Bacterial translocation from the gut microbiota is a source of sepsis in susceptible patients. Previous work suggests that overgrowth of gut pathobionts, including Klebsiella pneumoniae , increases the risk of disseminated infection. Our data from a human dietary intervention study found that, in the absence of fiber, K . pneumoniae bloomed during microbiota recovery from antibiotic treatment. We thus hypothesized that dietary nutrients directly support or suppress colonization of this gut pathobiont in the microbiota. Consistent with our study in humans, complex carbohydrates in dietary fiber suppressed the colonization of K . pneumoniae and allowed for recovery of competing commensals in mouse models. In contrast, through ex vivo and in vivo modeling, we identified simple carbohydrates as a limiting resource for K . pneumoniae in the gut. As proof of principle, supplementation with lactulose, a nonabsorbed simple carbohydrate and an FDA-approved therapy, increased colonization of K . pneumoniae . Disruption of the intestinal epithelium led to dissemination of K . pneumoniae into the bloodstream and liver, which was prevented by dietary fiber. Our results show that dietary simple and complex carbohydrates were critical not only in the regulation of pathobiont colonization but also disseminated infection, suggesting that targeted dietary interventions may offer a preventative strategy in high-risk patients.

The intestinal microbiome is dependent on nitrogen to support growth, yet the extent of nitrogen-limitation for microbial expansion in the mammalian gut remains debated. Classical perspectives describe the colon as nitrogen-limited due to the early absorption of dietary nitrogen in the small intestine, prompting the evolution of nitrogen-scavenging. In this mini-review, we focus on Enterobacteriaceae, facultative anaerobes, and clinically relevant pathobionts to examine nitrogen-scavenging and -assimilation systems. Drawing from in vitro, in vivo and ex vivo mono-colonization murine studies in Escherichia coli and Klebsiella pneumoniae, we highlight findings that introduced a paradigm shift by showing that nitrogen-scavenging mechanisms may be dispensable under certain conditions. Rather than refuting nitrogen limitation, we propose a re-evaluation of nutrient limitation in the gut, and a more nuanced model, with carbon and energy sources emerging as potential bottlenecks. This minireview emphasizes Enterobacteriaceae as a pathobiont model for investigating nitrogen metabolism and outlines key knowledge gaps to be addressed in future studies.

The Laplace law is commonly applied to calculate aortic wall stress by using the luminal pressure and the aortic diameter. Wall stress bears on the likelihood of aortic dissection in dilated aortas. However, the Laplace law applies only to circles and cylinders. It is not applicable for the aortic root, which can be more closely described as a cloverleaf shape, rather than a circle. We have recently developed a mathematically based measuring technique specifically for the aortic root. This Laplace diameter provides an appropriate means to measure a “diameter” for the cloverleaf shape of the aortic root. In this study, we assessed the predictive ability of the Laplace diameter vs the standard sinus-to-commissure measurement in 33 patients who underwent predissection computed tomographic scans for unrelated reasons in close temporal proximity to their acute aortic event. We analyzed 14 chest computed tomographic scans of 33 patients who received predissection scans for unrelated reasons. We observed a 16.1% increase in the mean root diameter using the Laplace diameter. We found that 21.4% of the analyzed predissection scans could have resulted in detection and prevention of the aortic dissection through surgery if the Laplace diameter had been applied. We validated the novel method of the Laplace diameter clinically in determining the aortic root diameter and detecting the risk of aortic dissection.

Background and Aims: We examined familial patterns and phenotypes of thoracic aortic aneurysms and dissections (TAAD) in the 3746 patients currently populating our Yale Aortic Institute Database. Methods: Patient charts and electronic medical records were retrospectively reviewed for the entire cohort. TAAD disease was categorized as syndromic (with extra-aortic manifestations) or non-syndromic (without) for each patient. Family patterns and whole exome sequencing results were assessed. Family history was considered ‘proven’ when a patient’s relative(s) had an arterial aneurysm or dissection confirmed by an imaging study, surgical treatment, or postmortem examination. Family history was termed ‘likely’ when at least one relative suffered sudden death at ages ≤50 for males and ≤60 for females, and ‘possible’ with a history of sudden death at any age. Results: Of the 3746 patients in the database, family history of aneurysm or dissection and connective tissue status was able to be determined for 3113 patients, divided into 109 (3.5%) syndromic and 3004 (96.5%) non-syndromic TAAD patients. Findings were as follows: (1) In the syndromic group, 46 (42.2%) patients had a ‘proven’ family history, 6 (5.5%) had a ‘likely’ family history, 4 (3.7%) had a ‘possible’ family history, and 18 (16.5%) had ‘none’. For 35 patients (32.1%) their family history was unknown. (2) In the non-syndromic group, 587 (19.5%) patients had ‘proven’ family history, 147 (4.9%) had ‘likely’ family history, 210 (7.0%) had ‘possible’ family history and 1444 (48.1%) had no family history, thus representing sporadic TAAD. A total of 616 (20.5%) had an unknown family history. (3) There was a significant difference between the rate for ‘proven’ and ‘none’ family history between the syndromic and non-syndromic groups (42.2% vs. 19.5% and 16.5% vs. 48.1%, respectively; p < 0.001). (4) Syndromic patients presented at a significantly younger age than non-syndromic or sporadic patients (41.2 vs. 63.3 or 63.6; p < 0.001). (5) There was no significant difference in age of presentation between familial non-syndromic (patients with ‘proven’, ‘likely’, and ‘possible’ family history) and sporadic patients (63.3 vs. 63.6; p = 0.64). (6) Overall, of the 3746 patients in the database, 631 patients (25 syndromic, 552 non-syndromic, and 54 with unknown status) underwent Whole Exome Sequencing (WES). Sequencing revealed 170 disease-causing or suspicious variants [13 pathogenic, 16 likely pathogenic, 7 not classified, and 134 Variants of Uncertain Significance (VUS)] found in the exomes of 141 (22.3%) patients (12 syndromic, 103 non-syndromic TAAD patients plus a remaining 26 of unknown connective tissue status). Seventy (49.6%) of these patients had a ‘proven’ family history. (7) Familial TAAD patients were more likely to find a variant in their WES result than patients without a family history (70 vs. 26; p < 0.001). Recognition of these strong familial patterns, even in non-syndromic cases, encourages intensive investigation of family in order to save lives by detecting silent TAA disease. Conclusions: Our large-scale, clinical and sequencing-based study clearly demonstrates the strongly familial and genetically mediated nature of thoracic aortic disease. We vividly demonstrate and characterize this familial nature of TAAD, both clinically and by genetic sequencing. Our findings strongly support vigorous family investigation when a new patient is diagnosed with thoracic aortic aneurysm, as well as vigorous application of whole exome sequencing for these families.

Background: ACTA2 encodes smooth muscle alpha-actin and is one of the most common genetic causes of inherited non-syndromic thoracic aortic aneurysm and dissection. Although murine models have provided important mechanistic insight, complementary vertebrate systems may enable more rapid in vivo phenotyping and future therapeutic screening. Methods: Utilizing a CRISPR/Cas9-based approach, we developed zebrafish acta2 mutant models and assessed phenotypes at larval and adult stages. At 3 days post-fertilization, larvae were screened by brightfield microscopy for edema, axis defects, hemorrhage, and a composite endpoint (any phenotype) under basal conditions and after exposure to 0.2 mM epinephrine. Phenotype occurrence was summarized as group-specific proportions across a 2 × 2 design defined by genotype (wild-type vs. acta2-deficient mutant) and treatment (DMSO control vs. epinephrine), with prespecified pairwise comparisons using Pearson’s chi-squared tests. Pooled fish-level logistic regression models were also fit for each endpoint. Adult follow-up was performed by genotyping all available acta2 fish at the facility and tracking staggered tank-level cohorts longitudinally. Results: Initial gross morphologic assessment did not reveal overt external phenotypic differences between heterozygous or homozygous acta2 mutant larvae and wild-type controls. In larval analyses, the mutant genotype was associated with a greater burden of adverse phenotypes than treatment exposure. For the composite endpoint, mutant larvae demonstrated higher proportions than normal larvae under both control (28.3% vs. 17.4%, p = 0.007) and epinephrine conditions (26.9% vs. 17.4%, p = 0.023), whereas epinephrine did not significantly alter composite phenotype frequency within either genotype. Similar genotype-associated trends were observed for axis defects and hemorrhage. In pooled logistic regression, acta2 deficiency was associated with increased odds of axis defects (OR 2.64, 95% CI 1.48–4.89, p = 0.001), hemorrhage (OR 2.40, 95% CI 1.09–5.68, p = 0.036), and the composite endpoint (OR 1.88, 95% CI 1.19–3.00, p = 0.008), whereas epinephrine exposure did not demonstrate a consistent independent effect across endpoints. Adult staggered follow-up showed greater attrition in homozygous mutant cohorts than in wild-type or heterozygous cohorts, with aggregated losses of 24%, 12%, and 3%, respectively. Conclusions: This preliminary zebrafish acta2 model demonstrated that acta2 deficiency is associated with increased adverse larval phenotype burden and suggested reduced long-term persistence of homozygous mutant fish in adulthood. The strongest signal in the current study was genotype-associated phenotype burden rather than a robust epinephrine-dependent effect. These findings support the feasibility of zebrafish-based ACTA2 phenotyping while highlighting the need for more specific vascular endpoints, refined longitudinal follow-up, and future variant-specific modeling.

Background: Giant cell myocarditis (GCM) is a rare, and often fatal subtype of myocarditis, with limited reports of association with systemic lupus erythematosus (SLE). Purpose: We are first to report a unique case of an 18-year-old patient presenting with biventricular heart failure and newly-onset SLE, ultimately diagnosed with GCM. Analysis/Results: The patient had a 6-month prodrome of fatigue, fever, and malaise, followed by acute decompensation. Echocardiography showed a severely reduced left ventricular ejection fraction (5%). Serology confirmed SLE, endomyocardial biopsy identified multinucleated giant cells, confirming GCM. Despite immediate initiation of extracorporeal membrane oxygenation (ECMO) and aggressive immunosuppressive therapy (methylprednisolone, antithymocyte globulin, cyclosporine), cardiac function did not recover. The patient received a biventricular assist device (BiVAD) as intermediate-term bridge-to-transplant. However, significant complications occurred in the form of multiorgan failure, thromboembolism, and hemodynamic deterioration, ultimately leading to death before transplantation was possible. Conclusions: This case underscores the importance of differentiating lupus myocarditis from GCM, given the dramatically different prognosis and treatment strategies. Early differential diagnosis via biopsy is essential, particularly in young patients with rapidly progressing cardiac decline and concurrent autoimmune serologies. Aggressive immunosuppression remains the cornerstone of treatment, attempting to reduce myocardial damage and the resulting need for transplantation. Clinicians should maintain suspicion of GCM in lupus patients with cardiac compromise to initiate timely interventions.