Abstract
Aims/hypothesisThe mechanisms for improved glycemic control after bariatric surgery in subjects with type 2 diabetes (T2D) are not fully known. We hypothesized that dynamic hepatic blood responses to a mixed-meal are changed after bariatric surgery in parallel with an improvement in glucose tolerance.MethodsA total of ten morbidly obese subjects with T2D were recruited to receive a mixed-meal and a glucose-dependent insulinotropic polypeptide (GIP) infusion before and early after (within a median of less than three months) bariatric surgery, and hepatic blood flow and volume (HBV) were measured repeatedly with combined positron emission tomography/MRI. Ten lean non-diabetic individuals served as controls.ResultsBariatric surgery leads to a significant decrease in weight, accompanied with an improved β-cell function and glucagon-like peptide 1 (GLP-1) secretion, and a reduction in liver volume. Blood flow in portal vein (PV) was increased by 1.65-fold (P = 0.026) in response to a mixed-meal in subjects after surgery, while HBV decreased in all groups (P < 0.001). When the effect of GIP infusion was tested separately, no change in hepatic arterial and PV flow was observed, but HBV decreased as seen during the mixed-meal test.Conclusions/interpretationEarly after bariatric surgery, PV flow response to a mixed-meal is augmented, improving digestion and nutrient absorption. GIP influences the post-prandial reduction in HBV thereby diverting blood to the extrahepatic sites.
Highlights
The liver plays a pivotal role in the regulation of human glucose metabolism, and defects in hepatic insulin signaling predispose to hyperglycemia and type 2 diabetes (T2D) (1, 2)
After surgery weight was decreased by a median of 14.7 (12.2–20.4) kg, accompanied with a significant reduction in liver volume and improvements in glucose sensitivity, insulin clearance and sensitivity, and glycemic control, with no difference between RYGB and VSG groups (Supplementary Table 1, see section on supplementary data given at the end of this article)
Bariatric surgery leads to rapid gastric emptying, enhanced effect of incretin hormones and reduced liver fat content (18, 19, 20, 21, 22), whereas little is known about splanchnic blood dynamics after surgical gastrointestinal anatomical change
Summary
The liver plays a pivotal role in the regulation of human glucose metabolism, and defects in hepatic insulin signaling predispose to hyperglycemia and type 2 diabetes (T2D) (1, 2). The incretin hormones glucose-dependent insulinotropic polypeptide (GIP) and glucagonlike peptide 1 (GLP-1) account for the gut-derived amplification of insulin secretion (4). In addition to the effect on pancreatic islets, we (5) and others (6) have shown that GIP contributes to the redistribution of gastrointestinal blood flow after meal ingestion. Whether these extrahepatic splanchnic vascular effects are reflected by changes in hepatic blood dynamics is not known
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