A Spoonful of Sugar Makes the Mitochondria Go Down

Part 6 of 7 — When the Cell Locks Its Own Doors

If you have made it this far through the series, I owe you a thank you and a warning. The thank you is sincere — most readers do not stay with a long piece like this through six chapters, and the fact that you have means you actually want to understand what is happening to your body. The warning is that this chapter is the one where the molecular biology connects directly to the diagnoses you may already be carrying, or that someone you love is carrying. It is the chapter where the fire we have been watching becomes diabetes, becomes hypertension, becomes Alzheimer's disease.

I am going to walk you through the door-locking mechanism — how the cell, after being flooded with sugar for years, stops responding to the hormone that is supposed to let sugar in. I am going to explain insulin resistance, because most patients have heard the term but very few have heard it explained in a way that makes the molecular sense of it clear. And then I am going to take you into the brain.

The story of type 3 diabetes is one of the most important developments in medicine in the last twenty years, and almost no one outside the research community knows about it. By the end of this chapter, you will.

How Insulin Is Supposed to Work

To understand how the system breaks, you have to first understand how it works when it is healthy.

When you eat carbohydrates, your blood glucose rises. Specialized cells in your pancreas — beta cells, organized into clusters called the Islets of Langerhans — detect the rise. They respond by releasing insulin into the bloodstream. The amount of insulin released is roughly proportional to how fast and how high the glucose is rising.[49]

Insulin's job is to tell cells throughout the body: glucose is here, take it in. It does this through a beautiful relay system that I want to walk you through carefully, because every step of this relay is a potential point of failure, and the failure is what we call insulin resistance.

Step one. Insulin, traveling through the bloodstream, encounters its receptor on the surface of a target cell — say, a muscle cell. The insulin receptor is a large protein embedded in the cell membrane. Think of it as the doorbell.

Step two. When insulin binds to the receptor, the receptor activates itself by adding phosphate groups to specific spots on its own structure. This is called autophosphorylation. The receptor has, in effect, turned itself on.[42][49]

Step three. The activated receptor then phosphorylates — adds phosphate groups to — a docking protein on the inside of the cell membrane called IRS-1 (Insulin Receptor Substrate 1). IRS-1 is the first relay station after the doorbell. The phosphate group is added at a specific spot on IRS-1, on an amino acid called tyrosine. Tyrosine phosphorylation activates IRS-1. Remember this detail. It is the molecular event we are about to see corrupted.[43]

Step four. Activated IRS-1 recruits and activates the next protein in the chain — a kinase called PI3K (phosphoinositide 3-kinase). PI3K is the next relay.

Step five. PI3K activates Akt (also called Protein Kinase B), the next-next relay.

Step six. Akt does many things, but the one we care about most is that it triggers the movement of a specific glucose-transporting protein called GLUT4 from inside the cell to the surface. GLUT4 is the actual door for glucose. Until insulin signaling activates it, GLUT4 sits in tiny vesicles inside the cell, not on the surface. When Akt is activated, the vesicles fuse with the cell membrane, and a wave of GLUT4 doors pops up on the surface, letting glucose flow in.[48][49]

That is the chain. Insulin → receptor → IRS-1 (tyrosine phosphorylated) → PI3K → Akt → GLUT4 to the surface → glucose into the cell.

When this chain is working, blood glucose drops back to normal within a couple of hours of a meal because glucose is being pulled out of the bloodstream and into cells. The pancreas senses the falling glucose and stops releasing insulin. Equilibrium. The system is elegant.

How the Chain Gets Cut

Now I want to show you exactly how it breaks.

Through the previous chapters, we have established that a chronically sugar-flooded body has chronically elevated mitochondrial ROS, chronically elevated AGE production and the RAGE-NF-κB inflammation it triggers, chronically activated NLRP3 inflammasomes, chronically elevated cytokines — TNF-α, IL-1β, IL-6 — circulating through the bloodstream and infiltrating tissues. In someone who is overweight, expanding visceral fat is also recruiting macrophages that secrete more TNF-α and IL-6 directly into the metabolic tissues.

All of this inflammation activates a family of enzymes called inflammatory kinases. The two most important for our story are JNK (c-Jun N-terminal kinase) and IKKβ (inhibitor of kappa B kinase beta). When you have chronic systemic inflammation, JNK and IKKβ are chronically active in muscle cells, in liver cells, in fat cells.[44][45][46][47]

Here is what JNK and IKKβ do. They phosphorylate IRS-1 — same protein we just talked about — but they phosphorylate it at the wrong amino acid. Instead of adding the phosphate group at a tyrosine residue (which would activate IRS-1), they add it at a serine residue. Serine phosphorylation of IRS-1 blocks tyrosine phosphorylation.[43][44]

In other words: the inflammatory kinases come along and stick a piece of tape over the spot where insulin's receptor is supposed to phosphorylate IRS-1. Insulin binds the receptor perfectly. The doorbell rings. The receptor activates. The receptor tries to phosphorylate IRS-1. But the relay station is blocked. The phosphate cannot be added at the proper spot. The signal cannot be passed down the chain.

The relay cable has been cut. Not at the doorbell. Not at the receptor. At the first relay station inside the cell.

PI3K does not get activated. Akt does not get activated. GLUT4 does not get moved to the cell surface. The glucose doors stay shut.

And here is the most important thing to understand: this happens despite the insulin working perfectly, the receptor working perfectly, and the cell being fully alive and functional. The cell is not broken. It has been disabled, by inflammation, from the inside.

This is insulin resistance. It is not the cell screaming "no more sugar, I'm full!" It is the inflammation, triggered by sugar's various campaigns of damage, physically modifying the proteins of the insulin signaling pathway so that the signal cannot get through. The doors are not closed because the cell has decided to close them. The doors are closed because the wiring inside has been corrupted.

In muscle biopsies from obese and type 2 diabetic patients, the serine phosphorylation on specific IRS-1 sites is dramatically elevated compared to lean controls.[42][50] This is not theory. This is measured, in real human tissue, in real patients with the disease. The mechanism is operating right now in millions of people.

The Vicious Cycle Locks In

Now imagine what happens next.

The cells are not taking up glucose efficiently. Blood glucose stays elevated. The pancreas senses the elevated glucose and releases more insulin to try to compensate. The blood is now high in both glucose and insulin.

The high glucose continues to drive all the damage cascades we have already discussed — mitochondrial ROS, AGE formation, inflammasome activation, more cytokine release. The high cytokine levels continue to drive serine phosphorylation of IRS-1, keeping the doors shut. The high insulin levels themselves — chronically elevated, day after day — begin to desensitize the system to insulin. The cells become even less responsive.

Eventually, after years of being asked to produce more and more insulin to overcome cell resistance, the pancreatic beta cells begin to fail.[91] This is mediated, in part, by IL-1β acting directly on the beta cells — the same inflammasome cytokine that is being driven by chronic high glucose now turns around and starts killing the cells that secrete insulin. The cruel irony is hard to overstate. The cells that exist to control blood glucose are being killed by the inflammation that high blood glucose causes.

As beta cells die, insulin output declines. Blood glucose, which was being held in check by enormous insulin output, now rises further. Fasting glucose climbs into the prediabetic range, then into the diabetic range. The patient is told they have type 2 diabetes.

But the type 2 diabetes is not the beginning of the disease. The type 2 diabetes is the end stage of a process that has been running, silently, for ten or fifteen years before the diagnosis. By the time the fasting glucose crosses one hundred and twenty-six, the patient has already lost roughly half of their beta-cell mass. They are already insulin resistant in muscle, liver, and brain. The arterial AGE damage is already substantial. The fatty liver is already present. The mitochondrial damage is already extensive.

This is why diabetes management is so much harder than diabetes prevention. By the time you have it, you are fighting on a battlefield that has been preparing itself for over a decade.

The Visceral Fat Amplifier

I want to add one more piece to the picture, because it explains a clinical observation that confuses many patients: why some skinny people have terrible metabolic numbers, and why some heavy people have normal ones.

The fat we carry under our skin — subcutaneous fat — is, on average, metabolically pretty quiet. It stores energy. It releases hormones (most famously leptin, which signals satiety to the brain). It is not, by itself, a major source of inflammation in most people.

The fat we carry around our internal organs — visceral adipose tissue, or VAT — is a different beast entirely. Visceral fat is metabolically active in a destructive way. When visceral fat cells get overfilled with triglycerides — as they do in a person eating a chronically high-sugar, high-calorie diet — they become hypoxic (low on oxygen), stressed, and they begin to die. Dying fat cells release damage signals that recruit immune cells, especially macrophages, into the fat tissue.[34][41]

In lean, healthy individuals, the macrophages that patrol fat tissue are of the M2 type — anti-inflammatory, gentle, focused on cleanup. As visceral fat expands and more fat cells start dying, the macrophages shift to the M1 type — pro-inflammatory, cytokine-secreting, aggressive. M1 macrophages embedded in expanding visceral fat secrete TNF-α, IL-6, IL-1β, and MCP-1 (which recruits even more macrophages from the bloodstream). The visceral fat becomes a low-grade chronic inflammation factory, dumping inflammatory cytokines directly into the venous blood that drains into the liver.[34][41]

This is why a person with a relatively normal weight but a high waist-to-hip ratio can be metabolically sick, while a person with overall higher body weight but mostly subcutaneous distribution can be metabolically healthy. The metabolic disease is being driven by where the fat is, not just how much there is.

A useful clinical heuristic: if your waist circumference is more than half your height, you almost certainly have more visceral fat than is metabolically healthy, regardless of what the scale says.

The Brain: The Most Important Chapter of This Story

Now I want to take you to the place where the consequences of all this become most devastating. The brain.

The brain is two percent of body weight but consumes twenty percent of total body energy. It is the most mitochondria-dense, most energy-hungry organ in the body. It cannot store fuel of its own to any significant degree. It must have a continuous, minute-by-minute supply of glucose and oxygen delivered through the bloodstream. If you cut off blood supply to the brain for four minutes, neurons start dying. If you cut it off for ten, the brain is destroyed. There is no other organ in your body with such razor-thin metabolic margins.

For most of medical history, the brain was thought to be insensitive to insulin — that is, that brain cells took up glucose without needing the insulin signal that the rest of the body needed. This turned out to be wrong. Many brain cells, especially in regions critical for memory and cognition (the hippocampus most notably), have insulin receptors, IRS-1, PI3K, Akt — the entire insulin signaling cascade we have been discussing — and they use it to regulate neuronal function in ways the body does not.[61][62][63]

When insulin signaling fails in the brain, several things happen at once, and they are all bad.[63][64]

First, neurons that depend on the insulin signal for normal glucose uptake become functionally hypoglycemic — energy-starved — even when blood glucose levels are normal or high. The fuel is in the bloodstream, but the doors to the neurons are stuck closed. The neuron is sitting in a feast and starving.

Second, insulin signaling in the brain normally activates an enzyme called insulin-degrading enzyme (IDE). IDE has, alongside its insulin-degrading function, another role: it also degrades amyloid-beta — the protein that, in clumps, forms the plaques characteristic of Alzheimer's disease. When insulin signaling is disrupted in brain cells, IDE activity falls. Amyloid-beta accumulates.[62][63]

Third, insulin signaling normally suppresses the activity of another enzyme called GSK-3β, which would otherwise hyperphosphorylate a protein called tau. When insulin signaling fails, GSK-3β runs unchecked. Tau gets hyperphosphorylated. Hyperphosphorylated tau forms tangles inside neurons. The "neurofibrillary tangles" are the second hallmark of Alzheimer's disease alongside the amyloid plaques.[64]

Fourth, the chronic inflammation that drove the original insulin resistance is also active in the brain. Brain microglia — the brain's resident immune cells — are activated by circulating inflammatory cytokines and by direct insults to the blood-brain barrier. Activated microglia secrete their own inflammatory cytokines, killing neurons and amplifying the local damage.[64]

Fifth, mitochondrial damage in neurons — the same fire we described in Part 3 — is now hitting the most mitochondria-dependent cells in the body. Cells that cannot make enough ATP cannot maintain the electrical gradients that neurons need to fire. Memory formation fails. Cognition slows. Mood is affected. The personality begins to subtly change.

Put all of this together and you have the cellular biology of Alzheimer's disease — and this is why it is increasingly called type 3 diabetes.[61][62] The brain is not being damaged by some random degenerative process unrelated to the rest of the body. The brain is suffering from a brain-specific form of the same insulin resistance, the same mitochondrial dysfunction, the same chronic inflammation, the same AGE accumulation, that is occurring everywhere else in the body of a person eating a chronically high-sugar diet.

The diabetic patient who develops dementia in their seventies is not unlucky. They are experiencing the predictable, mechanistic consequence of forty years of cellular damage finally reaching the most metabolically demanding tissue in their body. The Rotterdam Study and other large prospective cohorts have demonstrated a roughly doubled risk of dementia in patients with type 2 diabetes.[66][67] The mechanism is now well enough understood that we should not be surprised by this. We should be acting on it.

What This Means for the Patient Who Cannot Walk Up the Stairs

Let me bring this back to the patient I introduced in Part 1 — the sixty-three-year-old who could not walk up her own kitchen stairs.

What was happening inside her body, when I asked the right questions and ordered the right tests, was a complete tour of everything we have discussed in this series.

Her fasting blood glucose was one hundred and four — technically "normal" by old criteria, technically "prediabetic" by current ones. Her HbA1c was 5.9 — also prediabetic. Her fasting insulin (which most primary care physicians never bother to measure) was 18 microunits per milliliter, well above the optimal range of under 10. She was producing too much insulin to keep her glucose at one-oh-four. Translation: her cells were already resistant.

Her hs-CRP was 4.7 — well into the high-risk range. Her uric acid was 6.8 — at the very top of the reference range. Her triglycerides were 187 — above optimal. Her HDL was 38 — too low. Her ALT (a liver enzyme) was modestly elevated, consistent with non-alcoholic fatty liver. Her waist circumference was 41 inches, more than half her height of 5'5". Her blood pressure was 138 over 86, "high-normal" — meaning the AGE damage to her arteries was already showing.

She had no diagnosis. She had been told, repeatedly, that she was "fine."

She was not fine. She was a person whose mitochondrial reserve had been depleted by forty years of sweetened beverages, processed snacks, daily orange juice, "healthy" granola, white-flour pasta dinners, occasional sodas, and the slow, daily grinding accumulation of sugar-driven damage that no single test or symptom had ever caught. By the time she could not walk up her stairs, the damage was systemic. Her heart muscle was running short on ATP. Her skeletal muscles were running short on ATP. Her arteries were stiff. Her liver was fatty. Her pancreas was failing.

I am happy to tell you that, with eighteen months of disciplined work — eliminating added sugar, dramatically reducing refined carbohydrate, eating real food at meals, walking thirty minutes a day at first and progressing to forty-five minutes of varied exercise five days a week, intermittent fasting two days a week, and replacing the morning juice with whole fruit (in moderate, deliberate amounts) — she got her HbA1c down to 5.3, her fasting insulin to 6, her hs-CRP to 0.9, her triglycerides to 92, her HDL to 52, and her blood pressure to 118 over 74. She walks up her stairs without resting. She walks a five-kilometer route around her neighborhood three times a week. She has had her glasses prescription updated downward (her vision improved as her blood sugar stabilized). She tells me she has not felt this good since her thirties.

She is, in real biological terms, younger now than she was at sixty-three. Her mitochondrial population has rebuilt. The fire has been put out. The AGE damage she already had is mostly still there — that part is hard to fully reverse — but the new AGE production has slowed dramatically, the inflammation has come down, and the underlying biology that was driving her toward an early stroke or dementia or heart failure has been reversed.

That is what is possible. Even at sixty-three. Even with damage that was already substantial. The system is more forgiving than mainstream medicine has any business admitting, because if mainstream medicine admitted it, the entire processed-food industry would have a problem.

In Part 7, the final chapter, I am going to give you the playbook. Not the magazine-cover version. The actual playbook. What numbers to ask for, what they mean, how to interpret them, and what to do, in what order, to begin recovery. For yourself. For your kids. For your parents.