Effect of gemfibrozil on the regulation of HDL subfractions in hypertriglyceridaemic patients

OBJECTIVES

To study changes of HDL subfractions and their regulation during gemfibrozil treatment in hypertriglyceridaemia.

DESIGN

Twenty patients with hypertriglyceridaemia were randomized to receive either 1200 mg day-1 gemfibrozil or placebo for 3 months. After a 6-week, single-blind placebo period, the patients were randomized to receive either gemfibrozil or placebo for 3 months in a double-blind study.

SETTING

The patients were studied as outpatients in the Third Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland.

MAIN OUTCOME MEASURES

Ultracentrifugally isolated HDL subclasses; concentrations of apoA-I, apoA-II, LpA-I and LpA-I:A-II particles; post-heparin plasma lipoprotein lipase (LPL), hepatic lipase (HL) and plasma cholesteryl ester transfer protein (CETP) activities; phospholipid transfer protein (PLTP) and lecithine cholesteryl acyltransferase (LCAT) activities were measured in plasma from six patients from both groups.

RESULTS

Gemfibrozil increased the concentration of HDL cholesterol (+11.1%) because of the rise of HDL3 cholesterol (34.5%, P < 0.01). The concentration of LpA-I particles was reduced during gemfibrozil treatment (-12.4%, P < 0.05), while that of apoA-II increased (+12.3%, P < 0.01). The LpA-I to LpA-I:A-II ratio decreased significantly in the gemfibrozil group (-18.9%, P < 0.01). Gemfibrozil increased LPL and HL activities by 18.2% (P < 0.05) and by 19.6%, respectively. Plasma CETP activity was also increased during gemfibrozil treatment (+15.8%, P < 0.05).

CONCLUSION

The gemfibrozil-induced elevation of HDL3 and apoA-II may reflect the combined action of LPL, HL and CETP on plasma HDL metabolism.

ApoA-IHelsinki (Lys107-->0) associated with reduced HDL cholesterol and LpA-I:A-II deficiency

A Finnish kindred with premature coronary heart disease and decreased HDL cholesterol levels was identified as having an apoA-I variant, apoA-I (Lys107-->0), caused by a 3-bp deletion of nucleotides 1396 through 1398 in exon 4 of the apoA-I gene. These subjects (n = 10) were heterozygous for this mutation. The mean serum HDL cholesterol concentration (26.7 +/- 9.7 mg/dL) of affected family members was 36%, lower than that of unaffected family members (P < .05). Mean serum apoA-I and apoA-II concentrations in heterozygotes were reduced by 18% and 22%, respectively, compared with normal family members (P < .05). In heterozygotes the mean concentration of lipoprotein containing both apoA-I and apoA-II (LpA-I:A-II) was 31% lower than in those with normal apoA-I (P < .001), while the mean level of lipoproteins containing apoA-I without apoA-II was similar in the two groups. HDL density-gradient ultracentrifugation showed a lack of HDL2 and small dense HDL3 in heterozygotes compared with unaffected family members. The HDL particle size distribution, as analyzed by nondenaturing gradient gel electrophoresis of heterozygotes, revealed one major peak at 8.0 to 9.7 nm, a minor peak at 7.8 to 8.5 nm, and an absence of HDL2b and HDL2a peaks. These latter peaks were observed in unaffected family members. Serum levels of LDL cholesterol, triglycerides, VLDL, IDL, and LDL subclasses were similar in the two groups. However, in heterozygotes the cholesterol-to-triglyceride ratios in VLDL2, LDL1, LDL3, HDL2b, HDL2a, and HDL3a were 8% to 54% lower than in unaffected family members (P < .05). Cholesteryl ester transfer protein activity in heterozygotes was reduced by 25% compared with unaffected family members (P < .05), while the plasma lecithin:cholesterol acyltransferase (LCAT) activity did not differ between heterozygotes and unaffected family members. The ability of isolated variant apoA-I to serve as a cofactor for LCAT in vitro did not differ from that of normal apoA-I. Our data are consistent with the concept that a low HDL cholesterol level in subjects heterozygous for the apoA-IHelsinki mutation (Lys107-->0) having normal LCAT activity is a consequence of decreased concentration of LpA-I:A-II particles and of a smaller size and reduced cholesterol content of HDL particles.

HDLs containing apolipoproteins A-I and A-II (LpA-I:A-II) as markers of coronary artery disease in men with non-insulin-dependent diabetes mellitus

BACKGROUND

Abnormalities in HDL and an increased risk of coronary artery disease (CAD) coexist in non-insulin-dependent diabetes mellitus (NIDDM). HDLs can be separated by their apolipoprotein (apo) content into particles containing apoA-I but not apoA-II (LpA-I) and those containing both apoA-I and apoA-II (LpA-I:A-II). The LpA-I particles have been suggested to be more effective in conferring protection against CAD than the LpA-I:A-II particles. However, data are sparse, and no studies have defined the role of these two classes of particles in NIDDM.

METHODS AND RESULTS

LpA-I and LpA-I:A-II particles were quantified by a differential electroimmunoassay in four groups of men with similar age and body mass index (BMI) distributions. Group 1 consisted of 50 patients with NIDDM and angiographically verified CAD; group 2, 50 men with CAD but no diabetes; group 3, 50 men with NIDDM but no CAD; and group 4, 31 healthy men. Serum apoA-I and apoA-II concentrations were measured by immunoturbidimetry, and HDL2 and HDL3 were separated by ultracentrifugation. Concentrations of LpA-I:A-II particles in group 1 were 13.8%, 18.3%, and 26.9% lower than in groups 2 through 4, respectively. In a two-by-two factorial ANOVA, adjusted for age and BMI, the differences were significant for both CAD (P < .001) and NIDDM (P < .001), with no interaction between the factors. These results were confirmed by comparable differences in the serum concentrations of apoA-I and apoA-II. LpA-I particles were related to the presence or absence of CAD (P = .013), but the difference was lost in a multivariate analysis. A low HDL3 cholesterol concentration characterized both CAD (P = .002) and NIDDM (P = .024). HDL2 cholesterol differed significantly with regard to the presence of NIDDM (P = .033) but only borderline with respect to CAD (P = .073).

CONCLUSIONS

ApoA-II-containing lipoproteins and HDL3 cholesterol are powerful markers of CAD in men with NIDDM.

Insulin resistance and lipoprotein metabolism

Dyslipidaemia in insulin resistance comprises elevated plasma triglycerides, decreased HDL, a preponderance of small, dense LDL and increased postprandial lipaemia. In terms of cause and effect, small, dense LDL, alimentary hyperlipidaemia and changes in HDL are consequences of elevated triglycerides. These abnormalities can become frequent if triglycerides exceed a threshold value of approximately 1.5 mmol/l. Therefore, it is mandatory to maintain plasma triglycerides as low as possible in noninsulin-dependent diabetic and insulin-resistant individuals to prevent the potentially atherogenic and metabolic consequences of hypertriglyceridaemia.

Lipid intolerance in smokers

OBJECTIVES

Smokers have recently been shown to be insulin resistant and to exhibit several characteristics of the insulin resistance syndrome (IRS). In this study, we assessed fasting and postprandial lipid levels in healthy, normolipidaemic, chronic smokers and a matched group of non-smoking individuals.

DESIGN

A standardized mixed meal (containing 3.78 MJ and 51 g of fat) was given in the morning after an overnight fast. The smokers were either abstinent from tobacco for 48 h or were allowed to smoke freely, including being allowed to smoke six cigarettes during the study.

SUBJECTS

Twenty-two middle-aged, healthy male subjects, nine habitual smokers and 13 non-smoking control subjects, were recruited to the study. The smokers had all been smoking at least 10 cigarettes per day for at least 10 years.

RESULTS

The smokers exhibited a lipid intolerance in that their postprandial increase in triglyceride levels was more than 50% higher than in the non-smokers' group. This lipid intolerance could not be discerned in the postabsorptive state because the fasting triglyceride levels were the same in both groups, while the smokers had significantly lower high-density lipoprotein (HDL) cholesterol. The peak postprandial triglyceride level correlated closely and negatively with fasting HDL cholesterol, indicating an impaired lipolytic removal capacity in smokers.

CONCLUSIONS

Healthy, normotriglyceridaemic smokers exhibit an abnormal postprandial lipid metabolism consistent with lipid intolerance. It is suggested that postprandial hyperlipidaemia is a characteristic trait of the insulin resistance syndrome and that the defect in lipid removal is related to the low HDL cholesterol in this syndrome. The insulin resistance syndrome is likely to be an important reason for the increased propensity for cardiovascular disease in smokers.

Decreasing triglyceride by gemfibrozil therapy does not affect the glucoregulatory or antilipolytic effect of insulin in nondiabetic subjects with mild hypertriglyceridemia

We studied the effects of gemfibrozil on glucose and fatty acid metabolism in subjects with mild endogenous hypertriglyceridemia. Twenty subjects (serum triglycerides, 3.2 +/- 1.4 mmol/L; age, 52 +/- 7 years; body mass index, 27.8 +/- 1.8 kg/m2) were randomly allocated to receive either placebo or gemfibrozil 1,200 mg daily for 12 weeks in a double-blind study. Gemfibrozil decreased serum total and very-low-density lipoprotein (VLDL) triglycerides by 53% and 57%, respectively, and serum apolipoprotein (apo) B concentration by 21%. Gemfibrozil had no effect on the diurnal concentration of free fatty acids (FFA). Neither did gemfibrozil change diurnal blood glucose or serum insulin concentrations. The endogenous glucose production rate remained unchanged in both groups during the treatment period, and was similarly suppressed by hyperinsulinemia. The rate of insulin-induced whole-body glucose disposal increased similarly both before (basal 10.8 +/- 1.8, low-dose insulin 10.5 +/- 2.1, and high-dose insulin 20.9 +/- 11.9 mumol.kg-1.min-1) and after (11.1 +/- 1.7, 10.7 +/- 1.2, and 18.6 +/- 7.9, respectively) gemfibrozil treatment. Rates of oxidative and nonoxidative glucose metabolism remained unchanged during gemfibrozil treatment. Basal pretreatment and posttreatment FFA turnover rates were similar in both study groups, as were the rates of substrate oxidation. In summary, gemfibrozil proved to be an effective serum triglyceride-lowering agent in patients with mild hypertriglyceridemia, but had no effect on the insulin sensitivity of glucose metabolism or of antilipolysis. These data support the idea that triglycerides per se do not cause insulin resistance, and that the triglyceride-lowering effect of gemfibrozil is not mediated via antilipolytic action.

Changes of lipolytic enzymes cluster with insulin resistance syndrome. Botnia Study Group

The activities of hepatic and lipoprotein lipase and the levels of lipo- and apoproteins were compared in two groups of normoglycaemic men representing the highest (n = 18) and lowest (n = 15) fasting insulin quintiles of first degree male relatives of non-insulin-dependent diabetic patients. The high insulin group representing insulin-resistant individuals had significantly lower post-heparin plasma lipoprotein lipase activity than the low insulin group (14.2 +/- 4.0 vs 20 +/- 5.8 mumol NEFA.ml-1.h-1, p < 0.001); hepatic lipase activity did not differ between the two groups (24.2 +/- 11 vs 18.0 +/- 5.3 mumol NEFA.ml-1.h-1, NS). The lipoprotein lipase/hepatic lipase ratio in the high insulin group was decreased by 66% as compared to the low insulin group (0.75 +/- 0.57 vs 1.25 +/- 0.65, p < 0.01). In the high insulin group both total and VLDL triglycerides were higher than in the low insulin group (1.61 +/- 0.57 vs 0.86 +/- 0.26 mmol/l, p < 0.001 and 1.00 +/- 0.47 vs 0.36 +/- 0.16 mmol/l, p < 0.001, respectively) whereas HDL cholesterol and HDL2 cholesterol were lower (1.20 +/- 0.30 vs 1.43 +/- 0.22 mmol/l, p < 0.05 and 0.49 +/- 0.21 vs 0.71 +/- 0.17 mmol/l, p < 0.05, respectively). Total cholesterol, LDL cholesterol or HDL3 cholesterol did not differ between the two groups. The mean particle size of LDL was smaller in the high insulin group than in the low insulin group (258 +/- 7 vs 265 +/- 6 A, p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin resistance and abnormal albumin excretion in non-diabetic first-degree relatives of patients with NIDDM

Microalbuminuria has recently been associated with insulin resistance in both insulin-dependent and non-insulin-dependent (NIDDM) diabetes mellitus. To establish whether microalbuminuria in non-diabetic subjects as well is associated with insulin resistance and associated abnormalities in glucose and lipid metabolism, oral glucose tolerance tests were performed with measurement of urinary albumin excretion rate, lipids and lipoproteins in 582 male non-diabetic first-degree relatives of patients with NIDDM. In addition, insulin sensitivity was assessed in 20 of these subjects with the euglycaemic hyperinsulinaemic clamp technique. Abnormal albumin excretion rate (AER), defined as AER 15-200 micrograms/min, was associated with higher systolic blood pressure (p < 0.05), higher fasting glucose values (p < 0.05), lower HDL-cholesterol (p < 0.05) and lower apolipoprotein A-I (p < 0.05) concentrations than observed in subjects with normal AER. The rate of glucose metabolism was lower in subjects with abnormal compared to subjects with normal albumin excretion rate (38.0 +/- 2.8 vs 47.3 +/- 2.4 mumol.kg lean body mass-1.min-1; p = 0.028). This difference was almost completely accounted for by a reduction in non-oxidative glucose metabolism (17.7 +/- 1.9 vs 27.4 +/- 2.7 mumol.kg lean body mass-1.min-1; p = 0.010), which correlated inversely with the AER (r = -0.543; p = 0.013). These results suggest that in non-diabetic individuals genetically predisposed to NIDDM, abnormal AER is associated with insulin resistance and abnormalities in glucose and lipid metabolism.

High density lipoprotein subfractions in non-insulin-dependent diabetes mellitus and coronary artery disease

High density lipoprotein (HDL) subfractions (2b, 2a, 3a, 3b, and 3c) separated by gradient gel electrophoresis (GGE) and defined by Gaussian summation analysis, and the compositions of HDL2 and HDL3, separated by preparative ultracentrifugation, were studied in four groups of men with or without non-insulin-dependent diabetes mellitus (NIDDM) and coronary artery disease (CAD): group 1 (DM+CAD+, n = 50); group 2 (DM-CAD+, n = 50); group 3 (DM+CAD-, n = 50); and group 4 (DM-CAD-, n = 31). HDL GGE subfraction distributions, available in 125 subjects, were not significantly different among the groups. In contrast, dividing the whole study population into quartiles of serum triglyceride (TG) concentration showed that high TG levels were significantly associated with low HDL2b and high HDL3b concentrations. In a multivariate linear regression model, postheparin plasma hepatic lipase (HL) activity, and fasting serum insulin and TG concentrations were all associated independently and inversely with low HDL2b, but lipoprotein lipase or cholesteryl ester transfer protein activities were not correlated with HDL2b concentrations. Group 1 tended to have the smallest mean particle sizes in the HDL subfractions, significantly (P < 0.03, CAD vs. non-CAD) for HDL2b and for HDL2a. These differences were independent of TG, insulin and HL, but lost their significance when adjusted for beta-blocker therapy. Both HDL2 and HDL3 particles in group 1 were significantly depleted of unesterified cholesterol, and their HDL2 was TG-enriched (P = 0.053). A high HL activity, hyperinsulinemia and hypertriglyceridemia are independently associated with low levels of HDL2b and generally small HDL particle size. HDL particles in subjects with NIDDM and CAD are small-sized and have a low free cholesterol content. Both these characteristics may be markers of impaired reverse cholesterol transport.

LDL particle size in mildly hypertriglyceridemic subjects: no relation to insulin resistance or diabetes

We examined 18 Type 2 diabetic and 19 non-diabetic subjects in order to determine the association between insulin resistance and LDL particle size distribution in mildly hypertriglyceridemic and hyperinsulinemic subjects with and without Type 2 diabetes. Insulin sensitivity of the patients was characterized by their insulin-stimulated glucose uptake rate determined by euglycemic clamp technique. LDL particle size distribution was determined by nondenaturing polyacrylamide gradient gel electrophoresis. Type 2 diabetic and non-diabetic subjects had closely similar serum lipid and lipoprotein concentrations as well as the mean particle diameters of the major LDL peak (246 +/- 6 A and 244 +/- 6 A, respectively). To evaluate the effect of insulin resistance on LDL particle size the participants were categorized into two subgroups using the median of their insulin-stimulated glucose uptake rate (14.67 mumol/kg/min) as a cut-off point. Neither lipid and lipoprotein concentrations nor the LDL particle size distributions differed between the more insulin resistant group (nine diabetic and nine non-diabetic subjects) and less insulin resistant group (nine diabetic and ten non-diabetic subjects). LDL particle size was not associated with the insulin-stimulated glucose uptake rate or with the mean 24-h concentration of serum insulin. Mean 24-h concentration of serum triglycerides was the strongest discriminator for LDL particle size (r = -0.44, P < 0.01). In conclusion, neither Type 2 diabetes nor insulin resistance seem to have any direct effect on LDL particle size in mildly hypertriglyceridemic subjects. The fact that LDL particle size was associated with serum triglycerides indicates that the effect of diabetes and insulin resistance on LDL particle size could be explained by the effects of insulin resistance and/or hyperinsulinism on VLDL metabolism.

The insulin resistance syndrome in smokers is related to smoking habits

The relationship between smoking habits, insulin resistance, and related risk factors for cardiovascular disease was examined in 57 middle-aged male smokers whose degree of insulin resistance was quantified by using the euglycemic clamp technique. Smoking habits correlated with degree of insulin resistance and consequently with various manifestations of the insulin resistance syndrome including levels of insulin, high-density lipoprotein cholesterol, triglycerides, and plasminogen activator inhibitor-1 (PAI-1) activity. Smoking habits, independent of degree of insulin resistance, were also related to levels of total cholesterol and low-density lipoprotein cholesterol as well as triglycerides. Stepwise regression analyses considering the effects of age, lean body mass, body fat, body mass index, waist/hip ratio, and alcohol consumption showed that only smoking habits and percent body fat were independently related to degree of insulin resistance. This study shows that insulin resistance and the insulin resistance syndrome are important but not unique contributors to the strong risk profile for cardiovascular disease in middle-aged men who smoke.

Asymptomatic coronary artery disease in diabetes: relation to common risk factors, lipoproteins, apoproteins and apo E polymorphism

The risk factors for asymptomatic coronary artery disease (CAD) were examined in 138 diabetic patients. Following non-invasive screening examinations (exercise electrocardiography, dynamic thallium scintigraphy, 24-h electrocardiographic recording), CAD was confirmed angiographically in 21 symptom-free diabetic subjects with an ischaemic finding in at least one of the non-invasive tests. The prevalence of asymptomatic CAD in this cohort of diabetic patients was 21/132 (16%), which may be an underestimation because 6 patients refused angiography. Risk factors (age, diabetes, smoking, hypertension, serum lipoproteins, apoproteins and apo E phenotypes) were analysed according to the presence or absence of CAD. Multivariate logistic stepwise analysis did not show any definite changes of serum lipids, lipoproteins and apoproteins in type 1 (n = 72) and type 2 (n = 66) diabetic patients with or without asymptomatic CAD. The only factors associated with asymptomatic CAD were the duration of diabetes (P < 0.005) and the age of the patient (P < 0.05). These results suggest that in diabetic patients the major risk factor for premature coronary atherosclerosis is diabetes itself. Assessment of other risk factors does not seem to define any subgroup with asymptomatic CAD.

Lipoprotein(a) in type 1 diabetic patients with renal disease

Lp(a) was measured in 64 normoalbuminuric, 52 microalbuminuric, and 37 proteinuric Type 1 diabetic patients and 54 healthy subjects. Microalbuminuric and proteinuric Type 1 diabetic patients had higher median Lp(a) values (133 (16-1932) and 169 (17-1149) mg l-1) than patients with normal AER (73 (15-1078) mg l-1; p = 0.048 and p = 0.027). Lp(a) in healthy subjects (110 (15-1630)mg l-1) did not differ from the diabetic subgroups. The frequency of Lp(a) values in the upper quarter of the normal distribution was similar in the diabetic groups and did not differ between diabetic and control subjects. The cumulative distribution of Lp(a) was similar in all groups. Lp(a) concentrations were not related to AER, age, gender, duration of diabetes, body mass index, glycaemic control, serum creatinine, free insulin or systolic blood pressure. Cholesterol, LDL-cholesterol, triglycerides, and apo B were higher in microalbuminuric and proteinuric than in normoalbuminuric Type 1 diabetic patients. Lp(a) was independently related to diastolic blood pressure, fibrinogen, and macroangiopathy. In conclusion, median Lp(a) concentrations tend to be higher in Type 1 diabetic patients with early and established renal disease, although the differences are small and the overlap between groups large. Lp(a) is related to diastolic blood pressure and fibrinogen, and this association of powerful risk factors suggests that Lp(a) may play a role in the pathogenesis of cardiovascular disease in Type 1 diabetic patients with proteinuria. Whether Lp(a) is an independent determinant of increased cardiovascular risk in these patients needs to be elucidated by prospective studies.

Plasma cholesteryl ester transfer protein activity in non-insulin-dependent diabetic patients with and without coronary artery disease

The present study was designed to evaluate the potential role of plasma cholesteryl ester transfer protein (CETP) activity in the regulation of high-density lipoprotein (HDL) subclasses in non-insulin-dependent diabetes mellitus (NIDDM). We studied 45 men with NIDDM and angiographically defined coronary artery disease ([CAD] DM+CAD+, aged 54.4 +/- 6.1 years, mean +/- SD); 47 nondiabetic men with similarly proven CAD (DM-CAD+, aged 54.9 +/- 6.6 years; 43 men with NIDDM but no CAD (DM+CAD-, aged 55.2 +/- 7.3 years); and 29 nondiabetic men without CAD (DM-CAD-, aged 53.2 +/- 5.3 years). The groups were matched for age and body mass index (BMI). Plasma CETP activity was determined by measuring the ability of the plasma sample to transfer esterified cholesterol from exogenous 14C-cholesteryl ester-labeled low-density lipoprotein (LDL) to exogenous HDL. Plasma lipoproteins were separated by ultracentrifugation. The concentration of HDL cholesterol was reduced in the DM+CAD+ group as compared with the DM-CAD- group (P < .01). This change was due to a decrease of both HDL2 cholesterol (P < .05) and HDL3 cholesterol (P < .001). There was a clear-cut decrease in HDL3 cholesterol in the DM-CAD+ (P < .01) and DM+CAD- (P < .05) groups as compared with the DM-CAD- group. Plasma CETP activity was lower in the DM+CAD- group (1.06 +/- 0.24 arbitrary units [AU]) than in the DM-CAD- group (1.19 +/- 0.26 AU, P < .05). In the DM+CAD+ group, the mean of CETP activities was 1.09 AU.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of acute daytime and nocturnal insulinization on diurnal glucose homeostasis in NIDDM

OBJECTIVE

The question of whether to use insulin in the evening or in the morning during combination therapy in patients with non-insulin-dependent diabetes mellitus (NIDDM) is controversial. We compared the acute effects of 12-h nocturnal or daytime insulin infusions on the 24-h glucose profile in 20 patients with NIDDM.

RESEARCH DESIGN AND METHODS

NIDDM patients were 56 +/- 2 (mean +/- SE) years of age and had a body mass index of 29.6 +/- 1.1 kg/m2; fasting plasma glucose concentration of 12.2 +/- 0.5 mM; and fasting C-peptide concentration of 0.9 +/- 0.2 nM. Each patient was studied twice. On one occasion, the patient received a 12-h intravenous infusion of insulin (mean 1.5 +/- 0.1 IU/h) during the day, and on the other occasion an identical dose of insulin was infused during the night. Blood glucose, insulin, c-peptide, and free fatty acid concentrations were determined for 24 h.

RESULTS

The mean 24-h free insulin concentrations were similar in both studies (150 +/- 12 vs. 162 +/- 12 pM, daytime versus nocturnal insulin infusion). The mean 24-h free fatty acid concentration was 18% lower in the nocturnal than in the daytime (309 +/- 30 vs. 376 +/- 30 microM, P < 0.001) insulin infusion study. The mean 24-h C-peptide concentration was less suppressed if insulin was infused overnight than during the day (1.3 +/- 0.2 vs. 1.1 +/- 0.2 nM, P < 0.01). The mean 24-h plasma glucose concentrations were identical in both studies (11.1 +/- 0.6 vs. 11.4 +/- 0.7 mM, daytime versus nocturnal insulin infusion). We also searched for factors predicting the decrease in the blood glucose concentration during the nocturnal insulin infusion. The best predictors were a high initial blood glucose concentration at 2200 and a low fasting C-peptide concentration. These factors explained, independent of each other, 50% of the rate of decrease in the plasma glucose concentration.

CONCLUSIONS

Despite better suppression of lipolysis and less suppression of endogenous insulin secretion by nocturnal than daytime insulinization, the hypoglycemic effect of these two treatments is similar.

LDL subclasses in IDDM patients: relation to diabetic nephropathy

To answer the question whether the elevation of LDL-cholesterol in IDDM patients with incipient and established diabetic nephropathy is accompanied by changes in LDL size or composition, we studied distribution of LDL particles in 57 normoalbuminuric [AER 7 (1-9) micrograms/min, median and range], in 46 microalbuminuric [AER 50 (20-192) micrograms/min] and in 33 proteinuric [AER 422 (233-1756) micrograms/min] IDDM patients as well as in 49 non-diabetic control subjects with normoalbuminuria. The three diabetic groups were matched for duration of diabetes and glycaemic control. The mean particle diameter of the major LDL peak was determined by nondenaturing gradient gel electrophoresis. Composition and density distribution of LDL were determined in the subgroups of each patient group by density gradient ultracentrifugation. Normoalbuminuric IDDM patients had larger LDL particles than non-diabetic control subjects (260 A vs 254 A, p < 0.05). LDL particle diameter was inversely correlated with serum triglycerides in all groups (p < 0.05 for normoalbuminuric and p < 0.001 for other groups). Triglyceride content of LDL was higher in three IDDM groups compared to control group (p < 0.05). The elevation of LDL mass in microalbuminuric and proteinuric IDDM groups compared to normoalbuminuric IDDM group (p < 0.05 for both) was mainly due to the increment of light LDL (density 1.0212-1.0343 g/ml). There were no significant changes in the density distribution or composition of LDL between the three diabetic groups. In conclusion the increase of LDL mass without major compositional changes suggests that the elevation of LDL in incipient and established diabetic nephropathy is primarily due to the increased number of LDL particles.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma cholesteryl ester transfer protein and its relationship to plasma lipoproteins and apolipoprotein A-I-containing lipoproteins in IDDM patients with microalbuminuria and clinical nephropathy

OBJECTIVE

To study the distribution of high-density lipoprotein (HDL) subclasses in insulin-dependent diabetes mellitus (IDDM) patients with nephropathy and factors involved in the regulation of HDL, including plasma cholesteryl ester transfer protein (CETP) and postheparin plasma lipoprotein lipase (LPL) and hepatic lipase (HL) activities.

RESEARCH DESIGN AND METHODS

Participants included 52 microalbuminuric IDDM patients (with a urinary albumin excretion rate [UAER] of 20-200 micrograms/min), 37 macroalbuminuric IDDM patients (UAER > 200 micrograms/min), and 64 normoalbuminuric IDDM patients (UAER < 20 micrograms/min). Groups were matched for age, body mass index, duration of diabetes, and glycemic control (HbA1).

RESULTS

Median concentrations of HDL and HDL2 cholesterol were 11.6 (P = 0.01) and 22.7% (P = 0.01) less in microalbuminuric patients and 5.1 and 15.5% less in macroalbuminuric patients compared with normoalbuminuric patients. No significant differences were observed in the concentrations of apoA-I, apoA-II (apolipoprotein) or LpA-I or LpA-I:A-II (lipoprotein) particles between the groups. HDL cholesterol: apoA-I+apoA-II ratio was significantly lower in micro- (19.7 +/- 4.2 (+/- SD); P < 0.01) and macroalbuminuric patients (20.0 +/- 3.7, P < 0.05) than in normoalbuminuric patients (22.1 +/- 4.4). Postheparin plasma LPL:HL ratio was lower in microalbuminuric patients compared with normoalbuminuric patients (1.65 vs. 1.05 [median], P < 0.01). Plasma CETP activity was higher in the macroalbuminuric patients than in micro- (P < 0.05) and normoalbuminuric patients (P < 0.05) but did not correlate with HDL, HDL2, or HDL3 cholesterol. LPL:HL ratio correlated positively with HDL cholesterol (r = 0.372, P < 0.001), HDL2 cholesterol (r = 0.413, P < 0.001) and with LpA-I particles (r = 0.355, P < 0.001) but not with LpA-I:A-II particles (r = -0.065, NS).

CONCLUSIONS

IDDM patients with micro- and macroalbuminuria show only trivial changes in concentrations of different HDL parameters, which cannot explain the excess risk of coronary heart disease in these patients. Data also indicate that elevation of CETP activity in IDDM patients with nephropathy is probably not responsible for the lowering of HDL cholesterol.

Short-term effects of renal transplantation on plasma lipids and lipoprotein lipase in children with congenital nephrosis

Plasma lipoprotein and apoprotein (apo) A-I, A-II and B concentrations and post-heparin plasma lipoprotein lipase (LPL) activity and mass were measured in 13 children with congenital nephrotic syndrome of the Finnish type (CNF) six months after renal transplantation to determine whether the severe lipid abnormalities documented prior to and during peritoneal dialysis would normalize. Plasma total triglyceride decreased by 52% (p < 0.001), VLDL triglyceride by 55% (p < 0.01) and total cholesterol by 17% (p < 0.01). HDL cholesterol increased by 51% (p < 0.001), whereas no significant change was observed in LDL cholesterol. Despite these improvements, plasma lipoprotein concentrations were still abnormal after transplantation. Total (p < 0.01) and VLDL triglyceride (p < 0.05) as well as total (p < 0.01), VLDL (p < 0.01) and LDL cholesterol (p < 0.01) were higher than in control children. HDL cholesterol normalized. Plasma apo A-I and A-II concentrations were normal, but the apo B concentration remained high (p < 0.01). Post-heparin LPL activity and mass were normal (25.0 +/- 9.1 mumol FFA/ml/h and 227.2 +/- 88.4 ng/ml). The mean cyclosporine dose correlated positively with the serum creatinine concentration (r = +0.72, p < 0.01). Positive correlations were also observed between total (r = +0.68, p < 0.05) and VLDL triglyceride (r = +0.62, p < 0.05) and the serum creatinine concentrations. We conclude that renal transplantation substantially improves the triglyceride and cholesterol abnormalities in CNF but significant abnormalities still persist.

The effect of an antilipolytic agent (acipimox) on the insulin resistance of lipid and glucose metabolism in hypertriglyceridaemic patients

Hypertriglyceridaemia is associated with insulin resistance of both lipid and glucose metabolism. It is not known whether the insulin resistance affects both glucose oxidation and glycogen formation. To study the oxidative and non-oxidative pathways of non-esterified fatty acids (NEFA) and glucose metabolism, eight male hypertriglyceridaemic subjects were studied during insulin infusion (75 and 340 pmol/m2.min) in combination with indirect calorimetry and infusions of [3-3H]glucose and [1-14C]palmitate before and after 4 weeks of treatment with the antilipolytic agent acipimox (250 mg three times daily). Compared with eight healthy subjects the hypertriglyceridaemic subjects were resistant to the antilipolytic effect of insulin, both in the basal state (P < 0.05) and during insulin infusion (P < 0.05). This was associated with impaired insulin-stimulated glucose uptake (P < 0.05), predominantly in the non-oxidative pathway (P < 0.05). Acipimox decreased basal NEFA concentrations (P < 0.01) and reduced lipid oxidation during low-dose insulin infusion (P < 0.05). Glucose uptake, predominantly glycogen formation, was stimulated by acipimox (P < 0.05). In conclusion, the insulin resistance of glucose metabolism associated with hypertriglyceridaemia is largely due to a defect in non-oxidative glucose metabolism. Acipimox improves glucose metabolism both by affecting glucose oxidation (low-dose insulin) and non-oxidative glucose metabolism (high-dose insulin).

A novel amino acid substitution (His183-->Gln) in exon 5 of the lipoprotein lipase gene results in loss of catalytic activity: phenotypic expression of the mutant gene in a heterozygous state

We have identified a hitherto unrecognized mutation of the lipoprotein lipase gene (LPL) in a Finnish family with Russian and Swiss ancestors. A single base pair substitution of a guanine for cytosine in codon 183 of exon 5 of the LPL gene results in a change of histidine to glutamine in the mature enzyme protein. Expression of a mutant cDNA construct in COS cells resulted in secretion of inactive LPL enzyme protein confirming the functional significance of the mutation. The proband, a 50-year-old female and her two daughters were all heterozygous for the His183-->Gln mutation. Clinically, the proband was characterized by variable and occasionally severe hypertriglyceridemia, obesity, hypertension, coronary heart disease and non-insulin-dependent diabetes mellitus. The daughters, aged 24 and 19 years, were also obese but had milder hypertriglyceridemia. In conclusion, we have identified a novel LPL mutation that results in the synthesis of an inactive enzyme protein. Although the assessment of a causative link between the mutation and hyperlipidemia awaits further studies, our data suggest that heterozygosity for a functional defect of LPL should be considered in patients presenting with the metabolic dyslipidemic syndrome, "syndrome-X."

Pathology of renal arteries of dyslipidemic children with congenital nephrosis

Congenital nephrotic syndrome of the Finnish type (CNF) is well characterized in infants and associated with major lipid risk factors for atherosclerosis. This study was undertaken to investigate if any arterial pathology is present in children with CNF and, if so, to describe its nature in renal arteries collected at nephrectomy at a mean age of 12.5 +/- 4.4 months. Denuded endothelial injury and intimal thickening were seen in 9 out of 10 patient specimens of renal arteries. Intimal thickening contained loose abundant extracellular matrix with a few smooth muscle or myofibroblastoid cells. Only a few Sudan black- or oil red O-positive lipid droplets were found in six and seven samples, respectively. Areas immunoreactive with antibodies against apoprotein B were seen in only two specimens. Immunohistochemistry did not reveal any activated T or B cells, or any expression of IL-1 or IL-2 receptors. Macrophages were present in only two specimens. No foam cells were seen. We conclude that the vascular pathology together with altered lipoprotein metabolism indicates that children with CNF might be at risk for early atherosclerotic arterial disease, particularly if their hyperlipidemia persists.