Think diabetes is just a problem with blood sugar levels?
While managing blood sugar levels is important for diabetes, the truly frightening thing is that high blood sugar gradually damages blood vessels throughout the body, leading to life-threatening diseases such as myocardial infarction and stroke. Why does diabetes lead to problems with not only blood sugar levels but also the heart and blood vessels?
This article provides a clear explanation of the four main mechanisms by which diabetes damages the heart and blood vessels, as well as ways to prevent it.
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Why diabetes causes cardiovascular disease (heart disease and stroke)
When diabetes causes chronic hyperglycemia, arteriosclerosis progresses in blood vessels throughout the body. Arteriosclerosis occurs when cholesterol and other substances accumulate in the walls of blood vessels, forming lumps called plaques. Blood vessels narrow from the inside, and the walls themselves become hard, brittle, and prone to clogging.
The cause of arteriosclerosis is not just high blood sugar, but a combination of multiple factors specific to diabetes.
source:Ministry of Health, Labor and Welfare e-Health Net | Arteriosclerosis
Cause 1: High blood sugar causes blood vessels to "rust" (oxidative stress)
First, a sudden rise in blood sugar levels (especially postprandial hyperglycemia) damages blood vessels. When blood sugar levels rise suddenly, excessive amounts of reactive oxygen species are produced on the inside of blood vessels (vascular endothelium). These reactive oxygen species cause blood vessels to "rust."
The condition in which excessive active oxygen is generated is called oxidative stress, and it destroys the natural defense mechanisms of blood vessels. It also causes bad cholesterol (LDL) in the blood to corrode (oxidized LDL), creating the seeds of plaque that accumulates on the walls of blood vessels.
source:MDS Manual | Atherosclerosis
Cause 2: Insulin becomes less effective and blood vessels become "hardened"
Secondly, insulin resistance (a condition in which insulin is not effective), which is the cause of diabetes (especially type 2), also has a negative effect on blood vessels through a mechanism different from hyperglycemia.
Insulin not only lowers blood sugar levels, but also stimulates the production of nitric oxide (NO) from vascular endothelial cells, thereby inhibiting arteriosclerosis. However, when insulin resistance occurs, this function of protecting blood vessels from arteriosclerosis becomes weaker. As a result, blood vessels become hardened and lose their flexibility (endothelial dysfunction), making high blood pressure and arteriosclerosis more likely to progress.
source:Japanese Journal of Pharmacology | Vascular endothelial function and insulin resistance
Cause 3: High blood sugar burns blood vessels (AGEs and chronic inflammation)
Thirdly, when high blood sugar levels persist for a long time, proteins in the body bind with glucose and turn into substances called advanced glycation end-products (AGEs). For example, when you bake bread, the surface can burn and become hard. AGEs are substances created by a reaction (glycation) that is very similar to this burning.
AGEs are extremely difficult to break down, and once formed, they accumulate over a long period of time, adhering to the walls of blood vessels. Even if blood sugar control improves later, past burnt deposits continue to damage blood vessels. Specifically, these AGEs increase the production of inflammatory cytokines inside blood vessels, causing chronic inflammation and directly damaging the walls of blood vessels (endothelium), strongly promoting arteriosclerosis (atheroma formation).
source:MDS Manual | Atherosclerosis
source:Glycative Stress Research｜Glycative stress and anti-aging 5. Glycative stress and receptors for AGEs as ligands
Cause 4. Increased plaque "materials" (diabetes-specific lipid abnormalities)
Fourth, dyslipidemia in people with diabetes is not simply a matter of cholesterol levels, but is characterized by specific abnormalities based on insulin resistance that promote arteriosclerosis.Dyslipidemia caused by decreased insulin action is as follows:
- Increased triglyceride (TG)-rich LDL cholesterol (VLDL)
- Increased intermediate metabolite remnants in VLDL
- Increased levels of very bad cholesterol (small, dense LDL)
All of these lipid abnormalities promote the onset and progression of arteriosclerosis.
source:Journal of the Japanese Society of Internal Medicine｜Dyslipidemia Management in Diabetes
Diabetes risk data
The combined effects of these mechanisms significantly increase the cardiovascular risk in people with diabetes. A large-scale study of Japanese people (NIPPON DATA80) reported that people with high blood sugar levels had more than twice the risk of death from cardiovascular disease compared to those with low blood sugar levels.
Furthermore, recent reports investigating the causes of death among Japanese diabetic patients show that the most common cause of death is "malignant tumors (cancer)," followed by "heart disease" and "cerebrovascular disease," with vascular complications accounting for a significant proportion of deaths. Myocardial infarction (coronary artery disease) in diabetic patients often presents as "painless myocardial ischemia," meaning no chest pain is felt. Diabetics often experience a lack of symptoms, leading to delayed diagnosis, and in many cases, the condition is already severe by the time it is discovered. Other characteristics of coronary artery disease in diabetic patients include multivessel disease, advanced and diffuse lesions, and a high incidence of calcified lesions. This suggests that arteriosclerosis in diabetic patients is widespread, persistent, and prone to hardening and progression.
source:Relationship of elevated casual blood glucose level with coronary heart disease, cardiovascular disease and all-cause mortality in a representative sample of the Japanese population. NIPPON DATA80
source:Causes of death from diabetes in Japanese people based on a questionnaire survey: A study of 68,555 people over a 10-year period from 2011 to 2020
source:Atherosclerotic Disease Prevention Guidelines 2022 Edition | Chapter 3 Comprehensive Risk Assessment for Atherosclerotic Disease Prevention
Diabetes Management to Protect Your Heart | Prevention
In order to prevent myocardial infarction and stroke, it is essential to manage risk factors together. The first pillar is, of course, blood sugar control, and the target HbA1c value is set at less than 7.0% from the perspective of preventing complications. However, blood sugar levels alone are not enough to protect the heart.
High blood pressure and dyslipidemia, along with diabetes, are strong risk factors for arteriosclerosis, so it is important to keep all three in good condition at the same time. Based on lifestyle changes such as dietary and exercise therapy, blood sugar-lowering drugs, antihypertensive drugs, and dyslipidemia medications are used appropriately as needed. It is also important to regularly undergo tests such as electrocardiograms and carotid artery ultrasounds to check the condition of your blood vessels, even if you have no symptoms.
source:Japan Diabetes Society | Blood Glucose Control Goals for Elderly Diabetics
source:Guidelines for the Prevention of Atherosclerotic Diseases 2022 Edition | Chapter 3 Comprehensive Risk Management for the Prevention of Atherosclerotic Diseases
summary
The goal of treating lifestyle-related diseases, including diabetes, is not just to control the disease, but also to "protect blood vessels and prevent cardiovascular disease." It's important to correctly understand the complex risks, such as rust (oxidative stress) and burnt AGEs (AGEs) caused by high blood sugar, hardening of the blood vessels due to insulin resistance, and plaque materials (dyslipidemia). To extend your healthy lifespan, it's important to maintain a balanced management of blood sugar, blood pressure, and lipids. Check your own test results again and discuss treatment options with your doctor.