Investigation of insulin resistance in obese dogs

In this master's study, it was investigated whether or not insulin resistance develops in obese or overweight dogs. Insulin resistance and related type 2 diabetes mellitus (T2DM) are also more common in these dogs. In the study, 30 dogs of different ages, breeds and genders were used. Dogs were consisted of ideal weight (control, n=10) and overweight or obese (study group, n=20) groups according to the body condition score (BCS) chart. In addition, obese dogs were divided equally into two groups as overweight (n=10) and obese (n=10).Serum samples were collected from all dogs and lipid profile and insulin resistance parameters were analyzed. For the lipid profile, serum total cholesterol (total-C), high-density lipoprotein cholesterol (HDL-C), very low-density lipoprotein cholesterol (VLDL-C), triglyceride (Tg) and glucose (GLU) levels were measured using a biochemistry analyzer. Serum LDL-C levels were calculated by using the formula: total cholesterol–(HDL-C+Tg/5). Glucose metabolism related parameters, insulin (INS) and asprosin (ASP), were measured using dog-specific ELISA kits. In addition, serum fructosamine (FRU) levels were determined using Idexx test kits.HOMA-IR (homeostasis model assessment of insulin resistance), HOMA-β% (homeostasis model assessment of β cell function) and insulin-glucose ratio (IGR) were calculated using the fasting glucose and insulin values as follows. HOMA-IR: Fasting glucose (mg/dl) x fasting insulin (mU/L) /405. HOMA-β%: 20 X Fasting insulin (μIU/ml)/Fasting glucose (mmol/L) -3.5. IGR= fasting insulin (mU/L)/fasting glucose (mg/dl). In the study, total-C (p<0.05), Tg (p<0.01), ASP (p<0.01), INS (p<0.01) , FRU (p<0.001), HOMA-IR (p<0.01), HOMA-β (p<0.01) and IGR (p<0.01) values were significantly higher in overweight or obese dogs than those of in the control group. Furhermore, total-C (p<0.01), VLDL-C (p<0.05), LDL-C (p<0.01), HDL- C/LDL-C (p<0.05) values were found to be higher in obese dogs than in both control and overweight dogs. In addition, ASP (p<0.05), INS (p<0.05), HOMA-β (p<0.05) and IGR (p<0.05) values of both overweight and obese dogs were higher than the control group values. The HOMA-IR (p<0.01) and FRU (p<0.01) values of the obese dogs were found to be statistically higher than those of the dogs in the control group. The number and rates of increase in parameters of both lipid profile and glucose metabolism were higher in obese dogs than in overweight dogs. In addition, there were high level positive correlations were determined between total-C and HDL-C (p<0.01), VLDL-C (p<0.01), LDL-C (p<0.01), and between HDL-C and VLDL-C (p<0.01), between total C/LDL-C and HDL-C (p<0.01), Tg (p<0.01), between INS and HOMA-IR (p<0.01) 0.01), between HOMA-β (p<0.01), IGR (p<0.01), between HOMA-IR and HOMA-β (p<0.01), IGR (p<0.01), between HOMA-β and IGR (p<0.01). In addition, a high level of negative correlation was found between HDL-C/LDL-C and total-C (p<0.01), HDL-C (p<0.01).As a result, it has been revealed that there are significant changes in the lipid profile and glucose metabolism parameters of obese or overweight dogs. However, considering the cut-off values, it was shown that there was no increase in all of the obese or overweight dogs. Parameters belong to the some of these dogs were similar to the parameters those of the dogs in ideal weight. In addition, it was determined that the serum ASP, GLU, INS, FRU, HOMA-IR, HOMA-β and IGR values of obese or overweight dogs increased and insulin resistance developed in 75% of them. The xii presence of high-level correlations between both lipid profile parameters and insulin resistance indices such as HOMA-IR, HOMA-β and IGR, as well as parameters such as INS, FRU, and ASP, indicated that these parameters can be used in the determination of insulin resistance in obese dogs. Keywords: Asprosin, Dog, Insulin resistance, Lipid profile, Obesity