Parameter and coupling estimation in small networks of Izhikevich's neurons

Nowadays, experimental techniques allow scientists to have access to large amounts of data. In order to obtain reliable information from the complex systems that produce these data, appropriate analysis tools are needed. The Kalman filter is a frequently used technique to infer, assuming a model of the system, the parameters of the model from uncertain observations. A well-known implementation of the Kalman filter, the unscented Kalman filter (UKF), was recently shown to be able to infer the connectivity of a set of coupled chaotic oscillators. In this work, we test whether the UKF can also reconstruct the connectivity of small groups of coupled neurons when their links are either electrical or chemical synapses. In particular, we consider Izhikevich neurons and aim to infer which neurons influence each other, considering simulated spike trains as the experimental observations used by the UKF. First, we verify that the UKF can recover the parameters of a single neuron, even when the parameters vary in time. Second, we analyze small neural ensembles and demonstrate that the UKF allows inferring the connectivity between the neurons, even for heterogeneous, directed, and temporally evolving networks. Our results show that time-dependent parameter and coupling estimation is possible in this nonlinearly coupled system.

Inferring the connectivity of coupled chaotic oscillators using Kalman filtering

Inferring the interactions between coupled oscillators is a significant open problem in complexity science, with multiple interdisciplinary applications. While the Kalman filter (KF) technique is a well-known tool, widely used for data assimilation and parameter estimation, to the best of our knowledge, it has not yet been used for inferring the connectivity of coupled chaotic oscillators. Here we demonstrate that KF allows reconstructing the interaction topology and the coupling strength of a network of mutually coupled Rössler-like chaotic oscillators. We show that the connectivity can be inferred by considering only the observed dynamics of a single variable of the three that define the phase space of each oscillator. We also show that both the coupling strength and the network architecture can be inferred even when the oscillators are close to synchronization. Simulation results are provided to show the effectiveness and applicability of the proposed method.

Influence of vitamin D levels on the cardiovascular profile of hypogonadal men

PURPOSE

A large body of evidence suggests a role for vitamin D in conditioning cardiovascular risk. Therefore, it can be hypothesized that vitamin D might also play a role in influencing the metabolic profile of hypogonadal men. In this work, we aimed at evaluating if any relationship exists between vitamin D levels and cardiovascular parameters in male hypogonadism.

METHODS

Hypogonadal patients attending our andrology unit were retrospectively reviewed. Clinical and biochemical parameters were evaluated.

RESULTS

103 patients were studied (51 non-diabetic and 52 diabetic subjects). Mean age of the whole sample was 65 years (standard error of the mean: 0.62). Significant correlations of age, total testosterone, parathyroid hormone (PTH), calcemia, and 25-OH vitamin D with the metabolic profile were found. In logistic regression models including age, total testosterone, PTH, calcemia and 25-OH vitamin D as independent variables, lower levels of 25-OH vitamin D were associated with high values of body mass index (BMI) [odds ratio (OR) 0.910, p 0.019], insulin (OR 0.918, p 0.034), homeostatic model assessment (HOMA) index (OR 0.918, p 0.030), total cholesterol (OR 0.819, p < 0.001), triglycerides (OR 0.820, p < 0.001), and low-density lipoprotein cholesterol (OR 0.923, p 0.034). In non-diabetic subjects, lower levels of 25-OH vitamin D were associated with high values of BMI, insulin, HOMA, triglycerides, systolic, and diastolic blood pressure. On the other hand, in diabetic subjects, lower levels of 25-OH vitamin D were associated with high values of total cholesterol and triglycerides.

CONCLUSIONS

Our work shows the influence of vitamin D on cardiovascular profile in male hypogonadism. This effect seems to be more relevant in non-diabetic subjects. If these data were to be confirmed, vitamin D assessment might become mandatory in the clinical evaluation of cardiovascular profile in male hypogonadism.

Diabetes Mellitus-Associated Functional Hypercortisolism Impairs Sexual Function in Male Late-Onset Hypogonadism

Functional hypercortisolism is generated by conditions able to chronically activate hypothalamic-pituitary-adrenal axis and has been proven to have a negative role in several complications. However, no study has evaluated the possible influence of diabetes mellitus-associated functional hypercortisolism on male hypogonadism and sexual function. We aimed to identify any association of hypothalamic-pituitary-adrenal axis dysregulation measures with testosterone and sexual function in men simultaneously affected by diabetes mellitus and late-onset hypogonadism. Fifteen diabetes mellitus and late-onset hypogonadism subjects suffering from functional hypercortisolism and fifteen diabetes mellitus and late-onset hypogonadism subjects who were free of functional hypercortisolism were retrospectively reviewed. Clinical, hormonal, and sexual parameters were considered. Hypercortisolemic subjects showed higher values of body mass index, waist, and glycated hemoglobin and lower ones of testosterone compared to normocortisolemic ones. All sexual parameters, except for orgasmic function, were significantly worse in hypercortisolemic than in normocortisolemic subjects. Hypercortisolemic patients showed higher values of cortisol after dexamethasone and urinary free cortisol as well as a lesser ACTH response after corticotropin releasing hormone test (ACTH area under curve) compared to normocortisolemic ones. No significant association was found at Poisson regression analysis between hormonal and sexual variables in normocortisolemic patients. In hypercortisolemic subjects, negative and significant associations of cortisol response after corticotropin releasing hormone (cortisol area under curve) with erectile function (β: -0.0008; p: 0.015) and total international index of erectile function score (β: -0.0006; p: 0.001) were evident. This study suggests for the first time the impairing influence of the dysregulated hypothalamic-pituitary-adrenal axis on sexual function in diabetes mellitus-associated late-onset hypogonadism.

Influence of the hypothalamic-pituitary-adrenal axis dysregulation on the metabolic profile of patients affected by diabetes mellitus-associated late onset hypogonadism

BACKGROUND AND AIMS

Functional hypercortisolism (FH) is generated by clinical states able to chronically activate the hypothalamic-pituitary-adrenal (HPA) axis [e.g. diabetes mellitus (DM)]. No study has evaluated FH influence in worsening the metabolic profile of male patients affected by DM-associated hypogonadism. In this retrospective work, we assess the possible association between HPA axis-dysregulation and cardiovascular risk factors in men simultaneously affected by DM and late-onset hypogonadism (LOH).

METHODS AND RESULTS

Fourteen DM and LOH subjects affected by FH (Hypercort-DM-LOH) and fourteen DM and LOH subjects who were not suffering from FH (Normocort-DM-LOH) were retrospectively considered. Clinical, hormonal and metabolic parameters were retrieved. All metabolic parameters, except for systolic blood pressure, were significantly worse in Hypercort-DM-LOH than in Normocort-DM-LOH. After adjustment for body mass index, waist and total testosterone, Hypercort-DM-LOH subjects showed significantly worse metabolic parameters than Normocort-DM-LOH ones. In Normocort-DM-LOH, no significant correlation between general/hormonal parameters and metabolic variables was present. In Hypercort-DM-LOH, positive and significant correlations of cortisol area under the curve (AUC) after corticotropin releasing hormone with glycemia, triglycerides and blood pressure were evident; on the other hand, negative and significant correlation was present between cortisol AUC and high density lipoprotein (HDL) cholesterol. The associations of AUC cortisol with glycemia, HDL cholesterol and diastolic blood pressure (DBP) were further confirmed at quantile regression after adjustment for therapy.

CONCLUSIONS

FH may determine a worsening of the metabolic profile in DM-associated hypogonadism.

Bone density assessment in a cohort of pediatric patients affected by 22q11DS

OBJECTIVE

Hypoparathyroidism and hypocalcemia are two of the most frequent clinical characteristics of 22q11-deletion syndrome (22q11DS). The aim of this study was to evaluate bone metabolism and density in a cohort of patients affected by 22q11DS.

METHODS

In 8 pediatric patients (mean age 11.5 years; range 7-16.4) affected by 22q11DS, creatinine, albumin, total and ionized calcium, phosphate, 25(OH) vitamin D, parathyroid hormone, osteocalcin, C-terminal telopeptide and interleukin 6 were assessed. Furthermore, bone mineral density (BMD) was determined by dual-energy X-ray absorptiometry procedure. 14 healthy children were considered as controls.

RESULTS

Most of the studied subjects were overweight and lacked quality physical activity. 40 % of the subjects had reduced calcium levels in the absence of related clinical symptoms and all patients also had inadequate levels of Vitamin D. The values of L1-L4 BMD were within the reference range in all patients (z score <2). However, after comparing the age-matched indexes of bone mineralization of patients with those of controls, the former had lower bone mineralization indexes than the latter.

CONCLUSIONS

In pediatric patients with 22q11DS, an initial and slight bone loss is evident. The incidence of hypocalcemia is underestimated because hypocalcemia is asymptomatic. Several factors contribute to bone impairment in children who still have to achieve bone mass peak. Therefore, we suggest strict monitoring of bone metabolism as well as BMD measurement in patients affected by 22q11DS.

GLP-1: benefits beyond pancreas

INTRODUCTION

Glucagon-like peptide 1 (GLP-1) is an intestinal hormone secreted after the ingestion of various nutrients. The main role of GLP-1 is to stimulate insulin secretion in a glucose-dependent manner. However, the expression of GLP-1 receptor was found to be expressed in a variety of tissues beyond pancreas such as lung, stomach, intestine, kidney, heart and brain. Beyond pancreas, a beneficial effect of GLP-1 on body weight reduction has been shown, suggesting its role for the treatment of obesity. In addition, GLP-1 has been demonstrated to reduce cardiovascular risk factors and to have a direct cardioprotective effect, fostering heart recovery after ischemic injury. Further, data from both experimental animal models and human studies have shown beneficial effect of GLP-1 on bone metabolism, either directly or indirectly on bone cells.

MATERIALS AND METHODS

We review here the recent findings of the extra-pancreatic effects of GLP-1 focusing on both basic and clinical studies, thus opening future perspectives to the use of GLP-1 analogs for the treatment of disease beyond type 2 diabetes.

CONCLUSION

Finally, the GLP-1 has been demonstrated to have a beneficial effect on both vascular, degenerative diseases of central nervous system and psoriasis.

Central body fat changes in men affected by post-surgical hypogonadotropic hypogonadism undergoing testosterone replacement therapy are modulated by androgen receptor CAG polymorphism

BACKGROUND AND AIMS

Little is known about the effect of androgen receptor (AR) gene CAG repeat polymorphism in conditioning body composition changes after testosterone replacement therapy (TRT). In this study, we aimed to clarify this aspect by focussing our attention on male post-surgical hypogonadotropic hypogonadism, a condition often associated with partial or total hypopituitarism.

METHODS AND RESULTS

Fourteen men affected by post-surgical hypogonadotropic hypogonadism and undergoing several replacement hormone therapies were evaluated before and after TRT. Dual-energy X-ray absorptiometry (DEXA)-derived body composition measurements, pituitary-dependent hormones and AR gene CAG repeat polymorphism were considered. While testosterone and insulin-like growth factor-1 (IGF-1) levels increased after TRT, cortisol concentration decreased. No anthropometric or body composition parameters varied significantly, except for abdominal fat decrease. The number of CAG triplets was positively and significantly correlated with this abdominal fat decrease, while the opposite occurred between the latter and Δ-testosterone. No correlation of IGF-1 or cortisol variation (Δ-) with Δ-abdominal fat was found. At multiple linear regression, after correction for Δ-testosterone, the positive association between CAG triplet number and abdominal fat change was confirmed.

CONCLUSIONS

In male post-surgical hypogonadotropic hypogonadism, shorter length of AR CAG repeat tract is independently associated with a more marked decrease of abdominal fat after TRT.

Bone benefits of testosterone replacement therapy in male hypogonadism

Osteoporosis is an asymptomatic, systemic bone disease characterized by low bone mass and microarchitectural deterioration of bone tissue, resulting in increased bone fragility. Such condition is often underdiagnosed and undertreated, especially in men, therefore considerably increasing the fracture risk. Of note, fracture-related morbidity and mortality is generally higher in men, partly due to greater frailty. On the other hand, male hypogonadism is defined as the failure of the testes to produce androgens, sperm, or both and it is often due to the ageing process. This disorder, in turn, causes many systemic disorders, and it is the condition mainly associated with male osteoporosis. Testosterone replacement therapy (TRT) is usually prescribed to restore optimal hormone levels, but conflicting data are available about the efficacy of TRT treatment on bone mineral density. In this review we extensively examined literature data about the usefulness of TRT in improving hypogonadism-associated low bone mineral density. Furthermore, we considered the complex relationship between male osteoporosis and hypogonadism, by specifically addressing the role of androgens in male bone physiology and the diagnostic approach to male osteoporosis and hypogonadism and also by dealing with some new related aspects such as the new endocrine pathways between bone and testis and the role of androgen receptor CAG polymorphism on bone density.

Effects of testosterone replacement therapy on bone metabolism in male post-surgical hypogonadotropic hypogonadism: focus on the role of androgen receptor CAG polymorphism

INTRODUCTION AND AIM

The relationship between androgen receptor (AR) CAG polymorphism and bone metabolism is highly controversial. We, therefore, aimed to evaluate the independent role of AR CAG repeat polymorphism on bone metabolism improvement induced by testosterone replacement therapy (TRT) in male post-surgical hypogonadotropic hypogonadism, a condition frequently associated with hypopituitarism and in which the effects of TRT have to be distinguished from those resulting from concomitant administration of pituitary function replacing hormones.

METHODS

12 men affected by post-surgical hypogonadotropic hypogonadism [mean duration of hypogonadism 8.3 ± 2.05 (SD) months] were retrospectively assessed before and after TRT (from 74 to 84 weeks after the beginning of therapy). The following measures were studied: parameters of bone metabolism [serum markers and bone mineral density (BMD)], pituitary dependent hormones and genetic analysis (AR CAG repeat number).

RESULTS

Total testosterone, estradiol, free T4 (FT4) and insulin-like growth factor-1 (IGF-1) increased between the two phases, while follicle stimulating hormone (FSH) decreased. While serum markers did not vary significantly between the two phases, BMD improved slightly but significantly in all the studied sites. The number of CAG triplets correlated negatively and significantly with all the variations (Δ-) of BMDs. Conversely, Δ-testosterone correlated positively and significantly with all studied Δ-BMDs, while Δ-FSH, Δ-estradiol, Δ-FT4, and Δ-IGF-1 did not correlate significantly with any of the Δ-BMDs. Multiple linear regression analysis, after correction for Δ-testosterone, showed that CAG repeat length was negatively and significantly associated with ∆-BMD of all measured sites.

CONCLUSIONS

Our data suggest that, in post-surgical male hypogonadotropic hypogonadism, shorter AR CAG tract is independently associated with greater TRT-induced improvement of BMD.

Possible efficacy of Lavender and Tea tree oils in the treatment of young women affected by mild idiopathic hirsutism

BACKGROUND

Hirsutism is defined as the presence of excessive terminal hair in androgen-dependent areas of a woman's body. Regarding this it has been suggested that Lavender and Tea tree oils may have antiandrogenic activities.

AIM

To evaluate therapy based on Lavender and Tea tree oils in women suffering from mild idiopathic hirsutism (IH).

SUBJECTS AND METHODS

A prospective, open-label, placebo- controlled, randomized study was performed: women affected by mild IH were randomly assigned to receive oil spray containing Lavender and Tea tree oils (group T) (no. = 12) or placebo (group P) (no. = 12) twice a day for 3 months in areas affected by hirsutism. Evaluation of hirsutism was carried out at baseline and after 3 months by Ferriman-Gallwey score and by measuring hair diameter taken from some body areas. A hematological and hormonal evaluation was carried out at baseline and after 3 months.

RESULTS

No significant variations were found in any of the hormones studied in groups T and P between baseline and after 3 months. A statistically significant decrease of hirsutism total score and of hair diameter was found in group T, while no statistically significant difference in these two parameters was observed in group P; in group T percentual reduction of hair diameter was significantly greater than in group P.

CONCLUSIONS

Lavender and Tea tree oils applied locally on skin could be effective in reducing mild IH; this treatment could represent a safe, economic and practical instrument in the cure of this disease.

Gingival advanced glycation end-products in diabetes mellitus-associated chronic periodontitis: an immunohistochemical study

BACKGROUND AND OBJECTIVE

The accumulation of advanced glycation end-products (AGEs) seems to play an important role in the development of diabetes mellitus (DM)-associated periodontitis; however, some aspects of this issue are still scarcely known, such as the expression of AGEs in type 1 DM-associated periodontitis and the clinical factors able to affect their accumulation. This study aimed to clarify these points by evaluating the expression of AGEs in DM-associated periodontitis.

MATERIAL AND METHODS

Sixteen systemically and periodontally healthy subjects and 48 subjects suffering from generalized, severe, chronic periodontitis (16 with type 1 DM, 16 with type 2 DM and 16 systemically healthy subjects) were studied clinically, periodontally and metabolically. The immunohistochemical expression of AGEs in gingival tissues was also evaluated.

RESULTS

Subjects affected with type 1 DM presented a significantly higher percentage of AGE-positive cells than did subjects affected with type 2 DM, not only in the epithelium, but also in vessels and fibroblasts. A positive and significant correlation was found between gingival expression of AGEs and length of time affected with DM both in type 1 and type 2 DM; glycated hemoglobin, lipid profile, body mass index and age did not correlate significantly with gingival AGEs in any of the classes of subjects studied.

CONCLUSIONS

Gingival AGEs are increased in both type 1 and type 2 DM-associated periodontitis; however, the clinical parameter that determines their accumulation, and therefore their degree of influence on the development of DM-associated periodontitis, may be the duration of DM.

Fine-needle aspiration cytology of adrenal masses: a re-assessment with histological confirmation

BACKGROUND

Fine-needle aspiration (FNA) of adrenal masses is a method currently indicated in lesions suspected of being extra-adrenal in origin; even though its diagnostic reliability has already been determined in many studies, few have used histological examination obtained after adrenalectomy for diagnostic confirmation.

AIM

To analyze the diagnostic performance of adrenal FNA in subjects with an available histological confirmation.

SUBJECTS AND METHODS

Fifty subjects (26 benign adrenal lesions, 9 primary malignant lesions, and 15 metastatic lesions) who had undergone ultrasound (US)-guided adrenal FNA and then adrenalectomy were re-analyzed retrospectively.

RESULTS

FNA guaranteed a sensitivity of 85.7% and a specificity of 100% in all subjects; after having divided the subjects into oncologic and non-oncologic groups, the sensitivity of the test in oncologic patients (100%) increased significantly compared to non-oncologic (57.1%) with no difference in specificity (100% in both groups). Considering also non-diagnostic samples in our analysis (no.=11; 22% of all samples studied), FNA correctly diagnosed malignancy only in 75% of the cases and benignancy only in 66.6%; however, even after including non-diagnostic samples, the percentage of correct malignancy diagnosis remained significantly higher in oncologic (93.3%) than in non-oncologic patients (44.4%) without significant statistical difference between the 2 groups regarding the percentage of correct benignancy diagnosis (respectively 100% and 63.6%).

CONCLUSIONS

Our study, based on histological confirmation, underlines the low discriminant value of US-guided adrenal FNA, though the method may have value in oncologic patients.

Advances in the epidemiology, pathogenesis, and management of Cushing's syndrome complications

Cushing's syndrome (CS) is a clinical condition resulting from chronic exposure to glucocorticoid excess. As a consequence, hypercortisolism contributes significantly to the early development of systemic disorders by direct and/or indirect effects. Complications such as obesity, hypertension, diabetes, dyslipidemia, and hypercoagulability cause premature atherosclerosis and increase cardiovascular mortality. Impairment of the skeletal system is a relevant cause of morbidity and disability in these patients especially due to the high prevalence of vertebral fractures. In addition, muscle weakness, emotional lability, depression, and impairment of quality of life are very common. Clinical management of these patients is complex and should be particularly careful in identifying global cardiovascular risks and aim at controlling all complications. Although the primary goal in the prevention and treatment of complications is the correction of hypercortisolism, treatment does not completely eliminate these comorbidities. Given that cardiovascular risk and fracture risk can persist after cure, early detection of each morbidity could prevent the development of irreversible damage. In this review we present the various complications of CS and their pathogenetic mechanisms. We also suggest the clinical management of these patients based on our extensive clinical experience and on the available literature.

Diabetes mellitus-associated periodontitis: differences between type 1 and type 2 diabetes mellitus

BACKGROUND AND OBJECTIVE

Although many studies have appeared about diabetes mellitus-associated periodontitis, few have compared periodontitis inflammatory markers between type 1 (T1DM) and type 2 diabetes mellitus (T2DM), and information regarding this issue is scarce and contradictory. We evaluated the levels of plasma C-reactive protein and of interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumour necrosis factor-α (TNF-α) in gingival crevicular fluid in two groups of subjects affected by T1DM and T2DM, in order to identify possible differences between the two classes in the inflammatory mechanisms of diabetes mellitus-associated periodontitis.

MATERIAL AND METHODS

Plasma C-reactive protein and gingival crevicular fluid IL-1β, IL-6 and TNF-α were measured in periodontitis patients affected by type 1 (P-T1DM, n = 24) and type 2 diabetes mellitus (P-T2DM, n = 24).

RESULTS

Gingival crevicular fluid levels of IL-1β and TNF-α in P-T1DM subjects were significantly higher than in P-T2DM subjects. In P-T1DM subjects, we found significant negative correlations between the duration of diabetes mellitus and IL-1β and between the duration of diabetes mellitus and TNF-α.

CONCLUSION

This study shows that IL-1β and TNF-α levels in periodontitis patients with T1DM are affected by the duration of diabetes mellitus.

[A 'lucky' patient]

A 72-year-old male diabetic patient admitted to our operative unit of nephrology and dialysis underwent hemodialytic treatment because of rapidly progressive renal failure. A moderate hypertensive state was associated to nephrotic proteinuria and microematuria. Renal angiography showed a severe stenosis of the right renal artery and a smaller left kidney. Right renal artery stenting induced a significant reduction in serum creatinine (Cr) and the patient discontinued with the dialytic treatment.