Dietary Glucose Increases Glucose Absorption and Lipid Deposition via SGLT1/2 Signaling and Acetylated ChREBP in the Intestine and Isolated Intestinal Epithelial Cells of Yellow Catfish

Abstract

<jats:title>ABSTRACT</jats:title> <jats:sec> <jats:title>Background</jats:title> <jats:p>Dietary carbohydrate affects intestinal glucose absorption and lipid deposition, but the underlying mechanisms are unknown.</jats:p> </jats:sec> <jats:sec> <jats:title>Objectives</jats:title> <jats:p>We used yellow catfish and their isolated intestinal epithelial cells (IECs) to test the hypothesis that sodium/glucose cotransporters (SGLTs) 1/2 and acetylated carbohydrate response element binding protein (ChREBP) mediated glucose-induced changes in glucose absorption and lipid metabolism.</jats:p> </jats:sec> <jats:sec> <jats:title>Methods</jats:title> <jats:p>Yellow catfish (mean ± SEM weight: 4.68 ± 0.02 g, 3 mo old, mixed sex) were fed diets containing 250 g carbohydrates/kg from glucose (G, control), corn starch (CS), sucrose (S), potato starch (PS), or dextrin (D) for 10 wk. IECs were isolated from different yellow catfish and incubated for 24 h in a control or glucose (15 mM) solution with or without a 2-h pretreatment with an inhibitor [sotagliflozin (LX-4211) or tubastatin A (TBSA)]. Human embryonic kidney cells (HEK293T cells) were transfected with a Flag-ChREBP plasmid to explore ChREBP acetylation. Triglyceride (TG) and glucose concentrations and enzymatic activities were measured in the intestine and IECs of yellow catfish. They also were subjected to immunofluorescence, immunoprecipitation, qPCR, and immunoblotting. Immunoblotting and immunoprecipitation were performed with HEK293T cells.</jats:p> </jats:sec> <jats:sec> <jats:title>Results</jats:title> <jats:p>The G group had greater intestine TGs (0.99- to 2.30-fold); activities of glucose 6-phospate dehydrogenase, 6-phosphogluconate dehydrogenase, and isocitrate dehydrogenase (0.12- to 2.10-fold); and expression of lipogenic genes (0.32- to 2.34-fold) than the CS, PS, and D groups. The G group had greater intestine sglt1/2 mRNA and protein expression than the CS, S and D groups (0.35- to 1.12-fold and 0.40- to 4.67-fold, respectively), but lower mRNA amounts of lipolytic genes (48.6%–65.8%) than the CS and PS groups. LX-4211 alleviated the glucose-induced increase in sglt1/2 mRNA (38.2%–47.4%) and SGLT1 protein (48.0%) expression, TGs (29.3%), and lipogenic enzyme activities (27.7%–42.1%) and gene expression (38.0%–55.5%) in the IECs. TBSA promoted the glucose-induced increase in TGs (11.3%), fatty acid synthase activity (32.6%), and lipogenic gene expression (21.6%–34.4%) in the IECs and acetylated ChREBP (10.5%) in HEK293T cells.</jats:p> </jats:sec> <jats:sec> <jats:title>Conclusions</jats:title> <jats:p>SGLT1/2 signaling and acetylated ChREBP mediated glucose-induced changes in glucose absorption and lipid metabolism in the intestine and IECs of yellow catfish.</jats:p> </jats:sec>

Effects of dietary carbohydrate sources on lipid metabolism and SUMOylation modification in the liver tissues of yellow catfish

“…Expt 1: in vivo study Experimental procedures. The experimental protocols for fish culture and management have been described in our parallel study (18) . Briefly, yellow catfish from a local fish farm (Wuhan, China) were subjected to a 2-week acclimation in the indoor tanks.…”

“…Histological and histochemical observation. Haematoxylineosin and Oil Red O stainings were conducted based on our recent publication (18) .…”

“…Western blot analysis. Western blot analysis was performed according to our recent publication (18) . Antibodies against SREBP1 (ab28481; Abcam), SUMO1 (ab32058; Abcam), SCD1 (ab19862; Abcam), LXRα (ab41902; Abcam), GAPDH (10494-1-AP; Proteintech Group) and IgG (Alexa Fluor® 647, ab150079; Abcam) were used to measure the expression of the corresponding proteins.…”

Phospholipase C signal mediated the glucose-induced changes of glucose absorption and lipid accumulation in the intestinal epithelial cells of yellow catfishPelteobagrus fulvidraco

“…The intestinal tract is the predominant region of digestion and absorption of carbohydrates and also plays principal roles in glucose transport and metabolism (2) . Generally, glucose from the diet directly or from hydrolysis of other carbohydrates was taken up into the epithelial cells through specific glucose transporters, such as sodium/glucose co-transporters (SGLTs) (2)(3)(4)(5) . Among these SGLTs, SGLT1 and SGLT2 functions as glucose sensors in the intestine, and they transports glucose from the intestinal lumen to the cytosols of enterocytes (3)(4)(5) .…”

“…Carbohydrate response element binding protein (ChREBP) was a glucose-activated transcription factor (13,14) , and mediated the glucose-induced lipogenesis (15,16) . Many studies have suggested that the function of ChREBP is regulated by translocation from cytoplasm to nucleus and multiple post-translational modifications (5,(17)(18)(19)(20) . Importantly, ChREBP is modified by acetylation, and acetylated ChREBP increases ChREBP transcriptional activity.…”