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  • MSG model is well characterized and

    2024-02-23

    MSG model is well characterized and widely used because it is not influenced by dietary components and because it mimics a lesion in the arcuate nucleus and lateral hypothalamus that can occur in chronic obese patients (Moraes et al., 2009, Purkayasta and Cai, 2013). High fat fed diet is amongst the most important environmental factors leading to obesity, and it is known to induce apoptosis of neurons and a reduction of synaptic inputs in the arcuate nucleus and lateral hypothalamus (Moraes et al., 2009) with the loss of central leptin and insulin sensitivity. Insensitivity to these important anorexigenic messengers of nutritional status perpetuates the development of both obesity and peripheral insulin insensitivity (Williams, 2012). MSG model promotes this central lesion in a short period of time and consequently induces sustained obesity. It is an ideal model to be evaluated together with food deprivation, since the MSG obese animals are normophagic (Nardelli et al., 2011) and normoglycemic (Alponti and Silveira, 2010). Furthermore, MSG obese animals present hyperinsulinemia (Nardelli et al., 2011), hyperleptinemia (Perello et al., 2004) and increased mass of retroperitoneal depot of visceral adipose tissue (Alponti and Silveira, 2010). Hyperphagia is another feature of diet-induced obesity that occurs as consequence of the mandatory use of components with high palatability, usually unhealthy, in this diet (Hariri and Thibault, 2010). Thus, diet-induced obesity has variables related to these components, which complicate the analysis. On the other hand, the use of knockout animals makes it impossible to evaluate the ontogenetic influence in the development of obesity (Eisener-Dorman et al., 2009). Furthermore, obesity and food deprivation are opposite situations regarding an ω-Agatoxin TK substrate. In obesity there is an excess and in fasting there is a deficit of energy substrate. Food deprivation for periods ranging from 24 to 72 h has been applied experimentally to evaluate changes in various neuroendocrine factors that interact in nutritional and energy balance. Among the endocrine changes known to occur during food deprivation are hypoinsulinemia, hypoleptinemia (Finn and Dice, 2006), adipogenesis (Alponti et al., 2013), increased glucocorticoids (Finn and Dice, 2006), growth hormone (stimulation of lipolysis) (Finn and Dice, 2006) and ghrelin (Camiṅa et al., 2003), as well as decreased thyrotropin, triiodothyronine and thyroxine, with consequent reduction of lipolysis and proteolysis (Cinti, 2012). Thus, the identification and comparison of new subcellular aminopeptidase activities in adipocytes and their alterations in both conditions contribute to the knowledge about the regulatory mechanisms in adipocytes and sets the path for investigations of the pathophysiological role of these enzymes in energy metabolism. The present study shows that distribution of these activities in different subcellular compartments of adipocytes isolated from retroperitoneal depot of visceral adipose tissue was affected by obesity and food deprivation, and thus we compared the levels of these activities in each compartment among animal groups, evidencing alterations for AspAP, PSA and MetAP. The importance of the different fractional expressions and changes in obesity and food deprivation are related to functional role of each fractional compartment. The microsomal vesicles are artefacts formed from fragments of the endoplasmic reticulum when cells are disrupted by homogenization. The rough microsomes (high density microsomal fraction) have ribosomes adhered to their outer surface and they are more dense than smooth microsomes (low density microsomal fraction). The inner medium of rough microsomes are biochemically equivalent to endoplasmic reticulum lumen, while low density microsomal fraction are devoid of ribosomes, being derived from various sources, such as smooth portions of the endoplasmic reticulum, vesicles fragments of the Golgi apparatus and endosomes. The distribution of AP activities in adipocyte fractions permit to infer their physiological role in ω-Agatoxin TK protein synthesis, maturation and targeting to plasma membrane. The inhibition of MetAP is known to result in an effective and sustained weight loss and increased adiponectin levels along with increased energy expenditure and reduced calorie consumption in obese patients (Joharapurkar et al., 2014), but MetAP was detected in plasma membrane for the first time in the present study. For AspAP and PSA two implications in both statuses are quite probable. Absence of AspAP under food deprivation may disfavor lipolysis. High level of PSA in LDM containing proteasome suggests its activity against polyQ protein aggregation in obese. In turn, a high level of MetAP in plasma membrane reinforces the hypothesis of its participation in regulating adiponectin and pro-angiogenic factors in obese subjects.