Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
, 10 (7), e0133374
eCollection

The Effects of Leucine, Zinc, and Chromium Supplements on Inflammatory Events of the Respiratory System in Type 2 Diabetic Rats

Affiliations

The Effects of Leucine, Zinc, and Chromium Supplements on Inflammatory Events of the Respiratory System in Type 2 Diabetic Rats

Saeed Kolahian et al. PLoS One.

Abstract

Diabetes mellitus is a major cause of serious micro- and macrovascular diseases that affect nearly every system in the body, including the respiratory system. Non-enzymatic protein glycation due to hyperglycaemic stress has fundamental implications due to the large capillary network and amount of connective tissue in the lung. The current study was designed to determine whether leucine, zinc, and chromium supplementations influence the function and histological structure of the respiratory tract in a rat model of type 2 diabetes. Seventy-seven rats were divided into eleven groups, consisting of 7 animals each. One group served as negative control and insulin and glibenclamide were used as positive control drugs. Thus, eight groups received the nutritional supplements alone or in combination with each other. Nutritional supplements and glibenclamide were added to the drinking water and neutral protamine Hagedorn insulin was subcutaneously injected during the 4 weeks of treatment period. The induction of type 2 diabetes in the rats caused an infiltration of mononuclear cells and edema in the submucosa of the trachea and lung, severe fibrosis around the vessels and airways, and perivascular and peribronchial infiltration of inflammatory cells and fibrin. In the diabetic group, the total inflammation score and Reid index significantly increased. Diabetes induction significantly reduced the total antioxidant status and elevated the lipid peroxidation products in the serum, lung lavage and lung tissue of the diabetic animals. Treatment with nutritional supplements significantly decreased the histopathological changes and inflammatory indices in the diabetic animals. Supplementation of diabetic rats with leucine, zinc, and chromium, alone and in combination, significantly increased the total antioxidant status and lipid peroxidation level in the diabetic animals. The nutritional supplements improved the enzymatic antioxidant activity of catalase, glutathione peroxidase, myeloperoxidase, and superoxide dismutase in the diabetic rats. The present results demonstrate beneficial effects and amelioration of inflammation in the respiratory system of type 2 diabetic rats by leucine, zinc, and chromium supplements, probably due to their hypoglycaemic and antioxidant properties. Using safe and effective nutritional supplements, such as leucine, chromium and zinc, to replace proven conventional medical treatments may help to control diabetes and/or its complications.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Histopathological findings in the tracheas of rats in all of the experimental groups.
A. Control (CTR): normal architecture of trachea Bar: 125 micrometres; B. Diabetic group (T2D): sub-mucosal gland hyperplasia. Although most of the glands are serous glands (black arrows), one mucus secretory unit is observable (white arrow) Bar: 50 micrometres; C. Insulin-treated group (INS): the trachea is approximately normal. Bar: 125 micrometres; D. Glibenclamide-treated group (GLC): inflammatory cells are obvious in the lamina propria and submucosa (white arrows). Bar: 12.5 micrometres; E. Leucine-treated group (Leu): inflammatory mononuclear cells are present in the submucosa (white arrows). Hypertrophic and hyperplastic glands are present (black arrow) Bar: 50 micrometres; F. Zinc-treated group (Zn): severe inflammation in the lamina propria and submucosa. Bar: 12.5 micrometres; G. Chromium-treated group (Cr): edema (black arrows) and inflammation (white arrows) in the lamina propria and submucosa. Bar: 50 micrometres; H. Zinc and Cr-treated group (Zn-Cr): edema (black arrows) and slight inflammation (white arrows) in the lamina propria and submucosa. Bar: 12.5 micrometres; I. Leu plus Zn-treated group (Leu-Zn): edema (black arrows) and slight inflammation (white arrows) in the lamina propria and submucosa. Bar: 12.5 micrometres; J. Leu plus Cr-treated group (Leu-Cr): inflammation in the submucosa (arrows) Bar: 50 micrometres; K. Zinc plus Cr-treated group (Zn-Cr): the presence of different types of inflammatory cells in the lamina propria and submucosa (arrows) Bar: 12.5 micrometre; L. Leucine plus zinc plus chromium-treated group (Leu-Zn-Cr): slight edema in the submucosa (arrows) Bar: 50 micrometres.
Fig 2
Fig 2. Histopathological findings in the lungs of rat in all of the experimental groups.
Lung parenchyma. A. Control (CTR): lung normal parenchyma. Bar: 75 micrometres; B. Diabetic group (T2D): hypertrophy and hyperplasia of the smooth muscles in a secondary bronchiole wall (arrows). Bar: 20 micrometres; C. Diabetic group: severe inflammation around a blood vessel (white arrows) and alveolar epithelialization (black arrows). Bar: 75 micrometres. D. Insulin-treated group: slight edema (white arrows) and scattered inflammatory cells (black arrows) around a blood vessel. The lesions are less pronounced than those of the diabetic group. The alveolar walls are normal with less epithelialization. Bar: 75 micrometres. E. Leucine-treated group (Leu): increased numbers of intra-alveolar macrophage compared with the control (arrows). Bar: 75 micrometres. F. Glibenclamide-treated group (GLC): inflammatory cell infiltration around a secondary bronchiole (white arrow), edema and fibrin accumulation and fibrosis around a vessel (black arrow). Bar: 75 micrometres. G. Leu-treated group: severe inflammation around a secondary bronchiole (white arrow) and epithelialization in the alveolar walls. Bar: 75 micrometres. H. Zinc-treated group (Zn): Peribronchial inflammation (black arrows) and perivascular edema (white arrow). Bar: 75 micrometres. I. Zn-treated group: hypertrophy and hyperplasia of the smooth muscle in a secondary bronchiole wall (arrows) Bar: 20 micrometres. J. Cr-treated group: perivascular edema, fibrin accumulation and fibrosis (arrows). Bar: 75 micrometres. K. Chromium-treated group (Cr): alveolar epithelialization (arrows). Bar: 75 micrometre L. Zn plus Cr-treated group (Zn-Cr): perivascular edema and fibrin accumulation (white arrows) and scattered infiltration of inflammatory cells (black arrows). Bar: 75 micrometres. M. Leu plus Zn-treated group (Leu-Zn): perivascular edema and fibrin and collagen accumulation (arrows). Bar: 20 micrometres. N. Leu plus Cr-treated group (Leu-Cr): severe perivascular inflammation. Bar: 20 micrometres. O. Leu, Zn plus Cr-treated group (Leu-Zn-Cr): perivascular edema (white arrows) and slight infiltration of inflammatory cells (black arrows). The alveolar epithelialization is somewhat less than in the diabetic group. Bar: 75 micrometres.
Fig 3
Fig 3. Perivascular, peribronchial inflammation and total inflammation scores in the rat lungs of all of the experimental groups.
***P<0.001, **P<0.01, *P<0.05 compared with the control. ###P<0.001, ##P <0.01, #P<0.05 compared with the diabetic group. ¶¶¶P<0.001, ¶¶P<0.01, ¶P<0.05 compared with the insulin-treated group. OP<0.05 compared with the chromium-treated group. •P<0.05 compared with the zinc-treated group. □P<0.05 compared with the leucine plus chromium group.
Fig 4
Fig 4. Reid index in the experimental groups.
***P<0.001, *P<0.05 compared with the control. ##P<0.01, #P<0.05 compared with the diabetic group. CTR = control; T2D = type 2 diabetes; INS = NPH insulin; GLC = glibenclamide; Leu = leucine; Zn = zinc; Cr = chromium.
Fig 5
Fig 5. Blood insulin concentrations in the experimental groups.
Different superscript letters (a-d) indicate significant differences among the groups (P<0.05). CTR = control; T2D = type 2 diabetes; INS = NPH insulin; GLC = glibenclamide; Leu = leucine; Zn = zinc; Cr = chromium.
Fig 6
Fig 6. Blood antioxidant enzyme activities in the experimental groups.
Blood catalase (A), glutathione peroxidase (B), myeloperoxidase (C) and superoxide dismutase (D) activities was measured in all of the experimental groups. Different superscript letters (a-f) indicate significant differences among the groups (P<0.05). CTR = control; T2D = type 2 diabetes; INS = NPH insulin; GLC = glibenclamide; Leu = leucine; Zn = zinc; Cr = chromium.
Fig 7
Fig 7. Oxidative stress in the bronchoalveolar lavage fluid (BALF) of the experimental groups.
(A) TBARS (Thiobarbituric acid reactive substances) used as an index of lipid peroxidation and (B) FRAP (Ferric reducing ability of plasma) as an indicator of a total antioxidant status were measured in all of the experimental groups. Different superscript letters (a-e) indicate significant differences among the groups (P<0.05). CTR = control; T2D = type 2 diabetes; INS = NPH insulin; GLC = glibenclamide; Leu = leucine; Zn = zinc; Cr = chromium.
Fig 8
Fig 8. Protein leakage in the bronchoalveolar lavage fluid (BALF) of the experimental groups.
The total amounts of protein were measured in the BAL fluid in all of the experimental groups. Different superscript letters (a-d) indicate significant differences among groups (P<0.05). CTR = control; T2D = type 2 diabetes; INS = NPH insulin; GLC = glibenclamide; Leu = leucine; Zn = zinc; Cr = chromium.
Fig 9
Fig 9. Antioxidant enzymes activities in the lungs of the experimental groups.
The lung catalase (A), glutathione peroxidase (B), myeloperoxidase (C) and superoxide dismutase (D) activities were measured in all of the experimental groups. Different superscript letters (a-f) indicate significant differences among groups (P<0.05). CTR = control; T2D = type 2 diabetes; INS = NPH insulin; GLC = glibenclamide; Leu = leucine; Zn = zinc; Cr = chromium.
Fig 10
Fig 10. Oxidative stress in the lungs of the experimental groups.
(A) TBARS (Thiobarbituric acid-reactive substances), used as an index of lipid peroxidation, and (B) FRAP (Ferric reducing ability of plasma), used to indicate the total antioxidant status, were measured in all of the experimental groups. Different superscript letters (a-c) indicate significant differences among groups (P<0.05).

Similar articles

See all similar articles

Cited by 2 articles

References

    1. White MF. IRS proteins and the common path to diabetes. Am J Physiol Endocrinol Metab. 2002; 283: E413–E422. - PubMed
    1. Taniguchi CM, Emanuelli B, Kahn CR. Critical nodes in signaling pathways: insights into insulin action. Nat Rev Mol Cell Biol. 2006; 7: 85–96. - PubMed
    1. Kahn SE, Porte DJ. The pathophysiology of type II (noninsulindependent) diabetes mellitus: Implications for treatment In: Rifkin H, Porte DJ, editors. Ellenberg and Rijkin’s Diabetes Mellitus: Theory and Practice. New York: Elsevier Science; 1990. pp. 436–456.
    1. Flanagan AM, Brown JL, Santiago CA, Aad PY, Spicer LJ, Spicer MT. High-fat diets promote insulin resistance through cytokine gene expression in growing female rats. J Nutr Biochem. 2007; 19:505–513. - PubMed
    1. Nathan DM. Long-term complications of diabetes mellitus. N Engl J Med. 1993; 328(23):1676–1685. - PubMed

Publication types

MeSH terms

Grant support

This study was financially supported by the Tuberculosis and Lung Research Center of Tabriz University of Medical Sciences and the Research Council of University of Tabriz. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Feedback