Interspecies variability in diabetes mellitus (DM) represents a critical challenge for translational medicine, as metabolic pathways, pancreatic architecture, and therapeutic responses differ substantially across animal models. This systematic review, conducted according to PRISMA 2020 guidelines, synthesized evidence from 86 eligible studies published between 2001 and 2025. Comparative data from rodents, dogs, cats, pigs, non-human primates, and humans were analyzed to identify species-specific patterns in insulin secretion, insulin resistance (IR), β-cell dysfunction, microbiota–metabolism interactions, and susceptibility to diabetic complications. Results indicate that spontaneous diabetes in dogs closely mirrors human type 1 diabetes (T1DM), whereas feline obesity-associated diabetes reflects key features of human type 2 diabetes (T2DM). Rodent models remain essential for mechanistic and genetic studies but show limited chronicity and lower predictive fidelity for long-term outcomes. Non-human primates exhibit the highest physiological similarity to humans, especially regarding β-cell structure and incretin response, supporting their role in advanced translational studies. Major limitations included methodological heterogeneity and inconsistent molecular reporting. Integrating spontaneous models with standardized protocols and multi-omics approaches enhances translational relevance and supports more accurate model selection in diabetes research.

Stress is a major influencing behavior, health, and welfare in free-roaming dogs, particularly in environments characterized by unpredictability, social instability, and frequent human interactions. Although research on canine stress responses has expanded considerably, current knowledge remains fragmented across the neurobiological, physiological, and behavioral domains, limiting the development of comprehensive welfare assessment strategies. Importantly, free-roaming and shelter-housed dogs should not be viewed as entirely separate populations, since many shelter dogs originate from free-roaming environments and share similar stress-related experiences. This narrative review provides a comprehensive synthesis of current evidence on stress mechanisms in free-roaming and shelter-housed dogs The literature was explored across major scientific databases, and a total of 69 relevant studies were included. Particular emphasis was placed on the activation and regulation of the hypothalamic–pituitary–adrenal (HPA) axis, associated neuroendocrine alterations, and their behavioral expression. The strengths and limitations of commonly used physiological indicators, including cortisol measured in blood, saliva, feces and hair, were critically examined in relation to their applicability in real-world contexts. Behavioral manifestations of stress, such as fear- and anxiety-related responses, aggression, withdrawal, and stereotypic behaviors, were analyzed as functional outcomes of neurobiological activation and environmental challenges. Environmental stressors typical of shelter conditions as well as the role of human–dog interactions in stress modulation are also discussed. By combining neurobiological, physiological, and behavioral perspectives, this review highlights the importance of multidimensional stress assessment and proposes a conceptual framework linking biological mechanisms with observable behavioral indicators of welfare across the continuum from free-roaming to shelter environments. These findings may support the development of evidence-based welfare assessment and management strategies for free-roaming and shelter-housed dog populations.

Mammary tumors are among the most common neoplasms affecting female dogs and are typically diagnosed in middle-aged or older animals. The occurrence of malignant mammary tumors in very young dogs is uncommon and may present diagnostic and clinical management challenges. This case report describes a young female dog presenting with multiple mammary nodules accompanied by persistent hyperglycemia detected approximately one to 2 weeks before the onset of estrus. Clinical examination, hematological and biochemical testing, cytological evaluation, surgical excision of the mammary lesions, and histopathological analysis were performed. Histopathology confirmed the presence of multiple mammary carcinomas with different histological patterns. Despite surgical removal of the tumors, blood glucose concentrations remained elevated. Two weeks later, the patient underwent ovariohysterectomy, after which glycemic values gradually decreased and returned to normal within the following weeks. The temporal association between reproductive hormonal status and the observed metabolic alteration suggests a possible hormone-related insulin resistance rather than a direct metabolic effect of the tumors themselves. This case highlights the potential interaction between mammary neoplasia, reproductive hormonal status, and glucose metabolism in dogs and emphasizes the importance of comprehensive clinical and metabolic evaluation in young patients presenting with mammary tumors.