Justicia carnea leaf extract improves intestinal transit in high-fat diet induced delayed gut motility in Wistar rats

INTRODUCTION

In many food cultures, lipids are commonly added to food either during preparation or when serving. These can erroneously be added in very large amounts or in some forms regarded as high-fat diets. The high-fat diets are mainly flour- or margarine-based, highly processed foods sold in many fast-food restaurants.¹ Gastrointestinal motility is usually described in terms of regional transit times or as intraluminal pressure changes. Dietary habits and food preparation methods may influence both motility and secretory activities of the gastrointestinal tract.^2,3 The transit of food through the stomach, small intestine, and colon is essential for digestion and absorption of nutrients as well as excretion of waste products in feces. Intestinal transit time is an important factor to consider when determining the amount of nutrients absorbed throughout the intestine.^4–6 Prolonged transit time will increase the duration of exposure of the chyme to the absorptive surfaces, and therefore, more absorption will occur, leading to weight gain.⁷ When the transit time is rapid (as may occur in diarrhea), there will be less time allowed for absorption and consequently weight loss. Despite the activities of several physiological systems involved in body weight homeostasis, the consumption of large amounts of dietary fats increases the storage of fat depots in the body.⁸

Transit time is measured by different techniques, including the ingestion of a substance that can be tracked as it travels along the gastrointestinal tract or seen upon elimination from the body.^9–12 The measurement of intestinal transit time is dependent on the frequency of bowel movements as well as the composition and other characteristics of the meal ingested.^11,13 Another indirect method of assessing transit time is the Bristol stool chart, which describes the different types of stool shapes.¹⁴ Using this chart, some studies have shown a correlation between stool shape, consistency, and transit time.^15–17 The implication of this is that people with more prolonged transit time will tend to pass hard, lumpy stools while persons with shorter or more rapid transit time will tend to pass loose stools.

Studies have shown that consumption of a diet with a high concentration of fats has the capacity to modulate the gastrointestinal responses to the ingested fat and ultimately alter the appetite regulation mechanisms, resulting in obesity.^18–20 Upper intestinal transit consists of gastric emptying and small intestinal motility. These play a primary role in satiety, appetite regulation, glycemic control, and intestine hormone signalling.^21,22 Gastroparesis, constipation, irritable bowel syndrome, and functional dyspepsia are associated with alterations in gastrointestinal transit of food, chyme, and residue. Assessment of regional (e.g., gastric, small intestinal, or colonic) transit or whole intestinal transit time may be useful in the diagnosis and management of these disorders.²³

The use of medicinal plants for the treatment of induced fat disturbances remains greatly unexplored and might be a strategic key in the development of effective drugs safe for human consumption. Extracts of plants, which are defined as raw or refined products obtained from parts of plants (such as tubers, stems, roots, leaves, flowers, and buds), are used frequently in the management of diseases.²⁴ The plant Justicia carnea is endowed with many beneficial effects, as it has often been described as a “wonder” plant.²⁵

This research aims to evaluate the effect of the hydro-methanolic leaf extract of Justicia carnea on intestinal transit in high-fat diet-fed Wistar rats.

MATERIAL AND METHODS

The study involved 25 male Wistar rats weighing 200–240 g and separated into five groups of five rats each. Ethical approval was obtained from the University of Port Harcourt Ethics Committee (UPH/CEREMAD/REC/MM82/030). The leaves of Justicia carnea used in this study were identified and authenticated in the Plant Science and Biotechnology department, University of Port Harcourt. Thereafter, the leaves were processed to prepare the extract used for the study. A high-fat diet was used to induce delayed motility in groups 2–5. The groups include.

Group 1 served as the control (normal animal feed and water).

Group 2 (high-fat diet and water).

Group 3 (high-fat diet + 200 mg/kg of body weight of extract).

Group 4 (high-fat diet + 500 mg/kg body weight of extract).

Group 5 (high-fat diet + 1,000 mg/kg body weight of extract).

The animals were fed with the extract for 28 days, and thereafter, intestinal transit was measured using standard protocols. Intestinal motility was determined according to the method adopted by Charles et al.,²⁶ on the 28^th day as follows: for each experimental group, the extract was administered together with a mixture of Evans blue dye and Arabic gum and allowed for 1 hour. Each animal was, thereafter, anesthetized and the intestines dissected out. The total length of the intestine, as well as the distance traveled by the test meal from the pyloric sphincter, was measured and recorded. Intestinal transit in 1 hour was expressed as the percentage of the distance traveled by the test meal to the total length of the intestine.

Statistical Package for Social Sciences (SPSS) version 22.0 was used for data analysis. Results were presented in a graph. Variables were expressed as percentages. Statistical difference was determined using analysis of variance (ANOVA) at p < 0.05.

RESULTS

Results showed that a high-fat diet (HFD) induced delayed intestinal motility in the experimental groups. As shown in Figure 1, there was a significant reduction in the percentage of intestinal transit in all the groups that received HFD compared to their control.

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Figure 1:

Effect of Justicia carnea leaf extract on percentage intestinal transit (in 1 hour) of rats fed with high-fat diet. * Significantly different compared to control, # Significantly different compared to HFD, HFD: High fat diet, CI: Confidence interval.

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DISCUSSION

Our findings agree with other studies that demonstrated reduced intestinal motility following the administration of a high-fat diet.^27–29 Studies suggest that HFD can cause increased stimulation of cholecystokinin (CCK) release.^30–32 CCK is involved in the physiologic regulation of gastric emptying and gastric motility^33,34 and mediates inhibition of food intake. In HFD-induced obesity, there is a reduced number of enterochromaffin cells, resulting in less availability of serotonin in the colon and reduced motility, partly responsible for the constipation often associated with the consumption of HFD.^35–37

In the present study, different concentrations (200, 500, and 1,000 mg/kg) of the leaf extract of Justicia carnea (JC) were respectively added to HFD feeding in Wistar rats. All the concentrations given (as in groups 3, 4, and 5) caused a significant increase in the percentage of intestinal transit compared to group 2 (high-fat diet only group). A dose-dependent pattern is noted in the JC effect on intestinal transit such that the animals fed with the lowest dose had better outcomes than the higher doses (i.e., 200 mg/kg > 500 mg/kg > 1,000 mg/kg), suggesting a possible laxative effect at low doses. Therefore, moderate consumption of JC would improve the intestinal transit and thus ameliorate the delayed intestinal motility associated with HFD. This effect of JC on intestinal transit is beneficial in the management of constipation-related medical conditions. The mechanism by which JC improves intestinal transit has not been well studied. However, the plant is endowed with numerous phytochemical components.^38,39 The alkaloids and flavonoids components of the extract may stimulate intestinal motility by influencing the electrical activity of intestinal smooth muscles.^40,41

CONCLUSION

Conclusively, the results from the present study suggest that moderate consumption of JC could improve intestinal motility in HFD-fed Wistar rats. Our findings provide a reference for the use of Justicia carnea in the management of constipation-associated medical disorders.