Tuesday, October 4

Ketogenic diet and STZ-induced diabetes

High fat diets cause diabetes. At least this is what we are told. Researchers frequently use streptozotocin (STZ) to induce diabetes in experimental animals. So, following the logic, a low carbohydrate ketogenic diet (LCKD) plus STZ would make rats extremely diabetic, with a very reduced chance to survive in the long term. 

So let's see what happens when STZ-treated rats are fed a normal chow diet (ND), a LCKD and a high carbohydrate diet (HCHO) (1). The macronutrient ratios for the latter were (C/F/P): LCKD 10/60/30 and HCHO 70/10/20.

Bodyweight remained constant in the LCKD group, while it was reduced significantly in the HCHO and ND groups. In the latter, after the administration of STZ, blood glucose (BG) increased from 105mg/dL at baseline to 650mg/dL at the end of the experimental period. In contrast, the LCKD group maintained BG levels around 100mg/dL. Food intake also was drastically increased in HCHO and ND groups, showing polyphagia. The LCKD rats showed a little increased in food intake, then decreased and remained constant during the whole study. Water intake was also constant in the LCKD compared to HCHO and ND. Urine output was also increased in the latter groups. (Remember the "three P's" of diabetes: polydipsia, polyphagia and polyurea). Glucosuria after STZ injection reached 1000mg/dL. However, LCKD showed negative glucosuria. Summing up: LCKD rats didnt show any marker of diabetes comared to HCHO and ND rats. They maintained calorie intake, weight and BG levels normal. No polydipsia, polyphagia or polyurea. 

One recent study warned about the mechanism by which high fat diets could cause diabetes and beta-cell dysfunction. Yes, this is the famous study by Ohtsubo et al (2). For a more comprehensive review of this study please refer to the one written by Denise Minger. In a nutshell, what the authors found was that elevated concentration of free fatty acids (FFA) caused nuclear exclusion and reduced expression of FOXA2 and HNF1A transcription factors in beta cells. This resulted in depletion of GnT-4a glycosylation and glucose transporter expression, leading to beta-cell dysfunction. This is one mechanism by which lipotoxicity contributes to diabetes onset. However, STZ causes cell death in pancreatic beta-cells through methylation, the release of free radicals or by the formation of nitric oxide. The mechanism found by Ohtsubo might be reversible. Beta-cell destruction might not. This is one of the most important problems with advanced diabetes, and might be involved in the evolution of type 2 into type 1 diabetes (3). Thus, studies using models of beta-cell destruction might be more relevant for understanding the basis of autoimmune or chronic uncontrolled diabetes.

This leads us to the most interesting part of the resent study. The authors assessed the histology of the Langerhans islets in the different rats by H&E staining

Copyright © 2010 Elsevier GmbH. All rights reserved.

(a) and (b) show the sections of the pancreas from control HCHO and ND rats. Circles show islets of Langerhans and arrows show vacuoles. (d) and (e) are from diabetic HCHO and ND rats, respectively. As can be seen, there is almost no islet left after STZ administration. On the other hand, diabetic LCKD rats showed no reduction of islets compared to LCKD controls ((c) and (f)). 

To further assess the efect of the different diets on beta-cell destruction, the authors used Gomori's Chrome Alum Haematoxylin-Phloxine stain. 

Copyright © 2010 Elsevier GmbH. All rights reserved.

Beta-cells are stained blue, alfa-cells are stained red and delta-cells are stained pink. (a), (b) and (c) are control ND, HCHO and LCKD; (d), (e) and (f) are diabetic ND, HCHO and LCKD, respectively. 

Overall, there was a clear protection against beta-cell destruction in the diabetic LCKD rats, compared to diabetic HCHO and ND rats. However, the number of beta-cells in control rats was not different between groups. 

How can a ketogenic diet can prevent the onset of diabetes induced by STZ and a high-fat diet cause diabetes? Isnt a ketogenic diet a high-fat diet? First, a high-fat diet is not necessarily a ketogenic diet. The term "high-fat diet" is used without a consensus in the literature, so a high sugar-high fat diet might be promoted as a high-fat diet (this is why is EXTREMELY important to read the methods). Second, lipotoxicity is a major cause of metabolic dysfunction. However, lipotoxicity doesnt implies a high-fat diet. It implies dysregulation of lipid metabolism. If anything, a ketogenic diet should restore a normal lipid metabolism. Third, there is a difference in comparing in vitro results with in vivo results. I have highlighted the importance of this distinction before. Finally, diabetes is a highly complex disease. I believe that the most serious cases have definitely an immune component, so there is targeted destruction of beta-cells. The authors speculated that the ketogenic diet prevented diabetes by the antioxidant effect of ketone bodies (because one of the cytotoxic effects of STZ in beta-cells is mediated by the increase in free radicals).

In conclusion, saying that high-fat ketogenic diets cause diabetes is as silly as saying that high carbohydrate diets cause diabetes. There is an extreme metabolic flexibility present in healthy humans, which can adapt to a wide range of macronutrient ratios. Food toxins, as stressed by other authors are another source of problems, which can confound the effect of different diets. 

People with diabetes might benefit from low carbohydrate diets not only by the proximate effect of the diet (less dietary glucose, which treats the symptom, not the cause), but because of calorie restriction, which alleviates lipotoxicity. This can also be achieved with an hypocaloric high-carbohydrate diet. But with people in with autoimmune type I diabetes, LADA, or severe cases of type 2 diabetes, a ketogenic diet could prevent progression of the disease more efficiently, preventing oxidative stress-mediated cell death. 

ResearchBlogging.orgAl-Khalifa A, Mathew TC, Al-Zaid NS, Mathew E, & Dashti H (2011). Low carbohydrate ketogenic diet prevents the induction of diabetes using streptozotocin in rats. Experimental and toxicologic pathology : official journal of the Gesellschaft fur Toxikologische Pathologie, 63 (7-8), 663-9 PMID: 21943927


  1. Ryan

    Any idea the percentage of the diet used? A ketogenic diet is pretty unclear, as this could be 95% fat/5% protein roughly, as used in other mouse studies/human epilepsy(85-90% fat), or something like 70%f/15%p/5%carb.

    There is a big difference imo, being more ketones/lower BG versus less/little ketone and higher BG, which may explain such an impressive result.

  2. Hi Ryan,

    Ive updated the post. A very low carbohydrate-protein/extremely high fat diet is not a good idea:


  3. Ryan

    Hey Lucas,

    It's not optimal, for sure.(I have little comment about your post here, again, as I'm sure ketones hardly budged at all,if at all, with so much access to protein, and still a fair amount of carbs, relatively, to a true 'starvation mimic' diet, as this is simply a low carb diet)

    I am interested in whether there are antioxidant effects of the ketones, in areas other than the brain, such as pancreas and in cancer and muscle mitochondria, hence my query...

    A few points/thoughts:

    1. I am familiar with the study you posted, and actually read the full text a while ago. The authors promoted two interesting points, 1 being that the low protein/methionine/choline content could be responsible for such an effect on the liver, rather than a dietary effect. Perhaps supplementation here could be crucial. I haven't seen anything regarding children on the keto diet having liver problems, just occasionally pancreatitis. The authors also remark on how insulin action/liver AKT is completely preserved in the mice, even enahnced slightly vs control HF chow, despite the liver inflammation - the western mice in that study had much worse AKT status on this marker, despite lesser inflammation in the liver.

    2. Also, and despite basically no real evidence that SAT fat is safe, I feel the high SAT content could be responsible for the strong ER stress caused by keto diet here. I have quite a few studies showing harm from SAT versus mono, and, yes, PUFA, but the status quo in the 'paleo world' will probably never accept that omega 6 may just be good, or at least neutral, so...

    here is one study that promotes my thinking, on a high sat fat vs high pufa diet, on hepatic steatosis: http://www.ncbi.nlm.nih.gov/pubmed/16269465

    High pufa/control diet had similar results, and destroyed the high sat fat group on basically ever marker of liver injury tested...of course, over the years, plenty of mouse studies of all kinds of different disease have shown good/bad effects of all fatty acids...

    Anyways, just a jumble of thoughts, keep up the good work. Your unique thought processes make this one of the few blogs I follow.

  4. Ryan,

    That study is really interesting, as it shows roughly the same effects of a high sugar diet and a high saturated fat diet. ER stress is a really interesting topic, but I havent studied enough to give you a more throughout opinion. The first thing that comes to my mind is the different metabolism of PUFA vs. SAT.

    I think that any fanatic dogma is bad. I have my own reasons for believing that excess PUFA is bad, but Im always open to new hypotheses.

  5. As one of your faithful lay readers, most of the science is beyond me, but I have become very suspicious of studies that don't fully disclose all the nutrients and sources of them.

    For myself, I log my food daily on Livestrong so get a graph of the percentage of nutrients I take in, and while I do have a higher percentage of fat in my ketogenic diet than before, overall I eat fewer calories, including less fat than I did in my SAD days.

    BTW, did my water only fast in October,for seven days, and as always felt all the better for it. I consider the fast my annual "spring" cleaning.

  6. Lucas, I enjoyed your post and the links to the studies. When you made this statement...
    Ive updated the post. A very low carbohydrate-protein/extremely high fat diet is not a good idea:


    How did you come to this conclusion with regards to the human diet? I am curious as I am an insulin dependant diabetic after being pre, then Type 2. My diabetes was ushered along to the cliff theu a high carb/low fat diet. Looking forward to your thoughts. Andre

    1. Hi Andre,

      Because eating a protein deficient diet is not a good idea. If eating a ketogenic/very high fat diet, the body must adapt, and this adaptation takes somewhere about 6-12 weeks. This period is critical and one needs to up protein intake, because the body relies (slightly more) on gluconeogenesis. Once adapated, protein intake can be reduced. If you are eating an adequate amount of protein, animal-based diet, you should not worry.

    2. Thank you Lucas for your response. Question, where do you draw the lines on deficient protein? I am eating an animal based diet. Exercising , yoga, body building, MovNating etc.