Serine synthesis via reversed SHMT2 activity drives glycine depletion and acetaminophen hepatotoxicity in MASLD

Metabolic dysfunction-associated steatotic liver disease (MASLD) affects one-third of the global population. Understanding the metabolic pathways involved can provide insights into disease progression and treatment. Untargeted metabolomics of livers from mice with early-stage steatosis uncovered decreased methylated metabolites, suggesting altered one-carbon metabolism. The levels of glycine, a central component of one-carbon metabolism, were lower in mice with hepatic steatosis, consistent with clinical evidence. Stable-isotope tracing demonstrated that increased serine synthesis from glycine via reverse serine hydroxymethyltransferase (SHMT) is the underlying cause for decreased glycine in steatotic livers. Consequently, limited glycine availability in steatotic livers impaired glutathione synthesis under acetaminophen-induced oxidative stress, enhancing acute hepatotoxicity. Glycine supplementation or hepatocyte-specific ablation of the mitochondrial SHMT2 isoform in mice with hepatic steatosis mitigated acetaminophen-induced hepatotoxicity by supporting de novo glutathione synthesis. Thus, early metabolic changes in MASLD that limit glycine availability sensitize mice to xenobiotics even at the reversible stage of this disease.

Fatty liver-mediated glycine restriction impairs glutathione synthesis and causes hypersensitization to acetaminophen

Non-alcoholic fatty liver disease (NAFLD) affects nearly one third of the population worldwide. Understanding metabolic pathways involved can provide insights into disease progression. Untargeted metabolomics of livers from mice with early-stage steatosis indicated a decrease in methylated metabolites suggesting altered one carbon metabolism. The levels of glycine, a central component of one carbon metabolism, were lower in steatotic mice, in line with clinical evidence. Isotope tracing studies demonstrated that increased synthesis of serine from glycine is the underlying cause for glycine limitation in fatty livers. Consequently, the low glycine availability in steatotic livers impaired glutathione (GSH) synthesis under oxidative stress induced by acetaminophen (APAP), enhancing hepatic toxicity. Glycine supplementation mitigated acute liver damage and overall toxicity caused by APAP in fatty livers by supporting de novo GSH synthesis. Thus, early metabolic changes in NAFLD that lead to glycine depletion sensitize mice to xenobiotic toxicity even at a reversible stage of NAFLD.

Induction of glutathione biosynthesis by glycine-based treatment mitigates atherosclerosis

Lower circulating levels of glycine are consistently reported in association with cardiovascular disease (CVD), but the causative role and therapeutic potential of glycine in atherosclerosis, the underlying cause of most CVDs, remain to be established. Here, following the identification of reduced circulating glycine in patients with significant coronary artery disease (sCAD), we investigated a causative role of glycine in atherosclerosis by modulating glycine availability in atheroprone mice. We further evaluated the atheroprotective potential of DT-109, a recently identified glycine-based compound with dual lipid/glucose-lowering properties. Glycine deficiency enhanced, while glycine supplementation attenuated, atherosclerosis development in apolipoprotein E-deficient (Apoe^−/−) mice. DT-109 treatment showed the most significant atheroprotective effects and lowered atherosclerosis in the whole aortic tree and aortic sinus concomitant with reduced superoxide. In Apoe^−/− mice with established atherosclerosis, DT-109 treatment significantly reduced atherosclerosis and aortic superoxide independent of lipid-lowering effects. Targeted metabolomics and kinetics studies revealed that DT-109 induces glutathione formation in mononuclear cells. In bone marrow-derived macrophages (BMDMs), glycine and DT-109 attenuated superoxide formation induced by glycine deficiency. This was abolished in BMDMs from glutamate-cysteine ligase modifier subunit-deficient (Gclm^−/-) mice in which glutathione biosynthesis is impaired. Metabolic flux and carbon tracing experiments revealed that glycine deficiency inhibits glutathione formation in BMDMs while glycine-based treatment induces de novo glutathione biosynthesis. Through a combination of studies in patients with CAD, in vivo studies using atherosclerotic mice and in vitro studies using macrophages, we demonstrated a causative role of glycine in atherosclerosis and identified glycine-based treatment as an approach to mitigate atherosclerosis through antioxidant effects mediated by induction of glutathione biosynthesis.

Artificial intelligence-guided image acquisition on patients with implanted electrophysiological devices: results from a pivotal prospective multi-center clinical trial

Background

A novel, recently FDA-authorized software uses deep learning (DL) to provide prescriptive transthoracic echocardiography (TTE) guidance, allowing novices to acquire standard TTE views. The DL model was trained by >5,000,000 observations of the impact of probe motion on image orientation/quality. This study evaluated whether novice-acquired TTE images guided by this software were of diagnostic quality in patients with and without implanted electrophysiological (EP) devices, focusing on RV size and function, which were thought to be sensitive to EP devices. Some aspects of the study have previously been presented.

Methods

240 patients (61±16 years old, 58% male, 33% BMI >30 kg/m2, 91% with cardiac pathology) were recruited. 8 nurses without echo experience each acquired 10 view TTEs in 30 patients guided by the software. 235 of the patients were also scanned by a trained sonographer without assistance from the software. 5 Level 3 echocardiographers independently assessed the diagnostic quality of the TTEs acquired by the nurses and sonographers to evaluate the effect of EP devices on DL software performance.

Results

Nurses using the AI-guided acquisition software acquired TTEs of sufficient quality to make qualitative assessments of right ventricular (RV) size and function in greater than 80% of cases for patients with and without implanted EP devices (Table). There was no significant difference between nurse- and sonographer-acquired scans.

Conclusion

These results indicate that new DL software can guide novices to obtain TTEs that enable qualitative assessment of RV size even in the presence of implanted EP devices. The results of the comparison to sonographer-acquired exams indicate the software performance is robust to presence of pacemaker/ICD leads visible in the images (Figure).

Nurse-acquired TTE with visible ICD lead

Funding Acknowledgement

Type of funding source: Private company. Main funding source(s): Caption Health, Inc.

1386Reduction of mitral regurgitation in patients with heart failure and secondary mitral regurgitation: relationship between changes in brain natriuretic peptide and outcomes from the COAPT trial

Background

Brain natriuretic peptide (BNP) is a well-established predictor of hospitalization and death in patients with heart failure (HF). In the COAPT trial, treatment of patients with HF and secondary mitral regurgitation (SMR) with transcatheter mitral valve repair (TMVr) reduced the 2-year rates of all-cause mortality and HF hospitalization compared with maximally-tolerated guideline-directed medical therapy (GDMT) alone. Whether these improvements in outcomes were reflected in serial changes in BNP levels has not been reported.

Purpose

Herein, we report the first results of serial changes in BNP levels by treatment group in patients from the COAPT trial.

Methods

614 patients with HF and 3+ or 4+ SMR were randomized 1:1 to TMVr + GDMT or GDMT alone. Key inclusion criteria included NYHA functional class II-IVa (ambulatory), ischemic or non-ischemic cardiomyopathy with LVEF 20%-50% and LVESD ≤70 mm. Baseline BNP or NT-proBNP levels were drawn at baseline and at 6 and 12 months. For the present analysis NT-proBNP (pg/ml) values were converted to BNP values (pg/ml) using a ratio of 7 to 1.

Results

At baseline, mean values of BNP were not significantly different between treatment groups (945 pg/ml vs. 964 pg/ml in the TMVr + GDMT and GDMT groups respectively, p=0.84). At 6 months, mean values of BNP in the TMVr + GDMT group were significantly lower than in the GDMT alone group (690 pg/ml vs 893 pg/ml, p=0.02) but not at 12 months (584 pg/ml vs. 728 pg/ml, p=0.22). By analysis of covariance, BNP decreased to a greater degree after TMVr + GDMT compared with GDMT only at both 6 and 12 months (least squares mean differences of −121 pg/ml and −166 pg/ml respectively, both p<0.05) (Figure).

Change in BNP level from baseline

Conclusions

In patients with HF and 3+ or 4+ SMR enrolled in the COAPT trial, reduction of SMR with TMVr reduced BNP compared with maximally-tolerated GDMT only, a change which paralleled the reductions noted in all-cause mortality and HF hospitalizations with TMVr.

Acknowledgement/Funding

Abbott

Subgenual cingulate cortical activity predicts the efficacy of electroconvulsive therapy

Electroconvulsive therapy (ECT) is the most effective treatment for depression, yet its mechanism of action is unknown. Our goal was to investigate the neurobiological underpinnings of ECT response using longitudinally collected resting-state functional magnetic resonance imaging (rs-fMRI) in 16 patients with treatment-resistant depression and 10 healthy controls. Patients received bifrontal ECT 3 times a week under general anesthesia. We acquired rs-fMRI at three time points: at baseline, after the 1st ECT administration and after the course of the ECT treatment; depression was assessed with the Hamilton Depression Rating Scale (HAM-D). The primary measure derived from rs-fMRI was fractional amplitude of low frequency fluctuation (fALFF), which provides an unbiased voxel-wise estimation of brain activity. We also conducted seed-based functional connectivity analysis based on our primary findings. We compared treatment-related changes in HAM-D scores with pre- and post-treatment fALFF and connectivity measures. Subcallosal cingulate cortex (SCC) demonstrated higher BOLD signal fluctuations (fALFF) at baseline in depressed patients, and SCC fALFF decreased over the course of treatment. The baseline level of fALFF of SCC predicted response to ECT. In addition, connectivity of SCC with bilateral hippocampus, bilateral temporal pole, and ventromedial prefrontal cortex was significantly reduced over the course of treatment. These results suggest that the antidepressant effect of ECT may be mediated by downregulation of SCC activity and connectivity. SCC function may serve as an important biomarker of target engagement in the development of novel therapies for depression that is resistant to treatment with standard medications.

Clinical characteristics of familial B-CLL in the National Cancer Institute Familial Registry

In an ongoing study, families with two or more living cases of B-CLL in first-degree relatives have been recruited through physician and self-referral. Since 1967, 28 kindreds with 73 cases of B-CLL have been enrolled within the National Cancer Institute (NCI) Familial B-CLL Registry. Medical, clinical, and demographic information have been obtained from private physicians, patient interview, hospital records, and death certificates. We used SEER Registry data to compare characteristics of sporadic B-CLL to familial B-CLL. The mean age at diagnosis was approximately 10 years younger among familial cases (57.9 +/- 12.1) than that observed in sporadic cases (70.1 +/- 11.9). A higher percentage of second primary tumors among familial CLL cases compared to reports in sporadic was also observed (16% vs. 8.8%). However, the transformation rate to non-Hodgkin's lymphoma does not appear to be different from that reported for sporadic cases. In conclusion, we observed some differences between familial and sporadic cases; whether any of these characteristics affect survival time or severity of disease is unknown. The study of families with multiple B-CLL cases will aid in delineating the genes and environmental factors that may play a role in the development of both forms of B-CLL.

Some properties of the microfibrils of vascular elastic membranes in normal and copper-deficient swine

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