Fig. 3.

RYGB microbiota transfer reduces inflammation and enhances lipolysis and thermogenic activity in adipose tissue. a–e H&E staining on sections from epididymal (eWAT) and inguinal (iWAT) white adipose tissue (scale bars 200 μm) 5 weeks after fecal microbiota transfer (FMT) from RYGB-operated rats (FMT^RYGB) compared to their respective controls (DIO rats not receiving RYGB microbiota) (a). Relative mRNA expression of genes involved in lipolysis, fatty acid oxidation, and inflammatory cytokines in eWAT (b, c) and iWAT (d, e). f–i BAT weight (in % of total BW) (f), H&E and UCP1 staining of BAT sections (scale bars 200 μm) (g) and relative mRNA expression of genes involved in fatty acid oxidation and thermogenesis in BAT (h). Electron microscopy of ultra-thin sections of BAT depicting mitochondrial fine structure in DIO vs FMT^RYGB animals (scale bar 1 μm) (i). j–l Relative mRNA expression of genes involved in lipolysis in BAT (j), phosphorylation levels of HSL (p-HSL) (k) and free plasma glycerol levels (in mM) (l). m–r Representative infrared images (m) and corresponding rectal body temperature (in °C) after 6 h of cold-exposure (n). Oxygen consumption (VO₂; in ml/(h*kg)) (o), carbon dioxide production (VCO₂; in ml/(h*kg)) (p), heat production (in kcal/(h*kg)) (q) and locomotor activity (r) of FMT^RYGB and DIO rats (at 5 weeks of FMT treatment). Seahorse analysis of murine adipocytes after pretreatment with rat serum (DIO vs. FMT^RYGB, PBS as control) (s). Data are mean ± s.e.m; n = 3–8 animals per group with pooled data from 2 to 3 independent experiments. *P < 0.05, ** P < 0.01, *** P < 0.001; unpaired Student’s t test