Louis M. Havekes

Diet-induced hyperlipoproteinemia and atherosclerosis in apolipoprotein E3-Leiden transgenic mice.

Apolipoprotein E3-Leiden (APOE*3-Leiden) transgenic mice have been used to study the effect of different cholesterol-containing diets on the remnant lipoprotein levels and composition and on the possible concurrent development of atherosclerotic plaques. On high fat/cholesterol (HFC) diet, the high expressing lines 2 and 181 developed severe hypercholesterolemia (up to 40 and 60 mmol/liter, respectively), whereas triglyceride levels remained almost normal when compared with regular mouse diet. The addition of cholate increased the hypercholesterolemic effect of this diet. In lines 2 and 181, serum levels of apo E3-Leiden also increased dramatically upon cholesterol feeding (up to 107 and 300 mg/dl, respectively). In these high expressing APOE*3-Leiden transgenic mice, the increase in both serum cholesterol and apo E3-Leiden occurred mainly in the VLDL/LDL-sized fractions, whereas a considerable increase in large, apo E-rich HDL particles also occurred. In contrast to the high expressing lines, the low expressing line 195 reacted only mildly upon HFC diet. On HFC diets, the high expresser APOE*3-Leiden mice developed atherosclerotic lesions in the aortic arch, the descending aorta, and the carotid arteries, varying from fatty streaks containing foam cells to severe atherosclerotic plaques containing cholesterol crystals, fibrosis, and necrotic calcified tissue. Quantitative evaluation revealed that the atherogenesis is positively correlated with the serum level of cholesterol-rich VLDL/LDL particles. In conclusion, with APOE*3-Leiden transgenic mice, factors can be studied that influence the metabolism of remnant VLDL and the development of atherosclerosis.

Serum apolipoprotein e level is not increased in Alzheimer's disease: The Rotterdam study

The APOE*4 allele of the apolipoprotein E gene (APOE) is an important risk factor for Alzheimers disease. It has been suggested that levels of apolipoprotein E (apoE) in plasma are increased in Alzheimers disease. In this population-based study, we found that serum apoE levels were lower in Alzheimer patients compared to non-demented controls (0.75 micromol/l (SD 0.35), vs. 0.83 micromol/l (SD 0.40), P < 0.05). This finding is in accordance with lower serum apoE levels as observed in carriers of the APOE*4 allele, who are over-represented in Alzheimers disease. After adjustment for age, sex, total protein, albumin level, body mass index and the APOE genotype, the difference in serum apoE levels largely disappeared. Our population-based study suggests that the differences in serum apoE level between Alzheimer patients and controls are mainly the result of differences in the distribution of the APOE genotype.

Genetic analysis of sex and generation differences in plasma lipid, lipoprotein, and apolipoprotein levels in adolescent twins and their parents

In a sample of Dutch families consisting of parents aged 35–65 years and their twin offspring aged 14–21 years, a significant difference between generations was observed in phenotypic variances and in genetic heritabilities for plasma levels of total cholesterol, triglycerides, high density lipoprotein (HDL) and low density lipoprotein (LDL) cholesterol, and apolipoproteins (apo) A1, A2, B, and E. For all traits parents were more variable than their offspring. This increase in phenotypic variance was best explained by a genetic model in which individual specific environmental variance increased with increasing age. Genetic variance was the same across generations for nearly all traits except triglycerides and apoE, for which a decrease in genetic variance was observed. This model led to large intergenerational differences in genetic heritabilities. Heritabilities for children were between 65 and 87%, while heritabilities for their parents were between 10 and 50%. No evidence was found for effects of a shared family environment.

Anacetrapib reduces progression of atherosclerosis, mainly by reducing non-HDL-cholesterol, improves lesion stability and adds to the beneficial effects of atorvastatin

The present study is the first intervention study in a well-established, translational mouse model for hyperlipidaemia and atherosclerosis showing that anacetrapib dose-dependently reduces atherosclerosis development and adds to the anti-atherogenic effects of atorvastatin. This effect is mainly ascribed to the reduction in non-HDL-C despite a remarkable increase in HDL-C and without affecting HDL functionality. In addition, anacetrapib improves lesion stability.

Estimation of activity related energy expenditure and resting metabolic rate in freely moving mice from indirect calorimetry data

Physical activity (PA) is a main determinant of total energy expenditure (TEE) and has been suggested to play a key role in body weight regulation. However, thus far it has been challenging to determine what part of the expended energy is due to activity in freely moving subjects. We developed a computational method to estimate activity related energy expenditure (AEE) and resting metabolic rate (RMR) in mice from activity and indirect calorimetry data. The method is based on penalised spline regression and takes the time dependency of the RMR into account. In addition, estimates of AEE and RMR are corrected for the regression dilution bias that results from inaccurate PA measurements. We evaluated the performance of our method based on 500 simulated metabolic chamber datasets and compared it to that of conventional methods. It was found that for a sample time of 10 minutes the penalised spline model estimated the time-dependent RMR with 1.7 times higher accuracy than the Kalman filter and with 2.7 times higher accuracy than linear regression. We assessed the applicability of our method on experimental data in a case study involving high fat diet fed male and female C57Bl/6J mice. We found that TEE in male mice was higher due to a difference in RMR while AEE levels were similar in both groups, even though female mice were more active. Interestingly, the higher activity did not result in a difference in AEE because female mice had a lower caloric cost of activity, which was likely due to their lower body weight. In conclusion, TEE decomposition by means of penalised spline regression provides robust estimates of the time-dependent AEE and RMR and can be applied to data generated with generic metabolic chamber and indirect calorimetry set-ups.

LDL receptor deficiency results in decreased cell proliferation and presynaptic bouton density in the murine hippocampus

An aberrant cholesterol metabolism in the brain may contribute to the pathogenesis of Alzheimers disease (AD). The LDL receptor (LDLR) regulates plasma cholesterol levels and recently we and others obtained evidence that it is also involved in regulating brain cholesterol homeostasis. Moreover, we found that LDLR-deficient mice display impaired spatial memory. Because cholesterol, in part derived from cellular uptake via LDLR, is required for peripheral cell proliferation and growth, we examined the effect of absence of the LDLR on hippocampal proliferation and the density of synaptic connections. Mice deficient for the LDLR displayed a reduced number of proliferating (BrdU-labeled) cells in the hippocampus as compared to wild type control mice. In addition, the number of synaptophysin-immunoreactive presynaptic boutons in the hippocampal CA1 and the dentate gyrus (DG) areas, but not in cortical areas, was lower in the LDLR-knockout mice than in the control mice. In vitro experiments showed that LDLR activity is increased when cell growth is enhanced by the addition of N2 supplement. This further supports a role for the LDLR in the outgrowth of neurites. These findings support the notion that, similar to its role in the periphery, the LDLR is important for the cellular uptake of cholesterol in the brain and that disturbance of this process affects neuronal plasticity.

Rare Apolipoprotein E Variant Cosegregating with a Unique APOE-C1-C2 Haplotype in a Normolipidemic Family

The genes coding for the apolipoproteins E, C1 and C2 are clustered on the long arm of chromosome 19 in a region of approximately 45 kilobases (kb). In a normolipidemic individual, we detected a new apoE variant with an isoelectric point between that of E3 and E4. As this variant lacks cysteine residues and has probably arisen from an E*4 allele, it is designated E4*. To gain further insight into the origin of the mutation, the haplotypes of the propositus were extended by restriction fragment length polymorphism (RFLP) analysis of the family. The apoE variant cosegregates with the H2 allele of the HpaI polymorphism visualized with an APOE probe and with a new rare 4.5-kb fragment (T3) of the TaqI RFLP detectable with an APOC2 probe. As the propositus and the first-degree relatives with this unique haplotype are normolipidemic, this apoE variant does not seem to be associated with disturbances in the lipoprotein metabolism.

HDL functionality in South Asians as compared to white Caucasians

BACKGROUND AND AIMSnSouth Asians have an exceptionally high risk of developing cardiovascular disease compared to white Caucasians. A contributing factor might be dysfunction of high density lipoprotein (HDL). We aimed to compare HDL function in different age groups of both ethnicities.nnnMETHODS AND RESULTSnHDL functionality with respect to cholesterol efflux, anti-oxidation and anti-inflammation was determined using fasting, apoB-depleted, plasma samples from South Asian and white Caucasian neonates (nxa0=xa014 each), adolescent healthy men (nxa0=xa012 each, 18-25xa0y), and adult overweight men (nxa0=xa012 each, 40-50xa0y). Adolescents were subjected to a 5-day high fat high calorie diet (HCD) and adults to an 8-day very low calorie diet (LCD). Additionally, HDL composition was measured in adolescents and adults using (1)H-NMR spectroscopy. Anti-oxidative capacity was lower in South Asian adults before LCD (19.4xa0±xa02.1 vs. 25.8xa0±xa01.2%, pxa0=xa00.045, 95%-CIxa0=xa0[0.1; 12.7]) and after LCD (16.4xa0±xa02.4 vs. 27.6xa0±xa02.7%, pxa0=xa00.001, 95%-CIxa0=xa0[4.9; 17.5]). Anti-inflammatory capacity was reduced in South Asian neonates (23.8xa0±xa01.2 vs. 34.9xa0±xa01.3%, pxa0=xa00.000001, 95%-CIxa0=xa0[-14.6; -7.5]), and was negatively affected by an 8-day LCD only in South Asian adults (-12.2xa0±xa04.3%, pxa0=xa00.005, 95%-CIxa0=xa0[-5.9; -1.2]). Cholesterol efflux capacity was increased in response to HCD in adolescents (South Asians: +6.3xa0±xa02.9%, pxa0=xa00.073, 95%-CIxa0=xa0[-0.02; 0.46], Caucasians: +11.8xa0±xa03.4%, pxa0=xa00.002, 95%-CIxa0=xa0[0.17;0.65]) and decreased after LCD in adults (South Asians: -10.3xa0±xa02.4%, pxa0<xa00.001, 95%-CIxa0=xa0[-0.57; -0.20], Caucasians: -13.7xa0±xa01.9%, pxa0<xa00.00001, 95%-CIxa0=xa0[-0.67; -0.33]). Although subclass analyses of HDL showed no differences between ethnicities, cholesterol efflux correlated best with cholesterol and phospholipid within small HDL compared to other HDL subclasses and constituents.nnnCONCLUSIONnImpaired HDL functionality in South Asians may be a contributing factor to their high CVD risk.nnnCLINICAL TRIAL REGISTRATIONnNTR 2473 (URL: http://www.trialregister.nl/).

PS1 - 8. Brown adipose tissue volume is markedly lower in healthy lean adolescents from South Asian compared to white Caucasian origin

South Asians have a higher risk of developing type 2 diabetes than white Caucasians. Though the underlying cause is still poorly understood, we recently found that South Asian adolescents have reduced resting energy expenditure (REE) compared to white Caucasian adolescents.

PS1 - 5. The GLP-1 receptor agonist exendin-4 reduces atherosclerosis development and NASH in APOE*3.Leiden.CETP mice

The GLP-1 receptor agonist exendin-4 (ex-4) improves glucose intolerance and is currently being used in the treatment of type 2 diabetes mellitus.