Individual level changes in body weight among Finnish adult population during the COVID-19 pandemic

Background

The indirect effects of COVID-19 pandemic are yet undefined, but behavioral and lifestyle consequences of the containment measures may cause weight changes, with different concerns across demographic groups. Our aim was to determine weight changes based on the data collected from same individuals before (2017) and during (2020) the COVID-19 pandemic.

Methods

Participants aged 25+ years, from the nationally representative FinHealth 2017 Study and its follow-up survey in autumn 2020, with information on self-reported weight in both years were included (n = 4770). Weight maintenance was defined as < ± 5% change in body weight for each individual (i.e. weight loss = ≥5% loss; weight gain = ≥5% gain). Prevalence was estimated using inverse probability weights, acknowledging sampling design and non-response.

Results

Overall, two thirds of the population maintained weight during follow-up, but prevalence rates for weight change differed by age and sex. Prevalence of weight loss was highest among 70+ year olds (22% in men, 95% confidence interval (CI) 17-27; 26% in women, 95% CI 22-30), while they rarely experienced weight gain. Among 50-69 year olds weight gain was as common as loss, being around 15% for both indicators and sexes. Prevalence of weight gain was highest among 25-49 year olds (20% in men, 95% CI 18-23; 36% in women, 95% CI 33-40). Men with lowest education had gained weight more often (24%, 95% CI 19-30) than those with middle (16%, 95% CI 14-19) or high (14%, 95% CI 12-16) education, while for women no differences emerged, the prevalence ranging between 20-24% by education.

Conclusions

The weight loss among 70+ year olds seems worrying, but might be age related. Moreover, younger women and men with low education gained weight, groups known to be vulnerable for weight gain. Further analyses are required to evaluate whether containment measures related to COVID-19 pandemic have caused additional change compared to ageing and time related change.

Key messages

Few weight changes were observed in the Finnish adult population. As weight gain/loss may take longer time to develop, further studies are needed to address the long term effects of COVID-19 pandemic.

To avoid increasing health inequity after pandemic, public health promotion should stress obesity prevention among young women plus men with low education. Weight loss is a concern among the elderly.

Individual level lifestyle changes during the COVID-19 pandemic – A Finnish population-based study

Background

The COVID-19 pandemic containment measures may affect lifestyle. We aimed to examine the changes in key lifestyle factors based on the data from same individuals before (2017) and during (2020) the COVID-19 pandemic.

Methods

The study is based on the FinHealth 2017 Study representing the Finnish adult population, and its follow-up questionnaire conducted in autumn 2020. A total of 4814 individuals aged 25 and older at baseline answered the same questions on lifestyle in both years. Regular leisure-time physical activity (LPA), daily use of vegetables and/or fruits, experience of adequate sleep, daily use of nicotine products and high-risk use of alcohol, were dichotomized (yes/no) for the analysis. Weighted prevalence (no/favorable/unfavorable change) for three age groups (25-49, 50-69, 70+ years) was analyzed using multinomial logistic regression, sampling design and non-response acknowledged.

Results

In general, the prevalence of total changes observed varied 6 − 27% between lifestyle factors. The changes were both unfavorable and favorable for health. About 14% (95% CI 11,17) and 12% (95% CI 9,16) of older women and men, respectively, had LPA in 2017 but not in 2020. Corresponding prevalence for favorable change in LPA were smaller, 6% (95% CI 4,8) in older women and 7% (95% CI 4,9) in men. In older women, the results concerning daily use of vegetables and fruits were parallel. In contrast, in older women the changes observed in the experience of adequate sleep were mainly favorable. In all age groups, high-risk use of alcohol slightly decreased especially in men but the changes in use of nicotine products were minor.

Conclusions

The results highlight unfavorable changes in LPA and vegetable consumption especially in older women during the COVID-19 pandemic. Part of the unfavorable changes may be explained by aging, but the pandemic containment measures may have accelerated them indicating the need for health promotion actions among the elderly.

Key messages

The lifestyle changes observed during COVID-19 pandemic were complex, varying by sex and age groups and being both favorable and unfavorable for health.

Special attention should be given to promotion of physical activity in the elderly during and after the pandemic.

A systems biology approach to understand gut microbiota and host metabolism in morbid obesity: design of the BARIA Longitudinal Cohort Study

INTRODUCTION

Prevalence of obesity and associated diseases, including type 2 diabetes mellitus, dyslipidaemia and non-alcoholic fatty liver disease (NAFLD), are increasing. Underlying mechanisms, especially in humans, are unclear. Bariatric surgery provides the unique opportunity to obtain biopsies and portal vein blood-samples.

METHODS

The BARIA Study aims to assess how microbiota and their metabolites affect transcription in key tissues and clinical outcome in obese subjects and how baseline anthropometric and metabolic characteristics determine weight loss and glucose homeostasis after bariatric surgery. We phenotype patients undergoing bariatric surgery (predominantly laparoscopic Roux-en-Y gastric bypass), before weight loss, with biometrics, dietary and psychological questionnaires, mixed meal test (MMT) and collect fecal-samples and intra-operative biopsies from liver, adipose tissues and jejunum. We aim to include 1500 patients. A subset (approximately 25%) will undergo intra-operative portal vein blood-sampling. Fecal-samples are analyzed with shotgun metagenomics and targeted metabolomics, fasted and postprandial plasma-samples are subjected to metabolomics, and RNA is extracted from the tissues for RNAseq-analyses. Data will be integrated using state-of-the-art neuronal networks and metabolic modeling. Patient follow-up will be ten years.

RESULTS

Preoperative MMT of 170 patients were analysed and clear differences were observed in glucose homeostasis between individuals. Repeated MMT in 10 patients showed satisfactory intra-individual reproducibility, with differences in plasma glucose, insulin and triglycerides within 20% of the mean difference.

CONCLUSION

The BARIA study can add more understanding in how gut-microbiota affect metabolism, especially with regard to obesity, glucose metabolism and NAFLD. Identification of key factors may provide diagnostic and therapeutic leads to control the obesity-associated disease epidemic.

Every fifth child and adolescent in Finland is overweight

Background

Globally, the prevalence of child and adolescent overweight and obesity has increased during the preceding decades leading to childhood obesity being acknowledged as one of the most significant health hazards of the 21st century. Yet, in Finland comprehensive and up-to-date data on the prevalence of overweight and obesity among children and adolescents have been lacking. The aim of this study was to examine the prevalence of overweight and obesity among 2-16-year-old children and adolescents living in Finland in 2018.

Methods

The study was based on height and weight measurements taken at child welfare clinics and school health services between 5.7.2017 and 5.4.2019 (n = 375,561). The data was collected from the Register of Primary Health Care Visits. Child and adolescent overweight and obesity were defined according to international IOTF BMI criteria (age- and sex-specific BMI cut-off points corresponding to adults' cut-off points of 25 kg/m2 for overweight and 30 kg/m2 for obesity) and reported by age group and sex.

Results

In 2018, nearly 20% of boys and girls aged 2-16 years were classified as at least overweight while the prevalence of obesity was 5% among both sexes. The prevalence of overweight in pre-school-aged children (2-6 years) was 12% in boys and 15% in girls, in primary school-aged children (7-12 years) 23% in boys and 22% in girls and in adolescents (13-16 years) 25% in boys and 23% in girls.

Conclusions

In 2018, every fifth child and adolescent in Finland was classified as either overweight or obese. The prevalence of overweight and obesity appears to increase with age in both genders.

Key messages

Childhood and adolescent overweight and obesity were comparatively common in Finland in 2018. As overweight and obesity often persist into adulthood, multi-professional interventions targeted at prevention and early detection are essential.

Early risk factors of obesity in 5-year-old boys and girls in Finland

Background

Several potential early-life risk factors for childhood overweight and obesity have been identified. Yet results regarding early risk factors and obesity (BMI-for-age ≥30 kg/m2) at pre-school age are mixed and boys and girls have rarely been studied separately. Our aim was to study whether pre- and perinatal factors predict obesity in 5-year-old boys and girls.

Methods

National register data was used to identify children born in Finland between 2007 and 2014 with data available on pre- and perinatal factors as well as on height and weight at 5 years of age (n = 131,818). Multivariable logistic regression models were used to analyze sex-specific associations between pre- and perinatal factors (e.g. maternal age, parity, pre-pregnancy BMI, smoking, diabetes, delivery method, gestational-age-adjusted birth weight) and offspring obesity.

Results

Five percent of boys (n = 3,551) and 3% of girls (n = 1,949) had obesity. Adjusted for potential confounders, the strongest predictor of subsequent obesity at 5 years of age was severe maternal obesity (BMI ≥35 kg/m2) (boys: OR 6.5, 95% CI 5.8-7.4; girls: OR 7.5, 95% CI 6.4-8.8) followed by maternal obesity (BMI 30.0-34.9 kg/m²) (boys: OR 3.9, 95% CI 3.5-4.4; girls: OR 5.5, 95% CI 4.8-6.2) and maternal overweight (BMI 25.0-29.9 kg/m²) (boys: OR 2.3, 95% CI 2.1-2.5; girls: OR 2.6, 95% CI 2.3-3.0). Other factors associated with child obesity were maternal smoking during pregnancy (boys: OR 1.8, 95% CI 1.6-1.9; girls: OR 2.0, 95% CI 1.8-2.2) and being born large for gestational age (boys: OR 1.9, 95% CI 1.6-2.2; girls: OR 2.1, 95% CI 1.8-2.6).

Conclusions

These findings indicate that childhood obesity may partly originate before conception, gestation and birth. As prevention of obesity may be economically and socially more sustainable than treatment of its consequences, emphasis should be put on early interventions. Particular attention should be paid on preventing maternal overweight and obesity.

Key messages

Maternal obesity was the strongest predictor of child obesity at 5 years of age. Investing in maternal health from as early as before conception may help prevent offspring obesity.

Adults with young children are more satisfied with their lives than other adults

Background

Limited research exists on the differences in the wellbeing of adults with young children and those without. The aim of this study was to compare the well-being of adults with and without young children.

Methods

The study is based on the FinHealth 2017 Study of a nationally representative sample on adults aged 18-50-years (n = 4764, 58% participated). Information on wellbeing was collected through self-administered questionnaires. Adults living in a household with young children (under 7-years old, n = 762) were compared to adults living in a household without young children (n = 1864). Inverse probability weights were used in the analysis to correct for the effects of non-response and different sampling probabilities.

Results

Nearly 90 % of adults with young children rated their quality of life as good or very good and were more satisfied with their family life (women 84% vs. 76%, men 87 % vs. 78%) and life achievements (women 82% vs. 69%, men 78% vs. 58%) compared to other adults. No difference was observed in satisfaction with the financial situation. Differences in the experience of psychological distress (Mental Health Inventory, MHI-5 score ≤52) were statistically insignificant. 6% of women and 7% of men with young children experienced psychological distress while the equivalent percentage of other adults was 9% in both sexes. Differences in symptoms of depression (Beck Depression Inventory, 6 item score &gt;4) were also statistically insignificant, although the prevalence was somewhat lower for those with children (women 12% vs. 15%, men 6% vs. 12%). Adults with young children reported sufficient sleep less often compared to other adults (women 64% vs. 76%, men 67% vs. 77%).

Conclusions

Most parents of young children have a good quality of life and are satisfied with their life. Getting sufficient sleep is one of the main challenges of adults with young children.

Key messages

Adults with young children are more satisfied with their life compared to other adults. There is still a need for holistic lifestyle guidance, especially to promote mental well-being and sufficient sleep of adults with young children.

FinChildren Register: National monitoring of child and adolescent health and well-being in Finland

Background

Comprehensive and up-to-date data on child and adolescent health and well-being is essential for monitoring, service development and decision-making. Although nearly all children and adolescents in Finland attend annual health check-ups at child health clinics and school healthcare, the utilization of collected data has been limited. The objective is to produce timely and representative information on the health and well-being of children, adolescents and their families based on routinely collected register data.

Methods

Data are collected from health check-ups performed at child health clinics and school health care. Recorded data are transferred through patient information systems to the Register of Primary Health Care Visits. The data can be linked to other national registers with personal identity codes. The first phase aimed to evaluate the availability and quality of register-based data through inspection of data coverage on height and weight data of children and adolescents aged 2 to 16 years.

Results

In 2018, the coverage of height and weight data ranged from 0% to 100% between municipalities depending on age group. Results were published through an interactive map application and municipality-specific summaries by gender and age group at national and municipality levels. The data enabled reporting up-to-date results on the prevalence of child and adolescent overweight and obesity in Finland.

Conclusions

Data from health check-ups form an excellent database for monitoring child and adolescent health and well-being in Finland. The challenges of utilizing register data are mainly caused by difficulties in data transfer from patient information systems resulting in insufficient data coverage. Publishing local-level reports on data coverage as well as on the results promotes data availability and quality while enabling evaluation of actions needed for promoting the health and welfare of children and their families.

Lifestyle of young adults – changes and accumulation

Background

Young adulthood is a pivotal period for many lifestyle factors becoming established and later affecting health. However, current knowledge on key lifestyle factors among young adults is limited. This study aimed to examine the lifestyle of Finnish young adults and the changes in their lifestyle between the years 2000 and 2017. Further, the accumulation of health promoting and endangering lifestyle factors was evaluated.

Methods

The study is based on nationally representative data on young adults (aged 18 − 29 years) from the Health 2000 Survey (n = 1894; 90% participated) and the FinHealth 2017 Study (n = 1162; 54% participated). Lifestyle factors were assessed in the interview and by questionnaires. The five key lifestyle factors (use of vegetables, smoking, physical activity, sleep and alcohol consumption) were dichotomized for the evaluation of the accumulation. Weighted prevalences were analyzed by logistic regression taking into account the sampling design and non-response.

Results

In 2017, 32% (95% CI 25, 41) and 52% (95% CI 45, 60) of young men and women used fresh vegetables daily, respectively. In men, the prevalence had decreased in 2017 compared to 2000 (p &lt; 0.01). The prevalence of daily smoking had decreased (p &lt; 0.01) being 11% in both sexes in 2017. In men, the prevalence of the daily use of snuff had increased from 3% (95% CI 2, 5) to 8% (95% CI 5, 14) in 2017 (p = 0.01). In both years, three out of four were physically active at leisure-time and nine out of ten slept at least six hours per day. In 2017, half of the young adults reached 4 to 5 (maximum) health promoting factors whereas 17% (95% CI 11, 24) of men and 12% (95% CI 8, 18) of women reached only 0 to 2.

Conclusions

There have been both favourable and unfavourable changes in the lifestyle of young adults during the last decades. The accumulation of health promoting and endangering lifestyle factors was observed indicating needs to versatilely prevent risks for major public health problems.

Key messages

Many health-endangering lifestyle factors are comparatively common in young adults. It is important to prevent the accumulation of health-endangering lifestyle factors in young adulthood to lower the risks for major public health problems in future.

Evaluation of drug permeability calculation based on luminal disappearance and plasma appearance in the rat single-pass intestinal perfusion model

The rat single-pass intestinal perfusion (SPIP) model is commonly used to investigate gastrointestinal physiology and membrane drug transport. The SPIP model can be used with the intestinal segment inside or outside the abdomen. The rats can also be treated with parecoxib, a selective cycloxygenase-2 inhibitor that has been shown to affect some intestinal functions following abdominal surgery, such as motility, epithelial permeability, fluid flux and ion transport. However, the impact of extra-abdominal placement of the intestinal segment in combination with parecoxib on intestinal drug transport has not been investigated. There is also uncertainty how well intestinal permeability determinations based on luminal drug disappearance and plasma appearance correlate in the rat SPIP model. The main objective of this rat in vivo study was to investigate the effect of intra- vs. extra-abdominal SPIP, with and without, pretreatment with parecoxib. The effect was evaluated by determining the difference in blood-to-lumen ⁵¹Cr-EDTA clearance, lumen-to-blood permeability of a cassette-dose of four model compounds (atenolol, enalaprilat, ketoprofen, and metoprolol), and water flux. The second objective was to compare the jejunal permeability values of the model drugs when determined based on luminal disappearance or plasma appearance. The study showed that the placement of the perfused jejunal segment, or the treatment with parecoxib, had minimal effects on membrane permeability and water flux. It was also shown that intestinal permeability of low permeability compounds should be determined on the basis of data from plasma appearance rather than luminal disappearance. If permeability is calculated on the basis of luminal disappearance, it should preferably include negative values to increase the accuracy in the determinations.

Time-dependent effects on small intestinal transport by absorption-modifying excipients

The relevance of the rat single-pass intestinal perfusion model for investigating in vivo time-dependent effects of absorption-modifying excipients (AMEs) is not fully established. Therefore, the dynamic effect and recovery of the intestinal mucosa was evaluated based on the lumen-to-blood flux (J_abs) of six model compounds, and the blood-to-lumen clearance of ⁵¹Cr-EDTA (CL_Cr), during and after 15- and 60-min mucosal exposure of the AMEs, sodium dodecyl sulfate (SDS) and chitosan, in separate experiments. The contribution of enteric neurons on the effect of SDS and chitosan was also evaluated by luminal coadministration of the nicotinic receptor antagonist, mecamylamine. The increases in J_abs and CL_Cr (maximum and total) during the perfusion experiments were dependent on exposure time (15 and 60 min), and the concentration of SDS, but not chitosan. The increases in J_abs and CL_Cr following the 15-min intestinal exposure of both SDS and chitosan were greater than those reported from an in vivo rat intraintestinal bolus model. However, the effect in the bolus model could be predicted from the increase of J_abs at the end of the 15-min exposure period, where a six-fold increase in J_abs was required for a corresponding effect in the in vivo bolus model. This illustrates that a rapid and robust effect of the AME is crucial to increase the in vivo intestinal absorption rate before the yet unabsorbed drug in lumen has been transported distally in the intestine. Further, the recovery of the intestinal mucosa was complete following 15-min exposures of SDS and chitosan, but it only recovered 50% after the 60-min intestinal exposures. Our study also showed that the luminal exposure of AMEs affected the absorptive model drug transport more than the excretion of ⁵¹Cr-EDTA, as J_abs for the drugs was more sensitive than CL_Cr at detecting dynamic mucosal AME effects, such as response rate and recovery. Finally, there appears to be no nicotinergic neural contribution to the absorption-enhancing effect of SDS and chitosan, as luminal administration of 0.1 mM mecamylamine had no effect.

Acoustic formation of multicellular tumor spheroids enabling on-chip functional and structural imaging

Understanding the complex 3D tumor microenvironment is important in cancer research. This microenvironment can be modelled in vitro by culturing multicellular tumor spheroids (MCTS). Key challenges when using MCTS in applications such as high-throughput drug screening are overcoming imaging and analytical issues encountered during functional and structural investigations. To address these challenges, we use an ultrasonic standing wave (USW) based MCTS culture platform for parallel formation, staining and imaging of 100 whole MCTS. A protein repellent amphiphilic polymer coating enables flexible production of high quality and unanchored MCTS. This enables high-content multimode analysis based on flow cytometry and in situ optical microscopy. We use HepG2 hepatocellular carcinoma, A498 and ACHN renal carcinoma, and LUTC-2 thyroid carcinoma cell lines to demonstrate (i) the importance of the ultrasound-coating combination, (ii) bright field image based automatic characterization of MTCS, (iii) detailed deep tissue confocal imaging of whole MCTS mounted in a refractive index matching solution, and (iv) single cell functional analysis through flow cytometry of single cell suspensions of disintegrated MTCS. The USW MCTS culture platform is customizable and holds great potential for detailed multimode MCTS analysis in a high-content manner.

Fecal and Mucosa-Associated Intestinal Microbiota in Patients with Diarrhea-Predominant Irritable Bowel Syndrome

BACKGROUND

Irritable bowel syndrome (IBS) has been associated with changes in the intestinal microbiota. Only a few studies have explored differences in the mucosa-associated microbiota between IBS patients and healthy controls (HC).

AIMS

To characterize and compare the microbiota in mucosal and fecal samples from carefully selected patients with IBS-D and HC.

METHODS

The cohort was composed of 23 diarrhea-predominant IBS (IBS-D) patients and 24 HC. Fresh stool samples were collected from participants prior to the collection of colonic mucosal samples from an unprepped bowel. After DNA extraction, 16S rRNA genes were sequenced by 454 pyrosequencing and analyzed using the QIIME pipeline.

RESULTS

The fecal microbiota (luminal niche) of IBS-D patients was found to have reduced enteric richness compared to HC (P < 0.05), whereas no differences were observed between the two groups within the mucosal microbiota. Within the luminal niche, the relative proportions of Faecalibacterium genus were found to be lower in IBS-D than in HC and the Dorea genus was higher in IBS-D. None of the taxa proportions were significantly different in IBS-D patients versus HC using an FDR of ≤ 0.1 when analyzing samples that appeared in > 25% samples of either niche.

CONCLUSION

Fecal and mucosal microbiota of IBS-D patients and HC are very similar and are not sufficient to explain the reported altered physiology and symptomatology of IBS-D. Future studies should investigate intestinal microbiome-dependent functional activity in addition to the fecal and mucosal-associated microbial composition.

The effects of three absorption-modifying critical excipients on the in vivo intestinal absorption of six model compounds in rats and dogs

Pharmaceutical excipients that may affect gastrointestinal (GI) drug absorption are called critical pharmaceutical excipients, or absorption-modifying excipients (AMEs) if they act by altering the integrity of the intestinal epithelial cell membrane. Some of these excipients increase intestinal permeability, and subsequently the absorption and bioavailability of the drug. This could have implications for both the assessment of bioequivalence and the efficacy of the absorption-enhancing drug delivery system. The absorption-enhancing effects of AMEs with different mechanisms (chitosan, sodium caprate, sodium dodecyl sulfate (SDS)) have previously been evaluated in the rat single-pass intestinal perfusion (SPIP) model. However, it remains unclear whether these SPIP data are predictive in a more in vivo like model. The same excipients were in this study evaluated in rat and dog intraintestinal bolus models. SDS and chitosan did exert an absorption-enhancing effect in both bolus models, but the effect was substantially lower than those observed in the rat SPIP model. This illustrates the complexity of the AME effects, and indicates that additional GI physiological factors need to be considered in their evaluation. We therefore recommend that AME evaluations obtained in transit-independent, preclinical permeability models (e.g. Ussing, SPIP) should be verified in animal models better able to predict in vivo relevant GI effects, at multiple excipient concentrations.

Allopregnanolone involvement in feeding regulation, overeating and obesity

Obesity is strongly associated with ill health, primarily caused by consumption of excessive calories, and promoted (inter alia) by gamma-amino-butyric-acid (GABA) stimulating food intake by activating GABA_A receptors (primarily with α3 and α2 subunits) in the hypothalamic arcuate nucleus and paraventricular nucleus. Allopregnanolone is a potent positive GABA_A receptor modulating steroid (GAMS). As reviewed here, elevated allopregnanolone levels are associated with increases in food intake, preferences for energy-rich food, and obesity in humans and other mammals. In women with polycystic ovarian disease, high serum allopregnanolone concentrations are linked to uncontrolled eating, and perturbed sensitivity to allopregnanolone. Increases in weight during pregnancy also correlate with increases in allopregnanolone levels. Moreover, Prader-Willis syndrome is associated with massive overeating, absence of a GABA_A receptor (with compensatory >12-, >5- and >1.5-fold increases in α4, γ2, and α1, α3 subunits), and increases in the α4, βx, δ receptor subtype, which is highly sensitive to allopregnanolone. GABA and positive GABA-A receptor modulating steroids like allopregnanolone stimulates food intake and weight gain.

Cartilage oligomeric matrix protein neoepitope in the synovial fluid of horses with acute lameness: A new biomarker for the early stages of osteoarthritis

Background

Clinical tools to diagnose the early changes of osteoarthritis (OA) that occur in the articular cartilage are lacking.

Objectives

We sought to identify and quantify a novel cartilage oligomeric matrix protein (COMP) neoepitope in the synovial fluid from the joints of healthy horses and those with different stages of OA.

Study design

In vitro quantitative proteomics and assay development with application in synovial fluids samples obtained from biobanks of well‐characterised horses.

Methods

Articular cartilage explants were incubated with or without interleukin‐1β for 25 days. Media were analysed via quantitative proteomics. Synovial fluid was obtained from either normal joints (n = 15) or joints causing lameness (n = 17) or with structural OA lesions (n = 7) and analysed for concentrations of the COMP neoepitope using a custom‐developed inhibition enzyme‐linked immunosorbent assay (ELISA). Explants were immunostained with polyclonal antibodies against COMP and the COMP neoepitopes.

Results

Semitryptic COMP peptides were identified and quantified in cell culture media from cartilage explants. A rabbit polyclonal antibody was raised against the neoepitope of the N‐terminal portion of one COMP fragment (sequence SGPTHEGVC). An inhibition ELISA was developed to quantify the COMP neoepitope in synovial fluid. The mean concentration of the COMP neoepitope significantly increased in the synovial fluid from the joints responsible for acute lameness compared with normal joints and the joints of chronically lame horses and in joints with chronic structural OA. Immunolabelling for the COMP neoepitope revealed a pericellular staining in the interleukin‐1β‐stimulated explants.

Main limitations

The ELISA is based on polyclonal antisera rather than a monoclonal antibody.

Conclusions

The increase in the COMP neoepitope in the synovial fluid from horses with acute lameness suggests that this neoepitope has the potential to be a unique candidate biomarker for the early molecular changes in articular cartilage associated with OA.

Systems Pharmacology Approach for Prediction of Pulmonary and Systemic Pharmacokinetics and Receptor Occupancy of Inhaled Drugs

Pulmonary drug disposition after inhalation is complex involving mechanisms, such as regional drug deposition, dissolution, and mucociliary clearance. This study aimed to develop a systems pharmacology approach to mechanistically describe lung disposition in rats and thereby provide an integrated understanding of the system. When drug‐ and formulation‐specific properties for the poorly soluble drug fluticasone propionate were fed into the model, it proved predictive of the pharmacokinetics and receptor occupancy after intravenous administration and nose‐only inhalation. As the model clearly distinguishes among drug‐specific, formulation‐specific, and system‐specific properties, it was possible to identify key determinants of pulmonary selectivity of receptor occupancy of inhaled drugs: slow particle dissolution and slow drug‐receptor dissociation. Hence, it enables assessment of factors for lung targeting, including molecular properties, formulation, as well as the physiology of the animal species, thereby providing a general framework for rational drug design and facilitated translation of lung targeting from animal to man.

Cost-effectiveness of Screening for Abdominal Aortic Aneurysm in Combination with Medical Intervention in Patients with Small Aneurysms

OBJECTIVES

Screening for abdominal aortic aneurysm (AAA) among 65 year old men has been proven cost-effective, but nowadays is conducted partly under new conditions. The prevalence of AAA has decreased, and endovascular aneurysm repair (EVAR) has become the predominant surgical method for AAA repair in many centers. At the Malmö Vascular Center pharmacological secondary prevention with statins, antiplatelet therapy, and blood pressure reduction is initiated and given to all patients with AAA. This study evaluates the cost-effectiveness of AAA screening under the above mentioned conditions.

METHODS

This was a Markov cohort simulation. A total of 4,300 65 year old men were invited to annual AAA screening; the attendance rate was 78.3% and AAA prevalence was 1.8%. A Markov model with 11 health states was used to evaluate cost-effectiveness of AAA screening. Background data on rupture risks, costs, and effectiveness of surgical interventions were obtained from the participating unit, the national Swedvasc Registry, and from the scientific literature.

RESULTS

The additional costs of the screening strategy compared with no screening were €169 per person and year. The incremental health gain per subject in the screened cohort was 0.011 additional quality adjusted life years (QALYs), corresponding to an incremental cost-effectiveness ratio (ICER) of €15710 per QALY. Assuming a 10% reduction of all cause mortality, the incremental cost of screening was €175 per person and year. The gain per subject in the screened cohort was 0.013 additional QALYs, corresponding to an ICER of €13922 per QALY CONCLUSIONS: AAA screening remains cost-effective according to both the Swedish recommendations and the UK National Institute for Health and Care Excellence recommendations in the new era of lower AAA prevalence, EVAR as the predominant surgical method, and secondary prevention for all AAA patients.

Cripto-1 vaccination elicits protective immunity against metastatic melanoma

Metastatic melanoma is a fatal disease that responds poorly to classical treatments but can be targeted by T cell-based immunotherapy. Cancer vaccines have the potential to generate long-lasting cytotoxic CD8⁺ T cell responses able to eradicate established and disseminated tumors. Vaccination against antigens expressed by tumor cells with enhanced metastatic potential represents a highly attractive strategy to efficiently target deadly metastatic disease. Cripto-1 is frequently over-expressed in human carcinomas and melanomas, but is expressed only at low levels on normal differentiated tissues. Cripto-1 is particularly upregulated in cancer-initiating cells and is involved in cellular processes such as cell migration, invasion and epithelial–mesenchymal transition, which are hallmarks of aggressive cancer cells able to initiate metastatic disease. Here, we explored the potential of Cripto-1 vaccination to target metastatic melanoma in a preclinical model. Cripto-1 was overexpressed in highly metastatic B16F10 cells as compared to poorly metastatic B16F1 cells. Moreover, B16F10 cells grown in sphere conditions to enrich for cancer stem cells (CSC) progressively upregulated cripto1 expression. Vaccination of C57Bl/6 mice with a DNA vaccine encoding mouse Cripto-1 elicited a readily detectable/strong cytotoxic CD8⁺ T cell response specific for a H-2 Kb-restricted epitope identified based on its ability to bind H-2^b molecules. Remarkably, Cripto-1 vaccination elicited a protective response against lung metastasis and subcutaneous challenges with highly metastatic B16F10 melanoma cells. Our data indicate that vaccination against Cripto-1 represents a novel strategy to be tested in the clinic.

The Shape of the Dose-Response Relationship between Sugars and Caries in Adults

Dental caries is considered a diet-mediated disease, as sugars are essential in the caries process. However, some gaps in knowledge about the sugars-caries relationship still need addressing. This longitudinal study aimed to explore 1) the shape of the dose-response association between sugars intake and caries in adults, 2) the relative contribution of frequency and amount of sugars intake to caries levels, and 3) whether the association between sugars intake and caries varies by exposure to fluoride toothpaste. We used data from 1,702 dentate adults who participated in at least 2 of 3 surveys in Finland (Health 2000, 2004/05 Follow-up Study of Adults' Oral Health, and Health 2011). Frequency and amount of sugars intake were measured with a validated food frequency questionnaire. The DMFT index was the repeated outcome measure. Data were analyzed with fractional polynomials and linear mixed effects models. None of the 43 fractional polynomials tested provided a better fit to the data than the simpler linear model. In a mutually adjusted linear mixed effects model, the amount of, but not the frequency of, sugars intake was significantly associated with DMFT throughout the follow-up period. Furthermore, the longitudinal association between amount of sugars intake and DMFT was weaker in adults who used fluoride toothpaste daily than in those using it less often than daily. The findings of this longitudinal study among Finnish adults suggest a linear dose-response relationship between sugars and caries, with amount of intake being more important than frequency of ingestion. Also, daily use of fluoride toothpaste reduced but did not eliminate the association between amount of sugars intake and dental caries.

Prenatal and post-natal exposure to antibiotics and risk of asthma in childhood

BACKGROUND

Evidence on the association between post-natal exposure to antibiotics and the development of asthma is extensive, but inconsistent and even less is known about prenatal exposure.

OBJECTIVE

The aim of this study was to examine the associations between prenatal and post-natal exposure to different antibiotics and the risk of childhood asthma in a population- and register-based nested case-control study.

METHODS

All children who were born in 1996-2004 in Finland and diagnosed with asthma by 2006 were identified from a national health register. For each case, one matched control was selected. Information on asthma diagnoses, purchased anti-asthmatic drugs and antibiotics as well as putative confounders was obtained from national health registries. The associations were analysed using conditional logistic regression for children diagnosed at the age of 3 years or later (n = 6 690 case-control pairs).

RESULTS

Maternal use of any antibiotics during pregnancy was associated with an increased risk of asthma in the offspring [adjusted odds ratio (OR) = 1.31 (95% confidence interval (CI): 1.21-1.42)]. Several maternal specific antibiotics were associated with the risk of asthma, and the strongest association was observed for cephalosporins [OR = 1.46 (95% CI 1.30-1.64)]. Child's use of antibiotics during the first year of life was associated with an increased risk of asthma [OR = 1.60 (95% CI 1.48-1.73)]. Child's use of cephalosporins [OR = 1.79 (95% CI 1.59-2.01)], sulphonamides and trimethoprim [OR = 1.65 (95% CI 1.34-2.02)], macrolides [OR = 1.61 (95% CI 1.46-1.78)] and amoxicillin [OR = 1.46 (95% CI 1.35-1.58)] was associated with an increased risk of asthma.

CONCLUSIONS AND CLINICAL RELEVANCE

Both prenatal and post-natal exposure to antibiotics was associated with an increased risk of asthma. The potential role of adverse effects of antibiotics on the gut microbiota and the development of asthma should be further explored.

Genetic contributions to variation in general cognitive function: a meta-analysis of genome-wide association studies in the CHARGE consortium (N=53949)

General cognitive function is substantially heritable across the human life course from adolescence to old age. We investigated the genetic contribution to variation in this important, health- and well-being-related trait in middle-aged and older adults. We conducted a meta-analysis of genome-wide association studies of 31 cohorts (N=53,949) in which the participants had undertaken multiple, diverse cognitive tests. A general cognitive function phenotype was tested for, and created in each cohort by principal component analysis. We report 13 genome-wide significant single-nucleotide polymorphism (SNP) associations in three genomic regions, 6q16.1, 14q12 and 19q13.32 (best SNP and closest gene, respectively: rs10457441, P=3.93 × 10(-9), MIR2113; rs17522122, P=2.55 × 10(-8), AKAP6; rs10119, P=5.67 × 10(-9), APOE/TOMM40). We report one gene-based significant association with the HMGN1 gene located on chromosome 21 (P=1 × 10(-6)). These genes have previously been associated with neuropsychiatric phenotypes. Meta-analysis results are consistent with a polygenic model of inheritance. To estimate SNP-based heritability, the genome-wide complex trait analysis procedure was applied to two large cohorts, the Atherosclerosis Risk in Communities Study (N=6617) and the Health and Retirement Study (N=5976). The proportion of phenotypic variation accounted for by all genotyped common SNPs was 29% (s.e.=5%) and 28% (s.e.=7%), respectively. Using polygenic prediction analysis, ~1.2% of the variance in general cognitive function was predicted in the Generation Scotland cohort (N=5487; P=1.5 × 10(-17)). In hypothesis-driven tests, there was significant association between general cognitive function and four genes previously associated with Alzheimer's disease: TOMM40, APOE, ABCG1 and MEF2C.

Neuropsychological Aspects of Driving After Brain Lesion: Simulator Study and On-Road Driving

Twenty-nine patients with brain lesion and 29 matched controls participated in the study. The patients were socially well recovered with a high rate of employment. Compared with the controls, they performed significantly worse on a neuropsychological test battery, especially on executive and cognitive functions. Patients drove as well as controls in predictable situations in the advanced simulator used. In unpredictable situations, they demonstrated longer reaction times and safety margins, as well as difficulties in allocating processing resources to a secondary task. The patients showed significantly less attention, worse traffic behavior, and less risk awareness when driving in real traffic. Forty-one percent of the patients did not pass the driving test. The neuropsychological test battery was factor analyzed into four factors: executive capacity, cognitive capacity, automatic attentional capacity, and simple perceptual-motor capacity. The second factor was the mast significant with a simultaneous capacity test predicting driving performance with 78% confidence.

Natural killer cell immunotherapy for cancer: a new hope

Recently there has been a substantial gain in our understanding of the role NK-cells play in mediating innate host immune responses. Although NK cells have long been known to mediate antigen independent tumor cytotoxicity, the therapeutic potential of NK cell-based immunotherapy has yet to be realized. Manipulating the balance between inhibitory and activating NK receptor signals, sensitization of tumor target cells to NK cell-mediated apoptosis, and recent discoveries in NK-cell receptor biology have fueled translational research that has led to clinical trials investigating a number of novel methods to potentiate NK cytotoxicity against human malignancies.

Mutagen specificity for 71 lines resistant to barley powdery mildew race D1 and isolated in four highbred barley varieties

A search for practically valuable mutant genes conferring resistance to barley powdery mildew applied a screening system where four commercial varieties of barley without known genes for resistance were tested to the successful mildew race D1. Ionizing radiations and chemicals were used as mutagens. Among the 71 resistant lines isolated, 28 were recessive and belonging to locus ml-o, and 43 were dominant. In tests to a panel of 30 different races of barley powdery mildew, 27 among the dominant lines showed resistance spectra similar or identical to those characterizing 7 previously known genes. The remaining 16 lines formed 12 groups displaying new spectra of resistance to the panel of mildew races. Taking the frequency of recessive mutations in locus ml-o as a standard, ionizing radiations were significantly more efficient mutagens for producing dominant resistance to mildew. In spite of some possible sources of contaminant dominant resistance genes, the evidence points at a vast majority of the isolated lines representing genuine dominant mutations. Being produced in a single mutational step, such dominant genes for resistance offer evidence of having a regulatory function, regulating aspects of the host metabolism of importance for or interfering with the pathogen development.

Dominant resistance to barley powdery mildew race D1, isolated after mutagen treatments in four highbred barley varieties

After treatments with ionizing radiations and chemicals in the commercial barley varieties 'Bonus', 'Mari', 'Pallas', and 'Kristina', 43 lines with dominant resistance to the mildew race D1 were isolated, 34 in infection tests on M3 seedlings from M2 spikes, and 9 as resistant M2 seedlings from M1 spikes. Genetical analyses of these dominant resistant lines included crosses to susceptible material, crosses to the ml-o variety 'Refoma', crosses among the lines, crosses to sources of known dominant resistance genes, and tests to a panel of 30 different races of barley powdery mildew. In the panel tests, 27 among the lines showed resistance spectra similar or identical to Ml-a7, Ml-a9, Ml-a12, Ml-a13, Ml-a3 + Tu2 in Sv 57/510-44, Ml-g, and Ml-(La), whereas the remaining 16 lines formed 12 groups showing new spectra of resistance. The genetical analyses of F2 and F3 data from crosses indicate that the majority of the 43 lines are due to a restricted chromosomal segment in or close to the Ml-a region. There is ample evidence that the vast majority of the isolated dominant lines represent genuine mutations. Mutation breeding is suggested to offer a convenient way to introduce into the genome a tightly linked new dominant resistance gene, and so to create complex building-stones for further use in conventional combination breeding.

Cytokine responses in acute and persistent human parvovirus B19 infection

The aim of this study was to characterize the proinflammatory and T helper (Th)1/Th2 cytokine responses during acute parvovirus B19 (B19) infection and determine whether an imbalance of the Th1/Th2 cytokine pattern is related to persistent B19 infection. Cytokines were quantified by multiplex beads immunoassay in serum from B19-infected patients and controls. The cytokine responses were correlated with B19 serology, quantitative B19 DNA levels and clinical symptoms. In addition to a proinflammatory response, elevated levels of the Th1 type of cytokines interleukin (IL)-2, IL-12 and IL-15 were evident at time of the initial peak of B19 viral load in a few patients during acute infection. This pattern was seen in the absence of an interferon (IFN)-gamma response. During follow-up (20-130 weeks post-acute infection) some of these patients had a sustained Th1 cytokine response. The Th1 cytokine response correlated with the previously identified sustained CD8+ T cell response and viraemia. A cross-sectional study on patients with persistent B19 infection showed no apparent imbalance of their cytokine pattern, except for an elevated level of IFN-gamma response. No general immunodeficiency was diagnosed as an explanation for the viral persistence in this later group. Neither the acutely infected nor the persistently infected patients demonstrated a Th2 cytokine response. In conclusion, the acutely infected patients demonstrated a sustained Th1 cytokine response whereas the persistently infected patients did not exhibit an apparent imbalance of their cytokine pattern except for an elevated IFN-gamma response.

Nephrotic syndrome: an under-recognised immune-mediated complication of non-myeloablative allogeneic haematopoietic cell transplantation

Nephrotic syndrome (NS) is an extremely rare complication of myeloablative allogeneic haematopoietic cell transplantation (HCT) that usually occurs in association with chronic graft-versus-host disease (C-GVHD). We observed an unexpectedly high incidence of NS in a cohort of 163 consecutive patients undergoing non-myeloablative HCT from a related human leucocyte antigen-compatible donor. Seven patients developed NS at a median 318 d post-transplant (range 119-1203 d; cumulative incidence 6.1%). The median age at onset of NS was 46 years (range 33-59 years); three of the seven patients had no evidence of C-GVHD while four had accompanying limited C-GVHD. At diagnosis, median proteinuria was 16.5 g/24 h (range 3-24 g/24 h). Renal biopsy was performed in four cases and revealed membranous nephropathy. NS was not always associated with other symptoms of C-GVHD, and in contrast to previous reports, usually did not improve with the re-initiation of aggressive immunosuppression, resulting in progressive renal failure necessitating dialysis in three of seven cases. Membranous nephropathy resulting in NS is a previously unrecognised and clinically significant complication of non-myeloablative HCT.

Effects of human plasma proteins on maturation of monocyte-derived dendritic cells

Dendritic cells (DC) are a promising tool for vaccine therapy due to their unique properties as antigen presenting cells and their ability to prime naïve T cells. Increasing evidence suggests that maturation stage of DC critically influences the fate of the immune response. Generation of monocyte-derived DC for clinically applicable immunotherapy requires the use of well-defined components and stringent culture conditions. An alternative strategy is to use human autologous serum. However, its constituents are not stable and reflect the inflammatory condition of the donor. In order to investigate whether DC properties are influenced by proteins present in the plasma, we matured human monocyte-derived DC with four main plasma components: fibrinogen, fibronectin, plasminogen or C-reactive protein. These purified proteins were added at various concentrations on day 6 after the initial differentiation induced by IL-4 and GM-CSF. The maturation was assessed by phenotyping of maturation-associated marker (CD83) and co-stimulatory molecule CD86 as well as IL-12 production. Functional properties of DC were assessed by endocytic activity and mixed leukocyte culture. Our results indicate that fibrinogen had DC-maturation effect comparable to poly-I:C, TNF-alpha and PGE(2) as a positive control, but it failed to induce IL-12 production. The other plasma proteins had no effect on DC maturation. CRP at high concentration had rather inhibitory effect on DC induced lymphocyte function. We conclude that none of the tested plasma components and acute phase proteins sufficiently induce fully competent mature DC. This finding is important for the preparation of human DC-based vaccines supplemented by autologous sera.

Persistence of recipient plasma cells and anti-donor isohaemagglutinins in patients with delayed donor erythropoiesis after major ABO incompatible non-myeloablative haematopoietic cell transplantation

Delayed donor erythropoiesis and pure red-cell aplasia (PRCA) complicate major-ABO mismatched non-myeloablative allogeneic stem-cell transplantation. To characterize these events, we analysed red-cell serology and chimaerism in lymphohaematopoietic lineages, including plasma cells and B cells, in 12 consecutive major-ABO incompatible transplants following cyclophosphamide/fludarabine-based conditioning. Donor erythropoiesis was delayed to more than 100 days in nine (75%) patients including six (50%) who developed PRCA. During PRCA, all patients had persistent anti-donor isohaemagglutinins and recipient plasma cells (5-42%), while myeloid and T cells were completely donor in origin. In contrast, B-cell chimaerism was frequently full-donor when significant anti-donor isohaemagglutinins persisted. Four patients with early mixed haematopoietic chimaerism and the prolonged presence of anti-donor isohaemagglutinins and recipient plasma cells developed delayed-onset (>100 days post-transplant) red cell transfusion dependence and PRCA after myeloid chimaerism converted from mixed to full donor. These findings confirm that donor-erythropoiesis is impacted by temporal disparities in donor immune-mediated eradication of recipient lymphohaematopoietic cells during major-ABO incompatibility and suggest that plasma cells are relatively resistant to graft-versus-host haematopoietic effects.

A phase I trial of DNA vaccination with a plasmid expressing prostate-specific antigen in patients with hormone-refractory prostate cancer

Prostate-specific antigen (PSA) is a serine protease secreted at low levels by normal luminal epithelial cells of the prostate and in significantly higher levels by prostate cancer cells. Therefore, PSA is a potential target for various immunotherapeutical approaches against prostate cancer. DNA vaccination has been investigated as immunotherapy for infectious diseases in patients and for specific treatment of cancer in certain animal models. In animal studies, we have demonstrated that vaccination with plasmid vector pVAX/PSA results in PSA-specific cellular response and protection against tumour challenge. The purpose of the trial was to evaluate the safety, feasibility and biological efficacy of pVAX/PSA vaccine in the clinic. A phase I trial of pVAX/PSA, together with cytokine granulocyte/macrophage-colony stimulating factor (GM-CSF) (Molgramostim) and IL-2 (Aldesleukin) as vaccine adjuvants, was carried out in patients with hormone-refractory prostate cancer. To evaluate the biologically active dose, the vaccine was administered during five cycles in doses of 100, 300 and 900 μg, with three patients in each cohort. Eight patients were evaluable. A PSA-specific cellular immune response, measured by IFN-γ production against recombinant PSA protein, and a rise in anti-PSA IgG were detected in two of three patients after vaccination in the highest dose cohort. A decrease in the slope of PSA was observed in the two patients exhibiting IFN-γ production to PSA. No adverse effects (WHO grade >2) were observed in any dose cohort. We demonstrate that DNA vaccination with a PSA-coding plasmid vector, given with GM-CSF and IL-2 to patients with prostate cancer, is safe and in doses of 900 μg the vaccine can induce cellular and humoral immune responses against PSA protein.

Development of a technology platform for large-scale clinical grade production of DC

BACKGROUND

Clinical studies require protocols where a sufficient number of well-characterized highly immunogenic DC are produced according to good manufacturing practice (GMP) guidelines.

METHODS

In the present study, using leukapheresis products from 10 cancer patients, we validated an elutriation technology for large-scale clinical grade production of monocyte-derived DC.

RESULTS

The elutriation method gave a very high purity (mean+/-SD) (86+/-5.3%) and recovery (66+/-10.4%) of monocytes. Specifically for the two monocyte-rich fractions (3 and 4,) the recovery was 42+/-13% of viable cells that could be further differentiated into immature DC in hydrophobic culture bags using GM-CSF and IL-4. The immature DC exhibited<1% CD83+ expression and >98% phagocytic activity. Maturation with TNF-alpha or poly I:C resulted in DC with expression of CD80+, CD86+ and HLA-DR+ (>99%) and CD83+ (80+/-11.9%), as well as producing IL-12p70 and lacking phagocytic activity (<5%). This cell product can be cryopreserved with cell viability >85% and cell recovery >80% after thawing.

DISCUSSION

The elutriation procedure, when optimized and if the monocyte content of the starting material exceeds 5%, does not require further selection or depletion using affinity approaches.

Tissue distribution and differential expression of melanocortin 1 receptor, a malignant melanoma marker

The melanocortin 1 receptor is a G-protein-coupled receptor, described to be expressed on melanomas and melanocytes. Subsequent RT-PCR studies demonstrated the presence of melanocortin 1 receptor mRNA in other tissues such as pituitary gland and testis. Previously, we have demonstrated that three HLA-A2 binding nonamer peptides derived from melanocortin 1 receptor can elicit peptide-specific CTL which can recognize target cells transfected with the melanocortin 1 receptor gene and MHC class I matched melanoma lines. The potential of targeting melanocortin 1 receptor in therapy and diagnosis will depend on a preferential expression of this receptor in the majority of primary and metastatic melanomas vs normal tissues. We tested a panel of melanomas, carcinomas and other cell lines for the presence of melanocortin 1 receptor, using two monoclonal antibodies. The receptor was detected in 83% of the tested melanoma cell lines but not in other carcinoma lines. Immunohistochemistry revealed a strong expression of melanocortin 1 receptor in all tested primary and metastatic melanomas, but also demonstrated low levels of expression in adrenal medulla, cerebellum, liver and keratinocytes. Flow cytometry studies showed that melanocortin 1 receptor was expressed in in vitro activated monocytes/macrophages and in the THP-1 monocytic leukaemia line at levels of about 1 in 3 to 1 in 5 of that found in melanomas. Peripheral blood-derived dendritic cells, also express melanocortin 1 receptor in vitro. This extensive analysis of melanocortin 1 receptor tissue distribution may be of relevance not only for melanoma immunology, but also for research on the pathogenicity of inflammatory conditions in the skin and neurologic tissues. It remains to be seen if the over-expression of melanocortin 1 receptor in melanomas is sufficiently high to allow a 'therapeutic window' to be exploited in cancer immunotherapy.

Neuropsychological aspects of driving characteristics

Brain injury often causes impairments of cognitive functions, which may affect driving performance. The question of whether the brain-injured patient can resume car driving or not generally comes up during rehabilitation. The medical clinical examination, covering neurological status, screening of cognitive functions, and affective state, is insufficient in assessing relevant functions required for driving performance. A neuropsychological assessment and a driving test are additional parts of the driving assessment besides the medical examination. In this paper, neuropsychological test results and driving test results from four patients with brain injury are presented. The paper demonstrates the complementary value of neuropsychological assessment and a driving test: the relevance of cognitive factors for interpretation of driving problems, but also the relevance of a driving test to show compensatory capacity in some drivers with brain injury. Thus, collaboration between medical, neuropsychological and driving expertise can promote and deepen the total assessment of driving performance after brain injury.

Advantages of quantitative affinity chromatography for the analysis of solute interaction with membrane proteins

The use of membrane proteins as chromatographic stationary phases for the quantitation of biospecific interaction between the proteins and solutes is reviewed. This method is one among the few where a membrane protein is immobilized for repeated analyses of solute binding. To our knowledge, five transmembrane proteins have been immobilized in chromatographic matrices: the glucose and nucleoside transporters from human red blood cells, the photosynthetic reaction center from Rhodobacter sphaeroides, the nicotinic acetylcholine receptor from rat brain and a recombinant P-glycoprotein. Proteoliposomes and membrane vesicles have thereby been entrapped in size-exclusion beads, such as Superdex 200, and membrane proteins have been adsorbed on 'immobilized artificial membrane' monolayers of lipid analogs grafted to silica beads. Encouragingly, immobilized glucose transporter and P-glycoprotein showed constant interactant affinities for months. Analysis is done in the frontal mode at equilibrium because there is no separation between bound and free ligand. Both the affinity constant, which generally coincides with the corresponding constant determined by use of nonchromatographic methods, and the amount of active binding sites are obtained. The method has been successfully applied to functional analysis of membrane proteins in cells or reconstituted in lipid mono- or bilayers, screening of low-molecular interactants, investigation of protein-protein interaction and studies of effects of physico-chemical parameters on solute-protein interaction. The analyses require sensitive detection of the analyte and matching between amount of binding sites and affinity.