AnAge entry for Heterocephalus glaber

Classification (HAGRID: 02848)

Taxonomy
Kingdom: Animalia
    Phylum: Chordata
        Class: Mammalia (Taxon entry)
            Order: Rodentia
                Family: Bathyergidae
                    Genus: Heterocephalus
Species
Heterocephalus glaber
Common name
Naked mole-rat
Synonyms
Heterocephalus ansorgei, Heterocephalus dunni, Heterocephalus phillipsi, Heterocephalus progrediens, Heterocephalus scortecci, Heterocephalus stygius

Lifespan, ageing, and relevant traits

Maximum longevity
31 years (captivity)
Source
Rochelle Buffenstein, pers. comm.
Sample size
Large
Data quality
High
Observations

These bizarre underground animals from the Horn of Africa live in cooperative colonies, a protected and thermally buffered environment. Their body temperature is relatively low and they appear to be cold-intolerant. They are one of the longest-lived rodents and are extremely resistant to cancer [0689], though cases of cancer have been reported [1248]. The INK4 locus of naked mole rats encodes a functional p15/p16 hybrid isoform (in addition to the other products) which is expressed in response to a number of cancer related stresses. In cultured cells this hybrid product has a stronger ability to induce cell-cycle arrest than either p15 or p16 and may contribute to the increased cancer resistance of this species [1176]. These animals have higher levels of expression of the A2M gene, whose activated form has been shown to inhibit tumour growth in mice [1333].

Record longevity belongs to one specimen caught in the wild in 1980 that lived over 30 years in captivity until it died in 2010, making it at least 31 years of age when it died (Rochelle Buffenstein, pers. comm.). In the wild, breeders have been known to live up to 17 years but non-breeders do not commonly live more than 2 or 3 years (Stan Braude, pers. comm.).

Unlike other mammals, naked mole-rats appear to maintain good health for most of their lifespan and do not exhibit the typical age-associated increase in mortality [0756]. Older animals can be less active but few age-related changes have been described [0981]. Naked mole-rats maintain cardiac function with age and show no evidence of cardiac hypertrophy or arterial stiffening [1177]. Nonterminal pathologies like sarcopenia and kyphosis have been observed in old animals [0925]. In addition to their cancer resistance naked mole-rats appear to have natural protection against amyloid beta plaque formation, a process implicated in Alzheimer's disease (AD). In one study, the brains of the longest lived naked mole-rats contained similar levels of amyloid beta to mouse models of AD yet showed no evidence of extracellular plaque formation [1178]. Even young naked mole-rats have high levels of soluble amyloid beta in their brains, linked to lower levels of UPS-mediated amyloid beta degradation [1179]. Another study found that levels of phosphorylated tau protein, also implicated in AD, were higher in naked mole-rats than mouse models. Despite this, the phosphorylated tau protein maintained normal axonal localisation [1180]. This suggests naked mole-rats also have a resistance to neurodegenerative disease.

Studies into the microbiome of naked mole-rats have shown that these animals have a similarity in gut bacteria with another model of healthy ageing (extremely aged humans). Additionally, some of the gut microflora in the microbiome of naked mole-rats may have important functions regarding immune homeostasis and cancer [1331].

Naked mole-rats' fibroblasts have been shown to be considerably resistant to reprogramming. This could indicate that their epigenome is quite stable, which might contribute to their improved cancer resistance and longevity, when compared to other species [1332].

A study comparing rodent species has found that maximum longevity is associated with smaller rates of protein turnover. Animals of this long-lived species may have evolved towards reducing the energetic cost of continuous protein turnover, which in turn would lessen the quantity and the damage caused by reactive oxygen species produced in this process [1334].

These rodents' exceptional lifespan does not appear to be caused by the removal of the process of cellular senescence. Naked mole-rat cells have been found to undergo the same types of cellular senescence as those found in mice, favouring a senescence response to an apoptotic one [1336].

Studies comparing ageing-associated differentially methylated positions (aDMPs) between mouse, dog, naked mole-rat, rhesus monkey, humpback whale and human, have shown that lifespan in these mammalian species is strongly correlated with the rate of change of methylation levels in aDMPs. Additionally, these methylation dynamics are a measure of cellular ageing [1315]. One model was successfully built that could predict specimen age, based on the epigenetic clock. This model also predicted that skin tissue ages at a slower rate than liver for these animals [1340].

One possible reason for these animals being long-lived could be associated with their enhanced resistance to stress [1338]. These animals can retain the function of mild depolarization in their mitochondria, which allows for the production of large amounts of ATP without the production of ROS [1341]. Additionally, these animals have been found to possess differences in the constitution of their immune system compared to mouse, which includes the lack of natural killer cells [1339].

Telomere length was found to slightly increase with age, possibly aiding them reach extreme longevities [1342].

Life history traits (averages)

Female sexual maturity
228 days
Male sexual maturity
Gestation
70 days
Weaning
Litter size
7 (viviparous)
Litters per year
3.5
Inter-litter interval
81 days
Weight at birth
2 g
Weight at weaning
Adult weight
35 g
Postnatal growth rate
0.0046 days-1 (from Gompertz function)
Maximum longevity residual
368%

Metabolism

Typical body temperature
305ºK or 32.1ºC or 89.8ºF
Basal metabolic rate
0.1280 W
Body mass
35.3 g
Metabolic rate per body mass
0.003626 W/g

References

External Resources

Integrated Taxonomic Information System
ITIS 584677
Animal Diversity Web
ADW account (if available)
Encyclopaedia of Life
Search EOL
NCBI Taxonomy
Taxonomy ID 10181
Entrez
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Ageing Literature
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Internet
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