Zinc nanoparticles ameliorated obesity-induced cardiovascular disease: role of metabolic syndrome and iron overload

Abstract

Obesity is a complicated disease characterized by abundant fat accumulation. It is associated with cardiovascular disease. The current study aimed to appreciate the role of synthesized zinc oxide nanoparticles (ZnONPs) (18.72 nm in size) in curbing cardiovascular disease in an obesity model of a high fat/sucrose diet in male rats. For 16 weeks, 24 rats were fed a high-fat diet and a 25% sucrose solution to develop obesity, and after that, the rats were randomly allocated into four groups of rats. Group 1 served as the control group and consisted of normal, non-obese rats. Group 2 comprised obese rats that were injected with an equivalent volume of a neutral substance, serving as vehicle control. In Group 3 or 4, obese rats were treated with an intraperitoneal injection of 5 or 10mg/kg of zinc oxide nanoparticles (ZnONPs) for eight weeks. The treatment of obese rats with ZnONPs decreased plasma levels of monocyte chemoattractant Protein-1 (MCP-1), resistin, ENA78, tumor necrosis factor-alpha (TNF-α), interleukin 6 (IL6), and C reactive protein (CRP). Also, the remediation of obese rats with ZnONPs led to a significant decrease in body mass index (BMI), body weight gain, leptin, cholesterol, triglycerides, LDL (Low-density lipoprotein), glucose, and insulin resistance index (HOMA-IR). Moreover, ZnONPs treatment lowered troponin, creatine phosphokinase-MB (CK-MB), lactate dehydrogenase (LDH), cardiac or adipose tissue iron content, and malondialdehyde (MDA) either in blood or heart tissue. Otherwise, treating obese rats with ZnONPs enhanced plasma adiponectin levels, cardiac-reduced glutathione (GSH), and superoxide dismutase (SOD). In addition, ZnONPs displayed a significant influence on the cardiovascular system since they combat the rise in blood pressure and the pathological changes of the heart and aorta besides maintaining plasma nitric oxide levels. The results showed a positive correlation between BMI and MDA, MPC-1, CK-MB, and LDH. ZnONPs are convenient in treating cardiovascular disease in obese rats via reduced blood pressure, oxidative stress, cardiac iron accumulation, insulin resistance, and inflammatory markers.

Figure 1

Experimental design of the Zinc nanoparticles intervention in obese rats.

Figure 2

(a) XPS Survey scan spectra of nano zinc oxide, (b) C-1s XPS spectra, (c) O-1s XPS spectra, (d) Zn-2p XPS spectra, (e) XRD patterns of nano zinc oxide, (f) Particle diameters distributions, (g) EdX and (h) HRTEM of nano zinc oxide.

Figure 3

Effect of ZnONPs on plasma level of MPC-1, resistin, ENA-78, TNF-α, IL6, and CRP in obese rats. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.

Figure 4

Effect of ZnONPs on cardiac and adipose tissue trace elements in obese rats. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.

Figure 5

Effect of ZnONPs on plasma and cardiac tissue oxidative stress in obese rats. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.

Figure 6

Correlation of BMI with plasma MDA, SOD, GSH, MCP-1, LDH, CK-MB.

Figure 7

Effect of ZnONPs on insulin resistance parameters in obese rats. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.

Figure 8

Effect of ZnONPs on cardiac enzymes biomarker in obese rats. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.

Figure 9

Photomicrographs of H&E-stained heart sections of various experimental groups. (a) Heart of control rat showing normal orientation ad striation of cardia muscles’ fibers (MFs). (b–d) Heart of obese rat showing marked degeneration (arrow), loss of striation, and scattered eosinophilia (short arrow) of the myofibers with increase intermuscular fat (dotted arrow). (d) The coronary vessels showing vacuolization of medial muscles (arrow) and focal fibroid necrosis (dotted arrow), and inflammatory cells infiltration (IF). (e, f) Heart of low dose ZnONPs administrated rat showing moderate degree of myofibers degeneration (arrow), mild eosinophilia (short arrow) with some intermuscular fat (dotted arrow). (g, h) Heart of high dose ZnONPs administrated rat showing good restoration of the cardiac muscle fibers with mild degeneration (arrow) and decreased intermuscular fat.

Figure 10

Photomicrographs of H&E-stained aorta sections. (a) Aorta of control rat showing normal histological structure of the aortic three layers; intima (arrow), media (M) and adventitia (A). (b–d) Aorta of obese rat showing splitting of the medial muscles (M) with congested vessels, free RBCs, mononuclear inflammatory cells, atherosclerotic plaque, and many lipophages (insert and arrow). Aortae of (e) low and (f) high doses ZnONPs administrated rats showing significant improvement in the histological changes with absence of any plaque as well as lipophages. (g, h) Marked reduction in the aortic tunica thickening. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.

Figure 11

Photomicrographs of Orcein-stained aorta sections. showing (a) normal elastic lamellae (arrow). (b, c) Discontinues, disorganized, and fragmented elastic lamellae (arrow) in aorta of obese rat. (d) Low and (e) high doses ZnONPs administrated rats showing improvement in the deposition of elastic fibers. (f–j) Photomicrographs for the immunohistochemical expression of iNOS showing significant increased expression in obese rat’s aorta and significant decreased its expression in the aortic walls of obese model rats treated with ZnONPs at both low and high doses as quantified by image analysis of the optical density of the positive brown color. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.

Figure 12

Photomicrographs of the immunohistochemical expression of leptin in periaortic fat showing: (a) positively stained thin rim of adipocytes’ cytoplasm. intense expression of leptin in various types of adipocytes, marked decreased leptin expression in ZnONPs treated groups. The positive brown color is quantified as optical density by image analysis software. Each bar represents the mean ± SE of 8 rats. *vs normal control group, ^@vs obese group, ^#vs ZnONPs (5 mg/kg) at p < 0.05. ZnONPs: Zinc oxide nanoparticle.