Estrogen deficiency-induced Ca balance impairment is associated with decrease in expression of epithelial Ca transport proteins in aged female rats

Nonalcoholic fatty liver disease shows significant sex dimorphism

Nonalcoholic fatty liver disease (NAFLD), which has been renamed metabolic dysfunction-associated fatty liver disease, is a growing global medical problem. The incidence of NAFLD and its associated end-stage liver disease is increasing each year, and many research advancements have been achieved to date. This review focuses on the current knowledge of the sex differences in NAFLD and does not elaborate on areas without differences. Studies have revealed significant sex differences in the prevalence, influencing factors, pathophysiology, complications and therapies of NAFLD. Men have a higher incidence than women. Compared with women, men exhibit increased visceral fat deposition, are more susceptible to leptin resistance, lack estrogen receptors, and tend to synthesize fatty acids into fat storage. Male patients will experience more severe hepatic fibrosis and a higher incidence of liver cancer. However, once NAFLD occurs, women show a faster progression of liver fibrosis, higher levels of liver cell damage and inflammation and are less likely to undergo liver transplantation than men. In general, men have more risk factors and more severe pathophysiological reactions than women, whereas the development of NAFLD is faster in women, and the treatments for women are more limited than those for men. Thus, whether sex differences should be considered in the individualized prevention and treatment of NAFLD in the future is worth considering.

Dietary mulberry-leaf flavonoids improve the eggshell quality of aged breeder hens

Eggshell quality is subject to a significant decline in the late laying period, which results in huge economic losses. The purpose of this study was to investigate the effects of dietary mulberry-leaf flavonoids (MF) on the eggshell quality of aged breeder hens. A total of 270 (60-week-old) Qiling breeder hens were randomly assigned to 3 treatments with supplemental dietary MF doses (0, 30, and 60 mg/kg). The results showed that dietary MF improved the eggshell thickness and strength, following the reduced broken egg ratio (P < 0.05). Histological analysis showed that dietary MF increased glandular density and luminal epithelium height in the shell gland (P < 0.05). MF treatment reduced the apoptotic index of the shell gland, following by improved antioxidant capacity (P < 0.05). The protein expression of Caspase 3 was down-regulated, and Nrf2 was up-regulated by dietary MF (P < 0.05). Furthermore, calcium (Ca) content in the serum and shell gland, as well as the activity of Ca²⁺-ATPase in the shell gland were increased by dietary MF (P < 0.05). Ca transport-related genes (ESRα, ESRβ, KCNA1, OPN, CABP-28K and CDH6) in the shell gland were upregulated by dietary MF treatment (P < 0.05). In conclusion, dietary MF could ameliorate the eggshell quality of aged hens by improving antioxidative capability and Ca deposition in the shell gland of uterus.

Epithelial Barrier Function in Gut-Bone Signaling

The intestinal epithelial barrier plays an essential role in maintaining host homeostasis. The barrier regulates nutrient absorption as well as prevents the invasion of pathogenic bacteria in the host. It is composed of epithelial cells, tight junctions, and a mucus layer. Several factors, such as cytokines, diet, and diseases, can affect this barrier. These factors have been shown to increase intestinal permeability, inflammation, and translocation of pathogenic bacteria. In addition, dysregulation of the epithelial barrier can result in inflammatory diseases such as inflammatory bowel disease. Our lab and others have also shown that barrier disruption can have systemic effects including bone loss. In this chapter, we will discuss the current literature to understand the link between intestinal barrier and bone. We will discuss how inflammation, aging, dysbiosis, and metabolic diseases can affect intestinal barrier-bone link. In addition, we will highlight the current suggested mechanism between intestinal barrier and bone.

Sex steroids and the kidney: role in renal calcium and phosphate handling

Calcium and phosphate are vital for the organism and constitute essential components of the skeleton. Serum levels are tightly hormonally regulated and maintained by exchange with three major sources: the intestines, the kidney and the bone. The effects of sex steroids on the bone have been extensively studied and it is well known that sex steroid deficiency induces bone loss, indirectly influencing renal calcium and phosphate homeostasis. However, it is unknown whether sex steroids also directly regulate renal calcium and phosphate handling, hereby potentially indirectly impacting on bone. The presence of androgen receptors (AR) and estrogen receptors (ER) in both human and rodent kidney, although their exact localization within the kidney remains debated, supports direct effects. Estrogens stimulate renal calcium reabsorption as well as phosphate excretion, while the effects of androgens are less clear. Many of the studies performed with regard to renal calcium and/or phosphate homeostasis do not correct for the calcium and phosphate fluxes from the bone and intestines, which complicates the differentiation between the direct effects of sex steroids on renal calcium and phosphate handling and the indirect effects via the bone and intestines. The objective of this study is to review the literature and current insight of the role of sex steroids in calcium and phosphate handling in the kidney.

The Plasma Membrane Calcium ATPases and Their Role as Major New Players in Human Disease

The Ca²⁺ extrusion function of the four mammalian isoforms of the plasma membrane calcium ATPases (PMCAs) is well established. There is also ever-increasing detail known of their roles in global and local Ca²⁺ homeostasis and intracellular Ca²⁺ signaling in a wide variety of cell types and tissues. It is becoming clear that the spatiotemporal patterns of expression of the PMCAs and the fact that their abundances and relative expression levels vary from cell type to cell type both reflect and impact on their specific functions in these cells. Over recent years it has become increasingly apparent that these genes have potentially significant roles in human health and disease, with PMCAs1-4 being associated with cardiovascular diseases, deafness, autism, ataxia, adenoma, and malarial resistance. This review will bring together evidence of the variety of tissue-specific functions of PMCAs and will highlight the roles these genes play in regulating normal physiological functions and the considerable impact the genes have on human disease.

Effects of estrogen on esophageal function through regulation of Ca2+-related proteins

BACKGROUND

The calcium ion is important for physiological functions in all tissues and organs and essential to many vital functions, including hormone secretion and muscle contraction. The intracellular concentration of calcium is regulated by calcium related proteins such as CaBP-9k, PMCA1, and NCX1. In this study, we investigated the relationship between calcium regulation and esophageal functions such as mucin secretion and smooth muscle contraction.

METHODS

To evaluate the influence of sex steroid hormones, immature rats were treated for 3 days with estradiol (E2), progesterone (P4), and their antagonists (ICI 182,780, and RU486). Esophageal function, transcription level, and localization of CaBP-9k, PMCA1, NCX1, ERα, and MUC2 were examined in the esophagus.

RESULTS

Transcriptional level of Cabp-9k and Muc2 was increased by E2, but not by P4. CaBP-9k, PMCA1, and MUC2 were mainly localized in the mucosal layer. Acidic mucosubstances in the esophagus were increased by E2 and recovered by ICI treatment. Unlike the expression of Cabp-9k, mRNA levels of Pmca1, Ncx1, and Erα were only decreased in response to E2, and recovered by ICI co-treatment group. The contraction of the esophagus and mRNA level of Mylk were reduced by E2. Overall, E2 upregulated mucus secretion, but downregulated muscle contraction in the esophagus through regulation of the expression of calcium related genes and the resultant intracellular calcium level.

CONCLUSIONS

The regulation of E2 in the function of esophagus may be applied to treat esophageal diseases such as reflux esophagitis, achalasia, and esophageal cancer.

Ways of calcium reabsorption in the kidney

The role of the kidney in calcium homeostasis has been reshaped from a classic view in which the kidney was regulated by systemic calcitropic hormones such as vitamin D3 or parathyroid hormone to an organ actively taking part in the regulation of calcium handling. With the identification of the intrinsic renal calcium-sensing receptor feedback system, the regulation of paracellular calcium transport involving claudins, and new paracrine regulators such as klotho, the kidney has emerged as a crucial modulator not only of calciuria but also of calcium homeostasis. This review summarizes recent molecular and endocrine contributors to renal calcium handling and highlights the tight link between calcium and sodium reabsorption in the kidney.

Women may respond different from men to vitamin D supplementation regarding cardiometabolic biomarkers

Evidence has revealed that vitamin D status is associated with the cardiometabolic risk factors. Moreover, few gender-specific analyses have been performed in the clinical trials regarding vitamin D supplementation. As a result, assessing gender differences regarding the effects of vitamin D supplementation on some cardiometabolic biomarkers in patients with non-alcoholic fatty liver disease (NAFLD) was the aim of present study. We conducted a post hoc subgroup analysis of a double blind placebo controlled study. Patients with NAFLD randomly allocated to receive one oral pearl consisting of 50,000 IU vitamin D3 (n = 27, 13 men and 14 women) or a placebo (n = 26, 13 men and 13 women) every 14 days for four months. Serum lipid profiles, aminotransferases, high-sensitive C-reactive protein (hs-CRP), adiponectin as well as insulin resistance and dietary intakes were assessed pre- and post-study. In both genders, serum 25(OH) D3 increased significantly (P < 0.001). This increase was accompanied by significant decrease in serum total cholesterol (TC) (% of change: -7% in vitamin D vs. + 0.4% in placebo, P = 0.04) and LDL-C (%of change: -9.6% in vitamin D vs. -4% in placebo, P = 0.006) in women. However, in men, vitamin D supplementation increased the levels of serum TC (% of change: +9.2% in vitamin D vs. -10% in placebo, P = 0.02) with no significant effects on LDL-C. Moreover, vitamin D significantly reduced serum hs-CRP in women. The median daily calcium intake in both genders was well below the dietary reference intake for adults. In conclusion, improved vitamin D status might decrease serum TC and LDL-C levels as well as hs-CRP in women with NAFLD. However, it might increase serum TC in men who have low daily calcium intake. Further studies with larger sample sizes are needed to confirm these results.

Long-term treatment with eldecalcitol (1α, 25-dihydroxy-2β- (3-hydroxypropyloxy) vitamin D3) suppresses bone turnover and leads to prevention of bone loss and bone fragility in ovariectomized rats

The purpose of this study is to estimate the efficacy of eldecalcitol (1α, 25-Dihydroxy-2β- (3-hydroxypropyloxy) vitamin D3; ELD) on bone metabolism after long-term administration. Six-month-old Wistar-Imamichi rats were ovariectomized (OVX) and administered ELD orally at doses of 7.5, 15, or 30 ng/kg daily. Bone mineral density (BMD), urinary excretion of deoxypyridinoline (DPD), a bone resorption marker, and serum total alkaline phosphatase (ALP), a surrogate marker of bone formation, were assessed after 3, 6, and 12 months of treatment. After 12 months of treatment, the biomechanical strength of the L4 lumbar vertebra and femoral shaft was measured, and bone histomorphometry was performed on the L3 lumbar vertebra and the tibia diaphysis. ELD prevented OVX-induced decreases in BMD of the lumbar vertebrae and femur throughout the treatment period. ELD significantly suppressed OVX-induced increases in urinary DPD excretion throughout the treatment period with minimal effects on ALP. OVX resulted in significant decreases in ultimate load and stiffness of the L4 lumbar vertebra and femoral shaft, and ELD significantly prevented the reduction in these biomechanical parameters. Bone histomorphometry at the L3 lumbar vertebra revealed that OVX induced increases in bone resorption parameters (osteoclast surface and osteoclast number) and bone formation parameters (osteoblast surface, osteoid surface, and bone formation rate), and ELD suppressed these parameters after 12 months treatment. Activation frequency, which was elevated in the OVX/vehicle group, was significantly suppressed to baseline levels in ELD-treated groups, indicating that ELD maintained bone turnover at a normal level. ELD also prevented OVX-induced deterioration of microstructure in trabecular and cortical bone. These results indicated that long-term treatment of OVX rats with ELD suppressed bone turnover, and prevented OVX-induced bone loss, deterioration of bone microstructure, and reduction in bone biomechanical strength.