Antioxidant Activity and Glycemic Index of Resistant Starch From Black Glutinous Rice

Type 2 diabetes mellitus ((T2DM) is a global public health manifested by hyperglycemia due to insulin resistance. Rice is the main staple food for the world's population but has a high glycemia index (GI) value. Therefore, this research was aimed to produce resistance starch (RS) from black glutinous rice with different methods – autoclave and annealing, freeze-thawing, and acid methanol methods.  The RS content, total phenolic compound content, antioxidant activity, and estimated GI (pGI) were investigated.  Results showed that the autoclave and annealing method yielded highest RS content of 27.33±8.56%, followed by freeze-thawing, 15-day acid methanol, and 30-min acid methanol methods. The RS from the autoclave and annealing method also had highest total phenolic content (61.55±1.19 mg gallic acid/g sample) and antioxidant activity by 2,2-Diphenyil-picrylhydrazyl (DPPH, IC50 of 7.40±0.24 mg/ml) and ferric reducing antioxidant power (FRAP, 75.47±0.51 mg tocopherol equivalent/g extract). Moreover, The RS from the autoclave and annealing method also had the lowest pGI (57.32±0.74). In conclusion, the autoclave and annealing process gave the highest yield of RS with the highest total phenolic content and antioxidant activity; and with the lowest GI compared to the freeze-thawing and acid methanol methods

beta1-Adrenergic Receptor Signaling Activates the Epithelial Calcium Channel, Transient Receptor Potential Vanilloid Type 5 (TRPV5), via the Protein Kinase A Pathway.

Contains fulltext : 137289.pdf (publisher's version ) (Open Access)Epinephrine and norepinephrine are present in the pro-urine. beta-Adrenergic receptor (beta-AR) blockers administered to counteract sympathetic overstimulation in patients with congestive heart failure have a negative inotropic effect, resulting in reduced cardiac contractility. Positive inotropes, beta1-AR agonists, are used to improve cardiac functions. Active Ca2+ reabsorption in the late distal convoluted and connecting tubules (DCT2/CNT) is initiated by Ca2+ influx through the transient receptor potential vanilloid type 5 (TRPV5) Ca2+ channel. Although it was reported that beta-ARs are present in the DCT2/CNT region, their role in active Ca2+ reabsorption remains elusive. Here we revealed that beta1-AR, but not beta2-AR, is localized with TRPV5 in DCT2/CNT. Subsequently, treatment of TRPV5-expressing mouse DCT2/CNT primary cell cultures with the beta1-AR agonist dobutamine showed enhanced apical-to-basolateral transepithelial Ca2+ transport. In human embryonic kidney (HEK293) cells, dobutamine was shown to stimulate cAMP production, signifying functional beta1-AR expression. Fura-2 experiments demonstrated increased activity of TRPV5 in response to dobutamine, which could be prevented by the PKA inhibitor H89. Moreover, nonphosphorylable T709A-TRPV5 and phosphorylation-mimicking T709D-TRPV5 mutants were unresponsive to dobutamine. Surface biotinylation showed that dobutamine did not affect plasma membrane abundance of TRPV5. In conclusion, activation of beta1-AR stimulates active Ca2+ reabsorption in DCT2/CNT; an increase in TRPV5 activity via PKA phosphorylation of residue Thr-709 possibly plays an important role. These data explicate a calciotropic role in addition to the inotropic property of beta1-AR

Thrombin receptor deficiency leads to a high bone mass phenotype by decreasing the RANKL/OPG ratio.

Contains fulltext : 154292.pdf (publisher's version ) (Closed access)Thrombin and its receptor (TR) are, respectively, expressed in osteoclasts and osteoblasts. However, their physiological roles on bone metabolism have not been fully elucidated. Here we investigated the bone microarchitecture by micro-computed tomography (muCT) and demonstrated increased trabecular and cortical bone mass in femurs of TR KO mice compared to WT littermates. Trabecular thickness and connectivity were significantly enhanced. The physiological role of TR on both inorganic and organic phases of bone is illustrated by a significant increase in BMD and a decrease in urinary deoxypyridinoline (DPD) crosslink concentration in TR KO mice. Moreover, TR KO cortical bone expanded and had a higher polar moment of inertia (J), implying stronger bone. Bone histomorphometry illustrated unaltered osteoblast and osteoclast number and surface in femoral metaphyses, indicating that thrombin/TR regulates osteoblasts and osteoclasts at functional levels. Serum analysis showed a decrease in RANKL and an increase in osteoprotegerin (OPG) levels and reflected a reduced RANKL/OPG ratio in the TR KO group. In vitro experiments using MC3T3 pre-osteoblasts demonstrated a TR-dependent stimulatory effect of thrombin on the RANKL/OPG ratio. This effect was blocked by TR antagonist and p42/p44-ERK inhibitor. In addition, thrombin also intensified p42/p44-ERK expression and phosphorylation. In conclusion, the thrombin/TR system maintains normal bone remodeling by activating RANKL and limiting OPG synthesis by osteoblasts through the p42/44-ERK signaling pathway. Consequently, TR deficiency inhibits osteoclastogenesis, resulting in a high bone mass phenotype.1 maart 201

Urinary plasmin inhibits TRPV5 in nephrotic-range proteinuria

Contains fulltext : 110115.pdf (publisher's version ) (Closed access)Urinary proteins that leak through the abnormal glomerulus in nephrotic syndrome may affect tubular transport by interacting with membrane transporters on the luminal side of tubular epithelial cells. Patients with nephrotic syndrome can develop nephrocalcinosis, which animal models suggest may develop from impaired transcellular Ca(2+) reabsorption via TRPV5 in the distal convoluted tubule (DCT). In nephrotic-range proteinuria, filtered plasminogen reaches the luminal side of DCT, where it is cleaved into active plasmin by urokinase. In this study, we found that plasmin purified from the urine of patients with nephrotic-range proteinuria inhibits Ca(2+) uptake in TRPV5-expressing human embryonic kidney 293 cells through the activation of protease-activated receptor-1 (PAR-1). Preincubation with a plasmin inhibitor, a PAR-1 antagonist, or a protein kinase C (PKC) inhibitor abolished the effect of plasmin on TRPV5. In addition, ablation of the PKC phosphorylation site S144 rendered TRPV5 resistant to the action of plasmin. Patch-clamp experiments showed that a decreased TRPV5 pore size and a reduced open probability accompany the plasmin-mediated reduction in Ca(2+) uptake. Furthermore, high-resolution nuclear magnetic resonance spectroscopy demonstrated specific interactions between calmodulin and residues 133-154 of the N-terminus of TRPV5 for both wild-type and phosphorylated (S144pS) peptides. In summary, PAR-1 activation by plasmin induces PKC-mediated phosphorylation of TRPV5, thereby altering calmodulin-TRPV5 binding, resulting in decreased channel activity. These results indicate that urinary plasmin could contribute to the downstream effects of proteinuria on the tubulointerstitium by negatively modulating TRPV5