By: Laura Eggertson

People with Type 2 diabetes mellitus have a greater chance of getting cardiovascular disease, and consequently shorter lifespans, than people who never develop diabetes. That’s why researchers who designed a large clinical trial to see if intensive therapy to control the blood pressure of people with Type 2 diabetes could lower their risk.

Unfortunately, the results of the ACCORD (Action to Control Cardiovascular Risk in Diabetes) trial were disappointing, with the researchers reporting no significant differences in the participants who received the intensive therapy, compared to those who got standard treatment.

But third-year Masters’ student Samantha Lavallee wondered if the data was misleading. What if there was a difference in the participants’ sensitivity to the treatment, but the trial’s investigators just hadn’t teased that difference out?

Lavallee, who works with Dr. Leah Cahill in the Faculty of Medicine’s Nutrition Outcomes for Research-ish (NOURISH) lab, decided to investigate the differences in people with a type of protein in their blood called haptoglobin. These proteins bind to hemoglobin, the key component in red blood cells, and they help to reduce the oxidative stress that can increase blood pressure.

“There are three types of haptoglobin,” Lavallee explains. “Each person has one of those types.”

Lavallee suspected that people in the ACCORD study with distinct types of haptoglobin might have responded differently to the intensive blood pressure control therapy. So Lavallee and her colleagues in Dr. Cahill’s lab re-analyzed the data from the study, looking at the results according to what type of haptoglobin the participants had.

Just as they had hypothesized, Lavallee discovered people with the Hp-1-1 or Hp-2-1 types of haptoglobin had fewer cardiovascular events if they received the intensive blood pressure control therapy.

But people with the Hp-2-2 haptoglobin, which is a less functional type of protein, had a slightly higher risk of cardiovascular events, such as a heart attack or arrhythmia, even if they received the intensive therapy.

Black participants in the ACCORD study had a particularly elevated risk, Lavallee says.

“If they had Hp-2-2, they would have almost three times the risk. So that’s pretty significant,” she says.

Lavallee’s research not only suggests intensive blood pressure control therapy does work with certain individuals – those with the Hp-1-1- or Hp-2-2 haptoglobin – it also points the way to a precision medicine treatment.

By having an inexpensive haptoglobin test before beginning blood pressure medications, people could discover whether intensive therapies would benefit them, or not.

“You could potentially prevent putting people through any harm from intensive therapy, while identifying those who would benefit.”

For Lavallee, who is a member of the Metis Nation of Ontario, her love of the outdoors and the physical sciences led her into a research career. She’d like to obtain a job in field epidemiology before eventually getting a PhD.

By spreading the word about her research project, she hopes to inspire a larger study to validate her findings and have haptoglobin testing become standard for people with Type II diabetes who need blood pressure therapy.

“The more we get it (this information) out there, the closer we are to having it integrated into more treatment and tailoring them to people with Type II diabetes,” she says.