616 VI. OCCURRENCE OF LIPIDS IN THE ANIMAL 



tary extracts. 454 It is believed that this insulin effect is an indirect one 

 which causes glycogen deposition in the intrascapular fat of the normally 

 fed rat, even during fasting. 455 It has also been shown that insulin restores 

 the ability of alloxan-diabetic rats to store glycogen in their adipose tissue. 456 



Pauls and Drury, 457 and Stetten and Klein, 458 have demonstrated that in- 

 sulin participates in the carbohydrate -*■ fat transformation. It has been 

 reported that fat synthesis proceeds to the extent of only 5% of the normal 

 rate in the diabetic animal. 458 Since adipose tissue participates in fat for- 

 mation, 430 and insulin is a requirement for glycogen deposition in such tis- 

 sues, it is evident that normal fat deposition and mobilization will be in- 

 terrupted in the absence of this hormone. However, it is difficult to agree 

 with the interpretation of Wertheimer and Shapiro 401 that the fatty livers 

 result from a lack of insulin. The failure of the carbohydrate -*- fat syn- 

 thesis in the adipose tissue has been cited as the cause for the failure of fat 

 mobilization after adrenalectomy. 



d\ The Regulation by Thyroid Hormones: Although it is generally 

 assumed that the normal result of thyroidectomy is obesity, MacKay and 

 Sherril 459 reported that the total fat content of adult rats, fed on a fat-rich 

 diet, was actually decreased after thyroidectomy. The rats weighed ap- 

 proximately the same as the controls. In no case could these workers in- 

 duce obesity by removal of the thyroid gland. On the other hand, Tuer- 

 kischer and Wertheimer 120 found that the deposition of glycogen in the adi- 

 pose tissue was enhanced in thyroid-fed rats, but that the carbohydrate 

 level quickly reached zero thereafter. Thus, thyroxine did not interfere 

 with fat formation, but speeded up the transformation of carbohydrate to 

 'fat. 



(c) Nervous Control of Fat Mobilization and Deposition in Adipose Tissue. 

 Numerous experimental data have demonstrated that nerve stimuli play a 

 profound role in fat mobilization and deposition in the storage depots. 

 Goering 412 pointed out, on the basis of clinical experience, that excessive nerve 

 stimulation provokes a fat loss in the adipose tissue, while paralysis results 

 in a deposition of fat in these depots. Proof of these statements has been 

 obtained experimentally on animals. Thus, it was demonstrated 412 ' 414 - 460 

 that section of the femoral nerve of the rabbit caused an increase in 



464 J. Campbell, Am. J. Physiol, 147, 742-747 (1946). 



468 E. Wertheimer, /. Physiol, 103, 359-366 (1945). 



466 E. Tuerkischer and E. Wertheimer, J. Physiol, 104, 361-365 (1946). 



457 F. Pauls and D. R. Drury, J. Biol. Chem., 145, 481-485 (1942). 



«" De W. Stetten, Jr., and B. V. Klein, J. Biol Chem., 162, 377-382 (1946). 



469 E. M. MacKay and J. W. Sherril, Endocrinology, 28, 518 (1941). 



460 J. Mansfeld and F. Mttller, Arch. ges. Physiol. (Pfluger's), 152, 61-67 (1913). 



