R. de Vries

Decreased blood–brain barrier P-glycoprotein function in the progression of Parkinson’s disease, PSP and MSA

Decreased blood–brain barrier (BBB) efflux function of the P-glycoprotein (P-gp) transport system could facilitate the accumulation of toxic compounds in the brain, increasing the risk of neurodegenerative pathology such as Parkinson’s disease (PD). This study investigated in vivo BBB P-gp function in patients with parkinsonian neurodegenerative syndromes, using [11C]-verapamil PET in PD, PSP and MSA patients. Regional differences in distribution volume were studied using SPM with higher uptake interpreted as reduced P-gp function. Advanced PD patients and PSP patients had increased [11C]-verapamil uptake in frontal white matter regions compared to controls; while de novo PD patients showed lower uptake in midbrain and frontal regions. PSP and MSA patients had increased uptake in the basal ganglia. Decreased BBB P-gp function seems a late event in neurodegenerative disorders, and could enhance continuous neurodegeneration. Lower [11C]-verapamil uptake in midbrain and frontal regions of de novo PD patients could indicate a regional up-regulation of P-gp function.

Elevated plasma phospholipid transfer protein activity is a determinant of carotid intima-media thickness in type 2 diabetes mellitus

Aim/hypothesisThe plasma activity of phospholipid transfer protein (PLTP), which has putative pro- and anti-atherogenic roles in lipoprotein metabolism, is increased in type 2 diabetes mellitus. We analysed the relationship between carotid artery intima–media thickness (IMT), an established marker of atherosclerosis, and PLTP activity in diabetic patients and control subjects.MethodsThe IMT (mean of three segments in both carotid arteries by ultrasonography), clinical variables, plasma PLTP activity (phospholipid vesicle–HDL system), lipoproteins, C-reactive protein and insulin were measured in 87 non-smoking men and women, who had type 2 diabetes mellitus, no cardiovascular disease, and were not on insulin or lipid-lowering medication, and in 83 age-matched control subjects.ResultsIn diabetic patients, carotid IMT (p=0.02), pulse pressure (p=0.003), plasma PLTP activity (p<0.001), triglycerides (p=0.01), C-reactive protein (p<0.01) and insulin (p<0.001) were higher, whereas HDL cholesterol was lower (p<0.001) than in control subjects. Multiple stepwise linear regression analysis demonstrated that in type 2 diabetic patients IMT was independently associated with age (p<0.001), sex (p=0.001), pulse pressure (p=0.003), plasma PLTP activity (p=0.03) and HDL cholesterol (p=0.03), but not with very low density lipoprotein+LDL cholesterol, triglycerides, C-reactive protein and insulin (all p>0.20). The relationship between plasma PLTP activity and IMT was not significant in control subjects.Conclusions/interpretationPlasma PLTP activity is a positive determinant of IMT in type 2 diabetes mellitus, suggesting that high PLTP activity is involved in accelerated atherosclerosis in this disease.

Cellular cholesterol efflux to plasma from moderately hypercholesterolaemic type 1 diabetic patients is enhanced, and is unaffected by simvastatin treatment

Aim/hypothesisCellular cholesterol efflux to plasma is important in reverse cholesterol transport and may be affected by simvastatin in type 1 diabetes mellitus.MethodsIn 14 moderately hypercholesterolaemic type 1 diabetic and 13 healthy men we determined plasma (apo)lipoproteins, pre-β HDL formation, cholesteryl ester transfer protein (CETP) activity, phospholipid transfer protein (PLTP) activity, cholesterol esterification, cholesteryl ester transfer and the capacity of plasma to induce cholesterol efflux out of Fu5AH cells and fibroblasts. After diet run-in, diabetic patients were randomly treated with simvastatin 10, 20, 40xa0mg and placebo, once daily each, for 6 weeks in a double-blind crossover design.ResultsPlasma very low density lipid protein (VLDL)+LDL cholesterol, LDL cholesterol, HDL phospholipids, apolipoprotein (apo) A-I, apo B, CETP activity, PLTP activity, cholesterol esterification, cholesteryl ester transfer and the capacity of plasma to induce cholesterol efflux from Fu5AH cells and fibroblasts were higher in diabetic patients. Pre-β HDL formation was unaltered. Simvastatin treatment decreased VLDL+LDL cholesterol, LDL cholesterol, triglycerides and apo B, CETP activity, cholesterol esterification and cholesteryl ester transfer. HDL cholesterol increased and its change was correlated with the change in cholesteryl ester transfer. The ability to promote cholesterol efflux from Fu5AH cells and fibroblasts did not change after simvastatin.Conclusions/interpretationThe capacity of plasma from moderately hypercholesterolaemic type 1 diabetic patients to induce cholesterol efflux out of Fu5AH cells and fibroblasts is enhanced, probably due to higher apo A-I, HDL phospholipids and PLTP activity. Simvastatin increases HDL cholesterol in type 1 diabetic patients via lowering of plasma cholesteryl ester transfer. The HDL changes after simvastatin do not increase cellular cholesterol efflux further.

Apolipoprotein M predicts pre-beta-HDL formation: studies in type 2 diabetic and nondiabetic subjects

Objective.u2002 Studies in mice suggest that plasma apoM is lowered in hyperinsulinaemic diabetes and that apoM stimulates formation of pre‐β‐HDL. Pre‐β‐HDL is an acceptor of cellular cholesterol and may be critical for reverse cholesterol transport. Herein, we examined whether patients with type 2 diabetes have reduced plasma apoM and whether apoM is associated with pre‐β‐HDL formation and cellular cholesterol efflux.

Plasma lecithin:cholesterol acyltransferase activity modifies the inverse relationship of C-reactive protein with HDL cholesterol in nondiabetic men

Lecithin:cholesterol acyltransferase (LCAT) is instrumental in high-density lipoprotein (HDL) maturation, but high LCAT levels do not predict low cardiovascular risk. LCAT may affect antioxidative or anti-inflammatory properties of HDL. We determined the relationship of plasma high-sensitivity C-reactive protein (CRP) with LCAT activity and evaluated whether LCAT activity modifies the decreasing effect of HDL cholesterol (HDL-C) on CRP, as an estimate of its anti-inflammatory properties. Plasma HDL-C, apolipoprotein (apo) A-I and LCAT activity (exogenous substrate method) were measured in 260 nondiabetic men without cardiovascular disease. CRP was correlated inversely with HDL-C and apo A-I, and positively with LCAT activity (P<0.01 to 0.001). Multivariate regression analysis demonstrated that age- and smoking-adjusted plasma CRP levels were associated negatively with HDL-C (beta=-0.224, P<0.001) and positively with LCAT activity (beta=0.119, P=0.034), as well as with the interaction between HDL-C and LCAT activity (beta=0.123, P=0.026). There was also an interaction between apo A-I and LCAT activity on CRP (beta=0.159, P=0.005). These relationships remained similar after adjustment for apo B-containing lipoproteins. In conclusion, the inverse relationship of HDL-C with CRP is attenuated by LCAT activity at higher HDL-C levels. It is hypothesized that LCAT could mitigate HDLs anti-inflammatory or antioxidative properties at higher HDL-C concentrations.

Skin autofluorescence for the risk assessment of chronic complications in diabetes: a broad excitation range is sufficient

Skin autofluorescence (AF) is becoming an accepted clinical method for assessing the risk of chronic complications in diabetes mellitus (DM). In this study, the role of the excitation wavelength in the recognition of increased risk of diabetes-related chronic complications was investigated. An Excitation Emission Matrix Scanner (EEMS) was used to perform noninvasive measurements in four age-matched groups of patients with type 1 and type 2 DM, with and without chronic complications, as well as in a control group (N=97 in total). AF was calculated for excitation wavelengths in the range 355 - 405 nm. Mean spectra were assessed per group. AF values in both type 1 and type 2 DM patients with complications were increased compared to the control subjects (p < 0:01); this ratio remained practically constant, independent of the excitation wavelength. No emission peaks were distinctive for specific patient groups. We conclude that in these groups, no characteristic fluorophores dictate the use of a specific wavelength or set of wavelengths. The results show the validity of applying a broad excitation wavelength range for risk assessment of chronic complications in diabetes.

Vitamin K deficiency bleeding in cholestatic infants with alpha-1-antitrypsin deficiency.

Objective: Exclusively breastfed infants with unrecognised cholestatic jaundice are at high risk of a vitamin K deficiency (VKD) bleeding. It is presently unknown whether (the size of) this risk depends on the degree of cholestasis. Since alpha-1-antitrypsin deficiency (A1AD) induces a variable degree of cholestasis, we assessed the risk of VKD bleeding in infants with cholestatic jaundice due to A1AD. Patients and methods: Infants with a ZZ or SZ phenotype born in The Netherlands between January 1991 and December 2006 were identified from the databases of the five Dutch diagnostic centres for alpha-1-antitrypsin phenotyping and/or genotyping. We determined the risk of VKD bleeding upon diagnosis of A1AD in breastfed and formula fed infants and searched for correlations between serum levels of conjugated bilirubin and the risk of bleeding. Results: A total of 40 infants with A1AD were studied. VKD bleeding was noted in 15/20 (75%) of breastfed infants, compared with 0/20 of formula fed infants with A1AD. The relative risk for VKD bleeding in breastfed versus formula fed infants was at least 15.8 (95% CI 2.3 to 108). Conjugated bilirubin levels at diagnosis did not correlate with the risk of VKD bleeding. Conclusions: The risk of VKD bleeding in breastfed infants with A1AD was high and did not correlate with serum level of conjugated bilirubin at diagnosis. A similar absolute risk was previously reported in breastfed infants with biliary atresia under the same prophylactic regimen. This confirms that—without adequate prophylaxis—the risk of VKD bleeding is uniformly high in exclusively breastfed infants with cholestatic jaundice, irrespective of underlying aetiology.

Type 2 diabetes mellitus interacts with obesity and common variations in PLTP to affect plasma phospholipid transfer protein activity

Abstract.u2002 Dullaart RPF, Vergeer M, de Vries R, Kappelle PJWH, Dallinga‐Thie GM (University Medical Center Groningen, University of Groningen, Groningen; and Academic Medical Center Amsterdam, Amsterdam; The Netherlands). Type 2 diabetes mellitus interacts with obesity and common variations in PLTP to affect plasma phospholipid transfer protein activity. J Intern Med 2012; 271: 490–498.

A low‐saturated‐fat, low‐cholesterol diet decreases plasma CETP activity and pre β‐HDL formation but does not affect cellular cholesterol efflux to plasma from type 1 diabetic patients

The aim of this study was to evaluate the effect of a low‐saturated‐fat, low‐cholesterol diet on plasma lipopoproteins, pre β‐high density lipoprotein (HDL) formation, lecithin:cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP) and phospholipid transfer protein (PLTP) activities, as well as on the ability of plasma to stimulate cellular cholesterol efflux. Twelve male type 1 diabetic patients with plasma cholesterol >5.0u2005mmol/L were studied while consuming their usual diet and after 6 weeks of a low‐fat, low‐cholesterol diet. Pre β‐HDL formation was measured using crossed immuno‐electrophoresis. Plasma LCAT, CETP and PLTP activities were assayed by exogenous substrate methods. The ability of plasma to promote cellular cholesterol efflux out of Fu5AH rat hepatoma cells and out of human skin fibroblasts was also determined. Saturated fat intake was lowered (p = 0.001) due to replacement with carbohydrates, while mono‐ and polyunsaturated fat intake remained unchanged. Cholesterol intake decreased as well (p = 0.003). The changes in plasma total cholesterol, very low and low‐density lipoprotein (VLDL+LDL) cholesterol, HDL cholesterol, HDL phospholipids, apolipoprotein (apo) A‐I, plasma LCAT activity and PLTP activity were not significant. Plasma CETP activity (p = 0.008) and pre β‐HDL formation (p = 0.008) decreased. The ability of plasma to promote cholesterol efflux out of fibroblasts and Fu5AH cells remained unchanged. Reduction in dietary saturated fat and cholesterol intake does not adversely affect cellular cholesterol efflux to plasma from type 1 diabetic patients, despite a drop in pre β‐HDL formation.