Hepatic insulin resistance in NAFLD: relationship with markers of atherosclerosis and metabolic syndrome components

AIMS

Fat accumulation in the liver and in the muscle results in hepatic and muscle insulin resistance and has been associated with increased cardiovascular risk. It is unclear whether the individual role of hepatic and muscle insulin resistance in the onset of dyslipidaemia is observed in nonalcoholic fatty liver disease (NAFLD) patients and whether this association is mediated through traditional risk factors. The aim of this study was to assess hepatic and muscle insulin resistance in NAFLD and its relationship with carotid artery intima-media thickness (IMT) and the apoB/apoAI ratio as markers of atherosclerosis.

METHODS

We studied 132 patients with a non-invasive diagnosis of NAFLD stratified into two groups according to the severity of steatosis at ultrasound scan. In all subjects, we measured hepatic insulin resistance (H-IR) and muscle insulin sensitivity index (MISI) by oral glucose tolerance test as proposed by DeFronzo, IMT, apoB/apoAI and the components of the metabolic syndrome (MS) as defined by ATP III.

RESULTS

H-IR was significantly higher in moderate/severe steatosis than in the mild steatosis group (p < 0.0001). By contrast, MISI did not differ between the two groups. There was a significant correlation between H-IR, MISI and all of the components of MS. H-IR was significantly correlated with carotid IMT (r = 0.35; p < 0.0001) and the apoB/apoAI ratio (r = 0.43; p < 0.0001). Otherwise, a significant correlation was observed only between MISI and apoB/apoAI ratio. Multivariate analysis revealed that H-IR is related to early markers of atherosclerosis independent of MS components.

CONCLUSIONS

In our study population, NAFLD was positively associated with carotid IMT, and this association is independent of MS components, but strictly related to H-IR that might contribute to the development of atherosclerosis through an impairment of the lipid profile in terms of the apoB/apoAI ratio. By contrast, no significant relation was observed between MISI and carotid IMT.

Early phase insulin secretion is increased in subjects with normal fasting glucose and metabolic syndrome: a premature feature of beta-cell dysfunction

BACKGROUND AND AIMS

Metabolic syndrome (MS) has been mainly related to insulin resistance, but the role of changes in insulin secretion has not been thoroughly investigated.

METHODS AND RESULTS

Using an oral glucose tolerance test (OGTT) we studied beta-cell function and insulin sensitivity in subjects with normal fasting glucose with and without MS, and their relationship to fatty liver which was evaluated by abdominal-ultrasonography. In MS early phase insulin secretion, as measured by insulinogenic index (IG(30)), was increased (p<0.05) independently from insulin sensitivity. Furthermore IG(30) was progressively higher as the number of factors needed for the diagnosis of MS increased (p<0.01). Insulin and C-peptide AUC were also increased (p<0.01 and p<0.05, respectively) but, in contrast to IG(30), these differences disappeared when ISI was used as a covariate. After OGTT, 51% of the subjects with MS had altered post-load glucose tolerance compared to 24.9% without MS (p<0.01). In both groups, the altered glucose tolerance was associated with a similar IG(30) reduction. In normo-tolerant subjects with MS the IG(30) was higher (+54.1%, p<0.01), and this elevation occurred irrespective of ISI; however, the beta-cell compensatory capacity for insulin resistance (disposition index) was impaired (p<0.001). Fatty liver was more frequent (p<0.001) and more severe (p<0.01) in MS, and it was significantly related to total AUC-insulin (p<0.001), independently from ISI.

CONCLUSION

These findings indicate that the prevalence of altered tolerance is more frequent in subjects with normal fasting glucose and MS. The hyperinsulinemia might not only be an adaptive response to insulin resistance, but a primary defect of beta-cell function contributing to glucose intolerance.

Therapeutic options for elderly diabetic subjects: open label, randomized clinical trial of insulin glargine added to oral antidiabetic drugs versus increased dosage of oral antidiabetic drugs

Glycemic control in elderly persons with type 2 diabetes mellitus (T2DM) is challenging because they are more likely to have other age-associated medical conditions and to experience hypoglycemia during intensive therapy. A best therapeutic strategy for these patients has not yet been defined. We investigated the efficacy and safety of adding once-daily insulin glargine to patients' current oral antidiabetic drugs (OAD) regimen, compared to increasing the OAD doses. The study enrolled patients aged 65 years or more, with poor glycemic control. Patients were randomized to two groups and entered a 3-week titration period in which their actual therapy was adjusted to meet the study's glycemic goals, by either adding insulin glargine to current therapy (group A, 27 patients) or increasing current OAD dosages (group B, 28 patients). Thereafter, therapies were continued unchanged for a 24-week observation period. The mean therapeutic dosage of insulin glargine in group A was 14.9 IU/day (SD = 5.0 IU/day). During the observation period, mean levels of glycosylated hemoglobin (HbA1c) reduced by 1.5% in group A and 0.6% in group B (P = 0.381). An HbA1c level <7.0% was achieved by five patients in each group. Mean fasting blood glucose levels reduced by 29 and 15% in groups A and B, respectively (P = 0.029). Group A had fewer total hypoglycemic events (23 vs. 79, P = 0.030) and fewer patients experiencing any such event (9 vs. 17, P = 0.045). Neither a serious hypoglycemic event nor other adverse event occurred. These results suggest that, compared to increasing OAD dosage, the addition of insulin glargine to current OAD therapy is as effective but safer in terms of the risk for hypoglycemia in elderly patients with T2DM.

Increased augmentation index and central aortic blood pressure in osteoporotic postmenopausal women

Osteoporosis has been associated with cardiovascular disease. We found increased augmentation index, a measure of wave reflections and arterial stiffness, and central pressures in osteoporotic postmenopausal women. They also showed a higher estimated aortic pulse wave velocity, indicating a stiffer aorta. These changes may increase cardiovascular risk in postmenopausal osteoporosis.

INTRODUCTION

Evidence suggests a link between osteoporosis and cardiovascular disease. We investigated whether augmentation index (AIx), a measure of pulse wave reflections and arterial stiffness, is increased and related to the osteoprotegerin (OPG)/receptor activator of nuclear factor-kappa B ligand (RANKL) system in postmenopausal osteoporosis.

METHODS

AIx and central aortic haemodynamics were assessed using pulse wave analysis in 182 cardiovascular disease-free osteoporotic postmenopausal women and in 160 controls. Statistical analysis was performed by unpaired t test, Mann-Whitney test, Spearman's correlation coefficient, and multivariate linear regression analysis.

RESULTS

AIx (37.2 +/- 7.0 vs. 29.6 +/- 9.2 %, P < 0.0001) and central aortic systolic (117.5 +/- 12.1 vs. 111.4 +/- 12.2 mmHg, P < 0.0001) and pulse (40.5 +/- 10.3 vs. 36.4 +/- 8.1 mmHg, P = 0.0007) pressures were significantly higher in osteoporotic patients than in controls. The estimated aortic pulse wave velocity (PWV) was also significantly higher in the osteoporotic group. In multivariate analysis for osteoporotic patients, femoral neck and lumbar spine bone mineral density T scores were independent negative predictors of AIx (P < 0.0001). AIx was not correlated with serum levels of OPG and RANKL.

CONCLUSIONS

Osteoporotic postmenopausal women show increased AIx and central aortic pressures, and a higher estimated aortic PWV, indicating a stiffer aorta. Such alterations may increase cardiovascular risk in postmenopausal osteoporosis.

Effects of either LT4 monotherapy or LT4/LT3 combined therapy in patients totally thyroidectomized for thyroid cancer

After total thyroidectomy all thyroid cancer patients require lifelong treatment with thyroid hormones; the treatment of choice is synthetic levothyroxine (LT4). The question of whether these patients might benefit from the combined LT4 and liothyronine (LT3) treatment has been addressed with conflicting conclusions. The aim of the present study was to compare the effects of combined low LT4/LT3 molar ratio therapy versus LT4 monotherapy on various target organs and tissues in patients thyroidectomized for thyroid cancer. Urine collection (24 hour), a fasting blood sample for laboratory examinations, thyroid function clinical score, and cardiovascular, neurological, and neuropsychological evaluations were obtained. Clinical parameters and peripheral markers of thyroid function were measured during the two different treatment regimens in 20 patients. Mean serum aspartate aminotransferase, alanine aminotransferase, sex hormone binding globulin, and osteocalcin values were significantly higher during the combined treatment. No significant differences in the clinical score, the systolic and diastolic performance, and the neurological and neuropsychological evaluations were observed between the two treatment regimens. Moreover, no alteration due to subclinical hyperthyroidism or to the fluctuations in serum T3 concentrations during the combined therapy was observed. In conclusion, we found no evidence that combined therapy with a low LT4/LT3 molar ratio resulted in improved well-being and cognitive function or in increased thyroid hormone action on peripheral tissues in respect to LT4 monotherapy. Until future large, blind, randomized, and controlled trials prove otherwise, LT4 should remain the standard treatment for thyroid cancer patients.

Decreased high-density lipoprotein (HDL) particle size, prebeta-, and large HDL subspecies concentration in Finnish low-HDL families: relationship with intima-media thickness

OBJECTIVE

High-density lipoprotein (HDL) cholesterol correlates inversely with the risk of coronary heart disease (CHD). The precise antiatherogenic mechanisms of HDL subspecies are not thoroughly elucidated. We studied the relationship between carotid intima-media thickness (IMT) and HDL subspecies distribution in Finnish families with low HDL cholesterol and premature CHD.

METHODS AND RESULTS

Altogether, 148 members of Finnish low-HDL families and 133 healthy control subjects participated in our study. HDL particle size was significantly smaller in affected family members (HDL < or =10th Finnish age-sex specific percentile) compared with unaffected family members and control subjects (9.1+/-0.04 nm versus 9.5+/-0.05 nm, P<0.0001, versus 9.8+/-0.03 nm, P<0.0001 [mean+/-SE]). Large HDL2b particles as well as prebeta-HDL concentration were significantly decreased among the affected family members. Mean IMT was significantly higher in the affected family members than in the control subjects (0.85+/-0.01 mm versus 0.79+/-0.01 mm; P<0.0001). Age, HDL2b, systolic blood pressure, and prebeta-HDL were significant independent determinants of mean IMT.

CONCLUSIONS

The decreased levels of HDL2b and prebeta-HDL reflect the potentially efflux-deficient HDL subspecies profile in the affected low-HDL family members. Decreased HDL particle size caused by the decrease of plasma concentration of HDL2b and decreased prebeta-HDL levels correlate with increased IMT.

Acute changes in clinical parameters and thyroid function peripheral markers following L-T4 withdrawal in patients totally thyroidectomized for thyroid cancer

After total thyroidectomy, differentiated thyroid cancer (DTC) patients have to undergo L-T4 withdrawal for measuring serum thyroglobulin and 131I whole-body scan (131I WBS) to evaluate residual/recurrent malignant disease. The aim of the present work was to study in these patients the effects of acute thyroid hormone deficiency on various target organs and tissues. Clinical parameters and thyroid function peripheral markers were evaluated in 20 DTC patients, both before and after L-T4 withdrawal. A 24-h urine collection, a fasting blood sample for laboratory examinations, a clinical score for hypothyroidism and cardiovascular, neurological and neuropsychological evaluations were carried out. After L-T4 withdrawal, the clinical score significantly increased, as well as total cholesterol, triglycerides, creatine kinase, lactate dehydrogenase, aspartate aminotransferase and alanine aminotransferase, whereas SHBG, osteocalcin and urine hydroxyproline levels significantly decreased. The acute thyroid hormone deficiency caused a systolic dysfunction of the left ventricle associated with an increase in systemic vascular resistance without cardiac contractility alterations. A significant increase in the left ventricular mass and thickness was also observed. Carpal tunnel syndrome appeared in 30% of patients and a significant reduction in the immediate auditive memorization and in attentive performance was also detected. These observations indicate that acute hypothyroidism causes significant clinical alterations of peripheral tissue function. In the follow-up of DTC patients, therefore, L-T4 withdrawal procedure should be restricted to cases where the cost/benefit ratio is favorable. Alternative procedures, such as the use of recombinant human TSH, should be used whenever possible.

Left ventricular function in acute hypothyroidism: a Doppler echocardiography study

BACKGROUND

Acute changes in cardiac parameters may occur after L-thyroxine withdrawal in patients totally thyroidectomized for thyroid cancer. The literature data regarding cardiac function in acute hypothyroidism are limited and discordant.

METHODS

In order to evaluate the effects of acute hypothyroidism on cardiac function, 20 athyreotic patients (3 males, 17 females, mean age 46.4 +/- 8.6 years, range 18-58 years) underwent Doppler echocardiography during L-thyroxine therapy (euthyroid phase) and 5 weeks after hormone therapy withdrawal (hypothyroid phase).

RESULTS

Significant changes in the left ventricular mass (83 +/- 12 vs 93 +/- 17 g/m2, p = 0.004) and end-diastolic volume (56 +/- 9 vs 50 +/- 9 ml/m2, p = 0.01) were found. Among systolic function parameters, the pre-ejection period/left ventricular ejection time (PEP/LVET) ratio (0.33 +/- 0.07 vs 0.40 +/- 0.08, p = 0.0002), aortic peak flow velocity corrected for heart rate (3.9 +/- 0.7 vs 3.5 +/- 0.5 cm/s, p = 0.02) and mean aortic acceleration corrected for heart rate (45 +/- 15 vs 38 +/- 9 cm/s2, p = 0.007) showed significant variations, whereas the left ventricular fractional shortening (39 +/- 5 vs 40 +/- 6%, p = NS) and ejection fraction (69 +/- 6 vs 68 +/- 7%, p = NS) did not change. Among diastolic function parameters, only the E-wave velocity decreased (73 +/- 17 vs 65 +/- 12 cm/s, p = 0.01); no significant modification was found in the A-wave velocity (62 +/- 19 vs 58 +/- 14 cm/s, p = NS), E/A ratio (1.2 +/- 0.5 vs 1.1 +/- 0.3, p = NS), isovolumic relaxation time (93 +/- 16 vs 95 +/- 37 ms, p = NS) and E-wave deceleration time (233 +/- 48 vs 235 +/- 45 ms, p = NS). The pattern of left ventricular filling remained unchanged, except in 2 patients. The Suga-Sagawa's index, a known parameter of myocardial contractility, was unchanged (5.6 +/- 2 vs 6.1 +/- 2 mmHg/ml, p = NS). The systemic vascular resistance increased (1511 +/- 599 vs 2216 +/- 408 dynes-s-cm(-5), p = 0.002), while the stroke index (39 +/- 8 vs 33 +/- 7 ml/m2, p = 0.001) and cardiac index (2.74 +/- 0.6 vs 2.07 +/- 0.5 l/min/m2, p = 0.0001) significantly decreased.

CONCLUSIONS

Acute hypothyroidism was associated with left ventricular systolic dysfunction, probably due to pre- and afterload alterations rather than to an impaired myocardial contractility. The diastolic function was not significantly modified. An increase in cardiac mass was also found, possibly a consequence of early interstitial myxedema. Unlike the PEP/LVET ratio, both the fractional shortening and ejection fraction may be unreliable indicators of left ventricular systolic dysfunction in patients with acute hypothyroidism.

Low HDL cholesterol concentration is associated with increased intima-media thickness independent of arterial stiffness in healthy subjects from families with low HDL cholesterol

BACKGROUND

Low high-density lipoprotein cholesterol (HDL-C) is associated with increased risk for developing coronary artery disease. Cardiovascular disease is characterized by increased intima-media thickness (IMT) and arterial stiffness, but the effect of low HDL on these measurements has not been reported.

MATERIALS AND METHODS

We studied 18 apparently healthy subjects from families with low HDL-C and 18 control subjects, which were pair-matched to maximize statistical power. Intima-media thickness was assessed using ultrasound examination of the carotid arteries. Arterial stiffness was measured using applanation tonometry on the radial artery and pulse-wave analysis to obtain central aortic pulse-pressure waveform, from which the augmentation index, a measure of global large artery stiffness, was calculated.

RESULTS

Low HDL subjects (age 41 +/- 3 years, BMI 26.6 +/- 1.0 kg m(-2) had significantly lower HDL-C than the control subjects (age 41 +/- 3 years, BMI 26.5 +/- 1.0 kg m-2; 1.00 +/- 0.05 vs. 1.49 +/- 0.09 mmol L-1, low HDL vs. control subjects, P < 0.0001). Subjects with low HDL-C had significantly thicker mean IMTs than the control subjects (0.77 +/- 0.03 vs. 0.70 +/- 0.02 mm, low HDL vs. control subjects, P < 0.01). The maximal (0.99 +/- 0.04 vs. 0.89 +/- 0.03 mm, P < 0.01), far wall (0.76 +/- 0.04 vs. 0.69 +/- 0.02 mm, P < 0.05) and carotid bulb (1.11 +/- 0.06 vs. 0.97 +/- 0.04 mm) IMTs were also significantly increased, whereas the mean common carotid and the internal artery IMT were not. The age-related increase in mean IMT was more pronounced in the low HDL subjects than the control subjects (P < 0.01 for difference between elevations of age vs. IMT slopes). There were no differences in central pressure augmentation, the augmentation index, peripheral or central blood pressures between the groups.

CONCLUSIONS

A low HDL-C concentration is associated with thickening of carotid IMT independent of other risk factors in healthy affected members of low HDL families.

A low high density lipoprotein (HDL) level is associated with carotid artery intima-media thickness in asymptomatic members of low HDL families

Low serum high-density lipoprotein cholesterol (HDL-C) is a strong predictor of coronary heart disease (CHD). The aim of the present study was to evaluate the metabolic parameters predicting the atherosclerotic changes in asymptomatic members of low HDL-C families. We performed carotid B-mode ultrasonography with intima-media thickness (IMT) measurement for 89 asymptomatic members of Finnish low HDL-C families. The family members were categorized as affected or unaffected according to the 10th age-gender specific HDL-C percentile. In the affected group, the most marked decrease of HDL subclasses was observed for HDL2-C when compared with the unaffected (109% difference). In the partial correlation analyses, age and gender showed significant correlations with the mean IMT (for age, r=0.880, P<0.001, and for gender, r=-0.361, P=0.018). Importantly, HDL-C and HDL2-C were significantly inversely related to the mean carotid IMT, also after correction for age (for HDL-C, r=-0.186, P=0.043, for HDL2-C, r=-0.208, P=0.029, when adjusted for age). The correlation for HDL-C was significant also when adjusted for gender. In conclusion, low HDL-C is associated with increased carotid artery IMT in asymptomatic members of low HDL-C families.