改变基因表达以提升健康与表现的行为方式 | Dr. Melissa Ilardo

改变基因以提升健康与表现的行为 | Dr. Melissa Ilardo

摘要

犹他大学生物医学信息学教授 Dr. Melissa Ilardo 探讨了人类遗传学、epigenetics（表观遗传学）的交汇点，以及行为如何塑造基因表达——无论是在一个人的一生中，还是跨越数代人。对话探索了现实中存在于活体人群的自然选择案例，包括生理机能已遗传性地适应水下生活的屏气潜水社群。核心话题包括mammalian dive reflex（哺乳动物潜水反射）、脾脏功能、通过免疫系统气味进行配偶选择，以及创伤相关表观遗传变化的遗传传递。

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核心要点

• 表观遗传变化可以遗传：压力、饥荒与创伤可在基因组上留下分子修饰，并传递给后代——有时作为适应性优势，有时在环境改变后成为负担。
• 哺乳动物潜水反射可触发10%的氧气提升：在冷水（约10°C / 50°F）中屏气并将脸浸入水中，会导致脾脏收缩并将储存的红细胞释放到血液循环中——这是一种显著且可测量的表现效益。
• 脾脏大小与潜水能力相关：印度尼西亚的 Bajau 海上游牧民族的脾脏比附近非潜水人群大约50%，部分原因在于一种与高于平均水平甲状腺激素相关的基因变异。
• 人类基于免疫系统相容性选择配偶：人们会在潜意识中被拥有最不同major histocompatibility complex (MHC)（主要组织相容性复合体）的个体体味所吸引，从而优化后代的免疫多样性。
• 人类进化仍在持续：全球化正在产生人类历史上前所未有的基因组合，既创造出新的抗病韧性，也带来新型疾病风险。
• 屏气训练可显著降低心率：韩国 Haenyeo 潜水员在下水后15秒内心率可下降40次以上——这是一种通过毕生潜水实践获得的可训练适应。
• 妊娠期潜水推动了血压相关的遗传适应：Haenyeo 似乎携带一种在屏气期间降低舒张压的基因变异，可能对抗高血压妊娠并发症具有保护作用。
• 进化没有方向性：“适者生存”更准确的理解是”最适应当前环境”——进化没有终点或目标。
• 近亲繁殖会集中有害隐性变异：近亲之间的交配会大幅增加有害基因变异在后代中得以表达的概率。

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详细笔记

表观遗传学与行为基因表达

• Epigenetics（表观遗传学） 涉及分子物理性地附着在基因组上并修饰基因表达方式——而不改变底层 DNA 序列。
• 这些修饰可以传递给后代。
• 示例：荷兰饥荒幸存者将表观遗传变化传递给了子女。这些变化可能有助于后代在食物匮乏的环境中生存，但在现代食物充裕的环境中可能处于不利地位。
• 难民群体中的创伤也被记录为可遗传的表观遗传变化，尽管这些变化是适应性的还是不适应性的尚不完全清楚。
• 基因表达变化可发生在数分钟至数小时的时间尺度上（环境响应），也可跨越数代人（表观遗传遗传）。

自然选择的时间线

• 经典假设：有意义的遗传选择需要5,000–10,000年以上。
• 最新认识：在强烈的环境压力下，选择可以在短短1,000–2,000年内发生。
• 大多数突变是有害的——许多在出生前就被淘汰。
• 有益适应最常来源于现有变异：群体中已有的遗传多样性在新条件下变得有利。

配偶选择与免疫系统

• 将小鼠 MHC 研究在人类中复现的研究证实：人们更容易被拥有最不同免疫系统特征的异性个体体味所吸引。
• 参与者嗅闻来自异性的汗湿 T 恤；吸引力与MHC差异性呈正相关。
• 这表明嗅觉充当了后代免疫多样性的代理指标，作用于意识决策层面以下。
• 相反的模式——近亲繁殖——会大幅增加有害隐性变异的表达，在人类对遗传学有任何了解之前，各文化中早已对此加以禁止。

杂交优势与全球化

• 全球化正在创造人类历史上从未存在过的基因组合，有可能提升群体层面的抗病韧性。
• 历史案例：西藏高原适应很可能通过与丹尼索瓦人（古代人类）的杂交而获得，提供了能够在极端高海拔生存的基因。
• 与尼安德特人之间也发生了类似的基因渗入（物种/种群间的基因转移）。
• 新的基因组合在分别进化的变异首次相遇时，也可能产生新型疾病风险。

Bajau 海上游牧民族与哺乳动物潜水反射

• 印度尼西亚的 Bajau 人是世代从事屏气潜水的海上游牧民族。孩子们在学会走路之前就已学会游泳。
• 据报告的屏气时间：坊间流传最长可达13分钟（主动潜水，非静态漂浮）。
• mammalian dive reflex（哺乳动物潜水反射） 的触发条件：
  • 屏气
  • 冷水接触面部（刺激迷走神经）
  • 操作方案：面部浸入约10°C / 50°F 的水中
• 生理反应：
  • 心率减慢（外周血管收缩）
  • 四肢血管收缩（将血流集中到大脑和重要器官）
  • 脾脏收缩，将储存的富氧红细胞释放到循环中
• 脾脏收缩带来的氧气提升约为10%
• 屏气结束后，脾脏会重新充盈红细胞——这种提升是短暂的，仅在潜水过程中有效。
• 脾脏在运动期间也会收缩，这或许可以解释赛马和灰狗为何拥有异常大的脾脏。

脾脏大小、遗传学与甲状腺激素

• Bajau 潜水员及同一社群中的非潜水者的脾脏均比附近农耕人群大约50%——这表明这是一种遗传性差异，而非纯粹基于训练。
• 相关基因变异与高于平均水平（但未达临床异常）的甲状腺激素水平相关。
• 该变异在欧洲人群中也存在，同样预测着更大的脾脏体积。
• 推测机制：甲状腺激素水平较高 → 红细胞生成增加 → 脾脏增大 → 潜水时可用氧气更多。
• 同时还导致血红蛋白、血细胞比容及红细胞数量的增加。
• 重要的是，这似乎是一种不依赖促红细胞生成素（EPO）的红细胞增加机制——对运动表现增强研究可能具有重要意义。
• 定期屏气训练是否能增大非 Bajau 人群的脾脏仍是一个悬而未决的问题；部分训练研究表明确实如此。

Haenyeo：韩国女性潜水员

• 韩国济州岛的 Haenyeo（“海女”）是一个全女性潜水社群，平均年龄约70岁。
• 她们在极寒水域潜水，历史上不穿潜水服（直至1980年代前穿棉质泳衣）。
• 她们在整个妊娠期间坚持潜水，有时直到临产前一天，产后数天便重返水中。
• 近期研究中有一位81岁的潜水员参与；研究追踪记录的潜水深度约为10米（30英尺）。
• 她们是联合国教科文组织非物质文化遗产。

Haenyeo 身上发现的两种适应：

1. 训练性适应——心率反应

• Haenyeo 潜水员在入水后15秒内心率下降40次以上。
• 这种现象仅见于潜水员，在同一人群中的非潜水女性中不存在→证实这是一种训练性适应，而非遗传性的。
• 表明心脏通过数十年的潜水实践获得了显著的自主神经可塑性。

2. 遗传性适应——血压调节

• 妊娠期潜水模拟了睡眠呼吸暂停的缺氧状态，后者会增加子痫前期及其他妊娠高血压疾病的风险。
• Haenyeo 携带一种与屏气期间舒张压降低相关的基因变异。
• 这被认为是在数代潜水孕妇中经自然选择形成的保护性适应。
• 研究人员希望这

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English Original 英文原文

Behaviors That Alter Your Genes to Improve Your Health & Performance | Dr. Melissa Ilardo

Summary

Dr. Melissa Ilardo, professor of biomedical informatics at the University of Utah, discusses the intersection of human genetics, epigenetics, and how behavior shapes gene expression — both within a lifetime and across generations. The conversation explores real-world examples of natural selection in living human populations, including breath-hold diving communities whose physiology has genetically adapted to underwater life. Key topics include the mammalian dive reflex, spleen function, mate selection via immune system smell, and the inheritance of trauma-related epigenetic changes.

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Key Takeaways

• Epigenetic changes can be inherited: Stress, famine, and trauma can leave molecular modifications on the genome that are passed to subsequent generations — sometimes as adaptive advantages, sometimes as liabilities in changed environments.
• The mammalian dive reflex triggers a 10% oxygen boost: Holding your breath while submerging your face in cold water (~10°C / 50°F) causes the spleen to contract and release stored red blood cells into circulation — a significant, measurable performance effect.
• Spleen size correlates with diving ability: The Bajau sea nomads of Indonesia have spleens approximately 50% larger than nearby non-diving populations, partly due to a genetic variant linked to higher-than-average thyroid hormone levels.
• Humans select mates based on immune system compatibility: People are subconsciously attracted to the body odor of individuals with the most different major histocompatibility complex (MHC), optimizing immune diversity in offspring.
• Human evolution is ongoing: Globalization is producing genetic combinations never before seen in human history, creating both new resilience and novel disease risks.
• Breath-hold training slows heart rate dramatically: Korean Haenyeo divers show heart rate drops of 40+ beats per minute in under 15 seconds — a trainable adaptation through a lifetime of diving.
• Diving through pregnancy has driven genetic blood pressure adaptations: The Haenyeo appear to carry a variant that lowers diastolic blood pressure during breath-holds, potentially protecting against hypertensive disorders of pregnancy.
• Evolution is not directional: “Survival of the fittest” is better understood as “best fit for the current environment” — evolution has no endpoint or goal.
• Inbreeding concentrates harmful recessive variants: Mating between closely related individuals dramatically increases the chance that deleterious genetic variants will be expressed in offspring.

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Detailed Notes

Epigenetics and Behavioral Gene Expression

• Epigenetics involves molecules physically attaching to the genome and modifying how genes are expressed — without changing the underlying DNA sequence.
• These modifications can be passed to subsequent generations.
• Example: Dutch famine survivors passed epigenetic changes to their children. These changes likely helped descendants survive food scarcity but may be disadvantageous in modern environments of food abundance.
• Trauma in refugee populations has also been recorded in heritable epigenetic changes, though whether these are adaptive or maladaptive is not fully understood.
• Gene expression changes can occur on the timescale of minutes to hours (environmental response) or across generations (epigenetic inheritance).

Natural Selection Timelines

• Classical assumption: meaningful genetic selection requires 5,000–10,000+ years.
• Updated understanding: selection can occur in as little as 1,000–2,000 years under strong environmental pressure.
• Most mutations are deleterious — many are filtered out before birth.
• Beneficial adaptations most often come from standing variation: existing genetic diversity in a population that becomes advantageous under new conditions.

Mate Selection and the Immune System

• Studies replicating mouse MHC research in humans confirmed: people are more attracted to the body odor of individuals with maximally different immune system profiles.
• Participants smelled sweaty t-shirts from opposite-sex individuals; attraction correlated with MHC dissimilarity.
• This suggests smell functions as a proxy for offspring immune diversity, operating below conscious decision-making.
• The opposite pattern — inbreeding — dramatically increases expression of harmful recessive variants and has been culturally discouraged across human societies long before genetics was understood.

Hybrid Vigor and Globalization

• Globalization is creating genetic combinations that have never existed in human history, potentially increasing population-level resilience.
• Historical example: The Tibetan high-altitude adaptation was likely acquired through interbreeding with Denisovans (archaic hominids), providing genes enabling survival at extreme elevations.
• Similar introgression (gene transfer between species/populations) occurred with Neanderthals.
• New genetic combinations can also produce novel disease risks when variants that evolved separately are combined for the first time.

The Bajau Sea Nomads and the Mammalian Dive Reflex

• The Bajau people of Indonesia are sea nomads who have practiced breath-hold diving for generations. Children learn to swim before they walk.
• Reported breath holds: anecdotally up to 13 minutes (active diving, not static floating).
• The mammalian dive reflex is triggered by:
  • Breath-holding
  • Cold water on the face (stimulates the vagus nerve)
  • Protocol: face submerged in ~10°C / 50°F water
• Physiological responses:
  • Heart rate slows (peripheral vasoconstriction)
  • Blood vessels in extremities constrict (centralizes blood flow to brain and organs)
  • Spleen contracts, releasing stored oxygen-rich red blood cells into circulation
• The oxygen boost from spleen contraction: approximately 10%
• The spleen refills with red blood cells after the breath hold ends — the boost is transient and only active during the dive.
• The spleen also contracts during exercise, which may explain the disproportionately large spleens in horses and greyhounds.

Spleen Size, Genetics, and Thyroid Hormone

• Bajau divers and non-divers from the same community both have spleens ~50% larger than nearby farming populations — indicating a genetic, not purely training-based difference.
• The associated genetic variant correlates with higher-than-average (but not clinically elevated) thyroid hormone levels.
• This variant is also found in European populations, where it similarly predicts larger spleen size.
• Proposed mechanism: higher thyroid hormone → increased red blood cell production → larger spleen → more oxygen available during dives.
• Also results in increased hemoglobin, hematocrit, and red blood cell count.
• Importantly, this appears to be an erythropoietin (EPO)-independent mechanism of red blood cell increase — potentially relevant to performance enhancement research.
• Whether regular breath-hold training increases spleen size in non-Bajau individuals remains an open question; some training studies suggest it does.

The Haenyeo: Korean Female Divers

• The Haenyeo (“sea women”) of Jeju Island, South Korea, are an all-female diving community with an average age of approximately 70 years.
• They dive in extremely cold water, historically without wetsuits (cotton swimsuits until the 1980s).
• They dive throughout pregnancy, sometimes until the day of birth, returning to the water days postpartum.
• An 81-year-old diver participated in recent research; divers tracked diving to depths of approximately 10 meters (30 feet).
• They are a UNESCO Intangible Cultural Heritage.

Two Adaptations Found in the Haenyeo:

1. Trained Adaptation — Heart Rate Response

• Haenyeo divers show heart rate drops of 40+ beats per minute in under 15 seconds upon submersion.
• This is only present in divers, not in non-diving women from the same population → confirms it’s a training adaptation, not genetic.
• Suggests the heart develops significant autonomic plasticity through decades of diving practice.

2. Genetic Adaptation — Blood Pressure Regulation

• Diving through pregnancy mimics the oxygen deprivation of sleep apnea, which increases risk for preeclampsia and other hypertensive disorders of pregnancy.
• The Haenyeo carry a genetic variant associated with lowered diastolic blood pressure during breath-holds.
• This is believed to be a protective adaptation selected over generations of pregnant women diving.
• Researchers hope this