Prenyltransferase. Kinetic studies of the 1'-4 coupling reaction with avian liver enzyme.

Journal ArticlePrenyltransferase catalyzes the sequential, irreversible 1'-4 condensation of isopentenyl-PP with dimethylallyl-PP and geranyl-PP to yield farnesyl-PP. A kinetic study shows substrate inhibition by isopentenyl-PP at concentrations above 0.7 microM when the concentration of geranyl-PP is 1.0 microM or less as a result of binding by the homoallylic substrate to the allylic region of the active site. Inhibition studies were carried out with the products, farnesyl-PP and PPi, and dead-end inhibitors 2-F-isopentenyl-PP and 2-F-geranyl-PP, analogues for the normal substrates. Competitive patterns were seen for farnesyl-PP and 2-F-geranyl-PP when geranyl-PP was varied, while noncompetitive patterns were found for all other combinations. A minor form of PPi, MgHPPi-, is implicated as the species of PPi in the magnesium-containing buffer which binds most tightly to the enzyme. This observation explains why K's for PPi calculated from the total concentration of PPi are much larger than K's for the organic pyrophosphates. The lack of regiospecificity in the binding of isopentenyl-PP, as evidenced by substrate inhibition patterns, introduces an element of ambiguity into mechanistic interpretations, and it is not possible to distinguish between ordered and random mechanisms on the basis of inhibition studies

Impact of Visit-to-Visit Glycemic Variability on the Risks of Macrovascular and Microvascular Events and All-Cause Mortality in Type 2 Diabetes: The ADVANCE Trial

OBJECTIVE There is no consensus on the importance of visit-to-visit glycemic variability in diabetes. Therefore, we assessed the effects of visit-to-visit variability (VVV) in HbA1c and fasting glucose on major outcomes in the ADVANCE (Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation) trial. RESEARCH DESIGN AND METHODS ADVANCE was a factorial randomized controlled trial of intensive glucose control and blood pressure lowering in patients with type 2 diabetes. VVV in the intensive glucose treatment group was defined using the SD of five measurements of HbA1c and glucose taken 3–24 months after randomization. Outcomes were combined macro- and microvascular events and all-cause mortality occurring post 24 months. Sensitivity analyses were performed using other indices of variability and in the standard glucose treatment group. RESULTS Among 4,399 patients in the intensive group, an increase in VVV of HbA1c was associated with an increased risk of vascular events (P = 0.01) and with mortality (P < 0.001): highest versus lowest tenth hazard ratio (95% CI) 1.64 (1.05–2.55) and 3.31 (1.57–6.98), respectively, after multivariable adjustment. A clear association was also observed between VVV of fasting glucose and increased risk of vascular events (P < 0.001; 2.70 [1.65–4.42]). HbA1c variability was positively associated with the risk of macrovascular events (P = 0.02 for trend), whereas glucose variability was associated with both macro- and microvascular events (P = 0.005 and P < 0.001 for trend, respectively). Sensitivity analyses using other indices, and patients in the standard glucose treatment group, were broadly consistent with these results. CONCLUSIONS Consistency of glycemic control is important to reduce the risks of vascular events and death in type 2 diabetes

Circulating amino acids and the risk of macrovascular, microvascular and mortality outcomes in individuals with type 2 diabetes : results from the ADVANCE trial

Aims/hypotheses We aimed to quantify the association of individual circulating amino acids with macrovascular disease, microvascular disease and all-cause mortality in individuals with type 2 diabetes. Methods We performed a case-cohort study (N = 3587), including 655 macrovascular events, 342 microvascular events (new or worsening nephropathy or retinopathy) and 632 all-cause mortality events during follow-up, in a secondary analysis of the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) study. For this study, phenylalanine, isoleucine, glutamine, leucine, alanine, tyrosine, histidine and valine were measured in stored plasma samples by proton NMR metabolomics. Hazard ratios were modelled per SD increase in each amino acid. Results In models investigating associations and potential mechanisms, after adjusting for age, sex and randomised treatment, phenylalanine was positively, and histidine inversely, associated with macrovascular disease risk. These associations were attenuated to the null on further adjustment for extended classical risk factors (including eGFR and urinary albumin/creatinine ratio). After adjustment for extended classical risk factors, higher tyrosine and alanine levels were associated with decreased risk of microvascular disease (HR 0.78; 95% CI 0.67, 0.91 and HR 0.86; 95% CI 0.76, 0.98, respectively). Higher leucine (HR 0.79; 95% CI 0.69, 0.90), histidine (HR 0.89; 95% CI 0.81, 0.99) and valine (HR 0.79; 95% CI 0.70, 0.88) levels were associated with lower risk of mortality. Investigating the predictive ability of amino acids, addition of all amino acids to a risk score modestly improved classification of participants for macrovascular (continuous net reclassification index [NRI] +35.5%, p <0.001) and microvascular events (continuous NRI +14.4%, p = 0.012). Conclusions/interpretation We report distinct associations between circulating amino acids and risk of different major complications of diabetes. Low tyrosine appears to be a marker of microvascular risk in individuals with type 2 diabetes independently of fundamental markers of kidney function.Peer reviewe

Circulating amino acids and the risk of macrovascular, microvascular and mortality outcomes in individuals with type 2 diabetes : results from the ADVANCE trial

Aims/hypotheses We aimed to quantify the association of individual circulating amino acids with macrovascular disease, microvascular disease and all-cause mortality in individuals with type 2 diabetes. Methods We performed a case-cohort study (N = 3587), including 655 macrovascular events, 342 microvascular events (new or worsening nephropathy or retinopathy) and 632 all-cause mortality events during follow-up, in a secondary analysis of the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) study. For this study, phenylalanine, isoleucine, glutamine, leucine, alanine, tyrosine, histidine and valine were measured in stored plasma samples by proton NMR metabolomics. Hazard ratios were modelled per SD increase in each amino acid. Results In models investigating associations and potential mechanisms, after adjusting for age, sex and randomised treatment, phenylalanine was positively, and histidine inversely, associated with macrovascular disease risk. These associations were attenuated to the null on further adjustment for extended classical risk factors (including eGFR and urinary albumin/creatinine ratio). After adjustment for extended classical risk factors, higher tyrosine and alanine levels were associated with decreased risk of microvascular disease (HR 0.78; 95% CI 0.67, 0.91 and HR 0.86; 95% CI 0.76, 0.98, respectively). Higher leucine (HR 0.79; 95% CI 0.69, 0.90), histidine (HR 0.89; 95% CI 0.81, 0.99) and valine (HR 0.79; 95% CI 0.70, 0.88) levels were associated with lower risk of mortality. Investigating the predictive ability of amino acids, addition of all amino acids to a risk score modestly improved classification of participants for macrovascular (continuous net reclassification index [NRI] +35.5%, p <0.001) and microvascular events (continuous NRI +14.4%, p = 0.012). Conclusions/interpretation We report distinct associations between circulating amino acids and risk of different major complications of diabetes. Low tyrosine appears to be a marker of microvascular risk in individuals with type 2 diabetes independently of fundamental markers of kidney function.Peer reviewe

Plasma fatty acids and the risk of vascular disease and mortality outcomes in individuals with type 2 diabetes: results from the ADVANCE study

Aims/hypothesis: This biomarker study aimed to quantify the association of essential and other plasma fatty acid biomarkers with macrovascular disease, microvascular disease and death in individuals with type 2 diabetes. Methods: A case-cohort study (N = 3576), including 654 macrovascular events, 341 microvascular events and 631 deaths during 5 years of (median) follow-up, was undertaken as a secondary analysis of the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified-Release Controlled Evaluation (ADVANCE) study (full details of the study design and primary endpoints of the ADVANCE trial and its case-cohort have been published previously). This current study considers new data: fatty acids measured from baseline plasma samples by proton NMR analysis. The fatty acids measured were n-3, docosahexaenoic acid (DHA), n-6, linoleic acid, and polyunsaturated, monounsaturated and saturated fatty acids. HRs were modelled per SD higher (percentage) fatty acid. C statistics and continuous net reclassification improvement were used to test the added value of fatty acids compared with traditional cardiovascular risk factors. Results: After adjustment for traditional cardiovascular risk factors, an inverse association was observed for n-3 fatty acids and DHA with the risk of macrovascular events (HR [95% CI]: 0.87 [0.80, 0.95] and 0.88 [0.81, 0.96], respectively, per 1 SD higher percentage), and for n-3 fatty acids with the risk of death (HR 0.91 [95% CI 0.84, 0.99] per 1 SD higher percentage). Such associations were also evident when investigating absolute levels of fatty acids. There were no statistically significant associations between any fatty acids and microvascular disease after adjustment. However, there was limited improvement in the predictive ability of models when any fatty acid was added. Conclusions/interpretation: Plasma n-3 fatty acids and DHA were found to be inversely associated with macrovascular disease, while n-3 fatty acids were also inversely associated with death. These results support the cardioprotective effects of n-3 fatty acids and DHA and further merit testing the role of high-dose supplementation with n-3 fatty acids in individuals with type 2 diabetes. Trial registration: ClinicalTrials.gov NCT00145925

Cardiovasc Diabetol

Individuals with diabetes and lower-limb complications are at high risk for cardiovascular and all-cause mortality, but uncertainties remain in terms of cancer-related death in this population. We investigated this relationship in a large cohort of people with type 2 diabetes. We used data from the Action in Diabetes and Vascular Disease: PreterAx and DiamicroN Modified-Release Controlled Evaluation (ADVANCE) study. The primary outcome was adjudicated cancer death; secondary outcomes were overall and site-specific incident cancers, determined according to the International Classification of Diseases Code (ICD-10). We compared outcomes in individuals with (versus without) a baseline history of lower-limb complications (peripheral artery disease (PAD) or sensory peripheral neuropathy) using Cox regression models. Among 11,140 participants (women 42%, mean age 66 years), lower-limb complications were reported at baseline in 4293 (38%) individuals: 2439 (22%) with PAD and 2973 (27%) with peripheral neuropathy. Cancer death occurred in 316 (2.8%) participants during a median of 5.0 (25th-75th percentile, 4.7-5.1) years of follow-up corresponding to 53,550 person-years and an incidence rate of 5.9 (95% CI 5.3-6.6) per 1000 person-years. The risk of cancer death was higher in individuals with (versus without) lower-limb complication [hazard ratio 1.53 (95% CI, 1.21-1.94), p = 0.0004], PAD [1.32 (1.02-1.70), p = 0.03] or neuropathy (1.41 (1.11-1.79), p = 0.004], adjusting for potential confounders and study allocations. PAD, but not neuropathy, was associated with excess risk of incident cancers. PAD and peripheral neuropathy were independently associated with increased 5-year risk of cancer death in individuals with type 2 diabetes. PAD was also associated with increased risk of incident cancers. Our findings provide new evidence on the non-cardiovascular prognostic burden of lower-limb complications in people with type 2 diabetes

the relationship between alcohol consumption and vascular complications and mortality in individuals with type 2 diabetes

OBJECTIVE Moderate alcohol consumption has been associated with a reduced risk of mortality and coronary artery disease. The relationship between cardiovascular health and alcohol use in type 2 diabetes is less clear. The current study assesses the effects of alcohol use among participants in the Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified-Release Controlled Evaluation (ADVANCE) trial. RESEARCH DESIGN AND METHODS The effects of alcohol use were explored using Cox regression models, adjusted for potential confounders. The study end points were cardiovascular events (cardiovascular death, myocardial infarction, and stroke), microvascular complications (new or worsening nephropathy or retinopathy), and all-cause mortality. RESULTS During a median of 5 years of follow-up, 1,031 (9%) patients died, 1,147 (10%) experienced a cardiovascular event, and 1,136 (10%) experienced a microvascular complication. Compared with patients who reported no alcohol consumption, those who reported moderate consumption had fewer cardiovascular events (adjusted hazard ratio [aHR] 0.83; 95% CI 0.72–0.95; P = 0.008), less microvascular complications (aHR 0.85; 95% CI 0.73–0.99; P = 0.03), and lower all-cause mortality (aHR 0.87; 96% CI 0.75–1.00; P = 0.05). The benefits were particularly evident in participants who drank predominantly wine (cardiovascular events aHR 0.78, 95% CI 0.63–0.95, P = 0.01; all-cause mortality aHR 0.77, 95% CI 0.62–0.95, P = 0.02). Compared with patients who reported no alcohol consumption, those who reported heavy consumption had dose-dependent higher risks of cardiovascular events and all-cause mortality. CONCLUSION In patients with type 2 diabetes, moderate alcohol use, particularly wine consumption, is associated with reduced risks of cardiovascular events and all-cause mortality

Genetic susceptibility, evolution and the kuru epidemic

The acquired prion disease kuru was restricted to the Fore and neighbouring linguistic groups of the Papua New Guinea highlands and largely affected children and adult women. Oral history documents the onset of the epidemic in the early twentieth century, followed by a peak in the mid-twentieth century and subsequently a well-documented decline in frequency. In the context of these strong associations (gender, region and time), we have considered the genetic factors associated with susceptibility and resistance to kuru. Heterozygosity at codon 129 of the human prion protein gene (PRNP) is known to confer relative resistance to both sporadic and acquired prion diseases. In kuru, heterozygosity is associated with older patients and longer incubation times. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are predominantly PRNP codon 129 heterozygotes and this group show marked Hardy–Weinberg disequilibrium. The deviation from Hardy–Weinberg equilibrium is most marked in elderly women, but is also significant in a slightly younger cohort of men, consistent with their exposure to kuru as boys. Young Fore and the elderly from populations with no history of kuru show Hardy–Weinberg equilibrium. An increasing cline in 129V allele frequency centres on the kuru region, consistent with the effect of selection in elevating the frequency of resistant genotypes in the exposed population. The genetic data are thus strikingly correlated with exposure. Considering the strong coding sequence conservation of primate prion protein genes, the number of global coding polymorphisms in man is surprising. By intronic resequencing in a European population, we have shown that haplotype diversity at PRNP comprises two major and divergent clades associated with 129M and 129V. Kuru may have imposed the strongest episode of recent human balancing selection, which may not have been an isolated episode in human history

Variability in estimated glomerular filtration rate and the risk of major clinical outcomes in diabetes:Post hoc analysis from the ADVANCE trial

There are limited data on whether estimated glomerular filtration rate (eGFR) variability modifies the risk of future clinical outcomes in type 2 diabetes (T2D). We assessed the association between 20-month eGFR variability and the risk of major clinical outcomes in T2D among 8241 participants in the ADVANCE trial. Variability in eGFR (coefficient of variation [CVeGFR]) was calculated from three serum creatinine measurements over 20 months. Participants were classified into three groups by thirds of CVeGFR: low (6.4 to 12.1). The primary outcome was the composite of major macrovascular events, new or worsening nephropathy and all-cause mortality. Cox regression models were used to estimate hazard ratios (HRs). Over a median follow-up of 2.9 years following the 20-month period, 932 (11.3%) primary outcomes were recorded. Compared with low variability, greater 20-month eGFR variability was independently associated with higher risk of the primary outcome (HR for moderate and high variability: 1.07, 95% CI: 0.91-1.27 and 1.22, 95% CI: 1.03-1.45, respectively) with evidence of a positive linear trend (p = .015). These data indicate that eGFR variability predict changes in the risk of major clinical outcomes in T2D

Impact of age, age at diagnosis and duration of diabetes on the risk of macrovascular and microvascular complications and death in type 2 diabetes

Abstract Aims/hypothesis Data are inconsistent regarding the associations between age, age at diagnosis of diabetes, diabetes duration and subsequent vascular complications