Chronic hepatitis B virus (HBV) infection is the most common cause of hepatic fibrosis and hepatocellular carcinoma (HCC),mainly as a result of chronic necroinflammatory liver disease. A characteristic feature of chro...Chronic hepatitis B virus (HBV) infection is the most common cause of hepatic fibrosis and hepatocellular carcinoma (HCC),mainly as a result of chronic necroinflammatory liver disease. A characteristic feature of chronic hepatitis B infection,alcoholic liver disease and nonalcoholic fatty liver disease (NAFLD) is hepatic steatosis. Hepatic steatosis leads to an increase in lipid peroxidation in hepatocytes,which,in turn,activates hepatic stellate cells (HSCs). HSCs are the primary target cells for inflammatory and oxidative stimuli,and these cells produce extracellular matrix components. Chronic hepatitis B appears to progress more rapidly in males than in females,and NAFLD,cirrhosis and HCC are predominately diseases that tend to occur in men and postmenopausal women. Premenopausal women have lower hepatic iron stores and a decreased production of proinflammatory cytokines. Hepatic steatosis has been observed in aromatase-deficient mice,and has been shown to decrease in animals after estradiol treatment. Estradiol is a potent endogenous antioxidant which suppresses hepatic fibrosis in animal models,and attenuates induction of redox sensitive transcription factors,hepatocyte apoptosis and HSC activation by inhibiting a generation of reactive oxygen species in primary cultures. Variant estrogen receptors are expressed to a greater extent in male patients with chronic liver disease than in females. These lines of evidence suggest that the greater progression of hepatic fibrosis and HCC in men and postmenopausal women may be due,at least in part,to lower production of estradiol and a reduced response to the action of estradiol. A better understanding of the basic mechanisms underlying the sex-associated differences in hepatic fibrogenesis and carciogenesis may open up new avenues for the prevention and treatment of chronic liver disease.展开更多
Bone is an endocrine tissue expressing androgen and estrogen receptors as well as steroid metabolizing enzymes. The bioactivity of circulating sex steroids is modulated by sex hormone-binding globulin and local conver...Bone is an endocrine tissue expressing androgen and estrogen receptors as well as steroid metabolizing enzymes. The bioactivity of circulating sex steroids is modulated by sex hormone-binding globulin and local conversion in bone tissue, for example, from testosterone （T） to estradiol （E2） by aromatase, or to dihydrotestosterone by 5（x-reductase enzymes. Our understanding of the structural basis for gender differences in bone strength has advanced considerably over recent years due to increasing use of （high resolution） peripheral computed tomography. These microarchitectural insights form the basis to understand sex steroid influences on male peak bone mass and turnover in cortical vs trabecular bone. Recent studies using Cre/LoxP technology have further refined our mechanistic insights from global knockout mice into the direct contributions of sex steroids and their respective nuclear receptors in osteoblasts, osteoclasts, osteocytes, and other cells to male osteoporosis. At the same time, these studies have reinforced the notion that androgen and estrogen deficiency have both direct and pleiotropic effects via interaction with, for example, insulin-like growth factor 1, inflammation, oxidative stress, central nervous system control of bone metabolism, adaptation to mechanical loading, etc., This review will summarize recent advances on these issues in the field of sex steroid actions in male bone homeostasis.展开更多
文摘Chronic hepatitis B virus (HBV) infection is the most common cause of hepatic fibrosis and hepatocellular carcinoma (HCC),mainly as a result of chronic necroinflammatory liver disease. A characteristic feature of chronic hepatitis B infection,alcoholic liver disease and nonalcoholic fatty liver disease (NAFLD) is hepatic steatosis. Hepatic steatosis leads to an increase in lipid peroxidation in hepatocytes,which,in turn,activates hepatic stellate cells (HSCs). HSCs are the primary target cells for inflammatory and oxidative stimuli,and these cells produce extracellular matrix components. Chronic hepatitis B appears to progress more rapidly in males than in females,and NAFLD,cirrhosis and HCC are predominately diseases that tend to occur in men and postmenopausal women. Premenopausal women have lower hepatic iron stores and a decreased production of proinflammatory cytokines. Hepatic steatosis has been observed in aromatase-deficient mice,and has been shown to decrease in animals after estradiol treatment. Estradiol is a potent endogenous antioxidant which suppresses hepatic fibrosis in animal models,and attenuates induction of redox sensitive transcription factors,hepatocyte apoptosis and HSC activation by inhibiting a generation of reactive oxygen species in primary cultures. Variant estrogen receptors are expressed to a greater extent in male patients with chronic liver disease than in females. These lines of evidence suggest that the greater progression of hepatic fibrosis and HCC in men and postmenopausal women may be due,at least in part,to lower production of estradiol and a reduced response to the action of estradiol. A better understanding of the basic mechanisms underlying the sex-associated differences in hepatic fibrogenesis and carciogenesis may open up new avenues for the prevention and treatment of chronic liver disease.
文摘Bone is an endocrine tissue expressing androgen and estrogen receptors as well as steroid metabolizing enzymes. The bioactivity of circulating sex steroids is modulated by sex hormone-binding globulin and local conversion in bone tissue, for example, from testosterone （T） to estradiol （E2） by aromatase, or to dihydrotestosterone by 5（x-reductase enzymes. Our understanding of the structural basis for gender differences in bone strength has advanced considerably over recent years due to increasing use of （high resolution） peripheral computed tomography. These microarchitectural insights form the basis to understand sex steroid influences on male peak bone mass and turnover in cortical vs trabecular bone. Recent studies using Cre/LoxP technology have further refined our mechanistic insights from global knockout mice into the direct contributions of sex steroids and their respective nuclear receptors in osteoblasts, osteoclasts, osteocytes, and other cells to male osteoporosis. At the same time, these studies have reinforced the notion that androgen and estrogen deficiency have both direct and pleiotropic effects via interaction with, for example, insulin-like growth factor 1, inflammation, oxidative stress, central nervous system control of bone metabolism, adaptation to mechanical loading, etc., This review will summarize recent advances on these issues in the field of sex steroid actions in male bone homeostasis.
