Deleterious effect of glycation on the ability of HDL to counteract the inhibitory effect of oxidized LDL on endothelium-dependent vasorelaxation

BACKGROUND

Contrary to high-density lipoprotein (HDL) from normolipidaemic and normoglycaemic subjects, HDL from diabetic patients loses its ability to reverse the inhibition of vasorelaxation induced by oxidized low-density lipoprotein (LDL). The aim of this study was to analyze the role of glycation, a major abnormality observed in diabetes, on the impairment of the vasorelaxant effect of HDL.

METHODS

HDL from healthy subjects was glycated in vitro by incubation in glucose 200 mmol/L for 3 days. Vasoreactivity was evaluated by the relaxation response to acetylcholine of rabbit aorta rings pre-contracted with noradrenaline, before and after 2 h incubation with or without different lipoprotein fractions (Krebs buffer, oxidized LDL, normal or glycated HDL alone and with oxidized LDL).

RESULT

The fructosamine/apolipoprotein AI ratio was significantly increased in glycated HDL compared with native HDL (53.63 ± 7.91 vs 18.51 ± 4.10 µmol/g; p < 0.05). Oxidized LDL inhibited endothelium-dependent vasodilation compared with Krebs buffer [maximal relaxation (Emax) = 53.15 ± 6.50 vs 98.67 ± 2.07%, p < 0.001]. Native HDL was able to counteract the oxidized LDL-induced inhibition of vasorelaxation (Emax = 76.93 ± 5.41 vs 53.15 ± 6.50%, p < 0.001). On the other hand, glycated HDL had no effect on oxidized LDL-induced inhibition of endothelium vasorelaxation compared with incubation with oxidized LDL alone (Emax = 52.98 ± 2.07 vs 53.15 ± 6.50%, not significant).

CONCLUSION

Glycation of HDL induces the loss of the ability of HDL to counteract the inhibitory effect of oxidized LDL on endothelium-dependent vasorelaxation, this is likely contributing to the impairment of antiatherogenic properties of HDL in diabetic patients.

Glucose lowering therapeutic strategies for type 2 diabetic patients with chronic kidney disease in primary care setting in france: a cross-sectional study

Aim. To understand glucose lowering therapeutic strategies of French general practitioners (GPs) in the management of type 2 diabetes mellitus (T2DM) patients with chronic kidney disease (CKD). Methods. A multicenter cross-sectional study was conducted from March to June 2011 among a sample of French GPs who contribute to the IMS Lifelink Disease Analyzer database. Eligible patients were those with T2DM and moderate-to-severe CKD who visited their GPs at least once during the study period. Data were collected through electronic medical records and an additional questionnaire. Results. 116 GPs included 297 patients: 86 with stage 3a (Group 1, GFR = 45-60 mL/min/1.73 m(2)) and 211 with stages 3b, 4, or 5 (Group 2, GFR < 45 mL/min/1.73 m(2)). Patients' mean age was approximately 75 years. Insulin was used in 19% of patients, and was predominant in those with severe CKD. More than two-thirds of patients were treated with glucose lowering agents which were either contraindicated or not recommended for CKD. Conclusion Physicians most commonly considered the severity of diabetes and not CKD in their therapeutic decision making, exposing patients to potential iatrogenic risks. The recent patient oriented approach and individualization of glycemic objectives according to patient profile rather than standard HbA1c would improve this situation.

[Pheochromocytoma: rare lethal challenging diagnosis that may be encountered by gynecologists and obstetricians]

Pheochromocytomas are rare but potentially lethal tumors responsible for malignant hypertension. They may be encountered by gynecologists and obstetricians. The diagnosis is difficult because it can be mistaken for diseases more frequent like preeclampsia or other pelvic tumors. We report two cases highlighting clinical clues such as labile hypertension, headache, sweating, palpitations and failure to respond to conventional treatment should prompt physicians to screen patients for pheochromocytoma by measuring the 24-hour urinary catecholamines. The surgery must be performed after using an appropriate preoperative treatment, in order not to trigger lethal outcome. During pregnancy, C-section is recommended.

Beyond glucose lowering: glucagon-like peptide-1 receptor agonists, body weight and the cardiovascular system

AIM

Glucagon-like peptide-1 (GLP-1) belongs to the incretin hormone family: in the presence of elevated blood glucose, it stimulates insulin secretion and inhibits glucagon production. In addition, GLP-1 slows gastric emptying. GLP-1 secretion has also been reported to potentially affect patients with type 2 diabetes (T2DM) compared with non-diabetics and, as enzymatic inactivation by dipeptidyl peptidase-4 (DPP-4) shortens the GLP-1 half-life to a few minutes, GLP-1 receptor agonists such as exenatide twice daily (BID) and liraglutide have been developed, and have become part of the management of patients with T2DM. This review focuses on the potential beneficial effects of these compounds beyond those associated with improvements in blood glucose control and weight loss, including changes in the cardiovascular and central nervous systems.

METHODS

This was a state-of-the-art review of the literature to evaluate the relationships between GLP-1, GLP-1 receptor agonists, weight and the cardiovascular system.

RESULTS

GLP-1 receptor agonists improve glucose control and do not significantly increase the risk of hypoglycaemia. Also, this new class of antidiabetic drugs was shown to favour weight loss. Mechanisms may involve central action, direct action by reduction of food intake and probably indirect action through slowing of gastric emptying. The relative importance of each activity remains unclear. Weight loss may improve cardiovascular outcomes in patients with T2DM, although GLP-1 receptor agonists may have other direct and indirect effects on the cardiovascular system. Reductions in myocardial infarct size and improvements in cardiac function have been seen in animal models. Beneficial changes in cardiac function were also demonstrated in patients with myocardial infarcts or heart failure. Indirect effects could involve a reduction in blood pressure and potential effects on oxidation. However, the mechanisms involved in the pleiotropic effects of GLP-1 receptor agonists have yet to be completely elucidated and require further study.

CONCLUSION

These compounds may play an important role in the treatment of patients with T2DM as their potential effects go beyond glucose-lowering (weight loss, potential improvement of cardiovascular risk factors). However, to better understand their place in the management of T2DM, further experimental and clinical prospective studies are required.

Cardiovascular complications in type 1 diabetes mellitus

Although the issue of cardiovascular complications in type 2 diabetic patients is widely discussed, and recommendations for such screening are available, it is less common to do so for type-1 diabetes. Yet, independent of age, the mortality rate due to ischaemic cardiac disease is higher among type 1 diabetic patients (both male and female) than in the general population. Type 1 diabetic patients have certain specific characteristics related not only to atherosclerotic plaque and cardiovascular risk factors, but also to their capacity for physical activity and to the prevention of cardiovascular complications induced by hypoglycaemia.

Lipid disorders in type 1 diabetes

Patients with type 1 diabetes (T1D) also present with lipid disorders. Quantitative abnormalities of lipoproteins are observed in T1D patients with poor glycaemic control (increased plasma triglycerides and low-density lipoprotein [LDL] cholesterol) or nephropathy (increased triglycerides and LDL cholesterol, low level of high density lipoprotein [HDL] cholesterol). In cases of T1D with optimal glycaemic control, plasma triglycerides and LDL cholesterol are normal or slightly decreased, while HDL cholesterol is normal or slightly increased. Several qualitative abnormalities of lipoproteins, which are potentially atherogenic, are observed in patients with T1D, even in those with good metabolic control. These abnormalities include increased cholesterol-to-triglyceride ratios within very low-density lipoprotein (VLDLs), increased triglycerides in LDLs and HDLs, compositional changes in the peripheral layer of lipoproteins, glycation of apolipoproteins, increased oxidation of LDLs and an increase in small, dense LDL particles. These qualitative changes in lipoproteins are likely to impair their function. In vitro, VLDLs and LDLs from patients with T1D induced abnormal responses in the cellular cholesterol metabolism of human macrophages. HDLs from patients with T1D are thought to be less effective in promoting cholesterol efflux from cells, and have been shown to have reduced antioxidative and vasorelaxant properties. These qualitative abnormalities are not fully explained by hyperglycaemia and may be partly due to peripheral hyperinsulinaemia associated with subcutaneous insulin administration. However, the precise consequences of these qualitative lipid changes on the development of cardiovascular disease in T1D are, as yet, unknown.

Effects of 20 mg rosuvastatin on VLDL1-, VLDL2-, IDL- and LDL-ApoB kinetics in type 2 diabetes

AIMS/HYPOTHESIS

In addition to its efficacy in reducing LDL-cholesterol, rosuvastatin has been shown to significantly decrease plasma triacylglycerol. The use of rosuvastatin may be beneficial in patients with type 2 diabetes, who usually have increased triacylglycerol levels. However, its effects on the metabolism of triacylglycerol-rich lipoproteins in type 2 diabetic patients remains unknown.

METHODS

We performed a randomised double-blind crossover trial of 6-week treatment with placebo or rosuvastatin 20 mg in eight patients with type 2 diabetes who were being treated with oral glucose-lowering agents. In each patient, an in vivo kinetic study of apolipoprotein B (ApoB)-containing lipoproteins with [13C]leucine was performed at the end of each treatment period. A central randomisation centre used computer-generated tables to allocate treatments. Participants, caregivers and those assessing the outcomes were blinded to group assignment.

RESULTS

Rosuvastatin 20 mg significantly reduced plasma LDL-cholesterol, triacylglycerol and total ApoB. It also significantly reduced ApoB pool sizes of larger triacylglycerol-rich VLDL particles (VLDL1; p = 0.011), smaller VLDL particles (VLDL2; p = 0.011), intermediate density lipoprotein (IDL; p = 0.011) and LDL (p = 0.011). This reduction was associated with a significant increase in the total fractional catabolic rate of VLDL1-ApoB (6.70 +/- 3.24 vs 4.52 +/- 2.34 pool/day, p = 0.049), VLDL2-ApoB (8.72 +/- 3.37 vs 5.36 +/- 2.64, p = 0.011), IDL-ApoB (7.06 +/- 1.68 vs 4.21 +/- 1.51, p = 0.011) and LDL-ApoB (1.02 +/- 0.27 vs 0.59 +/- 0.13, p = 0.011). Rosuvastatin did not change the production rates of VLDL2-, IDL- or LDL-, but did reduce VLDL1-ApoB production rate (12.4 +/- 4.5 vs 19.5 +/- 8.4 mg kg(-1) day(-1), p = 0.035). No side effects of rosuvastatin were observed during the study.

CONCLUSIONS/INTERPRETATION

In type 2 diabetic patients rosuvastatin 20 mg not only induces a significant increase of LDL-ApoB catabolism (73%), but also has favourable effects on the catabolism of triacylglycerol-rich lipoproteins, e.g. a significant increase in the catabolism of VLDL1-ApoB (48%), VLDL2-ApoB (63%) and IDL-ApoB (68%), and a reduction in the production rate of VLDL1-ApoB (-36%). The effects of rosuvastatin on the metabolism of triacylglycerol-rich lipoproteins may be beneficial for prevention of atherosclerosis in type 2 diabetic patients.

Distinct patterns of heparin affinity chromatography VLDL1 and VLDL2 subfractions in the different dyslipidaemias

Very low density lipoprotein (VLDL) 1 and 2 were fractionated by heparin affinity chromatography into a bound and an unbound fraction and the different subfractions were quantified in 17 normolipidaemic (NL), 13 hypercholesterolaemic (HC), 10 hypertriglyceridaemic (HTG) and 11 combined hyperlipidaemic subjects (CHL). Unbound VLDL1 and VLDL2 were, respectively, 1.9- and 2.2-fold richer in triglycerides than bound VLDL1 and VLDL2. In HTG and CHL the concentration of all the VLDL subfractions was increased and plasma triglyceride level was correlated to unbound VLDL1 and to bound VLDL1 (respectively, r=0.86 (p<0.001) and r=0.77 (p<0.01) in HTG and r=0.73 (p<0.001) and r=0.62 (p<0.05) in CHL). In HC unbound VLDL2 and bound VLDL2 concentration were increased compared to NL and in CHL, the concentration of bound VLDL2 was particularly increased (3.2-fold compared to NL (p<0.001)). In both HC and CHL bound VLDL2 concentration was correlated to low density lipoprotein cholesterol (LDL-C) concentration (respectively, r=0.67 (p<0.01) and r=0.62 (p<0.05)). In hypertriglyceridaemic states the intravascular accumulation of both unbound and bound VLDL1 appears as the determinant of plasma triglyceride concentration, whereas in moderately hypercholesterolaemic states the concentration of bound VLDL2 is strikingly correlated to LDL-C concentration, suggesting that these two species are linked metabolically, e.g. bound VLDL2 contain the precursor pool of LDL.

HDL particles from type 1 diabetic patients are unable to reverse the inhibitory effect of oxidised LDL on endothelium-dependent vasorelaxation

AIMS/HYPOTHESIS

In healthy individuals, HDL can counteract the inhibition of vasorelaxation induced by oxidised LDL. Several abnormalities such as increased size, glycation and decreased paraoxonase activity have been reported for HDL from type 1 diabetic patients. Thus, we hypothesised that the ability of HDL to protect vessels against impairments of vasorelaxation would be decreased in these patients.

METHODS

We compared the ability of HDL from 18 type 1 diabetic patients and 12 control participants to counteract the inhibition of endothelium-dependent relaxation induced by oxidised LDL on rabbit aorta rings.

RESULTS

Serum triacylglycerol and total cholesterol, LDL- and HDL-cholesterol were similar in type 1 diabetic and control participants. Fasting glycaemia and the HDL-fructosamine level were higher in diabetic patients than in controls (9.06 +/- 3.55 vs 5.27 +/- 0.23 mmol/l, p < 0.005; and 10.2 +/- 3.2 vs 7.7 +/- 2.5 micromol/g protein, p < 0.05, respectively). HDL composition, size and paraoxonase activity were similar in both groups. HDL from controls reduced the inhibitory effect of oxidised LDL on maximal relaxation (E (max); 79.3 +/- 11.8 vs 66.4 +/- 11.7%, p < 0.05), whereas HDL from type 1 diabetic patients had no effect (E (max) = 70.6 +/- 17.4 vs 63.9 +/- 17.2%, NS). In type 1 diabetic patients, E (max) was not correlated with glycaemia or the HDL-fructosamine level.

CONCLUSIONS/INTERPRETATION

HDL particles from type 1 diabetic patients do not protect against inhibition of endothelium-dependent vasorelaxation induced by oxidised LDL, in contrast to HDL particles from healthy individuals. This defect cannot be explained by abnormalities in HDL composition, size or paraoxonase activity, and may contribute to the early development of atherosclerotic lesions in type 1 diabetic patients.

[The best of cardiac rehabilitation in 2006]

The meta-analysis showing the benefits of physical training revisited: Taylor examined only the cardiac rehabilitation trials of exercise intervention alone (versus usual care) and demonstrated that cardiac mortality is 28 % reduced and exercise appears to have an independent mortality benefit. An economic evaluation of cardiac rehabilitation: a systematic review of 15 economic evaluations. Evidence to support the cost-effectiveness of supervised cardiac rehabilitation compared with usual care in myocardial infarction and heart failure was identified. But further well-designed trials are required. Pronostic value of some variables determined by exercise testing entering cardiac rehabilitation and after physical training. A beneficial effect of physical training versus usual care on BNP and neurohormones in patients with chronic heart disease. Patients on beta blockers after myocardial infarction: determination of a more accurate training heart frequency derived from the classical Karvonen's formula. The combination of trimetazidine with exercise training provides greater improvements in functional capacity, left ventricular function and the endothelium-dependent relaxation of the brachial artery than exercise training alone in patients with ischaemic cardiomyopathy referred for cardiac rehabilitation. Guidelines for resistance exercise after cardiac event: a new paradigm less restrictive, safe and efficient to accelerate patients' return to daily activities. Recommendations for participation in leisure-time physical activity and competitive sports for patients with ischaemic heart disease: the result of consensus among experts from the ESC study group of sports cardiology.