Using genetic association data to guide drug discovery and development: Review of methods and applications.

Evidence on the validity of drug targets from randomized trials is reliable but typically expensive and slow to obtain. In contrast, evidence from conventional observational epidemiological studies is less reliable because of the potential for bias from confounding and reverse causation. Mendelian randomization is a quasi-experimental approach analogous to a randomized trial that exploits naturally occurring randomization in the transmission of genetic variants. In Mendelian randomization, genetic variants that can be regarded as proxies for an intervention on the proposed drug target are leveraged as instrumental variables to investigate potential effects on biomarkers and disease outcomes in large-scale observational datasets. This approach can be implemented rapidly for a range of drug targets to provide evidence on their effects and thus inform on their priority for further investigation. In this review, we present statistical methods and their applications to showcase the diverse opportunities for applying Mendelian randomization in guiding clinical development efforts, thus enabling interventions to target the right mechanism in the right population group at the right time. These methods can inform investigators on the mechanisms underlying drug effects, their related biomarkers, implications for the timing of interventions, and the population subgroups that stand to gain the most benefit. Most methods can be implemented with publicly available data on summarized genetic associations with traits and diseases, meaning that the only major limitations to their usage are the availability of appropriately powered studies for the exposure and outcome and the existence of a suitable genetic proxy for the proposed intervention.

Leveraging human genetic data to investigate the cardiometabolic effects of glucose-dependent insulinotropic polypeptide signalling.

AIMS/HYPOTHESIS: The aim of this study was to leverage human genetic data to investigate the cardiometabolic effects of glucose-dependent insulinotropic polypeptide (GIP) signalling. METHODS: Data were obtained from summary statistics of large-scale genome-wide association studies. We examined whether genetic associations for type 2 diabetes liability in the GIP and GIPR genes co-localised with genetic associations for 11 cardiometabolic outcomes. For those outcomes that showed evidence of co-localisation (posterior probability >0.8), we performed Mendelian randomisation analyses to estimate the association of genetically proxied GIP signalling with risk of cardiometabolic outcomes, and to test whether this exceeded the estimate observed when considering type 2 diabetes liability variants from other regions of the genome. RESULTS: Evidence of co-localisation with genetic associations of type 2 diabetes liability at both the GIP and GIPR genes was observed for five outcomes. Mendelian randomisation analyses provided evidence for associations of lower genetically proxied type 2 diabetes liability at the GIP and GIPR genes with lower BMI (estimate in SD units -0.16, 95% CI -0.30, -0.02), C-reactive protein (-0.13, 95% CI -0.19, -0.08) and triacylglycerol levels (-0.17, 95% CI -0.22, -0.12), and higher HDL-cholesterol levels (0.19, 95% CI 0.14, 0.25). For all of these outcomes, the estimates were greater in magnitude than those observed when considering type 2 diabetes liability variants from other regions of the genome. CONCLUSIONS/INTERPRETATION: This study provides genetic evidence to support a beneficial role of sustained GIP signalling on cardiometabolic health greater than that expected from improved glycaemic control alone. Further clinical investigation is warranted. DATA AVAILABILITY: All data used in this study are publicly available. The scripts for the analysis are available at: https://github.com/vkarhune/GeneticallyProxiedGIP .

Revision Anterior Cruciate Ligament Reconstruction with the All-Soft Tissue Quadriceps Tendon Autograft Has Acceptable Early and Intermediate-Term Outcomes.

PURPOSE: The purposes were to (1) examine early to intermediate-term clinical outcomes and complications of revision anterior cruciate ligament reconstruction (ACLR) using all-soft tissue quadriceps tendon (QT) autografts, and (2) compare quadriceps strength between patients who had hamstring versus patella tendon autografts in their previous reconstruction. METHODS: One hundred patients (52 males/48 females; 22.6 ± 8.0 years) undergoing revision ACLR with all-soft tissue QT autografts were prospectively followed. All revision procedures were performed by a single surgeon, using a minimally invasive graft harvest technique and suspensory fixation. Subjective assessment of knee function was obtained before and after surgery with the International Knee Documentation Committee (IKDC) survey. Postoperative knee laxity and isokinetic quadriceps strength were collected at regular intervals. Strength was reported as limb symmetry index (LSI; surgical side divided by nonsurgical side). Complications including hematomas, postoperative loss of knee extension, and graft failures were recorded. To determine clinical significance (P ≤ .05), outcomes were compared using analysis of variance or paired samples t-tests. RESULTS: The mean IKDC scores significantly improved (54.3 ± 13.0 vs 82.8 ± 13.8), with an average follow-up of 42.2 ± 21.2 months. There were no significant changes in knee laxity side-to-side differences: 6 weeks (1.2 ± 1.5 mm), 3 months (1.2 ± 1.8 mm), 6 months (1.4 ± 1.6 mm). Quadriceps LSIs significantly improved from 71.6% ± 19.3% at 6 months to 81.5% ± 19.3% at 12 months for 60°/s isokinetic testing and 76.6% ± 16.4% at 6 months to 83.9% ± 16.9% at 12 months for 180°/s testing. Graft harvest site hematomas developed in 2 patients, postoperative loss of knee extension in 4 patients, and graft failure in 11 patients. No significant differences in quadriceps or hamstrings LSIs were noted between patients with previous hamstring versus patella tendon autografts (P > .050). CONCLUSION: Revision ACLR with all-soft tissue QT autografts has acceptable early and intermediate-term outcomes with reasonable complication rates (11/80 patients with follow-up). Secondary insult to the extensor mechanism via QT autograft harvest does not adversely affect strength after prior patellar tendon versus hamstring autograft. LEVEL OF EVIDENCE: Level IV, cases series subgroup analysis.

Western diet-induced obesity disrupts the diurnal rhythmicity of hippocampal core clock gene expression in a mouse model.

Western diet (WD) feeding disrupts core clock gene expression in peripheral tissues and contributes to WD-induced metabolic disease. The hippocampus, the mammalian center for memory, is also sensitive to WD feeding, but whether the WD disrupts its core clock is unknown. To this end, male mice were maintained on a WD for 16 weeks and diurnal metabolism, gene expression and memory were assessed. WD-induced obesity disrupted the diurnal rhythms of whole-body metabolism, markers of inflammation and hepatic gene expression, but did not disrupt diurnal expression of hypothalamic Bmal1, Npas2 and Per2. However, all measured core clock genes were disrupted in the hippocampus after WD feeding and the expression pattern of genes implicated in Alzheimer's disease and synaptic function were altered. Finally, WD feeding disrupted hippocampal memory in a task- and time-dependent fashion. Our results implicate WD-induced alterations in the rhythmicity of hippocampal gene expression in the etiology of diet-induced memory deficits.

The effects of licogliflozin, a dual SGLT1/2 inhibitor, on body weight in obese patients with or without diabetes.

BACKGROUND: There is an unmet need for a safer and more effective treatment for obesity. This study assessed the effects of licogliflozin, a dual inhibitor of sodium-glucose co-transporter (SGLT) 1/2, on body weight, metabolic parameters and incretin hormones in patients with type 2 diabetes mellitus (T2DM) and/or obesity. METHODS: Patients with obesity (BMI, 35-50 kg/m2 ) were enrolled into a 12-week study (N = 88; licogliflozin 150 mg q.d.). Patients with T2DM were enrolled into a second, two-part study, comprising a single-dose cross-over study (N = 12; 2.5 - 300 mg) and a 14-day dosing study (N = 30; 15 mg q.d). Primary endpoints included effects on body weight, effects on glucose, safety and tolerability. Secondary endpoints included urinary glucose excretion (UGE24 ) and pharmacokinetics, while exploratory endpoints assessed the effects on incretin hormones (total GLP-1, PYY3-36 , and GIP), insulin and glucagon. RESULTS: Treatment with licogliflozin 150 mg q.d. for 12 weeks in patients with obesity significantly reduced body weight by 5.7% vs placebo (P < 0.001) and improved metabolic parameters such as significantly reduced postprandial glucose excursion (21%; P < 0.001), reduced insulin levels (80%; P < 0.001) and increased glucagon (59%; P < 0.001). In patients with T2DM, a single dose of licogliflozin 300 mg in the morning prior to an oral glucose tolerance test (OGTT) remarkably reduced glucose excursion by 93% (P < 0.001; incremental AUC0-4h ) and suppressed insulin by 90% (P < 0.01; incremental AUC0-4h ). Treatment with licogliflozin 15 mg q.d. for 14 days reduced 24-hour average glucose levels by 26% (41 mg/dL; P < 0.001) and increased UGE24 to 100 g (P < 0.001) in patients with T2DM. In addition, this treatment regimen significantly increased total GLP-1 by 54% (P < 0.001) and PYY3-36 by 67% (P < 0.05) post OGTT vs placebo, while significantly reducing GIP levels by 53% (P < 0.001). Treatment with licogliflozin was generally safe and well tolerated. Diarrhea (increased numbers of loose stool) was the most common adverse event in all studies (90% with licogliflozin vs 25% with placebo in the 12-week study), while a lower incidence of flatulence, abdominal pain and abdominal distension (25%-43% with licogliflozin vs 9%-11% with placebo in the 12-week study) were among the other gastrointestinal events reported. CONCLUSION: Licogliflozin treatment (1-84 days) leads to significant weight loss and favourable changes in a variety of metabolic parameters and incretin hormones. Dual inhibition of SGLT1/2 with licogliflozin in the gut and kidneys is an attractive strategy for treating obesity and diabetes.

The organization of prefrontal-subthalamic inputs in primates provides an anatomical substrate for both functional specificity and integration: implications for Basal Ganglia models and deep brain stimulation.

The identification of a hyperdirect cortico-subthalamic nucleus connection highlighted the important role of the subthalamic nucleus (STN) in regulating behavior. However, this pathway was shown primarily from motor areas. Hyperdirect pathways associated with cognitive and motivational cortical regions are particularly relevant given recent data from deep brain stimulation, both for neurologic and psychiatric disorders. Our experiments were designed to demonstrate the existence and organization of prefrontal-STN projections, help delineate the "limbic" STN, and determine whether convergence between cortico-STN fibers from functionally diverse cortical areas exists in the STN. We injected anterograde tracers in the ventromedial prefrontal, orbitofrontal, anterior cingulate, and dorsal prefrontal cortices of Macaca nemestrina and Macaca fascicularis to analyze the organization of terminals and passing fibers in the STN. Results show a topographically organized prefrontal hyperdirect pathway in primates. Limbic areas project to the medial tip of the nucleus, straddling its border and extending into the lateral hypothalamus. Associative areas project to the medial half, motor areas to the lateral half. Limbic projections terminated primarily rostrally and motor projections more caudally. The extension of limbic projections into the lateral hypothalamus, suggests that this region be included in the STN. A high degree of convergence exists between projections from functionally diverse cortical areas, creating potentially important interfaces between terminal fields. Taken together, the results provide an anatomical substrate to extend the role of the hyperdirect pathway in models of basal ganglia function, and new keys for understanding deep brain stimulation effects on cognitive and motivational aspects of behavior.

Sodium nitrite in patients with peripheral artery disease and diabetes mellitus: safety, walking distance and endothelial function.

Nitrite stores decrease after exercise in patients with peripheral artery disease (PAD) and diabetes represents decreased nitric oxide (NO) bioavailability that may contribute to endothelial dysfunction and limit exercise duration. The primary objective of this placebo-controlled study was the safety and tolerability of multiple doses of oral sodium nitrite in patients with PAD, predominantly with diabetes, over a period of 10 weeks. The primary efficacy endpoint was endothelial flow-mediated dilatation (FMD) and secondary efficacy endpoints included a 6-minute walk test and quality of life assessment. Of the 55 subjects, the most common side effects attributed to sodium nitrite were a composite of headache and dizziness occurring in 21% with the 40 mg dose and 44% with the 80 mg dose. There was no clinically significant elevation of methemoglobin. FMD non-significantly worsened in the placebo and 40 mg groups, but was stable in the 80 mg group. Diabetic patients receiving 80 mg had significantly higher FMD compared with the placebo and 40 mg groups. There was no significant change in 6-minute walk test or quality of life parameters over time compared to placebo. In conclusion, sodium nitrite therapy is well tolerated in patients with PAD. The possible clinical benefit of sodium nitrite should be studied in a larger and fully powered trial.

Finger volume pulse waveforms facilitate reliable assessment of heart rate variability, but not blood pressure variability or baroreflex function.

BACKGROUND: We sought to determine whether heart rate variability (HRV), blood pressure (BP) variability, and baroreceptor-heart rate reflex sensitivity can be reliably assessed using finger volume pulse waveforms obtained from the commercially available EndoPAT device. METHODS: Non-invasive BP (Finometer Pro as a non-invasive standard) and finger volume (EndoPAT) waveforms were recorded in 65 adults (37 ± 14 years; 60% female) and systolic BP and heart rate (HR) time series were derived after calibrating the EndoPAT signal based on systolic and diastolic BP values obtained by a sphygomomanometer. Transfer function analyses were performed to test for coherence between systolic BP and HR time series derived from the Finometer and EndoPAT devices. Time-domain HRV parameters, frequency domain HR and systolic BP variability parameters, and baroreflex sensitivity (sequence technique) were computed from Finometer- and EndoPAT-derived time series and intraclass correlation coefficients (ICC) were calculated. RESULTS: Squared coherence between systolic BP time series derived from the Finometer and EndoPAT devices was low, suggesting poor correlation. In contrast, squared coherence between HR time series derived from the two devices was excellent [High Frequency (HF) = 0.80, Low Frequency (LF) = 0.81], with gain values close to 1.0. ICC values for time- and frequency-domain HRV parameters were excellent (>0.9 except for relative HF HRV, which was 0.77), while ICC values for frequency-domain BP variability parameters and baroreceptor-HR reflex sensitivity were low. CONCLUSIONS: Finger volume pulse waveforms can be used to reliably assess both time-domain and frequency-domain HR variability. However, frequency domain BP variability parameters cannot be reliably assessed from finger volume pulse waveforms using the simple calibration technique used in this study.

Effects of antipsychotic drugs on cardiovascular variability in participants with bipolar disorder.

OBJECTIVE: The risk for cardiovascular diseases is elevated in persons with bipolar disorder. However, it remains unknown how much of this excess risk is secondary to pharmacologic treatment. We tested the hypothesis that current and cumulative antipsychotic drug exposure is associated with increased cardiovascular risk as indicated by lower heart rate variability (HRV) and increased blood pressure variability (BPV). METHODS: Fifty-five individuals with bipolar disorder (33 ± 7 years; 67% female) underwent noninvasive electrocardiogram assessment of time-domain and frequency-domain HRV, as well as BPV analysis. Medication histories were obtained through systematic review of pharmacy records for the past 5 years. RESULTS: Current antipsychotic exposure was associated with lower standard deviation of NN intervals. Second-generation antipsychotics were associated with lower standard deviation of NN intervals and root mean square of successive differences. There was no significant relationship between 5-year antipsychotic exposure and HRV in subjects with bipolar disorder. Exploratory analysis revealed a possible link between selective serotonin reuptake inhibitor exposure and increased low-frequency spectral HRV. CONCLUSIONS: Current antipsychotic use (particularly second-generation antipsychotics with high affinities for the D2S receptor) is associated with reduced autonomic-mediated variability of the HR. The absence of an association with cumulative exposure suggests that the effects are acute in onset and may therefore relate more to altered autonomic function than structural cardiovascular abnormalities. Future studies should prospectively examine effects of these antipsychotics on autonomic function.

Association of anxiety with resistance vessel dysfunction in human atherosclerosis.

OBJECTIVE: Anxiety predicts cardiovascular events, although the mechanism remains unclear. We hypothesized that anxiety symptoms will correlate with impaired resistance and conduit vessel function in participants aged 55 to 90 years. METHODS: Anxiety symptoms were measured with the Symptom Checklist-90--Revised in 89 participants with clinically diagnosed atherosclerotic cardiovascular disease and 54 healthy control participants. Vascular function in conduit arteries was measured using flow-mediated dilatation, and vascular function in forearm resistance vessels (FRVs) was measured using intra-arterial drug administration and plethysmography. RESULTS: Anxiety symptoms were not associated with flow-mediated dilatation in either group. Participants with atherosclerosis exhibited significant inverse associations of anxiety symptoms with FRV dilatation (acetylcholine: ß = -.302, p = .004). Adjustment for medication, risk factors, and depression symptoms did not alter the association between anxiety and FRV dysfunction, except for body mass index (BMI; anxiety: ß = -.175, p = .060; BMI: ß = -.494, p < .001). Although BMI was more strongly associated with FRV function than anxiety, combined BMI and anxiety accounted for greater variance in FRV function than either separately. Control participants showed no association of anxiety with FRV function. CONCLUSIONS: Anxiety is uniquely and substantially related to poorer resistance vessel function (both endothelial and vascular smooth muscle functions) in individuals with atherosclerosis. These relationships are independent of medication, depression, and cardiovascular risk factors, with the exception of BMI. These findings support the concept that anxiety potentially increases vascular events through worsening of vascular function in atherosclerotic disease.

White matter fractional anisotropy is inversely related to anxious symptoms in older adults with atherosclerosis.

OBJECTIVE: Clinical anxiety disorders are associated with white matter hyperintensities and diffusion abnormalities measured using diffusion tensor imaging. However, it is not known if this association extends into individuals with mild anxious symptoms without formal diagnosis, in those who are older, or in those who have atherosclerosis. The current study explores whether white matter integrity and/or organization significantly associates with anxious symptoms in older adults with and without atherosclerosis. METHODS: We recruited older adults (ages 55-90 years); 35 with clinically diagnosed atherosclerotic vascular disease (AVD) and 22 without AVD. Anxious symptoms were measured using the validated Symptom Checklist-90-Revised. Fractional anisotropy (FA), a proxy for white matter organization and health, was measured in the white matter globally, by lobe, and in several smaller regions of interest suggested by the literature. Partial correlations between anxious symptoms and FA were calculated, controlling for significant covariates. RESULTS: Participants with and without AVD did not differ in severity of anxious symptom endorsement. There was a unique inverse relationship between white matter health and anxious symptoms in the AVD participants, but not in healthy comparisons. Significant relationships were observed in the superior longitudinal fasciculus (r = -0.476, df = 32, p = 0.004), as well as the cingulum bundle, the frontal lobes, and the parietal lobes. CONCLUSIONS: Anxiety symptoms uniquely correlated with low FA in older adults with atherosclerosis. These findings may have implications for future research on the topic of anxiety in aging and vascular disease and warrant replication.

Relevant Dermatoses Among U.S. Military Service Members: An Operational Review of Management Strategies and Telemedicine Utilization.

Despite skin being the largest and most exposed organ of the human body, skin issues can be challenging to diagnose in deployed military service members. Common reasons deployed soldiers seek dermatological evaluation include infections, inflammatory skin conditions, and skin growth. Due to limited access to specialized care in deployed settings, dermatological conditions are undertreated and underdiagnosed. As a result, dermatological conditions are a leading contributor to decreased combat effectiveness among deployed medical forces. To lessen the burden of dermatological diseases, military providers should promptly identify operational skin diseases and alleviate modifiable barriers faced by service members. In a post-pandemic era with novel Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) and monkeypox infections, the duty to effectively treat operational skin lesions is ever important. The need for military dermatologists continues to rise as the global landscape continues to evolve with unprecedented infections and increased bioterrorism threats. Teledermatology offers many solutions to mitigate the high demand for dermatologists during pandemics. Dermatological consultations account for the highest number of telemedicine visits in the US Military Health System (MHS). As such, increased utilization of teledermatology will reduce infection-related dermatological sequelae and prevent the medical evacuation of service members from military operations. This review collates and categorizes relevant dermatological conditions encountered among deployed personnel. This report outlines the standard of care and modified treatments recommended according to potential barriers faced in operational settings.

Perceptions of the Emergency Medicine Resident Selection Process by Program Directors Following the Transition to a Pass/Fail USMLE Step 1.

Background: Beginning January 26th, 2022, the National Board of Medical Examiners transitioned scoring of the United States Medical Licensing Examination (USMLE) Step 1 from a 3-digit score to pass/fail. In the past, the Step 1 score has been weighted heavily by program directors (PDs) as one of the most important metrics when assessing medical student's competitiveness. Objective: The objective of this study was to evaluate the perceptions of emergency medicine (EM) PDs on the transition to a pass/fail USMLE Step 1 exam, and to elicit the opinions of EM PDs on the USMLE examinations' ability to predict resident performance. Methods: A survey consisting of ranking and multiple-choice questions was sent to EM PDs. The multiple-choice questions were asked to determine EM PDs level of confidence in the ability of Step 1 and Step 2 Clinical Knowledge (CK) to predict a student's ability to succeed in residency. The ranking questions focused on assessing each program's current resident selection practices in comparison to expected selection criteria changes following a transition to pass/fail Step 1. R studio and MATLAB were used for statistical analysis, and a P value <0.05 was considered significant. Results: The survey was completed by 57 (20.21%) EM PDs. When asked if Step 1 and Step 2 CK are accurate predictors of a resident's ability to perform clinically within EM, only 10.5% of PDs answered 'yes' to Step 1 being predictive, compared to 31.6% for Step 2 CK. Regarding selection criteria, the top quartile of attributes (standardized letters of evaluation [1st], away rotations [2nd], clerkship grades [3rd] and Step 2 CK score [4th]) remained the same following the transition. Conclusion: Our results indicate that the top quartile of attributes might remain the same, despite most PDs agreeing that Step 2 CK is a better predictor of a resident's performance.

Evaluating the impact of pass/fail United States Medical Licensing Examination Step 1 scoring on pathology residency selection.

Beginning 26 January 2022, the United States Medical Licensing Examination Step 1 changed from a numerical score to Pass/Fail. Historically, residency programs have used Step 1 scores as a valuable metric in assessing the competitiveness of applicants. We assessed how residency program criteria will change when evaluating applicants after Step 1 becomes Pass/Fail. A survey was distributed to the program directors of all 144 pathology residency programs accredited by Accreditation Council for Graduate Medical Education. Survey questions evaluated the importance of using Step 1 and Step 2 Clinical Knowledge (CK) scores when assessing applicants. Participants were asked to rank a list of applicant criteria used before and after Step 1 becomes Pass/Fail. Data were analyzed using chi-squared and paired t-tests with significance at P < 0.05. A total of 34 residency program directors (23.6%) responded to the survey. 76.5% (P< 0.001) of responders believed Step 1 scores were able to predict a resident's ability to pass their board exams, while 41.2% believed Step 2 CK could predict a resident's ability to pass board exams and perform clinically in pathology (P = 0.282). 61.8% of responders agreed that an applicant's medical school ranking would become more important (P = 0.001). There were no significant differences in the relative importance of 16 selection criteria after the change of Step 1 to Pass/Fail. It does not appear that Step 2 CK will become more important. Although results are constrained by a 23.6% response rate, it can be a start to guiding future students through residency applications.

A Survey of Otolaryngology Residency Programs on Adapting to the United States Medical Licensing Examination (USMLE) Step 1 Transitioning to Pass/Fail.

Objectives In February 2020, the National Board of Medical Examiners (NBME) announced that the United States Medical Licensing Examination (USMLE) Step 1 licensing examination would change from a numerical score to Pass/Fail (P/F). After implementation, many believe that USMLE-Step 2-Clinical Knowledge (CK) will become an important metric for students applying to otolaryngology (ENT). The purpose of this study is to determine factors important to resident selection after these changes. Methods A survey containing 15 questions related to resident selection practices and how changing USMLE Step 1 to P/F would impact future resident selection was designed. It was distributed to all ENT residency programs accredited by the Accreditation Council for Graduate Medical Education (ACGME). Results Forty percent of programs responded; 66% (95% confidence interval (CI): 51.1%-78.4%) felt that changing Step 1 scoring would not lead to students being more prepared for clinical rotations; 55% believe class rank will increase in significance (95% CI: 35.7%-64.3%). There was also an increase in the importance of Step 2 CK, which had a mean ranking of 10.67 prior to changes in Step 1 scoring and increased to 7.80 after P/F. Conclusions The changes in Step 1 scoring will likely lead to increasing importance of other objective measures like class rank or Step 2 CK. This may defeat the intended purpose put forth by the NBME. Therefore, further guidance on measures correlated with student performance as a resident will be integral to the selection process.

Ophthalmology Residency Program Director Survey on Pass/Fail U.S. Medical Licensing Exam Step 1 Scoring.

Background Beginning January 26, 2022, the U.S. Medical Licensing Exam (USMLE) Step 1 changed from a numerical score to pass/fail (P/F). The purpose of this study was to determine the perspective of ophthalmology program directors regarding this change in evaluating applicants. Methods After institutional review board approval, a survey was sent out to program directors of all 125 ophthalmology programs accredited by the Accreditation Council for Graduate Medical Education. Survey questions asked for program demographics, the utility of USMLE Step 1 and 2 Clinical Knowledge scores in assessing applicants, and the importance of 16 different applicant metrics before and after Step 1 becomes P/F. The metrics examined were: letters of recommendation; clerkship grades; class ranking; Alpha Omega Alpha Membership; Gold Humanism Honor Society Membership; Dean's Letter; involvement and leadership; personal statement; number of abstracts, presentations, and publications; mean number of research experiences in the specialty; Step 2 Clinical Knowledge score; volunteering; preclinical grades; away rotation in the specialty; the applicant having another graduate degree; and graduation from a top 40 National Institutes of Health-funded program. Data were analyzed using nonoverlapping 95% confidence intervals. Results The survey was completed by 50 (40%) program directors. Sixty-eight percent of respondents stated a student's ranking would be considered more after USMLE Step 1 scores become P/F, and 60% stated medical schools should share clerkship shelf exam scores with residency programs. There were no significant differences in program directors' rankings of applicant metrics following the transition to P/F Step 1. Conclusion Based on our data, program directors will likely not place a greater emphasis on Step 2 scores, despite it being the only remaining objective measure for all applicants following the switch to a P/F Step 1. Nevertheless, program directors expressed an interest in receiving other objective measures, such as shelf exam scores and class ranking, as part of the application process. Notably, we found no significant changes in the rankings of various applicant metrics before and after the transition to P/F Step 1, indicating that the metrics that were important to program directors prior to the change remain just as critical in the new era of admissions.

Generation of the NeoThy mouse model for human immune system studies.

Humanized mouse models, created via transplantation of human hematopoietic tissues into immune-deficient mice, support a number of research applications, including transplantation immunology, virology and oncology studies. As an alternative to the bone marrow, liver, thymus humanized mouse, which uses fetal tissues for generating a chimeric human immune system, the NeoThy humanized mouse uses nonfetal tissue sources. Specifically, the NeoThy model incorporates hematopoietic stem and progenitor cells from umbilical cord blood (UCB) as well as thymus tissue that is typically discarded as medical waste during neonatal cardiac surgeries. Compared with fetal thymus tissue, the abundant quantity of neonatal thymus tissue offers the opportunity to prepare over 1,000 NeoThy mice from an individual thymus donor. Here we describe a protocol for processing of the neonatal tissues (thymus and UCB) and hematopoietic stem and progenitor cell separation, human leukocyte antigen typing and matching of allogenic thymus and UCB tissues, creation of NeoThy mice, assessment of human immune cell reconstitution and all experimental steps from planning and design to data analysis. This entire protocol takes a total of ~19 h to complete, with steps broken up into multiple sessions of 4 h or less that can be paused and completed over multiple days. The protocol can be completed, after practice, by individuals with intermediate laboratory and animal handling skills, enabling researchers to make effective use of this promising in vivo model of human immune function.

Hepatocyte mARC1 promotes fatty liver disease.

Background & Aims: Non-alcoholic fatty liver disease (NAFLD) has a prevalence of ∼25% worldwide, with significant public health consequences yet few effective treatments. Human genetics can help elucidate novel biology and identify targets for new therapeutics. Genetic variants in mitochondrial amidoxime-reducing component 1 (MTARC1) have been associated with NAFLD and liver-related mortality; however, its pathophysiological role and the cell type(s) mediating these effects remain unclear. We aimed to investigate how MTARC1 exerts its effects on NAFLD by integrating human genetics with in vitro and in vivo studies of mARC1 knockdown. Methods: Analyses including multi-trait colocalisation and Mendelian randomisation were used to assess the genetic associations of MTARC1. In addition, we established an in vitro long-term primary human hepatocyte model with metabolic readouts and used the Gubra Amylin NASH (GAN)-diet non-alcoholic steatohepatitis mouse model treated with hepatocyte-specific N-acetylgalactosamine (GalNAc)-siRNA to understand the in vivo impacts of MTARC1. Results: We showed that genetic variants within the MTARC1 locus are associated with liver enzymes, liver fat, plasma lipids, and body composition, and these associations are attributable to the same causal variant (p.A165T, rs2642438 G>A), suggesting a shared mechanism. We demonstrated that increased MTARC1 mRNA had an adverse effect on these traits using Mendelian randomisation, implying therapeutic inhibition of mARC1 could be beneficial. In vitro mARC1 knockdown decreased lipid accumulation and increased triglyceride secretion, and in vivo GalNAc-siRNA-mediated knockdown of mARC1 lowered hepatic but increased plasma triglycerides. We found alterations in pathways regulating lipid metabolism and decreased secretion of 3-hydroxybutyrate upon mARC1 knockdown in vitro and in vivo. Conclusions: Collectively, our findings from human genetics, and in vitro and in vivo hepatocyte-specific mARC1 knockdown support the potential efficacy of hepatocyte-specific targeting of mARC1 for treatment of NAFLD. Impact and implications: We report that genetically predicted increases in MTARC1 mRNA associate with poor liver health. Furthermore, knockdown of mARC1 reduces hepatic steatosis in primary human hepatocytes and a murine NASH model. Together, these findings further underscore the therapeutic potential of targeting hepatocyte MTARC1 for NAFLD.

Rate of weight gain and cardiometabolic abnormalities in children and adolescents.

OBJECTIVE: To investigate whether the rate of weight gain is associated with cardiometabolic risk, independent of weight measured concurrently. STUDY DESIGN: Healthy 7- to 17-year-old risperidone-treated patients (N = 105, 88% were boys) had blood pressure, anthropometry, and laboratory tests performed. Growth history was extracted from medical records. The rate of change in age- and sex-adjusted weight and body mass index (BMI) z score after the initiation of risperidone was individually modeled. Multivariable linear regression analyses explored the association of the rate of weight or BMI z score change with cardiometabolic outcomes, independent of last measured weight or BMI z score, respectively. RESULTS: Following a mean of 1.9 years (SD = 1.0) of risperidone treatment, the absolute increase in weight and BMI z scores was 0.61 (SD = 0.61) and 0.62 (SD = 0.73), respectively. After controlling for the final weight z score, the rate of change in weight z score was significantly associated with final glucose (P < .04), C-peptide (P < .004), the homeostasis model assessment insulin resistance index (P < .02), high-density lipoprotein (HDL) cholesterol (P < .0001), a metabolic syndrome score (P < .005), adiponectin (P < .04), and high-sensitivity C-reactive protein (P < .04). After controlling for the final BMI z score, the rate of change in BMI z score was associated with final HDL cholesterol (P < .04), leptin (P < .03), and adiponectin (P < .04), with a suggestion of an association with the final homeostasis model assessment insulin resistance index (P < .08). CONCLUSIONS: Compared with weight measured concurrently, the rate of weight gain in risperidone-treated children accounts for an equal or larger share of the variance in certain cardiometabolic outcomes (eg, HDL cholesterol [ΔR(2) = 8% vs ΔR(2) = 11%] and high-sensitivity C-reactive protein [ΔR(2) = 5% vs ΔR(2) = 9%]) and may serve as a treatment target.

Membranous nephropathy with renal salt wasting: role of neurohumoral factors in sodium retention.

The role of neurohumoral factors in the sodium retention of nephrotic syndrome is controversial. We report a case with abrupt onset of severe nephrotic-range proteinuria and hypoalbuminemia due to membranous glomerulonephritis that was associated with renal salt wasting and hypovolemia without edema. Further evaluation showed hypoaldosteronism, hyporeninemia, and primary autonomic failure principally affecting the sympathetic nervous system, determined by the Valsalva maneuver. Administration of exogenous mineralocorticoid and oral salt caused edema and accelerated hypertension. The severe hypoaldosteronism likely was due to use of the angiotensin-converting enzyme inhibitor lisinopril, and it improved after this drug treatment was discontinued. The nephrotic proteinuria resolved after treatment with cyclosporine and prednisone, but the primary autonomic failure with hyporeninemic hypoaldosteronism persisted. The case shows that intratubular factors activated by nephrotic proteinuria are not sufficient to produce sodium retention in the absence of aldosterone and an intact sympathetic nervous system.