Mulberry Twig Alkaloids Combined With Insulin Infusion: Effects on Blood Glucose Variability in Type 2 Diabetes

Introduction

Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by chronically elevated blood glucose level due to insufficient insulin secretion and/or insulin resistance, the incidence of which has continued to rise in recent years. The International Diabetes Federation (IDF) estimated that the prevalence of diabetes is likely to reach 700 million by 2045, due to the rising incidence of obesity, population aging, and pandemics of infectious diseases such as coronavirus pneumonia [1]. As the disease progresses, most diabetic patients have a gradual decrease in pancreatic β-cell function and reduced ability to regulate blood glucose, resulting in large fluctuations in blood glucose levels [2], which can lead to long-term T2DM complications via activation of oxidative stress, exacerbation of inflammation, and damage to endothelial cells [3]. Therefore, the harm of poor blood variability is worse than that of long-term hyperglycemia. For patients with T2DM, choosing an appropriate anti-hyperglycemia treatment to restore the damaged islet β-cell function and effectively control blood glucose variability is the key to diabetes management.

Mulberry twig alkaloids (MTA) are active polyhydroxy alkaloids extracted from Morus alba L. twigs, a medicinal plant. The total alkaloid content can reach 50% in MTA, and its main active components are 1-deoxynojirimycin (DNJ), trigonelline, and tyrosol [4]. MTA has been reported as a natural α-glucosidase inhibitor and it lowered fasting glucose level and prolonged peak glucose concentration after starch loading [5,6]. Continuous subcutaneous insulin infusion (CSII) is a widely recognized insulin pump-based intensive treatment method. By simulating the physiological secretion of insulin, it delivers basal insulin continuously over 24 hours along with pre-prandial bolus doses, which can rapidly control blood glucose, eliminate the toxic effects of hyperglycemia, and reduce glucose viability. CSII therapy has become a relatively common clinical treatment for diabetic patients [7]. CSII primarily works by supplementing exogenous insulin to mimic physiological insulin secretion. It maintains stable fasting and pre-prandial blood glucose levels through basal insulin infusion, inhibits hepatic glycogenolysis and gluconeogenesis, and prevents excessive fasting blood glucose or nocturnal hypoglycemia. Pre-prandial bolus doses can counteract postprandial blood glucose elevation and reduce postprandial blood glucose peaks. However, it has no direct effect on the intestinal absorption of carbohydrates. If the proportion of carbohydrates in a patient’s diet is too high or digestion is too rapid, CSII alone may require a larger dose of pre-prandial insulin, which easily leads to increased postprandial blood glucose fluctuation or a risk of hypoglycemia in the late phase of the insulin action peak.

By inhibiting α-glucosidase, MTA slows the rate of carbohydrate breakdown into glucose, allowing glucose to enter the bloodstream slowly. This mechanism fundamentally reduces the sudden rise in postprandial blood glucose [5]. It precisely compensates for CSII’s inadequacy in regulating carbohydrate absorption, lowers the difference between postprandial blood glucose peaks and pre-prandial blood glucose levels, and reduces postprandial blood glucose variability. Meanwhile, due to the delayed absorption of glucose, the insulin demand curve becomes flatter and more aligned with the insulin action curve of CSII infusion, avoiding blood glucose fluctuation caused by the asynchrony between insulin action and glucose absorption. When used together with MTA, CSII can accurately supplement insulin and regulate the overall balance of blood glucose metabolism, while MTA delays carbohydrate absorption and optimizes the pattern of postprandial blood glucose elevation. CSII combined with MTA can effectively narrow the range of blood glucose fluctuation and brings blood glucose closer to the stable level under physiological conditions.

Xiaoke disease is a classic disease term in traditional Chinese medicine (TCM), which mainly corresponds to diabetes mellitus (DM) in modern Western medicine. The typical symptoms of Xiaoke disease, often summarized as “three polys (polydipsia, polyphagia, polyuria) and one emaciation” in TCM theory, are consistent with the common symptoms of diabetes. As a Chinese original antihyperglycemic drug, MTA tablet was released in 2020 to treat Xiaoke [8], and several studies showed that MTA can reduce blood glucose fluctuation by alleviating insulin resistance, increasing insulin secretion, and regulating the gut microbiota [9–11]. CSII was commonly used to treat poorly controlled diabetes mellitus with obvious blood glucose variability [12,13]. Few studies have assessed the effects of MTA and its combination with CSII in controlling blood glucose variability. The flash glucose monitoring system (FGM) can monitor blood glucose for 24 hours and is widely used to evaluate short-term glucose variability [14]. Therefore, we aimed to investigate the use of FGM in the practice of the combined scheme to treat type 2 diabetes and observe the effects of MTA+CSII on the blood glucose variability.

Material and Methods

STUDY DESIGN AND SUBJECTS:

We enrolled 60 hospitalized patients with type 2 diabetes in the Department of Integrated Chinese Medicine and Western Medicine of Chu Hisen-I Memorial Hospital of Tianjin Medical University from October 2023 to February 2024.

The a priori power analysis was performed with G*Power 3.1.9.7. by using a two-tailed α=0.05, 1-β=0.80, effect size=0.5, and 2 groups. The analysis yielded a minimum required total sample of N=60 (30 patients per group).

Blinding: (1) Participants were blinded to group allocation; (2) Treating physicians and nurses were not blinded (responsible for insulin administration and insulin titration); (3) Outcome investigators (for TCM scores, glycemic variability indicators) were not blinded; (4) Data analysts were blinded to group allocation during statistical analysis.

Inclusion criteria: type 2 diabetic patients diagnosed by the WHO criteria of 1999, duration of diabetes from 1 month to 10 years, age 18–60 years, baseline hemoglobin A1c (Hb_A1c) level 9.0–15.0%, body mass index (BMI) 24–35 kg/m², and no intention to undergo computed tomography or magnetic resonance imaging during the study.

Exclusion criteria: type 1 diabetes, severe diabetic complications such as diabetic ketoacidosis, coronary artery disease, severe liver or kidney diseases, infectious or gastrointestinal diseases, intolerance to α-glucosidase inhibitor, pregnancy or breast-feeding, receiving other α-glucosidase inhibitor, and other reasons making them unsuitable for this trial.

The diagnostic criteria for Xiaoke referred to the 2007 edition of “Guide to the Prevention and Treatment of Diabetes Mellitus by TCM (Chinese)”. The primary symptoms (dry mouth and pharynx, tiredness, and fatigue) and secondary symptoms (thirst, shortness of breath, lethargy, spontaneous sweating, night sweating, palpitations, and insomnia) were combined for diagnosis.

RANDOMIZATION AND TREATMENT:

Once enrolled, sealed numbers were generated consecutively for subjects and they were randomly assigned to the MTA group and control group according to the number at a 1: 1 ratio. After enrollment, all subjects received insulin aspartate (NoVo Rapid, 3 ml: 300 u, Novo Nordisk China Pharmaceutical Co., Ltd.) by continuous subcutaneous insulin infusion with an insulin pump (MiniMed 722, Medtronic, USA). The MTA group was treated with MTA (Beijing WuheBoao Pharmaceutical Co., Ltd.) 50 mg, 3 times per day based on the CSII. The initial insulin dosage was 0.5 IU/kg/day and the basal infusion was 50% of the total daily dosage. The other 50% was distributed as bolus dosage at each meal.

During the treatment, all subjects wore a FGM device (Abbott, USA) to monitor blood glucose fluctuation. The probe of FGM device was implanted by a single nurse who was specialized in diabetes care. The target of fasting blood glucose (FPG) was <7.0 mmol/L and postprandial blood glucose <10.0 mmol/L. Blood glucose is considered to normal at 7 to 10 mmol/L. A team of 2 dedicated endocrinologists, who strictly followed a standardized insulin titration protocol, adjusted the basal and bolus doses of insulin infusion by 2 to 8 units daily to maintain blood glucose within the target range throughout the study. The insulin dosage was adjusted according to the FGM results, which needed no calibration for analysis.

Throughout the trial, all subjects were provided with education on diabetic diet and exercise guidance. The daily diabetic diet was 50% of carbohydrate (300 g rice or noodle),15% fat, and 35% protein. For daily physical exercise, the diabetes education nurse led all subjects in performing traditional Chinese tai chi for 30 min after each meal.

Adverse events (AEs) were identified in the following methods: 1) Daily structured inquiries by nursing staff; 2) Spontaneous reporting by patients; 3)Clinical observation during routine assessments and recorded by using a standardized AE reporting form, including details on onset time, duration, symptoms, and interventions.

GENERAL INFORMATION:

We collected information on age, sex, duration of diabetes mellitus, blood pressure, BMI, insulin dosage, and FGM indicators on the first day of enrollment. The fasting blood glucose, 2-hour postprandial blood glucose, glycosylated hemoglobin, glomerular filtration rate, and urine albumin were measured.

FLASHING GLUCOSE MONITORING (FGM) INDICATORS:

Intra-day blood glucose variability indicators were mean blood glucose level (MBG), standard deviation (SDBG), average blood glucose fluctuation range (MAGE), coefficient of variation (CV), mean of daily difference (MODD), percentage of time in the target range between 3.9 and 10.0 mmol/L (TIR), percentage of time below the target range <3.9 mmol/L (TBR), and percentage of time above the target range >10.0 mmol/L (TAR).

TCM SYNDROME SCORE:

The TCM syndrome score was collected at enrollment and after 14 days of treatment.

The main symptoms (tiredness and fatigue, dry mouth and throat, thirst, shortness of breath, palpitations, insomnia, spontaneous sweating, and night sweating) were scored as mild (2 points), moderate (4 points), or severe (6 points). The total points were calculated for each group.

STATISTICAL METHODS:

SPSS 23.0 software was used to perform statistical analysis. For normally distributed variables, a paired t test was used to compare intra-group differences and the independent t test was used to compare differences between groups. Wilcoxon’s rank test was used for non normally distributed continuous variables. The chi-square test was used to analyze the differences in proportions. Differences were considered statistically significant at P<0. 05. We calculated 95% confidence intervals (CI) for the TCM symptom score mean change from baseline.

Results

COMPARISON OF GENERAL INFORMATION BETWEEN GROUPS:

There were no dropouts and no missing data throughout the trial. The general information and clinical characteristics of groups are summarized in Table 1. The groups were similar in sex, age, duration of diabetes mellitus, blood pressure, body mass index, glomerular filtration rate, fasting blood glucose, postprandial 2-hour blood glucose, glycosylated hemoglobin, proportion of diabetic retinopathy and neuropathy, microalbuminuria, and blood glucose fluctuation indexes (MBG, SDBG, CV) on the first day of enrollment (all P>0.05) (Table 1).

COMPARISON OF FLASHING BLOOD GLUCOSE MONITORING PARAMETERS BETWEEN GROUPS:

After 14 days of treatment, MBG, SDBG, CV, MODD, MAGE, TAR, and TBR were all decreased in both groups, but compared to the control group, the decrease of MODD, MAGE, TAR, and TBR was statistically significant in the MTA group (all P<0.05). There was no significant difference between the 2 groups in MBG, SDBG, and CV (all P>0.05). TIR (3.9–10.0 mmol/L) was significantly higher in the MTA group compared with the control group (P<0.01) (Table 2, Figure 1).

COMPARISON OF TCM SYMPTOM SCORE BETWEEN GROUPS:

In both groups, the total score of TCM symptoms (thirst, dry mouth and throat, tiredness and fatigue, shortness of breath, palpitations, insomnia, spontaneous sweating, and night sweating decreased after 14 days of treatment (all P<0.05). After treatment, the TCM score of the MTA group was significantly lower than in the control group (P<0.05), with a between-group difference (mean change from baseline (MTA group vs control group) of −8.23, 95% CI (−6.87, −12.72), which indicated that the TCM symptoms were significantly alleviated compared with the control group (Table 3).

HYPOGLYCEMIA INCIDENCE, BODY WEIGHT CHANGE, AND INSULIN DOSAGE AFTER TREATMENT:

All AEs were systematically graded for severity by using the Common Terminology Criteria for Adverse Events, CTCAE v5.0. No severe hypoglycemia (<2.6 mmol/L) occurred throughout the study. The incidence of hyperglycemia or hypoglycemia showed no significant difference between groups. The body weight loss of the MTA group was (−1.26±0.30), which is greater than in the control group (−0.38±0.22) (P<0.05) (Table 4), and the daily insulin dosage in the MTA group was significantly lower than in the control group (0.32±0.14 vs 0.61±0.11 IU/kg/day; P<0.05). Two cases of abdominal distension in the MTA group were recorded and no other gastrointestinal symptoms were reported. Time needed to reach the normal blood glucose range (3.9–10.0 mmol/L) was also compared, and the MTA group needed significantly fewer days than the control group (2.16±0.68 vs 4.16±1.16). Several hyperglycemic episodes were recorded in the control group and no severe hypoglycemia was recorded in either group.

Discussion

STUDY LIMITATION AND FUTURE DIRECTION:

Due to the lack of funding, the sample size was relatively small and the duration of this trial was short. This trial had a small-sample, short-term design, with its core advantage lying in maximizing subject adherence. The small sample size facilitates refined management of each subject by the research team, including full-process guidance on FGM device wear, real-time responses to usage queries, and regular follow-up monitoring. This effectively reduces the risk of decreased adherence caused by complex operations and heavy follow-up burdens. Ultimately, no patients dropped out, ensuring the completeness and continuity of research data, and avoiding sample bias due to loss to follow-up. The conventional wearing period for FGM devices is 14 days, a duration determined based on device technical characteristics, such as sensor lifespan and data storage capacity. Our findings were limited to short-term outcomes (eg, MAGE, MODD) and insulin dose changes over the 14-day study period. No conclusions can be drawn regarding long-term glycemic control, the durability of the observed effects, or the risk of diabetes-related complications (eg, microvascular or macrovascular complications), and long-term follow-up studies are needed to address these questions.

MTA can lower blood glucose through mechanisms such as inhibiting α-glucosidase and protecting pancreatic islet β-cells [9], while CSII can simulate the physiological insulin secretion pattern and precisely control basal and prandial blood glucose [7]. The combined regimen can reduce blood glucose variability and the risk of hypoglycemia, and is particularly suitable for patients with excessive blood glucose variability. For patients with insulin-dependent diabetes, MTA can reduce the insulin dosage and alleviate insulin resistance, and long-term use might help delay the decline of pancreatic islet function. In the future, it is necessary to further explore the molecular mechanisms underlying the synergistic effect between MTA and insulin – such as how these two jointly regulate insulin signaling pathways and the association between intestinal flora and glucose metabolism – to provide a theoretical basis for optimizing the combined therapy. Additionally, studies on the impact of MTA on insulin pharmacokinetics could be conducted to clarify whether they alter the absorption, distribution, and metabolism of insulin, thereby guiding the precise adjustment of clinical medication dosages. It is also essential to develop new formulations of MTA (eg, sustained-release formulation) and combine them with the closed-loop system of intelligent insulin pumps to achieve real-time regulation of blood glucose-lowering effects and improve the convenience and precision of the combined therapy. Furthermore, the application of the combination of MTA and CSII in special populations such as patients with gestational diabetes or elderly patients should be explored to develop personalized treatment plans.

Conclusions

The combined application of mulberry twig alkaloids and CSII in patients with type 2 diabetes mellitus can improve blood glucose variability and alleviate the clinical symptoms of diabetes in TCM. This study suggests that natural plant extracts like MTA can effectively improve blood glucose variability in diabetic patients, providing new treatment options for clinicians. Longer, multicenter studies with larger sample sizes are needed to further assess the effects of mulberry twig alkaloids in regulating glucose variability.