How Mitochondria Control Your Metabolism | Dr. Jared Rutter
Andrew Huberman
Mitochondria and reactive oxygen species 0:00
Dr. Jared Rutter opens by explaining a widely accepted idea in his field: mitochondria that hold too much energy tend to cause problems. When mitochondria become overpowered with the energy extracted from food before it turns into ATP, they become prone to producing reactive oxygen species. These are unstable forms of oxygen that spin out and damage proteins and nucleic acids, contributing to mutations and many of the problems seen in cells over time.
Introducing the guest and the topic 1:00
Andrew Huberman introduces Dr. Jared Rutter, a professor of biochemistry at the University of Utah and an investigator with the Howard Hughes Medical Institute, describing him as one of the world's top experts on mitochondria and metabolism. Huberman notes that mitochondria do far more than power cells, they also shape how much energy goes into making new cells, keeping cells healthy, and fighting disease. He frames the conversation as an opportunity to understand that your metabolism is not a single thing but a reflection of the combined metabolisms of every cell in your body.
What metabolism really means 3:31
Rutter explains that what people usually call metabolism, the calories in and calories out idea, is really the sum total of everything ingested through eating, drinking, and breathing, once it is processed by the body. That processing breaks food down into individual molecules like amino acids and sugars that travel to cells and enter cellular metabolism. He describes cellular metabolism as a kind of map, where a molecule like glucose enters a cell, gets chemically modified to meet that cell's needs, and eventually produces waste that the body eliminates. The metabolism of the whole body, he says, is really the sum of the metabolism happening inside roughly 30 trillion individual cells, each choosing how to take up and process nutrients to fulfill its own function.
Why energy seems to fade with age 6:31
Responding to a question about why people seem to have so much less energy as they age compared to when they were young, Rutter says this is a partial frontier of science. Mitochondria, he explains, almost universally become less energized and less effective as we age, though the exact reasons remain only partly understood. He points to the accumulation of damage over time, the cost of running the body's demanding metabolic machinery, as a strong correlate of aging, with genetic evidence from animal models supporting this link. He adds that aging is fundamentally a cellular phenomenon, since the body is made of cells, and that new tools are starting to let scientists trace the specific molecular causes behind it.
Mitochondria as former bacteria 9:00
Rutter explains that mitochondria are believed to have originated from an endosymbiotic event, in which a free-living bacterium was engulfed by another cell and effectively domesticated. Huberman restates this plainly: an ancient cell was invaded by a bacterium, and that bacterium became a permanent part of the genome, passed down through what is called the germ line, meaning it could be inherited from parent to child. This is different from the gut microbiome, which can be lost and replenished, because mitochondria became stably fixed within our lineage. Rutter adds that this partnership between two separate organisms enabled forms of metabolism that neither could achieve alone, and that all complex life, including plants, animals, and fungi, descended from this combined cell.
Was the partnership beneficial or a takeover 11:30
When Huberman asks whether the merger between the ancient cell and the bacterium was mutually beneficial or more like a takeover, similar to how a virus can hijack a cell for its own survival, Rutter calls it partly a philosophical question, since there is no direct record of what happened. Still, he argues that the fact all complex life descended from this event suggests it was beneficial, because it enabled a more efficient and diversified form of metabolism that allowed complex life to evolve in the first place.
A separate genome for mitochondria 16:32
Rutter describes how mitochondria carry their own separate genome, a circular one resembling bacterial DNA, distinct from the linear chromosomes held in the cell's nucleus. This mitochondrial genome codes for essential proteins that let mitochondria function as the cell's power generators. Because mitochondria live in the cytoplasm rather than the nucleus, and because sperm cytoplasm does not enter the egg during fertilization, mitochondrial DNA is inherited entirely from the mother. This maternal-only inheritance pattern has real implications for understanding diseases that originate from mitochondrial mutations.
Mitochondria spread throughout the cell 19:00
Rutter says there is essentially no place in a cell where mitochondria are absent. In neurons, for example, mitochondria travel down projections that can stretch a meter long, generating usable energy at the far ends to power neurotransmission. This local production of ATP, the energy currency used by nearly every cell, makes energy use more efficient, since it happens right where it is needed. He gives the example of a crawling immune cell, where mitochondria cluster near the leading edge of the cell because that is where energy demand for movement is highest.
Mitochondria tailored to each cell's job 22:00
Rutter explains that mitochondria differ subtly from cell to cell, shaped by the specific demands of the cell they inhabit. A heart muscle cell, for instance, has essentially one job, contracting continuously for a lifetime, so its mitochondria are wired mainly to produce ATP. By contrast, intestinal stem cells, which must replace the gut lining roughly every five to seven days, need mitochondria wired to help build entirely new cells, duplicating DNA, proteins, and membranes rapidly rather than simply generating energy. Recent research, including work from Craig Thompson at Sloan Kettering, has even shown that a single cell can contain two distinct kinds of mitochondria at once, one more focused on energy production and one more focused on building biomass, reflecting how finely tuned mitochondrial function can be to a cell's particular needs.
How the body allocates energy after eating 27:00
Huberman asks how energy gets distributed among cells after eating, whether it is a free-for-all where every cell grabs as much glucose as it can, or something more coordinated. Rutter explains that digestion breaks food into sugars, amino acids, and fats, which trigger hormonal signals such as GLP-1 and insulin. These hormones travel throughout the body to tell individual cells that food has arrived, but different cells respond differently. Some largely ignore the signal and continue as before, while others, like fat cells, respond strongly, turning on specific proteins in reaction to insulin.
Insulin as a signal, not just a shuttle 28:01
Rutter explains that when we eat, insulin does more than let glucose into cells. It causes fat cells to take up glucose, convert it into fat molecules, and store that fat safely for long periods, a system that likely kept our ancestors alive during prolonged fasting. Insulin also acts differently on different cells depending on their needs, so a fat cell, a muscle cell, and a neuron each respond to the same hormonal signal in their own way. The size of the insulin signal itself carries information, much like cortisol or melatonin levels do, telling a cell not just to act but how much has changed and what to prepare for next.
From glucose to pyruvate 32:32
Rutter walks through glycolysis, the chain of chemical reactions that breaks glucose, a six carbon molecule, down into a smaller molecule called pyruvate. He calls pyruvate a pivot point, because once it forms, the cell faces a decision about what to do with it next.
Burn it or build with it 34:01
Pyruvate can either be pulled into the mitochondria and oxidized, essentially burned with oxygen, to extract the maximum energy in the form of ATP, or it can be redirected to build biomass, the raw material for making new cells. Heart muscle cells favor burning pyruvate to keep the heart pumping, while intestinal stem cells, which must repopulate the gut lining every week, use pyruvate and related molecules to build new biomass instead. Huberman offers the analogy of lumber that can either be burned for heat or used to build more house, and Rutter agrees this captures the basic tradeoff every cell makes constantly.
Immune cells and resource allocation 35:30
An activated B cell, the immune cell responsible for making antibodies, needs large amounts of amino acids to build those antibody proteins, so it too must shift its metabolism toward biomass production rather than pure energy burning. Rutter frames this as a universal decision every cell makes every second, choosing how to allocate the resources it has.
Cancer as biomass gone wrong 38:00
Rutter uses PET imaging, specifically FDG PET, which tracks a labeled form of glucose, to show that tumors take up unusually large amounts of glucose because a cancer cell has shifted its resource allocation almost entirely toward building more of itself. A tumor begins when one cell decides to duplicate rather than perform its normal function, and that decision repeats until a mass of cells forms.
Comparing cancer to viral logic 39:31
Huberman raises the idea that viruses show a kind of adaptive logic, propagating themselves while sometimes keeping their host alive to spread further, as with rabies altering brain regions tied to aggression and biting. He asks whether cancer follows similar logic, and Rutter responds that cancer differs in a key way: while viruses evolve to jump between hosts and propagate widely, cancer cells evolve only within the single organism they arose in, acquiring mutations that help them divide, evade the immune system, and survive DNA damage, but with almost no ability to spread from one person to another, aside from a rare, unusual exception in Tasmanian devils where tumors reportedly spread through fighting and wounds.
The microbiome as a shuttle idea 48:31
Huberman brings up an idea from a colleague, Justin Sonnenberg, suggesting that humans might simply be vehicles for the gut microbiome to spread itself, since every handshake or shared breath exchanges microbes between people. Rutter agrees he cannot disprove this, noting that the bacteria in our gut and on our skin are driven by the same evolutionary pressures as viruses and humans, trying to propagate and fill their niche, and that serious research into the full implications of the microbiome has really only taken off in the last decade or so.
Discovering the mitochondrial pyruvate carrier 52:00
Rutter introduces MPC1 and MPC2, the mitochondrial pyruvate carrier, the protein that forms a specific opening in the mitochondrial membrane allowing pyruvate to enter so it can be burned for ATP. Scientists had known for sixty or seventy years that such a carrier must exist, but its identity remained a mystery until Rutter's lab, newly interested in mitochondria around 2008 or 2009, set out to find functions for mitochondrial proteins whose roles were still unknown. He begins describing the lab technique of fractionation, grinding up cells and passing them through columns with filters that separate components by size, as the starting point for tracking down what would become MPC1 and MPC2.
Finding the Mitochondrial Pyruvate Carrier 55:30
Rutter explains that scientists now know essentially every protein encoded by the human genome, even in a single heart cell, though they still do not know what all of those proteins do. That gap between knowing what a protein is and knowing what it does drove his lab to investigate two mysterious mitochondrial proteins found in every organism with mitochondria, from yeast to plants to animals. Working with fly geneticist Carl Thummel, and combining yeast, fly, and human cell data, Rutter's team identified these two proteins as the mitochondrial pyruvate carrier, or MPC, the machinery that pulls pyruvate into the mitochondria. The discovery was published in 2012 and was independently confirmed the same year by Jean-Claude Martinou's lab in Geneva.
Why the Discovery Mattered 59:02
Once pyruvate enters the mitochondria through the MPC, it gets used for energy production there rather than for other purposes in the cytosol, so the carrier acts as the first checkpoint in deciding how the cell allocates that resource. Rutter says the real excitement since the original discovery has been tracing what this allocation decision means across different cell types, especially in heart muscle cells, which rely heavily on the MPC to extract every bit of energy they can to keep contracting.
How Cells Sense Their Energy Levels 1:00:00
Asked how cells avoid overspending their energy reserves, Rutter says there is no fixed dial sending a set percentage of resources one way or another. Instead, cells appear to continuously monitor how much usable energy, in the form of ATP, they have on hand, and when levels drop, they trigger responses such as shutting down ATP-consuming processes and pulling in more glucose from the bloodstream. He extends this to other end products of metabolism, like the amino acids and nucleotides cells need for proteins and genetic material.
Fasting Hormones and Fat as Fuel 1:03:00
Rutter contrasts insulin, which signals the body to store incoming glucose, with glucagon, a fasting hormone that tells fat cells to release stored fat so other tissues, especially the heart, can use it. He notes that in a typical fasted person, an estimated 70 to 80 percent of the heart's energy comes from fat, and that the heart readily burns fat whether from the diet or from fat cells, making it something of a metabolic omnivore that can also run on glucose, lactate, ketones, and amino acids.
The Brain's Dependence on Glucose 1:04:31
Unlike the heart, neurons have very limited ability to burn fatty acids and rely heavily on glucose. Rutter points out that while diabetes, defined by chronically high blood sugar, can take years to cause serious harm, a drop in blood glucose that is too low can kill within minutes, largely because the brain needs a steady glucose supply to keep functioning. This asymmetry, he says, reflects the elaborate, constant coordination among different cell types each drawing on the fuel sources best suited to their needs.
What Happens Without the MPC 1:07:01
Using knockout mice, a technique built on Mario Capecchi's Nobel Prize winning work, researchers found that mice entirely lacking the MPC die around day 12 or 13 of development, roughly two-thirds of the way to birth. But mice engineered to lack the MPC only in the heart survive for weeks before dying of heart failure with grossly enlarged hearts. Rutter explains that these hearts do not fail from an inability to make ATP, since they can still burn fat, but because they redirect incoming glucose toward building more biomass instead of energy, causing the heart muscle cells to grow and the heart to become pathologically dilated and less effective at pumping.
Resource Allocation and Cell Identity 1:13:30
Rutter frames this as a resource allocation decision gone wrong, one that happens at the level of individual cells throughout the body all the time. He suggests this raises the question of whether disease is tied to a loss of cell identity, a difficult thing to measure since there is no simple test for what a cell thinks it is. He and Huberman discuss this through analogies, such as larger dog breeds living shorter lives than smaller ones, or sprinters tending to live longer than powerlifters, as examples where devoting more resources to size rather than function or longevity seems to carry a cost, though Rutter is careful to note this is a loose conceptual parallel rather than a proven mechanism.
Cheating the Cell, Cheating the Self 1:17:30
Extending the resource allocation idea, Rutter agrees that a cell cannot afford to cheat itself, and when enough cells make the wrong allocation choice, such as favoring growth over function, the result can be a heart too enlarged to pump properly, or immune cells becoming hyperactivated in ways that drive inflammatory disease. He connects this back to the MPC story by describing how the discovery was made: Carl Thummel's lab created flies lacking the MPC, which survived but showed specific metabolic defects, and parallel work in yeast and human cells confirmed that without the carrier, the pathway from glucose to pyruvate to mitochondrial ATP production was blocked specifically at the point of getting pyruvate into the mitochondria, a finding that led to the hypothesis about the proteins' function and was later validated repeatedly over the following decade.
Why yeast and flies matter 1:23:00
Rutter explains why scientists use organisms like yeast and fruit flies to study human biology. Yeast reproduce quickly, which makes experiments fast, and fruit flies also have short generation times while sharing many structural features with humans, letting researchers watch whole systems under a microscope. He stresses that his own major discovery could not have come from any single model organism alone. Only by combining data from yeast, flies, and human cells could his team triangulate the pattern and see that a particular hypothesis was worth pursuing, a strategy of using multiple model systems that scientists have relied on for a long time.
Lactate as a building block 1:24:31
Rutter reframes lactate, long dismissed as a waste product, as central to a crucial metabolic decision every cell makes constantly. Pyruvate has two fates, burning inside the mitochondria or being converted into lactate and exported, and choosing lactate preserves biomass rather than releasing it as carbon dioxide through breathing. That preserved material can become protein, carbohydrate, or fatty acid, feeding new cell construction. He credits Princeton professor Joshua Rabinowitz with experiments over the last five to ten years showing lactate is also an important fuel in its own right, one the heart readily burns alongside lipids and glucose.
Lactate, exercise, and the brain 1:28:02
During intense exercise, muscle becomes short on oxygen, forcing pyruvate to convert into lactate, which produces the burning sensation people feel. Huberman notes that lactate generated this way seems to signal the brain to release brain derived neurotrophic factor, or BDNF, which helps build new neural connections. Both point out how biology keeps overturning tidy labels, comparing this to the outdated idea of junk DNA, and joke that even calling mitochondria simply the powerhouse of the cell undersells everything else they do.
How the body prioritizes fuel 1:29:01
Asked why excess energy doesn't just get burned off, Rutter explains that cells prioritize burning fatty acids first because free fatty acids can quickly become toxic, unlike excess glucose, which is comparatively less dangerous over time. This applies whether the fatty acids are eaten or made by the body, since both end up in the same pathways. Lactate carries its own risk if it builds up too far, since lactic acidosis, too much lactate in circulation, can be lethal, which is why the body evolved efficient ways to handle it. He frames this prioritization as a product of evolutionary pressure, where ancestors who managed fatty acids well survived and passed on that trait.
The Warburg effect explained 1:31:31
Rutter walks through the Warburg effect, named after German scientist Otto Warburg, who observed in the 1920s that cancer cells consume less oxygen than surrounding cells and concluded their mitochondria must be broken. Decades later it's clear the mitochondria in cancer cells aren't broken at all, they are simply very good at building new material rather than burning fuel for energy. Since cancer cells need to duplicate themselves to form a tumor, this resource allocation toward building, rather than burning, explains their lower oxygen use, tying the Warburg effect directly to the same building versus burning framework discussed earlier.
Why cancer is hard to treat 1:37:30
Rutter lays out two core challenges of cancer therapy. First, cancer cells are the body's own cells and often lack antigens that would mark them as foreign, so the immune system struggles to distinguish them from healthy tissue, and treatments that target shared features, like stem cell pathways, risk damaging normal cells too, which explains many chemotherapy side effects. Second, tumors are under evolutionary pressure, so if a drug kills 99.9 percent of cells but a small fraction resist through mutation, that fraction can repopulate the tumor in a drug resistant form, mirroring what happens when cancers return after apparent remission.
Combination drugs as the future 1:43:00
Drawing a parallel to HIV, which is managed through triple combination therapy that makes simultaneous resistance far harder, Rutter argues cancer treatment is heading toward combining multiple safe, targeted drugs matched to a tumor's specific biochemistry. He points to newer drugs targeting specific oncogenic mutations, like those affecting Kras proteins, as a promising direction, since they hit only the cancer causing mutation without harming normal cells. Huberman brings up David Fajgenbaum, a University of Pennsylvania physician who treated his own Castleman's disease with combinations of already approved drugs and now runs the nonprofit Every Cure, using AI and lab assays to test drug combinations against patient tumors, including a finding that lidocaine used during breast cancer surgery lowers recurrence rates.
Classifying cancer by mutation, not location 1:46:01
Rutter suggests that classifying tumors by organ, breast cancer, liver cancer, colon cancer, is a historical artifact of how surgeons removed them, not a reflection of biology. Some breast cancers may share more in common with certain liver cancers than with other breast cancers, because what matters is the specific mutation driving uncontrolled growth and immune evasion. On top of the mutational instructions, each cancer's unique metabolism determines whether those instructions can actually be carried out, and efforts to block a cancer's resource allocation toward building new cells face the same resistance problem, since a cell can simply mutate and rewire its metabolism to build the same materials another way.
Imagining cell level metabolic imaging 1:48:31
Huberman describes a hypothetical future scan, a safe fluid taken at any age that would reveal, cell by cell, how much energy an organ allocates to basic function versus repair or replication, comparing a healthy heart cell's balance to one that looks unhealthy. He likens this to the leap from early functional MRI, which once just showed broad brain activity during simple tasks, to now seeing detailed pathway dynamics. Both agree the real difficulty is resolution without chaos, since an AI rendering of every protein in a single cell patch looks overwhelming, and the practical goal is to isolate one key metabolic node, know what healthy looks like there, and nudge it back toward that baseline.
Imaging Metabolism At Cellular Resolution 1:50:31
Rutter and Huberman discuss whether it will ever be possible to image metabolism with cellular resolution, similar to how neuroscience learned to visualize brain activity through blood flow, deoxyglucose uptake, and later voltage and calcium imaging. Rutter cautions that this is a genuinely hard problem, since metabolism itself has nothing visually observable about it, and both the spatial resolution needed to see individual cells inside a living body and the need for a reliable visual stand-in for metabolic activity remain major obstacles. He notes that tools from chemistry, bioengineering, physics, and computing have already improved biology substantially, and that experimental tools for measuring specific molecules, intermediates, and substrates in individual cells and mice are steadily getting better, though figuring out the single best parameter to measure cell health, and doing so without invasive damage, remains unresolved.
Scent Detection Of Disease 1:53:59
Huberman raises the phenomenon of dogs, and occasionally people, detecting cancer or Parkinson's disease by smell, including a validated case of a woman who could smell a musky scent associated with Parkinson's, later recognized by spouses of affected men. Rutter agrees this sits at the frontier of science, explaining that scents are chemical compounds, and that different metabolic states would produce different chemicals in different proportions, potentially detectable much like blood chemistry already reveals disease states. He compares this to how parents become remarkably astute at noticing subtle changes in an infant's stool or skin before anything is verbally communicated, suggesting breath chemistry could similarly reflect systemic or cellular energy regulation, even though the specific mechanisms remain unclear.
Energy Toxicity And Mitochondrial Overload 1:56:30
Referencing Dr. Layne Norton's concept of energy toxicity, Huberman asks how excess calories cause harm beyond simply adding body fat. Rutter explains the widely accepted idea that mitochondria overloaded with energy generate reactive oxygen species, reactive forms of oxygen that damage proteins and nucleic acids. When mitochondria are overpowered by energy extracted from food before it becomes ATP, this creates conditions prone to producing these damaging reactive species, contributing to mutations, protein damage, and pathologies including aging, making excess energy a concern from the level of the whole organism down to individual mitochondria.
Closing Reflections And Gratitude 1:58:30
Huberman reflects that cells, like societies, seem to face consequences for taking or misallocating too much energy, and thanks Rutter for clarifying that mitochondria do far more than generate energy, also praising the idea of viewing the body as a constellation of many microscopic metabolic units rather than a single generic metabolism. He expresses gratitude for Rutter's willingness to share decades of research publicly, thanking the University of Utah and Howard Hughes Medical Institute for supporting this kind of public education, before the episode closes with standard information about subscribing, leaving reviews, Huberman's new book Protocols, his social media presence, and the zero-cost Neural Network newsletter.
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