Therapeutic effects of fibrates in postprandial lipemia

Hypertriglyceridemia and Atherosclerotic Carotid Artery Stenosis

Both fasting and non-fasting hypertriglyceridemia have emerged as residual risk factors for atherosclerotic disease. However, it is unclear whether hypertriglyceridemia increases the risks of the progression of carotid artery stenosis. Statins are well known to prevent carotid plaque progression and improve carotid plaque instability. In addition, statin therapy is also known to reduce cerebrovascular events in patients with carotid artery stenosis and to improve clinical outcomes in patients undergoing revascularization procedures. On the other hand, there have been no randomized controlled trials showing that the combination of non-statin lipid-lowering drugs with statins has additional beneficial effects over statin monotherapy to prevent cerebrovascular events and stenosis progression in patients with carotid artery stenosis. In this article, the authors demonstrate the mechanisms of atherosclerosis formation associated with hypertriglyceridemia and the potential role of lipid-lowering drugs on carotid artery stenosis. The authors also review the articles reporting the relationships between hypertriglyceridemia and carotid artery stenosis.

Nonglycemic targets in diabetes

In conclusion, targets for patients with diabetes have actually become simpler with the release of new guidelines. The targets discussed in this article are summarized in Box 3. Finally, as clinicians and patients with diabetes struggle with the overwhelming burden of care, clinicians should consider the increasingly codified ethic of minimally disruptive medicine, which considers not just what patients and doctors can do but what patients' priorities, wishes, and needs are rather than the many specialist tests and treatment options available. Finding the balance may be easier with the new evidence-based and more straightforward guidelines.

Metabolic phenotypes of obesity influence triglyceride and inflammation homoeostasis

BACKGROUND

We examined the degree of postprandial triglyceride (TG) response over the day, representing a highly dynamic state, with continuous metabolic adaptations, among normal-weight, overweight and obese patients, according to their metabolically healthy or abnormal status.

MATERIALS AND METHODS

A total of 1002 patients from the CORDIOPREV clinical trial (NCT00924937) were submitted to an oral fat load test meal with 0·7 g fat/kg body weight (12% saturated fatty acids (SFA), 10% polyunsaturated fatty acids (PUFA), 43% monounsaturated fatty acids (MUFA), 10% protein and 25% carbohydrates). Serial blood test analysing lipid fractions and inflammation markers (high-sensitivity C-reactive protein (hs-CRP)) were drawn at 0, 1, 2, 3 and 4 h during postprandial state. We explored the dynamic response according to six body size phenotypes: (i) normal weight, metabolically healthy; (ii) normal weight, metabolically abnormal; (iii) overweight, metabolically healthy; (iv) overweight, metabolically abnormal; (v) obese, metabolically healthy; and (vi) obese, metabolically abnormal.

RESULTS

Metabolically healthy patients displayed lower postprandial response of plasma TG and large triacylglycerol-rich lipoproteins (TRLs)-TG, compared with those metabolically abnormal, independently whether or not they were obese (P < 0·001 and P < 0·001, respectively). Moreover, the area under the curve (AUC) of TG and AUC of large TRLs-TG were greater in the group of metabolically abnormal compared with the group of metabolically healthy (P < 0·001 and P < 0·001, respectively). Interestingly, metabolically abnormal subjects displayed higher postprandial response of plasma hs-CRP than did the subgroup of normal, overweight and obese, metabolically healthy patients (P < 0·001).

CONCLUSIONS

Our findings showed that certain types of the metabolic phenotypes of obesity are more favourable modulating phenotypic flexibility after a dynamic fat load test, through TG metabolism and inflammation homoeostasis. To identify, these phenotypes may be the best strategy for personalized treatment of obesity.

Postprandial lipemia as a cardiometabolic risk factor

High levels of fasting circulating triglycerides (TG) represent an independent risk factor for cardiovascular disease. In western countries, however, people spend most time in postprandial conditions, with continuous fluctuation of lipemia due to increased levels of TG-rich lipoproteins (TRLs), including chylomicrons (CM), very low density lipoproteins (VLDL), and their remnants. Several factors contribute to postprandial lipid metabolism, including dietary, physiological, pathological and genetic factors. The presence of coronary heart disease, type 2 diabetes, insulin resistance and obesity is associated with higher postprandial TG levels compared with healthy conditions; this association is present also in subjects with normal fasting TG levels. Increasing evidence indicates that impaired metabolism of postprandial lipoproteins contributes to the pathogenesis of coronary artery disease, suggesting that lifestyle modifications as well as pharmacological approaches aimed at reducing postprandial TG levels might help to decrease the cardiovascular risk.

Recent advances in pharmacotherapy for hypertriglyceridemia

Elevated plasma triglyceride (TG) concentrations are associated with an increased risk of atherosclerotic cardiovascular disease (CVD), hepatic steatosis and pancreatitis. Existing pharmacotherapies, such as fibrates, n-3 polyunsaturated fatty acids (PUFAs) and niacin, are partially efficacious in correcting elevated plasma TG. However, several new TG-lowering agents are in development that can regulate the transport of triglyceride-rich lipoproteins (TRLs) by modulating key enzymes, receptors or ligands involved in their metabolism. Balanced dual peroxisome proliferator-activated receptor (PPAR) α/γ agonists, inhibitors of microsomal triglyceride transfer protein (MTTP) and acyl-CoA:diacylglycerol acyltransferase-1 (DGAT-1), incretin mimetics, and apolipoprotein (apo) B-targeted antisense oligonucleotides (ASOs) can all decrease the production and secretion of TRLs; inhibitors of cholesteryl ester transfer protein (CETP) and angiopoietin-like proteins (ANGPTLs) 3 and 4, monoclonal antibodies (Mabs) against proprotein convertase subtilisin/kexin type 9 (PCSK9), apoC-III-targeted ASOs, selective peroxisome proliferator-activated receptor modulators (SPPARMs), and lipoprotein lipase (LPL) gene replacement therapy (alipogene tiparvovec) enhance the catabolism and clearance of TRLs; dual PPAR-α/δ agonists and n-3 polyunsaturated fatty acids can lower plasma TG by regulating both TRL secretion and catabolism. Varying degrees of TG reduction have been reported with the use of these therapies, and for some agents such as CETP inhibitors and PCSK9 Mabs findings have not been consistent. Whether they reduce CVD events has not been established. Trials investigating the effect of CETP inhibitors (anacetrapib and evacetrapib) and PCSK9 Mabs (AMG-145 and REGN727/SAR236553) on CVD outcomes are currently in progress, although these agents also regulate LDL metabolism and, in the case of CETP inhibitors, HDL metabolism. Further to CVD risk reduction, these new treatments might also have a potential role in the management of diabetes and non-alcoholic fatty liver disease owing to their insulin-sensitizing action (PPAR-α/γ agonists) and potential capacity to decrease hepatic TG accumulation (PPAR-α/δ agonists and DGAT-1 inhibitors), but this needs to be tested in future trials. We summarize the clinical trial findings regarding the efficacy and safety of these novel therapies for hypertriglyceridemia.

Lipid-lowering and antioxidant functions of bottle gourd (Lagenaria siceraria) extract in human dyslipidemia

The study validated the antidyslipidemic, antioxidant, and antihyperglycemic effects of Lagenaria siceraria fruit extract in human subjects with dyslipidemia along with subjects of normal health. A total of 200 mL of freshly prepared Lagenaria siceraria fruit extract was administered daily on empty stomach for 90 days. Significant reductions (P < .01) were found in triglycerides and total cholesterol levels in blood. Cardiac risk ratio, atherogenic coefficient, and atherogenicity index of plasma were also improved. Appreciable reductions in body mass index (P < .01) and blood pressure (systolic P < .01, diastolic P < .05) along with a significant reduction (P < .05) in fasting blood glucose levels were also observed in these subjects. Lagenaria siceraria fruit extract exhibited significant antioxidant activity in dyslipidemic subjects as evident from elevations in SOD (P < .05) and GSH levels (P < .01) with marked improvement in catalase (P < .01) and TBARS levels (P < .05). Phytochemical screening confirmed the presence of saponins, glycosides, flavonoids, terpenoids, and phenolic compounds. Lagenaria siceraria fruit extract serves as dietary adjunct in treatment of human dyslipidemia and cardiovascular disease.

Postprandial hypertriglyceridemia and cardiovascular disease: current and future therapies

Exaggerated postprandial hypertriglyceridemia is a risk factor for cardiovascular disease. This metabolic abnormality is principally due to overproduction and/or decreased catabolism of triglyceride-rich lipoproteins (TRLs) and is a consequence of pathogenic genetic variations and other coexistent medical conditions, particularly obesity and insulin resistance. Accumulation of TRL in the postprandial state promotes the formation of small, dense low-density lipoproteins, as well as oxidative stress, inflammation, and endothelial dysfunction, all of which compound the risk of cardiovascular disease. The cardiovascular benefits of lifestyle modification (weight loss and exercise) and conventional lipid-lowering therapies (statins, fibrates, niacin, ezetimibe, and n-3 fatty acid supplementation) could involve their favorable effects on TRL metabolism. New agents, such as dual peroxisome-proliferator-activated receptor α/δ agonists, diacylglycerol, inhibitors of diacylglycerol acyltransferase 1 and microsomal triglyceride transfer protein, antisense oligonucleotides for apolipoprotein B-100 and apolipoprotein C-III, and incretin-based therapies, may enhance the treatment of postprandial lipemia, but their efficacy needs to be tested in clinical end point trials. Further work is required to develop a simple clinical protocol for investigating postprandial lipemia, as well as internationally agreed management guidelines for this type of dyslipidemia.

Extended-release niacin acutely suppresses postprandial triglyceridemia

OBJECTIVE

Postprandial triglyceridemia predicts cardiovascular events. Niacin might lower postprandial triglycerides by restricting free fatty acids. Immediate-release niacin reduced postprandial triglycerides, but extended-release niacin failed to do so when dosed the night before a fat challenge. The study aims were to determine whether extended-release niacin dosed before a fat challenge suppresses postprandial triglycerides and whether postprandial triglycerides are related to free fatty acid restriction.

METHODS

A double-blinded, placebo-controlled, random-order crossover experiment was performed, in which healthy volunteers took 2 g extended-release niacin or placebo 1 hour before heavy cream. We sampled blood over 12 hours and report triglycerides and free fatty acid as means ± standard deviation for incremental area under the curve (AUC) and nadir.

RESULTS

By combining 43 fat challenges from 22 subjects, postprandial triglycerides incremental AUC was +312 ± 200 mg/dL*h on placebo versus +199 ± 200 mg/dL*h on extended-release niacin (33% decrease, P=.02). The incremental nadir for free fatty acid was -0.07 ± 0.15 mmol/L on placebo versus -0.27 ± 0.13 mmol/L on extended-release niacin (P<.0001), and free fatty acid incremental AUC decreased from +2.9 ± 1.5 mmol/L*h to +1.5 ± 1.5 mmol/L*h on extended-release niacin (20% decrease, P=.0015). The incremental AUC for triglycerides was strongly related to the post-dose decrease in free fatty acid (r = +0.58, P=.0007).

CONCLUSIONS

Given right before a fat meal, even a single dose of extended-release niacin suppresses postprandial triglyceridemia. This establishes that postprandial triglycerides suppression is an acute pharmacodynamic effect of extended-release niacin, probably the result of marked free fatty acid restriction. Further study is warranted to determine whether mealtime dosing would augment the clinical efficacy of extended-release niacin therapy.

Postprandial dyslipidaemia and diabetes: mechanistic and therapeutic aspects

PURPOSE OF REVIEW

There has been a resurgence of interest in the role of triglyceride-rich lipoproteins in the development of atherosclerosis and cardiovascular disease, and this is particularly relevant to diabetes mellitus and the postprandial state.

RECENT FINDINGS

Recent evidence suggests that insulin resistance in diabetes induces postprandial dyslipidemia by increasing the enterocytic production of chylomicrons and their remnant particles, but an impaired clearance capacity is also involved. Postprandial dyslipidaemia in diabetes induces oxidative stress, inflammation and endothelial dysfunction and this may be compounded by dysglycaemia. New guidelines for managing hypertriglyceridaemia in diabetes have been published, first-line therapies being improved glycaemic control, treatment of other secondary causes of dyslipidaemia and statin therapy, followed by judicious use of fibrates, n-3 fatty acids or niacin. A new role for incretin-based therapies in regulating dyslipidaemia has been identified.

SUMMARY

Postprandial dyslipidaemia is a pivotal mechanism whereby diabetes can induce and accelerate atherosclerosis. Regulating the plasma concentrations of triglyceride-rich lipoproteins may decrease the cardiovascular complications of diabetes. The mechanisms of action of incretin-based treatments on dyslipidaemia and endothelial dysfunction need further investigation. The efficacy of new therapies targeted at postprandial dysmetabolism in diabetes need to be confirmed, against best current levels of care, in clinical endpoint trials.

Evolution of lipid profiles after bariatric surgery

BACKGROUND

The most commonly encountered dyslipidemia in obese individuals is characterized by a cluster of interrelated plasma lipid and lipoprotein abnormalities including hypertriglyceridemia, low HDL cholesterol values, and increased small, dense LDL cholesterol particles. The aim of this study was to assess the changes in lipid profiles at baseline (pre-operatively) and at follow-up (6, 12, and 18 months) after a laparoscopic Roux-en-Y gastric bypass (LRYGBP). A retrospective observational study was performed involving all patients who consecutively underwent a LRYGBP between January 1, 2007 and December 31, 2009. Fasting lipids sub-fractions (total cholesterol, LDL cholesterol, HDL cholesterol, and triglycerides) were measured and HOMA-IR calculated pre-operatively and at follow-up post-LRYGBP. Pearson's correlation coefficients were used to assess the relationship between excess weight loss (EWL) and lipid sub-fractions. ANOVA was used to assess the differences between each lipid sub-fraction at various time-points.

METHODS

One hundred twenty eight (N = 128) medical charts were reviewed, and those containing data on lipid fractions at the three follow-up time-points were analyzed. One hundred fourteen patients (N = 114), 84 of whom were women (73.7%), were finally included in the study.

RESULTS

Total cholesterol, LDL cholesterol, triglycerides, and HOMA-IR were significantly reduced after LRYGBP (P < 0.0005 for all). Inversely, HDL cholesterol disclosed a significant rise (P < 0.0005). Noteworthy significant associations between lipid subfractions and EWL were detected overall (P < 0.0005 for all). A gender effect was found since female patients displayed a milder association than male patients (P < 0.0005).

CONCLUSIONS

LRYGBP-induced weight loss improves the lipid profile while reducing insulin resistance, with male patients showing a better profile than female patients.

Effects of oxidation on structural stability and remodeling of human very low density lipoprotein

Very low density lipoproteins (VLDL) are triglyceride-rich precursors of low-density lipoproteins (LDL) and a risk factor for atherosclerosis. The effects of oxidation on VLDL metabolism may be pro- or antiatherogenic. To understand the underlying biophysical basis, we determined the effects of copper (that preferentially oxidizes lipids) and hypochlorite (that preferentially oxidizes proteins) on the heat-induced VLDL remodeling. This remodeling involves VLDL fusion, rupture, and fission of apoE-containing high-density lipoprotein- (HDL-) like particles; HDL with similar size, density, and protein composition are formed upon VLDL remodeling by lipoprotein lipase, a key enzyme in triglyceride metabolism. Circular dichroism, turbidity, and electron microscopy show that mild oxidation promotes VLDL fusion and rupture, while advanced oxidation hampers these reactions. VLDL destabilization upon moderate oxidation results, in part, from the exchangeable apolipoprotein modifications, including proteolysis and limited cross-linking. VLDL stabilization against fusion and rupture upon advanced oxidation probably results from massive protein cross-linking on the particle surface. Electron microscopy and gel electrophoresis reveal that oxidation promotes fission of apoE-containing HDL-size particles; hydrolysis of apolar core lipids probably contributes to this effect. Copper and hypochlorite have similar effects on VLDL remodeling, suggesting that these effects may be produced by other oxidants. In summary, moderate oxidation that encompasses in vivo conditions destabilizes VLDL and promotes fission of HDL-size particles. Consequently, mild oxidation may be synergistic with lipoprotein lipase reaction and, hence, may help to accelerate VLDL metabolism.

In vivo efficacy of acyl CoA: diacylglycerol acyltransferase (DGAT) 1 inhibition in rodent models of postprandial hyperlipidemia

Postprandial serum triglyceride concentrations have recently been identified as a major, independent risk factor for future cardiovascular events. As a result, postprandial hyperlipidemia has emerged as a potential therapeutic target. The purpose of this study was two-fold. Firstly, to describe and characterize a standardized model of postprandial hyperlipidemia in multiple rodent species; and secondly, apply these rodent models to the evaluation of a novel class of pharmacologic agent; acyl CoA:diacylglycerol acyltransferase (DGAT) 1 inhibitors. Serum triglycerides were measured before and for 4h after oral administration of a standardized volume of corn oil, to fasted C57BL/6, ob/ob, apoE(-/-) and CD-1 mice; Sprague-Dawley and JCR/LA-cp rats; and normolipidemic and hyperlipidemic hamsters. Intragastric administration of corn oil increased serum triglycerides in all animals evaluated, however the magnitude and time-course of the postprandial triglyceride excursion varied. The potent and selective DGAT-1 inhibitor A-922500 (0.03, 0.3 and 3 mg/kg, p.o.), dose-dependently attenuated the maximal postprandial rise in serum triglyceride concentrations in all species tested. At the highest dose of DGAT-1 inhibitor, the postprandial triglyceride response was abolished. This study provides a comprehensive characterization of the time-course of postprandial hyperlipidemia in rodents. In addition, the ability of DGAT-1 inhibitors to attenuate postprandial hyperlipidemia in multiple rodent models, including those that feature insulin resistance, is documented. Exaggerated postprandial hyperlipidemia is inherent to insulin-resistant states in humans and contributes to the substantially elevated cardiovascular risk observed in these patients. Therefore, by attenuating postprandial hyperlipidemia, DGAT-1 inhibition may represent a novel therapeutic approach to reduce cardiovascular risk.

Relationship between adiponectin and left atrium size in uncomplicated obese patients: adiponectin, a link between fat and heart

BACKGROUND

It is well known that obesity is a risk factor for severe cardiovascular complications, such as coronary heart disease, heart failure, stroke, venous thromboembolic disease, and atrial fibrillation. Left ventricle (LV) and left atrium (LA) enlargement is a characteristic feature of these patients with the consequent cardiovascular risk. Factors other than hemodynamic may influence LA remodeling. The aim of the study is to evaluate the relationship between adiponectin and LA size in uncomplicated obese patients.

METHODS

Seventy-four asymptomatic obese patients and an age- and sex-matched control group (N = 70) were recruited. A detailed clinical, echocardiographic, and analytical study was performed. Insulin resistance was assessed using the homeostasis model assessment for insulin resistance (HOMA-IR) method. Insulin sensitivity was assessed measuring serum total adiponectin concentrations.

RESULTS

Adiponectin levels were lower in the obese group (P < 0.001) and particularly so in those obese participants with enlarged LA (32%; P < 0.0005). LA sizes were higher in the obese group (P < 0.0005). Adiponectin displayed significant correlations with body mass index, glucose, insulin, high-density lipoprotein cholesterol, and triglyceride concentrations as well as HOMA-IR (P < 0.001 for all). Adiponectin displayed significant correlations with LV mass and LA size, diastolic and systolic cardiac volumes and diameters, and cardiac output (P < 0.001 for all). Adiponectin correlations with LA size (r = -0.429; P < 0.001) persisted after adjustment for HOMA-IR, age, sex, and LV mass.

CONCLUSIONS

A novel inverse relationship between adiponectin and LA size independent of age, sex, insulin resistance, and LV mass appears in our series. Adiponectin could be a link between adipose tissue and the heart, having an influence on cardiac remodeling.