Comparative evaluation of the antidiabetic potential of three varieties of Ipomoea batatas L

Abstract

Sweet potato (Ipomoea batatas L.) is a nutrient-dense tuber often used in traditional diabetic treatment. This research compares the antidiabetic potential of three sweet potato varieties: orange-fleshed (OFSP), purple-peel white-fleshed (PPWSP), and white-peel white-fleshed (WPWSP), utilising in vitro and in vivo techniques. Sweet potatoes (OFSP, PPWSP, and WPWSP) boiled at 100°C for 20 minutes were incorporated into formulated diets and administered to streptozotocin-induced diabetic rats for 14 days. Aqueous extracts of the diets were tested in vitro for antioxidants and phytochemicals. Glycaemic control parameters, lipid profiles, oxidative stress indicators, and pancreatic histology were investigated. Gene expression analysis was performed on critical diabetes-related pathways. OFSP showed significant strong anti-diabetic benefits, including better glycemic control, weight maintenance, lower HOMA-IR scores, and lowered α-amylase and α-glucosidase activity. OFSP-fed rats had higher insulin, glycogen, and hexokinase activity than those given PPWSP and WPWSP. OFSP decreased mRNA expression of DPP-4 while increasing GLP-1 expression. OFSP also improved lipid profiles, increasing HDLc while decreasing LDLc and triglycerides more than other varieties. Histopathological examination revealed restorative effects in pancreatic beta cells. OFSP demonstrated more pronounced antidiabetic effects compared to PPWSP and WPWSP, particularly in terms of glycemic control, insulin regulation, and lipid profile improvement. These findings suggest that OFSP may offer significant potential for diabetes management. However, further clinical studies are needed to validate these results and explore the practical dietary applications of OFSP in diabetes control.

Keywords: Antioxidants; Diabetes; Dyslipidemia; Streptozotocin; Sweet potato.

Fig. 1

Purple-peel-white-fleshed sweet potato (PPWSP), orange- fleshed sweet potato (OFSP), and white-peel-white-fleshed sweet potato (WPWSP).

Fig. 2

Effect of different varieties of sweet potato-based diet on blood glucose level (mg/ml) of normal and streptozotocin-induced diabetic rats. Data are expressed as mean ± SD (n = 8).

Fig. 3

Effect of different varieties of sweet potato-based diet on (a) α-amylase (b) α-glucosidase activities of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, values with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 4

Effect of different varieties of sweet potato-based diet on (a) liver glycogen (b) serum insulin contents of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, values with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 5

Effect of different varieties of sweet potato-based diet on (a) Homeostasis model assessment-insulin resistance (HOMA-IR) (b) Homeostasis model assessment-β (HOMA- β) scores of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, values with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 6

Effect of different varieties of sweet potato-based diet on carbohydrate metabolizing enzymes (a) Hexokinase (b) Glucose-6-phosphatase (c) Fructose-1,6-bisphosphatase activities of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, values with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 7

Effect of different varieties of sweet potato-based diet on dipeptidyl peptidase IV (DPP-4) mRNA expression of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, values with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 8

Effect of different varieties of sweet potato-based diet on glucagon-like peptide 1 (GLP-1) mRNA expression of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, values with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 9

Effect of different varieties of sweet potato-based diet on protein tyrosine phosphatase 1B (PTP-1B) mRNA expression of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, values with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 10

Effect of different varieties of sweet potato-based diet on (a) total thiol (TSH) (b) non protein thiol (NPSH)(c) Total antioxidant capacity (TAC) (d) serum total protein levels of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, ^a-evalues with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 11

Effect of different varieties of sweet potato-based diet on (a) malondialdehyde (MDA) level (b) reactive oxygen species (ROS) level(c) superoxide dismutase (SOD) activity (d) catalase activity of normal and streptozotocin-induced diabetic rats. Each value is a mean of 8 determinations ± SD. Values are statistically different at ϕp < .05 versus CTRL, * *p < .05 versus STZ, ^a-evalues with different superscript letters are significantly different (p < .05), ns = not statistically different.

Fig. 12

Effect of different varieties of sweet potato-based diet on the structure of pancreatic islets of normal and streptozotocin-induced diabetic rats.Islet cells (yellow arrowhead), capillaries (black arrowhead), acinar cells (white arrowhead), blood vessels (star), long black arrow (Islet diameter). The magnification of parts of all a’s are × 800 and parts of all b’s are × 80. (Scale bar = 51 μm), H&E staining.(C and D) Graphical representation of the number of pancreatic islets mean diameter and pancreatic islets analyzed with the aid of ImageJ software (1.48 V). [1 = healthy rats (Non-diabetic rats) fed corn starch-based diet (basal diet), designated as control (CTRL), 2 = healthy rats (Non-diabetic rats) fed corn starch-based diet but given 1 ml of 0.1 mol L⁻¹ citrate buffer i.p once, designated as vehicle control (VEH CTRL), 3 = healthy rats (Non-diabetic rats) fed OFSP-based diet, designated as (OFSP), 4 = healthy rats (Non-diabetic rats) fed PPWSP-based diet rats, designated as (PPWSP), 5 = healthy rats (Non-diabetic rats) fed WPWSP-based diet, designated as (WPWSP), 6 = Diabetic control rats fed basal diet and were designated as STZ-induced untreated (STZ), 7 = diabetic rats fed OFSP-based diet, designated as (STZ + OFSP), 8 = diabetic rats fed PPWSP-based diet, designated as (STZ + PPWSP), 9 = diabetic rats fed WPWSP-based diet, designated as (STZ + WPWSP), 10 = diabetic rats fed basal diet and administered ACA orally (25 mg/kg body weight), designated as (STZ + ACA)].