Thyroid hormones increase Na+–Pi co-transport activity in intestinal brush border membrane: Role of membrane lipid composition and fluidity

Abstract

In the present study, we documented the promising role of thyroid hormones status in animals in modulation of Na+-Pi transport activity in intestinal brush border membrane vesicles (BBMV) which was accompanied with alterations in BBM lipid composition and fluidity. Augmentation of net Pi balance in hyperthyroid (Hyper-T) rats was fraternized with accretion of Pi transport across BBMV isolated from intestine of Hyper-T rats as compared to hypothyroid (Hypo-T) and euthyroid (Eu-T) rats while Na+-Pi transport across BBMV was decreased in Hypo-T rats relative to Eu-T rats. Increment in Na+-Pi transport in intestinal BBMV isolated from Hyper-T rats was manifested as an increase in the maximal velocity (Vmax) of Na+-Pi transport system. Furthermore, BBMV lipid composition profile in intestinal BBM from Hyper-T was altered to that of Hypo-T rats and Eu-T rats. The molar ratio of cholesterol/phospholipids was higher in intestinal BBM from Hypo-T rats. Fluorescence anistropy of diphenyl hexatriene (rDPH) and microviscosity were significantly decreased in the intestinal BBM of Hyper-T rats and decreased in Hypo-T rats as compared to Eu-T rats which corroborated with the alteration in membrane fluidity in response to thyroid hormone status of animals. Therefore, thyroid hormone mediated change in membrane fluidity might play an important role in modulating Na+-Pi transport activity of intestinal BBM.

Dyslipidemia in Subclinical Hypothyroidism: A Case-Control Study

“…The lipid metabolism is more influenced by the thyroid hormone [1]. Thyroid hormones are of vital importance in maintaining the initial level of phospholipids in cell membranes and fatty acids composition of the lipids [2]. Triiodothyronine (T3) plays a critical role in lipid metabolism by regulating genes involved in lipogenesis and lipolysis [3,4].…”

Effects of dietary phenylalanine on growth, digestive and brush border enzyme activities and antioxidant capacity in the hepatopancreas and intestine of young grass carp (Ctenopharyngodon idella)

“…Nevertheless, little evidence has been reported the effects of phenylalanine on the growth and development of fish digestive organs. There have been reported that thyroid hormone could change intestinal brush border membrane lipid composition in adult male rats (Prasad & Kumar ), as well as stimulate enterocyte differentiation in the human colorectal adenocarcinoma caco‐2 cell line (Malo et al . ).…”

Effect of thyroid hormone on the distribution and activity of Na, K-ATPase in ventricular myocardium

“…Alternatively, it is possible that the high cholesterol composition (and high cholesterol/phospholipid ratio) of the membrane domain in which the Na-pumps are localized makes the membrane more "rigid" and impedes the enzymatic turnover by requiring higher energies of activation. This explanation is given credence based on previous observations that the "fluidity" of membranes is reduced and their melting temperature (T m ) increases as the cholesterol/phospholipid ratio is increased [22][23][24][25]. It is known that Na, K-ATPase activity is affected by the cholesterol and phospholipid content of the membrane as well as the length of phospholipid acyl chains [36,37] In addition, increased cholesterol content of membranes induced by excess cholesterol feeding has been associated with decreases in Na, K-ATPase activity [38].…”

“…Finally, excess thyroid hormone has been reported to cause a decrement in the cholesterol content of membranes, largely reflecting the decrements in cholesterol content of plasma membranes; the decreased levels of cholesterol increases the phospholipids/cholesterol ratio and "fluidity" of membranes [22][23][24][25]. To verify this observation in our experimental system, we isolated total membranes from homogenates of ventricular myocardium of hypothyroid and hyperthyroid rats.…”