Hypoglycemic and antihyperlipidemic effects of hydroalcoholic extract of maize silk on dexamethasone-induced-hyperglycemic rats

Barnabé Lucien Nkono Ya Nkono; Rouamba Ablassé; Mc Jesus Kinyok; Soumiatou Nzikoué; Léocadie Mbella Kédi; Placide Yannick Amougou Noa; Paul Désiré Djomeni Dzeufiet; Sélestin Dongmo Sokeng; Pierre Kamtchouing

doi:10.4103/JCDM.JCDM_16_21

ORIGINAL ARTICLES

Year : 2022 | Volume : 2 | Issue : 1 | Page : 15-22

Hypoglycemic and antihyperlipidemic effects of hydroalcoholic extract of maize silk on dexamethasone-induced-hyperglycemic rats

Barnabé Lucien Nkono Ya Nkono¹, Rouamba Ablassé², Mc Jesus Kinyok³, Soumiatou Nzikoué¹, Léocadie Mbella Kédi¹, Placide Yannick Amougou Noa¹, Paul Désiré Djomeni Dzeufiet⁴, Sélestin Dongmo Sokeng⁵, Pierre Kamtchouing⁴
¹ Department of Biological Sciences, Higher Teacher Training College, University of Yaoundé I, Yaoundé, Cameroon
² Department of Chemistry, Laboratory of Applied Biochemistry and Chemistry, University Joseph KI-ZERBO, Ouagadougou, Burkina Faso
³ Department of Chemistry, Higher Teacher Training College, University of Yaoundé I, Yaoundé, Cameroon
⁴ Department of Animal Biology and Physiology, Faculty of Sciences, University of Yaoundé I, Yaoundé, Cameroon
⁵ Department of Biological Sciences, Faculty of Sciences, University of Ngaoundéré, Ngaoundéré, Cameroon

Date of Submission	06-Oct-2021
Date of Decision	18-Jan-2022
Date of Acceptance	25-May-2022
Date of Web Publication	29-Jun-2022

Correspondence Address:
Barnabé Lucien Nkono Ya Nkono
Department of Biological Sciences, Higher Teacher Training College, University of Yaoundé I, PO Box 8201 Yaoundé
Cameroon

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/JCDM.JCDM_16_21

Abstract

Context: Maize silk (Zea mays) is used in traditional medicine to treat high blood pressure, diabetes and obesity. It is also used as an immunostimulant but few scientific studies are available to validate these properties. Aims: The aim of this study was to scientifically validate the traditional use of maize silk in the regularization of lipid profile and blood glucose level. Material and Methods: Hydroalcoholic extract of maize silk (HAEMS) was prepared by decoction (30:70 Water-Ethanol) from the dry powder of corn silk (250 g/L). Hyperglycemia was induced by repeated single daily subcutaneous injection (s.c) of dexamethasone (5 mg/kg); dexamethasone negative control group (DNC) received dexamethasone exclusively throughout 14 days while negative normal control group (NNC) received only vehicle during the same period. Positive control group (glibenclamide) and plant extract groups (50 and 100 mg/kg) received dexamethasone from the eighth day and each group consisted of six animals. All the parameters (fasting blood glucose level, TC, HDL, LDL, VLDL, atherogenic index (AI) and TG) were measured on the first, seventh and fourteenth day of the experiment. Lipid profile was performed using a BIOLABO^® Kit and fasting blood glucose level was measured using a glucometer VivaCheck™ Ino. Results: Compared to the DNC group, HAEMS significantly reduced (P<0.001) on days seven and fourteen, fasting blood glucose level, TC, LDL, VLDL, artherogenic AI and TG (on day seven). In addition, only the dose of 50 mg/kg significantly increased serum HDL on the seventh (P<0.01) and fourteenth day (P<0.001). Conclusion: The results obtained in this study suggest that HAEMS have hypoglycemic and antihyperlipidemic properties.

Keywords: Dexamethasone, glycemia, hydroalcoholic extract, lipid profile, maize silk

How to cite this article:
Nkono Ya Nkono BL, Ablassé R, Kinyok MJ, Nzikoué S, Kédi LM, Noa PY, Djomeni Dzeufiet PD, Sokeng SD, Kamtchouing P. Hypoglycemic and antihyperlipidemic effects of hydroalcoholic extract of maize silk on dexamethasone-induced-hyperglycemic rats. J Cardio Diabetes Metab Disord 2022;2:15-22

How to cite this URL:
Nkono Ya Nkono BL, Ablassé R, Kinyok MJ, Nzikoué S, Kédi LM, Noa PY, Djomeni Dzeufiet PD, Sokeng SD, Kamtchouing P. Hypoglycemic and antihyperlipidemic effects of hydroalcoholic extract of maize silk on dexamethasone-induced-hyperglycemic rats. J Cardio Diabetes Metab Disord [serial online] 2022 [cited 2023 Jun 7];2:15-22. Available from: http://www.cardiodiabetic.org/text.asp?2022/2/1/15/349195

Introduction

Noncommunicable diseases (NCDs) currently cause more deaths than all other causes combined and NCD deaths are projected to increase from 38 million in 2012 to 52 million by 2030. Four major NCDs (cardiovascular diseases, cancer, chronic respiratory diseases and diabetes) are responsible for 82% of NCD deaths.^[1] Faced with the considerable increase in the number of patients due to NCDs, particularly in developing countries, treatment based on natural plants presents itself as an alternative. The latter would indeed be less expensive, available in abundance and would have fewer adverse effects compared to conventional treatments.

More than 80% of populations in low- and middle-income countries use the traditional pharmacopoeia to solve primary health problems, but most of the plants used for this purpose are not justified by scientific studies to validate their use with confidence. Maize silk is used in traditional medicine to treat NCDs such as high blood pressure, diabetes, and obesity.^[2],[3],[4] It is also used as an immunostimulant and diuretic^[5] but few scientific studies are available to validate these properties. However, scientific works show that maize silk contains antioxidant,^[6],[7] antibacterial and photoprotective properties against^[8] ultraviolet B-induced skin damage.^[9],[10] Given this, the present study was conducted to explore the effects of hydroalcoholic extract of maize silk on the regulation of the lipid profile, the strengthening of the immune system as well as its cytoprotective effect in order to scientifically validate its traditional use.

Material and Methods

Plant materials

Maize silk was harvested at a popular market in the square with fresh corn sellers. After harvesting, maize silk was previously washed with tap water to remove impurities and then drained with a strainer and dried in the shade for two weeks at room temperature in the laboratory. After drying, maize silk was pounded using a mortar and then crushed using an electric blender. The resulting powder was sieved using a 0.5 mm diameter sieve to obtain a finer powder, which was stored away from sunlight in a dark glass jar for the subsequent preparation of the hydroalcoholic extract.

Preparation of the extract

The preparation of HAEMS was made by infusion by introducing a one-liter Erlenmeyer 250 g of maize silk powder. One liter of solvent system 30:70 (300 mL of water and 700 mL of ethanol) boiling was then added in the Erlenmeyer to the gauge line. The set was left to rest for infusion at room temperature until the preparation cooled. The mixture was then filtered using Whatman Filter Paper n°4. The filtrate was dried in a rotary evaporator at 45°C until the solvent evaporated completely. Three days before the start of the experiment, the resulting dry extract was reconstituted in 100% dimethyl sulfoxide (DMSO) to eliminate any living cells that could contaminate the extract. The mixture was filtered using a microporous filter with a diameter of less than 5 μm and stored in a dark glass container in the refrigerator at 4°C for later use. Every morning, two concentrations of HAEMS (5 and 10 mg/mL) that corresponded to the respective doses of 50 and 100 mg/kg were prepared by diluting HAEMS solubilized in DMSO 100% in distilled water in order to obtain concentrations of extract containing DMSO at 1%, which is non-toxic to living organisms.

Experimental animals

The study was carried out on albino male rats of Wistar strain (Rattus norvegicus), eight weeks old at the beginning of the experiment. These rats were raised under conditions of ambient temperature (24 ± 2°C) and normal light/dark cycle in polypropylene cages. The animals had free access to water and food of standard composition (2900 Kcal/kg: 9% lipids, 68% carbohydrates and 23% proteins). All the animal experiments were carried out in accordance with the guidelines of Cameroon National Ethics committee (Ref. FWIRB 00001954).

Induction of hyperglycemia and experimental design

Hyperglycaemia was induced by daily injection of dexamethasone (RYAN PHARMA® – UK) at a dose of 5 mg/kg subcutaneously once daily following the method described by Kumar et al.^[11] Animals were considered hyperglycemic when their fasting blood glucose levels after 7 days were greater than 110 mg/dL. The different experimental groups were distributed as follows:

Group 1:

Served as a normal negative control (NNC) and did not receive any treatment except vehicle during the 14 days of experimentation (10 mL/kg distilled water, p.o. and 1 mL/kg of NaCl solution, s.c);

Group 2

Served as a hyperglycemic negative control and received during the 14 days of experimentation 10 mL/kg of distilled water p.o and 5 mg/kg of dexamethasone s.c (DNC);

Group 3

Served as a positive control and received simultaneously glibenclamide (5 mg/kg, bw) and 1 mL/kg of NaCl solution (s.c) during the first seven days of the experiment and from the eighth to the fourteenth day of the experiment received glibenclamide (p.o) and 5 mg/kg dexamethasone (s.c);

Group 4 and 5

Were used as HAEMS-treated groups at doses of 50 and 100 mg/kg, respectively. From day 1 to day 7 these groups received the plant extract at the respective doses (p.o) and 1 mL/kg of a Saline solution of NaCl (s.c). From the eighth to the fourteenth day, groups 4 and 5 received simultaneously the respective doses of plant extract (p.o) and dexamethasone (5 mg/kg).

Collection of samples and preparation

The blood samples were taken after ether anesthesia of the animals by the retro-orbital method on the first, seventh and fourteenth day of experiment. Rats were previously subjected to a food fasting of 12 hours before the blood sample. For realization of the determination of lipid parameters, the blood taken was centrifuged at 2500 revolutions per minute for 15 minutes in order to obtain the serum. The serum was taken from aliquots and frozen at –20°C for the subsequent determination of lipid parameters.

Concerning blood cell counts, blood samples were introduced into heparinized tubes and diluted (at 1/200^th for RBC count and 1/20^th for WBC count) with phosphate buffered saline (PBS), Sigma-Aldrich. Blood cell counts were performed immediately after dilution of the blood.

Biochemical parameters

Fasting blood glucose level (mg/dL) was measured using a glucometer (VivaCheck™ Ino) by depositing on the test strip a drop of blood obtained from the puncture of the rats’ tail part.

Lipid profile (TC, HDLc and TG) was measured spectrophotometrically (g/L) using the standards reagents obtained from Biolabo, France. LDLc and VLDLc were calculated using Friedewald’s formula as follows:

The atherogenicity index was also determined by calculation using the following formula:

The blood cell count was performed using the Neubauer hemacytometer and the cell count calculation was performed using the following formula:

Histopathological examination of liver tissue

At the end of the 14 days of experimentation, the animals were sacrificed under ketamine anesthesia at a dose of 45 mg/kg after a fasting 12 hours. The liver was removed and the histological sections of liver were carried out according to the method described by Okoduwa et al.^[12]

Statistical analysis

All analyses were performed using GraphPad Prism (version 5.0). Values were expressed as mean ± standard error of the mean (SEM). Analysis of variance (ANOVA, Bonferroni post-test) and pair t-test were done as the test of significance. A value of P <0.05 was considered statistically significant.

Results

Effect of treatment on fasting blood glucose level

The change in fasting blood glucose level of rats after seven days of treatment showed in the groups that received the plant extract at 50 mg/kg and 100 mg/kg as well as those in the glibenclamide groups, a highly significant decrease (P<0.001) in blood glucose compared to the NNC and DNC control groups [Table 1]. A highly significant decrease (P<0.001) in blood glucose level was also observed with concomitant administration of dexamethasone and the various treatments (plant extract and glibenclamide) compared to the DNC group that received exclusively dexamethasone during the 14 days of experimentation. Although these blood glucose values are significantly higher on the fourteenth day compared to those recorded on the seventh day of treatment (119.00 ± 3.11 and 114.40 ± 2.44 mg/dL, respectively, for the doses of 50 and 100 mg/kg of the plant extract and 86.600 ± 3.56 for the positive control group), it emerges from these results that the hyperglycemic effect induced by dexamethasone was strongly inhibited the increase in blood glucose compared to the value observed in the DNC group (160.60 ± 3.34) having exclusively received dexamethasone. On the other hand, compared to the NNC group that did not receive dexamethasone at any time during the experimental period, the plant extract at both doses tested had significantly high fasting blood glucose levels (P<0.001) unlike the group that received glibenclamide which showed a significant reduction (P<0.01) in fasting blood glucose compared to the NNC group.

Table 1: Effects of treatment with HAEMS on blood glucose level in normal and dexamethasone-induced-hyperglycemic rats

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Effect of treatment on serum lipid profile

The level of serum TC was significantly elevated on the seventh (P<0.05) and fourteenth day (P<0.001) of treatment in the DNC group compared to the NNC group [Table 2]. On the seventh day, the groups that received glibenclamide and plant extract at both doses had a non-significant reduction (P>0.05) in serum TC compared to the NNC group, but rather had a significant reduction compared to the DNC group of P<0.01 (glibenclamide and HAEMS 100 mg/kg) and P<0.001 (HAEMS 50 mg/kg). On the fourteenth day of experimentation, after one week of concomitant administration of dexamethasone and the various treatments, a reduction in serum TC was observed in all experimental groups compared to the DNC group, P<0.001 (glibenclamide and HAEMS 100 mg/kg) and P>0.05 (HAEMS 50 mg/kg).

Table 2: Effects of treatment with HAEMS on lipid profile in normal and dexamethasone-induced-hyperglycemic rats

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In normoglycemic rats, only the dose of 50 mg/kg of plant extract induced a significant increase (21.33 ± 1.57, P<0.01) on the level of serum HDL (mg/dL) after seven days of HAEMS pre-treatment compared to the DNC group (14.56 ± 1.39) [Table 2]. It should be noted that the NNC, glibenclamide and plant extract group (100 mg/kg) also had a non-significant increase (P>0.05) on the level of serum HDL (18.26 ± 1.10, 16.95 ± 1.35 and 17.90 ± 1.07, respectively). On the other hand, on the fourteenth day of treatment after concomitant administration of dexamethasone and the various treatments, in the experimental groups, there was a significant decrease in the amount of serum HDL P<0.001 (DNC and glibenclamide) and P<0.01 (HAEMS 100 mg/kg) compared to the NNC group (23.79 ± 0.84), with the exception of the group that received HAEMS at the dose of 50 mg/kg (P>0.05, 20.64 ± 1.24). In addition, compared to the DNC group, only the 50 mg/kg dose of plant extract had a significant increase (P<0.001) in serum HDL on the fourteenth day of treatment.

It was observed throughout the experimental period that there was no significant difference (P>0.05) between the NNC and DNC group with regard to the serum level of TG (mg/dL) [Table 2]. However, compared to the NNC group, there was a dose-dependent decrease P>0.05 and P<0.05 in serum TG on the seventh day of treatment at doses of 50 (43.87 ± 2.92) and 100 mg/kg (41.54 ± 3.10), respectively. Compared to the DNC group, there was a significant reduction P<0.01 (glibenclamide and HAEMS 50 mg/kg) and P<0.001 (HAEMS 100 mg/kg).

On the fourteenth day of treatment, only the dose of 50 mg/kg HAEMS showed a significant decrease (45.42 ± 5.20, P<0.05) compared to the DNC group.

[Table 2] shows the results of serum variation in the amount of LDL (mg/dl) after 14 days of experimentation. Compared to normoglycemic rats in lot NNC on the seventh (20.33 ± 4.27) and fourteenth (9.60 ± 3.80) test day, the non-treated dexamethasone-induced-hyperglycemic rats (DNC) showed a significant increase in serum LDL of P<0.05 and P<0.001, respectively, on the seventh (33.62 ± 1.34) and fourteenth (34.53 ± 0.74) treatment day.

Plant extract induced a highly significant reduction (P<0.001) in serum LDL in the seventh (50 mg/kg) and fourteenth (100 mg/kg) day of treatment compared to the DNC group. This effect of plant extract was also similar to that of glibenclamide when compared to the DNC group on the seventh (P<0.05) and fourteenth (P<0.001) day of treatment.

Repeated subcutaneous administration of dexamethasone in animals in the untreated dexamethasone-induced-hyperglycemic rats (DNC) resulted in a highly significant increase (P<0.001) in serum VLDL (mg/dL) in the seventh (12.37 ± 0.23) and fourteenth (11.58 ± 0.20) day of administration compared to the group of animals not receiving dexamethasone throughout the experimental period, 10.50 ± 0.22 and 9.50 ± 0.18, respectively, on the seventh and fourteenth day [Table 2]. On the seventh day, plant extract at both doses significantly reduced (P<0.001) the amount of serum VLDL compared to the NNC and DNC groups. However, on the fourteenth day of treatment, there was a significant decrease in the amount of VLDL only compared to the DNC group of 9.08 ± 0.26 and 10.67 ± 0.32, respectively, at doses of 50 (P<0.001) and 100 (P<0.05) mg/kg.

Concerning the AI, it was observed that rats in DNC group that received only dexamethasone throughout the experimental period were found to be highly elevated (P<0.001) on the seventh (4.276 ± 0.320) and fourteenth (4.772 ± 0.218) days of treatment compared to the NNC group (2.770 ± 0.384 and 1.824 ± 0.218 on the seventh and fourteenth day, respectively) who received only the vehicle during the entire treatment period [Table 2].

In normoglycemic rats, the plant extract at the two doses tested had no significant difference (P>0.05) compared to the NNC group on the seventh and fourteenth days of experimentation unlike the DNC group where there was a highly significant difference (P<0.001) with a greater reduction in AI at the 50 mg/kg dose (1.94 ± 0.13) than at the 100 mg/kg dose (2.61 ± 0.17). The same effect was observed on a dose-dependent manner on the fourteenth day after induction of hyperglycemia with dexamethasone. In addition, the positive control group had similar results to those of the plant extract on the seventh and fourteenth day compared to the NNC (P>0.05) and DNC groups (2.88 ± 0.35, P<0.01 and 1.63 ± 0.02, P<0.001 on the seventh and fourteenth day, respectively), with a greater reduction in AI than that of the plant extract on the fourteenth day.

Effect of treatment on blood cell counts

[Table 3] shows the effect of HAEMS on the variation of RBC count (x10⁶ cells/μL) in normoglycemic rats and dexamethasone-induced hyperglycemic rats. After seven days of pre-treatment with plant extract at doses of 50 and 100 mg/kg, the RBC count decreased significantly (P<0.001) compared to the NNC group (6.082 ± 0.154) by 1.988 ± 0.193 (50 mg/kg) and 2.864 ± 0.061 (100 mg/kg), respectively. The same reduction (P<0.001) was also observed in the DNC (2.028 ± 0.116) and glibenclamide (4.290 ± 0.170) groups. On the other hand, compared to the DNC group, plant extract induced a non-significant reduction (P>0.05) in the RBC count at the dose of 50 mg/kg and a significant increase (P<0.05) at the dose of 100 mg/kg.

Table 3: Effects of treatment with HAEMS on variation of serum RBC and WBC count in normoglycemic and dexamethasone-induced-hyperglycemic rats

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On the fourteenth day of testing, the positive control group that received glibenclamide (7.360 ± 0.280) and plant extract at doses of 50 (8.300 ± 0.141) and 100 mg/kg (9.860 ± 0.339) induced a highly significant increase (P<0.001) in the RBC count compared to the NNC (6.060 ± 0.225) and DNC (1.500 ± 0.072) groups.

The results obtained on the serum variation in the WBC count (x10³ cells/μL) are recorded in [Table 3]. On the seventh day of treatment, glibenclamide (10.625 ± 0.688) and HAEMS induced an increase (dose-dependent for HAEMS) in the WBC count compared to the NNC (7.500 ± 1.080) and DNC (5.250 ± 0.629) groups. Only the 100 mg/kg HAEMS dose had a significant increase (P<0.05) compared to the DNC group on day seven.

After concomitant administration of dexamethasone and the various treatments, both the positive control group receiving glibenclamide (43.750 ± 2.394) and those receiving HAEMS at doses of 50 (41.250 ± 2.394) and 100 mg/kg (46.250 ± 2.947) had a highly significant increase (P<0.001) in the WBC count compared to the NNC (15.00 ± 2.887) and DNC (23.750 ± 3.146, P<0.01 vs. NNC) groups.

Effect of treatment on histology of the liver tissue

[Figure 1] shows the histological sections of the liver made in all groups of this study.

Figure 1: Photographs of liver tissue of normal and dexamethasone-induced-hyperglycemic rats after fourteen days of treatment (H&E, stain, ×200). Gc = gallic canaliculus, Ha = hepatic artery, He = hepatocitis, Hc = hepatic cytolysis, Li = leukocyte infiltration, Pv = portal vein, Sc = sinusoidal capillary. (A) NNC: Negative normal control (non-hyperglycemic group): Section shows normal histology of the liver with a well-structured parenchyma and no presence of leukocyte infiltration. (B) DNC: Dexamethasone negative control (negative hyperglycemic group): Section shows several histopathological alterations such as hepatic cytolysis and leukocyte infiltration. (C) Glibenclamide (positive control) as well as those receiving the extract at different doses (50 and 100 mg/kg), respectively, (D) and (E) show a restructuring of liver tissue, close to that of the normal control

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Histological analysis showed in the normal control (NNC) a normal structuring of the hepatic parenchyma. Compared to normal control group, animals in the negative control group that received only dexamethasone (DNC) had several histopathological alterations such as cytolysis. Groups treated with glibenclamide as well as those receiving the extract at different doses (50 and 100 mg/kg) showed a restructuring of liver tissue, close to that of the normal control.

Discussion

The present study was conducted with the aim of scientifically demonstrating the empirical use of maize silk in the regulation of blood glucose, lipid profile and strengthening of the immune system in immunocompromised people.^[2],[4]

To carry out this study, we used an experimental model of dexamethasone-induced hyperglycemia and dyslipidemia in rats. Dexamethasone is a steroid that slows down the inflammatory process but, long-term steroid treatment has many side effects such as increased risk of infection, high blood pressure and development of diabetes. Adeneye and Olagunju^[11] reported that dexamethasone induces glycemic and lipid imbalance after subcutaneous administration at a dose of 10 mg/kg once daily for 30 days.

In the present study, fasting blood glucose levels of animals in the DNC group that received dexamethasone alone at a dose of 5 mg/kg throughout the experimental period increased by 41.709% and 76.986% from baseline of the first day before administration of dexamethasone. The hypoglycemic effect of HAEMS was evaluated after seven days of pre-treatment with plant extract with a fasting blood glucose reduction rate of 14.2% and 17.2%, respectively, at doses of 50 and 100 mg/kg. The same effect was observed with glibenclamide, a reference insulin-secretor that reduced fasting blood glucose by 28.6% after seven days of administration. Hydroalcoholic extract of maize silk could also have hypoglycemic activity similar to that of glibenclamide by stimulating pancreatic beta cells to release insulin. This suggests that HAEMS possesses one or more important active hypoglycemic biological principles because, despite endogenous counter-regulatory factors such as catecholamine, cortisol, and glucagon, hypoglycemia has been maintained.^[12] In addition, after concomitant administration of dexamethasone and plant extract for seven days, an increase in blood glucose of 27.199% and 22.216%, respectively, at doses of 50 and 100 mg/kg was observed. Although these blood sugar levels were quite high, the fact remains that they were well below the value of the negative control group which had increased by 76.986% compared to the blood glucose value on the first day of the experiment. Literature reveals the involvement of flavonoids and alkaloids as hypoglycemic active ingredients present in several medicinal plants.^[13],[14] The phytochemistry of the aqueous and methanolic extract of maize silk reveals the presence of proteins, vitamins, carbohydrates, Ca, K, Mg and Na salts, fixed and volatile oils, steroids such as sitosterol and stigmasterol, alkaloids, saponins, tannins and flavonoids.^[15] The high content of soluble fiber as well as the polysaccharides in the plant extract could justify the hypoglycemic activity of HAEMS.^[16],[17] Olaniyan and Fadare^[16] have shown in rabbits that the action of the aqueous and methanolic extract of maize silk on glycemic metabolism is not done by increasing glycogen and inhibiting gluconeogenesis, but by increasing insulin levels and recovering damaged beta cells.

Insulin resistance and hyperinsulinemia are often associated with a group risk factors such as obesity, dyslipidemia, hypertension and impaired glucose tolerance.^[18] In the present study, dexamethasone administered for 14 days in normoglycemic rats induced a serum increase in TC (P<0.001), TG (P>0.05), LDL (P<0.001), VLDL (P<0.001) and AI (P<0.001) while it induced a reduction in HDL (P<0.001) compared to the normal control group. These results are similar to previous studies.^{[18],[19],[20]} The hydroalcoholic extract of maize silk antagonized the hyperlipidemic effects induced by dexamethasone by significantly reducing the serum level in TC (P<0.001), TG (P<0.05), LDL (P<0.001), VLDL (P<0.001) and AI (P<0.001) while serum HDL was significantly elevated (P<0.001). The corticoid treatment is known to cause an increase in the secretion of VLDL by liver and in addition corticoids may also stimulate VLDL formation by the intestine.^[20] The lower level of liver lipoprotein lipase activity could have been responsible for the high VLDL-TG level and this also cause imbalance in lipid metabolism leading to hyperlipidemia.^[19] A drug that is found to be active in type 2 diabetes models may have some role in decreasing cholesterol and TG levels.^[21] This is similar to the present study which also revealed that the concomitant administration of dexamethasone in addition to HAEMS allowed a significant normalization of the effects induced by dexamethasone in particular on the increase in serum cholesterol, TG and AI. These results would support the therapeutic property of HAEMS against dexamethasone-induced hyperlipidemia and hypercholesterolemia in rats.

Anemia is the reduction of hemoglobin (Hb), or hematocrit (HCT) or RBC count^[22] It is noted that administered alone during the first seven days of the experiment, dexamethasone, glibenclamide and HAEMS significantly reduced (P < 0.001) RBC count at both doses tested compared to the normal control group. Like dexamethasone, HAEMS also contains steroids^[17] that could give it the significant decrease in RBC count observed after seven days of administration in normal animals and this in the same way as normal animals in the negative control group that received exclusively dexamethasone. On the other hand, after concomitant administration of dexamethasone and the different treatments, the groups that received glibenclamide and HAEMS, respectively, at the two doses tested induced on the fourteenth day, a highly significant increase in RBC count compared to the control group unlike the negative control group that received exclusively dexamethasone throughout the experimental period. These results indicate that HAEMS would boost erythropoiesis. Therefore, this extract could be indicated in situations of anemia characterized by a decrease in RBC count.^[23] Leukocytes or WBC are cells produced by the bone marrow and found in the blood. They increase with infection, inflammation, allergy, bone marrow dysfunction or due to certain medications. Dexamethasone is a steroid that reduces inflammation by mimicking the anti-inflammatory hormones produced by the body. The High Council of Public Health of France (HCSP) has demonstrated in people with corona virus that dexamethasone works by reducing the body’s immune system.^[24] Infection with the corona virus triggers inflammation when the body tries to fight. Nevertheless, sometimes the immune system is overloaded and it is this reaction that can prove fatal because this reaction that aims to fight the infection ends up attacking the body’s own cells. Dexamethasone calms this effect during a severe inflammatory process but is not advised during mild inflammatory symptoms. In addition, dexamethasone does not act on people with milder inflammatory symptoms, and weakening their immune system at this stage would not be helpful and could be fatal. Interestingly, when administered concomitantly with dexamethasone, we observed on the fourteenth day that HAEMS significantly increased the WBC count at both doses tested. The same variation was also observed in the positive control batch that received glibenclamide. Our results are consistent with those obtained by Saheed et al.^[6] who also noted a significant increase in white blood cell levels in rats given the aqueous extract of maize silk. These results indicate that HAEMS would stimulate the immune system and boost erythropoiesis.

In the present study, the histopathological results of the liver revealed the damage to liver tissue caused by dexamethasone in the negative control group that received this substance exclusively during the experimental period. On the other hand, groups treated simultaneously with dexamethasone and HAEMS at different doses (50 and 100 mg/kg) showed a restructuring of liver tissue, close to that of the normal control, which suggests that this plant extract has cytoprotective activity, in particular on hepatic cells.

Conclusion

The results obtained support the traditional use of maize silk in the treatment of obesity and blood sugar regulation. In the present study, we observed that HAEMS has significant hypoglycemic activities, antihyperlipidemic, immunostimulant, cardioprotective and hepatoprotective properties in normal and dexamethasone-induced-hyperglycemic rats. However, it remains to explore the mechanisms of action responsible for the pharmacological effects observed as well as a study on the toxicity of this plant extract. In view of the results obtained, the hydroalcoholic extract of maize silk could be the subject of clinical trials in order to definitively validate its traditional use.

Financial support and sponsorship

Not applicable.

Conflicts of interest

There are no conflicts of interest.

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