Effect of Aronia melanocarpa (Black Chokeberry) supplementation on the development of obesity in mice fed a high-fat diet

1 Introduction

The global prevalence of obesity has reached epidemic proportions in recent years [1]. Obese individuals have an increased risk of developing chronic diseases such as type 2 diabetes, hypertension and dyslipidemia [2]. Therefore, there is a need to develop successful nutritional interventions targeting obesity in order to treat or prevent weight gain and decrease risk for developing chronic disease. Epidemiological studies have demonstrated a correlation between consumption of fruits and vegetables with reduced incidence of obesity, diabetes and certain types of cancer [3–5], making increased consumption of fruits, such as berries, an ideal target for nutrition intervention. Berry fruits have shown considerable potential in the food industry and nutrition science community over the last two decades due to the high level of phenolic compounds (e.g. anthocyanins) they possess and the role these compounds play in maintaining health and preventing disease [6].

Aronia melanocarpa, also known as black chokeberry, is found in the eastern parts of North America and Northern and Eastern Europe. Products derived from black chokeberries are claimed to be beneficial in diseases associated with oxidative stress due to the high concentration of phenolic compounds (anthocyanins, procyanidins, hydroxycinnamic acids and flavonols) they possess [7–10]. Extracts from black chokeberries have been demonstrated to have anti-inflammatory [11], anticancer [12], cardio-protective [13] and anti-diabetic effects [14] in animal models. A recent study by Qin and Anderson [11] demonstrated that chokeberry extract prevented weight gain and decreased risk factors associated with insulin resistance in rats fed a fructose-rich diet through modulation of multiple pathways associated with insulin signaling, adipogenesis and inflammation [11]. In addition, supplementation with chokeberry juice reduced blood pressure and improved lipid status in both hypertensive individuals [15] and individuals with metabolic syndrome [16].

Although, there is emerging evidence regarding the ability of black chokeberries to prevent chronic disease, limited data exists on the potential for black chokeberry supplementation to prevent weight gain and the development of obesity. Therefore, the objective of this study was to determine if long-term supplementation with Aronia melanocarpa (black chokeberry) juice concentrate has anti-obesity properties in mice fed obesogenic diets.

2 Materials and methods

3 Results

4 Discussion

This is the first study to compare the effect of AJC supplementation on body weight, body composition and metabolic markers of obesity. The present study suggests that AJC supplementation has the potential to prevent weight gain and markers of obesity in a rodent model by decreasing weight gain and increasing levels of adiponectin. In addition, animals in this study were fed two different obesogenic diets, which manifested themselves in different ways. Animals fed the LFHS had higher liver weights and lower total weight gain, while the HF-fed mice had higher weight gain and higher levels of epididymal fat.

There was a trend for higher plasma levels of adiponectin with AJC supplementation. Adiponectin is the most abundant peptide secreted by adipocytes and is a key hormone in the inter-relationship between adiposity, insulin resistance and inflammation [22]. Circulating adiponectin levels are inversely related to body fat percentage [23]. Adiponectin increases the sensitivity to insulin through activating AMP kinase, promoting glucose uptake by muscles via intracellular translocation of the GLUT4 transporters and by reducing gluconeogenesis by inhibiting the hepatic enzyme phosphoenolpyruvate carboxylase, which inhibits the synthesis of fatty acids and stimulates their oxidation [22]. Our data support results from an earlier study, which demonstrates that chokeberry extract elevated plasma adiponectin in rats fed a high-fructose diet when compared with the controlgroup [11].

Peroxisome-proliferator receptor gamma (PPARγ) is a gene that regulates fatty acid and lipid metabolism [24]. In this study, we found no change in PPARγ expression in epididymal fat tissue with AJC supplementation. However, a recent study by Qin and Anderson [11] showed that animals fed a high-fructose diet supplemented with chokeberry extract in the drinking water for five weeks had increased PPARγ expression in epididymal fat.

In the present study, dietary supplementation with AJC did not appear to alter insulin resistance since AJC did not have any significant effect on HOMA-IR, HOMA-BCF or fasting insulin and glucose levels. However, HOMA-IR was increased in mice fed the HF diets. In studies by Heyman and Axling [25], mice fed a high fat diet (45 kcal% fat) and either lingonberries, blackcurrants, or bilberries, had a lower HOMA-IR index resulting from a lower fasting glucose and/or insulin, indicating that these three berries protected against high-fat induced insulin resistance. The diet supplemented with lingonberries was more effective than the other berries in that it provided an almost complete prevention of body weight gain which was an effect of reduced adiposity [25]. Body weight and epididymal fat gain was not changed with AJC supplementation in this study indicating that chokeberries may not exhibit the same effect as the berries described above.

In this study, there was a trend for AJC supplementation to reduce weight gain and adiposity in mice fed a LFHS diet, with no effect in mice fed a high-fat diet. The reasons for the apparent lack of consistency of results found in various studies related to the effectiveness of berries on obesity and obesity-related parameters are not clear. The type of diet used to induce obesity, the amount of berry in the diet, the format of supplementation (e.g. extract versus whole berry), and polyphenolic composition of the different berries are all possible factors. In the study by Heyman and Axling [25], 20% of the diet in the berry experimental groups came from freeze dried berries. Earlier studies comparing whole versus powdered blueberries or strawberries found that the whole berries were not effective in preventing obesity [26, 27] and, in some cases, tended to promote obesity in the context of a high-fat diet but not with a low-fat diet. Other studies have also reported either increased obesity [28] or equivalent adiposity [29] with supplementing a high-fat diet with whole blueberry powder at 2 or 4% of the total diet weight. Whole, freeze-dried black raspberry powder was also ineffective in preventing obesity [30]. In addition, whole strawberries did not promote obesity when supplemented in a high-fat diet, and some measures indicated possible antiobesity effects [26, 30–34]. However, feeding purified anthocyanins in the drinking water from blueberries (2.8 mg/day) or strawberries has been shown to reduce obesity in a rodent model [31]. One issue could be the anthocyanin concentration in the diets. However, the anthocyanin concentration in this study (1.44 g/kg diet) was comparable to published literature on purple corn (2 g/kg diet), blueberry powder (2.43 g/kg diet) [27], and cornelian cherry (1 g/kg diet) [35], and higher than studies using blueberry powder at lower concentrations (260 mg/kg diet) [26] and strawberry powder (33 mg/kg diet) [36]. The mechanisms as to why supplementation of purified anthocyanins delays the development of obesity and supplementation with the whole berry does not prevent obesity still need to be elucidated.

There was no effect of AJC supplementation on plasma triglyceride levels. This is in contrast to previous studies from our lab, which found that purified berry (blueberry and strawberry) anthocyanins supplemented in the drinking water, but not whole berries, decreased serum cholesterol and triglyceride level [26]. In addition, hypertensive adults who were fed chokeberry juice daily for four weeks showed significant reductions in triglyceride levels, total and LDL cholesterol and systolic and diastolic blood pressure [15]. Similar effects were observed in patients with metabolic syndrome who were supplemented with chokeberry juice for two months [16]. These differences could be due to bioavailability and method of administration of the supplement [37–39]. Furthermore, epidemiological data suggests that a high intake of anthocynins may reduce risk of myocardial infarctions, suggesting improved heart health [32]. In our study, AJC was incorporated into the powdered diet whereas the rodent study administered the purified berries in the drinking water and human studies the subjects were administered the berries in juice format. In addition, the studies discussed above were conducted in health-compromised individuals, while the mice were not health-compromised in this study.

Finally, the weight of the content in the cecum was higher with AJC supplementation. However, in a study by Frejnagel and Juskiewicz [40] differences in weights of the cecal contents were not observed with a chokeberry extract, but when an extract of polyphenols from green tea was fed, an increase in cecal content weight was observed [40]. In another study, feeding the polyphenol extract from chokeberries altered cecal parameters and metabolism as shown by a reduction in cecal digesta pH and ammonia concentrations in comparison to control animals [40]. In a previous study by Heyman and Axling [25] in which diets were supplemented with one of 8 different berries the mass of the cecum, including its contents, was increased in all berry supplemented groups compared to the control diet with the exception of the raspberry supplemented group [25]. Our data support these findings, which could be due a change in microbial fermentative activity in the cecum [41], however further research is needed to determine the mechanisms of action.

This study has several limitations. The high fat diet used in this study contained only 30% fat, while previously published studies have used 45% to 60% fat [31, 42]. Using a lower level of fat in the high-fat diet in this study may have influenced the amount of weight the animals gained and made metabolic parameters related to obesity less pronounced compared to studies using higher levels of fat in the diet. Additionally, some studies have studied the effect of berry supplementation on animals fed a high-fructose diet [11], which may have differing effects on metabolism when compared to high-fat feeding. In addition, one of our obesogenic diets, LFHS, was high in sucrose. High sucrose diets have been used to induce obesity and diabetes in rodent models [43–46]. The high levels of sucrose in the LFHS diets could explain why we did not find large differences between LFHS and HF groups. Additionally, the diets vary in percent of energy contributed by protein (21% in the LFHS and 16.4% in the HF), which could have impacted our results. Finally, we supplemented the AJC directly into the powdered diet, whereas the other chokeberry supplementation studies added the chokeberry concentrate to the drinking water. These differences in dietary manipulation may be responsible for the varying results.

In summary, this study demonstrates that supplementation with AJC increased adiponectin levels and reduced weight gain and body fat in mice fed a low-fat diet. However, there was no difference in fasting glucose, insulin or triglyceride levels with AJC supplementation. Further research is needed to define the health benefits of AJC supplementation and understand the underlying mechanisms of action.