Cell-mediated lipoprotein transport: a novel anti-atherogenic concept.

Lipoprotein transport is thought to occur in the plasma compartment of the blood, where lipoproteins are modulated by various enzymatic reactions. Subsequently, lipoproteins can migrate through the endothelial barrier to the subendothelial space or are taken up by the liver. The interaction between pro-atherogenic (apoB-containing) lipoproteins and blood cells (especially monocytes and macrophages) in the subendothelial space is well known. This lipoprotein-inflammatory cell interplay is central in the development of the atherosclerotic plaque. In this review, a novel interaction is described between lipoproteins and both leukocytes and erythrocytes in the blood compartment. This lipoprotein-blood cell interaction may also be related to the process of atherosclerosis by inducing inflammatory changes in the case of leukocytes (pro-atherogenic) and as an anti-atherogenic transport-system by adherence to erythrocytes. Triglyceride rich lipoprotein (TRL)-mediated leukocyte activation can lead to an inflammatory situation with generation of oxidative stress and the production of cytokines, ultimately resulting in acute endothelial dysfunction. Binding of apoB containing lipoproteins to erythrocytes may be a potential anti-atherogenic mechanism protecting the vessel wall from the pro-inflammatory effects of these lipoproteins and also playing a role in the removal of these particles from the circulation. One of the proposed mechanisms of this interaction implies complement activation on the lipoprotein surface and binding to the Complement Receptor 1 (CR1) on erythrocytes and leukocytes, followed by clearance by the liver.

A 'smart' type of Cushing's syndrome.

Cushing's syndrome results from lengthy and inappropriate exposure to excessive concentrations of either endogenous or exogenous glucocorticoids. This case report describes a patient with a novel type of Cushing's syndrome due to the use of party drugs. A 35-year-old woman had gained 8 kg body weight in 5 months and complained of anxiety. She showed a Cushing-like appearance and mild hypertension (blood pressure, BP 150/95 mmHg). She reported daily use of increasing doses of gamma-hydroxybutyric acid (GHB), a popular party drug. ACTH plasma levels were in the upper normal range (41 ng/l), with normal plasma cortisol (0.36 micromol/l). She showed an abnormal overnight 1 mg dexamethasone suppression test (cortisol 0.38 micromol/l). The urinary excretion of free cortisol in 24 h was also increased (0.47 micromol/24 h). CT scanning of the abdomen showed normal adrenals. After stopping GHB intake she lost 7 kg body weight and her BP normalized (BP 135/80 mmHg). GHB is a popular party drug in the Netherlands, but it is also used as a narcotic and for the treatment of narcolepsy. We hypothesize that GHB may bind to the pituitary gland gamma-aminobutyric acid-B receptors leading to ACTH overproduction.

Postprandial inflammation and endothelial dysfuction.

Postprandial hyperlipidaemia is a common metabolic disturbance in atherosclerosis. During the postprandial phase, chylomicrons and their remnants can penetrate the intact endothelium and cause foam cell formation. These particles are highly atherogenic after modification. People in the Western world are non-fasting for most of the day, which consequently leads to a continuous challenge of the endothelium by atherogenic lipoproteins and their remnants. Furthermore, atherosclerosis is considered a low-grade chronic inflammatory disease. Many studies have shown that the process of atherogenesis in part starts with the interaction between the activated leucocytes and activated endothelium. Postprandial lipoproteins can activate leucocytes in the blood and up-regulate the expression of leucocyte adhesion molecules on the endothelium, facilitating adhesion and migration of inflammatory cells into the subendothelial space. Another inflammatory process associated with postprandial lipaemia is the activation of the complement system. Its central component C3 has been associated with obesity, coronary sclerosis, the metabolic syndrome and fasting and postprandial TAGs (triacylglycerols). Moreover, chylomicrons are the strongest stimulators of adipocyte C3 production via activation of the alternative complement cascade. A postprandial C3 increment has been shown in healthy subjects and in patients with CAD (coronary artery disease) and with FCHL (familial combined hyperlipidaemia). Postprandial lipaemia has been related to TAG and free fatty acid metabolism. All of these mechanisms provide an alternative explanation for the atherogenicity of the postprandial period.

Effects of rosiglitazone on postprandial leukocytes and cytokines in type 2 diabetes.

OBJECTIVE: We postulated that in type 2 diabetes, the postprandial phase is a pro-inflammatory state that can be modulated by PPAR-gamma agonists. For this purpose, we determined the effects of rosiglitazone (8 mg/d) on postprandial leukocyte counts and pro-inflammatory cytokines (IL-6 and IL-8) in patients with type 2 diabetes. METHODS AND RESULTS: A randomized, 8-week, cross-over, placebo-controlled, double-blind clinical trial was performed in 19 patients with type 2 diabetes. Standardized 6-h oral fat-loading tests were performed after each treatment period. During placebo treatment, blood leukocytes increased to a maximum 6-h postprandially, due to significant increases in neutrophils and lymphocytes. Concomitant postprandial increases were observed for IL-6 and IL-8, the major chemokines responsible for leukocyte recruitment. Rosiglitazone reduced the incremental area under the curves (dAUCs) for IL-6 (-63%, p<0.01) and IL-8 (-16%, p<0.05). The dAUC for leukocytes decreased with 37% (p<0.05), due to a specific reduction of neutrophils (-39%, p<0.05). CONCLUSIONS: Rosiglitazone attenuated the postprandial increases of neutrophils, IL-6 and IL-8 in patients with type 2 diabetes. Since inflammation is a major force driving atherosclerosis, and man lives in a postprandial period most part of the day, a reduced inflammatory response after a meal may delay progression of atherosclerosis. CONDENSED ABSTRACT: We postulated that in type 2 diabetes, the postprandial phase is a pro-inflammatory state that can be modulated by PPAR-gamma agonists. Rosiglitazone attenuated the postprandial increases of neutrophils, IL-6 and IL-8 in patients with type 2 diabetes. These effects may contribute to cardiovascular risk reduction.

Effects of rosuvastatin on postprandial leukocytes in mildly hyperlipidemic patients with premature coronary sclerosis.

We investigated whether pro-inflammatory aspects of the postprandial phase can be modulated by rosuvastatin in premature coronary artery disease (CAD) patients. Herefore standardized 8 h oral fat loading tests were performed off-treatment and after rosuvastatin 40 mg/d in 20 male CAD patients (50 +/- 4 years). The expression of leukocyte activation markers CD11a, CD11b, CD62L and CD66b was studied using flowcytometry. Migration of isolated neutrophils towards chemoattractants was determined in a fluorescence-based assay. Rosuvastatin did not affect baseline leukocyte counts nor the postprandial neutrophil increment (maximum mean increase +10% pre- and +14% post-treatment, P < 0.01 for each). Rosuvastatin reduced baseline platelets (from 266 +/- 78 to 225 +/- 74 x 10(9) cells/L, P < 0.001) and blunted the postprandial platelet count change (maximum mean increase +6%, P = 0.01, and 0%, respectively). The baseline expression of CD11a, CD11b and CD62L increased on most types of leukocytes by rosuvastatin, whereas the postprandial responses were unaffected. Pretreatment, postprandial neutrophil migration increased dose-dependently, but there were no postprandial changes after rosuvastatin. The latter effect was unrelated to changes in lipoprotein concentrations. In conclusion, in CAD patients postprandial pro-inflammatory and pro-coagulant changes can be modified by rosuvastatin. These apparently lipid-lowering independent effects may render protection against atherosclerosis.

Coronary risk factors and metabolic disorders in first-degree relatives of normocholesterolaemic patients with premature atherosclerosis.

AIMS: Despite agreement on the need for screening for the presence of cardiovascular risk factors in first-degree family members of patients with premature coronary artery disease (CAD), this is not routinely carried out in relatives of normocholesterolaemic patients. We evaluated cardiovascular risk factors in family members of normocholesterolaemic patients with premature CAD. METHODS: Eligible index subjects were patients with premature CAD (<55 years in men and <65 years in women), who had undergone percutaneous transluminal coronary angioplasty. Patients with fasting total cholesterol levels >6.5 mmol/l were excluded. Sixteen index subjects were included with a mean age of 49±8 years and total cholesterol levels of 5.5±0.8 mmol/l. Sixty-four first-degree relatives from these 16 pedigrees were screened, namely 18 children, 42 siblings and four parents. National Cholesterol Education Program III guidelines were used to identify candidates for lipid-lowering treatment. Furthermore, the presence of four additional metabolic disorders was investigated: the metabolic syndrome, increased levels of lipoprotein(a) (Lp(a)), hyperhomocysteinaemia and postprandial hyperlipidaemia. RESULTS: Of 64 relatives free of CAD, 34 subjects (53%) fulfilled the criteria to receive therapeutic advice, 20 of whom (31% of the relatives) were candidates for drug therapy. Sixty-one relatives were available for a full assessment of metabolic disorders and in 37 relatives (61%) at least one metabolic abnormality was present. Twelve subjects had hyper-Lp(a), seven subjects had postprandial hyperlipidaemia and two had the metabolic syndrome. Furthermore, 16 subjects had a combination of at least two out of four metabolic disorders. CONCLUSION: Careful evaluation of coronary risk factors and metabolic variables in first-degree relatives of normocholesterolaemic CAD patients identifies a significant number of subjects at increased coronary risk in whom primary prevention measures should be initiated.

In vivo evidence of impaired peripheral fatty acid trapping in patients with human immunodeficiency virus-associated lipodystrophy.

The use of antiretroviral combination therapy in HIV has been associated with lipodystrophy and several metabolic risk factors. We postulated that patients with HIV-lipodystrophy have impaired adipose tissue free fatty acid (FFA) trapping and, consequently, increased hepatic FFA delivery. We investigated FFA, hydroxybutyric acid (HBA; reflecting hepatic FFA oxidation), and triglyceride (TG) changes after a high fat meal in HIV-infected males with (LIPO; n = 26) and without (NONLIPO; n = 12) lipodystrophy and in healthy males (n = 35). Because defective peripheral FFA trapping has been associated with impaired action of complement component 3 (C3), we also determined postprandial C3 concentrations. The LIPO group had higher homeostasis model assessment scores compared with the other groups. Areas under the curve (AUCs) for FFA, HBA, and TG were higher in the LIPO group than in the NONLIPO group or the controls. No differences in TG-AUC, FFA-AUC, and HBA-AUC were observed between the NONLIPO group and controls. In HIV-infected patients, FFA-AUC and HBA-AUC were inversely related to sc adipose tissue area. Plasma C3 showed a postprandial increase in healthy controls, but not in the HIV-infected groups. C3 was not related to body fat distribution, postprandial FFA, or HBA. The present data suggest disturbed postprandial FFA metabolism in patients with HIV-lipodystrophy, most likely due to inadequate incorporation of FFA into TG in sc adipose tissue, but do not support a major role for C3 in these patients. The higher postprandial HBA levels reflect increased hepatic FFA delivery and may aggravate insulin resistance and dyslipidemia, leading to increased cardiovascular risk.

Activation of leukocytes by postprandial lipemia in healthy volunteers.

Activation of leukocytes is obligatory for inflammation and atherogenesis by adhering to the endothelium via specific ligands. Although in vitro studies have shown that triglycerides (TG) can activate leukocytes, it is unknown whether this occurs in vivo. Using flowcytometry, we studied the expression of leukocyte activation markers CD11A, CD11B, CD62L (all involved in endothelium adhesion) and CD66B (a neutrophil degranulation marker) during a 6 h fat challenge (50 g/m2) and a water test in 10 healthy males (52 +/- 3 years). After fat, neutrophil counts were increased between t=1 and t =6 h, with a maximum at t=3 h (+32% versus t=0, P <0.05), while they remained unchanged after water. Both tests showed gradual lymphocyte count increments. The expression of activation markers on lymphocytes was low and showed comparable responses after both tests. After fat, a significant increase up to a maximum at t=6 h was seen for CD11B on monocytes and on neutrophils for CD11B, CD62L and CD66B. Postprandial activation of monocytes and neutrophils was higher after fat than after water. The maximal postprandial TG increment was significantly related to the increase of CD11B on monocytes (Pearson's R=0.64, P <0.05). In conclusion, postprandially there is a TG-specific increase of neutrophil counts and increased activation of monocytes and neutrophils. These results are suggestive of a pro-inflammatory situation that may correspond with increased adhesive capacity of these cells contributing to the inflammatory component of atherosclerosis.

Effects of atorvastatin on fasting plasma and marginated apolipoproteins B48 and B100 in large, triglyceride-rich lipoproteins in familial combined hyperlipidemia.

Large triglyceride (TG)-rich lipoproteins (TRLs) circulate in the blood, but they may also be present in a marginated pool, probably attached to the endothelium. It is unknown whether statins can influence this marginated pool in vivo in humans. Intravenous fat tests were performed in familial combined hyperlipidemia (FCHL) subjects before and after atorvastatin treatment and in controls to investigate whether acute increases in apoB in TRL fractions would occur, potentially reflecting the release of this TRL from a marginated pool. After a 12-h fast, a bolus injection of 10% Intralipid was given to 12 FCHL patients before and after 16-wk treatment with atorvastatin. Twelve carefully matched controls were included. For 60 min postinjection, apoB48, apoB100, and lipids were measured in TRLs. Fasting apoB100 in all TRL fractions were 2- to 3-fold higher in untreated FCHL compared with controls. ApoB48 concentrations in chylomicron fractions increased significantly within 10 min in FCHL before and after treatment, but not in controls. ApoB100 increased significantly in the chylomicron fractions in untreated FCHL and in controls, but not in FCHL after treatment. In very low density lipoprotein 1, apoB100 increased only in untreated FCHL. In very low density lipoprotein 2, apoB100 did not change in any group. These data show that increasing the number of circulating TRLs by chylomicron-like particles, results in increased plasma apoB-TRLs, probably by acute release from a marginated pool. This is a physiological process occurring in FCHL and in healthy normolipidemic subjects, but it is more pronounced in the former. Decreased marginated TRL particles in FCHL is a novel antiatherogenic property of atorvastatin.

In vivo regulation of plasma free fatty acids in insulin resistance.

Elevated plasma free fatty acid (FFA) concentrations as seen in obesity, insulin resistance, and type 2 diabetes are partly caused by impaired inhibition of intracellular lipolysis in adipose tissue, and this is considered to be part of the insulin resistance syndrome (IRS). Based on predicted insulin resistance at the level of intracellular lipolysis, patients with the IRS would loose weight by disinhibited lipolysis. Since this is not the case in clinical practice, impaired stimulation of intracellular lipolysis must also play a role. We studied acute plasma FFA changes, representing stimulation and inhibition of intracellular adipose tissue lipolysis, in obese patients with IRS and in healthy controls. Thirteen insulin-resistant (IR) subjects (7 men and 6 women) and 10 controls (6 men and 4 women) underwent a mental stress test (20 minutes) preceded by 60 minutes of rest. After mental stress, an oral glucose tolerance test (OGTT) was performed. Baseline FFA levels were higher in IR patients compared to controls (0.59 +/- 0.06 and 0.31 +/- 0.06 mmol/L, respectively; P =.004). During the 20 minutes of mental stress, FFAs increased significantly in IR subjects from 0.55 +/- 0.07 to 0.67 +/- 0.07 mmol/L (P <.001) and from 0.21 +/- 0.04 to 0.36 +/- 0.07 mmol/L in controls (P =.001). Although the absolute change of plasma FFA was not different, the relative increase was lower in IR subjects (28% +/- 7%) compared to controls (89 +/- 24%; P =.02). Despite the more pronounced mean maximal insulin concentration during the OGTT in IR subjects compared to controls (600.0 +/- 126.6 pmol/L and 208.1 +/- 30.0 pmol/L, respectively), the relative decrease of FFAs was lower in IR subjects (11% +/- 5% v 36% +/- 11% in controls after 30 minutes; P =.04). In conclusion, our study shows impaired acute responses of plasma FFAs upon stimulation by mental stress and inhibition by endogenous insulin in insulin resistance in vivo. The presence of both defects helps to understand weight maintenance in insulin resistance.

Normalization of daytime triglyceridemia by simvastatin in fasting normotriglyceridemic patients with premature coronary sclerosis.

Postprandial hyperlipidemia is associated with premature coronary sclerosis in fasting normolipidemic subjects. Self-determined daytime capillary triglyceride (cTG) profiles were compared between 26 fasting normotriglyceridemic patients with premature coronary artery disease (CAD) and 26 controls matched for gender, age and BMI. Daytime triglyceridemia was calculated as total area under the cTG-curve (cTG-AUC). Total and LDL cholesterol were not different between CAD patients (5.4+/-0.8 mmol/l and 3.6+/-0.7 mmol/l, respectively) and controls (5.0+/-0.9 mmol/l and 3.3+/-0.8 mmol/l, respectively). Patients with CAD were characterized by a 44% higher cTG-AUC than matched controls (P<0.01). Using logistic regression analysis, cTG-AUC was the strongest predictor of the presence of CAD (P<0.001). Adding apo AI to the model improved the predictive power from 71 to 77%. Sixteen patients were studied after increasing doses of simvastatin up to 80 mg/day. Although the target for LDL cholesterol was reached by simvastatin 20mg/day, significant effects on cTG-AUC were found only by higher doses of simvastatin. Simvastatin 40 mg/day decreased cTG-AUC by 28% (P<0.05 versus baseline), reaching comparable values as in controls, without further improvement with simvastatin 80 mg/day (26% reduction versus baseline; P<0.05). Daytime triglyceridemia is linked to premature coronary sclerosis in fasting normotriglyceridemic patients. A higher dose of simvastatin was needed to normalize daytime triglyceridemia than was required to "normalize" LDL cholesterol.

Gender differences in postprandial ketone bodies in normolipidemic subjects and in untreated patients with familial combined hyperlipidemia.

OBJECTIVE: An increased hepatic flow of free fatty acids (FFAs) is associated with impaired peripheral FFA trapping by malfunctioning of the complement component 3 (C3)/acylation-stimulating protein system and overproduction of VLDL in familial combined hyperlipidemia (FCHL). Postprandial ketone bodies reflect FFA oxidation in the liver, but the postprandial changes in male and female patients separately have not been determined yet. Gender differences in postprandial ketone bodies and C3 changes were investigated in normolipidemic patients and patients with untreated FCHL. METHODS AND RESULTS: Thirty-two normolipidemic patients (16 female and 16 male) and 19 patients with untreated normolipidemia (9 female and 10 male) underwent an oral fat-loading test. Total and incremental areas under the curves (AUC and dAUC, respectively) after the oral fat load were calculated. Triglyceride AUC was similar between genders in each group. Normolipidemic female subjects showed a higher levels of dAUC-hydroxybutyric acid than male subjects (1.37+/-0.49 and 0.98+/-0.43 mmol x h/L). In FCHL, a similar trend was observed in female (1.92+/-0.38) compared with male (1.55+/-0.87) subjects. In contrast to normolipidemia, FCHL did not show a postprandial increase in C3, although C3 was higher in FCHL. CONCLUSIONS: Women have higher postprandial ketone bodies than men, probably reflecting enhanced postprandial hepatic FFA oxidation. In FCHL, both genders have higher postprandial ketone bodies and therefore higher hepatic FFA delivery. The higher fasting and postprandial C3 levels in FCHL may reflect resistance of the C3/acylation-stimulating protein system to promote peripheral fatty acid trapping.

Postprandial leukocyte increase in healthy subjects.

Atherosclerosis is an inflammatory disorder involving leukocytes and lipids. To study the relationship between leukocytes and lipids in vivo, leukocyte changes were determined in 14 healthy males (age, 23 +/- 3 years; body mass index [BMI], 21.9 +/- 1.5 kg/m(2)) after an 8-hour oral fat load (50 g/m(2)) and after water. The postprandial triglyceride (TG) increment after fat was paralleled by a leukocyte increment, due to an increase in neutrophils in the first 2 hours (142% +/- 69% higher than baseline, P =.04). Neutrophil counts did not return to baseline at the end of the test. Water ingestion did not induce significant neutrophil changes. Blood lymphocytes increased gradually in both tests (142% +/- 30% higher than baseline, P <.001 after fat, and 128% +/- 36%, P =.02 after water). The total leukocyte increment after fat ingestion was related to the postprandial TG increase (Spearman's r = 0.73, P =.003). An early postprandial, lipid-specific, neutrophil increment is a new characteristic of the postprandial phase. Future studies will elucidate the role of postprandial leukocyte changes in the pathogenesis of atherosclerosis.

Insulin resistance and vessel endothelial function.

IRS is a complex disease consisting of a clustering of metabolic disorders, of which hyperglycaemia, hyper-insulinaemia and dyslipidaemia are the most important. Endothelial dysfunction plays an important role in the pathogenesis of atherosclerosis. The effects of hyperinsulinaemia seem to depend on lipidaemia and glycaemia. Hyperglycaemia and hyperlipidaemia have detrimental effects on endothelial function in the fasting as well as the postprandial states. In both situations, the generation of ROS and vasoactive molecules plays a major role in interfering with the atheroprotective endothelium-dependent NO system. Treatment of IRS in regard to endothelial function should be focused initially on lifestyle improvement, such as stopping smoking and eating a balanced diet containing antioxidant vitamins, folic-acid, L-arginine and long-chain omega-3 unsaturated FA. Strict glucose control has shown to improve endothelial function and decrease microvascular complications. However, macrovascular complications, in line with endothelial functional improvement, have so far been reduced only when treatment was focused on other characteristics of the IRS syndrome, in particular dyslipidaemia. Other relevant treatments include ACE inhibitors and thiazolidinediones, and probably tetrahydrobiopterin and folic acid supplementation. Future studies should address the effects of therapeutic neovascularization on endothelial dysfunction.

Delayed and exaggerated postprandial complement component 3 response in familial combined hyperlipidemia.

Very low density lipoprotein overproduction is the major metabolic characteristic in familial combined hyperlipidemia (FCHL). Peripheral handling of free fatty acids (FFAs) in vitro may be impaired in FCHL by decreased action of acylation-stimulating protein (ASP), which is identical to the immunologically inactive complement component 3a (C3adesArg). Because decreased FFA uptake by impaired complement component 3 (C3) response (as the precursor for ASP) may result in enhanced FFA flux to the liver in FCHL, we have evaluated postprandial C3 changes in vivo in FCHL patients. Accordingly, 10 untreated FCHL patients and 10 matched control subjects underwent an oral fat loading test. Fasting plasma C3 and ASP levels were higher in FCHL patients (1.33+/-0.09 g/L and 70.53+/-4.37 mmol/L, respectively) than in control subjects (0.91+/-0.03 g/L and 43.21+/-8.96 mmol/L, respectively; P=0.01 and P<0.05). In control subjects, C3 concentrations increased significantly after 4 hours (to 1.03+/-0.04 g/L). In FCHL, plasma C3 was unchanged after 4 hours. The earliest postprandial C3 rise in FCHL patients occurred after 8 hours (1.64+/-0.12 g/L). The maximal apolipoprotein B-48 concentration was reached after 6 hours in FCHL patients and control subjects. Postprandial FFA and hydroxybutyric acid (as a marker of hepatic FFA oxidation) were significantly higher in FCHL patients than in control subjects, and the early postprandial C3 rise was negatively correlated with the postprandial FFA and hydroxybutyric acid concentrations. The present data suggest an impaired postprandial plasma C3 response in FCHL patients, most likely as a result of a delayed response by C3, as the precursor for the biologically active ASP, acting on FFA metabolism. Therefore, an impaired postprandial C3 response may be associated with impaired peripheral postprandial FFA uptake and, consequently, lead to increased hepatic FFA flux and very low density lipoprotein overproduction.

In vivo modulation of plasma free fatty acids in patients with familial combined hyperlipidemia using lipid-lowering medication.

One of the best studied aspects of the insulin resistance syndrome in familial combined hyperlipidemia (FCHL) is impaired insulin-mediated suppression of FFA by diminished inhibition of hormone-sensitive lipase (HSL). In vitro experiments have shown that stimulation of HSL activity by catecholamines is decreased in FCHL. The aim of this study was to investigate HSL inhibition by insulin and stimulation by endogenous catecholamines in vivo in FCHL patients. Twelve FCHL subjects using lipid-lowering medication and 12 controls underwent a mental stress test after random ingestion of either 50 g glucose or placebo. After ingestion of glucose, insulin concentrations increased from 76.8 +/- 21.5 pM to a maximum of 520.2 +/- 118.4 pM (P < 0.01) in FCHL and from 38.0 +/- 5.0 to 221.7 +/- 25.1 pM (P < 0.01) in controls. The percent decreases in plasma FFA during the first hour after glucose ingestion were similar in FCHL and controls (67 +/- 5% vs. 72 +/- 3%, respectively), suggesting a comparable inhibition of HSL in both. During the placebo test, FFA increased similarly in FCHL (56 +/- 9%) and controls (57 +/- 19%). In contrast, FFA concentrations did not change during mental stress after ingestion of glucose (from 0.17 +/- 0.02 to 0.15 +/- 0.02 mmol/liter in FCHL and from 0.11 +/- 0.02 to 0.12 +/- 0.02 mmol/liter in controls). In conclusion, the present study provides in vivo evidence for intact insulin-mediated suppression of FFA in FCHL, although this inhibition of HSL was achieved by higher insulin levels, suggesting insulin resistance at the level of HSL. Secondly, the induction of HSL activity by endogenous catecholamines in vivo is not decreased in FCHL, in contrast to earlier in vitro findings. Finally, catecholamine-induced HSL activation can be inhibited by insulin in a similar manner in both FCHL and controls.