Insulin Resistance at AAV Diagnosis May Predict Cardiac Involvement
Increased insulin resistance — measured by the triglyceride glucose (TyG) index — may predict which people diagnosed with ANCA-associated vasculitis (AAV) are at a greater risk of developing heart problems, a study found.
Its predictive power may come from its association with metabolic disease at AAV diagnosis, data showed. Those with higher AAV disease activity might also be particularly susceptible to the emergence of cardiovascular disease.
“We suggest that the TyG index at the time of AAV diagnosis may be calculated for all patients, if possible,” the researchers wrote, adding that “when a patient has a TyG index within its highest tertile at AAV diagnosis, close attention should be paid to these patients, and frequent visits should be recommended.”
The study, “Triglyceride and Glucose Index Predicts Acute Coronary Syndrome in Patients with Antineutrophil Cytoplasmic Antibody-Associated Vasculitis,” was published in the journal Diagnostics.
While kidney and lung damage are the most common manifestations of AAV, cardiac involvement may also occur, with estimates of its prevalence ranging from 5–50%, depending on the AAV type. As cardiac involvement can significantly increase mortality risk in AAV patients, prompt identification of those at risk is needed.
The TyG index takes into account blood sugar (glucose) and the levels of fatty molecules (triglycerides) in the bloodstream to estimate insulin resistance — a condition that arises when cells no longer respond well to insulin and can’t properly use blood sugar to produce energy. The index has been previously linked to cardiovascular risk, with higher numbers associated with a greater risk of heart complications.
Researchers in Korea investigated whether the TyG index could be used to evaluate the risk of cardiac involvement in AAV patients at the time of their diagnosis. Specifically, the team evaluated whether the TyG index could predict the risk of acute coronary syndrome (ACS), a range of conditions that stop or significantly reduce blood flow to the heart’s muscle, like a heart attack.
Included in the analyses were 152 AAV patients seen at a clinic in Korea between March 2001 and May 2o21. Patients had a mean age at diagnosis of 57.2 and 32.9% of them were male. A total of 84 patients had microscopic polyangiitis (MPA), 35 had granulomatosis with polyangiitis (GPA), and 33 eosinophilic granulomatosis with polyangiitis (EGPA).
During follow-up, 12 patients (7.9%) died and 48 (31.6%) relapsed. End-stage kidney disease occurred in 31 people (20.4%), 12 people (7.9%) had a stroke, and 12 had ACS.
More patients in the highest third of TyG index values — with values at or above 9.011 — developed ACS compared with those with TyG index below that value. But in a final analysis adjusted for potentially related variables, TyG index was not found to be an independent predictor of ACS. Only male sex was an independent ACS predictor.
ACS occurrence was also higher among patients who scored at least 11.5 on the Birmingham Vasculitis Activity Score (BVAS) at diagnosis, reflecting that greater AAV disease activity may be linked to later heart problems.
The TyG index was a significant independent predictor of metabolic syndrome — a group of conditions that raise the risk of heart disease, such as high waist circumference, high blood pressure, or type 2 diabetes — at diagnosis. Body mass index and levels of hemoglobin — a protein in red blood cells responsible for oxygen transport — were also predictors of metabolic syndrome.
Ultimately, the researchers found that AAV patients with concurrent metabolic syndrome and higher disease activity — a BVAS score of 11.5 or greater — at diagnosis were significantly more likely to develop ACS.
Although TyG index and ACS were not directly linked, the index could serve as an ACS predictor through its relationship to metabolic syndrome, the researchers suggested, as metabolic syndrome is a known predictor of cardiovascular problems.
“Although the exact mechanism remains uncertain, we conclude that the TyG index at diagnosis can predict the occurrence of ACS during follow-up in AAV patients by easily assessing concomitant metabolic abnormalities that may contribute to the occurrence of coronary arterial disease in general,” the researchers wrote.
The study’s small number of patients and lack of information about other factors, such as smoking habits or medication use, that could influence its findings were pointed out as limitations.
“A prospective future study with a larger number of AAV patients will compensate for these limitations and provide more reliable information on the application to AAV patients in real clinical settings,” the scientists wrote.