Objective To compare the effects of metformin and insulin on the intestinal uptake of ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) in patients with diabetes mellitus undergoing PET/CT.

Methods The clinical and imaging data of 70 diabetic patients (41 males and 29 females, aged between 38 and 86 (62.9±12.4) years old) who underwent ¹⁸F-FDG PET/CT examination in the First Affiliated Hospital of Xi'an Jiaotong University from January 2017 to January 2019 were retrospectively analyzed. The patients were divided into the metformin treatment group and insulin treatment group according to the hypoglycemic drugs used. Non-diabetic patients undergoing physical examination or tumor screening (38 cases, including 22 males and 16 females, aged between 16 and 82 (55.0±13.0) years old) were collected as the control group. The PET/CT images of the intestine were visually rated, and the ¹⁸F-FDG maximum standardized uptake value (SUV_max) of each segment of the intestine was measured. The Chi-square test was used to compare the gender differences of the subjects in the three groups. The nonparametric Kruskal–Wallis rank sum test was used to compare the visual rating of the extent of intestinal uptake in the three groups, and paired analysis was conducted. One-way analysis of variance was used to compare the general data and the differences in the SUV_max of each segment of the intestine and the right rectus femoris muscle among the three groups. Further comparisons were made between the groups by LSD-t test.

Results Statistically significant differences were observed in the image visual score of the intestinal tract in the metformin treatment group and between the insulin treatment group and the control group (H=25.988, 21.548; both P<0.05). Compared with the control group, except for the duodenum, SUV_max of jejunum (2.23±0.51 vs. 2.60±0.57), ileum (2.19±0.66 vs. 2.95±1.66), ascending colon (2.65±1.03 vs. 4.56±3.09 ), transverse colon (2.09±0.83 vs. 3.37±2.15 ), descending colon (2.37±1.06 vs. 4.72±3.51), sigmoid colon (2.74±1.12 vs. 5.26±3.34), rectum (3.40±1.06 vs. 5.74±3.27) in metformin treatment group were significantly higher, and all differences were statistically significant (t=2.133–4.699, all P<0.05). Compared with the insulin treatment group, the SUV_max values of the jejunum (2.26±0.41 vs. 2.60±0.57), ileum (2.13±0.58 vs. 2.95±1.66), ascending colon (2.84±1.15 vs. 4.56±3.09), sigmoid colon (3.79±2.68 vs. 5.26±3.34), and rectum (3.89±2.34 vs. 5.74±3.27) in the metformin treatment group were significantly higher than those in the insulin treatment group, and all differences were statistically significant (t=2.002–2.977, all P<0.05).

Conclusion Metformin can increase the intestinal uptake of ¹⁸F-FDG in diabetic patients, whereas insulin has less effect on the intestinal uptake of ¹⁸F-FDG.