INTRODUCTION
1.1 Background to the Study
Diabetes mellitus is referred to as a metabolic disorder in which there is high glucose level in the blood as a result of insulin deficiency, resistance or both (American Diabetes Association, 2009). It has been deduced globally that the adult population with diabetes will rise by 69% for the year 2030 (Shaw et al., 2010). Type 2 diabetes (T2D) occurs when there is an advanced determent in insulin action (insulin resistance, IR), which proceeds to β-cell dysfunction due to the failed ability of pancreatic β-cells to compensate for IR (Srinivasan et al., 2005). The number of people suffering from diabetes worldwide is estimated to be 215 million and 80–90% of them from T2D (Procopiou and Philippe, 2005). Sedentary lifestyle such as taking high-calorie containing food, lack of exercise, ageing are all risk factors for T2D and hence conduce to the recent rising prevalence of obesity and T2D (Aude et al., 2004). Streptozotocin (STZ) has been utilized broadly for induction of diabetes both type 1 diabetes and T2D in experimental animals (Szkudelski, 2001). Unfortunately, it lacks the ability to induce IR directly which is one of the pathogenesis of T2D, rather, it induces diabetes from direct pancreatic β-cells damage which resembles a typical T1D (Srinivasan et al., 2005).
Reports gotten from various studies showed that high fat or fructose diet induced IR in experimental animals but failed to induce hyperglycemia (Srinivasan et al., 2005; Wilson and Islam, 2012). In as much as giving animals a high fructose load alone can induce IR, several weeks may be required to achieve this. Hence, the cost and duration of the study will be high. More so, the animals can naturally develop nutritional tolerance when exposed to longtime feeding with fructose without developing signs and symptoms of IR and impaired glucose tolerance (Stark et al., 2000). Therefore, the search and development of a suitable T2D rat model that will boycott the setbacks experienced in using fructose or STZ as single agents to induce IR and T2D came into place. Interestingly, the model has been achieved through a combined effect of fructose and STZ. High fructose load induced IR while a low dose of STZ caused the initial β cell dysfunction and subsequently hyperglycemia (Wilson and Islam, 2012; Stalin et al., 2016). This model is a close replica of the natural history of T2D and its metabolic features in humans. More so, it is cheaper, readily available and useful for investigation of various compounds. Plants have been used extensively for treatment of disease due to the fact that they can produce multifarious basic biochemical and organic substances such as carbohydrates, proteins, terpenes, steroids, alkaloids and glycosides (Andrews, 1982).
Buchholzia Coriacea (B. Coriacea) a perennial plant belonging to the family capparidaceae and genus Buchholzia is popularly known as wonderful kola (Quattrochi-Umbetto, 2007). Earlier studies carried out on different parts of this plant shows that it has great medicinal potentials (Oluseyi and Francisca, 2009; Fred-Jaiyesimi et al. 2011; Adisa et al., 2011; Obembe et al., 2012; Olaiya and Omolekan 2013; Ibrahim and Fagbohum, 2013; Enenchi and Nwodo 2014; Eze et al., 2015). However, there is currently no study carried out to assess the efficacy of B. Coriacea in T2D.
Therefore, this present study assessed the possible modulatory effects of BC on high fructose-fed, STZ-induced T2D in male Wistar rats in order to ascertain its involvement and as well characterize the active compounds that may be present.
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1.2 Statement of the Problem
Insulin resistance, hyperlipidaemia, β-cell dysfunction and their associations are major risk factors for the development of T2D and cardiovascular complications (Lender and Sysko, 2006). To mitigate these serious complications and negative outcome of T2D, the control not only of blood glucose but also of lipids is essential (Moller, 2001). More so, the available therapeutic options such as a combination of synthetic hypolipidaemic and antidiabetic drugs have their own setbacks (Lender and Sysko, 2006). Therefore, there is a need for new agents which will be more effective, readily available and with minimal side effects.
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1.3 Objective of the Study
The general objective of this study was to evaluate the possible modulatory effects of the B. coriacea seed extracts in high fructose-fed, streptozotocin-induced T2D in male Wistar rats. The specific objectives are to:
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1.4 Significance of the Study
This study will increase our understanding of the pathophysiological role of fructose-fed, streptozotocin-induced T2D in vivo as well as evaluate the possible modulatory role of B. coriacea. In addition, it is hope that constituent compounds present in B. coriacea would aid further scientific investigations while contributing to the field of diabetology and or harnessing drug discovery and development.