C3AR1 is found in macrophages, is modulated by MASLD/MASH in humans, and is induced by a murine dietary model of MASH.

A) Relative C3AR1 human tissue expression level by tissue, derived from deep sequencing of the mRNA combined dataset (HPA and GTEx) in the Human Protein Atlas, shown as normalized transcripts per million (nTPM). Liver is highlighted in purple and immunologic tissues are highlighted in red.

B) Single-cell RNA sequencing distribution of C3AR1 expression in human liver (tSNE, t-distributed Stochastic Neighbor Embedding).

C) Analysis of CFD and C3AR1 expression from liver biopsy samples in patients with MASH, MASLD, obesity without MASLD, and age-matched healthy controls (n = 12-16 per group, Welch t test with Holm-Šídák correction for multiple comparisons).

D) Weight curve in male and female flox/flox control mice placed on GAN high-fat diet compared to regular diet (RD) controls (males, n = 7; females, n = 6).

E) Representative liver section staining by Masson’s Trichrome in male control mice on RD or GAN diet for 28 weeks (scale bar = 100 mm).

F) Lipid droplet area quantification in liver sections from male control mice, excluding vessel lumens (RD, n = 3; GAN, n = 7).

G) Collagen area quantification in liver sections of male control mice (RD, n = 3; GAN, n = 7).

H) Gene expression of key macrophage or fibrosis genes in male control mice on GAN or RD (n = 6 per group).

Unpaired two-tailed Student’s t test (Except 1C as above). Annotations: *, p < 0.05; **, p < 0.01; ***, p < 0.001

C3aR1 deletion in all macrophages does not affect weight gain, glucose homeostasis, liver steatosis or fibrosis.

A) Expression of C3ar1 in isolated peritoneal F4/80+/CD68+ cells from flox/flox control mice (n = 6) or C3aR1-MjKO male mice (n = 3).

B) Expression of C3ar1 in whole liver from control or C3aR1-MjKO mice (n = 11-12 per male group, n = 13-14 per female group).

C) Body mass curve of control or C3aR1-MjKO mice on GAN high-fat diet starting at 5 weeks of age (n = 11-12 per male group, n = 14 per female group).

D) Body composition analysis by EchoMRI in control or C3aR1-MjKO mice after 30 weeks GAN diet (n = 6-9 per male group, n = 9-13 per female group).

E) Glucose tolerance test in control or C3aR1-MjKO mice with 14h fast after 28 weeks GAN diet (n = 6-9 per male group, n = 9-14 per female group).

F) Liver mass in control or C3ar1-MjKO male mice at time of euthanasia after 30 weeks GAN diet (n = 6-9 per male group, n = 9-14 per female group).

G) Representative liver section staining by Masson’s Trichrome in male control or C3ar1-MjKO mice (scale bar = 100 mm).

H) Lipid droplet area in liver sections from male control or C3ar1-MjKO mice, excluding vessel lumens (n = 6-7 per group).

I) Collagen area in liver sections from male control or C3ar1-MjKO mice (n = 6-7 per group).

J,K) Relative mRNA expression of key markers for inflammation, fibrosis, and liver metabolism in liver from male control or C3ar1-MjKO mice after 30 weeks of either GAN (J) diet (n = 11-12 per group) or regular (K) diet (n = 3-5 per group).

Unpaired two-tailed Student’s t test: Student’s t test: *, p < 0.05.

C3aR1 deletion in Kupffer cells does not affect weight gain, glucose homeostasis, liver steatosis or fibrosis.

A) Body mass curve on GAN diet in flox/flox control or C3aR1-KpKO mice beginning at 5 weeks of age (n = 8-10 per group).

B) Body composition analysis by EchoMRI in control or C3aR1-KpKO mice after 28 weeks GAN diet (n = 8-10).

C) Glucose tolerance test in control or C3aR1-KpKO mice with 14h fast after 26 weeks GAN diet (n = 8-10).

D) Liver mass in control or C3aR1-KpKO male mice at time of euthanasia after 30 weeks GAN diet (n = 8-10).

E) Representative liver section staining by Masson’s Trichrome in control or C3aR1-KpKO male mice (scale bar = 100 mm).

F) Lipid droplet area quantified on liver sections of control or C3aR1-KpKO male mice, excluding vessel lumens (n = 8-9).

G) Collagen area quantified on whole liver section of control or C3aR1-KpKO male mice (n= 8-9).

H) Relative gene expression in male control or C3aR1-KpKO mice after 30 weeks GAN diet (n = 5-6).

Unpaired two-tailed Student’s t test: **, p < 0.01.

Single cell RNA sequencing analysis of C3ar1 expression in mouse liver tissue (see text).

Percent lean and fat mass of flox/flox control mice after 20 weeks of GAN or RD (n = 6-7 per group).

Absolute lean and fat mass of flox/flox control mice after 20 weeks of GAN or RD (n = 6-7 per group).

Relative gene expression in control female mice after 33 weeks on RD (n = 4-6 per group).

Insulin tolerance test in control or C3aR1-MjKO male mice with 14h fast after 29 weeks GAN diet (n = 6-9 per group).

HOMA-IR measurement of insulin resistance in control or C3aR1-MjKO mice with 6h fast after 27 weeks GAN diet (n = 6-9 per male group, n = 9-13 per female group).

Serum alanine aminotransferase levels in control or C3aR1-MjKO male mice after 30 weeks GAN diet (n = 4 per group).

Relative gene expression in control or C3aR1-MjKO female mice after 30 weeks of either GAN (n = 13-14 per group) or RD (n = 5-6 per group).

Relative C3ar1 expression in control or C3aR1-KpKO female mice after 30 weeks RD (n = 2-3 per group).

Unpaired two-tailed Student’s t test: **, p < 0.01; ***, p < 0.001.