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Bilirubin increase linked to type 2 diabetes
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An increase in serum bilirubin concentration is associated with type 2 diabetes development, according to findings from a longitudinal study in Korea.
“Conventionally, bilirubin is considered a waste product of heme catabolism, but recent studies have described bilirubin as an in vivo antioxidant,” Jae Hyeon Kim, MD, PhD, clinical assistant professor in the department of medicine at Samsung Medical Center and Sungkyunkwan University School of Medicine, and colleagues wrote. “Bilirubin has potential anti-inflammatory, antioxidant and cytoprotective properties under oxidative stress conditions.”
Kim and colleagues analyzed data from 22,084 Korean adults who underwent annual checkups at least four times at Samsung Medical Center between 2006 and 2012. Patients provided fasting blood samples to asses HbA1c, fasting plasma insulin and serum bilirubin concentrations; insulin resistance and beta-cell function were assessed by homeostatic model assessment of insulin resistance (HOMA-IR) and homeostatic model assessment of beta-cell function (HOMA-B). Researchers followed the cohort for a mean of 5.12 years.
At baseline, 1,548 patients had type 2 diabetes; mean bilirubin concentration was lower in the diabetes group vs. those without diabetes (14.9 µmol/L vs. 15.4 µmol/L; P = .006). An additional 438 adults were diagnosed with type 2 diabetes at the second visit based on percent change in bilirubin, calculated from baseline until 1 year before the last date of diabetes diagnosis. Of the remaining 20,098 adults, 1,253 (6.2%) developed type 2 diabetes during follow-up, according to the data.
Among adults without diabetes at baseline, researchers found that as percent change in bilirubin increased, incidence of type 2 diabetes also increased (3.8% in first quartile; 4.6% in second quartile; 7% in third quartile and 9.7% in fourth quartile; P < .001). After adjustment for multiple factors, including age, sex, BMI, hypertension and HbA1c, patients in the highest quartile for percent change in bilirubin had a twofold greater risk for developing type 2 diabetes vs. patients in the lowest quartile (HR = 2.08; 95% CI, 1.19-1.31).
Additional analysis comparing the rate of percent change in bilirubin during follow-up revealed that the bilirubin level of the incident type 2 diabetes group increased before diabetes development and decreased rapidly thereafter vs. other patients (P < .001), according to researchers.
“[Serum bilirubin concentration] had no relationship with [type 2 diabetes] incidence, while [percent change in bilirubin] and [type 2 diabetes] were positively correlated,” the researchers wrote. “In other words, bilirubin increase over time is associated with [type 2 diabetes] development. In addition, we postulate that serum bilirubin level increases in early-stage [type 2 diabetes] and gradually decreases over time as [heme oxygenase-1] expression decreases.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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