Abstract
Male rats of Wistar strain were fed a standard diet (14% calories as fat or a high fait diet (80% calories as fat) for 4 to 5 weeks at 20°C. A high fat diet caused a marked hypertrophy of brown and white adipose tissue, but no change in the weight of thyroid, while there was a significant decrease in the thyroid activity as indicated by low T/S ratio. Also, the 48-hr conversion ratio of131I to protein-bound131I (PB131I) was lower. However, plasma PB131I level in this group was not different from that in the control group of rats. At 20°C plasma PB131I levels were progressively decreased over a period of 48 hours in the control group, while in the high fat diet group the initial level was maintained throughout the period. In the control group cold exposure at 3° to 5°C caused a significant elevation of PB131I level, but later it decreased to the level at 20°C. In the high fat diet group the plasma PB131I was not influenced by the same cold exposure. Fractional turnover rate of131I-thyroxine was similar in the two groups. It increased significantly on exposure to cold in the control group, while it remained unchanged in the high fat diet one. These results suggest that a high fat diet has some depressive influence on thyroidal activity and the responses to cold.
Zusammenfassung
Männliche Wistar Ratten lebten 4–5 Wochen bei 20°C und Standardfutter mit 14% Kalorien in Fett oder einem fettreichen Futter (80% Kalorien in Fett). Das fettreiche.Futter bewirkte eine starke Zunahme des braunen und weissen Fettgewebes ohne Änderung des Schilddrüsengewichtes, während die Schilddrüsenaktivität stark abfiel, erkennbar an dem niedrigen T/S Quotienten. Ebenso war die 24-Stunden Umwandlung von131I in proteingebundenes131I (PB131I) niedriger als bei den Kontroll-Tieren, jedoch war der Plasma PB131I-Spiegel der beiden Gruppen gleich. Bei 20°C fiel der PB131I-Spiegel der Kontroll-Tiere innerhalb 48 Stunden langsam ab, während er bei den fettreich gefütterten Tieren gleich blieb. In der Kontrollgruppe bewirkte 3°–5°C Kälteexponierung eine signifikante Erhöhung des PB131I Spiegels mit langsamen Abfall auf die Werte bei 20°C, während der Spiegel bei den fettreich gehaltenen Tieren unverändert blieb. Die fraktionierte Umsatzrate von131I-Thyroxin war in beiden Gruppen gleich.Sie stieg bei Kälteexponierung in der Kontrollgruppe signifikant an und blieb bei den fettreich gefütterten Tieren unverändert. Danach übt fettreiches Futter eine hemmende Wirkung auf die SD-Aktivität und Reaktionen auf Kälte aus.
Resume
On a élevé des rats mâles de la race Wistar à 20°C durant 4 à 5 semaines. Les uns recevaient une alimentation normale (14% des calories provenaient de graisses), les autres une alimentation très grasse (80% des calories étaient constitués par des corps gras). L'alimentation riche en graisses a eu pour effet une forte augmentation des tissues adipeux bruns et blancs, mais pas de modification du poids de la glande thyroïde. L'activité de celle-ci fut pourtant ralentie ce qui s'est traduit par une baisse du quotient T/S. La transformation en 24 heures de131I en iode proteïnique131I (PB131I) fut également inférieure que dans le cas des bêtes de contrôle. Pourtant, le taux de PB131I est resté le même dans le plasma des deux groupes. A 20°C, le taux de PB131I diminue lentement en 48 heures chez les bêtes de contrôle alors qu'il est resté le même chez les animaux soumis à un régime gras. Une exposition au froid (3° à 5°C) du groupe de contrôle y a provoqué une hausse significative du taux de PB131I, mais celuici redescendit au niveau antérieur, celui correspondant à 20°C. Dans le cas des rats soumis à un régime gras, on n'a pas constaté d'influence semblable lors de leur exposition au froid. Le taux fractionné de transformation de la thyroxine131I a réagi de même dans les deux groupes: Il y a ici aussi hausse significative dans le groupe de contrôle, mais pas dans celui soumis à un régime gras. Ces résultats laissent supposer, qu'un régime riche en graisses agit comme inhibiteur sur l'activité thyroïdienne et sur les réactions au froid.
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Kuroshima, A., Doi, K. & Itoh, S. Effects of a high fat diet on thyroid activity, with special reference to thyroidal responses to cold. Int J Biometeorol 15, 55–64 (1971). https://doi.org/10.1007/BF01804718
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DOI: https://doi.org/10.1007/BF01804718