Effect of Thyroxine on Δ6 and Δ9 Desaturation Activity

Dumm, I. N. T. de Gómez; Alaniz, María J. T. de; Brenner, Rodolfo R.

doi:10.1007/978-1-4684-3276-3_54

Cited by 25 publications

(10 citation statements)

References 23 publications

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“…Shaw & Hoch (1976 found increased C22:6 fatty acid levels in myocardial mitochondria but decreased levels in liver nuclei of hypothyroid animals. The increase in micosomal C20:5 and C22:6 fatty acid levels, products of linolenate desaturation and elongation, in hypothyroidism probably result from decreased utilization of these fatty acids, since there is no evidence of increased desaturation or chain elongation in hypothyroidism (Landriscina et al, 1976;deGomez Dumm et al, 1977).…”

Section: Discussionmentioning

confidence: 99%

“…for 2 days corrected the linoleate desaturase defect. Thus, the A6 desaturase enzyme is sensitive to thyroid hormone requiring normal hormone levels for normal activity in spite of the fact that hyperthyroid animals have decreased A6 desaturase activity (Faas & Carter, 1981;deGomez Dumm et al, 1977).…”

Section: Discussionmentioning

confidence: 99%

“…Rats treated with propylthiouracil had no change in either liver microsomal A9 or A6 desaturase activity (deGomez Dumm et al, 1977). More recently, Hoch et al (1980).…”

mentioning

confidence: 92%

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Fatty acid desaturation and microsomal lipid fatty acid composition in experimental hypothyroidism

Faas¹,

Carter²

1982

Biochemical Journal

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We have studied the influence of experimental hypothyroidism in the rat on the synthesis of unsaturated fatty acids and on liver microsomal lipid fatty acid composition. Hypothyroid rats demonstrated an 80% decrease in delta 9 (stearate) desaturation and a 43% decrease in delta 6 (linoleate) desaturation. Liver microsomal fatty acid composition was altered in the hypothyroid animals with a significantly decreased proportion of arachidonate and increased proportions of linoleate, eicosa-8,11,14-trienoate, eicosapentaenoate and docosahexaenoate. The bulk of these changes occurred in both of the two major phospholipid components, phosphatidylcholine and phosphatidylethanolamine. All of the changes were corrected by treatment of the hypothyroid rat with 25 micrograms of tri-iodothyronine/100 g body wt. twice daily. The diminished delta 9 desaturation did not lead to any changes in fatty acid composition. The increased linoleate and decreased arachidonate levels may be due to the diminished delta 6 desaturase activity, the rate-controlling step in the conversion of linoleate into arachidonate. The increases in the proportions of the other polyunsaturated fatty acid components cannot be explained by changes in the synthesis of unsaturated fatty acids, but are probably due to diminished utilization of these fatty acids.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Fatty acid desaturation and microsomal lipid fatty acid composition in experimental hypothyroidism

Faas¹,

Carter²

1982

Biochemical Journal

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“…Therefore, the most likely mechanism for the observed alterations of hepatic organelle membrane fatty acyl composition in hypothyroidism is a defect in the microsomal conversion of 18:26o6 to 20:4606 fatty acyls, which involves a chain elongation and A6-and A5-desaturations. Hypothyroidism has been reported to slow microsomal chain elongation by -35% (10), although others find no change (28). However, the elongation 18:36o6~20:36o6 normally proceeds 5.6 times faster than the A5-desaturation and 4.5 times faster than the A6-desaturation (29), and so would not seem to be ratecontrolling in any case.…”

Section: Discussionmentioning

confidence: 99%

“…deGomez Dumm et al (28) report that hypothyroidism (using female rats fed propylthiouracil) significantly decreases the 18:2 content of liver fatty acids and does not alter either the 20:4 content or the microsomal A9-or A6-desaturase activities. Their data on fatty acid composition disagree with Ellefson and Mason's (30) on liver total lipids and ours (Tables II, III; refs. 2,3) on liver organelle fatty acids.…”

Section: Discussionmentioning

confidence: 99%

Thyroid control over biomembranes: VI. Lipids in liver mitochondria and microsomes of hypothyroid rats

Hoch

Subramanian

Dhopeshwarkar

et al. 1981

Lipids

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The lipids of liver mitochondria prepared from normal rats and from rats made hypothyroid by thyroidectomy and injection with 131 INa contained similar amounts, per mg protein, of total lipids, phospholipids, neutral lipids and lipid phosphorus. Hypothyroidism caused a doubling of the relative amounts of mitochondrial cardiolipins (CL; to 20.5% of the phospholipid P) and an accompanying trend (although statistically not significant) toward decreased amounts of both phosphatidylcholines (PC) and phosphatidylserines (PS), with phosphatidylethanolamines (PE) remaining unchanged. The pattern of elevated 18:2 fatty acyl content and depleted 20:4 acyl groups of the mitochondrial phospholipids of hypothyroid preparations was reflected to varying degrees in the resolved phospholipids, with PC showing greater degrees of abnormality than PE, and CL showing none. Hypothyroidism produced the same abnormal pattern of fatty acyl distributions in liver microsomal total lipids as was found in the mitochondria. Hypothyroid rats, when killed 6 hr after injection of [1-14C] labeled linoleate, showed the following abnormalities: the liver incorporated less label into lipids, and converted 18:2 not exclusively to 20:4 (as normals do) but instead incorporated the label mainly into saturated fatty acids. These data, together with the known decrease in beta-oxidation, suggest that hypothyroidism involves possible defective step(s) in the conversion of 18:2 to 20:4.

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Effect of L-triiodothyronine on liver microsomal ?6 and ?5 desaturase activity of male rats

Ves-Losada

Peluffo

1993

Mol Cell Biochem

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The effect of different doses of L-triiodothyronine (T3) on the activity of delta 6 and delta 5 desaturases and lipid fatty acid composition was studied in liver microsomes of male rats. The activity of delta 6 and delta 5 desaturases was decreased 24 and 28%, respectively, in animals administered a daily intraperitoneal dose of 1000 micrograms T3/100 g body wt. for 5 days, whereas with 500 micrograms T3/100 g body wt. only delta 6 desaturase activity was decreased. On the other hand, no enzyme activity changed at a shorter period of hormone treatment. Changes in microsomal fatty acid composition did not seem to be a direct consequence of desaturation activity, since after 1 and 5 days of T3 treatment, the concentrations of 18:2 (n-6) and 20:3 (n-6) decreased and only after 1 day that of 20:4 (n-6) increased in spite of unchanged or decreased delta 6 and delta 5 desaturase activities. Other factors than desaturation activity must be involved in fatty acid composition of thyroid hormone-treated rats, such as diet, membrane lipid synthesis and degradation, fatty acid turn-over and oxidation.

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Effect of Thyroxine on Δ6 and Δ9 Desaturation Activity

Cited by 25 publications

References 23 publications

Fatty acid desaturation and microsomal lipid fatty acid composition in experimental hypothyroidism

Fatty acid desaturation and microsomal lipid fatty acid composition in experimental hypothyroidism

Thyroid control over biomembranes: VI. Lipids in liver mitochondria and microsomes of hypothyroid rats

Effect of L-triiodothyronine on liver microsomal ?6 and ?5 desaturase activity of male rats

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