Effects of Multiple Daily Insulin Injections and Intraperitoneal Insulin Therapy on Cholesteryl Ester Transfer and Lipoprotein Lipase Activities in NIDDM

Although the relationship between the actions of cholesteryl ester transfer protein (CETP) and atherosclerosis is complex, a strong body of evidence suggests that its activity (cholesteryl ester transfer [CET]) is proatherogenic. We have previously shown that CET is increased in IDDM patients receiving conventional subcutaneous insulin treatment and normalized when systemic insulin levels are lowered with intraperitoneal insulin delivery (IP). Since CET has been found by many observers to also be accelerated in NIDDM, we sought to determine whether the same salutary effect could be achieved in insulin-requiring NIDDM men before and 7 months after randomization to an intensive treatment regimen (Rx) of either IP (n = 9) or multiple daily insulin injections (MDI; n = 13). HbA_1c improved to the same degree in both groups (MDI group: 9.4 ± 1.1% pre-Rx vs. 7.2 ± 0.7% post-Rx [P < 0.001]; IP group: 9.2 ± 1.3% pre-Rx vs. 7.1 ± 0.5% post-Rx [P< 0.001]). Compared with pre-Rx levels, plasma triglycerides were not significantly changed by either treatment (MDI group: 136 ± 80 mg/dl pre-Rx vs. 139 ± 87 mg/dl post-Rx; IP group: 157 ± 63 mg/dl pre-Rx vs. 188 ± 89 mg/dl post-Rx), though an upward trend followed IP. Before randomization, CET estimated with both mass and isotopic assays was greater in the NIDDM subjects than in nondiabetic control subjects (P < 0.001). With improved glycemic control, CE mass transfer declined in both groups, but only reached normal levels in the IP group (MDI group at 2 h: 49.0 ± 13.7 [mean ± SD] μg pre-Rx vs. 29.5 ± 15.3 μg post-Rx [−39.7%, P < 0.01]; IP group at 2 h: 40.8 ± 23.3 μg pre-Rx vs. 10.9 ± 6.5 μg post-Rx [−73.2%, P < 0.05]) and remained abnormally increased (P < 0.005) in the subjects receiving MDI. Total lipolytic activity after intensive treatment was unchanged from pretreatment levels, which were similar to those of the reference group. Although directional changes in lipoprotein lipase (LpL) and hepatic triglyceride lipase (HTGL) similar to those found in IDDM after MDI and IP were observed, they were not statistically significant. Thus, while improved glycemic control alone achieved by either MDI or IP reduced the pathological increase in CET in these insulin-treated NIDDM men, normalization was only achieved in those treated with IP. Despite near-normal HbA_1c levels, CET remained abnormally increased in NIDDM patients treated rigorously with conventional subcutaneous insulin delivery.