Obesity and diabetes mellitus (DM) are pressing global health issues, largely driven by excessive sugar consumption and causing damage to different body organs, including the liver, brain, and cardiovascular system [[1], [2], [3], [4], [5], [6]]. Sucrose-induced metabolic disturbances led to hyperglycemia and dyslipidemia, triggering oxidative stress and suppressing nuclear factor erythroid 2–related factor 2 (Nrf2), a transcription factor that regulates enzymatic and non-enzymatic antioxidants [5,[7], [8], [9], [10], [11]]. This suppression activated the toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) pro-inflammatory pathway, promoting the release of cytokines and sustaining inflammation [3,7,12], which in turn activated glycogen synthase kinase-3 beta (GSK3β), further suppressing Nrf2 and promoting tissue apoptosis via increase the expression of apoptosis-related genes and to reduce anti-apoptotic factor, Bcl2 [[13], [14], [15], [16], [17]], resulting in progressive injury to different organs including; the liver, heart, and brain [3,4,7,17]. In the brain, sustained inflammation and GSK3β activation promoted amyloidogenic processing, increasing amyloid-β accumulation and tau dysregulation, thereby contributing to cognitive impairment and Alzheimer-like neurodegeneration; these effects were further amplified by oxidative stress–driven increases in acetylcholinesterase activity [5,[18], [19], [20], [21]]. Moreover, activation of GSK3β disrupted the Wnt/β-catenin signaling pathway, which is essential for neuronal survival and synaptic maintenance, and reduced brain-derived neurotrophic factor (BDNF), a key regulator of synaptic plasticity, learning, and memory, thereby exacerbating cognitive dysfunction [19,22,23]. In addition, sustained neuroinflammation and apoptosis in brain cells disrupted neuronal integrity and survival, leading to depletion of monoamine neurotransmitters and thereby exacerbating neurotoxicity and functional neural impairment [24].

Given the health risks associated with long-term consumption of caloric sweeteners, non-caloric alternatives have gained popularity for providing sweetness without added calories [25]; however, the long-term effects of their habitual intake on body weight regulation, glycemic control, liver function, cardiovascular health, and neurological outcomes remain insufficiently understood.

Non-caloric sweeteners are classified as artificial, such as aspartame, and natural, like stevia [26,27]. Aspartame, 180–200 times sweeter than sucrose, is widely used in foods and beverages [28]. Aspartame is metabolized into phenylalanine, which disrupts neurotransmitter synthesis (dopamine, norepinephrine, serotonin), impairing cognition and mood; aspartic acid, which overstimulates NMDA receptors, promoting excitotoxicity, tau pathology, and amyloid-β accumulation; and methanol, which generates oxidative stress, damaging neurons and other tissues [[29], [30], [31]]. Additionally, aspartame itself acts as a chemical stressor, inducing inflammation, apoptosis, and tissue injury in the brain, heart, and liver [28,32,33]. These drawbacks associated with aspartame had made its consumption a subject of debate, leading consumers to explore natural sweeteners, like stevia, as a hopeful alternative to synthetic options.

Stevia, a sweet glycoside from Stevia rebaudiana Bertoni (Asteraceae), is 200–300 times sweeter than sugar. Its sweetness is more pronounced and longer lasting than sucrose or aspartame, making it a popular sugar substitute worldwide [34]. However, studies report that stevia may induce hyperglycemia, insulin resistance, liver enzyme disruption, elevated urea and creatinine, oxidative stress, inflammation, and neurodegeneration, partly via increased COX-2 expression in the brain [6,35,36]. He chronic effects of non-caloric sweeteners on body weight, glycemic control, and liver, heart, and brain health, as well as the underlying molecular mechanisms, remain underexplored. Comparative histological and biochemical analyses are essential to identify safer sweetener alternatives and develop protective strategies for these organs.

Astaxanthin is a lipid-soluble carotenoid found in algae, salmon, shrimp, and crustaceans, widely used in aquaculture and as a valuable industrial pigment. ASTX exhibits potent antioxidant, anti-inflammatory, immunomodulatory, and anti-fibrotic effects by regulating redox and inflammatory pathways, including Nrf2 and NF-κB [10,[37], [38], [39]]. These features highlight ASTX’s broad therapeutic potential, with studies demonstrating its protective effects against cardiotoxicity across multiple models and its ability to support liver health [[40], [41], [42], [43], [44]]. Importantly, ASTX can cross the blood-brain barrier, offering protection against neurological disorders [45,46]. Its neuroprotective effects involve modulation of brain-derived neurotrophic factor (BDNF), prevent Aβ accumulation, promotion of axonal regeneration, suppression of neuroinflammation, and restoration of oxidative balance [45,[47], [48], [49]]. Given its potential antioxidant and anti-inflammatory properties, we chose ASTX to counteract the effects of the studied sweeteners on the liver, heart, and brain.

This study aimed to evaluate and compare the chronic effects of artificial (aspartame), natural (stevia), and caloric (sucrose) sweeteners on the liver, heart, and brain in rats. Heart and brain were selected for their central roles in metabolism, circulation, and cognition, making them particularly susceptible to oxidative stress, inflammation, and apoptosis induced by various stressors [[50], [51], [52], [53], [54]], including prolonged sweetener intake. Detailed analyses of the heart and brain were conducted because their proper function relies heavily on redox balance and inflammatory regulation, allowing focused assessment of diet-induced cardiotoxicity and neurodegeneration. The study examined key molecular pathways, including oxidative stress, Nrf2/HO-1 antioxidant defense, inflammatory signaling (TLR4/NLRP3 inflammasome and cytokines), apoptosis, tissue injury biomarkers, Wnt-3a/GSK-3β/β-catenin signaling, and amyloid-β synthesis. Additionally, the potential protective effects of ASTX were investigated, focusing on its systemic antioxidant, anti-inflammatory, and cytoprotective properties. This study compares the long-term effects of caloric and non-caloric sweeteners on the liver, heart, and brain, explores the molecular mechanisms of their toxicity, identifies safer alternatives, and assesses astaxanthin’s protective effects, providing insights to guide healthier dietary choices and prevent organ damage.

The study hypothesizes that chronic consumption of sweeteners; whether caloric (sucrose) or non-caloric (aspartame and stevia), induce toxicity in the liver, heart, and brain through interconnected mechanisms involving oxidative stress, impaired antioxidant defense, persistent inflammation, disrupted survival signaling, and activation of apoptotic and degenerative pathways. These organs were selected for their central roles in metabolism, circulation, and cognition, making them particularly susceptible to oxidative stress, inflammation, and apoptosis induced by prolonged sweetener intake. We further propose that ASTX exerts systemic protection by restoring redox balance, suppressing inflammatory signaling, preserving cellular integrity, and maintaining molecular and functional homeostasis across both the studied organs.