Gastric volume reduction is essential for the remission of type 2 diabetes mellitus after bariatric surgery in nonobese rats

Alteration of Ileal lncRNAs After Duodenal–Jejunal Bypass Is Associated With Regulation of Lipid and Amino Acid Metabolism

Metabolic and bariatric surgery (MBS) can generate a drastic shift of coding and noncoding RNA expression patterns in the gastrointestinal system, which triggers organ function remodeling and may induce type 2 diabetes (T2D) remission. Our previous studies have demonstrated that the altered expression profiles of duodenal and jejunal long noncoding RNAs (lncRNAs) after the duodenal–jejunal bypass (DJB), an investigational procedure and research tool of MBS, can improve glycemic control by modulating the entero-pancreatic axis and gut–brain axis, respectively. As an indiscerptible part of the intestine, the ileal lncRNA expression signatures after DJB and the critical pathways associated with postoperative correction of the impaired metabolism need to be investigated too. High-fat diet-induced diabetic mice were randomly assigned into two groups receiving either DJB or sham surgery. Compared to the sham group, 1,425 dysregulated ileal lncRNAs and 552 co-expressed mRNAs were identified in the DJB group. Bioinformatics analysis of the differently expressed mRNAs and predicted target genes or transcriptional factors indicated that the dysregulated ileal lncRNAs were associated with lipid and amino acid metabolism-related pathways. Moreover, a series of lncRNAs and their potential target mRNAs, especially NONMMUT040618, Pxmp4, Pnpla3, and Car5a, were identified on the pathway. In conclusion, DJB can induce remarkable alteration of ileal lncRNA and mRNA expression. The role of the ileum in DJB tends to re-establish the energy homeostasis by regulating the lipid and amino acid metabolism.

Upregulation of hypothalamic POMC neurons after biliary diversion in GK rats

BACKGROUND

Bile acids are important signaling molecules that might activate hypothalamic neurons. This study aimed to investigate possible changes in hypothalamic pro-opiomelanocortin (POMC) neurons after biliary diversion in diabetic rats.

METHODS

Ten GK rats were randomly divided into the biliary diversion (BD) and sham groups. The glucose metabolism, hypothalamic POMC expression, serum bile acid profiles, and ileal bile acid-specific receptors of the two groups were analyzed.

RESULTS

Biliary diversion improved blood glucose (P = 0.001) and glucose tolerance (P = 0.001). RNA-Seq of the hypothalamus showed significantly upregulated expression of the POMC gene (log2-fold change = 4.1, P < 0.001), which also showed increased expression at the protein (P = 0.030) and mRNA (P = 0.004) levels. The POMC-derived neuropeptide α-melanocyte stimulating hormone (α-MSH) was also increased in the hypothalamus (2.21 ± 0.11 ng/g, P = 0.006). In addition, increased taurocholic acid (TCA) (108.05 ± 20.62 ng/mL, P = 0.003) and taurodeoxycholic acid (TDCA) (45.58 ± 2.74 ng/mL, P < 0.001) were found in the BD group and induced the enhanced secretion of fibroblast growth factor-15 (FGF15, 74.28 ± 3.44 pg/ml, P = 0.001) by activating farnesoid X receptor (FXR) that was over-expressed in the ileum.

CONCLUSIONS

Hypothalamic POMC neurons were upregulated after BD, and the increased TCA, TDCA, and the downstream gut-derived hormone FGF15 might activate POMC neurons.

Glucose transporters in the small intestine in health and disease

Absorption of monosaccharides is mainly mediated by Na+-D-glucose cotransporter SGLT1 and the facititative transporters GLUT2 and GLUT5. SGLT1 and GLUT2 are relevant for absorption of D-glucose and D-galactose while GLUT5 is relevant for D-fructose absorption. SGLT1 and GLUT5 are constantly localized in the brush border membrane (BBM) of enterocytes, whereas GLUT2 is localized in the basolateral membrane (BLM) or the BBM plus BLM at low and high luminal D-glucose concentrations, respectively. At high luminal D-glucose, the abundance SGLT1 in the BBM is increased. Hence, D-glucose absorption at low luminal glucose is mediated via SGLT1 in the BBM and GLUT2 in the BLM whereas high-capacity D-glucose absorption at high luminal glucose is mediated by SGLT1 plus GLUT2 in the BBM and GLUT2 in the BLM. The review describes functions and regulations of SGLT1, GLUT2, and GLUT5 in the small intestine including diurnal variations and carbohydrate-dependent regulations. Also, the roles of SGLT1 and GLUT2 for secretion of enterohormones are discussed. Furthermore, diseases are described that are caused by malfunctions of small intestinal monosaccharide transporters, such as glucose-galactose malabsorption, Fanconi syndrome, and fructose intolerance. Moreover, it is reported how diabetes, small intestinal inflammation, parental nutrition, bariatric surgery, and metformin treatment affect expression of monosaccharide transporters in the small intestine. Finally, food components that decrease D-glucose absorption and drugs in development that inhibit or downregulate SGLT1 in the small intestine are compiled. Models for regulations and combined functions of glucose transporters, and for interplay between D-fructose transport and metabolism, are discussed.

Comparison of Diabetes Remission and Micronutrient Deficiency in a Mildly Obese Diabetic Rat Model Undergoing SADI-S Versus RYGB

BACKGROUND

Single-anastomosis duodeno-ileal bypass with sleeve gastrectomy (SADI-S) has launched a huge challenge to classic Roux-en-Y gastric bypass (RYGB). Our objective was to compare diabetes remission and micronutrient deficiency in a mildly obese diabetic rat model undergoing SADI-S versus RYGB.

METHODS

Thirty adult male mildly obese diabetic rats were randomly assigned to sham (S), SADI-S, and RYGB groups. Body weight, food intake, fasting plasma glucose (FPG), oral glucose tolerance test (OGTT), plasma insulin, GLP-1, and ghrelin levels were measured at indicated time points. Meanwhile, insulin sensitivity and pancreatic β cell function were assessed during OGTT. Finally, plasma micronutrient evaluation and islet β cell mass analysis were performed after all animals were sacrificed.

RESULTS

As compared to sham, the SADI-S and RYGB groups achieved almost equivalent efficacy in caloric restriction and FPG control without excessive weight loss. During OGTT, the SADI-S and RYGB groups also provided comparable effects on glycemic excursion, insulin sensitivity, and β cell function; however, only rats in the RYGB group showed significant changes in gut hormones, whereas the three groups were found to exhibit no significant difference in β cell mass. In addition, only vitamin E in the RYGB group was deficient as compared with the SADI-S and S groups.

CONCLUSION

In mildly obese diabetic rat, SADI-S and RYGB procedures have comparable efficacy in diabetes remission and risk of micronutrient deficiency. These data show that each of the surgery accomplishes diabetes improvements through both overlapping and distinct mechanisms requiring further investigation.

Duodenal long noncoding RNAs are associated with glycemic control after bariatric surgery in high-fat diet-induced diabetic mice

BACKGROUND

The duodenum plays a role in the mechanism of type 2 diabetes remission after bariatric surgery. Roux-en-Y gastric bypass (RYGB) may change gene expression in the duodenum and metabolism. Long noncoding RNAs (lncRNAs) constitute a novel class of RNAs that regulate gene expression. Little is known about how duodenal lncRNAs respond to RYGB. Logically, studies on the changes of duodenal lncRNAs potentially can lead to an understanding of the mechanisms of bariatric surgery, as well as discovery of antidiabetic drug targets and biomarkers predicting postoperative outcome.

OBJECTIVES

To investigate the expression signature of duodenal lncRNAs associated with glycemic improvement by duodenal-jejunal bypass (DJB), a component of RYGB, on a genome-wide scale in high-fat diet-induced diabetic mice.

SETTING

University medical center.

METHODS

High fat diet-induced diabetic mice were randomized into 2 groups receiving either the DJB or a sham procedure. Microarray was applied to screen the differentially expressed lncRNAs and messenger RNAs (mRNAs) in the duodenum between the DJB and sham groups, and the result was validated by quantitative real-time polymerase chain reaction in another cohort of animals. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were performed to predict the potential lncRNA functions. Based on Pearson correlation analysis, the lncRNA-mRNA and lncRNA-transcription factor (TF) interaction networks were constructed to identify and rank core regulatory lncRNAs and transcription factors.

RESULTS

A total of 301 lncRNAs, including 232 that were upregulated and 69 downregulated (fold change≥2.0), were differentially expressed in the duodenum between the DJB and sham groups. GO enrichment indicated that these lncRNA-coexpressed mRNAs were correlated with biological processes including cell proliferation, digestion, and catabolic and biosynthetic processes. KEGG pathway analysis revealed that in addition to the digestion and absorption signaling pathways, pancreatic secretion- and inflammatory process-related signaling pathways were mostly enriched in the DJB group. In addition, the lncRNA-mRNA interaction network combined with GO and KEGG pathway analysis suggested that as a top-ranked gene, NONMMUG021726 may play an important role in the mechanism of type 2 diabetes remission after DJB.

CONCLUSION

DJB leads to drastic changes in lncRNA and mRNA expressions in the duodenum. The majority of top-ranked lncRNAs and mRNAs have roles in pancreatic secretion and inflammatory processes, implying that bypass of the duodenum may initiate insulin secretion and attenuate inflammation. In addition, modulators of such lncRNAs, most likely NONMMUG021726, have potential to become therapeutic targets or biomarkers for prediction of the outcomes of bariatric surgery.