Diabetes-obesity-cancer link due to multiple causes
Type 2 diabetes is closely linked to obesity, which in turn, increases the risk for cardiovascular diseases (which includes mainly heart disease and stroke), muscle and bone diseases; and cancers. Obesity-related cancers include breast, endometrial, ovarian, colorectal, pancreatic, renal, liver and gallbladder cancer. [Lancet
Professor Lee in-Kyu, President of Korean Diabetic Association, Professor, Department of Internal Medicine, Kyungpook National University, said the reasons for this link hasn’t been thoroughly identified, but it is thought to be related to hyperinsulinaemia, hyperglycaemia and inflammation. There is a link between energy metabolism of the cell’s powerhouse, the mitochondria, and its alteration in cancer cells. This alteration is induced by starvation, nutrient deficiency, long-term high-fat diets and is found in patients with obesity and diabetes. [Cell Cycle 2014;13(6):890–897]
Speaking at the recent 12th International Diabetes Federation Western Pacific Region (IDF-WPR) Congress and 10th Asian Association for the Study of Diabetes (AASD) Scientific Meeting, Lee said obesity is recognized by the American Institute for Cancer Research (AICR) as a leading cause of cancer. In fact, AICR estimates that excess body fat is a cause of approximately 130,600 cancer cases in the US alone. The institute states that after not smoking, being at a healthy weight is the most important thing one can do to prevent cancer.
On the local front, the National Health and Morbidity Survey of 2016 found 30 percent of Malaysians are overweight and 17.7 percent of them are obese. This means 30 percent of the population are at increased risk of those cancers listed above.
As obesity and overweight are linked to cancer and type 2 diabetes mellitus, it should be logical that a healthy diet, physical activity and weight management would not only improve type 2 diabetes outcomes, but also reduce the risk of cancer.
Lee also alluded to the use of metformin, which is the first-line therapy for type 2 diabetes, and its link to a reduction in cancer risk. The drug has been around for many years and is widely used on its own or in combination with other antidiabetic medications. Metformin use has been linked to lower risks of cancer and a study in 2010 revealed that metformin could lower the relative risk of cancer by up to 30 percent. [Cancer Prev Res 2010;3(11):1451–1461]
Ed: A recent paper published in Lancet estimates that 5.7 percent of all incident cancers in 2012 were attributable to the combined effects of diabetes and high BMI as independent risk factors. This corresponded to 804,100 new cancer cases. 187,600 (24.5 percent) of 766,000 cases of liver cancer and 121,700 (38.4 percent) of 317 000 cases of endometrial cancer were attributable to these risk factors. The paper then suggested that a more conservative scenario would still result in 4.5 percent (629,000 new cases) of all incident cancers assessed attributable to diabetes and high BMI combined. Individually, high BMI (544,300 cases) was responsible for almost twice as many cancer cases as diabetes (293,300 cases). A total of 25.8 percent of diabetes-related cancers (75,600 new cases) and 31.9 percent of high BMI-related cancers (174,040 new cases) were attributable to increases in the prevalence of these risk factors from 1980 to 2002. [Lancet Diabetes Endocrinol 2018;6(6):e6–e15]