Women with neurofibromatosis 1 are at a moderately increased risk of developing breast cancer and should be considered for early screening

BACKGROUND

Malignancy risks in patients with neurofibromatosis 1 (NF1) are increased, but those occurring outside of the nervous system have not been clearly defined.

AIM

To evaluate the risk of breast cancer in women with NF1 in a population-based study.

METHODS

The risk of breast cancer in a cohort of 304 women with NF1 aged >or=20 years was assessed and compared with population risks over the period 1975-2005 using a person-years-at-risk analysis.

RESULTS

There were 14 cases of breast cancers in the follow-up period, yielding a standardised incidence ratio (SIR) of 3.5 (95% CI 1.9 to 5.9). However, six breast cancers occurred in women in their 40s, and the SIR of breast cancer in women aged <50 years was 4.9 (95% CI 2.4 to 8.8).

INTERPRETATION

Women with NF1 aged <50 years have a fivefold risk of breast cancer, are in the moderate risk category and should be considered for mammography from 40 years of age.

Phenocopies in BRCA1 and BRCA2 families: evidence for modifier genes and implications for screening

BACKGROUND

The identification of BRCA1 and BRCA2 mutations in familial breast cancer kindreds allows genetic testing of at-risk relatives. Those who test negative are usually reassured and additional breast cancer surveillance is discontinued. However, we postulated that in high-risk families, such as those seen in clinical genetics centres, the risk of breast cancer might be influenced not only by the BRCA1/BRCA2 mutation but also by modifier genes. One manifestation of this would be the presence of phenocopies in BRCA1/BRCA2 kindreds.

METHODS

277 families with pathogenic BRCA1/BRCA2 mutations were reviewed and 28 breast cancer phenocopies identified. The relative risk of breast cancer in those testing negative was assessed using incidence rates from our cancer registry based on local population.

RESULTS

Phenocopies constituted up to 24% of tests on women with breast cancer after the identification of the mutation in the proband. The standardised incidence ratio for women who tested negative for the BRCA1/BRCA2 family mutation was 5.3 for all relatives, 5.0 for all first-degree relatives (FDRs) and 3.2 (95% confidence interval 2.0 to 4.9) for FDRs in whose family all other cases of breast and ovarian cancer could be explained by the identified mutation. 13 of 107 (12.1%) FDRs with breast cancer and no unexplained family history tested negative.

CONCLUSION

In high-risk families, women who test negative for the familial BRCA1/BRCA2 mutation have an increased risk of breast cancer consistent with genetic modifiers. In light of this, such women should still be considered for continued surveillance.

No association between the +874T/A single nucleotide polymorphism in the IFN-gamma gene and susceptibility to TB

A single nucleotide polymorphism (SNP), +874T/A, in the first intron of the interferon-gamma (IFN-gamma) gene, has presented associations with human susceptibility to tuberculosis (TB) in some ethnic populations, but not in others. In this population-based case-control study with adult TB patients from Houston, Texas, we found no significant differences of + 874T/A genotypic frequencies between cases and ethnically-matched controls or between advanced forms of TB disease (extra-pulmonary involvement or presence of cavitary disease) and pulmonary TB. Given possible sample size limitations, our results suggest that the IFN-gamma +874T/A mutation has no association with TB susceptibility or TB disease severity.

Chemotherapy alternating gemcitabine and cisplatin concomitant with radiotherapy in locally advanced (LA) squamous cell carcinoma of the head and neck (SCCHN)

15514

Background: In the Pignon’s meta-analysis, the OS benefit was 8% with chemoradiation in LA SCCHN. Unfortunately it is still unclear what scheme is the best, cisplatin (CDDP) being the most widely used drug. Other drugs such as gemcitabine (GMZ) has promising results, although toxicity has been severe but tolerable. We have published an initial study using GMZ and radiotherapy (ann oncol. 2004;15:301). In the present study we wished to determine if a scheme in which GMZ is alternated with CDDP and concomitant radiotherapy reduced toxicity yet maintains our previously described therapeutic effectiveness. This is a preliminary report with a short follow-up period. Methods: Inclusion criteria: patients with SCCHN (EC: III, IVa and IVb ) or with recurring disease, and no sytemic metastases or patients rejection of surgery between 03/2003 and 09/2004. Chemotherapy scheme consisted of GMZ at 100 mg/m2 once a w, ws 1, 3, 5, 7 and CDDP at 50 mg/m2 once a w, ws 2, 4, y 6. Radiotherapy consisted of 2 Gy/day, for a total of 70 Gy during the 7 ws. Toxicity evaluation focused on mucositis, xerostomia, dysphagia y leukopenia. Results: 28 patients were treated. 7 (25%)/ stage III, 11 (39.3%) IVa, 10 (35.7%) IVb. The tumor sites distribution was as follows: 9 patients with oropharynx and larynx disease (32.1%), 6 patients with oral cavity disease (21.4%), 3 patients with paranasal sinus disease (10.7%), and 1 hypopharinx (3.5%). A CCR was observed in 21 patients (75%), a partial response was observed in 5 patients (17%). Organ preservation was achieved in 68% of the patients. Toxicity: mucositis Grade 3–4 was in 42% of patients, leucopenia grade III in 29%, dysphagia in 19% and xerostomia in 10%. 40%of the patients stopped treatment for one or two weeks due to toxicity without affecting the doses of both treatments. Conclusions: The scheme with alternating GMZ and CDDP concomitant with radiotherapy is safe and effective. We observed a lower incidence in mucositis and few systemic toxic effects. Our findings support further studies in which alternating chemotherapeutic schemes are utilized given that tumor response is increased without an increment in toxicity.

No significant financial relationships to disclose.

Phase II clinical trial preliminary report: Cetuximab, gemcitabine and simultaneous radiotherapy for locally advanced head and neck cancer: Preliminary report

15502

Background: Previous studies with cetuximab in SCCHN demonstrate to be clinically beneficial. In the present study we wished to evaluate the efficacy and safety of a chemotherapeutic scheme using gemcitabine, radiotherapy and cetuximab for SCCHN. Preliminary report of 20 of 40 enrolled patients into a phase II clinical trial. Methods: inclusion criteria; histological confirmation of epidermoid carcinoma, ages 18 to 70, K > 70%, normal renal, hepatic and haematologic functions, without previous treatment, surgically inoperable disease, or patients with operable disease that did not consent to surgery. All patients signed an informed consent form. Radiotherapy: 200 cGy/d/5/w until 70Gy were completed. Cetuximab: an initial dose of 400 mg/m2 one week prior to initiation of radiotherapy, followed by 250 mg/m2 weekly until completion of radiotherapy. Gemcitabine: 50 mg /m2 weeks 1–2, 4–5 and 7. Results: 20 patients were enrolled (16m/4f) from november of 2004 to november of 2005, (5 oral cavity, 5 oropharynx, 8 larynx, 1 hypopharynx and 1 paranasal sinus). Mean age 56 yrs (33–75). Tumor staging: 7/III, 8/IVa and 5/IVb. One female was excluded, 19 completed the study and were evaluated. GR 17/19 (89.5%), CR 13/17 (76.5%) and PR 4/17 (23.5%). 2/19 NR (10.5%). CR of the 1ary tumor 15/19 patients (78.9%); CR 6/11 patients with lymphatic disease at diagnosis (54.5%), PR 3/19 (27.3%). Toxicity: mucositis g/III-IV 8/19 patients; rash g/III 4 patients. 2/19 did not complete treatment with chemotherapy due to mucositis but did with radiotherapy. No relationship was found between clinical response and the severity of the rash. One patient developed leukopenia g/III. 4 patients developed disphagia g/II, one has not resolved after 8 month follow up. Xerostomia g/II was 7/19 patients. Dermatological toxicity resolved by the end of the treatment. Mean follow up: 6 months, 1 patient which did not respond died and 1 patient with a PR recurred. Conclusions: The scheme is safe and effective with tolerable toxicity. In our previously reported experience, the addition of cetuximab to gemcitabine and radiotherapy does not increment local toxicity, statistical validation of these findings require the completion of the 40 patient study.

No significant financial relationships to disclose.

Nephrotoxicity of uranyl acetate: effect on rat kidney brush border membrane vesicles

Since the Gulf war exposure to depleted uranium, a known nephrotoxic agent, there is a renewed interest in the toxic effects of uranium in general and its mechanism of nephrotoxicity which is still largely unknown in particular. In order to investigate the mechanism responsible for uranium nephrotoxicity and the therapeutic effect of urine alkalization, we utilized rat renal brush border membrane vesicles (BBMV). Uranyl acetate (UA) caused a decrease in glucose transport in BBMV. The apparent K (i) of uranyl was 139+/-30 microg uranyl/mg protein of BBMV. Uranyl at 140 microg/mg protein of BBMV reduced the maximal capacity of the system to transport glucose [V (max) 2.2+/-0.2 and 0.96+/-0.16 nmol/mg protein for control and uranyl treated BBMV (P<0.001), respectively] with no effect on the apparent K (m) (1.54+/-0.33 and 1.54+/-0.51 mM for control, and uranyl treated BBMV, respectively). This reduction in V(max) is at least partially due to a decrease in the number of sodium-coupled glucose transporters as apparent from the reduction in phlorizin binding to the uranyl treated membranes, V (max) was reduced from 247+/-13 pmol/mg protein in control BBMV to 119+/-3 pmol/mg protein in treated vesicles (P<0.001). The pH of the medium has a profound effect on the toxicity of UA on sodium-coupled glucose transport in BBMV: higher toxicity at neutral pH (around pH 7.0), and practically no toxicity at alkaline pH (7.6). This is the first report showing a direct inhibitory dose and pH dependent effect of uranyl on the glucose transport system in isolated apical membrane from kidney cortex.

Insulin resistance (metabolic) syndrome in children

The insulin resistance (metabolic) syndrome (IRS), also known as syndrome X, is characterized by a clustering of factors associated with cardiovascular risk (obesity, impaired glucose metabolism, hypertension, and dyslipidemia). As reported from the third National Health and Nutrition Examination survey, the IRS is present in approximately 24% of adults in the United States and is strongly associated with coronary heart disease, stroke, type 2 diabetes, and all-cause mortality. Of equal importance, it is now clear that the origins of the IRS extend back into childhood (the IRS is found in approximately 4-10% of children and adolescents) and that the high prevalence of adult IRS is strongly linked to the development of cardiovascular risk during childhood and tracking of the components of the IRS into adulthood. The goal of this review is to present a summary of the currently available information on the IRS in the pre-adult age group with reference to adult studies only when necessary for clarification. The review will specifically summarize insulin resistance in childhood; the important influence of obesity and, in particular, visceral fat, on insulin resistance and the IRS; differences between ethnic groups; relations to adipocytokines, inflammatory factors and oxidative stress; relations of hypertension and lipids to insulin resistance; familial factors; endocrine complications; and potential therapeutic effects from diet and physical activity. Despite the lesser amount of basic and clinical information on childhood IRS in comparison to information available from adult studies, there can now be little doubt that the adverse associations among risk factors comprising the IRS begin in childhood. The challenge is to identify etiologic relations and develop intervention strategies designed to reduce the increasing prevalence of type 2 diabetes and cardiovascular disease.

It's good to talk: children's views on food and nutrition

OBJECTIVE

To gain an insight into children's views about food and nutrition.

DESIGN

Data were collected in focus group discussions; two focus group sessions were undertaken with each school group.

SETTING

A total of 11 postprimary schools in Northern Ireland and England.

SUBJECTS

In all, 106 children aged 11-12-y-old (n = 52 boys, n = 54 girls).

RESULTS

Focus group transcripts were analysed using qualitative research methodology. Major barriers to healthy eating were taste, appearance of food, filling power, time/effort, cost, choice/availability, risk, rebellion, and body image/weight concerns. The main difference between sexes was in terms of motivating factors for eating well; girls tended to focus primarily on their appearance whereas boys appeared to be more influenced by sport. There was some mention of balance and variety within the focus group discussions, however, in practice, the children had a tendency to categorise foods as either 'good' or 'bad', 'healthy' or 'unhealthy'.

CONCLUSIONS

This study has revealed a number of barriers to, and motivations for, healthy eating, which should be taken into account when planning nutrition intervention strategies aimed at children moving into adolescence. While it may be possible to immediately attempt to address some of the barriers identified in this study, for example, in nutrition education initiatives, other barriers (such as the lack of available, attractive and affordable healthy foods in the school canteen) will prove more difficult to tackle without changes at the policy level. Overall, it appears that health promotion specialists have a major challenge ahead in order to encourage this age group to view healthy eating as an attractive and achievable behaviour.

SPONSORSHIP

Food Standards Agency, London, UK.

Comparison of body fatness measurements by BMI and skinfolds vs dual energy X-ray absorptiometry and their relation to cardiovascular risk factors in adolescents

OBJECTIVE

To compare estimates of adiposity by dual emission X-ray absorptiometry (DXA), skinfolds and body mass index (BMI); and to evaluate the relation of these measures to cardiovascular risk in adolescents.

DESIGN

In a cohort of adolescents participating in a longitudinal study of insulin resistance, Slaughter formulas were used to estimate adiposity from skinfolds and DXA was used to estimate adiposity as % body fat (%BF) and fat mass (FBM). BMI, blood pressure, lipids and insulin resistance were measured.

SUBJECTS

Male and female, 11-17 y old (n=130).

MEASUREMENTS

To compare DXA with two office-based methods of assessing fatness and cardiovascular risk.

RESULTS

Slaughter estimates were highly correlated with DXA (%BF r=0.92, P=0.0001; FBM r=0.96, P=0.0001). Correlations were similar in heavy and thin children. BMI was also highly correlated with DXA (%BF r=0.85, P=0.0001; FBM r=0.95, P=0.0001), and these relations were stronger in heavy than thin children. BMI and the Slaughter formulas were similar to DXA in their relations to cardiovascular risk factors.

CONCLUSIONS

Adiposity by BMI and Slaughter formulas are highly correlated with DXA and similarly related to cardiovascular risk factors. BMI is easy to obtain and is an acceptable method for initial office estimation of body fatness. BMI and skinfolds compare well with DXA in predicting adverse cardiovascular risk profile.

Bladder cancer: worse survival in women from deprived areas

In a case-note review of 120 women and 227 men presenting with muscle-invasive bladder tumours in 1998, survival was worse for women in 3 years of follow-up, with the greatest difference, of 19.9%, at 6 months. For more deprived women, 6-month survival was 52.3%, and 32 (37.2%) presented with advanced disease, compared with 73.5%, and three (8.8%) for less deprived women.

Evaluation of breast cancer risk assessment packages in the family history evaluation and screening programme

INTRODUCTION

Accurate individualised breast cancer risk assessment is essential to provide risk-benefit analysis prior to initiating interventions designed to lower breast cancer risk. Several mathematical models for the estimation of individual breast cancer risk have been proposed. However, no single model integrates family history, hormonal factors, and benign breast disease in a comprehensive fashion. A new model by Tyrer and Cuzick has addressed these deficiencies. Therefore, this study has assessed the goodness of fit and discriminatory value of the Tyrer-Cuzick model against established models namely Gail, Claus, and Ford.

METHODS

The goodness of fit and discriminatory accuracy of the models was assessed using data from 1933 women attending the Family History Evaluation and Screening Programme, of whom 52 developed cancer. All models were applied to these women over a mean follow up of 5.27 years to estimate risk of breast cancer.

RESULTS

The ratios (95% confidence intervals) of expected to observed numbers of breast cancers were 0.48 (0.37 to 0.64) for Gail, 0.56 (0.43 to 0.75) for Claus, 0.49 (0.37 to 0.65) for Ford, and 0.81 (0.62 to 1.08) for Tyrer-Cuzick. The accuracy of the models for individual cases was evaluated using ROC curves. These showed that the area under the curve was 0.735 for Gail, 0.716 for Claus, 0.737 for Ford, and 0.762 for Tyrer-Cuzick.

CONCLUSION

The Tyrer-Cuzick model is the most consistently accurate model for prediction of breast cancer. The Gail, Claus, and Ford models all significantly underestimate risk, although the accuracy of the Claus model may be improved by adjustments for other risk factors.

Novel modes of capillary electrophoresis for the determination of endocrine disrupting chemicals

The synthesis and usage of a wide range of organic chemicals has increased dramatically over the last five decades. These compounds sometimes termed endocrine disrupting chemicals include agricultural pesticides, industrial solvents, dyes, plasticisers, detergents and heat exchangers. Concerns have been raised about the potential adverse effects of these compounds on humans and wildlife species. Our objectives are to develop a method to identify, using novel capillary electrophoretic techniques, the endocrine disrupting compounds that are reported to be present in environmental samples. The CE modes, capillary zone electrophoresis, micellar electrokinetic chromatography (MEKC), cyclodextrin-modified MEKC (CD-MEKC) and electroosmotic flow-suppressed CD-MEKC were investigated for the determination of a range of endocrine disrupting chemical compounds. This paper shows some initial results obtained.

Association of physical activity with insulin sensitivity in children

BACKGROUND

Physical activity (PA) has been shown to improve insulin resistance and other cardiovascular disease risk factors in normal and diabetic adults and in obese youth, but not in non-diabetic, normal-weight children.

METHODS

Data from 357 non-diabetic children (10-16 y) were used to examine cross-sectional associations with PA. Insulin sensitivity was assessed with a euglycemic hyperinsulinemic clamp and expressed as M(ffm) (glucose utilization/kg of fat-free mass/min).

RESULTS

Correlations were adjusted for age, sex, race and Tanner stage. PA was significantly correlated with fasting insulin and insulin sensitivity (r=-0.12, P=0.03 and r=0.13, P=0.001, respectively), more strongly in children with above-median systolic blood pressure (r=-0.17, P=0.03 and r=0.35, P=0.0001, respectively). Further adjustment for body mass index, body fat percentage, waist circumference or lipids did not alter these observations.

CONCLUSIONS

Physical activity is correlated with lower fasting insulin and greater insulin sensitivity in childhood. These results are consistent with the hypothesis that increasing physical activity among youth may reduce the incidence of type 2 diabetes in children and adolescents.

Malignant peripheral nerve sheath tumours in neurofibromatosis 1

BACKGROUND

Cross sectional studies have shown that 1-2% of patients with neurofibromatosis 1 (NF1) develop malignant peripheral nerve sheath tumours (MPNST). However, no population based longitudinal studies have assessed lifetime risk.

METHODS

NF1 patients with MPNST were ascertained from two sources for our north west England population of 4.1 million in the 13 year period 1984-1996: the North West Regional NF1 Register and review of notes of patients with MPNST in the North West Regional Cancer Registry.

RESULTS

Twenty-one NF1 patients developed MPNST, equivalent to an annual incidence of 1.6 per 1000 and a lifetime risk of 8-13%. There were 37 patients with sporadic MPNST. The median age at diagnosis of MPNST in NF1 patients was 26 years, compared to 62 years in patients with sporadic MPNST (p<0.001). In Kaplan-Meier analyses, the five year survival from diagnosis was 21% for NF1 patients with MPNST, compared to 42% for sporadic cases of MPNST (p=0.09). One NF1 patient developed two separate MPNST in the radiation field of a previous optic glioma.

CONCLUSION

The lifetime risk of MPNST in NF1 is much higher than previously estimated and warrants careful surveillance and a low threshold for investigation.

Development of comparative methods using gas chromatography-mass spectrometry and capillary electrophoresis for determination of endocrine disrupting chemicals in bio-solids

Two analytical separation techniques are being investigated for their potential in determining a wide range of endocrine disrupting chemicals (EDCs) in the environment. Capillary electrophoresis (CE) in the micellar mode in conjunction with a cyclodextrin (CD) modifier is shown to have potential for determination of alkylphenol breakdown products. Gas chromatography with mass spectrometric (GC-MS) detection is being utilised for validation of the CE method development and in addition as a separation technique to optimise preconcentration using solid-phase extraction. GC has demonstrated potential for the separation of 26 priority chemicals suspected as being endocrine disrupting compounds. The challenge of the method development process lies in the fact that these compounds are of differing polarities, size and charge and therefore are difficult to separate in a single run. Capillary electrophoresis in the CD-MEKC (micellar electrokinetic chromatography) mode is showing potential in this regard. Limits of determination are in the low mg/l range for CE and GC, however, using preconcentration it is possible to improve detection sensitivity with >80% recovery for some analytes and up to 100% recovery for most target species.

Insulin resistance syndrome in childhood: associations of the euglycemic insulin clamp and fasting insulin with fatness and other risk factors

OBJECTIVE

Our objective was to describe in children the relation of fatness and insulin resistance to the risk factors associated with the insulin resistance syndrome and to compare fasting insulin with the euglycemic insulin clamp as a measure of insulin resistance in children.

STUDY DESIGN

This was a random selection of participants after blood pressure screening of 12,043 students in the fifth through eighth grades. Euglycemic insulin clamp studies with an insulin infusion rate of 1 mU/kg/min and a variable infusion of 20% glucose to maintain euglycemia, that is, plasma glucose at 5.6 mmol/L. Insulin sensitivity (M(lbm)) is defined as the amount of glucose required to maintain euglycemia (milligrams of glucose infused per kilogram lean body mass per minute).

RESULTS

Body mass index was significantly correlated with fasting insulin and significantly inversely correlated with M(lbm). Fasting insulin was significantly correlated with systolic blood pressure in both sexes, all lipids, except high-density lipoprotein-cholesterol in males and triglycerides and high-density lipoprotein-cholesterol in females, but after adjustment was done for body mass index, it was significantly related only to triglycerides. M(lbm) was significantly correlated only with triglycerides and high-density lipoprotein-cholesterol, and this did not change after adjustment was done for body mass index. A clustering effect for the risk factors was seen in children in the lowest quartile of M(lbm) (highest degree of insulin resistance) compared with children in the highest quartile of M(lbm) (lowest degree of insulin resistance).

CONCLUSIONS

As defined by M(lbm), there is an early association of insulin resistance, independent of body fat, with the risk factors. There is a significant relation between fasting insulin, as an estimate of insulin resistance, and the risk factors, but this is significantly influenced by body fatness. The clustering of risk factors according to level of M(lbm) suggests that adult cardiovascular disease is more likely to develop in children with the greatest degree of insulin resistance.

Insulin and glucose excursion following premeal insulin lispro or repaglinide in cystic fibrosis-related diabetes

OBJECTIVE

Insulin and glucose levels in response to premeal insulin lispro or repaglinide were evaluated in adult patients with cystic fibrosis-related diabetes (CFRD) without fasting hyperglycemia.

RESEARCH DESIGN AND METHODS

Seven patients with CFRD were fed 1,000-kcal liquid mixed meals. Three study conditions were administered in random order on separate mornings: 1) no premeal diabetes medication, 2) insulin lispro, 0.1 unit/kg body wt premeal and 3) repaglinide 1 mg premeal. Glucose and insulin levels were measured every 20 min for 5 h.

RESULTS

Fasting insulin and glucose levels were normal in patients with CFRD, but the peak glucose level was elevated. Insulin lispro significantly decreased the peak glucose level (P = 0.0004) and the 2-h (P = 0.001) and 5-h (P < 0.0001) glucose area under the curve (AUC). Repaglinide significantly decreased the 5-h glucose AUC (P = 0.03). Neither drug completely normalized cystic fibrosis glucose excursion at the doses used for this study. Insulin lispro significantly increased the 5-h insulin AUC (P = 0.04).

CONCLUSIONS

In response to subcutaneous insulin lispro, postprandial glucose excursion was significantly diminished and insulin secretion was enhanced compared with a control meal in which no medication was given to patients with CFRD. The oral agent repaglinide resulted in lesser corrections in these parameters. Neither drug completely normalized glucose or insulin levels, suggesting that the doses chosen for this study were suboptimal. Placebo-controlled longitudinal studies comparing the effectiveness of repaglinide and insulin on glucose metabolic control as well as overall nutrition and body weight are needed to help determine optimal medical treatment of CFRD.

A zinc-sensing receptor triggers the release of intracellular Ca2+ and regulates ion transport

Changes in extracellular zinc concentration participate in modulating fundamental cellular processes such as proliferation, secretion, and ion transport in a mechanism that is not well understood. Here, we show that a micromolar concentration of extracellular zinc triggers a massive release of calcium from thapsigargin-sensitive intracellular pools in the colonocytic cell line HT29. Calcium release was blocked by a phospholipase-C inhibitor, indicating that formation of inositol 1,4,5-triphosphate is required for zinc-dependent calcium release. Zinc influx was not observed, indicating that extracellular zinc triggered the release. The Ca(i)2+ release was zinc specific and could not be triggered by other heavy metals. Furthermore, zinc failed to activate the Ca(2+)-sensing receptor heterologously expressed in HEK293 cells. The zinc-induced Ca(i)2+ rise stimulated the activity of the Na(+)/H(+) exchanger in HT29 cells. Our results indicate that a previously uncharacterized extracellular, G protein-coupled, Zn(2+)-sensing receptor is functional in colonocytes. Because Ca(i)2+ rise is known to regulate key cellular and signal-transduction processes, the zinc-sensing receptor may provide the missing link between extracellular zinc concentration changes and the regulation of cellular processes.

Functional analysis of patient-derived mutations in the Fanconi anemia gene, FANCG/XRCC9

OBJECTIVE

Fanconi anemia (FA) is an autosomal-recessive cancer susceptibility syndrome with seven complementation groups. Six of the FA genes have been cloned (corresponding to subtypes A, C, D2, E, F, and G) and the encoded proteins interact in a common pathway. Patient-derived mutations in FA genes have been helpful in delineating functional domains of FA proteins. The purpose of this work was to subtype FA patient-derived cell lines in our repository and to identify FA gene mutations.

METHODS

We subtyped 62 FA patients as type A, G, C, or non-ACG by using a combination of retroviral gene transfer and immunoblot analysis. Among these FA patients, we identified six FA-G patients for further analysis. We used a strategy involving amplification of FANCG/XRCC9 exons and direct sequencing to identify novel FANCG mutations in cell lines derived from these FA-G patients. We functionally analyzed FANCG mutant alleles by transducing the corresponding cDNAs into a known FA-G indicator cell line and scoring correction of MMC sensitivity.

RESULTS

Our results demonstrate a wide range of mutations in the FANCG gene (splice, nonsense, and missense mutations). Based on this mutational screen, a carboxy terminal functional domain of the FANCG protein appears to be required for complementation of FA-G cells and for normal assembly of the FANCA/FANCG/FANCC protein complex.

CONCLUSION

The identification of patient-derived mutant alleles of FA genes can provide important insights to the function of FA proteins. FA subtyping is also a necessary precondition for gene therapy.

Protein metabolism in clinically stable adult cystic fibrosis patients with abnormal glucose tolerance

Cystic fibrosis (CF) patients are reported to experience chronic protein catabolism. Since diabetes or impaired glucose tolerance (IGT) is common in CF, we hypothesized that their protein catabolic state is related to reduced insulin secretion or reduced insulin action. A total of 12 clinically stable adult CF patients with abnormal glucose tolerance and 12 age-, sex-, and lean body mass-matched healthy control subjects underwent protein turnover studies using L-[1-(13)C]leucine, L-[(15)N]phenylalanine, and L-[(2)H(4)]tyrosine, with and without exogenous insulin infusion. In the baseline fasting state, protein metabolism was entirely normal in CF patients, with no evidence of increased protein catabolism. In contrast, striking abnormalities were seen in CF patients when insulin was infused, since they did not experience normal suppression of the appearance rates of leucine, phenylalanine, or tyrosine (indexes of protein breakdown). At an insulin concentration of 45 +/- 2 microU/ml, normal control subjects suppressed the leucine appearance rate by 19 +/- 5% (P < 0.01), ketoisocaproate appearance rate by 10 +/- 3% (P = 0.03), tyrosine appearance rate by 11 +/- 2% (P = 0.03), and phenylalanine appearance rate by 6 +/- 3% (P = 0.07). Phenylalanine conversion to tyrosine decreased by 22 +/- 7% (P = 0.03). At a similar insulin concentration of 44 +/- 3 microU/ml, normal suppression of amino acid appearance did not occur in CF. The leucine appearance rate decreased by 4 +/- 2% (P = 0.65), ketoisocaproate appearance rate by 1 +/- 2% (P = 0.94), tyrosine appearance rate by 0 +/- 6% (P = 0.56), phenylalanine appearance rate by 5 +/- 6% (P = 0.34), and phenylalanine conversion to tyrosine by 5 +/- 6% (P = 0.95). Poor suppression of the amino acid appearance rate in CF was not related to previously documented glucose tolerance status (IGT or CF-related diabetes without fasting hyperglycemia), fasting insulin levels, the acute insulin response, insulin sensitivity, cytokine or counterregulatory hormone levels, resting energy expenditure, caloric intake, pulmonary function, or clinical status. Protein synthesis was not significantly affected by insulin infusion in either normal control subjects or CF patients. In conclusion, clinically stable adult CF patients have normal indexes of protein breakdown and synthesis in the fasting state. In contrast, elevation of plasma insulin to physiological postprandial levels fails to normally suppress indexes of protein breakdown. It is therefore likely that inability to spare protein during the postprandial state is the cause of protein catabolism in these patients.

Adiposity in childhood predicts obesity and insulin resistance in young adulthood

OBJECTIVE

To determine whether adiposity in children predicts adiposity, insulin resistance, and abnormal lipid levels in young adults.

STUDY DESIGN

Children (n = 31) were recruited into an epidemiologic study at age 13.3 +/- 0.3 years and had blood pressure, weight, and height measured. They were reevaluated at age 21.8 +/- 0.3 years at which time the measurements were repeated, a euglycemic insulin clamp was performed, and fasting lipid levels were measured. All values are expressed as mean +/- SEM. Data were analyzed by analysis of variance and linear regression analysis.

RESULTS

Body mass index (BMI) in childhood (22.6 +/- 0.6) was highly correlated with BMI in young adulthood (26.9 +/- 0.9). Childhood BMI was also inversely correlated with young adult glucose utilization (r = -0.5, P = .006) and positively correlated with total cholesterol (r = 0.37, P = .05), and low-density lipoprotein (LDL) cholesterol (r = 0.48, P = .01).

CONCLUSIONS

These data confirm that adiposity in childhood is a strong predictor of young adult adiposity. In addition, these results demonstrate that cardiovascular risk in young adulthood is highly related to the degree of adiposity as early as age 13.

Smoking and quitting among Irish teenage males

Nicotine addiction in adulthood is usually preceded by exposure to cigarettes in adolescence. A minimal exposure may be sufficient to produce addiction. Strategies to reduce adult smoking must address those factors, which influence teenage smoking. In this study we aimed to establish the prevalence of smoking in male secondary schools, to measure the association between student's smoking status and parental, peer and sibling smoking and to describe attempted quitting. An anonymous questionnaire was given to 1070 male secondary school pupils in two schools in County Louth. Twenty-seven percent of respondents smoked every day or on most days. Having a best friend who smoked was associated with personal smoking (O.R. 11.75, C.I. 8.6-16.08) as was sibling smoking (O.R. 3.49, C.I. 2.67-4.57.) Seventy percent of smokers stated that they wanted to stop and 75% that they had tried to stop. Only five smokers (1.2%) had been advised to quit by their general practitioner. We conclude that smoking is as prevalent among teenage boys in Ireland as it has been shown to be elsewhere and that most teenagers are unable rather than unwilling to stop.