Use of C-peptide and homeostasis model assessment of insulin resistance to assess insulin resistance in dogs.

BACKGROUND

Insulin resistance (IR) is a common complication in diabetic dogs, impairing glycemic control and causing metabolic dysfunction.

HYPOTHESIS/

OBJECTIVES

To assess the utility and determine cutoff values of C-peptide, homeostasis model assessment of IR by C-peptide (HOMA-IR by C-peptide), HOMA-IR by C-Peptide version 2 (HOMA-IRCP2), and homeostasis model assessment 2 of IR (HOMA2-IR) as diagnostic tools for detecting IR and identifying factors related to IR in dogs with diabetes.

ANIMALS: Seventy-six dogs were enrolled from a referral center and classified into 4 groups: healthy dogs (Healthy group, n = 17), pre-diabetes mellitus (PreDM, n = 11), insulin-dependent diabetes mellitus (IDDM, n = 20), and insulin-resistant diabetes mellitus (DMIR, n = 28).

METHODS

A cross-sectional prospective study. Blood samples were collected from dogs from which food was withheld and analyzed for glucose, C-peptide, and other metabolic indicators. HOMA-IR by C-peptide, HOMA-IRCP2, and HOMA2-IR were determined and compared across groups.

RESULTS

The DMIR group exhibited the highest C-peptide and HOMA-IR by C-peptide, HOMA-IRCP2, and HOMA2-IR. Receiver Operating Characteristic curve analysis demonstrated that C-peptide, HOMA-IR by C-peptide, HOMA-IRCP2, and HOMA2-IR identified IR, with area under curve of 0.843 (95% CI, 0.756-0.930), 0.897 (95% CI, 0.819-0.975), 0.893 (95% CI, 0.812-0.973), and 0.789 (95% CI, 0.686-0.893), respectively (P < 0.001). A cutoff level of ≥0.7 ng/mL for C-peptide and ≥120 for HOMA-IR by C-peptide demonstrated the highest sensitivity (92.9%), whereas ≥1.65 for HOMA-IRCP2 showed the highest specificity (97.9%).

CONCLUSIONS AND CLINICAL

IMPORTANCE

C-peptide, HOMA-IR by C-peptide, HOMA-IRCP2, and HOMA2-IR are promising, non-invasive indicators of IR. Early identification of IR using these markers might improve clinical outcomes.