Real-World Efficacy of Glucagon-like Peptide-1 (GLP-1) Receptor Agonist, Dulaglutide, on Metabolic Parameters in Japanese Patients with Type 2 Diabetes: A Retrospective Longitudinal Study

The glucagon-like peptide-1 receptor agonist (GLP-1RA) dulaglutide has been shown to improve body weight and glycemic control and reduce major cardiovascular (CV) events. In Japan, dulaglutide is used at a fixed dose of 0.75 mg, which is lower than that in Europe and North America. However, the reports of real-world efficacy on metabolic parameters in Japanese patients with type 2 diabetes (T2DM) are limited. This study aimed to examine the real-world efficacy of GLP-1RA dulaglutide on metabolic parameters in Japanese patients with T2DM. We retrospectively selected patients with T2DM who had been prescribed dulaglutide continuously for 12 months or longer between September 2015 and December 2020 and compared metabolic parameters at baseline with the data at 12 months after the start of dulaglutide. One hundred twenty-one patients were enrolled in this study. The 12-month dulaglutide treatment reduced body weight by 1.7 kg and hemoglobin A1c by 1.1%. Significant improvements were also observed in serum high-density lipoprotein cholesterol (HDL-C), triglyceride (TG) and non-HDL-C. The change in HbA1c during dulaglutide treatment was significantly correlated with the changes in HDL-C (R = −0.236, p = 0.013), LDL-C (R = 0.377, p = 0.005) and non-HDL-C (R = 0.415, p < 0.001). The improvements in HbA1c, HDL-C, TG and non-HDL-C were greater in patients concurrently treated with SGLT2 inhibitors (SGLT2is) at baseline. In conclusion, the treatment with dulaglutide has beneficial effects on multiple CV risk factors in Japanese patients with T2DM.


Introduction
The prevalence of diabetes is increasing worldwide, and the situation is critical in Asia. It was estimated that 90 million adults in Southeast Asia suffered from diabetes in 2010, and the number was expected to reach 113 million by 2030 [1]. Despite recent developments in pharmacotherapy, the life expectancy of diabetes was shorter than the general population [2].
One of the leading causes of mortality in patients with diabetes is cardiovascular (CV) disease. CV diseases accounted for 14.9% of deaths in Japanese patients with diabetes [2]. Large-scale trials suggested the importance of interventions against CV risk factors such as hyperglycemia, dyslipidemia and obesity to prevent CV diseases in patients with diabetes [3].
Glucagon-like peptide-1 (GLP-1) is a peptide hormone that is secreted by enteroendocrine cells and promotes insulin secretion from pancreatic beta cells. Dulaglutide is one of the human GLP-1 receptor agonists (GLP-1RAs), administered as a once-weekly subcutaneous injection, and is used worldwide for the treatment of type 2 diabetes (T2DM) [4]. Previous reports revealed that dulaglutide improved glycemic control with a lower risk

Statistical Analysis
Comparison of the variables before and after the dulaglutide treatment was analyzed by the Wilcoxon signed-rank test. Pearson's simple correlation coefficients were performed to determine the correlations between the parameters. All data are expressed as mean ± SD, and p < 0.05 was considered to be statistically significant. Statistical analysis was conducted using SPSS version 23 (IBM, US).

Baseline Characteristics of Patients Studied
We found 197 patients who had been first prescribed dulaglutide between 1 September 2015 and 31 December 2020. Among them, 25 patients did not visit our hospital regularly. Five patients died during the observational period due to cancer (n = 3), cerebral infarction (n = 1) and pneumonia (n = 1). In 22 patients, dulaglutide prescription was suspended and switched to other antihyperglycemic agents in 18 patients (insulin 1, other GLP-1RAs 2, dipeptidyl peptidase-4 (DPP-4) inhibitors 13, metformin 1 and SGLT2 inhibitor 1). We also excluded 24 patients due to lack of sufficient data. Thus, we enrolled 121 patients in this study.
The baseline characteristics of the patients are presented in Table 1. Dulaglutide was administered at a dose of 0.75 mg in all patients. The mean age of the patients was 64.7 ± 15.6 years, and the mean BMI was 26.8 ± 5.7 kg/m 2 . Among the hypoglycemic agents, metformin was mostly used (47.9%), followed by SGLT2 inhibitors (43.0%) and Thiazolidinedione (30.0%). Insulin was used in 28 patients (23.1%). The most prescribed drug for hypertension was calcium channel blockers (47.9%) followed by angiotensin II receptor blockers (41.3%). Of all patients, 54.5% received statins. Antiplatelet drugs were prescribed in 18 patients (14.9%).

Changes in Metabolic Parameters during 12-Month Dulaglutide Parameters
Changes in metabolic parameters at 12 months after the start of dulaglutide are shown in Table 2. HbA1c decreased by 1.1%, and the body weight decreased by 1.7 kg during 12-month dulaglutide therapy. Significant improvements were also observed in systolic blood pressure, plasma glucose, serum albumin, HDL-C, TG and non-HDL-C. Serum γGTP and NFS were also improved, whereas HSI and FIB-4 index were not changed during the dulaglutide treatment. There were also no significant changes in eGFR, uric acid and ACR. Table 3 shows the gender differences in the changes in metabolic parameters during the 12-month dulaglutide treatment. Significant improvements in plasma glucose, HbA1c, γGTP and NFS were observed in both male and female patients. Body weight and BMI were improved significantly in males, and there were the same tendencies in females. Serum TG and non-HDL-C levels decreased only in males, whereas HDL-C levels increased only in females.

Correlations between the Baseline and the Changes in Metabolic Parameters
The significant correlations between the baseline values and the changes during 12 months of dulaglutide treatment were observed in NFS (R = −0.265, p = 0.007), the FIB-4 index (R = −0.325, p < 0.001) and ACR (R = −0.473, p < 0.001) ( Figure 1). The same tendency was also observed in HSI (R = −0.224, p = 0.064).

Correlations among the Changes in Metabolic Parameters
The correlations between the changes in metabolic parameters during the 12-month dulaglutide treatment are provided in Table 4. The changes in HbA1c were significantly correlated with the changes in HDL-C (R = −0.236, p = 0.013), LDL-C (R = 0.377, p = 0.005) and non-HDL-C (R = 0.415, p < 0.001). Nevertheless, the change in BMI was not correlated with the changes in HbA1c, TC, LDL-C and non-HDL-C. The change in HSI was correlated with the change in BMI, but not with the change in NFS or the FIB-4 index.

Correlations between the Baseline and the Changes in Metabolic Parameters
The significant correlations between the baseline values and the changes during 12 months of dulaglutide treatment were observed in NFS (R = −0.265, p = 0.007), the FIB-4 index (R = −0.325, p < 0.001) and ACR (R = −0.473, p < 0.001) (Figure 1). The same tendency was also observed in HSI (R = −0.224, p = 0.064).

Correlations among the Changes in Metabolic Parameters
The correlations between the changes in metabolic parameters during the 12-month dulaglutide treatment are provided in Table 4. The changes in HbA1c were significantly correlated with the changes in HDL-C (R = −0.236, p = 0.013), LDL-C (R = 0.377, p = 0.005) and non-HDL-C (R = 0.415, p < 0.001). Nevertheless, the change in BMI was not correlated with the changes in HbA1c, TC, LDL-C and non-HDL-C. The change in HSI was correlated with the change in BMI, but not with the change in NFS or the FIB-4 index.

Subgroup Analysis in Patients with or without Insulin Treatment
We analyzed the changes in metabolic parameters in the subgroups with or without insulin treatments (Table 5), since insulin has anabolic effects and is associated with weight gain [15]. In patients with insulin treatment, significant decreases were observed only in HbA1c, TC, non-HDL-C and NFS, whereas there were significant increases in diastolic blood pressure and uric acid levels. In patients without insulin treatment, there

Subgroup Analysis in Patients with or without Insulin Treatment
We analyzed the changes in metabolic parameters in the subgroups with or without insulin treatments (Table 5), since insulin has anabolic effects and is associated with weight gain [15]. In patients with insulin treatment, significant decreases were observed only in HbA1c, TC, non-HDL-C and NFS, whereas there were significant increases in diastolic blood pressure and uric acid levels. In patients without insulin treatment, there were significant improvements in body weight, BMI, systolic blood pressure, plasma glucose, HbA1c, γGTP, HDL-C, uric acid and NFS.

Subgroup Analysis in Patients with or without SGLT2i Treatment
Since SGLT2 inhibitors were previously reported to reduce body weight and improve glycemia, dyslipidemia and liver function [16][17][18], we divided the patients into two subgroups under the treatments with or without SGLT2 inhibitors and analyzed the changes in metabolic parameters during the 12-month dulaglutide treatment (Table 6). Significant improvements in body weight, plasma glucose, HbA1c and NFS were observed in both groups. TC, HDL-C, TG and non-HDL-C were improved only in the patients with the treatment with SGLT2i. There were no significant changes in HSI, the FIB-4 index and ACR in both groups. Values show mean ± SD. ACR, albumin-to-creatinine ratio; ALT, alanine aminotransferase; AST, aspartate aminotransferase; BMI, body mass index; eGFR, estimated glomerular filtration rate; γGTP, γ-glutamyl transferase; HbA1c, hemoglobin A1c; HDL-C, high-density lipoprotein cholesterol; HSI, hepatic steatosis index; LDL-C, lowdensity lipoprotein cholesterol; NFS, NAFLD fibrosis score; TC, total cholesterol; TG, triglyceride.

Discussion
In this study, we examined the real-world efficacy of once-weekly subcutaneous dulaglutide on metabolic parameters in Japanese patients with T2DM. The dulaglutide treatment was associated with improvement in obesity, glycemia and atherogenic lipid profile.
Reductions from baseline in HbA1c and body weight in dulaglutide-treated patients were consistent with previous clinical trials. It was reported that the 52-month dulaglutide treatment with a single oral hypoglycemic agent in Japanese patients with T2DM decreased HbA1c by 1.57% to 1.69% [7]. The other study also showed a reduction in HbA1c by 1.39% after the 52-month dulaglutide monotherapy [8]. In our study, the change in HbA1c during dulaglutide treatment was 1.1%, which was slightly smaller compared to such previous clinical trials. The higher age of the patients and multiple concomitant hypoglycemic agents in our study might influence the smaller degree of HbA1c changes.
Asian patients with T2DM were characterized by relatively lower BMI [19]. A previous study clarified that the degree of HbA1c change was greater during GLP-1RA treatment in normal BMI patients compared to obese patients [20]. It was also reported that GLP-1RAs were more effective in lowering HbA1c in Asian patients with T2DM compared to Caucasians [21]. Our results confirmed that dulaglutide effectively reduced HbA1c in Asian patients with T2DM.
GLP-1RAs have beneficial effects not only on glycemia and obesity but also on lipid profiles. Previous randomized controlled studies including REWIND or TODAY trials reported reductions in serum LDL-C and TG levels [6,22,23]. Moreover, a meta-analysis of four trials revealed that GLP-1RAs improved serum LDL-C, TG and HDL-C levels [24]. In our study, dulaglutide significantly increased serum HDL-C levels and decreased TG and non-HDL-C levels. A tendency for a reduction in LDL-C levels was also observed. These results coincided with previous clinical trials. In other several real-world studies, liraglutide or exenatide also showed improvements in carotid intima-media thickness, suggesting the preventive effects of GLP-1RAs against CV diseases [25,26].
Interestingly, the changes in LDL-C, HDL-C and non-HDL-C were significantly associated with the change in HbA1c, which suggests a close association between the improvements of glycemia and lipid profiles by dulaglutide. In an animal study using ApoE knockout mice, both glycemic control and lipid profile were improved but only observed in STZ-induced diabetic model mice and not in non-diabetic mice [27]. The presence of diabetes or insulin resistance elevates the expression and activity of hormone-sensitive lipase in adipose tissue, which catalyzes lipolysis and the release of free fatty acid (FFA). Increased entry of FFA to the liver inhibits the degradation of apoB-100 and elevated production of very-low-density lipoprotein (VLDL). Insulin resistance reduces the activity of lipoprotein lipase (LPL), which, in turn, increases TG-rich lipoproteins such as intermediate-density lipoprotein (IDL) and VLDL and reduces HDL. These are observed as elevated serum TG levels and decreased HDL-C levels in clinical laboratory tests [28]. Improved insulin action by GLP-1RA can play a crucial role in ameliorating both glycemia and dyslipidemia. GLP-1RAs can promote postprandial insulin secretion and inhibit insulin-mediated lipolysis in adipose tissue, resulting in reductions in FFA release in the bloodstream and entry in the liver [29,30]. GLP-1RAs were also reported to improve insulin resistance [31], which elevates the activity of LPL and ameliorates the lipid profile. Indeed, reductions in VLDL-C levels by GLP-1 RA treatment were already reported [32,33]. Reductions in apoB-100 comprising lipoproteins including IDL, VLDL and LDL can be observed as the improvement in non-HDL-C levels [34], which was observed in our study.
Previous studies reported the beneficial effects of GLP-1RAs in the progression of non-alcoholic fatty liver disease (NAFLD) [35,36]. In our study, dulaglutide treatments improved only NFS, but there were no changes in HSI and the FIB-4 index. Nevertheless, the associations between baseline values and changes in HSI, NFS and the FIB-4 index suggested that dulaglutide could ameliorate steatosis and fibrosis in the liver in patients with advanced steatosis and fibrosis at baseline. The lower dose of dulaglutide used in Japan or the limited number of subjects might influence our results.
The use of GLP-1RAs was also associated with reduced ACR and the risk of worsening kidney function [37,38]. In our study, there were no significant changes in ACR in the whole group or even in the group with SGLT2i treatment, despite the renoprotective effects of SGLT2is [39]. Our results might be affected by various factors, such as the lack of a control group, the limited number of available data on ACR, the short period of observation and the large standard deviation of ACR. Further studies with a control group and longer observation will be necessary to examine the effect of dulaglutide on the progression of NAFLD or diabetic kidney diseases.
Previous reports suggested that the addition of dulaglutide to insulin contributed to better glycemia, smaller doses of insulin and smaller weight gain compared to insulin monotherapy [40]. The combination of insulin and GLP-1RAs was also associated with better lipid profiles and lower blood pressure [41]. These reports suggested that GLP-1RAs might offset the adverse effects of insulin treatments. In our study, dulaglutide improved HbA1c and non-HDL-C in patients treated with insulin, but there were no significant changes in body weight and BMI, which might be influenced by the small number of patients with insulin treatments. Direct comparisons with insulin monotherapy will be needed to determine the effects of the combination therapy of insulin and dulaglutide.
SGLT2is have also been reported to improve obesity, glycemia and lipid profiles and were associated with reduced cardiorenal events [16,17,42]. The mechanisms of cardiorenal effects of SGLT2is include attenuation of CV risk factors, amelioration of substrate utilization in myocardial and renal cells, reduction in ventricular and vascular loading through diuresis and natriuresis, and mitigation of atherosclerosis through anti-inflammatory and anti-oxidative effects [42,43]. GLP-1RAs have also been reported to preserve ventricular function and reduce atherosclerosis [44]. These effects of SGLT2is and GLP-1RAs can be complementary in the prevention of CV diseases. Indeed, a meta-analysis revealed that the combination therapy of SGLT2i and GLP-1RA resulted in greater reductions in body weight, HbA1c and LDL-C [45]. Our real-world data confirmed the greater benefits of the combination of SGLT2i and GLP-1RA on glycemia and lipid profiles, suggesting a promising strategy to prevent the progression of CV and renal diseases in high-risk patients [46,47].
Our study has several limitations. First, it was a retrospective study with a limited number of patients in a single center. Second, we cannot exclude possible influences by modifications of the pharmacotherapy. Third, our study lacked information on diabetic durations, co-existing diabetic complications and lifestyle modifications. Fourth, a lack of data might influence the results. Fifth, we could not evaluate metabolites or inflammation markers which might be related to the effects of dulaglutide, since our study was based on real-world data.

Conclusions
Our findings based on real-world data showed that dulaglutide improved body weight, glycemic control and lipid profiles in Japanese patients with T2DM, suggesting dulaglutide as a promising therapy to control CV risk factors. Moreover, the close associations between the changes in lipid profiles and the change in HbA1c during dulaglutide treatments is intriguing in speculating the presence of common mechanisms of improving glycemia and dyslipidemia by dulaglutide. Informed Consent Statement: Informed consent was obtained by the opt-out approach because this study was a retrospective observational study.

Data Availability Statement:
The data supporting the findings of this study are available from the corresponding author upon reasonable request.