Calorigen

Caffeine increases the metabolic rate. This is a very early finding dating back to 1917. This calorigenic effect is probably the reason for the desire for caffeine beverages in cold climates. This effect is true in lean as well as obese subjects. 

The thermogenic mechanism best understood in plants is a cyanide-insensitive nonpho-sphorylating electron transport pathway that is found only in plant mitochondria (Raskin et al., 1987). This pathway is distinct from the electron transport pathway involved in mitochondrial ATP production, and is under the control of calorigens, molecules that can lead to a... 

M.K. Meier, L. Alic, M.E. Burgi-Sa-viLLE, and M. Muller, Phenethanola-mine derivatives with calorigenic and antidiabetic qualities, Int. J. Obes., 1984,... 

Because most of the energy produced by cellular respiration eventually appears as heat, an increase in cellular respiration necessarily leads to an increase in heat production (i.e., to a thermogenic or calorigenic effect). Thus, to the degree that thyroid hormones control BMR, they also control thermogenesis (17). 

A characteristic sign of hypothyroidism is a decrease in metabolic rate, with a reduction in calorigenic effect and defective thermoregulation. The elevated serum cholesterol level seen in hypothyroidism is the result of a decrease in cholesterol degradation that exceeds the decrease in cholesterol biosynthesis it reflects a... 

Dextrothyroxine, the synthetic D-(+)-stereoisomer isomer of L-(-)-T4, was introduced in hypocholesteremic-hypolipidemic therapy with the premise that it would be void of calorigenic effects. The possibility of trace contamination with and metabolic conversion to T4 and congeners has restricted its use, however, especially in patients with coronary heart disease. 

Jorgensen EC, Zenker N, Greenberg C. et al. Thyroxine analogues. III. Antigoitrogenic and calorigenic activity of some alkyl substituted analogues of thyroxine. J Biol Chem 1960 235 1732-1737. 

B. Chemical Structure and Calorigenic Potency of Thyroid Hormones in... 

The effect of thyroid hormones on oxidative processes has long been considered to be their most fundamental action in adult mammals. In 1895, Magnus-Levy made the classic observation that respiratory exchange is depressed in hypothyroidism and elevated in hyperthyroidism. Many factors modify the effect of thyroid hormones in the intact animal, such as nutrition, other endocrine secretions, and the general health of the animal (cf. Boothby and Sandiford, 1924 Sundaram el al., 1956 Money, 1956) a consideration of these fa( tors is beyond the scope of this review. It should be noted that the thyroid hormones appear to exert no calorigenic activity in lower vertebrates (cf. Fromm and Reineke, 1956). 

A calorigenic action of thyroid hormones can also be demonstrated in tissues excised from animals with experimentally induced hyperthyroidism. In 1924, Rohrer demonstrated increased oxygen consumption in liver, kidney, and muscle isolated from mice which had been made hyperthyroid with desiccated thyroid. Most subsequent experiments have been performed with tissue sUces excised from other species, especially the rat. Differences in the metabolic responses of various tissues to thyroid stimulation have been ob.served, depending upon the species studied and the thyroid preparations used these differences will be discussed in the subsequent section. In contrast to the response of isolated tissues to thyroid hor-... 

Compound Calorigenic potency Calorigenic potency in rats in man ... 

In Table I are listed the most potent of the various analogs of thyroxine, together with a list of their calorigenic potencies relative to that of L-thy-roxinc. The only analog reported to be more potent than L-thyroxine is 3,5, iV-L-triiodothyronine. However, this finding must be interpreted with some reservation the relative potency of the two ( ompounds is not the same at different time intervals following the injection of the hormone. L-Thyroxine produces in man a response which, after a lag period of from... 

Ismail-Beigi, F. and Edelman, I. S. (1971). The mechanism of calorigenic action of thyroid hormone stimulation of Na+ and K+-activated adenosine triphosphatase activity. J. Gen. Physiol. 57 710-722. 

Levitsky, D. A., Green, P. S., and Obarzanek, E., 1983, Calorigenic effect of nicotine depends upon the ingestion of food. Paper presented at International Congress of Obesity, Storr, Vermont. 

The natural thyroid hormone, levorotatory thyroxine (LTJ, is primarily responsible for the elevation of the basal metabolic rate (BMR) as reflected in the increase in oxygen consumption. This feature of thyroxine is denoted as the calorigenic effect. Another important property of thyroxine is its influence on the heart. The intrinsic heart-rate was found to be higher in patients with hyperthyroidism and lower than normal in patients with hypoth5U oidism. It has been concluded that the differences in heart-rate between subjects with hyper- and hypothyroidism are mainly due to thyroxine acting directly on the heart and not to its potentiation of the action of catecholamines [174]. 

Due to the available structure-activity relationship data accrued on thyroxine type compounds, a body of knowledge is now available which permits the medicinal chemist to approach the synthesis of analogs of thyroxine with the object of dissociating hypolipidemic activity from the calorigenic and cardiotropic prop-... 

---