Pioglitazone decreases postprandial accumulation of remnant lipoproteins in insulin-resistant smokers

Background:  Fasting hypertriglyceridaemia has been reported to occur commonly in cigarette smokers and is thought to increase cardiovascular disease (CVD) risk in these individuals. More recently, it has been suggested that an increase in non-fasting triglycerides, rather than fasting hypertriglyceridaemia, is an independent CVD risk factor.
Methods:  In this study, we divided 24 smokers into insulin-resistant (IR) and insulin-sensitive (IS) groups by determining their steady-state plasma glucose concentrations during the insulin suppression test and compared fasting and daylong postprandial accumulation of total triglycerides and remnant lipoprotein (RLP) concentrations, before and after 3 months of pioglitazone (PIO) administration.
Results:  The two groups were similar in age, body mass index, race and gender distribution, but differed dramatically in insulin sensitivity. Baseline fasting and postprandial triglyceride, RLP cholesterol and RLP triglyceride concentrations were significantly higher in the IR smokers (p = 0.01 to <0.01). Insulin sensitivity and both fasting and postprandial triglyceride and RLP triglyceride levels decreased significantly (p = 0.05 to <0.01) in PIO-treated IR smokers, without any significant increase in weight. In contrast, there were no significant changes in either insulin sensitivity or fasting and postprandial triglyceride, RLP cholesterol and RLP triglyceride levels in PIO-treated IS smokers.
Conclusions:  The postprandial accumulation of RLP particles is increased in the IR subset of smokers and is likely to contribute to the increased CVD risk in these individuals. Furthermore, PIO administration provides a possible therapeutic approach to decreasing postprandial lipaemia and CVD risk in IR smokers who are unwilling or unable to stop smoking.     

Protease inhibitor-based HAART, HDL, and CHD-risk in HIV-infected patients

ObjectiveTo study the effects of HIV-infection and protease inhibitor (PI)-based highly active anti-retroviral therapy (HAART) on the lipid and high-density lipoprotein (HDL) subpopulation profile and to relate the changes to coronary heart disease (CHD)-risk.Methods and designThe lipid and HDL subpopulation profiles of HIV-positive subjects (n = 48) were studied prospectively by comparing pre- and post-PI-HAART data as well as cross-section by comparing the profiles to HIV-negative subjects with (n = 96) and without CHD (n = 96).ResultsHIV-infected HAART-naïve subjects had lower concentrations of low-density lipoprotein cholesterol (LDL-C) and HDL-C and higher concentration of triglycerides (TG) than healthy controls. After receiving PI-based HAART, LDL-C and TG concentrations increased, while HDL-C concentrations remained unchanged. The HDL subpopulation profiles of HAART-naïve HIV-positive patients were significantly different from those of healthy controls and were similar to those with CHD. Moreover, the HDL subpopulation profile changed unfavorably after PI-based HAART, marked with increased concentrations of the small, lipid-poor pre-β-1 HDL (32% or 3.9 mg/dl; p < 0.001), and decreased concentration of the large, cholesterol-rich α-1 HDL(9% or 1 mg/dl ns).ConclusionAn already unfavorable lipid and HDL subpopulation profile of HIV-positive HAART-naïve subjects further deteriorated after receiving PI-based treatment, which may cause increased CHD-risk in these subjects.     

Effect of fibrates on postprandial remnant-like particles in patients with combined hyperlipidemia

We have investigated the effect of standard doses of two fibrates, gemfibrozil and fenofibrate, on fasting and postprandial remnant-like particles (RLP) in subjects with combined hyperlipidemia. Forty-eight subjects participated; of these, 14 underwent a Vitamin A-fat loading test before and after 6 months of treatment with gemfibrozil (n = 8) and fenofibrate (n = 6). Blood was drawn every 2h for 12h after the test meal. The postprandial response was calculated as the area under the curve (AUC). There was no difference in fasting levels and pre-treatment AUC for triglycerides (TG), RLP cholesterol (RLP-C), RLP triglycerides (RLP-TG) and retinyl palmitate (RetP) between the two treatment groups. There was also no difference in the treatment effect on all parameters between the two treatment groups. Combining the two treatment groups, treatment resulted in a significant reduction in fasting levels and AUC of all four parameters. Assigning the difference observed between pre-treatment AUC of the combined study group and AUC of a normolipidemic (NL) control group as 100%, fibrate treatment resulted in decreases in AUC for TG, RLP-C, RLP-TG and RetP of 68, 69, 69 and 94%, respectively. These results indicate that fibrates are effective agents in reducing the postprandial increase in remnant lipoprotein particles.     

Plasma remnant-like lipoprotein particles or LDL-C as major pathologic factors in sudden cardiac death cases

We have previously reported that the majority of sudden cardiac death (SCD) events were associated with postprandial hyperlipidemia in Japanese subjects. In this investigation, we have compared LDL-cholesterol (LDL-C) and remnant-like lipoprotein particles (RLP) as cardiovascular risk factors in SCD cases, especially in Pokkuri death syndrome (PDS) cases who had nearly normal coronary arteries. To predict the risk of plasma RLP-cholesterol, triglyceride (RLP-C, RLP-TG) and LDL-C in fatal clinical events associated with SCD cases with or without atherosclerosis (PDS), we calculated the cut-off values and likelihood ratio of these lipoproteins from ROC analysis. Sixty-eight percent of SCD cases were above cut-off value of RLP-C (>12.8 mg/dL) versus 32% for control death cases (P < 0.0001) and the likelihood ratio of RLP-C was 2.12. Significantly higher incidence of RLP-C above cut-off value (>10.1 mg/dL) was seen in PDS compared to controls (P < 0.0001) and the likelihood ratio was 3.13. Similarly, significantly higher incidence of RLP-TG above cut-off values, SCD > 53 mg/dL and PDS > 67 mg/dL, was seen compared to controls (P < 0.0001) and the likelihood ratio was 1.86 and 2.73, respectively. Further, significantly higher incidence of LDL-C above cut-off value (>93 mg/dL) was seen in SCD compared to controls (P < 0.0001) and the likelihood ratio was 1.68. However, the incidence of LDL-C above cut-off value (LDL-C > 106 mg/dL) was not significantly different between PDS and controls and the likelihood ratio was 1.52.

In conclusion, this study has shown high levels of plasma remnant lipoproteins in PDS and that PDS cases did not present with atherosclerotic lesions or elevated LDL-C. In contrast, SCD cases showed high levels of plasma remnant lipoproteins together with elevated plasma LDL-C. Accordingly, we believe that plasma remnant lipoproteins level rather than plasma LDL-C is a major pathologic factor in cardiovascular events.     

Postprandial remnant-like lipoproteins in hypertriglyceridemia.

It has been proposed that remnants of chylomicrons and very-low-density lipoproteins (VLDL) are atherogenic. We have used an immunochemical method to isolate remnant-like particles (RLP) and measured them in terms of their cholesterol and triglycerides (TG). RLP consist of apoB-48-containing triglyceride-rich lipoproteins and remnant-like VLDL containing apoB-100. The study aim was to look for information from postprandial RLP data that could not be known from other markers of triglyceride-rich lipoproteins and fasting TG and RLP data alone. A total of 41 subjects were studied. Eight subjects had hypertriglyceridemia (HTG) and low high-density lipoprotein (HDL), 14 had combined hyperlipidemia (CH), 5 had the apo E2/2 genotype receiving gemfibrozil, 10 were normolipidemic (NL) controls, and 4 had hypercholesterolemia. As a whole group, there was correlation among 1) fasting TG, RLP cholesterol (RLP-C), and RLP-TG but not VLDL apo B100, VLDL apo B48 and their respective postprandial responses measured as incremental area under the curve (IAUC), 2) fasting TG and postprandial IAUC of RLP-C and RLP-TG, 3) RLP-C IAUC, RLP-TG IAUC, and TG IAUC, retinyl palmitate (RP) IAUC, and VLDL apo B48 IAUC but not VLDL apo B100 IAUC. The HTG/low HDL-C and CH groups had higher IAUC for RLP-C, RLP-TG, TG, and RP than the NL group. Fasting and postprandial RLP were triglyceride enriched in the HTG/low HDL-C group and to a lesser extent in the CH group. The HTG/low HDL-C and CH groups had a delay in their RLP-C but not RLP-TG peaks suggesting a delay in hepatic clearance of RLP and/or a protracted period of lipolysis and/or processing of RLP. The fasting and postprandial RLP-C/RLP-TG and RLP-C/TG ratios were elevated in the apo E2/2 group in spite of gemfibrozil therapy. The increment in postprandial RLP was, however, not exaggerated. Our data indicate that 1) postprandial RLP lipemia is enhanced in HTG subjects when compared with NL subjects, 2) postprandial RLP lipemia is proportional to fasting RLP and TG levels and mirrors, to a large extent, increases in postprandial TG, RP, and VLDL apo B48 but not VLDL apo B100, 3) there are compositional differences in fasting and postprandial RLP in the three forms of HTG studied, RLP being triglyceride enriched in the HTG/low HDL-C group and to a lesser extent in the CH group, and cholesterol-enriched in the apo E2/2 group, and 4) apo E2/2 subjects had high fasting and postprandial RLP-C concentrations in spite of being on treatment with gemfibrozil and having normal fasting and postprandial TG concentrations.     

Differences in cellular activation and apoptosis in HIV-infected patients receiving protease inhibitors or nonnucleoside reverse transcriptase inhibitors

The mechanism of CD4(+) T cell depletion seen in HIV infection is largely mediated by increased apoptosis of these cells. The benefit of protease inhibitor (PI)-based antiretroviral therapy to CD4(+) T cell recovery seems to involve more than its antiviral activity, and a direct antiapoptotic effect of PIs has been proposed to explain it. To test this hypothesis we have analyzed directly, ex vivo, the effects of two different highly active antiretroviral therapy (HAART) regimens on the levels of activation and apoptosis of T lymphocytes. A total of 126 subjects (43 receiving PIs, 35 receiving NNRTIs, 27 untreated HIV carriers, and 21 uninfected control subjects) was included in the study. Apoptosis was measured in blood lymphocytes by flow cytometry, using annexin V labeling. A broad panel of monoclonal antibodies was used to characterize the different CD4(+) and CD8(+) lymphocyte subsets. Apoptosis was significantly increased in HIV-untreated subjects, whereas apoptosis levels did not differ when comparing HIV-positive subjects undergoing HAART and uninfected control subjects. Likewise, markers of activation were elevated in HIV-positive untreated patients, and declined in subjects receiving treatment. However, activated-memory CD8(+) T cells remained significantly higher in treated patients with respect to uninfected control subjects. No differences in the level of apoptosis or in immune activation markers were recognized when comparing subjects receiving PIs and those receiving NNRTIs. Antiretroviral therapy reduces apoptosis of CD4(+) and CD8(+) lymphocytes to normal levels without differences when comparing subjects receiving PI and NNRTI triple combinations. Despite complete suppression of viral replication, activated memory CD8(+) T cells remain significantly elevated in subjects receiving HAART, suggesting the persistence of residual HIV replication. If PIs provide a positive effect on CD4(+) counts beyond an antiviral effect, mechanisms other than apoptosis should be involved.     

Relationship between plasma insulin concentration and plasma remnant lipoprotein response to an oral fat load in patients with type 2 diabetes.

OBJECTIVES: The goal of this study was to evaluate the relative effects of hyperglycemia and hyperinsulinemia on postprandial remnant lipoprotein (RLP) concentrations in newly diagnosed type 2 diabetics. BACKGROUND: Increases in fasting RLP concentration have been described in type 2 diabetics, as well as in insulin-resistant nondiabetics. Given the atherogenicity of RLPs, we have extended these observations by assessing postprandial RLP concentrations and observing that hyperglycemia was necessary for the increase in RLP concentrations. METHODS: Patients with type 2 diabetes were subdivided on the basis of their plasma insulin response to oral glucose into hyperinsulinemic (H-DM) and normoinsulinemic (N-DM) groups of 15 patients each. Plasma triglyceride (TG), RLP-TG and RLP cholesterol (RLP-C) concentrations were determined before and 2 and 4 h after an oral fat load in these patients and 10 control (CTL) subjects. RESULTS: Plasma TG, RLP-TG and RLP-C concentrations peaked 2 h after the fat load in the CTL group, returning to baseline within 4 h. In contrast, concentrations of these variables increased throughout the 4-h study in both groups of patients with type 2 diabetes. Total integrated plasma RLP-TG and RLP-C responses above baseline after the oral fat load were significantly higher in the H-DM group compared with the CTL (p = 0.019 and 0.009, respectively) or N-DM (p = 0.026 and 0.029, respectively) groups. Post-heparin lipoprotein lipase activities and apo E phenotypes were similar in the H-DM and N-DM groups. CONCLUSIONS: Remnant lipoprotein response to an oral fat load is significantly increased in hyperinsulinemic patients with type 2 diabetes. These changes may increase the risk of coronary heart disease in these individuals.     

Plasma lipoprotein(a) [Lp(a)] concentrations and cardiovascular events in the elderly: evidence from the prospective study of pravastatin in the elderly at risk (PROSPER)

Using analyses of the large cohort (n = 5732) from the prospective study of pravastatin in the elderly at risk (PROSPER), we tested the hypothesis that Lp(a) concentration is an independent predictor of major vascular events and cognitive impairment in the elderly.

Baseline Lp(a) levels were measured on fresh samples from 5732 subjects aged 70–82, who were followed for 3.2 years on average.

Lp(a) levels were not significantly different across the age range in PROSPER, but were significantly higher in women (geometric mean 14.8 versus 12.4 mg/dl, P < 0.0001). Those with a history of vascular disease had significantly higher Lp(a) levels, which remained after adjustment (P < 0.0001). There was no statistically significant association between baseline Lp(a) and the risk of the primary endpoint (CHD death, non-fatal MI and fatal or non-fatal stroke) (hazard ratio 1.05, 95% CI 1.00–1.11, P = 0.077), but after adjustment for baseline risk factors this did achieve statistical significance (1.06, 1.005–1.12, P = 0.032). Finally, there was no statistically or clinically significant association between any adjusted baseline or dynamic cognition variables and Lp(a), and nor was there any significant association between Lp(a) and indices of disability throughout the study.

This is the first study of the association between Lp(a) and a range of cardiovascular endpoints including cognitive and disability indices in the elderly. The main finding is that Lp(a) level, while influenced by a number of baseline characteristics, is not a significant predictor of cognitive function or levels of disability, but is a predictor of combined cardiovascular events over an average 3.2 year follow-up.     

Comparison in patients with type 2 diabetes of fibric acid versus hepatic hydroxymethyl glutaryl-coenzyme a reductase inhibitor treatment of combined dyslipidemia

Patients with combined dyslipidemia are at greatly increased coronary heart disease (CHD) risk. The threat of rhabdomyolysis with dual pharmacologic treatment (hepatic hydroxymethyl glutaryl coenzyme A [HMG-CoA] reductase inhibitors plus fibric acid derivatives) has tended to limit therapy in patients with combined dyslipidemia to a choice of one or the other drug. Judgment of the potential benefits of either agent has rarely taken into account their effect on the postprandial accumulation of highly atherogenic, triglyceride (TG)-rich, remnant lipoprotein particles (RLPs). Because this information could be of substantial clinical relevance, we addressed this question in patients with type 2 diabetes and combined dyslipidemia by comparing the effects of gemfibrozil versus HMG-CoA reductase inhibitors (statins) on both fasting and postprandial lipid and lipoprotein concentrations. For this purpose, 22 patients with type 2 diabetes and combined dyslipidemia were randomized to treatment with either a statin or gemfibrozil for 3 months. Glycemic control was similar in both groups at baseline and did not change in response to treatment. Baseline lipid and lipoprotein concentrations were also similar in the 2 treatment groups, but the responses to therapy were quite different. Statin-treated patients had a statistically significant decrease in low-density lipoprotein (LDL) cholesterol concentration (156 mg/dL to 96 mg/dL, P <.001), whereas there was no change in patients treated with gemfibrozil. In contrast, there was a statistically significant decrease (P <.05) in plasma TG concentrations (116 mg/dL) in gemfibrozil-treated individuals, without any change in subjects treated with statins. However, the decrease in total integrated postprandial plasma RLP response measured hourly from 8 AM to 4 PM was not different in patients treated with either gemfibrozil (-43%) or statins (-34%). These results indicate that statin treatment, in addition to its beneficial effect on hypercholesterolemia, was as effective as gemfibrozil in reducing postprandial accumulation of triglyceride-rich, atherogenic RLPs in patients with type 2 diabetes and combined dyslipidemia. As such, the clinical utility of statin monotherapy in the treatment of combined dyslipidemia may have been underestimated.