Fig. 6

Identification of rhythmic serum ceramide species in collagen-induced arthritis (CIA) model in mouse. Serum samples were collected from CIA and control mice at the indicated times; time is Zeitgeber with ZT0 lights on and ZT12 lights off. a JTK cycle was used to estimate rhythmic species in control or CIA mice, and the number of ceramides in each class is recorded. b Heatmap of all detected serum ceramide concentrations in different classes in both CIA and control mice (mean line shown) for each group shown, examples of rhythmic species shown on the right). c Time course of index ceramide concentrations in CIA and control mice, CER[N(24)S(16)], CER[N(26)S(18)], CER[N(24)DS(20)] and CER[N(24)S(20)]. Adjusted p values are shown (n = 12 control and 15 arthritis). Ceramide synthase gene expression in livers from CIA and control mice. d Pathway map of ceramide species generation. Serine palmitoyltransferase long chain base subunit 1 (SPLTC1,2), dihydroceramide desaturase 1 (DEGS1), ketodihydrosphingosine reductase (KDSR), ceramide synthase 1–6 (CERS). e Livers from CIA or control mice were collected at the indicated times (ZT0–18), and RNA extracted. Ceramide synthase gene expression was determined by qPCR for CERS2, CERS4 and CERS6 at each time point. JTK cycle was used to determine rhythmicity, adjusted p values shown (n = 14 control and 14 arthritis). f Gene expression for CERS6 in liver from arthritis and control mice (n = 14). g NR1D1 (Rev-erbα) and DBP circadian gene expression in liver. h Mouse liver cells (AML12) were stimulated with IL-6 (25 ng/mL) or IL-1β (25 ng/mL) for 4 h. Ceramide synthase expression level determined for CERS2, CERS4 and CERS6 by qRT-PCR. Changes in expression were determined by a Wilcoxon rank sum test (n = 3)