Cancelliere, Rosa (2017) “Dalle fluttuazioni del peso corporeo ai disordini metabolici: ruolo della componente lipidica della dieta” "From body weight fluctuations to metabolic disorders: the role of the lipid component of the diet”. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: Italiano
Title: “Dalle fluttuazioni del peso corporeo ai disordini metabolici: ruolo della componente lipidica della dieta” "From body weight fluctuations to metabolic disorders: the role of the lipid component of the diet”
Date: 8 December 2017
Number of Pages: 147
Institution: Università degli Studi di Napoli Federico II
Department: dep03
Dottorato: phd007
Ciclo di dottorato: 30
Coordinatore del Corso di dottorato:
Date: 8 December 2017
Number of Pages: 147
Keywords: Restrizione Rialimentazione SFA-MUFA
Settori scientifico-disciplinari del MIUR: Area 05 - Scienze biologiche > BIO/09 - Fisiologia
Date Deposited: 09 Jan 2018 12:53
Last Modified: 05 Apr 2019 10:45

Collection description

Obesity is the result of genetic, behavioral, environmental, physiological, social and cultural factors that result in energy imbalance and promote excessive fat deposition. In particular, in Western society, which is characterized by sedentary lifestyles combined with excess energy intake, many people often try to lose weight with caloric restriction. However it is well known that the weight regain after caloric restriction results in accelerated storage of adipose tissue (De Andrade et al. 2015). The high efficiency of the recovery of the energy depots of body fat probably evolved in ancient times, when the food availability was intermittent and it was necessary to face up to long periods of famine. Nowadays, this efficiency is the key factor causing higher body fat gain relative to lean tissue, and the preferential catch-up fat phenomenon has also been linked to the hyperinsulinemic state of catch-up growth and the associated risks for later development of metabolic syndrome (Crescenzo et al. 2003; Dulloo et al.2006). Several studies on refeeding after caloric restriction have been conducted on laboratory rats, a very good model for obesity studies, because energy intake, diet composition and the level of physical activity can be easily monitored, and also, considering the standard housing conditions, laboratory rats exhibit a sedentary behavior, similarly to what happens in humans (Aydin et al. 2014; Buettner et al. 2007; Spangenberg et al. 2005): it was observed that during the refeeding with low fat diet the rats showed a reduction in energy expenditure and an increase in metabolic efficiency, causing high body fat deposition, even in absence of hyperphagia (Dulloo et al. 2008). In addition it has been shown that this high metabolic efficiency that drives catch-up fat on a low fat diet is exacerbated by refeeding on HFD (Crescenzo et al. 2003; Dulloo & Gerardier, 1992), although in different ways depending on the type of fat included in the diet (Dulloo et al. 2005). In this thesis, I assessed whether changing the type of fat, in the context of a high fat dietary regimen, could differently affect whole body homeostasis. For this reason I investigated the effect of two kind of HFD, rich in lard or safflower/linseed oil. I used two different experimental designs. In the first one, rats were divided in two groups with the same mean body weight and were pair fed with 380 kJ metabolisable energy (ME)/day (corresponding to the spontaneous energy intake of the same rats, as assessed in the days before the experiment) with a lard-based (SFA-MUFA, mainly monounsaturated and saturated fatty acids) or safflower-linseed based (PUFA, polyunsaturated fatty acids of ω-6 and ω-3 series) diets for 2 weeks. The two HFDs contained 58.2% energy from fat, 21.1% energy from protein and 20.7% energy from carbohydrate. During the treatments, body weight, food, and water intake were monitored daily. Faces and urine were collected daily and the respective energy content assessed with a bomb calorimeter. The day before the sacrifice, 24-h VO2 and VCO2 of the rats were recorded with a four-chamber indirect open-circuit calorimeter (Panlab S.r.l., Cornella, Spain). Measurements were performed for the whole 24 h-period every 15 min for 3 min in each cage. Urine was collected for the whole (24-h) period and urinary nitrogen levels were measured by an enzymatic colorimetric method (FAR S.r.l., Settimo di Pescantina, Italy). Daily energy expenditure and substrate oxidation rates were calculated for the whole 24-h period from VO2, VCO2, and urinary nitrogen according to Even et al. The day before the euthanasia, rats were fasted for 6 h and small blood samples were taken from the tail vein, placed in EDTA coated tubes and transferred on ice. Plasma glucose concentration was measured by colorimetric enzymatic method (Pokler Italia, Italy), while plasma insulin concentration was measured using an ELISA kit (Mercodia AB, Sweden). Basal postabsorptive values of plasma glucose and insulin were used to calculate Homeostatic Model Assessment (HOMA) index as [Glucose (mg/dL) × Insulin (mU/L)]/405. After the treatment, body composition and energy balance were measured. Plasma concentrations of triglycerides, cholesterol, non esterified fatty acids (NEFA), alanine aminotransferase (ALT) and lipid peroxidation were measured. Liver composition and oxidation, as well as respiratory capacity, oxidative status of liver mitochondria were measured. Quantification of uncoupling protein (UCP-1) in interscapular brown adipose tissue (IBAT) was performed. In the second experimental design, rats were food restricted for 14 days at approximately 50% of spontaneous intake. At the end of the semistarvation period, all the rats were separated into 3 groups (n = 8): one group was immediately euthanized by decapitation to calculate the body composition of restricted rats, while the other two groups were refed isocaloric amounts of two different HFDs (58.2% by energy), rich in lard or safflower/linseed oil. The amount of dietary energy provided to the refed animals corresponds to the metabolisable energy intake of spontaneously growing (non-restricted) weight-matched control animals fed on chow diet, as previously reported (Crescenzo et al., 2003). Furthermore, the level of fat in the HFDs utilized here (i.e., 58% of energy intake) corresponds to dietary fat levels often utilized in rehabilitation (energy-dense) diets of malnourished infants and children in order to meet their high energy requirements for catch-up growth (Prentice and Paul, 2000). In this second design, I performed the same measurement of the first one, but I also investigated the regulation of the pathway of de novo lipogenesis in liver, white adipose tissue (WAT) and brown adipose tissue (BAT). I also evaluated liver and muscle composition, mitochondrial activity, as well as parameters of oxidative stress and inflammation, since both these tissues are major contributors to daily metabolic rate (Rolfe & Brown, 1997) and it has been proposed that skeletal muscle is involved in the suppression of thermogenesis that underlines the high metabolic efficiency for accelerated body fat recovery after caloric restriction (Dulloo, 2005; Crescenzo et al. 2006). The results of the first experimental design suggest that, at the end of the treatment, the percent of body lipid doubled both in SFA-MUFA and in PUFA rats, although the final value was significantly lower in PUFA than in SFA-MUFA rats; conversely the percentage of body protein was maintained constant in PUFA rats, while it significantly decreased in SFA-MUFA rats. The percent of body epididymal and visceral WAT increased, reaching a final value that was significantly lower in PUFA rats than in SFA-MUFA rats. The percent of body IBAT was significantly higher in PUFA than in SFA-MUFA rats and its content of UCP-1 was markedly increased in PUFA rats compared to SFA-MUFA rats. PUFA rats exhibit lower lipid gain but higher protein gain compared to SFA-MUFA rats. The analysis of fuel oxidation showed that PUFA rats had reduced protein oxidation but higher lipid oxidation compared to SFA-MUFA rats. Plasma metabolic characterisation evidenced higher alanine aminotransferase activity in PUFA rats compared to SFA-MUFA rats. Livers from PUFA rats showed higher degree of steatosis and had higher lipid content, triglycerides and cholesterol, as well as higher lipid peroxidation, compared to SFA-MUFA rats. Liver mitochondria from PUFA rats displayed a significant decrease in basal and fatty acid-induced proton leak compared to SFA-MUFA rats. Both NAD, FAD and lipid-linked maximal oxidative capacities were significantly higher in isolated liver mitochondria from rats PUFA compared to SFA-MUFA rats. Evaluation of oxidative status showed that lipid peroxidation was significantly higher in mitochondria from PUFA rats compared to SFA-MUFA rats. The results of the second experimental design suggest that rats refed the PUFA-enriched diet had lower body lipids and higher body proteins compared to rats refed the SFA-MUFA-enriched diet, as well as lower amount of visceral and epididymal WAT, but higher amount of IBAT. Rats refed PUFA diet gained significantly less lipids and more proteins. At the end of the 2 weeks refeeding period, rats refed PUFA diet exhibited higher NPRQ values and non-protein energy utilisation was fulfilled by using proportionally more carbohydrates and less fat compared to rats refed SFA-MUFA diet, lower HOMA index and plasma insulin levels in the fasting and the fed state, together with lower plasma triglycerides and cholesterol levels. Plasma lipid peroxidation was not significantly different between the two groups of rats, while a significant decrease in ALT was found in rat refed PUFA diet. FAS activity, the rate-limiting enzyme in the pathway of de novo lipogenesis, was found to be significantly higher in liver, e-WAT and IBAT in rat refed PUFA diet. In the liver, higher triglyceride content was found in rat refed PUFA diet, but hepatic lipid peroxidation was significantly lower. SOD activity was found to be significantly higher in liver mitochondria of rat refed PUFA diet while no difference was found in skeletal muscle mitochondria. Lower degree of hepatic inflammation and unchanged hepatic content of the proinflammatory mediator TNF-α was found in rat refed PUFA diet. Expression of the UCP-1 protein in BAT was found significantly increased in rat refed PUFA diet. In conclusion, in this thesis I provide evidence that not only the amount, but also the type of dietary fat, is a primary obesogenic factor. In particular, when considering the composition of high fat diets for nutritional rehabilitation, the inclusion of PUFA could be useful for improving protein deposition and maintaining glucose homeostasis, while limiting lipid storage in adipose tissue and oxidative stress and inflammation in the liver.


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