2型糖尿病I:はじめに

Type 2 diabetes mellitus is characterized by insulin resistance, where tissues like the liver, muscle, and adipose tissue respond poorly to insulin, and progressive beta cell dysfunction, where pancreatic beta cells fail to produce sufficient insulin. Together, these abnormalities result in persistent hyperglycemia, the hallmark of the disease.

Type 2 diabetes develops through complex interactions between genetic predisposition and environmental triggers. Certain genetic variants, such as KCNQ1, have stronger effects when combined with environmental stressors like high-fat diets. Gene-environment interactions raise disease risk through additive and synergistic mechanisms, meaning both factors together amplify susceptibility beyond their individual effects.

Epigenetic changes contribute to impaired metabolic regulation by influencing the expression of genes such as FTO and TCF7L2. Environmental factors including obesity, physical inactivity, and unhealthy diets promote chronic inflammation and oxidative stress, which trigger these epigenetic modifications that worsen insulin resistance and increase disease risk.

Non-modifiable risk factors include family history, advanced age over 45, high-risk ethnicities such as South Asian, Hispanic, African, and Indigenous populations, and genetic susceptibility including rare monogenic forms like maturity-onset diabetes of the young. These factors cannot be changed but help identify individuals at elevated risk.

Obesity, especially visceral fat accumulation, and physical inactivity worsen insulin resistance by promoting chronic inflammation, oxidative stress, and hormonal imbalance. These environmental factors trigger epigenetic changes affecting metabolic genes and increase disease risk through multiple pathways, making them significant modifiable risk factors.

Cardiometabolic conditions such as hypertension, dyslipidemia, and a history of gestational diabetes or polycystic ovarian syndrome further increase type 2 diabetes risk. These conditions reflect underlying metabolic dysfunction and often coexist with insulin resistance, compounding disease susceptibility through shared pathophysiological mechanisms.

Poor sleep, smoking, alcohol use, socioeconomic stress, and environmental pollutants disrupt metabolic regulation and increase type 2 diabetes risk. These factors work alongside modifiable factors like central obesity and sedentary lifestyle to impair glucose homeostasis and promote disease development through multiple metabolic pathways.