Serum FAM19A5 in newly diagnosed type 2 diabetes mellitus and its association with metabolic and inflammatory parameters

We aimed to investigate serum levels of FAM19A5, a novel adipokine implicated in inflammation and metabolic regulation, and to examine its association with key metabolic and inflammatory markers in individuals newly diagnosed with type 2 diabetes mellitus (T2DM). This case-control study included 54 patients with newly diagnosed T2DM and 54 age- and sex-matched normoglycemic controls aged 35 to 65 years. Continuous variables were summarized according to their distributions and compared using the independent-samples t test or Mann–Whitney U test, as appropriate. Spearman rank correlation was used to examine associations in the pooled sample, with false discovery rate correction for multiple testing. Subgroup analyses were conducted by metabolic syndrome, insulin resistance, and body mass index (BMI) category. The incremental value of FAM19A5 beyond conventional markers was explored using multivariable logistic regression and DeLong comparisons of the areas under the curve (AUCs). Serum FAM19A5 was lower in the T2DM group than in controls (376.1 [312.1–577.6] vs 554.5 [365.6–1524.2] ng/L; P < .001). In the pooled sample, FAM19A5 was inversely correlated with fasting glucose (ρ = −0.266, P = .005), 2-hour oral glucose tolerance test (ρ = −0.308, P = .001), and HbA1c (ρ = −0.212, P = .028), but not with BMI, waist circumference, lipid parameters, homeostasis model assessment of insulin resistance (HOMA-IR), or high-sensitivity C-reactive protein (hs-CRP). After false discovery rate correction, the associations with fasting and 2-hour oral glucose tolerance test remained significant. Within the T2DM group, FAM19A5 was lower in patients with metabolic syndrome ( P = .004), insulin resistance (HOMA-IR > 2.71; P = .023), or BMI ≥25 kg/m² ( P = .021). FAM19A5 alone showed poor discrimination for T2DM (AUC: 0.684; sensitivity: 66.7%; specificity: 53.7%). Adding FAM19A5 to a model containing BMI, HOMA-IR, and hs-CRP improved model fit (likelihood-ratio χ² = 13.1, P < .001) but not discrimination (AUC: 0.920 vs 0.943; DeLong P = .154). Serum FAM19A5 levels were lower in newly diagnosed T2DM and remained independently associated with diabetes status after adjustment for BMI, HOMA-IR, and hs-CRP. Correlations with glycemic measures were weak, and FAM19A5 alone had poor discriminatory performance. These findings support further investigation of FAM19A5 as a molecule of potential mechanistic interest, but not as a clinically useful diagnostic biomarker. Larger longitudinal studies are needed.