Abstract Proper regulation of blood-lipid levels is crucial for preventing metabolic and cardiovascular disorders. The seeds of Citrullus colocynthis (CCO), traditionally used in Mediterranean folk medicine for their antidiabetic properties, are rich in unsaturated fatty acids and may correct dyslipidemia associated with diabetes. In this study, we investigated the metabolic effects of diets enriched with CCO, sunflower oil (SO), or olive oil (OO) in stz-induced diabetic rats (n = 5 per group) over two months. While all groups developed hyperglycemia after STZ injection, rats fed the CCO-enriched diet displayed significantly lower blood glucose levels than those fed SO or OO. Additionally, the CCO diet led to marked decreases in hepatic and plasma lipid parameters associated with atherogenesis, and improved fatty-acid profiles. These results suggest that C. colocynthis seed oil has beneficial regulatory effects on both glycemic and lipid metabolism, thereby offering potential as a dietary intervention to mitigate dyslipidemia and cardiovascular risk in diabetes.

Keywords: Diabetes, Rats, Diet, Citrullus colocynthis oil, Fatty acids, Lipid profile

Citation:  Daoudi, C-S., Zoubida, S-M., Amel, D., Sidi-Mohammed, Y., Tarik, C., Radjaa-Kawthar, M., Hamadi-Abderrahmane, L., and Meriem, C-S. 2026. Impact of Citrullus colocynthis seed oil on the plasma fatty acid profile in streptozotocin-induced diabetic rats. Natural and Life Sciences Communications. 25(3): e2026049.

Graphical Abstract:

INTRODUCTION

The incidence of type 2 diabetes is continually rising worldwide (Pinto et al., 2020; Ghosal and Sinha 2023). Several factors contribute to its onset, including age, family history of diabetes, overweight, and a sedentary lifestyle (Cao et al., 2023). Furthermore, some studies implicate diets high in fat as an additional risk factor. Approximately 80% of individuals with type 2 diabetes are overweight or obese, which underscores obesity as a major determinant in the development of this serious and often insidious disease. However, no one is entirely immune to diabetes, even when adhering to healthy lifestyle habits (Shubrook et al., 2022).

A varied and balanced diet plays a fundamental role in diabetes prevention. Dietary recommendations emphasize the consumption of foods low in fat, salt, and added sugars, while promoting a higher intake of fiber-rich foods. Following guidelines such as Canada’s Food Guide ensures adequate energy needs are met. Moreover, individuals with diabetes require personalized meal planning, as the distribution of macronutrients is essential for optimal glycemic control (Batulla et al., 2000).

An increased intake of monounsaturated (MUFA) fatty acids has been suggested to improve glycemic control and lipoprotein profiles in diabetic patients (Rojo et al., 2006). Epidemiological studies in both humans and rats indicate that high-fat diets (HFD) promote obesity. However, recent research highlights that beyond the overall quantity of fat, the type of dietary fatty acids critically influences insulin sensitivity. Saturated fatty acids (SFA) increase plasma cholesterol, triglycerides, and free fatty acids (FFA), while reducing insulin sensitivity. By contrast, polyunsaturated fatty acids (PUFA) enhance insulin sensitivity, lower triglyceride and LDL-cholesterol levels, and raise HDL-cholesterol concentrations (Okami et al., 2021). Numerous metabolic studies have demonstrated that replacing saturated fats with vegetable oils rich in linoleic acid significantly lowers LDL cholesterol and other atherogenic lipids. A recent meta analysis of 40 randomized controlled trials confirmed that dietary linoleic acid substantially reduces LDL C compared with other fats (Wang et al., 2023). The Nurses’ Health Study notably found that higher intakes of n-6 polyunsaturated fatty acids were significantly associated with a lower incidence of type 2 diabetes (Conlin et al., 2017).

Non-insulin-dependent diabetes is primarily characterized by decreased insulin sensitivity, leading to insulin resistance in target tissues such as the liver, skeletal muscle, and adipose tissue (Boden and Shulman, 2002; McGarry, 2002). Furthermore, impaired glucose-induced insulin secretion, correlated with reduced pancreatic β-cell mass, ultimately results in chronic hyperglycemia (Ferrannini et al., 2005).

Given the limitations and side effects of current antidiabetic drugs, there has been increasing interest in traditional medicinal plants with potential hypoglycemic properties, such as Citrullus colocynthis (colocynth).

Citrullus colocynthis (L.) Schrad. (bitter apple or colocynth) is a perennial vine of the gourd f Cucurbitaceae family native to arid and semi-arid regions of North Africa and the Middle East. It bears trailing stems with deeply lobed leaves and yellow monoecious blossoms that give rise to spherical fruits characterized by a strongly bitter mesocarp and seeds rich in fixed oils. Seed of Citrullus colocybthis rich in cucurbitacins, flavonoids, phenolic compounds, Fixed oils with high unsaturated-fatty-acid content. Traditionally used as antidiabetic and anti-inflammatory. Extracts from C. colocynthis seeds and fruit show hypoglycemic, lipid-modulating, antioxidant and antimicrobial effects in experiments. But too high doses can cause strong gastrointestinal and liver toxicity. (Benariba et al., 2009; Fallah-Huseini et al., 2023; Rao and Amrita, 2023). This profile identifies the plant as a potentially valuable but safety-dependent candidate for continued pharmacological studies in the field of metabolic disorders Among various vegetable oils, this study used C. colocynthis seed oil in an isocaloric diet administered to male Wistar rats rendered diabetic by streptozotocin (STZ). This plant is recognized for its many therapeutic properties, particularly its antidiabetic effects (Benariba et al., 2009). For the first time, this study evaluates the effect of C. colocynthis oil (CO) compared with sunflower (SO) and olive oils (OO) on carbohydrate and lipid metabolism as well as on hepatic function. Accordingly, glucose, insulin, and lipid parameters were measured in both diabetic and non-diabetic rats.

MATERIALS AND METHODS

Plant identification

The plant material was identified as Citrullus colocynthis (L.) Schrad. (Cucurbitaceae). Specimens were collected in Naâma Province, western Algeria, on the High Plateaus (33°32′37″ N, 0°15′22″ W; ca. 1 133 m a.s.l.). The species identification was confirmed by Gérard Bélsir, and a voucher specimen (Id: ph005_12; code Gdb/ANSA) has been deposited in the Herbarium of the National Higher School of Agronomy (ENSA), El Harrach, Algeria.

Seed collection and oil extraction

The fruits were sliced in half, and the seeds were manually removed. Only mature black seeds were selected, and the pulp was thoroughly discarded. The seeds were then ground into a fine powder in preparation for oil extraction.

 The lipid fraction was extracted using petroleum ether (40–60 °C) with a Soxhlet apparatus for 2 hours. The olive and sunflower oils used in this study were obtained from commercially available sources, and represent some of the most commonly consumed edible oils.

Fatty acids analysis of dietary oils (SO/CO/OO)

Fatty acids of dietary oils (SO/CO/OO), were identified by gas chromatography (GC) (Varian CP-3380) using a capillary column (Alltech EC-Wax, 30 m × 0.53 mm × 1.2 μm film thickness) equipped with a flame ionization detector (FID). Helium was used as the mobile phase. The oven temperature was maintained at 250°C and the injection volume was 1 μL.      

The column temperature was initially held at 180°C for 2 minutes, then increased to 220°C at a rate of 6°C/min. After reaching 220°C, the temperature was held constant for 10 minutes (Ulberth et al., 1999).

Selection of animal

The study was conducted on thirty (30) male Wistar rats, weighing 80 ± 5 g. The rats were housed in colony cages (five rats per cage) at an ambient temperature of 25 ± 2 °C, under a 12-hour light/12-hour dark cycle and constant humidity of 60%. They had free access to their respective diets and water ad libitum. Food was replenished daily, and uneaten portions were discarded. Food consumption and growth rates were comparable across all groups throughout the two-month experimental period.

The rats were treated ethically, following the international guidelines for treating laboratory animals. In vivo manipulations test on Wistar rat were approved by the Ethical Committee of the University of Tlemcen, Algeria, number 165–2,019. The study was conducted in accordance with the ethical principles of the Declaration of Helsinki. All effort were made to minimize pain and distress, ensuring appropriate housing and handling, and promoting the overall well-being of the animals. Animals were divided into six groups (G): Table 1

Table 1. Experimental groups and dietary regimens assigned to rats.

Note: All experimental diets contained 16% casein as the protein source and differed only by the type of oil (4%) administered. ND: non-diabetic; D: diabetic

All experimental diets contained 16% casein, 4% oil, and a standard mineral and vitamin mix. The mineral mix provided essential macro- and trace elements, including calcium, potassium, sodium, magnesium, iron, manganese, copper, and zinc. The vitamin mix included fat- and water-soluble vitamins such as vitamins A, D, E, C, B-complex vitamins, inositol, and biotin. Numerical values are omitted here for clarity. The composition of the diets is shown in Table 2.

Table 2. Ingredient composition (g/100g) of the diet groups:(D1/D2/D3).

Note: ∑ SFA: Sum of the saturated fatty acids; ∑ MUFA: Sum of the mono-unsaturated fatty acids; ∑ PUFA: Sum of the poly-unsaturated fatty acids.

Induction of experimental diabetes

Two weeks after the start of the study, 50% of the rats in each group were randomly selected to be rendered diabetic by a single intraperitoneal injection of STZ (Sigma Aldrich, C₁₈H₁₅N₃O₇) was dissolved in ice-cold 0.1 M citrate buffer (pH 4.5) at a concentration of 10 mg/mL, kept on ice, and administered intraperitoneally at a dose of 65 mg/kg body weight. This injection was performed after 3 weeks on the diet (15 rats). The remaining 15 rats served as non-diabetic controls and received an intraperitoneal injection of citrate buffer alone at the same time point.

All rats were fasted overnight prior to the induction of diabetes or control buffer injection 0.1 M citrate, pH 7.6 (Szkudelski, 2001).

Surgery and blood samples preparation

Fasting blood glucose was measured before the administration of STZ at t = 0 h, 48 h, 144 h, and 336 h after injection of STZ or citrate buffer. Blood samples were collected from the tip of the tail vein at these time points. Blood glucose was determined using a glucometer (Accu-Chek Active, Roche, Mannheim, Germany). Diabetes was confirmed by blood glucose levels exceeding 1.26 g/L.

At the end of the experiment, all rats were fasted for 12 hours and then euthanized by intraperitoneal injection of 10% chloral hydrate (300 μL/100 g body weight). Blood was immediately collected from the abdominal aorta into tubes containing EDTA. Plasma was separated by centrifugation at 3,500 rpm for 15 minutes and used for biochemical analyses. The liver was excised, weighed, and processed for further analyses.

Determination of total cholesterol (TC), triacylglycerol (TG) and free fatty acids (FFA)

Total cholesterol (TC), triacylglycerol (TG), and free fatty acids (FFA) were assayed using enzymatic kits, following the manufacturer’s instructions (Biosystem, Barcelona, Spain). Low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol fractions were isolated by precipitation (Matthews et al., 1985).

Plasma fatty acids analysis

At time (t) t = 0 h, 48 h, 144 h, and 336 h, as well as after two months of diet, total serum lipids were extracted according to the method of Folch et al. (1957). Phospholipids were isolated by thin-layer chromatography and then transmethylated using BF3/methanol following saponification. Fatty acid methyl esters were analyzed by gas-liquid chromatography (GLC) using a Becker gas chromatograph (Becker Instruments).

The chromatograph was equipped with a 50 m capillary glass column packed with Carbowax 20M (Spiral RD, Contemor, France). C17:0 methyl esters served as internal standard. Identification of different fatty acids was performed by comparison with commercial standards, and peak areas were calculated using an ENICA21 integrator (Delsi Instruments, Suresnes) (Folch et al., 1957).

Liver lipid determination

The livers were rapidly excised, rinsed with 0.15 mol/L NaCl, and weighed after blotting with filter paper. 1.0 g of liver tissue was homogenized in 9 mL of 0.25 M sucrose using a Teflon homogenizer to obtain a uniform suspension. Total lipids were extracted from the homogenates according to the method of Folch et al. (1957). Liver triacylglycerols (TG), total cholesterol (TC), and free fatty acids (FFA) were measured using commercial assay kits (Biomérieux, Lyon, France) (Folch et al., 1956).

Statistical analysis

All data are expressed as mean ± standard deviation (SD). Differences among the six groups were analyzed using one-way ANOVA, followed by Tukey’s post hoc test for pairwise comparisons. A P-value less than 0.05 was considered statistically significant.

To facilitate presentation and interpretation of multiple comparisons, we used a letter-grouping system: groups whose means share the same letter (e.g. “a”, “b”, “c”) are not significantly different from one another at P < 0.05, whereas groups bearing different letters are significantly different. Thus, each distinct letter (or combination of letters) defines a homogeneous subset of groups with statistically indistinguishable means. The resulting group-letter assignments are indicated in the tables summarizing the results.

RESULTS

Fatty acid composition of dietary oils

The analysis revealed distinct fatty acid profiles among the three oils (Table 3). Olive oil (D2) showed the highest content of monounsaturated fatty acids (MUFA), mainly oleic acid (C18:1, 64.8 ± 2.5 g/100 g). Colocynthis oil (D3) was remarkably rich in polyunsaturated fatty acids (PUFA), especially linoleic acid (C18:2, 76.4 ± 3.82 g/100 g), resulting in the highest PUFA/SFA ratio (5.43 ± 1.80). Sunflower oil (D1) had the highest saturated fatty acid (SFA) content (22.2 ± 0.90 g/100 g), particularly palmitic acid (C16:0, 17.2 ± 1.5 g/100 g). Overall, each oil exhibited a characteristic lipid profile with potential nutritional implications.

Table 3. Percentages composition of the main fatty acids of dietary oils :( D1/D2/D3).

Note:   ∑ SFA: Sum of the saturated fatty acids; ∑ MUFA: Sum of the mono-unsaturated fatty acids; ∑ PUFA: Sum of the poly-unsaturated fatty acids. Values are expressed as mean ±SEM. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference.

Effects of diet on food intake, body and liver weight, and glycemia in diabetic and control rats

At the end of the experiment, body weight was significantly lower in diabetic rats fed any of the three diets (groups 2, 4, and 6) compared to non-diabetic rats on the corresponding diets (groups 1, 3, and 5). However, the relative liver weight did not differ between diabetic and non-diabetic rats in any of the diet groups.

Moreover, both food and lipid intake, as well as glycemia, were higher in diabetic rats than in non-diabetic rats fed the same diet. Notably, glycemia in group 6 (diabetic rats fed C. colocynthis oil) was lower compared to groups 2 and 4 (diabetic rats fed sunflower oil and olive oil, respectively) throughout the experimental period. The results summarized in Table 4.

Table 4. Food intake, body weight (BW), relative liver weight, glycaemia, and insulinemia in diabetic and non-diabetic rats fed different diets (SO, OO and CO) (n=5).

Note: Values are expressed as mean ± SEM. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference.

Liver and plasma lipoproteins, total cholesterol (TC), triacylglycerol (TG), and free fatty acids (FFA) in diabetic and non-diabetic rats fed different diets

Liver and plasma lipoproteins, total cholesterol (TC), triacylglycerol (TG), and FFA levels in diabetic and non-diabetic rats fed diets 1, 2, and 3 are presented in Table 4.

The results showed that liver and plasma cholesterol levels were significantly higher in groups 2 and 6 (diabetic rats fed diets 2 and 3) compared to groups 1 and 5 (non-diabetic rats fed the same respective diets). LDL-cholesterol (LDL-C) was elevated in diabetic rats fed diets 1 and 2 compared to their non-diabetic counterparts. Conversely, HDL-cholesterol (HDL-C) levels decreased in these diabetic groups. However, diabetic rats fed diet 3 exhibited LDL-C and HDL-C concentrations similar to those of non-diabetic rats fed the same diet.

Triacylglycerol levels in both liver and plasma were significantly higher in diabetic rats compared to non-diabetic rats fed the same diet. In contrast, FFA levels were significantly decreased in diabetic rats across all diets compared to their respective non-diabetic controls.

Interestingly, plasma total cholesterol and LDL-C were decreased in diabetic rats compared to non-diabetic controls fed the different diets, while HDL-C levels remained unchanged in diabetic rats fed diets 1 and 2.

Regarding liver FFA concentrations, no significant differences were observed between diabetic and non-diabetic rats fed diets 1 and 3, but a significant decrease was found in diabetic rats fed diet 2 compared to their non-diabetic counterparts.

Total liver lipid content was significantly decreased in diabetic rats fed diets 2 and 3 compared to non-diabetic rats fed the same diets. In contrast, diabetic rats fed diet 1 showed a significant increase in liver lipid content compared to their controls.

Table 5. Liver, plasma and lipoproteins total cholesterol, triacylglycerol and FFA in diabetic and non diabetic rat fed with different diets (SO, OO and CO) (n=5).

Note: Values are expressed as mean ±SEM. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference. FFA liver: Non-Esterified Fatty Acids.

Lipid and fatty acid intake in diabetic and non-diabetic rats fed different diets

Compared with non-diabetic rats fed the same diets, diabetic rats had increased lipid intake. The composition of the dietary oils was reflected in the fatty-acid intake: groups 3 and 4 consumed more monounsaturated fatty acids (MUFA), while groups 5 and 6 showed elevated polyunsaturated fatty acids (PUFA). Notably, rats receiving diet 3 (groups 5 and 6) had significantly higher n-6 fatty acid levels compared to other groups, underlining the distinctive fatty-acid profiles conferred by the different dietary oils. The detailed fatty-acid intake data are presented in Table 5.

Table 6. Lipids and fatty acids intake in diabetic and non-diabetic rats fed with different diet (SO, OO and CO).

Note: Values are expressed as mean ± SEM. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference.

Fatty acid composition of serum in diabetic and non-diabetic rats fed different diets at various time points

The plasma fatty acid profiles of rats fed the different diets reflected the fatty acid composition of their respective dietary oils, with no major differences observed between diabetic and non-diabetic rats during the experimental period (Table 6, 7, 8, 9).

All groups fed with olive oil (OO) and sunflower oil (SO) diets exhibited significantly higher proportions of monounsaturated fatty acids (MUFA) compared to rats fed diet 3. This difference was mainly attributable to variations in oleic acid [18:1(n-9)] levels. Conversely, rats fed diet 3 showed a significant increase in polyunsaturated fatty acids (PUFA), consistent with the Colocynthis oil content of this diet.

Regarding n-6 and n-3 fatty acids, values were similar across all groups. Similar observations were made for the PUFA/saturated fatty acid (SFA) ratio. In summary, plasma fatty acid composition closely correlated with fatty acid intake.

Table 7. Fatty acids composition of serum in diabetic and non-diabetic rats fed at time 0 hours.

Note: Values are expressed as a percentage of the total fatty acids and are means ± S.E.M. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference.

Table 8. Fatty acids composition of serum in diabetic and non-diabetic rats fed at time 48 hours.

Note: Values are expressed as a percentage of the total fatty acids and are means ± S.E.M. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference.

Table 9. Fatty acids composition of serum in diabetic and non-diabetic rats fed time 144 hours.

Note: Values are expressed as a percentage of the total fatty acids and are means ± S.E.M. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference.

Table 10. Fatty acids composition of serum in diabetic and non-diabetic rats at the end of the feeding period.

Note: Values are expressed as a percentage of the total fatty acids and are means ± S.E.M. Different letters indicate significant differences between groups (P < 0.05, Tukey HSD). The same letters indicate no statistical difference.

DISCUSSION

Diabetes is a complex metabolic disorder characterized by insufficient insulin secretion and insulin resistance (IR) induced hyperglycemia (Zhong et al., 2019; Almanza-Aguilera et al., 2020). Lifestyle and diet can be highly efficient in preventing and treating diabetes (Knowler et al., 2002). Study show tha high-fat diet intake for 10 weeks increased triglyceride and cholesterol levels serum in mice (Ruanpang et al., 2018), however high intake of saturated fatty acids (SFAs) increases the risk of cardiovascular disease due to LDL cholesterol in the blood, although polyunsaturated fatty acids (PUFAs) have the opposite effect (Schwab et al., 2014). Intake of unsaturated fatty acids (UFA), including monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA), has been shown to reduce the risk of type 2 diabetes (T2D). Mediterranean diets rich in PUFA and MUFA have been asserted to be protective against the risk of T2D (Bozzetto et al., 2012; Martín-Peláez et al., 2020).

Medicinal plants can prevent diabetes complications by maintaining glycemic control, as well as the stability of lipid profiles. Vegetable seeds provide nutritionally beneficial compounds, including fats, fat-soluble vitamins, and phytosterols, which are important for human nutrition. C. colocynthis seed oil contains unsaturated fatty acids, may help reduce elevated plasma atherogenic parameters such as cholesterol and triglycerides linked to low-density lipoproteins, also Increased FFA flux to the liver, especially from visceral adipose tissue lipolysis, and promoted excessive endogenous glucose production (Qureshi and Abrams, 2007; Sebbagh et al., 2009).

In this context, we used Citrullus colocynthis seed oil, known for its therapeutic properties and traditional use among patients with non-insulin dependent diabetes mellitus (NIDDM), in an isocaloric diet model of STZ-induced diabetic male Wistar rats particularly its ability to preserve pancreatic β-cell mass, and insulin sensitivity. (Sebbagh et al., 2009).

Supplementation with C. colocynthis oil in this study may also affect adipose tissue function, explaining the lower body weight observed in this group compared to the others, despite comparable food intake. At a cellular level, PUFA has been observed to play a role in repartitioning metabolic fuels for storage and oxidation by down-regulating the transcription of lipogenic genes and up-regulating the genes that promote lipid oxidation and thermogenesis (Clarke, 2000). Indeed, in a whole of diet context (Jones and Schoeller, 1988; Jones et al., 1992), studies have confirmed a greater fat-oxidizing effect acutely when the ratio of PUFA/SFA increases like that in C. colocynthis oil. Supplementation of the diet using fish oil (PUFA rich) has also been shown to increase fat oxidation (Delarue et al., 1996; Couet et al., 1997). Greater fat oxidation implies a lower retention in the body. This differential effect of fat subtypes means that the incorporation of PUFA into a diet may be beneficial in the promotion of negative fat balance and leads to the use of endogenous fat as energy source. It may be an important consideration in weight management where adipose tissue accumulation is integral to the problem.

Increased insulin secretion represents a compensatory response of pancreatic β-cells to maintain glucose homeostasis under conditions of reduced insulin sensitivity (Zhu et al., 2023). The mechanisms underlying insulin resistance are complex, involving defects downstream of insulin receptor signaling, including impaired message transmission and reduced biosynthesis of enzymatic effectors. Elevated circulating FFA, resulting from impaired insulin action that promotes lipolysis, further inhibit insulin’s effects on glucose metabolism (Samuel and Shulman, 2016).

Fatty acids are also recognized modulators of insulin secretion, with their effects depending on chain length and degree of saturation (Poitout and Robertson, 2008). Pancreatic β-cell function is influenced by these lipids, as recently demonstrated by Feng et al. (2006); their ubiquitous presence in tissues affects lipid metabolism and broader physiological functions (Chen et al., 2019). The data concur with these findings. Mechanistically, free fatty acids (FFAs), through their interaction with the free fatty acid receptor 1 (FFAR1) expressed on β-cells, potentiate glucose-stimulated insulin secretion (GSIS), particularly in contexts of increased insulin demand such as insulin resistance. Intracellularly, FFAs are metabolized to generate signaling lipids like long-chain acyl-CoA and diacylglycerol (DAG). Long-chain acyl-CoA can acylate key proteins involved in insulin granule exocytosis, such as SNAP-25 and synaptotagmin, facilitating vesicle fusion. In parallel, DAG activates protein kinase C (PKC) and interacts with the priming protein Munc-13, both of which promote insulin secretion. Thus, the degree of fatty acid unsaturation can modulate these signaling pathways, ultimately influencing the efficiency of insulin release from β-cells (Gonzalo and Linder, 1998; Rhee et al., 2002). 

The results demonstrate that vegetable oils, particularly C. colocynthis oil, protect and correct metabolic disturbances such as hyperglycemia and fatty acid metabolism perturbations, in accordance with their fatty acid profiles and possibly other bioactive molecules. Thus, vegetable oils, especially C. colocynthis oil, are beneficial for diabetes regulation due to their polyunsaturated and monounsaturated fatty acid content alongside phytosterols (e.g., β-sitosterol), tocopherols (α-tocopherol), and phenolic compounds (such as caffeic and ferulic acids), which are known for their antioxidant, anti-inflammatory, and metabolic activities.

Several studies have confirmed the beneficial effects of these components in normalizing plasma glucose concentrations in diabetes management (Delplanque et al., 2002; Chen et al., 2019). However, the results showed decreased plasma insulin concentration only in diabetic rats fed diets 1 and 2, consistent with mounting evidence that fatty acids influence stimulus–response coupling in pancreatic β-cells (Elkanawati et al., 2024).

Insulin-resistant type 2 diabetes is commonly associated with increased plasma concentrations of triglycerides, FFA, and cholesterol (Yaney and Corkey, 2003). In the present study, we observed a significant increase in plasma total cholesterol, LDL-C, FFA, and triglyceride levels in diabetic rats fed different diets compared to non-diabetic controls, while HDL-C levels remained unchanged, as shown in Table 4. Elevated plasma LDL cholesterol and triglycerides are strongly associated with accelerated atherosclerosis (Fève et al., 2006), and numerous studies have demonstrated the beneficial effects of vegetable oils on these parameters (Howard, 1999). Moreover, Howard (1999) suggested that LDL particles isolated from rabbits fed high vegetable oil diets exhibited remarkable resistance to oxidative stress. Metabolic studies have also reported strong cholesterol-lowering effects of vegetable oils rich in linolenic acid (Sebbagh et al., 2007).

The plant under study exhibits promising pharmacological activities, including hypoglycemic and lipid-lowering effects, as demonstrated in this experimental model. However, its potential toxicity should not be overlooked. High doses or prolonged use may induce adverse effects, emphasizing the importance of carefully evaluating its safety profile in addition to its therapeutic potential. These considerations highlight the need for further studies to determine safe dosage ranges and to better understand the balance between efficacy and toxicity for potential clinical applications.

CONCLUSION

In conclusion, this study demonstrates that dietary supplementation with  Citrullus colocynthis seed oil significantly improves glucose homeostasis, and favorably modulates plasma lipid profiles in stz-induced diabetic rats. These beneficial effects are likely attributable to the oil’s unique composition, particularly its enrichment in polyunsaturated and monounsaturated fatty acids, which appear to contribute to improved insulin sensitivity and overall metabolic regulation.

Further studies should identify the bioactive compounds in C. colocynthis oil and clarify their molecular mechanisms. Additional preclinical and clinical research is also required to assess its safety and effectiveness. Overall, the findings indicate that C. colocynthis oil may serve as a supportive natural option for metabolic health.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the Laboratory of Natural Products for its generous support in providing the reagents and equipment required for this research.

AUTHOR CONTRIBUTIONS

Chaabane-Sari Daoudi: Supervision (Lead), Data Curation (Equal), Formal Analysis (Equal), Writing – Original Draft (Equal), Writing –Investigation (Lead); Soulem-Mami Zoubida: Data Curation (Equal), Formal Analysis (Equal), Writing – Review & Editing (Equal), Investigation (Lead); Didi Amel: Data Curation (Equal), Writing – Review & Editing (Supporting), Investigation (Supporting); Yazit Sidi-Mohammed: Conceptualization (Equal), Methodology (Lead), Formal Analysis (Lead), Writing – Review & Editing (Lead), Project administration (Equal);  Chaouche Tarek: Formal Analysis (Supporting), Validation (Equal), Data Curation (Lead), Investigation (Supportive), Supervision (Equal); Lazzouni Hamadi-Abderrahmane: Validation (Lead), Resource (Supporting), Writing – Review & Editing (Lead), Investigation (Equal); Chaabane-Sari Meriem: Data Curation (Equal), Validation (Supporting), Writing – Review & Editing (Lead), Investigation (Equal).

CONFLICT OF INTEREST

The authors declare that they hold no competing interests.

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