The pancreatic ATP-sensitive potassium (K ATP ) channel, a complex of four sulfonylurea receptor 1 (SUR1) and four potassium channel Kir6.2 subunits, regulates insulin secretion by linking metabolic changes to ␤-cell membrane potential. Sulfonylureas inhibit K ATP channel activities by binding to SUR1 and are widely used to treat type II diabetes. We report here that sulfonylureas also function as chemical chaperones to rescue K ATP channel trafficking defects caused by two SUR1 mutations, A116P and V187D, identified in patients with congenital hyperinsulinism. Sulfonylureas markedly increased cell surface expression of the A116P and V187D mutants by stabilizing the mutant SUR1 proteins and promoting their maturation. By contrast, diazoxide, a potassium channel opener that also binds SUR1, had no effect on surface expression of either mutant. Importantly, both mutant channels rescued to the cell surface have normal ATP, MgADP, and diazoxide sensitivities, demonstrating that SUR1 harboring either the A116P or the V187D mutation is capable of associating with Kir6.2 to form functional K ATP channels. Thus, sulfonylureas may be used to treat congenital hyperinsulinism caused by certain K ATP channel trafficking mutations. ATP-sensitive potassium (K ATP )1 channels present in the plasma membrane of pancreatic ␤-cells play a central role in mediating glucose-induced insulin secretion (1-4). The activity of K ATP channels, which regulates ␤-cell membrane potential, is determined by the relative concentrations of intracellular ATP and ADP. When the blood glucose level rises, the increased intracellular [ATP/ADP] ratio favors K ATP channel closure, resulting in membrane depolarization, Ca 2ϩ influx, and insulin secretion. When the blood glucose level falls, the above molecular events reverse, and insulin release is stopped. In the event where K ATP channels fail to open during glucose starvation, ␤-cell membrane potential remains depolarized, and insulin secretion persists, leading to severe hypoglycemia. These symptoms are found in patients suffering from congenital hyperinsulinism (5), also known as persistent hyperinsulinemia hypoglycemia of infancy (PHHI) (6). Indeed, mutations in the K ATP channel genes, sulfonylurea receptor 1 (SUR1) and the inward rectifier potassium channel Kir6.2, that lead to a loss of channel function have been shown to be major causes of PHHI (4, 6).The pancreatic K ATP channel complex consists of four poreforming Kir6.2 subunits and four regulatory SUR1 subunits (7-10). Gating of K ATP channels occurs as a result of the interplay between both channel subunits and intracellular ATP and ADP. Binding of ATP to the Kir6.2 subunit inhibits channel activity, whereas binding of Mg 2ϩ -complexed ATP or ADP to the SUR1 subunit stimulates channel activity (11)(12)(13)(14). SUR1 is a member of the ATP-binding cassette transporter family; it has three transmembrane domains: TM0, TM1, and TM2, and two large cytoplasmic nucleotide binding domains: NBD1 and NBD2 (15,16). Structure-function studies sugges...

Probiotics reduce stress-related inflammation and abnormal behaviors in humans and rodents via regulation of the microbiota-gut-brain axis. The objective of this study was to determine if probiotic, Bacillus subtilis, has similar functions in broiler chickens under heat stress (HS). Two hundred forty 1-d-old broiler chicks were assigned to 48 pens with 4 treatments: Thermoneutral (TN)-RD (regular diet), TN-PD (the regular diet mixed with 1 × 106 CFU/g feed probiotic), HS-RD and HS-PD. Probiotic (Sporulin) was fed from day 1; and HS at 32°C for 10 h daily was initiated at day 15. The data showed that final BW, average daily gain , and feed conversion efficiency were improved in PD groups as compared to RD groups regardless of the ambient temperature (P < 0.01). Heterophil to lymphocyte ratio was affected by treatment and its value was in the order of HS-RD > HS-PD > TN-RD > TN-PD birds (P < 0.01). Compared to TN birds, HS birds spent more time in wing spreading, panting, squatting close to the ground, drinking, sleeping, dozing, and sitting but spent less time in eating, standing, and walking (P < 0.05 or 0.01). In addition, HS birds had greater levels of hepatic IL-6, IL-10, heat shock protein (HSP)70, and HSP70 mRNA expression (P < 0.01) and greater levels of cecal IgA and IgY (P < 0.01) compared to TN birds. Within TN groups, TN-PD birds had greater concentrations of hepatic IL-10 (P < 0.05) and cecal IgA (P < 0.01) than TN-RD birds. Within HS groups, HS-PD birds spent less time in wing spreading, panting, squatting close to the ground, drinking, sleeping, dozing, and sitting but spent more time in eating, foraging, standing, and walking than HS-RD birds (P < 0.05 or 0.01). The HS-PD birds also had lower concentrations of hepatic IL-6 and HSP70 (P < 0.01), whereas greater levels of IL-10 (P < 0.05) and lower concentrations of cecal IgA and IgY (P < 0.01). These results indicate that broilers fed the probiotic, B. subtilis, are able to cope with HS more effectively by ameliorating heat-induced behavioral and inflammatory reactions through regulation of microbiota-modulated immunity.

The objective of the present study was to evaluate the effect of antioxidant inclusion and oil quality on broiler performance, meat quality, shelf life, and tissue oxidative status. Ross 308 male broilers were allotted to a randomized complete block design in a 2 × 2 factorial arrangement. Factors consisted of antioxidant (ethoxyquin and propyl gallate) inclusion at 2 levels (0 or 135 mg/kg) and oil quality (fresh soybean oil, control diet peroxide value <1 mEq/kg, or oxidized soybean oil, diet peroxide value 7 mEq/kg). Each treatment included 12 pen replicates comprising 24 birds for a total of 1,152 birds on trial allotted to 48 pens. On the final day of the study, 1 bird from each pen was killed by cervical dislocation and used for determination of tissue oxidative status. Another 5 broilers from each pen were processed at a commercial slaughtering facility. Immediately after processing, carcasses were transported to the University of Illinois Meat Science Laboratory (Urbana) for further analysis. With the exception of 2 responses (liver vitamin A and serum vitamin A), no interactions were found between antioxidant inclusion and oil quality. Body weight and weight gain were increased by dietary antioxidant inclusion (P < 0.001) and fresh oil (P < 0.001). Feed intake was increased in broilers fed the antioxidant (P = 0.047) and fresh oil (P = 0.062). Antioxidant inclusion had no effect on G:F (P = 0.18). Antioxidant supplementation had no effect on carcass weight (P = 0.202), dressing percentage (P = 0.906), breast yield (P = 0.708), or breast ultimate pH (P = 0.625) and had minimal effect on breast color. Antioxidant supplementation (P = 0.057) reduced breast thiobarbituric acid reactive substances after 7 d of display. Fresh oil decreased liver thiobarbituric acid reactive substances, whereas antioxidant inclusion increased serum and liver vitamin A and E concentration. The presence of an antioxidant in the feed protects lipids from further oxidizing, therefore increasing broiler performance and improving shelf life when using oxidized oil.

No abstract

ATP-sensitive K؉ channels (K ATP channels) of pancreatic ␤-cells play key roles in glucose-stimulated insulin secretion by linking metabolic signals to cell excitability. Membrane phosphoinositides, in particular phosphatidylinositol 4,5-bisphosphates (PIP 2 ), stimulate K ATP channels and decrease channel sensitivity to ATP inhibition; as such, they have been postulated as critical regulators of K ATP channels and hence of insulin secretion in ␤-cells. Here, we tested this hypothesis by manipulating the interactions between K ATP channels and membrane phospholipids in a ␤-cell line, INS-1, and assessing how the manipulations affect membrane excitability and insulin secretion. We demonstrate that disruption of channel interactions with PIP 2 by overexpressing PIP 2 -insensitive channel subunits leads to membrane depolarization and elevated basal level insulin secretion at low glucose concentrations. By contrast, facilitation of channel interactions with PIP 2 by upregulating PIP 2 levels via overexpression of a lipid kinase, phosphatidylinositol 4-phosphate 5 kinase, decreases the ATP sensitivity of endogenous K ATP channels by ϳ26-fold and renders INS-1 cells hyperpolarized, unable to secrete insulin properly in the face of high glucose. Our results establish an important role of the interaction between membrane phosphoinositides and K ATP channels in regulating insulin secretion. Diabetes 54:2852-2858, 2005 P ancreatic ␤-cells secrete insulin in response to glucose stimulus. The ATP-sensitive K ϩ (K ATP ) channel, a complex of four inwardly rectifying K ϩ channel Kir6.2 subunits and four sulfonylurea receptor 1 (SUR1) subunits, is a key component in this stimulus-secretion coupling process (1-3). The hallmark features of K ATP channels are their sensitivities to intracellular nucleotides ATP and ADP, the derivatives of glucose metabolism (1,2). ATP inhibits channel activity, whereas ADP, in complex with Mg 2ϩ , stimulates channel activity. It is now generally accepted that the physiological activity of K ATP channels is regulated primarily by the relative concentrations of ATP and ADP (1,4,5). As plasma glucose increases, ATP concentration increases and ADP concentration decreases, resulting in K ATP channel closure, membrane depolarization, Ca 2ϩ influx, and insulin release. Conversely, when glucose decreases, the concentration ratio of ATP to ADP decreases, leading to K ATP channel opening, membrane hyperpolarization, and termination of insulin secretion. The importance of ATP and ADP in regulating K ATP channels in vivo has been confirmed by the finding that mutations that reduce channel sensitivity to ATP or MgADP are causative in permanent neonatal diabetes or congenital hyperinsulinism, respectively (5-9).The discovery that membrane phosphoinositides, in particular the most abundant phosphoinositide phosphatidylinositol 4,5-bisphosphate (PIP 2 ) (10), stimulate K ATP channel activity and antagonize the inhibitory effect of ATP in isolated membrane patches (11,12) has led to the proposal that in addition ...

No abstract

Recent researches have showed that probiotics promote bone health in humans and rodents. The objective of this study was to determine if probiotics have the similar effects in laying hens. Ninety-six 60-week-old White Leghorn hens were assigned to four-hen cages based on their BW. The cages were randomly assigned to 1 of 4 treatments: a layer diet mixed with a commercial probiotic product (containing Enterococcus faecium, Pediococcus acidilactici, Bifidobacterium animalis and Lactobacillus reuteri) at 0, 0.5, 1.0 or 2.0 g/kg feed (Control, 0.5×, 1.0× and 2.0×) for 7 weeks. Cecal Bifidobacterium spp. counts were higher in all probiotic groups (P0.05). In addition, the plasma concentrations of cytokines (interleukin-1β, interleukin-6, interleukin-10, interferon-γ and tumor necrosis factor-α) and corticosterone as well as the levels of heterophil to lymphocyte ratio were similar between the 2.0× group and the control group (P>0.05). In line with these findings, no differences of cecal tonsil mRNA expressions of interleukin-1β, interleukin-6 and lipopolysaccharide-induced tumor necrosis factor-α factor were detected between these two groups (P>0.05). These results suggest that immune cytokines and corticosterone may not involve in the probiotic-induced improvement of eggshell quality and bone mineralization in laying hens. In conclusion, the dietary probiotic supplementation altered cecal microbiota composition, resulting in reduced shell-less egg production and improved bone mineralization in laying hens; and the dietary dose of the probiotic up to 2.0× did not cause negative stress reactions in laying hens.

This study evaluated the effects of dietary probiotic supplement and postmortem storage on meat quality of chicken breast during retail display. A total of 35 birds were randomly obtained from 3 feeding groups (control without probiotic supplement, 250 ppm Sporulin, and 500 ppm PoultryStar). The probiotic supplement had no influence on feed conversion ratio and body weight gain, as well as body weight at 29 and 44 d (P > 0.05). After slaughter, each side of the breast muscles (M. Pectoralis major) was assigned to either one d or 5 d of postmortem storage. Probiotic supplement had no influence on the rate of pH decline of chicken breast muscles during the initial 6 h postmortem (P > 0.05). No interactions between probiotic supplement and postmortem storage on meat quality were found (P > 0.05). Postmortem storage decreased drip loss from 25.30 to 18.05% (P < 0.05). Probiotics-fed chicken groups, particularly PoultryStar treatment, had a higher myofibrillar fragmentation index than the control group (P < 0.05). However, shear force values were not affected by the probiotic treatments. Decreases in color and lipid stabilities of breast muscles were found during display (P < 0.05), but were not affected by the probiotic supplement (P > 0.05). Our result suggests that probiotic supplement had no adverse impacts on proteolysis and oxidative changes during 5 d postmortem display storage.