Oestrogen replacement fails to fully revert ovariectomy-induced changes in adipose tissue monoglycerides, diglycerides and cholesteryl esters of rats fed a lard-enriched diet

Menopause may be accompanied by abdominal obesity and inflammation, conditions accentuated by high-fat intake, especially of saturated fat (SFA)-rich diets. We investigated the consequences of high-SFA intake on the fatty acid (FA) profile of monoglycerides, diglycerides and cholesteryl esters from retroperitoneal white adipose tissue (RET) of rats with ovariectomy-induced menopause, and the effect of oestradiol replacement. Wistar rats were either ovariectomized (Ovx) or sham operated (Sham) and fed either standard chow (C) or lard-enriched diet (L) for 12 weeks. Half of the Ovx rats received 17β-oestradiol replacement (Ovx + E2). Body weight and food intake were measured weekly. RET neutral lipids were chromatographically separated and FAs analysed by gas chromatography. Ovariectomy alone increased body weight, feed efficiency, RET mass, leptin and insulin levels, leptin/adiponectin ratio, HOMA-IR and HOMA-β indexes. OvxC + E2 showed attenuation in nearly all blood markers. HOMA-β index was restored in OvxL + E2. OvxC showed significantly disturbed SFA and polyunsaturated FA (PUFA) profile in RET cholesteryl esters (CE). OvxC also showed increased monounsaturated FA (MUFA) in the monoglyceride diglyceride (Mono–Di) fraction. Similar changes were not observed in OvxL, although increased SFA and decreased PUFA was observed in Mono–Di. Overall, HRT was only partially able to revert changes induced by ovariectomy. There appears to be increased mobilization of essential FA in Ovx via CE, which is a dynamic lipid species. The same results were not found in Mono–Di, which are more inert. HRT may be helpful to preserve FA profile in visceral fat, but possibly not wholly sufficient in reverting the metabolic effects induced by menopause.

Gene expression of peripheral blood mononuclear cells is affected by cold exposure

Because of the discovery of brown adipose tissue (BAT) in humans, there is increased interest in the study of induction of this thermogenic tissue as a basis to combat obesity and related complications. Cold exposure is one of the strongest stimuli able to activate BAT and to induce the appearance of brown-like (brite) adipocytes in white fat depots (browning process). We analyzed the potential of peripheral blood mononuclear cells (PBMCs) to reflect BAT and retroperitoneal white adipose tissue (rWAT) response to 1-wk cold acclimation (4°C) at different ages of rat development (1, 2, 4, and 6 mo). As expected, cold exposure increased fatty acid β-oxidation capacity in BAT and rWAT (increased Cpt1a expression), explaining increased circulating nonesterified free fatty acids and decreased adiposity. Cold exposure increased expression of the key thermogenic gene, Ucp1, in BAT and rWAT, but only in 1-mo-old animals. Additionally, other brown/brite markers were affected by cold during the whole developmental period studied in BAT. However, in rWAT, cold exposure increased studied markers mainly at early age. PBMCs did not express Ucp1, but expressed other brown/brite markers, which were cold regulated. Of particular interest, PBMCs reflected adipose tissue-increased Cpt1a mRNA expression in response to cold (in older animals) and browning induction occurring in rWAT of young animals (1 mo) characterized by increased Cidea expression and by the appearance of a high number of multilocular CIDE-A positive adipocytes. These results provide evidence pointing to PBMCs as an easily obtainable biological material to be considered to perform browning studies with minimum invasiveness.

Endocrine and Metabolic Signaling in Retroperitoneal White Adipose Tissue Remodeling during Cold Acclimation

The expression profiles of adiponectin, resistin, 5′-AMP-activated protein kinaseα(AMPKα), hypoxia-inducible factor-1α(HIF-1α), and key enzymes of glucose and fatty acid metabolism and oxidative phosphorylation in rat retroperitoneal white adipose tissue (RpWAT) during 45-day cold acclimation were examined. After transient suppression on day 1, adiponectin protein level increased following sustained cold exposure. In parallel, on day 1, the protein level of HIF-1αwas strongly induced and AMPKαsuppressed, while afterwards the reverse was seen. What is more, after an initial decrease on day 1, a sequential increase in pyruvate dehydrogenase, acyl-CoA dehydrogenase, cytochromecoxidase, and ATP synthase and a decrease in acetyl-CoA carboxylase (from day 3) were observed. Similar to adiponectin, protein level of resistin showed a biphasic profile: it increased after days 1, 3, and 7 and decreased below the control after 21 days of cold-acclimation. In summary, the data suggest that adiponectin and resistin are important integrators of RpWAT metabolic response and roles it plays during cold acclimation. It seems that AMPKαmediate adiponectin effects on metabolic remodeling RpWAT during cold acclimation.

A soyabean diet does not modify the activity of brown adipose tissue but alters the rate of lipolysis in the retroperitoneal white adipose tissue of male rats recovering from early-life malnutrition

Nutritional recovery with a soyabean diet decreases body and fat weights when compared with a casein diet. We investigated whether the reduced adiposity observed in rats recovering from early-life malnutrition with a soyabean diet results from alterations in lipid metabolism in white adipose tissue (WAT) and/or brown adipose tissue (BAT). Male rats from mothers fed either 17 or 6 % protein during pregnancy and lactation were maintained on 17 % casein (CC and LC groups), 17 % soyabean (CS and LS groups) or 6 % casein (LL group) diets over 60 d. The rats maintained on a soyabean diet had similar relative food intakes, but lower body and retroperitoneal WAT weights and a reduced lipid content in the retroperitoneal WAT. The insulin levels were lower in the recovered rats and were elevated in those fed a soyabean diet. Serum T3 concentration and uncoupling protein 1 content in the BAT were decreased in the recovered rats. The thermogenic capacity of the BAT was not affected by the soyabean diet. The lipogenesis rate in the retroperitoneal WAT was similar in all of the groups except for the LL group, which had exacerbated lipogenesis. The enhancement of the lipolysis rate by isoproterenol was decreased in white adipocytes from the soyabean-recovered rats and was elevated in adipocytes from the soyabean-control rats. Thus, in animals maintained on a soyabean diet, the proportions of fat deposits are determined by the lipolysis rate, which differs depending on the previous nutritional status.