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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The purpose of this study was to document the effect of age on alpha-glycerophosphate activity and pyridine nucleotide concentration in pancreatic islets isolated from rats. In order to do this, islets were isolated from pancreases of 2 and 12 month-old rats, and measurements made of alpha-glycerophosphate activity and of NAD+ and NADH, determinations were made following incubation at both basal (5.6 mM) and elevated glucose concentrations (28 mM). The results indicated that islet alpha-glycerophosphate dehydrogenase activity was decreased (P less than 0.001) by approximately 50% in the older rats. This was associated with an increase in mean (+/- SEM) basal NADH content (pmol/microgram DNA) in 12 month-old (4.48 +/- 0.31) as compared to 2 month-old rats (2.73 +/- 0.49). Although mean (+/- SEM) basal NAD+ levels (pmol/microgram DNA) were the same in 2 and 12 month-old rats (29.4 +/- 2.5 and 30.8 +/- 2.8, respectively), NAD+ content following incubation at elevated levels of glucose declined (absolutely and relatively) to a significantly greater degree in the younger rats. The incremental rise in islet NADH concentration following incubation at the elevated glucose concentration was similar in the two groups, but the relative increase was only approximately half as great in islets from 12 month-old rats. These data indicate that the age-related decline in the activity of alpha-glycerophosphate dehydrogenase, the enzyme regulating the glycerophosphate shuttle system in 12 month-old rats, is associated with alterations in islet pyridine nucleotide composition.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Evidence for age-related changes in pyridine nucleotide content of isolated rat islets. 305 68

The activities of three enzymes--two mitochondrial and one microsomal--were measured in isolated islets of Langerhans from 2-month-old and 12-month-old rats. Mitochondrial glycerophosphate dehydrogenase activity (expressed as nanomoles of iodonitrotetrazolium reduced per minute per milligram of protein), decreased (P less than 0.01) from a mean (+/- SEM) of 73.2 +/- 11.2 (2-month-old) to 34.7 +/- 5.9 (12-month-old). In contrast, activities of neither mitochondrial monoamine oxidase nor microsomal NADH cytochrome-c reductase changed with age. These results demonstrate that the activity of the glycerophosphate shuttle decreases as rats grow older, and it raises the possibility that the consequent difficulty in regenerating cytosolic NAD+ may play a role in the insulin secretory defect associated with aging.
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PMID:Evidence of an age-related decline in mitochondrial glycerophosphate dehydrogenase activity of isolated rat islets. 635 35

Despite the importance of brown adipose tissue (BAT) in the regulation of thermogenesis and energy expenditure in both newborn and adult mammals, the functional ontogenesis of this tissue is largely unknown. In the present study, we describe the maturation of several aspects of BAT thermogenesis in fetal and newborn sheep. Cell respiration of brown adipocytes isolated from perirenal BAT was measured using a Gilson differential respirometer. Cells were isolated from four fetal animals at 121-124 days gestation (group 1), five fetal animals at 137-140 days gestation (group 2), and five newborns between birth and 4 days of age (group 3). In addition to basal oxygen consumption, in vitro cell respiration also was measured after the addition of norepinephrine (NE), (Bu)2cAMP, alpha-glycerophosphate (alpha GP), and butyric acid. Mean (+/- SEM) basal respiration (in microliters of O2 per 10(6) cells/h) increased from 11 +/- 1 in group 1 to 31 +/- 2 in group 2 and 45 +/- 7 in group 3. Cell volume increased from 9 +/- 1 pl in group 1 to 13 +/- 2 pl in group 2 and 18 +/- 2 pl in group 3. After adjustment for variations in basal respiration due to differences in cell volume, basal respiration in group 2 was greater than that in group 1 and equal to that in group 3. Maximal NE (10(-6) M)-stimulated respiration increased from 74 +/- 16 in group 1 to 294 +/- 47 in group 2. Maximal NE-stimulated respiration in group 3 (133 +/- 30) was less than that in group 2, but equal to that in group 1. (Bu)2cAMP-stimulated respiration increased from 51 +/- 12 in group 1 to 175 +/- 22 in group II, with no further increase in group III. Neither NE- nor (Bu)2cAMP-stimulated respiration varied significantly with cell volume. alpha GP substrate respiration demonstrated significant increases from group 1 to group 2, with another significant increase in Group 3. Butyric acid substrate respiration in group 1 was less than those measured in groups 2 and 3, while respiration values in groups 2 and 3 were equal. After adjustments for variations due to differences in cell volume, the patterns of development of both alpha GP and butyric acid substrate respiration were unaltered. The following conclusions were reached 1) Full maturation of BAT catecholamine-stimulated cellular respiration occurs before delivery near term in the ovine fetus. 2) In the neonatal lamb, a decrease in catecholamine-stimulated respiration occurs without a decrease in (Bu)2cAMP-stimulated respiration. This suggests that a decrease in BAT sensitivity to NE occurs after delivery at the receptor adenyl cyclase level. 3) The perinatal increase in alpha GP substrate respiration without an increase in butyric acid substrate respiration suggests that mitochondrial alpha-glycerophosphate dehydrogenase activity is increased. This was confirmed by measuring increased alpha-glycerophosphate dehydrogenase activity in crude BAT mitochondrial fractions in group 3 animals.
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PMID:Development of brown adipose tissue thermogenesis in the ovine fetus and newborn. 640 32

This investigation intended to clarify the effects of malnutrition in utero on enzymes of glycerol metabolism and the stores of phosphorylated glycerol intermediates in liver, striated muscle, and brain in the rat. Pregnant Wistar rats were restricted to an intake of 50% (M) of ad libitum fed controls (C) from the seventh day of gestation onward. Fetuses were removed 2 days (-2), or 1 day (-1), before term, or at the day of birth (DOB) The M fetuses and newborn rats were stunted. Their hepatic alpha-glycerophosphate oxidase (GPO) levels were lower than those of C in utero (mean +/- SEM: M = 23.1 +/- 1.5, 15.8 +/- 1.1, and 31.6 +/- 4.5; C = 34.8 +/- 4.9, 39.8 +/- 7.0, and 23.6 +/- 5.0 nmol/min X cm at -2, -1, and DOB, respectively; F = 7.29 [1,57], P less than .01). In muscle, this enzyme, as well as liver and brain alpha-glycerophosphate dehydrogenase (GPD), alpha-glycerophosphate (GP), and dihydroxyacetone phosphate (DHAP), only varied with the developmental stage. Although the latter was a significant differential factor in all the determinations, maternal diet only affected brain DHAP stores (M = 1.85 +/- 0.36, 1.03 +/- 0.16, 0.74 +/- 0.10; C = 2.33 +/- 0.46, 1.87 +/- 0.21, 1.13 +/- 0.18 mumol/g at -2, -1, and DOB, respectively; F = 9.03 [1,53], P less than .01). These findings support the contention that intrauterine malnutrition can alter normal ontogenesis of glycerol metabolism enzymes in certain organs and become a negative factor disturbing normal gluconeogenesis and glycogenolysis, with potential disruption of energy homeostasis immediately after birth.
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PMID:Intrauterine malnutrition in the rat: alterations of fetal glycerol metabolism. 665 62

The main objective of this study was to determine whether the principal abnormality of thyroid function observed in patients with chronic renal failure, low serum triiodothyronine (T(3)) concentration, causes hypothyroidism at the tissue level. A partially nephrectomized (Nx) uremic rat model was developed and the following parameters of thyroid function were assessed: serum total thyroxine (TT(4)), total T(3) (TT(3)), and thyrotropin and liver T(3) content, and activity of two thyroid hormone-dependent enzymes, mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) and cytosol malate dehydrogenase (MDH). The results were compared to those of intact control (C), thyroidectomized (Tx), and nephrectomized-thyroidectomized (NxTx) littermates.Results expressed as mean+/-SEM showed that Nx rats had a fivefold increase in blood urea nitrogen, (112+/-20 mg/dl in Nx, and 22+/-1 mg/dl in C) and manifested all the changes of of thyroid function observed in uremic men, including a low serum TT(3) level (30+/-7 ng/dl in Nx and 50+/-6 ng/dl in C). In the liver, T(3) was significantly reduced (18+/-2 ng/total liver in Nx and 35+/-3 ng/total liver in C) as well as the activities of alphaGPD (8.8+/-1.0 and 16.1+/-1.5 DeltaOD/min per total liver in Nx and C, respectively) and MDH (6.3+/-1.6 and 12.6+/-2.2 U/total liver in Nx and C, respectively). The reduction in liver enzyme activities correlated significantly with the decrease in T(3) content. The changes in Tx rats were as expected, showing a profound reduction in serum hormone levels, liver T(3) content, and liver enzyme activities. Serum thyrotropin was markedly elevated to 2,390+/-212 ng/ml as compared to 703+/-61 in C and 441+/-87 ng/ml in Nx rats. The NxTx rats showed the combined effects of nephrectomy and thyroidectomy; blood urea nitrogen was elevated to 203, and serum levels of TT(4), TT(3), and thyrotropin were 0.4, <10, and 2,525, respectively. Total liver T(3) and alphaGPD and MDH were strikingly low; the corresponding values were 3.5, 2.4, and 2.5.l-triiodothyronine replacement (0.4 mug/100 g body wt/d) for 4 wk in the Nx rats resulted in significant increases in liver enzyme activities, alphaGPD and MDH rose by 70 and 60% over their respective basal values without alteration in the severity of azotemia. From these data, we conclude that the reduction of liver T(3) content in the uremic rats, accompanied by a decrease in alphaGPD and MDH activity, indicates the presence of hypothyroidism at the tissue level. Restoration of enzyme activities toward normal levels after T(3) administration provided further supporting evidence that the diminution in liver enzyme activity was causally related to tissue T(3) deficiency.
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PMID:Thyroid function in a uremic rat model. Evidence suggesting tissue hypothyroidism. 677 47

Basal and norepinephrine (NE) stimulated oxygen consumption was measured in BAT cells isolated from fetal and newborn rabbits at 24, 28, and 31 days gestation, and 3 and 10 days postnatal age. Maximum catecholamine stimulated respiration was measured at a final NE concentration of 10(-6) M. Cell diameter, calculated cell volume and mitochondrial alpha glycerophosphate dehydrogenase (alpha GPD) were also determined at each age. Basal respiration increased continuously during fetal and neonatal life from a mean (+/- SEM) of 12.2 +/- 0.4 mul O2/10(6) cells . hr at 24 days gestation to a mean of 70.5 +/- 4.2 mul O2/10(6) cells . hr at 24 days gestation to 670.5 +/- 60.4 mul O2/10(6) cells . hr at 31 days. A further increase of 30% measured at 10 days of age was also observed. BAT mitochondrial alpha GPD activity was several fold greater than that measured in liver. Both cell size and enzyme activity increased in parallel to increasing respiratory response to NE. We conclude from this data that the maturation of catecholamine stimulated BAT thermogenesis occurs primarily in the fetus prior to delivery. This increase is associated with both an increase in mitochondrial enzyme activity and an increase in cell size.
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PMID:Ontogenesis of brown adipose tissue thermogenesis in the rabbit. 678 86