Reduction of dietary saturated fatty acids correlates with increased plasma lecithin cholesterol acyltransferase activity in humans

Impaired Reverse Cholesterol Transport is Associated with Changes in Fatty Acid Profile in Children and Adolescents with Abdominal Obesity

BACKGROUND

Abdominal obesity is an important cardiovascular disease risk factor. Plasma fatty acids display a complex network of both pro and antiatherogenic effects. High density lipoproteins (HDL) carry out the antiatherogenic pathway called reverse cholesterol transport (RCT), which involves cellular cholesterol efflux (CCE), and lecithin:cholesterol acyltransferase (LCAT) and cholesteryl ester transfer protein (CETP) activities.

OBJECTIVES

Our aim was to characterize RCT and its relation to fatty acids present in plasma in pediatric abdominal obesity.

METHODS

Seventeen children and adolescents with abdominal obesity and 17 healthy controls were studied. Anthropometric parameters were registered. Glucose, insulin, lipid levels, CCE employing THP-1 cells, LCAT and CETP activities, plus fatty acids in apo B-depleted plasma were measured.

RESULTS

The obese group showed a more atherogenic lipid profile, plus lower CCE (Mean±Standard Deviation) (6 ± 2 vs. 7 ± 2%; P < 0.05) and LCAT activity (11 ± 3 vs. 15 ±5 umol/dL.h; P < 0.05). With respect to fatty acids, the obese group showed higher myristic (1.1 ± 0.3 vs. 0.7 ± 0.3; P < 0.01) and palmitic acids (21.5 ± 2.8 vs. 19.6 ± 1.9; P < 0.05) in addition to lower linoleic acid (26.4 ± 3.3 vs. 29.9 ± 2.6; P < 0.01). Arachidonic acid correlated with CCE (r = 0.37; P < 0.05), myristic acid with LCAT (r = -0.37; P < 0.05), palmitioleic acid with CCE (r = -0.35; P < 0.05), linoleic acid with CCE (r = 0.37; P < 0.05), lauric acid with LCAT (r = 0.49; P < 0.05), myristic acid with LCAT (r = -0.37; P < 0.05) ecoisatrienoic acid with CCE (r = 0.40; P < 0.05) and lignoseric acid with LCAT (r = -0.5; P < 0.01).

CONCLUSIONS

Children and adolescents with abdominal obesity presented impaired RCT, which was associated with modifications in proinflammatory fatty acids, such as palmitoleic and myristic, thus contributing to increased cardiovascular disease risk.

Investigating cholesterol metabolism and ageing using a systems biology approach

CVD accounted for 27 % of all deaths in the UK in 2014, and was responsible for 1·7 million hospital admissions in 2013/2014. This condition becomes increasingly prevalent with age, affecting 34·1 and 29·8 % of males and females over 75 years of age respectively in 2011. The dysregulation of cholesterol metabolism with age, often observed as a rise in LDL-cholesterol, has been associated with the pathogenesis of CVD. To compound this problem, it is estimated by 2050, 22 % of the world's population will be over 60 years of age, in culmination with a growing resistance and intolerance to pre-existing cholesterol regulating drugs such as statins. Therefore, it is apparent research into additional therapies for hypercholesterolaemia and CVD prevention is a growing necessity. However, it is also imperative to recognise this complex biological system cannot be studied using a reductionist approach; rather its biological uniqueness necessitates a more integrated methodology, such as that offered by systems biology. In this review, we firstly discuss cholesterol metabolism and how it is affected by diet and the ageing process. Next, we describe therapeutic strategies for hypercholesterolaemia, and finally how the systems biology paradigm can be utilised to investigate how ageing interacts with complex systems such as cholesterol metabolism. We conclude by emphasising the need for nutritionists to work in parallel with the systems biology community, to develop novel approaches to studying cholesterol metabolism and its interaction with ageing.

Myristic acid is associated to low plasma HDL cholesterol levels in a Mediterranean population and increases HDL catabolism by enhancing HDL particles trapping to cell surface proteoglycans in a liver hepatoma cell model

BACKGROUND

HDL-C plasma levels are modulated by dietary fatty acid (FA), but studies investigating dietary supplementation in FA gave contrasting results. Saturated FA increased HDL-C levels only in some studies. Mono-unsaturated FA exerted a slight effect while poly-unsaturated FA mostly increased plasma HDL-C.

AIMS

This study presents two aims: i) to investigate the relationship between HDL-C levels and plasma FA composition in a Sicilian population following a "Mediterranean diet", ii) to investigate if FA that resulted correlated with plasma HDL-C levels in the population study and/or very abundant in the plasma were able to affect HDL catabolism in an "in vitro" model of cultured hepatoma cells (HepG2).

RESULTS

plasma HDL-C levels in the population correlated negatively with myristic acid (C14:0, β = -0.24, p < 0.01), oleic acid (C18:1n9, β = -0.22, p < 0.01) and cis-11-Eicosenoic (C20:1n9, β = -0.19, p = 0.01) and positively with palmitoleic acid (C16:1, β = +0.19, p = 0.03). HepG2 cells were conditioned with FA before evaluating HDL binding kinetics, and only C14:0 increased HDL binding by a non-saturable pathway. After removal of heparan sulphate proteoglycans (HSPG) by heparinases HDL binding dropped by 29% only in C14:0 conditioned cells (p < 0.05). C14:0 showed also the highest internalization of HDL-derived cholesteryl esters (CE, +32% p = 0.01 vs. non-conditioned cells).

CONCLUSIONS

C14:0 was correlated with decreased plasma HDL-C levels in a Mediterranean population. C14:0 might reduce HDL-C levels by increasing HDL trapping to cell surface HSPG and CE stripping from bound HDL. Other mechanisms are to be investigated to explain the effects of other FA on HDL metabolism.

Novel risk factors for premature peripheral arterial occlusive disease in non-diabetic patients: a case-control study

Background

This study aimed to determine the prevalence of genetic and environmental vascular risk factors in non diabetic patients with premature peripheral arterial disease, either peripheral arterial occlusive disease or thromboangiitis obliterans, the two main entities of peripheral arterial disease, and to established whether some of them are specifically associated with one or another of the premature peripheral arterial disease subgroups.

Methods and Results

This study included 113 non diabetic patients with premature peripheral arterial disease (diagnosis <45-year old) presenting either a peripheral arterial occlusive disease (N = 64) or a thromboangiitis obliterans (N = 49), and 241 controls matched for age and gender. Both patient groups demonstrated common traits including cigarette smoking, low physical activity, decreased levels of HDL-cholesterol, apolipoprotein A–I, pyridoxal 5′-phosphate (active form of B6 vitamin) and zinc. Premature peripheral arterial occlusive disease was characterized by the presence of a family history of peripheral arterial and carotid artery diseases (OR 2.3 and 5.8 respectively, 95% CI), high lipoprotein (a) levels above 300 mg/L (OR 2.3, 95% CI), the presence of the factor V Leiden (OR 5.1, 95% CI) and the glycoprotein Ia^{807T,837T,873A} allele (OR 2.3, 95% CI). In thromboangiitis obliterans group, more patients were regular consumers of cannabis (OR 3.5, 95% CI) and higher levels in plasma copper has been shown (OR 6.5, 95% CI).

Conclusions

According to our results from a non exhaustive list of study parameters, we might hypothesize for 1) a genetic basis for premature peripheral arterial occlusive disease development and 2) the prevalence of environmental factors in the development of thromboangiitis obliterans (tobacco and cannabis). Moreover, for the first time, we demonstrated that the 807T/837T/873A allele of platelet glycoprotein Ia may confer an additional risk for development of peripheral atherosclerosis in premature peripheral arterial occlusive disease.

Moderate dietary intake of myristic and alpha-linolenic acids increases lecithin-cholesterol acyltransferase activity in humans

Cholesterol removal from tissues into HDL depends on the activity of lecithin-cholesterol acyltransferase (LCAT; E.C. 2.3.1.43) that is associated with lower cardiovascular diseases risk. HDL cholesterol concentration and LCAT activity can be modulated by dietary fatty acids. Original data with substrate models have shown a positive effect of myristic acid (MA) on the esterification rate of cholesterol. The purpose of this study was to examine the effect of moderate intakes of MA associated with recommended intake of alpha-linolenic acid (ALA) on LCAT activity in humans. Two experimental diets were tested for 3 months each. Diet 1-MA 1.2% of total energy (TE) and ALA 0.9% TE, diet 2-MA 1.8% and ALA 0.9% TE; a control diet (MA 1.2% and ALA 0.4% TE) was given 3 months before diet 1 and diet 2. The endogenous activity of LCAT was determined at completion of each diet. Compared with the control diet (13.2 +/- 3.1 micromol CE/(L x h)), LCAT activity increased significantly (P < 0.001) with diet 1 (24.2 +/- 3.6 micromol CE/(L x h)) and diet 2 (33.3 +/- 7.4 micromol CE/(L x h)); the increase observed with diet 2 was significantly (P < 0.001) greater than that due to diet 1. These results suggest that ALA (from rapeseed oil, mainly in sn-2 position) and MA (from dairy fat, mainly in sn-2 position) favor LCAT activity, by respective increases of 83 and 38%. When they are supplied together, a complementary effect was observed (average increase of 152%). Moreover, these observations were associated with a decrease of the ratio of total to HDL-cholesterol. In conclusion, our results suggest that moderate supply of MA (1.8% TE) associated with the recommended intake of ALA (0.9% TE) contributes to improve LCAT activity.