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Научни трудове на Съюза на учените в България-Пловдив. Серия Г. Медицина, фармация и дентална медицина т. XXII. ISSN 1311-9427 (Print), ISSN 2534-9392 (On-line). 2017. Scientific works of the Union of Scientists in Bulgaria-Plovdiv, series G. Medicine, Pharmacy and Dental medicine, Vol.XXII. ISSN 13119427 (Print), ISSN 2534-9392 (On-line). 2018.
ЕФЕКТ НА КОМБИНИРАНАТА ВИСОКОЛИПИДНА-ВИСОКОВЪГЛЕХИДРАТНА ДИЕТА ВЪРХУ СЕРУМНАТА КОНЦЕНТРАЦИЯ НА TNF-a ПРИ ЖЕНСКИ И МЪЖКИ ПЛЪХОВЕ Петър Хрисчев1, Катерина Георгиева1, Дора Терзиева2, Пенка Ангелова1, Илиана СтояноваЗ 1. Катедра по физиология, Медицински факултет, Медицински
Университет - Пловдив 2. Катедра по клинична лаборатория, Фармацевтичен факултет, Медицински Университет - Пловдив 3. Медицински университет - Пловдив
EFFECTS OF THE COMBINED HIGH-FAT-CARBOHYDRATE DIET ON THE SERUM TNF-a CONCENTRATION IN FEMALE AND MALE
RATS
Peter Hrischevi, Kalina Georgievai, Dora Terzieva2, Penka Angelovai,
Iliana Stoyanova3 1. Department of Physiology, Faculty of Medicine, Medical University -
Plovdiv
2. Department of Clinical Laboratory,Fac ulty of Pharmacy, Medical
University - Plovdiv 3. Medical University - Plovdiv
Abstract
Combined high-fat-carbohydrate (HFC) diet and reduced physical activity are key factors in the development of obesity and metabolic syndrome (MetS). Tumor necrosis factor alpha (TNF-a) is considered to be an adipokine involved in low-grade chronic inflammation, which is one of the elements of the obesity/MetS. It is not known whether there are gender differences in the TNF-a serum concentrations in rats with dietary-induced metabolic syndrome. The aim of the study was to assess the effect of the combined high-fat-carbohydrate diet on serum TNF-a levels in female and male rats. Same number of female and male Wistar rats were used in the experiment. Experimental animals were divided into four groups (n=8): control - female (FC) and male (MC) and dietary-manipulated - female (FD) and male (MD). The control groups were fed with standard
rat chew, and the dietary-manipulated rats were subjected to a combined HFC diet for 16 weeks. At the end of the experiment, the administered diet and the gender had significant main effects, as dietary-manipulated animals were with a higher weight (P<0.05) and BMI (P<0.01) compared to the controls and male rats had a higher body weight (P <0.001) and BMI (P<0.01) than females. The diet and the gender had significant effects on TNF-a concentration. Higher TNF-a values were found in the animals exposed to the combined HFC diet compared to those receiving standard rat chew (P<0.05), and male rats had higher concentrations than females (P<0.05). In our knowledge this data for the first time shows that the combined HFC diet leads to higher serum concentration of TNF-a in male compared to female rats. The observed gender dimorphism compliments the known evidence about the markers of low grade inflammation Key words: high-fat-carbohydrate diet, Wistar rats, metabolic syndrome, TNF-a
Introduction
Combined high-fat-carbohydrate (HFC) diet and reduced physical activity are key factors in the development of obesity and metabolic syndrome (MetS), which are widespread in modern society (Hamilton et al., 2007; Owen et al., 2010). It has been shown that fatty tissue (FT) is not only an energy organ - a triglyceride depot, but also an active endocrine organ. All adipose tissue, which contains not only adipocytes but also other stromal and vascular cells, secretes multiple substances, signaling molecules with various functions (Chaldakov et al., 2003). Tumor necrosis factor alpha (TNF-a) is secreted primarily by the cells of inflammation and lymphocytes, but also by adipocytes and stromal cells. Therefore, TNF-a is considered to be an adipokine involved in low-grade, local and systemic inflammation, and in proliferation and differentiation of cells (Paniagua, 2016). This cytokine has a determining role in regulating the amount of adipose tissue because it suppresses the transformation of young immature fat cells into mature. The level of TNF-a expression in humans correlates positively with the following parameters: body mass index (BMI), percentage of body fat, and hyperinsulinemia. Reduction in body weight has been shown to reduce TNF-a levels (Jellema et al., 2004). It is not known whether there are gender differences in the TNF-a serum concentrations in rats with dietary-induced metabolic syndrome. In order to follow the recommendations of the National Institutes of Health (NIH) to conduct parallel studies in both sexes, male and female experimental animals were used in this experiment. Aim
The aim of the study was to assess the effect of the combined high-fat-carbohydrate diet on serum TNF-a levels in female and male experimental animals.
Material and methods
Same number of female and male Wistar rats with an initial body weight of 160-180 g, were used in the experiment. They were grown in separate metabolic cages at a temperature of 20 ± 2° C, controlled humidity and a 12-12 h light-dark photo period. The experiment was approved by the Animal Welfare Committee of the Bulgarian Food Safety Agency (№ 119/18.06.2015). Experimental animals were divided into four groups (n=8): control - female (FC) and male (MC) and dietary-manipulated - female (FD) and male (MD). In the preparatory period, all rats were given standard rat chew for 2 weeks until they adapted to conditions in the metabolic cages. The controls (FC and MC) then remained on standard rat chew, and the dietary-manipulated groups (FD and MD) were subjected to a combined HFC diet for 16 weeks. The energy content of the controls' diet was 2908 kcalkg-1 and the combined high-fat-carbohydrate diet was with energy content of 4298 kcal.kg-1. The body mass of each animal was measured once a week and performed in the morning with a dial scale (ZAV, Bulgaria). BMI was calculated using the formula - BMI = weight (g)length (cm)-2. At the end of the experiment, animals were decapitated under narcosis with Thiopental 30 mgkg-1 i. p. and blood was collected for analysis. Serum TNF-a concentration was measured by a TNF-Alpha ELISA RAT Kit (EBIOSCIENCE) assay on a Sirio S microplate reader (SEAC, Italy). In order to study the main effects of gender and diet and their interactions, the results were analyzed by two-way ANOVA.
Results
There were no significant differences in the test animals' weights before the start of the experiment (MC-182.13± 9.64 g, MD-184.75± 13.66 g, FC-172.00± 16.49 g, FD-176.25± 14.39 g, P>0.05). At the end of the experiment, the administered diet had a significant main effect on body weight, dietary-manipulated animals were with a higher weight compared to the controls (357.41± 12.13 g vs 320.41± 12.13 g, P<0.05). The gender had a significant main effect as male rats had a higher body weight than females (383.00± 12.24 g vs 294.75± 12.24 g, P<0.001). No significant interaction between the gender and the HFC diet on body weight values of experimental animals was found (P>0.05). There were no differences in the BMI of the experimental rats at the beginning of the study (MC-0.45± 0.05 gxm-2, FC-0.50± 0.05 gxm-2, MD-0.4± 0.05 gxm-2, FD-0.47± 0.04 gxm-2, P>0.05). A significant main effect of the combined high-fat-carbohydrate diet on BMI at the end of the study was found, with dietary-manipulated animals having a higher body mass index than controls (0.69± 0.02 gxm"2 vs 0.63± 0.02 gxm"2, P<0.01). At the end of the experiment, we found a significant effect of gender on BMI, as male rats had a higher BMI than females (0.69± 0.02 gxm-2 vs 0.62± 0.02 gxm-2, P<0.01). A significant two-way interaction effect on BMI values was not found (P>0.05). The statistical analysis of the obtained results showed that the diet and the gender had a significant effect on TNF-a concentration. Experimental animals subjected to the combined HFC diet had a higher TNF-a concentration than those receiving standard rat chew (P<0.05) (Fig. 1), and male rats had higher concentrations of this factor than females (P<0.05) (Fig.2). No significant interaction effect between the gender and the HFC diet was found on TNF-a values (P>0.05).
100
TNF-a
M &
50
*
-L
1
Control (C)
Dietary-manipulated (D)
0
Figure 1. Serum concentration of TNF-a (pg-l-1) of control and dietary-manipulated rats at the end of the study. *P<0.05 control vs dietary-manipulated rats.
Figure 2. Serum concentration of TNF-a (pg-l-1) of male and female rats at the end of the study. *P<0.05 male vs female rats.
Discussion
Our results showed higher TNF-a values in male and female test animals subjected to the combined HFC diet versus such receiving a standard chew. These data, are similar to the results of Kuate et al. (2015), according to which, dietary induced MetS, with HFC diet in combination with a low dose of streptozotocin is manifested by weight gain, increased concentrations of serum glucose, insulin, C-reactive protein, leptin, TNF-a, IL-6 and decreased adiponectin concentration in male rats. We also found elevated concentrations of TNF-a in female rats threated with HFC
diet, which complements the previously known data. These results correspond to a study of MetS model, induced by a high-fructose diet, which found an increase in TNF-a levels along with the presence of obesity, hypertension, hyperlipidemia, insulin sensitivity in ovariectomized female rats (Conti et al., 2014).
Conclusion
It is known that MetS is characterized by low-grade chronic inflammation, which makes the role of adipokines in the pathogenesis of the syndrome extremely important. In our knowledge this data for the first time shows that the combined HFC diet leads to higher serum concentration of TNF-a in male compared to female rats. The observed gender dimorphism compliments the known evidence about the markers of low grade inflammation.
The study was funded by the Medical University of Plovdiv (Project № SDP 09 / 2015). References
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