What is metabolic syndrome?

Metabolic syndrome is a cluster of conditions that occur together, increasing the risk of heart disease, stroke, and type 2 diabetes. These conditions include:


  • Abdominal obesity: Excess fat around the waistline, often measured by waist circumference. In men, a waist circumference of 40 inches or more is considered indicative of abdominal obesity. In women, it’s 35 inches or more.


  • High blood pressure: Blood pressure levels consistently higher than 130/85 mmHg.


  • High blood sugar: Elevated fasting blood sugar levels, indicating insulin resistance or impaired glucose tolerance. A fasting blood sugar level of 100 mg/dL (5.6 mmol/L) or higher is considered indicative of high blood sugar.


  • High triglycerides: Elevated levels of triglycerides in the blood, which are fats found in the blood. A triglyceride level of 150 mg/dL (1.7 mmol/L) or higher is considered high.


  • Low HDL cholesterol: Low levels of high-density lipoprotein (HDL) cholesterol, often referred to as “good” cholesterol. In men, HDL levels below 40 mg/dL (1.0 mmol/L) and in women below 50 mg/dL (1.3 mmol/L) are considered low.


What is the relationship between metabolic syndrome and oxidative stress?

The relationship between metabolic syndrome and oxidative stress is significant and plays a crucial role in the development and progression of metabolic abnormalities associated with the syndrome. Here’s how metabolic syndrome and oxidative stress are interconnected:


  • Insulin Resistance: Insulin resistance, a hallmark feature of metabolic syndrome, occurs when cells in the body become less responsive to the effects of insulin, leading to impaired glucose uptake and metabolism. Insulin resistance is associated with increased production of reactive oxygen species (ROS) within cells, contributing to oxidative stress. ROS can interfere with insulin signaling pathways, exacerbating insulin resistance and further impairing glucose metabolism.


  • Obesity: Obesity, particularly visceral or abdominal obesity, is a key component of metabolic syndrome and is closely linked to oxidative stress. Adipose tissue (fat cells) in obese individuals produces and releases inflammatory cytokines and adipokines, which promote oxidative stress and inflammation. Excess fat accumulation also leads to mitochondrial dysfunction and increased production of ROS within adipocytes, contributing to oxidative stress and metabolic dysfunction.


  • Dyslipidemia: Dyslipidemia, characterized by elevated triglycerides, low high-density lipoprotein (HDL) cholesterol, and increased levels of small, dense low-density lipoprotein (LDL) particles, is common in metabolic syndrome. Oxidative stress plays a role in the development of dyslipidemia by promoting lipid peroxidation and oxidation of LDL cholesterol particles, leading to the formation of oxidized LDL (oxLDL). OxLDL is highly pro-inflammatory and contributes to atherosclerosis, a major complication of metabolic syndrome.


  • Hypertension: Hypertension, or high blood pressure, is another component of metabolic syndrome and is associated with oxidative stress. Increased oxidative stress can impair endothelial function, leading to endothelial dysfunction and reduced nitric oxide (NO) bioavailability. NO is a vasodilator that helps regulate blood pressure, and its deficiency contributes to hypertension. Oxidative stress also promotes vascular inflammation and remodeling, further exacerbating hypertension.


  • Chronic Inflammation: Metabolic syndrome is characterized by chronic low-grade inflammation, which is closely linked to oxidative stress. Inflammatory cytokines and chemokines produced by adipose tissue, immune cells, and other tissues activate inflammatory pathways and promote ROS production. Oxidative stress, in turn, enhances inflammatory signaling cascades, creating a vicious cycle of inflammation and oxidative damage.


  • Endothelial Dysfunction: Endothelial dysfunction, characterized by impaired vasodilation, pro-thrombotic state, and increased vascular permeability, is a common feature of metabolic syndrome. Oxidative stress contributes to endothelial dysfunction by reducing NO bioavailability, promoting oxidative damage to endothelial cells, and stimulating pro-inflammatory and pro-thrombotic pathways.


Overall, oxidative stress is intimately involved in the pathogenesis of metabolic syndrome and its associated complications, including insulin resistance, dyslipidemia, hypertension, chronic inflammation, endothelial dysfunction, and atherosclerosis.