Adipocyte beta-adrenoceptor sensitivity influences plasma lipid levels

Stimulation of the beta-2-adrenergic receptor with salbutamol activates human brown adipose tissue

While brown adipose tissue (BAT) is activated by the beta-3-adrenergic receptor (ADRB3) in rodents, in human brown adipocytes, the ADRB2 is dominantly present and responsible for noradrenergic activation. Therefore, we performed a randomized double-blinded crossover trial in young lean men to compare the effects of single intravenous bolus of the ADRB2 agonist salbutamol without and with the ADRB1/2 antagonist propranolol on glucose uptake by BAT, assessed by dynamic 2-[18F]fluoro-2-deoxy-D-glucose positron emission tomography-computed tomography scan (i.e., primary outcome). Salbutamol, compared with salbutamol with propranolol, increases glucose uptake by BAT, without affecting the glucose uptake by skeletal muscle and white adipose tissue. The salbutamol-induced glucose uptake by BAT positively associates with the increase in energy expenditure. Notably, participants with high salbutamol-induced glucose uptake by BAT have lower body fat mass, waist-hip ratio, and serum LDL-cholesterol concentration. In conclusion, specific ADRB2 agonism activates human BAT, which warrants investigation of ADRB2 activation in long-term studies (EudraCT: 2020-004059-34).

The Role of Childhood Asthma in Obesity Development: A Nationwide US Multicohort Study

RATIONALE

Asthma and obesity often co-occur. It has been hypothesized that asthma may contribute to childhood obesity onset.

OBJECTIVES

To determine if childhood asthma is associated with incident obesity and examine the role of asthma medication in this association.

METHODS

We studied 8,716 children between ages 6 and 18.5 years who were nonobese at study entry participating in 18 US cohorts of the Environmental influences on Child Health Outcomes program (among 7,299 children with complete covariate data mean [SD] study entry age = 7.2 [1.6] years and follow up = 5.3 [3.1] years).

MEASUREMENTS AND MAIN RESULTS

We defined asthma based on caregiver report of provider diagnosis. Incident obesity was defined as the first documented body mass index ≥95th percentile for age and sex following asthma status ascertainment. Over the study period, 26% of children had an asthma diagnosis and 11% developed obesity. Cox proportional hazards models with sex-specific baseline hazards were fitted to assess the association of asthma diagnosis with obesity incidence. Children with asthma had a 23% (95% confidence intervals [CI] = 4, 44) higher risk for subsequently developing obesity compared with those without asthma. A novel mediation analysis was also conducted to decompose the total asthma effect on obesity into pathways mediated and not mediated by asthma medication use. Use of asthma medication attenuated the total estimated effect of asthma on obesity by 64% (excess hazard ratios = 0.64; 95% CI = -1.05, -0.23).

CONCLUSIONS

This nationwide study supports the hypothesis that childhood asthma is associated with later risk of obesity. Asthma medication may reduce this association and merits further investigation as a potential strategy for obesity prevention among children with asthma.

ADRB2 polymorphisms and dyslipidemia risk in Chinese hypertensive patients

Single nucleotide polymorphisms (SNPs) within a β-adrenergic receptor (ADRB2) were shown to be related to lipid traits or hyperlipidemia in different ethnicities, but not in a Chinese population. We performed the present study to investigate the possible relationship between them in a Chinese hypertensive population. Seven hundred and eighty-three hypertensive subjects were enrolled in the hospital-based retrospective research. Using the TaqMan PCR method, three polymorphisms (C-47T, A46G, and C79G) of ADRB2 were detected. For the whole population, no significant statistical difference was found for all serum lipids. Similar findings were seen in men and women subgroups. Subsequently, in the case-control study, we observed that the A46G polymorphism was significantly associated with the elevated risk of hypertriglyceridemia in the dominant model (OR: 1.47, 95%CI: 1.05-2.06, P = 0.025). There are no significant differences in the other four models. With regard to C79G and C-47T, no significant association was seen in this population. In addition, haplotype analysis showed that the TAC haplotype carrying frequent alleles of the three SNPs played a reduced role in hypertriglyceridemia risk and the TGC haplotype carrying rare allele of A46G expressed a significant risk effect. In conclusion, these findings indicated that the ADRB2 SNPs might be a genetic risk factor for dyslipidemia in the Chinese hypertensive patients.

Restless legs syndrome: the most prevalent “unknown” disorder

Sleep disorders are also considered as significant chronic disorders, as their physiological and psycho-social consequences are well documented. Restless legs syndrome has high prevalence, as it occurs in 5–10 % of the general population. Since clinical presentation is not well appreciated by many of the health care professionals, only a small proportion of the patients with restless legs syndrome is diagnosed and treated. The consequences of disease, however, are not negligible. The majority of the patients suffer from insomnia, impaired daytime functioning and quality of life. Although, restless legs syndrome is frequently characterized as a sleep disorder, it does not only influence sleep but also the daytime functioning of the patients. Additionally, restless legs syndrome causes not only subjective complaints and sleep disruption, but it is also associated with cardiovascular disorders. Orv. Hetil., 2011, 152, 259–266.

Traumatic and non-traumatic spinal cord-injured patients in Quebec, Canada. Part 2: biochemical profile

STUDY DESIGN

Community-based, cross-sectional study.

OBJECTIVES

This study aimed at examining and comparing biochemical profiles (blood and urine) of traumatic and non-traumatic spinal cord-injured patients (TSCIs vs NTSCIs).

SETTING

The Interval Rehabilitation Center, Trois-Rivieres, Province of Quebec, Canada.

METHODS

Medical records from a cohort of 175 chronic spinal cord-injured patients (94 TSCI and 81 NTSCI individuals) were thoroughly studied.

RESULTS

Augmentations over time of red blood cell (erythrocyte), hematocrit and hemoglobin levels were generally found after spinal cord injury (SCI), specifically in NTSCI patients (late vs early chronic). In contrast, although leukocyte levels generally decreased over time after SCI, higher lymphocyte levels were detected only in NTSCI patients (late vs early chronic). Higher total cholesterol, triglyceride, high-density lipoprotein-cholesterol (HDL-C) and low-density lipoprotein-cholesterol (LDL-C), protein and albumin serum levels were generally found over time after SCI, again, specifically in chronic NTSCI patients (late vs early chronic), whereas increased (twofold) nitrite and decreased (twofold) ubilirogen urine levels were found specifically in TSCI individuals (late vs early chronic).

CONCLUSION

Clear differences were reported between subgroups of SCI patients strongly supporting the idea that therapeutic approaches aimed to treat these problems should be specifically designed for each type of patients (that is, NTSCI vs TSCI or early vs late chronic patients).

Lipid profiles of persons with paraplegia and tetraplegia: sex differences

BACKGROUND/OBJECTIVE

To examine the lipoprotein profiles of men and women with paraplegia and tetraplegia. Impairment of the sympathetic nervous system (dependent on the level of injury) and the extent of physical capacity and activity were correlated with the lipid profile in men with spinal cord injury (SCI). Sex-related differences of the lipoprotein profiles could be found in nondisabled and premenopausal women with SCI mainly because of the different effects of sexual hormones.

METHODS

Lipoprotein profiles of 112 participants with SCI (32 premenopausal women, 80 men) were analyzed and correlated to sex, lesion level, and physical performance capacity.

RESULTS

Women with tetraplegia or paraplegia showed significantly higher levels of high-density lipoprotein and lower ratios of total cholesterol to high-density lipoprotein-cholesterol compared with men with corresponding lesion levels, without a difference in peak oxygen consumption. Concentrations of very-low-density lipoproteins were lower in women with paraplegia than in men with paraplegia; no differences were found in total cholesterol, low-density lipoprotein-cholesterol, and triglycerides. Sex-independent elevations in total cholesterol and low-density lipoprotein-cholesterol were associated with paraplegia, and sex-independent elevations in triglyceride levels were associated with tetraplegia.

CONCLUSIONS

Persons with SCI showed sex-related differences in their lipoprotein profiles. Independent of physical fitness, the lipoprotein profile of premenopausal women with SCI did not exhibit the adverse lipoprotein characteristics observed in men with SCI, probably because of the influence of sexual hormones independent of lesion level.

Evolution of blood pressure and cholesterol in stage 1 hypertension: role of autonomic nervous system activity

OBJECTIVE

Controversy remains concerning the pathogenetic mechanisms for the relationship between sympathetic activity, hypertension and lipid abnormalities. We tested the hypothesis that a condition characterized by sympathetic predominance may affect the evolution of blood pressure and lipids in the early stage of hypertension.

METHODS

We prospectively studied 163 young stage 1 hypertensive individuals and 28 normotensive control individuals. The hypertensive subjects were divided by cluster analysis into two groups according to low frequency and high frequency components of heart rate variability. Large artery and small artery compliance was assessed at the end of the follow-up.

RESULTS

Fifty-nine subjects showed reduced total power and signs of sympathetic predominance in the resting condition, on standing and during mental stress (group 1). At baseline, they had similar blood pressure and metabolic data to the rest of the group (n = 104, group 2) and a greater white-coat effect (P = 0.03). During a 6-year follow-up, 23.7% of group 1 subjects versus 9.6% of group 2 subjects developed sustained hypertension requiring antihypertensive treatment (P = 0.02). In group 1 subjects, there was also a greater increase in total cholesterol (P = 0.01) than in group 2. In addition, at the end of follow-up group 1 subjects had impaired large artery compliance (P < 0.001 versus group 2).

CONCLUSIONS

These data indicate that a condition characterized by sympathetic predominance may favour the development of sustained hypertension and hypercholesterolemia early in life, and lead to increased susceptibility to vascular complications. They further indicate that the increased white-coat effect is not an innocent phenomenon.

Combining beta-adrenergic and peroxisome proliferator-activated receptor gamma stimulation improves lipoprotein composition in healthy moderately obese subjects

Current pharmacological regimens for hypertriglyceridemia and low high-density lipoprotein (HDL) are limited to the peroxisome proliferator-activated receptor (PPAR) alpha activating fibrates, niacin, and statins. This pilot study examined the impact of simultaneous stimulation of cyclic adenosine monophosphate with a beta-adrenergic agonist and PPARgamma with pioglitazone (PIO) on lipoprotein composition in moderately obese, healthy subjects. Subjects were treated with PIO (45 mg) to stimulate PPARgamma or a combination of ephedrine (25 mg TID), a beta-agonist, with caffeine (200 mg TID), a phosphodiesterase inhibitor (ephedrine plus caffeine), or both for 16 weeks. Lipoproteins were separated by gradient ultracentrifugation into very low-density lipoprotein (VLDL), intermediate-density lipoprotein, low-density lipoprotein (LDL), and 3 HDL (L, M, and D) subfractions. Apolipoproteins were measured by high-performance liquid chromatography. PIO alone reduced the core triglyceride (TG) content relative to cholesterol ester (CE) in VLDL (-40%), IDL (-25%), and HDL-M (-38%). Ephedrine plus caffeine alone reduced LDL CE (-13%), phospholipids (-9%), and apolipoprotein (apo) B (-13%); increased HDL-M LpA-I (HDL containing apoA-I without apoA-II, 28%), CE/TG (23%), and CE/apoA-I (8%) while reducing apoA-II (-10%); and increased HDL-L LpA-I (29%). Combination therapy reduced total plasma TG (-28%), LDL cholesterol (LDL-C, -10%), apoB (-16%), apoB/apoA-I ratio (-21%) while increasing HDL cholesterol (HDL-C, 21%), total plasma apoA-I (12%), LpA-I (43%), and apoC-I (26%). It also reduced VLDL total mass (-34%) and apoC-III (-39%), LDL CE (-13%), apoB (-13%), and total mass (-11%). Combination therapy increased HDL-L CE/TG (32%), apoC-I (30%), apoA-I (56%), and LpA-I (70%), as well as HDL-M CE (35%), phospholipids (24%), total mass (19%), apoC-I (25%), apoA-I (18%), and LpA-I (56%). In conclusion, simultaneous beta-adrenergic and PPARgamma activation produced beneficial effects on VLDL, LDL, HDL-L, and HDL-M. Perhaps the most important impact of combination therapy was dramatic increases in LpA-I and apoC-I in HDL-L and HDL-M, which were much greater than the sum of the monotherapies. Because LpA-I appears to be the most efficient mediator of reverse-cholesterol transport and a major negative risk factor for cardiovascular disease, this combination therapy may provide very effective treatment of atherosclerosis.

Association of β2 adrenergic receptor polymorphisms and related haplotypes with triglyceride and LDL-cholesterol levels

Adrenergic receptors regulate lipid mobilization, energy expenditure and glycogen breakdown. The beta(2) adrenergic receptor (beta(2)-AR) gene may constitute a potential candidate gene to explain part of the genetic predisposition to human obesity and correlated traits. With regard to the association between beta(2)-AR gene polymorphisms and obesity-related metabolic disorders, published reports give conflicting results. We investigated the role of three polymorphisms, and related haplotypes of the beta(2)-AR in the obesity and related traits in a cohort of overweight/obese subjects. We characterized one single nucleotide polymorphism (SNP) in the promoter region (5'LC-Cys19Arg) and two in the coding region (Gly16Arg and Gln27Glu) of the beta(2)-AR in 642 consecutively recruited overweight/obese subjects in whom extensive clinical and biochemical analysis was performed. The effect of the polymorphisms on quantitative variables was investigated using multiple linear regression analysis. 5'LC-Cys19 homozygous showed higher triglyceride and LDL-cholesterol levels compared to 5'LC-Arg19 homozygous (P=0.03 and P=0.01, respectively). Similar increase in triglyceride and LDL-cholesterol levels was observed for Arg/Arg genotype compared to Gly/Gly genotype of Gly16Arg polymorphism (P=0.02 and P=0.01, respectively) and for Gln/Gln genotype compared to Glu/Glu genotype of the Gln27Glu polymorphism (P=0.01 and P=0.03, respectively). The 5'LC-Cys(19)Arg(16)Gln(27) haplotype determined a significant increase in triglyceride and LDL-cholesterol levels compared to 5'LC-Arg(19)Gly(16)Glu(27) haplotype (P=0.05 and P=0.02, respectively). Our findings provide additional weight to previous observations on the influence of these three genetic variants on lipid phenotypes; particularly on the increase of triglycerides and LDL-cholesterol levels in overweight/obese subjects carrying the 5'LC-Cys(19)Arg(16)Gln(27) haplotype.

The beta(2)-adrenergic receptor Arg16-gly polymorphism and interactions involving beta(2)- and beta(3)-adrenergic receptor polymorphisms are associated with variations in longitudinal serum lipid profiles: the Bogalusa Heart Study

We examined the effects of combined genotypes of the beta(2)-adrenergic receptor (AR) Arg(16)-Gly and beta(3)-AR Trp(64)-Arg polymorphisms on longitudinal serum total (T-C) and low-density lipoprotein cholesterol (LDL-C) profiles in 1,198 subjects examined multiple times (6,488 observations) from 1973 to 1996 in the Bogalusa Heart Study, at ages from 4.5 to 38 years. Within 5-year age groups, T-C was significantly (P <.05) higher in beta(2)-AR Arg(16)/Arg(16) homozygotes than in Gly(16) carriers among those 4 to 8 (171.4 +/- 30.0 v 161.5 +/- 27.7 mg/dL), 9 to 13 (167.7 +/- 28.6 v 162.4 +/- 27.4 mg/dL), and 14 to 18 (158.8 +/- 29.6 v 154.7 +/- 27.5 mg/dL) years of age, but not in those 19 to 23, 24 to 28, 29 to 33, or 34 to 38 years of age. The beta(3)-AR polymorphism was not associated with variation in either T-C or LDL-C. In multilevel polynomial growth curve models, the combination of the beta(2)-AR Arg(16)/Arg(16) genotype with either the beta(3)-AR Arg(64)/Arg(64) or Trp(64)/Arg(64) genotypes, denoted AA/AX, was associated with variation in longitudinal T-C (P <.01) and LDL-C (P <.01) profiles. The association between combined beta(2)/beta(3)-AR genotype and lipid profiles differed among race/sex groups, being most marked in black females, in whom the AA/AX combination was associated with higher T-C and LDL-C profiles across all ages. In White males, the AA/AX combination was most strongly associated with higher lipids in adults. In black males and white females, lipid profiles differed little between genotype groups. Our findings suggest that the beta(2)-AR Arg(16)-Gly genotype influences T-C and LDL-C levels in an age-specific manner, that it may interact with beta(3)-AR Trp(64)-Arg genotypes to influence longitudinal T-C and LDL-C profiles, and that the effect of combined beta(2)/beta(3)-AR genotypes on T-C and LDL-C profiles may differ among race/sex groups.

Body weight characteristics of subjects on asthma medication

OBJECTIVE

Weight gain is a frequently documented side effect after long-term anti-inflammatory treatment with systemic corticosteroid drugs in patients with asthma. In recent years new types of inhaled corticosteroids have been introduced, which act locally and are more rapidly bio-transformed. Even such corticosteroids may have a detectable, clinically relevant systemic side effect on weight. The aim of this study is to investigate if there is any relationship between body weight and asthma medication.

DESIGN

The relationship between asthma medication and body weight was analysed in two combined randomized samples of the adult Swedish population 16-60 y of age (n = 17,912). Multivariate logistic regression analyses were carried out to obtain estimates for (1) body mass index (BMI) indicating 'obesity' (BMI > 29.9 kg/m2) in men and women controlling for self-reported asthma medication, and (2) self-reported asthma medication controlling for BMI. In both cases we furthermore controlled for interview period, age, Swedish region, smoking habits, physical activities and level of education.

RESULTS

We found no significantly higher odds for obesity in men (OR = 1.21 (0.55-2.64) or women (OR = 1.97 (0.89-4.38) on asthma medication compared to men and women with pharmacologically untreated asthma even after adjustment for smoking habits, physical activities, level of education and other related co-variables. However, we found significant positive associations between obesity and interview period, age and former smoking and inverse significant relationships with the degree of physical activity. We also found significantly higher adjusted odds for asthma, indicated by self-reported asthma medication, in women (OR = 2.74 (1.91-3.91)) but not in men (OR = 1.57 (0.96-2.56)) with BMI indicating 'obesity'.

CONCLUSION

There is no strong evidence to suggest that modern pharmacological asthma treatment may contribute much to the development of obesity in either men or women on asthma medication. Adjustment for smoking habits, physical activities, level of education and other related co-variables have minor effects on these relationships. Obesity may still be an independent risk factor for asthma since we observed significantly higher odds for self-reported asthma medication in women and an almost significant relationship in men even after control for BMI and other related co-variables.

Lipoproteins and free plasma catecholamines in spinal cord injured men with different injury levels

Persons with spinal cord injury (SCI) are especially prone to atherogenesis. This is partly explained by an unfavourable lipoprotein profile in these individuals. The impairment of the sympathetic nervous system, and the fact that SCI subjects are subject to extreme physical inactivity, may have an influence on their lipid profile and lipoprotein(a) concentration. We made a detailed investigation of the lipid profile as well as serum levels of adrenaline and noradrenaline in 80 men with SCI ranging from tetraplegia to low paraplegia and in 16 control subjects. The lipid profile of tetraplegics was characterized by elevated very low-density lipoprotein cholesterol and triglyceride levels and reduced high-density lipoprotein levels. In contrast, paraplegics had significantly higher low-density lipoprotein and total cholesterol levels. Tetraplegics had lower and the low-lesion paraplegics had higher adrenaline and noradrenaline levels than the high-lesion paraplegics and the control subjects. High-lesion SCI subjects also showed an extreme reduction in VO2max. The lipoprotein profile was dependent on the injury level and serum catecholamine concentrations. The lower the noradrenaline values, the lower the high-density lipoprotein cholesterol. The low-density lipoprotein also correlated to catecholamines and particularly adrenaline values. Despite the correlation between lipoprotein(a) and adrenaline, no significant differences in lipoprotein(a) were found within SCI individuals as well as between SCI individuals and control subjects, indicating the predominantly genetic determination of lipoprotein(a) and thus the cardiovascular risk. Different serum catecholamine levels due to impairment of sympathetic nervous system and VO2max levels were observed in SCI subjects. This was associated with a higher lipid risk profile for cardiovascular diseases; however, the risk profile is dependent on the lesion level.

The Q/E27 polymorphism in the beta2-adrenoceptor gene is associated with increased body weight and dyslipoproteinaemia involving triglyceride-rich lipoproteins

OBJECTIVES

To investigate whether a substitution of glutamine by glutamic acid at amino acid position 27 (Q/E27) and an arginine to glycine transition at amino acid 16 (R/G16) in the beta2-adrenoceptor gene are associated with lipid and lipoprotein disturbances and/or increased body weight in men.

DESIGN

Population-based study.

SETTING

Department of medicine at a university hospital.

SUBJECTS

A total of 180 healthy men, aged 30-45 years, were recruited at random from a register containing all permanent residents in Stockholm County (response rate of 70%).

MAIN OUTCOME MEASURES

Frequency of beta2-adrenoceptor genotypes and alleles in relation to plasma lipid and lipoprotein levels and body mass index.

RESULTS

Individuals carrying the E27 allele and/or the G16 allele had significantly higher body mass index (BMI). Furthermore, carriers of the E27 allele had significantly higher plasma concentrations of cholesterol, triglycerides, VLDL cholesterol and VLDL triglycerides than did subjects homozygous for the Q allele.

CONCLUSION

The E27 allele of the beta2-adrenoceptor gene is associated with slightly to moderately elevated BMI and dyslipoproteinaemia involving triglyceride-rich lipoproteins in healthy younger and middle-aged men.

Increased secretion of cholesteryl ester transfer protein from hamster adipose tissue: stimulation by beta-adrenergic agents

High levels of cholesteryl ester transfer protein (CETP) favours decreased plasma high density lipoprotein cholesterol and increased levels of cholesterol in apolipoprotein B containing lipoproteins. Adipose tissue is one of the major sources of circulating CETP. Previous studies by our group and others demonstrated that the production of CETP from hamster adipose tissue increases after fasting, a metabolic state known to affect the sympathoadrenal axis. The present study examines the influence of beta-adrenergic agonists on the secretion of CETP from hamster adipose tissue. Fifteen minutes after an intraperitoneal injection of isoproterenol (12 microg/kg), the release of CETP mass and activity from adipose tissue fragments incubated in vitro were significantly increased. This was associated with an elevation in CETP mass and activity in plasma. The effects of isoproterenol on CETP release from adipose tissue and plasma CETP levels were suppressed by propranolol, a beta-adrenoceptor inhibitor. Addition of 10(-6) M isoproterenol to adipose tissue in vitro increased the release of CETP mass and activity from adipose tissue and this was also blocked by propranolol. Isoproterenol-induced secretion of CETP activity from adipose tissue was partially inhibited by cytochalasin B, an inhibitor of actin cytoskeleton reorganization. Forskolin, a classical adenylate cyclase agonist and 8-bromo-cAMP, a functional analogue of cAMP, mimicked the effect of isoproterenol on CETP release from adipose tissue. Our results suggest that isoproterenol increases the secretion of CETP from hamster adipose tissue through a beta-adrenoceptor and a cAMP-dependent pathway. Actin cytoskeleton reorganization may be required for secretion of CETP. The findings imply that the secretion of CETP from adipose tissue is under neurosympathetic control.

Systolic blood pressure is related to catecholamine sensitivity in subcutaneous abdominal fat cells

A relationship between abdominal obesity and hypertension is well established. In search for an early-onset defect in adipocyte function linking these two conditions, we compared catecholamine sensitivity in subcutaneous abdominal fat cells with 24-hour systolic, mean arterial and diastolic blood pressure in 16 healthy, normotensive subjects. Clear inter-individual variations in the adipocyte lipolytic adrenoceptor sensitivity (pD2) for noradrenaline were observed in dose-response experiments (i.e., about 4 log units). An inverse and independent correlation was found between the 24-hour systolic blood pressure and pD2 for noradrenaline (r = -0.67, p < 0.01). The mean arterial blood pressure was also negatively correlated to peripheral noradrenaline sensitivity (r = -0.58, p < 0.05). However, no significant relationship between the 24-hour diastolic blood pressure and pD2 for noradrenaline was demonstrated. In conclusion we suggest that catecholamine resistance in subcutaneous fat cells may be associated with autonomic dysfunction and impaired blood pressure regulation. This finding is supported by the fact that both noradrenaline sensitivity and 24-hour systolic blood pressure also are correlated to the individual orthostatic heart rate responses, reflecting the sympathetic nervous system tone (r = 0.61, p = 0.01 and r = -0.53, p = 0.03, respectively). The relationship between noradrenaline sensitivity and systolic blood pressure may be of importance in the early development of hypertension in man.

Impaired activation of adipocyte lipolysis in familial combined hyperlipidemia

The pathophysiology of familial combined hyperlipidemia (FCHL) is unknown, but altered lipid turnover in peripheral tissues as well as hepatic overproduction of apolipoprotein B have been suggested as possible causes. In the present study, we explored whether a change in triglyceride breakdown by lipolysis in fat cells is present in FCHL. Lipolysis activation by catecholamines was examined in isolated subcutaneous adipocytes from 10 patients with FCHL and 22 healthy control subjects. Lipolysis rate was linear for at least 3 h in both groups. However, a marked (approximately 65%) decrease in the lipolytic response to noradrenaline was found in FCHL. This was also true when lipolysis was maximally stimulated at the receptor level with isoprenaline (nonselective beta-adrenergic agonist), at the adenylyl cyclase level with forskolin, or at the level of the protein kinase hormone-sensitive lipase complex with dibutyryl cAMP. The maximum enzymatic activity of hormone-sensitive lipase was decreased by approximately 40% in FCHL. On the other hand, the lipolytic sensitivity of alpha 2-, beta 1-, and beta 2-adrenoceptors was normal in this condition, as was the number and affinity of beta 1- and beta 2-adrenoceptors. Variations in the maximum lipolysis rate correlated significantly with the variations in hormone-sensitive lipase activity in the whole material, and with the serum values for triglycerides, HDL cholesterol and apoB lipoprotein within the control group, but the serum triglyceride values in FCHL were higher than this correlation predicted. In conclusion, the data demonstrate a marked resistance to the lipolytic effect of catecholamines in fat cells from patients with FCHL, in spite of normal adrenoceptor function. The lipolytic defect appears predominantly to be due to a defect in hormone-sensitive lipase, and may be of importance in the pathophysiology of FCHL.