The influence of zinc supplementation on the pancreas of streptozotocin-diabetic rats

Co-administration of "L-Lysine, Vitamin C, and Zinc" increased the antioxidant activity, decreased insulin resistance, and improved lipid profile in streptozotocin-induced diabetic rats

PURPOSE

We previously showed the beneficial effect of L-Lysine (Lys), a chemical chaperone, on reducing diabetic complications in diabetic rats and type 2 diabetic patients. Herein, we evaluated the effect of Lys co-administration with Vitamin C and Zinc (Lys+VC+Zn), in diabetic rats.

METHODS

The streptozotocin (50 mg/Kg) was injected into male adult Wistar rats to induce diabetes. Then, different groups of normal and diabetic rats were treated with Lys and Lys+VC+Zn for five months. So, there were 0.1 % Lys in the drinking water of both groups. The control groups received water alone. During the experiment, the body weight, and various parameters were determined in the blood, serum/plasma, and urine of the rats.

RESULTS

The determination of biochemical indexes confirmed diabetes induction and its complications in rats. Treatment with either Lys or Lys+VC+Zn resulted in reduced blood glucose and protein glycation (decreasing AGEs and HbA1c), increased insulin secretion, alleviated insulin resistance and HOMA-IR, improved lipid profile and HDL functionality (LCAT and PON1), enhanced antioxidant status (FRAP and AOPP), improved kidney function (decreased microalbuminuria, serum urea, and creatinine), and increased chaperone capacity (HSP70). Lys+VC+Zn showed better effects on these parameters than Lys alone.

CONCLUSIONS

The results of this study indicated that co-administration of Lys, a chemical chaperone, with two antioxidants (VC and Zn) potentiates its antidiabetic effects and prevent diabetic complications in rat model of diabetes.

Biological efficacy of zinc oxide nanoparticles against diabetes: a preliminary study conducted in mice

The antidiabetic, hypoglycemic and oral glucose tolerance test (OGTT) activities of zinc oxide nanoparticles (ZnONPs) were assessed in mice. ZnONPs were prepared by reacting Zn(NO3)2.6H2O and NaOH solution at 70°C with continuous stirring and then characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. Diabetes was induced by the intraperitoneal injection of streptozotocin (STZ) in mice, and then the blood glucose levels were determined by the glucose oxidase method. The experimental results revealed that ZnONPs suggestively (p<0.001) declined the blood glucose levels (39.79%), while these reductions were 38.78% for the cotreatment of ZnONPs and insulin, and 48.60% for insulin, respectively. In the hypoglycemic study, ZnONPs (8 and 14 mg/kg b.w) reduced approximately 25.13 and 29.15% of blood glucose levels, respectively. A similar reduction was found in the OGTT test, which is also a dose- and time-dependent manner. Overall, ZnONPs possess a potential antidiabetic activity, which could be validated by further mechanistic studies.

Protective role of zinc in liver damage in experimental diabetes demonstrated via different biochemical parameters

Diabetes mellitus is a serious worldwide metabolic disease, which is accompanied by hyperglycaemia and affects all organs and body system. Zinc (Zn) is a basic cofactor for many enzymes, which also plays an important role in stabilising the structure of insulin. Liver is the most important target organ after pancreas in diabetic complications. In this study, we aimed to investigate the protective role of Zn in liver damage in streptozotocin (STZ)-induced diabetes mellitus. There are four experimental groups of female Swiss albino rats: group I: control; group II: control + ZnSO₄ ; group III: STZ-induced diabetic animals and group IV: STZ-diabetic + ZnSO₄ . To induce diabetes, STZ was injected intraperitoneally (65 mg/kg). ZnSO₄ (100 mg/kg) was given daily to groups II and IV by gavage for 60 days. At the end of the experiment, rats were killed under anaesthesia and liver tissues were collected. In the diabetic group, hexose, hexosamine, fucose, sialic acid levels, arginase, adenosine deaminase, tissue factor activities and protein carbonyl levels increased, whereas catalase, superoxide dismutase, glutathione-S-transferase, glutathione peroxidase, glutathione reductase and Na⁺ /K⁺ -ATPase activities decreased. The administration of Zn to the diabetic group reversed all the negative effects/activities. According to these results, we can suggest that Zn has a protective role against STZ-induced diabetic liver damage.

Effect of the Zinc Oxide Nanoparticles and Thiamine for the Management of Diabetes in Alloxan-Induced Mice: a Stereological and Biochemical Study

This research was carried out to evaluate the antidiabetic effects of zinc oxide nanoparticles (ZnO NPs) and thiamine following experimental diabetes. Fifty-six 6-week-old female mice were used and divided into seven groups of eight animals. Diabetes was induced in fasted mice by using intraperitoneal (IP) injection of alloxan (180 mg/kg). Groups included (I) non-diabetic control, (II) thiamine (30 mg/l, IP), (III) alloxan-induced diabetic mice, (IV) diabetes + ZnO NPs (0.1 mg/kg IP), (V) diabetes + ZnO NPs (0.5 mg/kg IP), (VI) diabetes + ZnO NPs (0.1 mg/kg IP) + thiamine (30 mg/l, IP), and (VII) diabetes + ZnO NPs (0.5 mg/kg IP) + thiamine (30 mg/l, IP). Coincident with pancreas recovery, in diabetic treated mice (groups IV to VII), the mean islet volume, islets per square micrometer, and volume density of the pancreas had increased than in alloxan-induced diabetic mice. ZnO NPs and thiamine induced a decreasing blood glucose, lower serum triglyceride (TG), LDL, and total cholesterol (TC) levels in alloxan-induced diabetic mice treated with ZnO NPs and thiamine, simultaneously increasing HDL as well. In conclusion, ZnO NPs and thiamine are potent antidiabetic factors, and that, these compound supplementation possesses hypoglycemic properties and have effect on serum lipid parameters in diabetes mice.

Low perinatal zinc status is not associated with the risk of type 1 diabetes in children

AIM

Immunologic events during fetal life may play a part in the pathogenesis of type 1 diabetes (T1D). As zinc is involved in immunologic processes, the purpose was to investigate perinatal zinc status and the later risk of developing T1D and association to age at onset.

METHODS

A population-based case-control study based on data from Danish Childhood Diabetes Register and the Danish Newborn Screening Biobank. Cases and controls were matched by birth year and month. Zinc status was analyzed in dried blood spots collected 5 to 7 days after birth. Logistic regression model was used to test the influence of zinc on risk of T1D. Linear regression modeling was used to examine the association between zinc status and covariates as well as age at onset. Zinc status was adjusted for HLA-DQB1 genotype, birth data and maternal age.

RESULTS

Each doubling in perinatal zinc status was not associated with T1D risk; odds ratio (OR) = 1.06 (95% confidence interval [CI] 0.84, 1.32) ( P  = 0.62), adjusted for birth year and season. This finding persisted after adjustment for possible confounders; OR = 1.01 (95% CI 0.77, 1.34) ( P  = 0.93). In none of the cohorts there were significant associations to age at onset.

CONCLUSION

The risk of developing T1D in Danish children was not associated with perinatal zinc status nor age at onset.

The role of metallothionein-3 in streptozotocin-induced beta-islet cell death and diabetes in mice

Metallothionein-3 (Mt3), a zinc (Zn)-regulatory protein mainly expressed in the central nervous system, may contribute to oxidative cell death. In the present study, we examined the possible role of Mt3 in streptozotocin (STZ)-induced islet cell death and consequent hyperglycemia. Quantitative real-time polymerase chain reaction (RT-PCR) confirmed that islet cells expressed Mt3 mRNA. In all cases, wild-type (WT) mice injected with STZ exhibited hyperglycemia 7-21 days later. In stark contrast, all Mt3-null mice remained normoglycemic following STZ injection. STZ treatment increased free Zn levels in islet cells and induced their death in WT mice, but failed to do so in Mt3-null mice. Consistent with this, cultured Mt3-null islet cells exhibited striking resistance to STZ toxicity. Notably, PDE3a (phosphodiesterase 3A) was downregulated in islets of Mt3-null mice compared to those of WT mice, and was not induced by STZ treatment. Moreover, the PDE3 inhibitor cilostazol reduced islet cell death, likely by increasing cAMP levels, further supporting a role for PDE3 in STZ-induced islet cell death. Collectively, these results demonstrate that Mt3 may act through PDE3a to play a key role in Zn dyshomeostasis and cell death in STZ-treated islets.

Dietary zinc supplementation to the donor improves insulin secretion after islet transplantation in chemically induced diabetic rats

OBJECTIVES

Zinc (Zn) is related to insulin synthesis, storage, and secretion. This study demonstrates the effects of Zn supplementation in donor rats on the outcomes of islet transplantation.

METHODS

Donor rats received 3 different regimens of dietary Zn supplementation for 2 weeks before undergoing pancreas donation: a standard diet containing Zn at 50 ppm (control), 1 ppm (low-Zn group) or 1000 ppm (high-Zn group), respectively. Diabetic recipient rats underwent islet transplantation, and the blood glucose levels and insulin secretion were monitored for 7 days after transplantation.

RESULTS

The serum and pancreatic Zn levels at the time of donation were significantly lower in the low-Zn group (48.8 ± 25.5 µg/dL and 11.3 ± 1.9 µg/g) and higher in the high-Zn group (147.3 ± 17.6 µg/dL and 18.7 ± 2.2 µg/g) when compared with those observed in the controls (118.7 ± 7.9 µg/dL and 14.6 ± 2.0 µg/g) (P < 0.05). The blood glucose levels became re-elevated 2 days after transplantation in rats receiving islet grafts from the controls and the low-Zn groups. In contrast, in the rats that received islets from the high-Zn groups, these were maintained within a reference range (P < 0.01).

CONCLUSIONS

These data indicate that a Zn-rich diet for donor rats improves the function of islet grafts in chemically induced diabetic rats.

Zinc oxide nanoparticles show antidiabetic activity in streptozotocin-induced Type 1 and 2 diabetic rats

Aim: The correlation of diabetes and an imbalance in zinc homeostasis makes zinc-based therapy an attractive proposition. In this study, zinc oxide nanoparticles were evaluated for antidiabetic effects and safety. Materials & methods: Zinc oxide nanoparticles (1, 3 and 10 mg/kg) were tested for antidiabetic activity in streptozotocin-induced Type 1 and 2 diabetic rats. A single-dose pharmacokinetic study, cytotoxicity, hemolysis, acute and subacute toxicity tests, and mechanism-of-action studies were performed. Results: Oral administration of zinc oxide nanoparticles resulted in significant antidiabetic effects – that is, improved glucose tolerance, higher serum insulin (70%), reduced blood glucose (29%), reduced nonesterified fatty acids (40%) and reduced triglycerides (48%). Nanoparticles were systemically absorbed resulting in elevated zinc levels in the liver, adipose tissue and pancreas. Increased insulin secretion and superoxide dismutase activity were also seen in rat insulinoma (RIN-5F) cells. Nanoparticles were safe up to a 300 mg/kg dose in rats. Conclusion: Zinc oxide nanoparticles are a promising antidiabetic agent warranting further studies.

Original submitted 9 July 2012; Revised submitted 27 November 2012; Published online 21 February 2013

Antidiabetic and pancreas-protective effects of zinc threoninate chelate in diabetic rats may be associated with its antioxidative stress ability

Zinc exerts a wide range of important biological roles. The present study was carried out to investigate the effects of zinc threoninate chelate in blood glucose levels, lipid peroxidation, activities of antioxidant defense systems and nitrite concentration, and histology of the pancreas in diabetic rats. Wistar rats were intravenously injected with a single dose of streptozotocin to induce diabetes. Then, diabetic rats were administrated orally with zinc threoninate chelate (3, 6, and 9 mg/kg body weight) once daily for 7 weeks. Fasting blood glucose was monitored weekly. At the end of the experimental period, the diabetic rats were killed, and levels of serum insulin, malondialdehyde, and nitric oxide, activities of glutathione peroxidase, total superoxide dismutase, copper/zinc-superoxide dismutase, and nitric oxide synthase were determined; pancreas was examined histopathologically as well. Zinc threoninate chelate significantly reduced the blood glucose levels and significantly increased the serum insulin levels in diabetic rats. In addition, zinc threoninate chelate caused a significant increase in activities of antioxidant enzymes and significant decrease in nitrite concentration and malondialdehyde formation in the pancreas and serum of diabetic rats. These biochemical observations were supplemented by histopathological examination of the pancreas. These results suggested that the antidiabetic effect of zinc threoninate chelate may be related to its antioxidative stress ability in diabetic rats.

Zinc and zinc transporter regulation in pancreatic islets and the potential role of zinc in islet transplantation

The critical trace element zinc is essential for normal insulin production, and plays a central role in cellular protection against apoptosis and oxidative stress. The regulation of zinc within the pancreas and β-cells is controlled by the zinc transporter families ZnT and ZIP. Pancreatic islets display wide variability in the occurrence of these molecules. The zinc transporter, ZnT8 is an important target for autoimmunity in type 1 diabetes. Gene polymorphisms of this transporter confer sensitivity for immunosuppressive drugs used in islet transplantation. Understanding the biology of zinc transport within pancreatic islets will provide insight into the mechanisms of β-cell death, and may well reveal new pathways for improvement of diabetes therapy, including islet transplantation. This review discusses the possible roles of zinc in β-cell physiology with a special focus on islet transplantation.