The Hypocholesterolemic and Glucose Modulatory Effect of Fibre Enriched Snack in Hyperlipidemic/Hyperglycemic Rat Model Induced by High Cholesterol and High Fructose Diet

Introduction

Hyperlipidemia has significantly contributed to the increased risk of cardiovascular disease burden, the leading cause of mortality. Globally, hyperlipidemia is associated with more than 50% of ischemic heart disease and over 4 million deaths are recorded annually due to the diseases it degenerates into [1]. More so, defects in insulin action and Investigation Paper hyperglycemic conditions caused by hyperlipidemia leads to the pathogenesis of diabetes  [2]. Globally, the diabetic population has been projected to increase by 156% in 2045 [3]. Hyperlipidemia and hyperglycemia affect lipid and carbohydrate metabolism causing elevations in total cholesterol (TC), low density lipoprotein (LDL), triglycerides (TG) and glucose with reduction in high density lipoprotein (HDL). The elevations in glucose, TC and LDL causes an increased inflammatory response and triggers oxidative stress which further constricts the vascular endothelium causing complications [4]. The sustained inflammatory state in hypercholesterolemia deactivates the insulin signaling receptors in pancreatic beta cells causing insulin resistance, majorly responsible for pathogenesis and progression of complications in patients with type 2 diabetes mellitus [5].

The incorporation of dietary fibre into food products has been found to be effective, safe and readily available in comparison to the use of most conventional medications in the management of hypercholesterolemia [6]. Dietary fibre has been reported to reduce blood cholesterol and stabilize blood glucose levels by delaying glucose/ fatty acid absorption, increasing cholesterol and bile acid excretion [7]. Dietary fibre also reduces systemic inflammation by lowering pro-inflammatory cytokines and C-reactive protein (CRP) [8]. Snacks enriched with fruit fibres have been shown to improve insulin sensitivity, atherogenic index and demonstrate protective effect against oxidative stress related damage in brain, kidney and liver of diabetic rats [8, 9, 10]. Therefore, this research work was directed towards evaluating the effects of a fibre enriched snack on serum lipid profile, blood glucose and serum insulin levels in an experimental model using Wistar rats fed on a hyperlipidemic-hyperglycemic diet.

Results

The results obtained from this study are presented in Figures 1-5 and Table 1

Figure 1 shows the fasting blood glucose levels (mg/ dl) of animals in the different treatment groups. There was a significant increase in fasting blood glucose in Group 2 (HCD group) at week 6 (the final week of the experiment) compared with week 0 (the first week). There were, however, no significant differences across all the other experimental groups when week 6 was compared with week 1.

Blood cholesterol levels (mg/dl) of animals in the different treatment groups are presented in Figure 2.

The cholesterol level was significantly increased (P < 0.001) in group 2 (HCD) compared with group 1 (NCD). There was, however, a significant reduction in cholesterol level in group 3 (HCD + FES) and group 4 (HCDW + FES) at P < 0.001 as well as in group 5 (NCD +FES) P < 0.01 and Group 6 (HCD + CAD) P< 0.0001 compared with group 2.

C H O L E S T E R O L

2 0 0 # # #

C h o le s te ro l (m g /d l)

1 5 0 *

***

E x p e rim e n ta l G ro u p s Figure 2: Blood cholesterol level (mg/dl) of animals in different experimental group. Values are represented as mean + SD, N=5 ###P < 0.001 when compared to Group 1, **P < 0.0001 when compared to Group 2, *P < 0.001 when compared to Group 2, **P < 0.01 when compared to group 2.

The LDL level (mg/dl) of animals in the different treatment groups are presented in Figure 3. It can be observed that the LDL level was significantly increased (P < 0.0001) in group 2 in comparison to group 1. It was, however, significantly decreased in groups 3, 4 and 5 (P < 0.01), as well as in group 6 (P < 0.0001), compared with group 2.

L D L

1 5 0 # # # #

L D L (m g /d l)

1 0 0 * * ***

****

E x p e rim e n ta l G ro u p s Figure 3: LDL level (mg/dl) of animals in different experimental group. Values are represented as mean + SD, N=5 ####P < 0.0001 when compared to Group 1, *P < 0.001 when compared to Group 2, P < 0.01 when compared to Group 2.

Figure 4 shows HDL levels (mg/dl) of animals in the different treatment groups. The HDL level was significantly decreased (P < 0.01) in group 2 compared with group 1. There was no significant difference in HDL in groups 3, 4 and 6 compared with group 2, however, there was a significant increase (p< 0.05) in HDL level in group 5 in comparison with group 2.

H D L

5 0

4 0 # # * H D L (m g /d l)

E x p e rim e n ta l G ro u p s Figure 4: HDL level of animals in different experimental group. Values are represented as mean + SD, N=5 ##P < 0.01 when compared to Group 1, *P < 0.05 when compared to Group 2.

The LDL level (mg/dl) of animals in the different treatment groups are presented in Figure 3. It can be observed that the LDL level was significantly increased (P < 0.0001) in group 2 in comparison to group 1. It was, however, significantly decreased in groups 3, 4 and 5 (P<0.01), as well as in group 6 (P < 0.0001), compared with group 2.

Triglyceride level (mg/dl) of animals in the different treatment groups are presented in Figure 5. A significant increase (P < 0.001) in triglyceride levels was observed in group 2 in comparison to group 1. There was a significant decrease in triglyceride level in group 3 (p< 0.05) and group 4 (p < 0.001) compared with group 2. There was also a significant decrease in triglyceride level in Group 5 and 6 (P < 0.01) compared with group 2.

T R IG

1 5 0 # # #

T R IG (m g /d l) * * **

1 0 0 *

E x p e rim e n ta l G ro u p s Figure 5: Triglyceride level (mg/dl) of animals in different experimental group. Values are represented as mean + SD, N=5 ###P < 0.001 when compared to Group 1, *P < 0.05 when compared to Group 2, P < 0.01 when compared to Group 2, *P < 0.001 when compared to Group 2.

Serum Insulin level (ug/ml) of animals in the different treatment groups are presented in Table 1. There was a significant decrease (p< 0.05) in serum insulin levels in Group 2 (HCD) in comparison with Group 1 (NCD). The levels were significantly increased (p< 0.01) in Group 4 (HCDW + FES) and group 5 (NCD + FES) in comparison with Group 2 (HCD).

Discussion

The economic cost of managing diseases associated with hyperlipidemia and hyperglycemia are quite enormous.

Notwithstanding the continuous rise in the number of populations associated with these conditions especially the diabetic and obese population. The increase in diabetic population globally an especially in developing country is of great concern among the myriad of other non-communicable diseases affecting developing countries with their poor health infrastructures. Moreso, most conventional medications used in the management of such hyperlipidemic/ hyperglycemic conditions are not readily available and present a wide range of adverse effects such as diabetes, liver/ renal damage, muscle myopathy, insomnia, drowsiness and digestive disturbances. This has led to the quest for effective, safe, affordable and readily available treatment options. Incorporation of dietary fibre in snacks reduces their caloric content and enhances their nutritional value. In this study, we investigated the ability of fibre enriched snacks to reduce blood lipid and glucose level, while boosting blood insulin levels in hyperlipidemia-hyperglycemia induced rats.

Chronic hyperglycemia is a well-known hallmark for patients with type 2 diabetes causing further metabolic complications such as hyperlipidemia in such pathological state. Hyperlipidemia increases the levels of free fatty acids which impairs the function of pancreatic beta cells and induces insulin resistance facilitating increased blood glucose levels [16]. The significant increase of fasting blood glucose in the group fed on a high cholesterol diet and fructose solution (Figure 1) justifies this, such as has been confirmed by Afzal, et al. [17]. This corroborates the trend in the increased consumption of cholesterol rich fatty foods and sugary drinks causing an increase in diabetic population. The stability of blood glucose levels in the groups fed the fibre enriched snacks suggests hypoglycemic activity. This finding is similar to that of Yesmin, et al. [18], where the ingestion of dietary fibre along with a glucose drink reduced the sharp and sustained rise of postprandial glucose. Dietary fibre especially the soluble fibre slows the absorption of carbohydrates, improving blood sugar levels [19].

The significant reductions in cholesterol level and LDL by 13.74% and 21.21% respectively, (Figure 2 and Figure 3), suggests that the fibre enriched snacks was able to achieve a marked reduction in blood cholesterol and LDL levels. Administration of the fibre enriched snacks alongside normal diet was also able to significantly increase HDL levels (Figure 4). A similar study involving another variety of fibre enriched snacks showed that they significantly reduced cholesterol and LDL levels in diabetic rats [10], thus, suggesting the significant role of fiber enriched snacks in reducing blood lipid levels. Soluble dietary fibre has been reported to facilitate cholesterol reduction through various mechanisms involving an interplay of delayed intestinal absorption of glucose and lipids, binding of cholesterol to bile acids and increased excretion of bile acids [20], [21]. The CAD was observed to show a more significant reduction in lipid levels especially triglycerides (Figure 5), being a more targeted drug. However, various adverse effects, such as muscle aches, myalgia, headaches, nausea, abdominal cramping, increased risk of diabetes mellitus and renal damage, however, have been reported with the administration of the drug [22, 23, 24]. This justifies the use of alternative means, such as fibre enriched diet, as safer and more reliable especially in long term treatment of hyperlipidemia.

Studies have reported that hypercholesterolemia is capable of reducing insulin levels by inducing pancreatic β cell apoptosis through the oxidative stress pathway, enabling type 2 diabetes [25, 26]. The significant reduction of blood insulin concentration in group 2 (Table 1) was caused by the hypercholesterolemic state of the animals. The non-significant difference in insulin levels for the group administered the conventional antilipemic drug (CAD) indicates that the CAD used had no effect in stabilizing insulin levels in hypercholesterolemic animals. In fact, the class of CAD used has been suggested to impair β-cell insulin secretion and promote insulin resistance, thus increasing the risk of developing type 2 diabetes especially in high risk patients such as hyperglycemic patients and postmenopausal women [27]. Fibre enriched snacks boosts blood insulin concentrations with the withdrawal of the hyperlipidemic- hyperglycemic diet. This was observed with the significant increase in insulin concentration observed in the group that had the fibre enriched snack with the antilipemic diet withdrawn and the group administered the fibre enriched snack alongside normal diet. Lummela, et al. [28] have also reported that dietary fibre favorably affects insulin in healthy individuals. Dietary fibre exerts an anti-inflammatory effect and reduces oxidative stress at cellular and molecular levels boosting insulin concentrations in normal subjects.

Conclusion

This study has shown that incorporation of fibre enriched snacks in the diet caused significant reduction in cholesterol, LDL concentration and stabilized blood glucose after six weeks in hyperlipidemic test animals. Additional benefits of increasing HDL concentration and boosting insulin levels were also recorded, when the fibre enriched snacks was administered with the withdrawal of the hypercholesterol- hyperglycemic diet. The fibre enriched snacks can thus serve as an effective dietary intervention in managing hyperlipidemic conditions, especially in patients with type 2 diabetic dyslipidemia.

Further studies involving longer duration of exposure to high fibre snacks is hereby recommended.

Ethical Approval

All authors hear by declare that the ARRIVE guidelines were followed and the animal experiment was carried out in accordance with the U.S Public Health Service Policy on humane care and use of laboratory animals. ‘’All experiments have been examined and approved by the animal care and use research ethics committee in the institution in which it was performed’’.

Acknowledgement

This is to acknowledge the valuable help of Mr Dike during the animal sacrifice. We also appreciate Mr Sunday who assisted in the analysis of blood samples.

Author Contributions

Adetoboye Olubunmi Olajumoke: Methodology, formal analysis, investigation, writing-original draft. Osibanjo Adetokunbo: Methodology, Writing-Review and editing, Supervision Erukainure Ochuko: Conceptualization, methodology, validation. Obode Okukwe: methodology, investigation, Eboagwu Ijeoma: Investigation, Familola Oluwatosin: Investigation. Odega Joy: Investigation. Efuribe Nnenna: Investigation. Oke Oluwatoyin: Product development. Olonode Titilayo: Product development. Oluwole Oluwatoyin: Supervision, Project administration. Elemo Gloria: Funding acquisition.

All authors have revised and approved the final submitted version of this work

Author Disclosures

“Competing interests: None”