Physiologic and genetic evidence links hemopexin to triglycerides in mice and humans.

BACKGROUND/OBJECTIVES: Elevated triglycerides predict insulin resistance and vascular disease in obesity, but how the inert triglyceride molecule is related to development of metabolic disease is unknown. To pursue novel potential mediators of triglyceride-associated metabolic disease, we used a forward genetics approach involving inbred mice and translated our findings to human subjects. SUBJECTS/METHODS: Hemopexin (HPX) was identified as a differentially expressed gene within a quantitative trait locus associated with serum triglycerides in an F16 advanced intercross between the LG/J and SM/J strains of mice. Hpx expression was evaluated in both the reproductive fat pads and livers of mice representing three strains, LG/J (n=25), SM/J (n=27) and C57Bl/6J (n=19), on high- and low-fat diets. The effect of altered Hpx expression on adipogenesis was studied in 3T3-L1 cells. Circulating HPX protein along with HPX expression were characterized in subcutaneous white adipose tissue samples obtained from a cohort of metabolically abnormal (n=18) and of metabolically normal (n=24) obese human subjects. We further examined the relationship between HPX and triglycerides in human atherosclerotic plaques (n=18). RESULTS: HPX expression in mouse adipose tissue, but not in liver, was regulated by dietary fat regardless of genetic background. HPX increased in concert with adipogenesis in 3T3-L1 cells, and disruption of its expression impaired adipocyte differentiation. RNAseq data from the adipose tissue of obese humans showed differential expression of HPX based on metabolic disease status (P<0.05), and circulating HPX levels were correlated with serum triglycerides in these subjects (r=0.33; P=0.03). HPX was also found in an unbiased proteomic screen of human atherosclerotic plaques and shown to display differential abundance based on the extent of disease and triglyceride content (P<0.05). CONCLUSIONS: Our findings suggest that HPX is associated with triglycerides and provide a framework for understanding mechanisms underlying lipid metabolism and metabolic disease.

Reproducibility of glucose, fatty acid and VLDL kinetics and multi-organ insulin sensitivity in obese subjects with non-alcoholic fatty liver disease.

OBJECTIVE: Non-alcoholic fatty liver disease (NAFLD) is associated with abnormalities in basal glucose and free fatty acid (FFA) metabolism, multi-organ insulin resistance and alterations in lipoprotein kinetics. These metabolic outcomes can be evaluated in vivo by using stable isotopically labeled tracer methods. An understanding of the reproducibility of these measures is necessary to ensure adequate statistical power in studies designed to evaluate metabolic function in subjects with NAFLD. METHODS: We determined the degree of intra-individual variability of skeletal muscle, adipose tissue, and hepatic insulin sensitivity and basal plasma glucose, FFA, and very-low-density lipoprotein triglyceride and apolipoprotein B-100 (apoB-100) kinetics in eight obese subjects with NAFLD (age: 44 ± 3 years; body mass index: 38.2 ± 1.7 kg m(-2); intrahepatic triglyceride content: 24.5 ± 3.9%), by using the hyperinsulinemic-euglycemic clamp technique and stable isotope-labeled tracer methods and mathematical modeling on two separate occasions ∼2 months apart. RESULTS: The intra-individual variability (coefficient of variation) ranged from 6% for basal glucose production to 21% for insulin-stimulated glucose disposal (percentage increase from basal). We estimated that a 25% difference in any outcome measure can be detected with a sample size of ≤ 8 subjects for paired studies and ≤ 15 subjects per group for unpaired studies, assuming an α value of 0.05 and a ß value of 0.20 (that is, 80% power). CONCLUSION: These results demonstrate that only a small number of subjects are needed to detect clinically relevant effects in insulin sensitivity and hepatic lipoprotein metabolism in obese subjects with NAFLD, and will be useful to determine appropriate sample size for future metabolic studies.

Decrease in hepatic very-low-density lipoprotein-triglyceride secretion after weight loss is inversely associated with changes in circulating leptin.

AIM: Although weight loss usually decreases very-low-density lipoprotein-triglyceride (VLDL-TG) secretion rate, the change in VLDL-TG kinetics is not directly related to the change in body weight. Circulating leptin also declines with weight loss and can affect hepatic lipid metabolism. The aim of this study was to determine whether circulating leptin is associated with weight loss-induced changes in VLDL-TG secretion. METHODS: Ten extremely obese subjects were studied. VLDL-TG secretion rate and the contribution of systemic (derived from lipolysis of subcutaneous adipose tissue TG) and non-systemic fatty acids (derived primarily from lipolysis of intrahepatic and intraperitoneal TG, and de novo lipogenesis) to VLDL-TG production were determined by using stable isotopically labelled tracer methods before and 1 year after gastric bypass surgery. RESULTS: Subjects lost 33 +/- 12% of body weight, and VLDL-TG secretion rate decreased by 46 +/- 23% (p = 0.001), primarily because of a decrease in the secretion of VLDL-TG from non-systemic fatty acids (p = 0.002). Changes in VLDL-TG secretion rates were not significantly related to reductions in body weight, body mass index, plasma palmitate flux, free fatty acid or insulin concentrations. The change in VLDL-TG secretion was inversely correlated with the change in plasma leptin concentration (r = -0.72, p = 0.013), because of a negative association between changes in leptin and VLDL-TG secretion from non-systemic fatty acids (r = -0.95, p < 0.001). CONCLUSIONS: Weight loss-induced changes in plasma leptin concentration are inversely associated with changes in VLDL-TG secretion rate. Additional studies are needed to determine whether the correlation between circulating leptin and VLDL-TG secretion represents a cause-and-effect relationship.

Reduction of risk factors for cardiovascular diseases in morbid-obese patients following biliary-intestinal bypass: 3 years' follow-up.

BACKGROUND: Obese patients are often affected by hypertension, dyslipidaemia, impaired glucose metabolism, and suffer from cardiovascular disease (CVD), related to the characteristic metabolic alterations. AIM OF THE STUDY: To evaluate reduction of risk factors for CVDs in morbid-obese patients (body mass index (BMI)>40 kg/m2) after weight loss upon bariatric surgery intervention of biliary-intestinal bypass. SUBJECTS: 45 (17 men, 28 women) morbid-obese patients (age: 19-49 y, BMI>40 kg/m2). All patients were selected on the basis of medical history, physical and biochemical evaluation and of psychiatric tests, which were performed on all individuals admitted to our Day Hospital to verify the safety of surgical intervention. MEASUREMENTS: Body weight, body composition (by dual X-ray absorptiometry, DXA), blood pressure, lipid profile, fibrinogen and glucose metabolism were monitored at baseline and 1, 3, 6, 9, 12, 24 and 36 months after surgery. RESULTS: A significant and persistent weight loss was present in all patients at the end of the 3 y follow-up period (P<0.001), with a progressive reduction of total and trunk fat mass as evaluated by means of DXA. Additionally, a parallel significant reduction in systolic (P<0.001) and diastolic (P<0.001) blood pressure was observed. Total and LDL cholesterol were significantly reduced (P<0.001), while HDL showed no modifications; triglycerides declined progressively during the 3 y follow-up (P<0.001). Fibrinogen decreased from 364.5+/-82.4 to 266.4+/-45.7 mg/dl at the end of the period (P<0.001). Fasting glucose levels and glucose levels 120 min after an oral glucose tolerance test were reduced from 95.1+/-20.3 to 78.6+/-9.1 mg/dl (P<0.001) and from 116.9+/-34.7 to 77.6+/-15.5 mg/dl (P<0.001), respectively, at baseline and at the end of the study. Moreover, fasting insulin decreased from 30.0+/-20.4 to 8.6+/-2.9 microUI/ml (P<0.001) after 3 y, while insulin levels after (120 min) oral glucose load decreased from 105.5+/-61.5 to 12.0+/-6.0 microUI/ml (P<0.001). CONCLUSION: Our results show that biliary-intestinal bypass may represent a valid and alternative therapeutic approach in patients with morbid obesity since it induces a significant and stable reduction of body weight and obesity-related risk factors for CVD.

Leptin in reproduction.

In mammals, the function of the reproductive system is dependent on the availability of energy in the environment. It is well established that acute modifications of energy balance modulate the hypothalamic-pituitary-gonadal axis. In several species, fasting and caloric restriction have been shown to cause the suppression of pulsatile luteinizing hormone secretion, via an inhibition of the gonadotropin-releasing hormone pulse generator. Such a mechanism probably prevents energy being wasted for reproduction. By contrast, excessive energy storage and obesity interfere with the correct regulation of the reproductive axis. The identification of leptin and leptin receptors, along with studies performed in animal models of leptin deficiency and resistance, has focused attention on the role of this molecule in reproduction, and disclosed new aspects of the relationship between energy stores, adipose tissue and reproductive function. Here, we discuss the central and peripheral effects of leptin on reproductive tissues, and try to fit a complex reality into a simplified model. In particular, the roles of leptin in reproduction at different anatomical levels and in various clinical and experimental settings are discussed.

Androgens and penile erection: evidence for a direct relationship between free testosterone and cavernous vasodilation in men with erectile dysfunction.

OBJECTIVE: Androgens are essential in the maintenance of nitric oxide-mediated erectile activity in the rat. The objective of the present study was to investigate the role of androgens in regulating trabecular smooth muscle relaxation in the corpus cavernosum in response to vasoactive challenge in men with erectile dysfunction (ED). DESIGN: Retrospective, double-blind correlation analyses. PATIENTS: Fifty-two impotent patients without confounding risk factors for ED were obtained from a total of 250 undergoing diagnostic evaluation. MEASUREMENTS: All patients had dynamic colour duplex ultrasound (D-CDU) and hormonal evaluation for LH, total and free testosterone, SHBG and oestradiol. RESULTS: Based upon D-CDU results patients were diagnosed as having arteriogenic (AR, n = 18; mean age 51) or corporeal venocclusive (CVO, n = 13; mean age 49) ED; in other patients (n = 21, mean age 43) a diagnosis of psychogenic (P)-ED was made by comprehensive psychogenic testing and confirmed by normal D-CDU results. AR and CVO patients had altered compliance of cavernous arteries recorded by D-CDU [20-25% lower resistive index (RI) than patients with psychogenic ED], and lower free testosterone (FT) levels than psychogenic patients [42.3 +/-3.5 SE and 49.3+/-5.2 vs. 75.2+/-7.6 pmol/l, respectively; P<0.01]. More important, in all patients there was a strong direct correlation between resistive index values and FT levels (r = 0.47, P = 0.002); the relationship was maintained also when adjusted for age, SHBG and oestradiol (r = 0.37, P = 0.02). CONCLUSIONS: These results indicate that in men with erectile dysfunction low free testosterone may correlate independently of age with the impaired relaxation of cavernous endothelial and corporeal smooth muscle cells to a vasoactive challenge. These findings give clinical support to the experimental knowledge of the importance of androgens in regulating smooth muscle function in the penis.

Basal metabolic rate in anorexia nervosa: relation to body composition and leptin concentrations.

BACKGROUND: Leptin is thought to represent a peripheral signal involved in the regulation of energy balance. Its action has been studied in animals and obese subjects. Little is known about leptin's role during negative energy balance. OBJECTIVE: The objective was to evaluate the relation between energy turnover, body composition, and plasma leptin concentrations in anorexia nervosa (AN). DESIGN: Sixteen weight-stable women with AN were compared with 22 control subjects and 14 rehabilitated AN patients (R-AN). Basal metabolic rate (BMR) was measured by indirect calorimetry; fat-free mass (FFM) and fat mass (FM) were calculated according to a 4-compartment model. Plasma leptin was determined by radioimmunoassay. RESULTS: The BMR of AN patients (2.73 +/- 0.37 kJ/min) was significantly lower than that of control subjects (3.45 +/- 0.34 kJ/min) (P < 0.001), even after adjustment for FFM (2.92 +/- 0.33 kJ/min in AN patients and 3.30 +/- 0.26 kJ/min in control subjects; P < 0.004). Plasma leptin concentrations in AN patients were 76% lower than in control subjects, even after body fat was controlled for. In R-AN patients, BMR was not significantly different from that of control subjects and leptin concentrations were generally close to normal. Plasma leptin concentrations correlated significantly with FM (r(2) = 0.53, P < 0.0000) and BMR, even after adjustment for FFM (r(2) = 0.21, P < 0.0003). CONCLUSIONS: BMR and plasma leptin concentrations are depressed in patients with AN; this is not explained by body-composition changes. The relation between leptin and BMR suggests that leptin plays a role in the energy sparing response to exposure to chronic energy deficiency. The return of BMR to normal and the significant increase in leptin concentrations in R-AN patients suggests a full reversibility of this adaptation mechanism.

Body-fat distribution and responsiveness of the pituitary-adrenal axis to corticotropin-releasing-hormone stimulation in sedentary and exercising women.

Excess upper-body (android) fat is considered an health hazard. Exercise training is known to have the potential to modify body composition and to induce a preferential loss of abdominal fat. We studied and compared the composition of whole body and major body regions using dual-energy X-ray absorptiometry (DEXA) in 21 exercising (3-4 hours of intense physical activity/day) and 21 sedentary eumenorrhoic women of similar ages, body mass index (BMI), waist-to-hip ratio (WHR) and age of menarche. In a small number of women in each group (6 out of 21), the ACTH and cortisol response to CRH test and the 24-h urinary cortisol excretion was evaluated. Exercising women had 10% higher total and leg lean mass (p<0.05), and 38% lower total fat mass (p<0.01) than sedentary women. Furthermore, the proportion of android fat was 22% lower in exercising than sedentary women (p<0.01), while the proportion of lower-body (gynoid fat) was unchanged. BMI and WHR were not different between the two groups, while the android/gynoid fat ratios were 16% lower in exercising than in sedentary women (p<0.01). In the exercising women, ACTH and cortisol plasma levels, as well as the 24-h urinary cortisol excretion, were significantly (p<0.01) higher than in the sedentary women studied. In these subjects, a direct relationship between the peak delta percentage increases of ACTH and cortisol after the CRH test and the proportion of android fat was found (r=0.60, p<0.05 and r=0.69, p<0.02, respectively). These results demonstrate that in women who practise intense exercise there are significant differences in body fat distribution in comparison to sedentary women, with a marked less amount of android fat, and suggest that this difference may be related to a reduced response of the pituitary-adrenal axis to CRH.

[Pharmacology of male sexual dysfunction]. / Farmacologia delle disfunzioni sessuali maschili.

The understanding of pharmacology of impotence has shown a steady improvement over the last 15 years which has resulted in a better appreciation of the neurovascular mechanisms of the erectile process especially at the level of the corpora cavernosa; however, central mechanisms which control libido and erection are not yet completely elucidated. Frequent diseases most commonly encountered in elderly patients--i.e. diabetes, hypertension, atherosclerosis, depression, etc--represent a frequent cause of erectile dysfunction (ED) and are treated with medications that can interfere with sexual functioning at the central and/or peripheral level. Antidepressants, including the tricyclics and the monoamine oxidase inhibitors, have been implicated in ED, decreased libido, and impaired ejaculation. Most antihypertensives have been associated with some erectile impairment, but diuretics seem to have little effect on erectile function. The calcium channel blockers and ACE inhibitors are associated with a low incidence of ED. Sympatholytic antihypertensives seldom cause importence but can cause retrograde ejaculation because of the relaxation of the smooth muscles in the prostatic urethra and bladder neck. The most commonly prescription drugs that can affect sexual function are briefly discussed and an integrated pharmacological approach to the patient with drug-induced ED is proposed.

[Alteration of luteinizing hormone pulsatility in patients with arterial hypertension]. / Alterazione della pulsatilità dell'ormone luteinizzante in pazienti affetti da ipertensione arteriosa.

The pattern of luteinizing hormone (LH) secretion in men with mild and moderate hypertension was studied. LH pulsatility was evaluated for eight hours in 14 male patients, who were subdivided into two groups: group A, consisting of 8 patients, whose systolic blood pressure ranged between 180-160 mmHg and the diastolic between 104-95 mmHg; group B, 6 patients whose systolic blood pressure ranged between 220 and 180 mmHg and the diastolic between 115-105 mmHg. Seven healthy adult males were evaluated as a control. The major changes of LH pulsatility in group A included an increased peak width (p < 0.05), increased peak amplitude (p < 0.001) and increased peak area (p < 0.001). In group B the changes followed the same pattern as in group A, but were more pronounced. The number of LH peaks was reduced (p < 0.01), the peak width was increased (p < 0.05), and both peak amplitude and peak area were increased as compared to the control group (p < 0.001). Our study demonstrates that the pattern of LH pulsatility is altered in essential hypertension and the main feature is represented by the prolonged duration of LH peaks and their greater amplitude. The altered pattern of LH secretion is likely to reflect a primary hypothalamic derangement with the gonadotropin releasing hormone (Gn-RH) secreting neurons remaining synchronized for longer times and secreting larger Gn-RH masses than in normal subjects.