[Geriatric patient with neurological symptoms and prolonged aPTT]

A 73-year-old man with dementia was referred to our clinic with hypernatremia and volume depletion. New-onset neurogenic dysphagia was likely the reason for both. The patient had chronic embolic strokes on the computed tomography (CT) images. Documentation from previous hospitalizations in different hospitals revealed a repeatedly prolonged activated partial thromboplastin time (aPTT); 5 years prior, antiphospholipid antibody syndrome had already been suspected, but the necessary workup was never completed. We diagnosed the patient with primary antiphospholipid antibody syndrome and initiated therapy with vitamin K antagonists (phenprocoumon) and aspirin.

Does listening to audiobooks affect gait behavior?

BACKGROUND

The effect of listening to audiobooks, podcasts, and other audio files while walking on gait performance has not been well studied. Although the number of audio users is growing annually. Evidence suggests that a posture-first strategy contributes to gait stability in healthy individuals during dual-task conditions, but this effect may be diminished when the cognitive task is consciously prioritized.

OBJECTIVES

To study the effect of listening to an audiobook while walking, as a daily life-like dual-task, on spatiotemporal gait parameters.

METHODS

Forty young healthy (24.05 ± 3.66) subjects participated in the study. Spatiotemporal gait parameters were measured for 5 min on a treadmill once without (single-task) and once while listening to an audiobook through over-ear headphones (dual-task). Measured parameters included spatiotemporal parameters, gait phases, maximum pressure, and dual-task cost. Data were statistically analyzed using SPSS software.

RESULTS

There were no significant differences in any of the studied parameters between the single- and dual-task conditions, even though the subjective cognitive load of listening to audiobooks while walking was high. However, participants with different habits had significant differences in gait phases and maximum pressure. Rare listeners had a shorter stance phase, a longer swing phase, and a higher maximum pressure on the dominant heel. They also had significant differences in dual-task costs.

CONCLUSION

No differences in the spatiotemporal gait parameters for walking with and without listening to audiobooks, as a daily life-like dual-task, were observed. However, the difference between participants who listened rarely and participants who listened often may confirm the "posture first" strategy in young healthy people.

TRIAL REGISTRATION

DRKS00025837, retrospectively registered on 23.11.2021.

On Gait Stability: Correlations between Lyapunov Exponent and Stride Time Variability

Lyapunov exponent is a promising parameter to ascertain the stability of the human gait. In this work, we use a time-series model based on a second-order delay-system with inertial measurement units placed on the foot and wrist. Stability is analyzed in a localized sense, with the Lyapunov exponent computed in the temporal region between two heel-strike points, which are determined using a peak-detection algorithm. We have attempted to show correlations between variations in the stride time and stability of the gait under normal and abnormal conditions. In the latter case, we attach a weight on foot to emulate weakness. On comparison between both cases, we observe a statistical significance of p=0.0039 using Wilcoxon’s rank-sum test. Moreover, on observing the correlations between Lyapunov Exponent and Stride Time Variability, we notice a left-shift in the abnormal case, indicating a lower threshold for instability, with the Stride Time Variability being 0.07 as compared to 0.11 in the normal case.The results indicate that by exploiting the correlation between stride time variability and Lyapunov exponents, one can establish a threshold for gait stability.

Step Length Estimation with Wearable Wrist Sensor using ANN

Step Length is an important metric that can be used for the analysis and assessment of the gait. Proper dynamical models are not available in current literature associated with the wrist that can adequately determine the step length using recursive estimation techniques. This study presents a method to estimate the step length using angular velocity data from the wrist sensor. The technique maps the dynamical region corresponding to periods of activity of the gait manifested in angular velocity from the inertial measurement unit located at the wrist to that of the thigh using an artificial neural network, upon which an unscented Kalman filter is used to determine the horizontal position of the foot relative to the hip, and consequently, determine step length. The results for Step Length indicate an average accuracy of 81.8% and 91.1% for the young and elderly, respectively, when compared to a reference system, which, in our study, is data from a treadmill.

Estimation of Step Length with Wearable Thigh Sensor using an Unscented Kalman Filter

The determination of step length, an important gait parameter, has been a challenging task. Although unobtrusive sensors (inertial measurement units) have been developed recently, they cannot facilitate the automatic estimation of step length. In this article, we use a model-based technique to determine the step length using the Unscented Kalman Filter with angular velocity from a gyroscope inside the thigh pocket. We then propose a novel covariance estimation algorithm based on a screening technique that performs a search for the optimal Process Noise Covariance matrix. Upon implementing the Unscented Kalman Filter, the step length is found using the horizontal position of the foot relative to the hip using a patient-independent robust peak detection algorithm. This research article paves the way for algorithms that are computationally much faster than those stated in current literature, with more scope for the development of better algorithms for covariance estimation using the one proposed in this article as a foundation.

A Wearable, Multi-Frequency Device to Measure Muscle Activity Combining Simultaneous Electromyography and Electrical Impedance Myography

The detection of muscle contraction and the estimation of muscle force are essential tasks in robot-assisted rehabilitation systems. The most commonly used method to investigate muscle contraction is surface electromyography (EMG), which, however, shows considerable disadvantages in predicting the muscle force, since unpredictable factors may influence the detected force but not necessarily the EMG data. Electrical impedance myography (EIM) investigates the change in electrical impedance during muscle activities and is another promising technique to investigate muscle functions. This paper introduces the design, development, and evaluation of a device that performs EMG and EIM simultaneously for more robust measurement of muscle conditions subject to artifacts. The device is light, wearable, and wireless and has a modular design, in which the EMG, EIM, micro-controller, and communication modules are stacked and interconnected through connectors. As a result, the EIM module measures the bioimpedance between 20 and 200 Ω with an error of less than 5% at 140 SPS. The settling time during the calibration phase of this module is less than 1000 ms. The EMG module captures the spectrum of the EMG signal between 20–150 Hz at 1 kSPS with an SNR of 67 dB. The micro-controller and communication module builds an ARM-Cortex M3 micro-controller which reads and transfers the captured data every 1 ms over RF (868 Mhz) with a baud rate of 500 kbps to a receptor connected to a PC. Preliminary measurements on a volunteer during leg extension, walking, and sit-to-stand showed the potential of the system to investigate muscle function by combining simultaneous EMG and EIM.

Model-Based Step Length Estimation Using a Pendant-Integrated Mobility Sensor

The step length is an important parameter in gait analysis. Long-term monitoring applications for gait analysis are often based on inertial measurement units (IMUs) due to their low-cost and unobtrusive nature. Spatial gait parameters, such as step or stride length, are therefore not directly accessible. In this contribution, we focus on model-based algorithms for step length estimation based on a pendant-integrated IMU during slow walking speeds. We present a model-based approach to estimate the step length, which is divided into two successive steps. As the first part of our approach, we present an algorithm for estimation of the vertical displacement of the center of mass (CoM) during gait. Based on this estimate, we present a novel approach to estimate the step length, which we have deduced from a previously published, simplified gait model. The algorithm is compared to a commonly known approach for accelometry-based step length prediction and validated against reference data obtained from a force plate-integrated treadmill for gait analysis during a clinical study with ten healthy subjects. Due to the applicability to gait stability assessment in elderly or gait impaired patients, we focus on slow walking speeds (1-4 km h^-1). The presented algorithms outperform the existing approach and the proposed model calculations provide a more accurate prediction. For the vertical displacement, we achieved a precision of 9.3% (CoV) with an RMSE of 1.5 mm in terms of the trajectory amplitude during normal gait patterns. The step length estimation yields satisfying results with a relative prediction error of lower than 10% for walking speeds of 2-4kmh^-1.

Hypoglycemia in Older Adults: Time Trends and Treatment Differences in Patients Aged ≥75 Years With Type 2 Diabetes

OBJECTIVES

Hypoglycemia is a potentially life-threatening drug event under antidiabetic treatment. The aim of the study was to examine time trends in severe hypoglycemia in older adults with type 2 diabetes mellitus (T2DM) and antidiabetic treatment.

DESIGN

Multicenter prospective diabetes patient follow-up registry (DPV).

SETTING AND PARTICIPANTS

Patients aged ≥75 years with T2DM and documented treatment between 2005 and 2019.

METHODS

Outcomes of interest were rates of severe hypoglycemia, diabetes therapy, body mass index, HbA1c, and estimated glomerular filtration rate. Time trends of outcomes were analyzed in the whole cohort and compared between age groups (75-<80, 80-<85, ≥85 years).

RESULTS

A total of 136,931 patients from 188 diabetes centers were included. The adjusted HbA1c decreased from 7.3% (95% confidence interval 7.3-7.4) in 2005 to 7.2% (7.2-7.2) in 2019 (P < .001), with no significant difference between age groups (P = .47). Rates of severe hypoglycemia decreased from 6.7 (6.0-7.4) to 4.1 of 100 person-years (3.7-4.5) (P < .001) in the entire population. Patients aged ≥85 years had constantly lower HbA1c levels compared with younger groups (P < .001). Although severe hypoglycemia decreased the most in the ≥85 age group (P < .001), severe hypoglycemia remained consistently higher in this group compared with the 75 to <80 years group (P < .001).

CONCLUSIONS AND IMPLICATIONS

During the analyzed time, the risk for severe hypoglycemia decreased. Although drugs with intrinsic risk for hypoglycemia were used less frequently, antidiabetic treatment in older adults should be further improved to continue reducing severe hypoglycemia in this age group, potentially accepting less strict metabolic control and age-specific target ranges.

Noncontact Monitoring of Heart Rate and Heart Rate Variability in Geriatric Patients Using Photoplethysmography Imaging

OBJECTIVE

Geriatric patients, especially those with dementia or in a delirious state, do not accept conventional contact-based monitoring. Therefore, we propose to measure heart rate (HR) and heart rate variability (HRV) of geriatric patients in a noncontact and unobtrusive way using photoplethysmography imaging (PPGI).

METHODS

PPGI video sequences were recorded from 10 geriatric patients and 10 healthy elderly people using a monochrome camera operating in the near-infrared spectrum and a colour camera operating in the visible spectrum. PPGI waveforms were extracted from both cameras using superpixel-based regions of interests (ROI). A classifier based on bagged trees was trained to automatically select artefact-free ROIs for HR estimation. HRV was calculated in the time-domain and frequency-domain.

RESULTS

an RMSE of 1.03 bpm and a correlation of 0.8 with the reference was achieved using the NIR camera for HR estimation. Using the RGB camera, RMSE and correlation improved to 0.48 bpm and 0.95, respectively. Correlation for HRV in the frequency-domain (LF/HF-ratio) was 0.50 using the NIR camera and 0.70 using the RGB camera.

CONCLUSION

We were able to demonstrate that PPGI is very suitable to measure HR and HRV in geriatric patients. We strongly believe that PPGI will become clinically relevant in monitoring of geriatric patients.

SIGNIFICANCE

we are the first group to measure both HR and HRV in awake geriatric patients using PPGI. Moreover, we systematically evaluate the effects of the spectrum (near-infrared vs. visible), ROI, and additional motion artefact reduction algorithms on the accuracy of estimated HR and HRV.

Neurogeriatrics-a vision for improved care and research for geriatric patients with predominating neurological disabilities

Geriatric medicine is a rapidly evolving field that addresses diagnostic, therapeutic and care aspects of older adults. Some disabilities and disorders affecting cognition (e.g. dementia), motor function (e.g. stroke, Parkinson’s disease, neuropathies), mood (e.g. depression), behavior (e.g. delirium) and chronic pain disorders are particularly frequent in old subjects. As knowledge about these age-associated conditions and disabilities is steadily increasing, the integral implementation of neurogeriatric knowledge in geriatric medicine and specific neurogeriatric research is essential to develop the field. This article discusses how neurological know-how could be integrated in academic geriatric medicine to improve care of neurogeriatric patients, to foster neurogeriatric research and training concepts and to provide innovative care concepts for geriatric patients with predominant neurological conditions and disabilities.

Estimation of Stride Time Variability in Unobtrusive Long-Term Monitoring Using Inertial Measurement Sensors

Stride time variability is an important indicator for the assessment of gait stability. An accurate extraction of the stride intervals is essential for determining stride time variability. Peak detection is a commonly used method for gait segmentation and stride time estimation. Standard peak detection algorithms often fail due to additional movement components and measurement noise. A novel algorithm for robust peak detection in inertial sensor signals was proposed in a previous contribution. In this work, we present a novel approach for estimation of stride time variability based on the formerly proposed peak detection algorithm applied to an unobtrusive sensor setup for motion monitoring. The unobtrusive sensor setup includes a wrist sensor, a pocket or belt sensor, and a necklace sensor, all equipped with both accelerometer and gyroscope. The goal of this work is to implement a generalized approach for accurate and robust stride interval determining algorithm for different sensor locations. Therefore, treadmill and level ground walking experiments were conducted with ten healthy subjects at increasing walking speeds and an age-simulating suit. With the proposed algorithm, we achieved a RMSE of 0.07 s for the stride interval estimation during treadmill walking experiments. The results give promising indications that detection of variation of stride time variability is possible using the proposed unobtrusive sensor setup.

Using a Motion Capture System as Reference for Motion Tracking in Photoplethysmography Imaging

Photoplethysmography Imaging (PPGI) is a camera-based and non-contact technology for measurement of physiological signals. It has been shown that important physiological parameters such as heart rate, heart rate variability and respiratory rate can be derived from PPGI. However, as is the case with most non-contact measurement techniques, motion artefacts present a major challenge. Various algorithms for application to both the 2D PPGI video frames as well as the resulting 1D PPGI waveforms have been developed in order to enhance robustness against motion. In this paper, we focus on the aspect of feature point tracking in the 2D PPGI video sequences. We present an experimental setup, where we used a motion capture system in order to obtain a reference for motion during the recording of PPGI video sequences. In a laboratory experiment, PPGI video sequences were recorded from ten healthy volunteers, who were asked to perform various movements during the recording. The KLT tracking algorithm was applied to the recorded sequences and results compared with the reference values from the motion capture system. The results indicate, that tracking of measurement regions in PPGI video sequences is only one element towards motion robust PPGI. In most scenarios, tracking is not sufficiently precise, requiring further processing of the PPGI waveforms in order to reduce motion artefacts in PPGI signals. These indications were confirmed by further analysis when we looked into the effects of tracking on PPGI heart rate extraction.

Non-Contact Remote Measurement of Heart Rate Variability using Near-Infrared Photoplethysmography Imaging

Heart rate variability (HRV) is an important clinical parameter associated with the autonomous nervous system (ANS), age, as well as many diseases such as myocardial infarction, diabetes or renal failure. Gold standard for measurement of HRV is a high-resolution electrocardiogram (ECG). With the current trend towards non-contact and unobtrusive monitoring of vital signs, HRV has also become an interesting and important parameter for non-contact monitoring. In this paper, we present an approach towards non-contact and unobtrusive monitoring of heart rate variability using the camera-based technology of photoplethysmography imaging (PPGI). We investigated the suitability of invisible near-infrared illumination for PPGI, which would enable measurement of HRV in darkness. We compared results obtained using infrared illumination with those obtained using visible light as PPGI illumination and calculated both time-domain as well as frequency-domain HRV parameters. The results achieved with infrared illumination were on par with those using conventional illumination in the visible spectrum. We concluded that infrared illumination enables unobtrusive and non-contact remote HRV measurement in both darkness as well as regular daylight conditions using PPGI.

Walking with rollator: a systematic review of gait parameters in older persons

Background

The aging population increasingly needs assistive technologies, such as rollators, to function and live less dependently. Rollators are designed to decrease the risk of falls by improving the gait mechanics of their users. However, data on the biomechanics of rollator assisted gait of older adults are limited, or mostly derived from experiments with younger adults.

Methods and results

This review summarises the data from 18 independent studies on the kinematic and kinetic gait parameters of assisted gait of older persons. All of these studies evaluated spatio-temporal parameters, but not joint angles or moments.

Conclusion

Due to the limited research on rollator supported gait in older adults, the number of parameters that could be analysed in this systematic review was restricted. Further research in the analysis of spatio-temporal parameters and a higher standardisation in clinical research will be necessary.

Improve hip fracture outcome in the elderly patient (iHOPE): a study protocol for a pragmatic, multicentre randomised controlled trial to test the efficacy of spinal versus general anaesthesia

INTRODUCTION

Hip fracture surgery is associated with high in-hospital and 30-day mortality rates and serious adverse patient outcomes. Evidence from randomised controlled trials regarding effectiveness of spinal versus general anaesthesia on patient-centred outcomes after hip fracture surgery is sparse.

METHODS AND ANALYSIS

The iHOPE study is a pragmatic national, multicentre, randomised controlled, open-label clinical trial with a two-arm parallel group design. In total, 1032 patients with hip fracture (>65 years) will be randomised in an intended 1:1 allocation ratio to receive spinal anaesthesia (n=516) or general anaesthesia (n=516). Outcome assessment will occur in a blinded manner after hospital discharge and inhospital. The primary endpoint will be assessed by telephone interview and comprises the time to the first occurring event of the binary composite outcome of all-cause mortality or new-onset serious cardiac and pulmonary complications within 30 postoperative days. In-hospital secondary endpoints, assessed via in-person interviews and medical record review, include mortality, perioperative adverse events, delirium, satisfaction, walking independently, length of hospital stay and discharge destination. Telephone interviews will be performed for long-term endpoints (all-cause mortality, independence in walking, chronic pain, ability to return home cognitive function and overall health and disability) at postoperative day 30±3, 180±45 and 365±60. ETHICS AND DISSEMINATION: iHOPE has been approved by the leading Ethics Committee of the Medical Faculty of the RWTH Aachen University on 14 March 2018 (EK 022/18). Approval from all other involved local Ethical Committees was subsequently requested and obtained. Study started in April 2018 with a total recruitment period of 24 months. iHOPE will be disseminated via presentations at national and international scientific meetings or conferences and publication in peer-reviewed international scientific journals.

TRIAL REGISTRATION NUMBER

DRKS00013644; Pre-results.

Principles of the prolactin/vasoinhibin axis

The hormonal family of vasoinhibins, which derive from the anterior pituitary hormone prolactin, are known for their inhibiting effects on blood vessel growth, vasopermeability, and vasodilation. As pleiotropic hormones, vasoinhibins act in multiple target organs and tissues. The generation, secretion, and regulation of vasoinhibins are embedded into the organizational principle of an axis, which integrates the hypothalamus, the pituitary, and the target tissue microenvironment. This axis is designated as the prolactin/vasoinhibin axis. Disturbances of the prolactin/vasoinhibin axis are associated with the pathogenesis of retinal and cardiac diseases and with diseases occurring during pregnancy. New phylogenetical, physiological, and clinical implications are discussed.

C-terminal agrin fragment (CAF) reflects renal function in patients suffering from severe sepsis or septic shock

BACKGROUND

One of the main causes of acute kidney injury (AKI) in patients treated on an intensive care unit (ICU) is sepsis. The identification of new biomarkers indicating the early development and future course of AKI are of utmost medical interest. The C-terminal agrin fragment (CAF) is measurable in blood serum and might reflect kidney function. Therefore, this study evaluates CAF in patients presenting to an internal ICU with severe sepsis or septic shock. Serum levels of CAF are correlated with biomarkers of kidney function, markers of systemic inflammation, and the presence of AKI and renal replacement therapy (RRT).

METHODS

61 patients suffering from severe sepsis or septic shock were included during the first 24 hours of ICU treatment and blood samples for biomarker measurements, i.e., CAF, creatinine, cystatin C, procalcitonin (PCT), interleukin 6, C reactive protein (CRP), and white blood cells (WBC) were collected on the first day of intensive care treatment. The number of RRT days and the incidence of AKI were documented.

RESULTS

13% of the patients (8/61) suffered from SIRS/sepsis, 20% (12/61) from severe sepsis, and 67% (41/61) from septic shock. Serum levels of CAF significantly correlated with creatinine (r = 0.623, p < 0.001) and cystatin C (r = 0.578, p < 0.001). Multiple linear regression analyses adjusting CAF for inflammatory parameters (i.e., WBC, CRP, interleukin 6, PCT), age, and gender showed a strong correlation between CAF and creatinine (r = 0.643, p < 0.001). Serum levels of CAF were significantly associated with the need of RRT (area under the curve (AUC) = 0.772, 95% CI: 0.641-0.903, p = 0.002) and the incidence of AKI (AUC = 0.721, 95% CI: 591-0.850, p = 0.004) as indicated by ROC analysis.

CONCLUSIONS

In patients suffering from severe sepsis and septic shock, serum levels of CAF were significantly associated with kidney function and RRT and were not influenced by severe septic conditions.

Lipid accumulation in hepatocytes induces fibrogenic activation of hepatic stellate cells

Despite the initial belief that non-alcoholic fatty liver disease is a benign disorder, it is now recognized that fibrosis progression occurs in a significant number of patients. Furthermore, hepatic steatosis has been identified as a risk factor for the progression of hepatic fibrosis in a wide range of other liver diseases. Here, we established an in vitro model to study the effect of hepatic lipid accumulation on hepatic stellate cells (HSCs), the central mediators of liver fibrogenesis. Primary human hepatocytes were incubated with the saturated fatty acid palmitate to induce intracellular lipid accumulation. Subsequently, human HSCs were incubated with conditioned media (CM) from steatotic or control hepatocytes. Lipid accumulation in hepatocytes induced the release of factors that accelerated the activation and proliferation of HSC, and enhanced their resistance to apoptosis, largely mediated via activation of the PI-3-kinase pathway. Furthermore, CM from steatotic hepatocytes induced the expression of the profibrogenic genes TGF-beta, tissue inhibitor of metallo-proteinase-1 (TIMP-1), TIMP-2 and matrix-metallo-proteinase-2, as well as nuclear-factor kappaB-dependent MCP-1 expression in HSC. In summary, our in vitro data indicate a potential mechanism for the pathophysiological link between hepatic steatosis and fibrogenesis in vivo. Herewith, this study provides an attractive in vitro model to study the molecular mechanisms of steatosis-induced fibrogenesis, and to identify and test novel targets for antifibrotic therapies in fatty liver disease.

Fatty acid-induced induction of Toll-like receptor-4/nuclear factor-kappaB pathway in adipocytes links nutritional signalling with innate immunity

To study the effects of fatty acids and the involvement of the Toll-like receptor-4/nuclear factor-kappaB (TLR-4/NF-kappaB) pathway with respect to the secretion of adipokines from adipocytes 3T3-L1 adipocytes were stimulated with increasing doses of fatty acids. The secretion of adiponectin, resistin and monocyte chemoattractant protein-1 (MCP-1) was measured by enzyme-linked immunosorbent assay. The NF-kappaB p65 nuclear translocation and TLR-4 expression were investigated by Western blot. The effects mediated by NF-kappaB were tested using a specific NF-kappaB-inhibitor and TLR-4-induced effects were analysed with a neutralizing TLR-4 antibody. Binding of (14)C-labelled fatty acids to TLR-4/MD-2 was investigated using a FLAG-tagged extracellular part of TLR-4 fused to full-length MD-2 via a linker (lipopolysaccharide-Trap). The messenger RNA (mRNA) expression of adipokines in abdominal adipose tissue of rats fed a standard chow or a high-fat diet was investigated by reverse transcription-polymerase chain reaction. The TLR-4 is induced during adipocyte differentiation and its expression is enhanced following fatty acid stimulation. The stimulatory effects of stearic and palmitic acids on MCP-1 secretion and of palmitoleic acid on resistin secretion are mediated via NF-kappaB. The stimulatory effects of stearic, palmitic and palmitoleic acids on resistin secretion and the stimulatory effect of stearic acid on MCP-1 secretion are mediated via TLR-4. Fatty acid-mediated effects are caused by an endogenous ligand because fatty acids were shown not to bind directly to TLR-4/MD-2. Adipose tissue mRNA expression and serum levels of adipokines did not differ in rats fed a high-fat diet. These data provide a new molecular mechanism by which fatty acids can link nutrition with innate immunity.

Aldehyde oxidase 1 is highly abundant in hepatic steatosis and is downregulated by adiponectin and fenofibric acid in hepatocytes in vitro

Adiponectin protects the liver from steatosis caused by obesity or alcohol and therefore the influence of adiponectin on human hepatocytes was analyzed. GeneChip experiments indicated that recombinant adiponectin downregulates aldehyde oxidase 1 (AOX1) expression and this was confirmed by real-time RT-PCR and immunoblot. AOX1 is a xenobiotic metabolizing protein and produces reactive oxygen species (ROS), that promote cell damage and fibrogenesis. Adiponectin and fenofibric acid activate peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and both suppress AOX1 protein and this is blocked by the PPAR-alpha antagonist RU486. Obesity is associated with low adiponectin, reduced hepatic PPAR-alpha activity and fatty liver, and AOX1 was found induced in the liver of rats on a high-fat diet when compared to controls. Free fatty acids and leptin, that are elevated in obesity, failed to upregulate AOX1 in vitro. The current data indicate that adiponectin reduces AOX1 by activating PPAR-alpha whereas fatty liver disease is associated with elevated hepatic AOX1. High AOX1 may be associated with higher ROS well described to induce fibrogenesis in liver tissue but may also influence drug metabolism and activity.

Adiponectin and its receptors in rodent models of fatty liver disease and liver cirrhosis

AIM: To determine circulating and hepatic adiponectin in rodents with fatty liver disease or liver cirrhosis and investigate expression of the adiponectin receptors AdipoR1 on the mRNA and protein level and AdipoR2 on the mRNA level.

METHODS: Fat fed rats were used as a model for fatty liver disease and bile duct ligation in mice to investigate cirrhotic liver. Expression of AdipoR1 and AdipoR2 mRNA was determined by real time RT-PCR. AdipoR1 protein was analysed by immunoblot. Adiponectin was measured by ELISA.

RESULTS: Systemic adiponectin is reduced in fat-fed rats but is elevated in mice after bile duct ligation (BDL). Hepatic adiponectin protein is lower in steatotic liver but not in the liver of BDL-mice when compared to controls. Adiponectin mRNA was not detected in human liver samples or primary human hepatocytes nor in rat liver but recombinant adiponectin is taken up by isolated hepatocytes in-vitro. AdipoR1 mRNA and AdipoR1 protein levels are similar in the liver tissue of control and fat fed animals whereas AdipoR2 mRNA is induced. AdipoR2 mRNA and AdipoR1 mRNA and protein is suppressed in the liver of BDL-mice.

CONCLUSION: Our studies show reduced circulating adiponectin in a rat model of fatty liver disease whereas circulating adiponectin is elevated in a mouse model of cirrhosis and similar findings have been described in humans. Diminished hepatic expression of adiponectin receptors was only found in liver cirrhosis.