MRI adipose tissue segmentation and quantification in R (RAdipoSeg)

BACKGROUND

Excess adipose tissue is associated with increased cardiovascular and metabolic risk, but the volume of visceral and subcutaneous adipose tissue poses different metabolic risks. MRI with fat suppression can be used to accurately quantify adipose depots. We have developed a new semi-automatic method, RAdipoSeg, for MRI adipose tissue segmentation and quantification in the free and open source statistical software R.

METHODS

MRI images were obtained from wild-type mice on high- or low-fat diet, and from 20 human subjects without clinical signs of metabolic dysfunction. For each mouse and human subject, respectively, 10 images were segmented with RAdipoSeg and with the commercially available software SliceOmatic. Jaccard difference, relative volume difference and Spearman's rank correlation coefficients were calculated for each group. Agreement between the two methods were analysed with Bland-Altman plots.

RESULTS

RAdipoSeg performed similarly to the commercial software. The mean Jaccard differences were 10-29% and the relative volume differences were below ( ±) 20%. Spearman's rank correlation coefficient gave p-values below 0.05 for both mouse and human images. The Bland-Altman plots indicated some systematic and proporitional bias, which can be countered by the flexible nature of the method.

CONCLUSION

RAdipoSeg is a reliable and low cost method for fat segmentation in studies of mice and humans.

FUNCTIONAL INDEPENDENCE, ACCESS TO KIDNEY TRANSPLANTATION, AND WAITLIST MORTALITY

Although functional independence is a health priority for patients with advanced CKD, 50% of those who progress to end-stage kidney disease (ESKD) develop difficulties carrying-out essential day-to-day activities. Functional independence is not routinely assessed at kidney transplant (KT) evaluation; therefore, it is unclear what percentage of candidates are functionally independent and whether independence is associated with access to KT and waitlist mortality. We studied a prospective cohort of 3,168 ESKD participants (1/2009-6/2018) who self-reported functional independence in basic Activities of Daily Living (ADL) and more complex Instrumental Activities of Daily Living (IADL). We estimated adjusted associations between functional independence (separately) and listing (Cox), waitlist mortality (competing risks), and transplant rates (Poisson). At evaluation, 92.4% were independent in ADLs, but only 68.5% were independent in IADLs. Functionally independent participants had a higher chance of listing for KT (ADL:aHR=1.55,95%CI:1.30-1.87; IADL:aHR=1.39,95%CI 1.26-1.52). Among KT candidates, ADL independence was associated with lower waitlist mortality risk (SHR=0.66,95%CI:0.44-0.98) and higher rate of KT (IRR=1.58,95%CI:1.12-2.22); the same was not observed for IADL independence (SHR=0.86,95%CI:0.65-1.12; IRR=1.01,95%CI:0.97-1.19). ADL independence was associated with better KT access and lower waitlist mortality; clinicians should screen KT candidates for ADL independence, and identify interventions to maintain independence to improve waitlist outcomes.

POST-TRANSPLANT FUNCTIONAL STATUS TRAJECTORY AMONG ADULT KIDNEY TRANSPLANT RECIPIENTS

Frailty and disabilities are highly prevalent among kidney transplant (KT) recipients, but are not routinely measured in KT recipients. The Karnofsky Performance Scale (KPS) is a clinically perceived measure used to evaluate patient’s ability to manage daily activities, but little is known about its post-KT trajectories and its relationship to frailty and disability in KT recipients. We leveraged a cohort of 159,992 adult KT recipients from SRTR (1/2005-6/2018) and a cohort of 1,106 adult KT recipients from a prospective cohort study on aging and KT with recorded KPS (range 10%-100% integers). In each separate cohort, we used mixed effects models to assess differences in trajectories of KPS post-KT. In 159,992 KT recipients in SRTR, the mean unadjusted KPS score was 88.34% (95%CI: 88.28%, 88.40%) and declined at a rate of -0.59%/year (95%CI: -0.61%, -0.57%) post-KT, such that by 2-years post-KT the average was 87.00% (95%CI: 86.94%, 87.05%). Age at KT was associated with steeper decline in KPS (p0.05). KPS is a measure of functional status distinct from frailty, ADL, IADL, and SPPB at KT admission that declines with older age post-KT. Older KT recipients should be monitored closely for declines in physical function, and potentially undergo prehabilitation to improve functional status post-KT.

Absence of the proteoglycan decorin reduces glucose tolerance in overfed male mice

Studies have implicated the extracellular matrix (ECM) of adipose tissue in insulin resistance. The proteoglycan decorin, a component of ECM, has been associated with glucose tolerance, but possible causal effects on metabolism remain to be explored. We here sought to determine metabolic consequences of loss of decorin in mice (DcnKO). DcnKO mice were fed a low-fat (LF) or high-fat (HF) diet for 10 weeks and body weight and food intake was recorded. An intraperitoneal glucose tolerance test was performed after eight weeks. Blood samples and adipose, liver and muscle tissues were collected at sacrifice. Global gene expression was measured in adipose tissue, and expression of decorin was also analyzed in human adipose samples. DcnKO mice showed increased feed efficiency during overfeeding and impaired glucose tolerance. Adipose leptin mRNA and circulating leptin levels were elevated in DcnKO mice, along with a downregulation of genes involved in ECM organization and triglyceride biosynthesis, and an upregulation of adipose genes involved in complement and coagulation cascades. Consistent with a protective metabolic role for decorin, in obese patients we found increased adipose decorin expression after profound fat loss, particularly in the stromal vascular fraction. Loss of decorin in mice caused impaired glucose tolerance in association with increased feed efficiency and altered gene expression in adipose tissue. Our data provide evidence that decorin is an important factor for maintaining glucose tolerance.

IRX5 regulates adipocyte amyloid precursor protein and mitochondrial respiration in obesity

Objective

A causal obesity risk variant in the FTO locus was recently shown to inhibit adipocyte thermogenesis via increased adipose expression of the homeobox transcription factors IRX3 and IRX5. However, causal effects of IRX5 on fat storage remain to be shown in vivo, and discovery of downstream mediators may open new therapeutic avenues.

Methods

17 WT and 13 Irx5 knockout (KO) mice were fed low-fat control (Ctr) or high-fat (HF) diet for 10 weeks. Body weight, energy intake and fat mass were measured. Irx5-dependent gene expression was explored by transcriptome analysis of epididymal white adipose tissue (eWAT), confirmatory obesity-dependent expression in human adipocytes in vivo, and in vitro knock-down, overexpression and transcriptional activation assays.

Results

Irx5 knock-out mice weighed less, had diminished fat mass, and were protected from diet-induced fat accumulation. Key adipose mitochondrial genes Pparγ coactivator 1-alpha (Pgc-1α) and uncoupling protein 1 (Ucp1) were upregulated, and a gene network centered on amyloid precursor protein (App) was downregulated in adipose tissue of knock-out mice and in isolated mouse adipocytes with stable Irx5 knock-down. An APP-centered network was also enriched in isolated adipocytes from obese compared to lean humans. IRX5 overexpression increased APP promoter activity and both IRX5 and APP inhibited transactivation of PGC-1α and UCP1. Knock-down of Irx5 or App increased mitochondrial respiration in adipocytes.

Conclusion

Irx5-KO mice were protected from obesity and this can partially be attributed to reduced adipose App and improved mitochondrial respiration. This novel Irx5-App pathway in adipose tissue is a possible therapeutic entry point against obesity.

Three-year Results of a Pilot Program in Early Liver Transplantation for Severe Alcoholic Hepatitis

OBJECTIVE

To examine our pilot to transplant selected patients with acute alcoholic hepatitis, initiated in October 2012.

BACKGROUND

Six months of alcohol abstinence is typically required before liver transplant. A Franco-Belgian protocol showed that early transplant in severe alcoholic hepatitis could improve survival with low incidence of alcohol relapse. Application of this controversial indication is growing despite unclear generalizability.

METHODS

Data was collected on all patients with alcohol-related liver disease since initiation of the pilot through June 2015. Patients were stratified into two groups: severe alcoholic hepatitis as first liver decompensation (Group 1), alcoholic cirrhosis with ≥6 months abstinence (Group 2). Alcohol relapse was defined as any evidence of alcohol consumption after transplant, which was assessed for harmful patterns of binge or frequent drinking.

RESULTS

Forty-three patients underwent liver transplant, including 17 patients in Group 1. Six-month survival was 100% versus 89% for Groups 1 and 2, respectively (P = 0.27). Alcohol relapse was similar in Group 1 versus Group 2: 23.5% versus 29.2% (P > 0.99). Harmful drinking was higher in Group 1 versus Group 2, despite lack of statistical significance: 23.5% versus 11.5% (P = 0.42).

CONCLUSIONS

In this pilot with carefully selected patients, early liver transplant provided excellent short-term survival, and similar rates of alcohol relapse compared with patients with 6 months of abstinence. Harmful patterns of relapse remain challenging in this population, highlighting the need for validated models to predict alcohol relapse, and need for extreme caution in selecting patients for this exceptional indication. Larger prospective studies and longer follow up are necessary.

FTO Obesity Variant Circuitry and Adipocyte Browning in Humans

BACKGROUND

Genomewide association studies can be used to identify disease-relevant genomic regions, but interpretation of the data is challenging. The FTO region harbors the strongest genetic association with obesity, yet the mechanistic basis of this association remains elusive.

METHODS

We examined epigenomic data, allelic activity, motif conservation, regulator expression, and gene coexpression patterns, with the aim of dissecting the regulatory circuitry and mechanistic basis of the association between the FTO region and obesity. We validated our predictions with the use of directed perturbations in samples from patients and from mice and with endogenous CRISPR-Cas9 genome editing in samples from patients.

RESULTS

Our data indicate that the FTO allele associated with obesity represses mitochondrial thermogenesis in adipocyte precursor cells in a tissue-autonomous manner. The rs1421085 T-to-C single-nucleotide variant disrupts a conserved motif for the ARID5B repressor, which leads to derepression of a potent preadipocyte enhancer and a doubling of IRX3 and IRX5 expression during early adipocyte differentiation. This results in a cell-autonomous developmental shift from energy-dissipating beige (brite) adipocytes to energy-storing white adipocytes, with a reduction in mitochondrial thermogenesis by a factor of 5, as well as an increase in lipid storage. Inhibition of Irx3 in adipose tissue in mice reduced body weight and increased energy dissipation without a change in physical activity or appetite. Knockdown of IRX3 or IRX5 in primary adipocytes from participants with the risk allele restored thermogenesis, increasing it by a factor of 7, and overexpression of these genes had the opposite effect in adipocytes from nonrisk-allele carriers. Repair of the ARID5B motif by CRISPR-Cas9 editing of rs1421085 in primary adipocytes from a patient with the risk allele restored IRX3 and IRX5 repression, activated browning expression programs, and restored thermogenesis, increasing it by a factor of 7.

CONCLUSIONS

Our results point to a pathway for adipocyte thermogenesis regulation involving ARID5B, rs1421085, IRX3, and IRX5, which, when manipulated, had pronounced pro-obesity and anti-obesity effects. (Funded by the German Research Center for Environmental Health and others.).

Weight cycling promotes fat gain and altered clock gene expression in adipose tissue in C57BL/6J mice

Repeated attempts to lose weight by temporary dieting may result in weight cycling, eventually further gain of body fat, and possible metabolic adaptation. We tested this with a controlled experiment in C57BL/6J mice subjected to four weight cycles (WC), continuous hypercaloric feeding (HF), or low-fat feeding (LF). To search for genes involved in an adaptive mechanism to former weight cycling and avoid acute effects of the last cycle, the last hypercaloric feeding period was prolonged by an additional 2 wk before euthanization. Total energy intake was identical in WC and HF. However, compared with HF, the WC mice gained significantly more total body mass and fat mass and showed increased levels of circulating leptin and lipids in liver. Both the HF and WC groups showed increased adipocyte size and insulin resistance. Despite these effects, we also observed an interesting maintenance of circulating adiponectin and free fatty acid levels after WC, whereas changes in these parameters were observed in HF mice. Global gene expression was analyzed by microarrays. Weight-cycled mice were characterized by a downregulation of several clock genes (Dbp, Tef, Per1, Per2, Per3, and Nr1d2) in adipose tissues, which was confirmed by quantitative PCR. In 3T3-L1 cells, we found reduced expression of Dbp and Tef early in adipogenic differentiation, which was mediated via cAMP-dependent signaling. Our data suggest that clock genes in adipose tissue may play a role in metabolic adaptation to weight cycling.

The nuclear receptors NUR77, NURR1 and NOR1 in obesity and during fat loss

BACKGROUND

Adipose tissue is critical for systemic metabolic health. Identifying key factors regulating adipose tissue function is a research priority. The NR4A subfamily of nuclear receptors (NRs) (NR4A1/NUR77, NR4A2/NURR1 and NR4A3/NOR1) has emerged as important proteins in different disease states and in the regulation of metabolic tissues, particularly in liver and muscle. However, the expression of the NR4A members in human adipose tissue has not previously been described, and their target genes are largely unknown.

OBJECTIVE

To determine whether the NR4As are differentially expressed in human adipose tissue in obesity, and identify potential NR4A target genes.

DESIGN

Prospective analysis of s.c. adipose tissue before and 1 year after fat loss, and during in vitro differentiation of primary human preadipocytes. Case-control comparison of omental (OM) adipose tissue.

SUBJECTS

A total of 13 extremely obese patients undergoing biliopancreatic diversion with duodenal switch for fat loss, 12 extremely obese patients undergoing laparoscopic sleeve gastrectomy and 37 lean individuals undergoing hernia repair or laparotomy were included in the study. Measurements were done by quantitative PCR gene expression analysis of the NR4A members and in silico promoter analysis based on microarray data.

RESULTS

There was a strong upregulation of the NR4As in extreme obesity and normalization after fat loss. The NR4As were expressed at the highest level in stromal-vascular fraction compared with adipocytes, but were downregulated in both fractions after fat loss. Their expression levels were also significantly higher in OM compared with s.c. adipocytes in obesity. The NR4As were downregulated during differentiation of primary human preadipocytes. Moreover, the NR4As were strongly induced within 30 min of tissue incubation. Finally, promoter analysis revealed potential NR4A target genes involved in stress response, immune response, development and other functions. Our data show altered adipose tissue expression of the NR4As in obesity, suggesting that these stress responsive nuclear receptors may modulate pathogenic potential in humans.

Small core rib waveguides with embedded gratings in As2Se3 glass

Low-loss shallow-rib waveguides were fabricated using As2Se3 chalcogenide glass and polyamide-imide polymer. Waveguides were patterned directly in the As2Se3 layer by photodarkening followed by selective wet etching. Theory predicted a modal effective area of 3.5-4 microm2, and this was supported by near-field modal measurements. The Fabry-Perot technique was used to estimate propagation losses as low as ~0.25 dB/cm. First-order Bragg gratings near 1550 nm were holographically patterned in some waveguides. The Bragg gratings exhibited an index modulation on the order of 0.004. They were used as a means to assess the modal effective indices of the waveguides. Small core As2Se3 waveguides with embedded Bragg gratings have potential for realization of all-optical Kerr effect devices.

Photoinduced refractive index change in As2Se3 by 633nm illumination

Photodarkening of amorphous As2Se3 thin films was generated by a 633-nm HeNe laser. The refractive index and absorption coefficient of the chalcogenide glass was determined, both before and after exposure, by analyzing the material's transmission spectrum. In order to accurately determine the optical constants, the thin film's non-uniform thickness was accounted for. The increase in the refractive index and the coefficient of absorption was investigated and was found to demonstrate saturation with increased exposure time. Index changes as high as 0.05, or 2%, were obtained in As2Se3, a promising glass for all-optical switching.

MMI multiplexer for dual-channel erbium-doped waveguide amplifiers

A multimode interference coupler is proposed for pumping two erbium-doped waveguide amplifiers from a single 980 nm pump channel. Simulations predict that a device less than 2500 microm long can be made with signal and pump power losses of 0.28 dB and 0.63 dB respectively. The calculated 1 dB excess loss bandwidth of the device is 57 nm.

Six criteria to evaluate skill competency documentation

The documentation of critical care nurses' competence is essential so that required standards are met. The authors set criteria against which a competency documentation system can be evaluated.

Relationship of hydroxynortriptyline to nortriptyline concentration and creatinine clearance in depressed elderly outpatients

Plasma concentration of E-10-hydroxynortriptyline is increased in the elderly and may be related to both renal clearance of hydroxynortriptyline and rate of liver hydroxylation of nortriptyline. In 25 ambulatory, depressed elderly outpatients treated with therapeutic doses of nortriptyline, relationships among plasma levels of nortriptyline and E-10-hydroxynortriptyline, and an estimate of creatinine clearance were examined. Plasma levels of E-10-hydroxynortriptyline (corrected for varying dosage) were significantly correlated with age and inversely correlated (r = -0.50) with creatinine clearance but not with notriptyline or Z-10-hydroxynortriptyline concentration. E-10-hydroxynortriptyline concentration was about 5 1/2 times that of Z-10-hydroxynortriptyline. By best subsets multiple regression analyses, the ratio of E-10-hydroxynortriptyline to nortriptyline level was best predicted by plasma nortriptyline concentration, creatinine clearance, and age, all of which accounted for 63% of the variance. These results corroborate and extend previous findings in elderly inpatients in whom creatinine clearance was measured directly. In addition, age had an effect on E-10-hydroxynortriptyline independently of creatinine clearance. Since E-10-hydroxynortriptyline concentration has been related to both therapeutic efficacy and toxicity during nortriptyline treatment, it may be important to assess nortriptyline hydroxymetabolites in elderly patients and in those with renal insufficiency.

Retinal phototoxicity from the operating microscope. The role of inspired oxygen

The effect of the inspired oxygen concentration (FIO2) on the production of retinal phototoxicity by the operating microscope was studied in phakic rhesus monkeys. One eye of each monkey was exposed to light under conditions of 99% FIO2, and the other eye was exposed under 21% oxygen (O2). Three of four locations on each retina were exposed to light for durations varying from 1 1/2 to 20 minutes per exposure. Fundus photographs and fluorescein angiograms were obtained 24 to 72 hours after exposure. Animals were euthanatized for analysis of retinal histopathology at intervals from 2 weeks to 8 months after light exposure. Retinal phototoxic lesions were produced after an average of 5 minutes of light exposure under both 21 and 99% O2. O2 potentiated the light damage both clinically and histologically. Under both conditions, lesion size was directly related to the duration of light exposure (P less than 0.005). Lesions near threshold produced with 99% FIO2 were 1.6 to 6.9 (mean, 2.9) times larger than the corresponding lesions formed with 21% FIO2. Histologic damage was likewise more severe in lesions produced under high O2 conditions. Retinal repair occurred in lesions produced under high and low O2 conditions. Photoreceptor regeneration was nearly complete by 18 weeks, whereas retinal pigment epithelial (RPE) recovery lagged up to 1 1/2 months. The results of this study have important implications for clinical practice: the operating microscope can produce retinal phototoxicity rapidly, and O2 administered during ophthalmic procedures may potentiate the damage if appropriate precautions are not taken.