Increased NEFA levels reduce blood Mg2+ in hypertriacylglycerolaemic states via direct binding of NEFA to Mg2

AIMS/HYPOTHESIS

The blood triacylglycerol level is one of the main determinants of blood Mg²⁺ concentration in individuals with type 2 diabetes. Hypomagnesaemia (blood Mg²⁺ concentration <0.7 mmol/l) has serious consequences as it increases the risk of developing type 2 diabetes and accelerates progression of the disease. This study aimed to determine the mechanism by which triacylglycerol levels affect blood Mg²⁺ concentrations.

METHODS

Using samples from 285 overweight individuals (BMI >27 kg/m²) who participated in the 300-Obesity study (an observational cross-sectional cohort study, as part of the Human Functional Genetics Projects), we investigated the association between serum Mg²⁺ with laboratory variables, including an extensive lipid profile. In a separate set of studies, hyperlipidaemia was induced in mice and in healthy humans via an oral lipid load, and blood Mg²⁺, triacylglycerol and NEFA concentrations were measured using colourimetric assays. In vitro, NEFAs harvested from albumin were added in increasing concentrations to several Mg²⁺-containing solutions to study the direct interaction between Mg²⁺ and NEFAs.

RESULTS

In the cohort of overweight individuals, serum Mg²⁺ levels were inversely correlated with triacylglycerols incorporated in large VLDL particles (r = -0.159, p ≤ 0.01). After lipid loading, we observed a postprandial increase in plasma triacylglycerol and NEFA levels and a reciprocal reduction in blood Mg²⁺ concentration both in mice (Δ plasma Mg²⁺ -0.31 mmol/l at 4 h post oral gavage) and in healthy humans (Δ plasma Mg²⁺ -0.07 mmol/l at 6 h post lipid intake). Further, in vitro experiments revealed that the decrease in plasma Mg²⁺ may be explained by direct binding of Mg²⁺ to NEFAs. Moreover, Mg²⁺ was found to bind to albumin in a NEFA-dependent manner, evidenced by the fact that Mg²⁺ did not bind to fatty-acid-free albumin. The NEFA-dependent reduction in the free Mg²⁺ concentration was not affected by the presence of physiological concentrations of other cations.

CONCLUSIONS/INTERPRETATION

This study shows that elevated NEFA and triacylglycerol levels directly reduce blood Mg²⁺ levels, in part explaining the high prevalence of hypomagnesaemia in metabolic disorders. We show that blood NEFA level affects the free Mg²⁺ concentration, and therefore, our data challenge how the fractional excretion of Mg²⁺ is calculated and interpreted in the clinic.

Effect of a treat-to-target intervention of cardiovascular risk factors on subclinical and clinical atherosclerosis in rheumatoid arthritis: a randomised clinical trial

BACKGROUND

Patients with rheumatoid arthritis (RA) have an increased risk for cardiovascular disease (CVD). No long-term intervention trials on CVD risk factors have been published, and a debate on the efficacy of controlling traditional risk factors in RA is ongoing. We aimed to evaluate a treat-to-target approach versus usual care regarding traditional CVD risk factors in patients with RA.

METHODS

In this open-label, randomised controlled trial, patients with RA aged <70 years without prior CVD or diabetes mellitus were randomised 1:1 to either a treat-to-target approach or usual care of traditional CVD risk factors. The primary outcome was defined as change in carotid intima media thickness (cIMT) over 5 years, and the secondary outcome was a composite of first occurrence of fatal and non-fatal cardiovascular events.

RESULTS

A total of 320 patients (mean age 52.4 years; 69.7% female) with RA underwent randomisation and 219 patients (68.4%) completed 5 years of follow-up. The mean cIMT progression was significantly reduced in the treat-to-target group compared with usual care (0.023 [95% CI 0.011 to 0.036] mm vs 0.045 [95% CI 0.030 to 0.059] mm; p=0.028). Cardiovascular events occurred in 2 (1.3%) of the patients in the treat-to-target group vs 7 (4.7%) in those receiving usual care (p=0.048 by log-rank test).

CONCLUSION

This study provides evidence on the benefit of a treat-to-target approach of traditional CVD risk factors for primary prevention in patients with well-treated RA.

TRIAL REGISTRATION NUMBER

NTR3873.

Glucose-dependent leucocyte activation in familial hypercholesterolemia

BACKGROUND

Leucocyte activation is an obligatory factor in the development of atherosclerosis. The postprandial situation has been associated to increased leucocyte activation in several disorders, such as type 2 diabetes mellitus and familial combined hyperlipidaemia. Our study aim was to evaluate the effect of post-OGTT hyperglycaemia on leucocyte activation in patients with familial hypercholesterolemia (FH).

MATERIALS AND METHODS

Patients who met the diagnostic criteria for heterozygous FH and healthy volunteers were asked to undergo an oral glucose tolerance test. Leucocyte activation markers CD11b and CD66b were determined by flow cytometry. Post-OGTT changes were calculated as area under the curve (AUC) and the incremental area under the curve corrected for baseline values (dAUC). The impact of being an FH patient and using statins on the time-dependent profile of the leucocyte activation markers was studied with repeated measurements analysis.

RESULTS

Thirteen FH patients using statins, nine FH patients without statins and 14 healthy volunteers were included. FH subjects on statins had a slightly higher HbA1c than those not using these drugs or controls. Post-OGTT glucose levels were significantly higher in patients with FH when compared to healthy controls (P = 0·001). These effects were independent from the use of statins.

CONCLUSIONS

Surprisingly, our study shows impaired post-OGTT glucose excursions in patients with FH compared to healthy volunteers. Post-OGTT hyperglycaemia may be related to persistent post-OGTT activation of monocytes in FH patients compared to healthy controls, and therefore, it may contribute to the development of cardiovascular disease in patients with FH.

Erythrocyte-bound apolipoprotein B in atherosclerosis and mortality

BACKGROUND

The binding of apolipoprotein (apo) B-containing lipoproteins to circulating erythrocytes (ery-apoB) is associated with a decreased prevalence of atherosclerosis. In this study, we evaluated ery-apoB as a possible prognostic factor in cardiovascular events and all-cause mortality, in a prospective cohort study.

MATERIALS AND METHODS

Ery-apoB was measured by flow cytometry in subjects with and without cardiovascular disease (CVD). The primary endpoint was the cardiovascular event rate. Secondary endpoints were all-cause mortality and the combined endpoint of all-cause mortality and cardiovascular events (any event rate). A Cox regression analysis with univariate and multivariate analyses and Kaplan-Meier survival analysis was performed.

RESULTS

Follow-up data were available of 384 subjects. Subjects were divided according to high (> 2·0 au, n = 60), intermediate (0·2-2·0 au, n = 274) or low (< 0·2 au, n = 50) ery-apoB. Median follow-up was 1767 days (IQR 1564-2001). In univariate analysis, low ery-apoB was associated with increased all-cause mortality [HR 9·9 (1·2-79·0), P = 0·031] and any event rate [HR 3·4 (95% CI 1·3-8·7), P = 0·012]. In a Cox regression analysis, only a history of CVD was significantly associated with any event rate [HR 3·6 (1·6-8·0), P = 0·002], while low ery-apoB showed a trend [HR 2·4 (0·9-6·4), P = 0·07]. In a subgroup analysis, in subjects with a history of CVD, ery-apoB was significantly associated with all-cause mortality (log rank P = 0·021) and any event rate (log rank P = 0·009).

CONCLUSIONS

Low ery-apoB is associated with increased mortality and cardiovascular risk, especially in patients with a prior history of CVD. These subjects may benefit from more aggressive secondary prevention treatment.

Effect of a Single Dose of Vitamin D3 on Postprandial Arterial Stiffness and Inflammation in Vitamin D-Deficient Women

CONTEXT

Cholecalciferol (vitamin D3) improves vascular function and inflammation, potentially providing an explanation for the proposed cardiovascular protection of vitamin D.

OBJECTIVE

We investigated whether cholecalciferol supplementation reduces postprandial arterial dysfunction and inflammation.

DESIGN

Randomized, 1:1, double-blind trial.

SETTING

Diabetes and Vascular Center, Franciscus Gasthuis, Rotterdam, The Netherlands.

PATIENTS

Twenty-four healthy, premenopausal, overweight or obese, vitamin D-deficient women.

INTERVENTIONS

A single high (300,000 IU) or low dose (75,000 IU) of cholecalciferol.

MAIN OUTCOME MEASURES

The effect of low- and high-dose cholecalciferol on postprandial leukocyte activation markers, pulse wave velocity (PWV), and augmentation index (AIx) during an oral fat loading test, expressed as area under the curve (AUC).

RESULTS

High- and low-dose supplementation increased vitamin D by 163% ± 134% (P < 0.001) and 66% ± 59% (P < 0.001), respectively. Monocyte CD11b-AUC slightly increased after low but not high dose (6% ± 2%, P = 0.012, and 4% ± 1%, P = 0.339, respectively). There were no significant effects on postprandial PWV or AIx by high- or low-dose vitamin D. Fasting complement component 3 (C3) levels decreased by 5.9% (P = 0.004) in the high-dose group and by 4.0% (P = 0.018) in the low-dose group.

CONCLUSION

A single dose of vitamin D does not seem to reduce arterial stiffness and leukocyte activation in overweight, vitamin D-deficient women. Vitamin D may decrease fasting C3. Possibly, higher vitamin D concentrations may be needed to decrease inflammation and improve vascular function in overweight or obese vitamin D-deficient women.

Complement receptor 1 gene polymorphisms are associated with cardiovascular risk

Background and aims

Inflammation plays a key role in atherosclerosis. The complement system is involved in atherogenesis, and the complement receptor 1 (CR1) plays a role facilitating the clearance of immune complexes from the circulation. Limited evidence suggests that CR1 may be involved in cardiovascular disease. We investigated the relationship between CR1 gene polymorphisms and cardiovascular risk.

Methods

Single nucleotide polymorphisms (SNPs) within the CR1 region (n = 73) on chromosome 1 were assessed in 5244 participants in PROSPER (PROspective Study of Pravastatin in the Elderly at Risk) (mean age 75.3 years), who had been randomized to pravastatin 40 mg/day or placebo and followed for a mean of 3.2 years. Logistic regression, adjusted for gender, age, country and use of pravastatin, was used to assess the association between the SNPs and cardiovascular disease.

Results

All 73 SNPs within the genomic region of the CR1 gene on chromosome 1 were extracted. In this region, strong LD was present leading to the occurrence of two haploblocks. Twelve of the 73 investigated CR1 SNPs were significantly associated with the risk of fatal or nonfatal myocardial infarction (all p < 0.05). Moreover, most of the associated SNPs were also associated with levels of serum C-reactive protein (CRP). The global p-value for the tail strength method to control for multiple testing was 0.0489, implying that the null hypothesis of no associated SNPs can be rejected.

Conclusions

These data indicate that genetic variation within the CR1 gene is associated with inflammation and the risk of incident coronary artery disease.

•

The complement receptor 1 (CR1) may be involved in atherosclerosis.

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12 SNPs within the CR1 region were associated with myocardial infarction.

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7 SNPs were also associated with levels of C-reactive protein.

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These results imply that CR1 may be involved in atherogenesis.

Leucocyte-bound apolipoprotein B in the circulation is inversely associated with the presence of clinical and subclinical atherosclerosis

BACKGROUND

Atherosclerosis is a pro-inflammatory condition, in which leucocyte activation plays an important role. The interaction between circulating leucocytes and apolipoprotein (apo) B-containing lipoproteins results in pro-inflammatory changes of these cells. We aimed to evaluate the relationship between apo B bound to circulating leucocytes and atherosclerosis.

METHODS

Apo B on circulating leucocytes was measured by flow cytometry in subjects with and without cardiovascular disease (CVD), expressed as mean fluorescent intensity in arbitrary units (au). Carotid intima-media thickness (cIMT) was measured using B-mode ultrasound. Data are given as median (interquartile range).

RESULTS

A total of 396 subjects were included, of whom 183 had a history of CVD. Compared to subjects without CVD, patients with CVD had lower apo B bound to neutrophils (12·7 au (9·8-16·2) and 14·2 au (10·1-17·5), respectively, P = 0·038) and to monocytes (2·5 au (1·7-3·1) and 2·7 (1·9-3·6) au, respectively, P = 0·025). No differences were found for lymphocyte-bound apo B. Neutrophil- and monocyte-bound apo B were inversely correlated with cIMT (Spearman's rho: -0·123, P = 0·017 and -0·108, P = 0·035, respectively). Both monocyte- and neutrophil-bound apo B were inversely associated with different factors related to the metabolic syndrome, such as body mass index, triglycerides and complement C3. There was a positive association between erythrocyte-bound apo B and apo B bound to each of the leucocyte classes, possibly reflecting a similar mechanism. Discontinuation of statins in 54 subjects did not influence leucocyte-bound apo B.

CONCLUSION

Unexpectedly, the presence of noninternalized apo B-containing lipoproteins on circulating neutrophil and monocyte membranes may represent a protective mechanism against atherosclerosis.

In vivo evidence for chylomicrons as mediators of postprandial inflammation

BACKGROUND AND AIMS

The postprandial situation is a pro-inflammatory condition most likely linked to the development of atherosclerosis. We evaluated the relationship between apolipoprotein (apo) B48 and fasting and postprandial leukocyte activation markers.

METHODS

Leukocyte activation markers and apo B48 were determined in 80 subjects with and without coronary artery disease (CAD). Twelve healthy subjects underwent an oral fat loading test (up to 8 h).

RESULTS

Fasting apo B48 was significantly higher in patients with CAD (n = 47, 8.1 ± 5.2 mg/L) than in subjects without CAD (n = 33, 5.9 ± 3.9 mg/L, p = 0.022). Fasting apo B48 and triglycerides correlated positively with fasting monocyte CD11b and neutrophil CD66b expression. Plasma apo B48 and leukocyte activation markers increased after an oral fat load. No correlations were found between fasting or postprandial triglycerides and postprandial leukocyte activation markers. We observed no correlations between postprandial apo B48 and postprandial neutrophil CD11b or CD66b expression.

CONCLUSION

This study suggests that chylomicron remnants may be responsible for postprandial leukocyte activation in the circulation. The postprandial chylomicron response may be a stronger mediator of postprandial inflammation than postprandial triglyceridemia.

Glucose-dependent leukocyte activation in patients with type 2 diabetes mellitus, familial combined hyperlipidemia and healthy controls

BACKGROUND

Leukocyte activation has been associated with vascular complications in type 2 diabetes mellitus (T2DM). Hyperglycemia may be involved in this leukocyte activation. Our aim was to investigate the role of elevated glucose concentrations on leukocyte activation in patients with a wide range of insulin sensitivity.

METHODS

Leukocyte activation was determined after ingestion of 75 gram glucose in subjects with T2DM, familial combined hyperlipidemia (FCH) and healthy controls. Leukocyte activation markers were measured by flow cytometry. Postprandial changes were calculated as the area under the curve (AUC), and the incremental area under the curve corrected for baseline values (dAUC).

RESULTS

51 Subjects (20 T2DM, 17 FCH and 14 controls) were included. Fasting neutrophil CD66b expression and CD66b-AUC were respectively 36% and 39% higher in T2DM patients than in controls (p=0.004 and p=0.003). Fasting neutrophil CD66b expression correlated positively with glucose-AUC (Spearman's rho 0.481, p<0.001) and HbA1c (rho 0.433, p=0.002). Although fasting monocyte CD11b expression was not significantly different between subjects, monocyte CD11b-AUC was 26% higher in T2DM than in controls (p=0.006). Similar trends were observed for FCH patients. Monocyte CD11b-dAUC correlated positively with glucose-AUC (rho 0.322, p=0.022) and HbA1c (rho 0.319, p=0.023).

CONCLUSIONS

These data suggest that both acute and chronic hyperglycemia, associated with insulin resistance as seen in T2DM and FCH, are involved in the increased fasting and postprandial leukocyte activation observed in these conditions.

Differential complement activation pathways promote C3b deposition on native and acetylated LDL thereby inducing lipoprotein binding to the complement receptor 1

Lipoproteins can induce complement activation resulting in opsonization and binding of these complexes to complement receptors. We investigated the binding of opsonized native LDL and acetylated LDL (acLDL) to the complement receptor 1 (CR1). Binding of complement factors C3b, IgM, C1q, mannose-binding lectin (MBL), and properdin to LDL and acLDL were investigated by ELISA. Subsequent binding of opsonized LDL and acLDL to CR1 on CR1-transfected Chinese Hamster Ovarian cells (CHO-CR1) was tested by flow cytometry. Both native LDL and acLDL induced complement activation with subsequent C3b opsonization upon incubation with normal human serum. Opsonized LDL and acLDL bound to CR1. Binding to CHO-CR1 was reduced by EDTA, whereas MgEGTA only reduced the binding of opsonized LDL, but not of acLDL suggesting involvement of the alternative pathway in the binding of acLDL to CR1. In vitro incubations showed that LDL bound C1q, whereas acLDL bound to C1q, IgM, and properdin. MBL did neither bind to LDL nor to acLDL. The relevance of these findings was demonstrated by the fact that ex vivo up-regulation of CR1 on leukocytes was accompanied by a concomitant increased binding of apolipoprotein B-containing lipoproteins to leukocytes without changes in LDL-receptor expression. In conclusion, CR1 is able to bind opsonized native LDL and acLDL. Binding of LDL to CR1 is mediated via the classical pathway, whereas binding of acLDL is mediated via both the classical and alternative pathways. Binding of lipoproteins to CR1 may be of clinical relevance due to the ubiquitous cellular distribution of CR1.

Glucose-dependent leukocyte activation in patients with type 2 diabetes mellitus, familial combined hyperlipidemia and healthy controls

BACKGROUND

Leukocyte activation has been associated with vascular complications in type 2 diabetes mellitus (T2DM). Hyperglycemia may be involved in this leukocyte activation. Our aim was to investigate the role of elevated glucose concentrations on leukocyte activation in patients with a wide range of insulin sensitivity.

METHODS

Leukocyte activation was determined after ingestion of 75 gram glucose in subjects with T2DM, familial combined hyperlipidemia (FCH) and healthy controls. Leukocyte activation markers were measured by flow cytometry. Postprandial changes were calculated as the area under the curve (AUC), and the incremental area under the curve corrected for baseline values (dAUC).

RESULTS

51 Subjects (20 T2DM, 17 FCH and 14 controls) were included. Fasting neutrophil CD66b expression and CD66b-AUC were respectively 36% and 39% higher in T2DM patients than in controls (p=0.004 and p=0.003). Fasting neutrophil CD66b expression correlated positively with glucose-AUC (Spearman's rho 0.481, p<0.001) and HbA1c (rho 0.433, p=0.002). Although fasting monocyte CD11b expression was not significantly different between subjects, monocyte CD11b-AUC was 26% higher in T2DM than in controls (p=0.006). Similar trends were observed for FCH patients. Monocyte CD11b-dAUC correlated positively with glucose-AUC (rho 0.322, p=0.022) and HbA1c (rho 0.319, p=0.023).

CONCLUSIONS

These data suggest that both acute and chronic hyperglycemia, associated with insulin resistance as seen in T2DM and FCH, are involved in the increased fasting and postprandial leukocyte activation observed in these conditions.

Hepatitis E-associated encephalopathy in a renal transplant recipient

Hepatitis E virus genotype 3 is not rare in developed countries, and may cause chronic hepatitis in immunocompromised patients. This may not only lead to abnormalities in liver test and malaise, but to severe neurological symptoms as well. In this case, chronic hepatitis E infection caused encephalopathy, an atactic gait, Lhermitte's sign, incomplete bladder emptying and peripheral sensory neuropathy in a renal transplant recipient. The diagnosis was not performed until years after the onset of first symptoms and several months after the onset of neurological symptoms. If treated adequately, viral load can be reduced in over two-thirds of patients and neurological symptoms are often resolved. More widespread knowledge about this virus and its extrahepatic manifestations may lead to a quicker diagnosis, and may limit pathology. Serological screening should be added to standard pretransplant virological screening, so that, in the future, patients without antibodies could be vaccinated.