Manool restores glucose homeostasis by regulating JAK/STAT, mTOR, and antioxidant signaling in a type 2 diabetes rat model

Abstract

Objective: To evaluate the antidiabetic effects of manool in streptozotocin-induced diabetic rats and HepG2 cells.

Methods: Diabetes was induced in Wistar rats using streptozotocin and nicotinamide, and animals were treated with two doses of manool (1 and 2 mg/kg). Biochemical, oxidative stress, apoptotic, and inflammatory parameters were assessed, followed by histopathology of the pancreas. Expression of key marker genes in the liver and pancreas was analyzed via qRT-PCR. Catalase and superoxide dismutase activities, malondialdehyde level, and glucose consumption were examined in vitro.

Results: Manool significantly reduced fasting glucose level, improved insulin levels, and restored glucokinase and Ki67 expression in rats with diabetes. It also enhanced antioxidant defense, upregulated insulin signaling, activated the mTOR pathway, and promoted β-cell regeneration via increased expression of Pdx1, MAFA, Ngn3, and Ins1 in a dose-dependent manner. However, manool suppressed JAK/STAT pathway only at a higher dose of 2 mg/kg. Histopathological study showed near-normal islet architecture in manool-treated diabetic rats.

Conclusions: Manool exerts antidiabetic effects by modulating oxidative stress, inflammation, β-cell regeneration, and insulin sensitivity in diabetic rats. However, further pharmacological and clinical investigations are required before confirming its therapeutic applicability.

Keywords

Manool / Diabetes / Oxidative stress / β-cell regeneration / Inflammation / JAK/STAT / NFE2L2 / mTOR

Conflict of interest statement

The authors declare that there is no conflict of interest.

Funding

The study received no extramural funding.

Data availability statement

The data supporting the findings of this study are available from the corresponding author upon request.

Authors’ contributions

JN, HA, and IM contributed to the conception or design of the work. JN and HA performed data collection. IM, MR, and JN carried out data analysis and interpretation. MR and IM drafted the article. HA, and IM made critical revision of the article. All authors made final approval of the version to be published.

Publisher’s note

The Publisher of the Journal remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

References

[1] Ofonegbu MN, Dibua UM-E, Akaniro IR, Udechukwu CC, Jolayemi KO. Antidiabetic, antimicrobial, and wound healing activities of Dioscorea bulbifera L. methanol extract and its fractions in alloxan-induced diabetic Wistar rats’ model. Pharmacol Res Nat Prod 2025; 8. doi: 10.1016/j.prenap.2025.100321.

[2] Mustafa I, Irfan S, Hussain G, Ijaz MU, Ullah MI, Nisar J, et al. Conyza bonariensis ( L.) impact on carbohydrate metabolism and oxidative stress in a type 2 diabetic rat model. Bioinform Biol Insights 2024;18. doi: 10.1177/1177932224129223

[3] Muzaffar H, Qamar I, Bashir M, Jabeen F, Irfan S, Anwar H. Gymnema sylvestre supplementation restores normoglycemia, corrects dyslipidemia, and transcriptionally modulates pancreatic and hepatic gene expression in alloxan-induced hyperglycemic rats. Metabolites 2023; 13(4). doi: 10.3390/metabo13040516.

[4] Mustafa I, Faisal MN, Hussain G, Muzaffar H, Imran M, Ijaz MU, et al. Efficacy of Euphorbia helioscopia in context to a possible connection between antioxidant and antidiabetic activities: A comparative study of different extracts. BMC Complement Med Ther 2021; 21(1):62. doi: 10.1186/s12906-021-03237-x.

[5] Mustafa I, Anwar H, Irfan S, Muzaffar H, Ijaz MU. Attenuation of carbohydrate metabolism and lipid profile by methanolic extract of Euphorbia helioscopia and improvement of beta cell function in a type 2 diabetic rat model. BMC Complement Med Ther 2022; 22(1):23. doi: 10.1186/s12906-022-03507-2.

[6] Manisha DRB, Begam AM, Chahal KS, Ashok MA. Medicinal plants and traditional uses and modern applications. J Neonatal Surg 2025; 14(3):162-175.

[7] Ravera S, Esposito A, Degan P, Caicci F, Manni L, Liguori A, et al. The diterpene Manool extracted from Salvia tingitana lowers free radical production in retinal rod outer segments by inhibiting the extramitochondrial F1Fo ATP synthase. Cell Biochem Funct 2021; 39(4):528-535.

[8] Aćimović M, Pezo L, Čabarkapa I, Trudić A, Stanković Jeremić J, Varga A, et al. Variation of Salvia officinalis L. essential oil and hydrolate composition and their antimicrobial activity. Processes 2022; 10(8). 10.3390/pr10081608.

[9] Nicolella HD, Fernandes G, Ozelin SD, Rinaldi-Neto F, Ribeiro AB, Furtado RA, et al. Manool, a diterpene from Salvia officinalis, exerts preventive effects on chromosomal damage and preneoplastic lesions. Mutagenesis 2021; 36(2):177-185.

[10] Ben Farhat M, Jordán MJ, Chaouech-Hamada R, Landoulsi A, Sotomayor JA. Variations in essential oil, phenolic compounds, and antioxidant activity of Tunisian cultivated Salvia officinalis L. J Agric Food Chem 2009; 57(21):10349-10356.

[11] Nisar J, Ali Shah SM, Ayaz S, Akram M, Rashid A, Mustafa I, et al. In vitro comparative evaluation of Tamarix gallica extracts for antioxidant and antidiabetic activity. Exp Biol Med 2023; 248(3):253-262.

[12] Bergmeyer HU. Methods of enzymatic analysis. Amsterdam: Elsevier; 2012.

[13] Yu C, Xu Y, Zhao M, Song P, Yu J. New insights into mechanism of ellagic acid alleviating arsenic-induced oxidative stress through MAPK/keap1-Nrf2 signaling pathway response, molecular docking and metabolomics analysis in HepG2 cells. Ecotoxicol Environ Saf 2024;285. doi: 10.1016/j.ecoenv.2024.117029.

[14] Brahmanaidu P, Uddandrao VS, Sasikumar V, Naik RR, Pothani S, Begum MS, et al. Reversal of endothelial dysfunction in aorta of streptozotocin-nicotinamide-induced type-2 diabetic rats by S-Allylcysteine. Mol Cell Biochem 2017; 432:25-32.

[15] Kamboj A, Kumar S, Kumar V. Evaluation of antidiabetic activity of hydroalcoholic extract of Cestrum nocturnum leaves in streptozotocin-induced diabetic rats. Adv Pharmacol Pharm Sci 2013; 2013(1). doi: 10.1155/2013/150401.

[16] Percie du Sert N, Hurst V, Ahluwalia A, Alam S, Avey MT, Baker M, et al. The ARRIVE guidelines 2.0: Updated guidelines for reporting animal research. J Cereb Blood Flow Metab 2020; 40(9):1769-1777.

[17] Lawrence RA, Burk RF. Glutathione peroxidase activity in selenium-deficient rat liver. Biochem Biophys Res Commun 1976; 71(4):952-958.

[18] Jollow D, Mitchell J, Zampaglione NA, Gillette J. Bromobenzene-induced liver necrosis. Protective role of glutathione and evidence for 3,4-bromobenzene oxide as the hepatotoxic metabolite. Pharmacology 1974; 11(3):151-169.

[19] Chernysheva M, Ruchko E, Karimova M, Vorotelyak E, Vasiliev A. Development, regeneration, and physiological expansion of functional β-cells: Cellular sources and regulators. Front Cell Dev Biol 2024; 12. doi: 10.3389/fcell.2024.1424278.

[20] Samimi F, Baazm M, Nadi Z, Dastghaib S, Rezaei M, Jalali-Mashayekhi F. Evaluation of antioxidant effects of Coenzyme Q10 against hyperglycemia-mediated oxidative stress by focusing on Nrf2/Keap1/HO-1 signaling pathway in the liver of diabetic rats. Iran J Med Sci 2024; 49(10):661. doi: 10.30476/ijms.2023.100078.3222.

[21] Shah A, Varma M, Bhandari R. Exploring sulforaphane as neurotherapeutic: Targeting Nrf2-Keap & Nf-Kb pathway crosstalk in ASD. Metab Brain Dis 2024; 39(3):373-385.

[22] Sarmiento-Ortega VE, Moroni-González D, Diaz A, Brambila E, Treviño S. Curcumin treatment ameliorates hepatic insulin resistance induced by sub-chronic oral exposure to cadmium LOAEL dose via NF-κB and Nrf2 pathways. Biol Trace Elem Res 2024; 203:2382-2393.

[23] Camaya I, Donnelly S, O’Brien B. Targeting the PI3K/Akt signalling pathway in pancreatic β‐cells to enhance their survival and function: An emerging therapeutic strategy for type 1 diabetes. J Diabetes 2022; 14(4):247-260.

[24] Athauda D, Evans JR, Mahoney-Sanchez L, Virdi GS, Lopez-Garcia P, Wernick A, et al. GLP 1 receptor agonism ameliorates Parkinson’s disease through modulation of neuronal insulin signalling and glial suppression. bioRxiv 2024. doi: 10.1101/2024.02.28.582460.

[25] Islam MT, Bardaweel SK, Mubarak MS, Koch W, Gaweł-Beben K, Antosiewicz B, et al. Immunomodulatory effects of diterpenes and their derivatives through NLRP3 inflammasome pathway: A review. Front Immunol 2020;11. doi: 10.3389/fimmu.2020.572136.

[26] Gangwar T, Poonia N, Subudhi RN, Arora V. Therapeutic potential and underlying mechanisms of phytoconstituents: Emphasizing on resveratol, curcumin, quercetin, berberine, and hesperidin in ulcerative colitis. Naunyn Schmiedebergs Arch Pharmacol 2025; 398(6):6579-6596.

[27] Su B, Luan ZL, Liu H, Tuomilehto J, Ji X. Janus kinase and signal transducer and activator of transcription inhibitors in type 1 diabetes and immune checkpoint-related diabetes: Current status and future perspectives. Front Immunol 2025;16. doi: 10.3389/fimmu.2025.1571247.

[28] Jang HJ, Lim HJ, Park EJ, Lee SJ, Lee S, Lee SW, et al. STAT3-inhibitory activity of sesquiterpenoids and diterpenoids from Curcuma phaeocaulis. Bioorg Chem 2019; 93. doi: 10.1016/j.bioorg.2019.103267.

[29] Sahoo BM, Banik BK, Sharma S, Singh B. Current insights into therapeutic potential of terpenoids as anticancer agents. Anticancer Agents Med Chem 2025; 25(5):339-356.

[30] Acquaviva R, Malfa GA, Loizzo MR, Xiao J, Bianchi S, Tundis R. Advances on natural abietane, labdane and clerodane diterpenes as anti-cancer agents: Sources and mechanisms of action. Molecules 2022; 27(15). doi: 10.3390/molecules27154791.

[31] Dong L, Chen M, Huang Z, Tan Y, Zhang C, Zhang S, et al. A new labdane diterpenoid from Scoparia dulcis improving pancreatic function against islets cell apoptotic by Bax/Bcl-2/Caspase-3 pathway. J Ethnopharmacol 2024; 322. doi: 10.1016/j.jep.2023.117571.