Pancreatic beta cells are groups of endocrine cells responsible for the synthesis, storage, and release of insulin. Insulin is a hormone that counteracts antagonizes hyperglycemic hormones, like glucagon, glucocorticosteroids, and epinephrine, to keep circulating glucose concentrations within a narrow physiologic range (Marchetti et al., 2017). Damage to beta cells can lead to hyperglycemia (diabetes mellitus) a common metabolic disorder of carbohydrates, fats, and proteins that is quickly becoming an epidemic (Hudish et al., 2019). Statistics indicate that 9.3% of the world’s population in 2019 is presently living with diabetes; this figure is expected to increase to about 10.9% by 2045 (Saeedi et al., 2019). The disease’s high prevalence, progressive nature, diverse pathogenesis, and complications necessitate rapid treatment options (Osadebe et al., 2014). A variety of treatments, such as insulin therapy, pharmacotherapy, and diet therapy, are currently available for controlling this disease.

Glucose-lowering drugs have anti-diabetic effects through a variety of ways (Bathaie et al., 2012). Despite major advancement in diabetes treatment over the past 3 decades, the treatment outcome of treatment is far from perfect. Drug resistance, debilitating side effects, severe toxicity, and drug contraindications due to in vitro interactions are all problems that these treatments face (Kooti et al., 2016). Medicinal plant treatment regimens have been proposed by a number of researchers (Kooti et al., 2015). Hundreds of plants have been documented to have positive anti-diabetic effects, including Acacia Arabica (Hegazy et al., 2013), Allium sativum (Kazi, 2014), Azadirachta indica (Hashmat et al., 2012), Blighia sapida (Ojo et al., 2017), and Caesalpinia bonducella (Nazeerullah et al., 2012).

Cenchrus purpureus (Schumach.) Morrone (family: Poaceae) is a major multipurpose high yielding tropical grass also known as elephant grass, Napier grass, Uganda grass, among other names. It is a highly adaptable species that can thrive in a variety of environments and agricultural systems, and it is found all over the tropics (FAO, 2015). Because of its high productivity, elephant grass is a very important forage plant in the tropics. It is high in fiber, essential nutrients, and trace minerals, with a protein content that’s typical of forage plants (Evitayani et al., 2004). Soups and stews can be made with the young shoots (Akah and Onweluzo, 2014). Elephant grass, as implied by its name, is an important source of food for elephants in Africa (Francis, 2004) and is suited to feed cattle and buffaloes. C. purpureus is a fast-growing and high biomass-producing cellulosic source and has been a choice candidate for biofuel feedstock (Rocha et al., 2017) and weed control where it is used as a trap plant in push-pull management strategies to fight against stem borers in maize crops (Khan et al., 2007). Although there is less research and documentation on its efficacy as a medicinal plant in the treatment of various ailments, there are reports that the shoot and culm infusions have diuretic properties (Duke, 1983). Its phytochemical composition also revealed a higher proportion of terpenoids, alkaloids, calcium (Prinsen et al., 2012), and riboflavin than many vegetables including onion, cabbage, carrot, cauliflower, cucumber, chili pepper, and spinach (Burkill, 1985). C. purpureus was reported by Okaraonye and Ikewuchi, 2009 to contain alkaloids, cyanogenic glycosides, flavonoids, saponins, and tannins. C. purpureus has been reported as a traditional treatment for diabetes mellitus (Akuru et al., 2015). C. purpureus has been discovered to be a powerful antioxidant and hypoglycemic agent (Tsai et al., 2008; Okaraonye and Ikewuchi, 2009; Olorunsanya et al., 2011; Akuru et al., 2015; Tjeck et al., 2017). Although previous research has shown that C. purpureus shoot extract (CPSE) has anti-diabetic properties, its mechanism has yet to be investigated. As a result, this study used a diabetic rat model to assess the effects of AECPS on pancreatic-cell dysfunction and apoptosis, as well as to investigate the mechanism of action of C. purpureus in alloxan-induced diabetic rats.

The phytochemicals in AECPS were identified through HPLC analysis. AECPS contained the flavonoids 3-O-rutinoside, ellagic acid, catechin, rutin and kaempferol were present in AECPS. 3-O-rutinoside has been shown to be an effective inhibitor of α-glucosidase enzyme (Habtemariam, 2011). Ellagic acid works as an anti-diabetic agent by stimulating insulin secretion and decreasing glucose intolerance in pancreatic ß-cells (Fatima et al., 2015). Catechin works as an antidiabetic agent by boosting the antioxidant defenses (Samarghandian et al., 2017). Rutin exhibited significant antidiabetic activity, possibly by inhibiting inflammatory cytokines, enhancing antioxidant capacity in a diabetic model and may be useful as a diabetic modulator (Niture et al., 2014), whereas kaempferol may enhance glucose metabolism and inhibit gluconeogenesis (Alkhalidy et al., 2018). As a result, the therapeutic activities of AECPS, as demonstrated by our findings, could be attributed to these compounds identified.

Plants produce phenolic compounds through a series of activities that involve several biosynthetic pathways, including glycolysis, hexose monophosphate shunt, and shikimate pathways in the cytosol (Paucar-Menacho et al., 2017; Ajiboye et al., 2018). They play a significant role in health by regulating weight, metabolism, chronic disease, and cell proliferation (Rodríguez-García et al., 2019). In addition, they possess anti-inflammatory and antioxidant properties that may have preventive and/or curative effects for diseases and disorders, like diabetes mellitus (Adelek et al., 2018a; Rodríguez-García et al., 2019).

Diabetes is an enfeebling chronic metabolic disease with global relevance (Ojo et al., 2017). Diabetes treatment varies depending on the underlying cause of the disease. Insulin can be used to treat type I diabetes, whereas medications that inhibit specific enzymes, such as α-amylase, α-glucosidase, dipeptidyl peptidase IV, and protein tyrosine phosphatase, can be used to treat type II diabetes (Tundis et al., 2010). The primary aim of diabetic treatment is to maintain glycemic control in diabetic patients during both fasting and post-prandial states. Complications from side effects associated with the use of conventional drugs to treat diabetes have prompted a search for alternative anti-diabetic drugs derived from plant (Ojo et al., 2018b). It has been studied to use natural products to either inhibit the production of glucose from carbohydrates in the intestine or the absorption of glucose from the intestine (Ojo et al., 2018b). The α-amylase enzyme can be found in high concentrations in the pancreatic juice and saliva. Salivary a-amylase hydrolyzes the α-(1,4)-glycosidic bonds of large insoluble carbohydrates, the primary sources of glucose, into smaller molecules. In contrast, α-glucosidase is localized in the walls of the small intestine and acts by mediating the catabolism of starch and disaccharides into simpler sugars, such as glucose, which are absorbed in the intestine. Alpha-glucosidase regulates postprandial hyperglycemia and is considered to be a potential therapeutic target for diabetes treatment. Inhibiting the activities of these enzymes (α-amylase and α-glucosidase) in the gastrointestinal tract (GIT) of humans is known to be an effective diabetic control by lowering postprandial blood glucose (Tundis et al., 2010). The strong inhibitory activity of AECPS against a-amylase and a-glucosidase found in this study backs up previous reports from other plants (Ojo et al., 2018b). Because the AECPS inhibited the activity of α-glucosidase and α-amylase in a concentration-dependent manner, this inhibition could serve as an indicator of the potential antidiabetic role of the plant.

To reduce the global burden of diabetes mellitus (DM), researchers are searching for newer therapies, especially the use of natural plants, which are readily available and pose fewer or no side effects (Balogun and Ashafa 2017). Some drugs used in treating diabetes are known to have limited efficacy over time (Ojo O. A. et al., 2020). Modern drugs have been reported to losing efficacy over time and attention towards plant materials as s solution to this problem has be of utmost concern. Metformin was used as a standard drug because it has been the preferred and most significant drug for diabetes treatment for over a decade (Balogun and Ashafa 2017). In the current study, we investigated the hypoglycemic potential of AECPS in vivo to discover its antidiabetic potency via blood glucose levels.

A significant hallmark of a diabetic state is a reduction in body weight, which can sometimes be ascribed to abnormalities in the catabolism of macronutrients such as fat and protein leading to extreme tissue protein loss and muscle wastage (Balogun and Ashafa 2017). This is clear from our rat diabetic control group, which had a weight loss of more than 8%. AECPS treatment reduced the weight loss even more than the group treated with the standard drug (metformin). The improvement in body weight in the diabetic rats treated with AECPS suggests restoration of tissue and muscle protein as a result of the extract, substantiating the report by Balogun and Ashafa, 2017. The rats treated with AECPS (16.8 mg/kg) showed the highest percentage weight gain, which was higher than that of the normal control. The results from this study did not show any significant change in the organ-body weight ratio (for liver and pancreas) caused by DM even though there was a reduction in overall body weight caused by DM.

DM is a common result of a defect in the secretion or action of insulin and sometimes both Ojo et al., 2017; Ojo O. A. et al., 2020). The administration of the extract not only reduced the blood glucose concentration but also elevated the levels of insulin in the serum. The stimulation of insulin secretion by the extract apparently achieved the reduction in blood glucose level, as other researchers have reported that several plants produce their hypoglycaemic effect in this manner (Balogun and Ashafa 2017). The use of alloxan at a low dose causes partial destruction of the hepatic beta cells. Thus, the plant extract may have led to a regeneration of the surviving beta cells (Ojo O. A. et al., 2020). Higher HOMA-IR and lower HOMA-β scores in the diabetic control group indicate the induction of partial pancreatic beta-cell dysfunction and insulin resistance, which confirms the diabetic condition as previously noted elsewhere (Ojo et al., 2017). The reversal of the HOMA-IR and HOMA-β scores following treatment with the extract may, therefore, indicate decreased insulin resistance and restoration or regeneration of the hepatic beta cells.

Oxidative stress is linked to DM through free radicals. Free radical generation accompanied by antioxidant defense impairment could lead to the oxidation of glucose, glycation of protein, and oxidative degradation of protein glycation (Balogun and Ashafa 2017; Yusuf et al., 2021). DM induction by alloxan is said to be through the generation of ROS, leading to rapid destruction of the beta cells of the pancreas, causing hyperglycemia (Yusuf et al., 2021). Elevated pancreatic and hepatic MDA levels after alloxan administration indicate that oxidative stress has occurred because of a compromised antioxidant system in the diabetic condition (Ojo OA. et al., 2020). The reversal of this oxidative damage-prone condition with a reduction of the MDA level with administration of either metformin or AECPS may imply an improved antioxidant status. Thus, our findings may affirm the antioxidant and antidiabetic potential of the extract. Also, decreases in pancreatic and hepatic antioxidant (CAT, SOD, GPX, GSH, and GST) activities in the diabetic-induced rats reveal that oxidative stress resulted from alloxan administration. An increase in enzyme activity in diabetic rats treated with metformin and AECPS revealed an improved antioxidant status (Balogun and Ashafa 2017).

Cardiovascular complications are a common cause of death in diabetics, and postprandial glucose elevation is a risk factor for cardiovascular disease. One manifestation of cardiovascular disease is alteration of the lipid profile. Studies have associated diabetes with hypertriglyceridemia, which may be caused by insulin deficiency. In the current study, we found an abnormal lipid profile in rats after DM induction. In a normal state, it was reported that insulin activates lipoprotein lipase, which hydrolyzes triglycerides, however, in a diabetic state, the enzyme’s inactivation may result in hypertriglyceridemia (Yusuf et al., 2021). Insulin inhibits HMG-CoA reductase, an enzyme that catalyzes the rate-limiting step in cholesterol synthesis, resulting in hypercholesterolemia (Ojo O. A. et al., 2020). In this current study, diabetes induced by alloxan may have inhibited lipid metabolism, as evidenced by elevated TC, TG, VLDL-c, LDL-c, AI, and CRI levels and by decreased HDL-c levels. Another possible explanation for the observed hyperlipidemia is excessive fat mobilization from adipose tissue as a result of glucose underutilization (Ojo et al., 2017). The high levels of CRI in the diabetic control group indicate a proclivity for coronary disease (Ojo et al., 2017). The administration of metformin or the extract to the diabetic rats could have reduced the levels of these lipids with the extract performing better than the standard drug in reducing TG, VLDL-c, and LDL-c, lending credence to the antidiabetic activity of the AECPS. AECPS at 16.8 mg/kg performed better overall than the lower doses of extract administered.

Hexokinase, a vital enzyme for the regulatory step in glycolysis was reduced in the diabetic rat’s relative to the treatment groups. This finding correlates with results reported by Balogun and Ashafa, 2017 that showed a reduced activity of hexokinase attributable in part to declining insulin levels and a decreased mRNA expression of hexokinase in a diabetic state. The improved hexokinase activity by AECPS may facilitate glucose utilization for ATP production (Balogun and Ashafa, 2017).

Glucose-6-phosphatase (G-6-Pase) is a crucial enzyme in maintaining blood glucose homeostasis and is vital during hypoglycemia as it replenishes the blood glucose level. A depletion in the activity of G-6-Pase results in a metabolic disruption identified by hypoglycemic activity activated by cAMP and inhibited by insulin. Insufficient insulin activity in DM elevates G-6-Pase activity leading to elevated blood glucose levels. The result obtained in this study showed that either AECPS or metformin administration diminished G-6-Pase activity in alloxan-induced diabetic rats. The decline in G-6-Pase activity may indicate a decrease in gluconeogenesis and glucose production (Murali et al., 2013).

Fructose-1,6-bisphosphatase (F-1,6-BPase), a gluconeogenic enzyme, is essential in aiding glucose release for circulation in a diabetic state. We showed that its activity increased in diabetic rats because of insufficient insulin. Both AECPS and metformin treatment facilitated a reduction in the levels of F-1,6-BPase in diabetic rats. The activities of F-1,6-BPase enzyme as altered by AECPS or metformin could either occur because of suppression of gluconeogenic and glycolytic activities or modulation by activating metabolism (Balogun and Ashafa 2017; Yusuf et al., 2021).

PI3K and AKT are major players in the insulin signaling pathway in DM (Deng et al., 2018). The activation of the PI3K/AKT pathway inhibits increased blood glucose-induced apoptosis in cells (Cheng et al., 2013). The action of insulin is facilitated by the activation of PI3K and its effectors, the protein kinase B (PKB/AKT) kinases. The AMPK signaling pathway increases the impact of the insulin-independent response for glucose uptake. This study revealed that AECPS upregulates the mRNA expression of PI3K and AKT, lowering the FBG level, enhancing insulin levels, and protecting the liver and pancreas. AECPS may protect against alloxan-induced damage through an anti-apoptotic effect via raising the expression of phosphorylation of AKT (Cheng et al., 2013). AECPS upturned the reduced mRNA expression of PI3K and AKT levels in diabetic rats (Figure 4).

The anti-apoptotic Bcl-2 is a major molecule implicated in apoptosis and related to liver and pancreatic damage (Yao et al., 2017). The alloxan-induced diabetic rats had reduced Bcl-2 expression in the liver and pancreas tissues while treatment with AECPS altered the balance of the anti-apoptotic (Bcl-2) molecules and prevented cell death of the hepatic and pancreatic cells at 6.76 and 13.53 mg/kg. We observed a similar effect for the metformin treatment group. The apoptotic pathway, in this case, requires additional examination to determine whether caspase(s) and cytochrome c are involved as documented in other research experiments (Yao et al., 2017).

As a valuable proliferation marker, proliferating cell nuclear antigen (PCNA) expression performs exclusive functions at the onset of cell propagation by facilitating DNA polymerase. PCNA also performs key functions in the eukaryotic cell cycle and facilitates the formation of antibodies to foreign compounds (Omotuyi et al., 2018). In this study, the mRNA expression of PCNA was up-regulated in hepatocytes and pancreatic tissues of the normal rats and downregulated in the diabetic rats, and AECPS improved PCNA expression in the liver and pancreatic tissues of diabetic rats.

In summary, this study shows that AECPS could provide relief from diabetic indications in rats via regulating PI3K/AKT signaling and fatty acid metabolism. The findings from this study showed that AECPS could promote the breakdown of fatty acids, lower the blood glucose level, improve diabetic indications, and protect the liver and pancreas by avoiding apoptosis. Hence, this study implies that AECPS could be a promising candidate for developing an efficient hypoglycemic remedy to offer respite from diabetic indications.