Mechanism of Roux-en-Y gastric bypass treatment for type 2 diabetes in rats

Abstract

Objectives: Roux-en-Y gastric bypass (RYGB) is a novel therapy for diabetes. We aimed to explore the therapeutic mechanism of RYGB.

Methods: After RYGB, animal models were established, and gene expression profile of islets was assessed. Additionally, gastrointestinal hormones were measured using enzyme-linked immunosorbent assays. Ca(2+) was studied using confocal microscopy and patch-clamp technique. The morphology of islets and beta cells was observed using optical microscopy and electron microscopy.

Results: RYGB was an effective treatment in diabetic rats. Expression profiling data showed that RYGB produced a new metabolic environment and that gene expression changed to adapt to the new environment. The differential expression of genes associated with hormones, Ca(2+) and cellular proliferation was closely related to RYGB and diabetes metabolism. Furthermore, the data verified that RYGB led to changes in hormone level and enhanced Ca(2+) concentration changes and Ca(2+) channel activity. Morphological data showed that RYGB induced the proliferation of islets and improved the function of beta cells.

Conclusions: RYGB promoted a new metabolic environment while triggering changes to adapt to the new environment. These changes promoted the cellular proliferation of islets and improved the function of beta cells. The quantity of beta cells increased, and their quality improved, ultimately leading to insulin secretion enhancement.

Fig. 1

Effect of RYGB on the gene expression of islets. a Differentially expressed genes in islets were screened by fold analysis. Red plots indicate relatively increased expression (log ratio ≥2.0), black indicates median expression, and green indicates decreased expression (log ratio ≤0.5). b Pie chart of GO mapping illustrates the biological process, molecular function, and cellular component of the differentially expressed genes. Comparing the operation cohorts with the control cohorts, 685 differentially expressed genes were identified. The differentially expressed genes were analyzed using the Molecule Annotation System, and biological regulation-, regulation of biological process-, and metabolism-related genes accounted for a large proportion (up to 49.6 %). Thus, these differentially expressed genes were mainly associated with metabolic regulation. GO mapping suggested that the RYGB procedure led to the creation of a new metabolic environment, and the expression of genes that were primarily related to metabolic regulation was adjusted to adapt to the new metabolic environment. c Venn diagram of the differentially expressed genes according to the RYGB procedure and diabetes metabolism. The circle with “519” indicates 519 differentially expressed genes between WTO and WT, and the circle with “158” indicates 158 differentially expressed genes between GKO and GK. The intersection of the two circles with “30” indicates that the 30 genes were the result of RYGB. The circle with “469” indicates 469 differentially expressed genes between GK and WT. The intersection of the three circles with “13” indicates that 13 genes were closely related to the RYGB procedure and diabetes metabolism

Fig. 2

Effect of RYGB on fluorescence intensity changes of insulin and calcium. a Beta cells were imaged using confocal microscopy after intracellular insulin was labeled with FITC and free Ca²⁺ was labeled with fluo-4/AM. The red image shows the FITC channel, and the green image shows the fluo-4/AM channel. The scale bars in the images represent 8 μm. The fluorescence detection channel was set to the following ranges: fluo-4/AM, 494–516 nm; FITC, 490–495 nm. b Effect of RYGB on fluorescence intensity changes of insulin. c Effect of RYGB on fluorescence intensity changes of calcium. RYGB increased the fluorescence intensity changes in intracellular insulin and intracellular free Ca². *P < 0.05, **P < 0.01, significant difference

Fig. 3

Effect of RYGB on calcium channels. a Ramp depolarization potential-activated voltage-dependent Ca²⁺ influx. The T-type voltage-dependent Ca²⁺ channel (VDCC) opened at −50 mV membrane potential. The L-type VDCC opened with an increase in membrane potential and peaked at 0 mV, as observed by the twin peak pattern. b Effect of RYGB on L-type VDCC current density. c Effect of RYGB on T-type VDCC current density. L-type and T-type VDCC current densities in the GK cohort were higher than were those in the WT cohort. RYGB did not alter L-type or T-type VDCC current densities. d The stored operated calcium (SOC) current changed over time to −100 mV. The curve reflects SOC channel activation, deactivation, and inactivation. e Effect of RYGB on SOC current density. RYGB enhanced SOC current density. **P < 0.01, significant difference

Fig. 4

Effect of RYGB on the morphology of islets and beta cells. Sections were observed by OM. The islets were regular in shape and size in the WT cohort. The islets were irregular in shape and size in the GK cohort. At 4 weeks after RYGB, small islets were present in operation cohorts. Ultra-thin sections of islets were viewed by TEM. Secretory vesicles: LDCVs were abundant in beta cells of the WT cohort. LDCVs were relatively scarce in most beta cells of the GK cohort. At 4 weeks after RYGB, LDCVs were more abundant in beta cells of operation cohorts. The scale bars in the images represent 20 μm and 500 nm. OM optical microscopy, TEM electron microscopy