Blood TTR may be a biomarker of primary Sjögren’s disease activity
Protein used as poor nutrition biomarker, linked to autoimmune diseases
Blood levels of transthyretin (TTR) may be used as a biomarker to predict and monitor disease activity in people with primary Sjögren’s disease, a study in China suggests.
TTR is a protein that transports thyroxine, the main hormone secreted by the thyroid gland, to the liver and brain. It’s a common marker of metabolism, the processes that maintain normal bodily functions, and has been linked to other autoimmune conditions.
“These findings suggest that [blood] TTR is a potential marker for the evaluation of disease activity in patients with [primary Sjögren’s disease], providing insights that could enhance the clinical management of [the disease],” the researchers wrote.
The study, “Serum transthyretin levels and disease activity in patients with primary Sjögren’s syndrome,” was published in Therapeutic Advances in Musculoskeletal Disease.
Sjögren’s is an autoimmune disease that occurs when the immune system launches an inflammatory attack on the glands that produce tears and saliva, and leads mainly to eye and mouth dryness, although other organs can also be affected. The disease is classified as primary when it appears isolated, or secondary if it follows another autoimmune disease.
Evaluating disease activity is essential to determine the treatment and management of patients, and may include blood biomarkers, imaging tests, or measuring salivary flow. Other laboratory biomarkers, such as TTR, have recently emerged that could be used in routine clinical practice.
Studying TTR in Sjögren’s disease
TTR has been used as a biomarker of poor nutrition and in recent years an association between TTR and autoimmune diseases, such as rheumatoid arthritis or systemic sclerosis, has been found.
“However, to the best of our knowledge, information regarding the role of [blood] TTR in patients with [Sjögren’s disease] is limited,” wrote the researchers, who evaluated data from 84 people with Sjögren’s between March 2016 and May 2023 to investigate a possible association. A total of 135 age and sex-matched healthy people served as controls.
Almost all the patients were women (96.4%). The participants had a mean age of 51, and body mass index (BMI), a measure of body fat based on height and weight, was used to assess nutritional status. Compared to the controls, patients had significantly lower levels of TTR (181.9 vs. 241.8 mg/L), but there were no significant differences regarding levels of liver enzymes and creatinine, indicators of liver and kidney function.
Among the patients, low blood levels of TTR were significantly correlated with higher levels of C-reactive protein and immunoglobulin G (IgG) antibodies, which are markers of inflammation, and low BMI. Moreover, lower TTR was significantly correlated with higher disease activity, according to the EULAR Sjögren’s syndrome disease activity index (ESSDAI) and ClinESSDAI scores.
After adjusting for variables such as sex, age, and BMI, the significant correlations with C-reactive protein, disease activity and BMI were maintained, indicating “the association between serum TTR levels and disease activity is independent of nutritional status” in this patient population.
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