👤 Katsunori Ikewaki

Dietary unsaturated fat, protein, and carbohydrate have well-established effects on HDL (high-density lipoprotein) cholesterol levels, but whether these effects are connected causally to coronary heart disease (CHD) has been called into question. Protein-based minor HDL subspecies are emerging as novel and likely causal biomarkers, direct or inverse, for risk of CHD, diabetes, and other conditions. HDL-raising drugs such as CETP (cholesteryl ester transfer protein) inhibitors raise certain HDL subspecies that have adverse effects on CHD risk. We hypothesize that dietary unsaturated fat, protein, and carbohydrate differentially affect 15 minor protein-based HDL subspecies with diverse functionality in lipid metabolism, antioxidation, immunity, hemostasis, and protease inhibition. We analyzed the apo (apolipoprotein) A1 concentrations of 15 minor HDL subspecies after 4 weeks on each diet in 141 participants in the OmniHeart trial (Optimal Macronutrient Intake Trial to Prevent Heart Disease), a randomized 3-period crossover, controlled feeding study. The diet rich in carbohydrate contained 58% carbohydrate, 27% fat, and 15% protein, and the diets rich in unsaturated fat and protein replaced 10% of carbohydrate with unsaturated fat or protein, respectively. Unsaturated fat replacing dietary carbohydrate increased concentrations of apoA1 in lipid metabolism subspecies including HDL that contains apoA2, apoE, or apoC1 that has been associated with reduced risk of CHD. Protein replacing carbohydrate increased apoE HDL, consistent with lower CHD risk, and decreased concentrations of several other HDL subspecies that were associated with higher risk of CHD including HDL that contains PLMG (plasminogen), A2M (alpha-2-macroglobulin), or apoL1. Network analysis showed connections between functional groups of HDL subspecies that are quantitatively affected by dietary macronutrients. Replacing dietary carbohydrate with unsaturated fat or protein raised levels of protein-based HDL subspecies associated with lower risk of CHD or lowered the levels of those associated with higher risk of CHD. Minor HDL subspecies with diverse functions may mediate the association of dietary patterns with risk of CHD. URL: https://www.clinicaltrials.gov; Unique identifier: NCT00051350. Show less

High density lipoprotein (HDL) exerts an anti-atherosclerotic effect via reverse cholesterol transport (RCT). Several phases of RCT are transcriptionally controlled by Liver X receptors (Lxrs). Although macrophage Lxrs reportedly promote RCT, it is still uncertain whether hepatic Lxrs affect RCT in vivo. To inhibit Lxr-dependent pathways in mouse livers, we performed hepatic overexpression of sulfotransferase family cytosolic 2B member 1 (Sult2b1) using adenoviral vector (Ad-Sult2b1). Ad-Sult2b1 or the control virus was intravenously injected into wild type mice and Lxrα/β double knockout mice, under a normal or high-cholesterol diet. A macrophage RCT assay and an HDL kinetic study were performed. Hepatic Sult2b1 overexpression resulted in reduced expression of Lxr-target genes - ATP-binding cassette transporter G5/G8, cholesterol 7α hydroxylase and Lxrα itself - respectively reducing or increasing cholesterol levels in HDL and apolipoprotein B-containing lipoproteins (apoB-L). A macrophage RCT assay revealed that Sult2b1 overexpression inhibited fecal excretion of macrophage-derived Hepatic Lxr inhibition negatively regulates circulating HDL levels and RCT by reducing Lxr-target gene expression. Show less

Cardiovascular disease (CVD) is the leading cause of death in Western countries. A low HDL-C is associated with the development of CVD. However, recent epidemiology studies have shown U-shaped curves between HDL-C and CVD mortality, with paradoxically increased CVD mortality in patients with extremely high HDL-C levels. Furthermore, HDL-C raising therapy using nicotinic acids or CETP inhibitors mostly failed to reduce CVD events. Based on this background, HDL functions rather than HDL-C could be a novel biomarker; research on the clinical utility of HDL functionality is ongoing. In this review, we summarize the current status of HDL functions and their future perspectives from the findings of basic research and clinical trials. Show less

Xanthohumol, a prominent prenyl flavonoid from the hop plant (Humulus lupulus L.), is suggested to be antiatherogenic since it reportedly increases high-density lipoprotein (HDL) cholesterol levels. It is not clear whether xanthohumol promotes reverse cholesterol transport (RCT), the most important antiatherogenic property of HDL; therefore, we investigated the effects of xanthohumol on macrophage-to-feces RCT using a hamster model as a CETP-expressing species. In vivo RCT experiments showed that xanthohumol significantly increased fecal appearance of the tracer derived from intraperitoneally injected [ Show less

We aimed to assess the effects of cholesteryl ester transfer protein inhibitor anacetrapib added to statin ± other lipid-modifying therapies (LMT) in Japanese patients with dyslipidemia who were not at their LDL-C goal. Patients on a stable dose of statin ± other LMT with LDL-C ≥100 mg/dL to <145 mg/dL, ≥120 mg/dL to <165 mg/dL, ≥140 mg/dL or ≥160 mg/dL for patients with a history of coronary heart disease (CHD), high-, moderate- and low-risk patients respectively, were randomized 2:1, stratified by background therapy, to double-blind anacetrapib 100 mg (n = 204) or placebo (n = 103) for 24 weeks, followed by a 28-week open-label extension phase (anacetrapib 100 mg) and a 12-week off-drug safety follow-up phase. The primary endpoint was percent change from baseline in LDL-C (beta-quantification method), as well as the safety profile of anacetrapib at Week 24; HDL-C was a key secondary endpoint. Anacetrapib 100 mg further reduced LDL-C (38.0%), non-HDL-C (35.1%), ApoB (28.7%), and Lp(a) (48.3%) and increased HDL-C (148.9%) and ApoAI (50.7%) versus placebo (p < 0.001 for all). There were no meaningful differences between the groups in the proportion of patients with liver enzymes elevations (2.0% vs. 0%), creatine kinase elevations overall (0.5% vs. 0%) or with muscle symptoms (0.5% vs. 0%), blood pressure, electrolytes or adjudicated cardiovascular events (0.5% vs. 0%). In the open-label period, sustained effects on lipid parameters were observed with anacetrapib and the treatment was generally well tolerated. Long-term treatment with anacetrapib 100 mg substantially reduced LDL-C, increased HDL-C and was well tolerated in Japanese patients with dyslipidemia (ClinicalTrials.gov number NCT01760460). Show less

ATP-binding cassette transporters (ABC) A1 and G1 are key molecules in cholesterol efflux from macrophages, which is an initial step of reverse cholesterol transport (RCT), a major anti-atherogenic property of high-density lipoprotein (HDL). Astaxanthin is one of the naturally occurring carotenoids responsible for the pink-red pigmentation in a variety of living organisms. Although astaxanthin is known to be a strong antioxidant, it remains unclear through what mechanism of action it affects cholesterol homeostasis in macrophages. We therefore investigated the effects of astaxanthin on cholesterol efflux and ABCA1/G1 expressions in macrophages. Astaxanthin enhanced both apolipoprotein (apo) A-I- and HDL-mediated cholesterol efflux from RAW264.7 cells. In supporting these enhanced cholesterol efflux mechanisms, astaxanthin promoted ABCA1/G1 expression in various macrophages. In contrast, peroxisome proliferator-activated receptor γ, liver X receptor (LXR) α and LXRβ levels remained unchanged by astaxanthin. An experiment using actinomycin D demonstrated that astaxanthin transcriptionally induced ABCA1/G1 expression, and oxysterol depletion caused by overexpression of cholesterol sulfotransferase further revealed that these inductions in ABCA1/G1 were independent of LXR-mediated pathways. Finally, we performed luciferase assays using human ABCA1/G1 promoter-reporter constructs to reveal that astaxanthin activated both promoters irrespective of the presence or absence of LXR-responsive elements, indicating LXR-independence of these activations. In conclusion, astaxanthin increased ABCA1/G1 expression, thereby enhancing apoA-I/HDL-mediated cholesterol efflux from the macrophages in an LXR-independent manner. In addition to the anti-oxidative properties, the potential cardioprotective properties of astaxanthin might therefore be associated with an enhanced anti-atherogenic function of HDL. Show less

Pioglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) agonist, reportedly reduces cardiovascular events in diabetic patients. ATP cassette binding transporters (ABC) A1 and G1 are pivotal molecules for cholesterol efflux (ChE) from macrophages and high density-lipoprotein biogenesis, and the A1 transporter is regulated by a PPARγ-liver receptor X (LXR) pathway. Also, pioglitazone induces ABCG1 expression, though the exact mechanism remains unclear. We therefore investigated the effects of pioglitazone on ABCA1/G1 expression in vitro and ex vivo. The effects of pioglitazone on ChE and ABCA1/G1 expressions in macrophages were assessed. Then, mRNA was quantified in macrophages when PPARγ/LXR inhibition by siRNA or overexpression of oxysterol sulfotransferase was performed. ABCA1/G1 promoter activity with mutated LXR-responsive elements was also measured. As an ex vivo study, 15 type 2 diabetic patients were administered pioglitazone or placebo, and ChE assays and protein expressions were determined using macrophages cultured with the corresponding sera. Pioglitazone increased LXRα/ABCA1/G1 expressions, which enhanced ChE from macrophages. Inhibition of PPARγ/LXR pathways revealed that LXR was primarily involved in pioglitazone's transactivation of ABCA1 but only partially involved for ABCG1. Promoter assays showed that ABCG1 was regulated more by the promoter in intron 4 than that upstream of exon 1 but both promoters were responsive to LXR activation. Sera obtained after pioglitazone treatment promoted ChE and ABCA1/G1 expressions in macrophages. Pioglitazone enhanced ChE from macrophages by increasing ABCA1/G1 in LXR-dependent and -independent manners. Our comparable in vitro and ex vivo results shed new light on pioglitazone's novel anti-atherogenic property. Show less