Changes in high density lipoprotein cholesterol after initiation of insulin therapy in non-insulin dependent diabetes mellitus: relationship to changes in body weight

Association of Insulin Dose, Cardiometabolic Risk Factors, and Cardiovascular Disease in Type 1 Diabetes During 30 Years of Follow-up in the DCCT/EDIC Study

OBJECTIVE

The Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study demonstrated the beneficial effects of intensive therapy on atherosclerosis and clinical cardiovascular disease (CVD) outcomes. The current analyses evaluated the relationship between longitudinal changes in insulin dose and CVD risk factors and outcomes.

RESEARCH DESIGN AND METHODS

A total of 1,441 participants were randomly assigned to intensive or conventional diabetes therapy during the DCCT. After an average of 6.5 years of follow-up, 96% of the surviving cohort enrolled in the EDIC observational study, which included annual visits with detailed medical history, physical examination, and laboratory testing. CVD events were adjudicated by a review committee. Generalized linear mixed models and Cox proportional hazards regression models were used to assess the association between insulin dose and cardiometabolic risk factors and CVD risk, respectively, over a total of 30 years.

RESULTS

Higher insulin doses were significantly associated with a less favorable cardiometabolic risk profile (higher BMI, pulse rate, and triglycerides and lower HDL cholesterol) with the exception of lower diastolic blood pressure and lower LDL cholesterol. In a minimally adjusted model, a 0.1 unit/kg body wt/day increase in insulin dose was associated with a 6% increased risk of any CVD (95% CI 3, 9). However, the association with insulin dose was no longer significant after adjustment for other CVD risk factors.

CONCLUSIONS

During DCCT/EDIC, higher insulin doses were associated with adverse trends in several cardiometabolic risk factors, even after multivariable adjustment, but not with incident CVD outcomes.

Relationship between serum sex hormones and the glucose-insulin-lipid defect in men with obesity

It has been hypothesized that an alteration in the sex hormone milieu may underlie coronary heart disease (CHD) and its risk factors. Leading to this hypothesis and important to it was the observation that serum testosterone level correlated negatively and the estradiol to testosterone ratio (E/T) correlated positively with serum insulin and glucose levels in non-obese men. As a test of the validity of this observation, the present study was conducted to investigate these correlations in men with obesity. Obesity in men is associated with hyperestrogenemia, hypotestosteronemia, hyperinsulinemia, hyperglycemia, and CHD. To determine whether the relationships between sex hormone levels and insulin and glucose levels found in non-obese men also occur in obese men independent of obesity, fasting levels of these substances, as well as free testosterone (FT) and sex-hormone-binding globulin (SHBG), were measured in 55 obese men aged 21 to 70. Correlation coefficients of sex hormones with other risk factors for CHD, ie, cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), blood pressure, and waist to hip circumference ratio (W/H), were also calculated. As found previously, testosterone level correlated negatively with insulin (r = -.31, P = .01) and glucose (r = -.23, P < .05) levels and the insulin to glucose ratio ([I/G] r = -.26, P < .05), and E/T correlated positively with insulin (r = .41, P = .001) and glucose (r = .24, P < .05) levels and I/G (r = .37, P < .005). The above correlations were controlled for body mass index (BMI) and age.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin therapy in maturity-onset diabetes

A prime target of insulin action in patients with maturity onset diabetes is suppression of hepatic glucose production in both the fasting and postprandial states. In patients who fail to respond to oral treatment insulin improves glycaemic control, has an antiatherogenic effect on the serum lipoprotein pattern, and increases well being. The beneficial long-term effects of insulin therapy on morbidity and mortality are, however, still unproved. The regimens of insulin therapy are not established. In patients with normal or increased basal serum C-peptide concentration treatment may start with intermediate or long-acting insulin at bedtime together with oral medication, or in the morning with or without oral medication. If this fails two injections of intermediate-acting insulin or multiple injections of short-acting insulin should be started. Hypoglycaemia is uncommon in maturity onset diabetes treated with insulin, but moderate weight gain usually occurs. The possible role of hyperinsulinemia as a predisposing factor for atherogenesis remains unresolved. Despite controversies over treatment, any patient with maturity onset diabetes not responding to oral agents should be regarded as a candidate for insulin therapy.

Beta-blockers, lipoproteins and non-insulin dependent diabetes

In a study on 138 hypertensive non-insulin dependent diabetic subjects, factors influencing lipoproteins were assessed. Multiple regression analyses were carried out in order to assess the influence of beta-blocker antihypertensive therapy while making allowances for other confounding variables. In males, but not in females, on a beta-blocker for hypertension, total high density lipoprotein- (HDL-) and HDL-subfraction cholesterol were significantly lower while the serum triglyceride was increased, though not significantly. In male non-insulin dependent diabetics, regimens containing a beta-blocker may worsen an already abnormal lipoprotein profile and antihypertensive agents other than beta-blocking agents should be used if possible.

Insulin therapy induces antiatherogenic changes of serum lipoproteins in noninsulin-dependent diabetes

To study the effects of rigorous insulin therapy on serum lipoproteins in patients with noninsulin-dependent diabetes not controlled with oral agents only, we measured serum lipoproteins, apoproteins, lipolytic enzymes, and glucose disposal using an insulin clamp technique before and after 4 weeks of insulin therapy. Lipoproteins were isolated by ultracentrifugation and high density lipoprotein (HDL) subfractions, by rate-zonal density gradient ultracentrifugation. The group included 11 women and eight men (age 58 +/- 1 years and RBW 125 +/- 4%). Body weight, glycosylated hemoglobin, mean diurnal glucose, plasma free insulin, and glucose uptake (M-value) were 75 vs. 76 kg; 11.9 vs. 8.9%; 234 vs. 124 mg/dl; 12 vs. 27 microU/ml; and 5.0 +/- 0.4 vs. 7.1 +/- 0.6 mg/kg/min before and after insulin therapy, respectively. After insulin therapy there was a decrease of very low density lipoprotein (VLDL) triglyceride (-60%, p less than 0.001) but an increase of HDL2 cholesterol (+21%, p less than 0.001); HDL2 phospholipids (+38%, p less than 0.001); HDL2 proteins (+23%, p less than 0.01); and HDL2 mass (127 +/- 11 vs. 158 +/- 12 mg/dl, p less than 0.001). There was a decrease of HDL3 cholesterol (-13%, p less than 0.05); HDL3 phospholipids (-16%, p less than 0.05); HDL3 proteins (-18%, p less than 0.001); and HDL3 mass (179 +/- 6 vs. 146 +/- 6, p less than 0.01). Zonal profiles showed a redistribution of particles from HDL3 to HDL2. Serum apo A-I increased (p less than 0.05), apo A-II remained constant, but apo B decreased (-29%, p less than 0.001). The most marked change during insulin therapy was a 2.3-fold increase in adipose tissue lipoprotein lipase (LPL) activity (p less than 0.001). The changes of VLDL and HDL subfractions were not explained by respective changes of the blood glucose, free insulin, or M-value. The data indicate that intensive insulin therapy induces antiatherogenic changes in serum lipids and lipoproteins and suggest that the induction of LPL by insulin is the major factor responsible for redistribution of HDL particles from HDL3 to HDL2.

Effect of insulin therapy on lipoproteins in non-insulin dependent diabetes mellitus (NIDDM)

Thirty patients with NIDDM and severe hyperglycemia (fasting plasma glucose greater than 200 mg/dl) were initiated on insulin therapy. Lipoprotein concentrations were measured by the Vertical Autoprofile procedure before insulin therapy and 1, 3, 6 and 26 weeks after insulin initiation. Patients were divided into 4 phenotypes based on their pretreatment lipoprotein profile: HyperVLDL (elevated VLDL), HyperLDL (elevated LDL), HyperVLDL-LDL (elevated VLDL and LDL), and non-hyperlipidemic. There were no differences in the initial fasting plasma glucose, Hgb Alc, or fasting free insulin concentrations between the groups. Both the HyperVLDL and HyperLDL groups had significantly lower HDL-C concentrations that the non-hyperlipidemic group and the HyperVLDL-LDL group had significantly higher IDL-C than any of the other groups. Insulin therapy resulted in similar decreases in fasting plasma glucose and increases in fasting free insulin concentrations in all 4 groups. HDL-C increased in all 4 groups. The most marked improvements in HDL-C were seen in the non-hyperlipidemic (+37%) and HyperLDL (+42%) groups while the HyperVLDL group had only an 18% increase. VLDL-C fell in all groups but in the HyperVLDL group it fell dramatically to almost normal levels within the first week, whereas it took 6 weeks for the HyperVLDL-LDL group to reach its VLDL-C nadir and this was still significantly higher than normal. LDL-C improved modestly in only the HyperLDL patients after 6 weeks of insulin therapy. There were no statistically significant changes in either the IDL-C or Lp(a)-C in any of the groups during insulin therapy. The changes in HDL-C and IDL-C were negatively correlated with the fasting plasma glucose and Hgb Alc but not with the free insulin concentration. We conclude that: 1) Insulin therapy can cause dramatic improvements in HDL-C and VLDL-C while it has only a mild suppressive effect on LDL-C and no statistically significant effect on IDL-C or Lp(a)-C. The degree of improvement in the lipid profiles varied considerably between the different lipid phenotypes. 2) The hyperlipidemic phenotypes seen in these patients appear to be determined primarily by factors other than the degree of hyperglycemia and hypoinsulinemia.

HDL metabolism in diabetes

Based on the data reviewed, it is necessary to conclude that diabetes is associated with profound changes in HDL metabolism. However, once we go beyond this simple generalization, it is apparent that the relationship between diabetes and HDL metabolism is not a simple one. A good deal of the complication evolves from the fact that IDDM and NIDDM seem to affect HDL metabolism quite differently, with the only apparent similarity the fact that plasma HDL-cholesterol concentration can be low in untreated patients with either IDDM or NIDDM. Thus, in patients with IDDM the primary event seems to be related to the insulin-deficient state, which results in a decrease in HDL turnover rate and resultant decline in plasma HDL-cholesterol concentration. In contrast, HDL turnover appears to be accelerated, not reduced in patients with NIDDM, and the low plasma HDL-cholesterol concentration is a consequence of the increased turnover rate. In addition, patients with NIDDM are not absolutely insulin deficient, and available evidence suggests that the higher the plasma insulin level, the lower the plasma HDL-cholesterol concentration in these patients. The differences noted above in the effect of IDDM and NIDDM on HDL metabolism are of great interest, and, unfortunately, not very well understood. There is, however, one additional difference, which may be of paramount clinical importance. For reasons not totally clear, plasma HDL-cholesterol concentrations in patients with IDDM treated with insulin are not lower than normal, and even tend to be higher than these values in a nondiabetic population. Possibly as a result of this phenomenon, there is no evidence that changes in plasma HDL-cholesterol concentration play a role in the development of macrovascular complications in IDDM. Although it is apparent from the considerations discussed in this review that a great deal more needs to be learned about the effect of insulin deficiency on HDL metabolism, changes in HDL metabolism do not appear to be clinically important in patients with IDDM. Unfortunately, this does not appear to be the situation in patients with NIDDM. Plasma HDL-cholesterol concentrations are lower than normal in patients with NIDDM, and this finding seems to be related to increased morbidity and mortality from CAD. Furthermore, there is no form of anti-diabetic treatment, irrespective of how effective it has been in achieving glycemic control, that has been shown to substantially increase plasma HDL-cholesterol level. Indeed, it has been difficult to demonstrate a consistent effect of any therapeutic approach on plasma HDL-cholesterol concentration.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of glyburide therapy on lipoproteins in non-insulin-dependent diabetes mellitus

Twenty-seven patients with non-insulin-dependent diabetes mellitus and fasting plasma glucose values greater than 140 mg/dl began glyburide therapy. After entry into the study, patients were classified into three phenotypes on the basis of their initial lipoprotein profile: type IV, mixed, and normal. Glyburide lowered plasma glucose and raised plasma insulin concentrations in non-insulin-dependent diabetes mellitus. Patients with type IV hyperlipoproteinemia had higher fasting free insulin concentrations before and after therapy than patients without hyperlipoproteinemia and may have a slightly reduced hypoglycemic response to glyburide therapy. The drug caused a significant reduction in very-low-density lipoprotein cholesterol in patients with non-insulin-dependent diabetes mellitus and type IV hyperlipoproteinemia, along with a variable change in high-density lipoprotein cholesterol, independent of its effect on plasma glucose.

Effect of cigarette smoking cessation on risk factors for coronary atherosclerosis. A control clinical trial

The effect of cigarette smoking on other cardiovascular risk factors, serum lipids, body weight, blood pressure and blood sugar was assessed in a randomized control trial of reduction or cessation of cigarette smoking. In the intervention group (n = 107), reported cigarette use fell from 28.5 +/- 1.2 (+/- SEM) to 10.6 +/- 1.2 cigarettes/day and serum thiocyanate, a biochemical indicator of the extent of tobacco exposure, decreased -42.8 +/- 5.5 mumol/l (P less than 0.001). Compared to the control group, the intervention group showed significant (P less than 0.05) decreases in reported cigarette consumption and serum thiocyanate and significant (P less than 0.05) increases in body weight and skinfold thickness. Change in thiocyanate correlated significantly (P less than 0.05) and inversely with change in HDL-C, body weight and skinfold thickness, but not with change in LDL-C, triglycerides or blood pressure. These relationships remained significant even after adjusting in multivariate analysis, for initial measurements of these variables or regression to the mean. For those who quit smoking (n = 35) HDL-C increased 5.9 +/- 1.7 mg/dl (P less than 0.01). The usual inverse relationship between body weight and HDL-C does not exist with cessation of cigarette smoking. Thus, benefits of stopping cigarette smoking extend to favourable alterations in HDL-C and there are no adverse effects on blood pressure, fasting blood sugar, triglycerides or LDL-C.