Ligand-dependent interactions between SR-B1 and S1PR1 in macrophages and atherosclerotic plaques.

HDLs carry sphingosine-1-phosphate (S1P) and stimulate signaling pathways in different cells including macrophages and endothelial cells, involved in atherosclerotic plaque development. HDL signaling via S1P relies on the HDL receptor scavenger receptor class B, type I (SR-B1) and the sphingosine-1-phosphate receptor 1 (S1PR1), which interact when both are heterologously overexpressed in the HEK293 cell line. In this study, we set out to test if SR-B1 and S1PR1 interacted in primary murine macrophages in culture and atherosclerotic plaques. We used knock-in mice that endogenously expressed S1PR1 tagged with eGFP-(S1pr1eGFP/eGFP mice), combined with proximity ligation analysis to demonstrate that HDL stimulates the physical interaction between SR-B1 and S1PR1 in primary macrophages, that this is dependent on HDL-associated S1P and can be blocked by an inhibitor of SR-B1's lipid transfer activity or an antagonist of S1PR1. We also demonstrate that a synthetic S1PR1-selective agonist, SEW2871, stimulates the interaction between SR-B1 and S1PR1 and that this was also blocked by an inhibitor of SR-B1's lipid transport activity. Furthermore, we detected abundant SR-B1/S1PR1 complexes in atherosclerotic plaques of S1pr1eGFP/eGFP mice that also lacked apolipoprotein E. Treatment of mice with the S1PR1 antagonist, Ex26, for 12 h disrupted the SR-B1-S1PR1 interaction in atherosclerotic plaques. These findings demonstrate that SR-B1 and S1PR1 form ligand-dependent complexes both in cultured primary macrophages and within atherosclerotic plaques in mice and provide mechanistic insight into how SR-B1 and S1PR1 participate in mediating HDL signaling to activate atheroprotective responses in macrophages.

Neuroprotective Effects of Metformin Through AMPK Activation in a Neurotoxin-Based Model of Cerebellar Ataxia.

Cerebellar ataxia is a heterogeneous group of neural disorders clinically characterized by cerebellar dysfunction. The diagnosis of patients with progressive cerebellar ataxia is complex due to the direct correlation with other neuron diseases. Although there is still no cure for this pathological condition, some metabolic, hereditary, inflammatory, and immunological factors affecting cerebellar ataxia are being studied and may become therapeutic targets. Advances in studying the neuroanatomy, pathophysiology, and molecular biology of the cerebellum (CE) contribute to a better understanding of the mechanisms behind the development of this disorder. In this study, Wistar rats aged 30 to 35 days were injected intraperitoneally with 3-acetylpyridine (3-AP) and/or metformin (for AMP-activated protein kinase (AMPK) enzyme activation) and euthanized in 24 hours and 4 days after injection. We analyzed the neuromodulatory role of the AMPK on cerebellar ataxia induced by the neurotoxin 3-AP in the brain stem (BS) and CE, after pre-treatment for 7 and 15 days with metformin, a pharmacological indirect activator of AMPK. The results shown here suggest that AMPK activation in the BS and CE leads to a significant reduction in neuroinflammation in these regions. AMPK was able to restore the changes in fatty acid composition and pro-inflammatory cytokines caused by 3-AP, suggesting that the action of AMPK seems to result in a possible neuroprotection on the cerebellar ataxia model.

Apolipoprotein A1 Protects Against Necrotic Core Development in Atherosclerotic Plaques: PDZK1-Dependent High-Density Lipoprotein Suppression of Necroptosis in Macrophages.

BACKGROUND: Atherosclerosis is a chronic disease affecting artery wall and a major contributor to cardiovascular diseases. Large necrotic cores increase risk of plaque rupture leading to thrombus formation. Necrotic cores are rich in debris from dead macrophages. Programmed necrosis (necroptosis) contributes to necrotic core formation. HDL (high-density lipoprotein) exerts direct atheroprotective effects on different cells within atherosclerotic plaques. Some of these depend on the SR-B1 (scavenger receptor class B type I) and the adapter protein PDZK1 (postsynaptic density protein/Drosophila disc-large protein/Zonula occludens protein containing 1). However, a role for HDL in protecting against necroptosis and necrotic core formation in atherosclerosis is not completely understood. METHODS: Low-density lipoprotein receptor-deficient mice engineered to express different amounts of ApoA1 (apolipoprotein A1), or to lack PDZK1 were fed a high fat diet for 10 weeks. Atherosclerotic plaque areas, necrotic cores, and key necroptosis mediators, RIPK3 (receptor interacting protein kinase 3), and MLKL (mixed lineage kinase domain-like protein) were characterized. Cultured macrophages were treated with HDL to determine its effects, as well as the roles of SR-B1, PDZK1, and the PI3K (phosphoinositide 3-kinase) signaling pathway on necroptotic cell death. RESULTS: Genetic overexpression reduced, and ApoA1 knockout increased necrotic core formation and RIPK3 and MLKL within atherosclerotic plaques. Macrophages were protected against necroptosis by HDL and this protection required SR-B1, PDZK1, and PI3K/Akt pathway. PDZK1 knockout increased atherosclerosis in LDLRKO mice, increasing necrotic cores and phospho-MLKL; both of which were reversed by restoring PDZK1 in BM-derived cells. CONCLUSIONS: Our findings demonstrate that HDL in vitro and ApoA1, in vivo, protect against necroptosis in macrophages and necrotic core formation in atherosclerosis, suggesting a pathway that could be a target for the treatment of atherosclerosis.

Good Cholesterol Gone Bad? HDL and COVID-19.

The transmissible respiratory disease COVID-19, caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected millions of people worldwide since its first reported outbreak in December of 2019 in Wuhan, China. Since then, multiple studies have shown an inverse correlation between the levels of high-density lipoprotein (HDL) particles and the severity of COVID-19, with low HDL levels being associated with an increased risk of severe outcomes. Some studies revealed that HDL binds to SARS-CoV-2 particles via the virus's spike protein and, under certain conditions, such as low HDL particle concentrations, it facilitates SARS-CoV-2 binding to angiotensin-converting enzyme 2 (ACE2) and infection of host cells. Other studies, however, reported that HDL suppressed SARS-CoV-2 infection. In both cases, the ability of HDL to enhance or suppress virus infection appears to be dependent on the expression of the HDL receptor, namely, the Scavenger Receptor Class B type 1 (SR-B1), in the target cells. SR-B1 and HDL represent crucial mediators of cholesterol metabolism. Herein, we review the complex role of HDL and SR-B1 in SARS-CoV-2-induced disease. We also review recent advances in our understanding of HDL structure, properties, and function during SARS-CoV-2 infection and the resulting COVID-19 disease.

High Density Lipoprotein and Its Precursor Protein Apolipoprotein A1 as Potential Therapeutics to Prevent Anthracycline Associated Cardiotoxicity.

Cardiovascular disease and cancer are the leading causes of death in developed societies. Despite their effectiveness, many cancer therapies exhibit deleterious cardiovascular side effects such as cardiotoxicity and heart failure. The cardiotoxic effects of anthracyclines such as doxorubicin are the most well-characterized of cardiotoxic anti-cancer therapies. While other anti-neoplastic drugs also induce cardiotoxicity, often leading to heart failure, they are beyond the scope of this review. This review first summarizes the mechanisms of doxorubicin-induced cardiotoxicity. It then reviews emerging preclinical evidence that high density lipoprotein and its precursor protein apolipoprotein A1, which are known for their protective effects against ischemic cardiovascular disease, may also protect against doxorubicin-induced cardiotoxicity both directly and indirectly, when used therapeutically.

Selenium supplementation during pregnancy and lactation promotes metabolic changes in Wistar rats' offspring.

Epidemiological and animal studies have demonstrated a strong association between selenium (Se) supplementation and metabolic disorders, we aimed to evaluate whether maternal Se supplementation was able to change metabolic parameters in rats' offspring. Moreover, as Se is a deiodinase (DIO) cofactor, we decided to investigate how thyroid hormones (THs) would be involved in such metabolic changes. Thereby, two groups (n = 6, ~250 g) of female Wistar rats underwent isotonic saline or sodium selenite (1 mg/kg, p.o.) treatments. Although there were no significant differences in body weight between groups, the Se treatment during pregnancy and lactation increased milk intake and the visceral white adipose tissue (WAT) in offspring. The rats whose mothers were treated with Se also presented an improvement in the glucose tolerance test and in the glucose-stimulated insulin secretion. Regarding the lipid metabolism, the Se group had a reduction of triglycerides in the liver and in WAT. These metabolic changes were accompanied by an increase in serum triiodothyronine (T3 ) and in DIO 2 expression in brown adipose tissue (BAT). We further demonstrate an increased expression of peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α) and nuclear respiratory factor-1 (NRF-1) mRNA in the liver. In adulthood offspring, Se supplementation programs thyroid function, glucose homeostasis, and feeding behaviour. Taken together, there is no indication that Se programming causes insulin resistance. Moreover, we conjecture that these metabolic responses are induced by increased thyroxine (T4 ) to T3 conversion by DIO2 in BAT and mediated by altered transcription factors expression associated with oxidative metabolism control in the liver.

Fish oil supplementation during adolescence attenuates metabolic programming of perinatal maternal high-fat diet in adult offspring.

Perinatal maternal high-fat diet (HFD) increases susceptibility to obesity and fatty liver diseases in adult offspring, which can be attenuated by the potent hypolipidaemic action of fish oil (FO), an n-3 PUFA source, during adult life. Previously, we described that adolescent HFD offspring showed resistance to FO hypolipidaemic effects, although FO promoted hepatic molecular changes suggestive of reduced lipid accumulation. Here, we investigated whether this FO intervention only during the adolescence period could affect offspring metabolism in adulthood. Then, female Wistar rats received isoenergetic, standard (STD: 9 % fat) or high-fat (HFD: 28·6 % fat) diet before mating, and throughout pregnancy and lactation. After weaning, male offspring received the standard diet; and from 25 to 45 d old they received oral administration of soyabean oil or FO. At 150 d old, serum and hepatic metabolic parameters were evaluated. Maternal HFD adult offspring showed increased body weight, visceral adiposity, hyperleptinaemia and decreased hepatic pSTAT3/STAT3 ratio, suggestive of hepatic leptin resistance. FO intake only during the adolescence period reduced visceral adiposity and serum leptin, regardless of maternal diet. Maternal HFD promoted dyslipidaemia and hepatic TAG accumulation, which was correlated with reduced hepatic carnitine palmitoyl transferase-1a content, suggesting lipid oxidation impairment. FO intake did not change serum lipids; however, it restored hepatic TAG content and hepatic markers of lipid oxidation to STD offspring levels. Therefore, we concluded that FO intake exclusively during adolescence programmed STD offspring and reprogrammed HFD offspring male rats to a healthier metabolic phenotype in adult life, reducing visceral adiposity, serum leptin and hepatic TAG content in offspring adulthood.

A new lipid carrier protein in the cattle tick Rhipicephalus microplus.

Tick infestation in cattle reflects the main cause of economic loss to cattle producers. This is due to several reasons but mainly to their ability to feed on blood and generate a huge amount of eggs. Lipid transport in arthropods is achieved by highly specialized hemolymphatic lipoproteins, which resemble those described in vertebrate blood. Such lipoproteins continuously deliver lipids through the blood to growing eggs. The injection of radioactive [3H] palmitic acid into tick hemocoel showed that the gut, ovary, fat body and Gene's organ were the main organs of incorporation of this labeled fatty acid. The rate of [3H] palmitic acid incorporation by the organs was high up to 30 min after injection. The [3H] palmitic acid incorporated by these organs was later found in phospholipids and neutral lipids. Here, we describe the purification and characterization of a key player of lipid dynamics in tick hemolymph. The Rhipicephalus microplus lipid-apolipoprotein complex (RmLCP) is a new high-density lipoprotein (1.18 g/mL), which accounts for over 90% of [3H] palmitic acid present in the hemolymph. It has a native molecular weight of 420 kDa and is composed of one subunit of 122 kDa. Protein identification analysis of RmLPC subunit showed two better hits: vitellogenin 2 (23% protein coverage) and vitellogenin 5 (29% protein coverage), respectively and similarities with hemolymphatic apolipoproteins of arachnids such as the tick Ixodes scapularis (80%), the mite Galendromus occidentalis (44%) and the spider Parasteatoda tepidariorum (43%) and also for the insects Locusta migratoria (45%), Drosophila melanogaster (42%) and Manduca sexta (47%) to vitellogenin 2 and tick Ixodes scapularis (83%), the crab Limulus polyphemus (55%) and the oyster Crassostrea gigas (55%) to vitellogenin 5. Furthermore, it shows a distinct lipid composition from most arthropod lipoproteins, being composed of 40% free cholesterol, 27% phospholipids, 20% triacylglycerol and 15% hydrocarbons. In addition to binding most hemolymphatic fatty acids, this lipoprotein also binds and transports free cholesterol. In conclusion, the present study provides insight into the macromolecules involved in arachnid metabolism, which have significant potential for future use for the biological control of ticks.

Perinatal maternal high-fat diet promotes alterations in hepatic lipid metabolism and resistance to the hypolipidemic effect of fish oil in adolescent rat offspring.

SCOPE: Maternal high-fat diet (HFD) promotes obesity and metabolic disturbances in offspring at weaning and adult life. We investigated metabolic consequences of maternal HFD in adolescent rat offspring and the potential benefic effects of fish oil (FO) (n-3 polyunsaturated fatty acid source). METHODS AND RESULTS: Female rats received isocaloric, standard diet (STD: 9% fat) or HFD (28.6%) before mating, and throughout pregnancy and lactation. After weaning, male offspring received standard diet and, from 25th to 45th day, received oral administration of soybean oil (SO) or FO. HFD offspring showed higher body weight and adiposity, which was not attenuated by FO. In STD offspring, FO reduced serum triglyceride and cholesterol, as expected, but not in HFD offspring. Liver of HFD offspring groups showed increased free cholesterol and FO-treated HFD group showed lower expression of Abcg8, suggesting decreased cholesterol biliary excretion. HFD offspring presented higher hepatic expression of lipogenic markers, Srebf1 mRNA and acetyl CoA carboxylase (ACC). Serum n-3 PUFA were decreased in FO-treated HFD compared to FO-treated STD offspring, which may explain the reduced hypolipidemic FO effect. CONCLUSION: Maternal HFD impaired the ability of FO to reduce adiposity and serum lipids in adolescent offspring, suggesting a potential predisposition to future development of metabolic disorders.

Cinnamon extract improves the body composition and attenuates lipogenic processes in the liver and adipose tissue of rats.

In models of metabolic disorders, cinnamon improves glucose and lipid metabolism. This study explores the effect of chronic supplementation with aqueous cinnamon extract (CE) on the lipid metabolism of rats. Male adult Wistar rats were separated into a control group (CTR) receiving water and a CE Group receiving aqueous cinnamon extract (400 mg of cinnamon per kg body mass per day) by gavage for 25 consecutive days. Cinnamon supplementation did not change the food intake or the serum lipid profile but promoted the following changes: lower body mass gain (P = 0.008), lower relative mass of white adipose tissue (WAT) compartments (P = 0.045) and higher protein content (percentage of the carcass) (P = 0.049). The CE group showed lower leptin mRNA expression in the WAT (P = 0.0017) and an important tendency for reduced serum leptin levels (P = 0.059). Cinnamon supplementation induced lower mRNA expression of SREBP1c (sterol regulatory element-binding protein 1c) in the WAT (P = 0.001) and liver (P = 0.013) and lower mRNA expression of SREBP2 (P = 0.002), HMGCoA reductase (3-hydroxy-3-methylglutaryl-CoA reductase) (P = 0.0003), ACAT1 (acetyl-CoA acetyltransferase 1) (P = 0.032) and DGAT2 (diacylglycerol O-acyltransferase 2) (P = 0.03) in the liver. These changes could be associated with the reduced esterified cholesterol and triacylglycerol content detected in this tissue. Our results suggest that chronic ingestion of aqueous cinnamon extract attenuates lipogenic processes, regulating the expression of key enzymes and transcriptional factors and their target genes, which are directly involved in lipogenesis. These molecular changes possibly promote adaptations that would prevent an increase in circulating cholesterol and triacylglycerol levels and prevent lipid accumulation in tissues, such as liver and WAT. Therefore, we speculate that cinnamon may also be useful for preventing or retarding the development of lipid disorders.