Monitoring COVID-19 related changes in population mental health

Background

The COVID-19 pandemic, and its consequences in terms of control measures and restrictions to normal life, has affected the population mental health. One of the four case studies from the Population Health Information Research Infrastructure (PHIRI) for COVID-19 is focused on mental health with the objective to measure changes in incidence of mental health problems associated with the COVID-19 pandemic in several European countries.

Methods

Using electronic health records (EHR), data on new episodes of depression or anxiety, prescription of antidepressants and anxiolytics, and visits to primary care, specialized care or emergency units with an episode of depression/anxiety, were collected by participant data hubs at national/regional level for the period 2017-2021. A common data model to collect the data was defined for all participating data hubs and analysis of status prior and during the COVID-19 pandemic was performed using R.

Results

Data hubs from Austria, Finland, Spain (Aragon), and United Kingdom (Wales) were able to provide aggregated results from raw individual-level data. Preliminary analysis of trends suggests a decrease in new cases of depression and anxiety in the pandemic period (2020-2021) in comparison with previous years. Different trends were observed between data hubs regarding prescription of drugs and the number of primary/specialized care visits due to depression or anxiety. Issues in the access to data in some of the participating data hubs were observed, related to ethical and legal matters, and the lack of centralized registers and of private consultations statistics.

Conclusions

The results of this use case show that EHR for the secondary use can be retrieved in a common way across Europe to analyse and compare the impact of COVID-19 in population mental health in European countries. However, the process is more complicated and time consuming than expected.

Review of direct impact health indicators of COVID-19 in the scientific literature published between January 2020 and June 2021

Background

The Joint Action Population Health Information Research Infrastructure (PHIRI) seeks to create infrastructures to generate quality data on the COVID-19 pandemic between European countries. The aim of this study is to present a synthesis of health indicators used to evaluate the direct impact of COVID-19

Methods

Scoping review using a common search strategy in Pubmed, Embase and WHO Covid-19 databases. Health indicators of direct impact of COVID-19 were obtained from observational studies in the general population, hospitals and long-term care facilities from papers published worldwide in English between 01/01/2020 and 06/31/2021. Titles and abstracts were screened first by 15 reviewers using the Rayyan tool. Any discrepancies were solved by agreement between reviewers. Then, articles containing indicators of direct impact were selected in a full-text reading phase. Of them, a random sample of 35 was drawn and their indicators were described.

Results

After eliminating 262 duplicates 3891 records were reviewed. Screening discarded 3171 abstracts. Of 720 articles sought for retrieval, 445 met inclusion criteria for indicators extraction. In a sample of 35 papers (8.1%), 116 direct impact indicators of COVID-19 were identified. 28 morbidity indicators were found, classified as indicators of prevalence (n = 15), incidence (6), transmissibility (4) and underreported infection (4); 32 of mortality (mortality rate, 9; case fatality rate, 17; time to death, 2); and 54 for severity (complications, 27; mechanical ventilation, 12; hospitalization, 8; requiring ICU admission, 1; time from hospitalization to ICU admission, 1). Two composite indicators of severity and mortality were also identified.

Conclusions

According to the scientific literature, a wide variety of health indicators has been used to measure the direct impact of COVID-19. The systematization of indicators used in the current COVID-19 pandemic could help for future health crises management.

Nationwide health check program by patients with severe mental illness or long-term antidepressants

Background

The English NHS Health Check is a unique national risk assessment, awareness and management programme for preventing cardiovascular disease (CVD), diabetes and chronic kidney disease (CKD). We aimed to assess their uptake and association with new diagnoses (CVD, hypertension, type-2 diabetes and CKD) in patients with severe mental illness (SMI) compared to patients without this condition and for patients on long-term antidepressant treatment (LTAD) (≥6 prescriptions vs < 6).

Methods

Cohort study (2013-2017) using the QResearch database. 1,319 general practices across England contributed of over nine million patients aged 40-74 years. 3,492,186 patients were eligible for NHS Health Checks of which 590,218 attended. Outcomes: hazard ratios (HR) with 95% confidence intervals (CI) for uptake of NHS Health Checks and for new diagnoses within 1 year in attendees. Models were adjusted for sex, age, ethnicity, deprivation and region.

Results

65,490 people with SMI and 46,437 people on LTAD (20% of the total eligible with SMI/LTAD, respectively) attended an NHS Health Check. People with SMI or on LTAD were more likely to attend compared to people without those conditions, adjusted HRs 1.05 (95% CI 1.02-1.08) and 1.10 (95% CI 1.08-1.13), respectively. Among attendees, people with SMI and on LTAD were 23% and 55% more likely to be diagnosed with CKD (95% CI 1.12-1.34 and 1.42-1.70, respectively) than people without these conditions. Attendees on LTAD were 66% more likely to have a major CVD event within 1 year than those without LTAD (95% CI 1.41-1.94) or a new diagnosis of hypertension and type 2 diabetes, HRs 1.12 (95% CI 1.05-1.20) and 1.45 (95% CI 1.31-1.60), respectively.

Conclusions

People with SMI or on LTAD were more likely to attend NHS Health Checks than people without these conditions. Higher rates of CKD in patients with SMI/LTAD and CVD, hypertension and type 2 diabetes in the latter might indicate increased risks and unmet need in these patient groups

Key messages

People with SMI/LTAD were more likely to attend NHS Health Checks. People on LTAD were more likely to be diagnosed with CVD, CKD, hypertension and type-2 diabetes than people without these conditions. SMI attendees were more likely to be diagnosed with CKD.

The molecular profile of synovial fluid changes upon joint distraction and is associated with clinical response in knee osteoarthritis

OBJECTIVE

Surgical knee joint distraction (KJD) leads to clinical improvement in knee osteoarthritis (OA) and also apparent cartilage regeneration by magnetic resonance imaging. We investigated if alteration of the joint's mechanical environment during the 6 week period of KJD was associated with a molecular response in synovial fluid, and if any change was associated with clinical response.

METHOD

20 individuals undergoing KJD for symptomatic radiographic knee OA had SF sampled at baseline, midpoint and endpoint of distraction (6 weeks). SF supernatants were measured by immunoassay for 10 predefined mechanosensitive molecules identified in our previous pre-clinical studies. The composite Knee injury and OA Outcome Score-4 (KOOS₄) was collected at baseline, 3, 6 and 12 months.

RESULTS

13/20 (65%) were male with mean age 54°±°5yrs. All had Kellgren-Lawrence grade ≥2 knee OA. 6/10 analytes showed statistically significant change in SF over the 6 weeks distraction (activin A; TGFβ-1; MCP-1; IL-6; FGF-2; LTBP2), P < 0.05. Of these, all but activin A increased. Those achieving the minimum clinically important difference of 10 points for KOOS₄ over 6 months showed greater increases in FGF-2 and TGFβ-1 than non-responders. An increase in IL-8 during the 6 weeks of KJD was associated with significantly greater improvement in KOOS₄ over 12 months.

CONCLUSION

Detectable, significant molecular changes are observed in SF following KJD, that are remarkably consistent between individuals. Preliminary findings appear to suggest that increases in some molecules are associated with clinically meaningful responses. Joint distraction may provide a potential opportunity in the future to define regenerative biomarker(s) and identify pathways that drive intrinsic cartilage repair.

Impact of a national enhanced recovery after surgery programme on patient outcomes of primary total knee replacement: an interrupted time series analysis from "The National Joint Registry of England, Wales, Northern Ireland and the Isle of Man"

OBJECTIVE

We aimed to test whether a national Enhanced Recovery After Surgery (ERAS) Programme in total knee replacement (TKR) had an impact on patient outcomes.

DESIGN

Natural-experiment (April 2008-December 2016). Interrupted time-series regression assessed impact on trends before-during-after ERAS implementation.

SETTING

Primary operations from the UK National Joint Registry (NJR) were linked with Hospital Episode Statistics (HES) data which contains inpatient episodes undertaken in National Health Service (NHS) trusts in England, and Patient Reported Outcome Measures (PROMs).

PARTICIPANTS

Patients undergoing primary planned TKR aged ≥18 years.

INTERVENTION

ERAS implementation (April 2009-March 2011).

OUTCOMES

Regression coefficients of monthly means of Length of stay (LOS), bed day costs, change in Oxford knee scores (OKS) 6-months after surgery, complications (at 6 months), and rates of revision surgeries (at 5 years).

RESULTS

486,579 primary TKRs were identified. Overall LOS and bed-day costs decreased from 5.8 days to 3.7 and from £7607 to £5276, from April 2008 to December 2016. Oxford knee score (OKS) change improved from 15.1 points in April 2008 to 17.1 points in December 2016. Complications decreased from 4.1 % in April 2008 to 1.7 % in March 2016. 5-year revision rates remained stable at 4.8 per 1000 implants years in April 2008 and December 2011. After ERAS, declining trends in LOS and bed costs slowed down; OKS improved, complications remained stable, and revisions slightly increased.

CONCLUSIONS

Different secular trends in outcomes for patients having TKR have been observed over the last decade. Although patient outcomes are better than a decade ago ERAS did not improve them at national level.

Development and validation of a clinical prediction model for patient-reported pain and function after primary total knee replacement surgery

To develop and validate a clinical prediction model of patient-reported pain and function after undergoing total knee replacement (TKR). We used data of 1,649 patients from the Knee Arthroplasty Trial who received primary TKR across 34 centres in the UK. The external validation included 595 patients from Southampton University Hospital, and Nuffield Orthopaedic Centre (Oxford). The outcome was the Oxford Knee Score (OKS) 12-month after TKR. Pre-operative predictors including patient characteristics and clinical factors were considered. Bootstrap backward linear regression analysis was used. Low pre-operative OKS, living in poor areas, high body mass index, and patient-reported anxiety or depression were associated with worse outcome. The clinical factors associated with worse outcome were worse pre-operative physical status, presence of other conditions affecting mobility and previous knee arthroscopy. Presence of fixed flexion deformity and an absent or damaged pre-operative anterior cruciate ligament (compared with intact) were associated with better outcome. Discrimination and calibration statistics were satisfactory. External validation predicted 21.1% of the variance of outcome. This is the first clinical prediction model for predicting self-reported pain and function 12 months after TKR to be externally validated. It will help to inform to patients regarding expectations of the outcome after knee replacement surgery.

Evolution of acute hepatitis C virus infection in a large European city: Trends and new patterns

The aims of this study were to describe the evolution of acute hepatitis C virus (HCV) infections since 2004 and to determine its associated factors. Acute HCV infections diagnosed in Barcelona from 2004 to 2015 were included. Incidence ratios (IR) were then estimated for sex and age groups. Cases were grouped between 2004-2005, 2006-2011 and 2012-2015, and their incidence rate ratios (IRR) were calculated. In addition, risk factors for acute HCV infection were identified using multinomial logistic regression for complete, available and multiple imputed data. 204 new HCV cases were identified. Two peaks of higher IR of acute HCV infection in 2005 and 2013 were observed. Men and those aged 35-54 had higher IR. IRR for men was 2.9 times greater than in women (95% confidence intervals (CI): 1.8 ‒ 4.7). Factors related to the period 2012-2015 (versus 2006-2011) were: a) sexual risk factor for transmission versus nosocomial (relative-risk ratio (RRR): 13.0; 95% CI: 2.3 ‒ 72.1), b) higher educated versus lower (RRR: 5.4; 95% CI: 1.6 ‒ 18.7), and c) HIV co-infected versus not HIV-infected (RRR: 53.1; 95% CI: 5.7 ‒ 492.6). This is one of the few studies showing IR and RRRs of acute HCV infections and the first focused on a large city in Spain. Sexual risk for transmission between men, higher educational level and HIV co-infection are important factors for understanding current HCV epidemic. There has been a partial shift in the pattern of the risk factor for transmission from nosocomial to sexual.

Mortality, Causes of Death and Associated Factors Relate to a Large HIV Population-Based Cohort

INTRODUCTION

Antiretroviral therapy has led to a decrease in HIV-related mortality and to the emergence of non-AIDS defining diseases as competing causes of death. This study estimates the HIV mortality rate and their risk factors with regard to different causes in a large city from January 2001 to June 2013.

MATERIALS AND METHODS

We followed-up 3137 newly diagnosed HIV non-AIDS cases. Causes of death were classified as HIV-related, non-HIV-related and external. We examined the effect of risk factors on survival using mortality rates, Kaplan-Meier plots and Cox models. Finally, we estimated survival for each main cause of death groups through Fine and Gray models.

MORTALITY RESULTS

182 deaths were found [14.0/1000 person-years of follow-up (py); 95% confidence interval (CI):12.0-16.1/1000 py], 81.3% of them had a known cause of death. Mortality rate by HIV-related causes and non-HIV-related causes was the same (4.9/1000 py; CI:3.7-6.1/1000 py), external was lower [1.7/1000 py; (1.0-2.4/1000 py)].

SURVIVAL RESULTS

Kaplan-Meier estimate showed worse survival in intravenous drug user (IDU) and heterosexuals than in men having sex with men (MSM). Factors associated with HIV-related causes of death include: IDU male (subHazard Ratio (sHR):3.2; CI:1.5-7.0) and <200 CD4 at diagnosis (sHR:2.7; CI:1.3-5.7) versus ≥500 CD4. Factors associated with non-HIV-related causes of death include: ageing (sHR:1.5; CI:1.4-1.7) and heterosexual female (sHR:2.8; CI:1.1-7.3) versus MSM. Factors associated with external causes of death were IDU male (sHR:28.7; CI:6.7-123.2) and heterosexual male (sHR:11.8; CI:2.5-56.4) versus MSM.

CONCLUSION AND RECOMMENDATION

There are important differences in survival among transmission groups. Improved treatment is especially necessary in IDUs and heterosexual males.

A low-cost, sustainable, second generation system for surveillance of people living with HIV in Spain: 10-year trends in behavioural and clinical indicators, 2002 to 2011

A second-generation surveillance system of people infected with human immunodeficiency virus (HIV) has been implemented in Spain. Behavioural and clinical data were collected between 2002 and 2011 through an annual one-day, cross-sectional survey in public hospitals, including all in- and outpatients receiving HIVrelated care on the survey day. Mean age increased over time (from 38.7 years in 2002 to 43.8 years in 2011) and 68.4% of the 7,205 subjects were male. The proportion of migrants increased from 6.1% to 15.9%, while people who inject or used to inject drugs (PWID and Ex-PWID) decreased and men who have sex with men (MSM) and heterosexuals increased. Unprotected intercourse at last sex increased among MSM and PWID/Ex-PWID. Patients receiving antiretroviral treatment increased significantly from 76.0% to 88.2% as did those with CD4 T-cell counts ≥350 (from 48.2% to 66.9%) and viral copies <200 (from 47.0% to 85.2%). HIV-infected people with hepatitis C virus RNA decreased from 36.0% in 2004 to 29.9% in 2011, while those with HBsAg remained stable at around 4.4%. Implementation of a low-cost, sustainable system for second-generation surveillance in people living with HIV is feasible. In Spain, the information obtained has helped to define and refine public health policy and document treatment effectiveness.

Clinical, virological and biochemical evidence supporting the association of HIV-1 reverse transcriptase polymorphism R284K and thymidine analogue resistance mutations M41L, L210W and T215Y in patients failing tenofovir/emtricitabine therapy

Background

Thymidine analogue resistance mutations (TAMs) selected under treatment with nucleoside analogues generate two distinct genotypic profiles in the HIV-1 reverse transcriptase (RT): (i) TAM1: M41L, L210W and T215Y, and (ii) TAM2: D67N, K70R and K219E/Q, and sometimes T215F. Secondary mutations, including thumb subdomain polymorphisms (e.g. R284K) have been identified in association with TAMs. We have identified mutational clusters associated with virological failure during salvage therapy with tenofovir/emtricitabine-based regimens. In this context, we have studied the role of R284K as a secondary mutation associated with mutations of the TAM1 complex.

Results

The cross-sectional study carried out with >200 HIV-1 genotypes showed that virological failure to tenofovir/emtricitabine was strongly associated with the presence of M184V (P < 10^-10) and TAMs (P < 10^-3), while K65R was relatively uncommon in previously-treated patients failing antiretroviral therapy. Clusters of mutations were identified, and among them, the TAM1 complex showed the highest correlation coefficients. Covariation of TAM1 mutations and V118I, V179I, M184V and R284K was observed. Virological studies showed that the combination of R284K with TAM1 mutations confers a fitness advantage in the presence of zidovudine or tenofovir. Studies with recombinant HIV-1 RTs showed that when associated with TAM1 mutations, R284K had a minimal impact on zidovudine or tenofovir inhibition, and in their ability to excise the inhibitors from blocked DNA primers. However, the mutant RT M41L/L210W/T215Y/R284K showed an increased catalytic rate for nucleotide incorporation and a higher RNase H activity in comparison with WT and mutant M41L/L210W/T215Y RTs. These effects were consistent with its enhanced chain-terminated primer rescue on DNA/DNA template-primers, but not on RNA/DNA complexes, and can explain the higher fitness of HIV-1 having TAM1/R284K mutations.

Conclusions

Our study shows the association of R284K and TAM1 mutations in individuals failing therapy with tenofovir/emtricitabine, and unveils a novel mechanism by which secondary mutations are selected in the context of drug-resistance mutations.

[Characteristics of cases of infectious syphilis diagnosed in prisons, 2007-2008]

OBJECTIVE

To describe the characteristics of cases of syphilis amongst prison inmates.

MATERIALS AND METHODS

Descriptive study. Confirmed cases of primary, secondary and early latent syphilis were identified in prisons in Spain during 2007-2008. Socio-demographic and clinical information, as well as variables related to transmission, was collected by the attending physicians in a standard form. Frequency distributions of each variable were performed. Annual incidence rates were calculated. To evaluate the association between qualitative variables, the χ² and Fisher's exact tests were used; the Mann-Whitney test was utilized to compare quantitative variables.

RESULTS

During the study period, 94 syphilis cases were identified (35.1% primary, 20.2% secondary and 44.7% early latent). The incidence rates were 0.9 cases/1000 prisoners in 2007 and 0.7 cases/1000 prisoners in 2008. Most cases were male (90.4%), between 31-40 years old (30.9%) and foreigners (52.1%). The majority of patients were diagnosed through screening (80.9%). Heterosexual contact was the most frequent transmission route (83.0%). Overall HIV prevalence was 5.3%, and 16.0% of the patients had a history of previous sexually transmitted infections (STI). Almost 40% of the cases reported being a client of a sex worker.

CONCLUSIONS

Incidence of syphilis in prison is high. Many syphilis patients were detected through screening, highlighting the role of the Spanish prison health service in STI control.

Mechanisms involved in the selection of HIV-1 reverse transcriptase thumb subdomain polymorphisms associated with nucleoside analogue therapy failure

Previous studies showed an increased prevalence of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) thumb subdomain polymorphisms Pro272, Arg277, and Thr286 in patients failing therapy with nucleoside analogue combinations. Interestingly, wild-type HIV-1(BH10) RT contains Pro272, Arg277, and Thr286. Here, we demonstrate that in the presence of zidovudine, HIV-1(BH10) RT mutations P272A/R277K/T286A produce a significant reduction of the viral replication capacity in peripheral blood mononuclear cells in both the absence and presence of M41L/T215Y. In studies carried out with recombinant enzymes, we show that RT thumb subdomain mutations decrease primer-unblocking activity on RNA/DNA complexes, but not on DNA/DNA template-primers. These effects were observed with primers terminated with thymidine analogues (i.e., zidovudine and stavudine) and carbovir (the relevant derivative of abacavir) and were more pronounced when mutations were introduced in the wild-type HIV-1(BH10) RT sequence context. RT thumb subdomain mutations increased by 2-fold the apparent dissociation equilibrium constant (K(d)) for RNA/DNA without affecting the K(d) for DNA/DNA substrates. RNase H assays carried out with RNA/DNA complexes did not reveal an increase in the reaction rate or in secondary cleavage events that could account for the decreased excision activity. The interaction of Arg277 with the phosphate backbone of the RNA template in HIV-1 RT bound to RNA/DNA and the location of Thr286 close to the RNA strand are consistent with thumb polymorphisms playing a role in decreasing nucleoside RT inhibitor excision activity on RNA/DNA template-primers by affecting interactions with the template-primer duplex without involvement of the RNase H activity of the enzyme.

Mutational patterns and correlated amino acid substitutions in the HIV-1 protease after virological failure to nelfinavir- and lopinavir/ritonavir-based treatments

Human immunodeficiency virus type 1 (HIV-1) antiviral drug resistance is a major consequence of therapy failure and compromises future therapeutic options. Nelfinavir and lopinavir/ritonavir-based therapies have been widely used in the treatment of HIV-infected patients, in combination with reverse transcriptase inhibitors. The aim of this observational study was the identification and characterization of mutations or combinations of mutations associated with resistance to nelfinavir and lopinavir/ritonavir in treated patients. Nucleotide sequences of 1,515 subtype B HIV-1 isolates from 1,313 persons with different treatment histories (including naïve and treated patients) were collected in 31 Spanish hospitals over the years 2002-2005. Chi-square contingency tests were performed to detect mutations associated with failure to protease inhibitor-based therapies, and correlated mutations were identified using statistical methods. Virological failure to nelfinavir was associated with two different mutational pathways. D30N and N88D appeared mostly in patients without previous exposure to protease inhibitors, while K20T was identified as a secondary resistance mutation in those patients. On the other hand, L90M together with L10I, I54V, A71V, G73S, and V82A were selected in protease inhibitor-experienced patients. A series of correlated mutations including L10I, M46I, I54V, A71V, G73S, and L90M appeared as a common cluster of amino acid substitutions, associated with failure to lopinavir/ritonavir-based treatments. Despite the relatively high genetic barrier of some protease inhibitors, a relatively small cluster of mutations, previously selected under drug pressure, can seriously compromise the efficiency of nelfinavir- and lopinavir/ritonavir-based therapies.

DR_SEQAN: a PC/Windows-based software to evaluate drug resistance using human immunodeficiency virus type 1 genotypes

Background

Genotypic assays based on DNA sequencing of part or the whole reverse transcriptase (RT)- and protease (PR)-coding regions of the human immunodeficiency virus type 1 (HIV-1) genome have become part of the routine clinical management of HIV-infected individuals. However, the results are difficult to interpret due to complex interactions between mutations found in viral genes.

Results

DR_SEQAN is a tool to analyze RT and PR sequences. The program output includes a list containing all of the amino acid changes found in the query sequence in comparison with the sequence of a wild-type HIV-1 strain. Translation of codons containing nucleotide mixtures can result in potential ambiguities or heterogeneities in the amino acid sequence. The program identifies all possible combinations of 2 or 3 amino acids that derive from translation of triplets containing nucleotide mixtures. In addition, when ambiguities affect codons relevant for drug resistance, DR_SEQAN allows the user to select the appropriate mutation to be considered by the program's drug resistance interpretation algorithm. Resistance is predicted using a rule-based algorithm, whose efficiency and accuracy has been tested with a large set of drug susceptibility data. Drug resistance predictions given by DR_SEQAN were consistent with phenotypic data and coherent with predictions provided by other publicly available algorithms. In addition, the program output provides two tables showing published drug susceptibility data and references for mutations and combinations of mutations found in the analyzed sequence. These data are retrieved from an integrated relational database, implemented in Microsoft Access, which includes two sets of non-redundant core tables (one for combinations of mutations in the PR and the other for combinations in the RT).

Conclusion

DR_SEQAN is an easy to use off-line application that provides expert advice on HIV genotypic resistance interpretation. It is coded in Visual Basic for use in PC/Windows-based platforms. The program is freely available under the General Public License. The program (including the integrated database), documentation and a sample sequence can be downloaded from

Kinetic Characterization of Apical D-Fructose Transport in Chicken Jejunum

In mammals, D-fructose transport takes place across the brush-border membrane of the small intestine through GLUT5, a member of the facilitative glucose transporter family. In the present paper, we describe and characterize for the first time the apical transport of D-fructose in chicken intestine. Brush-border membrane vesicles (BBMV) were obtained from jejunum of 5- to 6-wk-old chickens. D-Fructose uptake by BBMV from chicken jejunum comprises a saturable component and a simple diffusion process. The maximal rate of transport ( V(max)) for D-fructose was 2.49 nmol.(mg prot)(-1).s(-1), the Michaelis constant ( K(m)) was 29 mM, and the diffusion constant ( K(d)) was 25 nl.(mg prot)(-1).s(-1). The apical transport of D-fructose was Na(+)-independent, phlorizin-, phloretin-, and cytochalasin B-insensitive, and did not show cis-inhibition by D-glucose or D-galactose. These properties, together with the detection of specific GLUT5 mRNA, indicate the presence of a low-affinity high-capacity GLUT5-type carrier in the chicken jejunum, responsible for the entry of D-fructose across the brush-border membrane of enterocytes.

Regional differences in transport, lipid composition, and fluidity of apical membranes of small intestine of chicken

Na+-dependent D-glucose transport was studied in brush-border membrane vesicles from duodenum, jejunum, and ileum of 5- to 6-wk-old chickens. Regional differences were found, and both initial rates and accumulation ratio of D-glucose were higher in the proximal part of the small intestine than in the ileum. To establish the mechanism(s) underlying these differences we have studied the density of Na+-dependent D-glucose cotransporter (SGLT1) as well as lipid composition and fluidity. Phlorizin-specific binding and Western blot analysis indicated a decrease in the amount of SGLT1 in the ileum when compared to the duodenum and jejunum. The distal part of the small intestine also showed a decrease in free cholesterol content and saturated-to-unsaturated fatty acid ratio together with an increase in lipid content and phosphatidylcholine-to-sphingomyelin ratio. These results were associated with a decrease in the diphenylhextriene fluorescence polarization found in brush-border membranes of the ileum. We can conclude that the decrease in the apical D-glucose transport found in the ileum is primarily due to a reduction in the amount of SGLT1 present in the brush-border membrane rather than the differences in the lipid composition and fluidity.

Aldosterone mediates the changes in hexose transport induced by low sodium intake in chicken distal intestine

1. In chickens, low Na+ diets markedly decrease the hexose transport in the rectal segment of the large intestine; transport in the ileum shows a lower, but significant reduction and transport in the jejunum is unaffected. These effects involve both apical (SGLT1) and basolateral (GLUT2) hexose transporters. 2. The role of the renin-angiotensin-aldosterone axis (RAAS) in the epithelial response to Na+ intake was studied in chickens fed high-NaCl (HS) and low-NaCl (LS) diets. The V(max) of alpha-methyl-D-glucoside and D-glucose were determined in vesicles from the brush-border (BBMVs) and basolateral (BLMVs) membranes, respectively. The binding of phlorizin to BBMV and cytochalasin B to BLMV were used as indicators of the abundance of SGLT1 and GLUT2, respectively. 3. In HS-adapted chickens, the serum concentration of aldosterone (means +/- S.E.M.) was 35 +/- 5 pg ml(-1) (n = 6) and that of renin was 20 +/- 2 ng ml(-1) (n = 3). In LS-fed birds, these values were 166 +/- 12 pg ml(-1) (n = 6) and 122 +/- 5 ng ml(-1) (n = 3), respectively. Administration of captopril, the inhibitor of the angiotensin-converting enzyme (ACE), to LS-chickens lowered the aldosterone serum concentration without affecting the renin concentration. Captopril also prevented the reduction of apical and basolateral hexose transport in ileum and rectum characteristic of the intestinal response to LS adaptation. 4. Administration of the aldosterone antagonist spironolactone to LS-adapted chickens did not affect the serum concentrations of aldosterone, but prevented the effects of LS intake on hexose transport in both apical and basolateral membranes. This suggests that the effects of aldosterone are mediated by cytosolic mineralcorticoid receptors. 5. Administration of exogenous aldosterone to HS-fed birds induced hexose transport and binding properties typical of the LS-adapted animals. These findings support the view that aldosterone, besides its primary role in controlling intestinal Na+ absorption, can also modulate the expression of apical and basolateral glucose transporters in the chicken distal intestine.

Effects of resalination on intestinal glucose transport in chickens adapted to low Na+ intakes

In chickens, we have shown that intestinal absorption of glucose via apical SGLT1 and basolateral GLUT2 transport systems is affected by dietary Na+; low-Na+ adapted birds show a dramatic reduction of glucose transporters in both membranes in the rectum, an intermediate response in the ileum and no effects in the jejunum. We have now studied the effect of resalination of low-Na+ adapted chickens on glucose kinetics across SGLT1 (using -methyl-D-glucoside as substrate) and GLUT2 (using D-glucose) and on the specific binding of phlorizin and cytochalasin B, respectively. Twelve-week-old male Leghorn chickens were fed wheat and barley with drinking water containing either 150 mM NaCl (high-Na+ group) or 0. 015 mM (low-Na+ group) for 14 days (serum aldosterone: 242 +/- 6 pg ml-1 in the low-Na+ and 46 +/- 4 pg ml-1 in the high-Na+ group). On day 14, the low-Na+ group was either resalinated with an oral dose of NaCl (9 g (kg body wt)-1) or switched to the high-Na+ condition, for 1 week. Serum aldosterone measured 4 h, 1 day and 7 days after the change in NaCl intake fell to between 30 and 39 pg ml-1. The changes in apical -methyl-D-glucoside and basolateral D-glucose transport observed in the ileum and rectum of low-Na+ adapted animals were completely reversed by resalination within 4 h of NaCl administration to the level of values observed for high-Na+ adapted birds. The good correlation between the -methyl-D-glucoside and D-glucose Vmax and the SGLT1 and GLUT2 density, respectively, supports the view that the increase in apical and basolateral hexose transport found in the ileum and rectum of both groups of resalinated birds is due to an increase in the number of protein transporters. The rapid changes in the number of glucose transporters observed suggest that the target of the regulatory signal(s) involved are the mature enterocytes present in the villi rather than the developing enterocytes in the crypt.

Expression of Na+-D-glucose cotransporter in brush-border membrane of the chicken intestine

We have studied the expression of Na+-D-glucose cotransporter in brush-border membrane vesicles (BBMVs) of chicken enterocytes to correlate the changes in the apical Na+-dependent transport with the changes in the amounts of transporter determined by Western blot analysis. Two different rabbit polyclonal antibodies were used simultaneously. The antibody raised against amino acids 564-575 of the deduced amino acid sequence of rabbit intestinal SGLT-1 (antibody 1) specifically detects a single 75-kDa band in the three segments, and this band disappeared when the antibody was preabsorbed with the antigenic peptide. The antibody raised against the synthetic peptide corresponding to amino acids 402-420 of the same protein (antibody 2) only reacts with jejunal and ileal samples, but no signal is found in BBMVs of rectum. Only when antibody 1 was used was there a linear correlation between the maximal transport rates of hexoses in BBMVs and the relative protein amounts determined by Western blot. These results indicate that the Na+-D-glucose cotransport in the jejunum, the ileum, and the rectum of chickens is due to an SGLT-1 type protein.

Hexose transport in the apical and basolateral membranes of enterocytes in chickens adapted to high and low NaCl intakes

1. The effect of a low-NaCl diet (LS diet) on the properties of hexose transport across the brush-border and basolateral membranes of enterocytes from jejunum, ileum and rectum of the chicken was investigated. 2. In the brush-border membrane, LS adaptation had no effect on Km for alpha-methyl-D-glucoside while Vmax values were significantly reduced in the ileum and in the rectum. All Scatchard plots of specific [3H]phlorizin binding give a straight line, consistent with a single population of binding sites. Phlorizin binding vs. alpha-methyl-D-glucoside maximal transport rates showed a linear correlation. 3. In the basolateral membrane, the LS diet did not modify the Km for D-glucose but reduced the Vmax in the ileum and in the rectum. Scatchard plots of [3H]cytochalasin B binding support the view that there is a single transport system in this membrane. There was a linear correlation between cytochalasin B binding and D-glucose Vmax values. 4. The response of the chicken intestine to LS intake consists of a dramatic reduction in the number of glucose transporters in both apical and basolateral membranes of the rectum, an intermediate response in the ileum and no significant effects in the jejunum.

Hexose transport across the basolateral membrane of the chicken jejunum

The characteristics of the basolateral transport of D-glucose (D-Glc) and D-fructose (D-Fru) have been studied in membrane vesicles from the jejunum of 5- to 6-wk-old chickens. Uptake of hexoses was measured using a rapid filtration method. The maximal rate of transport (Vmax) for D-Glc was 2.36 nmol x mg(-1) x s(-1) and for D-Fru was 3.79 nmol x mg(-1) x s(-1). The Michaelis constants were 17.3 mmol/l for D-Glc and 40.4 mmol/l for D-Fru. D-Glc inhibited its own transport (Ki = 17.4 mmol/l) and the transport of D-Fru (Ki = 18.7 mmol/l). D-Fru inhibited its own transport (Ki = 38.1 mmol/l) and the transport of D-Glc (Ki = 40.3 mmol/l). The transport of both hexoses was Na+ independent, theophylline and cytochalasin B sensitive, and showed cis-inhibition by structural analogs. In preloaded vesicles, the uptake of D-Fru was trans-stimulated by D-Glc and 2-deoxy-D-glucose. These properties indicate the presence of a low-affinity high-capacity glucose transporter isoform (GLUT-2)-type carrier in the chicken intestine, responsible for moving both D-Glc and D-Fru across the basolateral membrane.