Abstract Caloric restriction (CR) delays aging and extends healthy lifespan in multiple species. Alternative forms of dietary restriction (DR) such as intermittent fasting (IF) have drawn significant interest as a more sustainable regimen, but the landscape of longevity-promoting dietary interventions remains largely unexplored. Identifying the most robust, efficacious, and experimentally tractable modes of DR is key to better understanding and implementing effective longevity interventions for human healthspan. To that end, we have performed an extensive assessment of DR interventions, investigating the effects of graded levels of CR (20% and 40%) and IF (1 day and 2 days of fasting per week) on the health and survival of 960 genetically diverse female mice. All interventions extended lifespan, although only CR significantly reduced the mortality doubling time. Notably, IF did not extend lifespan in mice with high pre-intervention bodyweight. We carried out extensive phenotyping to determine the health effects of long-term DR and to better understand the mechanisms driving within-diet heterogeneity in lifespan. The top within-diet predictor of lifespan was the ability of mice to maintain bodyweight through periods of handling, an indicator of stress resilience. Additional predictors of long lifespan include specific changes in immune cells, red blood cell distribution width (RDW), and retention of adiposity in late life. We found that lifespan is heritable (h2 = 0.24), and that genetic background has a larger influence on lifespan than dietary interventions. We identified a significant association for lifespan and RDW on chromosome 18 that explained 4.3% of the diet-adjusted variation in lifespan. Diet-induced changes on metabolic traits, although beneficial, were relatively poor predictors of lifespan, arguing against the long-standing notion that DR works by counteracting the negative effects of obesity. These findings indicate that improving health and extending lifespan are not synonymous and that metabolic parameters may be inappropriate endpoints for evaluating aging interventions in preclinical models and clinical trials.

AbstractIn this study, we developed a three-dimensionally (3D) printed lung model that faithfully recapitulates the intricate lung environment. This 3D model incorporated alveolar and vascular components that allow for a comprehensive exploration of lung physiology and responses to infectionin vitro. In particular, we investigated the intricate role of ventilation on formation of the alveolar epithelial layer and its response to viral infections. In this regard, we subjected our 3D printed, perfused lung model to a continuous respiratory cycle at the air-liquid interface (ALI) for up to 10 days followed by infection with two viruses: influenza virus (Pr8) and respiratory syncytial virus (RSV), at two different concentrations for 24 or 48 h. The results revealed that ventilation induced increased tight-junction formation with better epithelial barrier function over time, facilitated higher expression of alveolar epithelial specific genes, enabled higher level of infection with an increased progression of viral spread and replication over time, and modulated the production of pro-inflammatory cytokines and chemokines. Our findings represent a critical step forward in advancing our understanding of lung-specific viral responses and respiratory infections in response to ventilation, which sheds light on vital aspects of pulmonary physiology and pathobiology.

Abstract Background: Chronological age alone does not sufficiently explain aging heterogeneity. Biological clocks and molecular biomarkers proposed to predict biological age can be difficult to implement in a clinical setting. Aim: In the framework of translational science, use of routinely collected hematological markers to develop a biological clock to predict biological age and estimate aging acceleration in mice. Methods: Data from 2,562 mice of both sexes and three strains were drawn from the Study of Longitudinal Aging in Mice and from The Jackson Laboratory’s longitudinal study of aging. Fourteen hematological variables and two metabolic indices were collected longitudinally (11,998 observations). Biological age was predicted using a deep neural network. Aging acceleration (positive or negative) was calculated as residuals from a nonlinear regression of predicted age on chronological age and tested for association with all-cause mortality. Results: Biological age was significantly correlated with chronological age (Mean Absolute Error [MAE] = 11.95 weeks, Root Mean Squared Error [RMSE] = 15.41 weeks, r = 0.87) and positive aging acceleration was associated with shorter lifespan. Conclusion: An aging clock based on routinely collected blood measures has the potential to provide a practical clinical tool to better understand individual variability in the aging process.

Alström syndrome (AS) is a rare genetic disease caused by ALMS1 mutations, characterized by short stature, and vision and hearing loss. Patients with AS develop the metabolic syndrome, long-term organ complications, and die prematurely. We explored the association between AS and a shortage of hematopoietic stem/progenitor cells (HSPCs), which is linked to metabolic diseases and predicts diabetic complications. We included patients with AS at a national referral center. We measured HSPCs with flow cytometry at baseline and follow-up. We followed patients up to January 2022 for metabolic worsening and end-organ damage. We evaluated HSPC levels and mobilization as well as bone marrow histology in a murine model of AS. In 23 patients with AS, we found significantly lower circulating HSPCs than in healthy blood donors (-40%; P = .002) and age/sex-matched patients (-25%; P = .022). Longitudinally, HSPCs significantly declined by a further 20% in patients with AS over a median of 36 months (interquartile range 30-44). Patients with AS who displayed metabolic deterioration over 5.3 years had lower levels of HSPCs, both at baseline and at last observation, than those who did not deteriorate. Alms1-mutated mice were obese and insulin resistant and displayed significantly reduced circulating HSPCs, despite no overt hematological abnormality. Contrary to what was observed in diabetic mice, HSPC mobilization and bone marrow structure were unaffected. We found depletion of HSPCs in patients with AS, which was recapitulated in Alms1-mutated mice. Larger and longer studies will be needed to establish HSPCs shortage as a driver of metabolic deterioration leading to end-organ damage in AS.

ABSTRACTMitochondrial damage is a hallmark of metabolic diseases, including diabetes and metabolic dysfunction-associated steatotic liver disease, yet the consequences of impaired mitochondria in metabolic tissues are often unclear. Here, we report that dysfunctional mitochondrial quality control engages a retrograde (mitonuclear) signaling program that impairs cellular identity and maturity across multiple metabolic tissues. Surprisingly, we demonstrate that defects in the mitochondrial quality control machinery, which we observe in pancreatic β cells of humans with type 2 diabetes, cause reductions of β cell mass due to dedifferentiation, rather than apoptosis. Utilizing transcriptomic profiling, lineage tracing, and assessments of chromatin accessibility, we find that targeted deficiency anywhere in the mitochondrial quality control pathway (e.g., genome integrity, dynamics, or turnover) activate the mitochondrial integrated stress response and promote cellular immaturity in β cells, hepatocytes, and brown adipocytes. Intriguingly, pharmacologic blockade of mitochondrial retrograde signalingin vivorestores β cell mass and identity to ameliorate hyperglycemia following mitochondrial damage. Thus, we observe that a shared mitochondrial retrograde response controls cellular identity across metabolic tissues and may be a promising target to treat or prevent metabolic disorders.

Abstract Increased inflammation with age (i.e., inflammaging) is a hallmark of aging conserved in human and mice, but the underlying mechanisms are poorly understood, partially because a systematic comparative study of mouse and human immune system aging is lacking. We uncovered epigenomic/transcriptomic signatures of aging in spleen and peripheral blood lymphocytes from young (3 months) and old (18 months) mice in two strains: C57BL/6J (long-lived) and NZO/HILtJ (short-lived) and compared these to the aging signatures of human peripheral blood cells. The most predominant and conserved genomic signature of aging in human and mice tissues studied here was the epigenetic activation of several AP-1 complex members (Fos, Fosl2, Junb, Jund). Footprinting analyses showed that these transcription factors ‘bind’ more frequently with age and target pro-inflammatory and effector molecules, including the pro-inflammatory Il6. Analysis of single cell RNA-seq data from the mouse aging cell atlas (Tabula Muris Senis) revealed that AP-1 activation with age is a common feature across all immune cell types within spleens, yet macrophages express these molecules more often than other cells. Functional assays confirmed that spleen cells from older animals have increased c-JUN protein binding and increased IL6 production upon myeloid cell activation using poly(I:C) via TLR3. Western blot data revealed that c-JUN activation with age is not post-transcriptional since its phosphorylation levels were similar between young and old mice. Together, these data established that Jun and Fos families in the AP-1 complex are transcriptionally activated with age and target pro-inflammatory molecules and aging-related increases in the binding of these proteins likely modulate increased inflammation with age.

ABSTRACTBackgroundRodent paradigms and human genome-wide association studies (GWASs) on drug use have the potential to provide biological insight into the pathophysiology of addiction.MethodsUsing GeneWeaver, we created rodent alcohol and nicotine gene-sets derived from 19 gene expression studies on alcohol and nicotine outcomes. We partitioned the SNP-heritability of these gene-sets using four large human GWASs: 1) alcoholic drinks per week, 2) problematic alcohol use, 3) cigarettes per day and 4) smoking cessation. We benchmarked our findings with curated human alcoholism and nicotine addiction gene-sets and performed specificity analyses using other rodent gene-sets (e.g., locomotor behavior) and other human GWASs (e.g., height).ResultsThe rodent alcohol gene-set was enriched for heritability of drinks per week, cigarettes per day, and smoking cessation, but not problematic alcohol use. However, the rodent nicotine gene-set was not significantly associated with any of these traits. Both rodent gene-sets showed enrichment for several non-substance use GWASs, and the extent of this relationship tended to increase as a function of trait heritability. In general, larger gene-sets demonstrated more significant enrichment. Finally, when evaluating human traits with similar heritabilities, both rodent gene-sets showed greater enrichment for substance use traits.ConclusionOur results suggest that rodent gene expression studies can help to identify genes that capture heritability of substance use traits in humans, yet the specificity to human substance use was less than expected due to various factors such as the genetic architecture of a trait. We outline various limitations, interpretations and considerations for future research.

Abstract Background: Late-onset Alzheimer’s Disease (AD) (LOAD) is the most common neurodegenerative disease. Despite extensive efforts to understand disease progression there are currently no approved disease modifying interventions to delay or reverse neurodegeneration caused by AD. Repeated failures in human trials, despite promising preclinical results in amyloidogenic mouse models, highlight the need for animals that better model human AD. MODEL-AD (Model organism development and evaluation for late-onset AD) are identifying and integrating disease-relevant, humanized gene sequences identified from public AD data repositories to create more translatable mouse models relevant to AD.Methods: Strong risk factors for LOAD, APOEε4 and Trem2*R47H, were expressed alone or in combination on a congenic C57BL/6J (B6) background, in cohorts of mice established on multiple sites and aged to between 4-24 months. A deep phenotyping approach was employed to assess phenotypes relative to human AD. Results: The LOAD1 mouse strain, expressing humanized APOEε4 and Trem2*R47H alleles, was designed to elucidate the disease state of animals expressing the two strongest genetic risk factors of LOAD at endogenous levels. Robust analytical pipelines measured behavioral, transcriptomic, metabolic, and neuropathological phenotypes in cross-sectional cohorts for progression of disease hallmarks at all life stages. In vivo PET/MRI neuroimaging revealed regional alterations in glycolytic metabolism and vascular perfusion. Transcriptional profiling by RNA-Seq of brain hemispheres identified sex and age as the main sources of variation between genotypes including age-specific enrichment of AD-related processes. Similarly, age, but not genotype, was the strongest determinant of behavioral change. In the absence of mouse amyloid plaque formation, many of the hallmarks of AD were not observed in this strain. However, these two alleles together form a sensitized, background strain which will serve as a platform for the characterization of additional genetic and environmental LOAD risk factors. Conclusions: Comprehensive phenotyping provided key insights into genetic and environmental effects aimed at modeling human disease, critical to understand the complex intergenic interactions and subsequent molecular signaling cascades. The data provided by these assays are important for understanding the relative contributions of subsequent risk factors amended to LOAD1.