Genetic mapping of Uba3 O.2.2 , a pupal lethal mutation in Drosophila melanogaster

An EMS mutagenesis screen was conducted in Drosophila melanogaster to identify growth control mutants. The multi-institution Fly-CURE consortium phenotypically characterized the O.2.2 mutant using the FLP/FRT system which displayed a mutant lethal phenotype with reduced head development, and darkened ocular tissue. Complementation mapping was conducted to identify the affected gene. A failure to complement was identified in Uba3 , resulting in the identification of the novel allele, Uba3 ^O.2.2 . Uba3 is a known disruptor of the cell cycle and our data are consistent with early larval/embryonic lethality displayed in numerous species.

It's about time; divergent circadian clocks in livers of mice and naked mole-rats

Light is the key regulator of circadian clock, the time-keeping system synchronizing organism physiology and behavior with environmental day and night conditions. In its natural habitat, the strictly subterranean naked mole-rat (Heterocephalus glaber) has lived in a light-free environment for millennia. We questioned if this species retains a circadian clock and if the patterns of this clock and concomitant rhythms differed in liver tissue from mice and naked mole-rats. As expected, in mice, the various circadian clock genes peaked at different times of the day; the Period gene (Per) group peaked in the evening, whereas Brain and Muscle ARNT-like1 (Bmal1) gene peaked in the morning; this phase shift is considered to be fundamental for circadian clock function. In sharp contrast, in the naked mole-rat both Per1 and Per2, as well as Bmal1, peaked at the same time in the morning-around ZT2-suggesting the organization of the molecular circadian oscillator was different. Moreover, gene expression rhythms associated with glucose metabolism and mTOR signaling also differed between the species. Although the activity of mTORC1 was lower, while that of mTORC2 was higher in naked mole-rat livers compared to mice, unlike that of mice where the expression profiles of glucose metabolism genes were not synchronized, these were highly synchronized in naked mole-rats and likely linked to their use of feeding times at zeitgebers.

Perinatal diet influences health and survival in a mouse model of leukemia

The goal of the current study was to determine the role of maternal diet in the perinatal period on the health and survival of the offspring. AKR/J mice, a model described to be susceptible to leukemia development, was used where females were maintained on either standard diet (SD), high sucrose diet, Western diet, or calorie restriction (CR) as they were mated with SD-fed males. Body weights, pregnancy rates, litter size, and litter survival were used as markers of successful pregnancy and pup health. Data indicated that maternal diet had significant effects on litter size, early pup survival, and early pup body weights. As pups matured, the makeup of their respective maternal diet was a predictor of adult metabolic health and survival. Overall, these results suggest that perinatal maternal diet is an important determinant of the health and survival of the offspring and that these effects continue well into adulthood, strongly correlating with lifespan.

Probing Pedomorphy and Prolonged Lifespan in Naked Mole-Rats and Dwarf Mice

Pedomorphy, maintenance of juvenile traits throughout life, is most pronounced in extraordinarily long-lived naked mole-rats. Many of these traits (e.g., slow growth rates, low hormone levels, and delayed sexual maturity) are shared with spontaneously mutated, long-lived dwarf mice. Although some youthful traits likely evolved as adaptations to subterranean habitats (e.g., thermolability), the nature of these intrinsic pedomorphic features may also contribute to their prolonged youthfulness, longevity, and healthspan.

Correction to: A window into extreme longevity; the circulating metabolomic signature of the naked mole-rat, a mammal that shows negligible senescence

The original version of this article unfortunately contained an error.

A window into extreme longevity; the circulating metabolomic signature of the naked mole-rat, a mammal that shows negligible senescence

Mouse-sized naked mole-rats (Heterocephalus glaber), unlike other mammals, do not conform to Gompertzian laws of age-related mortality; adults show no age-related change in mortality risk. Moreover, we observe negligible hallmarks of aging with well-maintained physiological and molecular functions, commonly altered with age in other species. We questioned whether naked mole-rats, living an order of magnitude longer than laboratory mice, exhibit different plasma metabolite profiles, which could then highlight novel mechanisms or targets involved in disease and longevity. Using a comprehensive, unbiased metabolomics screen, we observe striking inter-species differences in amino acid, peptide, and lipid metabolites. Low circulating levels of specific amino acids, particularly those linked to the methionine pathway, resemble those observed during the fasting period at late torpor in hibernating ground squirrels and those seen in longer-lived methionine-restricted rats. These data also concur with metabolome reports on long-lived mutant mice, including the Ames dwarf mice and calorically restricted mice, as well as fruit flies, and even show similarities to circulating metabolite differences observed in young human adults when compared to older humans. During evolution, some of these beneficial nutrient/stress response pathways may have been positively selected in the naked mole-rat. These observations suggest that interventions that modify the aging metabolomic profile to a more youthful one may enable people to lead healthier and longer lives.

Unraveling the message: insights into comparative genomics of the naked mole-rat

Animals have evolved to survive, and even thrive, in different environments. Genetic adaptations may have indirectly created phenotypes that also resulted in a longer lifespan. One example of this phenomenon is the preternaturally long-lived naked mole-rat. This strictly subterranean rodent tolerates hypoxia, hypercapnia, and soil-based toxins. Naked mole-rats also exhibit pronounced resistance to cancer and an attenuated decline of many physiological characteristics that often decline as mammals age. Elucidating mechanisms that give rise to their unique phenotypes will lead to better understanding of subterranean ecophysiology and biology of aging. Comparative genomics could be a useful tool in this regard. Since the publication of a naked mole-rat genome assembly in 2011, analyses of genomic and transcriptomic data have enabled a clearer understanding of mole-rat evolutionary history and suggested molecular pathways (e.g., NRF2-signaling activation and DNA damage repair mechanisms) that may explain the extraordinarily longevity and unique health traits of this species. However, careful scrutiny and re-analysis suggest that some identified features result from incorrect or imprecise annotation and assembly of the naked mole-rat genome: in addition, some of these conclusions (e.g., genes involved in cancer resistance and hairlessness) are rejected when the analysis includes additional, more closely related species. We describe how the combination of better study design, improved genomic sequencing techniques, and new bioinformatic and data analytical tools will improve comparative genomics and ultimately bridge the gap between traditional model and nonmodel organisms.

Organization of the Mammalian Metabolome according to Organ Function, Lineage Specialization, and Longevity

Biological diversity among mammals is remarkable. Mammalian body weights range seven orders of magnitude and lifespans differ more than 100-fold among species. While genetic, dietary, and pharmacological interventions can be used to modulate these traits in model organisms, it is unknown how they are determined by natural selection. By profiling metabolites in brain, heart, kidney, and liver tissues of 26 mammalian species representing ten taxonomical orders, we report metabolite patterns characteristic of organs, lineages, and species longevity. Our data suggest different rates of metabolite divergence across organs and reveal patterns representing organ-specific functions and lineage-specific physiologies. We identified metabolites that correlated with species lifespan, some of which were previously implicated in longevity control. We also compared the results with metabolite changes in five long-lived mouse models and observed some similar patterns. Overall, this study describes adjustments of the mammalian metabolome according to lifespan, phylogeny, and organ and lineage specialization.

Regulation of Nrf2 signaling and longevity in naturally long-lived rodents

The preternaturally long-lived naked mole-rat, like other long-lived species and experimental models of extended longevity, is resistant to both endogenous (e.g., reactive oxygen species) and environmental stressors and also resists age-related diseases such as cancer, cardiovascular disease, and neurodegeneration. The mechanisms behind the universal resilience of longer-lived organisms to stress, however, remain elusive. We hypothesize that this resilience is linked to the activity of a highly conserved transcription factor, nuclear factor erythroid 2-related factor (Nrf2). Nrf2 regulates the transcription of several hundred cytoprotective molecules, including antioxidants, detoxicants, and molecular chaperones (heat shock proteins). Nrf2 itself is tightly regulated by mechanisms that either promote its activity or increase its degradation. We used a comparative approach and examined Nrf2-signaling activity in naked mole-rats and nine other rodent species with varying maximum lifespan potential (MLSP). We found that constitutive Nrf2-signaling activity was positively correlated (P = 0.0285) with MLSP and that this activity was also manifested in high levels of downstream gene expression and activity. Surprisingly, we found that species longevity was not linked to the protein levels of Nrf2 itself, but rather showed a significant (P < 0.01) negative relationship with the regulators Kelch-like ECH-Associated Protein 1 (Keap1) and β-transducin repeat-containing protein (βTrCP), which target Nrf2 for degradation. These findings highlight the use of a comparative biology approach for the identification of evolved mechanisms that contribute to health span, aging, and longevity.

The naked mole-rat response to oxidative stress: just deal with it

SIGNIFICANCE

The oxidative stress theory of aging has been the most widely accepted theory of aging providing insights into why we age and die for over 50 years, despite mounting evidence from a multitude of species indicating that there is no direct relationship between reactive oxygen species (ROS) and longevity. Here we explore how different species, including the longest lived rodent, the naked mole-rat, have defied the most predominant aging theory.

RECENT ADVANCES

In the case of extremely long-lived naked mole-rat, levels of ROS production are found to be similar to mice, antioxidant defenses unexceptional, and even under constitutive conditions, naked mole-rats combine a pro-oxidant intracellular milieu with high, steady state levels of oxidative damage. Clearly, naked mole-rats can tolerate this level of oxidative stress and must have mechanisms in place to prevent its translation into potentially lethal diseases.

CRITICAL ISSUES

In addition to the naked mole-rat, other species from across the phylogenetic spectrum and even certain mouse strains do not support this theory. Moreover, overexpressing or knocking down antioxidant levels alters levels of oxidative damage and even cancer incidence, but does not modulate lifespan.

FUTURE DIRECTIONS

Perhaps, it is not oxidative stress that modulates healthspan and longevity, but other cytoprotective mechanisms that allow animals to deal with high levels of oxidative damage and stress, and nevertheless live long, relatively healthy lifespans. Studying these mechanisms in uniquely long-lived species, like the naked mole-rat, may help us tease out the key contributors to aging and longevity.

Perinatal exercise improves glucose homeostasis in adult offspring

Emerging research has shown that subtle factors during pregnancy and gestation can influence long-term health in offspring. In an attempt to be proactive, we set out to explore whether a nonpharmacological intervention, perinatal exercise, might improve offspring health. Female mice were separated into sedentary or exercise cohorts, with the exercise cohort having voluntary access to a running wheel prior to mating and during pregnancy and nursing. Offspring were weaned, and analyses were performed on the mature offspring that did not have access to running wheels during any portion of their lives. Perinatal exercise caused improved glucose disposal following an oral glucose challenge in both female and male adult offspring (P < 0.05 for both). Blood glucose concentrations were reduced to lower values in response to an intraperitoneal insulin tolerance test for both female and male adult offspring of parents with access to running wheels (P < 0.05 and P < 0.01, respectively). Male offspring from exercised dams showed increased percent lean mass and decreased fat mass percent compared with male offspring from sedentary dams (P < 0.01 for both), but these parameters were unchanged in female offspring. These data suggest that short-term maternal voluntary exercise prior to and during healthy pregnancy and nursing can enhance long-term glucose homeostasis in offspring.

Walking the oxidative stress tightrope: a perspective from the naked mole-rat, the longest-living rodent

Reactive oxygen species (ROS), by-products of aerobic metabolism, cause oxidative damage to cells and tissue and not surprisingly many theories have arisen to link ROS-induced oxidative stress to aging and health. While studies clearly link ROS to a plethora of divergent diseases, their role in aging is still debatable. Genetic knock-down manipulations of antioxidants alter the levels of accrued oxidative damage, however, the resultant effect of increased oxidative stress on lifespan are equivocal. Similarly the impact of elevating antioxidant levels through transgenic manipulations yield inconsistent effects on longevity. Furthermore, comparative data from a wide range of endotherms with disparate longevity remain inconclusive. Many long-living species such as birds, bats and mole-rats exhibit high-levels of oxidative damage, evident already at young ages. Clearly, neither the amount of ROS per se nor the sensitivity in neutralizing ROS are as important as whether or not the accrued oxidative stress leads to oxidative-damage-linked age-associated diseases. In this review we examine the literature on ROS, its relation to disease and the lessons gleaned from a comparative approach based upon species with widely divergent responses. We specifically focus on the longest lived rodent, the naked mole-rat, which maintains good health and provides novel insights into the paradox of maintaining both an extended healthspan and lifespan despite high oxidative stress from a young age.

Stress resistance in the naked mole-rat: the bare essentials - a mini-review

BACKGROUND

Studies comparing similar-sized species with disparate longevity may elucidate novel mechanisms that abrogate aging and prolong good health. We focus on the longest living rodent, the naked mole-rat. This mouse-sized mammal lives ~8 times longer than do mice and, despite high levels of oxidative damage evident at a young age, it is not only very resistant to spontaneous neoplasia but also shows minimal decline in age-associated physiological traits.

OBJECTIVES

We assess the current status of stress resistance and longevity, focusing in particular on the molecular and cellular responses to cytotoxins and other stressors between the short-lived laboratory mouse and the naked mole-rat.

RESULTS

Like other experimental animal models of lifespan extension, naked mole-rat fibroblasts are extremely tolerant of a broad spectrum of cytotoxins including heat, heavy metals, DNA-damaging agents and xenobiotics, showing LD(50) values between 2- and 20-fold greater than those of fibroblasts of shorter-lived mice. Our new data reveal that naked mole-rat fibroblasts stop proliferating even at low doses of toxin whereas those mouse fibroblasts that survive treatment rapidly re-enter the cell cycle and may proliferate with DNA damage. Naked mole-rat fibroblasts also show significantly higher constitutive levels of both p53 and Nrf2 protein levels and activity, and this increases even further in response to toxins.

CONCLUSION

Enhanced cell signaling via p53 and Nrf2 protects cells against proliferating with damage, augments clearance of damaged proteins and organelles and facilitates the maintenance of both genomic and protein integrity. These pathways collectively regulate a myriad of mechanisms which may contribute to the attenuated aging profile and sustained healthspan of the naked mole-rat. Understanding how these are regulated may be also integral to sustaining positive human healthspan well into old age and may elucidate novel therapeutics for delaying the onset and progression of physiological declines that characterize the aging process.

Nrf2, a guardian of healthspan and gatekeeper of species longevity

Although aging is a ubiquitous process that prevails in all organisms, the mechanisms governing both the rate of decline in functionality and the age of onset remain elusive. A profound constitutively upregulated cytoprotective response is commonly observed in naturally long-lived species and experimental models of extensions to lifespan (e.g., genetically-altered and/or experimentally manipulated organisms), as indicated by enhanced resistance to stress and upregulated downstream components of the cytoprotective nuclear factor erythroid 2-related factor 2 (Nrf2)-signaling pathway. The transcription factor Nrf2 is constitutively expressed in all tissues, although levels may vary among organs, with the key detoxification organs (kidney and liver) exhibiting highest levels. Nrf2 may be further induced by cellular stressors including endogenous reactive-oxygen species or exogenous electrophiles. The Nrf2-signaling pathway mediates multiple avenues of cytoprotection by activating the transcription of more than 200 genes that are crucial in the metabolism of drugs and toxins, protection against oxidative stress and inflammation, as well as playing an integral role in stability of proteins and in the removal of damaged proteins via proteasomal degradation or autophagy. Nrf2 interacts with other important cell regulators such as tumor suppressor protein 53 (p53) and nuclear factor-kappa beta (NF-κB) and through their combined interactions is the guardian of healthspan, protecting against many age-related diseases including cancer and neurodegeneration. We hypothesize that this signaling pathway plays a critical role in the determination of species longevity and that this pathway may indeed be the master regulator of the aging process.

Mechanical and degradation behavior of polymer-calcium sulfate composites

Calcium sulfate (CS) is one of the oldest bone graft materials still in use. Its main limitations are poor handling characteristics, poor mechanical properties, and a resorption rate that is too fast for some applications. The present study investigated the effect of viscous polymers, such as carboxymethylcellulose (CMC) and hyaluronan (HY), on the handling characteristics, mechanical properties, and degradation behavior of CS. CMC and HY were added to CS at concentrations from 1-10 wt%. Addition of CMC to CS at more than 4 wt% produced a putty-like material and decreased the density of the composite, while also increasing flexural and compressive strength at higher loadings. Incorporation of CMC produced a concentration-dependent increase in water absorption and degradation rate. At an equivalent loading, HY-containing CS composites showed better compressive strength than CS with CMC. Overall, addition of CMC or HY to CS resulted in composite materials with better handling characteristics and improved mechanical properties after set, however the degradation rate of the augmented materials was increased. These properties suggest that the enhanced CS materials may be useful in certain clinical situations, such as filling non-uniform bone defects and situations that require mechanical integrity of the bone graft substitute during implantation.