Voluntary wheel running increases bile acid as well as cholesterol excretion and decreases atherosclerosis in hypercholesterolemic mice

Exercise protects against PCB-induced inflammation and associated cardiovascular risk factors

Polychlorinated biphenyls (PCBs) are persistent environmental pollutants that contribute to the initiation of cardiovascular disease. Exercise has been shown to reduce the risk of cardiovascular disease; however, whether exercise can modulate PCB-induced vascular endothelial dysfunction and associated cardiovascular risk factors is unknown. We examined the effects of exercise on coplanar PCB-induced cardiovascular risk factors including oxidative stress, inflammation, impaired glucose tolerance, hypercholesteremia, and endothelium-dependent relaxation. Male ApoE(-/-) mice were divided into sedentary and exercise groups (voluntary wheel running) over a 12-week period. Half of each group was exposed to vehicle or PCB 77 at weeks 1, 2, 9, and 10. For ex vivo studies, male C57BL/6 mice exercised via voluntary wheel training for 5 weeks and then were administered with vehicle or PCB 77 24 h before vascular reactivity studies were performed. Exposure to coplanar PCB increased risk factors associated with cardiovascular disease, including oxidative stress and systemic inflammation, glucose intolerance, and hypercholesteremia. The 12-week exercise intervention significantly reduced these proatherogenic parameters. Exercise also upregulated antioxidant enzymes including phase II detoxification enzymes. Sedentary animals exposed to PCB 77 exhibited endothelial dysfunction as demonstrated by significant impairment of endothelium-dependent relaxation, which was prevented by exercise. Lifestyle modifications such as aerobic exercise could be utilized as a therapeutic approach for the prevention of adverse cardiovascular health effects induced by environmental pollutants such as PCBs.

Voluntary Exercise Stabilizes Established Angiotensin II-Dependent Atherosclerosis in Mice through Systemic Anti-Inflammatory Effects

We have previously demonstrated that exercise training prevents the development of Angiotensin (Ang) II-induced atherosclerosis and vulnerable plaques in Apolipoprotein E-deficient (ApoE^-/-) mice. In this report, we investigated whether exercise attenuates progression and promotes stability in pre-established vulnerable lesions. To this end, ApoE^-/- mice with already established Ang II-mediated advanced and vulnerable lesions (2-kidney, 1-clip [2K1C] renovascular hypertension model), were subjected to sedentary (SED) or voluntary wheel running training (EXE) regimens for 4 weeks. Mean blood pressure and plasma renin activity did not significantly differ between the two groups, while total plasma cholesterol significantly decreased in 2K1C EXE mice. Aortic plaque size was significantly reduced by 63% in 2K1C EXE compared to SED mice. Plaque stability score was significantly higher in 2K1C EXE mice than in SED ones. Aortic ICAM-1 mRNA expression was significantly down-regulated following EXE. Moreover, EXE significantly down-regulated splenic pro-inflammatory cytokines IL-18, and IL-1β mRNA expression while increasing that of anti-inflammatory cytokine IL-4. Reduction in plasma IL-18 levels was also observed in response to EXE. There was no significant difference in aortic and splenic Th1/Th2 and M1/M2 polarization markers mRNA expression between the two groups. Our results indicate that voluntary EXE is effective in slowing progression and promoting stabilization of pre-existing Ang II-dependent vulnerable lesions by ameliorating systemic inflammatory state. Our findings support a therapeutic role for voluntary EXE in patients with established atherosclerosis.

Bioenergetic cues shift FXR splicing towards FXRα2 to modulate hepatic lipolysis and fatty acid metabolism

Objective

Farnesoid X receptor (FXR) plays a prominent role in hepatic lipid metabolism. The FXR gene encodes four proteins with structural differences suggestive of discrete biological functions about which little is known.

Methods

We expressed each FXR variant in primary hepatocytes and evaluated global gene expression, lipid profile, and metabolic fluxes. Gene delivery of FXR variants to Fxr^−/− mouse liver was performed to evaluate their role in vivo. The effects of fasting and physical exercise on hepatic Fxr splicing were determined.

Results

We show that FXR splice isoforms regulate largely different gene sets and have specific effects on hepatic metabolism. FXRα2 (but not α1) activates a broad transcriptional program in hepatocytes conducive to lipolysis, fatty acid oxidation, and ketogenesis. Consequently, FXRα2 decreases cellular lipid accumulation and improves cellular insulin signaling to AKT. FXRα2 expression in Fxr^−/− mouse liver activates a similar gene program and robustly decreases hepatic triglyceride levels. On the other hand, FXRα1 reduces hepatic triglyceride content to a lesser extent and does so through regulation of lipogenic gene expression. Bioenergetic cues, such as fasting and exercise, dynamically regulate Fxr splicing in mouse liver to increase Fxrα2 expression.

Conclusions

Our results show that the main FXR variants in human liver (α1 and α2) reduce hepatic lipid accumulation through distinct mechanisms and to different degrees. Taking this novel mechanism into account could greatly improve the pharmacological targeting and therapeutic efficacy of FXR agonists.

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FXR variants regulate discrete gene programs with distinct biological outcomes.

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FXRα2 (but not α1) enhances fatty acid handling and insulin responsiveness.

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FXRα1 and α2 reduce liver lipid content through different mechanisms.

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Fasting and physical exercise dynamically regulate Fxr splicing in liver.

Aerobic exercise training enhances the in vivo cholesterol trafficking from macrophages to the liver independently of changes in the expression of genes involved in lipid flux in macrophages and aorta

Background

Regular exercise prevents and regresses atherosclerosis by improving lipid metabolism and antioxidant defenses. Exercise ameliorates the reverse cholesterol transport (RCT), an antiatherogenic system that drives cholesterol from arterial macrophages to the liver for excretion into bile and feces. In this study we analyzed the role of aerobic exercise on the in vivo RCT and expression of genes and proteins involved in lipid flux and inflammation in peritoneal macrophages, aortic arch and liver from wild type mice.

Methods

Twelve-week-old male mice were divided into sedentary and trained groups. Exercise training was performed in a treadmill (15 m/min, 30 min/day, 5 days/week). Plasma lipids were determined by enzymatic methods and lipoprotein profile by fast protein liquid chromatography. After intraperitoneal injection of J774-macrophages the RCT was assessed by measuring the recovery of ³H-cholesterol in plasma, feces and liver. The expression of liver receptors was determined by immunoblot, macrophages and aortic mRNAs by qRT-PCR. ¹⁴C-cholesterol efflux mediated by apo A-I and HDL₂ and the uptake of ³H-cholesteryl oleoyl ether (³H-COE)-acetylated-LDL were determined in macrophages isolated from sedentary and trained animals 48 h after the last exercise session.

Results

Body weight, plasma lipids, lipoprotein profile, glucose and blood pressure were not modified by exercise training. A greater amount of ³H-cholesterol was recovered in plasma (24 h and 48 h) and liver (48 h) from trained animals in comparison to sedentary. No difference was found in ³H-cholesterol excreted in feces between trained and sedentary mice. The hepatic expression of scavenger receptor class B type I (SR-BI) and LDL receptor (B-E) was enhanced by exercise. We observed 2.8 and 1.7 fold rise, respectively, in LXR and Cyp7a mRNA in the liver of trained as compared to sedentary mice. Macrophage and aortic expression of genes involved in lipid efflux was not systematically changed by physical exercise. In agreement, ¹⁴C-cholestrol efflux and uptake of ³H-COE-acetylated-LDL by macrophages was similar between sedentary and trained animals.

Conclusion

Aerobic exercise in vivo accelerates the traffic of cholesterol from macrophages to the liver contributing to prevention and regression of atherosclerosis, independently of changes in macrophage and aorta gene expression.

Ovariectomy results in differential shifts in gut microbiota in low versus high aerobic capacity rats

The increased risk for cardiometabolic disease with the onset of menopause is widely studied and likely precipitated by the decline in endogenous estradiol (E₂), yet the precise mechanisms are unknown. The gut microbiome is involved in estrogen metabolism and has been linked to metabolic disease, suggesting its potential involvement in the postmenopausal phenotype. Furthermore, menopause-associated risk factors, as well as gut ecology, are altered with exercise. Therefore, we studied microbial changes in an ovariectomized (OVX vs. Sham) rat model of high (HCR) and low (LCR) intrinsic aerobic capacity (n = 8–10/group) in relation to changes in body weight/composition, glucose tolerance, and liver triglycerides (TG). Nine weeks after OVX, HCR rats were moderately protected against regional adipose tissue gain and liver TG accumulation (P < 0.05 for both). Microbial diversity and number of the Bacteroidetes phylum were significantly increased in LCR with OVX, but unchanged in HCR OVX relative to Sham. Plasma short-chain fatty acids (SCFA), produced by bacteria in the gut and recognized as metabolic signaling molecules, were significantly greater in HCR Sham relative to LCR Sham rats (P = 0.05) and were decreased with OVX in both groups. These results suggest that increased aerobic capacity may be protective against menopause-associated cardiometabolic risk and that gut ecology, and production of signaling molecules such as SCFA, may contribute to the mediation.

Plasma bile acids show a positive correlation with body mass index and are negatively associated with cognitive restraint of eating in obese patients

Bile acids may be involved in the regulation of food intake and energy metabolism. The aim of the study was to investigate the association of plasma bile acids with body mass index (BMI) and the possible involvement of circulating bile acids in the modulation of physical activity and eating behavior. Blood was obtained in a group of hospitalized patients with normal weight (BMI 18.5–25 kg/m²), underweight (anorexia nervosa, BMI < 17.5 kg/m²) and overweight (obesity with BMI 30–40, 40–50 and >50 kg/m², n = 14–15/group) and plasma bile acid concentrations assessed. Physical activity and plasma bile acids were measured in a group of patients with anorexia nervosa (BMI 14.6 ± 0.3 kg/m², n = 43). Lastly, in a population of obese patients (BMI 48.5 ± 0.9 kg/m², n = 85), psychometric parameters related to disordered eating and plasma bile acids were assessed. Plasma bile acids showed a positive correlation with BMI (r = 0.26, p = 0.03) in the population of patients with broad range of BMI (9–85 kg/m², n = 74). No associations were observed between plasma bile acids and different parameters of physical activity in anorexic patients (p > 0.05). Plasma bile acids were negatively correlated with cognitive restraint of eating (r = −0.30, p = 0.008), while no associations were observed with other psychometric eating behavior-related parameters (p > 0.05) in obese patients. In conclusion, these data may point toward a role of bile acids in the regulation of body weight. Since plasma bile acids are negatively correlated with the cognitive restraint of eating in obese patients, this may represent a compensatory adaptation to prevent further overeating.

HDL and lifestyle interventions

The main lifestyle interventions to modify serum HDL cholesterol include physical exercise, weight loss with either caloric restriction or specific dietary approaches, and smoking cessation. Moderate alcohol consumption can be permitted in some cases. However, as these interventions exert multiple effects, it is often difficult to discern which is responsible for improvement in HDL outcomes. It is particularly noteworthy that recent data questions the use of HDL cholesterol as a risk factor and therapeutic target since randomised interventions and Mendelian randomisation studies failed to provide evidence for such an approach. Therefore, these current data should be considered when reading and interpreting this review. Further studies are needed to document the effect of lifestyle changes on HDL structure-function and health.

Exercise training decreases gene expression of endo- and xeno-sensors in rat small intestine

The purpose of the study was to test the hypothesis that gene expression of members of the nuclear receptor (NR) superfamily known to act as endo- and xeno-sensors is reduced in the ileum of exercise-trained (Tr) rats. Healthy female rats were either treadmill-trained for 8 weeks, 5 times/week, or remained sedentary (Sed). Training resulted in a significant (p < 0.05) decrease in plasma free fatty acid (0.18 ± 0.01 to 0.15 ± 0.01 mmol/L) and glycerol (24.8 ± 0.8 to 18.7 ± 0.8 mg/L) concentrations. Gene expressions of NRs farnesoid X receptor (FXR; p < 0.05), liver X receptor (LXR; p < 0.05), pregnane X receptor (PXR; p < 0.01), and retinoid X receptor (RXR; p < 0.06) were reduced in the ileum of Tr compared with Sed animals. Tr was also associated with a reduction (p < 0.05) in gene expression of FXR downstream heterodimeric organite solute transporters α (OSTα) and β (OSTβ) involved in the transport of bile acids, LXR downstream genes heterodimeric ATP-binding cassette transporters (ABCG5/G8) involved in transport of absorbed cholesterol back to the lumen, and Niemann-Pick C1-like 1 (NPC1L1) involved in cholesterol absorption. These data indicate that exercise training lowers the expression of molecules involved in the defense system of the ileum against endobiotic and xenobiotic insults under normal conditions, thus, suggesting that regular exercise contributes to the intestinal maintenance of cholesterol and bile acid homeostasis.

Serum metabolic signatures induced by a three-day intensified exercise period persist after 14 h of recovery in runners

This study investigated changes in the human serum metabolome elicited by a 3-day period of intensified training. Runners (N = 15, mean ± SD age, 35.2 ± 8.7 years) ran for 2.5 h/day on treadmills at ∼70% VO2max for 3 days in a row, with blood samples collected pre-exercise, and immediately and 14 h post-exercise. Samples were analyzed using gas and liquid chromatography/mass spectrometry (GC-MS, LC-MS), with compounds identified based on comparison to more than 2800 purified standards. Repeated measures ANOVA was used to identify metabolites that differed significantly across time, with multiple testing corrected by the false discovery rate (FDR) (q-value). Immediately following the 3-day exercise period, significant 2-fold or higher increases in 75 metabolites were measured, with all but 22 of these metabolites related to lipid/carnitine metabolism, 13 to amino acid/peptide metabolism, 4 to hemoglobin/porphyrin metabolism, and 3 to Krebs cycle intermediates (q-values < 0.001). After a 14 h overnight recovery period, 50 of the 75 metabolites remained elevated, with 8 decreased (primarily amino acid-related metabolites) (q-values < 0.05). Among the top 20 metabolites, the mean fold changes were 12.4 ± 5.3 and 2.9 ± 1.3 immediately and 14-h post-exercise, respectively. Significant decreases (40-70%, q < 0.01) in 22 metabolites (primarily related to lysolipid and bile acid metabolism) were measured post-exercise, with all but 4 of these still decreased after 14 h rest recovery (q < 0.025). Runners experienced a profound systemic shift in blood metabolites related to energy production especially from the lipid super pathway following 3 days of heavy exertion that was not fully restored to pre-exercise levels after 14 h recovery.

Treadmill Exercise Training Modulates Hepatic Cholesterol Metabolism and Circulating PCSK9 Concentration in High-Fat-Fed Mice

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a novel biomarker of LDL clearance and a therapeutic target of cardiovascular disease. We examined the effects of aerobic exercise training in modulating PCSK9 abundance and hepatic sterol regulation in high-fat-fed C57BL/6 mice. Mice (n = 8) were assigned to a low-fat (LF), high-fat (HF), or an HF with exercise (HF + EX) group for 8 weeks. The HF + EX group was progressively trained 5 days/week on a motorized treadmill. The HF + EX group was protected against body weight (BW) gain and diet-induced dyslipidemia compared with the HF group. The HF + EX group demonstrated an increase in hepatic PCSK9 mRNA (1.9-fold of HF control, P < 0.05) and a reduction in plasma PCSK9 (14%) compared with the HF group. Compared with HF mice, HF + EX mice demonstrated reduced hepatic cholesterol (14%) and increased (P < 0.05) nuclear SREBP2 protein (1.8-fold of HF group) and LDLr mRNA (1.4-fold of HF group). Plasma PCSK9 concentrations correlated positively with plasma non-HDL-C (P = 0.01, r = 0.84). Results suggest that treadmill exercise reduces non-HDL cholesterol and differentially modulates hepatic and blood PCSK9 abundance in HF-fed C57BL/6 mice.

Exercise attenuates PCB-induced changes in the mouse gut microbiome

BACKGROUND

The gut microbiome, a dynamic bacterial community that interacts with the host, is integral to human health because it regulates energy metabolism and immune functions. The gut microbiome may also play a role in risks from environmental toxicants.

OBJECTIVES

We investigated the effects of polychlorinated biphenyls (PCBs) and exercise on the composition and structure of the gut microbiome in mice.

METHODS

After mice exercised voluntarily for 5 weeks, they were treated by oral gavage with a mixture of environmentally relevant PCB congeners (PCB153, PCB138, and PCB180; total PCB dose, 150 µmol/kg) for 2 days. We then assessed the microbiome by determination of 16S rRNA using microarray analysis.

RESULTS

Oral exposure to PCBs significantly altered the abundance of the gut microbiome in mice primarily by decreasing the levels of Proteobacteria. The activity level of the mice correlated with a substantial shift in abundance, biodiversity, and composition of the microbiome. Importantly, exercise attenuated PCB-induced changes in the gut microbiome.

CONCLUSIONS

Our results show that oral exposure to PCBs can induce substantial changes in the gut microbiome, which may then influence their systemic toxicity. These changes can be attenuated by behavioral factors, such as voluntary exercise.

Bile acid sequestration normalizes plasma cholesterol and reduces atherosclerosis in hypercholesterolemic mice. No additional effect of physical activity

AIMS

Bile acid sequestrants (BAS) and physical activity (RUN) decrease incidence of cardiovascular events. Both treatments are often prescribed, yet it is not known whether their beneficial effects are additive. We assessed the effects of BAS treatment alone and in combination with RUN on cholesterol metabolism, heart function and atherosclerotic lesion size in hypercholesterolemic mice.

METHODS

Male Ldlr-deficient mice remained either sedentary (CONTROL), were treated with Colesevelam HCl (BAS), had access to a running wheel (RUN), or were exposed to BAS and RUN (BAS RUN). All groups were fed a high cholesterol diet for 12 weeks. Then, feces, bile and plasma were collected. Atherosclerotic lesion size was determined in the aortic arch and heart function by echocardiography.

RESULTS

BAS RUN ran more than RUN (6.4 ± 1.4 vs. 3.5 ± 1.0 km/day, p < 0.05). BAS and BAS RUN displayed ~3-fold reductions in plasma cholesterol levels (p < 0.001), ~2.5-fold increases in fecal neutral sterol (p < 0.001) and bile acid (p = 0.01) outputs, decreases in biliary secretions of cholesterol (~6-fold, p < 0.0001) and bile acids (~2-fold, p < 0.001) vs. CONTROL while no significant effects were observed in RUN. Compared to CONTROL, lesion size decreased by 78% in both BAS and BAS RUN, (p < 0.0001).

CONCLUSION

BAS reduce atherosclerosis in Ldlr-deficient mice, coinciding with a switch from body cholesterol accumulation to cholesterol loss. RUN slightly modulated atherosclerotic lesion formation but the combination of BAS and RUN had no clear additive effects in this respect.

An atherogenic diet decreases liver FXR gene expression and causes severe hepatic steatosis and hepatic cholesterol accumulation: effect of endurance training

PURPOSE

The aim of this study was to determine the effects of an atherogenic diet (AD; 40 % lipid, 1.25 % cholesterol, kcal) on triglyceride (TAG) and cholesterol accumulation in liver and on gene expression of liver X receptor (LXR) and farnesoid X receptor (FXR) and their target genes and to observe if these responses are affected by endurance training.

METHODS

Sprague-Dawley rats (n = 32) were divided into two groups and randomly assigned to an AD or a standard diet (SD) for 7 weeks. Half of the rats in each group were assigned to an exercise training program for 5 days/week.

RESULTS

The AD resulted in a large (P < 0.01) accumulation in liver TAG (4×) along with elevated liver and plasma cholesterol without any gain in peripheral fat mass. The liver TAG and cholesterol accumulations were associated with an important reduction (P < 0.01; 60 %) in FXR, but no change in LXR transcripts. Accompanying the reduction in FXR gene expression, we found an increase (P < 0.001) in SREBP-1c and a decrease (P < 0.01) in MTP mRNAs suggesting an increased lipogenesis and a reduced VLDL production, respectively. The AD was also associated with lower HMG-CoA-r, squalene synthase, and ABCG8 transcripts (P < 0.001). In the intestine, exercise training resulted in higher NPC1L1, ABCG5, and ABCG8 in SD-fed animals, while all these increases were suppressed under the AD feeding.

CONCLUSIONS

It is concluded that dietary cholesterol favors liver TAG and cholesterol accumulations associated with an important reduction in FXR transcripts.

Regulation of reverse cholesterol transport - a comprehensive appraisal of available animal studies

Plasma levels of high density lipoprotein (HDL) cholesterol are strongly inversely correlated to the risk of atherosclerotic cardiovascular disease. A major recognized functional property of HDL particles is to elicit cholesterol efflux and consequently mediate reverse cholesterol transport (RCT). The recent introduction of a surrogate method aiming at determining specifically RCT from the macrophage compartment has facilitated research on the different components and pathways relevant for RCT. The current review provides a comprehensive overview of studies carried out on macrophage-specific RCT including a quick reference guide of available data. Knowledge and insights gained on the regulation of the RCT pathway are summarized. A discussion of methodological issues as well as of the respective relevance of specific pathways for RCT is also included.

Head and neck manifestations of neurofibromatosis

Neurofibromatosis is a neurocutaneous systemic disease that occurs in 1:2500 to 3300 live births. Prevalence figures have shown it to be as common as cystic fibrosis or Down's syndrome and more than twice as common as muscular dystrophy. In this study, our experience with 257 cases of neurofibromatosis seen since 1972 is reviewed. Intracranial, bony, and extracranial anomalies are described in the 223 patients (87%) who presented with, or ultimately developed, head and neck manifestations of the disease. The most common intracranial tumor was optic glioma, found in 35 patients (14%), 19 younger than 10 years of age. Acoustic neuromas were diagnosed in eight individuals (3%) and were bilateral in three. The most common skull anomaly was macrocephaly, noted 78 times (30%). Absence of the sphenoid wing occurred in 11 patients (4%) and 19 others (7%) had facial asymmetry due to other skull abnormalities. Extracranial manifestations included neurofibromas of the plexiform and nonplexiform type, Lisch nodules, and cafe-au-lait spots.