A Protein Isolate from Moringa oleifera Leaves Has Hypoglycemic and Antioxidant Effects in Alloxan-Induced Diabetic Mice - PubMed (original) (raw)

A Protein Isolate from Moringa oleifera Leaves Has Hypoglycemic and Antioxidant Effects in Alloxan-Induced Diabetic Mice

Paulo C Paula et al. Molecules. 2017.

Abstract

Moringa oleifera has been used in traditional medicine to treat diabetes. However, few studies have been conducted to relate its antidiabetic properties to proteins. In this study, a leaf protein isolate was obtained from M. oleifera leaves, named _Mo_-LPI, and the hypoglycemic and antioxidant effects on alloxan-induced diabetic mice were assessed. _Mo_-LPI was obtained by aqueous extraction, ammonium sulphate precipitation and dialysis. The electrophoresis profile and proteolytic hydrolysis confirmed its protein nature. _Mo_-LPI showed hemagglutinating activity, cross-reaction with anti-insulin antibodies and precipitation after zinc addition. Single-dose intraperitoneal (i.p.) administration of _Mo_-LPI (500 mg/kg·bw) reduced the blood glucose level (reductions of 34.3%, 60.9% and 66.4% after 1, 3 and 5 h, respectively). The effect of _Mo_-LPI was also evidenced in the repeated dose test with a 56.2% reduction in the blood glucose level on the 7th day after i.p. administration. _Mo_-LPI did not stimulate insulin secretion in diabetic mice. _Mo-_LPI was also effective in reducing the oxidative stress in diabetic mice by a decrease in malondialdehyde level and increase in catalase activity. _Mo_-LPI (2500 mg/kg·bw) did not cause acute toxicity to mice. _Mo_-LPI is a promising alternative or complementary agent to treat diabetes.

Keywords: Moringa; antioxidant activity; diabetes therapy; hypoglycemic activity; plant protein.

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Conflict of interest statement

The authors declare no conflict of interest. The funding sponsors had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, and in the decision to publish the results.

Figures

Figure 1

Figure 1

Assessment of the in vitro digestibility of _Mo_-LPI by SDS-PAGE analysis. _Mo_-LPI was incubated with pepsin or trypsin at different times (0, 2 and 4 h). (a) Pepsin digestion; (b) Trypsin digestion. Bovine serum albumin (BSA) was used as control. Twenty microgram from each sample were loaded in each well. Vertical numbers indicate the molecular mass markers: phosphorylase B (97 kDa); BSA (67 kDa); ovalbumin (45 kDa); carbonic anhydrase (29 kDa); trypsin inhibitor (20.1 kDa) and α-lactalbumin (14.2 kDa). Horizontal numbers refer to the digestion times (h).

Figure 1

Figure 1

Assessment of the in vitro digestibility of _Mo_-LPI by SDS-PAGE analysis. _Mo_-LPI was incubated with pepsin or trypsin at different times (0, 2 and 4 h). (a) Pepsin digestion; (b) Trypsin digestion. Bovine serum albumin (BSA) was used as control. Twenty microgram from each sample were loaded in each well. Vertical numbers indicate the molecular mass markers: phosphorylase B (97 kDa); BSA (67 kDa); ovalbumin (45 kDa); carbonic anhydrase (29 kDa); trypsin inhibitor (20.1 kDa) and α-lactalbumin (14.2 kDa). Horizontal numbers refer to the digestion times (h).

Figure 2

Figure 2

Dot blot assay using human anti-insulin as primary antibodies. (a) Tris-buffered saline; (b) Human recombinant insulin (2 mg/mL) incubated with human anti-insulin IgG (1:250); (c–e) _Mo_-LPI (2 mg/mL) incubated with primary antibodies diluted 1:250, 1:500 and 1:1000, respectively.

Figure 3

Figure 3

Zn-induced precipitation. (a,c) zinc-free human recombinant insulin (5 mg/mL) and _Mo_-LPI (5 mg/mL) solutions in 0.05 M Tris-HCl, pH 7.5, respectively; (b,d) zinc-free human recombinant insulin and _Mo_-LPI solutions after the addition of 1 M zinc chloride, respectively. Arrows indicate the protein precipitate.

Figure 4

Figure 4

Effect of intraperitoneal administration of _Mo_-LPI on blood glucose level in alloxan-induced diabetic mice. Values are means ± S.E.M. (n = 10). Control: vehicle (0.05 M Tris-HCl, pH 7.5, containing 0.15 M NaCl). * Significant (p < 0.01) difference when compared with the corresponding value of the control at the same time.

Figure 5

Figure 5

Influence of temperature on the hypoglycemic activity of _Mo_-LPI administered to alloxan-induced diabetic mice by intraperitoneal injection. Values are means ± S.E.M. (n = 10). Control: vehicle (0.05 M Tris-HCl, pH 7.5, containing 0.15 M NaCl). _Mo_-LPI unheated and previously boiled to 98 °C for 1 h. * Significant (p < 0.01) difference when compared with the corresponding value of the control at the same time.

Figure 6

Figure 6

Effect of oral administration of _Mo_-LPI on blood glucose level in alloxan-induced diabetic mice. Values are means ± S.E.M. (n = 10). Control: vehicle (0.05 M Tris-HCl, pH 7.5, 0.15 M NaCl). * Significant (p < 0.01) difference when compared with the corresponding value of the control at the same time.

Figure 7

Figure 7

Effect of _Mo_-LPI on blood glucose level after seven consecutive days of intraperitoneal administration to alloxan-induced diabetic mice. Values are means ± S.E.M. (n = 10). Control: vehicle (0.05 M Tris-HCl, pH 7.5, 0.15 M NaCl). * Significant (p < 0.01) difference when compared with the corresponding value of the diabetic control.

Figure 8

Figure 8

Effect of _Mo_-LPI on serum insulin level in alloxan-induced diabetic mice. Values are means ± S.E.M. (n = 10). Five hours after _Mo_-LPI or 0.15 M NaCl i.p. administration in alloxan-diabetic mice, blood samples were collected via cardiac puncture to assay the insulin level. Control: vehicle (0.05 M Tris-HCl, pH 7.5, containing 0.15 M NaCl).

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