Usability of a digital health platform to support home hospitalization in heart failure patients: a multicentre feasibility study among healthcare professionals

AIMS

Heart failure (HF) is a common cause of mortality and (re)hospitalizations. The NWE-Chance project explored the feasibility of providing hospitalizations at home (HH) supported by a newly developed digital health platform. The aim of this study was to explore the perceived usability by healthcare professionals (HCPs) of a digital platform in addition to HH for HF patients.

METHODS AND RESULTS

A prospective, international, multicentre, single-arm interventional study was conducted. Sixty-three patients and 22 HCPs participated. The HH consisted of daily home visits by the nurse and use of the platform, consisting of a portable blood pressure device, weight scale, pulse oximeter, a wearable chest patch to measure vital signs (heart rate, respiratory rate, activity level, and posture), and an eCoach for the patient. Primary outcome was usability of the platform measured by the System Usability Scale halfway and at the end of the study. Overall usability was rated as sufficient (mean score 72.1 ± 8.9) and did not differ between the measurements moments (P = 0.690). The HCPs reported positive experiences (n = 7), negative experiences (n = 13), and recommendations (n = 6) for the future. Actual use of the platform was 79% of the HH days.

CONCLUSION

A digital health platform to support HH was considered usable by HCPs, although actual use of the platform was limited. Therefore, several improvements in the integration of the digital platform into clinical workflows and in defining the precise role of the digital platform and its use are needed to add value before full implementation.

REGISTRATION

clinicaltrials.gov NCT04084964.

Breathing pattern and pulmonary gas exchange in elderly patients with and without left ventricular dysfunction-modification with exercise-based cardiac rehabilitation and prognostic value

Background

Inefficient ventilation is an established prognostic marker in patients with heart failure. It is not known whether inefficient ventilation is also linked to poor prognosis in patients with left ventricular dysfunction (LVD) but without overt heart failure.

Objectives

To investigate whether inefficient ventilation in elderly patients with LVD is more common than in patients without LVD, whether it improves with exercise-based cardiac rehabilitation (exCR), and whether it is associated with major adverse cardiovascular events (MACE).

Methods

In this large multicentre observational longitudinal study, patients aged ≥65 years with acute or chronic coronary syndromes (ACS, CCS) without cardiac surgery who participated in a study on the effectiveness of exCR in seven European countries were included. Cardiopulmonary exercise testing (CPET) was performed before, at the termination of exCR, and at 12 months follow-up. Ventilation (VE), breathing frequency (BF), tidal volume (VT), and end-expiratory carbon dioxide pressure (PETCO2) were measured at rest, at the first ventilatory threshold, and at peak exercise. Ventilatory parameters were compared between patients with and without LVD (based on cardio-echography) and related to MACE at 12 month follow-up.

Results

In 818 patients, age was 72.5 ± 5.4 years, 21.9% were women, 79.8% had ACS, and 151 (18%) had LVD. Compared to noLVD, in LVD resting VE was increased by 8%, resting BF by 6%, peak VE, peak VT, and peak PETCO2 reduced by 6%, 8%, and 5%, respectively, and VE/VCO2 slope increased by 11%. From before to after exCR, resting VE decreased and peak PETCO2 increased significantly more in patients with compared to without LVD. In LVD, higher resting BF, higher nadir VE/VCO2, and lower peak PETCO2 at baseline were associated with MACE.

Conclusions

Similarly to patients with HF, in elderly patients with ischemic LVD, inefficient resting and exercise ventilation was associated with worse outcomes, and ExCR alleviated abnormal breathing patterns and gas exchange parameters.

Bringing the hospital to home: Patient-reported outcome measures of a digital health-supported home hospitalisation platform to support hospital care at home for heart failure patients

Background

Hospitalisations for heart failure are frequent and costly, linked with a lower quality of life, and lead to higher morbidity and mortality. Home hospitalisation interventions could be a substitute for in-hospital stays to reduce the burden on patients. The current study aims to investigate patient-reported satisfaction and usability in combination with the safety of a digital health-supported home hospitalisation intervention for heart failure patients.

Methods

We conducted an international, multicentre, single-arm, interventional study to investigate the feasibility and safety of a digital health-supported home hospitalisation platform. Patients with acute decompensation of known and well-assessed chronic heart failure with an indication for hospital admission were included. The primary outcome was patient satisfaction. Secondary outcomes were usability, adherence, and safety.

Results

A total number of 66 patients were included, of which the data of 65 patients (98.5%) was analysed. A total of 86.1% of patients reported being very satisfied or totally satisfied. No patients reported to be not satisfied with the home hospitalisation intervention. The patients reported a sufficient usability score (mean score: 75.8% of 100%) for the digital health-supported home hospitalisation platform. The adherence to the daily measurements of blood pressure and weight was very high, whereas the adherence to the daily interaction with the eCoach was lower (69.3%). In 7 patients (10.8%), a conversion from home hospitalisation to regular hospitalisation was needed. Furthermore, 6 patients (9.2%) had rehospitalisation within 30 days after the end of the home hospitalisation intervention.

Conclusion

A digitally supported home hospitalisation intervention is feasible. This study demonstrates high patient satisfaction and sufficiently high usability scores. The safety outcomes are comparable with traditional heart failure hospitalisations. This indicates that digitally supported home hospitalisation could be an alternative to in-hospital care for all age groups, yet further research is needed to prove the (cost-) effectiveness.

A Home Hospitalisation Strategy for Patients with an Acute Episode of Heart Failure Using a Digital Health-Supported Platform: A Multicentre Feasibility Study - A Rationale and Study Design

BACKGROUND

Heart failure (HF) is a common cause of hospitalisation and mortality in elderly. The frequent rehospitalisations put a serious burden on patients, health-care budgets, and health-care capacity. Frequent hospital admissions are also associated with a substantial additional hazard for serious complications and reduced quality of life. The NWE-Chance project will explore the feasibility and scalability of providing home hospitalisation supported by a newly developed digital health-supported platform and daily visits of specialised nurses.

METHODS/DESIGN

Hundred patients with chronic HF will be recruited over a 1-year period. The digital health-supported home hospitalisation strategy will be tested in 3 hospitals with different experience in delivering home hospitalisation: Isala Zwolle, Maastricht UMC+, both in The Netherlands, and Jessa Hospital, Hasselt in Belgium. The home hospitalisation intervention will have a maximal duration of 14 days. Feasibility will be measured with acceptability, satisfaction, and usability questionnaires for patients, nurses, and physicians. Furthermore, safety and costs will be assessed for 30 days after the start of the home hospitalisation intervention.

DISCUSSION

The NWE-Chance project will be one of the first studies to examine the feasibility of a digital health-supported home hospitalisation platform for HF patients. It has the potential to augment current standard HF care and quality of life of HF patients and to innovate the standard HF care to potentially lower the hospitalisation-related complications, the burden of HF on health-care systems, and to potentially implement more patient-centred care strategies.

Changes and prognostic value of cardiopulmonary exercise testing parameters in elderly patients undergoing cardiac rehabilitation: The EU-CaRE observational study

Objective

We aimed 1) to test the applicability of the previously suggested prognostic value of CPET to elderly cardiac rehabilitation patients and 2) to explore the underlying mechanism of the greater improvement in exercise capacity (peak oxygen consumption, VO₂) after CR in surgical compared to non-surgical cardiac patients.

Methods

Elderly patients (≥65 years) commencing CR after coronary artery bypass grafting, surgical valve replacement (surgery-group), percutaneous coronary intervention, percutaneous valve replacement or without revascularisation (non-surgery group) were included in the prospective multi-center EU-CaRE study. CPETs were performed at start of CR, end of CR and 1-year-follow-up. Logistic models and receiver operating characteristics were used to determine prognostic values of CPET parameters for major adverse cardiac events (MACE). Linear models were performed for change in peak VO₂ (start to follow-up) and parameters accounting for the difference between surgery and non-surgery patients were sought.

Results

1421 out of 1633 EU-CaRE patients performed a valid CPET at start of CR (age 73±5.4, 81% male). No CPET parameter further improved the receiver operation characteristics significantly beyond the model with only clinical parameters. The higher improvement in peak VO₂ (25% vs. 7%) in the surgical group disappeared when adjusted for changes in peak tidal volume and haemoglobin.

Conclusion

CPET did not improve the prediction of MACE in elderly CR patients. The higher improvement of exercise capacity in surgery patients was mainly driven by restoration of haemoglobin levels and improvement in respiratory function after sternotomy.

Trial registration

Netherlands Trial Register, Trial NL5166.

Effectiveness of Home-Based Mobile Guided Cardiac Rehabilitation as Alternative Strategy for Nonparticipation in Clinic-Based Cardiac Rehabilitation Among Elderly Patients in Europe: A Randomized Clinical Trial

Importance

Although nonparticipation in cardiac rehabilitation is known to increase cardiovascular mortality and hospital readmissions, more than half of patients with coronary artery disease in Europe are not participating in cardiac rehabilitation.

Objective

To assess whether a 6-month guided mobile cardiac rehabilitation (MCR) program is an effective therapy for elderly patients who decline participation in cardiac rehabilitation.

Design, Setting, and Participants

Patients were enrolled in this parallel multicenter randomized clinical trial from November 11, 2015, to January 3, 2018, and follow-up was completed on January 17, 2019, in a secondary care system with 6 cardiac institutions across 5 European countries. Researchers assessing primary outcome were masked for group assignment. A total of 4236 patients were identified with a recent diagnosis of acute coronary syndrome, coronary revascularization, or surgical or percutaneous treatment for valvular disease, or documented coronary artery disease, of whom 996 declined to start cardiac rehabilitation. Subsequently, 179 patients who met the inclusion and exclusion criteria consented to participate in the European Study on Effectiveness and Sustainability of Current Cardiac Rehabilitation Programmes in the Elderly trial. Data were analyzed from January 21 to October 11, 2019.

Interventions

Six months of home-based cardiac rehabilitation with telemonitoring and coaching based on motivational interviewing was used to stimulate patients to reach exercise goals. Control patients did not receive any form of cardiac rehabilitation throughout the study period.

Main Outcomes and Measures

The primary outcome parameter was peak oxygen uptake (Vo2peak) after 6 months.

Results

Among 179 patients randomized (145 male [81%]; median age, 72 [range, 65-87] years), 159 (89%) were eligible for primary end point analysis. Follow-up at 1 year was completed for 151 patients (84%). Peak oxygen uptake improved in the MCR group (n = 89) at 6 and 12 months (1.6 [95% CI, 0.9-2.4] mL/kg-1/min-1 and 1.2 [95% CI, 0.4-2.0] mL/kg-1/min-1, respectively), whereas there was no improvement in the control group (n = 90) (+0.2 [95% CI, -0.4 to 0.8] mL/kg-1/min-1 and +0.1 [95% CI, -0.5 to 0.7] mL/kg-1/min-1, respectively). Changes in Vo2peak were greater in the MCR vs control groups at 6 months (+1.2 [95% CI, 0.2 to 2.1] mL/kg-1/min-1) and 12 months (+0.9 [95% CI, 0.05 to 1.8] mL/kg-1/min-1). The incidence of adverse events was low and did not differ between the MCR and control groups.

Conclusions and Relevance

These results suggest that a 6-month home-based MCR program for patients 65 years or older with coronary artery disease or a valvular intervention was safe and beneficial in improving Vo2peak when compared with no cardiac rehabilitation.

Trial Registration

trialregister.nl Identifier: NL5168.

Offering, participation and adherence to cardiac rehabilitation programmes in the elderly: a European comparison based on the EU-CaRE multicentre observational study

AIMS 

Cardiac rehabilitation (CR) is strongly recommended but participation of elderly patients has not been well characterized. This study aims to analyse current rates and determinants of CR referral, participation, adherence, and compliance in a contemporary European cohort of elderly patients.

METHODS AND RESULTS 

The EU-CaRE observational study included data from consecutive patients aged ≥ 65 with acute coronary syndrome, revascularization, stable coronary artery disease, or heart valve replacement, recruited in eight European centres. Rates and factors determining offering, participation, and adherence to CR programmes and compliance with training sessions were studied across centres, under consideration of extensive-outpatient vs. intensive-inpatient programmes. Three thousand, four hundred, and seventy-one patients were included in the offering and participation analysis. Cardiac rehabilitation was offered to 80.8% of eligible patients, formal contraindications being the main reason for not offering CR. Mean participation was 68.0%, with perceived lack of usefulness and transport issues being principal barriers. Mean adherence to CR programmes of participants in the EU-CaRE study (n = 1663) was 90.3%, with hospitalization/physical impairment as principal causes of dropout. Mean compliance with training sessions was 86.1%. Older age was related to lower offering and participation, and comorbidity was associated with lower offering, participation, adherence, and compliance. Intensive-inpatient programmes displayed higher adherence (97.1% vs. 85.9%, P < 0.001) and compliance (full compliance: 66.0% vs. 38.8%, P < 0.001) than extensive-outpatient programmes.

CONCLUSION 

In this European cohort of elderly patients, older age and comorbidity tackled patients' referral and uptake of CR programmes. Intensive-inpatient CR programmes showed higher completion than extensive-outpatient CR programmes, suggesting this formula could suit some elderly patients.

Greater burden of risk factors and less effect of cardiac rehabilitation in elderly with low educational attainment: The Eu-CaRE study

AIMS

Socioeconomic status is a strong predictor of cardiovascular health. The aim of this study was to describe the immediate and long-term effects of cardiac rehabilitation (CR) across socioeconomic strata in elderly cardiac patients in Europe.

METHODS AND RESULTS

The observational EU-CaRE study is a prospective study with eight CR sites in seven European countries. Patients ≥65 years with coronary heart disease or heart valve surgery participating in CR were consecutively included. Data were obtained at baseline, end of CR and at one-year follow up. Educational level as a marker for socioeconomic status was divided into basic, intermediate and high. The primary endpoint was exercise capacity (peak oxygen consumption (VO2peak)). Secondary endpoints were cardiovascular risk factors, medical treatment and scores for depression, anxiety and quality of life (QoL). A total of 1626 patients were included; 28% had basic, 48% intermediate and 24% high education. A total of 1515 and 1448 patients were available for follow-up analyses at end of CR and one-year, respectively. Patients with basic education were older and more often female. At baseline we found a socioeconomic gradient in VO2peak, lifestyle-related cardiovascular risk factors, anxiety, depression and QoL. The socioeconomic gap in VO2peak increased following CR (p for interaction <0.001). The socioeconomic gap in secondary outcomes was unaffected by CR. The use of evidence-based medication was good in all socioeconomic groups.

CONCLUSIONS

We found a strong socioeconomic gradient in VO2peak and cardiovascular risk factors that was unaffected or worsened after CR. To address inequity in cardiovascular health, the individual adaption of CR according to socioeconomic needs should be considered.

Clinical outcomes after cardiac rehabilitation in elderly patients with and without diabetes mellitus: The EU-CaRE multicenter cohort study

Background

The prevalence of patients with concomitant cardiovascular disease and diabetes mellitus (DM) is increasing rapidly. We aimed to compare the effectiveness of current cardiac rehabilitation (CR) programs across seven European countries between elderly cardiac patients with and without DM.

Methods

1633 acute and chronic coronary artery disease (CAD) patients and patients after valve intervention with an age 65 or above who participated in comprehensive CR (3 weeks to 3 months, depending on centre) were included. Peak oxygen uptake (VO₂ peak), body mass index, resting systolic blood pressure, low-density lipoprotein-cholesterol (LDL-C), and glycated haemoglobin (HbA1c) were assessed before start of CR, at termination of CR (variable time point), and 12 months after start of CR, with no intervention after CR. Baseline values and changes from baseline to 12-month follow-up were compared between patients with and without DM using mixed models, and mortality and hospitalisation rates using logistic regression.

Results

430 (26.3%) patients had DM. Patients with DM had more body fat, lower educational level, more comorbidities, cardiovascular risk factors, and more advanced CAD. Both groups increased their VO₂ peak over the study period but with a significantly lower improvement from baseline to follow-up in patients with DM. In the DM group, change in HbA1c was associated with weight change but not with change in absolute VO₂ peak. 12-month cardiac mortality was higher in patients with DM.

Conclusions

While immediate improvements in VO₂ peak after CR in elderly patients with and without DM were similar, 12-month maintenance of this improvement was inferior in patients with DM, possibly related to disease progression. Glycemic control was less favourable in diabetic patients needing insulin in the short- and long-term. Since glycemic control was only related to weight loss but not to increase in exercise capacity, this highlights the importance of weight loss in obese DM patients during CR.

Trial registration NTR5306 at trialregister.nl; trial registered 07/16/2015; https://www.trialregister.nl/trial/5166

Cardiac rehabilitation of elderly patients in eight rehabilitation units in western Europe: Outcome data from the EU-CaRE multi-centre observational study

Aims

The European Cardiac Rehabilitation in the Elderly (EU-CaRE) HORIZON 2020 project compares the sustainable effects of cardiac rehabilitation (CR) in elderly patients.

Methods and results

A total of 1633 patients with coronary artery disease (CAD) or heart valve replacement (HVR), with or without revascularization, aged 65 or above, who participated in CR were included. Peak oxygen uptake (VO2peak), smoking, body mass index, diet, physical activity, serum lipids, psychological distress and medication were assessed before and after CR (T0 and T1) and after 12 months (T2). Patients undergoing coronary artery bypass surgery or surgical HVR had lower VO2peak at T0 and a greater increase to T1 and T2 (2.8 and 4.4 ml/kg/min, respectively) than CAD patients undergoing percutaneous or no revascularization (1.6 and 1.4 ml/kg/min, respectively). After multivariable adjustment, earlier CR uptake was associated with greater improvements in VO2peak. The proportion of CAD patients with three or more uncontrolled risk factors declined from 58.4% at T0 to 40.1% at T2 ( p < 0.0001). Psychological distress scores all improved and adherence to medication was overall good at all sites. There were significant differences in risk factor burden across sites, but no CR program was superior to others.

Conclusions

The outcomes of VO2peak in CR programs across Europe seemed mainly determined by timing of uptake and were maintained or even further improved at 1-year follow-up. Despite significant improvements, 40.1% of CAD patients still had three or more risk factors not at target after 1 year. Differences across sites could not be ascribed to characteristics of the CR programs offered.

Cardiac rehabilitation in the elderly patient in eight rehabilitation units in Western Europe: Baseline data from the EU-CaRE multicentre observational study

BACKGROUND

Due to the progressive deconditioning, comorbidities and higher complication rates, elderly patients are in particular need of cardiac rehabilitation. We compared elderly patients (65+ years old) participating in cardiac rehabilitation, focusing on baseline characteristics, risk factor control and functional assessment.

METHODS

The EU-CaRE study is a prospective study comparing cardiac rehabilitation in eight centres across Western Europe. Consecutive patients with acute coronary syndrome, stable coronary artery disease and heart valve replacement undergoing cardiac rehabilitation were included.

RESULTS

Of 1633 patients (median age 72 years) participating, 54% had acute coronary syndrome, 33% had stable coronary artery disease and 13% followed valve replacement. Fifty-five per cent had undergone percutaneous coronary intervention and 29% coronary artery bypass grafting. Characteristics varied across centres: 23% (17-27%) were women, 4% (0-12%) were of non-European origin and 16% (4-32%) were living alone. Median time from index event to start of cardiac rehabilitation varied from 11 to 49 days (p < 0.001). Mean VO_2peak was relatively low (16 mL/kg per min) and varied significantly between the participating centres, largely unaffected by multivariable adjustment. Overall patients received guideline recommended treatment: 93% (87-97%) were on a statin and 70% (55-85%) an angiotensin-converting enzyme inhibitor/angiotensin receptor blocker. However, risk factor control was inadequate: 58% had three or more risk factors not controlled.

CONCLUSION

EU-CaRE provides a snapshot of the elderly population with heart disease participating in cardiac rehabilitation across countries in Western Europe. Risk factors and exercise capacity indicate the continued need for cardiac rehabilitation in these patients. Of concern, the lag-time to start of cardiac rehabilitation needs improvement in many centres.

A EUropean study on effectiveness and sustainability of current Cardiac Rehabilitation programmes in the Elderly: Design of the EU-CaRE randomised controlled trial

BACKGROUND

Cardiac rehabilitation (CR) is an evidence-based intervention to increase survival and quality of life. Yet studies consistently show that elderly patients are less frequently referred to CR, show less uptake and more often drop out of CR programmes.

DESIGN

The European study on effectiveness and sustainability of current cardiac rehabilitation programmes in the elderly (EU-CaRE) project consists of an observational study and an open prospective, investigator-initiated multicentre randomised controlled trial (RCT) involving mobile telemonitoring guided CR (mCR).

OBJECTIVE

The aim of EU-CaRE is to map the efficiency of current CR of the elderly in Europe, and to investigate whether mCR is an effective alternative in terms of efficacy, adherence and sustainability.

METHODS AND RESULTS

The EU-CaRE study includes patients aged 65 years or older with ischaemic heart disease or who have undergone heart valve surgery. A total of 1760 patients participating in existing CR programmes in eight regions of Europe will be included. Of patients declining regular CR, 238 will be included in the RCT and randomised in two study arms. The experimental group (mCR) will receive a personalised home-based programme while the control group will receive no advice or coaching throughout the study period. Outcomes will be assessed after the end of CR and at 12 months follow-up. The primary outcome is VO_2peak and secondary outcomes include variables describing CR uptake, adherence, efficacy and sustainability.

CONCLUSION

The study will provide important information to improve CR in the elderly. The EU-CaRE RCT is the first European multicentre study of mCR as an alternative for elderly patients not attending usual CR.

Reverse cholesterol transport revisited

Reverse cholesterol transport was originally described as the high-density lipoprotein-mediated cholesterol flux from the periphery via the hepatobiliary tract to the intestinal lumen, leading to fecal excretion. Since the introduction of reverse cholesterol transport in the 1970s, this pathway has been intensively investigated. In this topic highlight, the classical reverse cholesterol transport concepts are discussed and the subject reverse cholesterol transport is revisited.

Reverse cholesterol transport: From classical view to new insights

Cholesterol is of vital importance for the human body. It is a constituent for most biological membranes, it is needed for the formation of bile salts, and it is the precursor for steroid hormones and vitamin D. However, the presence of excess cholesterol in cells, and in particular in macrophages in the arterial vessel wall, might be harmful. The accumulation of cholesterol in arteries can lead to atherosclerosis, and in turn, to other cardiovascular diseases. The route that is primarily thought to be responsible for the disposal of cholesterol is called reverse cholesterol transport (RCT). Therefore, RCT is seen as an interesting target for the development of drugs aimed at the prevention of atherosclerosis. Research on RCT has taken off in recent years. In this review, the classical concepts about RCT are discussed, together with new insights about this topic.

Transintestinal cholesterol efflux

PURPOSE OF REVIEW

Regulation of cholesterol homeostasis is a complex interplay of a multitude of metabolic pathways situated in different organs. The liver plays a central role and has received most attention of the research community. In this review, we discuss recent progress in the understanding of the emerging role of the intestine in cholesterol transport.

RECENT FINDINGS

In recent years, insight in the transport systems that mediate intestinal cholesterol excretion has deepened considerably. Evidence is emerging that the proximal part of the small intestine is able to secrete cholesterol actively, a pathway called transintestinal cholesterol efflux (TICE). In mice, TICE accounts for up to 70% of fecal neutral sterol excretion.

SUMMARY

The small intestine plays a significant role in the regulation of body cholesterol homeostasis. Active processes control both absorption and excretion of the sterol and the pathways involved are being elucidated. TICE might provide an attractive target for therapy aiming at reduction of atherosclerosis.

Peroxisome proliferator-activated receptor delta activation leads to increased transintestinal cholesterol efflux

Peroxisome proliferator-activated receptor delta (PPARdelta) is involved in regulation of energy homeostasis. Activation of PPARdelta markedly increases fecal neutral sterol secretion, the last step in reverse cholesterol transport. This phenomenon can neither be explained by increased hepatobiliary cholesterol secretion, nor by reduced cholesterol absorption. To test the hypothesis that PPARdelta activation leads to stimulation of transintestinal cholesterol efflux (TICE), we quantified it by intestine perfusions in FVB mice treated with PPARdelta agonist GW610742. To exclude the effects on cholesterol absorption, mice were also treated with cholesterol absorption inhibitor ezetimibe or ezetimibe/GW610742. GW601742 treatment had little effect on plasma lipid levels but stimulated both fecal neutral sterol excretion ( approximately 200%) and TICE ( approximately 100%). GW610742 decreased intestinal Npc1l1 expression but had no effect on Abcg5/Abcg8. Interestingly, expression of Rab9 and LIMPII, encoding proteins involved in intracellular cholesterol trafficking, was increased upon PPARdelta activation. Although treatment with ezetimibe alone had no effect on TICE, it reduced the effect of GW610742 on TICE. These data show that activation of PPARdelta stimulates fecal cholesterol excretion in mice, primarily by the two-fold increase in TICE, indicating that this pathway provides an interesting target for the development of drugs aiming at the prevention of atherosclerosis.

Micellar lipid composition profoundly affects LXR-dependent cholesterol transport across CaCo2 cells

Intraluminal phospholipids affect micellar solubilization and absorption of cholesterol. We here study cholesterol transport from taurocholate-phospholipid-cholesterol micelles to CaCo2 cells, and associated effects on ABC-A1 mediated cholesterol efflux. Micellar incorporation of egg-yolk-phosphatidylcholine markedly increased apical retention of the sterol with decreased expression of ABC-A1, an effect that is prevented by synthetic liver X receptor (LXR) or retinoid X receptor (RXR) agonists. On the other hand, incorporation of lyso-phosphatidylcholine (LysoPC) increased ABC-A1-HDL-dependent basolateral cholesterol efflux, an effect that is abated when LXR is silenced. Thus, the modulation of cholesterol metabolism via intraluminal phospholipids is related to the activity of the oxysterol nuclear receptor LXR.

Regulation of direct transintestinal cholesterol excretion in mice

Biliary secretion is generally considered to be an obligate step in the pathway of excess cholesterol excretion from the body. We have recently shown that an alternative route exists. Direct transintestinal cholesterol efflux (TICE) contributes significantly to cholesterol removal in mice. Our aim was to investigate whether the activity of this novel pathway can be influenced by dietary factors. In addition, we studied the role of cholesterol acceptors at the luminal side of the enterocyte. Mice were fed a Western-type diet (0.25% wt/wt cholesterol; 16% wt/wt fat), a high-fat diet (no cholesterol; 24% wt/wt fat), or high-cholesterol diet (2% wt/wt), and TICE was measured by isolated intestinal perfusion. Bile salt-phospholipid mixtures served as cholesterol acceptor. Western-type and high-fat diet increased TICE by 50 and 100%, respectively. In contrast, the high-cholesterol diet did not influence TICE. Intestinal scavenger receptor class B type 1 (Sr-B1) mRNA and protein levels correlated with the rate of TICE. Unexpectedly, although confirming a role for Sr-B1, TICE was significantly increased in Sr-B1-deficient mice. Apart from the long-term effect of diets on TICE, acute effects by luminal cholesterol acceptors were also investigated. The phospholipid content of perfusate was the most important regulator of TICE; bile salt concentration or hydrophobicity of bile salts had little effect. In conclusion, TICE can be manipulated by dietary intervention. Specific dietary modifications might provide means to stimulate TICE and, thereby, to enhance total cholesterol turnover.

Direct intestinal cholesterol secretion contributes significantly to total fecal neutral sterol excretion in mice

BACKGROUND & AIMS

Hepatobiliary secretion is generally believed to be an integral step in the pathway of cholesterol excretion from the body. Here we have investigated the validity of this paradigm in mice.

METHODS

Cholesterol balance was assessed by measuring intake, excretion, and biliary output in different mouse models. Direct secretion of cholesterol from the luminal side of enterocytes was studied by perfusion of isolated segments of the small intestine in mice.

RESULTS

Cholesterol input and output measurements in different mouse models revealed that fecal neutral sterol excretion was higher than the sum of dietary cholesterol intake and biliary cholesterol secretion indicating the existence of an alternative pathway. Here we show that substantial amounts of cholesterol can be secreted directly by enterocytes. Transintestinal cholesterol secretion is a specific process observed throughout the small intestine (proximal > medial > distal). Secretion depended on the presence of a cholesterol acceptor and was strongly stimulated by bile salts and phospholipids. The capacity of the pathway was sufficient to account for the missing cholesterol in the balance studies. The contribution of this pathway to cholesterol excretion in mice is approximately twice that of the biliary pathway.

CONCLUSIONS

In mice, the intestine plays a significant role in removal of cholesterol from the body.

Shifting gears: liver SR-BI drives reverse cholesterol transport in macrophages

Cholesterol efflux from macrophages, the first step in reverse cholesterol transport (RCT), is assumed to play a critical role in the pathogenesis of atherosclerosis. However, in vivo proof supporting this hypothesis is lacking, due to difficulties in determining the activity of this first step in RCT. In this issue of the JCI, Zhang et al. apply their recently developed method for measuring RCT in vivo to estimate RCT in mouse models with varying levels of HDL turnover. A surprisingly efficient clearance of cholesterol to feces is observed in mice overexpressing hepatic scavenger receptor class B type I (SR-BI), whereas in SR-BI-knockout mice, cholesterol clearance is diminished. The study demonstrates that hepatic SR-BI is a positive regulator of macrophage RCT in vivo.

Interplay between MRP Inhibition and Metabolism of MRP Inhibitors: The Case of Curcumin

The multidrug resistance proteins MRP1 and MRP2 are efflux transporters with broad substrate specificity, including glutathione, glucuronide, and sulfate conjugates. In the present study, the interaction of the dietary polyphenol curcumin with MRP1 and MRP2 and the interplay between curcumin-dependent MRP inhibition and its glutathione-dependent metabolism were investigated using two transport model systems. In isolated membrane vesicles of MRP1- and MRP2-expressing Sf9 cells, curcumin clearly inhibited both MRP1- and MRP2-mediated transport with IC(50) values of 15 and 5 microM, respectively. In intact monolayers of MRP1 overexpressing Madin-Darby canine kidney (MDCKII-MRP1) cells, curcumin also inhibited MRP1-mediated activity, although with a 3-fold higher IC(50) value than the one observed in the vesicle model. Interestingly, MRP2-mediated activity was hardly inhibited in intact monolayers of MRP2-overexpressing MDCKII (MDCKII-MRP2) cells upon exposure to curcumin, whereas the IC(50) value in the vesicle incubations was 5 microM. The difference in extent of inhibition of the MRPs by curcumin in isolated vesicles as compared to intact cells, observed especially for MRP2, was shown to be due to a swift metabolism of curcumin to two glutathione conjugates in the MDCKII cells. Formation of both glutathione conjugates was about six times higher in the MDCKII-MRP2 cells as compared with the MDCKII-MRP1 cells, a phenomenon that could be ascribed to the significantly lower glutathione levels in the cell line. The efflux of both conjugates, identified in the present study as monoglutathionyl curcumin conjugates, was demonstrated to be mediated by both MRP1 and MRP2. From dose-response curves with Sf9 membrane vesicles, glutathionylcurcumin conjugates appeared to be less potent inhibitors of MRP1 and MRP2 than their parent compound curcumin. In conclusion, curcumin clearly inhibits both MRP1- and MRP2-mediated transport, but the glutathione-dependent metabolism of curcumin plays a crucial role in the ultimate level of inhibition of MRP-mediated transport that can be achieved in a cellular system. This complex interplay between MRP inhibition and metabolism of MRP inhibitors, the latter affecting the ultimate potential of a compound for cellular MRP inhibition, may exist not only for a compound like curcumin but also for many other MRP inhibitors presently or previously developed on the basis of vesicle studies.