Obesity-associated inflammation worsens 'bad cholesterol' and makes it function abnormally, increasing the risk of cardiovascular diseases, diabetes and certain cancers, according to a new study.

Obesity is a public health problem worldwide that affects a large section and often involves hyperlipidemia (high concentrations of fats/lipids in the blood), diabetes, hypertension, chronic inflammation and oxidative stress, which increase susceptibility to cardiovascular diseases (CVD).

Low-density lipoprotein (LDL) is a nanoparticle that transports cholesterol in blood. While cholesterol is essential for normal cellular function, excess cholesterol can, however, be deposited in arteries causing CVD, and LDL cholesterol is dubbed “bad cholesterol”.

The study, published in the Journal of Lipid Research, showed that in obesity, it is not the quantity but the quality of LDL that contributes to the disease becoming worse due to obesity-associated inflammation.

"As a result, cholesterol delivery is shifted from normal to abnormal, so more cholesterol is retained in the arterial wall, ultimately forming plaques that occlude the blood flow," said Shobini Jayaraman, corresponding author, a senior research scientist in pharmacology, physiology and biophysics at Boston University, US.

For the study, the team compared blood lipoproteins from patients with severe obesity before bariatric surgery and 6 or 12 months after were compared with lipoproteins from a control group of lean healthy subjects.

The researchers found LDL particles became dysfunctional and were less efficient at delivering their cholesterol cargo to LDL receptors. Additionally, the LDL particle also tended to either preferentially deliver cholesterol to scavenger receptors or stick to the arterial wall matrix.

"This aberrant behaviour stemmed from alterations in LDL biochemical composition induced by obesity-associated inflammation. These harmful changes contributed to increased risk of CVD in patients with obesity," added Jayaraman.

"Our study shows that LDL quality continues to improve as a patient’s weight normalises, suggesting that the risk of CVD continues to decline," said Olga Gursky, Professor of pharmacology, physiology and biophysics at the varsity’s School of Medicine.

"This is promising not only for patients undergoing bariatric surgery but perhaps for many others who are overweight or obese and use various approaches to weight loss," Gursky added.