High-density lipoprotein cholesterol (HDL-C), commonly referred to as “good cholesterol,” may not be all it’s cracked up to be, according to a new report.

Researchers from the Harvard School of Public Health have discovered that when a small proinflammatory protein called apolipoprotein (apo) C-III is found on the surface of HDL, the risk for coronary heart disease (CHD) actually increases. The researchers studied blood samples from 18,225 men and 32,826 women. “We investigated whether the presence or absence of apoC-III differentiates HDL into subtypes with nonprotective or protective associations with risk of future CHD,” the study authors stated. To do this they measured HDL-C levels and separated findings into two groups: those with and those without apoC-III. They discovered that individuals with apoC-III had a greater CHD risk than those without. The at-risk individuals were also more likely to be overweight or obese, diabetic and hypertensive, and to have higher levels of triglycerides.

“The major HDL-C type lacking apoC-III has the expected protective association with CHD, whereas the small subfraction of HDL-C that has apoC-III present on its surface tended to be associated with higher risk of future CHD,” added the authors. “HDL that has apoC-III may represent a dysfunctional HDL lacking in cardioprotective function. This may also have implications for future development of novel therapeutic interventions aimed at HDL elevation, as the cardioprotective benefits may differ depending on the affected HDL subfraction.”

The study was published in the Journal of the American Heart Association (2012; doi: 10.1161/JAHA.111.000232).