ABSTRACT BACKGROUND The present study investigated the effect of thiamine disulfide (TD) on the pancreas in terms of hyperglycemia improvement and insulin sensitivity increase in diabetic

male rats. We also aimed to study the function of _Pdx1_ (pancreatic and duodenal homeobox 1) and _Glut2_ (glucose transporter 2) genes in pancreatic tissue. METHODS Type 1 diabetes was

induced through injection of 60 mg/kg streptozotocin (STZ). The diabetic rats were divided into four groups, namely diabetic control (DC), diabetic treated with thiamine disulfide (D-TD),

diabetic treated with insulin (D-insulin), and diabetic treated with TD and insulin (D-insulin+TD). The non-diabetic (NDC) and diabetic groups received a normal diet (14 weeks). Blood

expression could be measured. RESULTS We observed that TD therapy decreased blood glucose level, ITT, and serum glucagon levels in comparison with those of the DC group; it also increased

serum insulin levels, IIR, and expression of _Pdx1_ and _Glut2_ genes in comparison with those of the DC group. CONCLUSION Administration of TD could improve hyperglycemia in type 1 diabetic

animals through improved pancreas function. Therefore, not only does TD have a significant effect on controlling and reducing hyperglycemia in diabetes, but it also has the potential to

decrease the dose of insulin administration. SIMILAR CONTENT BEING VIEWED BY OTHERS GABA ADMINISTRATION IMPROVES LIVER FUNCTION AND INSULIN RESISTANCE IN OFFSPRING OF TYPE 2 DIABETIC RATS

Article Open access 30 November 2021 HIGH FRUCTOSE AND STREPTOZOTOCIN INDUCED DIABETIC IMPAIRMENTS ARE MITIGATED BY INDIRUBIN-3-HYDRAZONE VIA DOWNREGULATION OF PKR PATHWAY IN WISTAR RATS

Article Open access 21 June 2021 TERMINALIA CATAPPA AQUEOUS LEAF EXTRACT REVERSES INSULIN RESISTANCE, IMPROVES GLUCOSE TRANSPORT AND ACTIVATES PI3K/AKT SIGNALLING IN HIGH

FAT/STREPTOZOTOCIN-INDUCED DIABETIC RATS Article Open access 23 June 2022 INTRODUCTION Diabetes is a serious lifelong disease, always characterized by abnormally high blood glucose levels

due to insulin production disorder or decreased insulin sensitivity and function [1]. Type 1 diabetes (T1D) is an autoimmune disorder that leads to the destruction of pancreatic β-cells and

occurs at an early age [2, 3]. The pancreas plays an important role in regulating blood glucose levels by secreting insulin and glucagon hormones. There is a direct link between diabetes and

pancreatic damage (impaired insulin secretion) [4, 5]. Blood glucose levels begin to rise over time once affected by impaired insulin function. If insulin resistance develops, the

effectiveness of insulin decreases; [6, 7] insulin resistance (IR) is a dynamic pathological disorder resulting from inadequate cellular response to insulin [8, 9] in insulin-dependent

cells, which occurs in various metabolic disorders, including type 2 diabetes (T2D) and metabolic syndrome [10, 11]. Insulin resistance has also been suggested to occur in T1D. Previously,

intensive insulin therapy was applied in T1DM in order to keep the glucose level as close to normal as possible and prevent hypoglycemia [3, 12]; meanwhile, studies have shown that long-term

insulin administration leads to insulin resistance and exacerbates the complications of diabetes due to decreased insulin receptor regulation [13, 14]. Clinical and experimental evidence

has suggested that patients with insulin resistance in T1D may have abnormal glucagon action [3, 15]. Thiamine or vitamin B1 is a coenzyme involved in the metabolism of sugars; [16] it is

essential for the synthesis and secretion of insulin, and its level decreases in diabetes [17, 18]. In thiamine deficiency, glucose is metabolized through metabolic pathways that can

stimulate insulin resistance and the complications of diabetes [19, 20]. Previous studies have reported that taking thiamine supplements can improve diabetes [21, 22]. In addition, Glut2 is

a glucose transporter in pancreatic β-cells and its inactivation leads to impaired insulin secretion [23, 24]. Homeobox 1 and duodenal transcription factor (Pdx1) play an essential role in

the maintenance and survival of pancreatic cells [25]. Pdx1 is vital for the pancreatic β-cells differentiation [26, 27] and maintains the function of β-cells by regulating the genes

involved in glucose homeostasis, such as insulin, glucose transporter 2 (Glut2), and glucokinase (GK). Decreased expression of this gene causes a lack of response to glucose, decreased

glucose-stimulated insulin secretion, and increased β-cells apoptosis and diabetes [28]. Today, numerous thiamine compounds have been artificially innovated, which due to their biochemical

structure, have better and more desirable absorption and effectiveness than free thiamine, such as sulbutiamine or TD; in this combination, the two free thiamine are mixed using a disulfide

bond and structural modification [29, 30]. Unlike thiamine, the solubility of TD in fat is higher than that of water, which facilitates its absorption and has a good function in sugar

metabolism [31]. Considering the fact that insulin resistance developed after prolonged exogenous insulin intake in T1D patients as well as the complications of thiamine deficiency in these

patients, we evaluated the effect of TD on the improvement of blood glucose levels, pancreas function, and insulin sensitivity in STZ-induced diabetic rats. Insulin sensitivity was assessed

with hyperglycemic-euinsulinemic clamp technique and pancreatic gene expression of _Glut2_ and _Pdx1_. MATERIALS AND METHODS ANIMALS The animals were utilized according to the criteria

mentioned in (NIH No. 85 # 23, amended in 1985). The local animal ethics permission approved this work under the code IR. MUI.MED.REC.1398.572. Herein, 50 male Wistar rats, aged 4 weeks,

were kept in the weight range of 180–250 g for 14 weeks at room temperature (22 ± 20 °C) and relative humidity of 50 ± 5% with 12:12 hours of dark and light control cycles. The appropriately

classified rats were kept in special cages with free access to water and food. DIABETES INDUCTION Diabetes was induced through intraperitoneal (IP) injection with a single dose (60 mg/kg)

of STZ (Sigma-Aldrich Inc., USA) [32]. One week later, their blood glucose levels were determined via a glucometer (ACCU-CHEK Active, Germany), and the animals with blood glucose levels

above 250 mg/dl were considered diabetic [32]. The animals were randomly divided into five groups (n = 7): 1. control intact or non-diabetic group (NDC); 2. diabetic control (DC); 3.

diabetic treated with insulin (2.5 U/kg, BID (1/3 in the morning and 2/3 in the evening)) (D-insulin); 4. diabetic treated with TD (40 mg/kg/day, IP, was obtained based on the doses of the

pilot study) (D-TD); 5. diabetic treated with TD (40 mg/kg) and insulin (2.5 U/kg/day) (D-insulin+TD). All the diabetic and NDC groups were studied for 14 weeks under a normal diet and with

free access to water. All the animal-involved procedures in this research were in line with the standards of the local ethical committee. WEEKLY BLOOD GLUCOSE LEVELS AND BODY WEIGHT

Bodyweight and blood glucose levels were monitored on a weekly basis before and after STZ injection in all the groups. The rats were weighed using a digital scale. Their blood glucose levels

were recorded with a glucometer from the tail vein [33]. GLUCAGON TOLERANCE TEST (GTT) At the end of the treatment period (after 14 weeks), a glucagon tolerance test was done on the fasting

animals. After recording the fasting blood glucose, glucagon was injected (20 μg/kg, IP) and tail vein blood glucose was measured at 0, 20, 30, 40, 60, 90, and 120 minutes [34].

INTRAPERITONEAL INSULIN TOLERANCE TEST (ITT) The insulin tolerance test (ITT), an index of peripheral utilization of glucose and insulin resistance, was performed in the last month following

the treatment. All the groups received regular insulin (2.5 U/kg, IP) and blood glucose was measured at 0, 20, 30, 40, 60, 90, and 120 minutes. The results were expressed as an integrated

area under the curve of glucose (AUC glucose) [33]. BIOCHEMICAL ANALYSIS Monthly tail vein blood sampling was performed in all the groups under anesthesia; the serum was separated for

biochemical analysis. Serum insulin and glucagon were assessed according to ELISA kit instructions (Zell Bio GmbH, Germany) [33]. SURGERY The animals were anesthetized (100 mg/kg of ketamine

and 8 mg/kg of xylazine, IP) [35], and common carotid artery and jugular vein were cannulated by 50 heparinized polyethylene tubes and then fixed to the back of the animal’s neck. After

this operation, the animals were monitored for 3–5 days [33]. HYPERGLYCEMIC-EUINSULINEMIC CLAMP After recovery, the animals were fasted for 12 hours. After weighing, the carotid artery and

jugular vein cannula were connected to two microinjection pumps (New Era Pump System Inc. Farmingdale, New York, USA) that delivered insulin and glucose simultaneously. Slow injection

through the Y interface and carotid artery was carried out for blood sampling. In this method, constant amounts of 25% glucose and a variable amount of insulin (20 mu/kg/min) were injected

for 5 hours. Blood glucose level was checked every 10 minutes through a glucometer, and in the last half hour, it was recorded to be in the range of 95–100 mg/dl. In addition, to calculate

the sensitivity of the whole body to insulin, the amount of insulin injected in the last 30 minutes of the clamp on top of the amount of blood glucose levels in this range was measured [35].

PANCREAS TISSUE PREPARATION AND REAL-TIME PCR The pancreatic tissue was forthwith frozen in liquid nitrogen and stored at −80 °C for future measurements of gene expression of _Pdx1_ and

_Glut2_. We utilized 5 μl of extracted RNA (according to the protocol, Anacell, lot N: CS0021) for the synthesis of cDNA via Reverse Transcriptase (RT) according to the kit instruction

(Anacell, lot N: CS0021). The real-time PCR technique was performed using the SYBR-green method (Biosystems Applied); 1 μl of total cDNA was mixed with 10 microliters of 2×SYBR Green PCR

mixed with ROX, treated with water, and 10 pmol/ml of each of the sensory and antisense primers (Table 1) for the measured genes. Mean beta-actin expression was used as an internal reference

gene to normalize the input cDNA. Finally, the recorded CTs were examined to study the expression of the genes [35, 36]. STATISTICAL ANALYSIS The obtained data are expressed as mean ± SEM.

Kolmogorov–Smirnov test was used to check the normality of all the variables. The comparisons among the groups were studied with two-way analysis of variance followed by Tukey test, using

SPSS software; _P_ < 0.05 was considered to be significant. RESULTS EFFECT OF TD ON BLOOD GLUCOSE LEVELS AND BODY WEIGHT Changes in blood glucose levels were measured in all groups.

Induction of diabetes significantly increased (_p_ < 0.0001) blood glucose level in compare with NDC group (NDC: 102.5 ± 1.2 mg/dl, DC: 554.2 ± 42.4 mg/dl, Fig. 1a). Hyperglycemia in the

animals continued throughout the study. Compared to the DC group, the blood glucose levels in all treatment groups for 14 weeks were significantly reduced (_p_ < 0.0001) (Fig. 1a). The

D-TD group showed a greater improvement in glucose reduction than the other treatment groups (D-insulin and D-insulin +TD). (D-TD: 198.44 ± 1.8 mg/dl, D-insulin: 237.5 ± 9.1 mg/dl, D-insulin

+TD: 287.16 ± 14.1 mg/dl). Body weight was measured weekly and the results showed that induction of diabetes significantly decreased (_p_ < 0.0001) body weight compared to the NDC group

and this continued until the end of the study (NDC: 200 ± 3.2 g DC: 187.81 ± 4.22 g), (Fig. 1b). In all treatment groups, the animal’s weight significantly increased (_p_ < 0.0001) in

comparison to the DC group (Fig. 1b). Weight gain in the D-TD group was more than in the other treatment groups (D-insulin and D-insulin +TD) (Fig. 1b). Among treatment groups, there was a

significant difference (_p_ < 0.001) concerning the body weight (D-TD: 216.88 ± .78 g, D-insulin: 201.2 ± 2.07 g, D-insulin +TD: 202.33 ± 6.14 g). EFFECT OF TD ON GLUCAGON TOLERANCE TEST

(GTT) In the last month of treatment, a glucagon tolerance test was performed in all groups. In the DC group, the area under the glycemic curve (AUC) was higher than the NDC animals (_p_ 

< 0.0001; Fig. 2a, b). The AUC significantly decreased in all treatment groups (D-insulin vs D-TD _p_ < 0.001, D-insulin vs D-insulin +TD, _p_ < 0.001, Fig. 2a, b). The reduction

was more effective (_p_ < 0.001) in the D-TD group than other treatment (D-insulin and D-insulin+TD) groups. Also, all treatment groups showed a significantly positive difference in

comparison to the NDC group (_p_ < 0.0001; Fig. 2b). (NDC: 14123.75 ± 297.29 mg.min/ml DC: 59306.25 ± 2353.24 mg.min/ml D-insulin: 31960 ± 483.58 mg.min/ml D-TD: 25210 ± 318.44 mg.min/ml

D-insulin +TD: 25388.75 ± 148.58 mg.min/ml). EFFECT OF TD ON (ITT) At the end of the study, ITT was performed for all animals. The level of AUC in the DC group was higher than the NDC group

and all treatment groups (_p_ < 0.0001; Fig. 3a, b). But the AUC did not reach the NDC level in all treatment groups (Fig. 3b, c). There was not a significant difference between the two

groups of D-insulin and D-insulin +TD (Fig. 3c). (NDC: 10172.5 ± 442.82 mg.min/ml DC: 44086.25 ± 3027.47 mg.min/ml D-insulin: 16908.75 ± 356.85 mg.min/ml D-TD: 13927.5 ± 226.66 mg.min/ml

D-insulin +TD: 16161.25 ± 362.52 mg.min/ml). EFFECT OF TD IN THE IIR After 14 weeks of treatment, a hyperglycemic-euinsulinemic clamp test was performed to assess whole-body insulin

sensitivity in all animals. In this type of test, the blood glucose level was clamped at 100 ± 5 mg/dl. TD therapy significantly increased (_p_ < 0.0001) the rate of insulin injection

(IIR) required to maintain euglycemia during the injection of constant glucose rate in comparison with the DC group (Fig. 4). IIR was lower in D-TD group rats than in animals in the

D-insulin and D-insulin +TD groups. (_p_ < 0.001, Fig. 4). In all treatment groups, the rate of IIR was higher than in the NDC group (_p_ < 0.0001; Fig. 4). (NDC: 0.2678 ± 0.06 

μ/min/kgbw DC: 6.3027 ± 0.23 μ/min/kgbw D-insulin: 3.2905 ± 0.04 μ/min/kgbw D-TD: 2.0603 ± 0.08 μ/min/kgbw D-insulin +TD: 3.040 ± 0.05 μ/min/kgbw). CHANGES IN SERUM INSULIN AND GLUCAGON

LEVELS Serum insulin and glucagon levels were measured monthly for 14 weeks of treatment in all groups. After induction of diabetes, serum insulin levels in the DC group significantly

decreased over three months (_p_ < 0.001; Fig. 5b). Also, the serum insulin level in the DC group was significantly reduced in comparison to the NDC group (first month: (_p_ < 0.01),

second month (_p_ < 0.001), third month (_p_ < 0.0001); Fig. 5b). In the treatment groups, serum insulin levels significantly increased in comparison with DC animals during the three

months (first month: (_p_ < 0.01), second month (_p_ < 0.001), third month (_p_ < 0.0001); Fig. 5b). The highest serum insulin level was observed in the D-insulin group in

comparison to D-TD (_p_ < 0.05) and D-insulin+TD groups in the third month (Fig. 5b). Serum glucagon levels were also measured monthly and the results showed that serum glucagon levels in

the DC animals significantly increased in compared to the NDC group (first month: (_p_ < 0.01), second month (_p_ < 0.001), third month (_p_ < 0.0001), Fig. 5a). The treatment

groups had a significant decrease in serum glucagon levels compared to the DC group during the three months (Fig. 5a). The D-TD group showed a more effective reduction in serum glucagon

levels every three months than the other two treatments (D-insulin and D-insulin +TD) groups (Fig. 5a). In the third month, the decrease in serum glucagon level in the treatment groups (_p_ 

< 0.0001) was more than the DC group in other treatment months. _GLUT2_, _PDX1_ MRNA GENE EXPRESSIONS There was a significant decrease in _Pdx1_ gene expression in the DC group compared

to the NDC group (_p_ < 0.01, Fig. 6b). The expression of the _Pdx1_ gene in all treatment groups significantly increased compared to the DC (_p_ < 0.01) and NDC (_p_ < 0.001)

groups. The best expression of the _Pdx1_ gene was also observed in the D-TD group (Fig. 6b). In the DC group, _Glut2_ gene expression was significantly decreased compared to the NDC group

(_p_ < 0.01, Fig. 6a). The _Glut2_ gene expression, in all treatment groups, was significantly increased in comparison to the DC group (_p_ < 0.01, Fig. 6a), and in the D-insulin +TD

group was higher than in other treatment groups (D-TD and D-insulin) (_p_ < 0.01; Fig. 6a). DISCUSSION This study aimed to evaluate the effect of TD on improving blood glucose levels and

increasing insulin sensitivity in the T1D animal model. Herein, pancreatic function and insulin sensitivity in STZ-induced diabetic rats were evaluated by applying the

hyperglycemic-euinsulinemic clamp technique. Moreover, the expression of _Glut2_ and _Pdx1_ genes was studied. Our results revealed that administration of TD in STZ-induced diabetic rats

could significantly reduce blood glucose levels and insulin resistance after 14 weeks in comparison with those of the DC group. In addition, serum levels of insulin and glucagon and

expression of pancreatic genes (_Glut2, Pdx1_) showed a significant increase compared to the DC group. Furthermore, the administration of TD had a positive effect on insulin and glucagon

tolerance test 14 weeks following the treatment. In our study, all the rats were monitored daily for any signs of diabetes after STZ injection, including high blood glucose levels and weight

loss. Animal body weight and mean blood glucose level in the D-TD group showed a statistical difference with those of the D-insulin group. Thiamine or vitamin B1 is a coenzyme involved in

the metabolism of sugars, which is reduced in diabetes. Thiamine deficiency can exacerbate the side effects of diabetes. In thiamine deficiency, glucose is metabolized through metabolic

pathways that can stimulate insulin resistance and the complications of diabetes [19]. Thiamine maintains carbohydrate metabolism by participating in several cellular metabolic processes

[37]. In addition, it prevents the formation of AGEs in hyperglycemic conditions [38]. In the STZ-induced diabetic rats, the effect of a high dose of thiamine or benfotiamine (a lipophilic

form of thiamine) was previously reported on the reduction in plasma’s AGEs in [39]. We showed that following the induction of diabetes, the area under the glycemic curve of ITT compared to

the NDC group, increased while the response of insulin target cells to exogenous insulin decreased [35]. The hyperglycemic-euinsulinemic clamp technique demonstrated a decline in the

sensitivity of insulin target cells to insulin. A comparison of all the treatment groups implied that the protocol performed in the D-TD group was more effective in blood glucose and AUC

than that in D-insulin and D-insulin + TD groups. Previous studies have shown that all the pathological processes observed in the brain during thiamine deficiency are strongly associated

with the pathophysiology of insulin resistance and macrovascular disease; yet, thiamine supplementation can ameliorate all these complications [40, 41]. Thiamine deficiency impairs the

synthesis and secretion of insulin due to decreased glucose oxidation; on the other hand, insulin deficiency can aggravate thiamine deficiency [42], which is also strongly associated with

pathophysiological resistance in the body [43]. The results of GTT indicated that after glucagon injection, blood glucose levels in the DC group significantly rose compared to those in the

NDC group. The area under the glycemic curve also decreased in all the treatment groups compared to that of the DC group. Administration of TD improved the blood glucose level in the D-TD

and D-insulin+TD groups. Moreover, this amended the GTT’s result in the D-TD group, suggesting that the pancreatic β-cells in this group can secret insulin. In the DC group, IP injection of

glucagon raised blood glucose level, but could not return to its original state after 2 hours due to the inability to secrete insulin. In all the treatment groups, 30 minutes after glucagon

administration, the blood glucose level significantly decreased compared to that of the DC group; it is probably on account of the promoted function of the pancreas to secrete insulin in

these groups. Glucagon is involved in the hepatic gluconeogenesis pathway and can increase hyperglycemia. Glucagon increases hepatic glucose output through the gluconeogenesis pathway [44]

while this pathway is suppressed by insulin; thus, hepatic glucose output will decrease [45]. The reason why the blood glucose level in the D-TD group was lower than that in the DC group was

probably the inhibition of gluconeogenesis enzymes. Conceivably, TD could improve GTT; accordingly, glucagon prevented the overactivity of the glycogenolysis pathway and incomplete

carbohydrate metabolism. Therefore, the improvement of hyperglycemia in the D-TD group reduced the effect of glucagon on hepatic glucose production. The results of IIR showed that insulin

sensitivity increased in the DC group compared to that in the NDC group. However, in the treated groups, the sensitivity to insulin response increased compared to the DC group; insulin

sensitivity in the D-TD group was significantly higher than that in the D-insulin group. Insulin therapy in T1D can reduce insulin resistance and promote β-cells function by lowering blood

glucose levels. Euglycemic-hyperinsulinemic research on T1D patients has suggested that insulin sensitivity decreased in these patients and that there was a relationship between insulin

sensitivity, insulin dose, and HbA1c. A study reported that insulin-mediated glucose excretion is reduced in both euglycemic and hyperglycemic insulin clamps in T1D patients [46, 47]. There

are several hypotheses to explain the decrease in insulin sensitivity in T1D, including prolonged exposure to supraphysiological levels of exogenous insulin, genetic factors, failure to

deliver insulin into the bloodstream, decreased insulin delivery to the liver, decreased hepatic IGF-1 production, abnormal regulation of glucagon, fatty acid exposure, and lipid toxicity

(NEFA) [9, 48]. It has also been reported that thiamine deficiency is higher in T1D than in T2D; hence, thiamine deficiency has been suggested as a mediator of insulin resistance in diabetes

[43, 49]. Insulin plays a pivotal role in the insulin sensitivity of target tissues. Thiamine is essential for insulin synthesis and secretion; thiamine deficiency in diabetic conditions

affects insulin synthesis and secretion, serum insulin levels, and glucose transporters. All the above-mentioned procedures lead to metabolic dysfunction in hyperglycemic conditions and

decreased insulin sensitivity [21, 50]. Hence, thiamine supplements in diabetic patients during hyperglycemia could advance insulin function. The striking reduction in insulin-mediated

glucose uptake can infer hyperinsulinemia, which in turn increases free radical production. Herein, an improvement was observed in the D-TD group concerning glucose metabolism and insulin

function. It could be thus concluded that TD affects the maintenance of β-cells activity by reducing oxidative stress. We assessed insulin resistance via ITT index; the obtained findings

represented a significant decrease in blood glucose (20 min. after insulin administration) in all the treatment groups compared to the DC group. This response was better in the D-TD group

owing to a decrease in insulin resistance. After 14 weeks, a decreased insulin level and an increased glucagon level were observed in the DC group compared to the NDC group. However, in the

D-TD and D-insulin groups, insulin levels significantly increased whereas glucagon levels significantly decreased. Circulating insulin affected glucagon function; at high insulin levels, the

effect of glucagon on the liver declined, resulting in lower blood glucose levels [51, 52]. Numerous studies have shown that thiamine deficiency in diabetic rats reduces glucose oxidation

and insulin secretion [53], which is modified by thiamine administration. Other papers have suggested that high doses of thiamine may reduce the need for exogenous insulin [54]. We found

that the administration of TD positively affected glucose metabolism and insulin secretion. TD improved blood glucose level and insulin function in diabetic rats; accordingly, TD activates

glucose metabolism and insulin synthesis preventing glucose intoxication due to hyperglycemia in TDM. According to our results regarding the ITT and the GTT, it seems as if TD can repair

damaged pancreatic β-cells and increase insulin secretion. Furthermore, TD may reduce insulin resistance and increase insulin sensitivity by improving pancreatic β-cells function, increasing

insulin secretion, and decreasing glucagon levels. Thus, TD (a lipophilic form of vitamin B1) can improve hyperglycemia, which contributes to increased endogenous insulin secretion and

decreased glucagon secretion. We observed an increase in _Pdx1_ and _Glut2_ gene expression in the D-TD and D-insulin groups compared to the DC group, which leads to ameliorated glucose

tolerance and prominent insulin secretion by the pancreas. In conclusion, TD could play an effective role in improving hyperglycemia in T1D rats [16, 55]. TD may affect insulin and glucagon

secretion by increasing the expression of genes involved in pancreatic insulin secretion. In this regard, previous research has shown that _Pdx1_ and _Glut2_ nuclear transmission is impaired

in high-fat diabetic rats [56, 57]. TD seems to be able to improve the function of pancreatic β-cells in insulin secretion by affecting _Pdx1_ and _Glut2_ genes expression. Although insulin

therapy in diabetic animals increases the expression of these genes, it is not as effective as thiamine. The regulation effect of TD on glucose metabolism may be mediated by modifying the

expression of the β-cells genome in order to increase insulin secretion, elicit insulin responses at the insulin target cells, and increase insulin sensitivity. According to our findings,

administration of TD, as a lipophilic thiamine supplement, had interaction effects on the improvement of STZ-induced hyperglycemia. Thus, in addition to exogenous insulin, prescribing the

TD, as a natural supplement, contributes to the amelioration of diabetic patients. CONCLUSION In the current work, we showed that TD injection improved hyperglycemia in male type 1 diabetes

rats. Administration of TD had a positive effect on serum insulin and glucagon concentrations in diabetic rats by increasing serum insulin levels, decreasing serum glucagon levels, enhancing

insulin sensitivity, promoting the pancreas function and pancreatic cells survival via increased _Glut2_ and _Pdx1_ genes expression, and diminishing the dose of insulin exogenous. DATA

AVAILABILITY The data of the present study is available in the endocrine and metabolism lab in the physiology department REFERENCES * Atkinson MA, Eisenbarth GS, Michels AW. Type 1 diabetes.

Lancet. 2014;383:69–82. 9911 Article  PubMed  Google Scholar  * DiMeglio LA, Evans-Molina C, Oram RA. Type 1 diabetes. Lancet. 2018;391:2449–62. 10138 Article  PubMed  PubMed Central 

Google Scholar  * Katsarou A, Gudbjörnsdottir S, Rawshani A, Dabelea D, Bonifacio E, Anderson BJ, et al. Type 1 diabetes mellitus. Nat Rev Dis Prim. 2017;3:1–17. Google Scholar  * Ferrannini

E, Buzzigoli G, Bonadonna R, Giorico MA, Oleggini M, Graziadei L, et al. Insulin resistance in essential hypertension. N. Engl J Med. 1987;317:350–7. Article  CAS  PubMed  Google Scholar  *

Zhou Q, Melton DA. Pancreas regeneration. Nature. 2018;557:351–8. 7705 Article  CAS  PubMed  PubMed Central  Google Scholar  * Meek TH, Nelson JT, Matsen ME, Dorfman MD, Guyenet SJ, Damian

V, et al. Functional identification of a neurocircuit regulating blood glucose. Proc Natl Acad Sci USA. 2016;113:E2073–82. Article  CAS  PubMed  PubMed Central  Google Scholar  * Borai A,

Livingstone C, Ferns GA. The biochemical assessment of insulin resistance. Ann Clin Biochem. 2007;44:324–42. Article  CAS  PubMed  Google Scholar  * Kaul K, Apostolopoulou M, Roden M.

Insulin resistance in type 1 diabetes mellitus. Metabolism 2015;64:1629–39. Article  CAS  PubMed  Google Scholar  * Cleland S, Fisher B, Colhoun H, Sattar N, Petrie J. Insulin resistance in

type 1 diabetes: what is ‘double diabetes’ and what are the risks? Diabetologia. 2013;56:1462–70. Article  CAS  PubMed  PubMed Central  Google Scholar  * Samuel VT, Shulman GI. The

pathogenesis of insulin resistance: integrating signaling pathways and substrate flux. J Clin Investig. 2016;126:12–22. Article  PubMed  PubMed Central  Google Scholar  * Taylor R. Insulin

resistance and type 2 diabetes. Diabetes. 2012;61:778–9. Article  CAS  PubMed  PubMed Central  Google Scholar  * Kalyesubula M, Mopuri R, Asiku J, Rosov A, Yosefi S, Edery N, et al.

High-dose vitamin B1 therapy prevents the development of experimental fatty liver driven by overnutrition. Dis Models Mechanisms. 2021;14:dmm048355. Article  CAS  Google Scholar  * Group SS.

SEARCH for Diabetes in Youth: a multicenter study of the prevalence, incidence and classification of diabetes mellitus in youth. Controlled Clin Trials. 2004;25:458–71. Article  Google

Scholar  * Boucher J, Kleinridders A, Kahn CR. Insulin receptor signaling in normal and insulin-resistant states. Cold Spring Harb Perspect Biol. 2014;6:a009191. Article  PubMed  PubMed

Central  CAS  Google Scholar  * Peltoniemi P, Yki-Järvinen H, Oikonen V, Oksanen A, Takala TO, Rönnemaa T, et al. Resistance to exercise-induced increase in glucose uptake during

hyperinsulinemia in insulin-resistant skeletal muscle of patients with type 1 diabetes. Diabetes. 2001;50:1371–7. Article  CAS  PubMed  Google Scholar  * Anwar A, Azmi MA, Siddiqui JA,

Panhwar G, Shaikh F, Ariff M. Thiamine level in type I and type II diabetes mellitus patients: a comparative study focusing on hematological and biochemical evaluations. Cureus. 2020;12:5

Google Scholar  * Volvert M-L, Seyen S, Piette M, Evrard B, Gangolf M, Plumier J-C, et al. Benfotiamine, a synthetic S-acyl thiamine derivative, has different mechanisms of action and a

different pharmacological profile than lipid-soluble thiamine disulfide derivatives. BMC Pharmacol. 2008;8:1–11. Article  CAS  Google Scholar  * Beltramo E, Berrone E, Tarallo S, Porta M.

Effects of thiamine and benfotiamine on intracellular glucose metabolism and relevance in the prevention of diabetic complications. Acta Diabetologica. 2008;45:131. Article  CAS  PubMed 

Google Scholar  * Stoyanovsky DA, Wu D, Cederbaum AI. Interaction of 1-hydroxyethyl radical with glutathione, ascorbic acid and α-tocopherol. Free Radic Biol Med. 1998;24:132–8. Article  CAS

  PubMed  Google Scholar  * Portari GV, Marchini JS, Vannucchi H, Jordao AA. Antioxidant effect of thiamine on acutely alcoholized rats and lack of efficacy using thiamine or glucose to

reduce blood alcohol content. Basic Clin Pharmacol Toxicol. 2008;103:482–6. Article  CAS  PubMed  Google Scholar  * vinh quoc Luong K, Nguyen LTH. The impact of thiamine treatment in the

diabetes mellitus. J Clin Med Res. 2012;4:153. Google Scholar  * Thornalley P, Babaei-Jadidi R, Al Ali H, Rabbani N, Antonysunil A, Larkin J, et al. High prevalence of low plasma thiamine

concentration in diabetes linked to a marker of vascular disease. Diabetologia. 2007;50:2164–70. Article  CAS  PubMed  PubMed Central  Google Scholar  * Ghezzi C, Loo DD, Wright EM.

Physiology of renal glucose handling via SGLT1, SGLT2 and GLUT2. Diabetologia. 2018;61:2087–97. Article  CAS  PubMed  PubMed Central  Google Scholar  * Hinden L, Udi S, Drori A, Gammal A,

Nemirovski A, Hadar R, et al. Modulation of renal GLUT2 by the cannabinoid-1 receptor: implications for the treatment of diabetic nephropathy. J Am Soc Nephrol. 2018;29:434–48. Article  CAS

  PubMed  Google Scholar  * Jara MA, Werneck-De-Castro JP, Lubaczeuski C, Johnson JD, Bernal-Mizrachi E. Pancreatic and duodenal homeobox-1 [PDX1] contributes to β-cell mass expansion and

proliferation induced by Akt/PKB pathway. Islets. 2020;12:32–40. Article  PubMed  PubMed Central  Google Scholar  * Offield MF, Jetton TL, Labosky PA, Ray M, Stein RW, Magnuson MA, et al.

PDX-1 is required for pancreatic outgrowth and differentiation of the rostral duodenum. Development. 1996;122:983–95. Article  CAS  PubMed  Google Scholar  * Tang Z-C, Chu Y, Tan Y-Y, Li J,

Gao S. Pancreatic and duodenal homeobox-1 in pancreatic ductal adenocarcinoma and diabetes mellitus. Chin Med J. 2020;133:344. Article  PubMed  PubMed Central  Google Scholar  * Kim J, Kim

JH, Yoon SY, Kim JW. PLAG attenuates STZ-induced pancreatic beta cell damage by promoting GLUT2 endocytosis. Mol Cell Biol. 2019;39:e00157–19. * Du Boitesselin R, Hun M. Etude histochimique

de l’impregnation des formations cerebrales apres administration de sulbutiamine. Synth Med 1985. 1985;309:11–2. Google Scholar  * Kiew K, Mohamad WW, Ridzuan A, Mafauzy M. Effects of

sulbutiamine on diabetic polyneuropathy: an open randomised controlled study in type 2 diabetics. Malays J Med Sci. 2002;9:21. CAS  PubMed  PubMed Central  Google Scholar  * Sevim S,

Kaleağası H, Taşdelen B. Sulbutiamine shows promising results in reducing fatigue in patients with multiple sclerosis. Mult Scler Relat Disord. 2017;16:40–3. Article  PubMed  Google Scholar

  * Sohrabipour S, Kharazmi F, Soltani N, Kamalinejad M. Biphasic effect of Solanum nigrum fruit aqueous extract on vascular mesenteric beds in non-diabetic and streptozotocin-induced

diabetic rats. Pharmacogn Res. 2014;6:148. Article  Google Scholar  * Sohrabipour S, Sharifi MR, Talebi A, Sharifi M, Soltani N. GABA dramatically improves glucose tolerance in

streptozotocin-induced diabetic rats fed with high-fat diet. Eur J Pharmacol. 2018;826:75–84. Article  CAS  PubMed  Google Scholar  * Capozzi ME, Wait JB, Jepchumba Koech ANG, Coch RW,

Svendsen B, Finan B, et al. Glucagon lowers glycemia when β cells are active. JCI Insight. 2019;4:16. * Sohrabipour S, Sharifi MR, Sharifi M, Talebi A, Soltani N. Effect of magnesium sulfate

administration to improve insulin resistance in type 2 diabetes animal model: using the hyperinsulinemic‐euglycemic clamp technique. Fundamental Clin Pharmacol. 2018;32:603–16. 6 Article 

CAS  Google Scholar  * Rezazadeh H, Sharifi MR, Sharifi M, Soltani N. Gamma-aminobutyric acid attenuates insulin resistance in type 2 diabetic patients and reduces the risk of insulin

resistance in their offspring. Biomedicine Pharmacother. 2021;138:111440. Article  CAS  Google Scholar  * Pacei F, Tesone A, Laudi N, Laudi E, Cretti A, Pnini S, et al. The relevance of

thiamine evaluation in a practical setting. Nutrients. 2020;12:2810. Article  CAS  PubMed Central  Google Scholar  * Obrenovich ME, Monnier VM. Vitamin B1 blocks damage caused by

hyperglycemia. American Association for the advancement of science, 2003; p. pe6-pe. * Karachalias N, BABAEI‐JADIDI R, Kupich C, Ahmed N, Thornalley PJ. High‐dose thiamine therapy counters

dyslipidemia and advanced glycation of plasma protein in streptozotocin‐induced diabetic rats. Ann N. Y Acad Sci. 2005;1043:777–83. Article  CAS  PubMed  Google Scholar  * Stehouwer C,

Schaper N. The pathogenesis of vascular complications of diabetes mellitus: One voice or many? Eur J Clin Investig. 1996;26:535–43. Article  CAS  Google Scholar  * Hartge MM, Kintscher U,

Unger T. Endothelial dysfunction and its role in diabetic vascular disease. Endocrinol Metab Clin. 2006;35:551–60. Article  CAS  Google Scholar  * Mee L, Nabokina SM, Sekar VT, Subramanian

VS, Maedler K, Said HM. Pancreatic beta cells and islets take up thiamin by a regulated carrier-mediated process: studies using mice and human pancreatic preparations. Am J

Physiol-Gastrointest Liver Physiol. 2009;297:G197–206. Article  CAS  PubMed  PubMed Central  Google Scholar  * Page G, Laight D, Cummings M. Thiamine deficiency in diabetes mellitus and the

impact of thiamine replacement on glucose metabolism and vascular disease. Int J Clin Pract. 2011;65:684–90. Article  CAS  PubMed  Google Scholar  * Saltiel AR, Kahn CR. Insulin signalling

and the regulation of glucose and lipid metabolism. Nature. 2001;414:799–806. Article  CAS  PubMed  Google Scholar  * Ozcan L, Wong CC, Li G, Xu T, Pajvani U, Park SKR, et al. Calcium

signaling through CaMKII regulates hepatic glucose production in fasting and obesity. Cell Metab. 2012;15:739–51. Article  CAS  PubMed  PubMed Central  Google Scholar  * Sharp PS, Mohan V,

Vitelli F, Maneschi F, Kohner EM. Changes in insulin resistance with long-term insulin therapy. Diabetes Care. 1987;10:56–61. Article  CAS  PubMed  Google Scholar  * Greenbaum CJ. Insulin

resistance in type 1 diabetes. Diabetes/Metab Res Rev. 2002;18:192–200. Article  CAS  Google Scholar  * Houstis N, Rosen ED, Lander ES. Reactive oxygen species have a causal role in multiple

forms of insulin resistance. Nature 2006;440:944–8. Article  CAS  PubMed  Google Scholar  * Maguire D, Talwar D, Shiels PG, McMillan D. The role of thiamine dependent enzymes in obesity and

obesity related chronic disease states: a systematic review. Clin Nutr ESPEN. 2018;25:8–17. Article  PubMed  Google Scholar  * Dębski B, Kurył T, Gralak M, Pierzynowska J, Drywień M. Effect

of inulin and oligofructose enrichment of the diet on rats suffering thiamine deficiency. J Anim Physiol Anim Nutr. 2011;95:335–42. Article  CAS  Google Scholar  * El Youssef J, Castle JR,

Bakhtiani PA, Haidar A, Branigan DL, Breen M, et al. Quantification of the glycemic response to microdoses of subcutaneous glucagon at varying insulin levels. Diabetes Care. 2014;37:3054–60.

Article  CAS  PubMed  PubMed Central  Google Scholar  * Russell SJ, El-Khatib FH, Nathan DM, Damiano ER. Efficacy determinants of subcutaneous microdose glucagon during closed-loop control.

J Diabetes Sci Technol. 2010;4:1288–304. * Rathanaswami P, Pourany A, Sundaresan R. Effects of thiamine deficiency on the secretion of insulin and the metabolism of glucose in isolated rat

pancreatic islets. Biochem Int. 1991;25:577–83. CAS  PubMed  Google Scholar  * Abboud MR, Alexander D, Najjar SS. Diabetes mellitus, thiamine-dependent megaloblastic anemia, and

sensorineural deafness associated with deficient alpha-ketoglutarate dehydrogenase activity. J Pediatrics. 1985;107:537–41. Article  CAS  Google Scholar  * Al-Attas O, Al-Daghri N, Alfadda

A, Abd Al-Rahman S, Sabico S. Blood thiamine and derivatives as measured by high-performance liquid chromatography: levels and associations in DM patients with varying degrees of

microalbuminuria. J Endocr Invest. 2012;35:951–6. CAS  PubMed  Google Scholar  * Yamamoto Y, Miyatsuka T, Sasaki S, Miyashita K, Kubo F, Shimo N, et al. Preserving expression of Pdx1

improves β-cell failure in diabetic mice. Biochemical Biophysical Res Commun. 2017;483:418–24. Article  CAS  Google Scholar  * Gao T, McKenna B, Li C, Reichert M, Nguyen J, Singh T, et al.

Pdx1 maintains β cell identity and function by repressing an α cell program. Cell Metab. 2014;19:259–71. Article  CAS  PubMed  PubMed Central  Google Scholar  Download references

ACKNOWLEDGEMENTS This study was supported by Isfahan University of Medical Sciences, Isfahan, Iran [grant number 398778]. FUNDING The authors do not earn any financial income from publishing

this article. AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * Department of Physiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Mahtab Ghanbari Rad & 

Nepton Soltani * Department of Genetics and Molecular Biology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Mohammadreza Sharifi * Department of Clinical

Toxicology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran Rokhsareh Meamar Authors * Mahtab Ghanbari Rad View author publications You can also search for this

author inPubMed Google Scholar * Mohammadreza Sharifi View author publications You can also search for this author inPubMed Google Scholar * Rokhsareh Meamar View author publications You can

also search for this author inPubMed Google Scholar * Nepton Soltani View author publications You can also search for this author inPubMed Google Scholar CONTRIBUTIONS NS designed the

study, conceptualized the experiments, analyzed the data, and revised the manuscript. MGR performed the experiments and wrote the manuscript. MS and RM participated in the study design and

approved the final manuscript. CORRESPONDING AUTHOR Correspondence to Nepton Soltani. ETHICS DECLARATIONS COMPETING INTERESTS The authors declare no competing interests. ADDITIONAL

INFORMATION PUBLISHER’S NOTE Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. RIGHTS AND PERMISSIONS OPEN ACCESS This

article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as

you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party

material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s

Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/. Reprints and permissions ABOUT THIS ARTICLE CITE THIS ARTICLE Rad, M.G., Sharifi, M., Meamar, R. _et al._

The role of pancreas to improve hyperglycemia in STZ-induced diabetic rats by thiamine disulfide. _Nutr. Diabetes_ 12, 32 (2022). https://doi.org/10.1038/s41387-022-00211-5 Download citation

* Received: 24 January 2022 * Revised: 04 May 2022 * Accepted: 06 June 2022 * Published: 20 June 2022 * DOI: https://doi.org/10.1038/s41387-022-00211-5 SHARE THIS ARTICLE Anyone you share

the following link with will be able to read this content: Get shareable link Sorry, a shareable link is not currently available for this article. Copy to clipboard Provided by the Springer

Nature SharedIt content-sharing initiative