Prevalence and functionality of paucimorphic and private MC4R mutations in a large, unselected European British population, scanned by meltMADGE

Identification of unknown mutations has remained laborious, expensive, and only viable for studies of selected cases. Population-based "reference ranges" of rarer sequence diversity are not available. However, the research and diagnostic interpretation of sequence variants depends on such information. Additionally, this is the only way to determine prevalence of severe, moderate, and silent mutations and is also relevant to the development of screening programs. We previously described a system, meltMADGE, suitable for mutation scanning at the population level. Here we describe its application to a population-based study of MC4R (melanocortin 4 receptor) mutations, which are associated with obesity. We developed nine assays representing MC4R and examined a population sample of 1,100 subjects. Two "paucimorphisms" were identified (c.307G>A/p.Val103Ile in 27 subjects and c.-178A>C in 22 subjects). Neither exhibited any anthropometric effects, whereas there would have been >90% power to detect a body mass index (BMI) effect of 0.5 kg/m(2) at P=0.01. Two "private" variants were also identified. c.335C>T/p.Thr112Met has been previously described and appears to be silent. A novel variant, c.260C>A/p.Ala87Asp, was observed in a subject with a BMI of 31.5 kg/m(2) (i.e., clinically obese) but not on direct assay of a further 3,525 subjects. This mutation was predicted to be deleterious and analysis using a cyclic AMP (cAMP) responsive luciferase reporter assay showed substantial loss of function of the mutant receptor. This population-based mutation scan of MC4R suggests that there is no severe MC4R mutation with high prevalence in the United Kingdom, but that obesity-causing MC4R mutation at 1 in 1,100 might represent one of the commonest autosomal dominant disorders in man.     

Silicon substitution in the calcium phosphate bioceramics

Silicon (Si) substitution in the crystal structures of calcium phosphate (CaP) ceramics such as hydroxyapatite (HA) and tricalcium phosphate (TCP) generates materials with superior biological performance to stoichiometric counterparts. Si, an essential trace element required for healthy bone and connective tissues, influences the biological activity of CaP materials by modifying material properties and by direct effects on the physiological processes in skeletal tissue. The synthesis of Si substituted HA (Si-HA), Si substituted alpha-TCP (Si-alpha-TCP), and multiphase systems are reviewed. The biological performance of these Si substituted CaP materials in comparison to stoichiometric counterparts is discussed. Si substitution promotes biological activity by the transformation of the material surface to a biologically equivalent apatite by increasing the solubility of the material, by generating a more electronegative surface and by creating a finer microstructure. When Si is included in the TCP structure, recrystallization to a carbonated HA is mediated by serum proteins and osteoblast-like cells. Release of Si complexes to the extracellular media and the presence of Si at the material surface may induce additional dose-dependent stimulatory effects on cells of the bone and cartilage tissue systems.     

Lipid profile, obesity and bone mineral density: the Hertfordshire Cohort Study

BACKGROUND: Body mass index (BMI) and bone mineral density (BMD) are positively correlated in several studies, but few data relate bone density, lipid profile and anthropometric measures. AIM: To investigate these relationships in a large, well-characterized cohort of men and women (The Hertfordshire Cohort Study). METHODS: Men (n = 465) and women (n = 448) from Hertfordshire, UK were recruited. Information was available on demographic and lifestyle factors, anthropometric measurements, body fat percentage, fasting triglycerides, cholesterol (total, HDL, LDL), apolipoprotein (a) and apolipoprotein (b); bone mineral density (BMD) was recorded at the lumbar spine and total femur. RESULTS: BMD at the lumbar spine (males r = 0.15, p = 0.001; females r = 0.14, p = 0.003) and total femoral region (males r = 0.18, p = 0.0001; females r = 0.16, p = 0.0008) was related to serum triglyceride level, even after adjustment for waist-hip ratio, age, social class and lifestyle factors, but not if body fat percentage was substituted for waist-hip ratio in the regression model. Fasting HDL cholesterol level was related to lumbar spine BMD in women (r = -0.15, p = 0.001) and total femoral BMD in both sexes (males r = -0.15, p = 0.002; females r = -0.23, p < 0.0001); these relationships were also attenuated by adjustment for body fat percentage but not waist-hip ratio. No relationships were seen between total or LDL cholesterol with BMD. DISCUSSION: In this cohort, relationships between lipid profile and BMD were robust to adjustment for one measure of central obesity (waist-hip ratio), but not total body fat. This broadly supports the idea that adiposity may confound the relationship between lipids and bone mass.     

Extended long-term culture reveals a highly quiescent and primitive human hematopoietic progenitor population

Long-term culture-initiating cells (LTC-IC) are hematopoietic progenitors able to generate colony-forming unit-cells (CFU) after 5 to 8 weeks (35 to 60 days) of culture on bone marrow (BM) stroma and represent the most primitive progenitors currently detectable in vitro. We have recently reported that long-term cultures initiated with CD34+CD38- cells from BM or cord blood are able to continue generating CFU for at least 100 days, ie, beyond the standard LTC-IC period. In this report, single-cell cultures from cord blood and retroviral marking of cord blood and BM were used to study whether the subpopulation of CD34+CD38- cells able to generate CFU beyond 60 days ("extended long-term culture-initiating cells" or ELTC-IC) are functionally distinct from LTC-IC in terms of timing of initial clonal proliferation and generative capacity. All cord blood LTC-IC formed clones of greater than 50 cells by day 30. In contrast, cord blood ELTC- IC proliferated later in culture, 50% forming clones after day 30. Although efficient retroviral marking of LTC-IC was seen (25% to 45%), marking of ELTC-IC was inefficient (< 1%), consistent with a more quiescent progenitor population. There was a positive correlation between time of clonal proliferation and generative capacity. ELTC-IC generated threefold to fourfold more progeny than did LTC-IC (P < .002). These studies show that there is a functional hierarchy of progenitors in long-term culture which correlates with their level of quiescence. By extending the LTC-IC assay, a more primitive progenitor may be studied that may be functionally closer to the human long-term repopulation stem cell in vivo.     

Mechanism of the inhibition of mutagenicity of a benzo[a]pyrene 7,8-diol 9,10-epoxide by riboflavin 5''-phosphate.

Riboflavin 5'-phosphate (flavin mononucleotide; FMN) inhibits the mutagenicity of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (B[a]P diol epoxide), the only known ultimate carcinogenic metabolite of benzo[a]pyrene. Coincubation of 10, 25, and 50 nmol of FMN with strain TA100 of histidine-dependent Salmonella typhimurium inhibits the mutagenicity of 0.05 nmol of the diol epoxide by 50, 70, and 90%, respectively. Ribose 5-phosphate and riboflavin show no significant effects at comparable doses. Reaction of B[a]P diol epoxide with FMN in aqueous solution at neutral pH produces only tetraols, with no evidence for covalent adducts. At pH 7 the rate of hydrolysis of B[a]P diol epoxide in dioxane/water, 1:9 (vol/vol), at 25 degrees C is increased more than 10-fold in the presence of 100 muM FMN. Spectrophotometric studies and quantitative rate data for the reaction of the diol epoxide with FMN indicate that a complex is formed between the diol epoxide and the flavin moiety of FMN (Ke = 1,400-3,400 M-1) prior to general acid-catalyzed hydrolysis of the epoxide to tetraols by the phosphate monoanion of FMN. Comparable concentrations of ribose 5-phosphate and riboflavin do not significantly increase the rate of hydrolysis, although evidence for complex formation between riboflavin and the diol epoxide is observed. General acid-catalyzed hydrolysis of bay-region polycyclic hydrocarbon diol epoxides by compounds that have a high affinity for these ultimate carcinogens represents a potentially useful way of inhibiting their carcinogenic activity.     

Prevalence of Monogenic Causes in Pediatric Patients with Nephrolithiasis or Nephrocalcinosis

Background and objectives

Nephrolithiasis is a prevalent condition that affects 10%–15% of adults in their lifetime. It is associated with high morbidity due to colicky pain, the necessity for surgical intervention, and sometimes progression to CKD. In recent years, multiple monogenic causes of nephrolithiasis and nephrocalcinosis have been identified. However, the prevalence of each monogenic gene in a pediatric renal stone cohort has not yet been extensively studied.

Design, setting, participants, & measurements

To determine the percentage of cases that can be explained molecularly by mutations in one of 30 known nephrolithiasis/nephrocalcinosis genes, we conducted a high-throughput exon sequencing analysis in an international cohort of 143 individuals <18 years of age, with nephrolithiasis (n=123) or isolated nephrocalcinosis (n=20). Over 7 months, all eligible individuals at three renal stone clinics in the United States and Europe were approached for study participation.

Results

We detected likely causative mutations in 14 of 30 analyzed genes, leading to a molecular diagnosis in 16.8% (24 of 143) of affected individuals; 12 of the 27 detected mutations were not previously described as disease causing (44.4%). We observed that in our cohort all individuals with infantile manifestation of nephrolithiasis or nephrocalcinosis had causative mutations in recessive rather than dominant monogenic genes. In individuals who manifested later in life, causative mutations in dominant genes were more frequent.

Conclusions

We present the first exclusively pediatric cohort examined for monogenic causes of nephrolithiasis/nephrocalcinosis, and suggest that important therapeutic and preventative measures may result from mutational analysis in individuals with early manifestation of nephrolithiasis or nephrocalcinosis.     

Birth weight and muscle strength: A systematic review and meta-analysis

Objective: Lower muscle strength is associated with a range of adverse health outcomes in later life. The variation in muscle strength between individuals is only partly accounted for by factors in adult life such as body size and physical activity. The aim of this review was to assess the strength of the association between intrauterine development (indicated by birth weight) and subsequent muscle strength. Design: Systematic review and meta-analysis of studies that assessed the association between birth weight and subsequent muscle strength. Results: Nineteen studies met inclusion criteria with 17 studies showing that higher birth weight was associated with greater muscle strength. Grip strength was used as a single measure of muscle strength in 15 studies. Meta-analysis (13 studies, 20 481 participants, mean ages 9.3 to 67.5) showed a 0.86 kg (95% CI 0.58, 1.15) increase in muscle strength per additional kilogram of birth weight, after adjustment for age, gender and height at the time of strength measurement. Conclusion: This review has found consistent evidence of a positive association between birth weight and muscle strength which is maintained across the lifecourse. Future work will be needed to elucidate the biological mechanisms underlying this association, but it suggests the potential benefit of an early intervention to help people maintain muscle strength in later life.     

Does sarcopenia originate in early life? Findings from the Hertfordshire cohort study

BACKGROUND: Sarcopenia is defined as the loss of skeletal muscle mass and strength with aging. Recent epidemiological studies have shown that men and women who grew less well in early life have lower muscle strength. Our objective was to investigate the relationship between birth weight, infant growth, and the development of sarcopenia. METHODS: We studied 730 men and 673 women, of known birth weight and weight at 1 year, who were born in Hertfordshire, U.K., between 1931 and 1939. Participants completed a health questionnaire, and we measured their height, weight, and grip strength. Standard deviation scores for birth weight, and for infant growth conditional on birth weight, were analyzed in relation to grip strength before and after adjustment for adult size. RESULTS: Grip strength was most strongly associated with birth weight in men (r = 0.19, p < .001) and women (r = 0.16, p < .001). These relationships remained significant after adjustment for adult height and weight. In contrast, the associations with infant growth were weakened after allowing for adult size. Adjustment for age, current social class, physical activity, smoking, and alcohol did not affect these results. CONCLUSIONS: Birth weight is associated with sarcopenia in men and women, independently of adult height and weight. The influence of infant growth on long-term muscle strength appears to be mediated through adult size. Sarcopenia may have its origins in early life, and identifying influences operating across the whole life course may yield considerable advances in developing effective interventions.     

Isolated C3–C4 disc herniations present as a painless myelopathy

BACKGROUND CONTEXT: Cervical disc herniations at the C3-C4 level are distinctly uncommon. The authors present the first case series of isolated C3-C4 disc herniations presenting with myelopathy. PURPOSE: To elucidate a rare presentation of the uncommon C3-C4 disc herniation. STUDY DESIGN: Case series. PATIENT SAMPLE: The four patients who presented with myelopathy caused by isolated C3-C4 disc herniations, at the spine unit, Vancouver General Hospital between 1999 and 2005. OUTCOME MEASURE: Improvement in neurological status. METHODS: We retrospectively reviewed the files of the patients. The clinical features and outcome of surgery were assessed. RESULTS: The C3-C4 disc herniation can present as with no or mild pain, and hand numbness was a prominent symptom. Early recognition and treatment led to favorable outcome. CONCLUSIONS: Myelopathy is rarely caused by a C3-C4 disc herniation. This etiology may be underdiagnosed but has a more favorable outcome in those cases where rapid diagnosis is followed by spinal cord decompression.