Istituto Lombardo - Accademia di Scienze e Lettere - Incontri di Studio

SALUTO DEL PRESIDENTE DELL’ISTITUTO LOMBARDO

2020-07-05T06:26:50+00:00

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INTRODUZIONE AL CONVEGNO

2020-07-05T06:26:42+00:00

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OBESITÀ: PANDEMIA DEL XXI SECOLO. TRA AMBIENTE E GENETICA

2020-07-05T06:26:49+00:00

The increasing prevalence of overweight and obesity represents an important challenge, worldwide, for the various health systems. The obesity pandemic is associated with the rapid economic growth which has led to relevant lifestyle changes most of them favoring a chronically positive energy balance. On a global scale, between 1980 and 2013, the cumulative prevalence of overweight and obesity in adults has increased from 29% to 37%. This increase concerns also early youth and childhood: the prevalence of overweight and obesity has reached 23% in developed countries and 13% in developing countries. In Italy, a national surveillance program established in 2007 and financed by the Ministry of Health / CCM (Center for Disease Control and Prevention), provides the updated epidemiological framework for the analysis of the prevalence of weight excess and risky behaviors in primary school children. At the time of the last assessment, overweight children, were 20.9%, while obese children were 9.8%. The obesity pandemic is a maladaptive response to an environment enriched in energy availability and which is not exposed anymore to famine episodes. Individual susceptibility to obesity largely depends on the genetic background on which the environment exerts variable pressure. Obesity, in more than 95% of cases, has a multifactorial pathogenesis and can be considered the prototype of what is generally called "a complex phenotype". In facts, unlike diseases with Mendelian transmission, in which there is substantially a direct correlation between genotype and phenotype, obesity represents the result of an interaction between multiple genetic traits, environmental factor and socio-cultural habits. According to the "thrifty genotype" hypothesis, our genetic heritage has evolved in conditions of reduced food availability, selecting "thrifty genes" favoring the deposition of adipose tissue. In recent decades, the wide availability of high energy food has increased rapidly and the "thrifty" genotype has become a promoter for the development of obesity. Although many gene variants that can favor weight accumulation have been identified, a relevant portion of the genetic makeup underlying obesity remains unexplained until today. Beside allelic variants, quite common in the general population, probably exerting small effects on the risk of obesity, an additional contribution may derive from epigenetic modifications developed by living in an obesogenic environment.

IL CONTROLLO NEUROENDOCRINO DEL COMPORTAMENTO ALIMENTARE

2020-07-05T06:26:48+00:00

Appetite is regulated by a complex system of central and peripheral signals that interact in order to modulate eating behavior according the individual needs, i.e. the fasting or fed condition and the general nutritional status. Peripheral regulation includes adiposity signals and satiety signals, while central control is accomplished by several effectors, including the neuropeptidergic, monoaminergic and endocannabinoid systems. Adiposity signals inform the brain of the general nutritional status of the subject as indicated by the extent of fat depots. Indeed, leptin produced by the adipose tissue and insulin, whose pancreatic secretion tends to increase with the increase of fat mass, convey to the brain an anorexigenic message. Satiety signals, including cholecystokinin (CCK), glucagon-like peptide-1 (GLP-1) and peptide YY (PYY), originate from the gastrointestinal tract during a meal and, through the vagus nerve, reach the nucleus tractus solitarius (NTS) in the caudal brainstem. From NTS afferents fibers project to the arcuate nucleus (ARC) of the hypothalamus, where satiety signals are integrated with adiposity signals and with several hypothalamic and supra-hypothalamic inputs, thus creating a complex network of neural circuits that finally elaborate the most appropriate response, in terms of eating behavior. In more detail, ARC neurons secrete a number of neuropeptides with orexigenic properties, such as neuropeptide Y (NPY) and agouti-related peptide (AGRP), or anorexigenic effects such as pro-opiomelanocortin (POMC) and cocaine- and amphetamine-regulated transcript (CART). Other brain areas involved in the control of food intake are located downstream the ARC: among these, the paraventricular nucleus (PVN), which produces anorexigenic peptides such as thyrotropin releasing hormone (TRH), corticotrophin releasing hormone (CRH) and oxytocin, the lateral hypothalamus (LHA) and perifornical area (PFA), secreting the orexigenic substances orexin-A (OXA) and melanin concentrating hormone (MCH). Recently, a great interest has developed for endogenous cannabinoids, important players in the regulation of food intake and energy metabolism. In the same context, increasing evidence is accumulating for a role played by the microbiota, the trillion of microorganism populating the human gastrointestinal tract.

The complex interaction between the peripheral organs and the central nervous system has generated the concept of gut-brain axis, now incorporated into the physiology. A better understanding of the mechanisms governing the eating behavior will allow the development of drugs capable of reducing or enhancing food consumption.

IL MICROBIOTA INTESTINALE (1)

2020-07-05T06:26:43+00:00

⁽¹⁾ Sintesi dell'intervento.

LA FAME DENTRO IL CERVELLO

2020-07-05T06:26:47+00:00

The brain has two characteristics in relation to nutrition. The first is to consume 20% of the energy introduced, although it represents only 2% of body weight. In childhood, consumption can reach 60%. The second peculiarity concerns the regulation of the sense of hunger, satiety and thirst. Biological mechanisms for this purpose are reported. Particular attention is given to the function of emotions and feelings on this regulatory system, and the influence of social habits and cultures of different countries. These elements can affect pathologies such as anorexia and bulimia.

STAY HUNGRY, STAY FOOLISH: PER UNA STORIA NATURALE DELL’ANORESSIA

2020-07-05T06:26:45+00:00

Thanks to a broad historical-anthropological and clinical examination, the authors re-evaluate the role of hunger in the development of our species, and also in that of the individual. The alternation empty/full, internal/ external, the complex game that is established between need, object and desire, structures the childhood of the human cub. In the same way, the alternation between active and passive gaze inaugurates and accompanies the adolescent turbulence, often dictating the rhythms. The third stage of this speech, relating to the season of maturity, focuses on the (dangerous) intersection between food and air, between when we breathe and when we swallow. The lecture ends with the theme of fasting in old age, which engages the themes of depression, involution and detachment.

LA CLINICA DEI DISTURBI DEL COMPORTAMENTO ALIMENTARE: COMPLICANZE MEDICHE

2020-07-05T06:26:44+00:00

Anorexia nervosa, commonly occurring in peripubertal girls, is burdened by the highest mortality rate of any psychiatric disorder, due to the organic complications induced by the severe starvation and the high rate of suicide. Patients display dry, pale and yellowish skin, with lanugo hair growth. The clinical picture is characterized by muscle hypotrophy, dehydration, electrolyte disturbances, delayed gastric emptying, constipation, elevation of liver transaminases, leukopenia, bradycardia, hypotension, mitral valve prolapse, pericardial effusion, brain cortical atrophy. Endocrine complications, reversible with weight gain and recovery, can be interpreted as epiphenomena of the disease. Hypogonadotropic hypogonadism, of hypothalamic origin, is the cause of amenorrhea, which was considered in the past one of the diagnostic criteria of the disease. Gonadotropin secretion is characterized by a prepubertal pattern and serum sex steroid levels are low. The preferential conversion of T₄ to reverse T₃ rather than to T₃ in peripheral tissues, common in all malnourishment states, leads to the so called low T₃ syndrome. This mechanism, aimed at saving energy, although contributing to bradycardia in these patients, does not require replacement therapy. Like in other psychiatric disorders such as depression, the hypothalamic-pituitary-adrenal axis is activated: hypercortisolism might contribute to some clinical features of the disease such as osteopenia and brain cortical atrophy. The abnormalities of the somatotropin-somatomedin axis are substantially represented by a picture of acquired GH resistance: indeed, due to chronic malnutrition, circulating IGF-I is frankly low in spite of markedly enhanced GH release. Together with malnourishment and low body weight, hypogonadism, hypercortisolism and IGF-I deficiency contribute to bone demineralization, which in its turn leads to an increased fracture risk in the future of these patients.

L’INTERVENTO NUTRIZIONALE NEI DISTURBI DEL COMPORTAMENTO ALIMENTARE

2020-07-05T06:26:44+00:00

The nutritional intervention is a cornerstone of the treatment of eating disorders. Most serious cases are being treated first by parenteral and/or enteral nutrition, carefully to prevent the re-feeding syndrome that can have fatal consequences. Once patient is clinically stable, integrated intervention can be started: medical, nutritional, psychological, motor, rehabilitation and therapeutic education may take place initially in a hospital setting and then in an outpatient setting. The nutritional rehabilitation in anorexia nervosa can be conducted with the mode of the mechanical feeding or with that of desensitization of anxiety by food. Goal is the gradual normalization of weight and nutrition and improving the quality of life of the patient.