Abstract
Recently, cluster analysis has been used to classify adult onset diabetes based on pathophysiologic profile. Using autoimmunity status, BMI, insulin resistance, and beta cell function, this classification system can predict diabetes associated complications. Individuals with primarily insulin resistant phenotype have been associated with increased incidence of nephropathy while those with insulin deficient phenotype are associated with retinopathy. Clinically, patients with severe insulin resistance can be defined as those who require high doses of insulin to achieve glycemic control, such as patients on U-500 insulin requiring more than 200 units of insulin a day. To characterize the clinical and metabolic phenotype of insulin-resistant patients from a South Texas VA diabetes clinic, we evaluated presence of macro or microvascular complications and beta-cell autoimmunity and function in this population. A retrospective cohort study was completed at the South Texas VA Diabetes Clinic. Charts were reviewed for anthropometric measurements, presence of macro and microvascular complications, anti-diabetic medication, lipid profile and HbA1c over 3 visits, autoimmunity (anti-GADab), and beta-cell function (fasting C-peptide). Patients with insulin doses >200 U/day or on U-500 insulin were categorized as “severe insulin-resistant”. Those with insulin doses < 0.5 U/kg/day were categorized as “mild insulin resistance” as a control group. Out of 120 patients, 30 met criteria for severe insulin resistance (n=30, M/F=29/1 age 61±1.6 years (yr), BMI 41±0.9 kg/m2, duration of diabetes 18.3±0.3 yr, HbA1c -8.4±0.2%, total daily insulin dose (TDD) 301±31U). 30 patients with insulin use <0.5 U/kg/day met criteria for mild insulin resistance (N=30, M/F: 28/2, age 62±2 yr, BMI 30±1 kg/m2, duration of diabetes 12±1.2 yr, HbA1c 7.2±0.2%, TDD 17±2U). Prevalence of nephropathy was higher in the insulin resistant group vs the mild insulin resistant group (76% vs 43%, p<0.05). There was no difference in prevalence of retinopathy (p=0.095) or CAD (p=0.6) between the groups. There was no difference in use of ACE-i or SGLT-2i between the groups. Insulin resistant subjects had a higher plasma triglyceride (325±0.3 vs 202±0.3 mg/dl, p=0.04). Prevalence of GAD ab was not different between the groups (3% vs 0%). Fasting C-peptide concentrations were similar in both groups (5.6±0.3 vs 5.2±0.25 ng/ml, p=0.3). HbA1c in the insulin resistant group improved between visits 1 and 3 (p<0.01). Weight increased over three visits in the severe insulin resistant group as opposed to mild weight loss in the mild insulin resistant group.
Our results support the high prevalence of diabetic nephropathy in patients with severe insulin resistance, although it is unclear that insulin resistance is the etiology. Long-term follow up of these patients may provide insight into the underlying mechanisms of these complications.
Improving Microvascular Complications Screening Rates: Implementation of a Dedicated Diabetes Clinic (Diabetes 360) in an Underserved Area in Philadelphia, PA