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* Pediatric Gastroenterology and Nutrition Unit, E. Wolfson Medical Center, Holon, Israel
Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
Pediatric Gastroenterology and Nutrition Unit, Dana Children's Hospital, Tel Aviv, Israel
|| Molecular Genetics Laboratory, E. Wolfson Medical Center, Holon, Israel
¶ Pediatric Gastroenterology and Nutrition Unit, Tel-Hashomer Medical Center, Tel Aviv, Israel
# Pediatric Gastroenterology, Bnei Zion Medical Center, Haifa, Israel
** Gastroenterology Division, Rambam Medical Center, Haifa, Israel

Pediatric Gastroenterology, Carmel Medical Center, Haifa, Israel

Epidemiology Unit, E. Wolfson Medical Center, Holon, Israel
| ABSTRACT |
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Methods. Genotyping for 3 NOD2 single-nucleotide polymorphisms was performed in 93 patients with detailed growth records. Parameters including disease location, disease severity, and NOD 2 genotype and their effect on z scores for height and weight at disease onset and during follow-up were analyzed.
Results. NOD2 mutations were correlated with ileal location but not with disease severity or growth retardation. Ileal involvement was significantly associated with height retardation at disease onset and the lowest z score during follow-up. Use of steroids affected weight but not height. Regression models for growth variables revealed that the strongest association with impaired growth is with disease severity (weight- and height-failure odds ratios: 6.17 and 4.52, respectively).
Conclusions. Severity of disease is correlated with growth failure for both height and weight. Location of disease is a weaker predictor of disordered growth and is correlated with growth retardation but not growth failure. The NOD2 genotype was not correlated with growth retardation or growth failure.
Key Words: NOD2 height failure weight failure Crohn's disease growth inflammatory bowel disease genes pediatric
Abbreviations: CD, Crohn's disease SNP, single-nucleotide polymorphism PCR, polymerase chain reaction OR, odds ratio CI, 95% confidence interval
Growth retardation is a frequent feature of pediatric Crohn's disease (CD). Up to 30% of patients may suffer from severe growth failure, which may manifest as poor weight gain or short stature1,2 and may be the first presenting symptoms of CD.3 If not treated before puberty, this impairment may become irreversible.46
Several mechanisms have been implicated in the pathogenesis of growth retardation in CD. Nutritional factors have been shown to have a major contribution.710 Cytokine production induced by chronic inflammation may cause anorexia.1113 Reduced intake caused by anorexia and postprandial pain,14 together with increased requirements caused by chronic inflammation, create an ongoing caloric and protein deficit.1,9 Malabsorption in CD is caused by a combination of diseased intestinal absorptive surface,15 fistulas, bacterial overgrowth,16 and resection.1 Endocrine factors have been hypothesized, but conflicting data exist.17 Steroids have a well-documented effect on growth, causing growth suppression (although weight gain may be obtained),1820 but there are conflicting reports regarding their effect.9,21
Genetic susceptibility for CD is suggested by several observations: ethnic differences,22 familial clustering, twin concordance,23,24 and association with genetic disorders.25 The first disease-associated mutations for CD were found on the NOD2/CARD15 gene, located on the pericentromeric region of chromosome 16.2628 The intracellular product of this gene, expressed in macrophages, monocytes, Paneth cells, and intestinal epithelium, serves as a pattern-recognition receptor for bacterial signals, leading to activation of nuclear factor
B.29 Three loci on the NOD2 gene have been identified as independent risk factors for the development of CD.2628
NOD2 variants have been shown to correlate with ileal involvement and a fibrostenosing course of CD.3032 Involvement of the small intestine can lead to malabsorption and decreased intake,15 which are considered to be leading causes for growth failure in CD patients.1,4 A recent study has found an association between NOD2 mutations and lower weight at diagnosis,33 but an interaction of genotype, independent of phenotype, has not been preformed previously. It is unclear at present if the association between NOD2 mutations and lower weight at diagnosis is a true effect of genotype or is caused by the associated phenotype, which includes ileal involvement. Most of the previous studies investigating growth in CD have regarded height and weight at diagnosis. A drawback of this approach is that growth failure occurring after onset has not been evaluated longitudinally.
The aim of our study is to determine the role of NOD2 mutations on growth retardation in CD at onset and during follow-up and to evaluate if this association is related to genotype, phenotype, or severity of disease.
| PATIENTS AND METHODS |
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End points for this study were z scores for weight and height at onset and at the lowest point after diagnosis (z score nadirs), through the age of 16 years for height, and through the age of 18 years for weight. Presence of growth retardation was defined as a z score less than 1, and growth failure was defined as a z score less than 2. To define an independent association between genotype and growth, we carefully recorded location of disease and measures of severity that may have impacted on growth retardation at those points in time. In choosing parameters that reflect disease severity over prolonged time periods, we steered away from single-point measurements and chose measures that were well documented during the 12 months before the lowest recorded z scores for height and weight. Measures of severity included cumulative duration of hospitalization over 14 days, use of steroids, second line therapy, immunosuppressive therapy, and other medication use. Second-line therapy was defined as the need for corticosteroids or infliximab for active disease during the year before measured nadirs for height and weight. All data (analyzed retrospectively) were recorded from patient files by a single investigator (E.W.). The z score was calculated for each measurement by using ANTHRO 1.02 software (based on World Health Organization standard growth charts).
Genetic Analysis
Three loci on the NOD2 gene were examined: the single-nucleotide polymorphisms (SNPs) G908R, 1007fs, and R702W.
Genomic DNA was extracted from whole peripheral venous blood by using a commercially available kit (Gentra, Minneapolis, MN) in accordance with manufacturer instructions.
Mutations of the NOD2 gene were analyzed by pyrosequencing technology.34 The primer sequences for polymerase chain reaction (PCR) as well as for the pyrosequencing are summarized in Table 1. PCR was performed in a 50-µL volume containing 10 mM Tris · HCl (pH 8.3), 50 mM KCl, 1.5 mM MgCl2, 250 µM dNTPs, 1 µM of each primer, 200 ng of genomic DNA, and 1.25 U of AmpliTaq Gold DNA polymerase (Perkin-Elmer Applied Biosystems, Norwalk, CT) with an initial denaturation step of 10 minutes at 95°C to activate the polymerase followed by 35 cycles of 94°C for 15 seconds, 60°C for 45 seconds, 72°C for 45 seconds, and final elongation of 10 minutes at 72°C. Predicted sizes were confirmed by agarose gel electrophoresis. PCR products were prepared for pyrosequencing analysis by using the PSQ sample-preparation kit according to the standard protocol from Pyrosequencing AB (Uppsala, Sweden) and analyzed for the various SNPs on a PSQ 96MA Pyrosequencer using 0.2 µM sequencing primers and the SNP reagent kit according to standard protocols. The order of nucleotide dispensation was decided based on suggestions provided by PSQ HS 96 SNP 1.0 software (Pyrosequencing AB), which also was used for automatic assay evaluation and genotype scoring.
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2 test with 99% Monte Carlo confidence intervals was used to detect differences in categorical variables by mutation, disease location, or disease severity. Logistic regression analysis was used to model growth failure. All tests were 2-sided and considered significant at P < .05. | RESULTS |
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Genotype-Phenotype Correlation
NOD2 mutations were found to be correlated with ileal involvement. Of subjects with ileal disease location, 43.7% had a mutation, compared with 9.1% of subjects with disease located elsewhere. Alternatively, 91% of NOD2-positive patients had ileal involvement, compared with 67% in NOD2-negative patients (P = .004). Of the 21 patients with Crohn's colitis, only 2 had NOD2 mutations, compared with 11 of 28 with only ileal disease and 20 of 43 with ileocolic involvement (P = .03).
There was no correlation between disease severity and the presence of NOD2 mutations. Of the patients receiving steroids or immunosuppressive therapy, 46% were NOD2-positive and 54% were NOD2-negative (not significant).
The correlation between NOD2 and growth is presented in Tables 2 and 3. There was no correlation for height or weight with z scores at onset or for the lowest z score during childhood.
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Disease Severity and Growth
A clear connection was found between disease-severity measures and growth failure. Use of both steroids and immunosuppressive therapies were correlated to weight and growth failure during z score nadirs (P = .01 and .002, respectively). Immunosuppression was connected to height failure as well (P = .008). Hospitalization for
2 weeks in the year before the lowest growth measure was significantly correlated with height retardation (P = .04) and weight failure (P = .02). Overall severity, defined as the presence of
1 measures of severity, was correlated with growth failure for both height and weight (P = .01 and P < .0001, respectively), compared with subjects without any of the mentioned features of severity.
Growth-Failure Variables
Logistic regression was used to model each of the growth-variable models (Table 5). Age and gender were forced into all models. Immunosuppression increased the risk for both height and weight failure. Steroid therapy and hospitalization for
2 weeks in the year before the lowest growth measure increased the risk for weight failure. The presence of >1 marker of severity added an additional risk of 60% for growth failure to the previous risk (odds ratio [OR]: 1.64; 95% confidence interval [CI]: 1.2-2.3; P = .001).
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| DISCUSSION |
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Measures of disease severity were found in our study to be the best predictors of growth failure, demonstrating ORs of 4.5 for weight and 6.2 for height. Because influence of disease activity or severity on growth can occur over a period of time leading up to the growth nadir, we evaluated measures that we felt were adequately documented over a period of 1 year before the lowest documented growth period after disease diagnosis. Although steroid use could directly affect growth independent of disease severity, the presence of all disease-severity parameters were significantly and independently associated with growth failure. In fact, all other parameters chosen showed a higher risk for weight failure, although this result may be temporarily masked by fluid accumulation that can occur with steroid therapy. Although severity measures such as use of immune suppression were highly correlated with height failure, steroid use before height failure did not achieve statistical significance, which might indicate that the effect of steroids on growth may be limited and reflect growth loss occurring primarily during treatment periods. This finding is supported by a previous study.10
Disease severity, marked by intense inflammation and extent of disease, may act through malabsorption and secretion of anorexigenic cytokines. Cytokines such as tumor necrosis factor
and IL-1 have been correlated with growth failure.1113 Tumor necrosis factor
has been shown to induce cachexia, which can contribute to poor nutrition and growth failure.
Disease location can affect growth mainly by disrupting normal nutrient absorption or increasing losses through diarrhea. This connection has been demonstrated mainly for jejunal and ileal involvement.1,15 Reduced stature was recently correlated to jejunal involvement in a large prospective study.35 Our study found a significant connection between ileal involvement and height retardation (but not failure) at both disease onset and lowest point (P = .02 and 0.01, respectively). Although intestinal involvement may independently serve as a risk factor for decreased linear growth, regression analysis did not find that location was a reason for linear growth failure, indicating that location has less of an affect on growth than disease severity.
Carriage of the NOD2 variants was not correlated with either growth retardation or failure for height or weight in our cohort. A previous study found NOD2 to be associated with low weight at diagnosis.33 Limitations of that study include reference only to growth measurements at diagnosis and no correction for phenotype in analysis. NOD2 has a well-established association to ileal involvement,3032 which may affect growth, as demonstrated in several previous studies.1,15,35 Our study confirmed a significant correlation between ileal involvement and linear growth retardation. Another possible connection between NOD2 and growth could be through genotype effect on severity.36,37 Such an effect was not demonstrated in our study.
Evaluation of polymorphisms that affect inflammation, cytokine production, anorexia, and metabolism may cast some light on the interaction between inflammation, growth, and nutrition. Understanding the mechanisms involved in compromising growth in CD may enable us to optimize therapy by improving appetite, supplying adequate nutrition, and reducing the adverse effects of the resulting inflammatory response, which could alter present therapeutic strategies and lead to therapeutic options that are not available today.
| CONCLUSIONS |
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| FOOTNOTES |
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Address correspondence to Arie Levine MD, Pediatric Gastroenterology Service, E. Wolfson Medical Center, POB 5, Holon 58100, Israel. E-mail: alevine{at}wolfson.health.gov.il or a-levine{at}inter.net.il
| REFERENCES |
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