Insulin resistance and cardiovascular outcomes in the ORIGIN trial

In the Outcome Reduction with an Initial Glargine Intervention (ORIGIN) trial (Clinicaltrials.gov: NCT000069784), titrated doses of basal insulin glargine targeting fasting normoglycaemia had a neutral effect on cardiovascular outcomes. The dose of insulin required to achieve normoglycaemia provides a unique measurement of each individual's resistance to insulin's action, and was therefore used to examine the link between insulin resistance and cardiovascular outcomes.

Self-titration of insulin doses targeting a fasting plasma glucose ≤5.3 mmoL/L (95 mg/dL) was promoted at every visit and cardiovascular and other serious health outcomes were ascertained. All analyses were restricted to participants allocated to insulin glargine, who added it to lifestyle or 1 glucose-lowering oral agent at randomization. Normoglycaemia was defined as a fasting plasma glucose <5.6 mmol/L and HbA1c <6% at the 2-year visit. The median of the natural logarithm of insulin doses (expressed per kg of fat-free mass), recorded at every visit from randomization until either the penultimate visit or the first occurrence of a cardiovascular outcome, was analysed.

Higher median insulin doses did not reflect incident cardiovascular events overall or in the subset that achieved normoglycaemia. When the dose taken before a cardiovascular event or the penultimate visit was analysed, the adjusted hazard of the composite of cardiovascular death, myocardial infarction or stroke was 0.94 (95% CI 0.88, 1.00) per unit higher dose overall, and 0.91 (95% CI 0.81, 1.01) in the normoglycaemic subset.

Insulin resistance may not promote cardiovascular outcomes in individuals with dysglycaemia.