Basal Insulin and Insulin Dysregulation in Obese and Non-Obese Andalusian Horses with and Without Cresty Neck

REASONS FOR PERFORMING STUDY: Andalusian horses have been proposed as a breed predisposed to equine metabolic syndrome (EMS) phenotype [1] because they are prone to exhibiting regional, generalised adiposity and tendency to laminitis [2]. Insulin dysregulation represents the main pathophysiological cause for all the features of EMS, however there are no epidemiological studies in this breed. OBJECTIVE: To assess insulin dysregulation through insulin proxies in Andalusian horses with different levels of obesity. STUDY DESIGN: Cross‐sectional study. METHODS: One hundred and sixty‐four Andalusians (78 stallions and 86 mares, 2–15 years) were scored for overall (body condition score, BCS) and neck (cresty neck score, CNS) adiposity. Grain concentrate was withheld for 12 h before sampling. Blood samples were collected between 06.00–10.00 h for basal glucose, insulin concentrations, RISQI and MIRG proxies calculation. Conditions were defined as: obese horses (Ob), BCS ≥ 7; cresty neck horses (CN), CNS ≥ 3; hyperinsulinaemia, insulin ≥20 μu/ml; low insulin sensitivity, RISQI5.6muᵢₙₛᵤₗᵢₙ ²/[10.l.mggₗᵤcₒₛₑ]. Regarding BCS 2 groups were created: Ob and non‐Ob. These groups were subdivided depending on CNS: with CN and without it (nonCN). Ob‐nonCN group (n = 2) was excluded for the statistics due to the low number of horses. RESULTS: Of the horses studied, 26.8% were Ob‐CN, 42.1% were nonOb‐CN and 31.1% were nonOb‐nonCN. Ob horses presented higher insulin levels (P = 0.034) and lower RISQI values (P = 0.019) than all nonOb horses. When CN was considered, only RISQI was lower (P = 0.015) in Ob‐CN group respect to nonOb‐nonCN, however nonOb‐CN group does not differ from the other 2 groups. Furthermore, the percentage of Ob‐CN horses with hyperinsulinaemia (2.3%), abnormal RISQI (4.5%) and MIRG (9.1%) was very low. CONCLUSIONS: These results suggest that in Andalusians, increased adiposity was not clearly associated to insulin dysregulation and, similar to human beings, may coexist as a metabolically healthy but obese phenotype. Ethical animal research: Ethical University Committee approved all the procedures and owner informed consent was obtained. Source of funding: None. Competing interests: None declared.