Fracture healing and biomarker expression in a diabetic Zucker rat model.

BACKGROUND: Persons with diabetes have a higher incidence of fractures compared with persons without diabetes. However, there is little published information concerning the deleterious effect of late-stage diabetes on fracture healing. There are no studies using animal models that evaluate the effect of advanced diabetes on fracture healing. The purpose of our study was to evaluate cytokine expression, specifically macrophage inflammatory protein 1 (MIP-1) and vascular endothelial growth factor, in fracture healing in a type 2 diabetes rat model. METHODS: We evaluated biomarker expression after femur fracture using a rat model. The two groups consisted of 24 Zucker diabetic rats (study group) and 12 Zucker lean rats (control group). An independent reviewer was used to assess delayed union. We evaluated serum samples 2, 4, 7, and 14 days after surgery for MIP-1, vascular endothelial growth factor, leptin, and other cytokine levels. RESULTS: At 3 weeks, Kaplan-Meier estimates showed that 45.8% of femur fractures in Zucker diabetic rats had healed, whereas 81.8% of those in Zucker lean rats had healed (P = .02). A logistic regression model to predict fast healing that included the three cytokines and diabetes status showed that the only factor achieving significance was MIP-1α. Vascular endothelial growth factor was the only biomarker to show significance compared with delayed healing. CONCLUSIONS: These results confirm significant differences in biomarker expression between diabetic and nondiabetic rats during bone healing. The key factors for bone healing may appear early in the healing process, whereas differences in diabetes versus nondiabetes are seen later in the healing process. Increased levels of MIP-1α were associated with the likelihood of delayed healing.

Are the betaine-homocysteine methyltransferase (BHMT and BHMT2) genes risk factors for spina bifida and orofacial clefts?

Abnormalities in folate and/or homocysteine metabolism may adversely influence embryonic development, leading to the birth of infants with a variety of congenital malformations, including neural tube defects (NTDs) and craniofacial abnormalities. Based upon suggestive evidence that periconceptional folic acid supplementation is effective in preventing a significant proportion of the aforementioned birth defects, genetic variation in the folate biosynthetic pathways may influence the infant's susceptibility to these birth defects. The goal of our study was to investigate sequence variations in the betaine-homocysteine methyltransferase (BHMT) and betaine-homocysteine methyltransferase (BHMT2) genes as modifiers of risk of spina bifida, cleft palate, and cleft lip and palate. The results of this study indicated that individuals homozygous for the single nucleotide polymorphism R239Q in BHMT did not have elevated risks for spina bifida. Genotype frequencies for the BHMT2 rs626105 polymorphism also did not reveal any elevated risks for spina bifida, and only a modest, imprecise elevation of risk for orofacial clefts. The results of these experiments suggest that variants of the BHMT/BHMT2 genes in infants do not substantially contribute to the risk of spina bifida or orofacial clefts in our study population.

Molecular basis of Peters anomaly in Saudi Arabia.

Peters anomaly (PA) and primary congenital glaucoma (PCG) are genetically and phenotypically distinct conditions. Mutations in cytochrome P4501B1 (CYP1B1) are the most common cause of PCG in Saudi Arabia. Recent evidence suggests that there may be common genetic factors to these conditions. To determine the molecular basis of PA, 11 study subjects with PA from 10 Saudi Arabian families were recruited. Experienced ophthalmologists examined all affected subjects and most of their available unaffected relatives. The diagnosis of PA was confirmed by pathological examination of excised corneal buttons in seven subjects. The coding exons of FOXC1, PITX2, and PAX6 were screened and those of CYP1B1 and FOXE3 sequenced. Homozygous CYP1B1 mutations were identified in six individuals in five families. Five individuals were homozygous for G61E and one was homozygous for 143del10. No mutations were identified in FOXC1, PITX2, PAX6, or FOXE3. The clinical or pathologic phenotype of the subjects with CYP1B1 mutations was not different from that of the other PA patients in this study. Two families included at least one individual with homozygous CYP1B1 mutations and no ocular anomalies (nonpenetrant). Mutations in CYP1B1 may be a substantive cause for PA in this population. Thus, PA and PCG may share a common molecular pathophysiology. Indeed, PA and PCG may share the same spectrum of anterior segment dysgenesis. Finally, the occurrence of PA, PCG, and unaffected individuals with identical homozygous CYP1B1 mutations in the same sibship suggests the presence of modifiers that modulate the clinical severity of the phenotypic expression of the same CYP1B1 mutation(s).

Cytochrome P4501B1 mutations cause only part of primary congenital glaucoma in Ecuador.

PURPOSE: To determine the role of cytochrome P450IBI (CYP1B1) mutations in causing primary congenital glaucoma (PCG) in a cohort of Native Americans from Quito, Ecuador. MATERIALS AND METHODS: Seventeen patients with PCG from 15 Native American families were recruited from the Ophthalmology Clinic at Hospital Metropolitano, Quito, Ecuador. Experienced ophthalmologists examined all affected study subjects. Purified DNA was prepared from peripheral blood samples and CYP1B1 coding exons (exons 2 and 3) were amplified and sequenced. Southern blot was performed only on those affected patients who showed no mutations in the CYP1B1 coding exons. RESULTS: The molecular basis of PCG in two families was determined: two novel mutations (a deletion and a point mutation) and one novel polymorphism in CYP1B1 were identified in addition to a previously described single amino acid substitution. Southern blot analyses on whole genomic DNA from affected individuals in whom no mutations were identified by the direct PCR/sequencing approach did not detect any large rearrangements or mutations outside the coding region. CONCLUSION: These findings suggest that mutations in CYPIBI are not a major cause of PCG in this population and that at least one additional locus for this condition is responsible for most cases. Further, the PCG phenotype did not correlate readily with the molecular basis of the disorder, suggesting that careful clinical analysis of the phenotype cannot predict the molecular basis of the disease with accuracy.

Partial deletions of the long arm of chromosome 13 associated with holoprosencephaly and the Dandy-Walker malformation.

Two patients with partial deletions of the long arm of chromosome 13, del(13)(13q21-q34) and del(13)(13q22-q33), respectively, multiple congenital anomalies including holoprosencephaly (HPE) and the Dandy-Walker malformation (DWM) are described. The occurrence of HPE and the DWM in both of these patients suggests that, in addition to ZIC2, which is important for normal development of the forebrain, there is at least one other dosage-sensitive gene in 13q22-q33 that plays an important role in brain development. The DWM is anatomically and developmentally distinct from HPE. The presence of a DWM in each of these two patients with partial deletions of the long arm of chromosome 13 suggests that haploinsufficiency at a locus in 13q22-q33 may cause this anomaly. These findings suggest that microdeletions in 13q22-q33 may be found in a proportion of patients with an apparently isolated DWM. Therefore, careful high-resolution cytogenetic analysis (550 band level or greater) of 13q22-q33 may be considered in these patients. Furthermore, future molecular studies of this region may reveal candidate gene loci for the DWM.

Partial deletions of the long arm of chromosome 13 associated with holoprosencephaly and the Dandy-Walker malformation.

Two patients with partial deletions of the long arm of chromosome 13, del(13)(13q21-q34) and del(13)(13q22-q33), respectively, multiple congenital anomalies including holoprosencephaly (HPE) and the Dandy-Walker malformation (DWM) are described. The occurrence of HPE and the DWM in both of these patients suggests that, in addition to ZIC2, which is important for normal development of the forebrain, there is at least one other dosage-sensitive gene in 13q22-q33 that plays an important role in brain development. The DWM is anatomically and developmentally distinct from HPE. The presence of a DWM in each of these two patients with partial deletions of the long arm of chromosome 13 suggests that haploinsufficiency at a locus in 13q22-q33 may cause this anomaly. These findings suggest that microdeletions in 13q22-q33 may be found in a proportion of patients with an apparently isolated DWM. Therefore, careful high-resolution cytogenetic analysis (550 band level or greater) of 13q22-q33 may be considered in these patients. Furthermore, future molecular studies of this region may reveal candidate gene loci for the DWM.