The Nutrition Debate #86: Beta Cell Function and Insulin Sensitivity

 I recently visited (as a new patient) an endocrinologist in Florida. My purpose was to find out what was going on with my glucose metabolism. Specifically, I was interested in knowing my % Beta cell function and my % Insulin Sensitivity (and its reciprocal, Insulin Resistance, or IR). I had read about a test that determines those values and wanted to be tested. The HOMA Assessment determines these values by formula. There is also a more sophisticated model that Oxford University developed called the HOMA2 that employs a “calculator.”

I haven’t been seen by an endo in more than 20 years (the last time to measure my testosterone, as I recall). Five years before that I consulted an old-timer who had me visit the out-patient department of a local hospital for a 4-hour glucose tolerance test. That test just confirmed the diagnosis that had been made a few years earlier that I was a Type 2 diabetic. That endo also upped my prescription for a sulfonylurea, the only oral diabetes med permitted in the U.S. at the time. Eventually I was maxed out at 20mg of glyburide (the sulfonylurea).

It would be another 10 years (in 1995) before my current doctor added metformin, which by then was finally allowed in the U. S. It had been in use in Europe for some time. But before long I was maxed out on that drug too and was then started on a TZD (Avandia). That is when my doctor suggested I try the Atkins Induction diet to lose weight. He had just read the Gary Taubes cover story, “What If is All Been a Big Fat Lie?” in the NYT Magazine on July 7, 2002. Within a few days on Atkins Induction, I was having frequent hypos. I called my doctor, and he told me to drop the Avandia. When the hypos continued, he cut the sulfonylurea and the metformin dosages in half, and then soon afterwards, in half again.

I lost 60 pounds on Atkins Induction but, after a few years of stable weight, I gained back 12. I then decided to try the Bernstein diet for diabetics. I lost 100 pounds in the next 50 weeks and eventually another 22 for a total loss of 170 pounds. Along the way, I weaned myself off the final 5mg of Micronase (the brand-name of the sulfonylurea), by halving it to 2½ and then halving it again (cutting the 2½ mg pill in half). I still take 500mg metformin once a day. But, all told, I figured I had been on a sulfonylurea, which pushes the pancreas to secrete more insulin in response to a glucose challenge, for the better part of 20 years. Remembering Dr. Ralph DeFronzo’s Banting Lecture at the 2008 ADA Convention in San Francisco, I figured I had lost 80% of my Beta cell function by the time I was diagnosed in 1986. He also said, at the end of the introduction to the full paper published in the ADA magazine “Diabetes,” and available here, “Sulfonylureas are not recommended because, after an initial improvement in glycemic control, they are associated with a progressive rise in A1C and progressive loss of β-cell function” (emphasis added).

Given my history on sulfonylureas and Dr. DeFronzo’s prognostications, the implications for my Beta cell function were not promising. So, my visit to the endo in Florida was for the specific purpose of testing my % Beta cell function and % (Insulin) Sensitivity. I was surprised with the test results: Beta Cell function = 68.2%; Sensitivity = 94.6%; and IR = 1.1 (1.057). I don’t have a follow-up visit scheduled with the endo for another 10 weeks, so I decided to do a little homework on my own. I would also like to put these results “out there” for comment by others. Has anyone out there ever had a HOMA assessment done? The endo’s nurse said she had been working with this doctor for about 10 years, and he had never ordered the test before. She knew, she said, because she’s the one who places the orders for tests.

The doctor said the test was mostly used in research, and he would have to look up the formula to apply it. Okay, but, I wondered, if not commonly used in clinical practice, does the test have clinical value? What can be learned from it? My first read is that I am not in as bad a shape as I thought I was. True, I have been eating VLC “on and off” for over 10 years, and now “totally on” for the last four and a half months. My last HbA1C was 5.7, down from recent low 6s. I expect the one from blood taken last week will be 5.6 or even 5.5. And I have been eating a very restricted ketogenic diet, recently under 1000 calories a day (without hunger), which is the direct consequence of being ketoadapted and in ketosis virtually all the time. My body is in balance and happy with my dietary intake, my supplements, and with the fatty acids, glycerol and ketone bodies it is making every day from the body fat it is breaking down for energy.

But I have not been satisfied with my fasting blood glucose readings these last 4 months. I no longer have weekly averages around 90. I have to work hard to get them under 100, and they should never be higher than 95. My daily FBG readings should never be above 100. I am very careful to eat VLC and to never eat too much protein.

So, what does my HOMA assessment test reveal? If my Type 2 diabetes is in “clinical remission,” is it attributable solely to my VLC diet? If my diet has “reversed” my Type 2 diabetes, has it also “normalized” my Beta Cell function and improved my insulin sensitivity? If Beta Cells can regenerate themselves, can they do this over and over, year after year?

I hope to learn the answers to these questions from my new endo in my follow-up appointment. I can hardly wait.

© Dan Brown 2/2/13