Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37–1200 days (liver) and 331–1200 days (heart)

Murawski, U.; Kriesten, K.; Egge, Heinz

doi:10.1016/0305-0491(90)90375-4

Cited by 9 publications

(8 citation statements)

References 97 publications

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“…Podolin et al (32) reported a reduced protein expression of G s ␣ and G s ␣/ G i ␣ 2 ratio (20%) with aging in rat liver. Because liver triglycerides have been reported to increase with age (29), it is possible that the decreased hepatic ratio of G s ␣/G i ␣ 2 activity observed in these studies was influenced by the liver lipid content. On the whole, the present decrease in protein expression of G s ␣ and in the G s ␣/G i ␣ 2 ratio indicates that the HF diet-induced hepatic steatosis reduced not only glucagon receptor density but also glucagon-mediated signal transduction.…”

Section: Discussionmentioning

confidence: 75%

“…In addition, Podolin et al (32) reported that the age-related decline in glucagon signaling capacity and responsiveness may be attributed, in part, to a reduction in the G s -to-G i ratio. Obesity, diabetes, and aging (29) are conditions that very often result in an increase in liver lipid infiltration. Whether an increased liver lipid infiltration may result in an alteration in the G protein content in the liver is unknown.…”

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confidence: 99%

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Alterations in hepatic glucagon receptor density and in G_sα and G_iα₂protein content with diet-induced hepatic steatosis: effects of acute exercise

Charbonneau

Melançon²,

Lavoie³

et al. 2005

American Journal of Physiology-Endocrinology and Metabolism

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The present study was undertaken to test the hypothesis that a high-fat diet-induced liver lipid infiltration is associated with a reduction of hepatic glucagon receptor density (B(max)) and affinity (K(d)), and with a decrease in stimulatory G protein (G(s)alpha) content while enhancing inhibitory G protein (G(i)alpha(2)) expression. We also hypothesized that, under this dietary condition, a single bout of endurance exercise would restore hepatic glucagon receptor parameters and G protein expression to standard levels. Female Sprague-Dawley rats were fed either a standard (SD) or a high-fat diet (HF; 40% kcal) for 2 wk (n = 20 rats/group). Each dietary group was thereafter subdivided into a nonexercised (Rest) and an acute-exercised group (Ac-Ex). The acute exercise consisted of a single bout of endurance exercise on a treadmill (30 min, 26 m/min, and 0% slope) immediately before being killed. The HF compared with the SD diet was associated with significantly (P < 0.05) higher values in hepatic triglyceride concentrations (123%), fat pad weight, and plasma free fatty acid (FFA) concentrations. The HF diet also resulted in significantly (P < 0.05) lower hepatic glucagon receptor density (45%) and G(s)alpha protein content (75%), as well as higher (P < 0.05) G(i)alpha(2) protein content (27%), with no significant effects on glucagon receptor affinity. Comparisons of all individual liver triglyceride and B(max) values revealed that liver triglycerides were highly (P < 0.003) predictive of the decreased glucagon receptor density (R = -0.512). Although the 30-min exercise bout resulted in some typical exercise effects (P < 0.05), such as an increase in FFA (SD diet), a decrease in insulin levels, and an increase in plasma glucagon concentrations (SD diet), it did not change any of the responses related to liver glucagon receptors and G proteins, with the exception of a significant (P < 0.05) decrease in G(i)alpha(2) protein content under the HF diet. The present results indicate that the feeding of an HF diet is associated with a reduction in plasma membrane hepatic glucagon receptor density and G(s)alpha protein content, which is not attenuated by a 30-min exercise bout. It is suggested that liver lipid infiltration plays a role in reducing glucagon action in the liver through a reduction in glucagon receptor density and glucagon-mediated signal transduction.

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Section: Discussionmentioning

confidence: 75%

mentioning

confidence: 99%

Alterations in hepatic glucagon receptor density and in G_sα and G_iα₂protein content with diet-induced hepatic steatosis: effects of acute exercise

Charbonneau

Melançon²,

Lavoie³

et al. 2005

American Journal of Physiology-Endocrinology and Metabolism

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“…In total liver membrane extraction, Murawasky et al (21) reported that hepatic phospholipids increased, and other studies have reported both to have been unchanged (3,22), while decreased values have been reported in both plasma membranes and microsomes (23,24). However, data on the composition of lipid classes show that the amount of PC in the liver of older rats is decreased in hepatic membrane (3) and microsomes (25), even when the relative proportion of PC in membranes is increased in plasma membrane (23) and microsomes (25), with respect to all phospholipids.…”

Section: Discussionmentioning

confidence: 99%

Age-Related Variations in Hepatic Biosynthesis of Phosphatidylcholine: A Study of Choline Metabolism with Perfused Rat Liver

Ortu

Rivabene

Cantàfora

et al. 1997

Experimental Biology and Medicine

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This study investigated the age-related increase in phospholipid secretion previously described in perfused rat livers. The hypothesis of this study was that the increased secretion is mainly due to an enhanced hepatic biosynthesis of phosphatidylcholine (PC). Specifically, we evaluated the contribution to this increase of the major hepatic pathway of phosphatidylcholine formation (i.e., the conversion of choline into phosphatidylcholine via cytidine diphosphate [CDP]-choline). The measurements of [3H]choline incorporation into phosphatidylcholine and its precursors in liver and bile throughout the 2-hr duration of the experiments showed significant differences in the amount of newly synthesized labeled PC secreted in the bile produced by adult and young rat livers. However, the present findings do not support the idea that the age-related increase in phosphatidylcholine hepatic secretion was due only to a strong increase in phosphatidylcholine synthesis by via CDP-choline. Conversely, they suggest that future research should be directed towards the mechanisms regulating the diacylglycerol metabolism in the hepatocytes, as the alteration of the splitting ratio of hepatic diacylglycerol flow could lead to an age-related increase in conversion of diacylglycerol into phosphatidylcholine, rather than into triacylglycerol. This, in turn, may decrease the availability of triacylglycerol for hepatic very low density lipoprotein (VLDL) assembly and contribute to altered VLDL synthesis, as previously observed in the aging process.

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“…Although the effects of aging caw differ between male and female rats (Capasso et al 1983), old female Wistar rats can be considered fully representative of aging rats, since they exhibit changes in energetic status, particularly in lipid metabolism (Murawski et al 1990), and alterations in mechanical performances (Jullien et al 1989). …”

Section: Body and 1zeapt Masses Of Experimental Animalsmentioning

confidence: 99%

“…The reduction in IMPPA uptake by the kidney may be due to age-related alterations consecutive to nephrosclerosis or renal ischemia (Corman and Michel 1987;Lakatta 1989). The decrease in IMPPA uptake by the aging myocardium could be due either to changes in energetic status and lipid metabolism (Jullien et al 1989;Murawski et al 1990), since glycolysis is preferred to fatty acid metabolism in senescent female Wistar rats (Van der Vusse et al 1983), or to an altered blood flow, possibly inducing lesioned areas showing decreased [I4C]-IMPPA levels compared with control ones.…”

Section: Biodistribution Of [14c]zmppamentioning

confidence: 99%

Heterogeneous distribution of a fatty acid analogue uptake in the myocardium of aged rats

Communal¹,

Verdetti²,

Estrade³

et al. 1994

Can. J. Physiol. Pharmacol.

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The aim of this study was to determine the extent and location of damaged myocardial areas in senescent rats. The viability of myocardial cells was evaluated in virgin young (4 months old) and aged (29 months old) female Wistar rats by analysing the uptake of a slowly metabolisable radiolabelled fatty acid analogue, 15-p-iodophenyl-beta-methylpentadecanoic acid (IMPPA). The biodistribution of IMPPA was measured in various organs, and regional myocardial uptake was specifically assessed using quantitative autoradiography. Myocardial enzymatic activity and DNA content were also evaluated with nitro blue tetrazolium (NBT) and propidium iodide (PI) staining, respectively. In senescent rats, cardiac and renal IMPPA uptake showed a significant (50%) reduction compared with young adult rats and the uptake was not significantly changed in the liver, spleen, lungs, and skeletal muscle. Total ventricular NBT staining and IMPPA uptake were almost homogeneous in young adult rats, whereas they were very heterogeneous in aged rats. In the latter, approximately 11% of the total ventricular volume showed a significantly decreased (by 60% or more) IMPPA uptake compared with normal values, and this reduction was greater in ventricle base than in apex. The myocardial areas unlabelled or poorly labelled by IMPPA represented 4, 5, 6, and 21% of the right ventricular, left ventricular epicardial, septal, and left ventricular endocardial volume, respectively, and were poorly stained with NBT. In some of these areas, PI staining indicated the presence of living cells unable to pick up NBT staining. In conclusion, in young adult rats, no myocardial lesions were observed using three different labelling techniques.(ABSTRACT TRUNCATED AT 250 WORDS)

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Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37–1200 days (liver) and 331–1200 days (heart)

Cited by 9 publications

References 97 publications

Alterations in hepatic glucagon receptor density and in G_sα and G_iα₂protein content with diet-induced hepatic steatosis: effects of acute exercise

Alterations in hepatic glucagon receptor density and in G_sα and G_iα₂protein content with diet-induced hepatic steatosis: effects of acute exercise

Age-Related Variations in Hepatic Biosynthesis of Phosphatidylcholine: A Study of Choline Metabolism with Perfused Rat Liver

Heterogeneous distribution of a fatty acid analogue uptake in the myocardium of aged rats

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Age-related changes of lipid fractions and total fatty acids in liver lipids and heart lipids of female and male rats aged 37–1200 days (liver) and 331–1200 days (heart)

Cited by 9 publications

References 97 publications

Alterations in hepatic glucagon receptor density and in Gsα and Giα2protein content with diet-induced hepatic steatosis: effects of acute exercise

Alterations in hepatic glucagon receptor density and in Gsα and Giα2protein content with diet-induced hepatic steatosis: effects of acute exercise

Age-Related Variations in Hepatic Biosynthesis of Phosphatidylcholine: A Study of Choline Metabolism with Perfused Rat Liver

Heterogeneous distribution of a fatty acid analogue uptake in the myocardium of aged rats

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Alterations in hepatic glucagon receptor density and in G_sα and G_iα₂protein content with diet-induced hepatic steatosis: effects of acute exercise

Alterations in hepatic glucagon receptor density and in G_sα and G_iα₂protein content with diet-induced hepatic steatosis: effects of acute exercise