High density lipoprotein deficiency syndrome in chickens is not associated with an increased susceptibility to atherosclerosis

Effect of dietary essential oil of oregano on performance parameters, gastrointestinal traits, blood lipid profile, and antioxidant capacity of laying hens during the pullet phase

Many benefits have been found in supplementing essential oils such as oregano oil (EOO) to poultry, including increased body weight gain, antioxidant activity, and better gastrointestinal morphology. However, few studies tested the influence of EOO supplementation on laying hens and reported conflicting results regarding its efficacy in improving their health and performance. Therefore, we aimed to explore the effects of dietary EOO on performance, gastrointestinal (GIT) traits, blood lipid, and antioxidant capacity in laying hens during the rearing phase. A total of 300-day-old Hy-line-Brown chicks were used, and treatment diets consisted of corn-soybean based either without (CON) or with EOO (Ecodiar®, 0.275 g/kg diet). Birds were randomized across treatments with five pens/treatment and 30-birds/pen. Pen weights and feed rejected were recorded every two weeks (1-17 weeks of age), to calculate daily feed intake (ADFI), body weight (BW), and daily weight gain (ADWG). At 11 and 14 weeks of age, blood samples were collected from 3 birds/pen and analyzed for blood lipids and antioxidant levels, and 5-birds/treatment were euthanized, and GIT traits were tested. Differences in measured parameters across weeks and between treatments were assessed using GLMM with Tukey’s Post hoc test applied to significant results in R 3.3.1 (α set at 0.05). Body weights at weeks 3, 11, 13, and 17 were significantly higher in the EOO group compared to the CON group (all P ≤ 0.05), ADWG was significantly higher in EOO birds compared to CON birds at 9 and 13 weeks old (all P ≤ 0.05), while no significant differences in ADFI were observed between treatments across weeks of the trials. At both 11 and 17 weeks old, triglyceride levels were significantly lower, while high-density-lipoprotein levels were higher in EOO (all P ≤ 0.05). Malondialdehyde levels were lower in the EOO group versus CON (p=0.01), while EOO birds had higher glutathione levels (p=0.01) than CON. Finally, at 12 weeks old, the weight of the entire GIT and empty gizzard were higher in the EOO group versus CON (all P ≤ 0.05), while liver and spleen weights were not significantly different between groups. In conclusion, dietary oregano supplementation exerted promoting effects on the performance of Hy-Line Brown pullets.

Myeloid cell-specific ATP-binding cassette transporter A1 deletion has minimal impact on atherogenesis in atherogenic diet-fed low-density lipoprotein receptor knockout mice

OBJECTIVE

Transplantation studies suggest that bone marrow cell ATP-binding cassette transporter A1 protects against atherosclerosis development. However, the in vivo effect of macrophage ATP-binding cassette transporter A1 expression on atherogenesis is not fully understood because bone marrow contains other leukocytes and hematopoietic stem and progenitor cells. Myeloid-specific ATP-binding cassette transporter A1 knockout mice in the low-density lipoprotein (LDL) receptor knockout C57BL/6 background were developed to address this question.

APPROACH AND RESULTS

Chow-fed myeloid-specific ATP-binding cassette transporter A1 knockout/LDL receptor knockout (double knockout [DKO]) versus LDL receptor knockout (single knockout [SKO]) mice had similar plasma lipid concentrations, but atherogenic diet (AD)-fed DKO mice had reduced plasma very-LDL (VLDL)/LDL concentrations resulting from decreased hepatic VLDL triglyceride secretion. Resident peritoneal macrophages from AD-fed DKO versus SKO mice had significantly higher cholesterol content but similar proinflammatory gene expression. Atherosclerosis extent was similar between genotypes after 10 to 16 weeks of AD but increased modestly in DKO mice by 24 weeks of AD. Lesional macrophage content was similar, likely because of the higher monocyte flux through aortic root lesions in DKO versus SKO mice. After transplantation of DKO or SKO bone marrow into SKO mice and 16 weeks of AD feeding, atherosclerosis extent was similar and plasma apolipoprotein B lipoproteins were reduced in mice receiving DKO bone marrow. When differences in plasma VLDL/LDL concentrations were minimized by maintaining mice on chow for 24 weeks, DKO mice had modest, but significantly more, atherosclerosis compared with SKO mice.

CONCLUSIONS

Myeloid cell ATP-binding cassette transporter A1 increases hepatic VLDL triglyceride secretion and plasma VLDL/LDL concentrations in AD-fed LDL receptor knockout mice, offsetting its atheroprotective role in decreasing macrophage cholesterol content, resulting in a minimal increase in atherosclerosis.

Liver ABCA1 deletion in LDLrKO mice does not impair macrophage reverse cholesterol transport or exacerbate atherogenesis

OBJECTIVE

Hepatic ATP binding cassette transporter A1 (ABCA1) expression is critical for maintaining plasma high-density lipoprotein (HDL) concentrations, but its role in macrophage reverse cholesterol transport and atherosclerosis is not fully understood. We investigated atherosclerosis development and reverse cholesterol transport in hepatocyte-specific ABCA1 knockout (HSKO) mice in the low-density lipoprotein (LDL) receptor KO (LDLrKO) C57BL/6 background.

APPROACH AND RESULTS

Male and female LDLrKO and HSKO/LDLrKO mice were switched from chow at 8 weeks of age to an atherogenic diet (10% palm oil, 0.2% cholesterol) for 16 weeks. Chow-fed HSKO/LDLrKO mice had HDL concentrations 10% to 20% of LDLrKO mice, but similar very low-density lipoprotein and LDL concentrations. Surprisingly, HSKO/LDLrKO mice fed the atherogenic diet had significantly lower (40% to 60%) very low-density lipoprotein, LDL, and HDL concentrations (50%) compared with LDLrKO mice. Aortic surface lesion area and cholesterol content were similar for both genotypes of mice, but aortic root intimal area was significantly lower (20% to 40%) in HSKO/LDLrKO mice. Although macrophage (3)H-cholesterol efflux to apoB lipoprotein-depleted plasma was 24% lower for atherogenic diet-fed HSKO/LDLrKO versus LDLrKO mice, variation in percentage efflux among individual mice was <2-fold compared with a 10-fold variation in plasma HDL concentrations, suggesting that HDL levels, per se, were not the primary determinant of plasma efflux capacity. In vivo reverse cholesterol transport, resident peritoneal macrophage sterol content, biliary lipid composition, and fecal cholesterol mass were similar between both genotypes of mice.

CONCLUSIONS

The markedly reduced plasma HDL pool in HSKO/LDLrKO mice is sufficient to maintain macrophage reverse cholesterol transport, which, along with reduced plasma very low-density lipoprotein and LDL concentrations, prevented the expected increase in atherosclerosis.

Development of an avian model for restenosis

Recurrence of atherosclerotic plaque growth after interventional therapy, restenosis, is a significant clinical problem occurring in 20%-50% of cases. We have developed a new avian model for the investigation of restenosis after arterial injury in cholesterol fed White Leghorn roosters. Atherosclerotic plaque growth 1-30 weeks after angioplasty balloon mediated endothelial injury in the abdominal aorta was studied in 37 roosters. Roosters were maintained on either normal poultry diet or high cholesterol diet. Twelve cholesterol fed roosters were also fed a hormone supplemented diet in order to modify plaque morphology. The procedural success rate was high. Angiographic stenoses (mean 36% with maximum of 74%) were detectable in cholesterol fed roosters after balloon angioplasty with associated histological evidence of plaque growth (P < 0.017). Cholesterol feeding enhanced fatty plaque growth; hormone manipulation increased calcific and ulcerated plaque but with high associated morbidity. Three interventional devices were subsequently examined in 32 roosters (16 laser angioplasty, 7 atherectomy, and 9 stent implant). Plaque development was again assessed by contrast angiography and histological analysis. We conclude that balloon mediated arterial injury in cholesterol fed roosters produces early proliferative and late, complex atherosclerotic lesions providing an inexpensive model for plaque development after intimal injury.