNA sequence, their gene expression and DNA modification patterns can be significantly different and may play a crucial role in phenotypic outcomes. Processes regulating gene expression do not involve DNA sequence but are based on epigenetic mechanisms, which are heritable and potentially reversible chemical modifications of DNA and/or of the chromatin structure [28]. Epigenetic control of gene expression is mainly based on dynamic processes of DNA methylation which can change through different developmental stages and in different tissues and can be subjected to environmental factors, and stochastic events. Studying epigenetic modifications and their effects on gene expression in monozygotic twins discordant for phenotype may increase the understanding of diversity from common normal traits to diseases [29, 30]. We studied the intrapair association of QUS parameters in growing twins and adult ones, demonstrating that the linear associations of QUS parameters with age, height and weight are significantly higher in children than in adults. Furthermore, the positive association among QUS parameters and age, height and weight in children clearly reflects the effects of growth, whilst the negative association found in adults among QUS parameters and age, indicates the effect of increasing incidence of osteoporosis with age. These results are expected as already observed in the literature in healthy children and adult populations [31, 32].
13
280
Radiol med (2015) 120:277–282
Fig. 1 Scatter plots showing correlation coefficients for amplitudedependent speed of sound (AD-SoS) (m/s) and bone transmission time (BTT) (μs) between pairs of child and adult twins. In child pairs (upper scatter plots), data points are closely plotted along a straight
Table 3 Differences between twins for amplitude-dependent speed of sound (AD-SoS) and bone transmission time (BTT) are significantly higher in adults than children Children
Adults
t test
AD-SoS diff
14.5 ± 12.4
25.9 ± 21.9
0.0003
BTT diff
0.05 ± 0.04
0.08 ± 0.08
0.0039
Regarding similarity between pairs of twins, both QUS parameters showed extremely significant degrees of correlation, both in children and adult populations. The reported correlation coefficients indicate a similarity between each pair of twins. This is key information in order to demonstrate how QUS is able to reveal how close is the hereditary pattern between twin subjects. Similar results have been obtained by Drozdzowska et al. [33] and by Howard et al. [34], where groups of monozygotic and dizygotic twins were analysed. Even though correlation coefficients were extremely high for adults, in children they were significantly higher and close to the maximum value (r = 0.985, r = 0.987), emphasising how similarity between twins is more evident in children than in adults. This observation has never been previously reported in the literature for QUS measurements
13
line (high correlation) going from the origin out to high x- and y-values (positive correlation). Compared to adult pairs (lower scatter plots), the correlation coefficients for both AD-SoS and BTT are significantly higher in children
at the phalanges and underlines the importance of the genetic components in bone mass and structure metabolism suggesting in the meantime a delayed effect of environmental factors increasing with age [35]. The analysis on the mean difference between twins in the two groups also indicates that differences in ADSoS and BTT between twins are significantly higher in adults than in children (p = 0.0003 and p = 0.0039 for AD-SoS and BTT, respectively). Even the analysis of correlation among differences in AD-SoS and BTT with age results in a significantly positive association (r = 0.374 and r = 0.400, p < 0.0001 for AD-SoS and BTT, respectively), indicating a progressive linear trend toward increasing diversity between twins with increasing age. This aspect strengthens the hypothesis that environmental factors such as personal behaviour and lifestyle would co-regulate bone homeostasis influencing its progressive differentiation. Similar results were observed in another study conducted on an Italian twin cohort of males and females, where a positive correlation between differences in ADSoS and age was observed for females [36]. In that study the majority of subjects were adults, the group of children was limited to few cases and a separate analysis on children only was not possible.
Radiol med (2015) 120:277–282
Our study suffers some limitations: the lack of an extensive distribution of this group over all ages, especially older age: it was expected that only mobile older twins would have attended the meeting, introducing a bias in the population selection. Moreover, since the festival was essentially a social event, no information or questionnaires about the osteoporosis status of subjects could be collected. Furthermore, measurements were taken only at one skeletal site and a genetic investigation to further investigate its contribution to QUS parameters was not feasible. Apart from these limitations, separate analysis on child twins still remains an important strength of this study, showing QUS capability to highlight the genetic contribution to bone mass and quality. The age-related, progressive intra-pair differences in QUS parameters underline the importance of lifestyle, personal habits and other environmental factors for bone mass regulation probably associated with a different epigenetic modulation of bone metabolism. Conflict of interest Francesca De Terlizzi is employed by IGEA s.p.a Biophysics Lab. The other authors declare that they have no competing financial interests.
References 1. National Osteoporosis Foundation (1998) Osteoporosis: review of the evidence for prevention, diagnosis, and treatment and costeffectiveness analysis. Osteoporos Int 8:S1–S88 2. Riggs BL, Khosla S, Melton LJ III (1999) The assembly of the adult skeleton during growth and maturation: implications for senile osteoporosis. J Clin Invest 104:671–672 3. Dent CE (1973) Keynote address: problems in metabolic bone disease. In: Frame B, Parfitt MA, Duncan H (eds) Clinical aspects of metabolic bone disease. Excerpta Medica, Amsterdam, pp 1–6 4. Kreipe RE (1992) Bones of today, bones of tomorrow. Am J Dis Child 146:22–25 5. Ralston SH (1997) The genetics of osteoporosis. Q J Med 90:247–251 6. Andrew T, Mak YT, Reed P et al (2002) Linkage and association for bone mineral density and heel ultrasound measurements with a simple tandem repeat polymorphism near the osteocalcin gene in female dizygotic twins. Osteoporos Int 13:745–754 7. Brown MA, Haughton MA, Grant SF et al (2001) Genetic control of bone density and turnover: role of the collagen 1alpha1, estrogen receptor, and vitamin D receptor genes. J Bone Min Res 16:758–764 8. Jouanny P, Guillemin F, Kuntz C et al (1995) Environmental and genetic factors affecting bone mass. Arthritis Rheum 38:61–67 9. Kannus P, Palvanen M, Kaprio J et al (1999) Genetic factors and osteoporotic fractures in elderly people: prospective 25 year follow up of a nationwide cohort of elderly Finnish twins. Br Med J 319:1334–1337 10. Slemenda CW, Christian JC, Reed T et al (1992) Long-term bone loss in men: effects of genetic and environmental factors. Ann Intern Med 117:286–291 11. Ferrari S, Rizzoli R, Bonjour JP (1999) Genetic aspects of osteoporosis. Curr Opin Rheumatol 11:294–300
281 12. Bandirali M, Sconfienza LM, Aliprandi A et al (2014) In vivo differences among scan modes in bone mineral density measurement at dual-energy X-ray absorptiometry. Radiol Med 119:257–260 13. Guglielmi G, Grimston SK, Fischer KC, Pacifici R (1994) Osteoporosis: diagnosis with lateral and posteroanterior dual X-ray absorptiometry compared with quantitative CT. Radiology 192:845–850 14. Pacifici R, Rupich RC, Griffin MG et al (1990) Dual energy radiography versus quantitative computed tomography for the diagnosis of osteoporosis. J Clin Endocrinol Metab 70:705–710 15. Barkmann R, Lüsse S, Stampa B et al (2000) Assessment of the geometry of human finger phalanges using quantitative ultrasound in vivo. Osteoporos Int 11:745–755 16. De Terlizzi F, Battista S, Cavani F et al (2000) Influence of bone tissue density and elasticity on ultrasound propagation: an in vitro study. J Bone Min Res 15:2458–2466 17. Gluer CC, Wu CY, Jergas M et al (1994) Three quantitative ultrasound parameters reflect bone structure. Calcif Tissue Int 55:46–52 18. Hans D, Wu C, Njeh CF et al (1999) Ultrasound velocity of trabecular cubes reflects mainly bone density and elasticity. Calcif Tissue Int 64:18–23 19. Hartl F, Tyndall A, Kraenzlin M et al (2002) Discriminatory ability of quantitative ultrasound parameters and bone mineral density in a population-based sample of postmenopausal women with vertebral fractures: result of the Basel Osteoporosis Study. J Bone Min Res 17:321–330 20. Henk C, Lu Y, Krestan C et al (2001) Quantitative US of the calcaneus cutoff levels for the distinction of healthy and osteoporotic individuals. Radiology 220:400–405 21. Guglielmi G, Cammisa M, De Serio A et al (1999) Phalangeal US velocity discriminates between normal and vertebrally fractured subjects. Eur Radiol 9:1632–1637 22. Guglielmi G, Njeh CF, de Terlizzi F et al (2003) Phalan geal quantitative ultrasound, phalangeal morphometric variables, and vertebral fracture discrimination. Calcif Tissue Int 72:469–477 23. Ventura V, Mauloni M, Mura M et al (1996) Ultrasound velocity changes at the proximal phalanxes of the hand in pre-, peri- and postmenopausal women. Osteoporos Int 6:368–375 24. Wüster C, Albanese C, De Aloysio D et al (2000) Phalangeal osteosonogrammetry study: age-related changes, diagnostic sensitivity, and discrimination power. J Bone Min Res 15:1603–1614 25. Baroncelli GI, Federico G, Vignolo M et al (2006) The phalangeal quantitative ultrasound group. Cross-sectional reference data for phalangeal quantitative ultrasound from early childhood to young adulthood according to gender, age, skeletal growth, and pubertal development. Bone 39:159–173 26. Caffarelli C, Gonnelli S, Tanzilli L et al (2012) The relationship between serum ghrelin and body composition with bone mineral density and QUS parameters in subjects with Rett syndrome. Bone 50:830–835 27. Wuster C, Albanese C, De Aloysio D, Duboeuf F, Gambacciani M, Gonnelli S, Gluer CC, Hans D, Joly J, Reginster JY, De Terlizzi F, Cadossi R, the Phalangeal Osteosonogrammetry Study Group (2000) Phalangeal osteosonogrammetry study: age-related changes, diagnostic sensitivity, and discrimination power. J Bone Min Res 15:1603–1614 28. Bell JT, Spector TD (2011) A twin approach to unraveling epigenetics. Trends Genet 27:116–125 29. Martino D, Loke YJ, Gordon L et al (2013) Longitudinal, genome-scale analysis of DNA methylation in twins from birth to 18 months of age reveals rapid epigenetic change in early life and pair-specific effects of discordance. Genome Biol 14:R42
13
282 30. Wong CC, Meaburn EL, Ronald A et al (2013) Methylomic analysis of monozygotic twins discordant for autism spectrum disorder and related behavioural traits. Mol Psychiatry 4:1–9 31. Montagnani A, Gonnelli S, Cepollaro C et al (2000) Quantitative ultrasound at the phalanges in healthy Italian men. Osteoporos Int 11:499–504 32. Halaba ZP, Konstantynowicz J, Pluskiewicz W et al (2005) Comparison of phalangeal ultrasound and dual energy X-ray absorptiometry in healthy male and female adolescents. Ultrasound Med Biol 31:1617–1622 33. Drozdzowska B, Pluskiewicz W, de Terlizzi F (2002) Quantitative ultrasound at the hand phalanges in monozygotic twins: a preliminary report. Ultrasound Med Biol 28:1153–1156
13
Radiol med (2015) 120:277–282 34. Howard GM, Nguyen TV, Harris M et al (1998) Genetic and environmental contribution to the association between quantitative ultrasound and bone mineral density measurements: a twin study. J Bone Min Res 13:1318–1327 35. Bell JT, Saffery R (2012) The value of twins in epigenetic epidemiology. Int J Epidemiol 41:140–150 36. Guglielmi G, de Terlizzi F, Torrente I et al (2005) Quantitative ultrasound of the hand phalanges in a cohort of monozygotic twins: influence of genetic and environmental factors. Skelet Radiol 34:727–735
