Effects of hyperthyroidism, epinephrine, and diet on heart lipoprotein lipase activity

Abstract

Rats were fasted for several days, placed on diets high in carbohydrate, fat, or containing iodinated casein so as to produce hyperthyroidism, or were chronically injected with epinephrine. Lipoprotein lipase (LPL) activities of homogenates of the hearts of these animals were determined. Significant increases in LPL activity occurred in thyrotoxic animals, in rats receiving epinephrine injections chronically, or after prolonged fasting, while significant lowering of cardiac LPL activity was observed in rats on the high-carbohydrate or high-fat diets. Single doses of fat or single injections of epinephrine had no effect. Addition of epinephrine or of triiodothyronine to heart slices or homogenates in vitro caused no LPL increases. It is postulated that adaptive changes in cardiac LPL activity may occur in response to altered needs for utilization of fatty acids by the heart. Microsomal fractions of heart cells had the highest specific LPL activities, suggesting synthesis of the enzyme by these cellular components, or activity of the enzyme at the endoplasmic reticulum.

The Effect of Catecholamines and Cold Exposure on the Lipolytic Activity of Rat Heart

“…Hyperthyroidism caused a significant increase of the heart CFL activity in experim ents of Alousi and Mallow (1). The possibility exists that the im portant increase of heart CFL activity after the rat exposure to cold m ight be related to the activation of thyroid activity.…”

“…Nikkila, on the basis of preliminary experiments (8), pointed out that epinephrine may influence the clearing factor lipase (CFL) activity in heart. Alousi and Mallov (1) have recently ob served modifications of heart CFL after acute and chronic administration of epinephrine in rats. The present experiments have been designed in order to examine not only the effect of exogenous catecholamines on the lipolytic activity of the rat heart, but also that of a severe stressing condition (cold exposure).…”

Developmental Changes of Myocardial Metabolism

“…These cases influence the final average value of the FFA A-V difference. It has been reported that the feeding of fat to dogs results in a rise in circulating heparin with the consequent release of lipoprotein lipase from the heart [1,10,12]. We suppose that in our case, too, an activation of myocardial lipoprotein lipase occurred and thus a hydrolysis of circulating triglycerides that can imitate FA release from the heart [6].…”

Lipoprotein lipase and the uptake of lipids by adipose cells during development

“…Khoo et al, 1973) (Hamosh and Hamosh, 1975a ;Wilson et al, 1976). Glucocorticoids enhance the insulin effects (Ashby and Robinson, 1980) and have an independent stimulatory effect on adipose tissue lipoprotein lipase activity (de Gasquet et al, 1975) probably via a specific effect on specific-enzyme synthesis (Ashby and Robinson, 1980 (Robinson, 1970) whereas of the hormones suggested to stimulate total activity, glucagon (Borenstajn et al, 1973 ;de Gasquet et al, 1975 ;Kotlar and Borenstajn, 1977) catecholamines, thyroid hormones and corticosteroids (Alousi and Mallov, 1964 ;Torsti, 1965 ;Rodomski and Orme, 1971) are mentioned most often. Some studies also suggest that, additionally, norepinephrine (Hulsmann and Stam, 1978) and glucagon (Jansen et al, 1980 ;Simpson, 1979) (Chohan and Cryer, 1980 ;Cryer et al, 1981Cryer et al, , 1984a Chohan and Cryer, 1979) requires microtubular activity (Chajek et al, 1975 ;Cryer et al, 1975b) and it is probably at this stage, when the mature enzyme is ready for secretion, that the catecholamine-induced loss of activity comes about, possibly through an increased rate of specific protein degradation (Ashby et aL, 1978).…”