Treatment of severe hypertriglyceridemia lowers plasma viscosity

The influence of triglyceride and low-density-lipoprotein target levels on microcirculation: Is there a difference?

Background and aims

This study aimed to validate the role of high low-density lipoprotein cholesterol [LDL-C] and triglyceride [TG] treatment target levels on the microcirculation in a very high and high cardiovascular risk group.

Methods

119 patients with high or very high cardiovascular [CV] risk were included. We have registered the main co-morbidities, smoking habits, body mass index [BMI] and the lipid lowering medication. Hematocrit, whole blood viscosity [WBV] and plasma viscosity [PV], red blood cell [RBC] aggregation and deformability and fibrinogen, total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], LDL-C and TG levels were determined.

Results

The investigation found significantly higher PV values in patients with non-target LDL-C, associated with higher fibrinogen level. Non-target TG was related to deteriorated microcirculatory parameters, as significantly higher RBC aggregation, lower RBC deformability, and higher WBV and PV. The main microcirculatory benefit in diabetes could be gained from target level of TG, in chronic coronary syndrome [CCS] patients it is more advantageous to reach both LDL-C and TG target.

Conclusion

The results could highlight, that TG should play a role in failing microcirculation and cause potentially life-threatening complications, which would worsen the survival and quality of life of high or very high risk CV patients.

How viscoelastic is human blood plasma?

Blood plasma has been considered a Newtonian fluid for decades. Recent experiments (Brust et al., Phys. Rev. Lett., 2013, 110) revealed that blood plasma has a pronounced viscoelastic behavior. This claim was based on purely elastic effects observed in the collapse of a thin plasma filament and the fast flow of plasma inside a contraction-expansion microchannel. However, due to the fact that plasma is a solution with very low viscosity, conventional rotational rheometers are not able to stretch the proteins effectively and thus, provide information about the viscoelastic properties of plasma. Using computational rheology and a molecular-based constitutive model, we predict accurately the rheological response of human blood plasma in strong extensional and constriction complex flows. The complete rheological characterization of plasma yields the first quantitative estimation of its viscoelastic properties in shear and extensional flows. We find that although plasma is characterized by a spectrum of ultra-short relaxation times (on the order of 10-3-10-5 s), its elastic nature dominates in flows that feature high shear and extensional rates, such as blood flow in microvessels. We show that plasma exhibits intense strain hardening when exposed to extensional deformations due to the stretch of the proteins in its bulk. In addition, using simple theoretical considerations we propose fibrinogen as the main candidate that attributes elasticity to plasma. These findings confirm that human blood plasma features bulk viscoelasticity and indicate that this non-Newtonian response should be seriously taken into consideration when examining whole blood flow.

A Diabetic Patient with Abdominal Pain and Lactescent Serum

We present the case of a poorly controlled diabetic patient suffering from acute onset of abdominal pain and vomiting. A blood sample taken at the bedside revealed lactescent serum and provided an important clue to the patient's status of having severe hypertriglyceridaemia. The clinical diagnosis of hypertriglyceridaemia-induced acute pancreatitis was correctly made in the accident and emergency department. Clinical photos of the lactescent serum are shown. The incidence, risk factors and management of this particular type of acute pancreatitis are discussed.

Review of the correlation between blood flow velocity and polycythemia in the fetus, neonate and adult: appropriate diagnostic levels need to be determined for twin anemia-polycythemia sequence

Twin anemia-polycythemia sequence (TAPS) is recognized increasingly antenatally by the demonstration of an anemic twin and a polycythemic cotwin using the middle cerebral artery peak systolic velocity (MCA-PSV). While the MCA-PSV has been shown to correlate well with anemia in singleton fetuses, the evidence to support its use to diagnose fetal polycythemia appears to be less clear-cut. We aimed to evaluate fetal, neonatal and adult literature used to support the use of MCA-PSV for the diagnosis of polycythemia. Comprehensive literature searches were performed for ultrasound evidence of polycythemia in the human fetus, neonate and adult using key search terms. Only manuscripts in the English language with an abstract were considered for the review, performed in June 2014. Fifteen manuscripts were found for the human fetus, including 38 cases of TAPS. Nine of these defined fetal polycythemia as MCA-PSV < 0.8 multiples of the median (MoM), five used < 1.0 MoM and one used 0.8-1.0 MoM. Only two studies, involving a total of 15 cases, proposed a diagnostic level, acknowledging false-positive and -negative cases, though neither reported sensitivities or specificities. Six neonatal studies (96 neonates) demonstrated evidence of decreased cerebral velocities in polycythemia and a consequent increase with hemodilution. In the adult, five studies (57 polycythemic adults) demonstrated increased flow or velocity with hemodilution. Neither neonatal nor adult studies conclusively defined levels for screening for polycythemia. Despite widespread adoption of a cut-off of < 0.8 MoM in the published literature for the polycythemic fetus in TAPS, this is based upon minimal evidence, with unknown sensitivity and specificity. We recommend caution in excluding TAPS based purely upon the absence of a reduced MCA-PSV.

Effects of weight loss and pharmacotherapy on inflammatory markers of cardiovascular disease

Obesity is currently an epidemic, and the prevalence of cardiovascular risk factors is increasing dramatically as a result. Visceral adiposity is correlated with a proinflammatory and prothrombotic state that is believed to promote atherosclerosis and acute coronary syndromes. This article will review clinical trials on the effects of weight loss and pharmacotherapy on obesity associated inflammatory and thrombotic markers linked with cardiovascular disease.

Hemorheological abnormalities in lipoprotein lipase deficient mice with severe hypertriglyceridemia

Severe hypertriglyceridemia (HTG) is a metabolic disturbance often seen in clinical practice. It is known to induce life-threatening acute pancreatitis, but its role in atherogenesis remains elusive. Hemorheological abnormality was thought to play an important role in pathogenesis of both pancreatitis and atherosclerosis. However, hemorheology in severe HTG was not well investigated. Recently, we established a severe HTG mouse model deficient in lipoprotein lipase (LPL) in which severe HTG was observed to cause a significant increase in plasma viscosity. Disturbances of erythrocytes were also documented, including decreased deformability, electrophoresis rate, and membrane fluidity, and increased osmotic fragility. Scanning electron microscopy demonstrated that most erythrocytes of LPL deficient mice deformed with protrusions, irregular appearances or indistinct concaves. Analysis of erythrocyte membrane lipids showed decreased cholesterol (Ch) and phospholipid (PL) contents but unaltered Ch/PL ratio. The changes of membrane lipids may be partially responsible for the hemorheological and morphologic abnormalities of erythrocytes. This study indicated that severe HTG could lead to significant impairment of hemorheology and this model may be useful in delineating the role of severe HTG in the pathogenesis of hyperlipidemic pancreatitis and atherosclerosis.

Effects of paradoxical sleep deprivation on blood parameters associated with cardiovascular risk in aged rats

The effects of 96 h of paradoxical sleep deprivation (PSD) on blood parameters associated with cardiovascular risk were studied in young (3-month old) and aged (22-month old) rats. In general, aging was associated with an overall increase in most measures, irrespective of sleep deprivation condition. The latter manipulation also had significant effects on blood variables, but not in a consistent pattern. Thus, PSD significantly reduced triglyceride levels in both young and aged rats; it reduced blood viscosity in aged but not in young rats, and had no effect on the increased cholesterol levels observed in aged controls. Examinations of cholesterol fractions revealed significant increases in low density lipoprotein and high density lipoprotein in aged PSD rats compared to respective controls, whereas very low density lipoprotein was significant decreased after PSD in both young and aged animals. PSD increased vitamin B(12) levels in aged rats, and significantly decreased homocysteine levels in young but not in aged rats which in turn were already reduced. Folate levels were the only variable that was unaffected by aging and/or PSD. These results indicate that PSD has significant but heterogeneous physiological effects in aged rats and may intensify certain aging-related effects which contribute to cardiovascular disease risk while attenuating others.

Utility of inflammatory markers in the management of coronary artery disease

Certain markers of systemic inflammation are powerful predictors of cardiovascular events. Fibrinogen, C-reactive protein (CRP), and cytokines are among the inflammatory markers associated with various cardiovascular end points. Fibrinogen and CRP both have been associated with coronary artery disease (CAD) mortality in patients with stable angina. High-sensitivity CRP (hs-CRP) and fibrinogen also have prognostic value in patients with unstable angina. In addition to prognostic implications, several cardiovascular risk factors (eg, smoking, obesity, diabetes) are associated with high levels of fibrinogen and hs-CRP. Benefits from aspirin are more likely in patients whose hs-CRP levels are very high. Some fibrates decrease fibrinogen levels and hs-CRP. Statin therapy either reduces the CAD risk associated with system inflammation or lowers circulating levels of hs-CRP.

Effect of methyl testosterone administration on plasma viscosity in postmenopausal women

BACKGROUND

Coronary heart disease (CHD) is the leading cause of mortality in women, with an incidence that increases after menopause, hence suggesting a cardioprotective role of oestrogen. Menopause also results in a decline in androgen levels with resulting symptoms of decreased libido and sexual dysfunction. Recently, there has been a growing interest in the treatment of postmenopausal women with androgens. However, no data are available on plasma viscosity and fibrinogen levels in postmenopausal women on combined oestrogen/androgen therapy.

METHODS

We conducted a randomized, double-blind, parallel-group 16-week study evaluating the effects of methyltestosterone supplementation on plasma viscosity and fibrinogen levels in postmenopausal women already on oestrogen replacement therapy (ERT) for at least 3 months. Women 21 years and older who were menopausal (natural or surgical) for at least 12 months were enrolled in the study. Participants were randomized to (1) an oestrogen-only group taking 1.25 mg esterified oestrogen (E-group) and (2) an oestrogen plus methyltestosterone (1.25 mg esterified oestrogen and 2.5 mg methyltestosterone) group (EA-group). Progesterone was not administered during the study period and women with intact uteri were given medroxyprogesterone 10 mg daily for 14 days at the completion of the study.

RESULTS

After 16 weeks of treatment, both groups had a significant increase in serum oestradiol levels from baseline. The levels of total oestrogen were significantly higher in the E-group compared to the EA-group (P < 0.001). There was a greater decrease in the LH and SHBG levels in the EA-group (P = 0.01). There was no difference in total testosterone; however, free testosterone levels were significantly higher in the EA-group (P = 0.01). At the end of the study, there was a significant decrease in plasma viscosity only in the EA-group (P = 0.01). Fibrinogen levels increased in both the groups, reaching significance only in the EA-group (P = 0.006). Baseline weight, body mass index (BMI) and the duration of menopausal status did not have any significant impact on the changes in plasma viscosity or fibrinogen. Women in the EA-group showed significant reductions in total cholesterol (P = 0.009), high density lipoprotein (HDL) (P < 0.001) and triglyceride (TG) levels (P = 0.001). There was no significant change in these parameters in the E-group.

CONCLUSION

This prospective study shows that the treatment of postmenopausal women on oestrogen with low-dose oral methyltestosterone results in a significant reduction in plasma viscosity. This lowering of plasma viscosity was achieved despite an increase in fibrinogen levels. Significant lowering of lipoproteins, especially TG levels, might have been responsible for this benefit. The combination regimen did not result in major side-effects. Based on these results, we feel confident in recommending low-dose androgens to postmenopausal women with a history of sexual dysfunction and decreased libido.

Marked removal of bezafibrate-induced high-density lipoprotein-cholesterol by low-density lipoprotein apheresis

BACKGROUND

A case of marked reduction of the bezafibrate-induced increase of high-density lipoprotein (HDL)-cholesterol by low-density lipoprotein apheresis (LDL-apheresis) has not been previously reported.

METHODS

A 68-year-old Japanese man with arteriosclerosis obliterans (ASO), diabetes mellitus, and hyperlipidemia underwent LDL-apheresis, followed by the concomitant bezafibrate administration. Plasma lipids of pre- and post-LDL-apheresis were measured and apolipoprotein E (apoE) localization of the pre- and post-LDL-apheresis was detected by agarose gel electrophoresis.

RESULTS

Plasma concentrations of the total cholesterol, LDL-cholesterol, triglyceride, and HDL-cholesterol of pre-LDL-apheresis were 4.78 +/- 0.36, 2.74 +/- 0.24, 2.44 +/- 0.52, and 0.92 +/- 0.10 mmol/l, respectively; those of the post-LDL-apheresis were 1.94 +/- 0.31, 0.72 +/- 0.13, 0.81 +/- 0.38, and 0.86 +/- 0.11 mmol/l, respectively. LDL-apheresis reduced HDL-cholesterol by 6.4% (p=0.346). During the bezafibrate administration, plasma concentrations of the above of pre-LDL-apheresis were 5.24 +/- 0.34, 3.28 +/- 0.22, 1.26 +/- 0.25, and 1.39 +/- 0.21 mmol/l, respectively; those of the post-LDL-apheresis were 2.25 +/- 0.44, 0.80 +/- 0.12, 0.58 +/- 0.19, and 1.18 +/- 0.16 mmol/l, respectively. LDL-apheresis reduced HDL-cholesterol by 15.2% (p<0.01). Plasma apolipoprotein E detected between the prebeta- and alpha-mobility was markedly lower after the LDL-apheresis in the agarose gel electrophoresis.

CONCLUSIONS

The removal of the bezafibrate induced an increase of the HDL-cholesterol by LDL-apheresis.

Changes in hemostasis during treatment of hypertriglyceridemia with a diet rich in monounsaturated and n-3 polyunsaturated fatty acids in comparison with a low-fat diet

High levels of fibrinogen, factor (F) VIIc, plasminogen activator inhibitor-1 (PAI-1), and plasma viscosity are associated with an increased coronary risk. As positive correlations of these parameters with triglycerides have been shown, the increased coronary risk associated with high levels of triglycerides may be assumed to be due to alterations within the hemostatic system. To reduce the coronary risk to which hypertriglyceridemic patients are exposed, dietary treatment is recommended; the optimal composition of such a diet is, however, a matter of debate. With regard to the effects on hemostasis, we compared in a sequential approach two diets for treatment of 25 nonobese male patients (age, mean+/-S.D., 40.4+/-8.7 years) with fasting triglycerides >2.3 mmol/l. The first diet (high fat) was rich in monounsaturated fatty acids (MUFA) and marine n-3 polyunsaturated fatty acids (PUFA), whereas the second diet (low-fat) was rich in complex carbohydrates and dietary fiber. The high-fat diet induced a significant lowering of FIIc, FIXc, FXc, FVIIc, FVIIa, FXIIa, PAI-1, plasma viscosity, and platelet activity, but led to an increase in fibrinogen, whereas the low-fat diet lowered FXIIc values and induced a nonsignificant decrease in fibrinogen. Probands on this diet had a slightly higher FVIIa and platelet activity than those on the high-fat diet. However, as all changes appeared to be within the normal range of each hemostatic parameter, it remains to be clarified whether the likely beneficial effects of the high-fat diet on most hemostatic factors are outweighed by the small increase in fibrinogen levels.

Current, new and future treatments in dyslipidaemia and atherosclerosis

The new therapeutic options available to clinicians treating dyslipidaemia in the last decade have enabled effective treatment for many patients. The development of the HMG-CoA reductase inhibitors (statins) have been a major advance in that they possess multiple pharmacological effects (pleiotropic effects) resulting in potent reductions of low density lipoproteins (LDL) and prevention of the atherosclerotic process. More recently, the newer fibric acid derivatives have also reduced LDL to levels comparable to those achieved with statins, have reduced triglycerides, and gemfibrozil has been shown to increase high density lipoprotein (HDL) levels. Nicotinic acid has been made tolerable with sustained-release formulations, and is still considered an excellent choice in elevating HDL cholesterol and is potentially effective in reducing lipoprotein(a) [Lp(a)] levels, an emerging risk factor for coronary heart disease (CHD). Furthermore, recent studies have reported positive lipid-lowering effects from estrogen and/or progestogen in postmenopausal women but there are still conflicting reports on the use of these agents in dyslipidaemia and in females at risk for CHD. In addition to lowering lipid levels, these antihyperlipidaemic agents may have directly or indirectly targeted thrombogenic, fibrinolytic and atherosclerotic processes which may have been unaccounted for in their overall success in clinical trials. Although LDL cholesterol is still the major target for therapy, it is likely that over the next several years other lipid/lipoprotein and nonlipid parameters will become more generally accepted targets for specific therapeutic interventions. Some important emerging lipid/lipoprotein parameters that have been associated with CHD include elevated triglyceride, oxidised LDL cholesterol and Lp(a) levels, and low HDL levels. The nonlipid parameters include elevated homocysteine and fibrinogen, and decreased endothelial-derived nitric oxide production. Among the new investigational agents are inhibitors of squalene synthetase, acylCoA: cholesterol acyltransferase, cholesteryl ester transfer protein, monocyte-macrophages and LDL cholesterol oxidation. Future applications may include thyromimetic therapy, cholesterol vaccination, somatic gene therapy, and recombinant proteins, in particular, apolipoproteins A-I and E. Non-LDL-related targets such as peroxisome proliferator-activating receptors, matrix metalloproteinases and scavenger receptor class B type I may also have clinical significance in the treatment of atherosclerosis in the near future. Before lipid-lowering therapy, dietary and lifestyle modification is and should be the first therapeutic intervention in the management of dyslipidaemia. Although current recommendations from the US and Europe are slightly different, adherence to these recommendations is essential to lower the risk of atherosclerotic vascular disease, more specifically CHD. New guidelines that are expected in the near future will encompass global opinions from the expert scientific community addressing the issue of target LDL goal (aggressive versus moderate lowering) and the application of therapy for newer emerging CHD risk factors.

Contribution of fibrinogen and lipoproteins to plasma viscosity in hypercholesterolemia and hypertriglyceridemia: evaluation by selective depletion of low-density lipoproteins or fibrinogen

Epidemiological studies suggest that the plasma fibrinogen concentration is the main determinant of plasma viscosity (PV), but the concentration of other macromolecules (eg, immunoglobulins) and low-density lipoprotein (LDL) cholesterol and triglycerides are also correlated with PV. However, only a few data exist concerning the in vitro effects of these plasma constituents on PV. Therefore, we investigated PV before and after the specific elimination of fibrinogen and LDL in hypercholesterolemic and hypertriglyceridemic plasma. First, hypercholesterolemic samples (n = 7) were pumped simultaneously through 2 columns: a fibrinogen-depleting column containing the pentapeptide Gly-Pro-Arg-Pro-Lys (GPRPK) and a LDL-depleting column containing specific antibodies against apolipoprotein B-100. In the plasma and in each fraction from the column, the cholesterol level was measured enzymatically, fibrinogen was determined by immunonephelometry, and PV was analyzed using a low-shear rotation viscosimeter. After the fibrinogen-depleting column, the fibrinogen concentration decreased from 3.21 +/- 0.20 to 0.94 +/- 0.16 g/L (P < .005), inducing a decrease in PV from 1.27 +/- 0.02 to 1.17 +/- 0.01 mPas (milliPascal seconds) (P < .005). Despite a marked reduction of the LDL cholesterol after the LDL-depleting column (from 6.40 +/- 0.23 to 4.08 +/- 0.32 mmol/L, P < .005), PV remained unchanged. Second, hypertriglyceridemic samples (n = 7) were pumped through the fibrinogen-depleting column, which reduced the fibrinogen concentration from 4.29 +/- 0.79 to 1.62 +/- 0.69 g/L (P < .001) and PV from 1.42 +/- 0.06 to 1.03 +/- 0.05 mPas (P < .01) while the triglyceride concentration remained unchanged. Our results confirm the epidemiological correlation between the fibrinogen concentration and PV in patients with hypercholesterolemia and hypertriglyceridemia. The influence of fibrinogen on PV seems much more pronounced than the direct effect of lipoprotein concentrations. Therefore, the elevated PV in patients with hypercholesterolemia and especially with hypertriglyceridemia seems mainly due to elevated fibrinogen levels.

Basic mechanisms of stroke prevention with lipid-lowering therapy

Cholesterol-lowering therapy has not been considered an important risk factor for stroke; however, lipid-lowering therapies reduce cerebrovascular events in patients with coronary heart disease (CHD). The basic mechanisms of cerebrovascular protection have emphasized reduced atheroemboli from the left ventricle and aortic arch, delayed carotid artery disease progression, stabilization of vulnerable carotid atherosclerotic plaque, and improvement in cerebral blood flow.

Effects of lipids and lipoproteins on thrombosis and rheology

Atherosclerotic plaque rupture and erosions precipitate thrombus formation and may lead to an acute ischemic syndrome. Lipids and lipoproteins modulate the expression and/or function of thrombotic, fibrinolytic and rheologic factors, and thereby influence hemostasis and potential tissue damage resulting from vascular injury. Triglyceride-enriched lipoproteins are accompanied by elevations in factor VII clotting activity, plasminogen activator inhibitor (PAI-1) and viscosity of blood and plasma. Low density lipoprotein (LDL) promotes platelet activation and tissue factor expression and LDL levels correlate with levels of vitamin K dependent coagulation factors and fibrinogen. Conversely, LDL inhibits tissue factor pathway inhibitor (TFPI) which limits activation of the extrinsic coagulation pathway. High density lipoprotein (HDL) has anti-atherothrombotic properties that result from inhibition of platelet and erythrocyte aggregation, reduced blood viscosity and suppression of tissue factor activity and PAI-1 activity and antigen levels. The effects of lipids and lipoproteins on hemostasis and rheology may have important implications for the clinical sequelae following plaque disruption and erosion.