Adiposity blunts the positive relationship of thyrotropin with proprotein convertase subtilisin-kexin type 9 levels in euthyroid subjects

BACKGROUND

Effects of thyroid function status on lipoprotein metabolism may extend into the euthyroid range. Low-density lipoprotein (LDL) metabolism is governed by proprotein convertase subtilisin-kexin type 9 (PCSK9), which down-regulates LDL receptor expression, resulting in higher LDL cholesterol (LDL-C). Here, we tested whether plasma PCSK9 correlates with thyroid function in nonobese and obese euthyroid subjects.

METHODS

We assessed the extent to which plasma PCSK9 is determined by thyrotropin (TSH) in 74 euthyroid subjects (31 women; TSH between 0.5 and 4.0 mU/L and free thyroxine [FT4] between 11.0 and 19.5 pM) with varying degrees of obesity (body mass index [BMI] ranging from 20.2 to 40.4 kg/m(2)).

RESULTS

TSH, FT4, PCSK9, non-high-density lipoprotein cholesterol (non-HDL-C), LDL-C, and apolipoprotein B (apoB) levels were not different between 64 nonobese subjects (BMI<30 kg/m(2)) and 10 obese subjects (BMI≥30 kg/m(2); p>0.20 for each). PCSK9 correlated positively with TSH in nonobese subjects (r=0.285, p=0.023). In contrast, PCSK9 was not associated positively with TSH in obese subjects (r=-0.249, p=0.49). The relationship of PCSK9 with TSH was different between nonobese and obese subjects when taking age, sex, FT4, and the presence of anti-thyroid antibodies into account (multiple linear regression analysis: β=-0.320, p=0.012 for the interaction term between the presence of obesity and TSH on PCSK9), and was also modified by BMI as a continuous trait (β=-0.241, p=0.062 for the interaction term between BMI and TSH on PCSK9). Non-HDL-C, LDL-C, and apoB levels were dependent on PCSK9 in nonobese subjects (p≤0.01 for each), but not in obese subjects (p>0.50), Accordingly, BMI interacted negatively with PCSK9 on non-HDL-C (p=0.028) and apoB (p=0.071).

CONCLUSIONS

This study suggests that circulating PCSK9 levels correlate with thyroid function even in the normal range. This relationship appears to be blunted by obesity. Thyroid functional status may influence cholesterol metabolism through the PCSK9 pathway.

Skin Autofluorescence as a Measure of Advanced Glycation End Products Deposition Is Elevated in Peripheral Artery Disease

Objective—

Evidence for an important role of advanced glycation end products (AGEs) in the development of atherosclerosis and cardiovascular disease beyond diabetes mellitus and renal disease is growing. Skin autofluorescence (SAF) is a validated noninvasive measure of tissue AGEs. We hypothesized that SAF is elevated in peripheral artery disease (PAD).

Methods and Results—

A case–control study was performed in 492 patients with PAD and 164 controls, matched for age (mean 66±10 years) and presence of diabetes mellitus. Cardiovascular risk factors and comorbidity (coronary artery disease, cerebrovascular disease, abdominal aortic aneurysm) were assessed. SAF was measured with the AGE Reader. SAF was higher in patients compared with controls: geometric mean 2.77 (95% confidence interval [CI], 2.71–2.83) versus 2.44 (95% CI, 2.35–2.53) arbitrary units, P =0.4×10 −8 . In logistic regression, the adjusted odds ratio for the presence of PAD was 2.47 (95% CI, 1.66–3.69) per 1 unit increase of SAF. PAD patients with cardiovascular comorbidity had a higher SAF compared with those without: geometric mean 2.93 (95% CI, 2.85–3.02) versus 2.63 (95% CI, 2.55–2.71) arbitrary units, P =0.4×10 −6 , also after correction for confounders. Regression analysis showed that age, smoking, diabetes mellitus, chronic kidney disease, and a history of cerebrovascular disease or abdominal aortic aneurysm were independently associated with SAF in the patients with PAD.

Conclusion—

Accumulation of tissue AGEs is increased in patients with PAD, independent of cardiovascular risk factors and comorbidity, although these conditions are associated with a further increase. These findings underscore the importance of AGEs in PAD, irrespective of the presence of diabetes mellitus and renal insufficiency.

Accumulation of advanced glycation endproducts in patients with systemic lupus erythematosus

OBJECTIVE

To investigate whether advanced glycation endproducts (AGEs) are increased in patients with systemic lupus erythematosus (SLE), and are related to atherosclerosis, which is accelerated in SLE, and its traditional and non-traditional disease-related risk factors.

METHODS

Fifty-five SLE patients with inactive disease and 55 age- and sex-matched controls were included. The amount of skin autofluorescence (AF), as a measure for the accumulation of AGEs, was assessed by measuring UV-A light excitation-emission matrices (AF-EEMS). Traditional risk factors and disease-related factors were recorded. Plasma levels of C-reactive protein (CRP), as a marker for systemic inflammation, were assessed. Intima-media thickness (IMT) of the common carotid artery was determined by ultrasound.

RESULTS

Skin AF-EEMS was increased in SLE patients as compared with controls (1.50 +/- 0.5 a.u. vs 1.28 +/- 0.4 a.u., P = 0.006). Regarding all included risk factors, univariate analyses in patients revealed that AF-EEMS was associated with age (r = 0.48, P < 0.001), IMT (r = 0.35, P = 0.01), creatinine (r = 0.29, P = 0.03), SLICC damage index (r = 0.29, P = 0.03) and disease duration (r = 0.32, P = 0.02). In multivariate analysis, age and disease duration were independent predictors of accumulation of AGEs in SLE (P < 0.001, P = 0.03, respectively).

CONCLUSION

AGEs are increased in SLE compared with controls. Our findings indicate that AGE accumulation is associated with disease duration and might contribute to the development of accelerated atherosclerosis in SLE and, therefore, could be used for assessment of risk for long-term vascular complications.

[Diagnostic image (50) Positive Pemberton's sign]

A 32-year-old woman had a progressive euthyroid goitre and dyspnoea. Pemberton's sign was found to be positive: elevation of both arms resulted in an inspiratory stridor and venous congestion. Symptoms and signs resolved after total thyroidectomy.

Effects of growth hormone replacement on cortisol metabolism in hypopituitary patients treated with cortisone acetate

Growth hormone (GH) replacement may inhibit 11beta-hydroxysteroid dehydrogenase type 1 (11betaHSD1) activity, resulting in diminished conversion of cortisone to cortisol. Moreover, GH replacement may lower bioavailability of hydrocortisone tablets. Therefore, substitution therapy with cortisone acetate could be disadvantageous during GH replacement. We conducted a randomized, placebo-controlled GH replacement (1 to 2 U GH/day) study during 6 months, followed by a 6-month open extension study (2U GH/day). Twelve men and 12 women with GH deficiency, of whom 17 received cortisone acetate (25 to 37.5 mg/day), participated. Eight patients were randomized to placebo initially. At baseline, after 6 and 12 months, urinary cortisol and cortisone metabolites were measured. No changes in urinary cortisol metabolites were observed after 6 months placebo (n=8). After 6 months GH the urinary (tetrahydrocortisol+allotetrahydrocortisol)/tetrahydrocortison ratio ((THF+alloTHF)/THE ratio) was unaltered in cortisone acetate treated patients (n = 17) and in patients with intact adrenal function (n = 7), whereas after 12 months GH the (THF + alloTHF)/THE ratio decreased only in cortisone acetate treated patients (1 dropout, n=9). Urinary THF and alloTHF were higher in cortisone acetate treated patients than in patients with intact adrenal function before GH and remained so after 12 months GH (p < 0.05 to p < 0.01). The sum of cortisol + cortisone metabolites did not change after GH in either group. The urinary free cortisol/free cortisone ratio, presumably reflecting renal 11betaHSD2 activity, tended to decrease in cortisone acetate treated patients (p<0.07 and p<0.05 after 6 and 12 months GH, respectively), as well as in patients with intact adrenal function (p<0.05 and a decrease in five/six patients after 6 and 12 months GH, respectively). In conclusion, these results suggest that GH replacement decreases 11betaHSD1 activity, which becomes manifest in patients receiving cortisone acetate substitution therapy. 11betaHSD2 activity is unaltered or may even be increased. It is unlikely that the bioavailability of conventional doses of cortisone acetate is impaired after GH replacement.

Twenty four hour insulin infusion impairs the ability of plasma from healthy subjects and Type 2 diabetic patients to promote cellular cholesterol efflux

Removal of cholesterol from peripheral cells by high density lipoproteins (HDL) is regarded as an important defence mechanism against atherosclerosis development. PLTP is involved in the generation of pre beta-HDL that can act as initial acceptors of cellular cholesterol. Exogenous hyperinsulinaemia may not only decrease HDL cholesterol, but also plasma phospholipid transfer protein (PLTP) activity. The effect of 24-h insulin infusion (30 mU/kg/h) on the ability of plasma to promote cholesterol efflux from Fu5AH cells was examined in eight healthy men and eight male Type 2 diabetic patients, matched for HDL cholesterol. Baseline HDL cholesterol and phospholipids, pre beta-HDL in incubated plasma, plasma apolipoprotein (apo) AI, PLTP activity and cholesterol efflux to plasma were not different between the groups. In both groups, HDL lipids, as well as plasma apo AI and PLTP activity decreased after 24 h of insulin (P<0.05 to P<0.01) compared to baseline and recovery, i.e. 1 week after insulin. Pre beta-HDL in incubated plasma did not significantly change. Cholesterol efflux to plasma from both groups decreased after insulin (P<0.05). Using plasma from healthy subjects, cholesterol efflux was correlated positively with HDL cholesterol, HDL phospholipids, pre beta-HDL in incubated plasma, plasma apo AI and PLTP activity (P<0.05 to P<0.001). Using plasma from diabetic patients, cholesterol efflux was not significantly correlated with any of these parameters. In conclusion, 24-h moderate hyperinsulinaemia impairs the ability of plasma to promote cholesterol efflux from Fu5AH cells. It is suggested that, apart from HDL, plasma PLTP activity is a determinant of cholesterol efflux via stimulation of pre beta-HDL formation. Cellular cholesterol efflux to plasma from selected Type 2 diabetic patients is maintained, but the interaction of Fu5AH cells with HDL may be altered.

Short-term Acipimox decreases the ability of plasma from Type 2 diabetic patients and healthy subjects to stimulate cellular cholesterol efflux: a potentially adverse effect on reverse cholesterol transport

AIMS

To evaluate the effect of short-term administration of the anti-lipolytic agent, Acipimox, on the ability of plasma to stimulate cellular cholesterol removal, which represents one of the first steps in the anti-atherogenic process of reverse cholesterol transport.

METHODS

Eight male Type 2 diabetic patients and eight healthy subjects were studied after a 12-h fast at baseline, after 24 h of Acipimox administration, 250 mg every 4 h, and again after 1 week (recovery). Plasma lipids, apolipoprotein AI, phospholipid transfer protein (PLTP) activity, pre-beta high-density lipoproteins (HDL) in incubated plasma and efflux of radiolabelled cholesterol from Fu5AH rat hepatoma cells to plasma were measured at each time point.

RESULTS

Acipimox lowered plasma triglycerides in diabetic patients (P = 0.001) and healthy subjects (P = 0.002), whereas plasma non-esterified fatty acids were decreased in diabetic patients (P = 0.001) compared with the averaged values at baseline and recovery. Acipimox decreased HDL cholesterol in healthy subjects (P = 0.007) and plasma apolipoprotein AI in both groups (P = 0.001 for diabetic patients; P = 0.008 for healthy subjects). Not only plasma PLTP activity (P = 0.001 for diabetic patients; P = 0.01 for healthy subjects), but also pre-beta HDL in incubated plasma (P = 0.001 for diabetic patients; P = 0.03 for healthy subjects) and cellular cholesterol efflux to plasma (P = 0.04 for diabetic patients; P = 0.005 for healthy subjects) were lowered by Acipimox in both groups.

CONCLUSIONS

Short-term Acipimox administration impairs the ability of plasma from Type 2 diabetic patients and healthy subjects to stimulate cellular cholesterol efflux, in conjunction with alterations in HDL parameters and in PLTP activity. If the impairment of cellular cholesterol efflux to plasma is sustained with long-term treatment, this potentially adverse effect should be considered when treating diabetic dyslipidaemia with Acipimox. Diabet. Med. 18, 509-513 (2001)

Redistribution of blood volume in type I diabetes

AIMS/HYPOTHESIS

Impaired activity of endothelium-derived nitric oxide in Type I (insulin-dependent) diabetes mellitus will cause an increased vascular tone. Considering the lower production of nitric oxide in veins than in arteries, an impaired activity would have less vasoconstrictive effect in veins. The reported minimally changed total plasma volume in diabetes might, therefore, indicate a redistribution of blood volumes from the arterial to the venous side of the circulation. This could be more pronounced in patients with microalbuminuria.

METHODS

In 16 normoalbuminuric and 16 microalbuminuric Type I diabetic patients and 16 individually matched healthy control subjects, venous and arterial blood volumes, venous myogenic response and arterial distensibilities were assessed in the upper arm using an electrical bio-impedance method.

RESULTS

In diabetic patients, the venous blood volume and venous myogenic response were increased (p < 0.02 and p < 0.05, respectively), whereas the arterial blood volume did not change. Moreover, in diabetic patients the distensibility of the large arteries was decreased (p < 0.05) but increased in the total arterial bed (p < 0.05). Therefore, the distensibility of the small arteries must have been increased. No differences were found between normoalbuminuric and microalbuminuric diabetic patients.

CONCLUSION/INTERPRETATION

The increase in venous blood volume and myogenic response and the decrease in distensibility of the large arteries in the upper arm are in agreement with the expected shift towards venous blood volume distribution in Type I diabetes with and without microalbuminuria. Furthermore, they support the haemodynamic hypothesis of the pathogenesis of diabetic microangiopathy.

Differentiated thyroid carcinoma in the elderly

The overall prognosis of patients with differentiated thyroid cancer is excellent, but the prognosis is rapidly worsening, when the disease is diagnosed in elderly patients. Old patients more often present with poor prognostic features, such as large tumors, follicular or Hürthle cell subtypes, extrathyroidal growth and distant metastases. Therefore, an optimal therapeutic approach is recommended. Current therapy includes a total thyroidectomy, if necessary combined with a lymph node dissection and followed by high dose radioiodine ablation. Radioiodine therapy in elderly patients meets specific problems, concerning thyroid hormone withdrawal, side effects of 131I and nursing problems. Additional treatment of residual, recurrent or metastatic disease must be tailored, according to the stage of the disease, and should not be denied on the basis of chronological age. Lifelong treatment with suppressive thyroid hormone therapy does not lead to important long-term side effects at old age.

Time course of the antiproteinuric and renal haemodynamic responses to losartan in microalbuminuric IDDM

BACKGROUND

Interference in the renin-angiotensin system with angiotensin-converting enzyme (ACE) inhibitors has proven to be effective in lowering albuminuria in patients with insulin-dependent diabetes mellitus (IDDM). We studied whether angiotensin II receptor antagonism reduces urinary albumin excretion (UAE) in IDDM patients, and the relationship between the antiproteinuric effect and changes in systemic and renal haemodynamics.

METHODS

Nine IDDM patients with microalbuminuria (30-300 mg/24 h) were studied. Patients were studied after a 4 week placebo period, on days 3, 7 and 28 of treatment with losartan 50 mg once daily, and after a 4 week placebo-controlled recovery period.

RESULTS

Mean arterial pressure (MAP) was only slightly lowered during losartan treatment. Effective renal plasma flow (ERPF) was significantly increased on the third day of treatment and remained stable throughout the treatment period. Glomerular filtration rate (GFR) did not change throughout the study. Filtration fraction (FF) was maximally lowered on the third day of treatment and remained stable during treatment. UAE was already significantly lowered after 2 days of treatment, during both the day and night, and remained stable throughout the treatment period. The time course of the changes in UAE paralleled that of the changes in MAP, ERPF and FF.

CONCLUSIONS

The angiotensin receptor antagonist losartan effectively lowers UAE in microalbuminuric IDDM patients. The changes observed in renal haemodynamics and UAE are concordant in time and maximal within only a few days of treatment. These results support the importance of the specific effects of interference in the renin angiotensin system (RAS) in microalbuminuric IDDM on blood pressure and renal haemodynamics in reducing urinary protein leakage, rather than non-haemodynamic, structural changes of the glomerular basement membrane.

[Elevated hormone levels without endocrinopathy: hypercortisoluria and hypoglycemia as facticious disorders]

A 29-year-old female patient with weight gain and intermittent hypertension was suspected of having Cushing's syndrome due to conspicuous hypercortisoluria. Specific laboratory tests demonstrated that the urine samples contained prednisolone, which had resulted in a false positive elevation of urine-free cortisol measurements. The patient admitted to having taken prednisolone tablets and also to having added them to several urine collections. In a 21-year-old male patient with unexplained hypoglycaemia, hypoglycaemia was recorded during a 72-hour fast together with an elevated level of plasma insulin and a low level of plasma C-peptide. The presence of insulin autoantibodies could be excluded, making a diagnosis of factitious hypoglycaemia highly likely. Both patients were confronted with the factitious disorder and received psychiatric counselling, after which no further problems arose. Where excessive hormone levels occur, the possibility of a factitious disorder needs to be considered. In such cases, specific supplementary laboratory tests may prove helpful.

Plasma cholesteryl ester transfer and hepatic lipase activity are related to high-density lipoprotein cholesterol in association with insulin resistance in type 2 diabetic and non-diabetic subjects

We evaluated the hypothesis that plasma cholesteryl ester transfer (CET) and lipase activities are influenced by insulin sensitivity and contribute to the low high-density lipoprotein (HDL) cholesterol observed in type 2 diabetic patients and insulin-resistant non-diabetic subjects. Sixteen type 2 diabetic and 16 non-diabetic subjects participated. Diabetic and non-diabetic subjects were divided in equal groups of eight subjects with low or high insulin sensitivity, which was documented as the glucose infusion rate (M-value) during the last hour of a 3-h euglycaemic hyperinsulinaemic clamp (150 mU kg(-1) h(-1), blood glucose target 4.6 mmol L(-1)). Post-heparin plasma lipoprotein lipase (LPL) and hepatic lipase (HL) activities were measured in samples obtained 1-2 weeks before the clamp. Plasma CET was measured by a radioisotope method. Compared to non-diabetic men with high insulin sensitivity (n = 8) HDL cholesterol was lower in type 2 diabetic men (n=8, p<0.01) and non-diabetic men (n=8, p <0.05) with low insulin sensitivity, and the HDL cholesterylester content was lower in type 2 diabetic men with high insulin sensitivity (n=8, p<0.05). In non-diabetic subjects with high insulin sensitivity, plasma CET was lower than in the other groups (p<0.05 for all). Multiple regression analysis showed that plasma CET (p=0.001) and HL activity (p=0.02) were independently and negatively associated with the M-value. No association between the M-value and LPL activity was observed. Independent negative relationships of HDL cholesterol with plasma CET (p = 0.04) and HL activity (p=0.03) were observed. This study supports the hypothesis that a low HDL cholesterol associated with insulin resistance in type 2 diabetic and non-diabetic subjects is related to a high plasma CET and a high HL activity.

Role of phospholipid transfer protein and prebeta-high density lipoproteins in maintaining cholesterol efflux from Fu5AH cells to plasma from insulin-resistant subjects

Plasma phospholipid transfer protein (PLTP) enhances the generation of prebeta-high density lipoproteins (HDL) that may act as initial acceptors of cellular cholesterol, and are likely to play an important role in the antiatherogenic process of reverse cholesterol transport. We examined the interrelationships between insulin resistance, the ability of plasma to stimulate cellular cholesterol efflux, HDL cholesterol, plasma PLTP activity and prebeta-HDL in 12 non-diabetic, non-smoking, normotriglyceridaemic men. Cholesterol efflux from Fu5AH cells to plasma, plasma lipoproteins, PLTP activity and prebeta-HDL formation as measured in incubated plasma were determined after a 12-h fast. Insulin sensitivity was assessed by a euglycaemic, hyperinsulinaemic clamp (M-value). HDL cholesterol was positively correlated with the M-value (r=0.65, p< 0.05), whereas plasma PLTP activity (r= -0.59, p <0.05) and prebeta-HDL in incubated plasma (r= -0.66, p<0.05) were negatively correlated with the M-value. Thus, the lower the insulin sensitivity, the lower was HDL cholesterol and the higher were plasma PLTP activity and prebeta-HDL. Cellular cholesterol efflux tended to be correlated with HDL cholesterol (r=0.55, p < 0.10) as well as with plasma PLTP activity (r=0.56, p<0.10) and was positively correlated with prebeta-HDL in incubated plasma (r=0.74, p<0.01). No positive correlation between the M-value and cellular cholesterol efflux was found (r= -0.34, ns). These preliminary results support the hypothesis that, despite a lower HDL cholesterol, the ability of plasma from insulin-resistant subjects to promote cellular cholesterol efflux is not impaired, as a consequence of a higher plasma PLTP activity and enhanced prebeta-HDL formation.

Low plasma lecithin:cholesterol acyltransferase and lipid transfer protein activities in growth hormone deficient and acromegalic men: role in altered high density lipoproteins

Growth hormone (GH) deficiency and acromegaly may be associated with increased cardiovascular risk. Little is known about alterations in high density lipoproteins (HDL) in these conditions. Lecithin:cholesterol acyl transferase (LCAT) has the ability to esterify free cholesterol (FC) in HDL. Cholesteryl ester transfer protein (CETP) is able to transfer cholesteryl esters (CE) from HDL to very low and low density lipoproteins (VLDL and LDL). During phospholipid transfer protein (PLTP)-mediated HDL remodelling, small pre beta-HDL particles are generated which serve as acceptors for cellular cholesterol and provide the initial LCAT-substrate. We documented plasma lipids, LCAT, CETP and PLTP activity levels as well as plasma cholesterol esterification (EST) and cholesteryl ester transfer (CET) in 12 adult men with acquired GH deficiency, 12 acromegalic men and 24 healthy male subjects. All GH deficient and acromegalic patients received conventional hormonal replacement therapy if necessary. VLDL + LDL cholesterol and plasma triglycerides were higher in GH deficient (P < 0.01 and P < 0.05) and acromegalic patients (P < 0.05 and P < 0.01) than in healthy subjects. HDL cholesterol and HDL CE were lower (P < 0.05 for both) and the HDL FC/CE ratio was higher (P < 0.01) in these patient groups compared to healthy subjects. Plasma LCAT, CETP and PLTP activity levels were lower in acromegalic patients (P < 0.01 for all) and CETP activity was lower in GH deficient patients (P < 0.01) compared to healthy subjects. Plasma EST and CET were decreased in both acromegalic (P < 0.01 for both) and GH deficient patients (P < 0.05 for both). Multiple regression analysis demonstrated independent negative relationships of plasma insulin-like growth factor I with plasma LCAT (P = 0.0001), CETP (P = 0.009) and PLTP activity levels (P = 0.021). Plasma LCAT (P = 0.0001) and CETP activity (P = 0.0001) were also negatively associated with (substitution therapy for) adrenal insufficiency. In conclusion, GH deficient and acromegalic patients show abnormalities in HDL, consistent with impaired LCAT action. Decreases in plasma EST and CET in such patients, as well as a low PLTP activity in acromegaly suggest that reverse cholesterol transport may be impaired, contributing to increased cardiovascular risk.