Effects of maca (Lepidium meyenii) on nutrient digestibility and major nutrient transporters in rats fed a high‐fat diet

Abstract Scope This study was carried out to investigate the efficacy of a new combination of root extracts of the Lepidium meyenii (maca) plant, known for its nutritional and energizing features as well as its antioxidant properties, on nutrient digestibility and nutrient transporters expression. Methods and results A total of 28 Sprague‐Dawley rats (8‐week‐old) were divided into four groups: (i) control, (ii) Lepidium m., (iii) high‐fat diet (HFD), and (iv) HFD+Lepidium m. Maca was given to the rats as a powdered combination of the plant roots with a daily dose of 40 mg per kg BW. Maca administration significantly increased the digestibility of dry matter (DM), organic matter (OM), crude protein (CP), and ether extract (EE), and some nutrient transporter (Pept1/2, Fatp1, Glut1/2, and Sglt1)‐expressions compared with non‐treated control and HFD groups in the jejunum and ileum tissues (p < .0001). Conclusions Maca supplementation improved the digestibility of nutrients and expressions of nutrient transporters in the small intestine of the rats. These results indicate the positive communication between maca consumption and nutrient absorption in the small intestines of the animals.

risk of cardiovascular diseases (CVDs) (Statovci et al., 2017). The preventive roles of plant-based phytochemicals in obesity and related CVDs, together with supportive metabolic, molecular approaches, have created awareness about this field in recent years, enabling novel insights (Gencoglu et al., 2017).
Lepidium meyenii (maca), a plant from the Brassicaceae family, is an edible medicinal plant in Peruvian tradition and has been used as a food source for centuries (Gonzales, 2012). In recent years, bioactive compounds such as fatty acids, glucosinolates, isothiocyanates, phenols, and polysaccharides in the maca plant have been measured using different methods and reported to be effective in various metabolisms (Korkmaz, 2018). Besides the macaenes, macamides are the specific maca ingredients, and the total macamide fraction (TMM) has been shown to have antioxidant and significant antitumor efficacy against the five different cancer cell lines (Fu et al., 2021). However, a novel identified polyunsaturated macamide derivative of Lepidium meyenii was reported to relieve dextran sulfate sodium-induced colitis in mice as evidence of the beneficial efficacy of Lepidium meyenii in mice intestines (Zha et al., 2021).
The maca's phenolic compounds and polysaccharides represent their antioxidant effects against oxidative stress via inhibiting the free radicals (Silva Leitão Peres et al., 2020). Yet, the claims about the centuries-old health benefits of maca were partially supported by functional studies and clinical trials (Beharry & Heinrich, 2018;Silva Leitão Peres et al., 2020), and the role of nutrient-transporter proteins in the intestines has not been elucidated yet for its activity. It has been exposed that a metabolic response to different fat sources containing a high-fat diet (HFD) was linked with alterations in the hepatic peptidases, which are crucial in regulating glucose metabolism and oxidative stress (Domínguez-Vías et al., 2020). In a recent maca study with HFD rats, it has been shown that maca is a potential SIRT1 activator in the liver and can significantly increase IRS1 levels in the visceral adipose tissue (Gencoglu, 2020).
The apparent digestibility of bone minerals has been reported to significantly decrease in HFD diets, leading to reduced bone density (Frommelt et al., 2014). Prebiotics have health-enhancing effects due to the modulation of the human colon microbiota, which is selectively combined with living microbial species called probiotics in the human intestine; therefore, studies on polysaccharides have focused on probiotic activities in the intestines (Markowiak & Śliżewska, 2017). In a recent study, a neutral polysaccharide obtained from the maca roots induced a higher growth of probiotics and short-chain fatty acids than inulin and showed prebiotic properties, while it also improved the anti-inflammatory effects (Lee et al., 2020).
In the present study, we aimed to determine the effectiveness of maca on nutrient digestibility and the mRNA changes in nutrienttransporter proteins, including glucose transporters (Glut1/Glut2), peptide transporters (Pept1/Pept2), fatty acid transporter 1 (Fatp1), along with the sodium/glucose cotransporter 1 (Sglt1) in the intestinal tissues of HFD fed rats, for achieving novel molecular interaction mechanisms and also preventive choices.

| Animals
A total of 28 young adult male Sprague-Dawley rats (n = 7 in each group, 12 weeks old, and weighing 200 ± 20 g) were housed in individual cages under controlled temperature (22°C) and a 12 h' light-dark cycle and provided with ad-libitum standard and highfat diets and tap water (

| Study design
The rats were randomly divided into four groups as follows: (i) control group, rats fed with a standard diet. (ii) Lepidium meyenii group, in addition to the fed standard diet, rats were received maca powder extract at a daily dose of 40 mg/kg BW via intragastric gavage TA B L E 1 Composition of diets (g/kg) and chemical analysis

| Sample collection
Fecal samples were collected twice daily for 5 days from all rats after maca administration. The feces collection was started at 09.00 h on the morning of day 56 of the collection period and ended at 09.00 h on day 60 of the study. At the end of the 8-week study, all the rats were sacrificed with decapitation. Then, the abdominal cavity of rats was opened, and the small intestine was removed to isolate 2-3 cm segments of the duodenum, jejunum, and ileum. Tissues were rapidly put on the dry ice and then frozen at −80°C as well for the determination of mRNAs expression.

| Sample preparation
Individual fecal samples were mixed, homogenized, and pooled

| Determination of chromium concentration
The concentration of chromium in feed and feces was determined

| Calculation of nutrient digestibility
Nutrient digestibility was formulated as follow:

| Statistical procedures
The sample size was calculated with a power of 85%, and the p < .05 was reflected to be statistically significant. One-way ANOVA and Tukey's multiple comparison tests were used for evaluating the differences between means as appropriate and the data plotted with software (GraphPad Software, Inc.).

| Feed intake and body weight changes
Feed consumption in groups is presented in Figure 1a. Accordingly,

| Nutrient digestibility
The digestibility of DM, OM, CP, EE, and ash in the rats is shown in

| Gene expressions of the nutrient transporters
The jejunum and ileum Pept1, Pept2, and Fatp1, gene expression variations between the groups are presented in Figure 3a

| D ISCUSS I ON
Lepidium meyenii (maca), native to the Andean region, is a valuable source of fiber and nutrients, including niacin, thiamine, riboflavin, F I G U R E 2 Effects of Lepidium meyenii (Maca) on dry matter (DM, panel a), organic matter (OM, panel b), crude protein (CP, panel c), ether extract (EE, Panel d) and ash (Panel e). HFD; high-fat diet. Statistical significance between groups is shown as: *p < .05, **p < .01, ***p < .001, and ****p < .0001 compared with control group; # p < .05, ## p < .01, ### p < .001, and #### p < .0001, compared with HFD group, and & p < .05; && p < .01; &&& p < .001; and &&&& p < .0001 compared with HFD + Lepidium meyenii group zinc, manganese, copper, and iron, and contains bioactive compounds like macamides, that can benefit a healthy diet (Silva Leitão Peres et al., 2020;Zhu et al., 2020). Dried and minced maca roots have main dietary components, including 46%-74% of carbs and more than 10% of plant-derived proteins, while it also comprises a healthful ratio of unsaturated to saturated fatty acid (53% vs. 40%, respectively), as well as high levels of linoleic and oleic acids (Wang & Zhu, 2019). Dietary components can dramatically change intestinal physiology and mainly regulate the intestines' barrier integrity (Chelakkot et al., 2018). The small intestine is a central digestive system component, which permits the body to break down and absorb the vital nutrients that allow it to work at the highest capacity (Collins et al., 2021).
The regulation of nutrient transporters in the intestinal lumen of the gastrointestinal tract (GI) is not fully understood yet. In the present study, maca supplementation did not statistically improve feed intake and BW gain, whereas significantly enhanced the digestibility of DM, OM, CP, EE, and ash levels along with a distinct upregulation of peptide transporters (Pept1/2), fatty acid transporter (Fatp1), glucose transporters (Glut1/2), and sodium-dependent glucose transporter (Sglt1) expressions in the jejunum and ileum of the rats. Jejunum refers to the part of the small intestine that leaves the duodenum to one side, leading to the ileum, which is the primary purpose of the jejunum is to absorb monosaccharides, amino acids, and fatty acids, while the ileum absorbs the remnant nutrients that were not absorbed by the duodenum or jejunum, especially vitamin B12 and bile acids to be recycled (Collins et al., 2021). The glucose transporter families (Glut) and sodium-dependent glucose transporters (Sglt) are responsible for the absorption of glucose, while the peptide transporters 1 and 2 are the members of the proton-coupled F I G U R E 3 Effects of Lepidium meyenii (Maca) on rat jejunum Pept1 (a), ileum Pept1 (b), jejunum Pept2 (c), ileum Pept2 (d), jejunum Fatp1 (e), and ileum Fatpt1 (f), mRNA expressions (fold of control). Statistical significance between groups is shown as: *p < .05, **p < .01, ***p < .001, and ****p < .0001 compared with control group; ## p < .01, ### p < .001, and #### p < .0001, compared with HFD group, and && p < .01; &&& p < .001; and &&&& p < .0001 compared with HFD + Lepidium meyenii group oligopeptide transporter family and the Fatp1 mediates skeletal muscle cell fatty acid import (Byers et al., 2017;Guitart et al., 2014;Zwarycz & Wong, 2013). In a recent study, an HFD fed mouse with thyroid disorders for 16 weeks reported a significant reduction in Glut2, Pept1, and fatty acid translocase (FAT/CD36) expressions, indicating that HFD may impair nutrient intake in the small intestines (Torelli Hijo et al., 2019). Lepidium meyenii was suggested to be used as a natural antioxidant agent, which would be helpful in maintaining a balance between oxidants and antioxidants (Vecera et al., 2007) and could be a functional food consistently to our results. Maca supplementation was shown to decrease insulin levels while increasing IRS1, leptin, and antioxidant effective SIRT1 levels in rats fed a high-fat diet (Gencoglu, 2020). Pept1 and Pept2 (SLC15A1 and SLC15A2) are H+-coupled oligopeptide symporters, and current studies on the modulation of these genes in inflammatory gut diseases were suggested to provide useful data on the bioavailability choices as oral Pept medicine substrates (Ingersoll et al., 2011;Smith et al., 2013). In the present study, mRNA expressions of Pept1/2, Fatp1, Glut1/2, and Sglt1 levels increased in all maca-given groups compared to those who did not receive the supplement in agreement with the study as mentioned earlier. In a similar manner to our study, in the HFD diet given mice intestines, the Glut2, Pept1, and membrane receptor FAT-CD6 levels decreased, whereas Glut5 and Fatp4 remain unchanged (Losacco et al., 2018).
The results of this study could be considered in the investigation and identifying approaches for the prevention and/or managing basal or HFD-related nutritional intestinal disorders.