Physical activity less protective against type 2 diabetes in those more genetically predisposed

Yehuda Handelsman, MD, FACP, FACE, FNLA

The observation is nice and important. You can also take this study into a bit of a different dimension, addressing not just patients with type 1 diabetes but also patients with latent autoimmune diabetes in adults (LADA).

Today, many patients with type 1 diabetes are experiencing the same increase weight and inactivity just like the rest of the population increasing their cardiovascular risks. People with LADA have a similar presentation to the type 1 diabetes population, just later in life. They are diagnosed with positive antibodies and have similar autoimmune pathophysiology to type 1 diabetes, perhaps with a similar genetic relationship. The population with LADA are also not immune from the obesity epidemics, many have their condition accelerated by insulin resistance — consequent of obesity — and similarly develop CV risk.

Observing these populations, one can ask several questions: Would obesity and insulin resistance further aggravate and worsen the outcomes? Would this take place as part of the pathogenesis of the disease? We don’t know.

We know the surge of type 1 occurs in ages 5 to 7 years, and then again in ages 13 to 15 years, which coincides with puberty — and a time we find a high state of insulin resistance. From a clinical standpoint, and maybe simplistic, if a patient has an autoimmune condition causing a slow destruction of the islets that make insulin, and if on top of that process they would also have obesity and insulin resistance, which is so frequent in the society today, it would likely accelerate the development of frank diabetes and further subject them to risk of CVD.  

Examining patients with type 1 whose parents have type 2 diabetes they most likely also have insulin resistance — as it is accepted that type 2 diabetes is a familial condition, though the genetics are still being worked out — which may accelerate the development of diabetes as well as increasing their CV risk.  

Lifestyle modification, with reducing weight and increased physical activity, improves insulin sensitivity and glucose disposal, typically help people with type 1 diabetes, LADA & type 2 diabetes. However, we need to be aware of the fact that though lifestyle may halt or reverse progression to type 2 diabetes, in those people who also have autoimmune antibodies lifestyle may slow progression; however, the antibodies do not necessarily lose their ability to continue the destruction of insulin producing beta cells.

Thus the clinician ought to be able to recognize that some people who look like they have garden variety type 2 diabetes and yet their diabetes progression worsen, regardless of lifestyle modification, that they perhaps have something else going on, potentially genetically, causing further destruction of the islet cell. It is important to characterize these patients who are affected both genetically and environmentally where and when physical activity may not stop progression, though it could slow progression.

Continuing lifestyle modification in all patients, regardless of genetic risk or predisposition, is important. People with type 1 diabetes have learned that exercising improves their response to insulin therapy, helping them to achieve much better glucose control. It is also important to understand that in those patients with type 1 diabetes who are not obese, though good lifestyle should be part of their management, it’s not really necessary to always over restrict their diet because they can easily compensate with the appropriate amount of insulin. The clinician should exercise clinical sense addressing quality of life and individual management recommendations an approach which should be key part of this discussion.