Hyperlipidic diets limit glucose oxidation and favor amino acid preservation, hampering the elimination of excess dietary nitrogen and the catabolic utilization of amino acids. We analyzed whether reduced urea excretion was a consequence of higher NO x ; (nitrite, nitrate, and other derivatives) availability caused by increased nitric oxide production in metabolic syndrome. Rats fed a cafeteria diet for 30 days had a higher intake and accumulation of amino acid nitrogen and lower urea excretion. There were no differences in plasma nitrate or nitrite. NO(x) and creatinine excretion accounted for only a small part of total nitrogen excretion. Rats fed a cafeteria diet had higher plasma levels of glutamine, serine, threonine, glycine, and ornithine when compared with controls, whereas arginine was lower. Liver carbamoyl-phosphate synthetase I activity was higher in cafeteria diet-fed rats, but arginase I was lower. The high carbamoyl-phosphate synthetase activity and ornithine levels suggest activation of the urea cycle in cafeteria diet-fed rats, but low arginine levels point to a block in the urea cycle between ornithine and arginine, thereby preventing the elimination of excess nitrogen as urea. The ultimate consequence of this paradoxical block in the urea cycle seems to be the limitation of arginine production and/or availability.
White adipose tissue (WAT) produces lactate in significant amount from circulating glucose, especially in obesity;Under normoxia, 3T3L1 cells secrete large quantities of lactate to the medium, again at the expense of glucose and proportionally to its levels. Most of the glucose was converted to lactate with only part of it being used to synthesize fat. Cultured adipocytes were largely anaerobic, but this was not a Warburg-like process. It is speculated that the massive production of lactate, is a process of defense of the adipocyte, used to dispose of excess glucose. This way, the adipocyte exports glucose carbon (and reduces the problem of excess substrate availability) to the liver, but the process may be also a mechanism of short-term control of hyperglycemia. The in vivo data obtained from adipose tissue of male rats agree with this interpretation.
Lipid metabolism in the ventromedial hypothalamus (VMH) has emerged as a crucial pathway in the regulation of feeding and energy homeostasis. Carnitine palmitoyltransferase (CPT) 1A is the rate-limiting enzyme in mitochondrial fatty acid ?-oxidation and it has been proposed as a crucial mediator of fasting and ghrelin orexigenic signalling. However, the relationship between changes in CPT1A activity and the intracellular downstream effectors in the VMH that contribute to appetite modulation is not fully understood. To this end, we examined the effect of long-term expression of a permanently activated CPT1A isoform by using an adeno-associated viral vector injected into the VMH of rats. Peripherally, this procedure provoked hyperghrelinemia and hyperphagia, which led to overweight, hyperglycemia and insulin resistance. In the mediobasal hypothalamus (MBH), long-term CPT1AM expression in the VMH did not modify acyl-CoA or malonyl-CoA levels. However, it altered the MBH lipidomic profile since ceramides and sphingolipids increased and phospholipids decreased. Furthermore, we detected increased vesicular ?-aminobutyric acid transporter (VGAT) and reduced vesicular glutamate transporter 2 (VGLUT2) expressions, both transporters involved in this orexigenic signal. Taken together, these observations indicate that CPT1A contributes to the regulation of feeding by modulating the expression of neurotransmitter transporters and lipid components that influence the orexigenic pathways in VMH.
Adipose tissue (AT) is distributed as large differentiated masses, and smaller depots covering vessels, and organs, as well as interspersed within them. The differences between types and size of cells makes AT one of the most disperse and complex organs. Lipid storage is partly shared by other tissues such as muscle and liver. We intended to obtain an approximate estimation of the size of lipid reserves stored outside the main fat depots. Both male and female rats were made overweight by 4-weeks feeding of a cafeteria diet. Total lipid content was analyzed in brain, liver, gastrocnemius muscle, four white AT sites: subcutaneous, perigonadal, retroperitoneal and mesenteric, two brown AT sites (interscapular and perirenal) and in a pool of the rest of organs and tissues (after discarding gut contents). Organ lipid content was estimated and tabulated for each individual rat. Food intake was measured daily. There was a surprisingly high proportion of lipid not accounted for by the main macroscopic AT sites, even when brain, liver and BAT main sites were discounted. Muscle contained about 8% of body lipids, liver 1-1.4%, four white AT sites lipid 28-63% of body lipid, and the rest of the body (including muscle) 38-44%. There was a good correlation between AT lipid and body lipid, but lipid in "other organs" was highly correlated too with body lipid. Brain lipid was not. Irrespective of dietary intake, accumulation of body fat was uniform both for the main lipid storage and handling organs: large masses of AT (but also liver, muscle), as well as in the "rest" of tissues. These storage sites, in specialized (adipose) or not-specialized (liver, muscle) tissues reacted in parallel against a hyperlipidic diet challenge. We postulate that body lipid stores are handled and regulated coordinately, with a more centralized and overall mechanisms than usually assumed.
The use of Transwells™ for routine cultures of 3T3L1 cells results in a much improved rate of differentiation of fibroblasts to adipocytes (100% in 9 of 10 tests) compared with bottom-well layer cultures. Mean size of cells was not different, but the cell number and overall cell mass was 3× larger in transwell in spite of a smaller surface area. The difference between both models was the accessibility in transwells of both sides of the cells to the medium (and oxygen). Cells were counted, and their size estimated using a handheld cell counter, Scepter™, designed for blood cells, but adjusted to the larger size of adipocytes. Finally, the effect of nitric oxide was tested using spermineNONOate, a nitric oxide (NO·) donor. The product was released to cultures at a constant 1 ?l/h rate for up to 3 days using osmotic Alzet™ minipumps held in wells with water and discharging their contents to the cultured cell-laden wells through a short capillary tube. A rate of 0.3 pmol/min/ml of medium did not affect the cells size, but 0.4 pmol/min/ml significantly increased cell mass. The methodological improvements presented here allow for more uniform cultured cell yields and a more flexible environment for control of cell size and administration of signaling agents.
There is ample consensus that there is a neurophysiological basis for eating disorders (ED). Traits of personality translate into behavioral traits, purging being a well-defined transversal example. The direct implication of steroid hormones on ED has seldom been studied, despite their effects on behavior.
In the metabolic syndrome, glucocorticoid activity is increased, but circulating levels show little change. Most of blood glucocorticoids are bound to corticosteroid-binding globulin (CBG), which liver expression and circulating levels are higher in females than in males. Since blood hormones are also bound to blood cells, and the size of this compartment is considerable for androgens and estrogens, we analyzed whether sex or eating a cafeteria diet altered the compartmentation of corticosterone in rat blood. The main corticosterone compartment in rat blood is that specifically bound to plasma proteins, with smaller compartments bound to blood cells or free. Cafeteria diet increased the expression of liver CBG gene, binding plasma capacity and the proportion of blood cell-bound corticosterone. There were marked sex differences in blood corticosterone compartmentation in rats, which were unrelated to testosterone. The use of a monoclonal antibody ELISA and a polyclonal Western blot for plasma CBG compared with both specific plasma binding of corticosterone and CBG gene expression suggested the existence of different forms of CBG, with varying affinities for corticosterone in males and females, since ELISA data showed higher plasma CBG for males, but binding and Western blot analyses (plus liver gene expression) and higher physiological effectiveness for females. Good cross-reactivity to the antigen for polyclonal CBG antibody suggests that in all cases we were measuring CBG. The different immunoreactivity and binding affinity may help explain the marked sex-related differences in plasma hormone binding as sex-linked different proportions of CBG forms.
Oleoyl-estrone (OE) is a powerful slimming agent that is also present in plasma and adipose tissue, where it is synthesized. It acts through the formation of a derivative W. OE effects (and W levels) are proportional to the dose. OE reduces food intake but maintains energy expenditure (thermogenesis). The energy gap is fulfilled with adipose tissue fat, sparing body protein and maintaining glycemia (and glycogen) with lower insulin and leptin levels. OE (in fact W) acts through specific receptors, different from those of estrogen. OE increases cholesterol catabolism, reducing hypercholesterolemia in obese rats. The main metabolic effect on adipose tissue is lowering of lipid synthesis, maintaining unchanged the intracellular lipolytic processes; the imbalance favors the progressive loss of fat, which is largely used by the muscle. OE administration induces additive effects with other antiobesity agents, such as ?(3)-adrenergic agonists, forcing a massive loss of lipid. Corticosteroids markedly limit OE action by altering the liver control of lipogenesis. OE also inhibits the action of 17?-hydroxysteroid dehydrogenase, decreasing the synthesis of ?-estradiol and testosterone. Discontinuous treatment allows for maximal efficacy both in rats and humans. OE has the advantage that the loss of fat is maintained and does not require additional dietary limitations.
Oleoyl-estrone (OE) is a powerful anti-obesity compound that decreases food intake, decreases insulin resistance and circulating cholesterol. OE stimulates a severe loss of body fat by decreasing adipose tissue lipid synthesis and maintaining lipolysis. Therefore, the body economy loses lipid energy because energy expenditure is maintained. This study analyses the discrepancy between OE effects and the distribution of labelled OE in plasma. Estrone radioimmunoassay of organic solvent plasma extracts of rats treated with OE showed the massive presence of acyl-estrone, but saponification did not release estrone, but containing similar unknown compound. Analysis of label distribution in plasma after oral gavages of (3)H-OE showed the presence of a more hydrophilic compound than OE or any estrogen as well as (3)H(2)O, formed from (3)H-OE in the acidic stomach medium. OE was not attached to a specific transporter in plasma. Through serum HPLC analysis we found W, a labelled derivative more hydrophilic than OE or estrone. The results were confirmed using (14)C-OE. HPLC-MS/MS studies showed that plasma OE levels were one order of magnitude lower than those of W. When liver cell cytosols from rats laden with (3)H-OE were incubated with nuclei from untreated rats, the OE-derived label (i.e., Ws) was found attached to nuclear DNA. Neither estradiol nor estrone interfered with its binding. W is a fairly hydrophilic compound of low molecular weight containing the estrone nucleus, but it is not an ester because saponification or esterases do not yield estrone as OE does. It is concluded that OE acts through its conversion to W, its active form; which binds to a nuclear receptor different from that of estrogen. The estimated W serum levels are proportional to the pharmacological OE effects in vivo. We postulate W as a new type of hormone that exerts the full range of in vivo effects thus far attributed to OE. The full identification of W is anticipated to open the way for the development of new OE-like anti-obesity drugs.
It is generally assumed that steroid hormones are carried in the blood free and/or bound to plasma proteins. We investigated whether blood cells were also able to bind/carry sex-related hormones: estrone, estradiol, DHEA and testosterone. Wistar male and female rats were fed a cafeteria diet for 30 days, which induced overweight. The rats were fed the standard rat diet for 15 additional days to minimize the immediate effects of excess ingested energy. Controls were always kept on standard diet. After the rats were killed, their blood was used for 1) measuring plasma hormone levels, 2) determining the binding of labeled hormones to washed red blood cells (RBC), 3) incubating whole blood with labeled hormones and determining the distribution of label between plasma and packed cells, discounting the trapped plasma volume, 4) determining free plasma hormone using labeled hormones, both through membrane ultrafiltration and dextran-charcoal removal. The results were computed individually for each rat. Cells retained up to 32% estrone, and down to 10% of testosterone, with marked differences due to sex and diet (the latter only for estrogens, not for DHEA and testosterone). Sex and diet also affected the concentrations of all hormones, with no significant diet effects for estradiol and DHEA, but with considerable interaction between both factors. Binding to RBC was non-specific for all hormones. Estrogen distribution in plasma compartments was affected by sex and diet. In conclusion: a) there is a large non-specific RBC-carried compartment for estrone, estradiol, DHEA and testosterone deeply affected by sex; b) Prior exposure to a cafeteria (hyperlipidic) diet induced hormone distribution changes, affected by sex, which hint at sex-related structural differences in RBC membranes; c) We postulate that the RBC compartment may contribute to maintain free (i.e., fully active) sex hormone levels in a way similar to plasma proteins non-specific binding.
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