The Mechanisms of PLANT Rhizome Curcuma Longa Action on Carbohydrate Metabolism in Alloxan - Induced Diabetes Mellitus Rats

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Consequently, the intake of Curcuma longa rhizome powder resulted in the decrease of blood glucose concentration in control rats (group 2), while in animals with alloxan-induced diabetes there occurred a less significant increase and more rapid normalization of blood glucose.

One of the reasons for decreasing blood glucose after ingestion of turmeric may be a reduction of the absorption rate of carbohydrates in the gastrointestinal tract due to inhibition of the Na⁺-glucose cotransporter ^{[13, 14]}. To test this hypothesis, the experiment with perfusion of immobilized small intestine with 30 % glucose solution was performed. It can be seen that in the diabetic rats the rate of glucose absorption was more than 2-fold higher than in control ones(Table 2), which may be due to the activation of the Na⁺-glucose cotransporter ^[14]. Rhizomes of Curcuma longa powder even in control animals contributed to reducing the absorbed amount of glucose, while in diabetic rats of the 4-th group receiving Curcuma longa there was observed only the tendency toward the reduction of the absorption rate. Turmeric, probably, inhibits the Na⁺- glucose cotransporter (SGLT), and similarlysynthesized blockers ^[15], but under the conditions of diabetes this effect was less pronounced.

Table 2. Glucose absorption in the gut of rats of different groups (M ± m)

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The glycogenesis process may play an important role in maintaining the glucose concentration in plasma may play.

To elucidate the mechanisms causing the significantly lower hyperglycemia in rats treated with turmeric, the glycogen content in the liver tissue was analyzed.

In alloxan-induced diabetic ratsthe glycogen content in the liver was significantly lower than in the control group (Table 3). This is probably due to an impaired glycogen synthesis during diabetes as a result of reduced activity of glycogensintetaseand the decrease of glucose oxidation processes due to a defect in the pyruvate dehydrogenase complex ^[16]. However, in rats of the4-th group, the glycogen content in the liver was increased almost to the control level and significantly differed from that of animals of the 3-rd group. Note, that in healthy rats, while inducing turmeric, glycogen content in the liver was also significantly lower than in the control group 1.Probably,this was due to a decrease in the blood glucose concentration in animals of this group (N 2), owing to that there was a redistribution of carbohydrates between the organ-depot (liver) and the blood for maintenance of the glucose concentration in plasma on normal values.

Since atalloxan-induced diabetes the endocrine function of the pancreas is impaired, it was important to evaluate changes in the concentration of basic glucose regulating hormones.

Table 3. Glycogen content in the liver of rats (mg/100 g wet weight) ( M ± m)

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Analysis of the results showed that in diabetic rats (group 3) plasma insulin concentration was significantly lower than in control animals, that coincides with data obtained previously and confirms the development of diabetes type I ^{[11, 17]}. A similar trend was observed concerning the level of C-peptide. However, in animals receiving turmeric (group 4) the concentration of these hormones in plasma increased (Table 4).

Table 4. Concentration of hormones in the blood of rats with alloxan diabetes (M ± m)

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As increasing the endocrine activity of the pancreas under the influence of Curcuma longa may be due to structural changes in the islet apparatus of the gland, the morphology of the pancreas in rats with alloxan-induced diabetes has been investigated.

The morphometric analysis of samples from the pancreas of animals has been demonstrated that the area of the islets in rats with alloxan-induced diabetes was almost 2 times larger than similar samples from the control group (Table 5). These results do not agree with the data of other researchers, showing reduction of the area of the pancreatic islets in the model of alloxan diabetes ^[18]. To resolve this contradiction we applied a method of morphological analysis, which allowed for visualizin the morphology of the pancreatic islets.

Table 5. Area of the Langerhans’islets, µm ²

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Preparations at the light level of the pancreas had marked differences in the group of rats with an alloxan diabetes model from similar samples of the control group (Figure 1A, Figure 1B ).

Figure 1B shows that intercellular substance of gland stroma both in the periphery of islets of Langerhans, and in endocrine part of the gland have symptoms of disorder. On histologic sections pays attention plethora of blood vessels and perivascular edema of the intercellular substance of space. A typical feature of rat’s pancreas samples of this group was the sludge phenomenon of erythrocytes in the lumen of the capillaries. In the cytoplasm of endocrine cells there are numerous small and large optically clear vacuoles (Figure 1B). At the periphery of the islands are visible cells with signs of lethal damage. Thus, increase of the islets of Langerhans area was resulted from tissue edema.

Morphologic analysis of the pancreas samples of rats treated with turmeric demonstrated reduction of structural damage compared to the samples in the second group of rats (Figure 1C). Signs of edema of the intercellular substance of connective tissue stroma was visible only in insular part of the gland and was absent in the intercellular substance that separated the exocrine part from the endocrine, as was the case in similar samples of gland in rats of the second group. Therefore, the insula part of the gland had significantly less area compared with those in the rats of the 2-nd group and did not differ from the intact animals. In samples of rat’s pancreas in the 3-d group was observed multicellularity in periphery of endocrine part of the gland (Figure 1D). The cells in this compartment had various morphology. Among the identified cells there were cells with low and high level of differentiation as well as with sublethal damage. The signs of owater - salt homeostasis disorders in the structures of the gland had been revealed.

Figure 1. pancreas of control group rat (A), with alloxan diabetes model (B, C), and after intake of the rhizome turmeric powder (D).

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