Abnormalities of VLDL, IDL, and LDL characterize insulin-dependent diabetes mellitus

Nigerian Honey Ameliorates Hyperglycemia and Dyslipidemia in Alloxan-Induced Diabetic Rats

Diabetic dyslipidemia contributes to an increased risk of cardiovascular disease. Hence, its treatment is necessary to reduce cardiovascular events. Honey reduces hyperglycemia and dyslipidemia. The reproducibility of these beneficial effects and their generalization to honey samples of other geographical parts of the world remain controversial. Currently, data are limited and findings are inconclusive especially with evidence showing honey increased glycosylated hemoglobin in diabetic patients. It was hypothesized that this deteriorating effect might be due to administered high doses. This study investigated if Nigerian honey could ameliorate hyperglycemia and hyperlipidemia. It also evaluated if high doses of honey could worsen glucose and lipid abnormalities. Honey (1.0, 2.0 or 3.0 g/kg) was administered to diabetic rats for three weeks. Honey (1.0 or 2.0 g/kg) significantly (p < 0.05) increased high density lipoprotein (HDL) cholesterol while it significantly (p < 0.05) reduced hyperglycemia, triglycerides (TGs), very low density lipoprotein (VLDL) cholesterol, non-HDL cholesterol, coronary risk index (CRI) and cardiovascular risk index (CVRI). In contrast, honey (3.0 g/kg) significantly (p < 0.05) reduced TGs and VLDL cholesterol. This study confirms the reproducibility of glucose lowering and hypolipidemic effects of honey using Nigerian honey. However, none of the doses deteriorated hyperglycemia and dyslipidemia.

Implications of serum paraoxonase activity in obesity, diabetes mellitus, and dyslipidemia

Human serum paraoxonase 1 (PON1) is an enzyme with esterase activity, and is physically bound to high-density lipoproteins (HDL). It plays a key role in the action of HDL toward protection of lipoprotein and biological membrane against oxidative damage. It may have a protective role against atherosclerosis by virtue of its action on hydrolyzing lipid peroxides and preventing accumulation of phospholipids in oxidized low-density lipoprotein (LDL). PON1 is hypothesized to be an indicator of the risk of atherosclerosis and coronary artery disease development. Numerous studies have implicated PON1 activity in relation to various endocrine disorders. The current article reviews the clinical perspectives of PON1 activity with regards to obesity, diabetes mellitus with its complications, and dyslipidemia.

PKCδ signalling regulates SR-A and CD36 expression and foam cell formation

AIMS

The formation of foam cells is crucial in the initiation and progression of atherosclerosis. One of the critical steps in foam cell formation is the uptake of low-density lipoprotein (LDL) by macrophages via scavenger receptors (SRs). This study examined the role of protein kinase C (PKC) isoforms on foam cell formation.

METHODS AND RESULTS

The effects of short-hairpin RNA (shRNA) and small interfering RNA (siRNA) against classical PKC and novel PKC isoforms were investigated in THP-1-derived macrophages and primary macrophages. The knockdown of PKCδ inhibited oxidized LDL (OxLDL) uptake and intracellular cholesterol accumulation in both cell models. The reduction of PKCδ resulted in decreased expression of SR-A and CD36. Similar conclusions were obtained in examining the effects of a PKCδ inhibitor, rottlerin. Molecular investigation revealed that a decrease in PKCδ inhibited protein kinase B (PKB/Akt) expression and extracellular-signal-regulated kinase (ERK) phosphorylation. Surprisingly, PKCδ-knockdown selectively decreased protein but not the mRNA level of PKCβI and PKCβII. We showed that the inhibition of phosphatidylinositol 3-kinase (PI3K)/Akt upstream of ERK decreased SR-A and CD36 expression; however, the inhibition of ERK or PKCβ downstream of ERK attenuated SR-A but not CD36 expression. We further demonstrated that PKCδ could be induced by pro-atherogenic mediators, OxLDL and interferon-γ. Notably, PKCδ, phosphorylated ERK, Akt, and SR-A were highly expressed in human atherosclerotic arteries and CD68-positive macrophages as visualized by immunohistochemical staining.

CONCLUSION

Through regulating PI3K/Akt and ERK activity, PKCδ affects SR-A and CD36 expression and foam cell formation. The results suggest PKCδ as a potential target for atherosclerosis therapeutics.

Hypercholesterolemic LDL receptor-deficient mice mount a neutrophilic response to tuberculosis despite the timely expression of protective immunity

The prevalence of hypercholesterolemia is rising in industrialized and developing countries. We reported previously that host defense against Mtb was impaired by hypercholesterolemia in ApoE(-/-) mice, raising the possibility that people with HC could be more vulnerable to TB. The present study examined whether TB immunity was similarly impaired in a different hypercholesterolemic model, LDL-R(-/-) mice, which developed comparable elevation of total serum cholesterol as ApoE(-/-)mice when fed HC or LC diets. Like ApoE(-/-) mice, LDL-R(-/-) mice had an exaggerated lung inflammatory response to Mtb with increased tissue necrosis. Inflammation, foamy macrophage formation, and tissue necrosis in LDL-R(-/-) mice increased with the degree of hypercholesterolemia. Unlike ApoE(-/-) mice, LDL-R(-/-) mice fed a HC diet mounted a timely and protective adaptive immune response that restricted mycobacterial replication comparably with WT mice. Thus, ApoE(-/-) and LDL-R(-/-) mice share a cholesterol-dependent hyperinflammatory TB phenotype but do not share the impairment of adaptive immunity found in ApoE(-/-) mice. The impact of hypercholesterolemia on TB immunity is more complex than appreciated by total cholesterol alone, possibly reflecting the different functional effect of specific lipoprotein particles.

Glibenclamide or metformin combined with honey improves glycemic control in streptozotocin-induced diabetic rats

Diabetes mellitus is associated with deterioration of glycemic control and progressive metabolic derangements. This study investigated the effect of honey as an adjunct to glibenclamide or metformin on glycemic control in streptozotocin-induced diabetic rats. Diabetes was induced in rats by streptozotocin. The diabetic rats were randomized into six groups and administered distilled water, honey, glibenclamide, glibenclamide and honey, metformin or metformin and honey. The animals were treated orally once daily for four weeks. The diabetic control rats showed hypoinsulinemia (0.27 ± 0.01 ng/ml), hyperglycemia (22.4 ± 1.0 mmol/L) and increased fructosamine (360.0 ± 15.6 µmol/L). Honey significantly increased insulin (0.41 ± 0.06 ng/ml), decreased hyperglycemia (12.3 ± 3.1 mmol/L) and fructosamine (304.5 ± 10.1 µmol/L). Although glibenclamide or metformin alone significantly (p < 0.05) reduced hyperglycemia, glibenclamide or metformin combined with honey produced significantly much lower blood glucose (8.8 ± 2.9 or 9.9 ± 3.3 mmol/L, respectively) compared to glibenclamide or metformin alone (13.9 ± 3.4 or 13.2 ± 2.9 mmol/L, respectively). Similarly, glibenclamide or metformin combined with honey produced significantly (p < 0.05) lower fructosamine levels (301.3 ± 19.5 or 285.8 ± 22.6 µmol/L, respectively) whereas glibenclamide or metformin alone did not decrease fructosamine (330.0 ± 29.9 or 314.6 ± 17.9 µmol/L, respectively). Besides, these drugs or their combination with honey increased insulin levels. Glibenclamide or metformin combined with honey also significantly reduced the elevated levels of creatinine, bilirubin, triglycerides, and VLDL cholesterol. These results indicate that combination of glibenclamide or metformin with honey improves glycemic control, and provides additional metabolic benefits, not achieved with either glibenclamide or metformin alone.

Cholesterol metabolism and non-cholesterol sterol distribution in lipoproteins of type 1 diabetes: The effect of improved glycemic control

In type 1 diabetes, the ratios to cholesterol of serum absorption markers, e.g., cholestanol, are elevated and those of synthesis markers, e.g., lathosterol, are reduced suggesting perturbed cholesterol metabolism. We studied 17 subjects with type 1 diabetes in poor glycemic control at baseline to assess whether improvement of glycemic control affects lathosterol and cholestanol ratios to cholesterol and their distribution in lipoproteins. Cholesterol and the non-cholesterol sterols were assayed directly from serum, and free and ester fractions after thin-layer chromatographic separation of lipoprotein sterols with gas-liquid chromatography. After the 2-6 months follow-up, the mean value of HbA1(c) decreased from 10.8% to 8.6% (p=0.001). Even though the concentrations of serum and lipoprotein cholesterol remained unchanged, the serum lathosterol to cholesterol ratio increased by 28% (p<0.05) and the lathosterol/cholestanol proportion by 23% (p<0.05). The ratios of total and esterified lathosterol to cholesterol in serum, chylomicrons and LDL, and free lathosterol to cholesterol in serum and IDL, were negatively associated with HbA1(c) at baseline and after follow-up, suggesting that the better glycemic control, the higher was cholesterol synthesis. The absorption markers were less consistently associated with HbA1(c). About half of the serum lathosterol and cholestanol was carried in LDL and one-fourth to one-fifth in HDL, but the lathosterol ratios were roughly similar in all lipoproteins. In contrast, cholestanol accumulated in chylomicrons and HDL. Glycemic control did not affect the distributions of lathosterol and cholestanol. In conclusion, improvement in glycemic control increased cholesterol synthesis, but had no effect on cholesterol absorption as measured by the serum or lipoprotein cholestanol to cholesterol ratio. From a clinical point of view, the better the glycemic control, the more antiatherogenic cholesterol metabolism may be in type 1 diabetes.

Systemic inflammation and metabolic syndrome in cardiac allograft vasculopathy

BACKGROUND

Metabolic syndrome and elevation of inflammatory markers is common in transplant recipients. We investigated the role of insulin resistance and C-reactive protein (CRP) in predicting development of angiographic cardiac allograft vasculopathy (CAV).

METHODS

CRP and lipid profile were measured in 114 cardiac transplant recipients at 4.7 +/- 3.1 years post-transplant. A triglyceride/high-density lipoprotein cholesterol (TG/HDL) ratio of >or=3 was considered a marker of insulin resistance. Ninety-seven patients (mean age +/- SD: 48.2 +/- 16.7 years) subsequently underwent routine coronary angiography at 8.6 +/- 3.2 years post-transplantation. Diagnosis of CAV required the presence of stenosis of >or=40% in any major branch, and/or distal pruning of secondary side branches. Coronary artery stenosis >or=70% was defined as severe.

RESULTS

Eighty-one percent of patients were treated with statins. Low-density lipoprotein (LDL)-cholesterol level was 98 +/- 26 mg/dl at study entry. CRP and TG/HDL were found to be predictors of development of CAV. CAV severity correlated with TG/HDL (p < 0.005), but not with CRP level. Freedom from CAV 5 years after study entry was 9% in patients with TG/HDL >3, CRP >3 mg/liter, as compared with 65% in patients with TG/HDL <3, CRP <3 mg/liter (p = 0.003). The combination of CRP >3 mg/liter and TG/HDL >3 identified a sub-group of patients having a 2.8-fold increased odds ratio for a combined end-point of cardiovascular (CV) events (percutaneous coronary intervention, coronary artery bypass graft, left ventricular ejection fraction <45%) and death (95% confidence interval 0.90 to 8.45, p = 0.07) compared to patients with CRP <3 mg/liter and TG/HDL <3.

CONCLUSIONS

CRP >3 mg/liter and TG/HDL >3 are cumulative risk factors for angiographic CAV and the combined end-point of CV events and death in transplant patients and these patients should be targeted for intervention.

Normal metabolism of apolipoprotein B100-containing lipoproteins despite qualitative abnormalities in type 1 diabetic men

AIMS/HYPOTHESIS

Type 1 diabetic subjects are at increased risk of cardiovascular disease and exhibit multiple qualitative abnormalities of apolipoprotein (apo) B100-containing lipoproteins. This stable isotope kinetic experiment was designed to study whether these abnormalities are associated with changes in the synthesis and fractional catabolic rates of VLDL-, IDL- and LDL-apoB100.

METHODS

Using a bolus followed by a 16-h constant infusion of 13C-leucine, we performed a kinetic study in eight men with type 1 diabetes treated with a continuous subcutaneous insulin infusion administered by an external pump and in seven healthy men, in the fed state.

RESULTS

The mean HbA1c level in the type 1 diabetic patients was 8.00+/-1.48%. Plasma triglyceride, and total, LDL and HDL cholesterol levels were similar in patients and control subjects. VLDL were less triglyceride rich in type 1 diabetic patients than in control subjects (VLDL triglyceride : apoB 6.91+/-0.81 vs 8.29+/-1.24 mmol/g, p=0.05). Conversely, the IDL and LDL of the type 1 diabetic patients contained relatively higher levels of triglycerides (IDL triglycerides : apoB 2.16+/-0.36 vs 1.57+/-0.30 mmol/g, p<0.01; LDL triglycerides : apoB 0.27+/-0.06 vs 0.16+/-0.04 mmol/g, p<0.05). The apoB100 pool size, production and fractional catabolic rates in the two groups of subjects were similar for all lipoprotein fractions.

CONCLUSIONS/INTERPRETATION

Despite qualitative abnormalities, especially abnormalities of triglyceride content, the metabolism of apoB100-containing lipoproteins is not altered in type 1 diabetic men with fair glycaemic control with continuous subcutaneous insulin infusion. The high risk of atherosclerosis in these patients cannot be explained by kinetic abnormalities of apoB100-containing lipoproteins.

Short term effects of L-carnitine on serum lipids in STZ-induced diabetic rats

The aim of this study was to evaluate the effects of L-carnitine supplementation on serum triglyceride and total cholesterol levels in streptozotocin (STZ)-induced diabetic rats. Thirty-two male Wistar rats were divided into diabetic and diabetic-L-carnitine-supplemented groups. Diabetes was induced by injection of a single dose of streptozotocin (40 mg/kg, intraperitoneally) in citrate buffer. L-Carnitine was supplemented by IM injection of 100 mg/kg per day for 10 days. Serum glucose, triglyceride and total cholesterol levels were determined at days 0, 5 and 10. Rats receiving L-carnitine had lower triglyceride levels at both days 5 and 10 (P < 0.05). Total cholesterol levels in the carnitine-supplemented group were lower, but statistical significance was achieved only at day 10 (P < 0.05). These results suggest that L-carnitine exhibits hypotriglyceridemic and hypocholesterolemic effects in streptozotocin-induced diabetic rats. Clinical trials of L-carnitine supplementation on patients with diabetes induced hyperlipidemia must be further evaluated.

Expression of interleukin-1 beta and interleukin-1 receptor antagonist in oxLDL-treated human aortic smooth muscle cells and in the neointima of cholesterol-fed endothelia-denuded rabbits

The migration of vascular smooth muscle cells (VSMCs) from the media to the intima and the proliferation of intimal VSMCs are key events in restenotic lesion development. These events, which are preceded and accompanied by inflammation, are modulated by the proinflammatory cytokine, interleukin-1 beta (IL-1 beta), which induces vascular smooth muscle cells to express adhesion molecules and to proliferate. IL-1 beta action is complex and regulated, in part, by its naturally occurring inhibitor, the IL-1 receptor antagonist (IL-1ra). Whether there was a temporal and spatial correlation between IL-1 beta and IL-1ra expression in, and release by, oxidized low density lipoproteins (oxLDL)-stimulated human aortic smooth muscle cells (HASMCs) was determined by using ELISA and Western blot. In addition, IL-1 beta and IL-1ra expression was detected in the neointima of endothelia-denuded cholesterol-fed New Zealand white rabbits by immunohistochemistry and Western blot. In HASMCs, oxLDL induced IL-beta and IL-1ra expression and release in a dose- and time-dependent manner. Treatment with 20 microg/ml oxLDL resulted in increased IL-1 beta release after 6 h, which peaked at 24 h, and in increased IL-1ra release, first seen after 12 h, but continuing to increase for at least 48 h. In the cells, IL-beta expression showed a similar pattern to release, whereas IL-1ra expression was seen in unstimulated cells and was not increased by oxLDL treatment. Confocal microscopy showed colocalization of IL-beta and IL-1ra expression in oxLDL-stimulated HASMCs. oxLDL caused significant induction of nuclear factor kappa B and activator protein-1 DNA binding activity in HASMCs (6.6- and 3.3-fold, respectively). In cholesterol-fed endothelia-denuded rabbits, the notably thickened intima showed significant IL-1 beta and IL-1ra expression. These results provide further support for the role of IL-1 system in the pathogenesis of restenosis. This is the first demonstration of IL-1 beta and IL-1ra expression and secretion of oxLDL-treated HASMCs and their expression in the rabbit neointima, suggesting that the smooth muscle cells of the intima are an important source of these factors.

Rates of cholesterol esterification and esterified cholesterol net mass transfer between high-density lipoproteins and apolipoprotein B-containing lipoproteins in Type 1 diabetes

AIMS

Type 1 diabetes is associated with a high incidence of coronary heart disease (CHD) despite paradoxically normal or high high-density lipoprotein (HDL) cholesterol concentrations. Triglyceride (TG) concentrations have been shown to be important determinants of two aspects of HDL metabolism: cholesterol esterification rate and esterified cholesterol (EC) net mass transfer rate between HDL and the apolipoprotein B-containing lipoproteins. In order to try to explain the paradox, we aimed to assess the relationships between plasma TG and these two processes in Type 1 diabetic compared with non-diabetic subjects.

METHODS

Rates of cholesterol esterification and EC net mass transfer between HDL and the apolipoprotein B-containing lipoproteins were assessed by incubating whole plasma at 37 degrees C; intra-assay coefficients of variation were 6% and 30%, respectively.

RESULTS

Ten Type 1 diabetic and 10 non-diabetic subjects, with similar ages, sex distributions, body mass indices and total cholesterol and TG concentrations, were assessed. Apolipoprotein A1, HDL unesterified cholesterol, and HDL phospholipid concentrations were greater in the Type 1 diabetic subjects. There were no significant differences in the rates of cholesterol esterification or EC net mass transfer between the groups. There were strong associations between plasma TG and the rate of cholesterol esterification and between plasma TG and the rate of EC net mass transfer in Type 1 diabetic subjects (r = 0.83, P = 0.0027 and r = 0.88, P = 0.0009, respectively) and in non-diabetic subjects (r = 0.91, P = 0.0002 and r = 0.79, P = 0.0070, respectively). However, the slopes of the associations with plasma TG were significantly steeper in the Type 1 diabetic subjects (analyses of covariance P = 0.0053 and P = 0.0146, respectively).

CONCLUSIONS

Increases in TG may therefore promote more EC enrichment of atherogenic apolipoprotein B-containing lipoproteins in Type 1 diabetes while also promoting more cholesterol esterification, thereby maintaining HDL cholesterol concentrations. This could contribute to the paradox of high CHD incidence despite normal or high HDL cholesterol concentrations in Type 1 diabetes.

Vanadyl as a catalyst of human lipoprotein oxidation

Lipoprotein oxidation, which is relevant to atherogenesis, can be induced by redox-active transition metals, such as copper. Vanadium is a metal usually used as vanadyl to improve metabolic control in diabetic patients; given its redox-active properties, we have investigated possible oxidative effects of the metal on lipoproteins from healthy and diabetic subjects. Beginning from 10 microM, vanadyl, but not vanadate, induced oxidation of the non-HDL fraction, which was inhibited by EDTA, butylated hydroxytoluene and Vitamins E and C, but not by mannitol, SOD and catalase. Differently from copper, vanadyl could oxidize directly lipoprotein lipids, although it showed a lower oxidant activity against critical tryptophan residues of the lipoprotein protein moiety. Moreover, the non-HDL fraction of diabetic patients was more susceptible to vanadyl-dependent oxidation than that of controls. Thus, vanadium, in its reduced form which may be used in humans, can oxidize the non-HDL fraction through oxidative effects exerted especially on lipoprotein lipids; the specific pro-oxidant activity of vanadyl is more evident with lipoproteins of diabetic patients. Given also the tissue accumulating capacity of vanadium conceivably in a reduced form, its prolonged administration to humans, especially to diabetic patients without adequate antioxidant supplementation, needs caution.

Lipid transfer protein activities in type 1 diabetic patients without renal failure and nondiabetic control subjects and their association with coronary artery calcification

This study examined the role of cholesteryl ester transfer (CET), cholesteryl ester transfer protein (CETP) activity, and phospholipid transfer protein (PLTP) activity in the increased prevalence of coronary artery calcification (CAC) in diabetic subjects compared with nondiabetic subjects and in the loss of the sex difference in CAC in diabetes. CETP activity, PLTP activity, and CET were measured in 195 type 1 diabetic subjects without renal failure and 194 nondiabetic control subjects of similar age (30-55 years) and sex distribution (50% female). CAC was quantified with electron beam computed tomography. CETP activity was higher in diabetic subjects (mean 84 arbitrary units [AU]) than in nondiabetic subjects (80 AU, P = 0.028). PLTP activity was also higher in diabetic subjects (96 AU) than in nondiabetic subjects (81 AU, P < 0.001). However, CET was lower in diabetic men (geometric mean 32 nmol. ml(-1).h(-1)) than nondiabetic men (37 nmol.ml(-1).h(-1), P = 0.004) and did not differ between diabetic (30 nmol. ml(-1).h(-1)) and nondiabetic (32 nmol.ml(-1).h(-1), P = 0.3) women. CETP and PLTP activities were not associated with CAC. CET was positively associated with CAC in both diabetic and nondiabetic subjects (odds ratio per 10 nmol.ml(-1).h(-1) increase in CET in all subjects = 1.4, P = 0.001). The prevalence of CAC was similar in diabetic (51%) and nondiabetic (54%, P = 0.7) men but was much higher in diabetic (47%) than nondiabetic (21%, odds ratio 3.6, P < 0.001) women so that there was no sex difference in CAC in diabetic subjects. The odds of CAC in diabetic women compared with nondiabetic women was altered little by adjustment for CETP activity, PLTP activity, or CET (odds ratio on adjustment 3.7, P < 0.001). The greater effect of diabetes on CAC in women than in men, i.e., the loss of the sex difference in CAC, was independent of CETP and PLTP activity and CET. In conclusion, among both diabetic and nondiabetic subjects, higher cholesteryl ester transfer is a risk factor for CAC. However, abnormalities in cholesteryl ester transfer or lipid transfer protein activities do not underlie the increased CAC risk in diabetic women compared with nondiabetic women or the loss of the sex difference in CAC in diabetes.

Effect of acute exogenous hyperinsulinaemia on very low density lipoprotein subfraction composition in normal subjects

Subtle abnormalities of very-low-density lipoprotein (VLDL) composition and distribution seem to be associated with increased cardiovascular risk. The aims of this study were first, to evaluate whether hyperinsulinaemia per se is able to produce VLDL abnormalities and second, whether this occurs through a stimulation of lipolytic enzymes. Eight normal male volunteers, age 36 +/- 7 years (M +/- SD), body mass index (BMI) 26+/-3 kg m-2, underwent a 5-h euglycaemic hyperinsulinaemic clamp (1.2 mU insulin/kg b.w. min-1). Nine sex, age and BMI comparable subjects underwent control experiments (saline infusion). Three VLDL subfractions of decreasing size were isolated by density gradient ultracentrifugation; lipoprotein lipase (LPL) and hepatic lipase (HL) post-heparin plasma activities were determined by the 3H-labelled triolein method. Hyperinsulinaemia ( approximately 65 mU mL-1) produced the expected plasma free fatty acid suppression. Triglyceride levels were reduced in total VLDL (- 27 +/- 32% vs. + 38 +/- 52% after saline, P < 0.05) and in the larger VLDL (- 56 +/- 19 vs. + 34 +/- 38, P < 0.001). Moreover the relative contribution of the larger subfraction was decreased (- 39 +/- 15% vs. - 3 +/- 21%, P < 0.01), while the percentage of smaller particles was increased (+17 +/- 20 vs. - 9 +/- 22, P < 0.05). LPL and HL activities were decreased to the same degree during either insulin or saline infusion. Exogenous hyperinsulinaemia produced lipoprotein abnormalities partially similar to those previously shown in type 1 diabetic patients, indicating that these abnormalities may be secondary to insulin therapy.

Intensive lipid-lowering strategy in patients with diabetes mellitus

AIMS

To assess the feasibility of an intensive lipid-lowering strategy in diabetic subjects pursuing target plasma lipid levels.

METHODS

Patients with diabetes mellitus (DM), Type 1 or 2, with plasma lipid levels exceeding target values (LDL-cholesterol <2.6 mmol/l, triglycerides < 1.7 mmol/l, HDL-cholesterol > 0.9 mmol/l for men and > 1.1 mmol/l for women) were eligible. After 6-12 weeks of diet and glycaemic control, lipid-lowering medication (simvastatin/gemfibrozil/acipimox) was prescribed in steps of incremental dosages and combinations for 30 weeks.

RESULTS

Of all eligible clinic patients, 25% initially responded and finally 12% were entered. Thirty-six patients with Type 1 and 59 with Type 2 DM were studied. Mean baseline lipid levels in Type 1 and Type 2 diabetic subjects were: LDL-cholesterol 3.6 and 3.7 mmol/l, triglycerides 1.7 and 2.2 mmol/l, HDL-cholesterol for men 1.1 and 1.0 mmol/l, and for women 1.4 and 1.2 mmol/l, respectively. All three target values were reached in 66% of the patients. LDL-cholesterol was reduced by 1.2 mmol/l in Type 1 and 1.3 mmol/l in Type 2 diabetic patients and triglycerides by 0.7 mmol/l and 1.1 mmol/l, respectively. HDL-cholesterol increased by 0.15 mmol/l and 0.34 mmol/l in men and women with Type 1 diabetes mellitus, respectively. The cholesterol-triglyceride ratio decreased significantly in VLDL in Type 1 diabetes and in IDL in Type 2 diabetes and increased significantly in HDL in Type 2 DM.

CONCLUSIONS

A minority of subjects eligible for intensive lipid lowering agreed to participate in a feasibility study, suggesting a potentially large compliance problem for a general lipid-lowering programme in a diabetes clinic. Nevertheless, intensive lipid lowering with drug combinations can attain the recommended target lipid levels in 66% of subjects with diabetes. With this strategy the plasma lipoprotein composition shifts towards a less atherogenic profile. Subjects with diabetes should therefore receive lipid-lowering therapy tailored to reach target levels, rather than standard dosages, in order to reduce atherogenic risk.

Effects of a short-acting insulin analog (Insulin Lispro) versus regular insulin on lipid metabolism in insulin-dependent diabetes mellitus

Insulin Lispro (IL) is a short-acting insulin analog that better reproduces the physiological postprandial insulin profile. The aim of this study was to compare the effects of intensive insulin therapy on lipid metabolism using preprandial IL and regular insulin (RI) in 10 insulin-dependent diabetes mellitus (IDDM) subjects. The mean hemoglobin A1c (HbA1c) at baseline was 7.13% +/- 1.2% and did not change after both treatments. In IDDM patients, total cholesterol and triglyceride levels appeared lower after RI than after IL. The low-density lipoprotein (LDL) to high-density lipoprotein (HDL) ratio significantly decreased only after RI (baseline, 2.01 +/- 0.6; IL, 1.88 +/- 0.6; RI, 1.71 +/- 0.5, P < .05). Although no very-low-density lipoprotein (VLDL) composition abnormalities were observed at baseline, the protein content was lower (P < .05) after IL (8.13% +/- 2.93%) than after RI (11.93% +/- 3.41%). Intermediate-density lipoprotein (IDL) protein depletion at baseline (6.14% +/- 6.84%) was normalized after both treatments (IL, 11.09% +/- 12.14%; RI, 10.38% +/- 16.68%, P < .05). LDL, HDL, HDL2, and HDL3 composition abnormalities were similar after both treatments and did not normalize. IDDM and control subjects showed similar LDL subfraction distribution at baseline and after both treatments. Two-hour postprandial VLDL composition alterations, although improved after RI, completely normalized after IL (P < .05). Lipoprotein lipase (LPL) and cholesteryl ester transfer protein (CETP) activities were similar to the control group and did not change after both treatments. Hepatic lipase (HL) activity was lower in diabetic patients (39.6 +/- 35.2 v 87.0 +/- 27.1 U/L, P < .01) and remained lower after both treatments. In conclusion, in IDDM patients, IL (injected immediately before the meal) may offer small different effects on lipoprotein metabolism versus RI (injected 30 minutes before the meal) that, taken together, do not seem relevant.

Lipoprotein compositional abnormalities in type I diabetes: effect of improved glycaemic control

Major lipoprotein mass and composition were assessed in 45 subjects with insulin dependent diabetes mellitus (IDDM), before and after 2 months of intensive insulin therapy (IIT) and in 40 healthy control subjects. As compared to the control group, diabetic subjects at baseline had higher low density lipoprotein (LDL) and lower high density lipoprotein (HDL) masses. Expressing each lipoprotein constituent as a percent of total lipoprotein mass, very low density lipoprotein (VLDL) of diabetic patients was enriched in cholesterol and phospholipid and depleted in triglyceride and protein; IDL had higher triglyceride and phospholipid and lower cholesterol and protein proportion; LDL was depleted in protein and enriched in triglyceride; HDL was depleted in protein and enriched in triglyceride, cholesterol and phospholipid. After 2 months of IIT, HbA1c fell from 10.3 +/- 2 to 7.5 +/- 2% (P < 0.0001) and so did VLDL mass, which was lower than in control subjects. In addition, LDL and HDL masses, as well as triglyceride and cholesterol proportion in IDL particles normalized. The other compositional abnormalities improved without complete normalization. Thus, intensive insulin therapy in IDDM subjects brought quantitative lipoprotein alterations to normal even subnormal range, while most of the composition abnormalities improved without reaching complete normalization.

Effects of FR145237, an acyl-CoA:cholesterol acyltransferase inhibitor, on diet-induced hypercholesterolemia in diabetic rats

Recent studies have shown that acyl-CoA:cholesterol acyltransferase (ACAT) plays an important role in the initiation of diabetes-associated hypercholesterolemia. To confirm this hypothesis, effects of a potent ACAT inhibitor, FR145237, on diet-induced hypercholesterolemia were examined in streptozotocin (STZ)-induced diabetic rats. One-week feeding of 1% cholesterol and 0.5% cholic acid to normal rats and STZ-induced diabetic rats increased plasma cholesterol levels in both groups, and the response was more remarkable in the STZ rats than in the normal ones (1266 +/- 476 mg/dl and 146 +/- 7 mg/dl, respectively). FR145237 dose-dependently reduced the rise in plasma cholesterol levels in the STZ rats and the levels were almost normalized by treatment with 1 mg/kg/day of the compound. These results suggest that hyperresponse to dietary cholesterol was induced in the STZ rats and that ACAT is involved in the hyperresponse. The effects of FR145237 on other plasma lipids such as high density lipoprotein (HDL) cholesterol and triglyceride (TG) levels were also examined.

Very low density lipoprotein subfraction abnormalities in IDDM patients: any effect of blood glucose control?

Normolipidaemic insulin-dependent diabetic (IDDM) patients are characterized by an increase in the smaller VLDL particles, considered to be the most atherogenic. Since blood glucose control is one of the main regulators of lipid metabolism in diabetic patients, it could influence the shift in the distribution of VLDL subfractions towards smaller particles. To evaluate this possibility, VLDL subfractions, post-heparin lipoprotein lipase and hepatic lipase activities have been evaluated in male IDDM patients with either unsatisfactory blood glucose control (group 1, HbA1c > 8%, n = 18) or good blood glucose control (group 2, HbA1c < 8%, n = 16) and in 16 normoglycaemic individuals. The three groups were comparable for sex, age, body mass index, and plasma lipid levels. Three VLDL subfractions (large, Svedberg flotation unit (Sf) 175-400; intermediate, Sf 100-175; small, Sf 20-100) were separated by density gradient ultracentrifugation and analysed for cholesterol, triglyceride, and phospholipid levels. When compared to control subjects both groups of IDDM patients showed a clear shift in VLDL subfraction distribution with a significant increase in the proportion of small VLDL (group 1; 49 +/- 2%; p < 0.005; group 2: 51 +/- 3%, p < 0.01; control subjects 40 +/- 2%) (mean +/- SEM) in relation to total VLDL. By contrast, the absolute lipid concentration of small VLDL was higher only in group 1, compared to control subjects (35 +/- 4 vs 27 +/- 3 mg/dl, p = 0.05). Post-heparin hepatic lipase activity was significantly reduced in both IDDM groups (group 1: 254 +/- 19 mU/ml, p < 0.05; group 2: 202 +/- 19 mU/ml, p < 0.005; control subjects 317 +/- 31 mU/ml). In conclusion, normolipidaemic IDDM patients show an increase in the smallest VLDL, whatever their degree of blood glucose control. However, this abnormality may be clinically relevant only in patients with unsatisfactory blood glucose control, since absolute lipid concentration of these potentially atherogenic particles is only increased in this group.

Effect of fluvastatin on intermediate density lipoprotein (remnants) and other lipoprotein levels in hypercholesterolemia

The accelerated atherosclerosis in diseases associated with elevated remnant lipoprotein levels has directed interest toward the response of this lipoprotein species to lipid-lowering treatment. The effect of fluvastatin--a synthetic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor--was compared with that of placebo on parameters of remnant metabolism in 57 patients with moderate hypercholesterolemia, but not heterozygous familial hypercholesterolemia, type III hyperlipidemia, or endogenous hypertriglyceridemia. Fluvastatin therapy resulted in decreases versus baseline in plasma total cholesterol, low density lipoprotein cholesterol (LDL-C) and LDL apolipoprotein (apo) B levels of 18%, 20%, and 18%, respectively (p < 0.01). Plasma parameters related to remnant metabolism were also significantly decreased: intermediate density lipoprotein by 43% and apo E by 22% (p < 0.01). The percent decrease in plasma intermediate density lipoprotein cholesterol level was twice that of LDL-C and 50% greater than the decrease seen in very low density lipoprotein cholesterol (VLDL-C), which was decreased by 28%. Total triglycerides were reduced by 11% and VLDL apo B by 24%, whereas high density lipoprotein cholesterol (HDL-C) rose significantly by 8%, HDL2-C by 24%, and HDL3-C by 3%. There were no increases in apo A-I levels compared with placebo nor any significant change in plasma lipoprotein(a) levels. The composition of LDL and VLDL particles did not appear to be altered by therapy, as assessed by the LDL-C:LDL-B, VLDL-C:VLDL-B, or triglyceride:VLDL-B ratios.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous platelet aggregation in whole blood is increased in non-insulin-dependent diabetes mellitus and in female but not male patients with primary dyslipidemia

Increased platelet aggregability has been shown in hypercholesterolemia, and stirring-induced spontaneous aggregation in whole blood is increased in insulin-dependent diabetes mellitus (DM). We have determined spontaneous aggregation in citrated (10 mM) whole blood, from 27 primary dyslipidemic patients (DYS; 14F, 13M), 16 male non-insulin-dependent DM (NIDDM) patients, and 17 normolipidemic controls (N; 6F, 11M), using platelet counting to quantify aggregation. Spontaneous aggregation was significantly higher, both in the female DYS group (median 30% [interquartile range 25,50], P < 0.005) and the NIDDM group (33% [25,41], P < 0.005), than in the N group (17% [12,27]), but did not differ significantly in the male DYS group (23% [10,33]). Similar results were obtained in the presence of indomethacin (25 mumol/l) to prevent artefactual thromboxane (TX) A2 formation, indicating that increased spontaneous aggregation was TXA2-independent. Interestingly, increased spontaneous aggregation appeared to be independent of serum cholesterol and triglyceride concentrations, as well as age and sex per se. We conclude that spontaneous platelet aggregation was increased both in female primary dyslipidemic patients and NIDDM patients, but not in male DYS patients. The clinical significance of increased spontaneous platelet aggregability is that it may favour shear-induced aggregation which may occur at critical arterial stenoses in vivo leading to thrombus formation.

Efficacy and safety of fluvastatin in patients with non-insulin-dependent diabetes mellitus and hyperlipidemia

The purpose of this study was to investigate the triglyceride-lowering effect of fluvastatin, a new 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor, in the combined hyperlipidemia of non-insulin-dependent diabetes mellitus (NIDDM). In this double-blind trial, 66 patients with NIDDM (24 men and 42 women, age 37-71), with low-density lipoprotein cholesterol (LDL-C) levels of 130-300 mg/dL (3.4-7.8 mmol/L) and triglyceride (TG) levels of 200-1,000 mg/dL (2.3-11.3 mmol/L) despite an 8-week period of diet modification, were randomized to receive either fluvastatin at 20 mg once daily (at night) or placebo for 6 weeks, followed by an increase of fluvastatin to 20 mg twice daily for an additional 6 weeks of treatment. After 12 weeks, fluvastatin decreased plasma levels of total cholesterol by 19.9% (p < 0.001), LDL-C by 24.3% (p < 0.001), TG by 15.3% (p < 0.01), very low-density lipoprotein cholesterol (VLDL-C) by 19.7% (p < 0.001), apolipoprotein (apo) B by 21.3% (p < 0.001), and apo E by 18.1% (p < 0.05), whereas high-density lipoprotein cholesterol (HDL-C) levels were increased by 4.6% (p < 0.05). Within the intermediate-density lipoprotein cholesterol (IDL-C) fraction, a constituent analysis revealed a total cholesterol reduction of 35% (p < 0.01). Greater decreases in TG were seen in patients who had higher levels of TG at baseline. Slight increases in glycemic indices and body weight were seen in both treatment groups. The occurrence of clinical and laboratory abnormalities was similar with both active treatment and placebo, and no myositis was observed. Slight increases in aspartate (ASAT; mean 5.6 U/L at the higher dose) and alanine (ALAT; mean 5.1 U/L at the higher dose) aminotransferases were not clinically significant. In this first, parallel-group placebo-controlled trial of a reductase inhibitor in a free-living NIDDM population, fluvastatin safely improved the combined TG, VLDL-C, IDL-C, LDL-C, and HDL-C abnormalities associated with NIDDM.