High social status males experience accelerated epigenetic aging in wild baboons.
High social status males experience accelerated epigenetic aging in wild baboons.
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作者：
Anderson JA;Johnston RA;Lea AJ;Campos FA;Voyles TN;Akinyi MY;Alberts SC;Archie EA;Tung J
衰老对几乎所有生命来说都是不可避免的。然而，在人口中，生物老化率各不相同。了解这一过程中的变异来源是了解自然种群生物统计学的核心。我们构建了一个基于DNA甲基化的年龄预测因子，用于深入研究肯尼亚的野生狒狒种群。与人类的研究结果一致，由此产生的“表观遗传时钟”密切跟踪实际年龄，但预测个体比已知年龄稍大或更年轻。令人惊讶的是，这些偏差并不能用这一人群中寿命最强的预测因素，早期逆境和社会融合来解释。相反，他们最好是通过男性统治地位来预测的：高地位的男性被预测比他们的真实年龄要大，表观遗传年龄随着时间的推移跟踪排名的变化。我们的研究结果表明，雄性狒狒获得高排名--生殖成功的最佳预测因素--会带来与“活得快，死得早”生活史策略一致的成本。对于大多数动物来说，年龄是健康和生存的最强预测因素之一，但并非所有个体的年龄都相同。事实上，同一物种的动物即使活了相同的年数，也可能有不同的“生物年龄”。在人类和其他哺乳动物中，这种衰老的变化表现在被称为DNA甲基化标记的化学修饰中。一些研究人员称这些标记为“表观遗传”，字面意思是“基因”。一些DNA甲基化标记随着年龄的增长而变化，因此它们的组合变化模式通常被称为“表观遗传时钟”。环境压力因素，如吸烟或缺乏体力活动，可以使表观遗传时钟“滴答”更快，使一些个体的DNA看起来比基于实际年龄的预期更老。这些“生物学上的老年人”也可能经历更高的年龄相关疾病的风险。对人类的研究揭示了这种快速生物衰老背后的一些原因，但目前还不清楚这些结果是否适用于野外。早期生活事件可能会触发表观遗传时钟的变化，影响成年后的健康。例如，在灵长类动物中，早期生活中的逆境对生育力和生存有已知的影响。社会地位低也对健康产生负面影响。为了弄清楚早期经历和社会环境是否会影响表观遗传时钟，安德森、约翰斯顿等人追踪了狒狒的DNA甲基化标记。这表明表观遗传时钟是野生灵长类动物年龄的有力预测者，但早期的逆境和社会联系的强度都不会影响时钟的滴答声。事实上，正是社会地位的竞争对时钟的速度产生了最戏剧性的影响。在不同时期采集的男性样本表明，随着他们在社会阶梯上的上升或下降，他们的表观遗传时钟会加快或减慢，反映的是最近的社会经历，而不是他们生命早期的事件。平均而言，表观遗传时钟测量将阿尔法男性的年龄高估了近一年，这表明争夺优势是有代价的。这项研究强调了社会环境影响衰老的一种方式。下一步是了解动物获得社会地位的方式如何影响健康。这可以帮助研究进化的研究人员了解社会互动和环境条件如何影响生存和繁殖。它还可以深入了解社会地位对人类健康和衰老的影响。
Aging, for virtually all life, is inescapable. However, within populations, biological aging rates vary. Understanding sources of variation in this process is central to understanding the biodemography of natural populations. We constructed a DNA methylation-based age predictor for an intensively studied wild baboon population in Kenya. Consistent with findings in humans, the resulting ‘epigenetic clock’ closely tracks chronological age, but individuals are predicted to be somewhat older or younger than their known ages. Surprisingly, these deviations are not explained by the strongest predictors of lifespan in this population, early adversity and social integration. Instead, they are best predicted by male dominance rank: high-ranking males are predicted to be older than their true ages, and epigenetic age tracks changes in rank over time. Our results argue that achieving high rank for male baboons – the best predictor of reproductive success – imposes costs consistent with a ‘live fast, die young’ life-history strategy. For most animals, age is one of the strongest predictors of health and survival, but not all individuals age at the same rate. In fact, animals of the same species can have different 'biological ages' even when they have lived the same number of years. In humans and other mammals this variation in aging shows up in chemical modifications known as DNA methylation marks. Some researchers call these marks 'epigenetic', which literally means 'upon the genes'. And some DNA methylation marks change with age, so their combined pattern of change is often called the ‘epigenetic clock’. Environmental stressors, such as smoking or lack of physical activity, can make the epigenetic clock ‘tick’ faster, making the DNA of some individuals appear older than expected based on their actual age in years. These ‘biologically older’ individuals may also experience a higher risk of age-related disease. Studies in humans have revealed some of the reasons behind this fast biological aging, but it is unclear whether these results apply in the wild. It is possible that early life events trigger changes in the epigenetic clock, affecting health in adulthood. In primates, for example, adversity in early life has known effects on fertility and survival. Low social status also has a negative effect on health. To find out whether early experiences and the social environment affect the epigenetic clock, Anderson, Johnston et al. tracked DNA methylation marks in baboons. This revealed that epigenetic clocks are strong predictors of age in wild primates, but neither early adversity nor the strength of social bonds affected the rate at which the clocks ticked. In fact, it was competition for social status that had the most dramatic effect on the clock’s speed. Samples of males taken at different times during their lives showed that their epigenetic clocks sped up or slowed down as they moved up or down the social ladder, reflecting recent social experiences, rather than events early in their lives. On average, epigenetic clock measurements overestimated the age in years of alpha males by almost a year, showing that fighting to be on top comes at a cost. This study highlights one way in which the social environment can influence aging. The next step is to understand how health is affected by the ways that animals attain social status. This could help researchers who study evolution understand how social interactions and environmental conditions affect survival and reproduction. It could also provide insight into the effects of social status on human health and aging.