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Research Article

Agricultural Science Digest, volume 41 issue 4 (december 2021) : 548-553

Coconut Oil Promotes Greater Satiety and Reduces Blood Cholesterol, But Induces Obesity, Anxiety and Impaired Bone Formation in Adult Wistar Rats

Ítalo Gomes Reis1, Arthur Rocha-Gomes1, Alexandre Alves da Silva1, Mayara Rodrigues Lessa2, Nísia Andrade Villela Dessimoni Pinto2, Tania Regina Riul1,*
1Laboratório de Nutrição Experimental, Departamento de Nutrição, Universidade Federal dos Vales do Jequitinhonha e Mucuri, Diamantina-MG, Brazil.
2Laboratório de Tecnologia e Biomassas do Cerrado, Departamento de Nutrição, Universidade Federal dos Vales do Jequitinhonha e Mucuri, Diamantina-MG, Brazil.
Cite article:- Reis Gomes Ítalo, Rocha-Gomes Arthur, Silva da Alves Alexandre, Lessa Rodrigues Mayara, Pinto Dessimoni Villela Andrade Nísia, Riul Regina Tania (2021). Coconut Oil Promotes Greater Satiety and Reduces Blood Cholesterol, But Induces Obesity, Anxiety and Impaired Bone Formation in Adult Wistar Rats . Agricultural Science Digest. 41(4): 548-553. doi: 10.18805/ag.D-302.

ABSTRACT

Background: The aim of this study was to evaluate the nutritional effects of supplementation with virgin coconut oil (VCO) in Wistar rats over a sub-chronic period (6 weeks).

Methods: Twelve Wistar rats were used and randomly assigned to receive (n = 6): control - lab chow; coconut oil (CO) - lab chow with added virgin coconut oil (20%). Food and caloric intake, weight gain, food efficiency, body mass index, femur and tibia length, bone mineral composition and blood biochemistry were evaluated.

Result: The CO group showed an energy intake closed to control group. Also, the supplementation with VCO generated a decrease in total blood cholesterol as compared to the control group. However, the CO group showed accumulation of fat mass, shorter femur length and anxiogenesis in relation to the control group. These results indicate few beneficial effects from the sub-chronic use of VCO and indicate that its consumption in large quantities for long periods should be questioned.

INTRODUCTION

Worldwide rates of obesity and overweight have reached alarming proportions. It is estimated that approximately 39% of the adult population in the world has some degree of obesity. Despite having a multifactorial etiology, obesity rates are increasing mainly due to the high consumption of high-fat foods (WHO, 2017).
       
High-fat diets are common in western countries, mainly due to foods rich in saturated fatty acids (SFA), which can be even more harmful to health (Ruiz-Núñezet_al2016). There is strong evidence that SFA can provide accumulation of adipose tissue, dyslipidemia, cardiovascular diseases and deleterious effects on bone formation (Gomes Natal et al., 2016; Kolahdouzi et al., 2019).
       
The consumption of virgin coconut oil (VCO) has increased in recent years due to the popularity that this food has gained in the media as a beneficial food for health (Sacks, 2020). VCO is obtained through the pulp of mature coconut (Cocos nucifera L.), with its largest production and consumption coming from Asian countries (Philippines, Indonesia and India) and from the northeast of Brazil. VCO is composed of mostly SFA (~92%) and a smaller part of unsaturated fatty acids (oleic and linolenic acids) (Clegg, 2017). Some of the SFAs present in the VCO can be classified as medium-chain triglycerides (MCT’s), which are triglycerides with fatty acids chains that are 6-12 carbon atoms in length. In contrast to the other SFA intake, isolation consumption of MCT’s has already demonstrated health benefits, including weight loss, decreased risk of cardiovascular disease and anxiolytic effects (Eyres et al., 2016; Clegg, 2017).
       
Some studies showed that consumption of coconut oil can improve the oxidation of fats and decrease energy intake in addition to promoting weight loss (Amaral et al., 2016). Conversely, other studies showed no improvement in obesity or cardiovascular disease (Teng et al., 2020). Thus, there is still a controversy in the use of VCO due to its high amount of SFA, but also a high concentration of MCT’s. This study aimed to evaluate the nutritional, biochemical and behavioral effects of VCO consumption in adult Wistar rats.

MATERIALS AND METHODS

Ethical principles, animals and diets
 
The study was carried out during the period of January 2018 to December 2018, in the Department of Nutrition at the Universidade Federal dos Vales do Jequitinhonha e Mucuri (UFVJM). Twelve male Wistar rats (Rattus novergicus - 70 days old) were used following the ethical principles of use of animals, approved by the Ethics Committee Local Animal Use (protocol CEUA-UFVJM 020/13). These guidelines are in accordance with the National Institutes of Health Guide for the care and use of laboratory animals. The rats were housed in conditions of ambient humidity, temperature of 22±2°C and cycle of 12 hours of light and darkness (6:00 am-6:00 pm).
       
The animals were randomly assigned to receive during six weeks, the diets: Control-received lab chow (Nuvilab®-CR1) and water ad libitum (n=6); Coconut oil (CO)-received lab chow (Nuvilab®- CR1) with added coconut oil (20% w/w) and water ad libitum (n=6). To prepare the CO diet, lab chow was ground in a mill, manually mixed and homogenized with coconut oil (Copra®). The diet was stored under refrigeration (10±2°C) until use (Table 1).
 

Table 1: Chemical composition and energy density of the chow and the experimental diets.


 
Nutritional assessment
 
Total food intake was calculated by add up daily intake during the treatment period (López-Espinoza et al., 2015) and total caloric intake was estimated as described by Escobar et al., (2019). The animals were weighted weekly and weight gain was calculated by subtracting the initial weight from the final weight obtained on the 42nd day (Galindo et al., 2019). The feed efficiency was calculated by the ratio of weight gain on total food intake (Escobar et al., 2019). Body length was evaluated on the 43rd day and the body mass index (BMI) was calculated using the equation: BMI = final weight/body length2 (Escobar et al., 2019).
 
Elevated plus maze (EPM) test
 
Each animal was placed in the EPM with its head facing towards one of the closed arms and its movements were filmed for 300 seconds. At the end filming for each animal, the maze was cleaned using 70% alcohol. Experienced observers evaluated: entries in the open arms at least one time (Lordi et al., 2000); the frequency and duration of entries (when the animal entered with four legs) in each arm (closed or open) and frequency of head-dipping and false entries (Riul and Almeida, 2020).
 
Euthanasia and collection of biological samples
 
The rats were fasted for 12 hours, anesthetized (xylazine 20 mg.kg-1; ketamine 40 mg.kg-1) and euthanized by exsanguination. About 2 mL of blood serum were collected to determine the glucose, triglycerides and total cholesterol using Labtest® kits (Escobar et al., 2019).
       
The organs (spleen, heart, liver, kidneys, adrenals, testes) and abdominal adipose tissue (epididymal, retroperotonial and visceral) were removed, cleaned and weighted. The femur and tibia were measured with a digital capillary caliper and the mineral content was determined as described previously (Escobaret_al2019).
 
Statistical analysis
 
Statistical analysis was performed with Statistica® (10.0). Figures were made using GraphPad Prism® (7.0). Sample normality was evaluated using the Shapiro-Wilk test. Data were analyzed using parametric (Student’s T tests), non-parametric data (Mann Whitney’s) and Pearson correlation test. All tests were used with statistical significance at p<0.05 and the results were expressed as mean and standard deviation of the mean (SEM).

RESULTS AND DISCUSSION

Supplementation with coconut oil promoted significant differences in the caloric intake of macronutrients, even increasing the energy density of the diet. The CO group consumed less calories from protein (p<0.01) and carbohydrates (p<0.01) and more calories from fat (p<0.01), compared to the control group (Table 2).
 

Table 2: Nutritional assessment of the animals after 42 days of treatment with lab chow or supplementation with coconut oil.


       
Studies with high-fat diets (Gomes Natal et al., 2016; Martínez et al., 2018) showed different results, causing an increase in caloric intake. On the other hand, the inclusion of coconut oil in rodent diets has led to a change in energy consumption (Amaral et al., 2016). Therefore, the results presented here may indicate that the MCTs present in the VCO may be related to greater satiety.
       
The satiety process is characterized by an inhibition of hunger after a meal, which reduces the amount of calories ingested (Maher et al., 2020). MCTs are known to produce a rapid feeling of satiety, which may explain similar results of energy intake between the Control and CO groups. MCTs are quickly absorbed through the portal vein and become a ready source of energy supply in the liver. This mechanism contributes to increase satiety and energy expenditure (Maher and Clegg, 2020; Maher et al., 2020).
       
Diets with high levels of SFA’s can promote the accumulation of fat (Macri et al., 2012; López-Espinoza et al., 2014; Gomes Natal et al., 2016; Kolahdouzi et al., 2019). The CO group showed a greater accumulation of abdominal fat (p<0.01) compared to the control group, showing that the addition of VCO in the diet led to the development of obesity. Thus, even with the presence of MCTs in their composition and an energy intake close to that of the Control group, CO animals obtained an increase in fat mass (David et al., 2019). In addition, the strong correlation (r2 = 0.53; p<0.01) between fat energy intake (not total energy intake) and the accumulation of adipose tissue (Fig 1) confirms that fat intake during a subchronic period increased the accumulation of adipose tissue.
 

Fig 1: Adipose tissue weight


 
High-fat diets can be precursors of bone metabolism and result in low bone mass and low bone quality (Macri et al., 2012). In the present study, shorter femur length (p<0.05) was observed in the CO group compared to the control group (Bielohuby et al., 2010) (Table 3).
 

Table 3: Organs weight and bones evaluations of the animals after 42 days of treatment with lab chow or supplementation with coconut oil.


       
Two mechanisms are proposed for this bone dysfunction observed in animals with an SFA-rich diet. First, high-fat diets can lead to a decrease in growth hormone (GH) and insulin-like growth factor (IGF-1) in the bloodstream. The GH/IGF system potently stimulates bone growth, activating the osteoblast differentiation program (Bielohuby et al., 2010). Second, leptin has been suggested to control bone resorption that is thought to regulate osteoclast differentiation. Although the levels of these hormones (GH, IGF-1 and leptin) were not evaluated in this study, the failure to demonstrate a correlation between adipose tissue (the organ that secretes leptin) and the length of the femur leads to the hypothesis that the high energy consumption of fat might have influenced GH/IGF-1 levels (Bielohuby et al., 2010). Also, a negative correlation (r2 = 0.51; p<0.05) was reported between the length of the femur and fatty caloric intake (Fig 2).
 

Fig 2: Correlation between femur length and fat caloric intake


       
The diet added with VCO decreased the total cholesterol levels of the animals. The CO group had lower levels (p<0.01) compared to the control group (Fig 3). This decrease may be due to the presence of MCTs, by increasing the excretion of bile acids in the feces (Li et al., 2018). In particular, the decrease in LDL-c levels reduces the risk of atherosclerosis (Escobar et al., 2019; Singh et al., 2019).  Therefore, even with the increase in fat mass, the animals in the CO group had lower levels of total cholesterol, which was a beneficial effect of adding VCO to the diet.
 

Fig 3: Blood glucose


       
The CO group had higher adrenal weight (p<0.001) than the control group (Table 3). There are evidence that high-fat diets can promote hypertrophy of the adrenal glands (Hryhorczuk et al., 2017) and increase the release of corticosterone (Sasaki et al., 2013). Corticosterone is a hormone that plays an important role in regulating anxiety (Sasaki et al., 2013). Here, an increase in anxiety was demonstrated in the CO group, which obtained a low percentage of open arm entries (16,60%), when compared to the control group (33,33%) (Table 4). Therefore, the assumption raised is that the high composition of the SFA may have led to hyperactivity of the hypothalamic-pituitary-adrenal axis and anxiety.
 

Table 4: Behavioral evaluation in the elevated plus maze test of the animals after 42 days of treatment with lab chow or supplementation with coconut oil.


 
In summary, the present study found few beneficial effects from the sub-chronic use of VCO. Although the animals in the CO group obtained a similar energy intake and decreased the levels of total cholesterol, the development of obesity, anxiogenesis and impaired bone growth were observed. The increase in satiety and the reduction in total cholesterol seem to be related to the presence of MCT’s in the constitution of the VCO. However, due to its high concentration of SFA and also the chronicity of the diet, accumulation of fat mass, anxiogenesis and impaired bone formation were observed. These results indicate that the consumption of VCO in large quantities for long periods should be questioned.

CONCLUSION

The addition of VCO in the diet promoted greater satiety and decreased cholesterol in the animals. However, its sub-chronic consumption was responsible for the development of obesity, increased anxiety and impaired bone growth.

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