Effects of β3-adrenoceptor on scavenger receptor class B type 1 and its signal transduction pathway in apolipoprotein E knockout mice

Association of Circulating miR-145-5p and miR-let7c and Atherosclerotic Plaques in Hypertensive Patients

Aim: Hypertension is a strong risk factor for atherosclerosis. Increased carotid intima-media thickness (cIMT) and carotid plaques are considered subclinical markers of atherosclerosis. This study aimed at evaluating the serum expression of miRNAs previously related to adverse vascular remodeling and correlating them with carotid plaques and cIMT in hypertensive patients. Methods: We cross-sectionally evaluated the clinical and carotid characteristics as well as serum expression of miR-145-5p, miR-let7c, miR-92a, miR-30a and miR-451 in 177 hypertensive patients. Carotid plaques and cIMT were evaluated by ultrasound, and the expression of selected miRNAs was evaluated by a quantitative polymerase chain reaction. Results: Among all participants (age = 60.6 ± 10.7 years, 43% males), there were 59% with carotid plaques. We observed an increased expression of miR-145-5p (Fold Change = 2.0, p = 0.035) and miR-let7c (Fold Change = 3.8, p = 0.045) in participants with atherosclerotic plaque when compared to those without plaque. In the logistic regression analysis adjusted for relevant covariates, these miRNAs showed a stronger association with carotid plaques (miR-145-5p: Beta ± SE = 0.050 ± 0.020, p = 0.016 and miR-let7c: Beta ± SE = 0.056 ± 0.019, p = 0.003). Conclusions: Hypertensive patients with carotid plaques have an increased expression of miR-145-5p and miR-let7c, suggesting a potential role of these miRNAs as a biomarker for subclinical atherosclerosis in hypertensive individuals.

β3-Adrenoceptor activation upregulates apolipoprotein A-I expression in HepG2 cells, which might further promote cholesterol efflux from macrophage foam cells

Objective

The aim of this study was to explore the effects of β₃-adrenoceptor (β₃-AR) activation on HepG2 cells and its influence on cholesterol efflux from macrophage foam cells.

Materials and methods

HepG2 cells were cultured and treated with the β₃-AR agonist, BRL37344, and antagonist, SR52390A, and the expression of apolipoprotein (Apo) A-I, ApoA-II, ApoB, and β₃-AR in the supernatants and cells was determined. The expression of peroxisome proliferator-activated receptor (PPAR) γ and PPARα in the HepG2 cells was also assessed. Next, using the RAW264.7 macrophage foam cell model, we also assessed the influence of the HepG2 cell supernatants on lipid efflux. The cholesterol content of the foam cells was also measured, and the cholesterol efflux from the macrophages was examined by determining ³H-labeled cholesterol levels. Expression of ATP-binding cassette transporter (ABC) A1 and ABCG1 of the macrophage foam cells was also assessed.

Results

β₃-AR activation increased ApoA-I expression in both the HepG2 cells and the supernatants; PPARγ expression was upregulated, but PPARα expression was not. Treatment with GW9662 abolished the increased expression of ApoA-I induced by the β₃-AR agonist. The HepG2 cell supernatants decreased the lipid accumulation and increased the cholesterol efflux from the macrophage foam cells. ABCA1 expression, but not ABCG1 expression, increased in the macrophage foam cells treated with BRL37344-treated HepG2 cell supernatants.

Conclusion

Activation of β₃-AR in HepG2 cells upregulates ApoA-I expression, which might further promote cholesterol efflux from macrophage foam cells. PPARγ might be required for the induction of ApoA-I expression.

Effects of β(3)-adrenoceptor activation on expression of pancreatic adrenoceptors and angiotensin II receptors in ApoE(-/-) mice

Hyperlipidemia can be harmful to the pancreas and β3-adrenoceptor agonist can improve lipid metabolism disorder. We aimed to study the effects of β3-adrenoceptor activation on glucose, insulin and the expression of pancreatic adrenoceptors and angiotensin II receptors. Ten C57BL/6J mice at the age of 10 weeks served as normal control, and forty age-matched apolipoprotein E knockout (ApoE(-/-)) mice were randomly divided into hyperlipidaemia model group, low-dose and high-dose β3-adrenoceptor agonist group and β3-adrenoceptor antagonist group. After 26 weeks of high-fat diet, treatments were given for 12 weeks. Serum glucose and insulin levels in 48 weeks old mice were measured using an automatic biochemical detector. Quantitative rt-PCR and Western blot were used to analyze the mRNA and protein expression of α1A-, α2A-, β2-, β3-adrenoceptors and angiotensin II type 1 and type 2 receptors in pancreas. We found that β3-adrenoceptor agonist could decrease serum glucose and insulin levels in aged ApoE(-/-) mice (P<0.01) and down-regulate the expression of α1A-adrenoceptor and angiotensin II type 1 receptor which were significantly increased in model mice (P<0.05, P<0.01). Compared with the model mice, α2A-, β2-, β3-adrenoceptor and angiotensin II type 2 receptor expression were up-regulated in β3-adrenoceptor agonist treat mice (P<0.05, P<0.01). These results suggest that chronic β3-adrenoceptor activation regulated the expression of adrenoceptors and angiontensin II receptors towards contrary direction, which indicates that there are interactions between β3-adrenoceptor and subtypes of adrenoceptor and angiotensin II receptor, and these interactions may play a protective role in pancreas and improve glucose metabolism disorders.

Effect of beta-3 adrenoceptor stimulation on the levels of ApoA-I, PPARα, and PPARγ in apolipoprotein E-deficient mice

The beta-3 adrenoceptor (β3-AR) protects against the progression of atherosclerosis. However, the specific mechanism of this antiatherosclerotic effect is still not clear. Thus, the aim of this study was to understand the antiatherosclerotic effects of β3-AR. Thirty-six male homozygous apolipoprotein E-deficient mice and wild-type C57BL/6J mice were randomized into 6 treatment groups: wild-type, atherosclerotic model, atorvastatin, low-dose β3-AR agonist, high-dose β3-AR agonist, and β3-AR antagonist groups. The serum lipids, aortic-free cholesterol (FC), and cholesteryl ester (CE) concentrations were measured at the end of the treatments. The mRNA expression levels of liver apolipoprotein A-I (apoA-I), peroxisome proliferator-activated receptor-α (PPARα), and peroxisome proliferator-activated receptor-γ (PPARγ) were detected by quantitative real-time PCR. Protein expression levels of apoA1, PPARα, and PPARγ in the liver were determined by western blot analysis. Treatment with β3-AR significantly increased the plasma levels of high-density lipoprotein cholesterol and apoA-I, whereas the levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol decreased. The β3-AR agonist treatment markedly decreased both the FC and the CE concentrations in the aorta compared with the atherosclerotic model mice. The β3-AR agonist increased the mRNA and protein expression levels of apoA-I, PPARα, and PPARγ in the liver. This study demonstrates that long-term β3-AR activation can regulate lipid metabolic disorders and reduces the aortic FC and the CE concentrations. These effects may be related to apoA-I, PPARα, and PPARγ.

Effects of beta3-adrenoceptor activation on the interaction between adrenoceptors and angiotensin II receptors in apolipoprotein E knockout mouse lung

Hyperlipidemia can be harmful to the lung and β3-adrenoceptor agonist can improve lipid metabolism disorders. In this study, we aim to investigate the effects of β3-adrenoceptor activation on the interactions of adrenoceptors and angiotensin II receptors in aged apolipoprotein E gene knockout (ApoE(-/-)) mouse lung. Ten wild type C57BL/6J mice were included as normal control, 40 ApoE(-/-) mice were randomly divided into hyperlipidemia model (saline), low dose and high dose β3-adrenoceptor agonist and β3-adrenoceptor antagonist groups. After 26 weeks of high-fat diet, treatments were given for 12 weeks. Total cholesterol (TC), triglycerides (TG) and low-density lipoprotein cholesterol (LDL-C) were examined by an automatic biochemical analyzer. Quantitative real-time PCR and Western blot were used to analyze the mRNA and protein expression of α1A-, α1B-, α2A-, β1-, β2-, β3-adrenoceptors and angiotensin II type 1 and type 2 receptors in lung. We found that β3-adrenoceptor agonist could decrease TG, TC and LDL-C in aged ApoE(-/-) mice (P<0.01) and down-regulate the expressions of α1A-, α2A-adrenoceptors and angiotensin II type 1 receptor which were significantly increased in model mice (P<0.01, P<0.05). Compared with model mice, α1B-, β1-, β2-, β3-adrenoceptors and angiotensin II type 2 receptor expressions were increased in β3-adrenoceptor agonist-treat mice (P<0.01, P<0.05). These findings suggest that the expressions of adrenoceptors and angiotensin II receptors in lung are regulated towards adverse directions after taking β3-adrenoceptor agonist, which shows there are interactions between β3-adrenoceptor and other adrenoceptor subtypes and angiotensin II receptors. These interactions may play a protective role in lung under condition of hyperlipidemia.