---
title: "Metformin reduces metabolic and oxidative changes in a high-sucrose Drosophila model"
id: "plos-one-13-metformin-modulates-survival-oxidative-stress-and-gene-expression-in-a-high"
canonical_url: "https://medichelpline.com/clinical-feed/plos-one-13-metformin-modulates-survival-oxidative-stress-and-gene-expression-in-a-high"
content_type: "clinical_feed_article"
specialty: "Pharmacology"
source_name: "PLOS ONE (Medicine)"
source_url: "https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0359638"
published_at: "2026-10-01T14:00:00.000Z"
evidence_level: "Journal Feed"
license: "CC-BY-NC-4.0 / Informational Use"
---
# Metformin reduces metabolic and oxidative changes in a high-sucrose Drosophila model
## Provenance & Clinical Metadata
- **Canonical URL:** https://medichelpline.com/clinical-feed/plos-one-13-metformin-modulates-survival-oxidative-stress-and-gene-expression-in-a-high
- **Specialty:** [Pharmacology](https://medichelpline.com/clinical-feed/pharmacology.md)
- **Primary Source:** PLOS ONE (Medicine)
- **Source URL:** [Original Journal Publication](https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0359638)
- **Published At:** 2026-10-01T14:00:00.000Z
- **Evidence Rating:** Journal Feed
## Executive GIST (TL;DR)
- High-sucrose diets (5% and 15% sucrose) in Drosophila melanogaster produced multiple diabetes-like phenotypes: reduced pupation and survival, impaired locomotor performance, elevated trehalose, decreased antioxidant enzyme activities, and downregulation of stress- and antioxidant-related genes. - The study used Oregon R wild-type flies reared on defined diets for 10 days with independent cohorts for each endpoint to avoid confounding from mortality or destructive assays. - Experimental groups included normal control (0% sucrose), 5% sucrose, 15% sucrose, and the two corresponding sucrose diets supplemented with **metformin** (5 mM and 15 mM). - Endpoints measured after 10 days comprised pupation rate, adult survival, negative geotaxis (locomotor) performance, whole-fly **trehalose** quantification, antioxidant enzyme activities (SOD and **GST**), and expression of stress-related genes (Mn-SOD, Cu/Zn-SOD, MTH, CAT, Hsp40, Hsp70), with RpS20 as the reference gene. - High-sucrose treatment increased circulating trehalose and induced oxidative stress, with reduced SOD and GST activities and suppression of stress-responsive gene expression relative to the normal diet. - **Metformin** treatment partially attenuated several sucrose-induced alterations within the corresponding sucrose groups, improving pupation, survival, locomotor performance, metabolic parameters, antioxidant enzyme activity, and gene expression compared with sucrose-only groups. - The authors conclude that Drosophila melanogaster is a tractable model for diet-induced metabolic dysfunction and for evaluating pharmacological interventions such as **metformin**, which showed partial protective effects against sucrose-driven metabolic and oxidative disturbances.
## Clinical Analysis & Structured Key Points
Metformin modulates survival, oxidative stress, and gene expression in a high-sucrose Drosophila diabetes model | PLOS One Browse Subject Areas ? Click through the PLOS taxonomy to find articles in your field. For more information about PLOS Subject Areas, click here . Article Authors Metrics Comments Media Coverage Reader Comments Figures Figures Abstract Background Excess dietary sugar is a major contributor to metabolic disorders, including type 2 diabetes mellitus (T2DM). This study investigates the physiological, biochemical, behavioral, and molecular effects of high-sucrose diets in Drosophila melanogaster and evaluates the modulatory effects of metformin under these conditions. Methods Flies were reared on normal and high-sucrose diets (5% and 15%), with or without metformin treatment (5 mM and 15 mM). Pupation, survival, locomotor activity (negative geotaxis), trehalose levels, antioxidant enzyme activities (SOD, GST), and expression of stress-related genes (Mn-SOD, Cu/Zn-SOD, MTH, CAT, Hsp40, Hsp70) were assessed after 10 days of treatment. Gene expression levels were quantified relative to the normal control group using RpS20 as the housekeeping reference. Results High-sucrose diets significantly reduced pupation and survival rates, impaired locomotor performance, increased trehalose levels, and decreased antioxidant enzyme activities. These diets were also associated with downregulation of stress- and antioxidant-related genes. Metformin treatment partially attenuated several of these alterations relative to the corresponding sucrose-treated groups, including improvements in pupation, survival, locomotor performance, metabolic parameters, antioxidant enzyme activity, and gene expression. Conclusion High-sucrose diets induced metabolic disturbances in Drosophila melanogaster , including impaired developmental progression and survival, functional locomotor impairment, carbohydrate imbalance, oxidative stress, and suppression of stress-related gene expression. Metformin partially attenuated several of these changes within the corresponding sucrose-treatment groups. These findings support the utility of Drosophila melanogaster as a tractable model for studying diet-induced metabolic dysfunction and evaluating pharmacological interventions. Citation: Lotfy M, Al Sawai F, Alyammahi D, Kundu B (2026) Metformin modulates survival, oxidative stress, and gene expression in a high-sucrose Drosophila diabetes model. PLoS One 21(10): e0359638. https://doi.org/10.1371/journal.pone.0359638 Editor: Efthimios M. C. Skoulakis, BSRC Alexander Fleming: Biomedical Sciences Research Center Alexander Fleming, GREECE Received: August 1, 2025; Accepted: September 16, 2026; Published: October 1, 2026 Copyright: © 2026 Lotfy et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability: All relevant data are within the manuscript and its Supporting information files. Funding: I extend my sincere gratitude to the Research Office at UAE University and the Biology Department for their invaluable support, as well as to all individuals who contributed to the successful completion of this study. The funders had no involvement in the study design, data collection and analysis, decision to publish, or manuscript preparation. Competing interests: Conflict of Interest The authors state that their research was carried out without any commercial or financial affiliations that could be seen as potential conflicts of interest. The authors have declared that no competing interests exist. Introduction Diabetes mellitus (DM) is a chronic metabolic disorder marked by persistent hyperglycemia due to insufficient insulin secretion, impaired insulin action, or both. Under normal conditions, insulin-a hormone produced by the pancreas-facilitates the uptake of glucose from the bloodstream into cells for energy. In diabetes, this process is disrupted, leading to elevated blood glucose levels [ 1 ]. If left uncontrolled, chronic hyperglycemia can lead to severe complications affecting the cardiovascular system, kidneys, retina, and nervous system, significantly impacting quality of life and increasing the risk of premature mortality. The global prevalence of diabetes is rapidly increasing, with more than 537 million adults affected in 2021 and projections exceeding 592 million by 2035 [ 2 ]. While genetic predisposition contributes to disease risk, lifestyle factors such as physical inactivity and diets high in fat and sugar play a significant role in its onset and progression [ 3 ]. Type 2 diabetes is the most common form and is closely associated with obesity and insulin resistance. Excessive intake of dietary sugars has been linked to metabolic dysfunction, making dietary habits a major modifiable risk factor [ 4 ]. Alarmingly, type 2 diabetes is increasingly diagnosed in younger individuals, often progressing silently in its early stages [ 5 ]. Complications of diabetes include macrovascular issues like cardiovascular disease and stroke, as well as microvascular complications such as nephropathy, retinopathy, and neuropathy [ 6 ]. A central mechanism in the development of these complications is oxidative stress induced by prolonged hyperglycemia. This stress arises from pathways like glucose auto-oxidation, protein glycation, and the formation of advanced glycation end products (AGEs), which collectively generate reactive oxygen species (ROS) that overwhelm cellular antioxidant defences and cause tissue damage [ 7 ]. In recent years, Drosophila melanogaster has gained prominence as a model organism for studying metabolic disorders. The fruit fly possesses conserved insulin signalling pathways, a short life cycle, and is highly amenable to genetic manipulation, making it an effective system for exploring the molecular basis of diabetes and testing potential therapeutic interventions [ 8 ]. D. melanogaster has emerged as a powerful model for studying diabetes mellitus, owing to its highly conserved insulin/insulin-like growth factor (insulin/IGF) signalling pathway, genetic tractability, and metabolic parallels with humans [ 9 , 10 ]. The fly model replicates many core features of type 2 diabetes, including hyperglycemia, insulin resistance, and lipid accumulation, particularly when exposed to high-sugar diets [ 11 , 12 ]. High-sucrose feeding in Drosophila elevates circulating glucose and insulin-like peptides (ILPs), initially enhancing insulin signalling. However, prolonged exposure induces insulin resistance-mirroring early stages of type 2 diabetes in humans [ 13 ]. This resistance is especially evident in the fat body, the fly’s functional equivalent of the liver and adipose tissue, where impaired insulin sensitivity disrupts glucose uptake and storage [ 14 ]. High-sucrose feeding in Drosophila has been consistently shown to disrupt systemic carbohydrate homeostasis through dysregulation of Drosophila insulin-like peptides (DILPs), particularly DILP2, DILP3, and DILP5. In flies, insulin signaling is mediated by DILPs that activate the insulin receptor (InR), triggering the downstream PI3K-AKT cascade and modulating effectors such as dFOXO and d4EBP. This signaling axis is functionally analogous to mammalian insulin and insulin-like growth factor (IGF) pathways. Genetic ablation of insulin-producing cells or disruption of InR signaling results in elevated circulating sugars, including trehalose, confirming the tight regulatory relationship between DILP signaling and hemolymph carbohydrate levels [ 15 , 16 ]. Chronic high-sucrose exposure impairs insulin pathway responsiveness, leading to reduced AKT activation, altered dFOXO activity, and sustained trehalose accumulation-hallmarks of insulin resistance in this model [ 13 , 17 ]. Thus, the conserved DILP-InR-AKT-dFOXO axis provides a mechanistic framework through which diet-induced metabolic dysfunction and insulin/IGF-like signaling disruption can be investigated in Drosophila and supports the use of trehalose quantification as a validated functional surrogate of insulin pathway impairment [ 11 ] In addition to metabolic dysfunction, high-sugar diets in flies result in increased body fat, delayed development, reduced fertility, and shortened lifespan-further aligning the model with human diabetic pathophysiology [ 11 , 18 ]. These outcomes make sucrose-rich diets a reliable and reproducible method for inducing diabetic-like phenotypes in both longitudinal and interventional studies. Compared to vertebrate models, Drosophila offers several advantages, including a short generation time, low maintenance costs, and advanced genetic tools such as the GAL4/UAS and RNAi systems. These enable precise manipulation of gene expression to study gene-diet interactions, oxidative stress, mitochondrial function, and the regulation of metabolic genes during diabetes progression [ 19 ]. The simplified insulin signalling cascade in flies also reduces redundancy, facilitating clearer mechanistic insights [ 20 ]. Despite its simplicity, Drosophila complements mammalian models in diabetes research. Flies fed high-sugar diets reliably exhibit hallmarks of human metabolic disorders, making them a valuable system for screening antidiabetic compounds and investigating the molecular basis of diet-induced insulin resistance and metabolic stress. Furthermore, the model has proven effective for exploring how dietary factors influence redox balance, stress responses, and metabolic gene expression [ 11 , 12 ]. Metformin, a biguanide compound, is a widely prescribed first-line treatment for type 2 diabetes mellitus (T2DM). Its primary mechanism involves lowering hepatic glucose production and enhancing insulin sensitivity in peripheral tissues [ 21 ]. At the cellular level, metformin inhibits mitochondrial complex I, leading to an increased AMP/ATP ratio that activates AMP-activated protein kinase (AMPK)-a central energy sensor that regulates glucose and lipid metabolism [ 22 , 23 ]. Activation of AMPK promotes glucose uptake, particularly through GLUT4 translocation, and suppresses the mechanistic target of rapamycin (mTOR) pathway, which is involved in protein synthesis, cell growth, and autophagy [ 24 , 25 ]. Through these actions, metformin improves insulin signalling, enhances energy homeostasis, and helps cells adapt to metabolic stress. Furthermore, under conditions of impaired insulin signalling, AMPK activation upregulates stress-responsive genes, contributing to improved cellular resilience [ 26 , 27 ]. In addition to its metabolic effects, metformin exhibits significant antioxidant properties. It enhances the activity and expression of key antioxidant enzymes such as superoxide dismutase (SOD1), catalase (CAT), and peroxiredoxin 6 (Prdx6), while reducing intracellular levels of reactive oxygen species (ROS) [ 28 , 29 ]. These effects help counter oxidative stress-a major contributor to diabetic complications. In D. melanogaster , metformin has been shown to alleviate oxidative stress and improve stress resistance, particularly in models with compromised antioxidant defences, such as SOD1-deficient mutants [ 30 ]. These findings support the utility of Drosophila in exploring the dual metabolic and redox-modulatory effects of metformin, and in evaluating its potential for therapeutic interventions targeting diabetes-related oxidative damage. This study investigates the modulatory effects of metformin in a D. melanogaster model of diet-induced metabolic dysfunction caused by high-sucrose feeding. By examining survival and pupation rates, locomotor performance, trehalose levels, antioxidant enzyme activities (superoxide dismutase [SOD] and glutathione S-transferase [GST]), and the expression of key stress-related genes (manganese superoxide dismutase [Mn-SOD], copper/zinc superoxide dismutase [Cu/Zn-SOD], methuselah [MTH], catalase [CAT], heat shock protein 40 [Hsp40], and heat shock protein 70 [Hsp70]), the study evaluates whether metformin attenuates metabolic and oxidative stress under each predefined sucrose condition. The findings provide an integrated assessment of physiological, biochemical, behavioral, and molecular responses. The findings will provide insight into the mechanisms by which metformin improves metabolic health and stress resilience, highlighting the utility of Drosophila as an effective model for studying antidiabetic interventions. Materials and methods D . melanogaster strain and rearing Wild-type Drosophila melanogaster (Oregon R strain) was originally obtained from Carolina Biological Supply (Burlington, NC, USA) and is maintained in the Genetics Laboratory, Biology Department, United Arab Emirates University. Flies were reared on instant Drosophila medium (Formula 4–24, Carolina Biological Supply) supplemented with dry yeast under controlled environmental conditions at 23 ± 1°C with a 12:12 h light/dark cycle. Adult flies were transferred to fresh food vials every four days to maintain optimal nutrition and prevent overcrowding. These rearing conditions were maintained throughout all experiments. Experimental design and grouping To ensure sufficient biological material for all endpoints and to avoid confounding effects related to mortality, behavioral testing, and destructive downstream assays, independent parallel cohorts were established for survival assessment, pupation analysis, locomotor performance, biochemical assays, and gene expression analysis. Thus, each endpoint was evaluated using a dedicated experimental cohort rather than relying on the same surviving flies for all subsequent measurements. Flies were randomly assigned to five experimental groups: (1) Normal control (NC): standard diet containing 0% sucrose (2) 5% sucrose (S5): diet containing 5% sucrose (3) 15% sucrose (S15): diet containing 15% sucrose (4) 5% sucrose + 5 mM metformin (SM5): diet containing 5% sucrose supplemented with 5 mM metformin (5) 15% sucrose + 15 mM metformin (SM15): diet containing 15% sucrose supplemented with 15 mM metformin For each adult endpoint, each experimental condition consisted of three independent biological replicate vials, with 20 flies per vial (10 males and 10 virgin females). All treatment groups were established simultaneously within each experimental run and were maintained under identical environmental conditions. The complete experiment was independently repeated on three separate occasions using newly established fly cohorts. All treatments were administered for 10 days. Sucrose diets were prepared from analytical-grade sucrose dissolved in distilled water and diluted to the required concentrations before incorporation into the food medium. Metformin hydrochloride (Sigma-Aldrich, USA) was prepared as a 100 mM stock solution and added to the food to achieve final concentrations of 5 mM or 15 mM as indicated. Food vials were freshly prepared and replaced every 48 hours during the treatment period. Experimental conditions and dietary supplementation were adapted from previously established methods in D. melanogaster [ 31 – 34 ] by incorporating the two predefined sucrose conditions and their corresponding metformin treatments and by using independent cohorts for each endpoint to avoid confounding from mortality, repeated behavioral testing, or destructive sampling. Pupation rate assessment Pupation rate was assessed using a separate synchronized developmental cohort. For each treatment group, adult flies were transferred to freshly prepared food media and allowed to oviposit during the same defined collection period to generate synchronized embryos. An equal number of embryos was placed in each of three independent biological replicate vials per group. Vials were maintained under standard laboratory conditions (23 ± 1°C, 12:12 h light/dark cycle, 60% humidity). The larvae remained in the same developmental vials throughout the assay and were not transferred during development or subjected to the 48-hour adult food-replacement schedule. At the end of the observation period, the total number of visible pupae in each vial was recorded, and pupation rate was calculated as: pupation rate (%) = (number of pupae/initial number of embryos) × 100. The mean was calculated from the three independent replicate vials. The procedure was adapted from Sakaguchi and Suzuki [ 35 ] by incorporating the experimental sucrose and metformin conditions directly into the developmental medium and by using synchronized embryo collections to minimize developmental variation among groups. The control group represents the observed biological baseline rather than a theoretical 100% developmental success rate. Survival rate assessment A dedicated adult cohort was used for survival analysis. Flies were maintained on their assigned experimental diets for 10 days under controlled conditions. Mortality was recorded every 48 hours at the time of food replacement. Flies were considered dead when they failed to respond to gentle stimulation with a fine paintbrush. Food was replaced every 48 hours, but flies remained within their assigned replicate cohorts and were not redistributed among treatment vials. On day 10, survival rate was calculated as the number of live flies divided by the initial number of flies per vial, multiplied by 100 [ 36 , 37 ]. Negative geotaxis and locomotor performance Locomotor performance was evaluated using the negative geotaxis assay in a separate adult cohort on Day 10. Each assay used a mixed-sex group of 20 flies (10 males and 10 virgin females), preserving the same sex ratio across all treatment groups. Flies were placed in vertical glass tubes and allowed to acclimate for 30 min. All assays were conducted during the light phase under uniform ambient laboratory illumination, with identical lighting conditions maintained across treatment groups and biological replicates. They were then gently tapped to the bottom, and climbing success was quantified as the percentage of flies crossing the 8-cm mark within 10 s. Each biological replicate was tested three times, with sufficient recovery time between trials, and the mean of the three trials was used for analysis. Climbing behavior was recorded for 20 s, and video playback was paused at the 10-s time point. The assay was adapted from previous studies [ 36 , 38 ] by applying a standardized 8-cm threshold and 10-s endpoint to mixed-sex cohorts after chronic dietary treatment, thereby allowing consistent comparison of locomotor performance among groups. Biochemical assays Sample preparation. Biochemical markers were assessed in a dedicated adult cohort after 10 days of dietary treatment. For each group, flies were anesthetized using FlyNap and homogenized in 100 µL of cold phosphate-buffered saline (PBS, pH 7.4) using a motorized pestle. Homogenates were centrifuged at 1000 × g for 5 min at 4°C, and the supernatants were collected and maintained on ice until analysis. Trehalose quantification. Trehalose, the primary circulating sugar in D. melanogaster , was quantified as an indicator of carbohydrate metabolism and hyperglycemia-like metabolic disturbance [ 13 , 39 ]. After centrifugation, each whole-fly homogenate was divided into two aliquots. In the first aliquot, free glucose was measured directly using a glucose oxidase-based colorimetric assay (Pointe Scientific, USA), and absorbance was read at 500 nm according to the manufacturer’s protocol. The second aliquot was incubated with trehalase to hydrolyze trehalose into glucose, after which total glucose concentration (free glucose plus trehalose-derived glucose) was measured using the same assay. Trehalose-derived glucose was calculated by subtracting the initial free-glucose value from total glucose measured after trehalase digestion, and final values were determined using a glucose standard curve.
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