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Christine Graf

Publications and source records attributed to Christine Graf.

12 recordsLinked to original sources
PubMed2007

Enhanced ceramide-induced apoptosis in ceramide kinase overexpressing cells.

We evaluated how increased levels of ceramide kinase (CerK) would impact the growth of COS-1 fibroblasts and RBL-2H3 basophils. The low CerK activity in these cells was strongly up-regulated upon recombinant expression of CerK. CerK-overexpressing COS-1 cells depended on higher concentrations of serum for their growth and displayed many filipodia. The two CerK-overexpressing cell lines were more sensitive to C2-ceramide-mediated apoptosis, and this correlated with the production of C2-ceramide-1-phosphate by CerK. This study indicates that ceramide kinase may participate in the control of cell growth, and establishes a novel assay that will be valuable for testing ceramide kinase inhibitors.

Animals↗
PubMed2006

A critical beta6-beta7 loop in the pleckstrin homology domain of ceramide kinase.

CerK (ceramide kinase) produces ceramide 1-phosphate, a sphingophospholipid with recognized signalling properties. It localizes to the Golgi complex and fractionates essentially between detergent-soluble and -insoluble fractions; however, the determinants are unknown. Here, we made a detailed mutagenesis study of the N-terminal PH domain (pleckstrin homology domain) of CerK, based on modelling, and identified key positively charged amino acid residues within an unusual motif in the loop interconnecting beta-strands 6 and 7. These residues are critical for CerK membrane association and polyphosphoinositide binding and activity. Their mutagenesis results in increased thermolability, sensitivity to proteolysis, reduced apparent molecular mass as well as propensity of the recombinant mutant protein to aggregate, indicating that this loop impacts the overall conformation of the CerK protein. This is in contrast with most PH domains whose function strongly relies on charges located in the beta1-beta2 loop.

Amino Acid Sequence↗
PubMed2006

Effects of ceramide-1-phosphate on cultured cells: dependence on dodecane in the vehicle.

Ceramide-1-phosphate (C1P), the product of ceramide kinase, is a sphingophospholipid with recently recognized signaling properties. In particular, it was reported to be mitogenic and capable of direct stimulation of cytosolic phospholipase A(2alpha). Much of the present knowledge has relied on the use of C1P of various acyl chain lengths, together with diverse protocols to deliver it to cultured cells. A mixture of ethanol (or methanol) with dodecane, as the vehicle, has become popular. However, the contribution of this solvent to the observed effects of C1P has not been documented. Here, we show that addition of C1P in ethanol-dodecane to culture medium leads to irreversible cytotoxic effects. These culminate in mitochondrial swelling, vacuole formation, and cell death. Not only the toxicity of C1P, but also its ability to trigger prostaglandin E2 release, is fully dependent upon addition of a premade C1P-dodecane mixture. Furthermore, we show that these effects are not restricted to C1P. They result from the capacity of dodecane to interact with phospholipids; hence, they go undetected with a vehicle control. This study should raise awareness about the use of dodecane for phospholipid delivery and, in turn, help in unraveling C1P signaling, which is still poorly understood.

Alkanes↗
PubMed2006

[Overweight and obesity in childhood and adolescence. Is prevention possible?].

The prevalence of overweight and obesity in children and adolescents is increasing. In Germany, 10-20% of children and youth are overweight and obese. Childhood obesity is associated with cardiovascular and other comorbidities. 25% suffer from arterial hypertension and/or hypercholesterolemia, 1% from diabetes mellitus type 2. In addition, one third suffer from orthopedic and psychosocial disorders.Therefore, countermeasures are necessary. Kindergarten or school settings offer a possibility for preventive measures. Results, however, are inconsistent and depend on several factors such as socioeconomic status, parental integration, etc. To counteract the epidemic of obesity, national and international data should be collected, results and recommendations adapted to individual necessities of different settings. The implementation of such strategies is only possible with a combined and qualified procedure by a concerted and qualified action of all health care employees based on adequate political structures.

Adolescent↗
PubMed2006

Who benefits from intervention in, as opposed to screening of, overweight and obese children?

AIMS: StEP TWO is a school- and family-based intervention consisting of extra lessons, healthy nutrition and physical education for overweight and obese children in primary schools, aimed at reducing body mass index by maintenance or reduction of weight, and improving motor abilities. We analysed differences in changes in anthropometric, cardiovascular and obesity parameters between children who underwent intervention, non-participants in intervention, and controls. METHODS: Anthropometric data and waist circumference were recorded for 1678 children; body mass index and body mass index-standard deviation score were calculated. Blood pressure was measured after 5 minutes at rest. 121 overweight and obese children enrolled at 3 schools involved in programmes of intervention were invited to take part; 40 of them completed the programme from November 2003 to July 2004. Of these overweight children, 74 were invited, but did not take part. As controls, we enrolled 155 overweight and obese children from 4 other schools. RESULTS: After the programme, the children involved in intervention showed a lower increase in the body mass index (0.3 plus or minus 1.3 versus 0.7 plus or minus 1.2 kilograms per metre squared) and an approximately three times higher diminution of the body mass index-standard deviation score in comparison with their controls (-0.15 plus or minus 0.26 versus 0.05 plus or minus 0.27). Systolic blood pressure was significantly lowered by 9.5 plus or minus 19.6 millimetres of mercury in those involved in intervention, but increased in the control group by 0.5 plus or minus 16.5 millimetres of mercury. Among those invited but not participating, the increase of the body mass index (0.5 plus or minus 1.3 kilograms per metre squared) was less, and the reduction of the body mass index-standard deviation score (-0.09 plus or minus 0.31) and systolic blood pressure (-5.3 plus or minus 15.6 millimetres of mercury) was higher than in the control group. Overweight but not obese children seem to benefit from a screening examination alone. CONCLUSIONS: Early preventive measures in schools are necessary and effective for overweight and obese primary school children. The screening itself seems also to have a minor positive effect, especially for overweight children. Sustainability of the observed improvements over a longer period remains to be confirmed.

Blood Pressure↗
PubMed2006

Endothelial progenitor cells: a new target for the prevention of cardiovascular diseases.

Endothelial progenitor cells (EPCs) are circulating precursor cells that have been implicated recently in vascular and cardiac regeneration. There is an ongoing discussion on the immunocytological definition of EPCs, based on various surface markers, and currently different cell types are included in the term 'EPC'. This review summarizes the mechanisms that influence function, survival, mobilization and differentiation of EPCs. Furthermore, there are several reports on the clinical use of EPCs for the treatment of cardiovascular diseases. We have focused specifically on the influence of physical activity on EPC function.

Cardiovascular Diseases↗
PubMed2005

Characterization of a ceramide kinase-like protein.

Ceramide is a key player governing cell fate, and its conversion to ceramide-1-phosphate by ceramide kinase (CERK) is emerging as an important mean to regulate apoptosis and inflammatory processes. We identified a new ceramide kinase homolog, designated CERK-like protein (CERKL) and we compared it to the known CERK. Real time-PCR analysis of human tissues revealed a restricted pattern of expression for CERKL mRNA. Surprisingly, various ceramides, known substrates for CERK, were not phosphorylated by CERKL in vitro. Upon 32P(i)-pulse labeling of COS-1 cells transiently expressing CERKL, or incubation with NBD-C6-ceramide, ceramide-1-phosphate was not detected. After recombinant expression in COS-1 cells, CERKL was partially recovered in the soluble fraction, as a phosphorylated protein. Live cell imaging indicated localization of GFP-tagged CERKL to many cell compartments, including specific association with nucleoli. Two splice variants of CERKL did not localize to nucleoli nor did a CERKL variant with a point mutation in the putative ATP binding site. We also studied a naturally occurring CERKL mutant (R257X), recently linked to the pathology of retinitis pigmentosa. It accumulated in the nucleus but was not associated with nucleoli. Treatment with the calcium ionophore A23187 led to clearing of CERKL from nucleoli, but had no effect on the R257X CERKL mutant. Collectively, although kinase activity of CERKL remains to be proven, these findings suggest a functional link between CERKL and its nucleolar localization. Furthermore, we propose that the cause for retinitis pigmentosa in patients bearing the CERKL R257X mutation might be the accumulation of a truncated CERKL protein in the nucleus.

Amino Acid Sequence↗
PubMed2005

Data from the StEP TWO programme showing the effect on blood pressure and different parameters for obesity in overweight and obese primary school children.

UNLABELLED: Obesity in childhood, which is associated with cardiovascular risk factors such as hypertension, is on the increase. Countermeasures are necessary. In this paper, we present the baseline and final data from the StEP TWO programme, a prospective study to prevent overweight and obesity in primary schools. METHODS: We recorded and calculated, from 1689 children, anthropometric data, including analyses of bioelectric impedance, waist and hip circumferences, body mass index and its standard deviation, and the ratio of waist to hip. Blood pressure was measured after 5 minutes at rest. From the three schools involved in a programme of intervention, 121 children were invited to take part, and 40 (33.1 per cent) completed the programme. The effect was compared with 155 overweight and obese children identified at the 4 control schools. RESULTS: 830 (49.5 per cent) boys and 848 girls (50.5 per cent) took part. Their mean age was 8.2 plus or minus 1.3 years, their height was 1.31 plus or minus 0.09 metres, they weighed 30.0 plus or minus 8.2 kilograms, and their mean index of body mass was 17.1 plus or minus 2.9 kilograms per metre squared. Of the children, 7.3 per cent were obese, 10.4 per cent were overweight, 75.7 per cent had normal weights, and 6.6 per cent were underweight. Resting hypertension was observed in 2.3 per cent of the children. Increased blood pressure was associated with a higher body weight, body mass index, standard deviation score for body mass index, and waist and hip circumferences (each p < 0.001), but not with the ratio of waist to hip. Hypertension at rest was also found in 11.0 per cent of obese children, 4.4 per cent of those who were overweight, 1.2 per cent of those with normal weight, and 1.0 per cent of underweight children (p < 0.001). After the intervention, the increase of the body mass index tended to be lower in those in whom we had intervened (p = 0.069), and in these the decrease of the standard deviation score for body mass index was significantly higher (p = 0.028). Systolic blood pressure was reduced by about 10 millimetres of mercury in those in whom we had intervened (p = 0.002), while there were no changes in the control group. Diastolic blood pressure was lowered by 3 millimetres of mercury, but this was not significant. CONCLUSION: Obese children had the highest values for systolic and diastolic blood pressure. Increased levels of blood pressure are associated with other parameters of obesity, such as the circumference of the waist and hip. Early preventive measurements in childhood are necessary, and appropriate intervention appears to be effective.

Blood Pressure↗
PubMed2004

Ceramide kinase targeting and activity determined by its N-terminal pleckstrin homology domain.

The N-terminus of ceramide kinase (CERK) is thought to be myristoylated and to contain a pleckstrin homology (PH) domain. We found that deletion of this region (DeltaPH-CERK) ablates activity. This is not due to prevention of N-terminal myristoylation since a G2A CERK mutant, which cannot be myristoylated, was active. CERK was able to bind liposomes, as well as the isolated unmyristoylated PH domain; DeltaPH-CERK was not. Upon analysis of EGFP-tagged proteins, CERK was found associated with the Golgi complex. Osmotic cell swelling induced translocation of CERK to the plasma membrane and formation of large vesicles displaying bound CERK. None of these features occurred with DeltaPH-CERK, which remained disseminated throughout the cytoplasm. These findings show that the PH domain of CERK is essential for localization, translocation, and activity of this lipid kinase.

Animals↗
PubMed2004

Physical activity, leisure habits and obesity in first-grade children.

BACKGROUND: Overweight and obesity are already on the rise in early childhood years. The relationships between genetic factors, malnutrition and physical inactivity are the underlying mechanisms. In this study, we examine the association between body indices, motor abilities and active (sport) and passive (television/computer) leisure time activities in a cohort of first-grade pupils. METHODS: The study group consisted of 344 children (51.5% male, 48.5% female). They were 6.8+/-0.4 years old, height was 123.9+/-4.9 cm, weight 24.8+/-5.0 kg, body mass index (BMI) 16.1+/-2.3 kg/m. After determination of the anthropometric data, a fitness test was performed in order to determine motor abilities. Parents were questioned about their children's leisure time activities, using a standardized questionnaire. Differences between BMI groups were evaluated using multivariate ANCOVA, adjusted for gender and age. RESULTS: Based on German BMI references, overweight and obesity were found in 12% of the children. They had poorer results with respect to endurance (P<0.001), leg strength (P=0.002), co-ordination and balance (P=0.045) and spent more leisure time in watching television and at the computer (each P<0.001). No differences were found between their active leisure habits such as club sports. DISCUSSION: Our examinations with first-grade children show no differences in active leisure habits between obese children and their counterparts, although the former had poorer results in motor abilities, but they spend more time on sedentary leisure habits like audiovisual media. A possible explanation is their fewer regular daily activities.

Analysis of Variance↗
PubMed2002

[Arteriosclerosis -- a lifelong challenge].

BACKGROUND: Effective prevention of cardiovascular diseases is of utmost importance in Western civilizations as they are on top of mortality statistics. PRIMARY PREVENTION: Physical exercise plays an important role in optimizing the individuals cardiovascular risk profile. However in the absence of scientifically based studies the potential benefit of physical exercise is often being discussed. Recently by several population-based studies it has been proven that physical exercise is inversely related to long-term cardiovascular mortality in both man and women of all age groups, even after adjustment for other risk factors. SECONDARY PREVENTION: Even for secondary prevention in clinical studies and meta-analyses a reduction of all causes and cardiovascular mortality of 20-45% was found after physical exercise. TYPE OF SPORTS: At present it is being discussed controversially which type of sports would be most beneficial. Recent studies have shown that cardiovascular risk reduction is not only the consequence of vigorous exercise, especially endurance training, but can also be achieved by moderate training programs like walking or increased daily activities. CONCLUSION: Current epidemiological data reveal the necessity to perform more physical activity/exercise training, which would best be integrated in a health-oriented lifestyle. An early beginning, even in childhood, is important.

Arteriosclerosis↗