Acetate metabolism and aging: An emerging connection

Sirtuins are NAD⁺-dependent protein deacetylases that regulate gene silencing, energy metabolism and aging from bacteria to mammals. SIRT3, a mammalian mitochondrial sirtuin, deacetylates acetyl-CoA synthetase (AceCS2) in the mitochondria. AceCS2 is conserved from bacteria to humans, catalyzes the conversion of acetate to acetyl-CoA and enables peripheral tissues to utilize acetate during fasting conditions. Here, we review the regulation of acetate metabolism by sirtuins, the remarkable conservation of this metabolic regulatory pathway and its emerging role in the regulation of aging and longevity.     

Acetate metabolism in the isolated sheep foetus

1. Sheep foetuses over the age range 105-142 days and maintained on an extracorporeal circuit removed exogenous acetate at 2.0-4.9 mg/kg.min.2. Urinary loss of acetate was less than 12.5% of the administered amount.3. The rate of acetate removal appeared to be unaffected by the addition of glucose to the circuit. The removal of glucose also seemed to be unaffected by the presence of acetate.4. A decline in the plasma concentration of free fatty acids and ketone bodies was also observed during the perfusion.5. It is concluded that under these conditions acetate may have accounted for about one half of the oxygen consumption. The contribution of free fatty acids and ketone bodies must have been small. The relevance of these findings to the nutrition of the foetus in utero is discussed.     

Influence of route of administration on progesterone metabolism

While inducing similar progesterone levels, the ratio of 5α- and 5β-pregnanolone/progesterone plasma concentrations has been dramatically increased after oral as opposed to vaginal administration, in a cross-over study. The known psychotropic effects of 5α- and 5β-pregnanolone lead to different indications and precautions for oral and vaginal administration of progesterone.     

Intestinal immune response to cholera toxin: dependence on route and dosage of antigen for priming and boosting.

The influence in immunization with cholera toxin of the route and antigen dose on intestinal antibody formation and protective immunity against experimental cholera was studied in mice. Administration by either the intravenous or oral route induced effective priming as well as boosting of mucosal immunity, with the effects on intestinal immunoglobulin A antitoxin synthesis and protective antitoxic immunity showing excellent concordance. A strong antigen dose dependence was found for both priming and boosting of the local immunity, irrespective of route. Very efficient high-dose priming did, however, partially decrease the dose dependence of the booster response and, conversely, a high booster dose partly overcame the relative inefficiency of low-dose priming. The results suggest that the amount of antigen reaching the immunocompetent cells in the gut rather than the route of administration per se determines the mucosal immunizing effect.     

Cancer metabolism: The Warburg effect today

One of the first studies on the energy metabolism of a tumour was carried out, in 1922, in the laboratory of Otto Warburg. He established that cancer cells exhibited a specific metabolic pattern, characterized by a shift from respiration to fermentation, which has been later named the Warburg effect. Considerable work has been done since then, deepening our understanding of the process, with consequences for diagnosis and therapy. This review presents facts and perspectives on the Warburg effect for the 21st century.     

The effect of antigen dosage on the response of adoptively transferred cells

Mice were immunized with BSA or HSA in Freund's adjuvant, and their lymph node and spleen cells transplanted into syngeneic hosts, which in most experiments had been irradiated. After transplantation the cells do not synthesize much antibody if left without stimulation, but can be stimulated to do so by injection of BSA or HSA in solution. The response has been studied over a dose range of 10^-3–10⁵ μg. antigen. Stimulation can be detected down to 10^-3 μg. antigen, and reaches a maximum at middling doses. Middling doses stimulate proliferation of the primed cells to an extent which can be measured by ¹³¹IUdR uptake. At high doses both antibody production and IUdR uptake are inhibited. The conclusion is drawn that high concentrations of antigen can paralyse the immunological reaction of primed cells.     

Respiratory allergy in the dog: induction by the respiratory route and the effect of passive antibody.

A technique for inducing hypersensitivity to prairie sage pollen (Artemisia gnopheles) in the dog was developed. The allergen induced skin reactivity in most dogs and respiratory hypersensitivity in 7 of the 17 animals tested. The respiratory hypersensitivity resembled naturally occurring respiratory allergies in both man and dog. The route of allergy induction resembles the natural route and it is felt that this system provides a useful model system for the study of respiratory allergies. Animals in which hypersensitivity was induced were used to investigate the role of passive 'blocking' antibody in respiratory allergy. It was observed that passive antibody will greatly inhibit the respiratory response to inspired allergen while completely inhibiting the cutaneous response. The results of these studies are discussed in relation to other studies.     

大剂量硫酸锌与小剂量青霉胺对体外培养淋巴细胞染色体损伤的影响

目的　探讨大剂量硫酸锌与小剂量青霉胺对体外培养淋巴细胞染色体的损伤程度。方法　采用染色体分析技术对对照组、硫酸锌组、青霉胺组、(硫酸锌 +青霉胺 )组的姐妹染色单体互换 (SCE)频率进行观察。结果　硫酸锌组与对照组之间差异无显著性 (t =1.2 6 4 ,P >0 .0 5 ) ,(硫酸锌 +青霉胺 )组、青霉胺组与对照组差异有显著性 (t =8.12 ;6 .13,P <0 .0 0 1)结论　硫酸锌对染色体损伤无影响。青霉胺对染色体损伤有一定作用。     

A study of lactate metabolism without tracer during passive and active postexercise recovery in humans

Tracers have been used extensively to study lactate metabolism in humans during rest and exercise. Nevertheless, quantification of in vivo lactate kinetics as measured by lactate tracers remains controversial and new data are necessary to clarify the issue. The present study has developed a simple kinetic model which does not require labelled molecules and which yields proportional and quantitative information on lactate metabolism in humans during postexercise recovery performed at different levels of intensity. Five subjects took part in six experiments each of which began with the same strenuous exercise (StrEx; 1 min, 385 W, 110 rpm). The StrEx of each session was followed by a different intensity of recovery: passive recovery (PR) and active recoveries (AR) with power outputs of 60, 90, 120, 150 and 180 W, respectively. Blood lactate concentration was measured prior to and immediately after StrEX and regularly during the 1st h of recovery. Oxygen uptake ( ) was measured every 30 s during the whole session. The results showed that the disappearance rate constant (k_e) increases abruptly from PR [0.080 (SEM 0.004) min^–1] to moderate AR [60W: 0.189 (SEM 0.039) min^–1] and decreases slowly during more intense AR [180 W: 0.125 (SEM 0.027) min^–1]. The lactate apparent clearance (Cl·F^–1) was calculated from the area under the lactate concentration-time curve. The Cls·F^–1 increased 1.81 (SEM 0.17) fold from PR to moderate AR (60 W) and only 1.31 (SEM 0.14) from PR to the most intense AR (180 W). Using the model, the apparent lactate production (FK₀) was also calculated. The FK₀ increased regularly following a slightly curvilinear function of and was 2.61 (SEM 0.53) fold greater during the most intense AR (180 W) than during PR. Because of the lack of data concerning the size of apparent lactate distribution volume (V _d), the apparent turnover rate (R_bl) has been presented here related toV _d. The R_bl·V _d ^–1 increased also following a slightly curvilinear function of . The R_bl·V _d ^–1 was 85.90 (SEM 14.42) mol·min^–1·l^–1 during PR and reached 314.09 (SEM 153.95) mol·min^–1·l^–1 during the most intense AR (180 W). In conclusion the model presented here does not require labelled molecules and firstly makes it possible to follow the proportional change of apparent lactate clearance and apparent lactate production during active postexercise recovery in comparison with passive recovery conditions and secondly to estimate the blood lactate turnover.     

The effect of fasting on the cholesterol metabolism

Summary The author studied the effect of starvation upon the cholesterol content in the liver and blood, as well as on cholesterol synthesis in the liver. 1-C¹⁴ sodium acetate was injected intraperitoneally into rabbits (50 C per kg of body weight). The animals were bled to death 4 hours after C¹⁴ administration. Cholesterol-C¹⁴ was isolated in the form of the digitonide. Starvation was connected with a considerable increase of cholesterol concentration in the blood and liver and with an acute reduction of the rate of cholesterol synthesis in the liver. The correlation between specific activities of the liver and blood serum cholesterol is about the same in normal and starving animals. The reduced chloresterol excretion and breakdown possibly causes a rise of its level in starving animals.(Presented by Active Member AMN SSSR S. E. Severin) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 50, No. 8, pp. 87–89, August, 1960     

The effect of macrophages on the metabolism of glomerular cells: preliminary studies

Human glomerular epithelial and mesangial cells were grown in vitro and shown to have distinctive morphologic and functional characteristics. Glomerular epithelial cells or mesangial cells cultured in wells of flat-bottom microtiter plates were treated for 4 hr with dialyzed macrophage supernatants obtained from cultures of mouse peritoneal macrophages or human peripheral monocytes. DNA, RNA, and protein synthesis were evaluated by incorporation of radioactive precursors. Macrophage supernatants stimulated RNA and protein synthesis in epithelial cells but failed to stimulate DNA synthesis. The macrophage factor(s) showed a dose-response activity, was nondialyzable, was destroyed by freezing and thawing, and did not seem to be species specific. In contrast to the results obtained with glomerular epithelial cells, mesangial cell DNA synthesis was stimulated by macrophage supernatants. The observed metabolic effects of macrophage products on glomerular cells in vitro are consistent with observations of in vivo glomerular response to injury in which epithelial cells may be activated to form new basement membrane while mesangial cells may respond by proliferating. These data further support the theory of macrophage involvement in the pathology of glomerulonephritis.     

Gene dosage effect in acquired monosomy 7: distinct behaviour of beta-glucuronidase and phosphoserine phosphatase

Evidence for gene dosage effect for beta-glucuronidase (GUSB) and phosphoserine phosphatase (PSP), whose genes are mapped on chromosome 7, was searched in a group of 13 patients with myeloproliferative disorders and acquired monosomy 7. The monosomy 7 was the sole anomaly in nine patients and was associated with other chromosome changes in four. A group of 19 patients with similar diseases but with normal karyotype or with anomalies not involving chromosome 7 served as control. beta-galactosidase and arylsulphatase A, whose genes are not on chromosome 7, were tested as control enzymes. We obtained evidence for a gene dosage effect for GUSB, but not for PSP. When all cases with monosomy 7 were compared with controls, no dosage effect was observed for PSP, but when this group was split into two, according to the presence of anomalies additional to the monosomy 7, the values of activity in the group with additional anomalies were significantly lower than in the controls. Thus, in the case of PSP, the loss of one allele is not followed immediately by reduction in activity, and this could be due to the specific importance of PSP in nucleic acid metabolism. We postulate that some regulatory mechanisms are able to keep normal levels of PSP even in the presence of only one allele, and that they are overwhelmed only when additional chromosome changes are present. These changes tend to involve chromosomes carrying genes for enzymes involved in a metabolic pathway closely related to PSP functions, and only then is a gene dosage effect for PSP detectable.     

Learned taste aversions in rats as a function of dosage, concentration, and route of administration of LiCl

Rats drank a 15% sucrose solution for 10 min and were then injected intraperitoneally with various volumes of 0.15 M LiCl to produce a learned taste aversion to the sucrose. A dose response curve was obtained between the volume of 0.15 M LiCl injected and the degree of aversion. With additional groups, the LiCl concentration was varied inversely with volume injected and it was found that the aversion was dependent on the absolute quantity of LiCl and not on the concentration or volume of solution. LiCl was also found to be equally effective in producing learned aversions whether administered intraperitoneally, subcutaneously, or by stomach tube. The dose-response curve indicated that a very strong aversion occurs at a dose of 3.0 mEq/kg and that the threshold dose for producing an aversion is approximately 0.15 mEq/kg. The threshold dose was discussed in relation to the amount normally given to human patients as a therapeutic dose. It was concluded that the rat is highly sensitive to learning a taste aversion with LiCl.     

大剂量硫酸锌与小剂量青霉胺对体外培养淋巴细胞染色体损伤的影响

目的　探讨大剂量硫酸锌与小剂量青霉胺对体外培养淋巴细胞染色体的损伤程度。方法　采用染色体分析技术对对照组、硫酸锌组、青霉胺组、(硫酸锌 +青霉胺 )组的SCE频率进行观察。结果　硫酸锌组与对照组之间差异无显著性 (t=1.2 6 4 ,P >0 .0 5 ) ,(硫酸锌 +青霉胺 )组、青霉胺组与对照组差异有显著性 (t=8.12 ;6 .13　P <0 .0 0 1)。结论　硫酸锌对染色体损伤无影响。青霉胺对染色体损伤有一定作用。     

Fatty acid metabolism in adipose tissue of aging mice after direct tracer injection into fat pads

We have examined previously reported age-related defects in triglyceride synthesis from [1-¹⁴C]palmitate in adipose tissue of mice. Three techniques were used: in vitro, using adipocytes isolated from epididymal fat pads of young and old mice; and in vivo, using two new methods to measure free fatty acid (FFA) esterification by adipose tissue (direct injection of labeled palmitate-albumin complexes in large or small volumes into the extracellular spaces of the epididymal or inguinal fat pads of young and old mice). When the entire fat pad was filled with tracer we no longer observed heterogeneous labeling of adipocytes in epididymal fat pads that occurred in an earlier study in which an in vivo-in vitro method has been used. Free fatty acids were converted to triacylglycerol faster by adipocytes of large cells from older animal than by those of small cells from young mice; when the cell sizes of young and old mice were approximately equal, then the rates of FFA esterification were the same in young and old adipocytes. When FFA was injected as a small bolus the fractional rates of FFA disappearance and of FFA incorporation into triacylglycerol in the different fat pads, observed during a 60-min period, were the same (about 5 min or less) regardless of the region of the fat pad studied (distal or proximal epididymal fat pad), the type of fat pad (epididymal or inguinal), or the age of the mice (12–92 weeks). Other potential applications of the direct injection technique for studying FFA metabolism and structure-function in adipose tissue in vivo are discussed. Our findings, coupled with the earlier study in which labeled FFA was added to the outside of fat pads, indicate that, in adipose tissue of old mice, there exist barriers comprising mesothelial cells, collagenous structures, and/or the outer layer of adipocytes in fat pads, that interfere in the transport of FFA to the interior adipocytes when FFA is added outside the fat pad. This age-related defect may be circumvented by injecting tracer directly into the interstitial fluid compartment.     

Further studies on the chronotherapy of asthma with inhaled steroids: The effect of dosage timing on drug efficacy

Background: Chronotherapy studies with inhaled corticosteroids have shown optimal therapeutic benefit when steroids are administered four times per day (QID) or once daily at 3 PM.Objective: This study evaluated whether more convenient once-daily dosage times (8 AM and 5:30 PM) produce improvement in asthma equivalent to QID.Methods: Efficacy outcome measures included FEV₁, peak expiratory flow rates, bronchial responsiveness, use of β₂-agonists, nocturnal awakenings, and responses to a quality of life questionnaire. Systemic effects were blood eosinophil count, cortisol level, 24-hour urinary cortisol, and evaluation for oral candidiasis and dysphonia.Results: Baseline measurements for all three treatment groups were similar. For morning peak expiratory flow rate, significant improvement was seen for the QID group (p = 0.001) and the 5:30 PM group (p = 0.003), but not the 8 AM group (p = 0.75). For evening peak expiratory flow rate, significant improvement was seen for the QID group (p = 0.005) and the 5:30 PM group (p = 0.01), but not for the 8 AM group (p = 0.47). There were significant improvements in all other outcome variables for each group except PC₂₀. There was a significant improvement in PC₂₀ only in the QID group. The systemic effects of the three regimens were comparable.Conclusion: Dosing of inhaled steroid at 5:30 PM had no increased systemic effects and produced efficacy similar to QID dosing. Dosing at 8 AM did not produce results consistently comparable to QID dosing. Optimal once-daily dosing of inhaled steroid is between 3 PM and 5:30 PM.     

Low dosage monophasic oral contraceptive use and intermittent exercise performance and metabolism in humans

Nine untrained women using low dosage monophasic oral contraceptives (OC) performed an intermittent treadmill test on two different occasions within one pill-cycle to determine the effect of OC on performance and some commonly used metabolic markers. The first test was performed after 5–8 days of resuming the OC agents after menstrual bleeding while the other test was performed after 19–21 days. Performance time on the final exhausting run of six intermittent high intensity 20 s runs was no different between trials [mean days 5–8: 22.3 (SEM 1.2) s vs days 19–21: 22.7 (SEM 1.1) s]. There was no difference in heart rate [peak heart rate days 5–8: 183 (SEM 3) beats^.min^–1 vs days 19–21: 186 (SEM 2) beats^.min^–1], oxygen consumption during any run [run 5 of days 5–8: 1,392 (SEM 51) ml·min^–1 vs run 5 of days 19–21: 1,494 (SEM 3) ml·min^–1] or in any of the metabolic variables measured at any time in venous blood [peak blood lactate concentration days 5–8: 8.4 (SEM 0.3) mmol·l^–1 vs days 19–21: 8.1 (SEM 0.5) mmol·l^–1; peak blood glycerol concentration days 5–8: 0.39 (SEM 0.02) mmol·l^–1 vs days 19–21: 0.38 (SEM 0.02) mmol·l^–1; resting free fatty acids concentration days 5–8: 0.25 (SEM 0.05) mmol·l^–1 vs days 19–21: 0.29 (SEM 0.07) mmol·l^–1; peak blood glucose concentration days 5–8: 6.7 (SEM 0.5) mmol·l^–1 vs days 19–21: 6.6 (SEM 0.2) mmol·l^–1; peak capillary blood ammonia concentration days 5–8: 139 (SEM 18.3) μmol·l^–1 vs days 19–21: 170 (SEM 18.0) μmol·l^–1]. These results suggest neither intermittent high intensity exercise performance nor energy metabolism change between days 5–8 and days 19–21 of a low dosage monophasic OC pill during one pill-cycle. Electronic Publication