Increased adiponectin receptor-1 expression in adipose tissue of impaired glucose-tolerant obese subjects during weight loss

OBJECTIVE

To investigate the mRNA expression of adiponectin, AdipoR1 and AdipoR2, the two recently cloned adiponectin receptors and peroxisome proliferator activated receptor (PPAR)gamma2 in adipose tissue of obese individuals before and during a very low calorie diet (VLCD) inducing weight loss.

METHODS

Twenty-three non-diabetic obese subjects with normal (NGT, n = 11) or impaired glucose tolerance (IGT, n = 12) (age, 47 +/- 3 years; body mass index, 39.3 +/- 1.3 kg/m2) were studied before and after a 3-week 3.9 MJ diet daily without exercise. mRNA levels of nine IGT and six NGT subjects were measured by real-time PCR in s.c. abdominal adipose tissue.

RESULTS

Metabolic parameters and insulin sensitivity were improved by VLCD in the IGT group, but minimally affected in the NGT group. VLCD increased expression of AdipoR1 in the IGT (P = 0.02), but not in the NGT group. Adiponectin, AdipoR2 and PPARgamma2 mRNA levels did not change during VLCD in any group. In the IGT, but not in the NGT group, AdipoR1 and AdipoR2 expressions were positively related to that of PPARgamma2 and, after VLCD, AdipoR1 and AdipoR2 expressions were positively related to each other and to that of adiponectin.

CONCLUSION

In the NGT group, the 3-week VLCD inducing weight loss did not modify metabolic parameters, insulin sensitivity and the expression of the adiponectin system in adipose tissue. By contrast, in the IGT group, AdipoR1 expression increased and we found a coordinate regulation of the expression of adiponectin and its receptors. These modifications could participate, through adiponectin action on adipocytes, to the improved metabolic parameters observed in IGT subjects.

Adrénoleucodystrophie liée à l'X chez une proposante symptomatique : présentation clinique, diagnostic biologique et conséquences familiales

INTRODUCTION

X-linked adrenoleukodystrophy (ALD) is the most frequent type of leukodystrophy (1/17 000 males). The phenotypic range in male patients varies from the severe cerebral presentations in children to the milder myeloneuropathy and to isolate adrenal insufficiency. More than a half of the carrier females display clinical symptoms over the age of 40 years.

OBSERVATION

Diagnosis of ALD was raised in a 40 year-old female who presented with spastic paraparesis and sphincterian dysfunction, occurring after the delivery of her first child. There was no family history of ALD. Very long-chain fatty acids (VLFCA) were assayed in her one-year-old son in order to propose appropriate hormonal and neurological survey. His dosage was abnormal and an adrenal insufficiency was subsequently found. A brain MRI will be proposed biannually when he reaches to age of for years. The proband's mother had an increased level of VLCFA, showing that she was a carrier. Family screening was extended to the proband's sisters and maternal aunt who already had children, but also to her brother, who may express a mild form of the disease later on, and to her maternal uncles who might be asymptomatic carriers. A frameshift mutation was found in the ABCD1 gene and will allow accurate carrier identification and prenatal diagnosis in the family.

CONCLUSION

ALD diagnosis should be evoked in a woman affected by myelopathy despite the lack of family history. Such a diagnosis has severe consequences since some of the related males may carry the mutation although they do not display any symptom at time of diagnosis, and because carrier females have a risk to both have a clinical expression of the disease and give birth to an affected boy.

[Alpha 2 macroglobulin immunoturbidimetric assays (DakoCytomation reagents) on Roche Diagnostic analysers (Modular P, Cobas Integra). Application to FibroTest-Actic-Test]

BACKGROUND

Alpha2Macroglobulin (A2M) measure showed a revival since it was introduced into FibroTest-ActiTest-Fibro (FT-AT-Fibro) algorithm. More often than not, this assay is performed in immunonephelemetry. Progresses in the comprehension of fibrosis dynamics and better treatment efficacy follow-up will increase FT-AT-Fibro prescriptions. Despite efforts to standardize methods of enzymatic activity measure and proteins measure, we still observe important interlaboratory and intersystem variability.

AIM

The primary aim of the study is to validate immunoturbidimetric measure of A2M on Modular P and Cobas Integra analysers (Roche Diagnostics) in utility channel using DakoCytomation reagents in order to extend the analytical system range allowed to measure A2M. The secondary aim of the study is to verify transferability of the six FT-AT composants (A2M, haptoglobin, apolipoprotein A1, total bilirubin, GGT and ALT) to Roche Diagnostics equipment by comparing with results measured on the reference system.

RESULTS

A2M measures (n = 146) showed linearity, repetitiveness and were reproducible. Readjustments to adapt A2M measures were required. A corrector factor of 0.84 for Modular P and of 0.87 for Cobas Integra was introduced in order to readjust the immunoturbidimetric method to the immunonephelemetric method. The rationale of proposed corrector factors is based on the use of Dade Behring and DakoCytomation reagents (antisera and calibrant). Biologist vigilance is required to point out modifications or variations in reagents that could be done by the company. The six parameters results transferability from the reference system to Roche Diagnostics was demonstrated by statistic analysis. FT-AT showed excellent correlations to the reference system for Modular P and Cobas Integra analysers. In this study no difference more than 0.11 was recorded and only few subjects had differences between 0.05 and 0.10. Therefore this very low inter-analysers variability has no significant clinical impact.

CONCLUSION

This study showed that the analytical system made of Modular P, Cobas Integra, Roche Diagnostics and DakoCytomation reagents can be used for FibroTest-ActiTest-Fibro parameters assessment. Their statistical and clinical variability were acceptable compared to the reference system.

[Results transferability on RXL, ARX, X-Pand, BN2 (Dade Behring) and modular DP (Roche Diagnostics) analysers: application to component assays of fibrotest and Actitest]

The follow up of patients with chronic liver diseases and the data from multicentric clinical studies are affected by the variability of assay results for the same parameter between the different laboratories. Today, the main objective in clinical chemistry throughout the world is to harmonise the assay results between the laboratories after the confirmation of their traceability, in relation to defined reference systems. In this context, the purpose of our study was to verify the homogeneity of haptoglobin, apolipoprotein A1, total bilirubin, GGT activity, ALAT activity results, which are combined in Fibrotest and Actitest, between Dimension Analysers RXL, ARX and X-PAND (Dade Behring Society). Moreover, we verified the transferability of Fibrotest and Actitest results between the RXL, and either the BN2 (haptoglobin and apolipoprotein A1) or the Modular DP (total bilirubin, GGT and ALAT activity concentrations). The serum samples from 150 hospitalised patients were analysed on the different analysers. Specific protein assays were calibrated using solutions standardised against reference material on Dimension and BN2 analysers. Total bilirubin assays were performed by a diazoreaction on Dimension and Modular DP analysers. The GGT and ALAT activity measurements on the Dimension analysers were performed in accordance with the reference methods defined by the International Federation of Clinical Chemisty and Laboratory Medicine (IFCC). On the Modular, enzyme activity measurements were performed according to the Szasz method (L-gamma- glutamyl-4-nitroanilide as substrate) modified by Persijn and van der Slik (L-gamma- glutamyl-3-carboxy- 4-nitroanilide as substrat) for GGT and according to the IFCC specifications for ALAT. The methods of enzymatic activity measurement were calibrated on the Modular only. Liver fibrosis and necroinflammatory activity indices were determined using calculation algorithms, after having adjusted each component's result of Fibrotest and Actitest for gender and age. Our study has shown, for each parameter, harmonious results between the Dimension analysers and between RXL and BN2- Modular DP. Disregarding alpha-2 macroglobulin which cannot be assayed on RXL, the results of Fibrotest and Actitest were similar as performed on BN2- Modular DP and RXL.

New mutations of SCN4A cause a potassium-sensitive normokalemic periodic paralysis

BACKGROUND

Periodic paralysis is classified into hypokalemic (hypoPP) and hyperkalemic (hyperPP) periodic paralysis according to variations of blood potassium levels during attacks.

OBJECTIVE

To describe new mutations in the muscle sodium channel gene SCN4A that cause periodic paralysis.

METHODS

A thorough clinical, electrophysiologic, and molecular study was performed of four unrelated families who presented with periodic paralysis.

RESULTS

The nine affected members had episodes of muscle weakness reminiscent of both hyperPP and hypoPP. A provocative test with potassium chloride was positive in two patients. However, repeated and carefully performed tests of blood potassium levels during attacks resulted in normal potassium levels. Remarkably, two patients experienced hypokalemic episodes of paralysis related to peculiar provocative factors (corticosteroids and thyrotoxicosis). Similarly to hyperPP, electromyography in nine patients revealed increased compound muscle action potentials after short exercise and a delayed decline during rest after long exercise as well as myotonic discharges in one patient. With use of molecular genetic analysis of the gene SCN4A, three new mutations were found affecting codon 675. They resulted in an amino acid substitution of a highly conserved arginine (R) to either a glycine (G), a glutamine (Q), or a tryptophan (W). Interestingly, hypoPP is caused by both mutations affecting nearby codons as well as the change of an arginine into another amino acid.

CONCLUSION

A potassium-sensitive and normokalemic type of periodic paralysis caused by new SCN4A mutations at codon 675 is reported.

[Influence of pyridoxal phosphate in measuring aminotransferases activities in patients with viral hepatitis]

Effect of a pyridoxal phosphate (PP) supplementation of reagents used for ALT and AST measurement was studied in serum of 20 patients suffering from viral hepatitis. Measurements of enzyme activities were carried out at 37 degrees C, using an automate (AU 600, Olympus). Significant differences (p < 0.0001) were observed both for ALT and AST, meanwhile they were more marked for ALT than for AST. This difference was associated with a strong interindividual variability regarding PP activation effect on ALT. In conclusion, aminotransferase measurements should be carried out with a reagent supplemented with PP, when the enzyme activity is used to evaluate a cytolysis. The same recommendation applies when ALT results are integrated into various combinations developed for the evaluation of liver status.

Systemic low-grade inflammation is related to both circulating and adipose tissue TNFalpha, leptin and IL-6 levels in obese women

OBJECTIVE

We assessed the relationships between four circulating acute phase proteins and the circulating and adipose tissue levels of three adipocytokines.

SUBJECTS

In all, 15 nondiabetic obese women with a body mass index (BMI) above 32 kg/m(2) were investigated.

METHOD

Circulating concentrations of C-reactive protein (CRP), alpha 1 acid glycoprotein (AAG), fibrinogen, alpha 1 antitrypsin and both circulating and adipose tissue levels of interleukin (IL)-6, tumor necrosis factor (TNF)alpha and leptin were measured by either nephelometry or enzyme-linked immunosorbent assay.

RESULTS

We found a strong positive correlation between both circulating and adipose tissue levels of IL-6, TNFalpha and leptin and serum CRP levels. All these adipose tissue adipocytokines were also positively correlated with serum AAG levels. These correlations disappeared when adjusted for fat mass, suggesting that the relationship observed was dependent on fat amount.

CONCLUSION

Our results indicate a strong relationship between adipocytokines and inflammatory markers, and suggest that cytokines secreted by adipose tissue in obese subjects could play a role in increased inflammatory proteins secretion by the liver.

Low incidence of cardiac events with ?-blocking therapy in children with long QT syndrome

AIMS

To evaluate the effect of beta-blockers in children with long QT syndrome (LQTS) we reviewed the outcome of 122 patients (pts).

METHODS

LQTS was diagnosed in 24 neonates and in 98 pts aged 0.5-15 years. Diagnosis was made because of syncope in 51 pts, bradycardia in 10 neonates and family history in 61 pts. The longest QTc ranged from 400 to 700 ms. Thirteen pts had 2:1 atrioventricular block and/or ventricular arrhythmias. Screening for mutations was performed in 118 pts. All children were treated with beta-blockers, annually checked by exercise testing and/or 24 h ECG monitoring.

RESULTS

Four pts died. Survivors were followed-up for 1-18 years (7.5 +/- 5.3 years). Five neonates and 3 older pts received a prophylactic pacemaker (1 death) so that only 111/122 pts survived and were followed-up with beta-blockers alone. None of them died and five experienced a non-fatal cardiac event. There was no cardiac event among pts who were diagnosed because of familial history and among symptomatic KCNQ1 pts who were effectively treated with beta-blockers.

CONCLUSION

The outcome of children with LQTS under effective beta-blockers is favourable. Persisting arrhythmia or symptoms despite beta-blockers should aim at identifying other genotypes than KCNQ1.

[Neonatal forms of congenital long QT syndrome]

The neonatal congenital long QT syndrome (LQTS) is rare and of bad prognosis due to the presence of severe ventricular arrhythmia and conduction abnormalities.

METHODS

we included 24 propositus newborns from our population with LQTS. Genetic study was possible in 19 cases.

RESULTS

the diagnosis of LQTS was made according to a QT prolongation associated with a sinusal neonatal bradycardia (n=9) or a 2/1 AV block (n=15). The onset presentation consisted of syncope (n=2), torsades de pointes (n=7), cardiovascular collapse (n=5), cardiac arrest (n=1). The mean QTc was at 550+60 ms. During the neonatal period the treatment consisted of beta-blocking agents in all cases, associated with a definitive pacemaker implantation in 10 cases with 2/1 AV block. Three newborns with a 2/1 AV block died during the first month of life (one case due to a septecemia after implantation of a pacemaker, and two who were waiting for that implantation). All survivors remained asymptomatic during a follow-up period of 7 years. In all cases with a 2/1 AV block we identified mutations in HERG (n=8). Newborns with isolated sinusal bradycardia presented all a mutation in KCNQ1 (n=9).

CONCLUSION

the LTQS with 2/1 AV block is preferably associated with mutation in HERO with a bad initial prognosis.

Lack of association of the potassium channel-associated peptide MiRP2-R83H variant with periodic paralysis

A missense variant (R83H) of the gene (KCNE3) encoding a potassium channel-associated peptide, MinK-related peptide 2 (MiRP2), has been reported in periodic paralysis patients. In the current study, no difference in the frequency of the MiRP2-R83H variant between periodic paralysis patients and healthy individuals was found. Furthermore, there was no segregation of this gene variant with the disease. These observations weaken the proposal that MiRP2-R83H causes periodic paralysis.

Interpretation of circulating C-reactive protein levels in adults: body mass index and gender are a must

OBJECTIVE

The recently demonstrated association between C-reactive protein (CRP) level and body mass index (BMI) raised the question of the link between CRP and the degree of obesity. In the present study, we measured CRP in a healthy population with a wide range of BMI in order to appreciate the influence of overweight in the interpretation of CRP results in clinical use.

METHOD

Blood donors, aged from 19 to 65 years, were included in the study. According to BMI, subjects were classified into 3 groups: A (BMI<25 kg/m(2), n=611); B (25-30, n=147); C (> 30, n=34).

RESULTS

CRP values were different among women and men. CRP progressively increased with BMI in women. These results clearly showed that average level of CRP was quite different according to BMI and gender of the subjects and generated different normal ranges of CRP expressed in mg/L (median, 75(th) percentile): Group A: women: 0.44, 0.93; men: 0.40, 0.79, Group B: women: 1.28, 1.84; men: 0.84, 2.17, Group C: women: 3.61, 7.21; men: 1.16, 3.08.

CONCLUSION

Our results suggest that for an inflammatory disease diagnosis, a CRP concentration of 5 mg/L is normal for obese women but is five times the 75(th) percentile for normal people.

Genetic testing and genetic counselling in hypertrophic cardiomyopathy: the French experience

AIMS

A major breakthrough in the molecular genetics of hypertrophic cardiomyopathy (HCM) has made genetic testing now available in clinical practice, raising new questions about its implications, potential benefits, and the organisation of the procedure. The aim of this work was (1) to discuss the different questions related to genetic testing in HCM, and propose guidelines for the different situations, (2) to report our preliminary experience with a specific procedure.

METHODS AND RESULTS

The main questions asked by patients and relatives concern presymptomatic diagnosis and prenatal counselling/diagnosis, while clinicians sometimes discuss diagnostic and prognostic testing. To take into account the complex medical and psychological implications of this new approach, we developed a specific, multidisciplinary, and multiple step procedure, including a cardiologist, a geneticist, and a psychologist. Seventy subjects were examined, including (1) 29 adults for presymptomatic diagnosis (of whom 10 left the procedure after the first visit and 19 continued, among whom six had a mutation and two experienced negative psychological impact, observed during follow up), (2) nine couples of parents for presymptomatic diagnosis in their children (the procedure was stopped after the first visit in eight and continued in one), (3) 22 couples for prenatal counselling (no prenatal genetic testing was asked for after the first visit), and (4) 10 subjects for diagnostic testing. We decided to perform no prognostic testing.

CONCLUSION

Our preliminary experience confirms the complexity of the situation and suggests the necessity for a specific procedure to ensure good practice in genetic testing of HCM.

Hypokalaemic periodic paralysis type 2 caused by mutations at codon 672 in the muscle sodium channel gene SCN4A

Hypokalaemic periodic paralysis (hypoPP) is an autosomal dominant muscle disorder characterized by episodic attacks of muscle weakness associated with a decrease in blood potassium levels. Mutations in the gene encoding the skeletal muscle voltage-gated calcium channel alpha-1 subunit (CACNL1A3) account for the majority of cases. Recently, mutations in the gene coding for the skeletal muscle voltage-gated sodium channel alpha subunit (SCN4A) have been reported in a small number of hypoPP families. In order to determine the relative frequency of the CANCL1A3 and SCN4A mutations in a large population of hypoPP patients, and to specify the clinical and pathological features associated with each of them, we searched for mutations in 58 independent hypoPP index cases. We detected the causative mutation in 45 cases: 40 were linked to the CACNL1A3 gene and five to the SCN4A gene. One mutation has not been described before. Some remarkable clinical features were observed in a large hypoPP family carrying an SCN4A mutation: a complete penetrance in men and women, an early age at onset, postcritic myalgias and an increased number and severity of attacks induced by acetazolamide. A muscle biopsy, performed in two members of this family, revealed a peculiar myopathy characterized by tubular aggregates. In contrast, vacuoles were predominant in muscles from hypoPP patients carrying CACNL1A3 mutations. Our findings point to the usefulness of a molecular characterization of hypoPP patients in clinical practice. They also provide new clues for understanding the mechanisms behind functional and structural alterations of the skeletal muscle in hypoPP.

[T wave abnormalities on Holter monitoring of congenital long QT syndrome: phenotypic marker of a mutation of LQT2 (HERG)]

The two genes which code for the potassium channels, KCNQ1 and HERG, are responsible for the most common forms of the long QT syndrome, LQT1 and LQT2. Abnormalities of duration and morphology of the ventricular repolarisation are amongst the diagnostic criteria of this syndrome. The morphology of the T waves was studied by 24 hour Holter monitoring in 190 subjects with a long QT syndrome due to KCNQ1 (LQT1) [N = 133] or HERG (N = 57) and in 100 controls, and it was compared with the ECG T wave. The T wave was characterised according to 3 morphological features: grade 0 (G0) = normal, grade 1 (G&) = slight ST depression and grade 2 (G2) = presence of ST elevation of the descending phase of the T wave. The T wave morphology on Holter ECG was normal for most LQT1 and control subjects compared with LQT2 (92%, 96% and 19% respectively, p < 0.01). Grade 1 appearances were observed more often in LQT2 (18 vs 8% for LQT1 and 4% for controls, p < 0.01). Grade 2 appearances were only observed in the cases of LQT2 (63%). The predictive factors of G2 were young age and an anti-sense mutation of the transmembrane domaines of HERG. The authors conclude that Holter monitoring improves detection of T wave changes compared with the ECG. Grade 2 changes seem to be a phenotype marker for a HERG mutation, especially those situated in the transmembrane domaines.

Notched T waves on Holter recordings enhance detection of patients with LQt2 (HERG) mutations

BACKGROUND

The 2 genes KCNQ1 (LQT1) and HERG (LQT2), encoding cardiac potassium channels, are the most common cause of the dominant long-QT syndrome (LQTS). In addition to QT-interval prolongation, notched T waves have been proposed as a phenotypic marker of LQTS patients.

METHODS AND RESULTS

The T-wave morphology of carriers of mutations in KCNQ1 (n=133) or HERG (n=57) and of 100 control subjects was analyzed from Holter ECG recordings. Averaged T-wave templates were obtained at different cycle lengths, and potential notched T waves were classified as grade 1 (G1) in case of a bulge at or below the horizontal, whatever the amplitude, and as grade 2 (G2) in case of a protuberance above the horizontal. The highest grade obtained from a template defined the notch category of the subject. T-wave morphology was normal in the majority of LQT1 and control subjects compared with LQT2 (92%, 96%, and 19%, respectively, P:<0.001). G1 notches were relatively more frequent in LQT2 (18% versus 8% [LQT1] and 4% [control], P:<0.01), and G2 notches were seen exclusively in LQT2 (63%). Predictors for G2 were young age, missense mutations, and core domain mutations in HERG.

CONCLUSIONS

This study provides novel evidence that Holter recording analysis is superior to the 12-lead ECG in detecting G1 and G2 T-wave notches. These repolarization abnormalities are more indicative of LQT2 versus LQT1, with G2 notches being most specific and often reflecting HERG core domain missense mutations.

Variations in plasma soluble tumour necrosis factor receptors after diet-induced weight loss in obesity

The aim of this study was to investigate the variations in the plasma levels of the soluble tumour necrosis factor receptor type-I (sTNFR-I) and type-II (sTNFR-II) during weight loss which was induced by 3 weeks on a very low calorie diet (3.9+/-0.1 MJ/day), in 17 non-diabetic obese women. Plasma sTNFR-I concentrations decreased significantly after weight loss (p < 0.05), but there was no significant change in plasma sTNFR-II. As the diet was associated with a significant decrease in body fat mass (=2.5 kg), this result supports the emerging concept that adipose tissue can produce significant amounts of sTNFR-I and that this production can be modified by weight loss in human obesity.

Elevated levels of interleukin 6 are reduced in serum and subcutaneous adipose tissue of obese women after weight loss

The aim of this study was to investigate the potential role of adipose cytokines in the obesity-associated insulin resistance. To that end, we compared: 1) serum concentrations of interleukin 6 (IL-6), tumor necrosis factor alpha (TNFalpha), and leptin in eight healthy lean control females and in android obese female without (n = 14) and with (n = 7) type 2 diabetes; and 2) the levels of these cytokines both in serum and in sc adipose tissue in the 14 obese nondiabetic women before and after 3 weeks of a very low-calorie diet (VLCD). As compared with lean controls, obese nondiabetic and diabetic patients were more insulin resistant and presented increased values for leptin, IL-6, TNFalpha, and C-reactive protein. In the whole group, IL-6 values were more closely related to the parameters evaluating insulin resistance than leptin or TNFalpha values. VLCD resulted in weight loss and decreased body fat mass (approximately 3 kg). Insulin sensitivity was improved with no significant change in both serum and adipose tissue TNFalpha levels. In contrast, VLCD induced significant decreases in IL-6 and leptin levels in both adipose tissue and serum. These results suggest that, as for leptin, circulating IL-6 concentrations reflect, at least in part, adipose tissue production. The reduced production and serum concentrations after weight loss could play a role in the improved sensitivity to insulin observed in these patients.

Homozygotes for a R869G mutation in the beta -myosin heavy chain gene have a severe form of familial hypertrophic cardiomyopathy

Familial Hypertrophic Cardiomyopathy (FHC) is an autosomal dominant disease characterised by ventricular hypertrophy, with predominant involvement of the interventricular septum. It is a monogenic disease with a high level of genetic heterogeneity (nine genes and more than 110 mutations reported so far). We describe a family with a new R869G mutation in the beta -myosin heavy chain gene (MYH7). This mutation was found in the heterozygous status in both parents and in the homozygous status in the two children. A haplotype analysis on the MYH7 locus with microsatellite markers showed that the same haplotype is transmitted within the family, suggesting a founder effect. Clinically, the father was asymptomatic with mild left ventricular hypertrophy on echocardiography. The mother had a mild form of hypertrophic cardiomyopathy and remained asymptomatic until 60 years old when an atrial fibrillation occurred. For the two children, clinical diagnosis was performed at 12 and 8 years and atrial fibrillation occurred at 17 years. For both children, the evolution was characterized by left ventricle (LV) systolic dysfunction and a severe dilatation of the left atrium before 40 years of age.

CONCLUSIONS

In this family, a new R869G mutation in the MYH7 gene was found. Interestingly, a mutation was found at the homozygous status for the first time in FHC. This finding suggests that this particular mutation is compatible with life, but for homozygous subjects, age at onset of symptoms was earlier and the disease much more severe than in the heterozygous subjects, suggesting a gene-dose effect.

Genotype-phenotype analysis in four families with mutations in beta-myosin heavy chain gene responsible for familial hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy is a genetically heterogeneous disease in which one of the most frequently implicated gene is the gene encoding the beta-myosin heavy chain. To date, more than 40 distinct mutations have been found within this gene. In order to progress on the determination of genotype-phenotype relationship, we have screened the beta-myosin heavy chain gene for mutations in 18 probands from unrelated families. We identified the mutation implicated in the disease in four families. Two of them, the Glu930 codon deletion and the Ile263Thr mutation, are reported here for the first time. The two other mutations are the Arg723Cys mutation, that was previously described in a proband as a de novo mutation, and the Arg719Trp mutation. A poor prognosis was associated with the Glu930codon deletion (mean maximal wall thickness (MWT) = 19.5 mm +/- 5) and the Arg719Trp mutation (mean MWT = 15.3 mm +/- 7), whereas a good prognosis was associated with the Arg723Cys mutation (mean MWT = 20.1 mm +/- 7). The combination of clinical and genetic characteristics of each family member suggests that prognosis is related neither to the degree of left ventricular wall thickness nor to a change in the net electrical charge of the protein. Additional family studies are needed to confirm these findings and to contribute to stratify the prognosis according to the mutation involved.

Relationship between plasma plasminogen activator inhibitor 1 and insulin resistance

High plasminogen activator inhibitor 1 (PAI-1) levels are associated with an increased cardiovascular risk of atherothrombosis. Furthermore, increased plasma PAI-1 levels are associated with dyslipidemia, hyperinsulinemia and hypertension. This association between PAI-1 and metabolic components of the Metabolic Syndrome could explain the predisposition of insulin resistant patients to atherothrombosis. Recent studies have suggested that visceral adipose tissue might be the link between elevated plasma PAI-1 and insulin resistance in the Metabolic Syndrome. Indeed, visceral adipose tissue was proposed as a potentially important source of PAI-1 in humans. However, in light of recent studies, visceral adipose tissue appears to be involved in the increase of plasma PAI-1 via the metabolic disorders usually associated with central obesity, rather than directly. High plasma PAI-1 levels are undoubtedly related to insulin resistance, and the mechanisms which could explain such an increase in the Metabolic Syndrome appear to be multi-factorial and remain to be elucidated. These mechanisms may involve several metabolic disorders such as hyperinsulinemia, dyslipidemia, impaired glucose tolerance and hypertension, which would favor PAI-1 synthesis and release from different cell types.

Subcutaneous adipose tissue expression of tumour necrosis factor-alpha is not associated with whole body insulin resistance in obese nondiabetic or in type-2 diabetic subjects

BACKGROUND

An association with subcutaneous adipose tissue TNFalpha expression and insulin resistance has been suggested in obesity/type-2 diabetes, but this has not been examined directly. In the first part of the study we investigated whether this association is present in 7 lean, 10 obese nondiabetic and 9 type-2 diabetic men. In the second part of the study we examined the relationship between adipose tissue TNFalpha mRNA levels and BMI in 81 nondiabetic subjects spanning a wide range of BMIs.

METHODS

Subcutaneous adipose tissue TNFalpha mRNA levels and insulin sensitivity were determined with quantitative RT-competitive PCR and hyperinsulinaemic clamp, respectively.

RESULTS

Subcutaneous adipose tissue TNFalpha mRNA levels were similar in 7 lean and 10 obese nondiabetic and 9 type-2 diabetic men (P = 0.68), and did not change in response to 240-min hyperinsulinaemia. TNFalpha mRNA levels and insulin sensitivity were not correlated. Unexpectedly, no correlation between TNFalpha mRNA and BMI was found. The relationship between adipose tissue TNFalpha mRNA and BMI was examined further in 31 male and 50 female nondiabetic subjects. The subcutaneous adipose tissue TNFalpha mRNA level correlated with BMI in all subjects (rS = 0.32, P < 0.01), and in a subgroup analysis in men (rS = 0.55, P < 0.01) but not in women (rS = - 0.08). The correlation in men was dependent on a fourfold higher TNFalpha mRNA level in 5 morbidly obese men while there was no difference in TNFalpha mRNA levels in lean or obese men.

CONCLUSIONS

Subcutaneous adipose tissue TNFalpha expression does not correlate with insulin sensitivity in nondiabetic or type-2 diabetic men; is not regulated by acute hyperinsulinaemia; and is increased only in morbidly obese men.

Novel mutations in KvLQT1 that affect Iks activation through interactions with Isk

OBJECTIVES

We report the functional expression of four KCNQ1 mutations affecting arginine residues and resulting in Romano-Ward (RW) and the Jervell and Lange-Nielsen (JLN) congenital long QT syndromes.

RESULTS

The R539W and R190Q mutations were found in typical RW families with an autosomal dominant transmission. The R243H mutation was found in a compound heterozygous JLN patient who presents with deafness and cardiac symptoms. The fourth mutation, R533W, was a new case of recessive form of the RW syndrome since homozygous carriers experienced syncopes but showed no deafness, whereas the heterozygous carriers were asymptomatic. The R190Q mutation failed to produce functional homomeric channels. The R243H, R533W and R539W mutations induced a positive voltage shift of the channel activation but only when co-expressed with IsK, pointing out the critical role of these positively charged residues in the modulation of the gating properties of KvLQT1 by IsK. The positive shift induced by R533W was merely 15%. This small effect was compatible with the recessive character of the RW phenotype transmission. The average QTc was significantly longer (P < 0.01) in patients carrying mutations inducing a total loss of channel function and those patients were also prone to cardiac adverse symptoms (whether syncopes or sudden death) to a greater extent (62 vs. 21%, P < 0.001).

CONCLUSIONS

Novel mutations are described that induce a voltage shift of the channel activation only in the presence of IsK. They appear associated with a milder cardiac phenotype.

Deletion in the cardiac troponin I gene in a family from northern Sweden with hypertrophic cardiomyopathy

The cardiac troponin I gene has been described to be associated with hypertrophic cardiomyopathy. Until now, mutations in this gene have been found only in the Japanese population. We now present the first non-Japanese family, from northern Sweden, with a mutation in the cardiac troponin I gene. Clinical diagnose was based on echocardiography, with a maximum left ventricular wall thickness of >13 mm, or major electrocardiographic abnormalities, excluding subjects with other known causes of cardiac hypertrophy. Mutation screening was performed with a single-strand conformation polymorphism analysis and identification of mutation by direct DNA sequencing. We have identified a 33-bp deletion in exon 8 encompassing the stop codon. Nine individuals in three generations were tested, and four were carriers of this deletion. The mother was genetically affected and died of heart failure aged 90. Echocardiography at 71 years of age revealed no hypertrophy, but the electrocardiogram showed signs of left ventricular hypertrophy. Her two sons, also genetically affected, had left ventricular hypertrophy, with maximum wall thickness of 15 and 16 mm, respectively. One daughter and four grandchildren were clinically unaffected, but one of them, a 27-year-old woman with maximum wall thickness of 8 mm and normal electrocardiogram, was found to be genetically affected. In conclusion, we describe a non-Japanese family in which hypertrophic cardiomyopathy is due to a genetic defect in the cardiac troponin I gene. This mutation is a deletion of 33 bp in the last exon, whereas the previously described mutations in this gene are single nucleotide changes and a single codon deletion. The deletion of the C-terminal part of the cardiac troponin I protein, seems in this particular family to be associated with a mild phenotypic expression of familial hypertrophic cardiomyopathy.

First description of germline mosaicism in familial hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy is a genetically and phenotypically heterogeneous disease caused by mutations in seven sarcomeric protein genes. It is known to be transmitted as an autosomal dominant trait with rare de novo mutations.A French family in which two members are affected by hypertrophic cardiomyopathy was clinically screened with electrocardiography and echocardiography. Genetic analyses were performed on leucocyte DNA by haplotype analysis with microsatellite markers at the MYH7 locus and mutation screening by single strand conformation polymorphism analysis. Two subjects exhibited severe hypertrophic cardiomyopathy. A mutation in the MYH7 gene was found in exon 14 (Arg453Cys). The two affected patients were carriers of the mutation, which was not found in the circulating lymphocytes of their parents. Haplotype analysis at the MYH7 locus with two intragenic microsatellite markers (MYOI and MYOII) and the absence of the mutation in the father's sperm DNA suggested that the mutation had been inherited from the mother. However, it was not found in either her fibroblasts or hair. This is the first description of germline mosaicism shown by molecular genetic analysis in an autosomal dominant disorder and more especially in hypertrophic cardiomyopathy. This mosaicism had been inherited from the mother but did not affect her somatic cells. Such a phenomenon might account for some de novo mutations in familial hypertrophic cardiomyopathy.

Subcutaneous adipose tissue expression of plasminogen activator inhibitor-1 gene during very low calorie diet in obese subjects

OBJECTIVE

To determine whether changes in subcutaneous adipose tissue plasminogen activator inhibitor-1 (PAI-1) expression influence plasma PAI-1 level during weight loss in obese humans.

DESIGN

Study of the variations of PAI-1 levels both in plasma and in subcutaneous abdominal adipose tissue in 15 volunteer non-diabetic obese subjects, body mass index (BMI) 40.4.+/-1.9 kg/m2, aged 48+/-3 y, before and after a 3 week very low calorie diet (VLCD) programme (3.9+/-0.1 MJ/day).

MEASUREMENTS

Plasma and adipose tissue PAI-1 protein levels were measured by enzyme-linked immunosorbent assay and PAI-1 mRNA levels were quantified by quantitative RT-competitive PCR.

RESULTS

VLCD induced weight loss (5.8+/-0.8 kg) and decreased plasma PAI-1 concentration (-26% (P<0. 01)). Surprisingly, PAI-1 mRNA and protein abundance in subcutaneous adipose tissue increased by 87% (P<0.05) and by 44% (P<0.01), respectively.

CONCLUSION

These data indicate thus that changes in subcutaneous adipose tissue PAI-1 expression are not involved in the decrease of plasma PAI-1 levels during VLCD in obese subjects. International Journal of Obesity (2000)24, 70-74

COOH-terminal truncated cardiac myosin-binding protein C mutants resulting from familial hypertrophic cardiomyopathy mutations exhibit altered expression and/or incorporation in fetal rat cardiomyocytes

Mutations in human cardiac myosin-binding protein C (cMyBP-C) gene are associated with familial hypertrophic cardiomyopathy (FHC), and most of them are predicted to produce COOH-truncated proteins. To understand the molecular mechanism(s) by which such mutations cause FHC, we analyzed (i) the accumulation of human cMyBP-C mutants in fetal rat cardiomyocytes, and (ii) the protein sequence of the human wild-type (wt) cMyBP-C by hydrophobic cluster analysis with the aim of identifying new putative myosin-binding site(s). Accumulation and sarcomeric localization of the wt protein and of four FHC-mutant cMyBP-Cs (E542Q and three COOH-truncated proteins) were studied in cardiomyocytes by immunostaining and confocal microscopy after transfection with myc-tagged constructs. We found that: (i) 10 % of the cells expressing COOH-truncated mutants exhibit an incorporation into the A-band of the sarcomere without any alteration of the myofibrillar architecture versus 76 % of those expressing the wt or E542Q mutant cMyBP-Cs (p<0.001); (ii) 90 % of the cells expressing the truncated mutants show a diffuse localization of these proteins in the cardiomyocytes, out of which 45 % exhibit a significant alteration of the sarcomeric structure (p<0.0001 versus wt); and (iii) the two shortest mutant cMyBP-Cs accumulate at very low levels in fetal rat cardiomyocytes as compared to the wt (p<0.008). Protein sequence analysis indicated that a 45-residue sequence in the NH2-terminal C0 domain of cMyBP-C exhibits a consistent homology (sequence similarity score of 42 %) with a segment of the NH2-terminal domain of myomesin, another myosin-binding protein. This result suggests that the C0 domain of human cMyBP-C contains a novel putative myosin-binding site that could account for the A-band incorporation of the truncated mutants. In addition, the faint accumulation and the diffuse localization of truncated mutants could probably be explained by a low affinity of the C0 domain for myosin. We conclude that COOH-truncated cMyBP-Cs may act as poison polypeptides that disrupt the myofibrillar architecture and result in the defects observed in FHC.

Double heterozygosity for mutations in the beta-myosin heavy chain and in the cardiac myosin binding protein C genes in a family with hypertrophic cardiomyopathy

Familial hypertrophic cardiomyopathy is a genetically heterogeneous autosomal dominant disease, caused by mutations in several sarcomeric protein genes. So far, seven genes have been shown to be associated with the disease with the beta-myosin heavy chain (MYH7) and the cardiac myosin binding protein C (MYBPC3) genes being the most frequently involved. We performed electrocardiography (ECG) and echocardiography in 15 subjects with hypertrophic cardiomyopathy from a French Caribbean family. Genetic analyses were performed on genomic DNA by haplotype analysis with microsatellite markers at each locus involved and mutation screening by single strand conformation polymorphism analysis. Based on ECG and echocardiography, eight subjects were affected and presented a classical phenotype of hypertrophic cardiomyopathy. Two new mutations cosegregating with the disease were found, one located in the MYH7 gene exon 15 (Glu483Lys) and the other in the MYBPC3 gene exon 30 (Glu1096 termination codon). Four affected subjects carried the MYH7 gene mutation, two the MYBPC3 gene mutation, and two were doubly heterozygous for the two mutations. The doubly heterozygous patients exhibited marked left ventricular hypertrophy, which was significantly greater than in the other affected subjects. We report for the first time the simultaneous presence of two pathological mutations in two different genes in the context of familial hypertrophic cardiomyopathy. This double heterozygosity is not lethal but is associated with a more severe phenotype.

C-terminal HERG mutations: the role of hypokalemia and a KCNQ1-associated mutation in cardiac event occurrence

BACKGROUND

The long-QT syndrome (LQTS) is a genetically heterogeneous disease in which 4 genes encoding ion-channel subunits have been identified. Most of the mutations have been determined in the transmembrane domains of the cardiac potassium channel genes KCNQ1 and HERG. In this study, we investigated the 3' part of HERG for mutations.

METHODS AND RESULTS

New specific primers allowed the amplification of the 3' part of HERG, the identification of 2 missense mutations, S818L and V822 M, in the putative cyclic nucleotide binding domain, and a 1-bp insertion, 3108+1G. Hypokalemia was a triggering factor for torsade de pointes in 2 of the probands of these families. Lastly, in a large family, a maternally inherited G to A transition was found in the splicing donor consensus site of HERG, 2592+1G-A, and a paternally inherited mutation, A341E, was identified in KCNQ1. The 2 more severely affected sisters bore both mutations.

CONCLUSIONS

The discovery of mutations in the C-terminal part of HERG emphasizes that this region plays a significant role in cardiac repolarization. Clinical data suggests that these mutations may be less malignant than mutations occurring in the pore region, but they can become clinically significant in cases of hypokalemia. The first description of 2 patients with double heterozygosity associated with a dramatic malignant phenotype implies that genetic analysis of severely affected young patients should include an investigation for >1 mutation in the LQT genes.

Peroxisome proliferator activated receptor-gamma, leptin and tumor necrosis factor-alpha mRNA expression during very low calorie diet in subcutaneous adipose tissue in obese women

BACKGROUND

PPAR gamma, leptin and TNF alpha are three major factors that play a key role in influencing adipocyte differentiation and both adipose tissue function and metabolism. However, the regulation of these three genes during a dynamic period of weight loss is unknown. We therefore investigated the concomitant regulation of the mRNA expression of PPAR gamma, leptin and TNF alpha in adipose tissue during a 21-day very low calorie diet (VLCD) in 12 non-diabetic obese women.

METHODS

The mRNA levels of PPAR gamma, leptin and TNF alpha were quantified by quantitative RT-competitive PCR in abdominal subcutaneous adipose tissue before and during VLCD (940 kcal/day).

RESULTS

VLCD induced weight loss (approximately 6 kg) and improved insulin sensitivity. Simultaneously, VLCD induced the reduction in the adipose tissue mRNA abundances of PPAR gamma (-13%, p < 0.05) and of leptin (-58%, p < 0.005), whereas TNF alpha mRNA levels increased (+78%, p < 0.005). PPAR gamma and leptin mRNA levels were correlated before (r = 0.778, p < 0.01) and after VLCD (r = 0.797, p < 0.01). Serum HDL-cholesterol concentrations were positively associated with PPAR gamma (r = 0.696, p < 0.03) and leptin (r = 0.806, p < 0.01) mRNA levels.

CONCLUSIONS

The increase in TNF alpha mRNA levels suggested that a local increased expression of this cytokine in adipose tissue might play a role in the control of the fat mass during weight loss. PPAR gamma and leptin mRNA levels were positively associated both before and after VLCD, suggesting that common regulatory mechanism(s) might control their expression. More strikingly, we found strong positive correlations between circulating HDL-cholesterol and both PPAR gamma and leptin mRNA levels, suggesting the existence of physiological links between circulating lipoprotein metabolism and adipose tissue function.

Genomic organization of the KCNQ1 K+ channel gene and identification of C-terminal mutations in the long-QT syndrome

The voltage-gated K+ channel KVLQT1 is essential for the repolarization phase of the cardiac action potential and for K+ homeostasis in the inner ear. Mutations in the human KCNQ1 gene encoding the alpha subunit of the KVLQT1 channel cause the long-QT syndrome (LQTS). The autosomal dominant form of this cardiac disease, the Romano-Ward syndrome, is characterized by a prolongation of the QT interval, ventricular arrhythmias, and sudden death. The autosomal recessive form, the Jervell and Lange-Nielsen syndrome, also includes bilateral deafness. In the present study, we report the entire genomic structure of KCNQ1, which consists of 19 exons spanning 400 kb on chromosome 11p15.5. We describe the sequences of exon-intron boundaries and oligonucleotide primers that allow polymerase chain reaction (PCR) amplification of exons from genomic DNA. Two new (CA)n repeat microsatellites were found in introns 10 and 14. The present study provides helpful tools for the linkage analysis and mutation screening of the complete KCNQ1 gene. By use of these tools, five novel mutations were identified in LQTS patients by PCR-single-strand conformational polymorphism (SSCP) analysis in the C-terminal part of KCNQ1: two missense mutations, a 20-bp and 1-bp deletions, and a 1-bp insertion. Such mutations in the C-terminal domain of the gene may be more frequent than previously expected, because this region has not been analyzed so far. This could explain the low percentage of mutations found in large LQTS cohorts.

Modifications of alpha-tocopherol and fatty acid concentrations in blood and adipose tissue of obese patients during a weight loss programme

BACKGROUND AND AIM

The aim of the study was to describe qualitative and/or quantitative modifications of lipoproteins, including their fatty acid composition, in obese patients during a hypocaloric diet, and determine whether the variations observed paralleled modifications of alpha-tocopherol concentration in adipose tissue and blood.

METHODS AND RESULTS

15 healthy, obese volunteers (5 males, 10 females; age: 32-69 yr; BMI: 28.4-60.5 kg/m2) were given a 3-week hypocaloric diet (3.9 MJ (941 kcal)). Adipose tissue and blood samples were taken at the beginning and at the end of this period. At baseline and after 3 weeks measurements were made for alpha-tocopherol and fatty acids in total serum, lipoproteins and adipose tissue; thiobarbituric acid-reactive substances (TBARS) in serum. A significant drop in cholesterol-rich particles (LDL and HDL) was observed, in parallel to a significant enrichment of n-6 polyunsaturated fatty acids (PUFA) at the expense of both saturated and monounsaturated fatty acids in serum. A drop in alpha-tocopherol concentration (expressed as mumol alpha-tocopherol/g lipid) in serum and lipoprotein fractions paralleled the decrease in cholesterol-rich lipoproteins.

CONCLUSIONS

Our results suggest that a hypocaloric diet not only decreases cholesterol-rich particle levels in serum, but also leads to a significant modification of fatty acid composition which may reflect improvement of insulin sensitivity. We did not observe any modification in adipose tissue after diet with regard to both alpha-tocopherol and fatty acid concentrations. Despite a drop in alpha-tocopherol concentration and an increase in n-6 PUFA content in serum, we did not find any enhancement of serum lipid peroxidation level evaluated by the thiobarbituric acid-reactive substance (TBARS) assay. If we assume that dietary intakes of alpha-tocopherol were not modified during this diet, it can be supposed that adipose tissue released alpha-tocopherol without any specific regulation, in parallel to the release of fatty acids.

Familial hypertrophic cardiomyopathy: from mutations to functional defects

Hypertrophic cardiomyopathy is characterized by left and/or right ventricular hypertrophy, which is usually asymmetric and involves the interventricular septum. Typical morphological changes include myocyte hypertrophy and disarray surrounding the areas of increased loose connective tissue. Arrhythmias and premature sudden deaths are common. Hypertrophic cardiomyopathy is familial in the majority of cases and is transmitted as an autosomal-dominant trait. The results of molecular genetics studies have shown that familial hypertrophic cardiomyopathy is a disease of the sarcomere involving mutations in 7 different genes encoding proteins of the myofibrillar apparatus: ss-myosin heavy chain, ventricular myosin essential light chain, ventricular myosin regulatory light chain, cardiac troponin T, cardiac troponin I, alpha-tropomyosin, and cardiac myosin binding protein C. In addition to this locus heterogeneity, there is a wide allelic heterogeneity, since numerous mutations have been found in all these genes. The recent development of animal models and of in vitro analyses have allowed a better understanding of the pathophysiological mechanisms associated with familial hypertrophic cardiomyopathy. One can thus tentatively draw the following cascade of events: The mutation leads to a poison polypeptide that would be incorporated into the sarcomere. This would alter the sarcomeric function that would result (1) in an altered cardiac function and then (2) in the alteration of the sarcomeric and myocyte structure. Some mutations induce functional impairment and support the pathogenesis hypothesis of a "hypocontractile" state followed by compensatory hypertrophy. Other mutations induce cardiac hyperfunction and determine a "hypercontractile" state that would directly induce cardiac hypertrophy. The development of other animal models and of other mechanistic studies linking the genetic mutation to functional defects are now key issues in understanding how alterations in the basic contractile unit of the cardiomyocyte alter the phenotype and the function of the heart.

Diagnostic value of electrocardiography and echocardiography for familial hypertrophic cardiomyopathy in genotyped children

AIM

The aim of the study was to evaluate electrocardiography and echocardiography in the diagnosis of familial hypertrophic cardiomyopathy in children, using the genetic status as the criterion of reference.

METHODS AND RESULTS

We analysed 35 children (<18 years) from 13 families with identified mutations: 16 were genetically affected (11.2 +/- 3 years), 19 unaffected (13.1 +/- 2.8 years). Conventional major diagnostic criteria were: left ventricular wall thickness >95% confidence interval on the echocardiogram; abnormal Q waves, left ventricular hypertrophy (voltage >95th percentile), or marked ST-T changes on the electrocardiogram. Twenty-two minor electrocardiographic and echocardiographic criteria were also analysed. Using major criteria, the specificity of the electrocardiogram and echocardiogram was excellent (100% for both) but sensitivity was particularly low (38% and 50% respectively). However, when four relevant additional criteria (QRS axis, left atrium dimension, intraventricular septum/posterior wall ratio, E/A wave ratio) were taken into account, sensitivity increased to 88% and specificity remained high (95%).

CONCLUSIONS

(1) Familial hypertrophic cardiomyopathy was diagnosed in only approximately 50% of genetically affected children by conventional electrocardiographic and/or echocardiographic criteria. (2) Relevant additional diagnostic criteria were selected so that nearly all children considered as healthy carriers of a mutation (based on conventional criteria) could be identified with excellent specificity.

Clinical features and prognostic implications of familial hypertrophic cardiomyopathy related to the cardiac myosin-binding protein C gene

BACKGROUND

Little information is available on phenotype-genotype correlations in familial hypertrophic cardiomyopathy that are related to the cardiac myosin binding protein C (MYBPC3) gene. The aim of this study was to perform this type of analysis.

METHODS AND RESULTS

We studied 76 genetically affected subjects from nine families with seven recently identified mutations (SASint20, SDSint7, SDSint23, branch point int23, Glu542Gln, a deletion in exon 25, and a duplication/deletion in exon 33) in the MYBPC3 gene. Detailed clinical, ECG, and echocardiographic parameters were analyzed. An intergene analysis was performed by comparing the MYBPC3 group to seven mutations in the beta-myosin heavy-chain gene (beta-MHC) group (n=52). There was no significant phenotypic difference among the different mutations in the MYBPC3 gene. However, in the MYBPC3 group compared with the beta-MHC group, (1) prognosis was significantly better (P<0.0001), and no deaths occurred before the age of 40 years; (2) the age at onset of symptoms was delayed (41+/-19 versus 35+/-17 years, P<0.002); and (3) before 30 years of age, the phenotype was particularly mild because penetrance was low (41% versus 62%), maximal wall thicknesses lower (12+/-4 versus 16+/-7 mm, P<0.03), and abnormal T waves less frequent (9% versus 45%, P<0.02).

CONCLUSIONS

These results are consistent with specific clinical features related to the MYBPC3 gene: onset of the disease appears delayed and the prognosis is better than that associated with the beta-MHC gene. These findings could be particularly important for the purpose of clinical management and genetic counseling in familial hypertrophic cardiomyopathy.

PCR based mutation screening of the laminin alpha2 chain gene (LAMA2): application to prenatal diagnosis and search for founder effects in congenital muscular dystrophy

Classical congenital muscular dystrophy with merosin deficiency is caused by mutations in the laminin alpha2 chain gene (LAMA2). Extended sequencing of the introns flanking the 64 LAMA2 exons was carried out and, based on these sequences, oligonucleotide primers were designed to amplify the coding region of each exon separately. By PCR-SSCP analysis, we identified eight new mutations in nine families originating from various countries. All induced a premature truncation of the protein, either in the short arm or in the globular C-terminal domain. A 2 bp deletion in exon 13, 2098delAG, was found in three French non-consanguineous families and a nonsense mutation of exon 20, Cys967stop, in two other non-consanguineous families originating from Italy. Determination of rare intragenic polymorphisms permitted us to show evidence of founder effects for these two mutations suggesting a remote degree of consanguinity between the families. Other, more frequent polymorphisms, G to A 1905 (exon 12), A to G 2848 (exon 19), A to G 5551 (exon 37), and G to A 6286 (exon 42), were used as intragenic markers for prenatal diagnosis. This study provides valuable methods for determining the molecular defects in LAMA2 causing merosin deficient congenital muscular dystrophy.

Identification of two novel mutations in the ventricular regulatory myosin light chain gene (MYL2) associated with familial and classical forms of hypertrophic cardiomyopathy

Five disease genes encoding sarcomeric proteins and associated with familial and classical forms of hypertrophic cardiomyopathy have been determined since 1989. In 1996 two other genes encoding ventricular regulatory and essential myosin light chains were shown to be associated with a particular phenotype of the disease characterized by mid left ventricular obstruction. The aim of the present study was to search for mutations in the ventricular regulatory myosin light chain gene (MYL2), located on chromosome 12q23q24.3, in a panel of 42 probands presenting a classical phenotype of familial hypertrophic cardiomyopathy. Single-strand conformation polymorphism analysis was used to search for mutations in the coding segments of the MYL2 gene, and the abnormal products were sequenced. Two novel missense mutations, Phe18Leu in exon 2 and Arg58Gln in exon 4 were identified in three unrelated families. None of the affected patients had hypertrophy localized only at the level of the papillary muscle with mid left ventricular obstruction. By analysis of genetic recombinations, one of these mutations identified in a large family allowed us to refine the localization of the MYL2 gene on the genetic map, in an interval of 6 cM containing six informative microsatellite markers. In conclusion, we show that mutations in the MYL2 gene may be involved in familial and classical forms of hypertrophic cardiomyopathy, and we provide new tools for the genetic analysis of patients with familial hypertrophic cardiomyopathy.

[Hexose transporters in humans: their role in insulin sensitivity of peripheral tissues]

OBJECTIVES AND JUSTIFICATION: To describe facilitated diffusion glucose transporters (GLUT) in humans, and particularly the regulation of GLUT4 expression since it is predominantly responsible for insulin-mediated glucose transport in muscle and adipose tissue, and plays a crucial role in whole-body glucose homeostasis.

MAIN POINTS

Numerous studies have shown abnormal expression of GLUT4 in insulin responsive tissues in diabetes mellitus and other insulin resistant states. The recent development of transgenic mice that overexpress GLUT4 in muscle, adipose tissue, or both has also emphasized the importance of GLUT4 in glucose homeostasis.

PERSPECTIVES AND PROJECTS

The studies performed in transgenic mice suggest that strategies to increase GLUT4 transporters in insulin responsive tissues may lead to new therapeutic possibilities to improve insulin sensitivity in insulin resistant states such as non-insulin-dependent diabetes mellitus.

CONCLUSIONS

Glucose transport is a crucial process in mammals, which needs specific transmembrane hexose transporters. Each transporter is important in the regulation of glucose homeostasis. Advances in the knowledge of both the action and the regulation of the glucose transport system may provide new insights for the development of therapeutic interventions in diseases such as obesity or diabetes mellitus.