Insulin Resistance among Adults with Type 1 Diabetes Mellitus at the Philippine General Hospital

Background: Insulin resistance has been proven to increase the risks for cardiovascular complications in type 2 diabetes mellitus. Recently, insulin resistance has also been shown to play a bigger role in the natural history of type 1 diabetes mellitus (T1DM) disease process than is commonly recognized. Limitations and difficulties in assessing insulin resistance in patients with T1DM have been addressed by the creation of clinical scoring known as estimated glucose disposal rate (eGDR). Given the clear association of insulin resistance and cardiovascular complications in diabetic patients, detecting the prevalence of insulin resistance in T1DM population, will probably clarify the welldocumented gaps in the management of this type of diabetes. Objectives: The main objective of this study is to determine the prevalence of insulin resistance among Filipino adults with established type 1 diabetes mellitus at the Philippine General Hospital. The secondary objective is to describe the clinical features of type 1 diabetic patients with insulin resistance compared to patients without insulin resistance. Study Design and methods: This cross-sectional analytic study recruited 104 adult subjects, 19 years old and above, with established type 1 diabetes mellitus in Philippine General Hospital. Mixed meal stimulated C-peptide level was done to confirm the diagnosis of type 1 diabetes mellitus. The main outcome measure, insulin resistance, was determined using the validated clinical scoring, Estimated Glucose Disposal Rate (eGDR) with the following formula: eGDR=24.31 -(12.22 x Waist-to-hip ratio) -(3.29 x 1 if with hypertension or on anti-hypertensive or x 0 if no hypertension) -(0.57 x HbA1c). Patients with eGDR of =7.5 mg/kg/ min were considered to have insulin resistance. Results: The prevalence rate of insulin resistance was found to be 53% among adults with established type 1 diabetes mellitus. T1DM patients with insulin resistance were significantly older (mean=29.49 +/- 8.14 yr vs 25.63 +/- 6.32 yr, p=0.008), had higher waist-to-hip ratio (mean=0.95 +/- 0.03 vs 0.92 +/- 0.04, p=0.000), had higher systolic and diastolic blood pressure (mean=111.1 +/- 13.39 vs 105.76 +/- 10.83, p=0.028; mean=71.82 +/- 7.76 vs 68.98 +/- 6.55, p=0.048, respectively), and had poorer glycemic control (mean HbA1c=8.31 +/- 1.73 vs 7.67 +/- 0.90, p=0.017) compare to those T1DM without insulin resistance. There were also more T1DM with insulin resistance among subjects with duration of illness of more than 5 years (59.2% vs 40.8%, p=0.033), and among those who were either overweight or obese (52.6% vs 47.4% and 76.2% vs 23.8%, p=0.023, respectively). T1DM with insulin resistance group had higher insulin requirement per day than those without insulin resistance but the difference were not statistically significant (p> 0.5). Both groups had high prevalence of dyslipidemia and family history of diabetes mellitus. Conclusion: The result of this study showed a high prevalence rate of insulin resistance among Filipino adults with established type 1 diabetes mellitus. Old age, high waist-to-hip ratio, hypertension, poor glycemic control, long duration of diabetes and overweight/obesity are the features more common among type 1 diabetic patients with insulin resistance than those without insulin resistance.