Anti-obesity and anti-diabetic effects of L-citrulline are sex-dependent

Experimental Models of Type 2 Diabetes Mellitus Induced by Combining Hyperlipidemic Diet (HFD) and Streptozotocin Administration in Rats: An Integrative Review

Type 2 diabetes mellitus (DM2) is a metabolic disorder characterized by chronic hyperglycemia associated with low insulin production and/or insulin resistance. A high-fat diet (HFD) combined with a low dose of streptozotocin (STZ) in an animal model produces a disease that mimics type 2 diabetes mellitus in humans. However, there is wide variation in the methods of inducing diabetes in terms of the dose of STZ, the duration of the induction period, and the composition of the diet used, all of which could result in biological responses that are not typical of the disease. This review aims to investigate the characteristics of an experimental model of type 2 diabetes mellitus by combining a high-fat diet with low doses of streptozotocin in Wistar rats. This is an integrative review conducted by searching in the Medline, Lilacs, and Embase databases using the keywords "type 2 diabetes mellitus", "high-fat diet", "streptozotocin" and "Wistar rats". Articles published in English between 2018 and 2025 were included. The induction of DM2 in young male rats with a high-fat HFD for a period of at least 3 weeks followed by a low dose of STZ resulted in metabolic, histological, inflammatory, and oxidative changes, and alterations in the signaling pathways of glycemic and lipid metabolism in different tissues, replicating the characteristics observed in humans. HFD-fed + STZ-induced Wistar rats constitute an effective animal model for studying DM2.

Impact of L-Citrulline Supplementation and HIIT on Lipid Profile, Arterial Stiffness, and Fat Mass in Obese Adolescents with Metabolic-Dysfunction-Associated Fatty Liver Disease: A Randomized Clinical Trial

BACKGROUND

Metabolic-dysfunction-associated steatotic liver disease (MASLD) and obesity contribute to vascular dysfunction through oxidative stress, heightening cardiovascular risk. Oral supplementation with L-citrulline (L-cit), a precursor of L-arginine (L-arg) and nitric oxide, and high-intensity interval training (HIIT) may improve vascular function and cardiometabolic health.

OBJECTIVES

This study aimed to evaluate the combined effects of L-cit supplementation and HIIT on arterial stiffness, body composition, glucose metabolism, lipid profile, and blood pressure (BP) in adolescents with MASLD and obesity.

METHODS

In this double-blind, placebo-controlled, randomized clinical trial (ClinicalTrials.gov (NCT05778266), 44 adolescents (15-19 years) with MASLD and obesity were assigned to HIIT + L-cit (n = 14), HIIT + placebo (n = 14), or L-cit (n = 15) for 12 weeks. HIIT sessions (85% and 60% peak heart rate during intense and recovery periods) occurred thrice weekly. Training volume progressively increased, and participants performed 20 min of HITT per session in the last 8 weeks.

RESULTS

Outcomes included pulse wave velocity (PWV), augmentation index (Aix75), VO2peak, body composition, BP, glucose and lipid profiles, and hepatic steatosis. Compared to L-cit, HIIT + L-cit improved non-high-density lipoprotein cholesterol (p = 0.04), very-low-density lipoprotein cholesterol (p = 0.01), triglycerides (p = 0.02), and VO2peak (p = 0.001). No significant between-group changes were found in PWV, AIx75, hepatic steatosis, and body composition. HIIT + placebo improved VO2peak (p = 0.002), and L-cit decreased the degree of steatosis (p = 0.038).

CONCLUSIONS

HIIT + L-cit supplementation enhanced lipid profile and cardiorespiratory fitness, while HIIT + placebo improved cardiorespiratory capacity, and L-cit alone decreased hepatic steatosis. Thus, L-cit could be an adjuvant strategy to manage obesity-related MASLD in adolescents.

The high-fat diet and low-dose streptozotocin type-2 diabetes model induces hyperinsulinemia and insulin resistance in male but not female C57BL/6J mice

Translation of preclinical findings on the efficacy of dietary interventions for metabolic disease to human clinical studies is challenging due to the predominant use of male rodents in animal research. Our objective was to evaluate a combined high-fat (HF) diet and low-dose streptozotocin (STZ) model for induction of type-2 diabetes (T2D) in male and female C57BL/6J mice. We hypothesized that T2D biomarkers would differ significantly between sexes. Mice were administered either a low-fat (LF) diet (10% kcal from fat), or HF diet (60% kcal from fat) + STZ injections (30 mg/kg/d for 3 days). Both sexes gained weight and developed impaired postprandial oral glucose tolerance on the HF+STZ treatment compared to LF. Only male mice on HF + STZ developed fasting hyperglycemia, fasting hyperinsulinemia and insulin resistance, suggesting that the underlying causes of postprandial hyperglycemia differed between sexes. Principal component analysis of measures such as body weights, glucose and insulin concentrations indicated metabolic derangement for males only on HF+STZ treatment, while LF group males and both groups of females significantly overlapped. Based on our data, we accept our hypothesis that the combined high-fat diet and low-dose STZ model for T2D phenotypes differs significantly in its effect on mice based on sex. The HF diet + low-dose STZ model is not useful for studying insulin resistance in females. Other models are needed to model T2D, and study the effects of dietary interventions in this disease, in females. Sexual dimorphism remains a significant challenge for both preclinical and clinical research.