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Biomedical subjects

Peter Leedman

Publications and source records attributed to Peter Leedman.

8 recordsLinked to original sources
PubMed2005

Grb7-SH2 domain dimerisation is affected by a single point mutation.

Growth factor receptor bound protein 7 (Grb7) is an adaptor protein that is co-overexpressed and forms a tight complex with the ErbB2 receptor in a number of breast tumours and breast cancer cell lines. The interaction of Grb7 with the ErbB2 receptor is mediated via its Src homology 2 (SH2) domain. Whilst most SH2 domains exist as monomers, recently reported studies have suggested that the Grb7-SH2 domain exists as a homodimer. The self-association properties of the Grb7-SH2 domain were therefore studied using sedimentation equilibrium ultracentrifugation. Analysis of the data demonstrated that the Grb7-SH2 domain is dimeric with a dissociation constant of approximately 11 muM. We also demonstrate, using size-exclusion chromatography, that mutation of phenylalanine 511 to an arginine produces a monomeric form of the Grb7-SH2 domain. This mutation represents the first step in the engineering of a Grb7-SH2 domain with good solution properties for further biophysical and structural investigation.

Arginine↗
PubMed2005

A 20-week randomized controlled trial of estradiol replacement therapy for women aged 70 years and older: effect on mood, cognition and quality of life.

The results of several observational studies suggest that the use of estrogen replacement is associated with better mood, cognitive function and quality of life. Such findings are consistent with those of laboratory-based research showing that estrogen promotes neuronal sprouting, enhances cholinergic activity in the brain, decreases brain and plasma levels of beta-amyloid, increases serotonin postsynaptic responsivity and the turnover of noradrenaline, and inhibits monoamine oxidase activity. However, the findings from the Women's Health Initiative controlled trial showed that hormone replacement (estrogen plus progestin) not only failed to improve mood, cognition and quality of life but also increased the risk of dementia. At present, there is limited information about the effect of unopposed estradiol replacement therapy (ERT) on the mental health outcomes of women at increased risk of cognitive decline (aged 70 years and over). We designed the present randomized, double-blind, placebo-controlled trial to clarify this issue. One hundred and fifteen women were randomized to treatment with estradiol (n=58; 2mg per day) or placebo for a total period of 20 weeks. The outcomes of interest in this study included changes in the Beck Depression Inventory (BDI) scores between baseline and week 20, as well as changes in quality of life scores (as measured by the SF-36) and cognitive function (CAMCOG, Block Design, Memory for Faces, California Verbal Learning Test (CVLT) and verbal fluency (VF)). Nineteen women treated with estradiol and 10 of those treated with placebo discontinued the use of the medication during trial, most frequently due to adverse reactions (OR=4.11, 95% CI=1.29-15.37). Intention-to-treat analysis showed that the active and placebo groups did not differ in their response to treatment in any of the outcome measures (p>0.05). A separate analysis restricted to women who completed the 20-week-trial produced similar negative results. The results of this trial indicate that the use of a relatively high dosage of unopposed estrogen replacement for 20 weeks is not associated with significant changes in cognitive function, mood and quality of life. Other more efficacious and safer interventions need to be devised with the aim of improving the mental state and quality of life of older women.

Affect↗
PubMed2005

Contribution of the MTHFR gene to the causal pathway for depression, anxiety and cognitive impairment in later life.

Homocysteine (Hcy) is harmful to neurons and blood vessels, including the cerebral microvasculature. It is possible that such effects contribute to the cascade of events that leads to cognitive decline, dementia, and depression in later life. Hcy is produced during the metabolism of the essential amino-acid methionine, which also involves a methyl group transfer derived from folate and choline metabolism. Its plasma level can be influenced by factors such as age, vitamin deficiency, renal function, and a common mutation in the methylenetetrahydrofolate reductase (MTHFR) gene, where cytosine is replaced by thymidine (C-->T) at nucleotide position 677. Subjects with the TT genotype have higher homocysteine levels and may be particularly prone to experiencing depression as a result of high plasma Hcy and dysfunction of methylation metabolic pathways critical to the synthesis of noradrenaline and serotonin. We designed the present study to investigate whether older women with the TT genotype would have higher depression and lower cognitive scores than women with CT and CC genotypes. A total of 240 community-dwelling women aged 70 years or over volunteered to take part in the study - 29 carried the TT genotype, 113 the CT and 98 the CC genotype. The Beck Depression Inventory (BDI) score for subjects with the TT genotype was statistically similar to the other groups (P = 0.609). Plasma Hcy showed a modest and significant correlation with BDI scores (r = 0.21) that was independent from age, B12 and folate levels. There was no association between beck anxiety inventory (BAI) scores and MTHFR genotype or homocysteine levels. The cognitive assessment of participants included measures of verbal memory, memory for faces, verbal fluency, visuo-spatial abilities and the cognitive section of the Cambridge Examination For Mental Disorders Of The Elderly (CAMCOG)-MTHFR genotype had no clear association with cognitive scores. These results indicate that, in isolation, the MTHFR C677T gene variation does not play an important role in the modulation of mood and cognitive performance in later life.

Aged↗
PubMed2005

Association between physiological serum concentration of estrogen and the mental health of community-dwelling postmenopausal women age 70 years and over.

OBJECTIVE: The authors investigated the association between physiological levels of estrogen and mood/cognitive functioning among older postmenopausal women. METHODS: This was a cross-sectional study of 265 postmenopausal women (mean age: 74.6 years), who were given a semistructured psychiatric interview (CAMDEX-R) and self-rated their health with the Beck Depression and Anxiety Inventories (BDI and BAI) and the SF-36 Health Survey. Cognitive abilities were assessed with the cognitive subsection of the CAMDEX (CAMCOG), the Word Lists subtest of the Wechsler Memory Scale, and the Block Design and Verbal Fluency subtests of the Wechsler Adult Intelligence Scale. Estradiol- and estrone-sensitive immunoassays were used to measure serum estradiol and estrone. RESULTS: Women in the lowest 50th percentile of serum estradiol were more likely than women in the highest 50th percentile to have BDI scores suggestive of clinically significant or severe depression. Women in the lowest 50th percentile of serum estrone had higher BAI scores. There was no significant association between serum estradiol/estrone and cognitive functioning. CONCLUSIONS: Physiological serum concentrations of estradiol and estrone are inversely associated with depression and anxiety scores in older postmenopausal women. The association between serum estradiol and depression ratings is not linear and seems to be subject to a threshold effect.

Activities of Daily Living↗
PubMed2005

Subjective memory complaints with and without objective memory impairment: relationship with risk factors for dementia.

OBJECTIVE: The authors investigated the frequency distribution of well-established risk factors for dementia--high plasma homocysteine and the apolipoprotein E epsilon4 allele (APOE epsilon4)--among older women with subjective memory complaints (SMC) but no cognitive impairment, and with mild cognitive impairment (MCI). METHODS: This was a cross-sectional, community-based study. RESULTS: Women with MCI had higher total plasma homocysteine than healthy-comparison subjects. There was also a nonsignificant excess of APOE epsilon4 carriers in the MCI than in the healthy group. Participants with SMC had higher depression and anxiety scores than healthy-comparison subjects, but did not differ from subjects in the healthy-comparison group in relation to their total plasma homocysteine and APOE epsilon4 distribution. CONCLUSIONS: MCI seems to be more closely related to well-established risk factors for dementia than is SMC.

Aged↗
PubMed2003

Inherent instability of plasminogen activator inhibitor type 2 mRNA is regulated by tristetraprolin.

Plasminogen activator inhibitor type 2 (PAI-2) is a serine protease inhibitor that is subject to regulation at the post-transcriptional level. At least two mRNA instability elements reside within the PAI-2 transcript; one in the coding region and another within the 3'-untranslated region (UTR). For the latter, a functional AU-rich motif (ARE) has been identified that provides a binding site for a number of cellular proteins, including the mRNA stability protein, HuR. In this study, we used the yeast three-hybrid system to screen a human leukocyte cDNA library to identify other proteins that associate with the PAI-2 ARE. This screen identified tristetraprolin (TTP) as a PAI-2 mRNA ARE-binding protein. UV cross-linking and immunoprecipitation experiments showed that TTP expressed in HEK293 cells could associate with the PAI-2 ARE in vitro. Co-transfection of plasmids expressing TTP and PAI-2 in HEK293 cells resulted in an increase in the decay rate of PAI-2 mRNA and loss of PAI-2 protein in a process that was dependent upon the PAI-2 3'-UTR. The 29-nt PAI-2 AU-rich element alone was also capable of conferring TTP-dependent mRNA instability to a reporter transcript. The extent of PAI-2 mRNA stability was remarkably sensitive to TTP since TTP-dependent PAI-2 mRNA decay occurred at TTP levels that were below Western blot detection limits. This study identifies TTP as a functional PAI-2 ARE-binding protein that modulates the post-transcriptional regulation of the PAI-2 gene.

3' Untranslated Regions↗
PubMed2002

Contribution by different fuels and metabolic pathways to the total ATP turnover of proliferating MCF-7 breast cancer cells.

For the past 70 years the dominant perception of cancer metabolism has been that it is fuelled mainly by glucose (via aerobic glycolysis) and glutamine. Consequently, investigations into the diagnosis, treatment and the basic metabolism of cancer cells have been directed by this perception. However, the data on cancer metabolism are equivocal, and in this study we have sought to clarify the issue. Using an innovative system we have measured the total ATP turnover of the MCF-7 breast cancer cell line, the contributions to this turnover by oxidative and glycolytic ATP production and the contributions to the oxidative component by glucose, lactate, glutamine, palmitate and oleate. The total ATP turnover over approx. 5 days was 26.8 micromol of ATP.10(7) cells(-1).h(-1). ATP production was 80% oxidative and 20% glycolytic. Contributions to the oxidative component were approx. 10% glucose, 14% glutamine, 7% palmitate, 4% oleate and 65% from unidentified sources. The contribution by glucose (glycolysis and oxidation) to total ATP turnover was 28.8%, glutamine contributed 10.7% and glucose and glutamine combined contributed 40%. Glucose and glutamine are significant fuels, but they account for less than half of the total ATP turnover. The contribution of aerobic glycolysis is not different from that in a variety of other non-transformed cell types.

Adenosine Triphosphate↗