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  1. HNUE JOURNAL OF SCIENCE DOI: 10.18173/2354-1059.2018-0082 Natural Sciences 2018, Volume 63, Issue 11, pp. 142-146 This paper is available online at http://stdb.hnue.edu.vn CHARACTERISTICS OF WHITE ADIPOSE TISSUE SHAPE AND WEIGHT IN THE RESTRICTED HIGH-FAT DIET-FED MICE Le Ngoc Hoan1, Nguyen Phuc Hung1, Ho Thi Hong Van2 and Chu Dinh Toi1 1 Faculty of Biology, Hanoi National University of Education 2 Vietnam Institute of Educational Science Abstract. Obesity is associated with changes not only in tissue function but also in tissue morphology. We previously reported that arbitrarily high-fat diet feeding induced some moderate alterations in metabolic tissues. Here, we show that restricted high-fat diet feeding mice for 30 days led to a markedly increase in body weight. This was accompanied by strongly changes in gross morphology and weights of several white adipose tissues, including subcutaneous, axillary, and epididymal adipose tissues. Our data suggest that a restricted high-fat diet feeding shows an obvious effect on the change of body weight as well as on the alteration of adipose tissue size and weight. Hence, the restricted high-fat diet feeding may be used as a promise method to induce obese model at least partly in mouse. Keywords: High-fat diet, restricted feeding, body weight, tissue weight. 1. Introduction Obesity is increasing as worldwide epidemic [1]. Obesity is a condition which is usually accompanied by metabolic dysfunctions in humans, such as nonalcoholic fatty liver diseases, cardiovascular diseases, type 2 diabetes, and certain cancers [2]. There are evidences supporting that increased adipogenesis of white adipose tissues may contribute to increases in those metabolic malfunctions. Adipose tissues can also secrete cytokines such as monocyte chemoattractant protein (MCP)-1 who attracts the migration of immune cells. Then, the cross-talk between the migrated cells and local cells induced not only dysfunctions of the local tissues but also dysfunction of whole body [3]. Thus, study about the factor(s) that affects the adipogenesis of white adipose tissues in obesity may be a strategy to beat obesity. Several factors that play roles in induction of obesity have been uncovered. Among them, food is being important target for investigation of obesity causations. Increased food intake is main factor that causes weight gain and obesity in experimental animals and humans [4, 5]. However, with the same amount of food intake but food content difference could be also considered as causation of obesity. It is noteworthy that, studies about obesity in animals, especially in mice in Vietnam are remaining very less. Some recent studies have demonstrated the effect of lipid-rich diet on mouse weight. Unfortunately, the adverse effect of the diet on metabolic tissue weights and morphologies has not been much described yet [6, 7]. Received September 24, 2018. Revised November 7. Accepted November 14, 2018. Contact Le Ngoc Hoan, e-mail address: lengochoanspsinh@gmail.com 142
  2. Characteristics of white adipose tissue shape and weight in the restricted high-fat diet-fed mice Moreover, previous study has shown that mice arbitrarily fed with the high-fat diet have not strongly differed in the tissue morphology and size compared to the controls [8]. Thus, in the current study, we designed experiments to study the effect of restricted high-fat diet feeding on mice to see whether this can give highly effect on obesity induction and white adipose tissues. 2. Content 2.1. Materials and methods * Animals and diets Male Swiss mice at the four-week of age were purchased from the National Institute of Hygiene and Epidemiology (NIHE). Mice were housed in an animal facility at the Faculty of Biology, Hanoi National University of Education, where 12-12 h light-dark cycle was maintained. For 30 days, the mice were fed a regular diet (RD) (5% energy from lipid) or a high-fat diet (45% energy from lard) on the RD base. The RD was also purchased from the NIHE. The mice were fed restrictedly with food and arbitrarily with water and were weighted weekly to observer their body weight. After 30 days, the animals were killed by decapitation. White adipose tissues were dissected and measured. * Statistical Analysis The results were indicated as means ± standard error of the mean (SEM). Comparisons of variables were carried out by using Student’s t test or analysis of variation (ANOVA) with Duncan’s multiple-range examination. Differences were considered to be significant when P
  3. Le Ngoc Hoan, Nguyen Phuc Hung, Ho Thi Hong Van and Chu Dinh Toi 2.2.2. Effect of high-fat diet feeding on subcutaneous adipose tissue To test the effect of the HFD-feeding on changes in subcutaneous adipose tissue, we compared the size of the tissue of the two mouse groups after a 30 day-feeding time. Interestingly, in the present study, we did observe the magnificent increase in gross morphology of subcutaneous adipose tissue in the HFD-fed mice compared to that of the RD-fed mice (Figure 2A).Consistent with this, the weight of subcutaneous adipose tissues of the HFD-fed mice is significantly higher than that of the RD-fed mice (Figure 2B). Since increased subcutaneous adipose tissue size and weight are markers of obesity [9], our observed data could support the potential of the restricted HFD-feeding in induction of obesity. Figure 2. Changes in subcutaneous adipose tissue of the HFD-fed mice Four week-old male Swiss mice were fed a regular diet (RD) or a high-fat diet (HFD) for 30 days. (A) subcutaneous adipose tissue weight. (B) gross morphology of subcutaneous adipose tissues. Data are presented as means ± SEM; n = 6 in each group 2.2.3. Effect of high-fat diet feeding on axillary adipose tissue Figure 3.Changes in axillary adipose tissue of the HFD-fed mice Four week-old male Swiss mice were fed a regular diet (RD) or a high-fat diet (HFD) for 30 days. (A) axillary adipose tissue weight. (B) gross morphology of axillary adipose tissues. Data are presented as means ± SEM; n = 6 in each group Similar with subcutaneous adipose tissue, axillary adipose tissue is also a type of white adipose tissue distributed under the skin. Moreover, increased fat infiltration inaxillary adipose tissue has been shown as a sign of overweight and/or obese individuals [10]. We here, thus, checked if the HFD-feeding alter axillary adipose tissue size and weight. As a result, the mice fed with HFD showed magnificent change in gross morphology compared to those fed with RD (Figure 3A). This is accompanied by markedly increase in the weight of axillary adipose tissue of the HFD-fed mice compared with that of the RD-fed control mice (Figure 3B). 144
  4. Characteristics of white adipose tissue shape and weight in the restricted high-fat diet-fed mice Consistent changes in the both under the skin white adipose tissues may support the evidence that the restricted HFD-feeding may be useful to induce obesity in mice. 2.2.4. Effect of high-fat diet feeding on epididymal adipose tissue Previous studies have reported that increased inflammatory cytokines in obesity resulted in adverse effects on reproductive glands and leading to reduced reproductive ability in mice. This effect could result in changes in regulation of hormones that involve in control of spermgenesis or ovulation [11, 12]. In addition, epididymal fat tissue hypertrophy in obesity is usually associated with increased inflammatory responses [13]. Hence, in the current study, we examined whether the HFD-feeding led to changes in epididymal adipose tissue in mice. After 30 days of the feeding period, we observed that the mice fed with the HFD shown magnificent increase in the size of epididymal adipose tissue compared to the mice fed with the RD did (Figure 4A). The weight of epididymal adipose tissue of the HFD-fed mice was also significantly higher than that of the RD- fed control mice (Figure 4B). It has been reported that fat-rich diet induced increased fatty acid in plasma of mice that resulted in increase in fatty acid intake of adipocytes and finally, leading to enhanced adipogenesis of white adipose tissue [14]. However, white adipose tissue hypertrophy, in turn, contributes to increase plasma free fatty acid. This likes positive feedback loop [15]. Besides, increased white adipose tissue mass and size also induces changes in the local micro-environment which result in increases in production of pro-inflammatory cytokines (e.g., tumor necrosis factor (TNF)-, interleukin (IL)-6, and MCP-1). These cytokines, somehow, have adverse effects on lipid metabolism and stimulate adipocyte proliferation and hypertrophy [16]. Figure 4. Changes in epididymal adipose tissue of the HFD-fed mice. Four week-old male Swiss mice were fed a regular diet (RD) or a high-fat diet (HFD) for 30 days. (A) epididymal adipose tissue weight. (B) gross morphology of epididymal adipose tissues. Data are presented as means ± SEM; n = 6 in each group 3. Conclusions The present study indicates that restricted HFD-feeding for 30 days led to strongly increases in body weight and size of the mice just after 1 week of feeding period. This was accompanied by significantly increases in weight and size of white adipose tissues, including, subcutaneous adipose tissue, axillary adipose tissue as well as epididymal adipose tissue. These observed changes may be derived from a high amount of fat consumption of the HFD-fed mice compared with that of the RD-fed mice. As a result, our data may support a promise ability to use the restricted HFD-feeding to induce obesity in mice. This can be a stable model for further studies in obesity and its related metabolic disorders. 145
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