Maintaining glucose integrity ex-vivo: Impact of preanalytical specimen handling

BACKGROUND

Adopting the WHO protocol for glucose analysis is arguably impractical in the routine clinical setting. Deviations may develop due to a lack of understanding regarding the impact of glycolysis on the accuracy of results.

AIM

We sought to assess the stability of glucose in two different blood collection tubes (BCT), BD Vacutainer® FX 'Fl-Ox' and Greiner Vacuette® FC-Mix 'FC-Mix' stored at room temperature (RT:18-22°C) and 4°C over 8.5 days.

METHOD

Each participant provided venous whole blood collected into 51 BCTs; 'Fl-Ox' (n = 26) and 'FC-Mix' (n = 25). One Fl-Ox sample from each participant was handled according to the WHO recommended method. The remaining BCTs were stored at 4°C/RT prior to analyses at designated study timepoints. Glucose was measured using the hexokinase assay on the Cobas® 8000 platform.

RESULTS

Participants (n = 8, Male = 2) were aged 24-56 years. Plasma glucose measured in FI-Ox BCTs according to the WHO sample-handling method had a median concentration of 5.73 mmol/L (Range: 5.39-10.37 mmol/L). Glucose decreased by greater than minimal difference (>0.26 mmol/L) in blood collected into Fl-Ox and stored @4°C/RT within 24 h of phlebotomy. FC-Mix BCT maintained glucose <0.26 mmol/L @4°C over a period of 8.5 days and up to 4 days @RT when compared to the WHO recommended method.

CONCLUSION

Glucose in FC-Mix BCT stored @4°C demonstrated the best agreement with results determined using the WHO specifications. When FC-Mix tubes were stored @RT, glucose was stable for 4 days. These findings suggest that the FC-Mix BCT effectively inhibits glycolysis and should be introduced into routine clinical practice.

Female cricket pace bowling: kinematic and anthropometric relationships with ball release speed

Background

Despite an increase in the professionalism and participation of female cricket, the coaching of female pace bowling is still reliant on male-derived knowledge.

Objectives

To investigate the association between key male-derived kinematic and anthropometric parameters and ball release speed (BRS) in female pace bowlers.

Methods

Eleven female pace bowlers participated in this study. BRS, and four anthropometric and five kinematic parameters were determined. Stepwise linear regression and Pearson Product Moment correlations were used to identify anthropometric and kinematic parameters linked to BRS.

Results

The best predictor of BRS explaining 89% of the observed variance was the bowling shoulder angle at ball release. The best anthropometric predictor of BRS was height explaining 53% of the observed variance. Other parameters correlated with BRS included: run-up speed (r = 0.75, p = 0.013) and arm length (r = 0.61, p = 0.046). When height was controlled for, the front knee angle at front foot contact was also correlated to BRS (r = 0.68, p = 0.044). No relationship was found between trunk flexion and BRS.

Conclusion

Faster BRS were characterised by faster run-up speeds, straighter front knees, and delayed arm circumduction similar to male pace bowlers. The lack of relationship between trunk flexion and BRS may highlight female pace bowlers adopting a bowling technique where BRS is contributed to by trunk rotation as well as trunk flexion. This knowledge is likely to be useful in the talent identification and coaching of female pace bowlers.

The Relationship Between Sexual Behavior Stigma and Depression Among Men Who have Sex with Men and Transgender Women in Kigali, Rwanda: a Cross-sectional Study

To evaluate the role of sexual behavior stigma as a determinant of depressive symptoms among men who have sex with men (MSM) and transgender women (TGW) in Kigali, Rwanda. MSM/TGW aged ≥18 years were recruited using respondent-driven sampling (RDS) between March-August, 2018. Mental health was assessed using the Patient Health Questionnaire (PHQ-9). Sexual behavior stigma from friends and family, healthcare workers, and community members was assessed using a validated instrument. Multinomial logistic regression models were used to determine the association between sexual behavior stigma and depressive symptoms and depression. Secondary analyses further compared depression and depressive symptoms among MSM and TGW. Among the 736 participants included, 14% (106/736) identified as TGW. Depression 8.9% (RDS-adjusted, 7.6%; 95% CI, 4.6-10.6) and mild/moderate symptoms of depression 26.4% (RDS-adjusted, 24.1%; 95% CI, 19.4-28.7) were common and higher among TGW compared to MSM (p < 0.001). Anticipated (41%), perceived (36%), and enacted (45%) stigmas were highly prevalent, and were also significantly higher among TGW (p < 0.001). In multivariable RDS-adjusted analysis, anticipated (relative risk ratio (RRR), 1.88; 95% CI, 1.11-3.19) and perceived (RRR, 2.06; 95% CI, 1.12-3.79) stigmas were associated with a higher prevalence of depressive symptoms. Anticipated (RRR, 4.78; 95% CI, 1.74-13.13) and enacted (RRR, 3.09; 95% CI, 1.61-5.93) stigmas were also associated with a higher prevalence of depression. In secondary analyses, the significant differences between MSM and TGW were lost after adjusting for stigma. These data demonstrate a high burden of depressive symptoms and depression among MSM/TGW in Kigali. Conceptually, stigma is a likely antecedent of mental health stress among MSM and TGW suggesting the potential utility of scaling up stigma mitigation interventions to improve the quality of life and mental health outcomes among sexual and gender minority communities in Rwanda.

348 WHAT IS THE OLDER PATIENT’S VIEW ON RECEIVING DETAILED MEDICAL LETTERS?

Background

Sending copies of clinic letters to patients involves additional work for medical staff in formatting letters, administrative staff in printing and posting and is an added cost to the healthcare service. Though seen largely as good practice in some specialities, it is not done routinely in Geriatric medical services. We introduced this practice as standard in our service and wished to evaluate whether from the patient perspective, it is worthwhile.

Methods

We sent a questionnaire to n=80 older patients who were evaluated in the home setting (by the Integrated Care Team for Older People – ICTOP) or recently attended CGA (Comprehensive Geriatric Assessment) clinic or FLS (Fracture Liaison Service) clinic. We asked their opinion on the detailed medical letter sent to their General Practitioner (GP), which they received a copy of. The questionnaire could be completed by patient/carer/relative, and returned anonymously.

Results

N=30/80 were returned. Two said they found the letter difficult to understand; 1/30 said the letter caused them to worry but all said they still preferred that they had received it. N= 2 said they would like to have contributed to the letter for accuracy. All said they felt they should receive copies of all their medical correspondence. Free text comments showed overwhelming support for the process, in allowing them to self-manage their health, enhance communication with other healthcare professionals and was a useful document to refer back to when they are trying to process information during short consultations.

Conclusion

Though a small survey and limited by low response rate, older people expressed high levels of satisfaction in receiving copies of medical letters about their health. It supports the ongoing practice and should be adopted widely.

35 GERIATRIC EMERGENCY MEDICINE (GEM)’ PEARLS AND PITFALLS’- AN INTERDISCIPLINARY APPROACH TO EDUCATION

Background

In recent years we have seen increased awareness of the terms ‘frailty’ and ‘GEM’ in many of our Emergency Departments (ED). A clear understanding of these terms within the context of ED is essential to provide a holistic care and to best meet the needs of older adults. It has been highlighted internationally that current training programmes do not sufficiently address learning needs of trainees to optimise care of this cohort of patients. The European Geriatric Medicine Society and the European Society for Emergency Medicine has attempted to address this gap through the introduction of a core GEM curriculum in 2016, however, at a local level many EDs are not utilising this resource for a number of reasons including lack of awareness and prioritisation of other local learning needs as determined by specialist training. To address the GEM learning needs at a local level an initiative idea was trialled in the form of a GEM teaching wall with dedicated monthly topics chosen from the above curriculum.

Methods

The initiative was led by a Senior Physiotherapist working on the Frailty Intervention Therapy Team and a Senior House Officer (SHO) working in ED with collaboration from other ED members as identified. A brainstorming session took place to identify potential topics. A poster was created by the project leads each month focusing on a core topic including an overview on the subject, national/international guidelines and top tips how to best manage in ED. Relevant team members contributed to different topics. Monthly posters were displayed in the ED.

Results

The project has been successfully running for 4 months with topics including Abdominal pain, Silver trauma Delirium and Falls.

Conclusion

GEM teaching is a cornerstone of successful management of older adults presenting to our EDs. Novel MDT teaching approaches can address the identified learning gap in this area and highlight international recommendations with minimum cost.

Radium-223 in the Treatment of Metastatic Castrate-Resistant Prostate Cancer

Background Radium 223 (Ra-223) has been successfully utilised for the treatment of men with metastatic castrate resistant prostate cancer (mCRPC). To date, no real world outcomes from its use in the Irish population have been described. Methods All men referred to our institution for Ra-223 from September 2016 to March 2019 were included. Patient demographics, treatments received, toxicities and outcomes were recorded. Overall survival (OS) and progression free survival (PFS) were analysed using the Kaplan-Meier method. Results Complete data was available for 54 men. Median age was 75 years (range 61-86 years). The median number of prior systemic treatments for mCRPC was 2 (range 0-4). Median ECOG performance status was 1 at the start of treatment and 2 at completion. The median number of Ra-223 cycles received was 4 with 37%(n=20) completing all 6 planned cycles. The most common treatment-related toxicity was fatigue seen in 52% of patients ( n=28). Improved pain scores were documented in 76% of men requiring opioid analgesia at the start of treatment. The median OS was 7 months. A good ECOG performance status, fewer than 6 bone metastases, normal alkaline phosphatase level at start of treatment and chemotherapy naivety were associated with improved OS. Conclusions Ra-223 is a moderately well tolerated palliative treatment amongst Irish men with mCRPC.

114 FALLS AND SYNCOPE GUIDELINES APPLIED TO EMERGENCY DEPARTMENT ATTENDEES—HOW DO WE PERFORM?

Background

Falls and syncope are one of the most common presentations to emergency departments amongst older people. European Society of Cardiology (ESC) guidelines describe investigation of suspected syncope to assist care.

Methods

Following a previous audit we delivered an education program to Emergency Department (ED) staff, on assessment of fallers and syncope. This was a repeat cycle audit on consecutive patients aged who presented with a fall/faint/collapse/blackout/syncope, to assess impact of education sessions. We also conducted a survey of n = 23 ED staff members, on role of orthostatic blood pressures and ECGs in falls assessments.

Results

Of 80 consecutive attendees with a fall, n = 41 (51%) had possible syncope as documented in the history. ECG was done within the ED in 88% vs. 51% on baseline audit however only 14% (11/80) had lying and standing blood pressure checked vs. 15% on baseline audit. This is despite our survey showing that 17/23 (74%) of ED staff felt that orthostatic BP checks were essential in all fallers, and 44% stating they measure it themselves. Brain imaging was conducted in 44% vs. 40% in baseline audit, rationale for which was unclear in some. 31% (n = 25) were admitted compared to 42% previously. Of the n = 23 admitted, 24% (n = 6) had telemetry or Holter monitor, 20% had an echocardiogram.

Conclusion

Despite an education program on assessment of older fallers, embedding it to alter practice is challenging. While the education program resulted in some improvements, it supports a dedicated team for assessing fallers in the ED. Given the low rate of further investigations into causes for those admitted, a rapid access out patient pathway is warranted. Brain imaging is carried out relatively frequently though we cannot conclude on appropriateness in this limited audit.

49 ASSESSING EFFECTIVENESS OF AN OUTREACH VISIT PATHWAY FROM ED & REQUIRING FURTHER FOLLOW UP IN THEIR OWN ENVIRONMENT

Background

Falls are a leading cause of presentation to the Emergency Department for older adults. They often are at higher risk of admission to hospital which can lead to other complications of frailty such as development of delirium or deconditioning. The risks of admission were further complicated in the past year due to COVID and its adverse outcomes on our older frail population which further highlighted the need to manage their needs at home where possible.

These above changes have led to FITT reviewing the scope of our outreach service with a focus not just on facilitating discharge but preventing further presentation or deconditioning.

Methods

The aim of the project was to identify appropriate FITT patients to provide an Outreach visit from ED within 72 hours of discharge pending needs. This service was in conjunction with the existing Integrated Care Teams/community services but an outreach visit direct from ED may have been indicated due to; staffing levels, response time, catchment area or existing rapport with the individual patient. This was pending staffing levels with reconfiguration of existing staff to support the outreach therapist.

Appropriate patients included.

-Recurrent falls.

-Unresolved delirium/advanced dementia with ongoing therapy needs.—Bridging gap while awaiting community teams.

-Equipment provision.

Results

Over 10 months 34 outreach visits completed.

Average CFS: 6.

Reasons for: 

12 for safety checks.

15 equipment provision/fitting.

6 mobility reviews.

Onward referrals: 

22 (PCCC OT, Physio, PHN & day hospital & ICT).

Represent within 7 days = 0.

Represent within 30 day = 14 (41%).

Conclusion

The provision of an outreach services allowed a swift therapy review in the patient’s own home & onwards referrals as indicated. Often these patients were likely to be admitted however the outreach provided a safety net to facilitate direct discharge from the ED with no representations within the first 7 days.

50 A COMPARISON OF FRAILTY SCREENING TOOLS WITHIN THE EMERGENCY DEPARTMENT

Background

Increased awareness has been given to the value of identifying frail for risk stratification and to assist in providing frailty attuned care rather than disease specific input.

This increased awareness both nationally and internationally has led to many ED’s introducing the Clinical Frailty Scale (CFS) to triage however as a service we wanted to evaluate which tool would best meet our needs to screen appropriate patients and highlight the current level of frailty within the Emergency Department.

Methods

Over a 3 day period all patients over 75 who present during core hours were screened by a senior FITT member using a number of frailty tools (CFS, THINK frail, InterRai, PRIMSA 7 & compared against our own clinical reasoning if a FITT assessment was indicated).

Results

Total Patient’s over 75 screened by screener & FITT—48.

Average age: 82.

Sex: 51.62% male.

Discharges: 57% d/c’d.

Average CFS (Screener) = 5.

Average CFS (FITT) = 5.

28/48 CFS same = 58.33%.

15/48 CFS differ by 1 point = 31.25%.

Average THINK Frail (Screener): 3. 

Average THINK Frail (FITT): 2. 

17/47 THINK Frail same =36%.

21/47 THINK Frail differ by 1 point = 44%.

80.85% same or within 1 point difference.

Conclusion

The CFS score provided the most consistent when comparing scores by multiple disciplines/grades.

Although the majority of older adults who scored a CFS of 1–3 or deemed non frail at triage were unlikely to benefit from a CGA, those who presented with a new fall often did require FITT input.

This research has led us to move away from our current triage tool of THINK FRAIL to the CFS, whilst continuing to assess any new falls irrespective of score.

Lung megakaryocytes are immune modulatory cells

Although platelets are the cellular mediators of thrombosis, they are also immune cells. Platelets interact both directly and indirectly with immune cells, impacting their activation and differentiation, as well as all phases of the immune response. Megakaryocytes (Mks) are the cell source of circulating platelets, and until recently Mks were typically only considered bone marrow-resident (BM-resident) cells. However, platelet-producing Mks also reside in the lung, and lung Mks express greater levels of immune molecules compared with BM Mks. We therefore sought to define the immune functions of lung Mks. Using single-cell RNA sequencing of BM and lung myeloid-enriched cells, we found that lung Mks, which we term MkL, had gene expression patterns that are similar to antigen-presenting cells. This was confirmed using imaging and conventional flow cytometry. The immune phenotype of Mks was plastic and driven by the tissue immune environment, as evidenced by BM Mks having an MkL-like phenotype under the influence of pathogen receptor challenge and lung-associated immune molecules, such as IL-33. Our in vitro and in vivo assays demonstrated that MkL internalized and processed both antigenic proteins and bacterial pathogens. Furthermore, MkL induced CD4+ T cell activation in an MHC II-dependent manner both in vitro and in vivo. These data indicated that MkL had key immune regulatory roles dictated in part by the tissue environment.

Pre-oxygenation with facemask oxygen vs high-flow nasal oxygen vs high-flow nasal oxygen plus mouthpiece: a randomised controlled trial

High-flow nasal oxygen used before and during apnoea prolongs time to desaturation at induction of anaesthesia. It is unclear how much oxygenation before apnoea prolongs this time. We randomly allocated 84 participants to 3 minutes of pre-oxygenation by one of three methods: 15 l.min^-1 by facemask; 50 l.min^-1 by high-flow nasal cannulae only; or 50 l.min^-1 by high-flow nasal cannulae plus 15 l.min^-1 by mouthpiece. We then anaesthetised and intubated the trachea of 79 participants and waited for oxygen saturation to fall to 92%. Median (IQR [range]) times to desaturate to 92% after pre-oxygenation with facemask oxygen, high-flow nasal oxygen only and high-flow nasal oxygen with mouthpiece, were: 309 (208-417 [107-544]) s; 344 (250-393 [194-585]) s; and 386 (328-498 [182-852]) s, respectively, p = 0.014. Time to desaturation after facemask pre-oxygenation was shorter than after combined nasal and mouthpiece pre-oxygenation, p = 0.006. We could not statistically distinguish high-flow nasal oxygen without mouthpiece from the other two groups for this outcome. Median (IQR [range]) arterial oxygen partial pressure after 3 minutes of pre-oxygenation by facemask, nasal cannulae and nasal cannulae plus mouthpiece, was: 49 (36-61 [24-66]) kPa; 57 (48-62 [30-69]) kPa; and 61 (55-64 [36-72]) kPa, respectively, p = 0.003. Oxygen partial pressure after 3 minutes of pre-oxygenation with nasal and mouthpiece combination was greater than after facemask pre-oxygenation, p = 0.002, and after high-flow nasal oxygen alone, p = 0.016. We did not reject the null hypothesis for the pairwise comparison of facemask pre-oxygenation and high-flow nasal pre-oxygenation, p = 0.14.

The Oral Glucose Tolerance Test-Is It Time for a Change?-A Literature Review with an Emphasis on Pregnancy

Globally, gestational diabetes (GDM) is increasing at an alarming rate. This increase is linked to the rise in obesity rates among women of reproductive age. GDM poses a major global health problem due to the related micro- and macro-vascular complications of subsequent Type 2 diabetes and the impact on the future health of generations through the long-term impact of GDM on both mothers and their infants. Therefore, correctly identifying subjects as having GDM is of utmost importance. The oral glucose tolerance test (OGTT) has been the mainstay for diagnosing gestational diabetes for decades. However, this test is deeply flawed. In this review, we explore a history of the OGTT, its reproducibility and the many factors that can impact its results with an emphasis on pregnancy.

Osteopontin/secreted phosphoprotein-1 behaves as a molecular brake regulating the neuroinflammatory response to chronic viral infection

BACKGROUND

Osteopontin (OPN) as a secreted signaling protein is dramatically induced in response to cellular injury and neurodegeneration. Microglial inflammatory responses in the brain are tightly associated with the neuropathologic hallmarks of neurodegenerative disease, but understanding of the molecular mechanisms remains in several contexts poorly understood.

METHODS

Micro-positron emission tomography (PET) neuroimaging using radioligands to detect increased expression of the translocator protein (TSPO) receptor in the brain is a non-invasive tool used to track neuroinflammation in living mammals.

RESULTS

In humanized, chronically HIV-infected female mice in which OPN expression was knocked down with functional aptamers, uptake of TSPO radioligand DPA-713 was markedly upregulated in the cortex, olfactory bulb, basal forebrain, hypothalamus, and central grey matter compared to controls. Microglia immunoreactive for Iba-1 were more abundant in some HIV-infected mice, but overall, the differences were not significant between groups. TSPO+ microglia were readily detected by immunolabeling of post-mortem brain tissue and unexpectedly, two types of neurons also selectively stained positive for TSPO. The reactive cells were the specialized neurons of the cerebellum, Purkinje cells, and a subset of tyrosine hydroxylase-positive neurons of the substantia nigra.

CONCLUSIONS

In female mice with wild-type levels of osteopontin, increased levels of TSPO ligand uptake in the brain was seen in animals with the highest levels of persistent HIV replication. In contrast, in mice with lower levels of osteopontin, the highest levels of TSPO uptake was seen, in mice with relatively low levels of persistent infection. These findings suggest that osteopontin may act as a molecular brake regulating in the brain, the inflammatory response to HIV infection.

Apnoeic oxygenation in paediatric anaesthesia: a narrative review

Apnoeic oxygenation refers to oxygenation in the absence of any patient or ventilator effort to move the lungs. This phenomenon was first described in humans in the mid-20th century but has seen renewed interest in the last decade following the demonstration of apnoeic oxygenation with low-flow, and subsequently high-flow, nasal oxygen. This narrative review summarises our understanding of apnoeic oxygenation in the paediatric population. We examine the evidence supporting oxygenation via tracheal tube, modified laryngoscopes and nasal cannulae. The evidence for prolongation of safe apnoea time at induction of anaesthesia is also appraised. We explore the capacity for carbon dioxide clearance, flow rate selection with high-flow nasal oxygen and complications associated with the technique. It remains uncertain whether apnoeic oxygenation in paediatric patients results in a meaningful clinical benefit compared with standard care for outcomes such as the number of tracheal intubation attempts or the incidence of hypoxaemia. In particular, the role of apnoeic oxygenation in paediatric difficult airway management is unclear as this has not been the targeted focus of any published research to date.

Serotonergic regulation of insulin secretion

The exact physiological role for the monoamine serotonin (5-HT) in modulation of insulin secretion is yet to be fully understood. Although the presence of this monoamine in islets of Langerhans is well established, it is only with recent advances that the complex signalling network in islets involving 5-HT is being unravelled. With more than fourteen different 5-HT receptors expressed in human islets and receptor-independent mechanisms in insulin-producing β-cells, our understanding of 5-HT's regulation of insulin secretion is increasing. It is now widely accepted that failure of the pancreatic β-cell to release sufficient amounts of insulin is the main cause of type 2 diabetes (T2D), an ongoing global epidemic. In this context, 5-HT signalling may be of importance. In fact, 5-HT may serve an essential role in regulating the release of insulin and glucagon, the two main hormones that control glucose and lipid homoeostasis. In this review, we will discuss past and current understanding of 5-HT's role in the endocrine pancreas.

I Still Haven't Found What I'm Looking For... Bono, Google and Glaucoma Awareness

The effect of celebrity diagnosis on public awareness of health conditions has already been well documented. In October 2014, Bono, the lead singer with U2, revealed publicly for the first time that he has glaucoma. This study aimed to analyze the impact of Bono's announcement on public awareness of glaucoma using Google Search trends as an indicator of public interest in the disease. Google Trends was used to examine Google Search activity for the term 'Glaucoma' between 2009 and 2015 in both Ireland and the United Kingdom. Trend analyses were performed using Microsoft Excel Version 14.3.5. Increased Google Search activity for 'Glaucoma' in October 2014 was found in both Ireland and the United Kingdom. A five-fold increase from the mean Google Search activity for this term was found in Ireland and a two-fold increase from the mean Google Search activity for this term was found in the United Kingdom. No such increase in Google Search activity occurred during each country's 2014 Glaucoma Awareness week. Google Trends is useful in medical research as a means of assessing public awareness of, and/or interest in, health related topics. Current approaches to glaucoma related health promotion in both Ireland and the United Kingdom have failed to yield an increase in on-line Google Search activity. While there was an increase in interest in glaucoma it is unclear whether this led to an increase in health seeking behaviour.

Refractory patella tendinopathy with failed conservative treatment-shock wave or arthroscopy?

AIM

To identify whether the location of refractory patella tendinopathy (PT) has an effect on treatment modality (radial extracorporeal shock wave therapy (rESWT) or arthroscopic debridement).

METHODS

Between 2012 and 2014, 40 patients with PT underwent a magnetic resonance imaging (MRI) scan. This confirmed the diagnosis as either involving the tendon itself (group A, 20) or with retropatella fat pad extension (group B, 20). All patients underwent rESWT. If there was no improvement patients proceeded with surgery in the form of arthroscopic debridement (by senior authors CW and AG). Outcomes were assessed before and after treatment using the Victorian Institute of Sports Assessment-Patella (VISA-P) score.

RESULTS

There were 18 males and 2 females in group A and 15 males and 5 females in group B. The mean age was 41.4 years in group A (23-59) and 34.7 in group B (19-52). Seventeen of 20 in group A reported good or excellent outcomes and did not require surgical intervention (remaining three improved after second course of ESWT). All patients in group B failed to improve with rESWT, resulting in arthroscopic debridement and reported good or excellent outcomes. After 6 months, group A mean VISA-P score increased from 50.2 to 65.0 ( p = 0.01) and group B from 39.6 to 78.4 ( p = <0.001).

CONCLUSION

An MRI should be performed to determine the precise location of tendinosis in patients with refractory PT who fail standard conservative management. If the MRI scan shows intratendon changes only, ESWT should be performed and those with extension into the fat pad should proceed to arthroscopic debridement without rESWT.

High-Density Lipoprotein Proteomic Composition, and not Efflux Capacity, Reflects Differential Modulation of Reverse Cholesterol Transport by Saturated and Monounsaturated Fat Diets

BACKGROUND

Acute inflammation impairs reverse cholesterol transport (RCT) and reduces high-density lipoprotein (HDL) function in vivo. This study hypothesized that obesity-induced inflammation impedes RCT and alters HDL composition, and investigated if dietary replacement of saturated (SFA) for monounsaturated (MUFA) fatty acids modulates RCT.

METHODS AND RESULTS

Macrophage-to-feces RCT, HDL efflux capacity, and HDL proteomic profiling was determined in C57BL/6j mice following 24 weeks on SFA- or MUFA-enriched high-fat diets (HFDs) or low-fat diet. The impact of dietary SFA consumption and insulin resistance on HDL efflux function was also assessed in humans. Both HFDs increased plasma (3)H-cholesterol counts during RCT in vivo and ATP-binding cassette, subfamily A, member 1-independent efflux to plasma ex vivo, effects that were attributable to elevated HDL cholesterol. By contrast, ATP-binding cassette, subfamily A, member 1-dependent efflux was reduced after both HFDs, an effect that was also observed with insulin resistance and high SFA consumption in humans. SFA-HFD impaired liver-to-feces RCT, increased hepatic inflammation, and reduced ABC subfamily G member 5/8 and ABC subfamily B member 11 transporter expression in comparison with low-fat diet, whereas liver-to-feces RCT was preserved after MUFA-HFD. HDL particles were enriched with acute-phase proteins (serum amyloid A, haptoglobin, and hemopexin) and depleted of paraoxonase-1 after SFA-HFD in comparison with MUFA-HFD.

CONCLUSIONS

Ex vivo efflux assays validated increased macrophage-to-plasma RCT in vivo after both HFDs but failed to capture differential modulation of hepatic cholesterol trafficking. By contrast, proteomics revealed the association of hepatic-derived inflammatory proteins on HDL after SFA-HFD in comparison with MUFA-HFD, which reflected differential hepatic cholesterol trafficking between groups. Acute-phase protein levels on HDL may serve as novel biomarkers of impaired liver-to-feces RCT in vivo.