Pepino extract (Solanum muricatum Ait.) on HDL and LDL in type 2 diabetic rats

Abstract

Objective

Pepino contains of flavonoid and phenol as antioxidant which can reduce total cholesterol. This research was aimed to study the effect of pepino extract on high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C) in type 2 diabetic rats.

Method

The study was a randomized pre–posttest control group design. The subjects of this study were 20 male Wistar rats divided into 4 groups, they are control group, the group of pepino extract dosage 250 mg/kg BW, pepino extract dosage 500 mg/kg BW, and preventive group. Rats were induced diabetes with alloxan. Pepino extract was supplied for 2 weeks. Blood glucose level was evaluated on day 3 after alloxan injection, then HDL and LDL were monitored.

Results

The effect of pepino extract was not found significant to increase HDL or reduce LDL-C of diabetic rats at two different doses (p < 0.05). However, high dose of pepino extract (500 mg/kg BW) successfully inhibited the LDL increase in mice significantly.

Conclusion

Pepino extract can maintain HDL-C and LDL-C on alloxan induced diabetic rats. This food can potentially be a functional food that maintains the cholesterol profile.

Introduction

Cholesterol plays a major role in human heart health. Cholesterol can be both good and bad. High cholesterol in serum is a leading risk factor for human cardiovascular disease.¹ National Center for Health Statistics (NCHS) showed there were 12.4% of adults had high total cholesterol during 2015–2016 in United States.² Beseline Health Research 2013 showed 35.9% of ≥15 years old Indonesian had abnormal (high) cholesterol total, 22.9% had low level of high-density lipoprotein (HDL) and 15.9% had high level of low-density lipoprotein (LDL). Studies showed decreased of LDL level is the main target of abnormal cholesterol level management.³

The level of LDL is the single most important marker of atherosclerosis. Deranged LDL metabolism leads to coronary artery disease that is ofen fatal, especially in patients with diabetes. It has been found that not only elevated levels of LDL lead to coronary heart disease, but changes in composition can also result in the same. As we all know, cholesterol is an integral part of the plasma membrane, and a minimum level of LDL needs to be present to maintain structural integrity and sustain normal function of cells.⁴

Dietary component is important to consider the effects on cholesterol level, such as flavonoid-rich food.⁵ Dietary flavonoids commonly exert good antioxidant activity with the extent depending on the structure. Isoflavones, flavones, and flavanones reduce blood cholesterol levels through inhibition of cholesterol synthesis and increase of LDL receptor expression. Many studies reveal the potential role of flavonoids in the treatment of diabetes and indicate the hypoglycaemic actions of flavonoids in different experimental models and treatments.⁶

Flavonoids are abundant in plant-based food and beverages.⁵ Pepino (Solanum muricatum Ait.) is one of fruit that rich in phytochemicals and are a good source of dietary antioxidant. Study showed pepino aqueous extract had a higher content of ascorbic acid and total flavonoids. Pepino also showed a variety of biological effects. To begin with, the antioxidant effects attracted the most attention, involving the abundant phenolics (including chlorogenic acids) contained. Besides, anti-inflammatory effects were involved in a lot of other diseases such as diabetes and cancers.⁷ Study showed lower LDL was associated with higher intake of flavanones for participants with diabetes.⁸

This research was aimed to study the effect of pepino extract on HDL-C and LDL-C in type 2 diabetic rats. Pepino extract combined with alloxan was used to induce type 2 DM in rats.

Methods

Design

The study was a quasi-experimental design and used pepino extract for 2 weeks at 2 different doses (250 and 500 mg/kg BW).

Population and study setting

The study was done in Biofarmasi Laboratory of Universitas Hasanuddin and Laboratorium Kesehatan from June until October 2018. Population in this research are white rats in species of male Rattus novergicus strain Wister with 180–250 g body weight. Rats were adapted and fed with a normal diet. To induce type 2 diabetes, rats were injected once intraperitoneally with alloxan (140 mg/kg BW). The blood glucose level was monitored on day 3 after alloxan injection using a blood glucose meter. Rats with blood glucose level ≥200 mg/dL were used for this study, and their blood were used to monitor HDL-C and LDL-C. After diabetes was induced, rats were divided into 4 groups (5 rats per group).

Fresh purple pepino (S. muricatum Ait) was obtained from Malino, Sulawesi Selatan. Pepino were cleaned and thinly sliced before being dried in a vacuum oven at 55 °C. After drying, they were blended and kept at the room temperature prior to extraction. Sample mixed with ethanol 96% for 2 days in a comparison pepino and ethanol 1:5. After filtration through Whatman no. 1 filter paper, the extract was then rotary evaporated at 65 °C to dryness. The extract was stored in desiccator for further use.

Variables

Variables in this study are HDL-C and LDL-C which were monitored on the 1st and 15th day after diabetes induced. Rats were divided into 4 groups (5 rats per group). Group I was a negative control: diabetic rats with normal diet. Group II was the intervention group: diabetic rats with 250 mg/kg BW pepino extract. Group III was the intervention group: diabetic rats with 500 mg/kg BW pepino extract. Group IV was a preventive group: rats were fed 250 mg/kg BW pepino extract for 2 weeks, then induced by alloxan, and their HDL-C and LDL-C were monitored.

Data collection

Blood samples obtained 3 mL from tail vein of rat to monitor their HDL-C and LDL-C. An assistant of Biofarmasi Laboratory was responsible for collecting the blood samples before they were taken to Health Laboratory Center of Makassar to check the results of HDL-C and LDL-C.

Data analysis

Results expressed as mean ± SD. Statistical analysis used non-parametric Kruskal–Wallis.

Ethical aspect

Ethical aspect of this study was approved by Faculty of Public Health of Universitas Hasanuddin.

Results

Pepino extract was obtained according to the method described above and administrated to rats at two different doses to determine the effects on blood glucose level. In order to evaluate the effect of pepino to HDL and LDL of diabetic rats, diabetes was induced by i.p. injection of alloxan. Changes in HDL-C and LDL-C after oral administration of pepino extract were monitored for 2 weeks period and the results are given in Tables 1 and 2.

Table 1.

Effect of pepino extract on high-density lipoprotein-cholesterol (HDL-C) level of alloxan-induced diabetic rats.

Groups	Dose (mg/kg)	High-density lipoprotein-cholesterol (mg/dL) ± SD
		D-0	D-14
Control	–	51.60 ± 6.29	61.60 ± 16.21
Pepino extract	250	59.60 ± 8.98	60.80 ± 8.81
	500	69.00 ± 5.70	69.60 ± 3.64
Preventive	250	54.20 ± 8.40	55.60 ± 8.73

Number of animals in each group = 5, results compared to group control, SD: standard of deviation.

Table 2.

Effect of pepino extract on low-density lipoprotein-cholesterol (LDL-C) of alloxan-induced diabetic rats.

Groups	Dose (mg/kg)	Low-density lipoprotein-cholesterol (mg/dL) ± SD
		D-0	D-14
Control	–	9.60 ± 3.43	19.60 ± 8.82
Pepino extract	250	13.00 ± 4.30	19.20 ± 3.27
	500	14.60 ± 2.07	17.60 ± 2.30
Preventive	250	9.60 ± 1.81	14.40 ± 1.81

Number of animals in each group = 5, results compared to group control, SD: standard of deviation.

Table 1 shows that the average HDL-C of the four groups experienced an increase on the second week (D-14). Results showed that the average of LDL-C for all groups increased, as does HDL-C (Table 2). As for the highest difference in changes of HDL-C and LDL-C is the control group (Table 3).

Table 3.

The average difference in high-density lipoprotein-cholesterol (HDL-C) and on low-density lipoprotein-cholesterol (LDL-C) of alloxan-induced diabetic rats.

Variable	Groups	Dose (mg/kg)	n	Mean rank
HDL-C	Control	–	5	12.70
	Pepino extract	250	5	10.60
		500	5	9.00
	Preventive	250	5	9.70
LDL-C	Control	–	5	13.10
	Pepino extract	250	5	12.10
		500	5	6.80
	Preventive	250	5	10.00

Statistical analysis of Kruskal–Wallis showed p value of the average changes in HDL-C (p = 0.774) and LDL-C (p = 0.338) of diabetic rats. Based on the results, the effect of pepino extract was not found significant to increase HDL or reduce LDL-C of diabetic rats at two different doses (p < 0.05).

Discussion

In our experiments, there was no significant change in HDL-C and LDL-C levels of alloxan-induced diabetic rats. Pepino extract did not increase HDL-C levels or reduce LDL-C levels significantly, but the results showed that it can maintain HDL-C and LDL-C levels of diabetic rats. Pepino are rich in vitamin C, phenolic, flavonoid, and tannin.⁹ Phenolic and flavonoids are polyphenol compounds which can reduce total cholesterol levels in blood by inhibiting cholesterol absorption by intestine, increasing formation and excretion of bile acids through feces and reducing blood viscosity, increasing r-LDL, and binding to apolipoprotein thereby reducing occurrence of fat deposition in blood vessels.^10,11

A direct relationship between hyperglycemia level and cardiovascular disease morbidity and mortality has been demonstrated. Many studies reveal the potential role of flavonoids in the treatment of diabetes and indicate the hypoglycemic actions of flavonoids in different experimental models and treatments.⁶ The antioxidant defense boosting and anti-inflammatory properties of flavonoids show great potential for improving HDL function and cardiovascular health. Dietary flavonoid intake has been reported to be protective against cardiovascular disease (CVD) in a number of cross-sectional and prospective cohort studies. A recent meta-analysis examined the association between specific classes of flavonoid intake and CVD in prospective cohort studies.¹²

The study of Huffman et al. examined the effect of flavonoids to HDL-C and LDL-C with and without type 2 diabetes. They found that lower LDL was associated with higher intake of flavanones for participants with diabetes; whereas, higher flavan-3-ols, and flavanones and lower polyflavonoids were related to lower LDL in the group without diabetes. There was a positive association for HDL with anthocyanidins and flavan-3-ols and an inverse relationship with polyflavonoids for the group without diabetes. There was no relationship between HDL and flavonoids for the group with diabetes.⁸

The effect of living stone potato on hyperglycemia of STZ induced diabetic rats. Hypercholesterolemia and hypertriglyceridemia are recognized complications of diabetes mellitus, resulting from alterations in lipid metabolism. This study showed significant reduction of the serum total cholesterol, VLDL, triglycerides, and LDL-cholesterol together with the concomitant significant increase in the HDL levels of the diabetic rats fed with living stone potato.¹³

Tatary buckwheat (TBF) lowered total cholesterol, triglycerides, LDL cholesterol, and also enhanced the HDL cholesterol of diabetic rats. The improvement of lipid profile might be directly or indirectly related to the reducing of fasting blood glucose levels in diabetic rats.¹⁴ Beside its effect on cholesterol profile, pepino extract may have positive impact on blood glucose¹⁵ which strongly associated with cholesterol changes.¹⁶

Conclusion

In conclusion, results have shown that pepino extract in both doses (250 and 500 mg/kg BW) can maintain the HDL-C and LDL-C levels of alloxan induced diabetic rats. This food can be an alternative food for diabetic patients in order to maintain HDL-C and LDL-C levels. Further studies are needed to clarify the specific antioxidants and its mechanism for the relationship between cholesterol and type 2 diabetes.

Conflict of interests

The authors declare no conflict of interest.

Acknowledgement

This study was funded by a research grant from Universitas Hasanuddin year 2018.