Professor Chen Luyuan: How does diabetes develop?

People at high risk of diabetes

The high-risk group for diabetes refers to the group of people who have one or more diabetes risk factors and whose risk of developing diabetes is higher than that of non-high-risk groups. This group of people is one of the key targets of diabetes prevention and control work.

People who are obese, over 45 years old, have a family history of diabetes, high blood pressure and high blood lipids, have given birth to a baby weighing more than 8 kilograms, or have had abnormal blood sugar during pregnancy are at high risk of diabetes.

According to statistics, the incidence of diabetes in diabetic relatives with a family history of diabetes is four times higher than that in non-diabetic relatives. If one of the identical twins has diabetes, the probability of the other twin developing diabetes is more than 90%; however, the probability of non-identical siblings developing the disease is only 25% to 50%.

The prevalence of diabetes in overweight and obese people is higher than that in the general population, at 12.8% and 18.5% respectively. Insulin levels in obese patients are significantly increased, which in turn develops into impaired glucose tolerance, leading to diabetes.

In recent years, studies have found an interesting data: the prevalence of hypertension in diabetic people is as high as 57.9%, while the prevalence of diabetes in hypertensive people is as high as 33.6%. For every 20 mmHg increase in systolic blood pressure, the risk of new diabetes increases by 77%.

Prediabetes

Fasting blood sugar levels between 100 and 125 mg/dL, or between 6.1 and 7.0 mmol/L, mean you may have prediabetes, a common precursor to diabetes. It is estimated that one-third of American adults have prediabetes, although most of them don't know it. The prevalence of prediabetes in my country is also increasing, reaching 38.1% in 2018.

"If you have prediabetes, it's a sign to start trying to lose weight, because most people with prediabetes are overweight," said Dr. Om Ganda, an associate professor at Harvard Medical School and medical director of the Lipid Clinic at the Joslin Diabetes Center. Excess weight, especially around the abdomen, is a sign of insulin resistance -- a precursor to prediabetes.

How does diabetes develop?

Diabetes is a disease caused primarily by problems with insulin, a hormone secreted by the pancreas that enables cells throughout the body to absorb glucose (sugar) for energy. The most common form is type 2 diabetes, which occurs when the body becomes resistant to insulin or when the pancreas stops producing enough insulin.

The root cause of insulin resistance is not fully understood, but excess body fat and lack of exercise are thought to be the main causes. Research shows that abdominal fat produces certain hormones and other substances that trigger chronic inflammation, which can lead to insulin resistance. Many studies have linked lack of exercise to insulin resistance.

If you have insulin resistance, your muscle, fat, and liver cells can't easily absorb glucose from your blood, so your blood sugar levels rise. In response, your pancreas tries to keep up with the demand by secreting more insulin. But over time, the insulin-producing cells in the pancreas begin to weaken. This can lead to prediabetes and eventually diabetes.

The power of prevention

The high obesity rate among adults in the United States, currently around 35%, is largely due to the epidemic of prediabetes.

If your blood sugar is high, in addition to a diet low in sugar and oil, people who are overweight should reduce their daily calorie intake overall. It is usually required to consume no more than 25 calories per kilogram of body weight per day, and it is recommended to consume foods with a low glycemic index, such as whole grains (whole grain foods, etc.).

Exercise improves insulin sensitivity by increasing free fatty acids and improving skeletal muscle mitochondrial function, and reduces lipotoxicity in skeletal muscle and liver. It also increases glucose uptake by muscle cells. The Diabetes Prevention Program, a landmark study published 15 years ago, showed that cutting 150 calories per day and walking briskly for 30 minutes, five days a week, can reduce the risk of diabetes by more than half (58%). Refined carbohydrates such as white rice, foods made with white flour, and sugary foods such as desserts and soda should also be limited.

"I tell my patients, don't get discouraged if you're not losing weight," Dr. Ganda says. If you exercise regularly, your body composition will change even if your weight doesn't. Losing fat and gaining muscle will improve your response to insulin, as will exercise itself. "Think of exercise as having a little extra insulin in your body," he says.

Screening recommendations

Starting around middle age, all adults should be screened for diabetes. If you visit your community health center for regular checkups, you may get a fasting blood sugar test as part of your routine blood work.

If your blood sugar is between 100 and 125 mg/dL (or 5.7 to 6.4 percent A1C), your doctor will likely have you retested in a few weeks. If the results are the same, you're diagnosed with prediabetes, and from that point on, you'll have to redouble your efforts to avoid developing diabetes. Diabetes not only increases your risk of heart disease and stroke, but it can also damage your kidneys, nerves, and eyes.

Healthy eating and exercise habits can also improve blood pressure and cholesterol levels. If your fasting blood sugar level meets the criteria for clear diabetes (126 mg/dL or higher), the U.S. National Diabetes Guidelines recommend that you take a statin, even if your cholesterol is not elevated.

What about reports that taking statins may increase the risk of diabetes? Dr. Ganda believes that some studies do show that the risk of new-onset diabetes increases after people start taking statins. However, these people with new-onset diabetes are destined to develop diabetes based on common lifestyle or genetic risk factors. Overall, the benefits of taking statins outweigh the risks of diabetes. In fact, preventing cardiovascular disease is much more important than preventing diabetes.

Chen Luyuan

Chief Physician, Professor of Guangdong Institute of Cardiovascular Diseases

Former Director of Hypertension Research Laboratory of Guangdong Provincial People's Hospital

Deputy Director of the Second and Third Hypertension Group of the Cardiovascular Disease Branch of the Chinese Medical Association

Chairman of the First Hypertension Specialty Physician Branch of Guangdong Medical Doctor Association

Deputy Director of the Second and Third Hypertension Group of the Cardiovascular Disease Branch of the Guangdong Medical Association

Vice Chairman of the First Cardiovascular Pharmacology Committee of Guangdong Pharmacology Society

Current Vice Chairman of the Board of Directors of China Hypertension Alliance

Vice Chairman of Hypertension Committee of Chinese Gerontological Society

Vice Chairman of China Elderly Cardiovascular Disease Prevention and Treatment Alliance

Member of the Standing Committee of Hypertension Professional Committee of Chinese Medical Doctor Association