Identification of Proteins Associated with the Early Restoration of Insulin Sensitivity After Biliopancreatic Diversion

Abstract

Context: Insulin resistance (IR) is a risk factor for type 2 diabetes, diabetic kidney disease, cardiovascular disease and nonalcoholic steatohepatitis. Biliopancreatic diversion (BPD) is the most effective form of bariatric surgery for improving insulin sensitivity.

Objective: To identify plasma proteins correlating with the early restoration of insulin sensitivity after BPD.

Design: Prospective single-center study including 20 insulin-resistant men with morbid obesity scheduled for BPD. Patient characteristics and blood samples were repeatedly collected from baseline up to 4 weeks postsurgery. IR was assessed by homeostatic model assessment for insulin resistance (HOMA-IR), Matsuda Index, and by studying metabolic profiles during meal tolerance tests. Unbiased proteomic analysis was performed to identify plasma proteins altered by BPD. Detailed plasma profiles were made on a selected set of proteins by targeted multiple reaction monitoring mass spectrometry (MRM/MS). Changes in plasma proteome were evaluated in relation to metabolic and inflammatory changes.

Results: BPD resulted in improved insulin sensitivity and reduced body weight. Proteomic analysis identified 29 proteins that changed following BPD. Changes in plasma levels of afamin, apolipoprotein A-IV (ApoA4), and apolipoprotein A-II (ApoA2) correlated significantly with changes in IR.

Conclusion: Circulating levels of afamin, ApoA4, and ApoA2 were associated with and may contribute to the rapid improvement in insulin sensitivity after BPD.

Trial registration: ClinicalTrials.gov NCT01151917.

Keywords: afamin; apolipoprotein A-II; apolipoprotein A-IV; biliopancreatic diversion; insulin resistance; proteomic analysis.

© Endocrine Society 2020.

Figures

Figure 1.

Outline of study protocol. Timing of the visits in relation to Day zero when the biliopancreatic diversion (BPD) surgery was performed. Blood sampling and study procedures were conducted at visits illustrated with an x.

Figure 2.

Time course of body weight and CRP changes over the study period. Body weight (A) and CRP (B) were measured repeatedly throughout the study. Data are presented as mean ± 95% CI and all comparisons are made to B1. Mixed linear models were used to analyze repeated measures data with fixed effects for visit sequence and with a random patient effect. ***P < 0.0001 except B1 vs Day 3 P = 0.00035. Corrected for multiplicity with Dunnet’s method. n = 15-19.

Figure 3.

Rapid reduction in insulin resistance following BPD. Fasting plasma glucose (A), insulin (B) and HOMA-IR (C) were measured throughout the study. Data are presented as mean ± 95% CI and all comparisons are made to B1. Mixed linear models were used to analyze repeated measures data with fixed effects for visit sequence and with a random patient effect. Corrected for multiplicity with Dunnet’s method. A) ***P < 0.0001 except Day 5 vs B1 P = 0.000155; B) *P = 0.0455, ***P < 0.0001 except Day 5 vs B1 P = 0.000210; C) Day 0 vs B1 **P = 0.00621, Day 1 vs B1 ***P < 0.0001, Day 7 vs B1 **P = 0.00455, Day 14 vs B1 ***P = 0.000254, Day 28 vs B1 ***P = 0.000145. n = 15-19.

Figure 4.

Improved metabolic control 14 days after BPD. Glucose (A), Insulin (B), NEFA (C) and Matsuda index (D) following a meal tolerance test (MTT) on B1 and Day 14 after BPD. Data are presented as mean ± 95% CI. Statistical testing was performed on the AUC and on mean fasting values collected just before the MTT (−30 and −1 minutes), see results for values (A-C). Paired t-test was used for Matsuda index. *** P < 0.0001. n = 19.

Figure 5.

Change in protein expression following BPD. Unbiased LC-MS/MS proteomics identified 29 unique proteins that were significantly changed between baseline and 4 weeks postsurgery. Heatmap (A) visualizes that 10 proteins were upregulated and 19 were downregulated in response to surgery. The horizontal axis shows the 4 time-points when the samples were collected: fasted before MTT (t = −20), fed 90 minutes after initiation of MTT (t = 90) before and after BPD (B1 and P2, respectively) and on the vertical axis the gene symbols corresponding to the differentially regulated proteins are shown. The Volcano plot (B) shows the magnitude of change (x-axis) and statistical significance (y-axis) of the complete set of 289 assessed proteins in fasting samples only. Proteins appearing on the right and left of x = 0 are up- and downregulated, respectively, in response to BPD. Significantly changed proteins are colored in light red and selected proteins referred to in the text are labeled with gene symbols.

Figure 6.

Time-resolved protein expression and correlations to HOMA-IR and CRP. Two main profiles emerged when studying the MRM/MS protein profiles in plasma samples collected in fasting state throughout the study. One following the HOMA-IR profile as shown for afamin (A), ApoA2 (B), and ApoA4 (C) and the other one following the CRP profile as shown for C9 (D), SERPINA1 (E) and SERPINA3 (F). Gene names are used for simplicity and the corresponding protein names can be found in Supplemental Materials, Table S2 (17). To facilitate graphing all values have been normalized to have mean 0 and standard deviation 1. Absolute values are found in Fig. 2B (CRP), 3C (HOMA-IR), and Supplemental Materials, Figure S4 (17) (MRM/MS data). n = 19.