Phosphatidylinositol 3-kinase p85alpha regulatory subunit gene PIK3R1 haplotype is associated with body fat and serum leptin in a female twin population.

AIMS/HYPOTHESIS: Phosphatidylinositol 3-kinase (PI3K) couples the leptin and insulin signalling pathways via the insulin receptor substrates IRS1 and IRS2. Hence, defective activation of PI3K could be a novel mechanism of peripheral leptin or insulin resistance. We investigated associations of tagging single-nucleotide polymorphisms (tSNPs) in the PI3K p85alpha regulatory subunit gene PIK3R1 with anthropometry, leptin, body fat and insulin sensitivity in a female twin population of European extraction. MATERIALS AND METHODS: Eight tSNPs were genotyped in 2,778 women (mean age 47.4+/-12.5 years) from the St Thomas' UK Adult Twin Registry (Twins UK). RESULTS: SNP rs1550805 was associated with serum leptin (p=0.028), BMI (p=0.025), weight (p=0.019), total fat (p=0.004), total fat percentage (p=0.002), waist circumference (p=0.025), central fat (p=0.005) and central fat percentage (p=0.005). SNPs rs7713645 and rs7709243 were associated with BMI (p=0.020 and p=0.029, respectively), rs7709243 with weight, total and central fat (p=0.026, p=0.031 and p=0.023, respectively) and both SNPs with fasting glucose (p=0.003 and p=0.001, respectively) and glucose 2-h post OGTT (p=0.023 and p=0.007, respectively). Subjects with haplotype 222 (frequency 7.2%) showed higher serum leptin concentration (p=0.007) and body fat measures (p< or =0.001 for all), and those with haplotype 221 (frequency 38.7%) showed higher fasting and 2-h glucose (p=0.035 and p=0.021, respectively) compared with subjects with the most common haplotype, 111 (frequency 45.5%). CONCLUSIONS/INTERPRETATION: Association of the PIK3R1 SNP rs1550805 with serum leptin and body fat may reflect a diminished ability of PI3K to signal via IRS1 or IRS2 in response to leptin.

AMP-kinase alpha2 subunit gene PRKAA2 variants are associated with total cholesterol, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol in normal women.

BACKGROUND: 5'-AMP-activated protein kinase (AMPK) inactivates critial ensymes in fatty acid and cholesterol synthesis. We hypothesised that the serum lipid profile may be influenced by genetic variation in the AMPK catalytic alpha2 subunit. METHOD: We examined association of 5 tagging SNPs (tSNPs) in the PRKAA2 gene with serum lipids in 2777 normal Caucasian females (mean age 47.4+/-12.5 years). RESULTS: All tSNPs were associated with total- and LDL-cholesterol, (p<0.001 to 0.034), explaining variances of 0.13-0.59% and 0.11-0.55% respectively. One haplotype (frequency 34.7%) showed lower total- and LDL-cholesterol compared with the most common haplotype (frequency 45.7%) (p< or =0.001), explaining 0.78% of total- and 0.75% of LDL-cholesterol. Another haplotype (frequency 10.5%) was significantly associated with lower HDL-cholesterol (p = 0.005), explaining 0.59% of variance. CONCLUSIONS: PRKAA2 gene variants are significantly associated with serum lipoproteins in a large sample of normal female Caucasians.

Common polymorphisms in SOCS3 are not associated with body weight, insulin sensitivity or lipid profile in normal female twins.

AIMS/HYPOTHESIS: Inhibition of signal transduction by suppressor of cytokine signalling-3 (SOCS-3) potentially influences resistance to insulin and leptin. The aim of this study was to test the association between three single-nucleotide polymorphisms (SNPs) representative of common linkage disequilibrium clusters in SOCS3 (rs4969169, rs12953258 and rs8064821) and obesity measures, insulin sensitivity measures and serum lipids in the general population. METHODS: The three SNPs, which had rare allele frequencies >0.06, were genotyped in 2,777 female twins of European extraction (mean age 47.4+/-12.5 years) from the St Thomas' UK Adult Twin Registry (Twins UK). RESULTS: Minor allele frequencies were as follows: rs4969169=0.067, rs12953258=0.097 and rs8064821=0.101. Individual SOCS3 SNPs were not associated with general or central obesity, or with two indices of insulin sensitivity (homeostasis model assessment and insulin sensitivity measure). CONCLUSIONS/INTERPRETATION: The results do not indicate that any of the three SNPs studied are associated with obesity, insulin measures or lipid measures.

Leptin expression in the fetus and placenta during mouse pregnancy.

During pregnancy, leptin concentrations in the maternal circulation are elevated in both humans and rodents but decrease to pre-pregnancy levels at birth, suggesting a role for leptin in the maintenance of pregnancy. Synthesis of leptin by the human placenta is established but whether the murine placenta synthesizes leptin remains controversial. The aims of this study were to determine (a) if the mouse wild-type placenta expresses the ob gene using Reverse Transcription-Polymerase Chain Reaction (RT-PCR) and (b) whether the mouse fetus and placenta contribute to the significant increase of leptin in the maternal circulation during pregnancy. The mouse placenta did not express the ob gene at a level that could be readily detected using RT-PCR. Moreover, both maternal gain in weight and undetectable concentrations of leptin in sera in leptin-deficient ob/ob mothers bearing heterozygote (ob/+) fetuses suggested that the mouse fetus and placenta do not make a significant contribution to the dramatic increase in maternal plasma concentrations of leptin during late gestation. It is therefore concluded that neither fetal- nor placental-derived leptin modulates maternal weight gain during pregnancy.

The influence of back pain on balance and functional mobility in 65- to 75-year-old women with osteoporosis.

To determine whether the presence of back pain and its related disabilities are determinants of balance and functional mobility in a group of women with osteoporosis, we carried out a cross-sectional analysis of 93 community-dwelling women with osteoporosis between the ages of 65 and 75 years old. We assessed health history, anthropometrics, self-report of current physical activity level and self-report of back pain (intensity and pain-related disabilities). Balance was measured by computerized dynamic posturography and functional mobility was assessed by timed figure-of-eight test. The prevalence of back pain was high (75%) in this cohort of older women with osteoporosis. Age was the major determinant of both balance and functional mobility and accounted for 9% and 14% of the variance, respectively. After accounting for age, back pain explained an additional 9% of the variance in balance and 13% of the variance in functional mobility. The high prevalence of back pain demonstrates the importance of pain management in the treatment of osteoporosis. Furthermore, the finding of self-reported back pain as a determinant of both balance and functional mobility suggests that this measure may deserve attention when screening women with osteoporosis for fracture risk. Prospective studies are needed to determine whether pain management will improve balance and functional mobility.

T594M mutation of the beta-subunit of the epithelial sodium channel in Ghanaian populations from Kumasi and London and a possible association with hypertension.

We have tested 186 individuals from Ghana, 95 indigenous and 91 who have settled in the United Kingdom, for the presence of the T594M mutation in the beta-subunit of the epithelial sodium channel, which is associated with hypertension in black populations. The group living in Ghana had a mean age of 27 years and were normotensive, but had an increased frequency of the T allele compared to the London-based population. If this is reflected in larger studies, and the link with hypertension is maintained in the Ghanaian population, this mutation could be a significant cause of hypertension in Ghana.

Atrial natriuretic peptide gene G664A polymorphism and the risk of ischemic cerebrovascular disease.

The atrial natriuretic peptide (ANP) gene may underlie stroke susceptibility and sensitivity to cerebral ischemia in an animal model of stroke. The authors investigate its role in humans by genotyping a polymorphism (G664A) in 436 patients with ischemic cerebrovascular disease and 295 community control subjects. The frequency of this variant was similar in both groups and across the different stroke subtypes. The ANP gene G664A polymorphism is therefore unlikely to be an important risk factor for ischemic stroke in this population.

Leptin requirement for conception, implantation, and gestation in the mouse.

The ob/ob mouse has a complete absence of circulating leptin, resulting in obesity and infertility. Using the minimum daily dose of leptin required to maintain normal body weight and sexual maturation (5 mg/kg, ip), leptin-treated ob/ob females were mated with either wild-type (+/+) or leptin-treated ob/ob males. The leptin treatment continued throughout pregnancy until weaning or was withdrawn at 0.5, 3.5, 6.5, or 14.5 d post coitum (dpc). Normal pregnancy and parturition with pups of normal weight resulted when ob/ob females were mated with +/+ males and leptin treatment was continued throughout pregnancy (6 of 8 pregnancies), to 14.5 dpc (6 of 8 pregnancies), or to 6.5 dpc (9 of 12 pregnancies). Pregnancy did not result when treatment was stopped at 3.5 dpc (1 of 7 pregnancies) or 0.5 dpc (0 of 6 pregnancies). Similar results were obtained when leptin-treated ob/ob females were mated with leptin-treated ob/ob males. The newborn pups failed to survive after birth in groups treated with leptin up to 14.5 and 6.5 dpc despite reinstating leptin at birth. This appeared to be due to a lack of development of the mammary glands. In conclusion, we have shown that leptin is essential for normal preimplantation and/or implantation processes. It is also essential for normal development of the mammary glands, but is not required for pregnancy and parturition once implantation is established.

Results of a 10 week community based strength and balance training programme to reduce fall risk factors: a randomised controlled trial in 65-75 year old women with osteoporosis.

OBJECTIVE: To test the efficacy of a community based 10 week exercise intervention to reduce fall risk factors in women with osteoporosis. METHODS: Static balance was measured by computerised dynamic posturography (Equitest), dynamic balance by timed figure of eight run, and knee extension strength by dynamometry. Subjects were randomised to exercise intervention (twice weekly Osteofit classes for 10 weeks) or control groups. RESULTS: The outcome in 79 participants (39 exercise, 40 control) who were available for measurement 10 weeks after baseline measurement is reported. After confounding factors had been controlled for, the exercise group did not make significant gains compared with their control counterparts, although there were consistent trends toward greater improvement in all three primary outcome measures. Relative to the change in control subjects, the exercise group improved by 2.3% in static balance, 1.9% in dynamic balance, and 13.9% in knee extension strength. CONCLUSIONS: A 10 week community based physical activity intervention did not significantly reduce fall risk factors in women with osteoporosis. However, trends toward improvement in key independent risk factors for falling suggest that a study with greater power may show that these variables can be improved to a level that reaches statistical significance.

Circulating cardiac troponin-T in patients before and after renal transplantation.

BACKGROUND: The diagnostic and prognostic use of cardiac troponin T (cTnT) in patients with renal failure has been questioned. Raised serum concentrations of cTnT, with no apparent signs of cardiac damage using conventional methods of detection, have been reported. We aimed to relate circulating concentrations of cTnT to improved renal function following renal transplantation over a one-year period. METHOD: Plasma cTnT was analysed from patients with end stage renal disease before and after transplantation and subsequently at 1, 3, 6 and 12 months. Eight patients had diabetes, 14 had hyperlipidaemia, 8 were smokers and 4 were ex-smokers; all were hypersensitive. RESULTS: At the time of transplantation, 3 of the 32 patients (9.4%) had plasma cTnT concentrations above 0.1 microg/l. In addition to these three patients, five others showed raised cTnT over the one-year period. CONCLUSIONS: The overall trend in circulating cTnT concentrations did not seem to be affected by improved renal function. However, all of the patients that had raised cTnT concentrations at any stage of the one-year period had explainable pathologies or were exposed to multiple cardiac risk factors.

T594M and G442V polymorphisms of the sodium channel beta subunit and hypertension in a black population.

Polymorphisms of the epithelial sodium channel may raise blood pressure by increasing renal sodium reabsorption. This study examines frequency distributions and associations with hypertension of the T594M and of the G442V polymorphisms of the beta subunit of the epithelial sodium channel in a population-based sample. We studied a stratified random sample of 459 subjects (279 women), aged 40-59 years, of black African origin from general practices' lists within a defined area of South London. All were first generation immigrants. The polymorphic variants were detected using single strand conformational polymorphism technique (SSCP). The prevalence of hypertension (BP > or =160 and/or 95 mm Hg or on drug therapy) was 43%; of these, 76% were on drug therapy. The main analysis was carried out by three ordered blood pressure categories (I to III) according to increasing blood pressure and presence or absence of drug therapy. The frequency of the 594M variant (heterozygotes and homozygotes) was 4.6%; the frequency of the 442V variant was higher (27.0%). The frequency of the 594M variant increased with increasing blood pressure category (P = 0.05) and was more common in hypertensives than normotensives. By contrast the frequency of the 442V variant did not vary across increasing blood pressure categories (P = 0.62). No gender difference was observed. Adjustment for age, sex and body mass index did not alter these findings. These results suggest that the 594M variant may contribute to high blood pressure in black people of African origin whereas the G442V polymorphism is unlikely to influence blood pressure in this population.

Decreased wild-type full-length Et-A and -B receptors in neuroblastoma and Ewing sarcoma cells.

BACKGROUND: Endothelins and their receptors, Et-A and Et-B, play an essential role in differentiation and migration of neural crest cells. Expression of endothelin receptors has been examined in neuroblastoma and Ewing sarcoma cell lines. PROCEDURE: RNA was amplified for Et-A and Et-B by RT-PCR. Amplified products were cloned into the expression vector pLNCX, which was used to transfect CHO cells. Binding characteristics of transfected CHO cells were examined. RESULTS: Full-length Et-A mRNA was identified in all cell lines, in addition to a truncated Et-A product. CHO cells expressing full-length Et-A bound to endothelin, but cells expressing truncated Et-A did not. Full length Et-B mRNA was not detected, but two smaller molecular weight products were amplified. These are as yet uncharacterised. CONCLUSIONS: These results suggest that endothelins and their receptors may be important in the development and biology of neuroblastoma and Ewing sarcoma.

Exercise in the prevention of falls in older people: a systematic literature review examining the rationale and the evidence.

Falls are a major source of death and injury in elderly people. For example, they cause 90% of hip fractures and the current cost of hip fractures in the US is estimated to be about 10 billion dollars. Age-related changes in the physiological systems (somatosensory, vestibular and visual) which contribute to the maintenance of balance are well documented in older adults. These changes coupled with age-related changes in muscle and bone are likely to contribute to an increased risk of falls in this population. The integrated rehabilitation-based model of fall risk factors reveals multiple sites for interventions that may reverse fall risk factors. Regular exercise may be one way of preventing falls and fall-related fractures. The evidence for this contention comes from a variety of sources. On the basis of 9 randomised controlled studies conducted since 1996, exercise appears to be a useful tool in fall prevention in older adults, significantly reducing the incidence of falls compared with control groups. However, current limitations such as inconsistencies in the measurement of key dependent and independent variables do not, at present, permit a meta-analysis of intervention trials. Further investigation, using trials designed with the current limitations in mind, is necessary to establish the optimum exercise programme to maximise fall prevention in older adults.

Cardiac troponin T and creatine kinase MB are not increased in exterior oblique muscle of patients with renal failure.

BACKGROUND: Serum cardiac troponin T (cTnT) concentrations may be increased in patients with renal dysfunction without evidence of cardiac damage, as assessed by conventional methods. It has been suggested that these positive measurements result from the expression in skeletal muscle of fetal isoforms of cTnT, which are detected by the cTnT immunoassay. METHODS: Skeletal muscle (exterior oblique) biopsies were taken from healthy living kidney donors (n = 5) and transplant recipients (n = 19). The amounts of cTnT and creatine kinase (CK) isoenzymes in skeletal muscle of healthy controls were compared with those in patients with renal failure (Wilcoxon-Mann-Whitney test). cTnT was measured quantitatively by a second-generation assay, with a limit of detection of 1 microg/g of protein, and qualitatively by immunohistochemistry and immunoblotting. CK-MB was measured by quantitative electrophoresis. RESULTS: Minute quantities of cTnT were detected in 2 of the 5 (40%) control samples and 9 of the 19 (47%) renal failure samples, respectively, at mean concentrations of <5 microg/g of protein for both subject groups. This was <1/6000th that found in heart muscle. There was no significant difference in cTnT or CK-MB content in skeletal muscle between healthy controls and patients with renal failure. Increased serum cTnT did not predict detectable cTnT in skeletal muscle. cTnT was not detected qualitatively by immunoblotting or immunohistochemistry in any skeletal muscle samples. CONCLUSIONS: Uremia does not affect the content of cTnT or CK-MB in exterior oblique muscle, suggesting that cTnT detected in serum from patients with renal failure does not originate from skeletal muscle.

Cardiac troponins and creatine kinase content of striated muscle in common laboratory animals.

Animal models are important for the investigation of human heart pathology, novel treatments, and medical or surgical interventions for disease. Serum markers of myocardial damage may also be important tools within this field of research. In order to assess the cardiac specificity of widely utilised serum markers, we measured the cardiac troponins and creatine kinase (CK) isoenzymes in cardiac and skeletal muscle samples taken from dog, monkey, pig and rat. These samples were also analysed by immunoblotting for cardiac troponin I (cTnI) and cardiac troponin T (cTnT). The content of cTnI and cTnT in skeletal muscle was below 0.6% of that found in heart for all animal species studied. This low immunoreactivity in skeletal muscle was confirmed by immunoblot analysis. The content of CK was higher in skeletal muscle than in heart muscle for all species. The CK-MB/total CK ratio was lower in skeletal muscle than in cardiac muscle for all species. The differences in CK-MB content of skeletal muscle and heart muscle were much less pronounced than the tissue differences in the amounts of the cardiac troponins. The cardiac troponins are potentially useful serum markers of myocardial damage, with high specificity for myocardial muscle in these common laboratory animals. Creatine kinase-MB is much less cardiac-specific.

A connexin 26 mutation causes a syndrome of sensorineural hearing loss and palmoplantar hyperkeratosis (MIM 148350).

We report a missense mutation in the connexin 26 gene (GJB2) in a family with an autosomal dominant syndrome of hearing loss and hyperkeratosis. The affected family members have high frequency, slowly progressive, bilateral, sensorineural hearing loss and palmoplantar hyperkeratosis. The mutation causes an amino acid substitution (G59A), which may disrupt a reverse turn in the first extracellular loop of connexin 26. Connexin 26 mutations have been reported in syndromes of deafness and palmoplantar keratoderma. These data provide additional evidence for the role of connexin 26 in syndromes of this type.