Diabetes

BCH 120 β€” Metabolic & Endocrine Biochemistry Β· Dr. Radi

build Jul 17 Β· 11:11 Β· CC BY-NC-SA 4.0 Β· owned figures (RDKit / matplotlib / PyMOL)
Dr. Radi

By the end of this unit, you can…

  • Diagnose diabetes from the glucose criteria (FPG, OGTT, HbA1c, random) and explain how HbA1c reports 2–3 months of control
  • Explain type 1 diabetes β€” autoimmune Ξ²-cell destruction, autoantibodies (ICA/IAA/IA2/GAD), stages, and insulin therapy
  • Explain type 2 diabetes β€” insulin resistance, risk factors, the natural history through prediabetes, and metabolic syndrome
  • Describe diabetes management (the ABCs) and the Ominous Octet of type-2 defects
  • Explain incretins (GLP-1, GIP; DPP-4), the kidney's SGLT glucose reabsorption, and the mechanisms of the major drugs (metformin, DPP-4 inhibitors, SGLT2 inhibitors, GLP-1 agonists / Ozempic)
Dr. Radi

Today's route πŸ—ΊοΈ

  1. Diagnosing Diabetes & HbA1c
  2. Type 1 Diabetes
  3. Type 2 Diabetes & Prediabetes
  4. Managing Diabetes & the Ominous Octet
  5. Incretins, the Kidney & Diabetes Drugs
Dr. Radi

1 Β· Diagnosing Diabetes & HbA1c

"Diabetes is, at its core, one thing: chronically high blood glucose. Before we split it into types, let's nail down how it's diagnosed β€” and meet HbA1c, the clever blood test that remembers your last three months of sugar."

Dr. Radi

Diagnosing diabetes β€” the numbers

The diagnostic sign of diabetes is hyperglycemia, and there are four ways to catch it. Fasting plasma glucose β‰₯ 126 mg/dL. Oral glucose tolerance test β‰₯ 200. HbA1c β‰₯ 6.5%. Or a random glucose β‰₯ 200 with symptoms. In between sits pre-diabetes β€” a warning zone (fasting 100–125, A1c 6.0–6.4) where risk is already rising. One confirmed test over the line makes the call.

Dr. Radi

HbA1c: the blood test with a memory

Here's the elegant one. Glucose in the blood irreversibly sticks to hemoglobin β€” a bit of the sugar chemistry you saw in BCH 100 β€” forming glycated hemoglobin, HbA1c. Because red cells live 2–3 months, the A1c is a running average of your blood glucose over that whole window β€” no single reading can hide in it. Under 6% is good control; over 8% means act. The DCCT trial proved it matters: every 1% drop in A1c cuts complications 10–50%.

Dr. Radi

2 Β· Type 1 Diabetes

"Type 1 is an autoimmune tragedy with a triumphant treatment. The immune system destroys the insulin-making Ξ²-cells, so the body makes little or none β€” and the discovery of insulin in 1922 turned a death sentence into a manageable disease."

Dr. Radi

Type 1: the immune system attacks the Ξ²-cells

Type 1 diabetes is an autoimmune disease: the body's own "killer" T-cells destroy the pancreatic Ξ²-cells, so insulin falls to little or none. As the attack unfolds, autoantibodies show up in the blood and serve as early-warning markers β€” ICA, IAA, IA2, and GAD. Having 1–2 of them predicts >50% risk within a decade; 3–4 pushes it past 90%. MHC haplotypes set the genetic risk; an infection or stress may pull the trigger. (Old name "juvenile diabetes" is misleading β€” it can start at any age.)

Dr. Radi

The slow decline, then the cliff

Type 1 doesn't happen overnight β€” it's a staged loss of Ξ²-cell mass. It starts with genetic predisposition (MHC), waits for a precipitating event, then antibodies appear while insulin is still normal. Slowly the Ξ²-cells die, glucose tolerance slips, and finally you hit overt diabetes. A key marker: C-peptide (a leftover from insulin synthesis) is present while Ξ²-cells work and gone once they're destroyed β€” so it reads out how much function remains.

Dr. Radi

Treatment: insulin, the 1922 miracle

Because the Ξ²-cells are gone, insulin is mandatory β€” by injection or pump, with finger-stick monitoring to dose it. When Banting and Best first gave insulin in 1922, dying children recovered within weeks. Modern therapy mixes formulations by speed β€” rapid and short for meals, intermediate and long for steady background β€” matching the curves to the day to mimic a working pancreas.

Dr. Radi

3 Β· Type 2 Diabetes & Prediabetes

"Type 2 is the common one β€” and a different beast. Here insulin is present, sometimes even high, but the tissues stop listening. It creeps in through years of prediabetes, and it's the metabolic disease of our era."

Dr. Radi

Type 2: the tissues stop listening

Type 2 diabetes is fundamentally insulin resistance: insulin is there β€” sometimes even elevated β€” but the target tissues don't respond, so glucose stays high. Resistance in liver, muscle, fat, and kidney means more hepatic glucose output, less tissue uptake, more lipolysis, and more renal glucose retention all at once. Early on the Ξ²-cells compensate, pumping out extra insulin to keep up β€” which is why insulin can read high. Risk climbs with age and weight.

Dr. Radi

Who gets it β€” the risk factors

Type 2 is where lifestyle and genes collide. The modifiable drivers: obesity (especially visceral fat), physical inactivity, high triglycerides / low HDL, and hypertension β€” the cluster we call metabolic syndrome. The non-modifiable ones: a strong family history (about β…“ of a patient's relatives develop it), age, ethnicity, and conditions like PCOS or prior gestational diabetes. The genetics are real but tangled β€” no single "diabetes gene" β€” so prevention leans hard on the modifiable side.

Dr. Radi

The slow slide through prediabetes

Type 2 announces itself years in advance if you know the pattern. First, insulin resistance rises, and the Ξ²-cells compensate with more insulin β€” glucose stays normal. Then the Ξ²-cells start to fail: glucose creeps up, especially after meals β€” that's impaired glucose tolerance (IGT), a.k.a. prediabetes. When compensation can no longer keep up, fasting and post-meal glucose climb and it's overt type 2 diabetes. There's no sharp line β€” just a threshold of hyperglycemia where the long-term damage begins.

Dr. Radi

4 Β· Managing Diabetes & the Ominous Octet

"Treating diabetes isn't just about glucose β€” it's about protecting the heart, kidneys, and nerves that high sugar destroys. And to treat type 2 rationally, you need the map of everything that's broken: the Ominous Octet."

Dr. Radi

The ABCs of diabetes care

Diabetes doesn't usually kill through a high sugar reading β€” it kills slowly, through heart attacks, strokes, kidney failure, and blindness. So good management targets three numbers, easy to remember as the ABCs. A is A1c β€” keep average glucose in range. B is Blood pressure β€” protect the kidneys, eyes, and vessels. C is Cholesterol β€” cut cardiovascular risk. Add diet, exercise, weight control, and not smoking, and you attack the disease from every side.

Dr. Radi

The Ominous Octet

Type 2 isn't one broken thing β€” it's eight, and this map (the "Ominous Octet") is why. Glucose runs high because the Ξ²-cells make too little insulin, the Ξ±-cells make too much glucagon, the liver overproduces glucose, muscle underabsorbs it, fat floods the blood with fatty acids, the gut loses its incretin boost, the kidney reabsorbs too much glucose, and the brain drives appetite and resistance. Every modern drug targets a different one of these eight β€” which is exactly why they're combined.

Dr. Radi

5 Β· Incretins, the Kidney & Diabetes Drugs

"The newest, most talked-about diabetes drugs β€” Ozempic, the -flozins, the -gliptins β€” all come straight from this biochemistry: the gut's incretin hormones and the kidney's glucose-hoarding transporters. Learn the biology and the drugs explain themselves."

Dr. Radi

Incretins: the gut's heads-up to the pancreas

When you eat, the gut releases incretin hormones β€” GLP-1 (from L cells) and GIP (from K cells) β€” that reach the pancreas and, only when glucose is high, boost insulin and (for GLP-1) suppress glucagon. That "glucose-dependent" part is the magic: incretins push insulin only when it's needed, so they rarely cause hypoglycemia. The catch: an enzyme, DPP-4, chews them up in minutes. So two drug strategies write themselves β€” block DPP-4, or build a GLP-1 mimic that resists it.

Dr. Radi

The kidney hoards glucose

Here's a target most people never think about. Your kidneys filter ~180 grams of glucose every day β€” and then reabsorb essentially all of it in the proximal tubule, so none shows up in the urine. The workhorse is SGLT2 (sodium-glucose cotransporter 2), which grabs about 90% (SGLT1 handles the rest). In evolution, hoarding precious sugar made sense. In diabetes, it's the last thing you want β€” so blocking SGLT2 lets you literally pee the excess glucose out.

Dr. Radi

Four drugs, four targets

Now the payoff β€” each major drug hits a different node of the Octet. Metformin (first-line) tells the liver to make less glucose and improves insulin sensitivity. DPP-4 inhibitors (the "-gliptins") let your own incretins last longer. SGLT2 inhibitors (the "-flozins") make the kidney dump glucose in the urine. And GLP-1 receptor agonists β€” Ozempic (semaglutide) β€” are DPP-4-resistant incretin mimics that boost insulin and cut appetite (hence the weight loss). Different targets, often combined.

Dr. Radi

Can you…?

  • ☐ diagnose diabetes from the glucose criteria (FPG, OGTT, HbA1c, random) and explain how HbA1c reports 2–3 months of control?
  • ☐ explain type 1 diabetes β€” autoimmune Ξ²-cell destruction, autoantibodies (ICA/IAA/IA2/GAD), stages, and insulin therapy?
  • ☐ explain type 2 diabetes β€” insulin resistance, risk factors, the natural history through prediabetes, and metabolic syndrome?
  • ☐ describe diabetes management (the ABCs) and the Ominous Octet of type-2 defects?
  • ☐ explain incretins (GLP-1, GIP; DPP-4), the kidney's SGLT glucose reabsorption, and the mechanisms of the major drugs (metformin, DPP-4 inhibitors, SGLT2 inhibitors, GLP-1 agonists / Ozempic)?

If any box stays empty, the practice site has a drill for it. πŸ§ͺ

Dr. Radi